Protective effect of colchicine on acute liver damage induced by carbon tetrachloride

The Cumulative Risk Assessment of Hepatotoxic Chemicals: A Hepatic Histopathology Perspective

The increased concern on the consequence of exposure to multiple chemical combinations has led national regulatory authorities to develop different concepts to conduct risk assessments on chemical mixtures. Pesticide residues were identified as "problem formulation" in the respective European regulations and in this context, the European Food and Safety Authority has suggested to group pesticidal active ingredients (AIs) into cumulative assessment groups (CAGs) based on the toxicological properties of each AI. One proposed CAG, on the liver, currently consists of 15 subgroups, each representing a specific hepatotoxic effect observed in toxicity studies. Dietary cumulative risk assessments would then have to be conducted assuming dose additivity of all members of each CAG subgroup. The purpose of this publication is to group AIs based upon the knowledge of the pathogenesis of liver effects to discriminate between primary end points (direct consequence of chemical interaction with a biological target) and secondary end points (which are a consequence of, or that arise out of, a previous pathological change). Focusing on the relevant primary end points strengthens and simplifies the selection of compounds for cumulative risk assessment regarding the liver and better rationalizes the basis for chemical grouping. Relevant dose additivity is to be expected at the level of the primary/leading pathological end points and not at the level of the secondary end points. We recognize, however, that special consideration is needed for substances provoking neoplasia, and this category is included in the group of primary end points for which chemicals inducing them are grouped for risk assessment. Using the pathological basis for defining the respective CAGs, 6 liver subgroups and 2 gallbladder/bile duct groups are proposed. This approach simplifies the cumulative assessment calculation without obviously affecting consumer safety.

Electrophilicities and Protein Covalent Binding of Demethylation Metabolites of Colchicine

Colchicine, an alkaloid existing in plants of Liliaceous colchicum, has been widely used in the treatment of gout and familial Mediterranean fever. The administration of colchicine was found to cause liver injury in humans. The mechanisms of colchicine-induced liver toxicity remain unknown. The objectives of this study were to determine the electrophilicities of demethylation metabolites of colchicine and investigate the protein adductions derived from the reactive metabolites of colchicine. Four demethylated colchicine (1-, 2-, 3-, and 10-DMCs), namely, M1-M4, were detected in colchicine-fortified microsomal incubations. Four N-acetyl cysteine (NAC) conjugates (M5-M8) derived from colchicine were detected in the microsomes in the presence of NAC. M5 and M6 were derived from 10-DMC. M7 resulted from the reaction of 2-DMC or 3-DMC with NAC, and M8 originated from 10-DMC. Microsomal protein covalent binding was observed after exposure to colchicine. Two cysteine adducts (CA-1 and CA-2) derived from 10-DMC were found in proteolytically digested microsomal protein samples after incubation with colchicine. The findings allow us to define the chemical property of demethylation metabolites of colchicine and the interaction between protein and the reactive metabolites of colchicine generated in situ.

The effects of grape seed and colchicine on carbon tetrachloride induced hepatic damage in rats

This study aims to determine the effects of grape seed and colchicine on carbon tetrachloride (CCl4) induced hepatic damage and on some serum biochemical parameters. Sixty male Wistar albino rats (200-250 g) were randomly divided into six groups (ten rats/group) and included the control group the group were given isotonic sodium chloride (1 mL/kg b.w) intraperitonealy (i.p.), group 2 the group treated i.p. injection of CCl4 (1.0 mL/kg b.w) in corn oil twice in the first week, Groups 3 and 4 injected with CCl4 as described for group 2 and the rats were orally given (100 mg/kg b.w) GSE and i.p. injected (10 μg/rat) with colchicine for four weeks, respectively and groups 5 and 6 were the grape seed and colchicine control groups in which rats were orally given grape seed (100 mg/kg b.w) and i.p. injected with colchicine (10 μg/rat), respectively. Anorexia, weight loss, motionlessness and hepatic colour variation at necropsy were observed in groups 2, 3, and 4. Hyperemia, focal bleeding, fat degeneration, changes ranging from degenerative to necrotic, increase in connective tissue elements, pronounced in portal sites in particular, and infiltration of lymphoid series cell observed in the livers of the rats in group 2, treated with CCl4. Histological hepatic changes in the rats in group 3 and 4 were similar to those in group 2. The levels of serum total protein, albumin and globulin decreased in groups 2, 3, and 4, compared with groups 1, 5 and 6; aspartate transaminase (ALT) activities increased. The lowest alkaline phosphatase (ALP) activities were in groups 4 and 5. We concluded that GSE and colchicine have not sufficient ameliorative effects to CCl4 induced acute hepatic damage.

