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Am J Physiol Heart Circ Physiol 293: H2231-H2237, 2007. First published August 3, 2007; doi:10.1152/ajpheart.00717.2007
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Ebselen reduces nitration and restores voltage-gated potassium channel function in small coronary arteries of diabetic rats

Aaron H. Bubolz,1,2 Qingping Wu,3 Brandon T. Larsen,1,2 David D. Gutterman,1,2,3 and Yanping Liu4

1Departments of Medicine and 2Cardiovascular Center, The Medical College of Wisconsin and 3Veterans Administration Medical Center, Milwaukee, Wisconsin; and 4National Center for Research Resources, National Institutes of Health, Bethesda, Maryland

Submitted 20 June 2007 ; accepted in final form 30 July 2007

Small coronary arteries (SCA) from diabetic rats exhibit enhanced peroxynitrite (ONOO–) formation and concurrent impairment of voltage-dependent potassium (Kv) channel function. However, it is unclear whether ONOO– plays a causative role in this impairment. We hypothesized that functional loss of Kv channels in coronary smooth muscle cells (SMC) in diabetes is due to ONOO– with subsequent tyrosine nitration of Kv channel proteins. Diabetic rats and nondiabetic controls were treated with or without ebselen (Eb) for 4 wk. SCA were prepared for immunohistochemistry (IHC), immunoprecipitation (IP) followed by Western blot (WB), videomicroscopy, and patch-clamp analysis. IHC revealed excess ONOO– in SCA from diabetic rats. IP and WB revealed elevated nitration of the Kv1.2 {alpha}-subunit and reduced Kv1.2 protein expression in diabetic rats. Each of these changes was improved in Eb-treated rats. Protein nitration and Kv1.5 expression were unchanged in SCA from diabetic rats. Forskolin, a direct cAMP activator that induces Kv1 channel activity, dilated SCA from nondiabetic rats in a correolide (Cor; a selective Kv1 channel blocker)-sensitive fashion. Cor did not alter the reduced dilation to forskolin in diabetic rats; however, Eb partially restored the Cor-sensitive component of dilation. Basal Kv current density and response to forskolin were improved in smooth muscle cells from Eb-treated DM rats. We conclude that enhanced nitrosative stress in diabetes mellitus contributes to Kv1 channel dysfunction in the coronary microcirculation. Eb may be beneficial for the therapeutic treatment of vascular complications in diabetes mellitus.

diabetes; peroxynitrite; oxidative stress; coronary circulation


Address for reprint requests and other correspondence: Y. Liu, National Center for Research Resources, National Institutes of Health, 6701 Democracy Boulevard, Bethesda, MD 20892 (e-mail: liuyanp{at}mail.nih.gov)






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