Methyl mercury-induced encephalopathy in mice

An animal model of methyl mercury-induced encephalopathy was developed in mice to enable a study of the effects of various newly synthesized chelating agents on methyl mercury toxicity. Administration of methyl mercury to mice via drinking water produced neuropathological and behavioral responses similar to those seen in humans following chronic exposure to organic mercurials. Changes in cellular morphology were seen in the cerebellar cortex of mice exposed to 50 and 10 μg of Hg as CH₃HgCl per milliliter of drinking water after 8 days of exposure. At this time, posterior paresis began to develop in mice exposed to 50 μg of Hg/ml of drinking water. Histopathological changes were similar in both exposure groups, although paraplegia did not develop in the low dose group until 24 weeks of exposure. Development of overt clinical signs of methyl mercury toxicity correlated well with blood and whole-body mercury concentrations. There was a lack of correlation between blood and whole-body mercury concentrations and among morphological changes in the cerebellar cortex.     

Ethanol protection against hemicholinium toxicity in mice

The minimum lethal dose of hemicholinium-3 (HC-3) (intra-peritoneal) was determined in groups of male albino mice. Death occurred in the majority of cases within 10 min after injection and was attributed to the “curare-like” action of HC-3. However, pretreatment with ethanol (i.p.) was found to afford protection against these toxic effects. The site of action of ethanol protection appeared to be peripheral since ethanol (i.p.) also protected against a lethal dose of the post-synaptic neuromuscular blocking agent, d-tubocurarine (dtc) (intravenous). The time course of the protection suggested that a metabolite of ethanol might be involved. The phrenic nerve-diaphragm preparation was used to demonstrate the “curare-like” action of HC-3 and to investigate the effect of ethanol on this. Ethanol added to the bathing medium produced a transient reversal of the fall in twitch height produced by either HC-3 or dtc. This reversal may be primarily explained by depolarisation of the post-synaptic membrane by ethanol since this potentiated the blockade due to decamethonium and caused an increase in resting tension of the muscle.     

Glucocorticoid protection against PAF-acether toxicity in mice

Intravenous platelet activating factor (PAF-acether, 10 to 25 micrograms/kg body weight) produced dose-dependent mortality in both male and female mice. Pretreatment with indomethacin (50 mg/kg), verapamil (40 mg/kg) or nifedipine (4 mg/kg) failed to inhibit the lethal effect of 20 micrograms/kg PAF-acether. This suggests that neither arachidonate cyclo-oxygenase products nor availability of extracellular Ca2+ mediate the toxic action. In contrast, pretreatment with 100 mg/kg cortisone acetate (s.c.) daily for four days exerted a highly protective effect, i.e. 100% and 93% survival in males and females, compared to 13% and 7% respectively, in untreated animals. PAF-acether-induced death may be a useful model for the in vivo evaluation of pharmacological agents in anaphylactic shock.     

Zinc mediates normalization of hepatic drug metabolizing enzymes in chlorpyrifos-induced toxicity

The present study investigated the protective effects of zinc in attenuating the altered activities of drug metabolizing enzymes in the livers of rats intoxicated with chlorpyrifos. Male Sprague-Dawley rats received oral chlorpyrifos treatment (at a dose level of 13.5 mg/kg body weight in corn oil every alternate day), zinc supplementation alone (at a dose level of 227 mg/l in drinking water), or combined chlorpyrifos plus zinc treatments for a total duration of 8 weeks. The effects of different treatments were studied on the specific activities of various drug metabolizing enzymes including cytochrome P(450), cytochrome b(5), NADPH cytochrome-c-reductase, NADH cytochrome-c-reductase, aminopyrene-N-demethylase (APD) and aromatic hydrocarbon hydroxylase (AHH). Additionally, serum zinc levels were also determined in each of the treatment groups at the end of the study. Chlorpyrifos treatment resulted in a significant decrease in the serum zinc concentrations. Analogous to these changes, we observed significant depression in the activities of majority of the drug metabolizing enzymes investigated in the present study, except for AHH, where the decrease in enzyme activity was not statistically significant. However, zinc treatment to chlorpyrifos treated animals effectively restored the depressed serum zinc levels to within normal limits. Similarly, co-administration of zinc to chlorpyrifos intoxicated animals normalized the enzymatic activities of cytochrome P(450), NADPH cytochrome-c-reductase and NADH cytochrome-c-reductase within normal range. Collectively, these findings suggest that zinc plays an important role in regulating the hepatic activities of drug metabolizing enzymes in chlorpyrifos intoxicated animals, although it remains to be determined whether such protective effects of zinc are regulated directly, or through some indirect mechanism.     

