Estriol Enhances Lipopolysaccharide-Induced Increases in Nitric Oxide Production by Kupffer Cells via Mechanisms Dependent on Endotoxin

Molecular Changes in Relation to Alcohol Consumption and Hepatocellular Carcinoma

Alcohol is the one of the major causes of liver diseases and promotes liver cirrhosis and hepatocellular carcinoma (HCC). In hepatocytes, alcohol is converted to acetaldehyde, which causes hepatic steatosis, cellular apoptosis, endoplasmic reticulum stress, peroxidation, production of cytokines and reduces immune surveillance. Endotoxin and lipopolysaccharide produced from intestinal bacteria also enhance the production of cytokines. The development of hepatic fibrosis and the occurrence of HCC are induced by these alcohol metabolites. Several host genetic factors have recently been identified in this process. Here, we reviewed the molecular mechanism associated with HCC in alcoholic liver disease.

A Unifying Hypothesis Linking Hepatic Adaptations for Ethanol Metabolism to the Proinflammatory and Profibrotic Events of Alcoholic Liver Disease

The pathogenesis of alcoholic liver disease (ALD) remains poorly understood but is likely a multihit pathophysiological process. Here, we propose a hypothesis of how early mitochondrial adaptations for alcohol metabolism lead to ALD pathogenesis. Acutely, ethanol (EtOH) feeding causes a near doubling of hepatic EtOH metabolism and oxygen consumption within 2 to 3 hours. This swift increase in alcohol metabolism (SIAM) is an adaptive response to hasten metabolic elimination of both EtOH and its more toxic metabolite, acetaldehyde (AcAld). In association with SIAM, EtOH causes widespread hepatic mitochondrial depolarization (mtDepo), which stimulates oxygen consumption. In parallel, voltage-dependent anion channels (VDAC) in the mitochondrial outer membrane close. Together, VDAC closure and respiratory stimulation promote selective and more rapid oxidation of EtOH first to AcAld in the cytosol and then to nontoxic acetate in mitochondria, since membrane-permeant AcAld does not require VDAC to enter mitochondria. VDAC closure also inhibits mitochondrial fatty acid oxidation and ATP release, promoting steatosis and a decrease in cytosolic ATP. After acute EtOH, these changes revert as EtOH is eliminated with little hepatocellular cytolethality. mtDepo also stimulates mitochondrial autophagy (mitophagy). After chronic high EtOH exposure, the capacity to process depolarized mitochondria by mitophagy becomes compromised, leading to intra- and extracellular release of damaged mitochondria, mitophagosomes, and/or autolysosomes containing mitochondrial damage-associated molecular pattern (mtDAMP) molecules. mtDAMPs cause inflammasome activation and promote inflammatory and profibrogenic responses, causing hepatitis and fibrosis. We propose that persistence of mitochondrial responses to EtOH metabolism becomes a tipping point, which links initial adaptive EtOH metabolism to maladaptive changes initiating onset and progression of ALD.

Minus charge stimulation prevents LPS-induced liver injury by reduction of nitric oxide

The liver is one of the major target organs affected in sepsis that are usually accompanied with free radical formation. The use of minus charge for the prevention and cure of various radical related diseases is gaining wide importance in the medicinal field. Here, we investigate whether minus charge stimulation (MCS) inhibits nitric oxide (NO) production induced by lipopolysaccharide (LPS) in the mice liver. The survival rate was compared in LPS-treated group with MCS group. The liver NO radical was measured using electron spin resonance technique. Serum alanine transaminase (ALT) was estimated for liver injury. MCS significantly improved the survival rate of LPS-treated mice and inhibited increase of ALT in serum levels. MCS also reduced NO radical production significantly in the LPS-treated mice liver tissue. In conclusion, our results indicate that MCS prevents LPS-induced liver injury, which may be through the inhibition of liver NO radical production.

A voluntary oral ethanol-feeding rat model associated with necroinflammatory liver injury

BACKGROUND

The intragastric (IG) ethanol infusion model results in fatty liver, necrosis, inflammation and fibrosis. This model was utilized to study the pathogenesis of alcoholic liver disease (ALD). Disadvantages of the IG model include maintenance of the animals and equipment expense. To develop a voluntary feeding model for ALD, we took advantage of two important observations in the IG model: (i) female rats demonstrate greater severity of alcohol-induced liver injury than males and (ii) rats fed fish oil as a source of fatty acids develop more severe alcoholic liver injury than rats fed other fatty acids with ethanol.

