Early decreases in pulmonary, hepatic and renal glutathione levels in response to cadmium instillation into rat trachea

After instillation of cadmium (Cd) into the rat trachea, reduced and oxidized glutathione (GSH and GSSG) levels in the lung, liver and kidney were studied in relation to Cd concentrations and metallothionein (Mt) contents. Rats instilled with Cd developed haemorrhagic pneumonia, which deteriorated with a marked swelling of the lung throughout the experimental period of 48 h. The total glutathione (GSH + GSSG) level in the organs decreased after 6 h to 60-70% of the control levels. The decreased glutathione level was never restored to the control level within 48 h in the lung, and was possibly due to the pneumonia. Completely recovered glutathione was seen in other organs. The GSSG level did not decrease significantly in the lung or liver but lowered significantly after 12 h and 24 h. The GSSG fraction in the amount of total glutathione was 10% or more in the lung and 5% or less in the liver or kidney. This finding indicated that the total glutathione level was mainly changed by the decrease in the GSH fraction. Cadmium in the lung increased to 7.3 ppm 3 h after Cd instillation and decreased to 2.5 ppm within 48 h. Cadmium in the liver and kidney gradually increased with time, and after 48 h reached 1.1 and 2.3 ppm, respectively. This indicated a transportation of Cd from the lung to these organs. Moreover, the early stage of Cd accumulation coincided with the total glutathione decrease in the organs. After Cd instillation, pulmonary, hepatic and renal Mt started to increase at 3 or 6 h, and markedly increased at 24 h or later.(ABSTRACT TRUNCATED AT 250 WORDS)     

Toxicity of cadmium oxide instilled into the rat lung. I. Metabolism of cadmium oxide in the lung and its effects on essential elements

The metabolism of cadmium oxide (CdO, insoluble form) and cadmium chloride (CdCl2, soluble form) instilled intratracheally into the rat lung was investigated. CdO might be solubilized rapidly in the lung and consequently pulmonary clearance rate of CdO was not so different from that of CdCl2. At a dose of 5 micrograms Cd/rat about 20% of the dose was translocated to the liver within 12 h, whereas gradual and consistent accumulation of Cd was observed in the kidney up to 7 days. Both pulmonary clearance and translocation of Cd to the liver were accelerated with the dose of instilled CdO, however, Cd accumulated in the kidney was proportional to the dose. Lung weight was increased by the instillation of CdO. Lung essential elements such as S, P, Mg, Zn and Mn were not affected in the inflammatory-reparative proliferative process, but Cu content of unit lung weight was slightly decreased.     

Toxicity of cadmium oxide instilled into the rat lung. II. Inflammatory responses in broncho-alveolar lavage fluid

Biochemical and cytological responses in the broncho-alveolar lavage fluid were investigated after instillation of cadmium oxide (CdO) or cadmium chloride (CdCl2) into the rat lung. Although biochemical responses of the lung to CdO were similar to the CdCl2-exposed lung, cytological response was more sensitive to CdO than CdCl2. Increases of lactate dehydrogenase, protein content and number of cells in the lavage fluid were proportional to the dose over the range of 0.5-10 micrograms Cd/rat. beta-Glucuronidase activity in the fluid increased with dose at low doses of Cd, but the activity did not continue to increase above 2 micrograms Cd/rat. A dose-response profile of phosphorus content in the lavage fluid, which might indicate amount of surfactant produced by Type II cells was similar to that observed for beta-glucuronidase in CdO-treated rats. Thus, tolerable level of instilled CdO for the rat lung was about 2 micrograms Cd/rat.     

