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Increased p53 Level, Bax/Bcl-x_L Ratio, and TRAIL Receptor Expression in Human Emphysema

¹ Centre de Recherche de l'Hôpital Laval, Institut Universitaire de Cardiologie et de Pneumologie de l'Université Laval, Quebec City, Canada

Correspondence and requests for reprints should be addressed to Julie Milot, M.D., Ph.D., Hôpital Laval, 2725 Chemin Sainte-Foy, Québec, PQ, Canada G1V 4G5. E-mail: julie.milot{at}crhl.ulaval.ca

	ABSTRACT

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Rationale: Emphysema is mainly known for the complex inflammatory processes associated with its development. In addition to lung inflammation, it is now accepted that increased alveolar cell apoptosis is also part of emphysema pathophysiology. However, little is known about the mechanisms involved in alveolar apoptosis. We postulate that oxidative stress and proinflammatory cytokines could lead to p53 accumulation, Bax/Bcl-x_L ratio elevation, and higher tumor necrosis factor (TNF)–related apoptosis-inducing ligand (TRAIL) receptor levels in the emphysematous lung.

Objectives: To evaluate the expression of p53, Bax, Bcl-x_L, TRAIL, and TRAIL receptors in lung parenchyma from nonemphysematous nonsmokers and smokers and emphysematous smokers and ex-smokers and to determine whether H₂O₂ and/or TNF can modulate the expression of these apoptotic proteins.

Methods: p53, Bax, Bcl-x_L, and TRAIL receptor protein levels in lung parenchyma were measured by Western blot, and TRAIL mRNA levels were measured by real-time polymerase chain reaction. Changes in TRAIL receptor, Bax, Bcl-x_L, and p53 protein levels after in vitro H₂O₂ and/or TNF stimulation of A549 cells were also assessed by Western blot.

Measurements and Main Results: The p53 protein levels, the Bax/Bcl-x_L ratio, and TRAIL receptors 1, 2, and 3 protein levels were significantly higher in subjects with emphysema. Moreover, they were also increased after H₂O₂ and TNF treatments of A549 cells.

Conclusions: These findings suggest that oxidative stress and proinflammatory cytokines may be involved in the elevation of p53 levels, the Bax/Bcl-x_L ratio, and TRAIL receptor levels, new mechanisms that may be implicated in the increased alveolar cell apoptosis that occurs in emphysema.

Key Words: chronic obstructive pulmonary disease • cell death • oxidative stress • inflammation

AT A GLANCE COMMENTARY TOP ABSTRACT AT A GLANCE COMMENTARY METHODS RESULTS DISCUSSION REFERENCES   Scientific Knowledge on the Subject Little is known of the mechanisms involved in increased alveolar cell apoptosis in emphysema. What This Study Adds to the Field p53 and the TRAIL apoptotic system are mechanisms that may be responsible for the increased alveolar cell apoptosis in emphysema.

 
Chronic obstructive pulmonary disease (COPD) is associated with cigarette smoking. Among the features of COPD, emphysema is characterized by a loss of alveolar integrity leading to an alveolar space enlargement and a decrease in diffusion capacity (1). The accumulation of immune cells (e.g., neutrophils, macrophages, CD8⁺ T lymphocytes) and the increase in cytokine (e.g., tumor necrosis factor [TNF], IFN-) and chemokine (e.g., CXCL10) levels in the emphysematous lung (2) revealed that emphysema is a complex inflammatory disease.

In addition to inflammation, increased alveolar apoptosis has been linked to the development of emphysema (3–6). In fact, emphysematous alveolar tissue presents higher levels of apoptosis markers, such as fragmented DNA (3–6), active caspase-3 (6), and cleaved poly (ADP-ribose) polymerase (PARP) (6) compared with normal alveolar tissue. However, the main cause, mechanisms, and involvement of apoptosis in alveoli loss observed in emphysema remain to be clarified.

