Procontractile influence of ROS, produced by NADPH oxidase, is greater during contraction induced by thromboxane A ₂ than α ₁ -adrenoceptor activation

Reactive oxygen species (ROS), produced by NADPH oxidase, promote contraction of the arteries. We hypothesized that (1) procontractile influence of NADPH oxidase derived ROS differs between α1- and thromboxane A2-receptor activation and (2) that such an influence is realized by the activation of different signaling pathways. Mesenteric arteries of rats were studied using wire-myography, Ca2+-fluorimetry and qPCR. Pan-NADPH oxidase inhibitor VAS2870 weakened contractile responses and [Ca2+]i rise to methoxamine (α1-adrenoceptor agonist) and U46619 (thromboxane A2 receptor agonist), this effect was more pronounced when U46619 was used. Suppression of Rho-kinase activity by Y27632 did not eliminate the effect of VAS2870 on both U46619- and methoxamine-induced contraction. The effect of VAS2870 persisted in the presence of LTCC (L-type voltage-gated Ca2+ channels) blocker nimodipine during U46619-induced, but not methoxamine-induced contraction. In contrast, the effect of VAS2870 persisted in the presence of protein kinase C inhibitor GF109203X during methoxamine-induced, but not U46619-induced contraction. Among all NADPH oxidase isoforms mRNAs of Nox2 and Nox4 were the most abundant. NOX2 inhibitor GSK2795039 (10 μM), but not NOX1/4 inhibitor GKT137831, weakened significantly both methoxamine- and U46619-induced contraction. This effect was more pronounced in case of U46619-induced contraction. Thus, procontractile influence of ROS, produced by NADPH oxidase (mainly, by NOX2), is greater during contraction induced by thromboxane A2 than α1-adrenoceptor activation in rat mesenteric arteries. Such influence is realized by activation of LTCC when α1-adrenoceptors are stimulated and by activation of protein kinase C when thromboxane A2 receptors are stimulated.