Effects and mechanisms of extract from Paeonia lactiflora and Astragalus membranaceus on liver fibrosis induced by carbon tetrachloride in rats

Paeonia lactiflora and Astragalus membranaceus are two popular traditional Chinese medicines, commonly used in Chinese herb prescription to treat liver disease. The extract prepared from the roots of Paeonia lactiflora and Astragalus membranaceus (PAE) demonstrated more excellent hepato-protective activity than the single herbs used individually as indicated in our preliminary studies. The present study was carried out to investigate the effects of PAE on liver fibrosis in rats induced by carbon tetrachloride (CCl(4)) and to explore its possible mechanisms. Liver fibrosis was induced in male Sprague-Dawley rats by injection with 50% CCl(4) subcutaneously twice a week for 8 weeks. At the same time, PAE (40, 80 and 160 mg/kg) was administered intragastrically. Upon pathological examination, the PAE-treated rats significantly reduced the liver damage and the symptoms of liver fibrosis. Administration of PAE decreased CCl(4)-induced elevation of serum transaminase activities, hyaluronic acid, laminin and procollagen type III levels, and contents of hydroxyproline in liver tissue by approximately 30-60%. It also restored the decrease in SOD and GSH-Px activities and inhibited the formation of lipid peroxidative products during CCl(4) treatment. Moreover, PAE (80, 160 mg/kg, ig) decreased the elevation of TGF-beta1 by 47.7% and 53.1%, respectively. In the primary cultured hepatic stellate cells (HSCs), PAE also significantly decreased [(3)H] thymidine incorporation in cells stimulated with platelet-derived growth factor-B subunit homodimer (PDGF-BB) and suppressed [(3)H] proline incorporation. These results suggested that PAE significantly inhibited the progression of hepatic fibrosis induced by CCl(4), and the inhibitory effect of PAE on hepatic fibrosis might be associated with its ability to scavenge free radicals, decrease the level of TGF-beta1 and inhibit collagen synthesis and proliferation in HSCs.

Postulated carbon tetrachloride mode of action: a review

Under the 2005 U.S. EPA Guidelines for Carcinogen Risk Assessment (1), evaluations of carcinogens rely on mode of action data to better inform dose response assessments. A reassessment of carbon tetrachloride, a model hepatotoxicant and carcinogen, provides an opportunity to incorporate into the assessment biologically relevant mode of action data on its carcinogenesis. Mechanistic studies provide evidence that metabolism of carbon tetrachloride via CYP2E1 to highly reactive free radical metabolites plays a critical role in the postulated mode of action. The primary metabolites, trichloromethyl and trichloromethyl peroxy free radicals, are highly reactive and are capable of covalently binding locally to cellular macromolecules, with preference for fatty acids from membrane phospholipids. The free radicals initiate lipid peroxidation by attacking polyunsaturated fatty acids in membranes, setting off a free radical chain reaction sequence. Lipid peroxidation is known to cause membrane disruption, resulting in the loss of membrane integrity and leakage of microsomal enzymes. By-products of lipid peroxidation include reactive aldehydes that can form protein and DNA adducts and may contribute to hepatotoxicity and carcinogenicity, respectively. Natural antioxidants, including glutathione, are capable of quenching the lipid peroxidation reaction. When glutathione and other antioxidants are depleted, however, opportunities for lipid peroxidation are enhanced. Weakened cellular membranes allow sufficient leakage of calcium into the cytosol to disrupt intracellular calcium homeostasis. High calcium levels in the cytosol activate calcium-dependent proteases and phospholipases that further increase the breakdown of the membranes. Similarly, the increase in intracellular calcium can activate endonucleases that can cause chromosomal damage and also contribute to cell death. Sustained cell regeneration and proliferation following cell death may increase the likelihood of unrepaired spontaneous, lipid peroxidation- or endonuclease-derived mutations that can lead to cancer. Based on this body of scientific evidence, doses that do not cause sustained cytotoxicity and regenerative cell proliferation would subsequently be protective of liver tumors if this is the primary mode of action. To fulfill the mode of action framework, additional research may be necessary to determine alternative mode(s) of action for liver tumors formed via carbon tetrachloride exposure.

An experimental animal model of fulminant hepatic failure in pigs

The objective of this study was to develop an experimental animal model of fulminant hepatic failure to test the efficacy of the bioartificial liver system. The portal vein and the hepatic artery were clamped intermittently and then the hepatic artery was ligated (ligation group, n=5). Pigs whose hepatic arteries were not ligated after clamping were assigned to the non-ligation group (n=5). The biochemical changes in blood, histologic alterations of the liver and neurologic examination for pigs were checked up. All animals died within 17 hr in the ligation group. On the other hand, all animals survived more than 7 days in the non-ligation group. In the ligation group, the levels of ammonia, lactic acid and creatinine showed a progressively increasing pattern. Prothrombin time was also prolonged gradually. Cytoplasmic condensation and nuclear pyknosis of hepatocytes were detected histologically at autopsy. Neurologic findings such as decreased pain sensation, tachypnea and no light reflex of pupils were observed. The findings shown in the ligation group are similar to the clinical features of fulminant hepatic failure in human and this animal model is reproducible. Therefore, this can be a suitable animal model to evaluate the efficacy of the bioartificial liver system for treating fulminant hepatic failure.

