Prevention of deoxycholate-induced gastric apoptosis by aspirin: roles of NF-kappaB and PKC signaling.
BACKGROUND
Apoptosis is a major mechanism of gastric cell death induced by deoxycholate (DC) and aspirin (ASA), and the caspase cascade and protein kinase C (PKC) signaling play key roles in this process. The transcription factor kappa B (NF-kappaB) has been shown to modulate apoptosis by regulating the transcription of numerous pro- and anti-apoptotic genes. The aim of this study was to investigate the effect of DC and ASA on NF-kappaB signaling, and determine its role in programmed cell death in a human gastric carcinoma cell line.


METHODS
Cells were incubated with DC in the presence or absence of ASA or proteasome inhibitors (PI- I, lactacystin, and MG-132). Cell lysates were evaluated by Western blotting. NF-kappaB (p65) was measured in the cytosol and nuclear fractions.


RESULTS
DC induced a translocation of NF-kappaB into the nuclear compartment that was completely blocked by proteasome inhibitors. Although, ASA itself had no effect on the NF-kappaB pathway, nor did it reduce DC-induced NF-kappaB translocation, it did prevent DC-induced caspase-3, -6 and -9 activation, poly (ADP-ribose) polymerase and lamin A processing, DNA degradation, and PKC signaling, all indices of apoptosis. In contrast, proteasome inhibitors had no effect on DC-induced apoptosis.


CONCLUSIONS
Deoxycholate activates NF-kappaB at the same time that it induces apoptosis in gastric epithelial cells. Prevention of NF-kappaB activation does not alter DC-induced apoptosis, indicating that in our experimental conditions, NF-kappaB is not essential for apoptosis to proceed. In contrast, the ability of aspirin to restore the alterations in PKC isoforms induced by DC and at the same time prevent caspase cascade activation suggests the importance of the PKC signaling system in this process.
Redlak
Maria J
MJ
Department of Surgery, Medical College of Virginia Campus of Virginia Commonwealth University, Richmond, Virginia.
Power
Jacinda J
JJ
Miller
Thomas A
TA
D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D001241:Aspirin / Q000494:pharmacology*; D061945:Caspase Inhibitors; D045744:Cell Line, Tumor; D002756:Cholagogues and Choleretics / Q000009:adverse effects / Q000494:pharmacology; D024161:Collagen Type XI / Q000037:antagonists & inhibitors; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D003840:Deoxycholic Acid / Q000009:adverse effects / Q000494:pharmacology*; D006801:Humans; D016328:NF-kappa B / Q000378:metabolism*; D011493:Protein Kinase C / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects; D013274:Stomach Neoplasms / Q000473:pathology*
D000894:Anti-Inflammatory Agents, Non-Steroidal; C499319:COL11A2 protein, human; D061945:Caspase Inhibitors; D002756:Cholagogues and Choleretics; D024161:Collagen Type XI; D015853:Cysteine Proteinase Inhibitors; D016328:NF-kappa B; D003840:Deoxycholic Acid; D011493:Protein Kinase C; D001241:Aspirin