PROTECTIVE EFFECTS OF BILE-ACIDS AGAINST LIPOPOLYSACCHARIDE-INDUCED MEMBRANE FRAGILITY IN RAT ERYTHROCYTES

The interaction between lipopolysaccharide (LPS) and bile acids was studied in rat erythrocyte membranes. Addition of LPS isolated from E. coli (J5 mutant) to erythrocytes resulted in a decrease in the membrane fluidity as determined by spin labeling using electron spin resonance (ESR). This was accompanied by membrane fragility. The generation of hydroxyl radicals in the LPS-treated erythrocytes was detected by ESR spin trapping. However, pretreatment of erythrocytes with taurine-conjugated bile acids, i.e., taurocholic acid (TCA), tauroursodeoxycholic acid (TUDCA), and taurochenodeoxycholic acid (TCDCA), modified the membrane damage induced by LPS. TCA and TUDCA prevented the decrease in membrane fluidity induced by LPS; and as a result, the membrane integrity was maintained although no significant changes were observed in the amount of hydroxyl radicals produced by LPS addition. However, TCDCA exhibited little beneficial effect on the dynamic properties and function of the erythrocyte membrane, although the hydroxyl radical content declined markedly in erythrocytes treated with it. Therefore, our data suggest that TCA and TUDCA have a protective effect against LPS-induced membrane fragility by modulating membrane fluidity.