ABSTRACT
Macrophages are known to release a number of different inflammatory mediators with cytotoxic potential. In the present studies we analyzed the role of two macrophage-derived mediators, tumor necrosis factor-alpha (TNF-alpha) and nitric oxide, in liver injury induced by carbon tetrachloride (CCl4). Treatment of mice with CCl4 resulted in a dose- and time-dependent induction of centrilobular hepatic necrosis. This was observed within 12 h with 0.3 ml/kg CCl4 and was correlated with increases in serum transaminase levels. CCl4 administration also caused increases in hepatic TNF-alpha mRNA expression and serum TNF-alpha levels, as well as inducible nitric oxide synthase (NOS II) protein expression in the liver. To study the role of TNF-alpha and nitric oxide in hepatotoxicity, we used knockout mice lacking the gene for the 55-kDa TNF-alpha receptor (TNFR1/p55), the TNF-alpha cytokine, or NOS II. We found that CCl4 was significantly less effective in inducing hepatotoxicity in mice lacking TNFR1/p55 or the TNF-alpha cytokine. In contrast, CCl4-induced liver injury was increased in knockout mice lacking the gene for NOS II. This was associated with an increase in hepatic TNF-alpha mRNA expression and serum TNF-alpha levels. These data suggest that the hepatoprotective effects of nitric oxide in this model may be due in part to inhibition of TNF-alpha.
Subject(s)
Carbon Tetrachloride/toxicity , Chemical and Drug Induced Liver Injury/metabolism , Liver/metabolism , Nitric Oxide/metabolism , Tumor Necrosis Factor-alpha/metabolism , Acute Disease , Animals , Blotting, Western , Chemical and Drug Induced Liver Injury/pathology , Dose-Response Relationship, Drug , Female , Liver/drug effects , Liver/pathology , Mice , Mice, Inbred C57BL , Mice, Knockout , Mice, Transgenic , Nitric Oxide/genetics , Nitric Oxide Synthase/genetics , Nitric Oxide Synthase/metabolism , Nitric Oxide Synthase Type II , RNA/isolation & purification , RNA, Messenger/metabolism , Reverse Transcriptase Polymerase Chain Reaction , Species Specificity , Tumor Necrosis Factor-alpha/geneticsABSTRACT
Chronic ethanol consumption is associated with increased incidence of hepatic and pulmonary infections. To determine if this is correlated with altered macrophage activity, we analyzed the functional properties of cells isolated sequentially from the liver and lung of rats fed a liquid diet containing ethanol (35% of calories) or malto-dextrin control for 9-12 weeks. Hepatic and alveolar macrophages from control animals were found to exhibit distinct morphologic and functional properties. Thus, hepatic macrophages were highly vacuolated and appeared larger and more irregular in shape than alveolar macrophages. These cells also displayed greater phagocytic activity and random migration. In contrast, lung macrophages produced more superoxide anion and nitric oxide, and exhibited enhanced chemotactic activity toward the complement fragment C5a. Whereas administration of ethanol to rats for 9-12 weeks resulted in decreased chemotaxis and superoxide anion production by alveolar macrophages, cell adhesion molecule expression was reduced in hepatic macrophages. Nitric oxide production and inducible nitric oxide synthase protein expression were decreased in both macrophage populations. These effects were not observed after 3-6 weeks of ethanol administration to rats. Our results suggest that changes in macrophage functioning may play a role in decreased host defense following chronic ethanol exposure.
