Misoprostol modulates cytokine expression through a cAMP pathway: Potential therapeutic implication for liver disease.

Dysregulated cytokine metabolism plays a critical role in the pathogenesis of many forms of liver disease, including alcoholic and non-alcoholic liver disease. In this study we examined the efficacy of Misoprostol in modulating LPS-inducible TNFα and IL-10 expression in healthy human subjects and evaluated molecular mechanisms for Misoprostol modulation of cytokines in vitro. Healthy subjects were given 14day courses of Misoprostol at doses of 100, 200, and 300µg four times a day, in random order. Baseline and LPS-inducible cytokine levels were examined ex vivo in whole blood at the beginning and the end of the study. Additionally, in vitro studies were performed using primary human PBMCs and the murine macrophage cell line, RAW 264.7, to investigate underlying mechanisms of misoprostol on cytokine production. Administration of Misoprostol reduced LPS inducible TNF production by 29%, while increasing IL-10 production by 79% in human subjects with no significant dose effect on ex vivo cytokine activity; In vitro, the effect of Misoprostol was largely mediated by increased cAMP levels and consequent changes in CRE and NFκB activity, which are critical for regulating IL-10 and TNF expression. Additionally, chromatin immunoprecipitation (ChIP) studies demonstrated that Misoprostol treatment led to changes in transcription factor and RNA Polymerase II binding, resulting in changes in mRNA levels. In summary, Misoprostol was effective at beneficially modulating TNF and IL-10 levels both in vivo and in vitro; these studies suggest a potential rationale for Misoprostol use in ALD, NASH and other liver diseases where inflammation plays an etiologic role.

S-adenosylmethionine (SAMe) modulates interleukin-10 and interleukin-6, but not TNF, production via the adenosine (A2) receptor.

S-adenosylmethionine (SAMe) is the first product in methionine metabolism and serves as a precursor for glutathione (GSH) as well as a methyl donor in most transmethylation reactions. The administration of exogenous SAMe has beneficial effects in many types of liver diseases. One mechanism for the hepatoprotective action is its ability to regulate the immune system by modulating cytokine production from LPS stimulated monocytes. In the present study, we investigated possible mechanism(s) by which exogenous SAMe supplementation modulated production of TNF, IL-10 and IL-6 in LPS stimulated RAW 264.7 cells, a murine monocyte cell line. Our results demonstrated that exogenous SAMe supplementation inhibited TNF production but enhanced both IL-10 and IL-6 production. SAMe increased intracellular GSH level, however, N-acetylcysteine (NAC), the GSH pro-drug, decreased the production of all three cytokines. Importantly, SAMe increased intracellular adenosine levels, and exogenous adenosine supplementation had effects similar to SAMe on TNF, IL-10 and IL-6 production. 3-Deaza-adenosine (DZA), a specific inhibitor of S-adenosylhomocysteine (SAH) hydrolase, blocked the elevation of IL-10 and IL-6 production induced by SAMe, which was rescued by the addition of exogenous adenosine. Furthermore, the enhancement of LPS-stimulated IL-10 and IL-6 production by both SAMe and adenosine was inhibited by ZM241385, a specific antagonist of the adenosine (A(2)) receptor. Our results suggest that increased adenosine levels with subsequent binding to the A(2) receptor account, at least in part, for SAMe modulation of IL-10 and IL-6, but not TNF production, from LPS stimulated monocytes.

The use of selected nutrition supplements and complementary and alternative medicine in liver disease.

Almost all patients with liver disease, especially advanced liver disease, have some evidence of malnutrition, including mineral/vitamin deficiency. A major health trend in the United States has been the significant growth in the use of complementary and alternative medicine (CAM), including nutrition supplements and herbal agents. In the 1990s, the United States government created the National Center for Complementary and Alternative Medicine (NCCAM), as well as the Office on Dietary Supplements, to extend our knowledge in these areas. CAM users are often highly educated and frequently use CAM therapy for chronic diseases, including chronic liver disease. Indeed, most studies suggest that patients with chronic liver disease frequently use nutrition supplements and CAM agents in addition to their traditional medicines. The purpose of this review is to provide an update on the role of nutrition supplements and herbals in liver disease. This article will focus mainly on 7 selected agents (vitamin E, zinc, magnesium, S-adenosylmethionine, betaine, silymarin, and glycyrrhizin), for which there have been not only in vitro and animal studies but also human clinical trials, and we will review both potential efficacy and safety issues.