The potential effect of berberine in mercury-induced hepatorenal toxicity in albino rats

Mercury (Hg) is the third most dangerous heavy metal after arsenic and lead. Mercury’s toxicity brings serious risks to health through negative pathological and biochemical effects. The study was designed to investigate the possible protective role of berberine (BN) in mercuric chloride (HgCl₂) induced oxidative stress in hepatic and renal tissues. Adult male albino Wistar rats were exposed to mercuric chloride (HgCl₂; 0.4 mg/kg bwt) for 7 days. Treatment with HgCl₂ induced oxidative stress by increasing lipid peroxidation and nitric oxide production along with a concomitant decrease in glutathione and various antioxidant enzymes, namely superoxide dismutase, catalase, glutathione peroxidase and glutathione reductase. HgCl₂ intoxication increased the activities of liver enzymes and the bilirubin level, in addition to the levels of urea and creatinine in serum. BN (100 mg/kg bwt) treatment inhibited lipid peroxidation and nitric oxide production, whereas it increased glutathione content. Activities of antioxidants enzymes, superoxide dismutase, catalase, glutathione peroxidase and glutathione reductase, were also restored concomitantly when compared to control after BN administration. BN also inhibited the apoptotic effect of HgCl₂ by increasing the expression of Bcl-2 protein in liver and kidney. Histopathological examination of the liver and kidney tissues proved the protective effect of BN against HgCl₂ toxicity. These results demonstrated that BN augments antioxidant defense against HgCl₂-induced toxicity and provides evidence that it has therapeutic potential as hepato- and reno-protective agent.     

Role of renal cortical sulfhydryl groups in development of mercury-induced renal toxicity

The effect of lowering renal cortical sulfhydryl concentration on development of acute renal failure (ARF) was evaluated in rats receiving HgCl2 (15 mg/kg body weight, im). Within 90 min after HgCL2 injection urine flow rate and fractional excretion of sodium (FENa) were significantly elevated above control levels, and they remained elevated throughout the 3-h experimental period. Urine flow rate and FENa were not significantly elevated above control levels in animals injected with diethyl maleate (3 mmol/kg, ip) 30 min before and 90 min after HgCl2 (DEM/HgCl2). Administration of DEM alone did not alter renal function. Although lower than control levels, concentrations of protein-bound sulfhydryl groups (PBSH) were comparable in HgCl2- and DEM/HgCl2-treated animals. In contrast, concentrations of nonprotein sulfhydryl groups (NPSH) were 62% lower in DEM/HgCl2 animals than in those treated with HgCl2 alone. Similarly, Hg accumulation was 54% lower in DEM/hgCl2-treated animals than in animals treated with HgCl2 alone. These results suggest that NPSH play an important role in Hg uptake and subsequent development of Hg toxicity.     

