Inhibition of hepatic cell nuclear DNA fragmentation by zinc in carbon tetrachloride-treated rats

Ectopic expansion and vascularization of engineered hepatic tissue based on heparinized acellular liver matrix and mesenchymal stromal cell spheroids

Engineered liver organogenesis is not yet a viable therapeutic option, but ectopic liver histogenesis may be possible. Accumulating evidence has suggested that cell-cell interactions and cell-matrix interactions play an important role in determining the properties of engineered hepatic tissue in vitro and in vivo. In the current study, we utilized heparinized decellularized liver scaffolds and bone marrow mesenchymal stromal cell spheroids to fabricate engineered hepatic tissue, which was subsequently implanted into the omentum of Sprague-Dawley rats with or without liver injury. The survival, liver-specific functions, differentiation level and regenerative potential of the implanted hepatocyte-like cells in this ectopic liver system were evaluated, together with the vascularization status and therapeutic potential of the engineered hepatic tissue. We demonstrated that these hepatic grafts could survive and possess hepatocyte specific function in this ectopic liver system but could also efficiently anastomose with host vascular networks. Furthermore, we found that hepatocyte-like cells within grafts expanded more than 9-fold over the course of 4 weeks in immunocompetent rats with injured livers. Immunostaining revealed that these hepatocyte-like cells could self-organize into cord-like structures in vivo. In addition, these hepatic grafts exhibited therapeutic potential in liver injury induced by CCl₄. To our knowledge, this is the first report demonstrating the generation of long-term vascularized hepatic parenchyma at ectopic sites based on decellularized liver scaffolds and stem cells. These results provide an economic and feasible method for engineering hepatic tissue from construction to transplantation. This methodology may be applicable in clinical medicine, especially metabolic liver diseases. STATEMENT OF SIGNIFICANCE: In this manuscript, we presented an optimized method for the hepatic engineered tissue (HET) from construction to transplantation. The core of this method is utilizing the combination of heparinized decellularized liver scaffolds and stem cell spheroids, which could provide necessary cell-cell and cell-extracellular matrix interactions for HET in vitro and in vivo. We proved that these hepatic grafts could possess hepatocyte specific function and exhibit strong proliferative activity in ectopic liver system, but also able to anastomose with the host vascular networks efficiently and be compatible with the host immune system. This methodology may be possible one day to apply in clinical medicine, especially metabolic liver diseases.

Trace Elements and Paraoxonase-1 Activity in Lower Extremity Artery Disease

Oxidative stress and inflammation are candidate mechanisms to explain the potential role of exposure to metals and reduced activity of paraoxonase-1 (PON1) in age-related diseases. Both may be risk factors contributing to atherosclerosis. In the present study, inductively coupled mass spectrometry was used to explore multiple trace elements, while in-house methods were employed to measure PON1-related variables in patients with lower extremity artery disease (LEAD). Healthy controls were matched for sex, age, body weight, and relevant genotype variants. Serum concentrations of As, Ba, Cu, and Sr were higher in patients than those in controls, with a strong predictive ability to discriminate between groups. Differences in serum Pb, Cd, and Zn were negligible. Serum Cu increased when the disease was more severe, but a negative trend was noted for serum As, B, Ba, and Zn. The only variable associated with ankle-brachial index was serum Zn. Serum PON1 activity was significantly lower in LEAD patients. When the ability of serum trace elements to modulate PON1 activity was explored, the analysis revealed a unique association with serum Zn. The current results strongly suggest that Zn may have a protective effect in non-coronary atherosclerosis and indicate that this element may exert its anti-inflammatory and antioxidant functions through interactions with PON1 activity. These findings deserve confirmation and further research. In particular, the periodic evaluation of serum trace elements and the prescription of Zn supplements are easy measures to implement and that can improve the treatment of patients with LEAD.

Lactational exposure to abamectin induced mortality and adverse biochemical and histopathological effects in suckling pups

Information about the adverse effects of lactation transfer of abamectin (ABA) is important for human health, especially in the third-world countries where breastfeeding is the only source of nutrition for infants. So, the present study was undertaken to evaluate the adverse effects of breastfeeding exposure to ABA on oxidative damage and liver and kidney dysfunction in suckling rats. Dams were orally administered ABA at a doses 22.10, 11.05, and 2.21 mg a.i./kg b.wt from postnatal day 1 (PND1) until day 20 (PND20). The signs of toxicity and high mortality were recorded in suckling male (67.5%) and female (55.0%) pups whose mother exposed to the ABA at dose 22.1 mg a.i./kg b.wt. ABA induced significantly decrease in body weights of mothers and their male and female pups and significant increase in relative liver weights. It caused oxidative stress in the liver and kidney of mothers and their pups by increasing the level of malondialdehyde (MDA) and decreased activities of superoxide dismutase (SOD) and glutathione-transferase (GST). ABA altered the level of serum liver and kidney dysfunction biomarkers either in the mothers or their male and female pups in a dose-dependent manner. It caused histopathological alterations in the liver and kidney tissues. It can be decided that ABA was accumulated in mother's milk, transferred through breast feeding, and induced mortality in their suckling pups. It caused oxidative stress, lipid peroxidation, and biochemical and histopathological alterations in the liver and kidney of mothers and their suckling pups. The results in the present study add some information about the adverse effect of lactation transfer of ABA, which is important for human health in the third-world countries where breastfeeding may be the only source of nutrition for infants in the first and most critical weeks of life.

Administration of zinc against arsenic-induced nephrotoxicity during gestation and lactation in rat model

Background

Free radicals production by toxicity of arsenic (Ar) is most important in the nephrotoxicity. There is accumulating evidence that zinc (Zn), has anti-oxidant properties.

Objectives

The aim of present study was to evaluate protective and ameliorative effects of Zn against Ar-induced nephrotoxicity in rat pups during gestation and lactation.

Materials and Methods

Twenty-four adult pregnant wistar rats were randomly divided into four groups (n = 6). Group one was given vehicle only. Group two received Zn (ZnSO4) at 20 mg/kg/d. Group three received Ar at 5 mg/kg/d as sodium meta-arsenite. Group four received Ar + Zn at the same dose that mentioned in groups of two and three. At the end of the study, 24 hours after the last treatment, samples were killed with overdose of sodium pentobarbital and kidneys were harvested for measuring malondialdehyde (MDA), glutathione (GSH) and histopathological assessment.

Results

The MDA level in kidney was increased in the Ar group, which was decreased after Zn administration in the Ar + Zn group. The GSH level in kidney was decreased in the Ar group, which were increased after Zn administration in the Ar + Zn group. Also, the histopathological changes which were detected in the Ar group attenuated after Zn consumption.

Conclusions

Our findings suggested that administration of Zn during gestation and lactation could have protective and prevent effect in Ar-induced oxidative stress in kidney tissue.