S-adenosylmethionine (SAMe) protects against acute alcohol induced hepatotoxicity in mice.

Although S-Adenosylmethionine (SAMe) has beneficial effects in many hepatic disorders, the effects of SAMe on acute alcohol-induced liver injury are unknown. In the present study, we investigated effects of SAMe on liver injury in mice induced by acute alcohol administration. Male C57BL/6 mice received ethanol (5 g/kg BW) by gavage every 12 hrs for a total of 3 doses. SAMe (5 mg/kg BW) was administrated i.p. once a day for three days before ethanol administration. Subsequent serum ALT level, hepatic lipid peroxidation, enzymatic activity of CYP2E1 and hepatic mitochondrial glutathione levels were measured colorimetrically. Intracellular SAMe concentration was measured by high-performance liquid chromatography (HPLC). Histopathological changes were assessed by H&E staining. Our results showed that acute ethanol administration caused prominent microvesicular steatosis with mild necrosis and an elevation of serum ALT activity. SAMe treatment significantly attenuated the liver injury. In association with the hepatocyte injury, acute alcohol administration induced significant decreases in both hepatic SAMe and mitochondrial GSH levels along with enhanced lipid peroxidation. SAMe treatment attenuated hepatic SAMe and mitochondrial GSH depletion and lipid peroxidation following acute alcohol exposure. These results demonstrate that SAMe protects against the liver injury and attenuates the mitochondrial GSH depletion caused by acute alcohol administration. SAMe may prove to be an effective therapeutic agent in many toxin-induced liver injuries including those induced by alcohol.

The regulation of Fas (CD95/Apo-1)-mediated liver apoptosis in Kupffer cell-depleted mice.

The purpose of this study was to further characterize Fas-mediated liver apoptosis. We investigated whether Fas-mediated apoptosis in the liver requires induction of apoptosis-related regulators and whether Kupffer cells play a role in this process. Mice were injected with GdCl(3) to deplete/suppress Kupffer cells, followed by treatment with an anti-Fas agonistic antibody, Jo2. Hepatic mRNA levels of several pro- and anti-apoptotic regulators were determined 0.5, 1.5 and 4.0 h after Jo2 injection. Liver histology, TUNEL response, the activity of caspases-3, -8, and -9, and reduced and oxidized glutathione, were also evaluated. Jo2 dramatically increased the number of apoptotic nuclei in the liver, up-regulated mRNA for Bcl-w, Bfl-1, and Bcl-X(L,) but did not affect pro-apoptotic regulator mRNA expression. Caspase-3, -8 and -9 activity increased at 1.5 h after Jo2-injection. GdCl(3) treatment was associated with an increase in the apoptotic effect of Jo2. No effect of Jo2 was recorded on redox state of the free cellular thiol system. These data suggest that: (1) the prompt apoptotic response to Fas-mediated signaling in the liver does not require induction of pro-apoptotic factors; (2) Kupffer cells may play a major role in the liver apoptotic response to Fas ligation by clearing apoptotic cells by phagocytosis; (3) oxidative stress does not seem to play an important role in Fas-mediated liver apoptosis.

Monocyte activation in alcoholic liver disease.

