Increased oxidative capacity of circulating polymorphonuclear neutrophils (PMNs) in non-diabetic NASH patients

Background: Inflammation and oxidative stress are key factors in the pathogenesis of non-alcoholic steatohepatitis (NASH). Polymorphonuclear neutrophils are capable to produce significant amounts of reactive oxygen species (ROS) via the NADPH oxidase complex. Increased hepatic neutrophil infiltration has been described in steatohepatitis. We aimed to investigate the in vitro ROS generation by neutrophils of NASH patients and the hepatic NADPH oxidase activity in murine steatohepatitis. Material and methods: PMNs were isolated from peripheral blood of NASH patients (n=16) and healthy controls (n=16). In vitro ROS production was measured by luminol chemiluminescence after phorbol myristate acetate (PMA) or opsonized zymosan stimulation. Hepatic lipid peroxidation and NADPH oxidase activation were measured in mice fed with methionine-choline-deficient (MCD) or -supplemented (MCS) diets. Results: PMA activated oxidative burst both in patients and controls. However, ROS production was significantly increased in non-diabetic NASH patients (n=9) compared to controls 30 min after the PMA stimulation. PMNs from NASH patients with diabetes mellitus (n=7) did not have higher ROS production after PMA-stimulation compared to controls. The PMA-induced peak chemiluminescence was significantly higher in the non-diabetic NASH patients compared to controls and diabetic NASH patients. No significant difference was observed without any stimulation and in opsonized zymosan induced chemiluminescence. Consistent with the increased oxidative capacity of PMNs in NASH patients, we found increased hepatic lipid peroxidation, higher expression and activation of the NADPH oxidase complex in MCD-steatohepatitis. Conclusion: Our finding supports the role of neutrophil oxidative stress in NASH. Our novel data suggests that the increased oxidative capacity of the PMNs it is not only localized to the liver but can have systemic effects and serve as a potential biomarker of NASH

IL-1 receptor antagonist ameliorates inflammasome-dependent alcoholic steatohepatitis in mice

Alcoholic liver disease (ALD) is characterized by steatosis and upregulation of proinflammatory cytokines, including IL-1beta. IL-1beta, type I IL-1 receptor (IL-1R1), and IL-1 receptor antagonist (IL-1Ra) are all important regulators of the IL-1 signaling complex, which plays a role in inflammation. Furthermore, IL-1beta maturation is dependent on caspase-1 (Casp-1). Using IL-1Ra-treated mice as well as 3 mouse models deficient in regulators of IL-1beta activation (Casp-1 and ASC) or signaling (IL-1R1), we found that IL-1beta signaling is required for the development of alcohol-induced liver steatosis, inflammation, and injury. Increased IL-1beta was due to upregulation of Casp-1 activity and inflammasome activation. The pathogenic role of IL-1 signaling in ALD was attributable to the activation of the inflammasome in BM-derived Kupffer cells. Importantly, in vivo intervention with a recombinant IL-1Ra blocked IL-1 signaling and markedly attenuated alcohol-induced liver inflammation, steatosis, and damage. Furthermore, physiological doses of IL-1beta induced steatosis, increased the inflammatory and prosteatotic chemokine MCP-1 in hepatocytes, and augmented TLR4-dependent upregulation of inflammatory signaling in macrophages. In conclusion, we demonstrated that Casp-1-dependent upregulation of IL-1beta and signaling mediated by IL-1R1 are crucial in ALD pathogenesis. Our findings suggest a potential role of IL-1R1 inhibition in the treatment of ALD

MicroRNA-155 Deficiency Attenuates Liver Steatosis and Fibrosis without Reducing Inflammation in a Mouse Model of Steatohepatitis

