title: Contribution of guanine nucleotide exchange factor Vav2 to NLRP3 inflammasome activation in mouse podocytes during hyperhomocysteinemia.
abstract: NADPH oxidase (NOX)-derived reactive oxygen species (ROS) have been demonstrated to mediate the activation of NOD-like receptor protein 3 (NLRP3) inflammasomes in podocytes in response to elevated levels of homocysteine (Hcys). However, it remains unknown how NLRP3 inflammasome activation is triggered by NOX. The present study tested whether the guanine nucleotide exchange factor Vav2 mediates Rac1-mediated NOX activation in response to elevated Hcys leading to NLRP3 inflammasome activation in podocytes and consequent glomerular injury. In a mouse model of hyperhomocysteinemia (hHcys), we found that mice with hHcys (on the FF diet) or oncoVav2 (a constitutively active form of Vav2) transfection in the kidney exhibited increased colocalization of NLRP3 with apoptosis-associated speck-like protein (ASC) or caspase-1 and elevated IL-1β levels in glomeruli, indicating the formation and activation of the NLRP3 inflammasome. This glomerular NLRP3 inflammasome activation was accompanied by podocyte dysfunction and glomerular injury, even sclerosis. Local transfection of Vav2 shRNA plasmids significantly attenuated hHcys-induced NLRP3 inflammasome activation, podocyte injury, and glomerular sclerosis. In cultured podocytes, Hcys treatment and oncoVav2 transfection were also found to increase NLRP3 inflammasome formation and activation, which were all inhibited by Vav2 shRNA. Furthermore, Vav2 shRNA prevented Hcys-induced podocyte damage as shown by restoring Hcys-impaired VEGF secretion and podocin production. This inhibitory action of Vav2 shRNA on Hcys-induced podocyte injury was associated with reduction of Rac1 activity and ROS production. These results suggest that elevated Hcys levels activate Vav2 and thereby increase NOX activity leading to ROS production, which triggers NLRP3 inflammasome activation, podocyte dysfunction and glomerular injury.
authors.affiliation: Department of Pharmacology & Toxicology, Virginia Commonwealth University, School of Medicine, Richmond, VA 23298, USA.
authors.forename: Sabena M
authors.initials: SM
authors.lastname: Conley
authors.affiliation: Department of Pharmacology & Toxicology, Virginia Commonwealth University, School of Medicine, Richmond, VA 23298, USA.
authors.forename: Justine M
authors.initials: JM
authors.lastname: Abais-Battad
authors.affiliation: Department of Pharmacology & Toxicology, Virginia Commonwealth University, School of Medicine, Richmond, VA 23298, USA.
authors.forename: Xinxu
authors.initials: X
authors.lastname: Yuan
authors.affiliation: Department of Pharmacology & Toxicology, Virginia Commonwealth University, School of Medicine, Richmond, VA 23298, USA.
authors.forename: Qinghua
authors.initials: Q
authors.lastname: Zhang
authors.affiliation: Department of Pharmacology & Toxicology, Virginia Commonwealth University, School of Medicine, Richmond, VA 23298, USA; Department of Pharmacological and Pharmaceutical Sciences, College of Pharmacy, University of Houston, Houston, TX 77204, USA.
authors.forename: Krishna M
authors.initials: KM
authors.lastname: Boini
authors.affiliation: Department of Pharmacology & Toxicology, Virginia Commonwealth University, School of Medicine, Richmond, VA 23298, USA. Electronic address: pin-lan.li@vcuhealth.org.
authors.forename: Pin-Lan
authors.initials: PL
authors.lastname: Li
mesh_terms: D000818:Animals; D053468:CARD Signaling Adaptor Proteins / Q000235:genetics / Q000378:metabolism; D004195:Disease Models, Animal; D006710:Homocysteine / Q000096:biosynthesis; D006801:Humans; D020138:Hyperhomocysteinemia / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D058847:Inflammasomes / Q000235:genetics / Q000378:metabolism; D007678:Kidney Glomerulus / Q000293:injuries / Q000378:metabolism / Q000473:pathology; D051379:Mice; D000071199:NLR Family, Pyrin Domain-Containing 3 Protein / Q000235:genetics / Q000378:metabolism*; D009479:Neuropeptides / Q000235:genetics / Q000378:metabolism*; D050199:Podocytes / Q000378:metabolism / Q000473:pathology; D051567:Proto-Oncogene Proteins c-vav / Q000235:genetics / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000235:genetics; D017382:Reactive Oxygen Species / Q000378:metabolism; D020830:rac1 GTP-Binding Protein / Q000235:genetics / Q000378:metabolism*
chemical_list: D053468:CARD Signaling Adaptor Proteins; D058847:Inflammasomes; D000071199:NLR Family, Pyrin Domain-Containing 3 Protein; D009479:Neuropeptides; C492716:Nlrp3 protein, mouse; D051567:Proto-Oncogene Proteins c-vav; C498534:Pycard protein, mouse; D034741:RNA, Small Interfering; C484602:Rac1 protein, mouse; D017382:Reactive Oxygen Species; C490565:Vav2 protein, mouse; D006710:Homocysteine; D020830:rac1 GTP-Binding Protein
keywords: End-stage renal disease; Hyperhomocysteinemia; Inflammatory machinery; Podocytes