title: Upregulation of mitochondrial Nox4 mediates TGF-β-induced apoptosis in cultured mouse podocytes.
abstract: Injury to podocytes leads to the onset of chronic renal diseases characterized by proteinuria. Elevated transforming growth factor (TGF)-β in kidney tissue is associated with podocyte damage that ultimately results in apoptosis and detachment. We investigated the proapoptotic mechanism of TGF-β in immortalized mouse podocytes. Exogenous TGF-β1-induced podocyte apoptosis through caspase-3 activation, which was related to elevated ROS levels generated by selective upregulation of NADPH oxidase 4 (Nox4). In mouse podocytes, Nox4 was predominantly localized to mitochondria, and Nox4 upregulation by TGF-β1 markedly depolarized mitochondrial membrane potential. TGF-β1-induced ROS production and caspase activation were mitigated by an antioxidant, the Nox inhibitor diphenyleneiodonium, or small interfering RNA for Nox4. A TGF-β receptor I blocker, SB-431542, completely reversed the changes triggered by TGF-β1. Knockdown of either Smad2 or Smad3 prevented the increase of Nox4 expression, ROS generation, loss of mitochondrial membrane potential, and caspase-3 activation by TGF-β1. These results suggest that TGF-β1-induced mitochondrial Nox4 upregulation via the TGF-β receptor-Smad2/3 pathway is responsible for ROS production, mitochondrial dysfunction, and apoptosis, which may at least in part contribute to the development and progression of proteinuric glomerular diseases such as diabetic nephropathy.
authors.affiliation: Dept. of Physiology and Institute of Lifestyle Medicine, Yonsei Univ. Wonju College of Medicine, Ilsan-dong, Wonju, Gangwon-Do 220-701, Republic of Korea. qsang@yonsei.ac.kr.
authors.forename: Ranjan
authors.initials: R
authors.lastname: Das
authors.forename: Shanhua
authors.initials: S
authors.lastname: Xu
authors.forename: Xianglan
authors.initials: X
authors.lastname: Quan
authors.forename: Tuyet Thi
authors.initials: TT
authors.lastname: Nguyen
authors.forename: In Deok
authors.initials: ID
authors.lastname: Kong
authors.forename: Choon Hee
authors.initials: CH
authors.lastname: Chung
authors.forename: Eun Young
authors.initials: EY
authors.lastname: Lee
authors.forename: Seung-Kuy
authors.initials: SK
authors.lastname: Cha
authors.forename: Kyu-Sang
authors.initials: KS
authors.lastname: Park
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D015153:Blotting, Western; D002467:Cell Nucleus / Q000502:physiology; D002478:Cells, Cultured; D007150:Immunohistochemistry; D020287:In Situ Nick-End Labeling; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D051379:Mice; D008928:Mitochondria / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000502:physiology; D000074663:NADPH Oxidase 4; D019255:NADPH Oxidases / Q000096:biosynthesis* / Q000235:genetics*; D018384:Oxidative Stress / Q000187:drug effects; D050199:Podocytes / Q000187:drug effects*; D060888:Real-Time Polymerase Chain Reaction; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics / Q000502:physiology; D051899:Smad2 Protein / Q000502:physiology; D051900:Smad3 Protein / Q000502:physiology; D016212:Transforming Growth Factor beta / Q000494:pharmacology*; D015854:Up-Regulation / Q000502:physiology
chemical_list: D051899:Smad2 Protein; C497783:Smad2 protein, mouse; D051900:Smad3 Protein; C497791:Smad3 protein, mouse; D016212:Transforming Growth Factor beta; D000074663:NADPH Oxidase 4; D019255:NADPH Oxidases; C422943:Nox4 protein, mouse; D020928:Mitogen-Activated Protein Kinases
keywords: NADPH oxidase 4; apoptosis; mitochondria; podocyte; transforming growth factor-β