Protective effect of zinc on carbon tetrachloride-induced liver injury in rats

Emu Oil and zinc monoglycerolate independently reduce disease severity in a rat model of ulcerative colitis

Ulcerative colitis is characterized by colonic inflammation. Previously, Emu Oil protected the intestine against experimentally-induced inflammatory intestinal disorders. Zinc monoglycerolate (ZMG) polymer, formed by heating zinc oxide with glycerol, demonstrated anti-inflammatory and wound healing properties. We aimed to determine whether ZMG, alone or in combination with Emu Oil, could reduce acute colitis severity in rats. Male Sprague Dawley rats (n = 8/group) were orally-administered either vehicle, ZMG, Emu Oil (EO) or ZMG combined with EO (ZMG/EO) daily. Rats were provided ad libitum access to drinking water (Groups 1-4) or dextran sulphate sodium (DSS; 2%w/v; Groups 5-8) throughout the trial (days 0-5) before euthanasia on day 6. Disease activity index, crypt depth, degranulated mast cells (DMCs) and myeloperoxidase (MPO) activity were assessed. p < 0.05 was considered significant. DSS increased disease severity (days 3-6) compared to normal controls (p < 0.05). Importantly, in DSS-administered rats, ZMG/EO (day 3) and ZMG (day 6) reduced disease activity index compared to controls (p < 0.05). Following DSS consumption, distal colonic crypts lengthened (p < 0.01), occurring to a greater extent with EO compared to ZMG and ZMG/EO (p < 0.001). DSS increased colonic DMC numbers compared to normal controls (p < 0.001); an effect decreased only by EO (p < 0.05). Colonic MPO activity increased following DSS consumption (p < 0.05); notably, ZMG, EO and ZMG/EO treatments decreased MPO activity compared to DSS controls (p < 0.001). EO, ZMG and ZMG/EO did not impact any parameter in normal animals. Emu Oil and ZMG independently decreased selected indicators of colitic disease severity in rats; however, the combination did not reveal any additional benefit.

Arsenic (III) induces oxidative stress and inflammation in the gills of common carp, which is ameliorated by zinc (II)

Arsenic (As) is widely present in the environment in form of arsenite (As^III) and arsenate (As^V). Oxidative stress and inflammation are believed to be the dominant mechanisms of As^III toxicity in vivo and in vitro. The aim of this study was to investigate whether zinc (Zn²⁺) alleviates exogenous gill toxicity in carp induced by As^III and to gain insight into the underlying mechanisms. Exposure of carp to 2.83 mg As₂O₃/L for 30 days reduced superoxide dismutase activity by 4.0%, catalase by 41.0% and glutathione by 19.8%, while the concentration of malondialdehyde was increased by 16.4% compared to the control group, indicating oxidative stress. After the exposure of carp to As^III the expression of inflammatory markers, such as interleukin-6, interleukin-8, tumor necrosis factor α and inducible nitric oxide synthase in gill tissue were significantly increased. In addition, the phosphorylation of nuclear factor kappa-B (NF-κB) was increased by 225%. 1 mg ZnCl₂/L can relieve the toxicity of As^III based on histopathology, antioxidase activity, qRT-PCR and western results. Zn²⁺ attenuated As^III-induced gill toxicity that suppressed intracellular oxidative stress and NF-κB pathway by an upregulation of metallothionein. Therefore, the toxic effect of As^III on the gill cells of carp was reduced. This study provides a theoretical basis for exploring the alleviation of the toxic effects of metalloids on organisms by heavy metals and the biological assessment of the effects.

Zinc offers splenic protection through suppressing PERK/IRE1-driven apoptosis pathway in common carp (Cyprinus carpio) under arsenic stress

Arsenic (As) occurs naturally and concentrations in water bodies can reach high levels, leading to accumulation in vital organs like the spleen. Being an important organ in immune response and blood development processes, toxic effects of As on the spleen could compromise immunity and cause associated disorders in affected individuals. Splenic detoxification is key to improving the chances of survival but relatively little is known about the mechanisms involved. Essential trace elements like zinc have shown immune-modulatory effects humans and livestock. This study aimed to investigate the mechanisms involved in As-induced splenic toxicity in the common carp (Cyprinus carpio), and the protective effects of zinc (Zn). Our findings suggest that environmental exposure to As caused severe histological injuries and Ca²⁺ accumulation in the spleen of common carp. Additionally, transcriptional and translational profiles of endoplasmic reticulum stress, apoptosis and autophagy-related genes of the spleen showed upward trends under As toxicity. Treatment with Zn appears to offer protection against As-induced splenic injury in common carp and the pathologic changes above were alleviated. Our results provide additional insight into the mechanism of As toxicity in common carp while elucidating the role of Zn, a natural immune-modulator, as a potential antidote against As poisoning.

Zinc alleviates arsenism in common carp: Varied change profiles of cytokines and tight junction proteins among two intestinal segments

This study was designed to evaluate the effects of zinc on inflammation and tight junction (TJ) in different intestinal regions of common carp under sub-chronic arsenic insult. Fish were exposed to zinc (0, 1 mg/L) and arsenic trioxide (0, 2.83 mg/L) in individual or combination for a month. Inflammatory infiltration and TJ structure changes were displayed by H&E staining and transmission electron microscope. To further explore these changes, biochemical indicator (SOD), gene or protein expressions of inflammatory responses (NF-κB, IL-1β, IL-6 and IL-8) and TJ proteins (Occludin, Claudins and ZOs) were determined. In the anterior intestine, arsenic decreased activity of SOD, mRNA levels of Occludin, Claudins and ZOs, increased mRNA levels of ILs. However, unlike the anterior intestine, arsenic has an upregulation effects of Occludin and Claudin-4 in the mid intestine. These anomalies induced by arsenic, except IL-8, were completely or partially recovered by zinc co-administration. Furthermore, transcription factor (NF-κB) nuclear translocation paralleled with its downstream genes in both intestinal regions. In conclusion, our results unambiguously suggested that under arsenic stress, zinc can partly relieve intestinal inflammation and disruption of tight junction segment-dependently.

Ciprofloxacin-induces free radical production in rat cerebral microsomes

In the presence of ciprofloxacin (CPFX), free radical adduct formation was demonstrated in rat cerebral microsomes using a spin trap α-(4-pyridyl-1-oxide)-N-tert-butyl-nitrone by electron spin resonance spectroscopy. Active microsomes, dihydronicotinamide-adenine dinucleotide phosphate, and ciprofloxacin were necessary for the formation of a spin trap/radical adduct. Adduct formation increased dose-dependently at 0.5-1 mM CPFX concentration for 180 min, and 0.3-1 mM concentration level for 240 min. The addition of SKF 525A, ZnCl₂ or desferrioxamine to the incubation system caused complete inhibition of the radical formation. However, pretreatment of microsomal system with superoxide dismutase (SOD) did not induce any protective effect. Induction of lipid peroxidation, and depletion of thiol levels by CPFX were also shown in the system. These results strongly suggested that CPFX produces free radical(s) in the cerebral microsomes of rats.

