Endothelial inwardly rectifying potassium channels regulates receptor‐mediated vasodilation via PI3K/Akt/eNOS signal pathway

Abstract

We recently demonstrated that endothelial inwardly rectifying potassium (Kir) channels play a key role in flow‐induced vasodilation (FIV) of resistance arteries via regulating nitric oxide (NO) production with Akt/eNOS pathway. However, the role of endothelial Kir channels in receptor‐mediated vasodilation remains unknown. Therefore, we tested the role of Kir channels in receptor‐mediated vasodilation of mesenteric arteries. A significant reduction in the vasodilation to bradykinin was observed in mesenteric arteries from Kir2.1+/‐ mice, which we have shown earlier to lack functional expression of Kir2.1 in endothelial cells, as compared to arteries from WT mice. Moreover, blocking Kir channels with barium, Ba2+, significantly reduced bradykinin‐induced vasodilation in WT but not in Kir2.1+/‐ mice. Inhibition of eNOS withN(G)‐Nitro‐L‐arginine methyl ester (L‐NAME), which is known to reduce bradykinin‐induced vasodilation in WT mice, also had no effect in Kir2.1+/‐ mice. However, the vasodilation was completely blocked in Kir2.1+/‐ mice with apamin, a well‐known inhibitor of small‐conductance calcium activated potassium (SK) channels. These findings indicate that endothelial Kir2.1 channels play a key role in receptor‐mediated NO production, an effect that is independent of SK channel‐dependent dilation. In mechanistic terms, we tested the activation of PI3K/Akt1/eNOS pathway known to be a major contributor of receptor‐mediated NO production and vasodilation. In the mesenteric arterial endothelial cells (ECs) derived from Kir deficient mouse, there was no significant activation of PI3K, Akt, and eNOS in response to bradykinin (10‐6 M), whereas the ECs from WT mice showed significant activation in 3 minutes after the application of bradykinin. The application of adenoviral construct overexpressing WT Kir2.1 resulted in the recovery of the activation of PI3K/Akt/eNOS in Kir deficient ECs, whereas no further increase of activation in WT ECs was observed. In addition, bradykinin‐induced NO production was significantly reduced in Kir deficient ECs compared to WT ECs, and it was recovered by overexpressing WT Kir2.1. Taken together, we conclude that Kir2.1 channels regulate bradykinin‐induced NO production in ECs through PI3K/Akt/eNOS pathway, similar to our observations regarding flow‐induced vasodilation.