The oxidative stress caused by cigarette smoke and the inflammatory burden has been well established in the emphysematous lung (7). Oxidative stress can damage DNA (8) and lead to the activation of transcription factors such as p53 (9), which influence cell survival. p53 is strongly linked to the DNA damage response through the up-regulation of proapoptotic factors such as Bax, Puma, Noxa, and Fas (10). TNF-related apoptosis-inducing ligand (TRAIL) receptors are also p53 transcriptional targets (11). TRAIL, a member of the TNF family, has two proapoptotic receptors (TRAIL-R1 and TRAIL-R2) and two nonapoptotic receptors (TRAIL-R3 and TRAIL-R4) (11). The TRAIL apoptotic system has been well studied in cancer and is believed to be implicated in neurodegenerative pathologies, such as Alzheimer's disease, where apoptosis is involved (12, 13). In addition to p53, TRAIL receptors can be up-regulated after nuclear factor-B activation (14), an important transcription factor that is induced by cytokines like TNF (15), and by oxidative stress (16). To the best of our knowledge, no data are available on p53 activation or on TRAIL system modulation in emphysema, even if it has been reported that more alveolar cells express Bax in subjects with emphysema (4, 6). In the present study, we hypothesized that factors at play in emphysema, such as oxidative stress and inflammatory mediators, lead to p53 activation, Bax/Bcl-x_L ratio elevation (proapoptotic balance), and TRAIL receptor up-regulation.

Our objectives were to compare p53, Bax, Bcl-x_L, TRAIL, and TRAIL receptor expressions in lung parenchyma samples obtained from nonemphysematous nonsmokers and smokers and in smokers and ex-smokers with emphysema, and to evaluate their expression in A549 cells after hydrogen peroxide (H₂O₂) and/or TNF treatments. We found that p53 protein levels, the Bax/Bcl-x_L ratio, and TRAIL-R1, TRAIL-R2, and TRAIL-R3 protein levels were higher in subjects with emphysema. Moreover, H₂O₂ increased p53 protein levels, the Bax/Bcl-x_L ratio, and TRAIL-R1, TRAIL-R2, and TRAIL-R3 protein levels in A549 cells, whereas TNF increased TRAIL-R1 and TRAIL-R2 levels. Some results contained in this study have been previously reported in the form of abstracts (17, 18).

	METHODS

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Human Lung Samples
Human lung parenchyma samples were provided by the Banque de Tissus de l'Hôpital Laval (Quebec City, Canada). The samples, which were obtained from tumor resection, were located far from the tumor and analyzed by a pathologist. Fifty-two subjects were included in the study: 13 nonemphysematous nonsmokers, 14 nonemphysematous smokers, 13 smokers with emphysema, and 12 ex-smokers with emphysema. All subjects had to be between 50 and 75 years old and the smoking history of smokers and ex-smokers had to be greater than 15 pack-years. Subjects with emphysema were classified using the Global Initiative for Chronic Obstructive Lung Disease (GOLD) classification (19). Presence or absence of emphysema was confirmed by computed tomography scan analysis for all subjects. Subjects were matched for age and smoking history. The Hôpital Laval Research Ethics Committee approved the study and all subjects provided written consent.

Lung Parenchyma Processing for Protein Analyses
Human lung parenchyma samples were homogenized in ice-cold lysis buffer with a Potter-Elvehjem tissue grinder before protein quantification. The method is described in the online supplement.

Cell Culture and Stimulations
The commercial alveolar epithelial cell line A549 was purchased from the American Type Culture Collection (ATCC, Manassas, VA) and grown in Dulbecco's modified Eagle medium (Invitrogen, Burlington, ON, Canada) with 10% fetal bovine serum (Cansera; PAA Laboratories, Etobicoke, ON, Canada). Cells were plated in six-well plates in a humidified 95% air/5% CO₂ atmosphere. Confluent culture were starved overnight in serum-free medium and stimulated with H₂O₂ (0, 200, 500, 1,000 µM) (Laboratoire Mat, Quebec City, PQ, Canada) and/or recombinant human TNF (0, 1, 10, 100 ng/ml) (Serotec, Raleigh, NC) for 2, 6, 12, and 24 hours. Cells were lysed with 70 µl of lysis buffer (150 mM NaCl; 1 mM ethylenediamine tetraacetic acid; 25 mM Tris-HCl, pH 8.0; 1% Triton-X100; 0.5 mM phenylmethylsulfonylfluoride) and proteins quantified with DC Protein Assay (Biorad, Hercules, CA) before Western blotting. All experiments were repeated three times.

