Antimicrobial peptides for the treatment of pulmonary

Send Orders for Print-Reprints and e-prints to [email protected] Current Pharmaceutical Design, 2018, 24, 1-10

1

REVIEW ARTICLE

Antimicrobial peptides for the treatment of pulmonary tuberculosis, allies or foes? Bruno Rivas-Santiago* and Flor Torres-Juarez 1

Medical Research Unit Zacatecas-IMSS, Zacatecas, Mexico

ARTICLE HISTORY Received: February 16, 2018 Accepted: March 21, 2018 DOI: 10.2174/1381612824666180327162357

Abstract: Tuberculosis is an ancient disease that has become a serious public health issue in recent years, although increasing incidence has been controlled, deaths caused by Mycobacterium tuberculosis have been accentuated due to the emerging of multi-drug resistant strains and the comorbidity with diabetes mellitus and HIV. This situation is threatening the goals of world health organization (WHO) to eradicate tuberculosis in 2035. WHO has called for the creation of new drugs as an alternative for the treatment of pulmonary tuberculosis, among the plausible molecules that can be used are the antimicrobial peptides (AMPs). These peptides have demonstrated remarkable efficacy to kill mycobacteria in vitro and in vivo in experimental models, nevertheless, these peptides not only have antimicrobial activity but also have a wide variety of functions such as angiogenesis, wound healing, immunomodulation and other well-described roles into the human physiology. Therapeutic strategies for tuberculosis using AMPs must be well thought prior to their clinical use; evaluating comorbidities, family history and risk factors to other diseases, since the wide function of AMPs, they could lead to collateral undesirable effects.

Keywords: Anti-inflammatory, antimicrobial peptides, immunomodulation, treatment, pro-inflammatory, tuberculosis. 1. INTRODUCTION Mycobacterium tuberculosis (Mtb) is the causative agent of tuberculosis (TB), which although sounds like a past-century disease, is present nowadays, emerging as a serious public health problem. Indeed, World Health Organization (WHO) declared that the TB epidemic was worse than previously thought, with an estimated 10.4 million new TB cases in 2015 and 1.8 million deaths caused by Mtb, making TB a bigger killer than HIV and malaria combined [1]. Although biomedical knowledge has grown exponentially regarding TB vaccinology, immunology, diagnostics and pharmacology the concerted efforts by researchers, governments and industry seem insufficient to stop TB. For worsening the landscape, Mtb has developed resistance to multiple antibiotics, making even harder the controlling task. The emerging of multidrug-resistant (MDR) and extensively drug-resistant strains has led to the searching for new antibiotics and/or immunomodulators that can kill directly Mtb or activate immune response to make it capable to content mycobacteria growth. Researchers have started to look back into the past to try to find these new molecules and have found the antimicrobial peptides (AMPs) as “new candidates”, which are regarded as major effectors of microbial killing in the animal kingdom. AMPs have been recognized in prokaryotic cells since 1939 when antimicrobial substances, named gramicidins, were isolated from Bacillus brevis and were found to exhibit activity both in vitro and in vivo against a wide range of Gram-positive bacteria [2]. It was until 1950s and 1960s that was shown that cationic proteins were responsible for the ability of human neutrophils to kill bacteria via oxygenindependent mechanisms [3-5]. Thereafter, there were other important studies that have helped to understand the major features of AMPs, for instance Boman et al. injected bacteria into the pupae of the silk moth, Hyalophora cecropia, and isolated the inducible cationic antimicrobial proteins, from the hemolymph of these pupae later known as cecropins thereby constituting the first major α helical AMPs to be reported [6, 7]. In the decade of the 1980s and *Address correspondence to this author at the Medical Research Unit Zacatecas-IMSS, Interior de la Alameda #45, col. Centro, Cp. 98000, Zacatecas, México; E-mail: [email protected] 1381-6128/18 $58.00+.00

1990s, there was growing evidence that AMPs produced by human cells had significant antimicrobial activity but also possessed a remarkable immunomodulatory effect going from chemotaxis to macrophage activation and inclusive angiogenesis. All these features have suggested in the last decade, that AMPs could be a feasible option to create new antibiotics against the emerging tuberculosis epidemic, based mainly in the wide antimicrobial activity, however, other important activities of the AMPs have been forgotten in the pursuing to stop TB epidemic. This review will focus on the possible side effects that could arise with the use of AMPs as exogenous anti-tuberculosis molecules. 2. ANTIMICROBIAL OR IMMUNOMODULATORS? Antimicrobial peptides are a large group of small peptides which length varies from 50 to 100 amino acids, that exhibit antimicrobial activity against several pathogens. These peptides have special physicochemical features, the most of them have a positive charge at neutral pH (due to the presence of arginine and lysine residues), and about 50% of hydrophobic amino acids. They are produced by almost all living organisms and are the most evolutive conserved innate immunity molecules [8]. AMP production can be constitutive or induced in response to inflammation, infection or injury, depending on the organism, cell type and peptide. They are produced by different blood cells, such as neutrophils, eosinophils and platelets, and also by other cell types found at sites frequently exposed to pathogens, such as epithelial cells [9]. Although AMPs were initially described as antimicrobial compounds, accumulating studies suggest that antimicrobial activity is not as strong as thought, indeed a great proportion of the responses to eliminate pathogens is due to the activation of the immune system by these peptides, worthwhile to mention that not all described antimicrobial peptides have similar antimicrobial spectrum or efficiency, whereas lysozyme and defensins have remarkable antimicrobial activity, cathelicidin antimicrobial activity is mild [10]. Besides, several peptides lose their antimicrobial activity at physiological salt concentrations because of their charge. Thus, immunomodulation could be the main action of antimicrobial peptides, leading some authors to re-name AMPs to host defense peptides (HDPs) [8, 10-12]. Initial studies showed that antimicrobial peptides had pro© 2018 Bentham Science Publishers

2 Current Pharmaceutical Design, 2018, Vol. 24, No. 00

inflammatory properties inducing chemotaxis and other immunerelated activities. Nevertheless, it has been demonstrated that AMPs also have anti-inflammatory activity depending on the surrounding milieu, moreover, it has been well documented that AMPs are essential for wound healing through the promotion of keratinocyte migration and proliferation, angiogenesis and induction of growing factors [13]. We, therefore, suggest using host defense peptides or cationic immunomodulatory peptides instead of AMPs to better encompass the wide variety of immune activities of this versatile peptides. 3. ANTIMICROBIAL MECHANISM OF HDPs Since HDPs have been preserved along with the vertebrate’s evolution, antimicrobial mechanisms essentially remain the same among species; when the peptides are at a high concentration, they can insert into the bacterial membrane, causing alterations in the lipid bilayer and making it permeable, hence triggering bacterial death by osmotic shock [14, 15], Nevertheless, this is not the only mechanism of action known for HDPs; it has been shown that members of the buforines and cathelicidins family are able to cross the membrane and bind to DNA and RNA by electrostatic charges, interfering with vital processes [16]. This mechanism probably evolved because some bacteria developed the ability to expel HDPs through efflux pumps; in this way, HDPs target intracellular organelles. Other mechanisms have been reported for instance, there are peptides such as mersacidin that inhibits cell wall synthesis by interacting with peptidoglycan precursors [17]. Some other peptides, such as PR 39, Human Neutrophil Peptide (HNP)-1 and -2, inhibit the synthesis of several proteins needed for bacterial survival [18]. Hepcidin, on the other hand, besides damaging the bacterial cell membrane, also decrease systemically the iron levels [19] (Fig. 1). 4. IMMUNOMODULATORY ACTIVITIES During the last two decades, it has been widely described that HDPs not only have antimicrobial activity but also can modulate efficiently the immune response, indeed there are a wide variety of

