| Popis: |
Multiple lines of experimental evidence demonstrate that chronic alcoholconsumption causes mitochondrial injury, as well as acinar cell oxidative and metabolicstress. Alcoholics are more susceptible to acute and chronic pancreatitis. Despite alcoholrelatedacinar cell injury, apoptosis, or programmed cell death, appears to be reduced inacinar cells rather than increased, as is seen in the liver.This work describes the possible mechanisms through which alcohol affects theacinar cell apoptosis pathways in the rat pancreas. Two apoptotic pathways wereinvestigated: (1) receptor-mediated apoptosis via Fas/FasL and caspase-8, and (2)mitochondrial-mediated apoptosis via Bcl-2/Bax and caspase-9. Both pathways canactivate the final apoptosis executer caspase-3. Using the Lieber-DeCarli alcohol/controldiet, rats fed alcohol for 14 weeks had a significant decrease of key mediators of theFas/Fas ligand receptor-mediated pathway, while the mitochondria-associated apoptoticpathway is inappropriately deactivated. In addition, this study describes the mRNAexpression of inflammatory cytokines, such as IL-1??, IL-6, TNF??, IL-18 and TGF??,which are reported to influence inflammation and apoptosis. The anti-inflammatoryeffects of alcohol were confirmed with decreased expression of regulatory cytokinesincluding IL-1??, IL-18, TGF?? and IL-6 in alcohol-fed rats.Alcohol appears to block apoptosis in the pancreas through multiple mechanisms.Activity of the Fas/Fas ligand receptor-mediated pathway appears to be suppressed at thelevel of caspase-8, with further inhibition by down-regulation of caspase-3. Despiteknown acinar cell stress and mitochondria injury, the mitochondria-mediated apoptoticpathway was not activated. This data suggest that alcohol consumption suppresses theremoval of mitochondria injured acinar cells, promoting apoptosis resistance, and mayincrease the susceptibility to pancreatitis. The increased susceptibility to pancreatic injurywas further investigated by using lipopolysaccharide (LPS). Alcohol exacerbates LPSinducedpancreatoxicity by enhanced pancreatic apoptosis. The attenuation of apoptosisby ethanol increased the threshold of apoptosis in response to LPS and acceleratesapoptosis. Here it is hypothesized that alcoholics are more susceptible to endotoxinmediatedacute pancreatitis and the response is more severe than in non-alcoholics. |