Western Blot
Western blot was used to evaluate p53, Bax, Bcl-x_L, TRAIL receptor, and β-actin protein levels in lung parenchyma homogenates and A549 cell lysates. The method is described in the online supplement.

Immunohistochemistry
Immunochemical staining was used to evaluate the localization of TRAIL-R1, TRAIL-R2, and TRAIL-R3 in the lung parenchyma. The method is described in the online supplement.

Lung Parenchyma RNA Extraction and Real-Time Polymerase Chain Reaction Analyses
Total RNA was extracted from lung parenchyma samples, quantified, reverse transcribed, and analyzed by real-time polymerase chain reaction (PCR) for TRAIL and 18S rRNA expression. A detailed method is provided in the online supplement.

The 2^Ct method was used to quantify differences in TRAIL mRNA expression in the lung samples (20). On the basis of the 18S rRNA crossing threshold (Ct), the Ct of each gene was determined for each subject. Then, for each group of subject, the mean expression of each gene was compared with the nonemphysematous nonsmoker group that represents the baseline expression. PCR efficiency was confirmed to ensure that amplification rate was comparable to 18S rRNA.

Statistical Analysis
Data from human lung parenchyma samples (ex vivo study) and the A549 cell stimulations (in vitro study) were compared using one-way analysis of variance followed by, if P < 0.05, a Tukey-Kramer test. Correlations were evaluated using Pearson's test and the significance using a one-sample t test. A significant difference was assumed when P values were lower than 0.05.

	RESULTS

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Ex Vivo Study
Clinical findings.
The characteristics of the subjects are presented in Table 1. The mean age and smoking history of the four groups were similar (except for the smoking history of nonsmokers). Smokers and ex-smokers with emphysema had moderate airflow obstruction with a mean FEV₁ at 57% of predicted value (39–69%) and 50% of predicted value (19–71%), respectively. Diffusion capacity of carbon monoxide (DL_CO) was reduced in smokers and ex-smokers with emphysema with a mean value at 50% of predicted (16–63%) and 54% of predicted (26–71%), respectively. Most subjects with emphysema had stage II and III disease according to GOLD classification. Nonemphysematous smokers and nonsmokers had normal lung function.

View larger version (20K): [in this window] [in a new window]   Figure 1. Protein expression of (A) p53, (B) Bax, and (C) Bcl-xL, and (D) Bax/Bcl-xL ratio in lung parenchyma were measured by Western blot. Western blot results are expressed as protein/β-actin ratio reported in fold increase of the nonemphysematous nonsmokers. Nonemphysematous nonsmokers (open bars), nonemphysematous smokers (light gray bars), smokers with emphysema (dark gray bars), and ex-smokers with emphysema (solid bars). Bars represent mean and error bars the SEM. Bars with different lowercase letters are significantly different (P < 0.05). White horizontal bars at the bottom of (A) through (D) show that the y axis has been truncated. (E) Correlation between FEV1 and p53 protein level in subjects from all groups. Patients from all four groups were pooled into a single cohort. Each patient is represented by a symbol.

View larger version (21K): [in this window] [in a new window]   Figure 2. Protein expression of (A) proapoptotic tumor necrosis factor–related apoptosis-inducing ligand (TRAIL)-R1 and TRAIL-R2 and (B) nonapoptotic TRAIL-R3 and TRAIL-R4 in lung parenchyma were measured by Western blot. (C) Correlation between TRAIL-R1 and TRAIL-R2 protein levels in subjects from all groups. (D) Correlation between TRAIL-R1 and p53 protein levels in subjects from all groups. (C) and (D) Patients from all four groups were pooled together into a single cohort. Each patient is represented by a symbol. (E) TRAIL mRNA levels in lung parenchyma were measured by real-time polymerase chain reaction (PCR). Western blot results are expressed as protein/β-actin ratio reported in fold increase of the nonemphysematous nonsmokers. Real-time PCR results are expressed according to the 2ct method (see METHODS) using nonemphysematous nonsmokers as baseline. Nonemphysematous nonsmokers (open bars), nonemphysematous smokers (light gray bars), smokers with emphysema (dark gray bars), and ex-smokers with emphysema (solid bars). Bars represent mean (n = 5/group for E) and error bars the SEM. Bars with different lowercase letters are significantly different (P < 0.05). White horizontal bars at the bottom of (A) and (B) show that the y axis has been truncated.

