Abstract
This study demonstrates that exposure of primary rat hepatocytes or mouse BNL Cl.2 liver cell line to ethanol causes potentiation of tumor necrosis factor-α (TNF-α)- and lipopolysaccharide (LPS)-stimulated nitrite accumulation. The potentiating effect of ethanol (0.02–2 mm ) appears to be time and concentration dependent. Consistent with nitrite production, the amount of inducible nitric oxide synthase (iNOS) mRNA and protein is initially detected at 4 hr after treatment with TNF-α/LPS/ethanol. Furthermore, the capability of these agents to induce iNOS expression is primarily determined by the age of the animals. Interestingly, antioxidants such asN-acetylcysteine (NAC), ascorbic acid, or α-tocopherol fail to inhibit TNF-α/LPS/ethanol-induced increase in iNOS protein. In addition, several kinase inhibitors, including staurosporine, genistein, curcumin, and herbimycin A, were used to examine their effects on this induction. Among them, only herbimycin A potently inhibits the accumulation of nitrite and iNOS expression. In vitro kinase assay verifies that Src tyrosine kinase is rapidly activated with a peak at 1 hr after treatment with TNF-α/LPS/ethanol but is not activated by these agents singly or doubly. As expected, herbimycin A can block Src kinase activity under circumstances in which iNOS expression is also inhibited. However, our results do not indicate that the mitogen-activated protein kinase is activated after treatment with these agents. The study results suggest that Src tyrosine kinase plays a prominent role in transducing the signal to induce iNOS expression in hepatocytes treated with TNF-α/LPS/ethanol.
- The American Society for Pharmacology and Experimental Therapeutics
MolPharm articles become freely available 12 months after publication, and remain freely available for 5 years.Non-open access articles that fall outside this five year window are available only to institutional subscribers and current ASPET members, or through the article purchase feature at the bottom of the page.
|