Cytotoxicity of cultured macrophages exposed to antimicrobial zinc oxide (ZnO) coatings on nanoporous aluminum oxide membranes

Zinc oxide (ZnO) is a widely used commercial material that is finding use in wound healing applications due to its antimicrobial properties. Our study demonstrates a novel approach for coating ZnO with precise thickness control onto 20 nm and 100 nm pore diameter anodized aluminum oxide using atomic layer deposition (ALD). ZnO was deposited throughout the nanoporous structure of the anodized aluminum oxide membranes. An 8 nm-thick coating of ZnO, previously noted to have antimicrobial properties, was cytotoxic to cultured macrophages. After 48 h, ZnO-coated 20 nm and 100 nm pore anodized aluminum oxide significantly decreased cell viability by ≈65% and 54%, respectively, compared with cells grown on uncoated anodized aluminum oxide membranes and cells grown on tissue culture plates. Pore diameter (20–200 nm) did not influence cell viability.

Zinc deficiency enhances sensitivity to carbon tetrachloride-induced hepatotoxicity in rats

Zinc (Zn) is an essential nutrient that is required in humans and animals for many physiological functions, including immune and antioxidant functions, growth and reproduction. The present study was conducted to examine the influence of Zn deficiency on the protective action against mild oxidative stress induced by a low dose of carbon tetrachloride (CCl(4)) in rats. Male Wistar rats were administered 125 or 250 μL/kg body weight CCl(4), which caused mild or no elevation of serum LDH, AST and ALT enzyme levels in rats fed a diet with adequate Zn. Treatment with CCl(4) (125 μL/kg) caused a significant release of these enzymes into the serum of rats fed a Zn-deficient diet but not in those given a diet with adequate Zn. Furthermore, no histological abnormalities were observed in CCl(4)-untreated rats fed either a diet with adequate Zn or a Zn-deficient diet or in CCl(4) (125 μL/kg)-treated rats fed a diet with adequate Zn. In CCl(4) (125 μL/kg)-treated rats fed a Zn-deficient diet, however, we observed associated collagen accumulation in the liver and hepatic necrosis. The degree of fibrosis was also more severe in CCl(4) (250 μL/kg)-treated rats fed a Zn-deficient diet. These results show that zinc deficiency during an oxidative stress injury negates the protective actions of certain treatments that normally block oxidative damage. The present study suggests that Zn plays an important role in regulating the antioxidative defense system under mild CCl(4) toxic conditions.

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.

Changes in zinc uptake in response to ascorbic acid and folic acid in rat liver slices under normal and oxidative stress conditions

Zinc plays a dual role, as an integral part of metabolic machinery and in defense against reactive oxygen species. Hepatocytes are important sites for zinc metabolism for synthesis of zinc metalloproteins and maintaining its homeostasis. However, the factors influencing post absorptive zinc metabolism under normal and oxidative stress (OS) conditions are not well understood. Using rat liver slices, we conducted a series of four in vitro zinc uptake experiments to study influence of ascorbic acid and folic acid in normal and oxidative stress conditions with Zn concentrations representing deficient to excess states (7.7-30.7 millimole/L). Zinc uptakes under OS at these four zinc levels were lower than the normal conditions. Folic acid showed significant inhibitory effect on zinc uptake under both normal and OS conditions in a dose response manner. Nevertheless, dose response of ascorbic acid at four zinc levels indicated its marked enhancing effect under OS condition. Differences in zinc uptake trend lines between the normal and OS conditions for interaction of both the vitamins narrowed down as the zinc levels increased. Our results suggest that folic acid causes inhibitory effect, while ascorbic acid may be protective in OS with reference to zinc uptake.

Role of reactive oxygen species in zinc deficiency-induced hepatic stellate cell activation

We previously reported that zinc deficiency caused a reduction in intracellular glutathione at 8 h after the addition of zinc chelator, diethylenetriamine pentaacetic acid (DTPA), compared with control levels in rat hepatic stellate cells. In this study, we investigated the role of reactive oxygen species and glutathione on the mechanism of zinc deficiency-induced hepatic stellate cell activation, via assessing collagen synthesis. Isolated hepatic stellate cells were incubated with or without DTPA. Type I collagen expression in hepatic stellate cells was detected by immunohistochemistry, and then quantification of the intensity of type I collagen expression was analyzed using a computer with NIH image. Intracellular glutathione was measured using HPLC. H(2)O(2) release from hepatic stellate cells into the overlying medium was assayed using a fluorimetric method. H(2)O(2) release by DTPA-treated hepatic stellate cells significantly increased from 4 h, but returned to control levels after zinc supplementation. When catalase was added to the culture at 6 h after the addition of DTPA, the staining for type I collagen was as weak as at control levels. Diphenyliodonium chloride, the inhibitor of NADPH oxidase, produced a marked reduction in zinc deficiency-induced H(2)O(2) release. The results of this study show that the depletion of intracellular glutathione levels triggers a progression of collagen synthesis in zinc deficient-hepatic stellate cells and this depletion may be induced by the stimulation of cellular production of H(2)O(2).

Oxidative stress, toxic hepatitis, and antioxidants with particular emphasis on zinc

Hepatic metabolism of biological toxins, industrial poisons, and medicinal agents involves disturbed hepatic cell biochemistry with augmented generation of reactive oxygen species and free radicals and redox imbalance with secondary damage to proteins, nucleic acids, lipids, and carbohydrates. The xenobiotic hepatotoxicity ranging from a subclinical anicteric state to severe necroinflammatory hepatitis (acute, recurrent or chronic) and cirrhosis depends on the nature, dosage, and duration of exposure to the xenobiotic, the antioxidant defence, and concomitant exposure to other diseases or xenobiotics. Experimental and clinical studies suggest that xenobiotic hepatotoxicity with variable depletion of antioxidants can be avoided or ameliorated by administration of an unusually high dosage of zinc or by a combination of antioxidants above normal daily requirements. Therefore reassessment of optimal prophylactic and therapeutic nutritional requirements of antioxidants (particularly zinc) to defend humans against xenobiotic induced oxidative stress is advocated.