Rivas-Santiago and Torres-Juarez

receptors involved in the immune response that respond to HDPs interaction such as CCR6, P2X7, FPRL-1, EGFR, TLR4, GAPDH, GPCR and MrgX2, however it cannot be discarded that HDPs might interact with several other proteins and receptors, indeed, studies in silico have revealed that LL-37 can interact with at least 1000 proteins [10, 20]. Most of the immunomodulatory effects caused by HDPs are at nanomolar scale, which suggests that probably some HDPs such as the cathelicidin LL-37 evolved more as modulators instead of antimicrobials. Nowadays, it is known that AMPS not only have pro-inflammatory conditions but also antiinflammatory responses, induce angiogenesis and promote wound healing [13, 21-25]. During infection HDPs are secreted primarily to induce the recruitment of leukocytes to the site of the infection and activating innate immune functions in response to pro-inflammatory responses required to control infection, afterwards this inflammation should be controlled to prevent chronic inflammation, thus it seems that both activities can be elicited by HDPs, but data suggest that the pro-inflammatory function or anti-inflammatory function will depend on the extracellular environment [12, 24, 26]. Infection leads to the expression of a wide variety of HDPs, however the most studied are β-defensins and cathelicidins. LL-37 can attract neutrophils, monocytes, T cells, and mast cells using formyl peptide receptor-like 1 (FPRL1) a G protein-coupled receptor at nanomolar concentrations [27, 28]. The binding of LL-37 to FPRL-1 lead to monocyte chemotactic protein (MCP)-1 and interleukin (IL)-8 release[29], besides the chemotactic activity, it also induces several other responses in leukocytes, epithelial and endothelial cells, modifying gene expression to improve or modulate immune response for instance it has been reported that stimulation of primary human monocytes and macrophages with LL-37 led to the induction of a wide range of chemokines, chemokine receptors, and other genes involved in cell adhesion, communication, and motility [30]. Besides, LL-37 elevates the expression of FcγRs, Toll-like receptor (TLR)-4 and CD14 on macrophages to facilitate phagocytosis [31].

Fig. (1). Antimicrobial peptide in the pathogenesis of tuberculosis. M. tuberculosis enters the lung and secretes a wide variety of soluble antigens (1), which are able to induce AMPs from epithelial cells and macrophages (2), these secreted AMPs can directly disrupt mycobacterium cell wall (3) or go further for intracellular targets such as DNA (4) or blocking protein synthesis interacting with mycobacteria ribosomes (5). Besides direct antimicrobial activity AMPs are a link between innate and adaptive immunity binding to several receptors in dendritic cells such as CCR6 and TLR-4 (6) promoting cell maturation and proinflammatory cytokines production (7).

AMPs for the Treatment of Tuberculosis?

Once in the site of infection attracted-phagocytes will engulf bacteria, persistent bacteria such as Mycobacterium tuberculosis are eliminated by autophagocytosis, in this process LL-37 is also involved, given that this cathelicidin activates genes such as Beclin-1 and Atg5 to promote autophagy in a vitamin D-dependent manner. In several bacterial or viral infection autophagocytosis is not enough to stop infection, thus infected-cells start an ultimate alternative to stop infection: apoptosis or pyroptosis, LL-37 is involved in both process, for example, LL-37 preferentially promotes cellular apoptosis through the activation of caspases 3 and 9 in airway epithelium infected with Pseudomonas aeruginosa, and this may represent a mechanism to promote pathogen clearance. By contrast, LL-37 can inhibit apoptosis of neutrophils, increasing their usually short half-life, this process is regulated through purinoceptor 7 (P2X7) and G protein-coupled receptors, it can be considered as a mechanism to enhance innate host responses [32]. Regarding pyroptosis, LL-37 inhibits LPS/Adenosine triphosphate (ATP)induced pyroptosis in macrophages through the inhibition of P2X7 association with ATP and consequent caspase-1, reducing drastically the harmful effects of excessive inflammation [33]. Besides the innate immune functions, antimicrobial peptides are a link between innate and adaptive immune, for instance, it has been described that Granulocyte-macrophage colony-stimulating factor (GM-CSF), IL-4 and LL-37 together, are a potent modifier of human dendritic cell differentiation and activation. This was correlated with upregulation of endocytic activity, costimulatory molecule expression, and modified phagocytic receptor expression and function [34], in addition, cathelicidin modulate immunoglobulin IgG1 production in B cells by suppressing the production of IL-4 [35]. The bulk of studies suggest that LL-37 promotes a marked proinflammatory milieu and that activity is dependent on the cell type, activation status, timing of exposure, presence of cytokines and the micro environment. However, parallel studies have reported an anti-inflammatory effect of LL-37 which also suggest that this peptide also promotes and maintains anti-inflammatory responses depending on the surrounding micro-environment. Pioneer studies showed that a microarray carried out to LPS-treated human monocytes which afterwards were treated with LL-37 suggested that cathelicidin had a direct but selective impact on the TLR to NF-kB pathway, regulating genes such as TNFAIP2 and the activation of NF-kB1 p105/p50, suggesting that LL-37 suppresses LPS-induced nuclear translocation of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) subunits p50 and p65 [30, 36]. Later, it was also demonstrated that LL-37 is capable of inhibiting Th1 immune responses produced in response to interferon (IFN)-γ by suppressing the production of tumor necrosis factor (TNF)-α and IL-12 in monocytes, macrophages and dendritic cells (DCs), as well as inhibiting the activation of class-switching in splenic B cells. These inhibitory effects were mediated through suppression of STAT1independent signaling pathway, which involved both the p65NF-κB and p38 mitogen-activated protein kinase (MAPK) subunits [24]. On the other hand, it has been reported that in Mtb infected macrophages, exogenous LL-37 decreased TNF-α and IL-17 production while induces anti-inflammatory IL-10 and transforming growth factor (TGF)-β production. The decreased production of antiinflammatory cytokines did not reduce anti-mycobacterial activity [12], which suggest that LL-37 can modulate the expression of cytokines during mycobacterial infection, physiologically this modulation could be to induce balanced inflammation avoiding damage for the hostage. Similar studies reported that combining LL-37 and IL-1β synergize and enhance the recruitment of new macrophages to the site of infection given the upregulation of chemokines such as MCP-1 and MCP-3, interestingly, the production of IL-10 was greatly upregulated, thus demonstrating the LL37 ability to balance both pro- and anti-inflammatory responses according to different cellular responses [37]. The anti-

