Induction of Apoptosis by Glyoxal in Human ... - Semantic Scholar

Induction of Apoptosis by Glyoxal in Human Embryonic Lung Epithelial Cell Line L132 Michael Kasper, Cora Roehlecke, Martin Witt, Heinz Fehrenbach, Andreas Hofer, Toshio Miyata, Cora Weigert, Richard H. W. Funk, and Erwin D. Schleicher Institute of Anatomy and Institute of Pathology, Technical University of Dresden, Dresden; Department of Internal Medicine, Division of Endocrinology, Metabolism and Pathobiochemistry, University of Tübingen, Tübingen, Germany; and Institute of Medical Science and Department of Internal Medicine, Tokai University School of Medicine, Isehara, Japan

Oxidative stress has been suggested to play a central role in the pathogenesis of lung fibrosis and lung epithelial cell apoptosis is considered to be a key event during fibrogenesis. Studies from various laboratories have indicated that metabolic conditions may initiate oxidative stress, thereby contributing to epithelial cell death. This study was designed to test the hypothesis that glyoxal, an intermediate product in the glycation reaction leading to advanced glycation end products (AGEs), may induce lung epithelial cell apoptosis. We investigated the in vitro effects of glyoxal on fetal human lung epithelial L132 cells. Immunocytochemical analysis of paraffin-embedded cells and fluorescence-activated cell sorter analysis revealed a dose-dependent accumulation of the glycoxidation product εN-carboxymethyllysine (CML) in all compartments of the cell. It has been shown that CML modification of proteins may serve as an indicator for oxidative stress. To examine the role of apoptosis in epithelial lung cells we investigated glyoxal-dependent changes in proand antiapoptotic mediators bax and activated caspase-3, and galectin-3 and bcl-2, respectively. Increasing concentrations of glyoxal (50 to 400 ␮M) induced an increase in the number of apoptotic cells. The apoptotic changes were confirmed by transmission electron microscopy. Immunocytochemical analysis of treated cells revealed the presence of other AGEs such as pentosidine as well as products of lipid peroxidation.

Glyoxal is a reactive ␣-oxoaldehyde and a physiologic metabolite, formed by lipid peroxidation, oxidative degradation of glucose, and degradation of glycated proteins (1). Like other ␣-oxoaldehydes, for example, methylglyoxal and 3-deoxyglucosone, glyoxal is capable of inducing cellular damage but may also accelerate the glycation process leading to advanced glycation end products (AGEs) which, in turn, may also be toxic for the cell. The formation of AGEs is the final result of a process characterized by addition of sugar aldehydes or ketone groups to free amino groups of proteins by a nonenzymatic reaction known as Maillard reaction (reviewed in Reference 2). Because carbonyl groups are involved in all these reactions, the term “carbonyl stress” has been suggested for this cellular stress (3). Under conditions of normal cell metabolism, glyoxal is detoxified by the cytosolic glutathione-dependent glyoxalase system (4), which converts glyoxal to the less-reactive (Received in original form February 2, 2000 and in revised form April 18, 2000) Address correspondence to: Prof. Dr. Michael Kasper, Institute of Anatomy, Medical Faculty, Technical University of Dresden, Fetscherstr. 74, D-O1307 Dresden, Germany. E-mail: [email protected] Abbreviations: advanced glycation end product, AGE; bovine serum albumin, BSA; carboxymethyllysine, CML; 4-hydroxynonenal, HNE; immunoglobulin, Ig; keratinocyte growth factor, KGF; phosphate-buffered saline, PBS; room temperature, RT. Am. J. Respir. Cell Mol. Biol. Vol. 23, pp. 485–491, 2000 Internet address: www.atsjournals.org