Emblica officinalis reverses thioacetamide-induced oxidative stress and early promotional events of primary hepatocarcinogenesis

Emblica officinalis is widely used in Indian medicine for the treatment of various diseases. In the present study, it was found that fruits of E. officinalis inhibit thioacetamide-induced oxidative stress and hyper-proliferation in rat liver. The administration of a single necrotic dose of thioacetamide(6.6 mM kg(-1)) resulted in a significant (P < 0.001) increase in serum glutamic oxaloacetic transaminase(SGOT), serum glutamic pyruvic transaminase (SGPT) and gamma-glutamyl transpeptidase (GGT) levels compared with saline-treated control values. Thioacetamide caused hepatic glutathione (GSH) depletion and a concomitant increase in malanodialdehyde (MDA) content. It also resulted in an increase(P < 0.001) in the activity of glutathione-S-transferase (GST), glutathione reductase (GR), glucose 6-phosphate dehydrogenase (G6PD) and a decrease in glutathione peroxidase (GPx) activity (P < 0.001). Hepatic ornithine decarboxylase activity and thymidine incorporation in DNA were increased bythioacetamide administration. Prophylactic treatment with E. officinalis for 7 consecutive days before thioacetamide administration inhibited SGOT, SGPT and GGT release in serum compared with treated control values. It also modulated the hepatic GSH content and MDA formation. The plant extract caused a marked reduction in levels of GSH content and simultaneous inhibition of MDA formation. E. officinalis also caused a reduction in the activity of GST, GR and G6PD. GPx activity was increased after treatment with the plant extract at doses of 100 mg kg(-1) and 200 mg kg(-1). Prophylactic treatment with the plant caused a significant down-regulation of ornithine decarboxylase activity (P < 0.001) and profound inhibition in the rate of DNA synthesis (P < 0.001). In conclusion, the acute effects of thioacetamide in rat liver can be prevented by pre-treatment with E. officinalis extract.     

The critical role of the cellular thiol homeostasis in cadmium perturbation of the lung extracellular matrix

Cadmium (Cd) inhalation can result in emphysema. Cd exposure of rat lung fibroblasts (RFL6) enhanced levels of metal scavenging thiols, e.g., metallothionein (MT) and glutathione (GSH), and the heavy chain of γ-glutamylcysteine synthetase (γ-GCS), a key enzyme for GSH biosynthesis, concomitant with downregulation of lysyl oxidase (LO), a copper-dependent enzyme for crosslinking collagen and elastin in the extracellular matrix (ECM). Cd downregulation of LO in treated cells was closely accompanied by suppression of synthesis of collagen, a major structure component of the lung ECM. Using rats intratracheally instilled with cadmium chloride (30 μg, once a week) as an animal model, we further demonstrated that although 2-week Cd instillation induced a non-significant change in the lung LO activity and collagen synthesis, 4- and 6-week Cd instillation resulted in a steady decrease in the lung LO and collagen expression. The lung MT and total GSH levels were both upregulated upon the long-term Cd exposure. Emphysematous lesions were generated in lungs of 6-week Cd-dosed rats. Increases of cellular thiols by transfection of cells with MT-II expression vectors or treatment of cells with GSH monoethyl ester, a GSH delivery system, markedly inhibited LO mRNA levels and catalytic activities in the cell model. Thus, Cd upregulation of cellular thiols may be a critical cellular event facilitating downregulation of LO, a potential mechanism for Cd-induced emphysema.     

Effects of fasting on cadmium toxicity, glutathione metabolism, and metallothionein synthesis in rats