BACKGROUND & AIM: MicroRNAs (miRs) regulate hepatic steatosis, inflammation and fibrosis. Fibrosis is the consequence of chronic tissue damage and inflammation. We hypothesized that deficiency of miR-155, a master regulator of inflammation, attenuates steatohepatitis and fibrosis. METHODS: Wild type (WT) and miR-155-deficient (KO) mice were fed methionine-choline-deficient (MCD) or -supplemented (MCS) control diet for 5 weeks. Liver injury, inflammation, steatosis and fibrosis were assessed. RESULTS: MCD diet resulted in steatohepatitis and increased miR-155 expression in total liver, hepatocytes and Kupffer cells. Steatosis and expression of genes involved in fatty acid metabolism were attenuated in miR-155 KO mice after MCD feeding. In contrast, miR-155 deficiency failed to attenuate inflammatory cell infiltration, nuclear factor kappa beta (NF-kappaB) activation and enhanced the expression of the pro-inflammatory cytokines tumor necrosis factor alpha (TNFalpha) and monocyte chemoattractant protein-1 (MCP1) in MCD diet-fed mice. We found a significant attenuation of apoptosis (cleaved caspase-3) and reduction in collagen and alpha smooth muscle actin (alphaSMA) levels in miR-155 KO mice compared to WTs on MCD diet. In addition, we found attenuation of platelet derived growth factor (PDGF), a pro-fibrotic cytokine; SMAD family member 3 (Smad3), a protein involved in transforming growth factor-beta (TGFbeta) signal transduction and vimentin, a mesenchymal marker and indirect indicator of epithelial-to-mesenchymal transition (EMT) in miR-155 KO mice. Nuclear binding of CCAAT enhancer binding protein beta (C/EBPbeta) a miR-155 target involved in EMT was significantly increased in miR-155 KO compared to WT mice. CONCLUSIONS: Our novel data demonstrate that miR-155 deficiency can reduce steatosis and fibrosis without decreasing inflammation in steatohepatitis

Molecular hepatic carcinogenesis: impact of inflammation

Hepatocellular cancer (HCC) represents one of the most rapidly spreading cancers in the world. Most HCC develops in cirrhotic livers after prolonged inflammation, supporting the hypothesis that inflammation contributes to cancer development. Increasing evidence suggests that inflammatory cell recruitment and activation is an important contributor to promoting cancerous malformation in hepatocytes. Intracellular signaling pathways involved in classical inflammatory pathway activation can be altered in parenchymal cells, hepatocytes, in the liver to promote HCC development. Inflammation is triggered by pathogen-derived or endogenous danger-associated molecular patterns via pattern recognition receptors. Activation of the pattern recognition receptors triggers downstream signaling cascades to induce proinflammatory cytokine production, release of reactive oxygen species and modulate cellular responses. Many of these inflammatory mediators have adverse effects on DNA repair and induce DNA methylation, both of which are important elements in HCC development. This review summarizes the key points and discusses recent findings related to the role of inflammation in cancer and HCC development

Micro-RNA-155 Deficiency Prevents Alcohol-Induced Serum Endotoxin Increase and Small Bowel Inflammation in Mice

BACKGROUND: Chronic alcohol impairs gut barrier function and induces inflammatory cytokines. The effects of acute alcohol binge on the gut are partially understood. Micro-RNA-155 (miR-155), a modulator of cytokine and T-cell immune response in the gut, stabilizes tumor necrosis factor-alpha (TNFalpha) mRNA. Here, we investigated the role of the inflammation modulator miR-155 as well as the effects of acute binge and chronic alcohol feeding in the small bowel (SB) in mice. METHODS: For the acute alcohol binge, wild-type (WT) mice received 5 g/kg 50% alcohol/d or equal amount of water oral gavage for 3 days. WT and miR-155-deficient (miR-155-knockout [KO]) mice received ethanol containing Lieber-DeCarli or isocaloric control diet for 5 weeks. MiR-155, antimicrobial peptide, regenerating islet-derived 3-beta (Reg3b), inflammation markers, Src homology 2-containing inositol phosphatase-1 (SHIP1), TNFalpha, and nuclear factor-kappaB (NF-kappaB) were measured in proximal intestinal tissue. Endotoxin was measured in the serum. RESULTS: Acute alcohol binge enhanced, whereas chronic alcohol feeding decreased, Reg3b mRNA and protein levels in the SB. Both acute binge and chronic alcohol feeding increased serum endotoxin levels, intestinal NF-kappaB activation and TNFalpha mRNA levels. However, TNFalpha protein and miR-155 were increased only after chronic alcohol feeding in the SB. Furthermore, miR-155-KO mice were protected from chronic alcohol-induced increase in serum endotoxin, intestinal TNFalpha, and NF-kappaB activation. Also, alcohol-fed miR-155-KO mice had no decrease of Reg3b and SHIP1 levels. CONCLUSIONS: These results demonstrate that both acute binge and chronic ethanol administration result in increased serum-endotoxin levels. Our study identifies a novel role for miR-155 in chronic alcohol-induced intestinal inflammation and barrier dysfunction

Chronic alcohol-induced microRNA-155 contributes to neuroinflammation in a TLR4-dependent manner in mice.

