Protection of cultured endothelial cells from hydrogen peroxide-induced injury by antibody-conjugated catalase

The cytoprotective features of catalase-antibody conjugate prepared by covalent conjugation of catalase to rabbit antibody against mouse IgG is described. The bifunctional cross-linking agent m-maleimidobenzoic acid N-hydroxysuccinimide ester (MBS) was used for conjugation. Functionally active conjugate binds specifically to the plastic-adsorbed mouse IgG and to the surface of live human endothelial cells treated with mouse antiserum against human endothelial cells. Up to 4 units of catalase activity can bind to 1 cm2 of the endothelial monolayer. The targeted catalase protects endothelial cells from cytotoxic action of hydrogen peroxide: the minimal cytotoxic concentration of H2O2 for protected cells is 80-times higher than for intact cells. This effect is attributed partly to local reduction of H2O2 concentration in the cell microenvironment. Targeted catalase was estimated to reduce H2O2 concentration 8-fold near the cell surface with respect to average total concentration.