Potentiation of hepatic stellate cell activation by extracellular ATP is dependent on P2X7R-mediated NLRP3 inflammasome activation.

Purinergic receptor P2x7 (P2x7R) is a key modulator of liver inflammation and fibrosis. The present study aimed to investigate the role of P2x7R in hepatic stellate cells activation. Lipopolysaccharide (LPS) or the conditioned medium (CM) from LPS-stimulated RAW 264.7 mouse macrophages was supplemented to human hepatic stellate cells, LX-2 for 24h and P2x7R selective antagonist A438079 (10µM) was supplemented to LX-2 cells 1h before LPS or CM stimulation. In addition LX-2 cells were primed with LPS for 4h and subsequently stimulated for 30min with 3mM of adenosine 5'-triphosphate (ATP). A438079 was supplemented to LX-2 cells 10min prior to ATP. Directly treated with LPS on LX-2 cells, mRNA expressions of interleukin (IL)-1ß, IL-18 and IL-6 were increased, as well as mRNA expressions of P2x7R, caspase-1, apoptosis-associated speck-like protein containing CARD (ASC) and NOD-like receptor family, pyrin domain containing 3 (NLRP3) mRNA. LPS also increased α-smooth muscle actin (α-SMA) and type I collagen mRNA expressions, as well as collagen deposition. Interestingly treatment of LX-2 cells with LPS-activated CM exhibited the greater increase of above factors than those in LX-2 cells directly treated with LPS. Pretreatment of A438079 on LX-2 cells stimulated by LPS or LPS-activated CM both suppressed IL-1ß mRNA expression. LPS combined with ATP dramatically increased protein synthesis and cleavage of IL-1ß and its mRNA level than those in HSC treated with LPS or ATP alone. Additionally LX-2 cells primed with LPS and subsequently stimulated for 30min with ATP greatly increased mRNA and protein expression of caspase-1, NLRP3 and P2x7R, as well as liver fibrosis markers, α-SMA and type I collagen. These events were remarkably suppressed by A438079 pretreatment. siRNA against P2x7R reduced protein expression of NLRP3 and α-SMA, and suppressed deposition and secretion of type I collagen. The involvement of P2X7R-mediated NLRP3 inflammasome activation in IL-1ß production of HSC might contribute to ECM deposition and suggests that blockade of the P2x7R-NLRP3 inflammasome axis represents a potential therapeutic target to liver fibrosis.

Salidroside Regulates Inflammatory Response in Raw 264.7 Macrophages via TLR4/TAK1 and Ameliorates Inflammation in Alcohol Binge Drinking-Induced Liver Injury.

The current study was designed to investigate the anti-inflammatory effect of salidroside (SDS) and the underlying mechanism by using lipopolysaccharide (LPS)-stimulated RAW 264.7 macrophages in vitro and a mouse model of binge drinking-induced liver injury in vivo. SDS downregulated protein expression of toll-like receptor 4 (TLR4) and CD14. SDS inhibited LPS-triggered phosphorylation of LPS-activated kinase 1 (TAK1), p38, c-Jun terminal kinase (JNK), and extracellular signal-regulated kinase (ERK). Degradation of IκB-α and nuclear translocation of nuclear factor (NF)-κB were effectively blocked by SDS. SDS concentration-dependently suppressed LPS mediated inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) protein levels, as well as their downstream products, NO. SDS significantly inhibited protein secretion and mRNA expression of of interleukin (IL)-1ß and tumor necrosis factor (TNF)-α. Additionally C57BL/6 mice were orally administrated SDS for continuous 5 days, followed by three gavages of ethanol every 30 min. Alcohol binge drinking caused the increasing of hepatic lipid accumulation and serum transaminases levels. SDS pretreatment significantly alleviated liver inflammatory changes and serum transaminases levels. Further investigation indicated that SDS markedly decreased protein level of IL-1ß in serum. Taken together, these data implied that SDS inhibits liver inflammation both in vitro and in vivo, and may be a promising candidate for the treatment of inflammatory liver injury.

Protective effect of cornuside against carbon tetrachloride-induced acute hepatic injury.