METHODS

Female Wistar rats (205 to 220 g) were fed for 8 weeks a diet containing 8% ethanol, fish oil (30% of calories), protein, and dextrose. Pair-fed controls (FD) received dextrose in amounts isocaloric to ethanol. The following measurements were made: liver pathology [fatty liver (0 to 4), necrosis, inflammation and fibrosis by Sirius Red], endotoxin and alanine aminotransferase (ALT) in plasma, urine ethanol, lipid peroxidation, nuclear factor kappa-B (NF-kappaB) and mRNA levels for tumor necrosis factor-alpha (TNF-alpha), cyclooxygenase-2 (COX-2), and inducible nitric oxide synthase (iNOS). Protein levels for iNOS and nitrotyrosine were evaluated by immunohistochemistry and Western Blot analysis. Liver proteasome and cytochrome P450 2E1 activity and protein levels of asialoglycoprotein receptor (ASGPR) were also evaluated. In addition, mRNA levels of fibrogenic markers were assessed.

RESULTS

All animals lost weight for the initial 2 to 3 weeks but then gained weight until killing at 8 weeks. There was, however, a significant difference (p < 0.05) in weight between the ethanol-fed (Etoh) and (FD) groups at the end of the experiment. The mean urine ethanol levels ranged between 190 and 240 mg/dl. The severity of pathological changes was greater (p < 0.01) in Etoh vs. FD: fatty liver, 3.0 +/- 1.2 vs. 1.2 +/- 0.4; necrosis (foci/mm(2)), 3.9 +/- 2.3 vs. 0.4 +/- 0.3; inflammation (cells/mm(2)), 19.0 +/- 6.3 vs. 1.8 +/- 0.6. Centrilobular collagen deposition (% area), assessed by Sirius Red staining, was greater in Etoh vs. FD. Levels of endotoxin, ALT, CYP2E1 and lipid peroxidation markers were also higher (p < 0.01) in Etoh vs. FD. Levels of NF-kappaB and mRNA of pro-inflammatory mediators (TNF-alpha, COX-2, iNOS) and procollagen-I were increased (p < 0.05) in ethanol-fed rats. Immunohistochemical analysis showed more intense staining for both iNOS and nitrotyrosine in the centrilobular areas in the Etoh vs. FD groups. The greater area of positive staining for iNOS and nitrotyrosine in Etoh vs. FD was confirmed by Western Blot analysis. An increase in the expression of mRNA for profibrogenic genes (p < 0.05) was seen in ethanol-fed rats.

CONCLUSIONS

A voluntary feeding regimen consisting of fish oil and ethanol in female rats is technically less demanding yet produces pathological and biochemical changes similar to those observed with the IG model. Pathological changes include fatty liver, necrosis and inflammation. Increased NF-kappaB and mRNA and protein levels of the pro-inflammatory mediators TNF-alpha, COX-2 and iNOS, coincided with the presence of necroinflammatory changes. The voluntary feeding regimen is proposed as an alternative to the IG model in the study of alcoholic liver injury.

Alcohol metabolism: role in toxicity and carcinogenesis

This article contains the proceedings of a symposium at the 2002 RSA Meeting in San Francisco, organized and co-chaired by Thomas M. Badger, Paul Shih-Jiun Yin, and Helmut Seitz. The presentations were (1) First-pass metabolism of ethanol: Basic and clinical aspects, by Charles Lieber; (2) Intracellular CYP2E1 transport, oxidative stress, cytokine release, and ALD, by Magnus Ingelman-Sundberg; (3) Pulsatile ethanol metabolism in intragastric infusion models: Potential role in toxic outcomes, by Thomas M. Badger and Martin J.J. Ronis; (4) Free radicals, adducts, and autoantibodies resulting from ethanol metabolism: Role in ethanol-associated toxicity, by Emanuele Albano; and (5) Gastrointestinal metabolism of ethanol and its possible role in carcinogenesis, by Helmut Seitz.