Ethanol increases tumor necrosis factor-alpha receptor-1 (TNF-R1) levels in hepatic, intestinal, and cardiac cells

Abstract

Chronic ethanol consumption leads to cell injury in virtually every tissue. Tumor necrosis factor-alpha (TNF-α) constitutes a major factor in the development of alcohol-induced liver injury. In alcohol-dependent subjects, elevated levels of plasma TNF-α are strongly predictive of mortality. Binding of TNF-α to TNF-α receptor-1 (TNF-R1) activates death domain pathways, leading to necrosis and apoptosis in most tissues, and it also increases the expression of intercellular adhesion molecules (i.e., ICAM-1), which promote inflammation. We determined whether ethanol exposure leads to increases in cellular TNF-R1. We incubated HepG2 human hepatoma cells and H4-II-E-C3 rat hepatoma cells with 25, 50, and 100 mM ethanol for various intervals of time up to 48 h. Human colonic adenocarcinoma cells (Caco-2 cells) and neonatal rat primary cardiomyocytes were also incubated with different concentrations of ethanol. Levels of TNF-R1 were measured either by a sandwich enzyme-linked immunosorbent assay (ELISA) method or by determining the extracellular transmembrane domain of TNF-R1 by an intact-cell ELISA method. Ethanol exposure for 48 h increased TNF-R1 levels in human hepatoma cells in a dose-dependent manner. Levels increased significantly by 164% at 50 mM and by 240% at 100 mM ethanol. Effects were time dependent and did not reach a plateau at 48 h. Similar increases in TNF-R1 were also observed in rat hepatoma cells (90% at 50 mM and 230% at 100 mM ethanol). Under similar conditions, Caco-2 cells showed a significant 80% increase in TNF-R1 levels at 200 mM ethanol, a concentration found in intestine. Neonatal rat primary cardiomyocytes showed TNF-R1 increases of 36% at 50 mM and 44% at 100 mM ethanol. These results indicate that exposure of different cell types to pharmacologic concentrations of ethanol increases TNF-R1 levels and may augment TNF-α-mediated cell injury in different tissues.

Keywords: Tumor necrosis factor-alpha (TNF-α), Ethanol, Hepatoma, Tumor necrosis factor receptor-1 (TNF-R1), Liver injury