Reactive Oxygen Species Signaling Facilitates FOXO-3a/FBXO-Dependent Vascular BK Channel β1 Subunit Degradation in Diabetic Mice

  1. Hon-Chi Lee1
  1. 1Department of Internal Medicine, Mayo Clinic, Rochester, Minnesota
  2. 2Department of Physiology, Institute of Basic Medicine, Shandong Academy of Medical Sciences, Jinan, People’s Republic of China
  3. 3Department of Cardiology, Fujian Province Hospital, Fuzhou, People’s Republic of China
  4. 4Department of Anesthesiology, Mayo Clinic, Rochester, Minnesota
  1. Corresponding author: Tong Lu, lu.tong{at}mayo.edu.

Abstract

Activity of the vascular large conductance Ca2+-activated K+ (BK) channel is tightly regulated by its accessory β1 subunit (BK-β1). Downregulation of BK-β1 expression in diabetic vessels is associated with upregulation of the forkhead box O subfamily transcription factor-3a (FOXO-3a)–dependent F-box–only protein (FBXO) expression. However, the upstream signaling regulating this process is unclear. Overproduction of reactive oxygen species (ROS) is a common finding in diabetic vasculopathy. We hypothesized that ROS signaling cascade facilitates the FOXO-3a/FBXO-mediated BK-β1 degradation and leads to diabetic BK channel dysfunction. Using cellular biology, patch clamp, and videomicroscopy techniques, we found that reduced BK-β1 expression in streptozotocin (STZ)-induced diabetic mouse arteries and in human coronary smooth muscle cells (SMCs) cultured with high glucose was attributable to an increase in protein kinase C (PKC)-β and NADPH oxidase expressions and accompanied by attenuation of Akt phosphorylation and augmentation of atrogin-1 expression. Treatment with ruboxistaurin (a PKCβ inhibitor) or with GW501516 (a peroxisome proliferator–activated receptor δ activator) reduced atrogin-1 expression and restored BK channel-mediated coronary vasodilation in diabetic mice. Our results suggested that oxidative stress inhibited Akt signaling and facilitated the FOXO-3a/FBXO-dependent BK-β1 degradation in diabetic vessels. Suppression of the FOXO-3a/FBXO pathway prevented vascular BK-β1 degradation and protected coronary function in diabetes.

  • Received November 28, 2011.
  • Accepted March 3, 2012.

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  1. Diabetes vol. 61 no. 7 1860-1868
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