Current Pharmaceutical Design, 2018, Vol. 24, No. 00

3

inflammatory role of AMPs is also substantiated by the observation that cathelicidin knockout mice exhibit increased inflammatory responses when compared to wild-type [38]. It is obvious that during an infection not only LL-37 will be present, several other antimicrobial peptides will be induced and will act in parallel with cathelicidin, the most studied are defensins. Human beta defensin (HBD) is predominantly mediated by NF-κB and MAPK pathways leading to activator protein (AP)-1 transcriptional activation [39]. Indeed, consensus NF-κB and AP-1 binding sites are present in the gene promoters of all inducible HBDs [40, 41], these peptides have potent antimicrobial but also remarkable immunoregulatory activity, certainly, defensins efficiently link innate and adaptive immunity mostly by directly stimulating immune cell migration, promoting the release of pro-inflammatory cytokines and by recruiting antigen-presenting cells and/or activating them to induce a T helper (h)1-skewed immune response, defensins engage several cell surface receptors promoting chemotaxis, mainly in immature DC and T lymphocytes, for example, HBD-2 can bind to the CCR6 chemokine receptor and HBD-3 can modulate CXCR4 and CCR5 [42] [43]. Additionally, murine βdefensin and HBD-3 have shown to act directly on immature DCs as an endogenous ligand for TLR-4, TLR-2 and TLR-3, inducing up-regulation of co-stimulatory molecules and DC maturation, triggering a robust Th1 polarized adaptive immune responses or inducing the production of chemokines such as IL-8 [44]. HBDs also induce their activation as assessed by the up-regulation of human leucocyte antigen complexes and surface costimulatory molecules such as CD80 and CD86. HBD-3 activates mDCs and monocytes independently of CCR6 or CCR2 via TLR1/2-MyD88 signaling pathway [45]. Additionally, HBD-2 and HBD-3 can activate mDCs via indirect mechanisms. These two defensins attach to host or foreign DNA and support CpG nucleotide uptake by plasmacytoid DCs (pDCs) through endosomal TLR-9 which in turn stimulates their activation. Activated pDCs consecutively release IFN-α, which activates mDCs to present antigens and initiate a T-cell immune response [46]. Parallel, both HBD-2 and HBD-3 stimulate the production of IL-6, IL-8 and CCL2 by peripheral blood mononuclear cells. [47]. Defensins are active also with other type of cells, in mast cells induce the release of prostaglandin D2 and histamine which cause vascular permeability triggering an inflammatory process and anaphylactic process [48, 49]. On the other hand, defensins have shown anti-inflammatory activity over several cells such as endothelial cells, macrophages and human myeloid DC [50]. It has been reported that when phagocytic cells are treated with the HNP-1 after exposure to lipolysaccharide (LPS), it could be observed that HNP-1 blocked the release of IL-1β from LPS-activated monocytes, but not the expression and release of TNF-α [51]. Other studies have demonstrated that apoptotic and necrotic neutrophils inhibit the secretion of pro-inflammatory cytokines from macrophages by the release of HNPs in the presence bacteria. HBD-3 also can attenuate the production of IL-6, IL-10, GM-CSF and TNF-α response of human myeloid DC [52]. Another anti-inflammatory activity of HDPs is mediated by their ability to bind antigenic molecules preventing the activation of immune responses. One clear example is the binding of cathelicidins and defensins to LPS to prevent TNF-α secretion [53]. Additionally, HNP-1 binds to Bacillus anthracis lethal factor inducing conformational changes that prevent enzymatic conversion and protects mice from B. anthracis lethal factor intoxication and death [54]. HNP-1, HNP-3 and HD-5 bind to toxin B from Clostridium inhibiting glycosylation in vitro of Rho guanosinetriphosphatases [55]. In general terms and as it was mentioned above, it can be summarized that AMPs have a wide variety of immunomodulatory activities including modulating pro- and anti-inflammatory responses altering signaling pathways, directly and indirectly, recruit-



Fig. (2). The immunomodulatory role of AMPs. There are different AMPs receptors which trigger either pro-inflammatory, anti-inflammatory responses or both. LL-37 can bind to P2X7 and FPRL1, both receptors produce an intracellular calcium mobilization, FPRL1 induces the phosphorylation of ERK and finally increases the production of IL-8, MCP-1 and ROS; P2X7 induces the inflammasome activation and the production of IL-1β, but this receptor has antiinflammatory response too since is capable to decrease the apoptosis. On the other hand, LL-37 is a ligand of EGFR and GAPDH receptors, EGFR interaction with cathelicidin, triggers Akt activation, increasing IL-10, TGF-β and MCP-3 production thru NF-κB; Akt also can induce cell proliferation, cell migration and wound healing thru mTOR activation. The binding of LL-37 to GAPDH receptor increases IL-10 expression. The HNPs can bind to several proinflammatory molecules such as clostridium B toxin, B. anthracis lethal factor and lipopolysaccharide, blocking their inflammatory activity. HBD-3 is a ligand of CCR6 and EGFR receptors inducing cell migration and chemotaxis of neutrophils, dendritic cells and memory lymphocytes. HBD-3 is a ligand of TLR-4, CXCR4 and EGFR receptors; TLR-4 activation induces dendritic cell activation and IL-8 secretion. CXCR4 activation induces chemotaxis through MAPK activation, and the activation of EGFR receptor induces the same signaling described above.

ing effector cells, promoting polarized dendritic cell maturation, macrophage differentiation, and modulating wound repair including angiogenesis, apoptosis, and pyroptosis (Fig. 2). Will these activities might modulate the tuberculosis outcome? 5. WHAT’S KNOWN ABOUT HDPs AND TUBERCULOSIS The pioneer studies to determine the relationship between HDPs and TB were focused on the antimycobacterial activity of HDPs (Table 1). These studies were performed using nonpathogenic strains, observing the antimicrobial activity reflected in the decrease of bacilli burden in an in vitro model [56]. However, further studies demonstrated that similar results were observed in pathogenic strains, suggesting that HDPs could be the “new era” antibiotics [57, 58]. To support the efficacy of antimicrobial peptides to kill Mtb, several studies were performed by several groups worldwide, including macrophage transfection to promote HDPs production, in this field, Kisich et al. demonstrated that cellular synthesis of HBD-2 after mRNA transfection to human macrophages conferred efficient mycobactericidal activities [58]. Considering that the first cells that encounter Mtb during infection are epithelial cells, our group sought to determine whether these cells used HDPs to counterattack infection. Both in vitro and in vivo, results showed that defensins are very important to control Mtb growth. Indeed, a mouse strain that was susceptible to develop TB showed markedly lower levels of defensins than the resistant strain. Working with this murine model, it was demonstrated that during the early stage of experimental tuberculosis, there was a higher expression of beta-defensins, and this expression decreased during the late active infection, which correlated with the severity of the disease and the increase of pulmonary bacillary loads.

Whereas in the TB latent infection mouse model, a constant high production of defensins was observed, which could be associated with bacillary growing control, to achieve reactivation in this model mice were treated with corticosteroids which was further reflected in a substantial decrease in the production of defensins and correlated with high a increase of mycobacterial pulmonary loads [59]. Further studies in this mouse latent model, using immunoelectron microscopy showed that Mtb can actually infect epithelial cells and induced significant higher production of β-defensin-3 associated to mycobacteria even more than those found in infected macrophage, suggesting that β-defensins could be involved in bacteriostasis during latent infection, probably, by binding to mycobacterial DNA or proteins related to the bacterial growth machinery, contributing to maintain latency[60]. Another very important HDP that has been involved in the immune response to Mtb is the cathelicidin LL-37, as well as its mice orthologue cathelicidin-related antimicrobial peptide (CRAMP). Gupta et al. evaluated the in vivo susceptibility of Cramp-/- mice to Mtb infection and dissected various pro-inflammatory immune responses during early stages of infection. They reported an increased susceptibility of Cramp-/- mice to Mtb as compared with wild-type mice. Macrophages from Cramp-/- mice were unable to control Mtb growth in an in vitro infection model, were deficient in intracellular calcium influx, and were defective in stimulating T cells. Additionally, CD4+ and CD8+ T cells from Cramp-/- mice produced less IFN-β upon stimulation [61]. Similar studies by our group in a TB mouse model, showed that during Mtb infection there are 3 peaks of cathelicidin expression at 1, 21 and 60 days postinfection. Intriguingly, cathelicidin is highly expressed once the pneumonia is established; however, this high production is not re-



5

Table 1. Peptide

Source

Strain

Model of study

Reference

LL-37

Human

H37Rv/MDR

In-vitro

[12, 69, 90]