Acute oral toxicity of Cd (as cadmium chloride) was enhanced in rats fasted 24 hr, as shown by a markedly decreased LD50. To examine the relationship among Cd toxicity, hepatic glutathione (GSH), and metallothionein (MT) during fasting, rats were administered 75 mg Cd/kg orally 24 hr after fasting and euthanized after a further 4 or 24 hr for various assays. Serum glutamic-pyruvic transaminase activity 24 hr after Cd treatment was higher in fasted rats than in fed rats. Both total GSH and nonprotein sulfhydryl (NPSH) concentrations in liver decreased to 50% of control levels after 28 hr of fasting and returned to 75% of control values by 48 hr. Total hepatic GSH concentration in fed rats decreased 4 and 24 hr after Cd treatment, whereas that in fasted rats remained unchanged at 4 hr and decreased significantly at 24 hr. Cd uptake by the liver (both concentration and content) 24 hr after Cd treatment was higher in fasted rats than in fed rats. Hepatic MT concentration was markedly increased by Cd treatment and higher in fasted rats than in fed rats. There was no relationship between Cd toxicity and hepatic thiobarbituric acid (TBA) value, an indicator of lipid peroxidation. Fasting had no effect on hepatic GSH peroxidase and GSH reductase activities. These enzymes probably are not involved in Cd toxicity. On histological examination, focal degenerative and necrotic changes were observed from the midlobular to the pericentral region in the livers of fed rats 24 hr after Cd treatment. These changes were enhanced by fasting, diffusing from the pericentral to the periportal region. Histochemical examination revealed a heterogeneous distribution of GSH in the livers of fed rats, with strong staining of GSH in the periportal region. This heterogeneous distribution of GSH in liver was not observed in fed rats 4 hr after Cd treatment or in fasted rats at 24 hr. The present results suggest that hepatic GSH plays an important role in protection against Cd toxicity before the onset of MT synthesis. Animals in bad condition, such as that resulting from interruption of nutrient supply, cannot be protected against Cd toxicity even if the hepatic MT level is high.     

Comparative study of natural antioxidants - curcumin, resveratrol and melatonin - in cadmium-induced oxidative damage in mice

The present study was designed to examine the antioxidative effect of curcumin, resveratrol and melatonin pre-treatment on cadmium-induced oxidative damage and cadmium distribution in an experimental model in mice. Male CD mice were treated once daily for 3 days with curcumin (50mg/kg b.w., p.o.), resveratrol (20mg/kg b.w., p.o.) or melatonin (12mg/kg, p.o.), dispersed in 0.5% methylcellulose. One hour after the last dose of antioxidants cadmium chloride was administered (7mg/kg b.w., s.c.) to pre-treated animals and control animals receiving methylcellulose. At 24th h after Cd administration the lipid peroxidation (LP - expressed as malondialdehyde production), reduced glutathione (GSH), catalase (CAT) and glutathione peroxidase (GPx) were estimated in liver homogenates. Cadmium concentration was measured in the liver, kidneys, testes and brain by AAS. Cadmium chloride administration to mice induced hepatic lipid peroxidation (to 133%, p<0.001), decreased GSH content (to 65%, p<0.001) and inhibited catalase (to 68%, p<0.001) and GPx activity (to 60%, p<0.001) in the liver. Curcumin, resveratrol and melatonin oral pre-treatment completely prevented the Cd-induced lipid peroxidation and Cd-induced inhibition of GPx hepatic activity. Resveratrol was effective against Cd-induced inhibition of catalase activity (p<0.001). The decrease in hepatic GSH level was not prevented by curcumin, resveratrol or melatonin pre-treatment. In mice treated with antioxidants alone the level of LP, GSH, GPx or CAT was not different from control levels. The pre-treatment with antioxidants did not affect cadmium distribution in the tissues of Cd-intoxicated mice. The results demonstrate that curcumin, resveratrol and melatonin pre-treatment effectively protect against cadmium-induced lipid peroxidation and ameliorate the adverse effect of cadmium on antioxidant status without any reduction in tissue Cd burden.     