glycolate. There is experimental evidence that glyoxal concentration is increased in oxidative stress because of decreased availability of reduced cofactors for the enzymatic detoxification (4). Impairment of ␣-oxoaldehyde detoxification may contribute to cytotoxicity and to the induction of apoptotic cell death by ␣-oxoaldehydes (5). In a previous study we reported on the in vitro formation of AGEs by human lung cells L132 after treatment with glyoxal (6). This finding may be relevant for the molecular pathogenesis of pulmonary fibrosis inasmuch as immunohistochemical evidence suggests that the increased formation of AGEs may be linked to the pathologic accumulation of extracellular matrix proteins during the development of this human disease (7). The alveolar epithelium plays an important role in this process. Previously, one major oxidatively formed AGE has been characterized as carboxymethyllysine (CML). Because Glomb and Monnier (8) have clearly shown that the presence of glyoxal leads to CML modification of proteins under physiologic conditions, the demonstration of CML formation may be used as a marker for intracellular glyoxal activity. Besides CML, characteristic AGEs formed by the reaction of glyoxal with proteins are the imidazolium crosslink GOLD (glyoxal lysin dimer) and hydroimidazolone (reviewed in Reference 9). The human embryonic lung cell line L132 (10) has been shown to be an excellent tool for cytotoxic tests (11) and for the study of radiation-induced injury (12). In the present study we investigated the effects of glyoxal on lung epithelial cells L132 with particular emphasis on the cytotoxic (apoptotic) effects of glyoxal. Apoptosis was studied by immunostaining for the activated caspase-3 and its cleavage product by the CytoDeath Kit and by determination of the proapoptotic protein bax and the antiapoptotic proteins bcl-2 and galectin-3 (reviewed in References 13 and 14).

Materials and Methods Cell Culture and Treatment Human L132 embryonic lung cells (ATCC, Rockville, MD) were grown in Dulbecco’s modified Eagle’s medium/F12 medium supplemented with 5% fetal calf serum (FCS) and gentamycin (6.4 mg/ml) at 37⬚C in 5% CO2. Glyoxal (Sigma, Deisenhofen, Germany) at various concentrations (20 to 400 ␮M) was added to the culture medium for 24 h. The viability of the lung cells was evaluated by the trypan blue exclusion test and did not exceed 7% nonviable cells in the experiments using glyoxal concentrations up to 100 ␮M. In additional experiments, L132 cells were maintained for 24 h in a culture medium that was supplemented with recombinant human keratinocyte growth factor (KGF) (Amgen, Inc., Thousand Oaks, CA) at a concentration of 50 ng/ml. After

486

AMERICAN JOURNAL OF RESPIRATORY CELL AND MOLECULAR BIOLOGY VOL. 23 2000

changing culture conditions to medium free of KGF, the cells were exposed to glyoxal as described earlier. The experiments described later, except the immunoelectron microscopy, were repeated three times for each condition.

Immunocytochemistry For light-microscopic detection of apoptotic markers in cultured cells we used a simple paraffin technique using a fibrin glue as embedding medium (6, 15). The 4-␮m-thick paraffin sections were dewaxed, dried overnight, and treated with microwaves in 0.01 M sodium citrate buffer (16). After washing in phosphatebuffered saline (PBS), pH 7.4, the conventional immunohistochemical procedure followed using a commercially available detection system (Vectorstain Elite Kit; Vector Laboratories, Burlingame, CA). The peroxidase activity was developed with 3⬘3⬘-diaminobenzidine and counterstaining with hemalaun was performed. The primary antibodies and their origins, dilutions, and sources are listed in Table 1. The suitability of antibodies to detect apoptosis has been shown in a previous study using in parallel the terminal deoxynucleotidyl transferase–mediated deoxyuridine triphosphate nick-end labeling method with two different kits (17). The specificity of the antipentosidine antibody has already been described (18). The corresponding inhibition experiment was performed with synthesized pentosidine–bovine serum albumin (BSA) (1 mg/ml; compare Figure 1D). The specificity of the CML-recognizing antiserum (19) was verified by preabsorption with CML–human serum albumin (5 mg/ml cell culture medium). As marker of oxidative stress an antiserum to 4-hydroxynonenal (HNE) pyrrole was used to determine sites of HNE modifications in lung cells. For the specificity of the antiserum, see Reference 20. For control, the primary antibody was replaced by nonspecific rabbit or mouse immunoglobulin (Ig) G.

Electron Microscopy For transmission electron microscopy, cells were fixed in 0.1 M PBS containing 4% paraformaldehyde and 0.05% glutaraldehyde for 1 h at room temperature (RT), dehydrated through a graded series of alcohols, and embedded in Epon as described previously (6). For immunoelectron microscopy, fixed L132 cells were embedded in Lowicryl HM20 (Polysciences Europe, Hamburg, Germany; for details see Reference 6). Ultrathin sections were mounted on pioloform-coated mesh nickel grids; preincubated with 10% normal goat serum in Tris-buffered saline (TBS), pH 7.6, for 45 min; and incubated overnight with the polyclonal rabbit anti-CML antiserum (dilution 1:100) at 4⬚C. After washings with buffer (TBS with 0.2% BSA) followed the incubation with 10-nm goldconjugated antirabbit IgG (Biocell, Cardiff, UK), dilution 1:50. After a further rinse in buffer, the sections were stained with 2% aqueous uranyl acetate (8 min) and lead citrate (2 min). A Zeiss EM 906 transmission electron microscope (Zeiss, Oberkochen, Germany) operated at 80 kV was used for ultrastructural analysis.