Colchicine treatment of alcoholic cirrhosis: a randomized, placebo-controlled clinical trial of patient survival

BACKGROUND & AIMS

Colchicine improved survival and reversed cirrhosis in several small clinical trials. We compared the efficacy and safety of long-term colchicine, as compared with placebo, in patients with advanced alcoholic cirrhosis.

METHODS

Five hundred forty-nine patients with advanced (Pugh B or C) alcoholic cirrhosis were randomized to receive either colchicine 0.6 mg twice per day (n = 274) or placebo (n = 275). Treatment lasted from 2 to 6 years. The primary outcome was all-cause mortality. Secondary outcomes were liver-related morbidity and mortality. Liver biopsy was requested prior to entry and after 24 months of treatment.

RESULTS

Attendance at scheduled clinic visits and adherence with study medication were similar in colchicine and placebo groups. Alcohol intake was less than 1 drink per day in 69% of patients. In an intention-to-treat analysis, all-cause mortality was similar in colchicine (49%) and placebo (45%) patients (P = .371). Mortality attributed to liver disease was 32% in colchicine and 28% in placebo patients (P = .337). Fewer patients receiving colchicine developed hepatorenal syndrome. In 54 patients with repeat liver biopsies after 24 or more months of treatment, cirrhosis improved to septal fibrosis in 7 patients (3 colchicine, 4 placebo) and to portal fibrosis in 1 patient (colchicine).

CONCLUSIONS

In patients with advanced alcoholic cirrhosis, colchicine does not reduce overall or liver-specific mortality. Liver histology improves to septal fibrosis in a minority of patients after 24 months of treatment, with similar rates of improvement in patients receiving placebo and colchicine. Colchicine is not recommended for patients with advanced alcoholic cirrhosis.

Treatment of alcoholic hepatitis

Cirrhosis and its sequelae are responsible for close to 2% of all causes of death in the United States. Some studies have suggested that the costs of liver disease may account for as much as 1% of all health care spending, with alcohol-related liver disease (ALD) representing a major portion. It accounts for between 40% to 50% of all deaths due to cirrhosis, with an accompanying rate of progression of up to 60% in patients with pure alcoholic fatty liver over 10 years, and a 5-year survival rate as low as 35% if patients continue to drink. A subset of patients with ALD will develop an acute, virulent form of injury, acute alcoholic hepatitis, which has a substantially worse prognosis. Despite enormous progress in understanding the physiology of this disease, much remains unknown, and therefore, a consensus regarding effective therapy for ALD is lacking. Conventional therapy is still based largely on abstinence from alcohol, as well as general supportive and symptomatic care. Unfortunately, hepatocellular damage may progress despite these measures. Multiple treatment interventions for both the short- and long-term morbidity and mortality of this disease have been proposed, but strong disagreement exists among experts regarding the value of any of the proposed specific therapeutic interventions.

Repeated hepatocyte injury promotes hepatic tumorigenesis in hepatitis C virus transgenic mice

Although hepatitis C virus (HCV) is a well-known causative agent of hepatocellular carcinoma (HCC), the mechanism by which HCV induces HCC remains obscure. To elucidate the role of HCV in hepatocarcinogenesis, a model of hepatocyte injury was established using HCV core transgenic mice, which were developed using C57BL/6 mice transfected with the HCV core gene under control of the serum amyloid P component promoter. After 18-24 months, neither steatosis nor hepatic tumors were found in transgenic mice. The extent of hepatocyte injury and tumorigenesis were then examined in transgenic mice following repeated administration of carbon tetrachloride (CCl(4)) using various protocols (20%, 1/week; 10%, 2/week and 20%, 2/week). Serum alanine aminotransferase (ALT) levels did not differ among HCV core transgenic mice and non-transgenic littermates; however, after 40 weeks, hepatic adenomas preferentially developed in transgenic mice receiving 20% CCl(4) once weekly. Moreover, HCC was observed in transgenic mice receiving 2 weekly injections of a 20% solution of CCl(4), and was not observed in the non-transgenic control mice. In conclusion, the HCV core protein did not promote hepatic steatosis or tumor development in the absence of hepatotoxicity. However, the HCV core protein promoted adenoma and HCC development in transgenic mice following repeated CCl(4) administration. These results suggest that hepatotoxicity resulting in an increased rate of hepatocyte regeneration enhances hepatocarcinogenesis in HCV-infected livers. Furthermore, this experimental mouse model provides a valuable method with which to investigate hepatocarcinogenesis.