Acetaminophen increases the risk of arsenic‐mediated development of hepatic damage in rats by enhancing redox‐signaling mechanism

We evaluated whether the commonly used analgesic‐antipyretic drug acetaminophen can modify the arsenic‐induced hepatic oxidative stress and also whether withdrawal of acetaminophen administration during the course of long‐term arsenic exposure can increase susceptibility of liver to arsenic toxicity. Acetaminophen was co‐administered orally to rats for 3 days following 28 days of arsenic pre‐exposure (Phase‐I) and thereafter, acetaminophen was withdrawn, but arsenic exposure was continued for another 28 days (Phase‐II). Arsenic increased lipid peroxidation and reactive oxygen species (ROS) generation, depleted glutathione (GSH), and decreased superoxide dismutase (SOD), catalase, glutathione peroxidase (GPx), and glutathione reductase (GR) activities. Acetaminophen caused exacerbation of arsenic‐mediated lipid peroxidation and ROS generation and further enhancement of serum alanine aminotransferase and aspartate aminotransferase activities. In Phase‐I, acetaminophen caused further GSH depletion and reduction in SOD, catalase, GPx and GR activities, but in Phase‐II, only GPx and GR activities were more affected. Arsenic did not alter basal and inducible nitric oxide synthase (iNOS)‐mediated NO production, but decreased constitutive NOS (cNOS)‐mediated NO release. Arsenic reduced expression of endothelial NOS (eNOS) and iNOS genes. Acetaminophen up‐regulated eNOS and iNOS expression and NO production in Phase‐I, but reversed these effects in Phase‐II. Results reveal that acetaminophen increased the risk of arsenic‐mediated hepatic oxidative damage. Withdrawal of acetaminophen administration also increased susceptibility of liver to hepatotoxicity. Both ROS and NO appeared to mediate lipid peroxidation in Phase‐I, whereas only ROS appeared responsible for peroxidative damage in Phase‐II. © 2011 Wiley Periodicals, Inc. Environ Toxicol 29: 187–198, 2014.     

Effect of BDE-209 on glutathione system in Carassius auratus

In this study, the oxidative stress induced by deca-polybromodiphenyl ether (BDE-209) was investigated in livers of Carassius auratus. Six groups of fish were exposed to blank and 0, 0.004, 0.04, 0.4, 4 μM BDE-209 (in 0.1% DMSO) for 1, 4, 7, 10, 13 d, respectively. The following oxidative stress markers were analyzed: reduced glutathione (GSH), glutathione reductase (GR), glutathione peroxidases (GPx) and glutathione S-transferases (GSTs). No significant difference was observed in the content of GSH over the whole period of exposure (p > 0.05). Increases in hepatic GR and GPx activities were in concomitant with the decrease in GST activity. GR activity was induced after 1 d exposure, while GPx activity reached maximum at 4 d after exposure to 0.04 μM BDE-209 and GST activity was significantly inhibited at 7-13 d in all the treatment groups (0.004-4 μM group).     

Selenium modulates β‐cyfluthrin‐induced liver oxidative toxicity in rats

This study was designed to investigate the possibility of β‐cyfluthrin to induce oxidative stress and biochemical perturbations in rat liver and the role of selenium in alleviating its toxic effects. Male Wister rats were randomly divided into four groups of seven each, group I served as control, group II treated with selenium (200 µg/kg BW), group III received β‐cyfluthrin (15 mg/kg BW, 1/25 LD₅₀), and group IV treated with β‐cyfluthrin plus selenium. Rats were orally administered their respective doses daily for 30 days. The administration of β‐cyfluthrin caused elevation in lipid peroxidation (LPO) and reduction in the activities of antioxidant enzymes including catalase (CAT), superoxide dismutase (SOD), glutathione S‐transferase (GST), glutathione peroxidase (GPx), and glutathione reductase (GR). A decrease in reduced glutathione (GSH) content was also observed. Liver aminotransferases (AST and ALT) and alkaline phosphatase (ALP) were decreased, whereas lactate dehydrogenase (LDH) was increased. Selenium in β‐cyfluthrin‐induced liver oxidative injury of the rats modulated LPO, CAT, SOD, GSH, GST, GPx, and GR. Also, liver AST, ALT, ALP, and LDH were maintained near normal level due to selenium treatment. It is concluded that selenium scavenges reactive oxygen species and render a protective effect against β‐cyfluthrin toxicity. © 2013 Wiley Periodicals, Inc. Environ Toxicol 29: 1323–1329, 2014.     