Cytofluorimetric Analysis To detect intracytoplasmatic antigens, cultured cells were fixed in 2% (wt/vol) formaldehyde in PBS for 20 min and centrifuged. The cells were then resuspended in a washing buffer consisting of 0.5% BSA in PBS. The cells were permeabilized for 20 min using 0.5% (wt/vol) saponin (Sigma) in washing buffer. Activation of caspase-3 was measured using the polyclonal antibody anti–active caspase-3 (PharMingen Europe, Hamburg, Germany) which recognizes an active human caspase-3 fragment and binds to a conformational epitope that is exposed by activation-induced cleavage or denaturation of the inactive enzyme. To detect CML-modified proteins, polyclonal rabbit anti-CML antiserum (dilution 1:1,500) was used. After incubation of cells with anti–active caspase-3 or CML-antiserum for 60 min, the cells were washed twice in PBS containing 0.5% BSA and 0.5% (wt/vol) saponin and incubated with a fluorescein isothiocyanate antimouse IgG (Sigma) for 60 min at RT. Cells were washed again and resuspended in 400 ␮l of PBS, and analyzed by flow cytometry (FACSCalibur; Becton Dickinson, San Jose, CA). For each analysis, 10,000 events were recorded.

Western Blots Cytosolic and nuclear proteins were separated and prepared as described by Andrews and Faller (21) and the protein concentrations were determined according to Bradford using the Bio-Rad protein assay reagent (22). Cytosolic and nuclear extracts were separated by sodium dodecyl sulfate (SDS) polyacrylamide (7.5%) gel electrophoresis. Proteins were transferred to nitrocellulose by semidry electroblotting (transfer buffer: 48 mM Tris, 39 mM glycine, 0.0375% SDS, 20% [wt/vol] methanol). After blotting, the nitrocellulose membranes were blocked with NET buffer (150 mM NaCl, 50 mM Tris/HCl [pH 7.4], 5 mM ethylenediaminetetraacetic acid, 0.05% Triton X-100, and 0.25% gelatine) and incubated with the CML antibody (diluted 1:8,000 in NET) overnight at 4⬚C. After washing with NET, the membranes were incubated with horseradish peroxidase–conjugated antirabbit or antigoat IgG for 1 h at RT. Visualization of immunocomplexes was performed by enhanced chemiluminescence as described by Bouaboula and colleagues (23).

Results Immunocytochemical Detection of the AGE Products CML and Pentosidine and the Lipid Peroxidation Product HNE in L132 Cells In fetal epithelial lung cells we observed an increasing percentage of cells immunoreactive to the CML-specific antibody with increasing glyoxal concentrations ranging from 0 to 400 ␮M (Figures 2A–2D; compare also the fluorescence-activated cell sorter [FACS] data given later). At

TABLE 1

Antibodies used for immunohistochemistry Antibody

Anti-CML Anti-pentosidine H4A3 Clone 124 Bax (I-19) Caspase-3 M30 CytoDeath

Specificity

Species

Dilution

Pretreatment

Source

CML Pentosidine LAMP-1 Bcl-2 Bax Active caspase-3 CK18 cleavage product

Rabbit, polyclonal Rabbit, polyclonal Mouse, monoclonal Mouse, monoclonal Rabbit, polyclonal Rabbit, polyclonal Mouse, monoclonal

1:3,000 1:200 1:10 1:40 1:50 1:50 1:10

Microwave Microwave Microwave Microwave Microwave — Microwave

Dr. E. Schleicher (26) Dr. T. Miyata (18) Dr. J. T. August, DSHB* DAKO, Hamburg, Germany Santa Cruz Biotechnologies, Santa Cruz, CA PharMingen Europe Boehringer Mannheim, Mannheim, Germany

*DSHB: Developmental Studies Hybridoma Bank.

the light-microscopic level, in contrast to the dose-depenKasper, Roehlecke, Witt, et al.: Apoptosis in Lung Epithelial Cells 487 dent increase of CML, first positive reactions with the antibodies against pentosidine (another nonglyoxal-derived AGE), and HNE (a product of lipid peroxidation), were found at glyoxal concentrations of 200 ␮M (Figure 1C, HNE immunostaining not shown) and remained positive at higher doses of glyoxal treatment (not shown). The technique of paraffin embedding and cutting of the cells allowed a precise detection of the antigen in different compartments of the cell. Positive immunostaining for CML was seen in the cytoplasm, at the cell membrane, and in a large number of cells also in the nuclei (Figure 2). Immunoelectron microscopy confirmed this staining of the entire cell body (Figure 5).