View larger version (60K): [in this window] [in a new window]   Figure 3. Immunohistochemical staining presenting the localization of tumor necrosis factor–related apoptosis-inducing ligand (TRAIL)-R1, TRAIL-R2, and TRAIL-R3 in the lung parenchyma. The stained cells are mostly alveolar cells. One representative immunohistochemical analysis shown per receptor. Arrowheads point at immune cells. Original magnification, x200.

View larger version (48K): [in this window] [in a new window]   Figure 4. A549 cells were exposed to H2O2 (0 [open bars], 200 [light gray bars], 500 [dark gray bars], and 1,000 [solid bars] µM) for 2, 6, and 12 hours. Cells were lysed and (A) tumor necrosis factor–related apoptosis-inducing ligand (TRAIL)-R1, (B) TRAIL-R2, (C) TRAIL-R3, and (D) p53 protein levels were assessed by Western blot. Results are expressed as protein/β-actin ratio reported in fold increase of the appropriate stimulation time control [0 µM H2O2]. Bars represent mean (n = 3) and error bars the SEM. Bars with different lowercase letters are significantly different (P < 0.05). White horizontal bars at the bottom of the graphs show that the y axis has been truncated.

View larger version (25K): [in this window] [in a new window]   Figure 5. A549 cells were exposed to H2O2 (0 [open bars], 200 [light gray bars], 500 [dark gray bars], and 1,000 [solid bars] µM) for 24 hours. Cells were lysed and Bax and Bcl-xL protein levels were assessed by Western blot. Results are expressed as protein/β-actin ratio (Bax and Bcl-xL expression) or as Bax/Bcl-xL ratio and reported in fold increase of the control [0 µM H2O2]. Bars represent mean (n = 3) and error bars the SEM. Bars with different lowercase letters are significantly different (P < 0.05). White bars at the bottom of the graphs show that the y axis has been truncated.

View larger version (37K): [in this window] [in a new window]   Figure 6. A549 cells were exposed to tumor necrosis factor (TNF) (0 [open bars], 1 [light gray bars], 10 [dark gray bars], and 100 [solid bars] ng/ml) for 2, 6, and 12 hours. Cells were lysed and (A) TNF-related apoptosis-inducing ligand (TRAIL)-R1 and (B) TRAIL-R2 protein levels were assessed by Western blot. Results are expressed as protein/β-actin ratio reported in fold increase of the appropriate stimulation time control [0 µM H2O2]. Bars represent mean (n = 3) and error bars the SEM. Bars with different lowercase letters are significantly different (P < 0.05). White horizontal bars at the bottom of the graphs show that the y axis has been truncated.

View larger version (30K): [in this window] [in a new window]   Figure 7. A549 cells were exposed to H2O2 (500 µM) and/or tumor necrosis factor (TNF) (10 ng/ml) for 12 hours. Cells were lysed and TNF-related apoptosis-inducing ligand (TRAIL)-R1, TRAIL-R2, and TRAIL-R3 protein levels were assessed by Western blot. Results are expressed as protein/β-actin ratio reported in fold increase of the control (no TNF and H2O2 exposure). Bars represent mean (n = 3) and error bars the SEM. Bars with different lowercase letters are significantly different (P < 0.05). White horizontal bars at the bottom of the graphs show that the y axis has been truncated.

	DISCUSSION

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The different subject groups of the present study, nonemphysematous nonsmokers, nonemphysematous smokers, smokers with emphysema, and ex-smokers with emphysema, gave us the opportunity to compare the effects of cigarette smoking (nonemphysematous nonsmokers vs. nonemphysematous smokers), emphysema (nonemphysematous smokers vs. smokers with emphysema), and smoking cessation (smokers with emphysema vs. ex-smokers with emphysema) on the expression of TRAIL receptor, p53, Bax, and Bcl-x_L. In fact, most of the observed modulations were attributable to emphysema and, interestingly, were not affected by smoking cessation once the disease is established.