Acute acetaminophen toxicity in transgenic mice with elevated hepatic glutathione

Previous studies demonstrated that elevation of hepatic glutathione (GSH) concentrations protect against acetaminophen (APAP) hepatotoxicity in mice. Employing transgenic mice overexpressing glutathione synthetase, this study was conducted to determine if sustained elevation of hepatic GSH concentrations could ameliorate or prevent APAP toxicity. International Cancer Research transgenic mouse males and matched (ie same strain, sex, and age) control nontransgenic mice were pretreated ip with GSH synthetase substrate gamma-glutamylcysteinyl ethyl ester (gamma-GCE) or with saline. After a 16-h fast, mice received a single dose of 500 mg APAP/kg bw in saline ip and were sacrificed 4 h later. Other mice similarly pretreated were killed without APAP challenge. The elevated GSH concentrations in transgenic mice livers did not lessen APAP hepatotoxicity. Instead higher degrees of hepatotoxicity and nephrotoxicity were observed in transgenic mice than in controls as indicated by higher serum alanine aminotransferase activity and more severe histopathological lesions in transgenic mice livers and kidneys. Pretreatment with gamma-GCE did not affect either initial or post-APAP treatment tissue GSH concentrations or observed degrees of toxicity. Detection of a higher level of serum APAP in transgenic mice and the histopathological lesions found in transgenic mice kidneys together with no observable nephrotoxicity in control mice indicated early kidney damage in transgenic mice. Our findings suggest that high levels of GSH-APAP conjugates resulting from increased GSH concentrations in the livers of transgenic mice caused rapid kidney damage. Compromised excretory ability may have caused retention of APAP, which, in effect, elicited higher hepatotoxicity than that observed in nontransgenic mice.     

Perfluorooctanoic acid-induced hepatic toxicity following 21-day oral exposure in mice

Perfluorooctanoic acid (PFOA) is a member of the perfluoroalkyl acids that have wide commercial applications and is a widespread pollutant of toxicological importance that has been detected in environmental matrices. The NOAEL and LOAEL of PFOA in rodent were reported 1 and 10 ppm, respectively. The current study characterizes the hepatic toxicities of PFOA in mice. Male ICR mice were exposed continuously to 0, 2, 10, 50 and 250 ppm of PFOA in drinking water for 21 days. Food and water consumption decreased in mice exposed to 250 ppm of PFOA. Mean body weight gain was reduced in mice exposed to 50 and 250 ppm of PFOA. The size and relative weight of the liver increased dose-dependently in PFOA-treated mice. Serum enzyme activities, alanine aminotransferase and aspartate aminotransferase, increased in mice exposed to PFOA in a dose-dependent manner. In the histopathological evaluation, the liver of PFOA-treated mice showed remarkable hepatocytomegaly and acidophilic cytoplasm. At the high doses of PFOA, diffuse hepatic damage by multifocal coagualation and liquefaction necrosis were noted. In contrast to the remarkable change of liver, the kidney had little change. The size and relative weights of the kidney, biomarkers of kidney damage (blood urea nitrogen, creatinine), and histopathological changes had no differences between PFOA-untreated and PFOA-treated mice. In conclusion, our results demonstrate that PFOA causes a toxic effect on the liver but not to the kidney. Hee-Young Son, Sang-Hyun Kim authors contributed equally to this work.     

A nutrient mixture suppresses carbon tetrachloride-induced acute hepatic toxicity in ICR mice

We examined the effect of a nutrient mixture (NM) that contains lysine, proline, ascorbic acid, and green tea extract in mice treated with carbon tetrachloride (CCl4), a model of liver injury in which free radical, oxidative stress, and cytokine production are closely linked. Seven-week-old male Imprinting Control Region (ICR) mice were divided into four groups (A-D) of five animals each. Groups A and C mice were fed a regular diet for 2 weeks, whereas groups B and D mice were supplemented with 0.5% NM (w/w) during that period. Groups A and B received corn oil i.p., whereas groups C and D received CCl4 (25 microL/kg, in corn oil, i.p.). All animals were killed 24 h after CCl4 administration, serum was collected to assess liver and kidney functions, and livers and kidneys were excised for histology. Mean serum aspartate aminotransferase and alanine aminotransferase were comparable in groups A and B, increased markedly in group C, and significantly lowered in group D compared with group C. CCl4 had no significant effect on renal markers (blood urea nitrogen [BUN], creatinine, and BUN/creatinine ratio). CCl4 administration caused an intense degree of liver necrosis that was less severe in the NM fed group D. These results indicate that NM could be a useful supplement in preventing acute chemical-induced liver toxicity.     