Involvement of intracellular glutathione in zinc deficiency-induced activation of hepatic stellate cells

Hepatic stellate cells (HSC) play an important role in the development of liver cirrhosis. They are a major source of extracellular matrix and during fibrogenesis undergo an activation process characterized by increased proliferation and collagen synthesis. In this study, we investigated the anti-fibrogenic effect of zinc supplementation on zinc deficiency induced HSC activation. Isolated HSC were incubated with or without zinc chelator, diethylenetriamine penta-acetic acid (DTPA). Type I collagen expression in HSC was detected by immunohistochemistry. The involvement of glutathione (GSH) homeostasis in the anti-fibrogenic action of zinc was also investigated, as GSH is implicated in many cellular events, such as regulation of cell proliferation, remodeling of extracellular matrix and oxidative stress. Intracellular GSH was measured by HPLC. Enhanced type I collagen expression, apoptosis and cell cycle arrest were found in HSC when DTPA was added, but they were inhibited with supplementation with zinc. Zinc deficiency caused a reduction in intracellular GSH 8 h after the addition of DTPA compared with control levels. The results of this study show that in HSC, the chelation of zinc triggers a progression of collagen synthesis and this involves the depletion of intracellular GSH levels after the addition of DTPA.

Evidence supporting zinc as an important antioxidant for skin

Antioxidants play a critical role in keeping skin healthy. The antioxidant benefits of vitamin C and E are well known, but the importance of the trace mineral, zinc, has been overlooked. This article reviews the evidence supporting zinc's antioxidant role in protecting against free radical-induced oxidative damage. Zinc protects against UV radiation, enhances wound healing, contributes to immune and neuropsychiatric functions, and decreases the relative risk of cancer and cardiovascular disease. All body tissues contain zinc; in skin, it is five to six times more concentrated in the epidermis than the dermis. Zinc is required for the normal growth, development and function of mammals. It is an essential element of more than 200 metalloenzymes, including the antioxidant enzyme, superoxide dismutase, and affects their conformity, stability, and activity. Zinc also is important for the proper functioning of the immune system, and for glandular, reproductive and cell health. Abundant evidence demonstrates the antioxidant role of zinc. Topical zinc, in the form of divalent zinc ions, has been reported to provide antioxidant photoprotection for skin. Two antioxidant mechanisms have been proposed for zinc: zinc ions may replace redox active molecules, such as iron and copper, at critical sites in cell membranes and proteins; alternatively, zinc ions may induce the synthesis of metallothionein, sulfhydryl-rich proteins that protect against free radicals. No matter how they work, topical zinc ions may provide an important and helpful antioxidant defense for skin.

Microsomal metabolism of ciprofloxacin generates free radicals

Ciprofloxacin (CPFX) is a widely used fluoroquinolone antibiotic with a broad spectrum of activity. However, clinical experience has shown a possible incidence of undesirable adverse effects including gastrointestinal, skin, hepatic, and central nervous system (CNS) functions, and phototoxicity. Several examples in the literature data indicate that free radical formation might play a role in the mechanism of some of these adverse effects, including phototoxicity and cartilage defects. The purpose of this study is to investigate free radical formation during the metabolism of CPFX in hepatic microsomes using electron spin resonance (ESR) spectroscopy and spin trapping technique. We then investigate the effects of a cytochrome P450 inhibitor, SKF 525A, Trolox, and ZnCl2 on CPFX-induced free radical production. Our results show that CPFX induces free radical production in a dose- and time-dependent manner. The generation of 4-POBN/radical adduct is dependent on the presence of NADPH, CPFX, and active microsomes. Furthermore, free radical production is completely inhibited by SKF 525A, Trolox, or ZnCl2.

Metallothionein expression protects against carbon tetrachloride-induced hepatotoxicity, but overexpression and dietary zinc supplementation provide no further protection in metallothionein transgenic and knockout mice

Metallothionein and zinc have been implicated in cellular defense against a number of cytotoxic agents. With respect to the free radical-generating hepatotoxin carbon tetrachloride, conclusions about a defensive role were reached from in vitro studies, in vivo studies using inducers of metallothionein and studies using injections of pharmacological amounts of zinc. Metallothionein knockout (null) and metallothionein transgenic mice are more direct models to examine the effects of metallothionein expression on induced cytotoxicity. Similarly, zinc presented via the diet is a more physiological model than that presented via injection. We examined whether metallothionein-overexpressing mice or metallothionein knockout mice had altered sensitivity to carbon tetrachloride and whether supplemental dietary zinc reduced sensitivity to carbon tetrachloride in these genotypes. Metallothionein knockout mice produced no metallothionein and were unable to sequester additional hepatic zinc in response to elevated dietary zinc. Hepatotoxicity, as measured by serum alanine aminotransferase activity, histological analyses and hepatic thiol levels, was greater in the knockout mice than in controls 12 h after carbon tetrachloride treatment but not at later time points (up to 48 h). In contrast, metallothionein-overexpressing mice produced more metallothionein and sequestered more liver zinc than control mice, but hepatotoxicity was similar between genotypes. Supplemental dietary zinc had no effect on hepatotoxicity with either genotype. These data suggest metallothionein null mice were more susceptible to carbon tetrachloride-induced hepatotoxicity than were control mice. However, neither metallothionein overexpression nor supplemental dietary zinc provided further protection.

The antioxidant properties of zinc

The ability of zinc to retard oxidative processes has been recognized for many years. In general, the mechanism of antioxidation can be divided into acute and chronic effects. Chronic effects involve exposure of an organism to zinc on a long-term basis, resulting in induction of some other substance that is the ultimate antioxidant, such as the metallothioneins. Chronic zinc deprivation generally results in increased sensitivity to some oxidative stress. The acute effects involve two mechanisms: protection of protein sulfhydryls or reduction of (*)OH formation from H(2)O(2) through the antagonism of redox-active transition metals, such as iron and copper. Protection of protein sulfhydryl groups is thought to involve reduction of sulfhydryl reactivity through one of three mechanisms: (1) direct binding of zinc to the sulfhydryl, (2) steric hindrance as a result of binding to some other protein site in close proximity to the sulfhydryl group or (3) a conformational change from binding to some other site on the protein. Antagonism of redox-active, transition metal-catalyzed, site-specific reactions has led to the theory that zinc may be capable of reducing cellular injury that might have a component of site-specific oxidative damage, such as postischemic tissue damage. Zinc is capable of reducing postischemic injury to a variety of tissues and organs through a mechanism that might involve the antagonism of copper reactivity. Although the evidence for the antioxidant properties of zinc is compelling, the mechanisms are still unclear. Future research that probes these mechanisms could potentially develop new antioxidant functions and uses for zinc.

The influence of environmental contaminants on lysosomal activity in the digestive cells of mussels (Mytilus galloprovincialis) from the Venice Lagoon

Lysosomes are subcellular organelles bounded by a semipermeable lipoprotein membrane that contain a battery of hydrolytic enzymes that are collectively capable of degrading all classes of indogenous and exogenous macromolecules. Lysosomes accumulate a diverse range of chemical contaminants which can lead to membrane damage resulting in leakage of their contents into the cytosol and damage to cells. Total lysosomal activity for two acid hydrolases, N-acetyl-beta-D-hexosaminidase and beta-glucuronidase, with different substrate specificities was determined histochemically in digestive gland sections of mussels, Mytilus galloprovincialis from a series of sites in the Venice Lagoon and the Adriatic Sea and correlated, using multi-stepwise regression analysis, with tissue contaminant burdens in order to explore causality. The results indicated that whilst activity of N-acetyl-beta-D-hexosaminidase correlated with body burdens of mercury, beta-glucuronidase, by contrast, correlated with DDT, Arochlor 1254 and eight PCB congeners in combination with iron or zinc.

