Protection against liver injury by PGE1 or anti‐TNF‐α is associated with a reduction of TNF‐R1 expression in hepatocytes

Abstract

Background: Tumour necrosis factor‐α (TNF‐α) has been shown to exacerbate or protect against liver injury in different experimental models. In a previous study, we observed that enhancement of TNF‐α expression in hepatocytes by prostaglandin E ₁ (PGE ₁ ) pre‐administration induced iNOS expression and cytoprotection against experimental liver injury in rats. Nevertheless, the reduction of TNF‐α bioactivity by anti‐TNF‐α antibodies also reduced liver injury by D‐GalN. The purpose of the present study was to evaluate whether protection by PGE ₁ or anti‐TNF‐α was related to a common effect on the membrane‐bound TNF‐α receptor expression. Methods: Liver injury was induced in male Wistar rats by intraperitoneal injection of D‐galactosamine (D‐GalN) (1 g/kg). PGE ₁ or anti‐TNF‐α was administered at 30 or 60 min before D‐GalN, respectively. Liver injury was evaluated by alanine aminotransferase (ALT) activity in serum and histological examination in liver sections. TNF‐αwas determined by ELISA in serum. The expression of TNF‐α receptor type 1 (TNF‐R1) and TNF‐α receptor type 2 (TNF‐R2) in hepatocytes was assessed by immunohistochemistry and immunoprecipitation + Western‐blot analysis. Results: PGE ₁ or anti‐TNF‐α reduced liver injury induced by D‐GalN. Although PGE ₁ enhanced and anti‐TNF‐α reduced TNF‐α concentration in serum, both protective treatments reduced the expression of TNF‐R1 in hepatocytes. TNF‐R2 was not detected in our experimental conditions. Conclusions: Our study showed that reduction of liver injury by PGE ₁ or anti‐TNF‐α antibodies was related to a reduction of TNF‐R1 expression in hepatocytes.

• D‐galactosamine
• liver injury
• prostaglandin E1
• receptor
• TNF‐α
• TNF‐R1
• TNF‐R2