This study elucidated the effects of cornuside on carbon tetrachloride (CCl4)-induced hepatotoxicity. Rats were treated intraperitoneally with 0.5 mL/kg of CCl4. Sixteen h after CCl4 treatment, the levels of serum aminotransferases, tumor necrosis factor-α (TNF-α), and lipid peroxidation were significantly elevated, whereas the hepatic antioxidative enzyme activities were decreased. These changes were attenuated by cornuside. Histological studies also indicated that cornuside inhibited CCl4-induced liver damage. Furthermore, the contents of hepatic nitrite, inducible nitric oxide synthase (iNOS), and cyclooxygenase-2 (COX-2) were elevated after CCl4 treatment, while cytochrome P450 2E1 (CYP2E1) expression was suppressed. Cornuside treatment inhibited the formation of liver nitrite, and reduced the overexpression of iNOS and COX-2 proteins, but restored the liver CYP2E1 content as compared with the CCl4-treated rats. Our data indicate that cornuside protects the liver from CCl4-induced acute hepatotoxicity, perhaps due to its ability to restore the CYP2E1 function and suppress inflammatory responses, in combination with its capacity to reduce oxidative stress.

Liver kinase B1/AMP-activated protein kinase-mediated regulation by gentiopicroside ameliorates P2X7 receptor-dependent alcoholic hepatosteatosis.

BACKGROUND AND PURPOSE: Regulating P2X7 receptor-mediated activation of NLRP3 inflammasomes could be a therapeutic strategy to treat alcoholic hepatosteatosis. We investigated whether this process was modulated by gentiopicroside, the main active secoiridoid glycoside from Gentiana manshurica Kitagawa. EXPERIMENTAL APPROACH: In vivo models of acute and chronic alcoholic hepatosteatosis were established by intragastrically administered ethanol or using chronic plus binge ethanol feeding of Lieber-DeCarli liquid diet to male C57BL/6 mice. In vitro, HepG2 cells were treated with ethanol. RAW 264.7 macrophages and murine bone marrow-derived macrophages (BMDMs) were stimulated with LPS and ATP. KEY RESULTS: In both the acute and chronic alcohol-induced mouse hepatosteatosis models, gentiopicroside decreased serum aminotransferases and triglyceride accumulation. Up-regulated SREBP1, down-regulated PPARα and phosphorylated acetyl-CoA carboxylase caused by acute and chronic alcohol feeding were modulated by gentiopicroside, through the elevation of LKB1 and AMPK. Suppression of P2X7 receptor-NLRP3 activation by gentiopicroside inhibited IL-1ß production. In ethanol-exposed HepG2 cells, gentiopicroside reduced lipogenesis and promoted lipid oxidation via activation of P2X7 receptor-NLRP3 inflammasomes. Genetic or pharmacological blockade of P2X7 receptors enhanced AMPK activity and reduced SREBP1 expression in ethanol-treated HepG2 cells. Gentiopicroside down-regulated P2X7 receptor-mediated inflammatory responses in LPS/ATP-stimulated RAW 264.7 macrophages and BMDMs. IL-1ß from macrophages accelerated lipid accumulation in hepatocytes. Depleting macrophages by clodronate liposomes ameliorated alcoholic hepatosteatosis, and it was further alleviated by gentiopicroside. CONCLUSIONS AND IMPLICATIONS: Activation of LKB1/AMPK signalling by gentiopicroside was mediated by the P2X7 receptor-NLRP3 inflammasome, suggesting the therapeutic value of blocking P2X7 receptors in the treatment of alcoholic hepatosteatosis.

Acanthoic acid suppresses lipin1/2 via TLR4 and IRAK4 signalling pathways in EtOH- and lipopolysaccharide-induced hepatic lipogenesis.

OBJECTIVES: In alcoholic liver disease, alcohol and lipopolysaccharide (LPS) are major stimulation factors of hepatic lipogenesis. Our objective was to determine the protective mechanism of acanthoic acid (AA) in EtOH- and LPS-induced hepatic lipogenesis. METHODS: HSC-T6 cells were treated with ethanol (200 mm) plus LPS (1 µg/ml) for 1 h, followed by AA (10 or 20 µm) for another 6 h. C57BL/6 mice were pretreated with of AA (20 and 40 mg/kg) or equal volume of saline and then exposed to three doses of ethanol (5 g/kg body weight) within 24 h. The mice were sacrificed at 6 h after the last ethanol dosing. KEY FINDINGS: Acanthoic acid significantly decreased the expressions of α-SMA, collagen-I, SREBP-1, and lipin1/2 induced, also decreased fat droplets caused by EtOH/LPS. AA treatment decreased the protein expressions of TLR4, CD14, IRAK4, TRAF3, p-TAK1 and NF-κB increased by EtOH/LPS on HSC cells. Results in vivo were consistent with results in vitro. CONCLUSIONS: Our data demonstrated that AA might modulate hepatic fibrosis and lipid deposition in HSC-T6 cell stimulated with ethanol combined with LPS by decreasing lipin1/2 via TLR4 and IRAK4 signalling pathways, and AA might be considered as a potential therapeutic candidate for alcoholic liver disease.