Figure 1. Paraffin sections of glyoxal-treated L132 cells (A: control; B–D: 200 ␮M glyoxal–treated cells; E and F: 100 ␮M glyoxal– treated cells. Cells in F were treated in addition with 50 ng/ml KGF). Immunohistochemical staining for LAMP-1 protein (A and B) and for pentosidine (C and D). (Note the negative immunoreactivity for pentosidine after inhibition with a pentosidine preparation in D.) E and F: Immunostaining for active caspase-3 is not present in KGF-treated cells (F). Hematoxylin and eosin (H&E) counterstain; original magnification: ⫻300.

Assessment of Apoptosis Only occasional apoptotic cells were seen in sections of untreated L132 cells stained with antibodies against active caspase-3 and the cytokeratin cleavage product (Figures 2E and 2I). In cells treated with increasing glyoxal concentrations, an increasing number of cells immunopositive with antibodies specific for caspase-3 (Figures 2F–2H) and CytoDeath (Figures 2J–2L) were observed, indicating that in these cells apoptosis had been induced. To evaluate the activation pathway of apoptosis the expression of pro- and antiapoptotic molecules was studied. The proapoptotic bax was enhanced with increasing glyoxal concentrations (Figures 4A–4D). In contrast, staining of molecules with antiapoptotic effects such as bcl-2 and galectin-3 was most intense in untreated cells and decreased with increasing glyoxal concentrations (Figures 4E–4H and 4I–4L).

Figure 2. Paraffin sections of glyoxal-treated L132 cells (A, E, I: control; B, F, J: 100 ␮M; C, G, K: 200 ␮M; D, H, L: 400 ␮M glyoxal). Immunohistochemical demonstration of CML (A–D), caspase-3 (E–H), and caspasecleavage product CytoDeath (I– L). H&E counterstain; original magnification: ⫻300.

488


Figure 3. Effect of glyoxal on apoptosis in L132 cells. Electron microscopy features of L132 cells cultured alone (A) or in the presence of 200 ␮M glyoxal for 24 h (B). Compared with the untreated cells (A), after glyoxal treatment L132 cells show apoptotic nuclei with condensed chromatin, abnormal cytoplasmic vesicles, and blebbing of the cell membrane (B). Original magnification: ⫻4,170.

To assess the integrity of lysosomal membranes in our experimental conditions, a monoclonal antibody specific for the lysosomal membrane protein LAMP-1 was included in immunocytochemical studies. There were no remarkable alterations of immunoreactivity for LAMP-1 detectable in both untreated and glyoxal-treated cells (Figures 1A and 1B). Treatment of cells with KGF, an inhibitor of apoptosis as demonstrated in several in vivo and in vitro experiments (24, 25), resulted in strong reduction in the expression of the caspase-3 immunoreactivity (Figures 1E and 1F). This effect could be achieved only at low concentrations (50 to 100 ␮M) of glyoxal. Figure 3 illustrates the key changes in the ultrastructure of L132 cells occuring in the majority of cells at concentrations of 200 ␮M glyoxal pretreatment: formation of membrane blebs, fragmentation of nuclei, and condensation of chromatin. Using an antiserum with high affinity to protein-bound CML (26), immunoreactivity for this AGE product was detected by immunoelectron microscopy at the cell membrane and in the cytosol as well as in the nucleus of epithelial lung cells (Figure 5). To confirm the immunocytochemically found nuclear localization of CML-modified proteins, nuclear extracts from glyoxal-treated cells were isolated and CML-modi-

Figure 4. Paraffin sections of glyoxal-treated L132 cells (A, E, I: control; B, F, J: 100 ␮M; C, G, K: 200 ␮M; D, H, L: 400 ␮M glyoxal). Immunohistochemical demonstration of bax (A–D), galectin-3 (E–H), and bcl-2 (I– L). H&E counterstain; original magnification: ⫻300.