Activated monocytes and macrophages have been postulated to play an important role in the pathogenesis of alcoholic liver disease (ALD). Monocyte activation can be documented by measurement of neopterin, adhesion cell molecules, and certain proinflammatory cytokines and chemokines. We first became interested in the role of monocytes and monocyte-derived cytokines in ALD in relation to altered zinc metabolism that occurs regularly in ALD. Patients with ALD have hypozincemia, which responds poorly to oral zinc supplementation. We have shown that in ALD monocytes make a low-molecular-weight substance that, when injected into rabbits, causes prominent hypozincemia. Subsequently, multiple cytokines [especially tumor necrosis factor (TNF) and interleukin (IL)-8] have been shown to be overproduced by monocytes in ALD. We initially showed that monocytes in ALD spontaneously produce TNF and overproduce TNF in response to a lipopolysaccharide (LPS) stimulus, and this could be attenuated by antioxidants in vitro and in vivo. Alterations in the endotoxin-binding protein LPS-binding protein, in CD14, and in the endotoxin receptor Toll-like receptor 4 all may play roles in enhanced proinflammatory cytokine signaling in ALD. Moreover, several groups have documented increased TNF receptor density in monocytes in ALD. Inadequate negative regulation of TNF occurs at multiple levels in ALD. This includes decreased monocyte production of the important antiinflammatory cytokine IL-10 and blunted response to the antiinflammatory properties of adenosine. Finally, generation of reactive oxygen species (which occurs during alcohol metabolism) and products of lipid peroxidation induce production of cytokines, such as TNF and IL-8. In conclusion, there are multiple overlapping potential mechanisms for enhanced proinflammatory cytokine production by monocytes in ALD. We postulate that activation of monocytes and macrophages with subsequent proinflammatory cytokine production plays an important role in certain metabolic complications of ALD and is a component of the liver injury of ALD.

Gene expression in the liver of rats fed alcohol by means of intragastric infusion.

It has become increasingly evident that one of the most fruitful approaches to understanding cellular processes and their relation to disease consists of large-scale gene profiling of cells, tissues, and organs. This also constitutes a first step in exploring the molecular biologic basis of various diseases. In the current study, we used cDNA microarray technology to assess possible changes in the expression of a large number of genes in the liver of rats fed alcohol (ethanol) chronically (4 weeks) by means of intragastric infusion. This animal model resembles closely the alcoholic liver disease in human beings. Of a total of 8,740 probe sets arrayed on the microchip, 2,069 were expressed by the liver. After a correction for false discovery rate at 10%, 72 genes were found to be significantly up-regulated (40) or down-regulated (32). Forty-two genes were suppressed, and four genes were induced, by alcohol. These genes are involved in a wide spectrum of cellular functions. Also, the genes that underwent significant changes were categorized into two groups: genes that have been implicated in alcoholic liver disease and genes that have not been tested for possible changes in expression. Large-scale gene profiling of the liver reveals changes in the expression of a number of genes that have never been implicated in alcohol-induced injury. Further investigation of such genes may cast light on mechanisms underlying alcohol-induced liver injury and help in the design of new therapeutic approaches.

Mechanisms of non-alcoholic steatohepatitis.

In 1980, the term non-alcoholic steatohepatitis was coined to describe a new syndrome occurring in patients who usually were obese (often diabetic) females who had a liver biopsy picture consistent with alcoholic hepatitis, but who denied alcohol use. The causes of this syndrome were unknown, and there was no defined therapy. More than two decades later, this clinical syndrome is only somewhat better understood, and still there is no Food and Drug Administration-approved or even generally accepted drug therapy. Patients with primary non-alcoholic steatohepatitis typically have the insulin resistance syndrome (synonymous with the metabolic syndrome, syndrome X, and so forth), which is characterized by obesity, diabetes, hyperlipidemia, hypertension, and, in some instances, other metabolic abnormalities such as polycystic ovary disease. Secondary non-alcoholic steatohepatitis may be caused by drugs such as tamoxifen, certain industrial toxins, rapid weight loss, and so forth. The cause of non-alcoholic steatohepatitis remains elusive, but most investigators agree that a baseline of steatosis requires a second hit capable of inducing inflammation, fibrosis, or necrosis for non-alcoholic steatohepatitis to develop. Our research group has focused its efforts on the interactions of nutritional abnormalities, cytokines, oxidative stress with lipid peroxidation, and mitochondrial dysfunction in the induction of steatohepatitis, both alcoholic and non-alcoholic in origin. Research findings from other laboratories also support the role of increased cytokine activity, oxidative stress, and mitochondrial dysfunction in the pathogenesis of non-alcoholic steatohepatitis. The objectives of this article are to review the (1) definition and clinical features of non-alcoholic steatohepatitis, (2) potential mechanisms of non-alcoholic steatohepatitis, and (3) potential therapeutic interventions in non-alcoholic steatohepatitis.

