PGE1-induced NO reduces apoptosis by D-galactosamine through attenuation of NF-κB and NOS-2 expression in rat hepatocytes
✍ Scribed by Emilio Siendones; Dalia Fouad; María José M. Díaz-Guerra; Manuel de la Mata; Lisardo Boscá; Jordi Muntané
- Publisher
- John Wiley and Sons
- Year
- 2004
- Tongue
- English
- Weight
- 235 KB
- Volume
- 40
- Category
- Article
- ISSN
- 0270-9139
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✦ Synopsis
Prostaglandin E 1 (PGE 1 ) reduces cell death in experimental and clinical liver dysfunction. We have previously shown that PGE 1 preadministration protects against NO-dependent cell death induced by D-galactosamine (D-GalN) through a rapid increase of nuclear factor B (NF-B) activity, inducible NO synthase (NOS-2) expression, and NO production. The present study investigates whether PGE 1 -induced NO was able to abolish NF-B activation, NOS-2 expression, and apoptosis elicited by D-GalN. Rat hepatocytes were isolated following the classical method of collagenase perfusion of liver. PGE 1 (1 mol/L) was administered 2 hours before D-GalN (5 mmol/L) in primary culture rat hepatocytes. PGE 1 reduced inhibitor B␣ degradation, NF-B activation, NOS-2 expression, and apoptosis induced by D-GalN. The administration of an inhibitor of NOS-2 abolished the inhibitory effect of PGE 1 on NF-B 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 PGE 1 regulate NOS-2 expression through NF-B during the initial stage of hepatocyte treatment. PGE 1 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 PGE 1 to hepatocytes produces low levels of NO, which inhibits its own formation during D-GalN-induced cell death through the attenuation of NF-Bdependent NOS-2 expression. Therefore, a dual role for NO in PGE 1 -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.)
P rostaglandins are biologically active polyunsaturated fatty acids derived from arachidonic acid present in most mammalian tissues. 1 Prostaglandin E 1 (PGE 1 ) reduces liver injury induced experimentally 2 and in fulminant viral hepatitis in humans. 3 PGE 1 exerts most of its effects by promoting membrane stabilization, 4 , hepatocyte proliferation, 5 vasodilation, 6 and inhibition of fibrogenesis. 7 The preadministration of PGE 1 also reduces liver injury through the enhancement of inducible NO synthase (NOS-2) expression in hepatocytes. 8 Nevertheless, the detailed molecular mechanism through which PGE 1 regulates NOS-2 expression is not completely understood. It is clearly established that the effects of PGE result from its binding to its receptors, EP 1 , EP 2 , and EP 4 , all of which can stimulate the production of the second messenger cyclic 3Ј,5Ј adenosine monophosphate (cAMP). This messenger induces NOS-2 expression in numerous cell types, including vascular smooth