Ebselen Reduces Kv1 Channel Nitration and Restores Kv1 Channel Function in Diabetic Rat Coronary Arteries

Abstract

Rat small coronary arteries (RSCA) from rats with diabetes mellitus (DM) exhibit enhanced peroxynitrite (ONOO−) formation and concurrent impairment of Kv1 channel function. It is unclear whether ONOO− plays a causative role in this impairment. We hypothesized that functional loss of Kv1 channels in coronary smooth muscle cells (SMC) in DM is due to overproduction of ONOO− and subsequent tyrosine nitration of Kv1 channel proteins. Methods DM rats and their controls were treated with ebselen (Eb) for 4 weeks. RSCA were prepared for mmunohistochemistry (IHC), immunoprecipitation (IP) followed by Western blot (WB), videomicroscopic, and patch clamp analysis. Results eneration of ONOO− was markedly reduced in RSCA from DM rats treated with Eb. IP+WB revealed elevated nitration of Kv1.2 α–subunits in RSCA from DM rats (DM vs non DM, 1.4±0.1 vs 1±0, n=5, P<0.05 vs non DM). This augmentation was normalized through treatment with Eb. The attenuated dilation to forskolin and correolide seen in DM RSCA, was restored after treatment with Eb (Max dilation, DM vs DM+Eb, 39±4% vs 67±8%). The basal Kv current density and the response to forskolin were improved in SMCs from Eb treated DM rats. These results suggest that hyperglycemia stimulates ONOO− formation and subsequent protein nitration. Thus, excess production of ONOO− may be one of the mechanisms by which Kv1 channel function is impaired in DM (Supported by NIH grants).