S-Adenosylmethionine, cytokines, and alcoholic liver disease.

Hepatic deficiency of S-adenosylmethionine (AdoMet) is a critical acquired metabolic abnormality in alcoholic liver disease (ALD) and in many experimental models of hepatotoxicity. Subnormal AdoMet, elevated serum tumor necrosis factor (TNF), and endotoxemia (LPS) are hallmarks of ALD and experimental liver injury. AdoMet deficiency is attributed to its subnormal synthesis, but mechanisms for increased TNF are not known. AdoMet deficiency may affect the critical balance of proinflammatory (e.g., TNF) and antiinflammatory [e.g., interleukin (IL)-10] cytokines. Rats maintained on a choline-deficient diet with limited amounts of methionine (MCD diet) developed AdoMet deficiency. When challenged with LPS, rats fed MCD diet had significantly increased serum TNF levels and worse liver injury compared with findings for controls. Exogenous AdoMet attenuated liver injury and serum TNF levels. Results of in vitro studies with the use of RAW 264.7 cells demonstrated that exogenous AdoMet supplementation lowered LPS-induced TNF formation in a dose-dependent manner, and AdoMet deficiency enhanced TNF secretion and TNF gene expression. AdoMet also dose-dependently decreased LPS-stimulated TNF production from monocytes obtained from patients with alcoholic hepatitis. Finally, AdoMet supplementation stimulated production of the antiinflammatory cytokine IL-10. Interleukin-10 plays a critical role in the modulation of TNF production, and IL-10 may inhibit hepatic fibrosis. This article will review (1) the role of AdoMet in ALD/liver injury, (2) the role of TNF/proinflammatory cytokines in ALD, (3) potential roles of AdoMet in TNF/proinflammatory cytokine regulation in ALD, and (4) conclusions and future directions.

Involvement of AMP-activated protein kinase in beneficial effects of betaine on high-sucrose diet-induced hepatic steatosis.

Although simple steatosis was originally thought to be a pathologically inert histological change, fat accumulation in the liver may play a critical role not only in disease initiation, but also in the progression to nonalcoholic steatohepatitis and cirrhosis. Therefore, prevention of fat accumulation in the liver may be an effective therapy for multiple stages of nonalcoholic fatty liver disease (NAFLD). Promising beneficial effects of betaine supplementation on human NAFLD have been reported in some pilot clinical studies; however, data related to betaine therapy in NAFLD are limited. In this study, we examined the effects of betaine on fat accumulation in the liver induced by high-sucrose diet and evaluated mechanisms by which betaine could attenuate or prevent hepatic steatosis in this model. Male C57BL/6 mice weighing 20 +/- 0.5 g (means +/- SE) were divided into four groups (8 mice per group) and started on one of four treatments: standard diet (SD), SD+betaine, high-sucrose diet (HS), and HS + betaine. Betaine was supplemented in the drinking water at a concentration of 1% (wt/vol) (anhydrous). Long-term feeding of high-sucrose diet to mice caused significant hepatic steatosis accompanied by markedly increased lipogenic activity. Betaine significantly attenuated hepatic steatosis in this animal model, and this change was associated with increased activation of hepatic AMP-activated protein kinase (AMPK) and attenuated lipogenic capability (enzyme activities and gene expression) in the liver. Our findings are the first to suggest that betaine might serve as a therapeutic tool to attenuate hepatic steatosis by targeting the hepatic AMPK system.

Palmitic acid induces production of proinflammatory cytokine interleukin-8 from hepatocytes.

