Activation of Kupffer cells during the course of carbon tetrachloride-induced liver injury and fibrosis in rats

Kupffer cells are involved in the pathogenesis of chemically mediated liver injury through release of biologically active mediators that promote the pathogenic process. The purpose of this study was to elucidate specific biochemical and molecular changes occurring in Kupffer cells throughout a time course of carbon tetrachloride (CCl4)-mediated liver injury and fibrosis. Rats were administered 1 ml/kg of CCl4 (10% v/v olive oil) twice weekly for up to 6 weeks. Plasma alanine aminotransferase values and hematoxylin-and-eosin- and trichrome-stained liver sections indicated minor liver damage at 2 weeks followed by increased damage and collagen deposition by 4 and 6 weeks. Additionally, mRNA levels in Kupffer cells isolated from CCl4-treated rats demonstrated significant increases in tumor necrosis factor alpha (TNFalpha); tumor growth factor beta; interleukin-6 (IL-6); interleukin 1beta; cyclooxygenase 2; CD 14, and IkappaBalpha transcripts after 2 and 4 weeks of treatment. However, the expression of these genes at 6 weeks was similar to that of controls. Increased gene expression of cytokines in Kupffer cells isolated from CCl4-treated rats was accompanied by increases in protein production of TNFalpha, IL-6, IL-1beta, and interleukin 10 following lipopolysaccharide stimulation. Further, liver sections stained for ED2-positive cells demonstrated an increase in the number of resident macrophages at 2 and 4 weeks with a slight decrease in ED2-positive cells by week 6 but still significantly more than control. Analysis of reduced glutathione (GSH) and oxidized glutathione (GSSG) indicated that Kupffer cells from CCl4-treated animals exhibited a 50% decrease in GSH at 2 and 4 weeks, whereas no significant changes were observed for GSSG. In conclusion, these data implicate Kupffer cells as a critical mediator of the inflammatory and fibrogenic responses during CCl4-mediated liver damage and provide new insight into the temporal molecular and biochemical changes associated with the ability of these resident macrophages to modulate liver injury. (C) 2001 Elsevier Science.