Kasper, Roehlecke, Witt, et al.: Apoptosis in Lung Epithelial Cells

fied proteins were analyzed by Western blotting. As shown in Figure 6, distinct proteins ranging from ⬍ 39 up to 220 kD showed increased CML staining with increasing glyoxal concentrations. To detect whether very low glyoxal concentrations also cause CML modification, cells were also incubated with 20 ␮M glyoxal. Even at this concentration an increase of CML modification was found when compared with control. It is noteworthy that nuclear extracts previously not exposed to exogeneous glyoxal also showed faint CML staining of distinct proteins, particularly in the range of 66 to 160 kD. The glyoxal-induced formation of CML-modified proteins and parallel expression of caspase-3 was studied by FACS analysis. As shown in Figure 7, elevation of glyoxal concentration substantially enhanced the number of CML-positive cells. Even at low concentrations of 50 ␮M glyoxal, significant cellular CML modification was found. Similar to the CML modification shown in Figure 7, activated caspase-3 was dose-dependently enhanced with increasing glyoxal concentrations (Figure 8).

Discussion As described in a previous paper, glyoxal is a suitable metabolite able to induce the in vitro formation of AGEs in epithelial lung cell line L132 (6). Knowing that ␣-oxoaldehydes such as methylglyoxal and 3-deoxyglucosone have apoptotic effects (5), we speculated that glyoxal or one of its AGEs—e.g., CML—may induce apoptosis in living cells. Our study showed the presence of AGEs in L132 cells and a dose-dependent induction of apoptosis. The presence of CML modifications in all cellular compartments indicates that glyoxal or glyoxal-derived modifications of cellular proteins directly contributed to the apoptotic cell death in the present experiment. The exact mechanisms, however, by which either one of these me-

Figure 5. Lowicryl HM 20–embedded L132 cells. Immunoelectron microscopic demonstration of CML in untreated (A) and glyoxal-treated (200 ␮M) (B) cells. Note the strong labeling of cytoplasmic and nuclear components (B). Original magnification: ⫻19,400.

489

Figure 6. Effect of increasing glyoxal concentrations on CML modification of nuclear proteins in L132 cells. Cells were incubated with 0 to 200 ␮M glyoxal for 24 h. Nuclear extracts were prepared and Western blots with CML antibody were performed as described in MATERIALS AND METHODS.

tabolites exerts its apoptotic activity remains unknown. Because we were cultivating the cells in FCS-containing medium, preformed AGEs may also contribute synergistically to the metabolic changes. Results from a preliminary experiment have indicated that CML-modified proteins are formed in cell culture medium upon incubation with 50 to 200 ␮M glyoxal for 24 h inasmuch as CML antibody reactivity was blocked after incubation with the glyoxaltreated medium for 1 h (Kasper, unpublished data). It is noteworthy that 0.1 to 1-␮M glyoxal has been found in plasma of normal and diabetic subjects (27) whereas intra-

Figure 7. Flow cytometric analysis of CML in L132 cells incubated with glyoxal. Relative CML concentrations in the cells were quantified by flow cytometry. Cells were treated for 24 h with (black area) or without (white area) 50 ␮M (A), 100 ␮M (B), 150 ␮M (C), or 200 ␮M (D) glyoxal.

490


Figure 8. Flow cytometric analysis of active caspase-3 expression in L132 cells incubated with glyoxal. Cells were untreated (A) or treated for 24 h with 50 ␮M (B), 100 ␮M (C), 150 ␮M (D), or 200 ␮M (E) glyoxal. The vertical line indicates the mean fluorescence intensity of active caspase-3 in untreated cells (A).

cellular concentrations of ␣-oxoaldehydes may be much higher, e.g., 300 ␮M for methylglyoxal (28). From our experiments we cannot distinguish whether glyoxal itself or glyoxal-derived protein modifications are initiating the apoptosis. Because it has recently been shown that CML-modified proteins may bind to the receptor for AGEs (RAGE) and activate signal transduction leading to nuclear factor (NF)-␬B activation (2), it may well be that glyoxal-induced CML modification rather than glyoxal may initiate and/or propagate cellular apoptosis. Pulmonary fibrosis is characterized by a complex process involving alveolitis, fibroblast proliferation, and abnormal accumulation and deposition of interstitial collagen. This process could be the result of DNA damage and apoptosis. There is experimental evidence that Fas ligand and Fas antigen are upregulated in fibrosing lung disease (29). Other investigators describe a potential role of bax and bcl-2 expression in diffuse alveolar damage (30). Fibroblasts isolated from fibrotic lung produce factors capable of inducing apoptosis and necrosis of alveolar epithelial cells in vitro, and in fibrotic lung apoptotic alveolar epithelial cells are located immediately adjacent to activated myofibroblasts (31). Possible pathogenetic factors implicated in the development of pulmonary fibrosis are AGE-modified proteins, which accumulate in pulmonary fibrosis (7). They induce the generation of reactive oxygen intermediates and the upregulation of proinflammatory

