PGE1-induced NO reduces apoptosis by D-galactosamine through attenuation of NF-kappaB and NOS-2 expression in rat hepatocytes

Prostaglandin E1 (PGE1) reduces cell death in experimental and clinical liver dysfunction. We have previously shown that PGE1 preadministration protects against NO-dependent cell death induced by D-galactosamine (D-GalN) through a rapid increase of nuclear factor κB (NF-κB) activity, inducible NO synthase (NOS-2) expression, and NO production. The present study investigates whether PGE1-induced NO was able to abolish NF-κB activation, NOS-2 expression, and apoptosis elicited by D-GalN. Rat hepatocytes were isolated following the classical method of collagenase perfusion of liver. PGE1 (1 μmol/L) was administered 2 hours before D-GalN (5 mmol/L) in primary culture rat hepatocytes. PGE1 reduced inhibitor κBα degradation, NF-κB activation, NOS-2 expression, and apoptosis induced by D-GalN. The administration of an inhibitor of NOS-2 abolished the inhibitory effect of PGE1 on NF-κB activation and NOS-2 expression in D-GalN–treated hepatocytes. Transfection studies using different plasmids corresponding to the NOS-2 promoter region showed that D-GalN and PGE1 regulate NOS-2 expression through NF-κB during the initial stage of hepatocyte treatment. PGE1 was able to reduce the promoter activity induced by D-GalN. In addition, a NO donor reduced NOS-2 promoter activity in transfected hepatocytes. In conclusion, administration of PGE1 to hepatocytes produces low levels of NO, which inhibits its own formation during D-GalN–induced cell death through the attenuation of NF-κB–dependent NOS-2 expression. Therefore, a dual role for NO in PGE1-treated D-GalN–induced toxicity in hepatocytes is characterized by a rapid NO release that attenuates the late and proapoptotic NOS-2 expression. Supplementary material for this article can be found on the HEPATOLOGY website (http://interscience.wiley.com/jpages/0270-9139/suppmat/index.html). (HEPATOLOGY 2004;40:1295–1303.)