Caffeic acid phenethyl ester protects against tamoxifen-induced hepatotoxicity in rats

Tamoxifen (TAM) is widely used in the treatment and prevention of breast cancer. Adverse effects of TAM include hepatotoxicity. Caffeic acid phenethyl ester (CAPE), an active component of propolis, has been used in folk medicine for diverse ailments. In the current study, the protective effects of CAPE against TAM-induced hepatotoxicity in female rats were evaluated. TAM (45 mg/kg/day, i.p., for 10 consecutive days) resulted in an elevation of serum alanine aminotransferase (ALT), aspartate aminotransferase (AST) and alkaline phosphatase (ALP), depletion of liver reduced glutathione (GSH) and accumulation of oxidized glutathione (GSSG) and lipid peroxidation (LPO). Also, TAM treatment resulted in inhibition of hepatic activity of glutathione reductase (GR), glutathione peroxidase (GPx), superoxide dismutase (SOD) and catalase (CAT). Further, it raised liver tumor necrosis factor-alpha (TNF-α) level and induced histopathological changes. Pretreatment with CAPE (2.84 mg/kg/day; i.p., for 20 consecutive days, starting 10 days before TAM injection) significantly prevented the elevation in serum activity of the assessed enzymes. CAPE significantly inhibited TAM-induced hepatic GSH depletion and GSSG and LPO accumulation. Consistently, CAPE normalized the activity of GR, GPx, SOD and CAT, inhibited the rise in TNF-α and ameliorated the histopathological changes. In conclusion, CAPE protects against TAM-induced hepatotoxicity.     

A comparative study of the effects of inhaled cadmium chloride and cadmium oxide: pulmonary response

The effects of aerosols of cadmium chloride (CdCl2) and cadmium oxide (CdO) on pulmonary biochemical function were compared. Rats and rabbits were exposed to 0.25, 0.45, or 4.5 mg Cd/m3 for 2 h. Pulmonary toxicity was determined histologically and biochemically. Cadmium chloride and CdO showed a deposition response that was linearly related to the chamber concentration. Both compounds caused multifocal, interstitial pneumonitis 72 h after exposure, but the CdO lesion was more severe with proliferation of fibrocytic-like cells as well as pneumocytes. Comparing the two Cd compounds at the highest concentration (4.5 mg Cd/m3), the biochemical responses in the rat were similar. The majority of the effects occurred 72 h after exposure, with significant increases in lung weight, lung-to-body weight ratio, GSH reductase, GSH transferase, and G-6-PDH. However, GSH peroxidase was inhibited immediately after the CdO exposure. Cadmium oxide-related alterations in the parameters studied could easily be distinguished from those of CdCl2 at the exposure concentration of 0.45 mg Cd/m3. The response pattern in the rabbit resembled that of the rat. In both species Cd had a consistent inhibitory effect on pulmonary GSH peroxidase, even at the lowest concentration of 0.25 mg Cd/m3. Based on these findings, inhaled CdO appeared to be more toxic to the lung than inhaled CdCl2.     

Biochemical effects of intratracheal instillation of cadmium chloride on rat lung.

Selected biochemical parameters in rat lung tissue were examined after intratracheal instillation of 0.5 μmole/kg of cadmium chloride (CdCl₂), which produces levels of approximately 10 μg Cd/g of lung wet weight 1 hr following instillation. Lungs were examined 2 hr, 1 day, 3 days and 7 days after CdCl₂ instillation and compared with matched controls receiving saline instillations. Cytosolic lysosomal enzymes, Superoxide dismutase (SOD), catalase, and glutathione (GSH) peroxidase-associated enzymes increased significantly 24 hr after CdCl₂ insult. Peak increases of enzyme activities occurred about 3 days after CdCl₂ instillation. Levels of lung nonprotein sulfhydryl (NPSH) groups, thiobarbituric acid (TBA)-reactive products, protein and DNA increased after CdCl₂ instillation in a similar manner. By 7 days most measured biochemical parameters either remained at the peak 3-day values or decreased toward normal levels. The biochemical changes are consistent with known reported CdCl₂-induced edema and inflammation accompanied by phagocyte recruitment into lung tissue and reparative proliferation of lung cell types.     