Effect of prior sporidesmin intoxication on the pancreopathy associated with zinc oxide toxicity

AIM

To demonstrate the effect of prior sporidesmin-induced liver injury on the pancreopathy of zinc-induced toxicity.

METHODS

Four groups, each of 15 sheep, were given 2 x 2 treatments of sporidesmin (0.3 mg/kg bodyweight spread over 3 consecutive days prior to zinc) and zinc (200 mg Zn/kg bodyweight as ZnO spread over 24 days) starting 4 days after the end of sporidesmin dosing. Liver and pancreatic changes were assessed by serum enzyme changes (serum amylase and gamma glutamyltransferase) or scoring for injury at post-mortem examination (hepatopathy) or by histopathological examination (pancreopathy).

RESULTS

Minor pancreatic injury was caused by the administration of zinc. The pancreopathy associated with zinc oxide toxicity was significantly greater in those sheep receiving zinc after the sporidesmin-induced injury. Pathological and body weight changes associated with sporidesmin toxicity also occurred in both groups dosed with sporidesmin. These were slightly less in the group of sheep receiving zinc after the sporidesmin challenge than in those receiving sporidesmin alone.

CONCLUSIONS

Zinc-induced pancreatic injury is greater if the zinc is administered after liver injury has been caused by sporidesmin. Only minor protection is given by zinc if it is administered after the challenge with sporidesmin.

CLINICAL SIGNIFICANCE

The safety margin for the use of zinc is reduced if zinc is administered after significant liver injury has been caused by prior exposure to high Pithomyces chartarum spore counts.

The possible role of zinc and metallothionein in the liver on the therapeutic effect of IFN-alpha to hepatitis C patients

We have studies zinc deficiency in hepatitis C patients (complete responder [CR] 22, nonresponder [NR] 25) with relation to the therapeutic effect of interferon-alpha (IFN-alpha). Circadian variations in serum zinc levels were high in the morning (basal level) and then gradually decreased during the day in both chronic hepatitis C patients and healthy controls. Basal zinc levels in serum were significantly lower in chronic hepatitis C patients (73 +/- 3 micrograms/dL, n = 12) than in controls (93 +/- 5 micrograms/dL). An injection of 10 MU of IFN-alpha to hepatitis C patients augmented the serum zinc reductions, up to 40% in 8 h. Serum cortisol levels were significantly elevated 8 h (25.6 +/- 2.3 micrograms/dL) after IFN-alpha dose. Forty-seven chronic hepatitis C patients were treated with IFN-alpha for 24 wk, and serum zinc and copper levels were determined 12 and 24 wk during and after the completion of IFN-alpha therapy. Serum zinc levels and zinc/copper ratio were higher in CRs than in NRs to IFN therapy at each time-point. Hepatic metallothionein staining became prominent after IFN therapy in most of CRs, whereas it diminished NRs. These data suggest that nutritional status of zinc influences the effect of IFN on hepatitis C patients.

Relationships between metal ions and oxygen free radicals in ethanol-induced damage to cultured rat gastric mucosal cells

The current study investigated whether metal ions were cytoprotective against ethanol-induced injury to cultured rat gastric mucosal cells in vitro. Secondly, the relationships between oxygen free radicals and cytoprotection by metal ions were examined. Cultured cells exposed to ethanol produced superoxide anion, as assessed by reduction of cytochrome c, in a time-related fashion, and the production of superoxide anion increased dose-dependently as the concentration of ethanol increased. Cellular damage increased proportionately to the production of superoxide anion. ZnCl2, AlCl3, CoCl2, CuCl2, and CdCl2 significantly diminished ethanol-induced injury dose-dependently. All of the agents studied decreased the reduction of cytochrome c in ethanol-induced damage dose-dependently. These results led to the conclusions that: (1) cultured rat gastric mucosal cells exposed to ethanol generate oxygen free radicals; (2) the production of oxygen free radicals is closely linked with ethanol-induced damage to the cells; and (3) metal ions decrease ethanol-induced gastric mucosal cell damage in vitro. Metal ions protect cultured rat gastric mucosal cells from ethanol-induced damage in which oxygen free radicals participate.

Evidence for potential application of zinc as an antidote to acetaminophen-induced hepatotoxicity

The therapeutic application of zinc sulphate as an antidote to acetaminophen overdose was examined in ICR mice. Hepatotoxicity was induced by a single oral dose of acetaminophen (750 mg/kg). Various treatments (normal saline, 15 or 30 mg/kg zinc sulphate, 150 mg/kg N-acetylcysteine, 15 mg/kg zinc sulphate + 150 mg/kg N-acetylcysteine) were given i.p. 1 h after acetaminophen overdose. Serum alanine aminotransferase, hepatic glutathione and malondialdehyde levels were measured before experiments and at various intervals after the administration of acetaminophen. Serum acetaminophen levels were also measured at different different intervals. Zinc sulphate showed protection by dose-dependently reducing alanine aminotransferase and malondialdehyde levels. The drug also partially prevented the depletion of hepatic glutathione. These effects were not as good as those of N-acetylcysteine. However, the combination of zinc sulphate with N-acetylcysteine produced even better protective effects. Furthermore, drug treatments did not affect serum acetaminophen levels. It is concluded that both drugs attenuate acetaminophen-induced hepatic toxicity, and the action is likely to be mediated through replenishment of hepatic glutathione levels. The use of zinc sulphate alone or in combination with N-acetylcysteine could be another alternative for the treatment of acetaminophen overdose in view of possible side effects produced by N-acetylcysteine.

The hepatoprotective cytochrome P-450 enzyme inhibitor isolated from the Nigerian medicinal plant Cochlospermum planchonii is a zinc salt

Aqueous extracts of Cochlospermum planchonii Hook.f. (Cochlospermaceae) rhizomes are used by native medical practitioners in northern Nigeria to treat jaundice. An extract prepared by a laboratory adaptation of their method was hepatoprotective in carbon tetrachloride-treated rats (CCl4), and it inhibited cytochrome P-450 enzymes, which constitutes a plausible hepatoprotective mechanism. A crystalline inhibitor (0.3% of dry weight of rhizomes) was isolated using inhibition of two rat cytochrome P-450 enzymes, aminopyrine-N-demethylase and aniline hydroxylase, as bioassays to guide fractionation by solvent partitioning, polyamdie column chromatography, preparative thin layer chromatography and fractional crystallization. The inhibitor was identified as zinc formate by inductively coupled plasma atomic emission spectroscopy, nuclear magnetic resonance spectroscopy and comparison with synthetic material by power X-ray diffraction crystallography. Synthetic and plant-derived zinc formate were equally effective as inhibitors of cytochrome P-450 enzymes and as hepatoprotective agents in carbon tetrachloride-treated rats. Cochlospermum planchonii rhizomes contain unusually high levels of manganese and zinc, although much higher levels have been observed in plants considered to be hyperaccumulators of these metals.