Murine

H37Rv/MDR

In-vivo

Hepcidin

Human

H37Rv

In-vitro

[92]

HNP 1-3

Human

H37Rv

In-vivo

[56, 57, 93]

BCG

In-vitro

M. avium HBD-4

Human

H37Ra

In-vitro

[94]

HBD-2

Human

Erdman

In-vitro

[58, 59, 95]

In-vitro

[96, 97]

In-vitro

[96]

H37Rv MDR HBD-1

Human

H37RV MDR RM22

Protegrin-1

Porcine

H37Rv MDR RM22

RNase7, RNase3

Human

M. vaccae

In-vitro

[98]

Scorpion-derivatives

Scorpion

H37Rv

In-vitro

[99, 100]

In-vivo

[90]

In-vivo

[90]

MDR HH2

Synthetic

H37Rv MDR

IDR-1018

Synthetic

H37Rv MDR

flected into a decrease of bacillary loads in lung, which probably means that cathelicidin is acting more as an immunomodulator than antimicrobial, promoting an anti-inflammatory response [62]. Similar results were obtained in TB patients, in which they showed high production of cathelicidin during active disease, while in latent infected individuals LL-37 levels were comparable with those found in healthy donors [63]. Ex vivo studies, showed that mycobacteria induce the production of LL-37 in human alveolar macrophages and the overproduction of this AMP will lead to bacterial lysis [64]. Another important molecule related with LL-37 is the vitamin D and its receptor. It has been shown that stimulation of TLR-2 and TLR-1 increase the expression of these receptors as well as the enzyme CYP27B1, which catalyzes the conversion to the active form of vitamin D, and finally leads to the induction of cathelicidin LL-37, increasing the intracellular killing of the bacilli [65].This group also has shown the direct participation of cathelicidin induction by vitamin D (vitD) in the intracellular killing of Mtb, using interfering RNA specific for this antimicrobial peptide. They observed that macrophages with silenced cathelicidin had a higher bacillary burden than in macrophages that didn’t receive the small interfering RNA [66]. Other studies have shown that 1,25D3dependent autophagy activation promotes the maturation of mycobacterial phagosomes in a cathelicidin-dependent fashion while concomitantly suppressing mycobacterial survival [67]. Based on the capacity of LL-37 to induce autophagy, some research groups have designed synthetic autophagy-inducer–peptides as adjuvants for the treatment of TB [68]. Whereas other groups have proposed

4-phenylbutyrate (PBA), as an inducer of LL-37-inducedautophagy and intracellular killing of Mtb. PBA and 1,25D3 separately or in combination, induce the reactivation of autophagy occurred by stimulation of macrophages with PBA and promoted colocalization of LL-37 and LC3-II in autophagosomes. Importantly, PBA treatment failed to induce autophagy in Mtb-infected monocytes, when the expression of LL-37 was silenced. PBAinduced autophagy was restored when the LL-37 knockdown cells were supplemented with synthetic LL-37 [69]. Though most of the reported studies have been performed in vitro, clinical trial suggest that oral adjunctive therapy with 5,000IU vitD3 or 2x500 mg PBA or PBA+vitD3 (both twice a day) to standard chemotherapy would lead to enhanced recovery in sputum smear-positive pulmonary TB patients therapy with vitD3 alone or in combination with PBA showed increased sputum culture conversion at week 4 and vitD3 alone at week 8 compared to the placebo group. Importantly, treatment with PBA, vitD3 or the combination also resulted in reduced clinical symptoms. In line with an improvement of the primary outcomes, treatment with PBA and vitD3 also resulted in a synergistic increased expression of LL-37 in immune cells that was paralleled with an enhanced intracellular killing of Mtb in macrophages ex vivo [70]. However, authors showed that VitD3 supplementation did not have an impact on time to sputum smear conversion which coincides with previous reports [71-73]. Another single group has shown significantly hastened sputum culture conversion in a sub-group of patients with polymorphism in TaqI vitD receptor genotype with improved responsiveness to supplementation [74], such differences could be due cathelicidin has different activities


depending on the surrounding milieu, and each patient probably had different inflammation levels. Besides the induction of autophagy, another important effect of cathelicidin in mycobacteria-infected macrophages is the modulation of cytokine production. LL-37 and analogues, decreased the production of pro-inflammatory cytokines such as IL-6, TNF-α, IFN-β, IL-17 and IL-12p40, while increasing anti-inflammatory cytokines such as IL-10 and TGF-β, without affecting the antimicrobial capacity of the infected macrophages [12, 75, 76]. Other studies have found that glucocorticoids triggered the expression of cathelicidin, in BCG-infected macrophages independent of the intracellular vitD metabolism. Despite upregulating cathelicidin, glucocorticoids failed to promote macrophage antimycobacterial activity [77]. Similar results were found in Mtb-infected macrophages by our group (Data not published). Conversely, Mtb infected-mice treated with 1mg/kg of LL-37 or CRAMP showed a modest decrease of bacilli burden but pneumonia was considerably increased [78]. Taken all together these data suggest that cathelicidin is essential for innate immunity against mycobacteria, however, once the infection has been established cathelicidin promotes an anti-inflammatory response. Thus LL-37 has a dual effect during infection, in early infection increases phagocytosis, expression of co-stimulatory molecules in DC and induce a higher production of cytokines type Th1 [34], and during late infection inhibits TNF-α secretion from monocytes and some others pro-inflammatory cytokines [30], besides reduces the response of monocytes, macrophages and DC to IFN-γ [24] which is the principal cytokine of Th1 response. These characteristics show


the duality of this cathelicidin during the infectious process by avoiding inflammation and contributing directly with the elimination of the microorganism. Recently our group showed that the addition of LL-37 to non-infected macrophages led to the production of proinflammatory cytokines, but when macrophages were infected, led to the production of cytokines such as IL-10 and TGF-β. These experiments correlate with the previous finding in experimental animal models [12, 62] (Fig. 3). 6. COULD BE ANTIMICROBIAL PEPTIDES USEFUL FOR THE TREATMENT OF TUBERCULOSIS? Tuberculosis is a very complex disease which in general terms results in one of the two clinical states: latent tuberculosis or active/progressive disease, however, nowadays is known that tuberculosis encompass a range of latent or progressive infections [79], that is, in the same individual several processes can be carried out at the same time. In laboratory-controlled conditions this heterogeneity cannot be observed, however, it has been reported that only one patient can harbor at the same time different Mtb strains, different granuloma stages, different immune responses according to the stage of granuloma (reviewed elsewhere [80]). Host genotype is definitely associated with variation in host susceptibility, immune response and therefore with the outcome of infection, and in some cases with hormone status [81] which in turn also modulates LL-37 [77]. During Mtb tuberculosis infection, several pathologic lesions can be developed all over the lung in the same patient, including granulomas, cavitation or/and consolidation areas, these lesions have their particular inflammatory stage con-

Fig. (3). Activity of AMPs during the different stages of tuberculosis. Tuberculosis has different stages during infection, in early infection, the first cell to be in contact with Mtb are lung epithelial cells, this interaction leads to HBD-2, HBD-3 and LL-37 production; also the infected macrophages produce LL-37 and this peptide regulates the IFN-β production by lymphocyte CD8+ and CD4+ T cells; besides LL-37 is able to induce autophagy in infected macrophages to eliminate mycobacteria. LL-37 is also able to induce dendritic cells maturation increasing the costimulatory molecules and phagocytosis. In latency infection, AMPs are associated with a control of Mtb replication. Showing a higher expression of antimicrobial peptides mainly defensin accompanied with low bacillary loads. Finally, during active infection, there is a low concentration of HBDs but higher LL-37 levels inducing anti-inflammatory cytokines and down-regulating pro-inflammatory cytokines. At this stage, LL-37 blocks the activation and maturation of dendritic cells, monocyte and macrophage generated by IFN-γ.