A nutrient mixture prevents acetaminophen hepatic and renal toxicity in ICR mice

Acetaminophen (APAP) overdose is often fatal, leading to fulminant hepatic and renal tubular necrosis in humans and animals. We studied the effect of a nutrient mixture (NM) containing, among other nutrients, lysine, proline, ascorbic acid, N-acetyl cysteine, and green tea extract, which has previously been demonstrated to exhibit a broad spectrum of therapeutic properties on APAP-induced hepatic and renal damage in ICR (Imprinting Control Region) mice. Seven-week-old male ICR mice were divided into four groups (A-D) of five animals each. Groups A and C mice were fed a regular diet for 2 weeks, while groups B and D mice were supplemented with 0.5% NM (w/w) during that period. Groups A and B received saline i.p., while groups C and D received APAP (600 mg/kg) i.p. All animals were killed 24 h after APAP administration, serum was collected to assess the liver and kidney functions, and the livers and kidneys were excised for histology. Mean serum aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase, BUN (Blood Urea Nitrogen), creatinine, and BUN/creatinine ratios were comparable in groups A and B, increased markedly in group C and significantly lower in group D compared with group C. APAP caused significant centrilobular necrosis and glomerular damage in unsupplemented animals, while NM prevented these alterations. The results indicate that NM has potential to protect against APAP-induced liver and kidney damage.     

Pulmonary toxicity,hepatic, and extrahepatic metabolism of 2-methylnaphthalene in mice

Male mice ($\text{C57BL}\text{6J}$) were injected once ip with 0.1, 1, 100, 200, 400, 600, 800, or 1000 mg/kg of 2-methylnaphthalene dissolved in corn oil. After 24 hr, the animals were killed and the lungs, livers, and kidneys were prepared for light microscopy. In addition, some lungs were subjected to scanning and transmission electron microscopy. A dose of 200 mg/kg produced a bronchiolar necrosis which affected the nonciliated bronchiolar (Clara) cell; the parenchymal cells remained unaffected. At higher doses of 2-methylnaphthalene (800 mg/kg), in addition to the damaged Clara cell, severe damage to the upper respiratory tract was noted. No liver or kidney pathology was detected by light microscopy in animals treated with the highest dose. No cellular damage was noted in any organ at doses less than 200 mg/kg. Forty-eight hours after a dose of 200–1000 mg/kg of 2-methylnaphthalene, less pulmonary damage was detected by light microscopy. The metabolism of 2-methylnaphthalene was investigated in hepatic, pulmonary, and renal microsomes from $\text{C57BL}\text{6J}$ mice. Lung and liver microsomes produced three isomeric dihydrodiols of 2-methylnaphthalene as well as other monohydroxylated metabolites. Only trace amounts of these metabolites were produced by the kidney.     

Protection against mercury-induced renal damage in Swiss albino mice by Ocimum sanctum