Industrial solvents and liver toxicity: risk assessment, risk factors and mechanisms

Organic solvents utilized in various industrial processes may be associated with hepatotoxicity. The hepatotoxicity of some of the solvents was recognized as early as 1887, 1889 and 1904. Factors contributing to the hepatotoxicity of solvents include 1) species differences, 2) liver blood flow, 3) protein binding, 4) point of binding intracellularly, 5) genetic factors, 6) different cellular enzymatic degradation, 7) age, 8) nutritional condition, 9) interaction with alcohol, and 10) interaction with medications of use and abuse. The hepatotoxicity of solvents in general and of carbon tetrachloride, trichloroethylene, tetrachloroethylene, toluene, and 1,1,1-trichloroethene are discussed. Experimental animal data, human data, and in vitro studies are explored. Suggested mechanisms of direct toxicity, indirect toxicity and autoimmune mechanisms are elaborated. The most important message from this review is that laboratory testing that is commonly used by clinicians to detect liver toxicity may not be sensitive enough to detect early liver hepatotoxicity from industrial solvents and new methodologies are being encouraged and utilized in the early recognition and diagnosis of hepatotoxicity for solvents. The final clinical assessment of hepatotoxicity and industrial solvents must take into account synergism with medications, drugs of use and abuse, alcohol, age, and nutrition. Early recognition and reporting will be helpful in further understanding the incidence, cofactors and possible mechanisms.

Protective effect of carnosol on CCl(4)-induced acute liver damage in rats

BACKGROUND

We recently reported that (Lamiaceae) may alleviate CCl(4)-induced acute hepatotoxicity in rats, possibly blocking the formation of free radicals generated during CCl(4) metabolism. Carnosol, one of the main constituents of Rosmarinus, has been shown to have antioxidant and scavenging activities. Therefore, it is plausible to expect that carnosol may mediate some of the effects of Rosmarinus on oxidative stress consequences induced by CCl(4) in the liver.

DESIGN

We evaluated the effectiveness of carnosol to normalize biochemical and histological parameters of CCl(4)-induced acute liver injury.

METHODS

Male Sprague Dawley rats (n = 5) injured by CCl(4) (oral dose 4 g/kg of body weight) were treated with a single intraperitoneal dose (5 mg/kg) of carnosol. Twenty-four hours later, the rats were anaesthetized deeply to obtain the liver and blood, and biochemical and histological parameters of liver injury were evaluated.

RESULTS

Carnosol normalized bilirubin plasma levels, reduced malondialdehyde (MDA) content in the liver by 69%, reduced alanine aminotransferase (ALT) activity in plasma by 50%, and partially prevented the fall of liver glycogen content and distortion of the liver parenchyma.

CONCLUSIONS

Carnosol prevents acute liver damage, possibly by improving the structural integrity of the hepatocytes. To achieve this, carnosol could scavenge free radicals induced by CCl(4), consequently avoiding the propagation of lipid peroxides. It is suggested that at least some of the beneficial properties of Rosmarinus officinalis are due to carnosol.

Evaluation of the effectiveness of Rosmarinus officinalis (Lamiaceae) in the alleviation of carbon tetrachloride-induced acute hepatotoxicity in the rat

The effect of oral administration of Rosmarinus officinalis L. (Lamiaceae) on CCl(4)-induced acute liver injury was investigated. Rats were daily treated with the plant extract at a dose of 200 mg/kg corresponding to 6.04 mg/kg of carnosol as determined by reverse phase high-performance liquid chromatography. The treatment was initiated 1 h after CCl(4) administration and Rosmarinus officinalis fully prevented CCl(4) effect on hepatic lipid peroxidation after 24 h of CCl(4) administration. The increase in bilirubin level and alanine aminotransferase activity in plasma induced by CCl(4) was completely normalized by Rosmarinus officinalis. The treatment also produced a significant recovery of CCl(4)-induced decrease in liver glycogen content. CCl(4) did not modify the activity of liver cytosolic glutathione S-transferase (GST) compared with that of control groups. However, Rosmarinus officinalis increased liver cytosolic GST activity and produced an additional increment in plasma GST activity in rats treated with CCl(4). Histological evaluation showed that Rosmarinus officinalis partially prevented CCl(4)-induced inflammation, necrosis and vacuolation. Rosmarinus officinalis might exert a dual effect on CCl(4)-induced acute liver injury, acting as an antioxidant and improving GST-dependent detoxification systems.