INTRODUCTION: Alcohol-induced neuroinflammation is mediated by pro-inflammatory cytokines and chemokines including tumor necrosis factor-α (TNFα), monocyte chemotactic protein-1 (MCP1) and interleukin-1-beta (IL-1β). Toll-like receptor-4 (TLR4) pathway induced nuclear factor-κB (NF-κB) activation is involved in the pathogenesis of alcohol-induced neuroinflammation. Inflammation is a highly regulated process. Recent studies suggest that microRNAs (miRNAs) play crucial role in fine tuning gene expression and miR-155 is a major regulator of inflammation in immune cells after TLR stimulation. AIM: To evaluate the role of miR-155 in the pathogenesis of alcohol-induced neuroinflammation. METHODS: Wild type (WT), miR-155- and TLR4-knockout (KO) mice received 5% ethanol-containing or isocaloric control diet for 5 weeks. Microglia markers were measured by q-RTPCR; inflammasome activation was measured by enzyme activity; TNFα, MCP1, IL-1β mRNA and protein were measured by q-RTPCR and ELISA; phospho-p65 protein and NF-κB were measured by Western-blotting and EMSA; miRNAs were measured by q-PCR in the cerebellum. MiR-155 was measured in immortalized and primary mouse microglia after lipopolysaccharide and ethanol stimulation. RESULTS: Chronic ethanol feeding up-regulated miR-155 and miR-132 expression in mouse cerebellum. Deficiency in miR-155 protected mice from alcohol-induced increase in inflammatory cytokines; TNFα, MCP1 protein and TNFα, MCP1, pro-IL-1β and pro-caspase-1 mRNA levels were reduced in miR-155 KO alcohol-fed mice. NF-κB was activated in WT but not in miR-155 KO alcohol-fed mice. However increases in cerebellar caspase-1 activity and IL-1β levels were similar in alcohol-fed miR-155-KO and WT mice. Alcohol-fed TLR4-KO mice were protected from the induction of miR-155. NF-κB activation measured by phosphorylation of p65 and neuroinflammation were reduced in alcohol-fed TLR4-KO compared to control mice. TLR4 stimulation with lipopolysaccharide in primary or immortalized mouse microglia resulted in increased miR-155. CONCLUSION: Chronic alcohol induces miR-155 in the cerebellum in a TLR4-dependent manner. Alcohol-induced miR-155 regulates TNFα and MCP1 expression but not caspase-dependent IL-1β increase in neuroinflammation

microRNA-122 regulates hypoxia-inducible factor-1 and vimentin in hepatocytes and correlates with fibrosis in diet-induced steatohepatitis

BACKGROUND and AIMS: miR-122 is the most abundant miRNA in the liver particularly in hepatocytes where it targets cholesterol metabolism. Steatosis, a key component of non-alcoholic fatty liver disease, is regulated by hypoxia-inducible factor-1alpha (HIF-1alpha). Here, we hypothesized that reduced miR-122 has a pathogenic role in steatohepatitis. METHODS: miR-122 and its target genes were evaluated in mouse livers and/or isolated hepatocytes after methionine-choline-deficient (MCD) or methionine-choline-supplemented (MCS) diet. RESULTS: Liver and hepatocyte miR-122 expression was significantly decreased in steatohepatitis. A maximum reduction in miR-122 occurred at the fibrosis stage (8 weeks of MCD diet). MAP3K3, a miR-122 target gene, was induced at all stages of non-alcoholic steatohepatitis (NASH; 3-8 weeks) only at the mRNA level. Increased NF-kappaB activation was found in MCD diet-fed mice and MAP3K3 regulated the NF-kappaB DNA binding in naive hepatocytes. HIF-1alpha mRNA and DNA binding and expression of the HIF-1alpha target gene, profibrotic lysyl oxidase, was increased in advanced steatohepatitis (8 weeks). In addition, increase in vimentin and Sirius red staining (liver fibrosis) was found at 8 weeks of MCD diet. Using miR-122 overexpression and inhibition approaches, we confirmed that HIF-1alpha, vimentin and MAP3K3 are novel miR-122 targets in hepatocytes. We report transcriptional repression of miR-122 in NASH. Decreased liver miR-122 was associated with elevated circulating miR-122 in both exosome-rich and protein-rich serum fractions. CONCLUSIONS: Our novel data suggest that decreased liver miR-122 contributes to upregulation of modulators of tissue remodelling (HIF-1alpha, vimentin and MAP3K3) and might play a role in NASH-induced liver fibrosis