Mercury is being widely used in the industry, medical, agriculture and other fields. However, mercury deposition affects the nervous, cardiovascular, pulmonary, gastrointestinal and renal systems, as well as the embryo. In most animals' species, including man, the kidney is one of the main sites of deposition of inorganic mercury and target organ for its toxicity. The present investigation reports protection against mercury-induced toxicity by Ocimum sanctum (a traditional sacred medicinal plant, family: Labiatae). Swiss albino mice were divided into four groups. (i) Control group-only vehicle (0.9% NaCl) was given (ii) HgCl(2)-treated group-5.0mg/kg b.w. HgCl(2) administered as i.p. (iii) Ocimum treated group-10mg/kg b.w. Ocimum leaves extract was administered orally. (iv) Combination group-Ocimum leaves extract was administered 10 days prior to mercuric chloride administration and continued upto 30 days after mercuric chloride administration (5.0mg/kg b.w.). The animals were autopsied on day 1, 3, 7, 15 and 30 after treatment. Activity of alkaline phosphatase (ALP), acid phosphatase (ACP), lactate dehydrogenase (LDH) and lipid peroxidation (LPO) were measured in kidney homogenates. The results indicated that there was a significant increase in LPO content, ACP activity and decrease in LDH and ALP activity after HgCl(2) treatment. The animals treated with Ocimum alone did not show any significant alterations in ACP and ALP activity. However, a significant increase in LDH activity and decrease in LPO level was observed. In combined treatment of Ocimum with HgCl(2), a significant decrease in LPO content and ACP and elevation in LDH and ALP activity was observed as compared to HgCl(2)-treated group. Ocimum extract is also effective in reducing the pathological alterations in the kidney. Thus, the results from the present study suggest that pre-and post-treatment of Ocimum sanctum leaves extract can significantly protect the renal damage against mercuric chloride-induced toxicity.     

Induction of zinc-thionein by estradiol and protective effects on inorganic mercury-induced renal toxicity

The castrated or unoperated male rats received an intravenous injection of HgCl2 at a dose of 0.7 mg/kg of body weight (b.w.) after pretreatment with 30% ethanol or estradiol dissolved in 30% ethanol at a dose of 0.5 mg/kg b.w. subcutaneously twice a day for six consecutive days. Renal total protein, gamma-GTP and K excretion in the rats treated with Hg and estradiol were significantly lower than the corresponding values in the rats treated with Hg alone, suggesting that pretreatment with estradiol ameliorates the renal toxicity of Hg in male rats. Pretreatment with estradiol significantly increased Hg and Hg-thionein(Hg-MT) concentrations in the renal cortex of the animals treated with Hg, though in the liver this agent did increase the Hg-MT without elevation of Hg concentration. Treatment with estradiol alone (0.5 mg/kg, s.c., twice a day, for six consecutive days) significantly increased the zinc-thionein (Zn-MT) concentration in the kidney and liver. Simultaneous treatment with 10(-5) M estradiol and Hg in human amniotic-fluid cells caused a significant increase in the uptake of Hg and the synthesis of Hg-MT, suggesting that estradiol may directly stimulate an accumulation of Hg into the cells and the synthesis of Hg-MT. Together, all of the above findings suggest that pretreatment with estradiol may increase the uptake of Hg, which in turn leads to the increase in the Hg-MT concentration. The induction of Zn-MT by pretreatment with estradiol may account for the protective effect of estradiol on Hg-induced renal toxicity.     

Oxidative stress associated hepatic and renal toxicity induced by ricin in mice.

Ricin a glycoprotein from the Ricinus communis seeds, is known to have diverse toxic effects on cells of different visceral organs. We have studied the hepatotoxicity, nephrotoxicity, and oxidative stress following i.p. administration of ricin (25 microg/kg) in Swiss albino male mice. The results of this study revealed that activities of various enzymes like glutamic pyruvic transaminase (GPT), alkaline phosphatase (ALP), gamma glutamyl transpeptidase (gamma-GT), and lactate dehydrogenase (LDH) were increased in plasma, liver, and kidney tissues indicating damage in liver and kidney. Blood urea level was also increased. However, blood creatinine and bilirubin were not altered. Lipid peroxidation increased to 49 and 25% in hepatic and renal tissue. Total non-protein sulfhydryl content decreased in plasma (12%), hepatic (29%), and renal (16%) tissues. Superoxide dismutase activity decreased significantly in liver (43%) and kidney (37%). The activity of glutatione peroxidase was also decreased. The decrease was more prominent in kidney than liver. A significant increase, 20 to 27% in the activity of catalase was observed in plasma, liver, and kidney. These results indicate that ricin produces hepatoxicity, nephrotoxicity, and oxidative damage at 24 h of post treatment. The hepatotoxicity was more prominent than nephrotoxicity.     

