Hydrogen peroxide induces leukocyte rolling: Modulation by endogenous antioxidant mechanisms including NO

In this study, intravital microscopy was used to examine the mechanisms that regulate H2O2-induced leukocyte rolling within rat mesenteric venules in vivo. H2O2 elicited leukocyte rolling within a narrow response window between 10 and 500 mu M H2O2. Continuous superfusion with 100 mu M H2O2 induced a large but transient increase in the flux of rolling leukocytes, whereas a short 5-min pulse elicited a sustained increase in rolling flux. Both treatments caused increases in leukocyte adhesion. H2O2-induced increases in leukocyte flux and adhesion could be prevented with an anti-P-selectin antibody. Inhibition of endogenous catalase (aminotriazole), glutathione (diethyl maleate), or nitric oxide (N-G-nitro-L-arginine methyl ester) shifted the effective concentration of H2O2; continuous superfusion with 10 mu M H2O2 now elicited large and sustained increases in leukocyte rolling flux, whereas 100 mu M H2O2 elicited less than optimal responses. Dual antioxidant inhibition further reduced the effective H2O2 concentration to 1 mu M H2O2. A nitric oxide donor prevented the increased rolling flux induced by 100 mu M H2O2. These findings suggest that endogenous antioxidants are important regulators of H2O2-induced, P-selectin-dependent leukocyte rolling in vivo.