cytokines (32). Reactive oxygen intermediates are involved in the formation of early glycation adducts such as CML (33). Interaction of AGEs with specific cell-surface receptors (for example, RAGE) on macrophages and probably also on certain epithelial cells induces oxidative stress, which results in activation of the transcription factor NF-␬B and subsequent gene expression, which might be relevant for chronic diseases (reviewed in Reference 2). The involvement of oxidative stress in induction of apoptosis by glyoxal is supported by the detection of lipid peroxidation products such as HNE and the formation of other nonglyoxal-derived AGEs such as pentosidine in our study. Finally, glyoxal-triggered apoptosis was also suppressed by KGF. In our in vitro model, KGF could have reduced the AGE-induced apoptosis by decreasing the expression of the activated caspase-3 enzyme. KGF has been used successfully to prevent alveolar damage induced by oxygen-induced injury in mice (25). Further, treatment with KGF protects epithelial cells against tumor necrosis factor-␣– or Actinomycin D–induced apoptosis (24). KGF also protects type II epithelial cells cultured from hyperoxic rats against oxygen-induced DNA damage and subsequent apoptosis (34). Inasmuch as apoptotic cell death plays an essential role in the development of pulmonary fibrosis, KGF may prevent AGE-induced lung injury by limiting the oxidative stress. In conclusion, our data show that treatment of L132 lung cells with glyoxal induces apoptosis. At the ultrastructural level, L132 cells showed dramatic and characteristic changes in nuclear shape and organization, which is an early and relatively unequivocal hallmark of apoptosis (35). In addition, pro- and antiapoptotic markers were increased or decreased, respectively, with increasing glyoxal concentrations. Further, increasing glyoxal concentrations cause an enhanced formation of AGE products, particularly CML modification. The experimental induction of apoptosis in L132 cells described here will provide a suitable system to study the role of AGEs for apoptotic processes in alveolar epithelial cells in vitro. The usage of in vitro glyoxal-modified extracellular matrix proteins or the glycation of more lung-specific products such as surfactant protein are the necessary steps to improve this model in the future. Acknowledgments: The monoclonal antibody H4A3 developed by J. T. August and J. E. K. Hildreth was obtained from the Developmental Studies Hybridoma Bank, developed under the auspices of the NICHD, and maintained by the Department of Biological Sciences, University of Iowa, Iowa City, Iowa. The antibody to HNE-pyrrole was kindly provided by Dr. George Perry, Division of Neuropathology, Case Western Reserve University, Cleveland, Ohio. The authors thank Dr. M. Wilsch-Bräuninger for immunoelectron microscopical work; Mrs. S. Bramke, B. Jahnke, K. Pehlke, and S. Thieme for skilful technical assistance; and T. Schwalm and M. Nicklisch for photographic reproduction. This work was supported by the BMBF, 01ZZ9604 to three authors (M.K., A.H., and M.W.).

References 1. Wells-Knecht, K. J., D. V. Zyzak, J. E. Litchfield, S. R. Thorpe, and J. W. Baynes. 1995. Mechanism of autoxidative glycosylation: identification of glyoxal and arabinose as intermediates in the autoxidative modification of proteins by glucose. Biochemistry 34:3702–3709. 2. Nawroth, P. P., A. Bierhaus, G. E. Vogel, M. A. Hofmann, M. Zumbach, P. Wahl, and R. Ziegler. 1999. Non-enzymatic glycation and oxidative stress in chronic illnesses and diabetes mellitus. Med. Klin. 94:29–38. 3. Miyata, T., and K. Kurokawa. 1999. Carbonyl stress: increased carbonyl

Kasper, Roehlecke, Witt, et al.: Apoptosis in Lung Epithelial Cells

4. 5.

6.