Heme oxygenase is the main protective enzyme in rat liver upon 6-day administration of cobalt chloride

Changes in the activities of rat liver heme oxygenase (HO), superoxide dismutase (SOD), catalase, glutathione peroxidase (GPx) and glutathione reductase (GR), as well as changes in lipid peroxidation and reduced glutathione (GSH) levels were measured after acute loading and chronic administration of cobalt chloride (CoCl2). Acute loading was achieved by a single subcutaneous injection of 60 mg CoCl2/kg body weight for 24 h. Chronic administration was performed by giving the same total amount of CoCl2 in small doses over longer periods of time: 30 mg CoCl2/kg daily for 2 days, 15 mg CoCl2/kg daily for 4 days, or 10 mg CoCl2/kg daily for 6 days. The results showed that HO activity was increased both after acute loading (7-fold increase) and upon 6-day administration of CoCl2 (5-fold increase). The GSH level, 24 h after a single injection of CoCl2, was lower than that of the control animals. However, upon chronic administration of small doses CoCl2, the level of GSH increased and was accompanied by an increase in GR activity. Chronic administration of CoCl2 produced persistent oxidative stress, which was illustrated with a continuous increase in lipid peroxidation. At the same time, under these conditions, the activities of oxidative-stress-protective enzymes were either inhibited (SOD, catalase) or not significantly changed (GPx). Collectively, these findings suggest that the sustained up-regulation of HO activity in rat liver upon 6 day administration of CoCl2 would be beneficial by providing the cells with antioxidants, biliverdin and bilirubin, and together with the increased levels of GSH would act as a part of the defence mechanisms against the cobalt-induced oxidative stress.     

Selenium supplementation ameliorates static magnetic field-induced disorders in antioxidant status in rat tissues

The aim of this study was to investigate the effect of selenium supplementation on the antioxidant enzymatic system (such as GPx, GR and SOD), GSH and selenium level in liver, kidney, muscle and brain of static magnetic field (SMF) exposed rats. Male adult rats were divided into control rats (n=6), SMF-exposed rats (128 mT; 1h/day for 5 days), selenium-treated rats (Na(2)SeO(3), 0.2mg/l, in drinking water for 4 weeks) and co-exposed rats (selenium for 4 weeks and SMF during the last 5 consecutive days). Sub-acute exposure to SMF induces a decrease of selenium levels in kidney, muscle and brain. Our results also revealed a decrease of GPx activities in kidney and muscle. By contrast, SMF exposure increased total GSH levels and total SOD activities in liver, while glutathione reductase activity is unaffected. Selenium supplementation in SMF-exposed rats restored selenium levels in kidney, muscle and brain and elevated the activities of GPx in kidney and muscle to those of control group. In the liver, selenium supplementation failed to bring down the elevated levels of total GSH and SOD activity. Our investigations suggested that sub-acute exposure to SMF altered the antioxidant response by decreasing the level of total selenium in kidney, muscle and brain. Interestingly, selenium supplementation ameliorates antioxidant capacity in rat tissues exposed to SMF.     