Antioxidant properties of colchicine in acute carbon tetrachloride induced rat liver injury and its role in the resolution of established cirrhosis

Antioxidant and antifibrotic properties of colchicine were investigated in the carbon tetrachloride (CCl(4)) rat model. (1) The protective effect of colchicine pretreatment on CCl(4) induced oxidant stress was examined in rats subsequently receiving a single lethal dose of CCl(4). Urinary 8-isoprostane, kidney and liver malondialdehyde and kidney glutathione levels increased following CCl(4) treatment, but only the rise in kidney malondialdehyde was significantly inhibited by colchicine pretreatment. Serum total antioxidant levels were significantly higher in the colchicine pretreatment group. (2) The long term effects of colchicine treatment on CCl(4) induced liver damage were investigated using liver histology and biochemical markers (hydroxyproline and type III procollagen peptide). Co-administration of colchicine with sub-lethal doses of CCl(4) over 10 weeks did not prevent progression to cirrhosis. However, rats made cirrhotic with repeated CCl(4) challenge and subsequently treated with colchicine for 12 months, all showed histological regression of cirrhosis. (3) The antioxidant effect of colchicine in vitro was evident only at very high concentrations compared to other plasma antioxidants. In summary, colchicine has only weak antioxidant properties, but does afford some protection against oxidative stress; more importantly, long term treatment with this drug may be of value in producing regression of established cirrhosis.

Animal models of fulminant hepatic failure: a critical evaluation

Few conditions in medicine are more dramatic or more devastating than acute liver failure. Our understanding and treatment of this condition have been limited by the lack of satisfactory animal models. The most widely used models consist of surgical anhepatic and devascularization procedures and hepatotoxins, such as galactosamine and acetaminophen. Potential disadvantages with surgical models are their inability to recreate the inflammatory milieu that exists in acute liver failure and their reliance on surgical expertise. Models using hepatotoxins are free of such constraints. Galactosamine-induced hepatotoxicity is more predictable than acetaminophen, but its cost and lack of a human equivalent clinical syndrome has restricted its use. Acetaminophen-based models offer the greatest potential but have proven the most difficult to develop because of difficulties with reproducibility and refractory anemia. Although progress has been made, research must continue in this area to establish an animal model with minimal disadvantages that would accurately reflect the clinical syndrome seen in humans.

Biphasic effect of colchicine on acute liver injury induced by carbon tetrachloride or by dimethylnitrosamine in mice

BACKGROUND/AIMS

The effects of colchicine on acute liver injury induced by carbon tetrachloride or by dimethylnitrosamine in mice were examined.

METHODS

Nonlethal acute liver injury was induced in male BALB/c mice by a single intraperitoneal injection of 0.8 ml/kg carbon tetrachloride or 15 mg/kg dimethylnitrosamine. 0.6 mg/kg colchicine was administered 18 h or 2 h intraperitoneally before hepatotoxin treatment.

RESULTS

Reversible centrilobular to mid-zone necrosis and apoptosis occupying half the liver lobular area was evoked by carbon tetrachloride, and dimethylnitrosamine, respectively. Administration of colchicine 18 h before hepatotoxins markedly suppressed liver injury, whereas colchicine administration 2 h before the hepatotoxins accelerated it. The hepatoprotective effect evoked by colchicine was due to reduction in liver cytochrome P450 content and P450 2E1 activity. In contrast, the hepatodestructive effect seen in the carbon tetrachloride model was related to the extent of lipid peroxidation promoting plasma membrane destruction, while the hepatodestructive effect in the dimethylnitrosamine model was due to suppression of Bcl-X(L) expression, leading to acceleration of apoptosis.

CONCLUSIONS

A biphasic effect of colchicine on carbon tetrachloride- and dimethylnitrosamine-induced acute liver injury was seen. The time interval between colchicine administration and the hepatotoxin treatment is crucial to the subsequent development of liver lesions.

An improved model of galactosamine-induced fulminant hepatic failure in the pig

Fulminant hepatic failure is a serious condition with very high mortality. Development of new therapies designed to bridge the patient through the acute period of their disease has been hampered by the lack of a large animal model that closely reproduces the changes in humans. We have established an improved model of fulminant hepatic failure in the pig by administration of an aminosugar d-galactosamine hydrochloride. Galactosamine in a dose of 1.0 g/kg was dissolved in 5% dextrose in water (D5W) and given intravenously to seven young pigs weighing 8 to 15 kg. Seven control pigs received an equal volume of D5W alone. Two days prior to injection, a baseline ultrasound-guided liver biopsy was done in each pig under general anesthesia using isofluorane. Clinical data were recorded and blood for laboratory determinations was drawn at 0 h (baseline), 24 h, 48 h, and 72 h after infusion of galactosamine or D5W alone, under general anesthesia. Neurological data were recorded at the same intervals before inducing anesthesia. Galactosamine-treated animals showed 100% mortality. All of them died by 86 h after injection of galactosamine, with death resulting from fulminant hepatic failure characterized by marked increases in total bilirubin, liver enzymes, ammonia, and lactate; associated coagulopathy; hypoglycemia; and coma. Liver histology showed massive hepatocellular necrosis in all seven galactosamine-treated animals. This large and highly reproducible animal model appears promising for future evaluation of bioartificial liver support systems designed to treat fulminant hepatic failure in humans.