p53 accumulation/activation in the emphysematous lung parenchyma (Figure 1A) is extremely relevant to the pathogenesis of the disease because p53 is closely associated with many apoptotic mechanisms, mainly those related to mitochondria-dependent apoptosis, such as Bax up-regulation (10). Cigarette smoke extract has been shown to induce p53 activation in normal human lung fibroblasts (21) and rats exposed to cigarette smoke present higher levels of activated p53 and Bax in the alveolar tissue (22). However, the fact that p53 levels and that Bax/Bcl-x_L ratio were higher in smokers with emphysema than in nonemphysematous smokers and that, even with smoking cessation, p53 levels and Bax/Bcl-x_L ratio remained elevated in ex-smokers with emphysema suggest that the inflammation associated with emphysema that persists after smoking cessation may be involved in the increase and the maintenance of p53 levels and the Bax/Bcl-x_L ratio. Macrophages and neutrophils, which are present in higher numbers in the lung of subjects with emphysema (2), produce large quantities of reactive oxygen species that cause oxidative stress (7). We showed in vitro that oxidative stress alone (H₂O₂) (Figures 4 and 5) induces p53 activation and increases the Bax/Bcl-x_L ratio in A549 cells, suggesting that oxidative stress may be responsible for the high p53 levels and Bax/Bcl-x_L ratios in smokers and ex-smokers with emphysema.

Like p53 levels and the Bax/Bcl-x_L ratio, the expression of TRAIL-R1, TRAIL-R2, and TRAIL-R3 proteins was also higher in the lung parenchyma of subjects with emphysema despite smoking cessation (Figures 2A and 2B). Immune cells were not responsible for this increase, because they were in the minority compared with alveolar cells (Figure 3). Moreover, they do not overexpress TRAIL receptors upon activation (23, 24). Thus, we can say that alveolar cells are responsible for the differential expression of TRAIL receptors that we observed in lung parenchyma. In addition, we observed that the expression of TRAIL-R1, TRAIL-R2, and TRAIL-R3 was correlated in all four groups (Figure 2C; example for TRAIL-R1 and TRAIL-R2), which suggests that the higher expression of these three TRAIL receptors in subjects with emphysema may be regulated by the same pathway(s). In line with those findings, TRAIL-R1, TRAIL-R2, and TRAIL-R3, but not TRAIL-R4, expression was associated with p53 levels in all groups (Figure 2D). We demonstrated in vitro that H₂O₂ can up-regulate TRAIL-R1, TRAIL-R2, and TRAIL-R3 in A549 cells, whereas TNF up-regulates TRAIL-R1 and TRAIL-R2 protein expression. Moreover, stimulation of A549 cells with both H₂O₂ and TNF resulted in the same TRAIL receptor up-regulation pattern observed in subjects with emphysema ex vivo. These findings on TRAIL receptor modulation by H₂O₂ and TNF in A549 cells could explain the concomitant increase of TRAIL-R1, TRAIL-R2, and TRAIL-R3 expression in the subjects with emphysema and the correlation with p53 levels in all groups.

As another part of the TRAIL apoptotic system, we evaluated TRAIL mRNA expression in five lung samples from each group that were representative of the mean in terms of TRAIL receptor protein expression and found that TRAIL mRNA levels were significantly lower in the lung parenchyma of smokers with or without emphysema than in nonemphysematous nonsmokers (Figure 2E), which is clearly a different pattern than that of TRAIL receptor protein expression (Figures 2A and 2B). It is known that TRAIL is widely expressed in the lung; immune cells like macrophages and lymphocytes are major sources (25, 26). Our results suggest that active tobacco smoking may be responsible for a decrease in the expression of TRAIL mRNA. Proulx and colleagues (27) have demonstrated that cigarette smoke extract can reduce the amount of TNF released from alveolar macrophages exposed to lipopolysaccharides. Therefore, it is possible that cigarette smoke has similar inhibitory effects on the expression of TRAIL, a member of the TNF family. Moreover, decreased TRAIL mRNA expression in the emphysematous lung may not be as important as the observed up-regulation of TRAIL receptors, p53, and Bax/Bcl-x_L ratio, because a cell's response to TRAIL is more affected by intracellular modifications than by the amount of TRAIL in the cell environment (28).