UNLABELLED: Obesity and the metabolic syndrome are closely correlated with hepatic steatosis. Simple hepatic steatosis in nonalcoholic fatty liver disease can progress to nonalcoholic steatohepatitis (NASH), which can be a precursor to more serious liver diseases, such as cirrhosis and hepatocellular carcinoma. The pathogenic mechanisms underlying progression of steatosis to NASH remain unclear; however, inflammation, proinflammatory cytokines, and oxidative stress have been postulated to play key roles. We previously reported that patients with NASH have elevated serum levels of proinflammatory cytokines, such as interleukin-8 (IL-8), which are likely to contribute to hepatic injury. This study specifically examines the effect of hepatic steatosis on IL-8 production. We induced lipid accumulation in hepatocytes (HepG2, rat primary hepatocytes, and human primary hepatocytes) by exposing them to pathophysiologically relevant concentrations of palmitic acid to simulate the excessive influx of fatty acids into hepatocytes. Significant fat accumulation was documented morphologically by Oil Red O staining in cells exposed to palmitic acid, and it was accompanied by an increase in intracellular triglyceride levels. Importantly, palmitic acid was found to induce significantly elevated levels of biologically active neutrophil chemoattractant, IL-8, from steatotic hepatocytes. Incubation of the cells with palmitate led to increased IL-8 gene expression and secretion (both mRNA and protein) through mechanisms involving activation of nuclear factor kappaB (NF-kappaB) and c-Jun N-terminal kinase/activator protein-1. CONCLUSION: These data demonstrate for the first time that lipid accumulation in hepatocytes can stimulate IL-8 production, thereby potentially contributing to hepatic inflammation and consequent liver injury.

Interactions of cytokines, S-Adenosylmethionine, and S-Adenosylhomocysteine in alcohol-induced liver disease and immune suppression.

Alcoholic liver disease (ALD) remains a leading cause of death in the USA. Defining mechanisms for liver cell death in ALD in order to develop potential new agents for therapeutic intervention is a major focus of the authors' work. Abnormal cytokine metabolism is a major feature of ALD, and a thorough understanding of both mechanisms and interactions of cytokine overproduction and sensitization are critical to developing a possible treatment for ALD. S-Adenosylmethionine has been used in a variety of animal studies and clinical trials and has been reported to improve biochemical parameters of liver function. Last, immunosuppression associated with chronic alcohol abuse is an important predisposing factor to opportunistic infections and cancer. It is the authors' working hypothesis that alcohol consumption leads to chronic activation of the immune system.

Dysregulated cytokine metabolism, altered hepatic methionine metabolism and proteasome dysfunction in alcoholic liver disease.

Alcoholic liver disease (ALD) remains an important complication and cause of morbidity and mortality from alcohol abuse. Major developments in our understanding of the mechanisms of ALD over the past decade are now being translated into new forms of therapy for this disease process which currently has no FDA approved treatment. Cytokines are low molecular weight mediators of cellular communication, and the pro-inflammatory cytokine tumor necrosis factor (TNF) has been shown to play a pivotal role in the development of experimental ALD. Similarly, TNF levels are elevated in the serum of alcoholic hepatitis patients. Abnormal methionine metabolism is well documented in patients with ALD, with patients having elevated serum methionine levels, but low S-adenosylmethionine levels in the liver. On the other hand, S-adenosylhomocysteine and homocysteine levels are elevated in ALD. Recent studies have documented potential interactions between homocysteine and S-adenosylhomocysteine with TNF in the development of ALD. Altered proteasome function also is now well documented in ALD, and decreased proteasome function can cause hepatocyte apoptosis. Recently it has been shown that decreased proteasome function can also act synergistically to enhance TNF hepatotoxicity. Hepatocytes dying of proteasome dysfunction release pro-inflammatory cytokines such as Interleukin-8 to cause sustained inflammation. This article reviews the interactions of cytokines, altered methionine metabolism, and proteasome dysfunction in the development of ALD.

S-adenosylmethionine (AdoMet) modulates endotoxin stimulated interleukin-10 production in monocytes.

