title: NADPH oxidase-mediated triggering of inflammasome activation in mouse podocytes and glomeruli during hyperhomocysteinemia.
abstract: OBJECTIVE
  Our previous studies have shown that NOD-like receptor protein (NALP3) inflammasome activation is importantly involved in podocyte dysfunction and glomerular sclerosis induced by hyperhomocysteinemia (hHcys). The present study was designed to test whether nicotinamide adenine dinucleotide phosphate (NADPH) oxidase-mediated redox signaling contributes to homocysteine (Hcys)-induced activation of NALP3 inflammasomes, an intracellular inflammatory machinery in podocytes in vitro and in vivo.
  
  
  RESULTS
  In vitro confocal microscopy and size-exclusion chromatography revealed that upon NADPH oxidase inhibition by gp91(phox) siRNA, gp91ds-tat peptide, diphenyleneiodonium, or apocynin, aggregation of inflammasome proteins NALP3, apoptosis-associated speck-like protein (ASC), and caspase-1 was significantly attenuated in mouse podocytes. This NADPH oxidase inhibition also resulted in diminished Hcys-induced inflammasome activation, evidenced by reduced caspase-1 activity and interleukin-1β production. Similar findings were observed in vivo where gp91(phox-/-) mice and mice receiving a gp91ds-tat treatment exhibited markedly reduced inflammasome formation and activation. Further, in vivo NADPH oxidase inhibition protected the glomeruli and podocytes from hHcys-induced injury as shown by attenuated proteinuria, albuminuria, and glomerular sclerotic changes. This might be attributed to the fact that gp91(phox-/-) and gp91ds-tat-treated mice had abolished infiltration of macrophages and T-cells into the glomeruli during hHcys.
  
  
  METHODS
  Our study for the first time links NADPH oxidase to the formation and activation of NALP3 inflammasomes in podocytes.
  
  
  CONCLUSIONS
  Hcys-induced NADPH oxidase activation is importantly involved in the switching on of NALP3 inflammasomes within podocytes, which leads to the downstream recruitment of immune cells, ultimately resulting in glomerular injury and sclerosis.
authors.affiliation: Department of Pharmacology and Toxicology, Medical College of Virginia, Virginia Commonwealth University, Richmond, VA 23298, USA.
authors.forename: Justine M
authors.initials: JM
authors.lastname: Abais
authors.forename: Chun
authors.initials: C
authors.lastname: Zhang
authors.forename: Min
authors.initials: M
authors.lastname: Xia
authors.forename: Qinglian
authors.initials: Q
authors.lastname: Liu
authors.forename: Todd W B
authors.initials: TW
authors.lastname: Gehr
authors.forename: Krishna M
authors.initials: KM
authors.lastname: Boini
authors.forename: Pin-Lan
authors.initials: PL
authors.lastname: Li
mesh_terms: D000818:Animals; D051017:Apoptosis Regulatory Proteins; D053468:CARD Signaling Adaptor Proteins; D020170:Caspase 1 / Q000378:metabolism; D003598:Cytoskeletal Proteins / Q000235:genetics; D020868:Gene Silencing; D006710:Homocysteine / Q000494:pharmacology; D020138:Hyperhomocysteinemia / Q000235:genetics / Q000378:metabolism*; D058847:Inflammasomes / Q000378:metabolism*; D053583:Interleukin-1beta / Q000378:metabolism; D007678:Kidney Glomerulus / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism; D051379:Mice; D008822:Mice, Transgenic; D000074662:NADPH Oxidase 2; D019255:NADPH Oxidases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D050199:Podocytes / Q000187:drug effects / Q000378:metabolism*; D013481:Superoxides / Q000378:metabolism
chemical_list: D051017:Apoptosis Regulatory Proteins; D053468:CARD Signaling Adaptor Proteins; D003598:Cytoskeletal Proteins; D058847:Inflammasomes; D053583:Interleukin-1beta; D008562:Membrane Glycoproteins; C498534:Pycard protein, mouse; D006710:Homocysteine; D013481:Superoxides; C488842:Cybb protein, mouse; D000074662:NADPH Oxidase 2; D019255:NADPH Oxidases; D020170:Caspase 1