Zinc toxicity to freshwater algae

Studies with natural phytoplankton from Lake Ontario as well as with pure cultures of two green and one diatom freshwater algal species revealed that the International Joint Commission water quality objective of 30 μg Zn/L was toxic to primary productivity and cell multiplication. The toxicity of Zn varied with its anionic forms, with nitrate being the most toxic, followed by chloride, sulphate, and acetate. Experiments with radioactive ⁶⁵Zn indicated that Zn was rapidly taken up by the algae, and incorporated mainly into polysaccharide and nucleic acid fractions. These results indicate that an objective for Zn of 30 μg/L is too high to protect algae in the Great Lakes. Based on our results and other published data, a new objective of 10 μg Zn/L has been recommended to the International Joint Commission.     

Modification of mercury-induced biochemical alterations in blood of Swiss albino mice by Spirulina fusiformis

The present investigation has been undertaken to evaluate the role of Spirulina fusiformis in modifying the mercury-induced biochemical alterations in Swiss albino mice. Animals were divided into four groups: (i) control group - only vehicle (0.9% NaCl/olive oil) was given; (ii) HgCl(2) treated group - 5.0mg/kg b.w. HgCl(2) administered as i.p.; (iii) Spirulina treated group - 800mg/kg b.w. Spirulina extract was administered orally; (iv) combination group -S. fusiformis was administered 10 days before mercuric chloride administration and continued up to 30 days after mercuric chloride administration (5.0mg/kg b.w.). The animals were sacrificed on 1, 3, 7, 15 and 30 days and the activity of serum alkaline and acid phosphatase, serum iron level, serum calcium level, blood lipid peroxidation content and blood glutathione (GSH) level were measured. In the present investigation, mercury intoxication causes significant increase (P<0.001) in calcium level, acid phosphatase and lipid peroxidation content and significant decrease in iron level, alkaline phosphatase and glutathione level. Spirulina pre- and post-treatment with mercury prevented or reduces mercury-induced alterations in terms of calcium level, iron level, acid and alkaline phosphatase activity in serum, and lipid peroxidation and GSH level in blood. Thus from the present investigation, it can be concluded that Spirulina pre- and post-treatment with HgCl(2) significantly modulate or modify mercury-induced biochemical alteration in blood of Swiss albino mice.     

An investigation of the role of vitamin E in the protection of mice against microcystin toxicity

The presence of cyanobacterial toxins in drinking and recreational waters represents a potential public health risk. Microcystin-LR (MC-LR) is a potent cyclic heptapeptide hepatotoxin produced by the blue-green alga Microcystis aeruginosa. Chemoprotectant studies have indicated that membrane-active antioxidants such as vitamin E may offer protection against microcystin toxicity. This study investigated the effect of vitamin E supplementation on microcystin toxicity in mouse liver. Groups of mice were fed vitamin E supplements (8.33 or 33.3 U/mouse/day) for 4 weeks, with intraperitoneal doses of MC-LR extract (70% LD(50)) every 3 days from day 8. The potential benefits of vitamin E were evaluated based on lipid peroxidation, alanine transaminase (ALT), and glutathione S-transferase (GST) levels. Vitamin E supplementation at 33.3 U/mouse/day offered some protection against lipid peroxidation induced by repeated exposure to MC-LR extract and limited both the toxin-induced increase in ALT leakage and decrease in GST activity. Vitamin E supplementation at 66.6 U/mouse/day significantly increased the time to death and reduced the increase in liver percentage body weight induced in mice given a lethal dose challenge of MC-LR extract. Therefore, vitamin E, taken as a dietary supplement, may have a protective effect against chronic exposure to MC-LR.