Oxidative stress induced by intermittent hypoxia exacerbates lipid accumulation and inflammation in a cell model of non-alcoholic steatohepatitis

Oral PresentationBackground/Aims: The prevalence of obstructive sleep apnea (OSA) is high in patients with non-alcoholic fatty liver disease (NAFLD) and NASH is a progressive hallmark of the pathogenesis of NAFLD. Chronic intermittent hypoxia is associated with recurrent episodes of oxygen desaturation and reoxygenation in OSA patients, leading to excessive production of reactive oxygen species (ROS). The causal link between OSA and NAFLD is not known and the mechanistic effect of intermittent hypoxia (IH) on the pathogenesis of NAFLD remains elusive. Here we tested the hypothesis that IH-induced oxidative stress aggravates lipid accumulation and inflammation induced by sodium palmitate in HepG2 cells. Materials and Methods: HepG2 cells were treated with sodium palmitate or vehicle under normoxia (Nx) or IH condition for 72 hours in the present or absence of a ROS scavenger MnTBAP. Cell viability was detected by MTT assay and intracellular lipid deposit was examined by oil red staining. Lipid peroxidation was measured by malondialdehyde (MDA) assay and levels of reactive oxygen species (ROS) were detected by CM-H2DCFDA staining. The expressions of pro-inflammatory cytokines (IL-1β, TNF-α, IL-6), fatty acid uptake-associated genes (caveolin-1 and FATP5), fatty acid synthesis genes (SREBP1 and ACC1) and fatty acid β-oxidation gene ACOX were determined by real-time PCR. Results: Results showed that sodium palmitate increased lipid deposit in the cells and it also decreased cell viability. The effect of sodium palmitate was more prominent in the group co-treated with hypoxia. Levels of MDA and ROS and the expressions of IL-1β, TNF-α, IL-6 and caveolin-1, but not FATP5, were significantly increased in the palmitate- or hypoxia-treated group and were remarkably elevated in the co-treated group. These effects were abolished by MnTBAP treatment. In addition, levels of the expression of ACOX, SREBP1 and ACC1 were significantly lowered in the cells treated with palmitate or hypoxia and the expressions were much less in the cotreated group. Treatment of MnTBAP prevented the decreased expression of ACOX but had no effect on the SREBP1 and ACC1 expression. Conclusion: IH-induced oxidative stress exacerbates lipid accumulation and inflammation induced by sodium palmitate in HepG2 cells, probably mediated by an increase in lipid uptake and a decrease in the fatty acid β-oxidation.published_or_final_versio

Reduction in Hepatic Apoptosis Modulated by Garlic Derived S-Allylmercaptocysteine (SAMC) in Non-Alcoholic Fatty Liver Disease Rat Model Through P53-Dependent Pathways

Poster PresentationPurpose Previous study demonstrated that administration of garlic-derived antioxidant S-allylmercaptocysteine (SAMC) ameliorated hepatic injury in a non-alcoholic fatty liver disease (NAFLD) rat model. In the present study, we investigated the effect and mechanism of SAMC on NAFLD-induced cellular apoptosis in the liver. Methods Adult Sprague-Dawley female rats were fed with a diet comprising of highly unsaturated fat diet (30% fish oil) for 8 weeks to develop NAFLD with or without intraperitoneal injection of 200 mg/kg SAMC three times per week. After chemical euthanasia, liver samples were collected for histological, biochemical and molecular analyses. Results During NAFLD development, increased apoptotic cells were observed in the liver. Hepatic apoptosis was accompanied by activated intrinsic apoptotic pathway as shown by expressional changes of cytochrome c and Bcl-2 family genes. Extrinsic apoptotic pathway was also activated as shown by expressional changes of Fas, TRAIL, FADD and cleaved caspase-8. Increased activity of caspase-3 further confirmed the activation of apoptosis. In addition, reduced activity of LKB1/AMPK and PI3K/Akt pathways could be observed with increased expression of pro-apoptotic regulator p53 in NAFLD rats. Administration of SAMC reduced the number of apoptotic cells through down-regulation of both intrinsic and extrinsic apoptotic mechanisms. Phosphorylation status of LKB1, AMPK, PI3K, and Akt were also restored by SAMC co-treatment, leading to the reduction of p53 expression. Conclusion Administration of SAMC during NAFLD development in rats protects liver from apoptosis through p53-dependent intrinsic and extrinsic apoptotic pathways.published_or_final_versio

Garlic-derived S-allylmercaptocysteine is a hepato-protective agent in non-alcoholic fatty liver disease in vivo animal model

