Increased p53 level, Bax/Bcl-x(L) ratio, and TRAIL receptor expression in human emphysema.
BACKGROUND
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.


OBJECTIVE
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.


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.
Centre de Recherche de l'Hôpital Laval, Institut Universitaire de Cardiologie et de Pneumologie de l'Université Laval, Quebec City, Canada.
Mathieu C
MC
Morissette
Guillaume
G
Vachon-Beaudoin
Julie
J
Parent
Jamila
J
Chakir
Julie
J
Milot
D000368:Aged; D017209:Apoptosis / Q000502:physiology; D002460:Cell Line; D015331:Cohort Studies; D004847:Epithelial Cells / Q000378:metabolism; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D018384:Oxidative Stress / Q000502:physiology; D011650:Pulmonary Alveoli / Q000378:metabolism* / Q000503:physiopathology; D011656:Pulmonary Emphysema / Q000378:metabolism* / Q000503:physiopathology; D012907:Smoking / Q000009:adverse effects / Q000503:physiopathology; D053221:TNF-Related Apoptosis-Inducing Ligand / Q000378:metabolism*; D014409:Tumor Necrosis Factor-alpha / Q000502:physiology; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*; D051028:bcl-2-Associated X Protein / Q000378:metabolism*; D051020:bcl-X Protein / Q000378:metabolism*
C494811:BCL2L1 protein, human; D053221:TNF-Related Apoptosis-Inducing Ligand; C505653:TNFSF10 protein, human; D014409:Tumor Necrosis Factor-alpha; D016159:Tumor Suppressor Protein p53; D051028:bcl-2-Associated X Protein; D051020:bcl-X Protein