Alcohol-induced IL-1beta in the brain is mediated by NLRP3/ASC inflammasome activation that amplifies neuroinflammation

Alcohol-induced neuroinflammation is mediated by proinflammatory cytokines, including IL-1beta. IL-1beta production requires caspase-1 activation by inflammasomes-multiprotein complexes that are assembled in response to danger signals. We hypothesized that alcohol-induced inflammasome activation contributes to increased IL-1beta in the brain. WT and TLR4-, NLRP3-, and ASC-deficient (KO) mice received an ethanol-containing or isocaloric control diet for 5 weeks, and some received the rIL-1ra, anakinra, or saline treatment. Inflammasome activation, proinflammatory cytokines, endotoxin, and HMGB1 were measured in the cerebellum. Expression of inflammasome components (NLRP1, NLRP3, ASC) and proinflammatory cytokines (TNF-alpha, MCP-1) was increased in brains of alcohol-fed compared with control mice. Increased caspase-1 activity and IL-1beta protein in ethanol-fed mice indicated inflammasome activation. TLR4 deficiency protected from TNF-alpha, MCP-1, and attenuated alcohol-induced IL-1beta increases. The TLR4 ligand, LPS, was not increased in the cerebellum. However, we found up-regulation of acetylated and phosphorylated HMGB1 and increased expression of the HMGB1 receptors (TLR2, TLR4, TLR9, RAGE) in alcohol-fed mice. NLRP3- or ASC-deficient mice were protected from caspase-1 activation and alcohol-induced IL-1beta increase in the brain. Furthermore, in vivo treatment with rIL-1ra prevented alcohol-induced inflammasome activation and IL-1beta, TNF-alpha, and acetylated HMGB1 increases in the cerebellum. Conversely, intracranial IL-1beta administration induced TNF-alpha and MCP-1 in the cerebellum. In conclusion, alcohol up-regulates and activates the NLRP3/ASC inflammasome, leading to caspase-1 activation and IL-1beta increase in the cerebellum. IL-1beta amplifies neuroinflammation, and disruption of IL-1/IL-1R signaling prevents alcohol-induced inflammasome activation and neuroinflammation. Increased levels of acetylated and phosphorylated HMGB1 may contribute to alcoholic neuroinflammation

Mitochondrial antiviral signaling protein defect links impaired antiviral response and liver injury in steatohepatitis in mice

Mitochondrial dysfunction is a pathogenic feature of nonalcoholic steatohepatitis (NASH). NASH complicates hepatotropic viral disease. The mitochondrial antiviral signaling protein (MAVS) is the adapter of helicase receptors involved in sensing double-stranded RNA (dsRNA). We hypothesized that impaired MAVS function may contribute to insufficient antiviral response and liver damage in steatohepatitis. We identified reduced MAVS protein levels and increased MAVS association with the proteasome subunit alpha type 7 (PSMA7) in livers from mice given a methionine-choline-deficient (MCD) diet. Decreased association of MAVS with mitochondria and increased cytosolic cytochrome c indicated mitochondrial damage in steatohepatitis. In vivo administration of the synthetic dsRNA polyinosinic:polycytidylic acid [poly(I:C)], but not lipopolysaccharide or cytidine-phosphate-guanosine-rich DNA, resulted in impaired induction of type I interferons (IFNs) and proinflammatory cytokines in steatohepatitis. Consistent with a defect in helicase receptor-induced signaling, there was loss of poly(I:C)-induced translocation of MAVS to the cytosol and decreased IFN regulatory factor 3 phosphorylation. Caspases 1 and 8, both of which cleave MAVS, were increased in MCD diet-fed mice. At baseline, steatohepatitis was associated with increased serum alanine aminotransferase (ALT), apoptosis and caspase 3 activation compared with controls. In contrast to apoptosis in controls, necrosis was induced by poly(I:C) stimulation in steatohepatitis. Hepatocyte necrosis was indicated by elevated serum high-mobility group box protein-1 and ALT and was correlated with increased expression of receptor-interacting protein 3 (RIP3), a master regulator of necrosis. Increased expression of MAVS, PSMA7, and RIP3 messenger RNA was also present in human NASH livers. CONCLUSION: Our novel findings suggest that mitochondrial damage in steatohepatitis extends to MAVS, an adapter of helicase receptors, resulting in inefficient type I IFN and inflammatory cytokine response but increased hepatocyte necrosis and RIP3 induction in response to a dsRNA viral challenge. These mechanisms may contribute to progressive liver damage and impaired viral clearance in NASH