IL-10 is produced by a large variety of cells including monocytes, macrophages, B and T lymphocytes, as well as natural killer cells and is an important suppressor for both immunoproliferative and inflammatory responses. IL-10 exerts antifibrotic effects in the liver, and decreased monocyte synthesis of IL-10 is well documented in alcoholic cirrhosis. Intracellular deficiency of S-adenosylmethionine (AdoMet) is a hallmark of toxin-induced liver injury. Although the administration of exogenous AdoMet attenuates this injury, the mechanisms of its actions are not fully established. This study was performed to investigate the effect of exogenous AdoMet on IL-10 production in LPS-stimulated RAW 264.7 cells, a murine macrophage cell line. Our results demonstrated that exogenous AdoMet administration enhanced both protein production and gene expression of IL-10 in RAW 264.7 cells. Ethionine, an inhibitor for methionine adenosyltransferases, inhibited LPS-stimulated IL-10 both at the protein and mRNA levels. Exogenous AdoMet increased the intracellular cAMP concentration as early as 3 h and continued for 24 h after AdoMet treatment; however, the inhibitors for both adenylyl cyclase and PKA did not significantly affect IL-10 production. On the basis of these results, we conclude that AdoMet administration may exert its anti-inflammatory and hepatoprotective effects, at least in part, by enhancing LPS-stimulated IL-10 production.

Diagnosis and treatment of alcoholic liver disease and its complications.

Alcoholic liver disease (ALD) is a serious and potentially fatal consequence of alcohol use. The diagnosis of ALD is based on drinking history, physical signs and symptoms, and laboratory tests. Treatment strategies for ALD include lifestyle changes to reduce alcohol consumption, cigarette smoking, and obesity; nutrition therapy; and pharmacological therapy. The diagnosis and management of the complications of ALD are important for alleviating the symptoms of the disease, improving quality of life, and decreasing mortality.

Recent advances in alcoholic liver disease. IV. Dysregulated cytokine metabolism in alcoholic liver disease.

Alcoholic liver disease (ALD) remains a leading cause of death from liver disease in the United States for which there is no FDA-approved therapy. Abnormal cytokine metabolism is a major feature of ALD. Elevated serum concentration levels of TNF-alpha and TNF-alpha-inducible cytokines/chemokines, such as IL-6, -8, and -18, have been reported in patients with alcoholic hepatitis and/or cirrhosis, and levels correlated with markers of the acute phase response, liver function, and clinical outcome. Studies in animal models support an etiologic role for cytokines in the liver injury of ALD. Cytokines, such as transforming growth factor-beta, play a critical role in the fibrosis of ALD. Multiple new strategies are under investigation to modulate cytokine metabolism as a form of therapy for ALD.

Cytokines and NASH: a pilot study of the effects of lifestyle modification and vitamin E.

There are few data evaluating plasma and/or peripheral blood monocyte cytokine concentrations/production or attempts to manipulate proinflammatory cytokines in nonalcoholic steatohepatitis (NASH). A pilot project in a general clinical research center evaluated the effects of a step 1 American Heart Association diet plus aerobic exercise with or without 800 IU of vitamin E daily on cytokine profiles and liver enzyme levels in 16 patients with biopsy-proven NASH. Biochemical assessment of liver function, lipid profiles, and body mass index significantly improved during the first 6 weeks of therapy and remained stable during the following 6 weeks. Plasma hyaluronic acid (HA) concentrations decreased in parallel with weight loss. Plasma tumor necrosis factor (TNF) concentrations were significantly elevated in patients with NASH and similar to patients with stable alcoholic cirrhosis but not as elevated as in patients with acute alcoholic steatohepatitis (AH). Although plasma TNF, interleukin 8 (IL-8), and IL-6 concentrations were all significantly elevated compared with control values, only plasma IL-6 levels significantly decreased with therapy. Peripheral blood monocyte TNF, IL-8, and IL-6 production was significantly elevated in patients with NASH but did not significantly decrease. Independent effects of vitamin E were not observed in this small sample. In conclusion, patients with NASH have dysregulated cytokine metabolism similar to, but less pronounced than abnormalities documented in AH. Cytokine values generally did not decrease significantly with weight loss with or without vitamin E over the duration of the study. Lifestyle modifications (low-fat diet and exercise) were associated with improvement in liver enzymes, cholesterol, and plasma HA levels in patients with NASH, whereas the level of vitamin E supplementation used in this short-term pilot study provided no apparent added benefit.

