Sinusoidal intercellular adhesion molecule-1 up-regulation precedes the accumulation of leukocyte function antigen-1-positive cells and tissue necrosis in a model of carbontetrachloride-induced acute rat liver injury

Abstract

The mechanisms leading to the infiltration of inflammatory cells into the liver and to liver cell necrosis remain undefined. To elucidate this process, the present work analyzes the kinetics of the expression of intercellular adhesion molecule-1 (ICAM-1) and the accumulation of inflammatory leukocyte function antigen-1 (LFA-1)-positive cells in relation to the appearance of hepatocellular necrosis in the model of acute carbontetrachloride (CCl4)-induced liver injury. ICAM-1- and LFA-1-immunoreactivity was analyzed in normal livers and in livers obtained 3, 6, 9, 12, 18, 24, 48, and 72 hours after CCl4-administration, as well as in liver cells isolated 3, 6, 9, 12, 18, and 24 hours after CCl4-administration. Total RNA extracted from livers and cells was used for Northern blot analysis. ICAM-1-positivity, which was detected along the sinusoids in normal rat livers, increased 3 to 6 hours after CCl4-administration and finally accumulated in the necrotic areas (24 to 48 hours post-administration). ICAM-1 steady-state mRNA levels in liver tissue increased 3 to 6 hours after CCl4-treatment and returned to normal levels at 48 hours after treatment. Increased amounts of ICAM-1-specific transcripts could be observed in isolated sinusoidal endothelial cells and in hepatocytes as early as 3 to 6 hours after CCl4-administration. In normal rat livers, a few LFA-1-immunoreactive cells were present around the vessel walls. Starting 12 hours after CCl4-administration, the number of LFA-1-immunoreactive cells increased around the vessel walls and along the sinusoids, accumulating later in the necrotic areas. In accordance, the number of mononuclear phagocytes isolated from the liver increased 12 hours after CCl4-treatment. These data demonstrate an early up-regulation of ICAM-1 in liver cells and the accumulation of LFA-1-expressing cells prior to the development of necrotic areas. The up-regulation of ICAM-1 and accumulation of inflammatory cells seem to be critical for the induction of CCl4-induced hepatotoxicity.