taining different cells, including macrophages with different stages and profile of activation, T cells, B cells, foamy macrophages, fibroblast etcetera, then each separate lesion represents a localized microenvironment that can be independently influenced by the immune response, state of bacteria (replicating or dormant) and for the possible use of exogenous HDPs. As mentioned above HDPs have many functions that can influence the onset of the immune system, on one hand, promoting inflammatory response and on the other hand promoting antiinflammation and delaying bacteria elimination. Given the heterogeneity of the immunopathology during tuberculosis, the use of antimicrobial peptides as therapeutics must be deeply evaluated. Skewing towards a robust pro-inflammatory state can lead to remodeling the well-formed granuloma, liquefaction of caseum [82] and the destruction of the surrounding parenchyma, which in turn could exacerbate inflammation and release granuloma-contained bacteria, in this case, resolution of inflammation within the granuloma is associated with better host outcome [80, 82]. Indeed, in mice models with progressive tuberculosis, the treatment with HNP-1 and/or with HBD-2 intratracheally, although decreased the bacilli burden, increased inflammation areas comparable with nontreated animals, suggesting that though Mtb was efficiently controlled inflammation reduces survival curves [83]. Another important point to underline is that patients often are infected with more than on Mtb strain simultaneously [84], which besides that they have different drug susceptibility each strain promotes different immune profiles and transmission rates [85], even once stablished, Mtb continues acquiring mutations during disease [86], which may explain why isoniazid monotherapy for latent tuberculosis is a risk factor for the emergence of isoniazid resistance and probably could be the same case for antimicrobial peptides, intriguingly our group reported that lysX gene which is responsible for confering antimicrobial peptide resistance to Mtb, was differentially expressed among Mtb stains correlating with virulence. Strains with higher lysX expression showed increased levels of intracellular survival in vivo and in vitro and induced more severe lesion related to pneumonia and an increased ability to replicate intracellularly [87]. Thus, it is plausible that with the indiscriminate use of antimicrobial peptides for TB therapy, eventually, resistant strains will be common and probably more virulent. The spectrum of TB lesions is a continuum with a large overlap in the lesion types found in latently infected and active TB patients. Tuberculosis lesions in humans are very complex with a wide range of pathological, microbiological, and immunological features that often evolve over a period of many months, sometimes even years, prior to the emergence of symptoms and diagnosis of disease. Primary disease is characterized by hematologic spread and a characteristic miliary pattern of disease, while post-primary disease includes a wide spectrum of pathologies. This spectrum is observed between individual patients with disease. For instance, some patients develop large air-filled cavities, while others develop only solitary nodules in the lung parenchyma or have infection limited to the lymphatic system or other extra-pulmonary sites. Importantly though, a wide spectrum of pathology is observed even within a single individual patient at a given moment in time [88]. This complexity makes arise the question: when could be useful the HDPs? Probably the use of HDPs should be evaluated in each patient depending on the status of the disease, otherwise, their use will be detrimental. 7. DO WE HAVE A CHANCE WITH THE USE OF HDPs FOR THE TREATMENT OF TUBERCULOSIS? In recent years, several synthetic innate defence regulator (IDR) peptides have been generated, these peptides promote key protective functions such as chemotaxis, wound healing, and antiinfective activity mediated by the immune system, while suppressing pro-inflammatory responses to non-pathological levels [89, 90],


7

some of them have been tested in experimental models of tuberculosis showing reduced bacillary loads in animal models with both, the virulent drug susceptible H37Rv strain and a MDR isolate showing for both cases a considerable reduction in lung inflammation as revealed by decreased pneumonia [90], nevertheless, these studies were carried out in syngenic mice strains under strict laboratory conditions, which do not reflect the heterogeneity of human tuberculosis, though these peptides showed promising results further clinical experiments are urgently needed. Some of these derivative peptides, as well as HBD-2 and LL37, have also shown important angiogenic properties [36], worthy to mention that a recent study reported that the potent angiogenic factor vascular endothelial growth factor (VEGF) is secreted by Mtb-infected macrophages, in an RD1-dependent manner. In vivo, these factors promote the formation of blood vessels in murine models of the disease. Inhibiting angiogenesis, via VEGF inactivation, abolished mycobacterial spread from the infection site. Similar results were observed in Mtb patients where VEGF was elevated and that endothelial progenitor cells are mobilized from the bone marrow. These results suggest that mycobacteria take advantage of the formation of new blood vessels to disseminate [91]. Therefore, would be it right to use HDPs during active phase? Further studies need to be done to achieve the correct answer. We also have to take into account that production of synthetic or recombinant HDPs is going to be very expensive and in the most of the cases unreachable for most of the patients, thus the use of molecules enhancing the expression of HDPs could be an alternative to the problem of production cost, delivery and stability, nonetheless, the question remains the same will the HDPs be allies or foes in the treatment of tuberculosis. CONCLUSION The use of antimicrobial peptides and their synthetic derivatives is still a promise for the treatment of TB, however, there is a lot to study regarding all the effects they have and how these effects could be used in the different stages of pulmonary tuberculosis. The growth in the knowledge of TB immunology and the designing of new peptides selectively developed to achieve a specific function for the TB therapy are branches that should be considered as a priority in the scientist agenda. LIST OF ABBREVIATIONS AMPs = Antimicrobial peptides AP = Activator protein ATP = Adenosine triphosphate CRAMP = Cathelicidin-related antimicrobial peptide DCs = Dendritic cells FPRL1 = Formyl peptide receptor-like 1 GM-CSF = Granulocyte-macrophage colony-stimulating factor HBD = Human beta defensin HDPs = Host defense peptides HNP = Human Neutrophil Peptide IDR = Innate defence regulator IFN = Interferon IL = Interleukin LPS = Lipolysaccharide MAPK = Mitogen-activated protein kinase MCP = Monocyte chemotactic protein MDR = Multidrug-resistant Mtb = Mycobacterium tuberculosis


NF-κB

=

PBA pDCs P2X7 tb TGF Th TNF TLR VEGF vitD WHO

= = = = = = = = = = =

Nuclear factor kappa-light-chain-enhancer of activated B cells 4-Phenylbutyrate Plasmacytoid DCs Purinoceptor 7 Tuberculosis Transforming growth factor T helper Tumor necrosis factor Toll-like receptor Vascular endothelial growth factor Vitamin D World health organization

CONSENT FOR PUBLICATION Not applicable. CONFLICT OF INTEREST The authors declare no conflict of interest, financial or otherwise. ACKNOWLEDGEMENTS This work was supported in part by FIS/IMSS/PROT/1545.

