Article

Leptin is key to peroxynitrite-mediated stress and Kupffer cell activation in experimental non-alcoholic steatohepatitis

Environmental Health and Disease Laboratory, Department of Environmental Health Sciences, University of South Carolina, Columbia 29208 USA
Journal of Hepatology (Impact Factor: 11.34). 11/2012; 58(4). DOI: 10.1016/j.jhep.2012.11.035
Source: PubMed

ABSTRACT

Background & aims:
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.

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Available from: Ronald P Mason, Jun 11, 2015
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    • "To study the patterns of macrophage activation and M1 polarization bias in NASH, we estimated the intrahepatic M1 cytokine levels of IL-1b, IL- 12, IL-23, and Dectin-1. Because macrophages play a distinct role in the polarization, we administered the macrophage toxin GdCl 3 to deplete the residential and infiltrating macrophages in the liver only in the toxin model of NASH to show the mechanistic role of the macrophages (Chatterjee et al., 2013). NASH develops over a period of time and is progressive in nature. "
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    • "Researchers have found that leptin not only affects appetite, but also produces reactive oxygen species that induces functional damage in endothelial cells [43,44]. Animal studies suggested that increased leptin level in obese rat, through induction of iNOS and NADPH oxidase, caused the peroxynitrite-mediated oxidative stress [45]. Our study results of decreased antioxidants and the increased leptin support our hypothesis that obesity with dyslipidemia will cause lower antioxidant protection and increased oxidative stress than obesity without dyslipidemia. "
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