Colchicine-induced elevation of tissue metallothionein contents is mediated by inflammation-independent serum factor

Subcutaneous injection of colchicine caused dose-dependent and time-dependent induction of hepatic MT in mice. Other than colchicine, similar MT induction was observed in vincristine- or vinblastine-injected mice, but not in beta-lumicolchicine-injected mice. MT contents were also elevated in the kidney, spleen, lung and heart by colchicine injection. Isoforms of colchicine-induced MT in the liver were identified to be MT-I and II by immunoblot analysis. Unlike turpentine-induced MT synthesis, dexamethasone, an anti-inflammatory agent, could not block the MT-inducing activity of colchicine. Therefore, the MT-inducing activity of colchicine does not appear to be due to inflammation. Mouse serum, obtained at 4-24 h after colchicine treatment, stimulated MT induction in rat hepatoma H4IIEC3 cells. The MT-inducing activity in the serum from colchicine-treated mice was determined to be highest at 12 h after colchicine injection. The MT-inducing activity from sera of colchicine-treated mice was completely blocked by glucocorticoid antagonist, RU38486, similar to such activity in the serum from lipopolysaccharide-treated mice. The ability of sera to induce MT was abolished by heat treatment (56 degrees C, 30 min). The molecular weight of the MT-inducing factor estimated by gel filtration was approximately 20 000 Da. Thus, colchicine-induced stimulation of MT production is mediated by some humoral factor. The production of the MT-inducing factor was not blocked by dexamethasone. We conclude that the mediator is not an inflammatory cytokine or a glucocorticoid and suspect that the disruption of microtubule triggers production or release of such humoral mediator which stimulates MT induction.

Effect of colchicine and trimethylcolchicinic acid on CCl4-induced cirrhosis in the rat

Colchicine is one of the most promising drugs for the treatment of cirrhosis. However, due to its toxicity, other drugs are being evaluated and colchicine-like molecules may be good alternatives. The aim of this work was to compare the beneficial effects of colchicine and trimethylcolchicinic acid (a colchicinoid less toxic than colchicine) on CCl4-cirrhosis. The drugs were administered either through CCl4 administration (8 weeks) or after CCl4 intoxication for 4 weeks at a dose of 10 micrograms/rat/day, orally. Liver plasma membranes were isolated for high affinity Ca(2+)-ATPase, gamma-glutamyl transpeptidase and alkaline phosphatase activities. The activities of gamma-glutamyl transpeptidase and alkaline phosphatase were also measured in serum. Liver glycogen content and a marker for lipid peroxidation were determined in liver samples. We found that both compounds preserved and significantly reversed high affinity Ca(2+)-ATPase, gamma-glutamyl transpeptidase and alkaline phosphatase plasma membrane and serum enzyme activities as well as the hepatic glycogen content.

Protective effect of colchicine on acute liver damage induced by CCl4. Role of cytochrome P-450

The aim of this work was to study if colchicine protects against. CCl4-induced changes in hepatic biochemical parameters by reducing cytochrome P-450, by comparing the effects of colchicine and SKF 525-A, a well-known inhibitor of cytochrome P-450. Our results show that both drugs reduced the cytochrome P-450 content and p-nitroanisole o-demethylase activity to the same extent. However, colchicine afforded a total protection from markers of liver injury, while SKF 525-A protected only partially. The difference in the hepatoprotective activity of both drugs indicates that the beneficial effect of colchicine cannot be attributed solely to the inhibition of the activation of CCl4. Other actions, perhaps at the level of the propagation of lipid peroxidation or a 'membrane-stabilizing' effect cannot be ruled out.

Prevention of carbon tetrachloride-induced lipid peroxidation in liver microsomes from dehydroepiandrosterone-pretreated rats

Dehydroepiandrosterone (DHEA), a lipid soluble steroid, administered to rats (100 mg/kg b.wt) by a single intraperitoneal injection, increases to twice its normal level in the liver microsomes. Microsomes so enriched become resistant to lipid peroxidation induced by incubation with carbon tetrachloride in the presence of a NADPH-regenerating system: also the lipid peroxidation-dependent inactivation of glucose-6-phosphatase and gamma-glutamyl transpetidase due to the haloalkane are prevented. Noteworthy, the liver microsomal drug-metabolizing enzymes and in particular the catalytic activity of cytochrome P450IIE1, responsible for the CCl4-activation, are not impaired by the supplementation with the steroid. Consistently, in DHEA-pretreated microsomes the protein covalent binding of the trichloromethyl radical (CCl3 degrees), is similar to that of not supplemented microsomes treated with CCl4. It thus seems likely that DHEA protects liver microsomes from oxidative damage induced by carbon tetrachloride through its own antioxidant properties rather than inhibiting the metabolism of the toxin.