Hepatoprotective effect of grape seed oil against carbon tetrachloride induced oxidative stress in liver of γ-irradiated rat

Carbon tetrachloride (CCl4) and ionizing radiation are well known environmental pollutants that generate free radicals and induce oxidative stress. The liver is the primary and major target organ responsible for the metabolism of drugs, toxic chemicals and affected by irradiation. This study investigated the effect of grape seed oil (GSO) on acute liver injury induced by carbon tetrachloride (CCl4) in γ-irradiated rats (7Gy). CCl4-intoxicated rats exhibited an elevation of ALT, AST activities, IL-6 and TNF-α level in the serum. Further, the levels of MDA, NO, NF-κB and the gene expression of CYP2E1, iNOS and Caspase-3 were increased, and SOD, CAT, GSH-Px, GST activities and GSH content were decreased. Furthermore, silent information regulator protein 1 (SIRT1) gene expression was markedly down-regulated. Additionally, alterations of the trace elements; copper, manganese, zinc and DNA fragmentation was observed in the hepatic tissues of the intoxicated group. These effects were augmented in CCl4-intoxicated-γ-irradiated rats. However, the administration of GSO ameliorated these parameters. GSO exhibit protective effects on CCl4 induced acute liver injury in γ-irradiated rats that could be attributed to its potent antioxidant, anti-inflammatory and anti-apoptotic activities. The induction of the antioxidant enzymes activities, down-regulation of the CYP2E1, iNOS, Caspase-3 and NF-κB expression, up-regulation of the trace elements concentration levels and activation of SIRT1 gene expression are responsible for the improvement of the antioxidant and anti-inflammatory status in the hepatic tissues and could be claimed to be the hepatoprotective mechanism of GSO.

Paraoxonases and chemokine (C-C motif) ligand-2 in noncommunicable diseases

Oxidative stress and inflammation underpin most diseases; their mechanisms are inextricably linked. Chronic inflammation is associated with oxidation, anti-inflammatory cascades are linked to decreased oxidation, increased oxidative stress triggers inflammation, and redox balance inhibits the inflammatory cellular response. Whether or not oxidative stress and inflammation represent the cause or consequence of cellular pathology, they contribute significantly to the pathogenesis of noncommunicable diseases (NCD). The incidence of obesity and other related metabolic disturbances are increasing, as are age-related diseases due to a progressively aging population. Relationships between oxidative stress, inflammatory signaling, and metabolism are, in the broad sense of energy transformation, being increasingly recognized as part of the problem in NCD. In this chapter, we summarize the pathologic consequences of an imbalance between circulating and cellular paraoxonases, the system for scavenging excessive reactive oxygen species and circulating chemokines. They act as inducers of migration and infiltration of immune cells in target tissues as well as in the pathogenesis of disease that perturbs normal metabolic function. This disruption involves pathways controlling lipid and glucose homeostasis as well as metabolically driven chronic inflammatory states that encompass several response pathways. Dysfunction in the endoplasmic reticulum and/or mitochondria represents an important feature of chronic disease linked to oxidation and inflammation seen as self-reinforcing in NCD. Therefore, correct management requires a thorough understanding of these relationships and precise interpretation of laboratory test results.

Protective role of zinc during aluminum-induced hepatotoxicity

The study was carried out to assess the role of zinc (Zn) in mitigating the biochemical alterations induced by aluminum (Al) in rat liver. Rats were divided into four groups: normal control, Al treated (AlCl3, 100 mg/kg b.wt./day), Zn treated (ZnSO4, 227 mg/L drinking water), and combined Al + Zn treated. Al and zinc treatments were given for a total duration of 2 months. Al treatment caused a significant increase in the activity of alkaline phosphatase (ALP), but decreased aspartate aminotransferase (AST) and alanine aminotranferase (ALT) activities, which showed the reverse trend following Zn supplementation. Levels of lipid peroxidation (LPx) and activities of catalase and glutathione-S-transferase (GST) were significantly decreased following Al treatment, which, however, were increased significantly in Zn co-treated rats. Further Al exposure showed a significant increase in reduced glutathione (GSH) content as well as activities, of superoxide dismutase (SOD) and glutathione reductase (GR). However, Zn supplementation to Al-treated rats brought down the raised levels of reduced (GSH) and SOD to within normal limits, but caused no effect on GR activity. Furthermore, Al treatment also resulted in alterations in liver histoarchitecture with disruption of hepatic cords and increased vacuolization, which were close to normal following Zn supplementation. The present study reveals that Zn is effective in attenuating the liver damage inflicted by Al toxicity.

Effectiveness of Zinc in Modulating the CCl (4) - Induced Oxidative Stress in Rat Liver

The present study was designed to evaluate the role of zinc on the enzymes involved in oxidative defense mechanism in conditions of carbon tetrachloride (CCl (4)) -induced rat liver toxicity. To carry out the study, rats were divided into four groups: group I (normal control), group II (CCl (4) treated), group III (zinc control), and group IV (zinc + CCl (4) treated). Animals in group II and group IV were administered 0.1 mL of CCl (4) mixed with 0.1 mL of groundnut oil on alternate days for a period of 8 weeks. Zinc in the form of zinc sulphate was given to animals of group II and group IV at a dose level of 227 mg/L in drinking water. Animals given CCl (4) treatment alone showed a significant increase in the activities of superoxide dismutase (SOD), catalase, glutathione peroxidase (GPx), and the concentration of malondialdehyde (MDA) product, whereas a significant depression was observed in the levels of reduced glutathione (GSH). Zinc treatment to CCl (4) -treated rats brought the altered levels of GSH, MDA, and SOD as observed following CCl (4) -treatment alone to within normal limits. However, the activities of catalase and glutathione peroxidase, which were increased under carbon tetrachloride treatment, were significantly attenuated and tended to become normal. Hence, the present study suggests that zinc may play an important role in regulating the activities of the enzymes involved in antioxidative defense system under CCl (4) toxic conditions.

Hepatoprotective effect of Crossostephium chinensis (L.) Makino in rats

The hepatoprotective potential of Crossostephium chinensis (L.) Makino water extract (CCW) on carbon tetrachloride (CCl(4)) induced liver damage was evaluated in preventive and curative rat models. Not only were indicators of hepatic damage including GPT, GOT, lipid peroxides and TBARS were examined, the activities of antioxidant enzymes (SOD, CAT, GPx) and GSH were examined as well. The results showed that CCW (0.1, 0.5 and 1.0 g/kg) significantly reduced the elevated levels of GPT and GOT by CCl(4) administration (p < 0.05). TBARS level was dramatically reduced, and SOD, CAT, GPx and GSH activities were significantly increased. In addition, CCW decreased NO production and TNF-α activation in CCl(4)-treated rats. Therefore, we speculate that CCW protects against acute liver damage through its radical scavenging ability. CCW inhibited the expression of MMP-9 protein, indicating that MMP-9 played an important role in the development of CCl(4)-induced chronic liver damage in rats. In LC-MS-MS analysis, the chromatograms of CCW with good hepatoprotective activities were established. Scopoletin may be an important bioactive compound in CCW.