Purpose: To investigate the hepato-protective properties and underlying mechanisms of SAMC in a non-alcoholic fatty liver disease (NAFLD) rat model. Methods: Female rats were fed with a diet comprising highly unsaturated fat diet (30% fish oil) for 8 weeks to develop NAFLD with or without an intraperitoneal injection of 200 mg/kg SAMC three times per week. After euthanasia, blood and liver samples of rats were collected for histological and biochemical analyses. Results: Co-treatment of SAMC attenuated NAFLD-induced liver injury, fat accumulation, collagen formation and free fatty acids (FFAs). At the molecular level, SAMC decreased the lipogenesis marker and restored the lipolysis marker. SAMC also reduced the expression levels of pro-fibrogenic factors and diminished liver oxidative stress partly through the inhibition in the activity of cytochrome P450 2E1-dependent pathway. NAFLD-induced inflammation was also partially mitigated by SAMC treatment via reduction in the pro-inflammatory mediators, chemokines and suppressor of cytokine signaling. The protective effect of SAMC is also shown partly through the restoration of altered phosphorylation status of FFAs-dependent MAP kinase pathways and diminished in the nuclear transcription factors (NF-κB and AP-1) activity during NAFLD development. Conclusions: SAMC is a novel hepato-protective agent against NAFLD caused by abnormal liver functions. Garlic or garlic derivatives could be considered as a potent food supplement in the prevention of fatty liver disease. © 2012 The Author(s).published_or_final_versio

Garlic-derived S-allylmercaptocysteine ameliorates nonalcoholic fatty liver disease in a rat model through inhibition of apoptosis and enhancing autophagy

published_or_final_versio

The iron-chelating drug M30 down-regulates carbon tetrachloride (CCI4)-induced hepatic oxidative stress, inflammation and apoptosis in vitro

Topic: 2 Acute Liver FailureThis journal suppl. entitled: APASL Liver Week 2013BACKGROUND/AIMS: The novel multifunctional brain permeable ironchelator M30 possesses neuroprotective activities against several insults applicable to various neurodegenerative diseases. However, the effect of M30 on CCl4 induced acute liver damage is still unknown. The aim of this study is to investigate whether the multifunctional drug M30 could ameliorate CCl4 induced hepatic injury in human HepG2 cell line. METHODS: HepG2 cells were grown in DMEM supplemented with ...postprin

Zeaxanthin Dipalmitate Therapeutically Improves Hepatic Functions in an Alcoholic Fatty Liver Disease Model through Modulating MAPK Pathway

published_or_final_versio

Intermittent hypoxia aggravates early pathogenesis of non-alcoholic fatty liver disease in rats

BACKGROUND/AIMS: Chronic intermittent hypoxia (CIH) is associated with recurrent episodes of oxygen desaturation and reoxygenation in obstructive sleep apnea (OSA) patients. The prevalence of OSA is high in patients with non-alcoholic fatty liver disease (NAFLD). The mechanistic effect of CIH on the early pathogenesis of NAFLD remains elusive. Here we tested the hypothesis that IH aggravates oxidative stress and inflammation induced by high fat diet at an initial stage of pathogenesis ...postprin

Polysaccharides from Lycium barbarum attenuates hepatic steatosis, fibrosis and inflammation in a non-alcoholic fatty liver diseases (NAFLD) rat model

Topic: 4.a Basic ScienceThis journal suppl. entitled: APASL Liver Week 2013BACKGROUND/AIMS: Lycium barbarum polysaccharides (LBP) are derivative from Wolfberry with antioxidant and neuroprotective properties. Although it shows beneficial effects against aging and oxidative stress in neuron, but whether LBP possesses protective effects in chronic liver injury, such as in non-alcoholic fatty liver disease, (NAFLD), is still unknown. We aimed to investigate the protective effects of ...postprin

Lycium barbarum polysaccharides therapeutically improve hepatic functions in non-alcoholic steatohepatitis rats and cellular steatosis model

link_to_OA_fulltex

Chronic intermittent hypoxia induces local inflammation of the rat carotid body via functional upregulation of proinflammatory cytokine pathways

Maladaptive changes in the carotid body (CB) induced by chronic intermittent hypoxia (IH) account for the pathogenesis of cardiovascular morbidity in patients with sleep-disordered breathing. We postulated that the proinflammatory cytokines, namely interleukin (IL)-1β, IL-6 and tumor necrosis factor (TNF)-α, and cytokine receptors (IL-1r1, gp130 and TNFr1) locally expressed in the rat CB play a pathophysiological role in IH-induced CB inflammation. Results showed increased levels of oxidative stress (serum 8-isoprostane and nitrotyrosine in the CB) in rats with 7-day IH treatment resembling recurrent apneic conditions when compared with the normoxic control. Local inflammation shown by the amount of ED1-containing cells (macrophage infiltration) and the gene transcripts of NADPH oxidase subunits (gp91phox and p22phox) and chemokines (MCP-1, CCR2, MIP-1α, MIP-1β and ICAM-1) in the CB were significantly more in the hypoxic group than in the control. In addition, the cytokines and receptors were expressed in the lobules of chemosensitive glomus cells containing tyrosine hydroxylase and the levels of expressions were significantly increased in the hypoxic group. Exogenous cytokines elevated the intracellular calcium ([Ca2+]i) response to acute hypoxia in the dissociated glomus cells. The effect of cytokines on the [Ca2+]i response was significantly greater in the hypoxic than in the normoxic group. Moreover, daily treatment of IH rats with anti-inflammatory drugs (dexamethasone or ibuprofen) attenuated the levels of oxidative stress, gp91phox expression and macrophage infiltration in the CB. Collectively, these results suggest that the upregulated expression of proinflammatory cytokine pathways could mediate the local inflammation and functional alteration of the CB under chronic IH conditions