Rivas-Santiago and Torres-Juarez [16]

[17] [18]

[19] [20] [21] [22]

[23] [24] [25]

REFERENCES [1] [2] [3] [4] [5] [6]

[7] [8] [9] [10] [11] [12]

[13]

[14] [15]

Organization WH. Global Tuberculosis Report. In: 2016b, ed.^eds. World Health Organization: Geneva, Switzerland, 2016. Dubos RJ. Studies on a bactericidal agent extracted from a soil bacillus : I. Preparation of the Agent. Its Activity in Vitro. J Exp Med 1939; 70(1): 1-10. Hirsch JG. Phagocytin: A bactericidal substance from polymorphonuclear leucocytes. J Exp Med 1956; 103(5): 589-611. Zeya HI, Spitznagel JK. Cationic proteins of polymorphonuclear leukocyte lysosomes. I. Resolution of antibacterial and enzymatic activities. J Bacteriol 1966; 91(2): 750-4. Zeya HI, Spitznagel JK, Schwab JH. Antibacterial action of PMN lysosomal cationic proteins resolved by density gradient electrophoresis. Proc Soc Exp Biol Med 1966; 121(1): 250-3. Hultmark D, Steiner H, Rasmuson T, Boman HG. Insect immunity. Purification and properties of three inducible bactericidal proteins from hemolymph of immunized pupae of Hyalophora cecropia. Eur J Biochem 1980; 106(1): 7-16. Steiner H, Hultmark D, Engström A, Bennich H, Boman HG. Sequence and specificity of two antibacterial proteins involved in insect immunity. Nature 1981; 292(5820): 246-8. Silva T, Gomes MS. Immuno-Stimulatory Peptides as a Potential Adjunct Therapy against Intra-Macrophagic Pathogens. Molecules 2017; 22(8): 22. Yeung AT, Gellatly SL, Hancock RE. Multifunctional cationic host defence peptides and their clinical applications. Cell Mol Life Sci 2011; 68(13): 2161-76. Hancock RE, Haney EF, Gill EE. The immunology of host defence peptides: beyond antimicrobial activity. Nat Rev Immunol 2016; 16(5): 321-34. Cole AM, Cole AL. HIV-Enhancing and HIV-Inhibiting Properties of Cationic Peptides and Proteins. Viruses 2017; 9(5): 9. Torres-Juarez F, Cardenas-Vargas A, Montoya-Rosales A, et al. LL-37 immunomodulatory activity during Mycobacterium tuberculosis infection in macrophages. Infect Immun 2015; 83(12): 4495503. Gonzalez-Curiel I, Trujillo V, Montoya-Rosales A, et al. 1,25dihydroxyvitamin D3 induces LL-37 and HBD-2 production in keratinocytes from diabetic foot ulcers promoting wound healing: An in vitro model. PLoS One 2014; 9(10): e111355. Lehrer RI, Ganz T. Defensins of vertebrate animals. Curr Opin Immunol 2002; 14(1): 96-102. Zasloff M. Inducing endogenous antimicrobial peptides to battle infections. Proc Natl Acad Sci USA 2006; 103(24): 8913-4.

[26]

[27] [28]

[29] [30] [31]

[32]

[33] [34] [35] [36] [37]

[38]

Park CB, Kim HS, Kim SC. Mechanism of action of the antimicrobial peptide buforin II: buforin II kills microorganisms by penetrating the cell membrane and inhibiting cellular functions. Biochem Biophys Res Commun 1998; 244(1): 253-7. Brötz H, Bierbaum G, Leopold K, Reynolds PE, Sahl HG. The lantibiotic mersacidin inhibits peptidoglycan synthesis by targeting lipid II. Antimicrob Agents Chemother 1998; 42(1): 154-60. Miyakawa Y, Ratnakar P, Rao AG, et al. In vitro activity of the antimicrobial peptides human and rabbit defensins and porcine leukocyte protegrin against Mycobacterium tuberculosis. Infect Immun 1996; 64(3): 926-32. Yamaji S, Sharp P, Ramesh B, Srai SK. Inhibition of iron transport across human intestinal epithelial cells by hepcidin. Blood 2004; 104(7): 2178-80. Niyonsaba F, Kiatsurayanon C, Chieosilapatham P, Ogawa H. Friends or Foes? Host defense (antimicrobial) peptides and proteins in human skin diseases. Exp Dermatol 2017; 26(11): 989-98. Zanetti M. Cathelicidins, multifunctional peptides of the innate immunity. J Leukoc Biol 2004; 75(1): 39-48. Zheng Y, Niyonsaba F, Ushio H, et al. Cathelicidin LL-37 induces the generation of reactive oxygen species and release of human alpha-defensins from neutrophils. Br J Dermatol 2007; 157(6): 112431. Brown KL, Poon GF, Birkenhead D, et al. Host defense peptide LL-37 selectively reduces proinflammatory macrophage responses. J Immunol 2011; 186(9): 5497-505. Nijnik A, Pistolic J, Wyatt A, Tam S, Hancock RE. Human cathelicidin peptide LL-37 modulates the effects of IFN-gamma on APCs. J Immunol 2009; 183(9): 5788-98. Salvado MD, Di Gennaro A, Lindbom L, Agerberth B, Haeggström JZ. Cathelicidin LL-37 induces angiogenesis via PGE2-EP3 signaling in endothelial cells, in vivo inhibition by aspirin. Arterioscler Thromb Vasc Biol 2013; 33(8): 1965-72. Amatngalim GD, Nijnik A, Hiemstra PS, Hancock RE. Cathelicidin peptide LL-37 modulates TREM-1 expression and inflammatory responses to microbial compounds. Inflammation 2011; 34(5): 412-25. Niyonsaba F, Iwabuchi K, Someya A, et al. A cathelicidin family of human antibacterial peptide LL-37 induces mast cell chemotaxis. Immunology 2002; 106(1): 20-6. De Yang , Chen Q, Schmidt AP, et al. LL-37, the neutrophil granule- and epithelial cell-derived cathelicidin, utilizes formyl peptide receptor-like 1 (FPRL1) as a receptor to chemoattract human peripheral blood neutrophils, monocytes, and T cells. J Exp Med 2000; 192(7): 1069-74. Bergman P, Walter-Jallow L, Broliden K, Agerberth B, Söderlund J. The antimicrobial peptide LL-37 inhibits HIV-1 replication. Curr HIV Res 2007; 5(4): 410-5. Mookherjee N, Brown KL, Bowdish DM, et al. Modulation of the TLR-mediated inflammatory response by the endogenous human host defense peptide LL-37. J Immunol 2006; 176(4): 2455-64. Wan M, van der Does AM, Tang X, Lindbom L, Agerberth B, Haeggström JZ. Antimicrobial peptide LL-37 promotes bacterial phagocytosis by human macrophages. J Leukoc Biol 2014; 95(6): 971-81. Barlow PG, Beaumont PE, Cosseau C, et al. The human cathelicidin LL-37 preferentially promotes apoptosis of infected airway epithelium. Am J Respir Cell Mol Biol 2010; 43(6): 692702. Hu Z, Murakami T, Suzuki K, et al. Antimicrobial cathelicidin peptide LL-37 inhibits the LPS/ATP-induced pyroptosis of macrophages by dual mechanism. PLoS One 2014; 9(1): e85765. Davidson DJ, Currie AJ, Reid GS, et al. The cationic antimicrobial peptide LL-37 modulates dendritic cell differentiation and dendritic cell-induced T cell polarization. J Immunol 2004; 172(2): 1146-56. Qin XJ, Shi HZ, Deng JM, Liang QL, Jiang J, Ye ZJ. CCL22 recruits CD4-positive CD25-positive regulatory T cells into malignant pleural effusion. Clin Cancer Res 2009; 15(7): 2231-7. Mansour SC, Pena OM, Hancock RE. Host defense peptides: frontline immunomodulators. Trends Immunol 2014; 35(9): 443-50. Yu J, Mookherjee N, Wee K, et al. Host defense peptide LL-37, in synergy with inflammatory mediator IL-1beta, augments immune responses by multiple pathways. J Immunol 2007; 179(11): 768491. Morioka Y, Yamasaki K, Leung D, Gallo RL. Cathelicidin antimicrobial peptides inhibit hyaluronan-induced cytokine release and