Effect of dietary zinc on lipid peroxidation, glutathione, protein thiols levels and superoxide dismutase activity in rat tissues

Dietary zinc deficiency can cause increased lipid peroxidation while zinc supplementation inhibited this process. The aim of this study was to investigate the effect of dietary zinc on malondialdehyde (MDA) product as an index of endogenous lipid peroxidation, glutathione (GSH) and protein thiols (PrSHs) as well as superoxide dismutase (SOD) activity in rat blood, liver and pancreas. Young male rats were fed a zinc deficient (ZD) basal diet containing congruent to 0.5 ppm zinc or were fed ad libitum (AL) a zinc adequate diet (30 ppm zinc) for 3 weeks. The ZD rats were then fed the basal diet supplemented with either 100 ppm zinc or 1000 ppm zinc for another 3 weeks. The zinc concentration of the investigated tissues reflected the dietary zinc content. Plasma, liver and pancreas MDA measurements from ZD rats revealed significant increases (P < 0.05, < 0.001) as compared to AL control values, the highest increase was in pancreas. ZD rats also displayed significant decreases in their blood and liver GSH content (P < 0.001, < 0.05) and SOD activity (P < 0.001) as well as serum PrSHs (P < 0.001) as compared to AL control values. However, these measurements in pancreas were insignificantly changed except GSH content was significantly increased (P < 0.05). Feeding ZD rats a diet containing 100 ppm or 1000 ppm zinc resulted in a significant reduction of the endogenous MDA formation (P < 0.05, < 0.001) in their tissues with the reversal of changes in the other parameters, so that their levels were nearly restored to AL control values especially in response to 1000 ppm zinc.(ABSTRACT TRUNCATED AT 250 WORDS)

Hepatoprotective effects of Liv-52 and its indirect influence on the regulation of thyroid hormones in rat liver toxicity induced by carbon tetrachloride

This study was undertaken to investigate the protective effect of Liv-52, a herbal formulation, on various serum and liver marker enzymes, lipid peroxidation and histological changes in the liver of male albino rats suffering long-term carbon tetrachloride (CCl4) poisoning. It was observed that the activities of serum marker enzymes, hepatic enzymes and NADPH-dependent lipid peroxidation were significantly elevated after treatment with CCl4. However, in rats given Liv-52 at the same time as CCl4, the levels of all the marker enzymes were closer to those found in control animals. A similar trend was seen in the case of lipid peroxidation after Liv-52 treatment. CCl4 alone caused severe liver damage, but when Liv-52 was simultaneously given, there was much less effect on the structure of the organ. Circulating T3 and T4 concentrations were also determined after 6 weeks of simultaneous treatment with Liv-52 and CCl4. Concentrations of T3 were significantly lowered after CCl4 treatment alone, but Liv-52 administration together with CCl4 resulted in maintenance of the T3 activity within normal limits, thus suggesting indirect beneficial effects of Liv-52 on the regulation of thyroid hormone concentrations.

Fibrogenic and collagenolytic activity in carbon-tetrachloride-injured rats: beneficial effects of zinc administration

Collagen synthesis and degradation in normal and carbon-tetrachloride-injured male Wistar rats at early and late stages of liver fibrosis, and the potential beneficial effects of zinc supplementation on liver fibrogenesis and collagenolysis have been assessed by measuring hepatic collagen content and prolyl hydroxylase and collagenase activities. No significant changes in hepatic collagen and prolyl hydroxylase activities were observed between control rats (82 +/- 25 cpm/mg protein) and rats with induced cirrhosis (107 +/- 23 cpm/mg protein) after 4 weeks of carbon tetrachloride injury. By this time, hepatic collagenase activity was significantly lower in rats with induced cirrhosis (61 +/- 9 micro units/mg protein) than in control rats (133 +/- 31 micro units/mg protein) (p < 0.05). This result was prevented by zinc administration, since hepatic collagenase activity was similar in zinc-supplemented, carbon-tetrachloride-injured rats and normal rats (148 +/- 19 micromicrons/mg protein). After 16 weeks, all carbon-tetrachloride-injured rats had cirrhosis. Hepatic collagen content and prolyl hydroxylase activity were significantly higher in carbon-tetrachloride-injured rats than in controls. These effects were partially prevented by zinc administration, since only two of the seven zinc-supplemented, carbon-tetrachloride-injured rats had cirrhosis. Moreover, prolyl hydroxylase activity was significantly lower in zinc-supplemented injured rats (263 +/- 27 cpm/mg protein) than in the non-supplemented respective controls (389 +/- 52 cpm/mg protein) (p < 0.05). No significant changes in hepatic collagenase activity were observed at this stage of liver injury.(ABSTRACT TRUNCATED AT 250 WORDS)

Evaluation of zinc in the regulation of serum T3 and T4 levels and hepatic functions in carbontetrachloride-intoxicated rats

Circulating tri-iodothyronine (T3) and thyroxine (T4) concentrations were determined after 6 wk of zinc treatment to carbontetrachloride (CCl4) intoxicated male albino rats. Concentrations of T3 were observed to be significantly depressed following CCl4 treatment alone. On the contrary, no significant change was noticed in the concentrations of T4 when compared to controls. However, zinc administration to hepatotoxic animals resulted in restoring the T3 activity to within normal limits, thus indicating the indirect effects of zinc on the regulation of thyroid hormone concentrations. The activities of all the serum and hepatic marker enzymes were found to be significantly elevated following CCl4 treatment. However, following zinc supplementation to these intoxicated animals, the levels of the marker enzymes decreased significantly when compared to the CCl4-treated animals. A similar trend was seen in the case of lipid peroxidation following zinc treatment.

Reactive oxygen species produced in metal-catalyzed oxidation of bis(trifluoromethyl)disulfide and protection by ZE

Bis(trifluoromethyl)disulfide (TFD), used as an industrial fumigant, was found to generate a thiyl free radical as seen by EPR/spin trapping. Oxygen appears to be an absolute requirement for radical production. The results obtained in this investigation implicate the production of thiyl and reactive oxygen species (ROS), superoxide radical anion and hydroxyl radicals, during TFD autoxidation. The rate of production of these free radical intermediates was found to increase in the presence of iron(III) and copper(II). In addition, the metal ion chelator DETAPAC and ROS scavengers ethanol, mannitol, and PEG-SOD/catalase were found to inhibit free radical production. Reactive oxygen species were not formed when a high-potency zinc plus antioxidant, ZE caps, was present. These results provide support for the pro-oxidation of TFD and a protective role for zinc.

