NADPH oxidase activity is higher in cerebral versus systemic arteries of four animal species: role of Nox2.

We previously reported that NADPH oxidase activity is greater in intracranial cerebral versus systemic arteries of the rat. Here, we first tested whether NADPH oxidase activity is also greater in intracranial cerebral than systemic arteries of three other animal species, i.e., mouse, rabbit, and pig. Second, using Nox2-deficient mice, we evaluated the involvement of Nox2-containing NADPH oxidases in any such regional differences. NADPH-stimulated superoxide (O(2)(-)) production by basilar, middle cerebral arteries (MCA), and common carotid arteries (CA) and thoracic aorta (AO) from rat, mouse, rabbit, and pig was measured using lucigenin-enhanced chemiluminescence. Basal production of O(2)(-) and hydrogen peroxide (H(2)O(2)) by cerebral arteries, AO, and CA from wild-type (WT) and Nox2(-/-) mice was measured using L-012-enhanced chemiluminescence and Amplex Red fluorescence, respectively. Western blotting was used to measure Nox2 and SOD1-3 protein expression, and immunofluorescence was used to localize Nox2, in mouse arteries. In rats, WT mice, rabbits, and pigs, NADPH-stimulated O(2)(-) production by cerebral arteries was up to 40-fold greater than that in AO and CA. In WT mice, basal O(2)(-) and H(2)O(2) production by cerebral arteries was ninefold and approximately 2.5-fold higher, respectively, than that in AO and CA and was associated with approximately 40% greater expression of Nox2 protein. Nox2 immunofluorescence was localized to the endothelium, and to a lesser extent the adventitia, in all mouse arteries and appeared to be more intense in endothelium of MCA than AO or CA. In Nox2(-/-) mice, NADPH-stimulated O(2)(-) production by cerebral arteries was approximately 35% lower than that in WT mice, whereas Nox2 deletion had no significant effect on O(2)(-) production by AO or CA. Thus NADPH oxidase activity is greater in intracranial cerebral versus systemic arteries of several animal species and is associated with higher cerebrovascular expression and activity of Nox2.

Adventitial application of the NADPH oxidase inhibitor apocynin in vivo reduces neointima formation and endothelial dysfunction in rabbits.

OBJECTIVE: Reactive oxygen species including superoxide have been shown to promote atherogenesis. We previously showed that a major source of superoxide, the NADPH oxidase system, is upregulated in the intima and adventitia during remodelling induced by periarterial collars in rabbits. We have now examined the action of the NADPH oxidase inhibitor apocynin, given via the adventitia, on the neointima formation and endothelial function in this model. METHODS: Perivascular collars were implanted around the common carotid arteries of male NZW rabbits for 14 days to induce intimal thickening. The periarterial space of one collar was filled with apocynin (1 mM) while the contralateral collar with the vehicle (0.1% DMSO). RESULTS: After 14 days, local treatment with apocynin via the adventitia, reduced superoxide generation. In addition, apocynin significantly reduced neointima formation and proliferation of cells in both the neointima and adventitia. Moreover, NO-dependent vasorelaxation to acetylcholine, which is normally impaired in collared arteries, was improved, and apocynin suppressed the endothelial expression of intracellular adhesion molecule-1 and vascular cell adhesion molecule-1. CONCLUSIONS: NADPH oxidase is implicated in vascular remodelling and superoxide-stimulated cell proliferation in the neointima contributes to intimal hyperplasia in this collar model. Targeting NADPH oxidase via adventitial drug delivery not only reduces superoxide generation, but also normalises endothelial cell function. Targeting the primary source of NADPH oxidase-derived superoxide is an effective approach to prevent deleterious arterial remodelling, providing a rationale for designing more efficacious and selective inhibitors of vascular NADPH oxidase as potential therapeutics for human vascular disease.

Connexin37 is the major connexin expressed in the media of caudal artery.

OBJECTIVE: To determine the connexins (Cxs) involved in intercellular coupling within vascular muscle, the present study has quantified mRNA and protein expression for Cx37, Cx40, Cx43, and Cx45 in the caudal artery (CA) and thoracic aorta (ThA) of the rat. METHODS AND RESULTS: Real-time polymerase chain reaction and immunohistochemistry identified Cx37 as the most abundantly expressed Cx in the CA, with fine punctate staining observed in the media. Conversely, mRNA for Cx43 was 40-fold greater in the ThA than in the CA, with punctate staining in the endothelium and media of the ThA but confined to the endothelium in the CA. Western blotting confirmed the differences in the relative amounts of Cx43 between the 2 vessels. For both arteries, Cx45 was expressed to a lesser degree in the media but not in the endothelium, whereas Cx40 was found only in the endothelium. Cx37, Cx40, and Cx43 were expressed in the endothelium of both vessels, although the density of Cx40 plaques was significantly greater in the CA. CONCLUSIONS: The demonstration of Cx37 as the dominant Cx in the media of the CA highlights the potential heterogeneity in Cx involvement in vascular smooth muscle.