[39] [40] [41] [42] [43] [44]

[45] [46]

[47] [48]

[49]

[50] [51] [52]

[53] [54] [55] [56]

[57] [58]

[59]

[60]

modulate chronic allergic dermatitis. J Immunol 2008; 181(6): 3915-22. Allaker RP. Host defence peptides-a bridge between the innate and adaptive immune responses. Trans R Soc Trop Med Hyg 2008; 102(1): 3-4. Froy O. Regulation of mammalian defensin expression by Toll-like receptor-dependent and independent signalling pathways. Cell Microbiol 2005; 7(10): 1387-97. Suarez-Carmona M, Hubert P, Delvenne P, Herfs M. Defensins: “Simple” antimicrobial peptides or broad-spectrum molecules? Cytokine Growth Factor Rev 2015; 26(3): 361-70. Yang D, Chertov O, Bykovskaia SN, et al. Beta-defensins: linking innate and adaptive immunity through dendritic and T cell CCR6. Science 1999; 286(5439): 525-8. Feng Z, Dubyak GR, Lederman MM, Weinberg A. Cutting edge: human beta defensin 3--a novel antagonist of the HIV-1 coreceptor CXCR4. J Immunol 2006; 177(2): 782-6. Tjabringa GS, Aarbiou J, Ninaber DK, et al. The antimicrobial peptide LL-37 activates innate immunity at the airway epithelial surface by transactivation of the epidermal growth factor receptor. J Immunol 2003; 171(12): 6690-6. Funderburg N, Lederman MM, Feng Z, et al. Human -defensin-3 activates professional antigen-presenting cells via Toll-like receptors 1 and 2. Proc Natl Acad Sci USA 2007; 104(47): 18631-5. Tewary P, de la Rosa G, Sharma N, et al. β-Defensin 2 and 3 promote the uptake of self or CpG DNA, enhance IFN-α production by human plasmacytoid dendritic cells, and promote inflammation. J Immunol 2013; 191(2): 865-74. Boniotto M, Jordan WJ, Eskdale J, et al. Human beta-defensin 2 induces a vigorous cytokine response in peripheral blood mononuclear cells. Antimicrob Agents Chemother 2006; 50(4): 1433-41. Chen X, Niyonsaba F, Ushio H, et al. Antimicrobial peptides human beta-defensin (hBD)-3 and hBD-4 activate mast cells and increase skin vascular permeability. Eur J Immunol 2007; 37(2): 43444. Niyonsaba F, Someya A, Hirata M, Ogawa H, Nagaoka I. Evaluation of the effects of peptide antibiotics human beta-defensins-1/-2 and LL-37 on histamine release and prostaglandin D(2) production from mast cells. Eur J Immunol 2001; 31(4): 1066-75. Kohlgraf KG, Pingel LC, Dietrich DE, Brogden KA. Defensins as anti-inflammatory compounds and mucosal adjuvants. Future Microbiol 2010; 5(1): 99-113. Shi J, Aono S, Lu W, et al. A novel role for defensins in intestinal homeostasis: regulation of IL-1beta secretion. J Immunol 2007; 179(2): 1245-53. Pingel LC, Kohlgraf KG, Hansen CJ, et al. Human beta-defensin 3 binds to hemagglutinin B (rHagB), a non-fimbrial adhesin from Porphyromonas gingivalis, and attenuates a pro-inflammatory cytokine response. Immunol Cell Biol 2008; 86(8): 643-9. Motzkus D, Schulz-Maronde S, Heitland A, et al. The novel betadefensin DEFB123 prevents lipopolysaccharide-mediated effects in vitro and in vivo. FASEB J 2006; 20(10): 1701-2. Kim C, Gajendran N, Mittrücker HW, et al. Human alphadefensins neutralize anthrax lethal toxin and protect against its fatal consequences. Proc Natl Acad Sci USA 2005; 102(13): 4830-5. Giesemann T, Guttenberg G, Aktories K. Human alpha-defensins inhibit Clostridium difficile toxin B. Gastroenterology 2008; 134(7): 2049-58. Ogata K, Linzer BA, Zuberi RI, Ganz T, Lehrer RI, Catanzaro A. Activity of defensins from human neutrophilic granulocytes against Mycobacterium avium-Mycobacterium intracellulare. Infect Immun 1992; 60(11): 4720-5. Sharma S, Verma I, Khuller GK. Antibacterial activity of human neutrophil peptide-1 against Mycobacterium tuberculosis H37Rv: in vitro and ex vivo study. Eur Respir J 2000; 16(1): 112-7. Kisich KO, Heifets L, Higgins M, Diamond G. Antimycobacterial agent based on mRNA encoding human beta-defensin 2 enables primary macrophages to restrict growth of Mycobacterium tuberculosis. Infect Immun 2001; 69(4): 2692-9. Rivas-Santiago B, Schwander SK, Sarabia C, et al. Human betadefensin 2 is expressed and associated with Mycobacterium tuberculosis during infection of human alveolar epithelial cells. Infect Immun 2005; 73(8): 4505-11. Rivas-Santiago B, Contreras JC, Sada E, Hernández-Pando R. The potential role of lung epithelial cells and beta-defensins in experimental latent tuberculosis. Scand J Immunol 2008; 67(5): 448-52.

Current Pharmaceutical Design, 2018, Vol. 24, No. 00 [61]

[62]

[63]

[64]

[65] [66]

[67] [68] [69]

[70]

[71]

[72]

[73] [74] [75] [76] [77]

[78]

[79] [80] [81]

