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

Abstract

Background and 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 DIO mice 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 steatotic liver through induction of iNOS and NADPH oxidase caused peroxynitrite-mediated oxidative stress thus activating Kupffer cells.

NADPH Oxidase–Derived Peroxynitrite Drives Inflammation in Mice and Human Nonalcoholic Steatohepatitis via TLR4-Lipid Raft Recruitment

“…18 Here, we used a dual approach to study the formation of peroxynitrite via NADPH oxidase, by using a general decomposition catalyst, FeTPPS, and by helping peroxynitrite react with a novel boronic compound, FBA, in vivo. 41 Modeling human NASH using rodents remains a challenge to researchers.…”

“…19 NOX2 is involved in NASH development. 16,18,20 NOX2 stimulation by high leptin results in peroxynitrite generation, thus causing Kupffer cell activation in NASH. 18 NOX2 has also been shown to facilitate the recruitment of TLR4 into lipid rafts and to help in receptor dimerization and its association with myeloid differentiation 2 in several inflammatory diseases.…”

“…16,18,20 NOX2 stimulation by high leptin results in peroxynitrite generation, thus causing Kupffer cell activation in NASH. 18 NOX2 has also been shown to facilitate the recruitment of TLR4 into lipid rafts and to help in receptor dimerization and its association with myeloid differentiation 2 in several inflammatory diseases. 21 Because there is no evidence of the molecular events that follow NADPH oxidase activation concerning the type of reactive species formation and the mechanisms that link TLR4 activation, we investigated the role of peroxynitrite in TLR4 activation in NASH.…”

“…We used a decomposition catalyst and a scavenger of peroxynitrite to support the involvement of peroxynitrite. 18,19 The results of the study, which used transgenic mice and a pharmacological approach, show for the first time a molecular basis of NADPH oxidaseemediated, peroxynitrite-driven TLR4 activation in causing sinusoidal injury, inflammation, and stellate cell proliferation in NASH.…”

Non-alcoholic fatty liver disease in the patients presenting with abdominal obesity

“…Были изучены механизмы участия лептина в избыточном отложении липидов в пече ночной ткани и запуске фиброгенеза [19]. Лептин усиливает фагоцитарную активность и выработку цитокинов купферовскими клетками и макрофага ми, стимулирует пролиферацию эндотелиоцитов и продукцию ими активных форм кислорода, то есть участвует в запуске «второго толчка» (оксидативно го стресса) в патогенезе НАЖБП [20,21]. Он может рассматриваться в качестве предиктора развития стеатоза, воспалительных изменений в печеночной ткани, фиброза при НАЖБП, но результаты прове денных исследований противоречивы [22].…”