Rafael Bruck

The hydroxyl radical scavengers dimethylsulfoxide and dimethylthiourea protect rats against thioacetamide-induced fulminant hepatic failure

BACKGROUND/AIMS Reactive oxygen species, proinflammatory cytokines, glutathione depletion and nitric oxide have all been implicated in the pathogenesis of fulminant hepatic failure. The aim of the present study was to examine the respective roles of these factors in the pathogenesis of thioacetamide-induced fulminant hepatic failure in rats. METHODS Fulminant hepatic failure was induced by 3 consecutive intraperitoneal injections of thioacetamide (400 mg/kg) at 24-h intervals. Rats were pretreated with one of the following agents: the free radical scavengers dimethylsulfoxide (4 g/kg every 6 h) or dimethylthiourea (200 mg/kg every 12 h), the glutathione donor, N-acetylcysteine (130 or 200 mg/kg every 6 h), or the anti-tumor necrosis factor-alpha agents pentoxifylline (100 and 200 mg/kg) and soluble tumor necrosis factor receptor (100 or 1000 microg/rat). The nitric oxide synthase inhibitor N-mono-methyl arginine ester (L-NAME, 0.1 mg/ml) was administered in the drinking water, starting 7 days prior to thioacetamide administration. RESULTS Serum levels of liver enzymes, blood ammonia and prothrombin time and the stage of hepatic encephalopathy were significantly improved in rats treated with dimethylsulfoxide or dimethylthiourea compared to the other treatment groups (p<0.001). Liver histology and the survival rate in these rats were not adversely affected by thioacetamide administration (p<0.001), while in all the other treatment groups those parameters were similar to control rats with fulminant hepatic failure. Furthermore, dimethylsulfoxide ameliorated liver damage and improved survival even when its administration was initiated 8 and 16 h after the first thioacetamide injection. The hepatic concentration of methanesulfinic acid, which is produced after direct interaction of dimethylsulfoxide with hydroxyl radicals, was increased five-fold in rats treated with thioacetamide+dimethylsulfoxide (p<0.001), suggesting a role for hydroxyl radical scavenging in the protection from fulminant hepatic failure in this model. In the group of thioacetamide-treated rats that were pretreated with L-NAME, liver enzymes, blood ammonia levels and the mortality rate were higher than in the control group, treated with thioacetamide only. CONCLUSIONS In thioacetamide-induced fulminant hepatic failure, the hydroxyl radical scavengers dimethylsulfoxide and dimethylthiourea prevent liver injury. Neither N-acetylcysteine nor antagonists of tumor necrosis factor-alpha are protective in this rat model. Inhibition of nitric oxide formation aggravates liver damage and reduces the survival of rats with thioacetamide-induced liver damage.

Melatonin inhibits nuclear factor kappa B activation and oxidative stress and protects against thioacetamide induced liver damage in rats

BACKGROUND/AIMS Free radical-mediated oxidative stress has been implicated in the pathogenesis of acute liver injury. The aim of our study was to investigate whether melatonin, a potent free radical scavenger could prevent fulminant hepatic failure in rats. METHODS Liver damage was induced by two consecutive injections of thioacetamide (TAA, 300 mg/kg/i.p.) at 24 h intervals. Treatment with melatonin (3 mg/kg/daily, i.p) was initiated 24 h prior to TAA. RESULTS Twenty-four h after the second TAA injection, serum liver enzymes and blood ammonia were lower in rats treated with TAA+melatonin compared to TAA (P<0.001). Liver histology was significantly improved and the mortality in the melatonin-treated rats was decreased (P<0.001). The increased nuclear binding of nuclear factor kappa B in the livers of the TAA-treated rats, was inhibited by melatonin. The hepatic levels of thiobarbituric acid reactive substances, protein carbonyls and inducible nitric oxide synthase were lower in the TAA+melatonin-treated group (P<0.01), indicating decreased oxidative stress and inflammation. CONCLUSIONS In a rat model of TAA-induced fulminant hepatic failure, melatonin improves survival and reduces liver damage and oxidative stress. The results suggest a causative role of oxidative stress in TAA-induced hepatic damage and suggest that melatonin may be utilized to reduce liver injury associated with oxidative stress.

Curcumin ameliorates acute thioacetamide-induced hepatotoxicity.