Augmentation of endotoxin hepatotoxicity by zinc

The present study was undertaken in rats to determine whether zinc protects against endotoxin hepatotoxicity and mortality. Treatment with zinc (50-200 mumol/kg body weight) alone or endotoxin (lipopolysaccharide B, Escherichia coli 026:B6, Difco, 2 mg/kg body weight) alone did not induce significant morphological changes in the liver parenchyma or any abnormalities in liver function tests. The mortality rate was 0%. In the rats pretreated with 100 mumol of zinc and then injected with endotoxin, the mortality rate, the incidence of focal hepatocellular coagulative necrosis and serum transaminase activity increased markedly. Eleven of the 12 rats pretreated with 200 mumol of zinc died within 4 h after endotoxin injection. In the rats pretreated with 50 mumol of zinc and then injected with endotoxin, there was no conspicuous change, in the mortality rate, liver function tests or morphology of the liver. These experimental data indicate that zinc increases the mortality rate in endotoxemic rats and augments biochemical and morphological evidence of endotoxin hepatotoxicity.

Pathophysiology and pharmacologic modulation of hepatic fibrosis

Most chronic liver disorders are accompanied morphologically by the deposition of fibrous tissue within the hepatic parenchyma. This fibrotic tissue compromises hepatic function and contributes significantly to hepatic failure. Fibrosis is a dynamic process associated with the continual deposition and resorption of connective tissue. Therapeutic strategies are emerging whereby this dynamic process can be modulated. Since collagen is the major component of the extracellular matrix deposited in hepatic fibrosis, most anti-fibrotic therapies have been directed toward the control of collagen metabolism. After collagen genes are transcribed and translated into precursor procollagen proteins, a number of post-translational modifications that ensure the deposition of structurally sound collagen within the extracellular matrix occur. A number of drugs can specifically modulate collagen biosynthesis at the transcriptional level or at various post-translational stages. These anti-fibrotic drugs include corticosteroids, azathioprine, penicillamine, colchicine, zinc, prostaglandins, cyclosporine, and interferons. The pharmacologic action of these drugs and the clinical role in veterinary and human fibrotic hepatopathies will be discussed.

Combined effect of vanadium and zinc on certain selected haematological indices in rats

1. Two-month-old Wistar rats of both sexes received, as sole drinking liquid, an aqueous solution of ammonium metavanadate (AMV) and zinc chloride (ZC) at concentrations of 0.30 mg V/cm3 and 0.12 mg Zn/cm3 respectively, for a period of 4 weeks. 2. The reference groups received for drinking at this time: water, AMV or ZC solutions at the same concentration. 3. In all groups of animals there was a statistically significant decrease in the uptake of food, AMV or ZC, as well AMV-ZC solutions, as compared with the food and water taken up by the control group. 4. In the group of animals receiving AMV or AMV-ZC solution for drinking the body weight increment diminished significantly. 5. In the animals drinking the AMV-ZC solution a statistically significant decrease in the erythrocyte count and haemoglobin level in the peripheral blood were recorded, similar to the groups drinking AMV or ZC solution. 6. In rats drinking aqueous AMV or ZC solutions and in females receiving AMV-ZC solution the percentage of reticulocytes and polychromatophilic erythrocytes increased, moreover, in the peripheral blood. It was not, however, associated with marked percentage changes in the composition of the bone marrow cells.

Monitoring of serum markers for fibrosis during CCl4-induced liver damage. Effects of anti-fibrotic agents

Liver fibrosis was induced in rats by repeated peritoneal injections of carbon tetrachloride (CCl4) over a period of 2-11 weeks. Serum procollagen III peptide (SPIIINP), prolidase (SP) and alanine aminotransferase (SALT) levels were monitored during the period of induction. The extent of fibrosis was semi-quantitatively estimated after collagen staining, and the anti-fibrotic effects of 16,16-dimethyl prostaglandin E2 (DMPGE2), colchicine, and zinc sulphate were studied. SPIIINP and SP were increased the first 2 weeks after CCl4 administration and peaked at 6 weeks. Alterations in SPIIINP and SP correlated well to the semi-quantitative histological score of liver sections during the first 6 weeks, and SP was positively related to SPIIINP throughout the whole induction period. DMPGE2 decreased SPIIINP, SP and SALT significantly in addition to a markedly decreased formation of liver collagens. Colchicine had a similar but less dramatic effect, whereas zinc sulphate only reduced SPIIINP without influencing liver damage. In conclusion SPIIINP seems to be a valuable indicator of liver fibrogenesis, and SP may play a limited role in indicating accelerated collagen metabolism in the liver. DMPGE2 obviously inhibited the production of collagens induced by CCl4. Colchicine also had an apparent effect on liver fibrosis, whereas zinc sulphate merely seemed to postpone it.

Recent advances in the role of reactive oxygen intermediates in ischemic injury. I. Evidence demonstrating presence of reactive oxygen intermediates; II. Role of metals in site-specific formation of radicals

This article has attempted to bring the reader up to date on advances in selected facets of the area of reactive oxygen intermediate-induced ischemic injury. Specifically, we have discussed the more recent reports that provide evidence for the presence of these species in reperfused ischemic tissue. In addition, we have attempted to introduce the reader to the relatively new concept of "site-specific" formation of radicals and how the use of "push-pull" techniques, such as chelation by high-affinity chelators or displacement by non-redox-active metals such as zinc, may decrease postischemic reperfusion injury. Finally, we have identified a class of compounds that affect the oxidation state of redox-active metals, and have demonstrated how these compounds may also represent a new therapeutic modality. In conclusion, both academic and nonacademic surgeons should have profited from reading this article. For the academic surgeon, who may do research, several new cytoprotectants requiring further study in both in vitro and in vivo models have been identified. For the nonacademic surgeon in clinical practice the realization that there are several promising areas of research that may yield new therapies to mitigate postischemic reperfusion injury should have been gained.