Interrelationships between paraoxonase-1 and monocyte chemoattractant protein-1 in the regulation of hepatic inflammation

Oxidative stress and inflammation play a central role in the onset and development of liver diseases irrespective of the agent causing the hepatic impairment. The monocyte chemoattractant protein-1 is intimately involved in the inflammatory reaction and is directly correlated with the degree of hepatic inflammation in patients with chronic liver disease. Recent studies showed that hepatic paraoxonase-1 may counteract the production of the monocyte chemoattractant protein-1, thus playing an anti-inflammatory role. The current review summarises experiments suggesting how paraoxonase-1 activity and expression are altered in liver diseases, and their relationships with the monocyte chemoattractant protein-1 and inflammation.

Protective effects of zinc and selenium against benzene toxicity in rats

The presented study investigates the protective role of zinc (Zn) and selenium (Se) in attenuating benzene-induced toxicity in rats. Male Sprague—Dawley rats were injected with benzene (0.5 mL/kg body weight ip) and received a diet supplement containing Zn and Se. Several hematological and biochemical parameters (representing antioxidant status) were estimated. Histopathological examinations were performed. Results showed that food intake and body weight gain of benzene-injected rats were significantly lower than that of the control rats. Benzene-injected rats showed increased plasma malondialdehyde (MDA) and decreased activity of: glutathione peroxidase (GSH-Px), catalase, superoxide dismutase (SOD) enzymes, as well as reduced glutathione (GSH) when compared to the control group. Histopathological investigations revealed structural changes in benzene-injected rats’ liver. Supplementation with Zn and Se resulted in a significant decrease in MDA, elevation in GSH, GSH-Px, SOD and catalase levels. This study shows that Zn and Se supplementation can improve the activity of antioxidant enzymes in rats and decrease the histological anomalies induced by benzene toxicity as well.

Effect of different dietary zinc levels on hepatic antioxidant and micronutrients indices under oxidative stress conditions

Dietary zinc (Zn) status exerts a powerful influence on the degree of oxidative damage caused by free radicals. We examined the effect of dietary Zn variations with oxidative stress (OS) treatment on antioxidant status, liver function, and status of vitamins in male Wistar rats. Oxidative stress was generated by intraperitoneal injections of tert-butyl hydroperoxide; and dietary Zn variations done were Zn deficient, normal, and excess, with 8, 30, and 60 mg Zn per kilogram diet, respectively. After 21-day dietary regimen, the animals were killed; and plasma aspartate aminotransferase, alanine aminotransferase, hepatic antioxidant enzymes (catalase, superoxide dismutase, glutathione peroxidase), Zn, reduced glutathione, lipid peroxidation (LPO), and hepatic riboflavin, nicotinic acid, and ascorbic acid estimations were done. The alanine aminotransferase and aspartate aminotransferase levels were elevated in rats with OS and Zn-deficient diet, which were restored to normal levels with excess dietary Zn. Hepatic antioxidant enzymes and reduced glutathione levels were significantly decreased with concomitant increase in LPO due to OS induction in animals with Zn-deficient diet. Corresponding enhanced enzyme activities, higher hepatic Zn, and lowered LPO were observed in animals with normal- and excess-Zn diet. A dose-dependent increase in hepatic nicotinic acid accumulation was observed as the dietary Zn level increased from deficient to excess; however, there was no influence on riboflavin and ascorbic acid status. The results suggest that Zn may have a therapeutic potential in treatment of oxidative liver damage along with enhanced nicotinic acid absorption.

Uptake and retention of 65Zn in lithium-treated rat liver: role of zinc

AIM

To evaluate the effects of zinc on the biokinetics of (65)Zn in rat and its distribution in various organs and in subcellular compartment following lithium therapy.

METHODS

Female wistar rats received either lithium treatment at a dose of 1.1g/kg in diet, zinc alone at a dose of 227 mg/L in drinking water, and combined lithium plus zinc for duration of four months.

RESULTS

After four months of lithium treatment, liver enzymes increased significantly (glutamic oxaloacetic transaminase, +66.73%; glutamic pyruvic transaminase, +63.70%; alkaline phosphatase, +40.28%; p< or =0.001); zinc supplementation to lithium-treated rats significantly reduced liver enzymes (glutamic oxaloacetic transaminase, -13.11%; glutamic pyruvic transaminase, -21.78%; alkaline phosphatase, -11.77%; p< or =0.001). The biological half-lives of (65)Zn showed an initial fast component (Tb(1)) and a slower component (Tb(2)). A significant increase in Tb(2) (38.82%, p< or =0.001) in liver was observed following lithium treatment, which significantly decreased following zinc treatment (21.71%, p< or =0.001). A significant decrease in the uptake of (65)Zn (53.93%, p< or =0.01) in liver was observed and in nuclear (p< or =0.01), mitochondrial (p< or =0.01), and microsomal (52.67%, p< or =0.001) fractions. A significant increase in the uptake of (65)Zn (82.92%, p< or =0.05) in liver microsomal fraction (34.09%, p< or =0.001) was observed in lithium-treated rats receiving zinc supplementation.

CONCLUSION

The study suggests that zinc has the potential to regulate the biokinetics of (65)Zn and its subcellular distribution in rat liver following lithium therapy.

Paraoxonase-1 is related to inflammation, fibrosis and PPAR delta in experimental liver disease

BACKGROUND

Paraoxonase-1 (PON1) is an antioxidant enzyme synthesized by the liver. It protects against liver impairment and attenuates the production of the pro-inflammatory monocyte chemoattractant protein-1 (MCP-1). We investigated the relationships between hepatic PON1 and MCP-1 expression in rats with liver disease and explored the possible molecular mechanisms involved.

METHODS

CCl4 was administered for up to 12 weeks to induce liver damage. Serum and hepatic levels of PON1 and MCP-1, their gene and protein expression, nuclear transcription factors, and histological and biochemical markers of liver impairment were measured.

RESULTS

High levels of PON1 and MCP-1 expression were observed at 12th week in the hepatocytes surrounding the fibrous septa and inflammatory areas. CCl4-administered rats had an increased hepatic PON1 concentration that was related to decreased gene transcription and inhibited protein degradation. Decreased PON1 gene transcription was associated with PPARdelta expression. These changes were accompanied by increased hepatic MCP-1 concentration and gene expression. There were significant direct relationships between hepatic PON1 and MCP-1 concentrations (P = 0.005) and between PON1 and the amount of activated stellate cells (P = 0.001).

CONCLUSION

Our results from this experimental model suggest a hepato-protective role for PON1 against inflammation, fibrosis and liver disease mediated by MCP-1.

Paraoxonase-1 is related to inflammation, fibrosis and PPAR delta in experimental liver disease

BACKGROUND

Paraoxonase-1 (PON1) is an antioxidant enzyme synthesized by the liver. It protects against liver impairment and attenuates the production of the pro-inflammatory monocyte chemoattractant protein-1 (MCP-1). We investigated the relationships between hepatic PON1 and MCP-1 expression in rats with liver disease and explored the possible molecular mechanisms involved.

METHODS

CCl4 was administered for up to 12 weeks to induce liver damage. Serum and hepatic levels of PON1 and MCP-1, their gene and protein expression, nuclear transcription factors, and histological and biochemical markers of liver impairment were measured.

