HO-mediated relaxation in a swine model of ischemic heart disease and exercise training: mechanistic insights and the role of Kv7 channels.

We previously reported that HO-mediated arteriolar dilation impaired by chronic occlusion is corrected with exercise training and that BKCa and Kv channels both contribute to these adaptations. To gain additional understanding of the specific Kv channel isoforms influenced by ischemia and exercise, we hypothesized that the redox-sensitive Kv1, Kv2, and Kv7 channel subfamily isoforms would be the primary end effectors of this exercise-augmented channel contribution. Yucatan miniature swine were surgically instrumented with an ameroid occluder around the proximal left circumflex coronary artery, inducing an ischemic vascular bed, while arterioles fed by the left anterior descending artery served as nonoccluded, control vessels for each animal. Animals were randomly assigned to sedentary (normal pen activity) or exercise-trained (treadmill; 5 days/week; 14 weeks) groups. Kv channels were targeted, ex vivo, in wire myography and electrophysiology studies for functional analyses, while arteriolar lysates and isolated vascular smooth muscle cells were utilized for immunoblot and immunofluorescence. We show that coronary occlusion impairs Kv7 channel contribution to HO-mediated relaxation that is reversed with exercise training. Whole-cell voltage clamp recordings demonstrated no changes in XE991-sensitive currents among groups, and no significant differences in Kv7 channel protein were detected. Immunofluorescent analyses revealed a decrease in colocalization of PKA with Kv7.1 channels following occlusion and increased localization with both Kv7.1 and Kv7.5 channels following exercise training. Taken together, these studies demonstrate that Kv7 channel uncoupling from a prominent vasorelaxation signaling axis results from coronary occlusion and is restored following exercise training, highlighting this subfamily as a potential therapeutic target.