EFFECT OF DEOXYCHOLIC-ACID AND URSODEOXYCHOLIC ACID ON LIPID-PEROXIDATION IN CULTURED MACROPHAGES

Background-Kupffer cells are essential for normal hepatic homeostasis and when stimulated, they secrete reactive oxygen species, nitric oxid e, eicosanoids, and cytokines. Some of these products are cytotoxic an d attack nucleic acids, thiol proteins, or membrane lipids causing lip id peroxidation. Hydrophobic bile acids, such as deoxycholic acid (DCA ), can damage hepatocytes by solubilising membranes and impairing mito chondrial function, as well as increasing the generation of reactive o xygen species. Objectives-The hypothesis that hydrophobic bile acids c ould stimulate Kupffer cells to increase their capacity to generate re active oxygen species by measuring cellular lipid peroxidation was tes ted. Because the hydrophilic bile acid, ursodeoxycholic acid (UDCA) ca n block hydrophobic bile acid induced cellular phenomena, it was also hypothesised that UDCA could antagonise macrophage activation by hydro phobic bile acids to blunt their capacity to generate reactive oxygen species. Methods-J-774A.1 murine macrophages were incubated for 24 hou rs with either 10(-5) M and 10(-4) M (final concentration) DCA alone, or 10(-4) M UDCA alone, or a mixture of 10(-4) M 1:1 molar ratio of DC A and UDCA. At the end of the incubation period, the culture medium wa s collected for determination of cellular lipid peroxidation by measur ing the malondialdehyde (MDA) content in the medium with the thiobarbi turic acid reactive substances assay. Results-10(-5) M and 10(-4) M DC A increased MDA generation by cultured macrophages. 10(-4) M UDCA alon e did not increase MDA generation but blocked the peroxidative actions of DCA. Conclusions-Hydrophobic bile acids, after their hepatic reten tion, can oxidatively activate Kupffer cells to generate reactive oxyg en species. Because UDCA can block this action, the beneficial effect of UDCA is, in part, related to its ability to act as an antioxidant.