MODIFICATION OF RED-CELL MEMBRANE-LIPIDS BY HYPOCHLOROUS ACID AND HEMOLYSIS BY PREFORMED LIPID CHLOROHYDRINS

Hypochlorous acid (HOCl), a strong oxidant generated by the myeloperox idase system of neutrophils and monocytes, has been implicated in infl ammatory tissue damage by these cells. Reaction of HOCl with the doubl e bonds of unsaturated lipids produces alpha, beta-chlorohydrin isomer s. We have exposed red cell membranes to HOCl and used thin layer chro matography (TLC) of the extracted lipids and enzyme-linked immunosorbe nt assay (ELISA), using an antichlorohydrin monoclonal antibody, to sh ow that fatty acyl chlorohydrins are formed. The ELISA was approximate ly 25 fold more sensitive than TLC, and chlorohydrins were detected wh en membranes from 10(6) cells were treated with greater than or equal to 0.16 nmoles HOCl. Lipid chlorohydrins are more polar and bulky than their parent lipids and as such could affect membrane stability and f unction. To determine the effect of incorporation of lipid chlorohydri ns into cell membranes, preformed fatty acid and cholesterol chlorohyd rins were incubated with red cells. Lysis was measured as release of h aemoglobin and incorporation of lipids was determined by C-14 scintill ation counting. Addition of HOCl-treated oleic acid to red cells resul ted in rapid lysis of a fraction of the cells in a concentration depen dent manner. HOCl-treated cholesterol also caused a small amount of ce ll lysis that was predominantly due to chlorohydrin 3, one of the thre e major cholesterol chlorohydrin products. Chlorohydrin 3, which has a decreased planarity and polarity, was also primarily responsible for altering the critical micelle concentration of HOCl-treated cholestero l-containing liposomes.