It is well known that most normal cells and some cancer/transformed cells are resistant to TRAIL-mediated apoptosis (29). However, the resistance mechanisms have not all been identified and seem to differ among cell types (28). We found that the expression of TRAIL-R3 protein was higher in lung parenchyma from subjects with emphysema and increased in H₂O₂-treated A549 cells (Figures 2B and 4C). TRAIL-R3 is a decoy receptor that may confer TRAIL resistance (11, 28). However, TRAIL-R1 and TRAIL-R2, two proapoptotic receptors, were also up-regulated in the same conditions and may enhance alveolar TRAIL sensitivity. Moreover, it is important to note that TRAIL sensitivity is not only based on TRAIL receptor expression (28). Hu and colleagues (30) showed that TRAIL-resistant LNCaP human prostate cancer cells treated with inorganic selenium, a reactive oxygen species–generating agent, became sensitive to TRAIL-mediated apoptosis despite the fact that TRAIL-R1 and TRAIL-R2 levels did not change. They observed that oxidative stress induced p53 activation and Bax up-regulation, as we did in our in vitro study (Figures 1A and 1B), and that TRAIL sensitization induced by oxidative stress was dependent on p53 activation and Bax translocation to mitochondria. On the basis of our ex vivo and in vitro observations and on the work of Hu and coworkers (30), higher TRAIL-R1, TRAIL-R2, and p53 levels, and Bax/Bcl-x_L ratio may lead to oxidative stress–mediated TRAIL sensitivity, which could contribute to the increased alveolar apoptosis seen in emphysema.

Limitations in this study were restricted to the in vitro evaluation of the effects of oxidative stress on A549 cells. Short-term exposure to H₂O₂ was used to reproduce the long-term chronic oxidative stress found in subjects with emphysema. However, the use of H₂O₂ is one of the most common and widely accepted approaches for studying the effects of oxidative stress (8), and the use of H₂O₂ at concentrations up to 1,000 µM is common with A549 cells (31–33). Moreover, trypan blue coloration showed that the concentrations used here were not affecting cells viability (data not shown).

Increased alveolar cell apoptosis, oxidative stress, and proinflammatory cytokines such as TNF in the lung of subjects with emphysema are well-established events (2–7, 34). However, the mechanisms linking those events are not as clear. In the present study, we found that, in general, p53 levels, the Bax/Bcl-x_L ratio, and TRAIL-R1, TRAIL-R2, and TRAIL-R3 levels were higher in the lung parenchyma of subjects with emphysema than in nonemphysematous subjects. We also showed that treating A549 cells with H₂O₂ and TNF reproduced the ex vivo results observed in the lung tissue of subjects with emphysema. These results are a first step toward exploring the involvement of transcription factor p53 and the TRAIL apoptotic system in the increase of alveolar apoptosis observed in emphysema. Studies on oxidative stress–mediated TRAIL sensitization and the mechanisms responsible for TRAIL receptor up-regulation will be required to fully decipher the role of the TRAIL apoptotic system in the pathogenesis of emphysema.

	Acknowledgments

 
The authors thank Christine Racine, Sabrina Biardel, and Marie-Claude Bernier from the Banque de Tissus de l'Hôpital Laval for their great help providing the lung parenchyma samples.

	FOOTNOTES

 
M.C.M. is the recipient of a studentship from the Fonds de Recherche en Santé du Québec. J.M. has received unrestricted research grant from the Groupe de Recherche en Santé Respiratoire/Altana Pharma.

This article has an online supplement, which is accessible from this issue's table of contents at www.atsjournals.org

Originally Published in Press as DOI: 10.1164/rccm.200710-1486OC on May 29, 2008

Conflict of Interest Statement: M.C.M. does not have a financial relationship with a commercial entity that has an interest in the subject of this manuscript. G.V.-B. does not have a financial relationship with a commercial entity that has an interest in the subject of this manuscript. J.P. does not have a financial relationship with a commercial entity that has an interest in the subject of this manuscript. J.C. does not have a financial relationship with a commercial entity that has an interest in the subject of this manuscript. J.M. has received an unrestricted grant from Altana Pharma.