RESULTS

High levels of PON1 and MCP-1 expression were observed at 12th week in the hepatocytes surrounding the fibrous septa and inflammatory areas. CCl4-administered rats had an increased hepatic PON1 concentration that was related to decreased gene transcription and inhibited protein degradation. Decreased PON1 gene transcription was associated with PPARdelta expression. These changes were accompanied by increased hepatic MCP-1 concentration and gene expression. There were significant direct relationships between hepatic PON1 and MCP-1 concentrations (P = 0.005) and between PON1 and the amount of activated stellate cells (P = 0.001).

CONCLUSION

Our results from this experimental model suggest a hepato-protective role for PON1 against inflammation, fibrosis and liver disease mediated by MCP-1.

Hepatoprotective Role of Zinc in Lead-Treated, Protein-Deficient Rats

The current study was designed to evaluate the hepatoprotective role of zinc after lead (Pb) treatment of protein-deficient (PD) rats. The animals were subjected to seven different treatment groups: G-1 (normal control, 18% protein), G-2 (protein-deficient, 8% protein), G-3 (Pb-treated, 100 mg/kg body weight of lead acetate), G-4 (Zn-treated, zinc sulfate at a dose level of 227 mg/L drinking water), G-5 (PD + Pb-treated), G-6 (PD + Zn-treated), and G-7 (PD + Pb + Zn-treated). Serum albumin levels and total serum protein contents were estimated to assess the severity of protein deficiency at the end of 8 weeks in all the treatment groups. Also, the study explored the role of zinc on antioxidative defense system enzymes in liver of protein-deficient rats subjected to lead toxicity treatment. Further, the study was extended to elucidate the levels of zinc and lead in liver tissue after different treatments of rats using positron-induced X-ray emission technique (PIXE). The current study indicated a significant change in the levels of various antioxidative enzymes and serum albumin as well as total protein contents of protein-deficient rats subjected to lead treatment. A significant increase in the levels of malondialdehyde (MDA), catalase, and glutathione peroxidase (GPx) was seen after 8 weeks of lead treatment of protein-deficient rats. On the contrary, levels of albumin, total protein content, superoxide dismutase (SOD), GSH, were found to be decreased. Interestingly, zinc supplementation has tended to normalize the altered levels of these enzymes to a significant extent. The levels of zinc in liver tissue was found to be decreased significantly in protein-deficient as well as lead-treated rats. However, hepatic zinc concentration was increased to a significant extent in protein-deficient rats supplemented with zinc when compared with protein-deficient rats. Further, the presence of lead was also observed in livers of lead-treated animals. In conclusion, the study revealed the antioxidative role of zinc in hepatotoxic conditions induced by subjecting the rats to protein-deficient diet and lead treatment.

Zinc modulates lithium-induced hepatotoxicity in rats

AIM

The present study explored the hepatoprotective role of zinc in lithium-induced hepatotoxicity.

METHODS

Rats received either lithium treatment in diet at a dose level of 1.1 g/kg diet, zinc alone at a dose level of 227 mg/L in drinking water, and combined lithium plus zinc or drinking water alone for different time durations of 1, 2 and 4 months. This study explored the hepatic marker enzymes, antioxidant status and histopathological investigations in the liver of rats following different treatments.

RESULTS

The activities of glutamic oxaloacetic transaminase, glutamic pyruvic transaminase and alkaline phosphatase were found to be elevated significantly following 2 and 4 months of lithium treatment. Lithium-treated rats showed a significant increase in the levels of lipid peroxidation and superoxide dismutase and a significant inhibition in the levels of reduced glutathione, catalase and glutathione-S-transferase, following 2 and 4 months of treatment. However, zinc co-administration revealed significant improvement in the altered activities of hepatic marker and antioxidant enzymes in comparison with lithium-treated animals. Lithium-treated rats also indicated drastic alterations in hepatic histoarchitecture and zinc co-administration resulted in improvement in the structure of hepatocytes.

CONCLUSION

The present study suggests the protective potential of zinc in lithium-induced hepatotoxicity.

Moderately high folic acid supplementation exacerbates experimentally induced liver fibrosis in rats

Under certain clinical circumstances, folic acid can have undesirable effects. We investigated the following: (i) the effects of moderately high folic acid supplementation on the course of liver impairment in CCl(4)-treated rats and (ii) the influence of folic acid supplements on the hepatic recovery following the interruption of the CCl(4)-induced toxic injury. Four experimental groups of rats were used: CCl(4)-treated rats (0.5 ml of CCl(4) twice a week i.p.) fed standard chow for up to 12 weeks (Group A); treated rats fed chow supplemented with 25 mg/kg folic acid from weeks 6 to 12 (Group B); treated rats fed a standard diet but with CCl(4) discontinued after 6 weeks to allow for tissue recovery over 4 weeks (Group C); rats as Group C but fed a diet supplemented with 25 mg/kg folic acid from weeks 6 to 10 (Group D). Liver and blood samples were obtained for biochemical, histological, and gene expression analyses. Animals that received the supplement had a higher content of collagen, activated stellate cells, and apoptotic parenchymal cells in biopsy tissue at weeks 8 and 10 of treatment and more extensive alterations in serum albumin and bilirubin concentrations (Group B vs. Group A). In some of the time periods analyzed, alterations were observed in the expression of genes related to apoptosis (B-cell leukemia/lymphoma 2, inhibitor of apoptosis 2) and to fibrosis (procollagen I, matrix metalloproteinase 7). In the recovery period (Groups C and D), folic acid administration was associated with increased hepatic inflammation and apoptosis and with a decrease in the tissue inhibitor of metalloproteinase-3 expression following 1 week of recovery. We conclude that folic acid administration aggravates the development of fibrosis in CCl(4)-treated rats. Follow-up studies are needed to determine whether folic acid treatment would be contraindicated in patients with chronic liver diseases.

Evaluating genotoxicity data to identify a mode of action and its application in estimating cancer risk at low doses: A case study involving carbon tetrachloride

In the new USEPA cancer risk assessment guidelines, mode of action (MoA) information, combined with a determination of whether or not a chemical is mutagenic, plays an important role in determining whether a linear or nonlinear approach should be used to estimate cancer risks at low doses. In this article, carbon tetrachloride (CT) is used as an example to illustrate how mixed genotoxicity data can be evaluated and used to identify a likely MoA. CT is essentially negative in inducing gene mutations in Salmonella, but is consistently positive in inducing recombination and aneuploidy in fungi. Negative or equivocal results were seen in most in vitro and in vivo studies in mammals, including mutation studies in transgenic mice. However, DNA adducts, primarily those derived from oxidation- and lipid-peroxidation-derived products as well as DNA double-strand breaks and micronucleated cells, have been seen repeatedly in the liver of CT-treated animals. On the basis of the weight of evidence, CT should not be considered a directly mutagenic agent. Mutagenic as well as other genotoxic effects, as they occur, will most likely be generated through indirect mechanisms resulting from oxidative and lipid peroxidative damage and/or damage occurring during necrosis or apoptosis. As key events in this process are expected to occur in a nonlinear fashion, the expected relationship between CT dose and carcinogenic response in the liver is likely to be nonlinear with a steep dose response. This conclusion is consistent with rodent cancer bioassay results in which steep nonlinear dose responses have been seen.