Zinc supplementation reduces blood ammonia and increases liver ornithine transcarbamylase activity in experimental cirrhosis

Zinc deficiency is common in cirrhosis and may be involved in the alteration of ammonia metabolism. Rats with carbon tetrachloride-induced cirrhosis have high plasma ammonia and low serum and tissue zinc levels. We used this model to examine the effects of oral zinc supplementation on activities of plasma ammonia and liver ornithine transcarbamylase (a key enzyme in the urea cycle). These parameters were examined in two consecutive experiments. Each experiment included two groups of rats treated with carbon tetrachloride; one group received zinc in the drinking water during the induction of cirrhosis, and another served as a control group. Regardless of zinc supplementation, all carbon tetrachloride-treated rats exhibited similar micronodular cirrhosis, with similar histological appearance and liver function impairment. Cirrhotic rats without zinc supplementation showed high plasma ammonia and low serum and hepatic zinc levels and reduced liver ornithine transcarbamylase activity. Serum, hepatic zinc and liver ornithine transcarbamylase activity increased significantly in the zinc-supplemented group, and these rats' plasma ammonia levels became normal. Plasma ammonia level was significantly inversely correlated with liver ornithine transcarbamylase activity and positively correlated with serum and hepatic zinc content. Our results suggest that zinc deficiency may modify hepatic ornithine transcarbamylase activity and, therefore, ammonia disposal.

Protective effect of zinc on liver injury induced by D-galactosamine in rats

The protective effects of zinc on liver injury induced by D-galactosamine (GalN) were investigated in rats in vivo and in vitro. Zinc supplementation (50 mg/kg/d) for 5 d of rats treated with GalN (1.5 g/kg, ip) could reduce their mortality rate, restore liver pathomorphological changes, maintain zinc content, inhibit the lipid peroxidation, hasten the protein synthesis, and improve liver function. In vitro, zinc supplement could abate the death of GalN-intoxicated hepatocytes, decrease malonaldehyde (MDA) content, and maintain reduced glutathione (GSH). It is concluded that zinc has protective effects on GalN-induced liver damage. Its effects may be owing to inhibition of lipid peroxidation and hastening of protein syntheses.

Metallothionein in human retinal pigment epithelial cells: expression, induction and zinc uptake

The retinal pigment epithelium (RPE) plays several important roles in the continual support and renewal of photoreceptor outer segments. In the present study, we have demonstrated that RPE cells contain a low molecular weight protein with a high capacity for zinc binding that is dependent on available sulfhydryl groups. This protein is inducible by a 24 hour incubation of cultured RPE in medium supplemented with zinc, cadmium, or dexamethasone. The induction of this protein is correlated with an increased capacity for zinc-65 uptake into cultured RPE. Analysis with a cDNA probe specific for the human metallothionein II gene corroborated the existence and induction of metallothionein gene products in RPE cells. Based on these properties, we have identified this protein as metallothionein. The induction of metallothionein likely has a critical influence on the zinc economy of the RPE.

The membrane-stabilizing action of zinc carnosine (Z-103) in stress-induced gastric ulceration in rats

Zinc compounds have been shown to antagonize various types of gastric ulceration in rats. Zinc carnosine (Z-103), a newly developed agent was, therefore, examined for its antiulcer effect in stress-induced ulceration and also its membrane stabilizing action in rat stomachs. Cold-restraint (restrained at 4 degrees C for 2 h) stress induced severe hemorrhagic lesions together with increased mast cell degranulation and beta-glucuronidase release in the gastric glandular mucosa. Z-103 pretreatment with a single oral dose (3, 10 or 30 mg/kg) reversed these actions in a dose-dependent manner. When the compound was incubated in concentrations of 10(-7, 10(-6), 10(-5) or 10(-4) M, with isolated hepatic lysosomes, it significantly reduced the spontaneous release of beta-glucuronidase in the medium. The present study not only demonstrates the antiulcer effect of Z-103 but also indicates that the protective action is likely to be mediated by its membrane-stabilizing action on mast cells and lysosomes in the gastric glandular mucosa.

The physiological role of zinc as an antioxidant

The purpose of this review is to consider whether an essential biochemical function of zinc (Zn) is to serve as an antioxidant. Zn has been shown to have an antioxidant role(s) in defined chemical systems. Two mechanisms have been elucidated; the protection of sulfhydryl groups against oxidation and the inhibition of the production of reactive oxygens by transition metals. Supraphysiological concentrations of Zn have antioxidant-like effects in organelle-based systems and isolated cell-based systems in vitro. Administration of pharmacological doses of Zn in vivo has a protective effect against general and liver-specific prooxidants. Dietary Zn deficiency causes increased susceptibility to oxidative damage in membrane fractions from some tissues suggesting that increased oxidative stress may be a small but significant component of the pathology observed in dietary Zn deficiency. However, the biochemical basis for Zn deficiency pathology remains unelucidated; critical antioxidant functions for Zn may still be uncovered.

Effects of zinc and cholesterol/choleate on serum lipoproteins and the liver in rats

The effects of short-term treatment with orally-administered zinc sulphate and/or a mixture of cholesterol/choleate on serum lipoprotein and hepatic enzyme levels were studied. Administration of graded doses of zinc sulphate (20 or 40 mg/kg, as zinc ion) for 5 days, dose-dependently increased serum and hepatic zinc levels but depressed the serum high-density lipoprotein-cholesterol (HDL-C) concentration and liver cytochrome P-450 activity. However, it did not affect hepatic concentrations of malondialdehyde and free beta-glucuronidase. Cholesterol/choleate treatment for 5 days markedly damaged the liver, as reflected by elevations of hepatic concentrations of malondialdehyde (both in the mitochondrial and microsomal fractions) and of free beta-glucuronidase; total cholesterol and low-density lipoprotein-cholesterol in the blood were increased, whereas HDL-C was decreased significantly. Concomitant administration of zinc sulphate with cholesterol/choleate further lowered HDL-C levels, but reversed the high hepatic concentrations of both malondialdehyde and free beta-glucuronidase. The present study indicates that both zinc ions and cholesterol can decrease circulatory HDL-C levels and that zinc protects against cholesterol-induced hepatic damage by reducing lysosomal enzyme release and preventing lipid peroxidation in the liver.

A pathologic and toxicologic evaluation of veal calves fed large amounts of zinc

Tissues were examined from 26 male Holstein veal calves given large amounts of dietary zinc. All calves had been fed 706 micrograms zinc/g of milk replacer for 28 days before the first death occurred. Calves died naturally (14, group A) or were euthanatized (12, group B) after 23 days of feeding a lower concentration of zinc (150 micrograms/g). Average amounts of zinc in liver (wet weight) were 345.72 micrograms/g (group A) and 344.84 micrograms/g (group B). Mean kidney zinc concentrations were 219.0 micrograms/g (group A) and 252.38 micrograms/g (group B). Tissue manganese, copper, and iron levels were normal. Changes at necropsy included pneumonia, fluid digesta, and petechiae and infarcts in liver, kidney, and heart (as a result of bacterial infections). Histological changes that were directly attributed to dietary zinc intake were: marked atrophy and necrosis of pancreatic acinar tissue (group A); multifocal fibrosis of pancreatic acini (group B); multifocal renal cortical fibrosis with necrosis in convoluted tubules and loops of Henle, and with intratubular mineralization (groups A and B). Hepatic midzonal mineralization and fibrosis of the adrenal zona glomerulosa were seen in group B calves.