Background and Aim:  Increased production of reactive oxygen species and nitric oxide and activation of nuclear factor κ B are implicated in the pathogenesis of various liver diseases, including fulminant hepatic failure. Curcumin is a naturally occurring anti‐oxidant that reduces oxidative stress and inhibits nuclear factor κ B and nitric oxide formation. The aim of the present study is to assess curcumins therapeutic potential in acute thioacetamide hepatotoxicity, a rat model of fulminant hepatic failure.

Prevention of liver cirrhosis in rats by curcumin

Background and Aim: Curcumin, the major polyphenolic compound in turmeric, has been shown to attenuate hepatic damage in several animal models of liver injury. The aim of the present study was to examine the efficacy of curcumin in preventing thioacetamide‐induced cirrhosis and to unravel the mechanism of curcumins effect on hepatic fibrosis in rats.

Heat Shock Protein 60 Inhibits Th1-Mediated Hepatitis Model via Innate Regulation of Th1/Th2 Transcription Factors and Cytokines

Extracellular heat shock protein 60 (HSP60) has been considered a proinflammatory danger signal. Yet, HSP60 can also down-regulate experimental immune arthritis and diabetes models by specific inhibition of Th1-like responses. We now report that HSP60 in vitro differentially modulates the expression of Th1/Th2 transcription factors in human T cells: HSP60 down-regulates T-bet, NF-κB, and NFATp and up-regulates GATA-3, leading to decreased secretion of TNF-α and IFN-γ and enhanced secretion of IL-10. These effects depended on TLR2 signaling and could not be attributed to LPS or to other contaminants. In BALB/c mice, HSP60 in vivo inhibited the clinical, histological, and serological manifestations of Con A-induced hepatitis associated with up-regulated T cell expression of suppressor of cytokine signaling 3 and GATA-3 and down-regulated T-bet expression. These results provide a molecular explanation for the effects of HSP60 treatment on T cell inflammation via innate regulation of the inflammatory response.

Polyphenols in the treatment of inflammatory bowel disease and acute pancreatitis

Polyphenols are phytochemicals that are abundant in food and beverages derived from plants. Although no deficiency state has been described for them, increased intake of polyphenols appears to protect against disease in virtue of their anti-inflammatory and vasculoprotective properties. This article focuses on four polyphenols with established anti-inflammatory properties: resveratrol, epigallocatechin gallate, curcumin and quercetin. In rodents, ingestion or systemic administration of these agents inhibits nuclear factor κ B-dependent gene expression and induces phase II antioxidant and detoxifying proteins. Conditions prevented and/or ameliorated by these polyphenols include inflammatory colitis and acute pancreatitis. Polyphenols also attenuate ischaemia-reperfusion injury and endotoxemic sepsis, which has a role in the development of multiple organ dysfunction in severe acute pancreatitis. Enteral nutrition has an important role in the management of inflammatory bowel disease (IBD)—mainly of Crohn’s disease, and of acute pancreatitis. Parenteral nutrition is reserved for refractory cases and disease-associated complications. Artificial nutrition attempts to safely administer the essential and otherwise beneficial constituents of food to patients with an impaired ability to ingest or digest food; yet, polyphenols are not included in the formulas. We suggest that the addition of polyphenols to artificial nutritional formulas would improve the outcome of patients with IBD and acute pancreatitis in need of enteral or parenteral nutrition. Plants, like other unicellular and multicellular organisms, contain ubiquitous organic molecules (eg, amino acids, carbohydrates and fatty acids) termed primary metabolites that are essential to cell structure and basic metabolism. These compounds also serve as substrates for the synthesis of an array of chemicals called secondary plant metabolites, which are accumulated at lower concentrations and are more variably distributed among different species. Once thought to be waste products, these agents are now considered to have a role in ecological interactions with friendly and hostile microorganisms and macroorganisms, and protection from environmental stressors. …

The therapeutic potential of long-chain omega-3 fatty acids in nonalcoholic fatty liver disease.

OBJECTIVES The pharmacologic approach to disease management has not (as of yet) demonstrated safety and efficacy in nonalcoholic fatty liver disease (NAFLD). The current article introduces the long-chain omega-3 polyunsaturated fatty acids (LC-ω3s), and reviews the evidence and mechanisms by which their increased intake or supplementation may ameliorate NAFLD. METHODS A literature search was performed through Ovid Medline, using such terms as NAFLD, NASH, nonalcoholic, steatosis, polyunsaturated fatty acids, fish oil and omega-3. RESULTS The LC-ω3s display pleiotropic properties that are of benefit in cardiovascular disease. Deficiency of omega-3 fatty acids results in hepatic steatosis, whereas fish oil displays powerful hypotriglyceridemic properties. Intake and/or metabolism of omega-3 fatty acids are commonly impaired in NAFLD patients. A number of pre-clinical and clinical studies have demonstrated an ameliorative effect of supplemental fish oil, seal oil and purified LC-ω3s in reducing hepatic lipid content in NAFLD. There is less evidence that hepatic inflammation and fibrosis are safely reduced by LC-ω3s. CONCLUSIONS Supplementation of LC-ω3s appears to safely reduce nutritional hepatic steatosis in adults. Whether other histopatholgic features of NAFLD also respond to LC-ω3s is being addressed by clinical trials. Any recommendation for omega-3 supplementation in NAFLD/NASH is contingent on these results.