9

Gupta S, Winglee K, Gallo R, Bishai WR. Bacterial subversion of cAMP signalling inhibits cathelicidin expression, which is required for innate resistance to Mycobacterium tuberculosis. J Pathol 2017; 242(1): 52-61. Castañeda-Delgado J, Hernández-Pando R, Serrano CJ, et al. Kinetics and cellular sources of cathelicidin during the course of experimental latent tuberculous infection and progressive pulmonary tuberculosis. Clin Exp Immunol 2010; 161(3): 542-50. Gonzalez-Curiel I, Castañeda-Delgado J, Lopez-Lopez N, et al. Differential expression of antimicrobial peptides in active and latent tuberculosis and its relationship with diabetes mellitus. Hum Immunol 2011; 72(8): 656-62. Rivas-Santiago B, Hernandez-Pando R, Carranza C, et al. Expression of cathelicidin LL-37 during Mycobacterium tuberculosis infection in human alveolar macrophages, monocytes, neutrophils, and epithelial cells. Infect Immun 2008; 76(3): 935-41. Liu PT, Stenger S, Li H, et al. Toll-like receptor triggering of a vitamin D-mediated human antimicrobial response. Science 2006; 311(5768): 1770-3. Liu PT, Stenger S, Tang DH, Modlin RL. Cutting edge: vitamin Dmediated human antimicrobial activity against Mycobacterium tuberculosis is dependent on the induction of cathelicidin. J Immunol 2007; 179(4): 2060-3. Yuk JM, Shin DM, Lee HM, et al. Vitamin D3 induces autophagy in human monocytes/macrophages via cathelicidin. Cell Host Microbe 2009; 6(3): 231-43. Muciño G, Castro-Obregón S, Hernandez-Pando R, Del Rio G. Autophagy as a target for therapeutic uses of multifunctional peptides. IUBMB Life 2016; 68(4): 259-67. Rekha RS, Rao Muvva SS, Wan M, et al. Phenylbutyrate induces LL-37-dependent autophagy and intracellular killing of Mycobacterium tuberculosis in human macrophages. Autophagy 2015; 11(9): 1688-99. Mily A, Rekha RS, Kamal SM, et al. Significant Effects of Oral Phenylbutyrate and Vitamin D3 Adjunctive Therapy in Pulmonary Tuberculosis: A Randomized Controlled Trial. PLoS One 2015; 10(9): e0138340. Ralph AP, Waramori G, Pontororing GJ, et al. L-arginine and vitamin D adjunctive therapies in pulmonary tuberculosis: A randomised, double-blind, placebo-controlled trial. PLoS One 2013; 8(8): e70032. Salahuddin N, Ali F, Hasan Z, Rao N, Aqeel M, Mahmood F. Vitamin D accelerates clinical recovery from tuberculosis: results of the SUCCINCT Study [Supplementary Cholecalciferol in recovery from tuberculosis]. A randomized, placebo-controlled, clinical trial of vitamin D supplementation in patients with pulmonary tuberculosis’. BMC Infect Dis 2013; 13: 22. Wejse C, Gomes VF, Rabna P, et al. Vitamin D as supplementary treatment for tuberculosis: A double-blind, randomized, placebocontrolled trial. Am J Respir Crit Care Med 2009; 179(9): 843-50. Martineau AR, Wilkinson RJ, Wilkinson KA, et al. A single dose of vitamin D enhances immunity to mycobacteria. Am J Respir Crit Care Med 2007; 176(2): 208-13. Sato E, Imafuku S, Ishii K, et al. Vitamin D-dependent cathelicidin inhibits Mycobacterium marinum infection in human monocytic cells. J Dermatol Sci 2013; 70(3): 166-72. Silva JP, Gonçalves C, Costa C, et al. Delivery of LLKKK18 loaded into self-assembling hyaluronic acid nanogel for tuberculosis treatment. J Control Release 2016; 235: 112-24. Steiger J, Stephan A, Inkeles MS, et al. Imatinib triggers phagolysosome acidification and antimicrobial activity against mycobacterium bovis bacille calmette-guérin in glucocorticoid-treated human macrophages. J Immunol 2016; 197(1): 222-32. Rivas-Santiago B, Rivas Santiago CE, Castañeda-Delgado JE, León-Contreras JC, Hancock RE, Hernandez-Pando R. Activity of LL-37, CRAMP and antimicrobial peptide-derived compounds E2, E6 and CP26 against Mycobacterium tuberculosis. Int J Antimicrob Agents 2013; 41(2): 143-8. Barry CE III, Boshoff HI, Dartois V, et al. The spectrum of latent tuberculosis: rethinking the biology and intervention strategies. Nat Rev Microbiol 2009; 7(12): 845-55. Cadena AM, Fortune SM, Flynn JL. Heterogeneity in tuberculosis. Nat Rev Immunol 2017; 17(11): 691-702. Bottasso O, Bay ML, Besedovsky H, Del Rey A. Adverse neuroimmune-endocrine interactions in patients with active tuberculosis. Mol Cell Neurosci 2013; 53: 77-85.

10 Current Pharmaceutical Design, 2018, Vol. 24, No. 00 [82] [83]

[84] [85]

[86] [87]

[88] [89] [90]

[91]

Kaplan G, Post FA, Moreira AL, et al. Mycobacterium tuberculosis growth at the cavity surface: A microenvironment with failed immunity. Infect Immun 2003; 71(12): 7099-108. Rivas-Santiago B, Rivas-Santiago C, Sada E, Hernández-Pando R. Prophylactic potential of defensins and L-isoleucine in tuberculosis household contacts: An experimental model. Immunotherapy 2015; 7(3): 207-13. Kontsevaya I, Nikolayevskyy V, Kovalyov A, et al. Tuberculosis cases caused by heterogeneous infection in Eastern Europe and their influence on outcomes. Infect Genet Evol 2017; 48: 76-82. Hernández-Pando R, Marquina-Castillo B, Barrios-Payán J, MataEspinosa D. Use of mouse models to study the variability in virulence associated with specific genotypic lineages of Mycobacterium tuberculosis. Infect Genet Evol 2012; 12(4): 725-31. Ford CB, Lin PL, Chase MR, et al. Use of whole genome sequencing to estimate the mutation rate of Mycobacterium tuberculosis during latent infection. Nat Genet 2011; 43(5): 482-6. Montoya-Rosales A, Provvedi R, Torres-Juarez F, et al. lysX gene is differentially expressed among Mycobacterium tuberculosis strains with different levels of virulence. Tuberculosis (Edinb) 2017; 106: 106-17. Lenaerts A, Barry CE III, Dartois V. Heterogeneity in tuberculosis pathology, microenvironments and therapeutic responses. Immunol Rev 2015; 264(1): 288-307. Pena OM, Afacan N, Pistolic J, et al. Synthetic cationic peptide IDR-1018 modulates human macrophage differentiation. PLoS One 2013; 8(1): e52449. Rivas-Santiago B, Castañeda-Delgado JE, Rivas Santiago CE, et al. Ability of innate defence regulator peptides IDR-1002, IDR-HH2 and IDR-1018 to protect against Mycobacterium tuberculosis infections in animal models. PLoS One 2013; 8(3): e59119. Polena H, Boudou F, Tilleul S, et al. Mycobacterium tuberculosis exploits the formation of new blood vessels for its dissemination. Sci Rep 2016; 6: 33162.

Rivas-Santiago and Torres-Juarez [92]

[93] [94] [95]

[96]

[97] [98]

[99] [100]

Sow FB, Florence WC, Satoskar AR, Schlesinger LS, Zwilling BS, Lafuse WP. Expression and localization of hepcidin in macrophages: A role in host defense against tuberculosis. J Leukoc Biol 2007; 82(4): 934-45. Driss V, Legrand F, Hermann E, et al. TLR2-dependent eosinophil interactions with mycobacteria: role of alpha-defensins. Blood 2009; 113(14): 3235-44. Liu PT, Schenk M, Walker VP, et al. Convergence of IL-1beta and VDR activation pathways in human TLR2/1-induced antimicrobial responses. PLoS One 2009; 4(6): e5810. Corrales-Garcia L, Ortiz E, Castañeda-Delgado J, Rivas-Santiago B, Corzo G. Bacterial expression and antibiotic activities of recombinant variants of human β-defensins on pathogenic bacteria and M. tuberculosis. Protein Expr Purif 2013; 89(1): 33-43. Fattorini L, Gennaro R, Zanetti M, et al. In vitro activity of protegrin-1 and beta-defensin-1, alone and in combination with isoniazid, against Mycobacterium tuberculosis. Peptides 2004; 25(7): 1075-7. Sharma R, Saikia UN, Sharma S, Verma I. Activity of human beta defensin-1 and its motif against active and dormant Mycobacterium tuberculosis. Appl Microbiol Biotechnol 2017; 101(19): 7239-48. Pulido D, Torrent M, Andreu D, Nogués MV, Boix E. Two human host defense ribonucleases against mycobacteria, the eosinophil cationic protein (RNase 3) and RNase 7. Antimicrob Agents Chemother 2013; 57(8): 3797-805. Ramírez-Carreto S, Jiménez-Vargas JM, Rivas-Santiago B, et al. Peptides from the scorpion Vaejovis punctatus with broad antimicrobial activity. Peptides 2015; 73: 51-9. Rodríguez A, Villegas E, Montoya-Rosales A, Rivas-Santiago B, Corzo G. Characterization of antibacterial and hemolytic activity of synthetic pandinin 2 variants and their inhibition against Mycobacterium tuberculosis. PLoS One 2014; 9(7): e101742.