Integrated redox sensitivity of vascular Kv1 channels.

Voltage-gated potassium (Kv) channels in vascular smooth muscle are responsive to a range of molecular signals that link local metabolic demand to blood supply. We recently found that elevation of local lactate:pyruvate, reflective of enhanced tissue oxygen demand and consequent changes in smooth muscle cytosolic NADH:NAD , potentiate native Kv1 activity in a manner that is dependent on pore complex-associated Kvβ proteins (i.e., Kvβ1 and Kvβ2). Considering that these proteins also participate in the regulation of Kv function in response to oxidants, we tested the hypothesis that Kv1-dependent vasoreactivity to the endogenous dilator hydrogen peroxide (H O ) is modified by intracellular NAD(H) redox status. Application of H O to preconstricted (100 nM U46619, 80 mmHg intravascular pressure) mesenteric arteries from mice resulted in concentration-dependent vasodilation (0.1-10 μΜ). However, the magnitude of vasodilation in response to 10 μM H O was significantly enhanced when applied in the presence of 10 mM L-lactate (10 μΜ Η Ο : 16 ± 9%; 10 mM L-lactate + 10 μM H O : 80 ± 15% dilation), but not in the presence of 10 mM pyruvate (~11% H O -induced constriction). Consistent with direct effects of pyridine nucleotide redox state on oxidant-induced Kv potentiation, increases in single Kv1 channel open probability in excised membrane patches from isolated vascular smooth muscle cells in response to 10 μM H O were significantly enhanced in the presence of 1 mM NADH. Based on these results, we examined the role of the intracellular Kvβ subunit complex in redox-modified vasodilation in response to H O . Arteries isolated from double transgenic mice with doxycycline-inducible increases in smooth muscle Kvβ1:Kvβ2 protein ratio exhibited a complete loss of L-lactate-induced enhancement of vasodilation to H O . Together, our results suggest that the Kvβ subunit complex in vascular smooth muscle may integrate multiple redox signals to enable tight control over Kv1 gating, vascular tone, and blood flow upon dynamic changes in metabolic demand.