Prevention of hepatic cirrhosis in rats by hydroxyl radical scavengers

BACKGROUND/AIMS Reactive oxygen species and oxidative stress were implicated in hepatic stellate cell activation and liver fibrosis. The aim of the present study was to examine whether the administration of free radical scavengers in vivo would prevent experimentally-induced hepatic cirrhosis in rats. METHODS Cirrhosis was induced by administration of thioacetamide (TAA; 200 mg/kg, i.p.) twice/week, for 12 weeks. Rats were treated concurrently with either dimethylsulfoxide (DMSO; 4 g/kg, s.c. or p.o.) or dimethylthiourea (DMTU; 200 mg/kg i.p.) three times a week. RESULTS Liver fibrosis (histopathological score, spleen weight, and hepatic hydroxyproline) was abolished in rats treated with TAA and either DMSO or DMTU (P < 0.001). Accordingly, the hepatic expression of alpha smooth muscle actin, tissue inhibitor of metalloproteinase 2 and collagen alpha1 (I) gene were inhibited. The hepatic level of methane-sulfinic acid (produced by the interaction of DMSO with hydroxyl radicals) was increased in rats treated with TAA + DMSO (P = 0.0005) and decreased after pretreatment of these rats with DMTU (P = 0.008). However, the hepatic levels of malondialdehyde, lipid peroxides and protein carbonyls were not lower in the DMSO- and DMTU-treated groups. CONCLUSIONS The administration of free radical scavengers prevented the development of TAA-induced liver cirrhosis probably associated with decreased oxidative stress.

Pyrrolidine dithiocarbamate protects against thioacetamide-induced fulminant hepatic failure in rats

BACKGROUND/AIMS Reactive oxygen species and nuclear factor kappa B (NF-kappaB) activation have been implicated in the pathogenesis of cell injury in experimental models of liver damage. The aim of the present study was to examine whether pyrrolidine dithiocarbamate (PDTC), an anti oxidant and inhibitor of NF-kappaB activation, would prevent hepatic damage induced in a rat model of thioacetamide (TAA)-induced liver failure. METHODS Fulminant hepatic failure was induced in the control and treatment groups by two intraperitoneal injections of TAA (either 300 or 400 mg/kg) at 24-h intervals. In the treatment groups, rats were treated also with PDTC (60 mg/kg/24 h, i.p.), initiated 24 h prior to TAA. RESULTS Liver enzymes, blood ammonia, and hepatic levels of thiobarbituric acid reactive substances (P<0.001) and protein carbonyls (P<0.05) were significantly lower in rats treated with PDTC compared to TAA only. Liver histology and the survival rate in the PDTC-treated rats were also improved (P<0.01 compared to TAA only). NF-kappaB activation, 2 and 6 h after TAA administration, was inhibited by PDTC. CONCLUSIONS In a rat model of fulminant hepatic failure, the administration of PDTC attenuated liver damage and improved survival. This effect may be due to decreased oxidative stress and inhibition of NF-kappaB activation.

Insulin-like actions of vanadate are mediated in an insulin-receptor-independent manner via non-receptor protein tyrosine kinases and protein phosphotyrosine phosphatases

Most or all mammalian cells contain vanadium at a concentration of 0.1–1.0 μM. The bulk of the vanadium in cells is probably in the reduced vanadyl (IV) form. Although this element is essential and should be present in the diet in minute quantities, no known physiological role for vanadium has been found thus far. In the years 1975–1980 the vanadate ion was shown to act as an efficient inhibitor of Na+,K+-ATPase and of other related phosphohydrolyzes as well. In 1980 it was observed that vanadate vanadyl, when added to intact rat adipocytes, mimics the biological actions of insulin in stimulating hexose uptake and glucose oxidation. This initiated a long, currently active, field of research among basic scientists and diabetologists. Several of the aspects studied are reviewed here.