Zinc supplementation prevents the increase of transaminase in chronic hepatitis C patients during combination therapy with pegylated interferon alpha-2b and ribavirin

We investigated the effects of zinc supplementation on clinical observations in chronic hepatitis C patients receiving pegylated interferon (PEG-IFN) alpha-2b plus ribavirin combination therapy. Patients were randomly allocated to receive 150 mg polaprezinc (zinc group, n=11) or no supplement (control group, n=12) daily in addition to PEG-IFN alpha-2b plus ribavirin therapy and 300 mg vitamin E and 600 mg vitamin C supplementation daily for 48 wk. Among the patients who continued treatment, the serum alanine aminotransferase (ALT) level at 12 wk in the zinc group was significantly lower than that in the control group. All patients in the zinc group (9/9) and 67% (8/12) of the control patients at 24 wk, and all patients in the zinc group (7/7) and 60% (6/10) of the control patients at 48 wk showed a decrease in serum ALT levels to within the normal range (7-44 U/L). HCV RNA disappeared in all patients (7/7) in the zinc group and in 8 of 10 control patients at 48 wk. Polaprezinc supplementation decreased plasma thiobarbituric acid reactive substances and prevented the decrease of polyunsaturated fatty acids of erythrocyte membrane phospholipids. No significant differences were observed in the dosage of medicines or other clinical data during the treatment. These observations indicate that polaprezinc supplementation may have induced some antioxidative functions in the liver which resulted in reduced hepatocyte injury during PEG-IFN alpha-2b plus ribavirin therapy.

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.

Zinc and the liver: an active interaction

Zinc is an essential trace element, exerting important antioxidant, anti-inflammatory, and antiapoptotic effects. It affects growth and development and participates in processes such as aging and cancer induction. The liver is important for the regulation of zinc homeostasis, while zinc is necessary for proper liver function. Decreased zinc levels have been implicated in both acute and chronic liver disease states, and zinc deficiency has been implicated in the pathogenesis of liver diseases. Zinc supplementation offers protection in experimental animal models of acute and chronic liver injury, but these hepatoprotective properties have not been fully elucidated. In the present review, data on zinc homeostasis, its implication in the pathogenesis of liver diseases, and its effect on acute and chronic liver diseases are presented. It is concluded that zinc could protect against liver diseases, although up to now the underlying pathophysiology of zinc and liver interactions have not been defined.

Possible inhibitory effect of oral zinc supplementation on hepatic fibrosis through downregulation of TIMP-1: A pilot study

AIM

To investigate the effect of oral zinc supplementation (polaprezinc) for 24 weeks (34 mg/day zinc) on liver fibrosis in patients with advanced chronic liver disease.

METHODS

Various markers of liver fibrosis, and fibrogenic and fibrolytic enzyme activities were measured before and after zinc supplementation in 17 patients with early cirrhosis.

RESULTS

Serum zinc levels were decreased in the patients as compared with healthy controls. No side-effect was noted in any of the patients who received zinc supplementation. Serum levels of zinc increased by up to 156% over baseline levels in the group of patients who took oral zinc for 24 weeks. In patients whose serum zinc levels increased, the serum levels of type IV collagen and the activity of tissue inhibitors of metalloproteinase-1 (TIMP-1) were significantly reduced, but no such change was observed in the other groups of patients, and no other serum markers changed.

CONCLUSION

These results suggest that oral zinc supplement therapy with polaprezinc is safe and may be a novel and useful strategy for antifibrosis therapy in patients with early liver cirrhosis.

Zinc mediated normalization of histoarchitecture and antioxidant status offers protection against initiation of experimental carcinogenesis

The present study evaluated the inhibitory effects of zinc on colonic antioxidant defense system and histoarchitecture during 1,2 dimethylhydrazine (DMH) induced colon carcinogenesis in male Spraque Dawley rats. The rats were segregated into four groups viz., normal control, DMH treated, zinc treated, DMH + zinc treated. Colon carcinogenesis was induced through weekly subcutaneous injections of DMH (30 mg/kg body weight) for 8 weeks. Zinc (in the form of zinc sulphate) was supplemented to rats at a dose level of 227 mg/l in drinking water, ad libitum for the entire duration of the study. Increased lipid peroxidation was accompanied by a decrease in reduced glutathione (GSH), glutathione reductase (GR), glutathione-s-transferase (GST), superoxide dismutase (SOD), and catalase. Administration of zinc to DMH treated rats significantly decreased the lipid peroxidation levels with simultaneous enhancement of GSH, GR, GST, SOD, and Catalase. Histopathological studies from DMH treated rats revealed disorganization of colonic histoarchitecture. However, zinc treatment to DMH treated rats greatly restored normalcy in the colonic histoarchitecture, with no apparent signs of abnormality. Energy Dispersive X-Ray Fluorescence (EDXRF) studies revealed a significant decrease in tissue concentrations of zinc in the colon following DMH treatment, which upon zinc supplementation were recovered to near normal levels. In conclusion, the results of this study suggest that zinc has a beneficial effect during the initiation of key events leading to the development of experimentally induced carcinogenesis.

Role of zinc in mitigating the toxic effects of chlorpyrifos on hematological alterations and electron microscopic observations in rat blood

The present study determined the protective potential of zinc in attenuating the toxicity induced by chlorpyrifos in rat blood. Male Sparque Dawley (SD) rats received either oral chlorpyrifos (13.5 mg/kg body weight) treatment every alternate day, zinc alone (227 mg/l in drinking water) or combined chlorpyrifos plus zinc treatment for a total duration of 8 weeks. The effects of different treatments were studied on various parameters in rat blood including haemoglobin (Hb) levels, total leukocyte count (TLC), differential leukocyte count (DLC), zinc protoporphyrins (ZPP), serum trace elemental concentrations and Scanning Electron Microscopic (SEM) observation of the blood cells. Chlorpyrifos treatment to normal control animals resulted in a significant decrease in TLC and ZPP concentration after 4 and 8 weeks. Chlorpyrifos treated animals also showed significant neutrophilia and lymphopenia after 8 weeks of toxicity. In addition, a significant decrease in serum zinc and iron concentrations were observed following chlorpyrifos intoxication, however, these animals responded with increased serum copper levels following the toxic treatment with this organophosphate. SEM studies of the red blood cells from chlorpyrifos treated animals indicated marked alterations in the topographical morphology of the various cell types, with the prominent feature being common aniscocytosis of the erythrocytes. Oral zinc treatment to the chlorpyrifos treated animals significantly improved the total leukocyte, neutrophil and lymphocyte counts, as well as the otherwise reduced concentrations of ZPP and the levels of various serum trace elements. Protective effects of zinc were also evident in the electron microscopic observations where most blood cell types depicted reverted to a close to the normal appearance. Based upon these data, the present study is first of its kind and suggests that zinc treatment considerably attenuates chlorpyrifos induced toxicity induced in restoring the altered hematological indices and morphological changes.

