title: Leptin is key to peroxynitrite-mediated oxidative stress and Kupffer cell activation in experimental non-alcoholic steatohepatitis.
abstract: OBJECTIVE
  Progression from steatosis to steatohepatitic lesions is hypothesized to require a second hit. These lesions have been associated with increased oxidative stress, often ascribed to high levels of leptin and other proinflammatory mediators. Here we have examined the role of leptin in inducing oxidative stress and Kupffer cell activation in CCl4-mediated steatohepatitic lesions of obese mice.
  
  
  METHODS
  Male C57BL/6 mice fed with a high-fat diet (60%kcal) at 16 weeks were administered CCl₄ to induce steatohepatitic lesions. Approaches included use of immuno-spin trapping for measuring free radical stress, gene-deficient mice for leptin, p47 phox, iNOS and adoptive transfer of leptin primed macrophages in vivo.
  
  
  RESULTS
  Diet-induced obese (DIO) mice, treated with CCl4 increased serum leptin levels. Oxidative stress was significantly elevated in the DIO mouse liver, but not in ob/ob mice, or in DIO mice treated with leptin antibody. In ob/ob mice, leptin supplementation restored markers of free radical generation. Markers of free radical formation were significantly decreased by the peroxynitrite decomposition catalyst FeTPPS, the iNOS inhibitor 1400W, the NADPH oxidase inhibitor apocynin, or in iNOS or p47 phox-deficient mice. These results correlated with the decreased expression of TNF-alpha and MCP-1. Kupffer cell depletion eliminated oxidative stress and inflammation, whereas in macrophage-depleted mice, the adoptive transfer of leptin-primed macrophages significantly restored inflammation.
  
  
  CONCLUSIONS
  These results, for the first time, suggest that leptin action in macrophages of the steatotic liver, through induction of iNOS and NADPH oxidase, causes peroxynitrite-mediated oxidative stress thus activating Kupffer cells.
authors.affiliation: Environmental Health and Disease Laboratory, Department of Environmental Health Sciences, University of South Carolina, Columbia, SC 29208, USA. schatt@mailbox.sc.edu
authors.forename: Saurabh
authors.initials: S
authors.lastname: Chatterjee
authors.forename: Douglas
authors.initials: D
authors.lastname: Ganini
authors.forename: Erik J
authors.initials: EJ
authors.lastname: Tokar
authors.forename: Ashutosh
authors.initials: A
authors.lastname: Kumar
authors.forename: Suvarthi
authors.initials: S
authors.lastname: Das
authors.forename: Jean
authors.initials: J
authors.lastname: Corbett
authors.forename: Maria B
authors.initials: MB
authors.lastname: Kadiiska
authors.forename: Michael P
authors.initials: MP
authors.lastname: Waalkes
authors.forename: Anna Mae
authors.initials: AM
authors.lastname: Diehl
authors.forename: Ronald P
authors.initials: RP
authors.lastname: Mason
mesh_terms: D000818:Animals; D016207:Cytokines / Q000378:metabolism; D004195:Disease Models, Animal; D005234:Fatty Liver / Q000209:etiology / Q000378:metabolism*; D018836:Inflammation Mediators / Q000378:metabolism; D007728:Kupffer Cells / Q000378:metabolism* / Q000473:pathology; D020738:Leptin / Q000378:metabolism*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D019255:NADPH Oxidases / Q000378:metabolism; D052247:Nitric Oxide Synthase Type II / Q000378:metabolism; D065626:Non-alcoholic Fatty Liver Disease; D009765:Obesity / Q000150:complications; D018384:Oxidative Stress; D030421:Peroxynitrous Acid / Q000378:metabolism
chemical_list: D016207:Cytokines; D018836:Inflammation Mediators; D020738:Leptin; D030421:Peroxynitrous Acid; D052247:Nitric Oxide Synthase Type II; C496317:Nos2 protein, mouse; D019255:NADPH Oxidases