7. 8. 9. 10. 11.

12. 13. 14. 15.

16. 17.

18.

19.

modification of proteins by autoxidation products of carbohydrates and lipids in uremia. Int. J. Artif. Organs 22:195–198. Abordo, E. A., H. S. Minhas, and P. J. Thornalley. 1999. Accumulation of alpha-oxoaldehydes during oxidative stress: a role in cytotoxicity. Biochem. Pharmacol. 58:641–648. Kikuchi, S., K. Shinpo, F. Moriwaka, Z. Makita, T. Miyata, and K. Tashiro. 1999. Neurotoxicity of methylglyoxal and 3-deoxyglucosone on cultured cortical neurons: synergism between glycation and oxidative stress, possibly involved in neurodegenerative diseases. J. Neurosci. Res. 57:280–289. Kasper, M., R. Schinzel, T. Niwa, G. Munch, M. Witt, H. Fehrenbach, M. Wilsch-Bräuninger, K. Pehlke, A. Hofer, and R. H. Funk. 1999. Experimental induction of AGEs in fetal L132 lung cells changes the level of intracellular cathepsin D. Biochem. Biophys. Res. Commun. 261:175–182. Matsuse, T., E. Ohga, S. Teramoto, M. Fukayama, R. Nagai, S. Horiuchi, and Y. Ouchi. 1998. Immunohistochemical localisation of advanced glycation end products in pulmonary fibrosis. J. Clin. Pathol. 51:515–519. Glomb, M. A., and V. M. Monnier. 1995. Mechanism of protein modification by glyoxal and glycolaldehyde, reactive intermediates of the Maillard reaction. J. Biol. Chem. 270:10017–10026. Thornalley, P. T. 1999. The clinical significance of glycation. Clin. Lab. 45: 263–273. Bradburne, A. F. 1969. Sensitivity of L132 cells to some “new” respiratory viruses. Nature 221:85–86. Hildebrand, H. F., M. C. D’Hooghe, P. Shirali, C. Bailly, and J. P. Kerckaert. 1990. Uptake and biological transformation of beta NiS and alpha Ni3S2 by human embryonic pulmonary epithelial cells (L132) in culture. Carcinogenesis 11:1943–1950. Singh, B., J. E. Arrand, and M. C. Joiner. 1994. Hypersensitive response of normal human lung epithelial cells at low radiation doses. Int. J. Radiat. Biol. 65:457–464. Huppertz, B., H. G. Frank, and P. Kaufmann. 1999. The apoptosis cascade: morphological and immunohistochemical methods for its visualization. Anat. Embryol. (Berl) 200:1–18. Perillo, N. L., M. E. Marcus, and L. G. Baum. 1998. Galectins: versatile modulators of cell adhesion, cell proliferation, and cell death. J. Mol. Med. 76:402–412. Schulze, E., M. Witt, M. Kasper, C. W. Lowik, and R. H. Funk. 1999. Immunohistochemical investigations on the differentiation marker protein E11 in rat calvaria, calvaria cell culture and the osteoblastic cell line ROS 17/ 2.8. Histochem. Cell. Biol. 111:61–69. Kasper, M., S. D. Fuller, D. Schuh, and M. Muller. 1994. Immunohistological detection of the beta subunit of prolyl 4-hydroxylase in rat and mini pig lungs with radiation-induced pulmonary fibrosis. Virchows Arch. 425:513–519. Fehrenbach, H., M. Kasper, T. Tschernig, T. Pan, D. Schuh, J. M. Shannon, M. Muller, and R. J. Mason. 1999. Keratinocyte growth factor-induced hyperplasia of rat alveolar type II cells in vivo is resolved by differentiation into type I cells and by apoptosis. Eur. Respir. J. 14:534–544. Horie, K., T. Miyata, K. Maeda, S. Miyata, S. Sugiyama, H. Sakai, C. Y. Strihou, V. M. Monnier, J. L. Witztum, and K. Kurokawa. 1997. Immunohistochemical colocalization of glycoxidation products and lipid peroxidation products in diabetic renal glomerular lesions: implication for glycoxidative stress in the pathogenesis of diabetic nephropathy. J. Clin. Invest. 100:2995–3004. Nerlich, A. G., and E. D. Schleicher. 1999. N(epsilon)-(carboxymethyl)lysine in atherosclerotic vascular lesions as a marker for local oxidative stress. Atherosclerosis 144:41–47.