Water-soluble extract of Salvia miltiorrhiza ameliorates carbon tetrachloride-mediated hepatic apoptosis in rats

Apoptosis is one of the events that are involved in liver fibrogenesis. Thus, factors that affect apoptosis may be used to modulate liver fibrosis. We have recently reported that Salvia miltiorrhiza plays a protective role in carbon tetrachloride (CCl4)-induced hepatic fibrosis. In this study, we aimed to evaluate whether S. miltiorrhiza modulated CCl4-induced hepatic apoptosis in rats. Male Wistar rats were given orally either vehicle or water-extract of S. miltiorrhiza (50 mg kg(-1) twice daily) for nine weeks beginning from the start of CCl4 administration. A group of normal rats was included for comparison. Hepatocyte DNA fragmentation and cytosolic caspase-3 and caspase-8 activity were determined in the experimental animals. Hepatic cytosolic Bax, Bcl-2, cytochrome c, and calpain-mu expressions were measured by Western blot analysis. Hepatic mitochondrial glutathione levels were assessed by colorimetric assay. Compared with normal rats, rats receiving CCl4 alone showed profound DNA fragmentation associated with an increased cytosolic fraction of cytochrome c and calpain-mu protein expressions and a decreased mitochondrial glutathione level. In contrast, a decreased laddering of DNA fragmentation was noted in rats receiving CCl4 plus S. miltiorrhiza extract. The mitochondrial glutathione level was significantly increased in rats receiving CCl4 plus S. miltiorrhiza extract compared with those receiving CCl4 alone. Additionally, cytosolic caspase-3 activity and cytosolic fractions of Bax, Bcl-2, cytochrome c, and calpain-mu protein expressions were decreased in rats receiving CCl4 plus S. miltiorrhiza extract compared with those receiving CCl4 alone. The cytosolic caspase-8 activity in rats receiving CCl4 alone was no different from those receiving CCl4 plus S. miltiorrhiza extract. These results indicated that chronic administration of S. miltiorrhiza ameliorated CCl4-mediatd hepatic apoptosis in rats. This effect may be related to the antioxidant properties of S. miltiorrhiza.

Paraoxonase-1 is associated with oxidative stress, fibrosis and FAS expression in chronic liver diseases

BACKGROUND/AIMS

We previously reported that paraoxonase-1 activity measurement may be useful for the evaluation of liver diseases. Because oxidative stress plays a role in liver apoptosis, and lipid peroxides are hydrolyzed by paraoxonase-1, we have extended our studies to explore the relationships between this enzyme and oxidative stress, fibrosis and apoptosis.

METHODS

We measured paraoxonase-1 activity and concentration, soluble FAS concentration, serum fibrosis markers, and total peroxides in a group of patients with minimal hepatic changes (n=25), chronic hepatitis (n=51), or liver cirrhosis (n=17). We also measured the Knodell activity index in liver biopsies and performed FAS and PON1 immunostaining.

RESULTS

Patients with liver diseases showed an increase in soluble FAS, fibrosis markers and paraoxonase-1 concentrations, as well as a decrease in PON1 activity. Paroxonase-1 activity and concentration were correlated with soluble FAS (r=-0.43, P<0.001 and r=0.27, P=0.007, respectively). Paraoxonase-1 concentration showed a significant inverse association with FAS immunostaining (P=0.013) and a direct association with PON1 immunostaining (P<0.001).

CONCLUSIONS

These results suggest an active role of PON1 in the regulation of oxidative stress, fibrosis and hepatic cell apoptosis in chronic liver diseases.

Chlorpyrifos-induced alterations in the activities of carbohydrate metabolizing enzymes in rat liver: The role of zinc

The present study was conducted to evaluate the adverse effects of chlorpyrifos on the key enzymes of carbohydrate metabolism in liver, and also to assess the role of zinc under these toxic conditions. Male Sprague-Dawley (SD) rats received either oral chlorpyrifos treatment (13.5 mg/kg body weight in corn oil) every alternate day, zinc alone (227 mg/l in drinking water), or combined chlorpyrifos and zinc treatments for a total duration of 8 weeks. The effects of different treatment regimens were studied on various enzymes of carbohydrate metabolism in the rat livers, which included hexokinase, glucose-6-phosphatase, fructose-1,6-diphosphatase, glycogen phosphorylase, succinate dehydrogenase (SDH), lactate dehydrogenase (LDH) and the levels of glycogen. In vitro uptake of (14)C-D-glucose was also assessed in liver slices after similar treatments. Chlorpyrifos intoxication resulted in a significant increase in the activities of glucose-6-phosphatase and glycogen phosphorylase, whereas, it caused a significant inhibition in the levels of hexokinase, SDH, LDH and glycogen content. However, zinc treatment to chlorpyrifos-intoxicated animals was able to normalize the activities of most of these enzymes to either close to, or within normal limits. Chlorpyrifos intoxication demonstrated significantly inhibited (14)C-D-glucose uptake in liver slices, which again was reversed to normal limits following simultaneous zinc treatment. Levels of metallothionein were also found to be depressed in chlorpyrifos-treated animals, but tended to increase significantly on co-administration of zinc to chlorpyrifos-treated group. Hence, the present study clearly suggests that zinc plays an important role in regulating the hepatic activities of the enzymes involved in carbohydrate metabolism under conditions of chlorpyrifos toxicity.

Protective effects of zinc on lipid peroxidation, antioxidant enzymes and hepatic histoarchitecture in chlorpyrifos-induced toxicity

The present study investigated the hepatoprotective role of zinc in attenuating the toxicity induced by chlorpyrifos in rat liver. Male Sprague-Dawley (SD) rats received either oral chlorpyrifos (13.5mg/kg body weight), zinc alone (227mg/l in drinking water) or combined chlorpyrifos plus zinc treatment for a total duration of 8 weeks. The effects of these treatments were studied on various parameters in rat liver, including lipid peroxidation, antioxidant enzymes, levels of metallothionein (MT) and hepatic histoarchitecture. Chlorpyrifos treatment resulted in a significant increase in hepatic lipid peroxidation and activities of superoxide dismutase (SOD), glutathione peroxidase (G-Px) and glutathione reductase (GR). On the contrary, chlorpyrifos intoxication caused a significant inhibition in the levels of reduced glutathione (GSH), catalase (CAT) and glutathione-S-transferase (GST) activities. However, zinc treatment to chlorpyrifos-intoxicated animals normalized the otherwise raised levels of lipid peroxidation to within normal limits. Moreover, zinc treatment to these animals resulted in an elevation in the levels of GSH, catalase and GST, as well as a significant decrease in the levels of SOD. Levels of MT were also found to be depressed in chlorpyrifos-treated animals, but tended to increase following co-administration of zinc. Additionally, chlorpyrifos-treated animals demonstrated increased vacuolization, necrosis and ballooning of the hepatocytes and dilatation of sinusoids as well as increase in the number of binucleated cells. However, zinc administration to chlorpyrifos-treated animals resulted in overall improvement in the hepatic histoarchitecture, emphasizing the protective potential of zinc. Hence, the present study suggests the protective potential of zinc in alleviating the hepatic toxicity induced by chlorpyrifos.