Reversal of carbon tetrachloride induced changes in microviscosity and lipid composition of liver plasma membrane by colchicine in rats

Colchicine is beneficial in the treatment of cirrhotic patients, it prevents changes in plasma membrane bound enzymes induced by CCl4 intoxication. In this study, lipid composition and microviscosity were measured in liver plasma membranes isolated from rats given CCl4. Microviscosity values increased in rats given CCl4 for six weeks but fell considerably in those given CCl4 for 10 weeks. Both these changes were absent when colchicine was given with CCl4. The cholesterol/phospholipid molar ratios and lipid peroxide values increased but plasma membrane phospholipids, the length of fatty acyl chains, and the unsaturation index fell significantly after CCl4 intoxication. Colchicine treatment also prevented these changes. Changes in the lipid composition of liver plasma membranes were significantly correlated with lipid peroxidation. Colchicine prevents changes in the physicochemical properties of liver plasma membranes induced by longterm CCl4 treatment, probably by blocking peroxidation of unsaturated fatty acids.

Effect of colchicine on acetaminophen-induced liver damage

The effect of colchicine on liver damage induced by acetaminophen (APAP) intoxication was studied. Wistar male rats pretreated (72 h) with 3-methylcholanthrene (3-MC) (20 mg/kg i.p.) were divided into six groups: animals in group 1 were treated with acetaminophen (APAP) (500 mg/kg p.o.); group 2 consisted of animals that received colchicine (65 micrograms/kg/day p.o.) for 7 days before APAP intoxication; group 3 was treated like group 2, but the dose of colchicine was 300 micrograms/kg/day; animals in groups 4 and 5 received the same doses of colchicine as groups 2 and 3, respectively, but received the vehicle instead of APAP; and rats in group 6 (control) received the equivalent amount of the vehicles. Animals were sacrificed at different times after APAP administration. Reduced glutathione (GSH), lipid peroxidation and glycogen were measured in liver and, gamma-glutamyl transpeptidase (gamma-GTP), and glutamic pyruvic transaminase (GPT) activities were measured in serum. After APAP intoxication, GSH and glycogen decreased very fast (1 h) and remained low for 6 h. Lipid peroxidation increased three times over control 4 h after APAP treatment. Enzyme activities increased at 18 h after intoxication. Pretreatment with 65 micrograms/kg of colchicine failed to prevent liver damage induced by APAP. However, when a dose of 300 micrograms/kg of colchicine was given, levels of lipid peroxidation and serum gamma-GTP activity remained within the control values, while GPT activity and glycogen content were only partially attenuated. It was concluded that colchicine protects against APAP intoxication, probably through its antioxidant properties, possibly acting as a free radical scavenger.

Effect of colchicine on hepatobiliary function in CCl4 treated rats

A number of toxic chemicals affect the biliary excretory function of liver. Organochlorines and halomethanes are known to enhance bile flow. Despite the demonstration that a diversity of agents modify biliary function, the mechanism by which these chemicals manifest this effect is not fully understood. This study was designed to assess the effect of colchicine (0.1, 1.0, or 2.5 mg/kg, i.p., in saline) administration on biliary excretory function 6 and 24 hr later. Additionally, the effect of colchicine (1 mg/kg, i.p. in saline) pretreatment in rats 2 hr prior to the administration of a single low dose of CCl4 (100 microL/kg, i.p., in corn oil) or corn oil alone (1 mL/kg, i.p.) on hepatic biliary excretory function was also assessed at 6 and 24 hr after the last treatment. The hepatotoxicity was evaluated by serum enzymes, alanine and aspartate aminotransferases, and histopathological alterations of the liver. Biliary excretion of intravenously administered phenolphthalein glucuronide (PG) was assessed in bile duct cannulated anesthetized rats. Only the highest dose of colchicine (2.5 mg/kg) resulted in detectable liver injury as revealed by elevations of serum transaminases. While the lowest dose of colchicine (0.1 mg/kg) did not influence bile secretion, the two higher doses caused a slight choleretic effect at 24 hr. The highest dose caused a transient inhibition of bile flow, but this effect was no longer evident at 6 hr. Biliary excretion of PG was inhibited significantly by colchicine within 6 hr after administration, an effect that was also persistent at 24 hr. Colchicine at a 1 mg/kg dose did not cause any adverse effect on hepatobiliary function. Therefore, for the interactive toxicity study with CCl4, 1 mg colchicine/kg was chosen as a moderate dose which did not cause any significant adverse effect on hepatobiliary function. Biliary excretion of PG was significantly lower in rats at 6 and 24 hr after the combination treatment with colchicine + CCl4 than in rats receiving either CCl4 or colchicine alone. In contrast, rats receiving CCl4 alone or colchicine + CCl4 showed a significant increase in cumulative bile flow at 6 hr, whereas, at 24 hr, the bile flow was increased significantly in rats receiving colchicine regardless of CCl4 treatment. The data suggest that colchicine pretreatment leads to significant inhibition of hepatobiliary excretion in CCl4 treated rats. Serum alanine transaminase and aspartate transaminase levels were elevated significantly after the colchicine + CCl4 combination, indicating hepatic injury.(ABSTRACT TRUNCATED AT 400 WORDS)

