TUMOR-NECROSIS-FACTOR-ALPHA CELL-SURFACE RECEPTORS OF LIVER PARENCHYMAL AND NONPARENCHYMAL CELLS DURING ACUTE AND CHRONIC ALCOHOL ADMINISTRATION TO RATS

Tumor necrosis factor-alpha (TNF-alpha) has been shown to contribute t o the alcohol [ethanol (ETOH)]-induced alteration of hepatic function. Therefore we tested the hypothesis that the hepatic action of TNF-alp ha could be due, at least in part, to alterations in TNF-alpha cell-su rface receptors of hepatic parenchymal (hepatocytes) and nonparenchyma l (Kupffer and sinusoidal endothelial) cells. Rats were either acutely treated with ETOH by a primed, continuous 7-hr intravenous infusion o f 20% (w/v) ETOH (30 mg/100 g body weight/h) or chronically fed an ETO H-containing liquid diet(5.2% ETCH, w/v, with ETOH as 36% of total cal ories) for 14 weeks. Control rats in the acute group were infused with sterile saline, whereas control rats in the chronic group were fed li quid diet containing dextrin to replace ETOH in isocaloric amounts. Th ree hr before killing, the rats were injected intravenously with Gram- negative bacterial lipopolysaccharide [(LPS) inn (mu g/100 g body weig ht] or saline. Hepatocytes, Kupffer cells, and sinusoidal endothelial cells were isolated after liver perfusion with collagenase (without pr onase), separated by centrifugal elutriation, and used to determine th e affinity (K-d) and capacity (B-max) of binding sites, using recombin ant human-[I-125]TNF-alpha as the ligand. Two binding sites were detec ted on Kupffer cells and sinusoidal endothelial cells isolated from co ntrol animals: a high-affinity (K,,, in the range of 150-200 pm), low- capacity (B-max1), in the range of 2-3 fmol/10(6) cells) binding site and a low-affinity (K-d2 in the range of 2-9 nM), high-capacity (B-max 2 in the range of 3-15 fmol/10(6) cells) binding site. One binding sit e was detected on hepatocytes isolated from control rats (K-d1 = 1.0 n M and a B-max = 95 fmol/10(6) cells). Acute ETCH administration caused an increase in K-d1 on both Kupffer and sinusoidal endothelial cells; a decrease in K-d1 on hepatocytes; and an increase in K-d2, B-max1 an d B-max2 on endothelial cells. A second binding site on hepatocytes (K -d2 = 5.8 nM, B-max2 = 188 fmol/10(6) cells) was observed only in the ETOH; treated group after LPS administration. Chronic alcohol exposure markedly elevated K-d1 and B-max1 on hepatocytes. Overall, LPS-induce d changes mimicked those induced by alcohol, except for a decrease in B-max1 on Kupffer cells of rats in the acute treatment group. Also, th e liquid diet containing alcohol or dextrin abrogated the high-affinit y, low-capacity binding sites on both Kupffer cells and sinusoidal end othelial cells, and low-affinity, high-capacity binding sites on the h epatocyte. After LPS administration, the high-affinity binding sites o n Kupffer and sinusoidal endothelial cells were reexpressed. These dat a show that: (1) ETCH induces changes in both the capacity (B-max) and affinity (K-d) of TNF-alpha cell-surface receptors of hepatocytes, Ku pffer cells, and sinusoidal endothelial cells; and (2) ETOH-induced ch anges are consistent with an increased sensitivity of these cells to t he action of TNF-alpha.