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


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.

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.

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.

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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    ABSTRACT: Activation of M1 macrophages in the nonalcoholic steatohepatitis (NASH) following several external or endogenous factors viz inflammatory stimuli, oxidative stress and cytokines are known. However, any direct role of oxidative stress in causing M1 polarization in NASH has been unclear. We hypothesized that CYP2E1-mediated oxidative stress causes M1 polarization in experimental NASH and NO donor administration inhibits CYP2E1 mediated inflammation with concomitant attenuation of M1 polarization. Since CYP2E1 takes center stage in these studies we use a toxin model of NASH which uses a ligand and a substrate of CYP2E1 for inducing NASH. Subsequently we use a methionine and choline deficient diet induced rodent NASH model where CYP2E1 role in disease progression has been shown. Results show that CYP2E1 causes M1 polarization bias that includes a significant increase in IL-1β and IL-12 in both models of NASH while CYP2E1 null mice or diallyl sulfide administration prevented it. Administration of GdCl3, a macrophage toxin attenuated both the initial M1 response and subsequent M2 response showing the observed increase in cytokine levels is primarily from macrophages. Based on the evidence of an adaptive NO increase, NO donor administration in vivo, that mechanistically inhibited CYP2E1 catalyzed oxidative stress during the entire study in NASH abrogated M1 polarization and NASH progression. The results obtained show the association of CYP2E1 in M1 polarization and that inhibition of CYP2E1 catalyzed oxidative stress by NO donor (DETA NONOate) can be a promising therapeutic strategy in NASH.
    Full-text · Article · Oct 2014 · Journal of Pharmacology and Experimental Therapeutics
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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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    ABSTRACT: BACKGROUD/OBEJECTIVES It is hypothesized that obese people with dyslipidemia is more likely to have increased oxidative stress and decreased antioxidant status, in comparison with the controls who were obese without dyslipidemia. Thus, the aims of the present study were to determine the dietary intakes, plasma adipokines, and antioxidative systems between obese with dyslipidemia and obese without dyslipidemia were investigated. SUBJECTS/METHODS Female subjects who were between 20 and 55 years old, and whose BMI was 23 or greater were recruited. Subjects who met the criteria of BMI ≥ 23, total cholesterol ≥ 200 mg/dL, LDL cholesterol ≥ 130 mg/dL, and TG ≥ 110 mg/dL were categorized Obese with dyslipidemia. Anthropometric measurements and blood biochemical tests were conducted. The diet survey was conducted by a trained dietitian using two days of 24 hour dietary recall. The lipid peroxidation, the plasma total antioxidant capacity (TAC), the activities of antioxidantive enzymes, and various antioxidantive vitamins levels were determined. RESULTS Plasma adiponectin and leptin levels were also determined. There were no significant differences for age, Body Mass index (BMI), and body fat (%), waist-size between two groups. Obese with dyslipidemia had significantly high levels of total cholesterol, triglyceride, LDL-cholesterol, the ratio of total cholesterol/HDL-C, and the ratio of HDL-C/LDL-C, respectively. Blood alkaline phosphatase level was statistically different between the two groups (P < 0.05). No statistical significance in dietary intake between two groups was shown. In case of obese with dyslipidemia group, the levels of GSH-Px (P < 0.05) and catalase (P < 0.05) as well as adjusted blood retinol (P < 0.05) and tocopherol level (P < 0.05) were significantly low. However, the plasma concentration of leptin was significantly high (P < 0.05). CONCLUSIONS Obesity with dyslipidemia was shown to have high arthtrogenic index, depleted antioxidant status, and higher blood leptin levels which suggest higher risks of oxidative stress and cardiovascular diseases.
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    • "The proinflammatory nature of obesity is marked by increased release of cytokines and adipokine leptin, the levels of which are increased in circulation following leptin resistance (Munzberg, 2010; Parola and Marra, 2011). Our research has indicated that free radical metabolism of carbon tetrachloride, a known hepatotoxin, increases hepatic leptin levels over and above the amounts found in obesity (Chatterjee et al., 2012a). Fibrosis of liver, which is a feature of full-blown NASH, causes a significant reprogramming of the hepatic carbohydrate and lipid metabolism, in order to accommodate the changed metabolic microenvironment of the obese liver (Chen et al., 2012). "
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