Repeated acetaminophen dosing in rats: adaptation of hepatic antioxidant system

Repeated dosing of acetaminophen (paracetamol) to rats is reported to decrease their sensitivity to its hepatotoxic effects, which are associated with oxidative stress and glutathione depletion. We determined if repeated acetaminophen dosing produced adaptive response of key antioxidant system enzymes. Male rats (Sprague-Dawley, 10 weeks) were given 800, 1200, or 1600 mg/kg/day acetaminophen by oral gavage for 4 days. Liver was assayed for oxidative stress and antioxidant markers: malondialdehyde (MDA), thiobarbituric acid reactive substance (TBARS), total antioxidant status (TAS), glutathione (GSH), glutathione reductase (GR), glutathione peroxidase (GPx), glucose-6-phosphate dehydrogenase (G6PD), catalase (CAT), and superoxide dismutase (SOD), and alanine transaminase (ALT) as a marker of hepatocellular injury. Acetaminophen at 1200/1600 mg/kg decreased GSH 26/47%, GPx 21/26%, CAT 35/28%, SOD 21/12%; and TAS 28/18% (correlated with CAT, r=0.91; SOD, r=0.66; GPx, r=0.45). Despite antioxidant deficiencies, and no TBARS change, MDA decreased 26%/33%/37% at 800/1200/1600 mg/kg, which correlated with increased GR (61%/62%/76%, r=0.77) and G6PD (130%/110%/190%, r=0.78). Both MDA (r=0.68) and G6PD (r=0.71) correlated with hepatic ALT, which decreased 27%/43%/48%, respectively. Resistance to acetaminophen hepatotoxicity produced by repeated exposure is partially attributable to upregulation of hepatic G6PD and GR activity as an adaptive and protective response to oxidative stress and glutathione depletion.     

Glutathione peroxidase and glutathione reductase activities are partially responsible for determining the susceptibility of cells to oxidative stress

Different cell types response differently to toxic insult. In a previous study, it was demonstrated that the C6 glioma cell is more sensitive to Cd induced oxidative stress than the HepG2 cells. To explain the difference between the two cell lines in their response to oxidative stress, it was hypothesized that the activity of glutathione metabolizing enzymes may be different. The objective of this study is to determine the activities of glutathione peroxidase (GPx) and glutathione reductase (GR) in the two cell lines and to explain how these differences may affect the susceptibility of the two cells to oxidative stress. In the HepG2 cells, the activity of GPx was 2.24+/-0.18 micromol/mg protein/min and that for GR was 5.63+/-0.58 micromol/mg protein/min. For the C6 glioma cells, GPx and GR activities were 1.29+/-0.14 and 1.07+/-0.11 micromol/mg protein/min, respectively. Using the kinetic equilibrium: K(eq)=([GSSG]x[NADPH]x[H(+)])/([GSH](2)x[NADP(+)]), and the GSH/GSSG previously published (HepG2: 2.6 and C6 glioma: 3.6), resting NADPH/NADP(+) for the cell lines were calculated. The results showed that NADPH/NADP(+) for HepG2 cells (17.8) is higher than that in the C6 glioma cells (10.8). These data supported the notion that the reducing power (NADPH/NADP(+)) in the HepG2 cells is higher than that in the C6 glioma cell and thus, the later would be more susceptible to oxidative stress. The results also suggested that besides GSH/GSSG, the activities of GPx and GR are important in predicting tissue redox state. Applying this hypothesis to animal tissues, the ratio of the activities of the two enzymes in mouse liver, cerebral cortex, hippocampus and cerebellum were measured. It was demonstrated that the activities of GPx and GR were different in the different tissues studied. The possible correlation between enzymatic activities and the redox state in the different tissues were discussed.     

Protective roles of metallothionein and glutathione in hepatotoxicity of cadmium.

