title: Abundance of TRPC6 protein in glomerular mesangial cells is decreased by ROS and PKC in diabetes.
abstract: The present study was performed to investigate the underlying mechanism, particularly the roles of reactive oxygen species (ROS) and protein kinase C (PKC), in the diabetes-induced canonical transient receptor potential 6 (TRPC6) downregulation. We found that high glucose (HG) significantly reduced TRPC6 protein expression in cultured mesangial cells (MCs). TRPC6 protein was also significantly reduced in the glomeruli but not in the heart or aorta isolated from streptozotocin-induced diabetic rats. In the cultured MCs, H(2)O(2) suppressed TRPC6 protein expression in a dose- and time-dependent manner, which emulated the HG effect. Catalase as well as superoxide dismutase were able to prevent the inhibitory effect of HG on TRPC6. The antioxidant effect observed in cultured cells was also observed in diabetic rats treated with tempol for 2 wk, which exhibited a preservation of TRPC6 in the glomeruli. Specific knockdown of Nox4, a component of NADPH oxidase, increased TRPC6 protein expression. Furthermore, the PKC activator phorbol 12-myristate 13-acetate (PMA), but not its analog 4α-phorbol 12, 13-didecanoate (4α-PDD), suppressed TRPC6 expression, and this PMA effect was not affected by catalase. Moreover, Gö6976, but not LY333531, attenuated the negative effect of HG on TRPC6 expression. Gö6976 also inhibited H(2)O(2) effect on TRPC6. Furthermore, either knockdown of TRPC6 or HG treatment significantly decreased ANG II-stimulated MC contraction, and the HG-impaired MC contraction was rescued by overexpression of TRPC6. These results suggest that hyperglycemia in diabetes downregulated TRPC6 protein expression in MCs through a NADPH oxidase Nox4-ROS-PKC pathway, proving a mechanism for impaired MC contraction in diabetes.
authors.affiliation: Department of Integrative Physiology and Cardiovascular Research Institute, University of North Texas Health Science Center, Fort Worth, TX 76107, USA.
authors.forename: Sarabeth
authors.initials: S
authors.lastname: Graham
authors.forename: Yves
authors.initials: Y
authors.lastname: Gorin
authors.forename: Hanna E
authors.initials: HE
authors.lastname: Abboud
authors.forename: Min
authors.initials: M
authors.lastname: Ding
authors.forename: Duck Yoon
authors.initials: DY
authors.lastname: Lee
authors.forename: Honglian
authors.initials: H
authors.lastname: Shi
authors.forename: Yanfeng
authors.initials: Y
authors.lastname: Ding
authors.forename: Rong
authors.initials: R
authors.lastname: Ma
mesh_terms: D000704:Analysis of Variance; D000804:Angiotensin II / Q000378:metabolism; D000818:Animals; D000975:Antioxidants / Q000494:pharmacology; D001786:Blood Glucose / Q000378:metabolism; D048430:Cell Shape; D002478:Cells, Cultured; D003921:Diabetes Mellitus, Experimental / Q000150:complications* / Q000201:enzymology / Q000473:pathology; D003928:Diabetic Nephropathies / Q000201:enzymology / Q000209:etiology* / Q000473:pathology; D004305:Dose-Response Relationship, Drug; D015536:Down-Regulation; D004789:Enzyme Activation; D020536:Enzyme Activators / Q000494:pharmacology; D005947:Glucose / Q000378:metabolism*; D006801:Humans; D008297:Male; D050527:Mesangial Cells / Q000187:drug effects / Q000201:enzymology* / Q000473:pathology; D000074663:NADPH Oxidase 4; D019255:NADPH Oxidases / Q000235:genetics / Q000378:metabolism; D016877:Oxidants / Q000494:pharmacology; D018384:Oxidative Stress / Q000187:drug effects; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism*; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D034622:RNA Interference; D051381:Rats; D017207:Rats, Sprague-Dawley; D017382:Reactive Oxygen Species / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D015398:Signal Transduction; D050052:TRPC Cation Channels / Q000235:genetics / Q000378:metabolism*; D000074287:TRPC6 Cation Channel; D013997:Time Factors
chemical_list: D000975:Antioxidants; D001786:Blood Glucose; D020536:Enzyme Activators; D016877:Oxidants; D047428:Protein Kinase Inhibitors; D017382:Reactive Oxygen Species; D011993:Recombinant Fusion Proteins; D050052:TRPC Cation Channels; D000074287:TRPC6 Cation Channel; C117032:TRPC6 protein, human; C492145:Trpc6 protein, rat; D000804:Angiotensin II; D000074663:NADPH Oxidase 4; D019255:NADPH Oxidases; C498911:Nox4 protein, rat; D011493:Protein Kinase C; D005947:Glucose