491

20. Sayre, L. M., D. A. Zelasko, P. L. Harris, G. Perry, R. G. Salomon, and M. A. Smith. 1997. 4-Hydroxynonenal-derived advanced lipid peroxidation end products are increased in Alzheimer’s disease. J. Neurochem. 68:2092–2097. 21. Andrews, N. C., and D. V. Faller. 1991. A rapid micropreparation technique for extraction of DNA-binding proteins from limiting numbers of mammalian cells. Nucleic Acids Res. 19:2499 (Abstr.). 22. Bradford, M. M. 1976. A rapid and sensitive method for the quantitation of microgram quantities of protein utilizing the principle of protein-dye binding. Anal. Biochem. 72:248–254. 23. Bouaboula, M., P. Legoux, B. Pessegue, B. Delpech, X. Dumont, M. Piechaczyk, P. Casellas, and D. Shire. 1992. Standardization of mRNA titration using a polymerase chain reaction method involving co-amplification with a multispecific internal control. J. Biol. Chem. 267:21830–21838. 24. Senaldi, G., C. L. Shaklee, B. Simon, C. G. Rowan, D. L. Lacey, and T. Hartung. 1998. Keratinocyte growth factor protects murine hepatocytes from tumor necrosis factor-induced apoptosis in vivo and in vitro. Hepatology 27:1584–1591. 25. Barazzone, C., Y. R. Donati, A. F. Rochat, C. Vesin, C. D. Kan, J. C. Pache, and P. F. Piguet. 1999. Keratinocyte growth factor protects alveolar epithelium and endothelium from oxygen-induced injury in mice. Am. J. Pathol. 154:1479–1487. 26. Schleicher, E. D., E. Wagner, and A. G. Nerlich. 1997. Increased accumulation of the glycoxidation product N(epsilon)-(carboxymethyl)lysine in human tissues in diabetes and aging. J. Clin. Invest. 99:457–468. 27. Odani, H., T. Shinzato, Y. Matsumoto, J. Usami, and K. Maeda. 1999. Increase in three alpha,beta-dicarbonyl compound levels in human uremic plasma: specific in vivo determination of intermediates in advanced Maillard reaction. Biochem. Biophys. Res. Commun. 256:89–93. 28. Chaplen, F. W. R., W. E. Fahl, and D. C. Cameron. 1998. Evidence of high levels of methylglyoxal in cultured Chinese hamster ovary cells. Proc. Natl. Acad. Sci. USA 95:5533–5538. 29. Kuwano, K., H. Miyazaki, N. Hagimoto, M. Kawasaki, M. Fujita, R. Kunitake, Y. Kaneko, and N. Hara. 1999. The involvement of Fas-Fas ligand pathway in fibrosing lung diseases. Am. J. Respir. Cell Mol. Biol. 20:53–60. 30. Guinee, D., Jr., E. Brambilla, M. Fleming, T. Hayashi, M. Rahn, M. Koss, V. Ferrans, and W. Travis. 1997. The potential role of BAX and BCL-2 expression in diffuse alveolar damage. Am. J. Pathol. 151:999–1007. 31. Uhal, B. D., I. Joshi, W. F. Hughes, C. Ramos, A. Pardo, and M. Selman. 1998. Alveolar epithelial cell death adjacent to underlying myofibroblasts in advanced fibrotic human lung. Am. J. Physiol. 275:L1192–L1199. 32. Westwood, M. E., and P. J. Thornalley. 1996. Induction of synthesis and secretion of interleukin 1 beta in the human monocytic THP-1 cells by human serum albumins modified with methylglyoxal and advanced glycation endproducts. Immunol. Lett. 50:17–21. 33. Fu, M. X., J. R. Requena, A. J. Jenkins, T. J. Lyons, J. W. Baynes, and S. R. Thorpe. 1996. The advanced glycation end product, Nepsilon-(carboxymethyl)lysine, is a product of both lipid peroxidation and glycoxidation reactions. J. Biol. Chem. 271:9982–9986. 34. Buckley, S., L. Barsky, B. Driscoll, K. Weinberg, K. D. Anderson, and D. Warburton. 1998. Apoptosis and DNA damage in type 2 alveolar epithelial cells cultured from hyperoxic rats. Am. J. Physiol. 274:L714–L720. 35. Willingham, M. C. 1999. Cytochemical methods for the detection of apoptosis. J. Histochem. Cytochem. 47:1101–1109.