Chronic alcohol exposure of rats exacerbates apoptosis in hepatocytes and sinusoidal endothelial cells

Background/aims: The liver apoptotic response to chronic alcohol consumptio n remains poorly characterized. The purpose of this study was to determine in rats the effects of chronic alcohol consumption on the relative magnitud e of apoptosis in two major targets of alcohol-induced liver injury: the he patocyte (Hep) and sinusoidal endothelial cell (SEC). Methods: Rats were fe d a liquid diet containing either alcohol or isocaloric amounts of maltose- dextrin for 14 weeks. Hep and SEC were isolated by liver perfusion with col lagenase followed by centrifugal elutriation. The state of the liver was as sessed on the basis of light microscopic appearance, plasma liver enzymes ( alanine and aspartate:2-oxoglutarate amino transferases), and the content o f malondialdehyde in Hep. Apoptosis was assessed on the basis of DNA fragme ntation in the whole organ (TUNEL), and caspase-3 and -8 activity in isolat ed cells, A mechanistic approach was also undertaken by measuring mRNA expr ession and the amount of protein for Fas/CD95, Fas ligand, caspase-3, Bax, Bcl-X-L, and Bcl-2 in the isolated Hep and SEC. Results: The livers of alco hol-fed rats displayed prominent steatosis. Oxidative stress was also prese nt as reflected by an increase in the malondialdehyde content of Hep. Alcoh ol consumption increased apoptosis in the whole liver assessed on the basis of TUNEL procedure and in Hep and SEC as reflected by significant increase in caspase-3 activity. Of the multiple pro- and anti-apoptotic factors det ermined in this study, significant changes as assessed by both mRNA express ion and the amount of proteins, were observed only in the SEC compartment. Conclusions: The data presented in this study indicate that: (1) chronic al cohol consumption in rats leads to a moderate augmentation of apoptosis in the whole liver and in two liver cell types which are targets for injury in alcoholic liver disease: Hep and SEC; (2) the mechanisms recruited/activat ed by these two types of liver cells to initiate and execute apoptosis in r esponse to alcohol vary with the cell type. (C) 2001 Elsevier Science Irela nd Ltd. All rights reserved.