Vascular Kinin B₁ and B₂ Receptors Determine Endothelial Dysfunction through Neuronal Nitric Oxide Synthase

B₁- and B₂-kinin receptors are G protein-coupled receptors that play an important role in the vascular function. Therefore, the present study was designed to evaluate the participation of kinin receptors in the acetylcholine (ACh)-induced vascular relaxation, focusing on the protein-protein interaction involving kinin receptors with endothelial and neuronal nitric oxide synthases (eNOS and nNOS). Vascular reactivity, nitric oxide (NO·) and reactive oxygen species (ROS) generation, co-immunoprecipitation were assessed in thoracic aorta from male wild-type (WT), B₁- (B₁R^-/-), B₂- (B₂R^-/-) knockout mice. Some vascular reactivity experiments were also performed in a double kinin receptors knockout mice (B₁B₂R^-/-). For pharmacological studies, selective B₁- and B₂-kinin receptors antagonists, NOS inhibitors and superoxide dismutase (SOD) mimetic were used. First, we show that B₁- and B₂-kinin receptors form heteromers with nNOS and eNOS in thoracic aorta. To investigate the functionality of these protein-protein interactions, we took advantage of pharmacological tools and knockout mice. Importantly, our results show that kinin receptors regulate ACh-induced relaxation via nNOS signaling in thoracic aorta with no changes in NO· donor-induced relaxation. Interestingly, B₁B₂R^-/- presented similar level of vascular dysfunction as found in B₁R^-/- or B₂R^-/- mice. In accordance, aortic rings from B₁R^-/- or B₂R^-/- mice exhibit decreased NO· bioavailability and increased superoxide generation compared to WT mice, suggesting the involvement of excessive ROS generation in the endothelial dysfunction of B₁R^-/- and B₂R^-/- mice. Alongside, we show that impaired endothelial vasorelaxation induced by ACh in B₁R^-/- or B₂R^-/- mice was rescued by the SOD mimetic compound. Taken together, our findings show that B₁- and B₂-kinin receptors regulate the endothelium-dependent vasodilation of ACh through nNOS activity and indicate that molecular disturbance of short-range interaction between B₁- and B₂-kinin receptors with nNOS might be involved in the oxidative pathogenesis of endothelial dysfunction.