Protective effects of caffeic acid phenethyl ester (CAPE) on carbon tetrachloride-induced hepatotoxicity in rats

In the present study, protective effects of caffeic acid phenethyl ester (CAPE) have been evaluated on carbon tetrachloride (CCl4)-induced hepatotoxicity in rat. Twenty-four male Wistar rats were divided in three groups. Group I was used as control. Rats in group II were injected every other day with CCl4 for 1 month, whereas rats in group III were injected every other day with CCl4 and CAPE for 1 month. At the end of the experiment, all animals were killed by decapitation and blood samples were obtained. Serum aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase, total and conjugated bilirubin levels and hepatic malondialdehyde (MDA) contents were determined. For histopathological evaluation, livers of all rats were removed and processed for light microscopy. All biochemical parameters in serum and the hepatic MDA content were significantly higher in animals treated with CCl4 than in the controls. Rats treated with CCl4 and CAPE showed a significant reduction in biochemical parameters in serum and hepatic MDA content. Livers of rats treated with CCl4 showed classic histology of cirrhosis, whereas the histopathological changes were reduced after administration of CCl4 and CAPE. A normal lobular appearance was observed in livers in this group except for fatty degeneration. The results of our study indicate that CAPE treatment prevents CCl4-induced liver damage in rats.

Protective effects of melatonin against carbon tetrachloride-induced hepatotoxicity in rats: a light microscopic and biochemical study

The aim of this study was to examine the protective effects of melatonin against CCl4-induced hepatotoxicity in the rat. Twenty-four male Wistar rats were divided into three groups. Group I was used as a control. Rats in group II were injected every other day with CCl4 for 1 month, whereas rats in group III were injected every other day with CCl4 and melatonin for 1 month. At the end of the experiment, all animals were killed by decapitation and blood samples were obtained. Serum aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP), total and conjugated bilirubin levels were determined. For histopathological evaluation, livers of all rats were removed and processed for light microscopy. All serum biochemical parameters were significantly higher in animals treated with CCl4 than in the controls. When rats injected with CCl4 were treated with melatonin, significantly reduced elevations in serum biochemical parameters were found. In liver sections of the CCl4-injected group, necrosis, fibrosis, mononuclear cell infiltration, haemorrhage, fatty degeneration and formation of regenerative nodules were observed. Additionally, apoptotic figures, microvesicular steatosis and hydropic degeneration in hepatocytes were seen in this group. In contrast, the histopathological changes observed after administration of CCl4 were lost from rats treated with CCl4 and melatonin. Except for mild hydropic degeneration of the hepatocytes, a normal lobular appearance was seen in the livers of this group. The results of our study indicate that melatonin treatment prevents CCl4-induced liver damage in rats.

Opuntia ficus indica (L.) Mill. fruit juice protects liver from carbon tetrachloride-induced injury

The protective effects of the juice of Opuntia ficus indica fruit (prickly pear) against carbon tetrachloride (CCl(4))-induced hepatotoxicity were examined in rats. The animals were treated orally with the juice (3 mL/rat) 2 h after administration of the hepatotoxic agent. Preventive effects were studied by giving the juice (3 mL/rat) for 9 consecutive days. On day 9 the rats received the hepatotoxic agent. Morphological and biochemical evaluations were carried out 24, 48 and 72 h after induction of the hepatic damage. Data show that O. ficus indica fruit juice administration exerts protective and curative effects against the CCl(4)-induced degenerative process in rat liver. Histology evaluation revealed a normal hepatic parenchyma at 48 h; the injury was fully restored after 72 h. Moreover, a significant reduction in CCl(4)-induced increase of GOT and GPT plasma levels is evident; these data are in agreement with the functional improvement of hepatocytes. O. ficus indica fruit juice contains many phenol compounds, ascorbic acid, betalains, betacyanins, and a flavonoid fraction, which consists mainly of rutin and isorhamnetin derivatives. Hepatoprotection may be related to the flavonoid fraction of the juice, but other compounds, such as vitamin C and betalains could, synergistically, counteract many degenerative processes by means of their antioxidant activity.

The effect of zinc sulphate in the prevention of radiation-induced dermatitis

There is currently substantial clinical interest in zinc (Zn) as a protective agent against radiation-related normal tissue injury. To further assess this drug's potential, the effect of Zn was studied in rats using a radiation-induced skin injury model. Sprague-Dawley rats were divided into four groups. Group 1 received neither Zn nor irradiation (control group). Group 2 received 30 Gy of gamma irradiation as a single dose to the right hind legs of the rats (RT Group). Groups 3 and 4 received the same irradiation plus 5 mg/kg/day Zn (RT+5 Zn group) or 10 mg/kg/day Zn orally (RT+10 Zn group), respectively. The rats were irradiated using a cobalt-60 teletherapy unit. Acute skin reactions were assessed every three days by two independent radiation oncology experts. At the endpoint of the study, light-microscopic findings were assessed by two independent expert pathology physicians. Clinically and histopathologically, irradiation increased dermatitis when compared with the control group (p < 0.05). The severity of radiodermatitis of the rats in the RT+5 Zn and RT+10 Zn groups was significantly lower than in the RT group (p < 0.05); radiodermatitis was seen earlier in the RT group than in the other groups (p < 0.05). Zn was found to be efficacious in preventing epidermal atrophy, dermal degeneration such as edema and collagen fiber loss, and hair follicle atrophy. The most protection for radiation dermatitis was observed in the RT+10 Zn group. It would be worthwhile studying the effects of zinc sulphate supplements in radiation-treated cancer patients, in the hope of reducing radiation-induced toxicity.

Liver Protection by Bis(Maltolato)Zinc(II) Complex

The aim of this study was to perform screening of a novel drug for treating liver injury. Bis(maltolato)zinc(II) complex [Zn(Mal)(2)], which was previously reported to possess insulinomimetic activity, was found to have potency against experimentally induced liver injury both in vitro and in vivo. Cultured rat hepatocytes were treated with bromobenzene for 24 h to induce cellular injury. Zn(Mal)(2) of various concentrations was added along with bromobenzene in order to evaluate the hepatoprotective activity of Zn(Mal)(2) in vitro. The number of viable hepatocytes decreased by 42% in the culture with bromobenzene. However, hepatocyte viability was maintained when Zn(Mal)(2) was added to the bromobenzene culture. The hepatoprotective activity of Zn(Mal)(2) in vivo was investigated using a concanavalin A-induced liver injury model in BALB/c mice. Changes in serum aminotransferase activities and the secretion of several cytokines were measured. The hepatoprotective effect of Zn(Mal)(2) was also demonstrated in vivo by the suppression of serum aspartate aminotransferase and alanine aminotransferase elevation. No significant changes in serum cytokines associated with the induction of hepatic damage were observed in the concanavalin A-induced injury model. However, examination of concanavalin A-treated mouse splenocytes revealed a dose-dependent suppression of cytokine secretions by Zn(Mal)(2). Zn(Mal)(2) possessed hepatoprotective activity and might exert its effect by a number of mechanisms.