Ginsenoside Rh2 Downregulates LPS-Induced NF- κ B Activation through Inhibition of TAK1 Phosphorylation in RAW 264.7 Murine Macrophage.

The present study was carried out to evaluate the inhibitory effects of ginsenoside Rh2 on nuclear-factor- (NF-) κ B in lipopolysaccharide- (LPS-) activated RAW 264.7 murine macrophages. RAW 264.7 cells were pretreated with indicated concentrations of ginsenoside Rh2 for 1 h prior to the incubation of LPS (1 µ g/mL) for indicated time period. Ginsenoside Rh2 reduced CD14 and Toll-like receptor 4 (TLR4) expressions 24 h after LPS stimulation. Furthermore, ginsenoside Rh2 significantly inhibited TGF-beta-activated kinase 1 (TAK1) phosphorylation 30 min after LPS stimulation. Ginsenoside Rh2 was further shown to inhibit NF- κ B p65 translocation into the nucleus by suppressing I κ B- α degradation. Also, LPS increased mRNA expression of TNF- α and IL-1 α time-dependently, while TQ reduced TNF- α within 3 h and IL-1 α within 1 h. And we firstly found that pretreatment of ginsenoside Rh2 successively inhibited hypoxia-inducible factor- (HIF-) 1 α expression increased by LPS. In conclusion, ginsenoside Rh2 may inhibit LPS-induced NF- κ B activation and reduce HIF-1 α accumulation, suggesting that ginsenoside Rh2 may be considered as a potential therapeutic candidate for chronic inflammatory diseases.

Betulinic acid prevention of d-galactosamine/lipopolysaccharide liver toxicity is triggered by activation of Bcl-2 and antioxidant mechanisms.

OBJECTIVES: The hepatoprotective activity and molecular mechanism of betulinic acid (BA) was investigated on acute liver failure induced by d-galactosamine (D-GalN)/lipopolysaccharide (LPS) in vivo. METHODS: Mice were administered with different doses of BA (20 mg/kg or 50 mg/kg, i.p.) 1 h before injection of D-GalN (700 mg/kg)/LPS (10 µg/kg) and sacrificed 6 h after treatment with D-GalN/LPS. KEY FINDINGS: Pretreatment with BA significantly prevented the increases of serum aspartate aminotransferase and alanine aminotransferase, while it increased the content of glutathione and catalase, and reduced malondialdehyde. BA showed obvious anti-oxidant effects and prevented D-GalN/LPS-induced apoptosis, as indicated by DNA ladder. BA treatment resulted in regulation of the mitogen-activated protein kinase. We found that BA mediated production of c-jun NH(2) -terminal protein kinase and extracellular signal-regulated kinase induced by D-GalN/LPS, promoted the expression of B-cell CLL/lymphoma 2 (Bcl-2) and restored mitochondrial outer membrane permeabilization. CONCLUSIONS: The results suggested that BA prevented D-GalN/LPS-induced acute liver failure by upregulation of Bcl-2 and antioxidation and mediation of cytokines causing apoptotic cell death and lessened liver damage.

Gentiana manshurica Kitagawa reverses acute alcohol-induced liver steatosis through blocking sterol regulatory element-binding protein-1 maturation.

This study was undertaken to investigate the protective effects of Gentiana manshurica Kitagawa (GM) on acute alcohol-induced fatty liver. Mice were treated with ethanol (5 g/kg of body weight) by gavage every 12 h for a total of three doses to induce acute fatty liver. Methanol extract of GM (50, 100, or 200 mg/kg) or silymarin (100 mg/kg) was gavaged simultaneously with ethanol for three doses. GM administration significantly reduced the increases in serum ALT and AST levels, the serum and hepatic triglyceride levels, at 4 h after the last ethanol administration. GM was also found to prevent ethanol-induced hepatic steatosis and necrosis, as indicated by liver histopathological studies. Additionally, GM suppressed the elevation of malondialdehyde (MDA) levels, restored the glutathione (GSH) levels, and enhanced the superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPX) activities. The concurrent administration of GM efficaciously abrogated cytochrome P450 2E1 (CYP2E1) induction. Moreover, GM significantly reduced the nuclear translocation of sterol regulatory element-binding protein-1 (nSREBP-1) in ethanol-treated mice. These data indicated that GM possessed the ability to prevent ethanol-induced acute liver steatosis, possibly through blocking CYP2E1-mediated free radical scavenging effects and SREBP-1-regulated fatty acid synthesis. Especially, GM may be developed as a potential therapeutic candidate for ethanol-induced oxidative damage in liver.