The protective roles of metallothionein (MT) and glutathione (GSH) in acute hepatotoxicity of cadmium (Cd) were investigated in an in vitro system. Liver slices were incubated in a buffer containing cadmium chloride (20-50 ppm) at 37 degrees C for 3 h. Viability of the slices was monitored by measuring intra-cellular potassium (K) content and GSH concentrations. A dose-dependent decrease of intracellular K content of GSH concentrations was observed. Pre-induction of MT (100-fold increase) by injection of zinc sulphate (30 mg Zn/kg body weight) showed protection against decrease in both intracellular K and GSH concentrations in liver slices. Decrease of hepatic GSH (90%) by an injection of buthionine sulfoximine (BSO)(4 mmol/kg body weight) to the rats further enhanced the Cd toxicity in the liver slices. This enhanced toxicity resulting from BSO treatment can be totally overvome by induction of MT by Zn pre-treatment. The cellular uptake of Cd remained unaltered in all experiments. These results demonstrate that hepatic toxicity of Cd may be due to its binding to intracellular sulfhydryl groups and both intracellular GSH and MT levels may provide protection against cytotoxicity of Cd in liver. Moreover, even at low GSH levels, MT could partially protect the hepatic cells from Cd cytotoxicity.     

Metallothionein attenuates carmustine-induced oxidative stress and protects against pulmonary fibrosis in rats

The present study was carried out to evaluate the effect of exogenously administered metallothionein (MT) against carmustine (BCNU)-induced lung toxicity in rats. A total of 60 rats were randomly divided into four groups (15/group): control group in which the animals received 0.5 ml physiologic saline containing 10% ethanol (IP) weekly, MT-administered group in which rats received MT (30 μmol/kg, IP) weekly, BCNU-administered group in which rats received BCNU (5 mg/kg, IP) weekly and MT + BCNU group in which rats received weekly doses of BCNU (5 mg/kg, IP) followed 24 h later by MT (30 μmol/kg, IP). At the end of the experiment (after 6 weeks), lung histological changes, collagen staining, the activity of glutathione reductase (GR) and contents of reduced glutathione (GSH) and hydroxyproline (Hpr) in the lung as well as serum level of tumor necrosis factor-alpha (TNF-α) were evaluated. The obtained data revealed that BCNU induced pathological changes and markedly increased lung collagen and level of Hpr but decreased GSH content and GR activity and increased serum TNF-α compared to both control and MT-administered rats. Administration of MT + BCNU markedly improved histological features and decreased staining of collagen along with increased GR activity, GSH content but decreased level of Hpr in lung tissue as well as decreased serum level of TNF-α compared with BCNU-treated rats. Based on our results, it is possible to postulate that exogenous MT can act against BCNU-induced lung toxicity by a mechanism related, at least in part, to its ability to decrease oxidative stress and fibrosis.     

Pi*S and Pi*Z alpha 1 antitrypsin polymorphism and the risk for asbestosis in occupational exposure to asbestos

The effect of meso 2,3-dimercaptosuccinic acid (DMSA) and monoisoamyl DMSA (MiADMSA) on gallium arsenide (GaAs) induced liver damage was studied. The oral feeding rat model was used in this study. The animals were exposed to 10 mg/kg GaAs, orally, once daily, 5 days a week for 24 weeks and treated thereafter with single oral daily dose of either 0.3 mmol/kg DMSA or MiADMSA for two course of 5 days treatment. The animals were sacrificed thereafter. Lipid peroxidation was assessed by measuring liver thiobarbituric acid reactive substance (TBARS). Liver damage was assessed by number of biochemical variables and by light microscopy. The activity of superoxide dismutase (SOD) and delta-aminolevulinic acid dehydratase (ALAD) beside reduced glutathione (GSH) concentration was measured in blood. Exposure to GaAs produced a significant reduction in GSH while, increased the oxidized glutathione (GSSG) concentration. Hepatic glutathione peroxidase (GPx) and catalase activity increased significantly while level of serum transaminase increased moderately. Gallium arsenide exposure also produced marked hepatic histopathological lesions. Overall, treatment with MiADMSA proved to be better than DMSA in the mobilization of arsenic and in the turnover of some of the above mentioned GaAs sensitive biochemical alterations. Histopathological lesions also, responded more favorably to chelation treatment with MiADMSA than DMSA.