Metallothionein 2A induction by zinc protects HEPG2 cells against CYP2E1-dependent toxicity

Zinc has been shown to have antioxidant actions, which may be due, in part, to induction of metallothionein (MT). Such induction can protect tissues against various forms of oxidative injury because MT can function as an antioxidant. The objective of this study was to investigate if zinc or MT induction by zinc could afford protection against CYP2E1-dependent toxicity. HepG2 cells overexpressing CYP2E1 (E47cells) were treated with 60 microM arachidonic acid (AA), which is known to be toxic to these cells by a mechanism dependent on CYP2E1, oxidative stress, and lipid peroxidation. E47 cells were preincubated overnight in the absence or presence of metals such as zinc or cadmium that can induce MT. The culture medium containing the metals was removed, AA was added, and cell viability determined after 24 h incubation. Preincubation overnight with 150 microM zinc sulfate or 5 microM cadmium chloride induced a 20- to 30-fold increase of MT2A mRNA; high levels of MT2A mRNA were maintained during the subsequent challenge period with AA, even after the zinc was removed. MT protein levels were increased about 4- to 5-fold during the overnight preincubation with zinc and a 20- to 30-fold increase was observed 24 h after zinc removal during the AA challenge. The treatment with zinc was associated with significant protection against the loss of cell viability caused by AA in E47 cells. The zinc pretreatment protected about 50% against the DNA fragmentation, cell necrosis, the enhanced lipid peroxidation and increased generation of reactive oxygen species, and the loss of mitochondrial membrane potential induced by AA treatment in E47 cells. CYP2E1 catalytic activity and components of the cell antioxidant defense system such as glutathione (GSH), glutathione-S-transferase (GST), glutathione peroxidase (GPX), catalase, Cu,Zn superoxide dismutase (SOD), and MnSOD were not altered under these conditions. Zinc preincubation also protected the E47 cells against BSO-dependent toxicity. When E47 cells were coincubated with zinc plus AA for 24 h (i.e., zinc was not removed, nor was there a preincubation period prior to challenge with AA), AA toxicity was increased. Thus, zinc had a direct pro-oxidant effect in this model and an indirect antioxidant effect, perhaps via induction of MT. MT may have potential clinical utility for the prevention or improvement of liver injury produced by agents known to be metabolized by CYP2E1 to reactive intermediates and to cause oxidative stress.

CCl4-induced acute liver injury in mice is inhibited by hepatocyte growth factor overexpression but stimulated by NK2 overexpression

Hepatocyte growth factor (HGF) inhibits acute liver injury. NK2 acts as an antagonist to HGF in vitro, but its in vivo function has reached no consensus conclusions. We have investigated in vivo effects of HGF and NK2 on CCl4-induced acute liver injury. Elevation of the serum alanine aminotransferase level and extension of centrilobular necrosis were inhibited in HGF transgenic mice but were promoted in NK2 transgenic mice. Hepatocyte proliferation after liver injury was not inhibited in NK2 transgenic mice. Thus, this study indicates that HGF inhibits liver injury, and NK2 antagonizes HGF on liver injury, however, NK2 may not antagonize HGF on hepatocyte proliferation.

Enhancing effect of zinc on hepatoprotectivity of epigallocatechin gallate in isolated rat hepatocytes

The influence of metal ions (Fe2+, Cu2+, Zn2+) on the hepatoprotective activity of epigallocatechin gallate (EGCG) against hepatotoxin-induced cell injury was investigated. Primary cultures of rat hepatocytes were treated with a well-known hepatotoxin, bromobenzene (BB), in the presence of EGCG only or EGCG plus each metal ion. After 24 h, 0.02 mM EGCG did not show protective activity on the cultured hepatocytes. In contrast, the hepatocytes were protected against BB in the presence of 0.02 mM EGCG and 0.02 mM zinc. The addition of only zinc could not protect hepatocytes against BB. These results suggest that the formation of the zinc-EGCG complex is very important in the enhancement of the hepatoprotective activity of EGCG. The complexation of EGCG with zinc was confirmed by UV-VIS absorption spectroscopy.

Distinct roles of tumor necrosis factor-alpha and nitric oxide in acute liver injury induced by carbon tetrachloride in mice

Macrophages are known to release a number of different inflammatory mediators with cytotoxic potential. In the present studies we analyzed the role of two macrophage-derived mediators, tumor necrosis factor-alpha (TNF-alpha) and nitric oxide, in liver injury induced by carbon tetrachloride (CCl4). Treatment of mice with CCl4 resulted in a dose- and time-dependent induction of centrilobular hepatic necrosis. This was observed within 12 h with 0.3 ml/kg CCl4 and was correlated with increases in serum transaminase levels. CCl4 administration also caused increases in hepatic TNF-alpha mRNA expression and serum TNF-alpha levels, as well as inducible nitric oxide synthase (NOS II) protein expression in the liver. To study the role of TNF-alpha and nitric oxide in hepatotoxicity, we used knockout mice lacking the gene for the 55-kDa TNF-alpha receptor (TNFR1/p55), the TNF-alpha cytokine, or NOS II. We found that CCl4 was significantly less effective in inducing hepatotoxicity in mice lacking TNFR1/p55 or the TNF-alpha cytokine. In contrast, CCl4-induced liver injury was increased in knockout mice lacking the gene for NOS II. This was associated with an increase in hepatic TNF-alpha mRNA expression and serum TNF-alpha levels. These data suggest that the hepatoprotective effects of nitric oxide in this model may be due in part to inhibition of TNF-alpha.

Induction of metallothionein in the liver of carbon tetrachloride intoxicated rats: an immunohistochemical study

Metallothioneins (MTs), are low molecular weight proteins, mainly implicated in metal ion detoxification. In the present study, we investigated the expression of hepatic MT in a rat model of injury and regeneration, induced by carbon tetrachloride (CCl(4)) administration. A single intraperitoneal injection of 1 ml CCl(4)/kg body weight was performed in male Wistar rats, killed at different time points post-administration. The enzymatic activities of aspartate and alanine aminotransferases in serum were determined, in addition to the liver histological findings, to estimate hepatotoxicity. The rate of tritiated thymidine incorporation into hepatic DNA, the enzymatic activity of thymidine kinase in liver tissue and the assessment of the mitotic index in hepatocytes, were used as indices of regeneration. MT was detected immunohistochemically in liver tissue sections. CCl(4) administration caused severe hepatic injury, followed by regeneration. MT expression became prominent as early as 12 h after the administration of CCl(4), in the nuclei of hepatocytes, while at 24 and 36 h intense cytoplasmic staining for MT appeared in the hepatocytes in the vicinity of necrotic areas. The peak of hepatocyte proliferative capacity, occurring at 48 h post-CCl(4) administration coincides with the maximum nuclear and cytoplasmic MT expression. At further time points MT expression presented a decreasing trend. Induction of MT expression was observed in the liver after a single administration of CCl(4), being more prominent at the time of maximum hepatocellular proliferation, participating actively in the replication of hepatocytes.