Enhanced Renal Afferent Arteriolar Reactive Oxygen Species and Contractility to Endothelin-1 Are Associated with Canonical Wnt Signaling in Diabetic Mice

BACKGROUND/AIMS: Canonical Wnt signaling is involved in oxidative stress, vasculopathy and diabetes mellitus but its role in diabetic renal microvascular dysfunction is unclear. We tested the hypothesis that enhanced canonical Wnt signaling in renal afferent arterioles from diabetic mice increases reactive oxygen species (ROS) and contractions to endothelin-1 (ET-1). METHODS: Streptozotocin-induced diabetes or control C57BI/6 mice received vehicle or sulindac (40 mg·kg(−1)·day(−1)) to block Wnt signaling for 4 weeks. ET-1 contractions were measured by changes of afferent arteriolar diameter. Arteriolar H(2)O(2), O(2)(.−), protein expression and enzymatic activity were assessed using sensitive fluorescence probes, immunoblotting and colorimetric assay separately. RESULTS: Compared to control, diabetic mouse afferent arteriole had increased O(2)(−)(+ 84%) and H(2)O(2) (+ 91%) and enhanced responses to ET-1 at 10(−8) mol·l(−1) (−72±4% of versus −43±4%, P<0.05) accompanied by reduced protein expressions and activities for catalase and superoxide dismutase 2 (SOD2). Arteriolar O(2)(.−) was increased further by ET-1 and contractions to ET-1 reduced by PEG-SOD in both groups whereas H(2)O(2) unchanged by ET-1 and contractions were reduced by PEG-catalase selectively in diabetic mice. The Wnt signaling protein β-catenin was upregulated (3.3-fold decrease in p-β-catenin/β-catenin) while the glycogen synthase kinase-3β (GSK-3β) was downregulated (2.6-fold increase in p-GSK-3β/GSK-3β) in preglomerular vessels of diabetic mice. Sulindac normalized the Wnt signaling proteins, arteriolar O(2)(.−), H(2)O(2) and ET-1 contractions while doubling microvascular catalase and SOD2 expression in diabetic mice. CONCLUSION: Increased ROS, notably H(2)O(2) contributes to enhanced afferent arteriolar responses to ET-1 in diabetes, which is closely associated with Wnt signaling. Antioxidant pharmacological strategies targeting Wnt signaling may improve vascular function in diabetic nephropathy.