Hypochlorous acid and human blood low density lipoproteins modified by hypochlorous acid increase erythrocyte adhesion to endothelial cells

The ability of hypochlorous acis (HOCl) (anion form - hypochlorite, OCl-) a nd HOCl/OCl- modified human blood low density lipoproteins (HOCl-LDLs) to s timulate erythrocyte adhesion to endothelial cell monolayers was studied. L DLs were modified by incubating at different HOCl/OCl- concentrations, This lead to a damage of proteins and lipids. We found (1) a more than 20-fold decrease of LDL fluorescence intensity (exinction at 285 nm. emission at 34 0 nm), (2) accumulation of secondary (TBA-reactive substances) and final (S chiff bases) products of lipid peroxidation, and (3) increase in the electr ophoretic mobility of LDL. Preincubation of endothelial cells (ECs) with HO Cl/OCl- (up to 50 mu M) enhanced erythrocyte adhesion to the EC monolayer. Preincubation of ECs with HOCl-LDLs (up to 250 mu M of HOCl/OCl- during LDL modification) (1) caused an increase in the cholesterol/phosplolipid molar ratio in ECs and (2) enhanced adhesion of erythrocytes to the endothelium. Application of HOCl/OCl- at concentrations above 50 mu M or treatment of L DLs with 500 mu M HOCl resulted in the cytotoxic effect on ECs and led to d ecreases in the molar cholesterol/phospholipid ratio in ECs and adhesion of erythocytes to the endothelium. The results suggest that HOCl/OCl- at phys iological concentrations stimulates the adhesion of blood cells to the endo thelium and cholesterol accumulation in the Vessel wall ECs either directly or due to LDL modification. Both effects might be important in the develop ment of many vascular diseases.