Animal models of fulminant hepatic failure

The six requirements for a satisfactory animal model of fulminant hepatic failure are reversibility, reproducibility, death from liver failure, a therapeutic window, a large animal model, and minimal hazard to personnel. Different models may be required to evaluate the various types of liver failure seen in man. The available models include surgical anheptic and devascularization procedures, as well as hepatotoxic drug administration using agents such as carbon tetrachloride, acetaminophen, or galactosamine. Currently combined surgical and drug models appear to provide the best model but the search for the ideal models continues.

Erythrocyte defects precede the onset of CCl4-induced liver cirrhosis. Protection by silymarin

The time-course of some alterations produced in erythrocytes during the onset of CCl4-induced liver cirrhosis was studied in rats. Erythrocyte membranes were isolated to measure Na+, K+ and Ca+2-ATPase activities. Membrane lipid composition was determined to calculate the cholesterol/phospholipid ratio and serum samples were used to measure lipoperoxidation. The results demonstrated that as CCl4 treatment progressed, serum lipoperoxidation and membrane cholesterol/phospholipid ratio increased while ATPase activities decreased. ATPase activities in red blood cells of cirrhotic rats were 50% below normal values but those determined in cells of animals treated simultaneously with CCl4 + silymarin were significantly improved. Silymarin co-treatment also preserved the normal cholesterol/phospholipid ratio in the membranes. Our results suggest that the measure of ATPase activities in erythrocytes membranes could be a simple, safe and useful early marker of liver damage and also valuable to test the effectiveness of a given drug therapy.

Failure of colchicine to improve short-term survival in patients with alcoholic hepatitis

Colchicine treatment was used in this randomized placebo-controlled trial in patients with severe acute alcoholic hepatitis [serum bilirubin greater than or equal to 5 mg/dL (85.5 mumol/L) mean, 17.5 +/- 7.5 mg/dL (299.25 +/- 128.25 mumol/L)]. Hospitalization mortality and morbidity and the effect on biochemical test results were the end points of the treatment. Patients in the two groups were evenly matched by demographics and laboratory test results. Mean time to study entry was less than 7 days from admission. The duration of the trial was 30 days. Thirty-six patients (24 men, 12 women) received colchicine (1 mg orally every morning) and 36 (25 men, 11 women) received an identical placebo. Seven (19%) colchicine-treated and six (17%) control patients died during the index hospitalization after a mean of 17.4 +/- 10.8 and 17.8 +/- 5.3 days, respectively (NS). During a 4-month follow-up period from entry into the trial, there were two additional deaths in each group. No differences between placebo- and colchicine-treated patients were observed in any of the laboratory parameters (serum bilirubin, aspartate transaminase, alanine transaminase, prothrombin activity, albumin, white blood cell count, hemoglobin, and creatinine) that were followed up over the 30-day treatment period. The frequency of complications did not differ statistically between the two groups. This study showed no effect of colchicine treatment on mortality and morbidity of severe alcoholic hepatitis. Colchicine cannot be recommended for the treatment of patients with alcoholic hepatitis.

Protective effect of colchiceine against acute liver damage

Pretreatment of rats with colchiceine (10 micrograms/day/rat) for seven days protected against CCl4-induced liver damage. CCl4 intoxication was demonstrated histologically and by increased serum activities of alanine amino transferase (ALT), alkaline phosphatase (Alk. Phosph.) gamma glutamyl transpeptidase (GGTP), bilirubins and decreased activity of glucose-6-phosphatase (G-6Pase). Furthermore, an increase in liver lipid peroxidation and a decrease in plasma membrane GGTP and Alk. Phosph. activities were found. Colchiceine increased 1.5-fold the LD50 of CCl4 and prevented the release of intracellular enzymes as well as the decrease in GGTP and Alk. Phosph. activities in plasma membranes. It also completely prevented the lipid peroxidation induced by CCl4 and limited the extent of the histological changes.