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Role of Vav2 in Podocyte Inflammasome Activation and Glomerular Injury during Hyperhomocysteinemia
Author(s) -
Conley Sabena M.,
Chen Zhida,
Xia Min,
Boini Krishna M.,
Gehr Todd W.,
Li PinLan
Publication year - 2016
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.30.1_supplement.1220.8
Subject(s) - podocyte , inflammasome , nadph oxidase , guanine nucleotide exchange factor , microbiology and biotechnology , chemistry , medicine , activator (genetics) , endocrinology , biology , signal transduction , biochemistry , reactive oxygen species , kidney , receptor , proteinuria
Recently, our lab has reported that Vav2, a member of the guanine nucleotide exchange factor (GEF) family contributes to the activation of NADPH oxidase (NOX) in a membrane lipid signaling platform in response to elevated levels of homocysteine (Hcys). However, it remains unknown whether Vav2‐mediated NOX activation is able to trigger NLRP3 inflammasomes in podocytes and thereby lead to podocyte dysfunction and glomerular injury associated with hyperhomocysteinemia (hHcys). The present study was designed to answer this question by using pharmalogical interventions in vitro and in vivo . In our experiments, murine podocytes were pretreated with either a Rac‐1 inhibitor, NSC23766 or Vav2 activator, uridine triphosphate (UTP) and then stimulated with Hcys for 24 hours. Confocal microscopic analysis showed that treatment with UTP increased the colocalization of inflammasome proteins NLRP3 with ASC or with caspase‐1, suggesting NLRP3 inflammasome formation. However, pretreatment of podocytes with NSC23766 blocked Hcys‐induced inflammasome formation. Similar to Hcys, Vav2 activator, UTP increased caspase‐1 activation and consequent IL‐1β production in podocytes, signifying NLRP3 inflammasome activation. However, attenuated caspase‐1 activation and lower IL‐1β levels were observed when podocytes were treated with Vav2 inhibitor, NSC23766. Furthermore, Hcys and UTP treatment resulted in increased levels of GTP‐bound Rac‐1 in comparison to NSC23766 treated podocytes. In our in vivo studies using mice fed a folate‐free (FF) diet to induce hHcys, we found that these mice had increased inflammasome formation, enhanced desmin expression, elevated urinary protein or albumin, and decreased podocin expression in glomeruli. These hHcys‐induced changes were substantially attenuated in mice receiving NSC23766. Our results suggest that Vav2 is a key signaling molecule in mediating Hcys‐induced podocyte inflammasome formation and activation and consequent podocyte dysfunction and glomerular injury. Support or Funding Information Supported by NIH grants DK054927, HL07356 & HL057244.