Nitric oxide and cGMP regulate endothelial permeability and F-actin distribution in hydrogen peroxide-treated...

We have previously reported that hydrogen peroxide (H2O2) has a concentration-dependent effect on endothelial permeability and F-actin distribution. In the present study, we considered the involvement of endogenous production of nitric oxide (NO) in the indicated effect of H2O2. This was done by measuring endothelial permeability to sodium fluorescein (MW 376 Da, Na-F) and to different-sized fluorescein-isothiocynate-labeled dextrans (FITC-dextrans) and by staining F-actin with rhodamine-labeled phalloidin in cultured bovine aortic endothelial cells growing on filters. A low concentration of H2O2 (10(-5) M) had no effect on either dense peripheral bands of F-actin (DPBs) or permeability. When N-nitro-l-arginine methylester (l-NAME), an inhibitor of NO production, was coadministrated with 10(-5) M H2O2, DPBs were disrupted and the permeability to FITC-dextran 40 and FITC-dextran 70, but not to Na-F and FITC-dextran 20, was increased. Combining of 10(-5) M H2O2 with l-arginine, a substrate for nitric oxide synthase, caused an increase in DPBs and a decrease in permeability to FITC-dextran 40 and FITC-dextran 70. l-arginine or l-NAME alone had no effect on either F-actin structure or endothelial permeability. A 10-fold higher concentration of H2O2 caused a disruption of DPBs and an increase in permeability; this could be prevented by adding l-arginine. An analogue of cGMP, i.e., 8-Br-cGMP, maintained DPBs and abolished the increase in permeability induced by the treatment with either 10(-4) M H2O2 or a combination of H2O2 and l-NAME. These results suggest that the endogenous production of NO is involved in maintaining endothelial junctions in H2O2-treated cells and that this involvement occurs via a cGMP-dependent mechanism.