Submitted on June 20, 2007
Accepted on July 30, 2007
Ebselen Reduces Nitration and Restores Voltage-gated Potassium Channel Function in Small Coronary Arteries of Diabetic Rats
Aaron H Bubolz1, Qingping Wu2, Brandon T Larsen3, David D Gutterman4, and Yanping Liu5*
1 The Department of Medicine, Medical College of Wisconsin, Milwaukee, Wisconsin, United States; The Cardiovascula center, Milwaukee, Wisconsin, United States
2 The Veterans Administration Medical Center, Milwaukee, Wisconsin, United States
3 The department of Medicine, Medical College of Wisconsin, Milwaukee, Wisconsin, United States; The cardiovascular center, United States
4 The department of Medicine, Medical College of Wisconsin, Milwaukee, Wisconsin, United States; The cardiovascular center, United States; The Veterans Administration Medical Center, Milwaukee, Wisconsin, United States
5 National Center for Research and Resource, National Institute of Health, Bethesda, Maryland, United States
* To whom correspondence should be addressed. E-mail: liuyanp{at}mail.nih.gov.
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. Methods: Diabetic rats and non-diabetic controls were treated with or without ebselen (Eb) for 4 weeks. SCA were prepared for immunohistochemistry (IHC), immunoprecipitation (IP) followed by Western blot (WB), videomicroscopy, and patch clamp analysis. Results: IHC revealed excess ONOO- in SCA from diabetic rats. IP and WB revealed elevated nitration of the Kv1.2 
-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 non-diabetic 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 SMCs from Eb-treated DM rats. Conclusion: Enhanced nitrosative stress in DM contributes to Kv1 channel dysfunction in the coronary microcirculation. Eb may be beneficial for the therapeutic treatment of vascular complications in DM.