Synergism of organic zinc salts and sulfhydryl compounds (thiols) in the protection of mice against acute ethanol toxicity, and protective effects of various metal salts

Organic zinc salts such as zinc aspartate, zinc orotate, zinc histidine and zinc acetate protected mice against the lethality of an acute intraperitoneal challenge with ethanol. A similar activity was also provided by salts of cobalt, zirconium, lithium and magnesium. Organic zinc salts acted synergistically with sulfhydryl compounds in protecting the mice and potentiation between the two categories of agents was seen. The results are in analogy to radioprotective effects by zinc and thiols and imply that organic zinc salts may, alone or in conjunction with thiols, reduce in a wider context tissue injury caused by free radical-mediated mechanisms.

Inhibition of cell membrane lipid peroxidation by cadmium- and zinc-metallothioneins

The effects of all-zinc metallothionein (Zn-metallothionein) and predominantly cadmium metallothionein (Cd/Zn-metallothionein) on free radical lipid peroxidation have been investigated, using erythrocyte ghosts as the test system. When treated with xanthine and xanthine oxidase, Zn-metallothionein and Cd/Zn-metallothionein underwent thiolate group oxidation and metal ion release that was catalase-inhibitable, but superoxide dismutase-non-inhibitable. Similar treatment in the presence of ghosts and added Fe(III) resulted in metallothionein oxidation that was significantly inhibited by superoxide dismutase. Ghosts incubated with xanthine/xanthine oxidase/Fe(III) underwent H2O2- and O2--dependent lipid peroxidation, as measured by thiobarbituric acid reactivity. Neither type of metallothionein had any effect on xanthine oxidase activity, but both strongly inhibited lipid peroxidation when added to the membranes concurrently with xanthine/xanthine oxidase/iron. This inhibition was far greater and more sustained than that caused by dithiothreitol at a concentration equivalent to that of metallothionein thiolate. Significant protection was also afforded when ghosts plus Cd/Zn-metallothionein or Zn-metallothionein were preincubated with H2O2 and Fe(III), and then subjected to vigorous peroxidation by the addition of xanthine and xanthine oxidase. These results could be mimicked by using Cd(II) or Zn(II) alone. Previous studies suggested that Zn(II) inhibits xanthine/xanthine oxidase/iron-driven lipid peroxidation in ghosts by interfering with iron binding and redox cycling. Therefore, the primary determinant of metallothionein protection appears to be metal release and subsequent uptake by the membranes. These results have important implications concerning the antioxidant role of metallothionein, a protein known to be induced by various prooxidant conditions.

Effect of malotilate on chronic liver injury induced by carbon tetrachloride in the rat

The effect of malotilate, a new drug proposed for the treatment of chronic liver diseases, was studied in carbon tetrachloride (CCl4)-induced chronic liver injury in the rat. Treatment with CCl4 (0.5 ml/kg twice per week, intraperitoneally for 6 or 9 weeks) led to marked necrosis, steatosis and fibrosis, as shown by both biochemical and histological examinations, and a significant decrease of the bromosulfophtaleine (BSP) clearance test. Malotilate (50 mg/kg p.o., 5 days per week given simultaneously with CCl4 for 6 weeks), suppressed the increase of plasma aminotransferase activity and decreased significantly the accumulation of lipid and collagen in the liver; histology confirmed this protective effect of malotilate. The BSP clearance test returned to normal values and the rise in hepatic collagen synthesis activity in the malotilate-treated and intoxicated rats was reduced as compared with intoxicated control rats. The same effect was found when malotilate (100 mg/kg, p.o., 5 days per week), was given for 3 weeks to rats already intoxicated during the 6 previous weeks. Malotilate was able to prevent the increase of hepatic alterations that appeared during the last 3 weeks of CCl4 intoxication. These results show clearly that malotilate can markedly reduce the hepatic disorders induced by a chronic CCl4 intoxication in the rat.

A review of the environmental and mammalian toxicology of nitrilotriacetic acid

This article provides a review of available information on the chemistry, environmental toxicology, and mammalian toxicology of nitrilotriacetic acid (NTA). The ability of NTA to chelate metal ions such as Mg++ and Ca++ into water soluble complexes makes NTA useful as an additive to boiler water, as a builder in laundry detergents, and as a stabilizer in textile, paper, and pulp processing. Environmental fate studies show NTA biodegrades in wastewater treatment plants, in natural waters, and in soils under a wide variety of conditions. Studies on the environmental effects of NTA indicate that no adverse effects occur in treatment plants or receiving waters at anticipated levels. Monitoring programs have established that only low steady-state concentrations of NTA occur in natural waters as a result of NTA usage. In mammalian systems, NTA is not metabolized and is excreted rapidly by filtration in the kidney. No reproductive, teratogenic, or adverse bone effects have been observed at highly exaggerated doses. In numerous genotoxicity assay systems, both in vivo and in vitro, NTA is nongenotoxic. Chronic oral exposure of rodents to high doses of NTA is associated with tumorigenicity in, and restricted to, the urinary tract. The urinary tract tumors are the consequence of chronic toxicity that is caused by changes in Zn and Ca distributions between the urinary tract tissues and urine at high doses of NTA. Thresholds for the effects of NTA on Zn and Ca distributions are 10(5) to 10(6) greater than the possible maximum human exposure resulting from the low levels of NTA that are known to occur in the environment.

Inhibitory effect of zinc(II) on free radical lipid peroxidation in erythrocyte membranes

New evidence in support of zinc's role as a membrane antioxidant is presented. Human erythrocyte membranes in buffered saline underwent catalase- and superoxide dismutase-inhibitable lipid peroxidation when incubated with xanthine, xanthine oxidase, and Fe(III). Free radical mediated peroxidation was measured in terms of thiobarbituric acid reactivity and iodometric determination of lipid hydroperoxides. Whereas Ca(II) had relatively little effect on lipid peroxidation, Zn(II) strongly inhibited the reaction and suppressed peroxidation-dependent lysis of resealed membranes. Inhibition of lipid peroxidation was essentially complete in the presence of 0.1 mM Zn(II), a concentration equivalent to that of added Fe(III). By contrast, Zn(II) had no effect on rose bengal-photosensitized lipid peroxidation, a predominantly nonradical, singlet oxygen-driven process. Zinc(II) also interfered with xanthine/xanthine oxidase/iron-induced peroxidation of Triton X-100-dispersed membranes, but had no effect if EDTA was present. Trivial reasons for inhibition, for example, inactivation of xanthine oxidase or complex formation with O2-, were ruled out by showing that the rate of reduction of cytochrome c by xanthine/xanthine oxidase is not affected by Zn(II). We speculate that Zn(II) acts by interfering with the redox cycling of iron, possibly by competing with the latter for membrane binding sites.