The major function of liver endothelial cells (LECs) is in host defense and homeostasis via their so-called """"""""scavenger"""""""" function whereby they recognize, internalize an degrade a variety of extracellular matrix components and modified proteins. Reports from out laboratory have shown that LECs from control rats are capable of binding to and degrading the recently characterized malondialdyhyde-acetaldehyde (MAA) adduct, chronic ethanol consumption results in a 50-60 percent decrease in degradation of this ligand to LECs frm either ethanol-fed or control rates were observed. It has also been shown that soluble MSS-adducts cause LECs to upregulate the expression of adhesion molecules (ICAM-1, VCAM-1), and increase the secretion of various cytokines/chemokines (TNF-alpha, MCP-1 and MIP-2). Thus these data stronglyu suggest that there are a family of receptors, designated scavenger receptors, which appear to mediate many of the biological functions of LECs in response to MAA-modified proteins. Under normal conditions, MAA-modified proteins appear to bind to scavenger receptors on LECs and are degraded. However, following chronic ethanol consumption, there is a decrease in the degradation of these adducts. This may cause th MAA-adducts to bind to another receptor(s), thereby initiating a signal cascade in LECs that may result in the stimulation of inflammatory and/or fibrotic responses. Therefore, these studies have led to the hypothesis that following chroni ethanl consumption, hepatocyte MAA- modified protein(s) are released into the surrounding tissues. However, chronic alochol exposure alters the binding of MAA-modified proteins to its receptor(s) such that there is a decrease in protein degradation and an increased in the release of pro-inflammatory and pro-fibrotic mediators. Therefore, the principal objective of this research project is to define and characterize the receptor(s) on LECs responsible for the binding of MAA- modified proteins. Initially, the functional consequences of binding of MAA-modified proteins to LECs will be addressed by examining the effects of MAA-adducts on the expression of adhesion molecules, the secretion of the chemokines/cytokines and the release of fibronectin. The specificity of this/these receptor(s) will then be investigated using various ligands, antibodies and chemical inhibitors for scavenger receptor. Additionally, two factors regulating the expression of genes in inflammatory (AP-1) will be examined as mediators of MAA-adduct induced effects. Finally, we will evaluate the role of MAA-adducts in hepatotoxicity in animal models known to perpetuate MAA- adducts formation by way of chronic ethanol ingestion and administration of agents that induce lipid peroxidation.