Received in original form October 8, 2007; accepted in final form May 28, 2008

	REFERENCES

TOP ABSTRACT AT A GLANCE COMMENTARY METHODS RESULTS DISCUSSION REFERENCES

 

1. Mannino DM. COPD: epidemiology, prevalence, morbidity and mortality, and disease heterogeneity. Chest 2002;121:121S–126S.[CrossRef][Medline]
2. Barnes PJ. Mediators of chronic obstructive pulmonary disease. Pharmacol Rev 2004;56:515–548.[Abstract/Free Full Text]
3. Segura-Valdez L, Pardo A, Gaxiola M, Uhal BD, Becerril C, Selman M. Upregulation of gelatinases A and B, collagenases 1 and 2, and increased parenchymal cell death in COPD. Chest 2000;117:684–694.[CrossRef][Medline]
4. Yokohori N, Aoshiba K, Nagai A. Increased levels of cell death and proliferation in alveolar wall cells in patients with pulmonary emphysema. Chest 2004;125:626–632.[CrossRef][Medline]
5. Kasahara Y, Tuder RM, Cool CD, Lynch DA, Flores SC, Voelkel NF. Endothelial cell death and decreased expression of vascular endothelial growth factor and vascular endothelial growth factor receptor 2 in emphysema. Am J Respir Crit Care Med 2001;163:737–744.[Abstract/Free Full Text]
6. Imai K, Mercer BA, Schulman LL, Sonett JR, D'Armiento JM. Correlation of lung surface area to apoptosis and proliferation in human emphysema. Eur Respir J 2005;25:250–258.[Abstract/Free Full Text]
7. Rahman I. Oxidative stress in pathogenesis of chronic obstructive pulmonary disease: cellular and molecular mechanisms. Cell Biochem Biophys 2005;43:167–188.[CrossRef][Medline]
8. Ryter SW, Kim HP, Hoetzel A, Park JW, Nakahira K, Wang X, Choi AM. Mechanisms of cell death in oxidative stress. Antioxid Redox Signal 2007;9:49–89.[CrossRef][Medline]
9. Martindale JL, Holbrook NJ. Cellular response to oxidative stress: signaling for suicide and survival. J Cell Physiol 2002;192:1–15.[CrossRef][Medline]
10. Roos WP, Kaina B. DNA damage-induced cell death by apoptosis. Trends Mol Med 2006;12:440–450.[CrossRef][Medline]
11. Kimberley FC, Screaton GR. Following a TRAIL: update on a ligand and its five receptors. Cell Res 2004;14:359–372.[CrossRef][Medline]
12. Huang Y, Erdmann N, Peng H, Zhao Y, Zheng J. The role of TNF related apoptosis-inducing ligand in neurodegenerative diseases. Cell Mol Immunol 2005;2:113–122.[Medline]
13. Uberti D, Ferrari-Toninelli G, Bonini SA, Sarnico I, Benarese M, Pizzi M, Benussi L, Ghidoni R, Binetti G, Spano P, et al. Blockade of the tumor necrosis factor-related apoptosis inducing ligand death receptor DR5 prevents beta-amyloid neurotoxicity. Neuropsychopharmacology 2007;32:872–880.[CrossRef][Medline]
14. Wajant H. TRAIL and NFkappaB signaling–a complex relationship. Vitam Horm 2004;67:101–132.[Medline]
15. Li X, Stark GR. NFkappaB-dependent signaling pathways. Exp Hematol 2002;30:285–296.[CrossRef][Medline]
16. Gloire G, Legrand-Poels S, Piette J. NF-kappaB activation by reactive oxygen species: fifteen years later. Biochem Pharmacol 2006;72:1493–1505.[CrossRef][Medline]
17. Morissette M, Parent J, Milot J. TRAIL and Bax-mediated apoptosis, pathways by which apoptosis may be induced in emphysema. ERS Munich 2006. Eur Respir J 2006;28:825S.
18. Morissette M, Parent J, Milot J. Upregulation of the "TNF-related apoptosis-inducing ligand" (TRAIL) receptors and the pro-apoptotic factor bax in emphysematous subjects. FASEB Washington 2007. FASEB J 2007;21:709.1.
19. Rabe KF, Hurd S, Anzueto A, Barnes PJ, Buist SA, Calverley P, Fukuchi Y, Jenkins C, Rodriguez-Roisin R, van Weel C, et al. Global strategy for the diagnosis, management, and prevention of chronic obstructive pulmonary disease: 2006 update. Am J Respir Crit Care Med 2007;176:532–555.[Abstract/Free Full Text]
