title: Palmitate induces ER calcium depletion and apoptosis in mouse podocytes subsequent to mitochondrial oxidative stress.
abstract: Pathologic alterations in podocytes lead to failure of an essential component of the glomerular filtration barrier and proteinuria in chronic kidney diseases. Elevated levels of saturated free fatty acid (FFA) are harmful to various tissues, implemented in the progression of diabetes and its complications such as proteinuria in diabetic nephropathy. Here, we investigated the molecular mechanism of palmitate cytotoxicity in cultured mouse podocytes. Incubation with palmitate dose-dependently increased cytosolic and mitochondrial reactive oxygen species, depolarized the mitochondrial membrane potential, impaired ATP synthesis and elicited apoptotic cell death. Palmitate not only evoked mitochondrial fragmentation but also caused marked dilation of the endoplasmic reticulum (ER). Consistently, palmitate upregulated ER stress proteins, oligomerized stromal interaction molecule 1 (STIM1) in the subplasmalemmal ER membrane, abolished the cyclopiazonic acid-induced cytosolic Ca(2+) increase due to depletion of luminal ER Ca(2+). Palmitate-induced ER Ca(2+) depletion and cytotoxicity were blocked by a selective inhibitor of the fatty-acid transporter FAT/CD36. Loss of the ER Ca(2+) pool induced by palmitate was reverted by the phospholipase C (PLC) inhibitor edelfosine. Palmitate-dependent activation of PLC was further demonstrated by following cytosolic translocation of the pleckstrin homology domain of PLC in palmitate-treated podocytes. An inhibitor of diacylglycerol (DAG) kinase, which elevates cytosolic DAG, strongly promoted ER Ca(2+) depletion by low-dose palmitate. GF109203X, a PKC inhibitor, partially prevented palmitate-induced ER Ca(2+) loss. Remarkably, the mitochondrial antioxidant mitoTEMPO inhibited palmitate-induced PLC activation, ER Ca(2+) depletion and cytotoxicity. Palmitate elicited cytoskeletal changes in podocytes and increased albumin permeability, which was also blocked by mitoTEMPO. These data suggest that oxidative stress caused by saturated FFA leads to mitochondrial dysfunction and ER Ca(2+) depletion through FAT/CD36 and PLC signaling, possibly contributing to podocyte injury.
authors.affiliation: Department of Physiology and Institute of Lifestyle Medicine, Yonsei University Wonju College of Medicine, Wonju, Korea.
authors.forename: S
authors.initials: S
authors.lastname: Xu
authors.affiliation: Department of Physiology and Institute of Lifestyle Medicine, Yonsei University Wonju College of Medicine, Wonju, Korea.|Department of Internal Medicine, Daejeon Sun Hospital, Daejeon, Korea.
authors.forename: S M
authors.initials: SM
authors.lastname: Nam
authors.affiliation: Department of Physiology and Institute of Lifestyle Medicine, Yonsei University Wonju College of Medicine, Wonju, Korea.
authors.forename: J-H
authors.initials: JH
authors.lastname: Kim
authors.affiliation: Department of Physiology and Institute of Lifestyle Medicine, Yonsei University Wonju College of Medicine, Wonju, Korea.
authors.forename: R
authors.initials: R
authors.lastname: Das
authors.affiliation: Department of Physiology and Institute of Lifestyle Medicine, Yonsei University Wonju College of Medicine, Wonju, Korea.
authors.forename: S-K
authors.initials: SK
authors.lastname: Choi
authors.affiliation: Department of Physiology and Institute of Lifestyle Medicine, Yonsei University Wonju College of Medicine, Wonju, Korea.
authors.forename: T T
authors.initials: TT
authors.lastname: Nguyen
authors.affiliation: Department of Physiology and Institute of Lifestyle Medicine, Yonsei University Wonju College of Medicine, Wonju, Korea.
authors.forename: X
authors.initials: X
authors.lastname: Quan
authors.affiliation: Department of Microbiology, Yonsei University Wonju College of Medicine, Wonju, Korea.
authors.forename: S J
authors.initials: SJ
authors.lastname: Choi
authors.affiliation: Department of Internal Medicine, Yonsei University Wonju College of Medicine, Wonju, Korea.
authors.forename: C H
authors.initials: CH
authors.lastname: Chung
authors.affiliation: Department of Internal Medicine, Soonchunhyang University Cheonan Hospital, Cheonan, Korea.
authors.forename: E Y
authors.initials: EY
authors.lastname: Lee
authors.affiliation: Department of Internal Medicine, Kyungpook National University Hospital, Daegu, Korea.
authors.forename: I-K
authors.initials: IK
authors.lastname: Lee
authors.affiliation: Nestlé Institute of Health Sciences, Lausanne, Switzerland.
authors.forename: A
authors.initials: A
authors.lastname: Wiederkehr
authors.affiliation: Department of Cell Physiology and Metabolism, University of Geneva, Geneva, Switzerland.
authors.forename: C B
authors.initials: CB
authors.lastname: Wollheim
authors.affiliation: Department of Physiology and Institute of Lifestyle Medicine, Yonsei University Wonju College of Medicine, Wonju, Korea.
authors.forename: S-K
authors.initials: SK
authors.lastname: Cha
authors.affiliation: Department of Physiology and Institute of Lifestyle Medicine, Yonsei University Wonju College of Medicine, Wonju, Korea.
authors.forename: K-S
authors.initials: KS
authors.lastname: Park
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology; D002118:Calcium / Q000378:metabolism*; D004721:Endoplasmic Reticulum / Q000187:drug effects* / Q000378:metabolism; D051379:Mice; D008928:Mitochondria / Q000187:drug effects* / Q000378:metabolism; D018384:Oxidative Stress / Q000187:drug effects*; D010168:Palmitates / Q000494:pharmacology*; D050199:Podocytes / Q000187:drug effects* / Q000378:metabolism
chemical_list: D010168:Palmitates; D000255:Adenosine Triphosphate; D002118:Calcium