Modulation of endotoxin stimulated interleukin-6 production in monocytes and Kupffer cells by S-adenosylmethionine (SAMe).

Interleukin-6 (IL-6) is a multifunctional cytokine having primarily anti-apoptotic and anti-inflammatory effects. Recent reports have documented that IL-6 plays a key role in liver regeneration. Intracellular deficiency of S-adenosylmethionine (SAMe) is a hallmark of toxin-induced liver injury. Although the administration of exogenous SAMe attenuates liver injury, its mechanisms of action are not fully understood. Here we investigated the effects of exogenous SAMe on IL-6 production in monocytes and Kupffer cells. RAW 264.7 cells, a murine monocyte cell line, and isolated rat Kupffer cells were stimulated with lipopolysaccharide (LPS) in the absence or presence of exogenous SAMe. IL-6 production was assayed by ELISA and intracellular SAMe concentrations were measured by HPLC. We have found that exogenous SAMe administration enhanced both IL-6 protein production and gene expression in LPS-stimulated monocytes and Kupffer cells. Cycloleucine (CL), an inhibitor for extrahepatic methionine adenosyltransferases (MAT), inhibited LPS-stimulated IL-6 production. The enhancement of LPS-stimulated IL-6 production by SAMe was inhibited by ZM241385, a specific antagonist of adenosine (A2) receptor. Our results demonstrate that SAMe administration may exert its anti-inflammatory and hepatoprotective effects, at least in part, by enhancing LPS-stimulated IL-6 production.

A role for interleukin-10 in alcohol-induced liver sensitization to bacterial lipopolysaccharide.

BACKGROUND: Proinflammatory cytokines play an important role in alcohol-induced liver injury. The role of anti-inflammatory cytokines in the initiation and progression of alcoholic liver disease has received little attention. This study tested the hypothesis that an imbalance exists between pro- and anti-inflammatory cytokines in the liver during chronic exposure to alcohol. Alcohol exposure results in predominantly proinflammatory cytokine secretion and liver injury. METHODS: IL-10 knock-out and their C57BL/6J counterpart wild-type mice were fed alcohol in drinking water for 7 weeks. At the end of alcohol feeding, Gram-negative bacterial lipopolysaccharide (LPS) was administered, and the animals were killed after 3 and 8 hr. Liver histology, plasma alanine aminotransferase and aspartate aminotransferase activity, tumor necrosis factor-alpha, interleukin (IL)-1beta and IL-10 levels, and liver cytokine messenger RNA levels were measured. RESULTS: Alcohol feeding and LPS treatment did not change plasma enzyme activity levels in wild-type mice. In the IL-10 knock-out mice, LPS alone increased aspartate aminotransferase and alanine aminotransferase enzyme activity, and this was potentiated by alcohol. Alcohol induced liver steatosis in both wild-type and knock-out mice. LPS markedly enhanced the histological effects further, especially in the knock-out mice, with the emergence of focal necrosis, polymorphonuclear infiltration, and microabscesses in the liver. Plasma tumor necrosis factor-alpha and IL-1beta levels were not affected by alcohol alone. Proinflammatory cytokine levels were increased by LPS and further enhanced by alcohol treatment, particularly in the IL-10 knock-out mice. IL-10 plasma levels in the wild-type animals were down-regulated by alcohol. Changes in liver cytokine messenger RNA paralleled those seen in plasma cytokine levels. CONCLUSIONS: Alcohol-induced liver sensitization to LPS in wild-type mice may involve down-regulation of IL-10. This anti-inflammatory cytokine, known for its hepatoprotective effects, is secreted simultaneously with proinflammatory cytokines. IL-10 may also limit alcohol-induced liver damage by counteracting the effects of proinflammatory cytokines.