20. Livak KJ, Schmittgen TD. Analysis of relative gene expression data using real-time quantitative PCR and the 2(-Delta Delta C(T)) Method. Methods 2001;25:402–408.[CrossRef][Medline]
21. Nyunoya T, Monick MM, Klingelhutz A, Yarovinsky TO, Cagley JR, Hunninghake GW. Cigarette smoke induces cellular senescence. Am J Respir Cell Mol Biol 2006;35:681–688.[Abstract/Free Full Text]
22. Wu CH, Lin HH, Yan FP, Wu CH, Wang CJ. Immunohistochemical detection of apoptotic proteins, p53/Bax and JNK/FasL cascade, in the lung of rats exposed to cigarette smoke. Arch Toxicol 2006;80:328–336.[CrossRef][Medline]
23. Griffith TS, Wiley SR, Kubin MZ, Sedger LM, Maliszewski CR, Fanger NA. Monocyte-mediated tumoricidal activity via the tumor necrosis factor-related cytokine, TRAIL. J Exp Med 1999;189:1343–1354.[Abstract/Free Full Text]
24. Morales JC, Ruiz-Magana MJ, Ruiz-Ruiz C. Regulation of the resistance to TRAIL-induced apoptosis in human primary T lymphocytes: role of NF-kappaB inhibition. Mol Immunol 2007;44:2587–2597.[CrossRef][Medline]
25. Robertson NM, Zangrilli JG, Steplewski A, Hastie A, Lindemeyer RG, Planeta MA, Smith MK, Innocent N, Musani A, Pascual R, et al. Differential expression of TRAIL and TRAIL receptors in allergic asthmatics following segmental antigen challenge: evidence for a role of TRAIL in eosinophil survival. J Immunol 2002;169:5986–5996.[Abstract/Free Full Text]
26. Robertson NM, Rosemiller M, Lindemeyer RG, Steplewski A, Zangrilli JG, Litwack G. TRAIL in the airways. Vitam Horm 2004;67:149–167.[Medline]
27. Proulx LI, Pare G, Bissonnette EY. Alveolar macrophage cytotoxic activity is inhibited by 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), a carcinogenic component of cigarette smoke. Cancer Immunol Immunother 2007;56:831–838.[CrossRef][Medline]
28. Zhang L, Fang B. Mechanisms of resistance to TRAIL-induced apoptosis in cancer. Cancer Gene Ther 2005;12:228–237.[CrossRef][Medline]
29. Bonavida B, Ng CP, Jazirehi A, Schiller G, Mizutani Y. Selectivity of TRAIL-mediated apoptosis of cancer cells and synergy with drugs: the trail to non-toxic cancer therapeutics. Int J Oncol 1999;15:793–802.[Medline]
30. Hu H, Jiang C, Schuster T, Li GX, Daniel PT, Lu J. Inorganic selenium sensitizes prostate cancer cells to TRAIL-induced apoptosis through superoxide/p53/Bax-mediated activation of mitochondrial pathway. Mol Cancer Ther 2006;5:1873–1882.[Abstract/Free Full Text]
31. Avila PC, Kropotov AV, Krutilina R, Krasnodembskay A, Tomilin NV, Serikov VB. Peroxiredoxin v contributes to antioxidant defense of lung epithelial cells. Lung 2008;186:103–114.[Medline]
32. Langie SA, Knaapen AM, Houben JM, van Kempen FC, de Hoon JP, Gottschalk RWH, Godschalk RWL, van Schooten FJ. The role of glutathione in the regulation of nucleotide excision repair during oxidative stress. Toxicol Lett 2007;168:302–309.[CrossRef][Medline]
33. Smit-de Vries MP, van der Toorn M, Bischoff R, Kauffman HF. Resistance of quiescent and proliferating airway epithelial cells to H2O2 challenge. Eur Respir J 2007;29:633–642.[Abstract/Free Full Text]
34. Di Stefano A, Caramori G, Ricciardolo FL, Capelli A, Adcock IM, Donner CF. Cellular and molecular mechanisms in chronic obstructive pulmonary disease: an overview. Clin Exp Allergy 2004;34:1156–1167.[CrossRef][Medline]

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