Strain differences of cadmium-induced hepatotoxicity in Wistar–Imamichi and Fischer 344 rats: involvement of cadmium accumulation

Protective efficacy of naringenin against cadmium-induced redox imbalance in Labeo rohita: an integrated biomarker approach

The protective efficacy of dietary naringenin (NG) has been investigated against the toxicity caused by cadmium chloride (CdCl₂) using biomarkers of oxidative stress in the liver, gills and kidney of Labeo rohita. The fish were exposed to environmentally relevant concentrations of CdCl₂ (0.37 and 0.62 mg/L) and simultaneously orally administered with NG (50 mg/kg bw/day) for 60 days. Tissue (gills, liver and kidney) samples were collected on days 15, 30 and 60 of the experiment and analysed for endogenous antioxidants and oxidative stress biomarkers. CdCl₂ exposure for 15 and 30 days induced the development of adaptive mechanism as demonstrated by the enhanced activities of superoxide dismutase, catalase, glutathione peroxidase and glutathione-S-transferase in all three tissues. However, on the 60th day, CdCl₂-induced oxidative damage was stipulated by a decline in the enzyme activities and reduced glutathione (GSH) content significantly (p < 0.05) below control levels along with enhanced levels of lipid peroxidation. Oral administration of NG in toxicant exposed fish significantly restored the altered levels of antioxidants, oxidative enzymes and lipid peroxidation. Besides, integrated biomarker response (IBR) analysis was applied by combining all the biomarkers to indicate the overall stress response index. IBR analysis confirmed the altered levels of biomarkers, the oxidative stress induced by CdCl₂ exposure and the ameliorative potential of NG. The present study suggested that NG might have protective role against Cd-induced oxidative insult which might be ascribed to the ability of NG to chelate metals and scavenge free radicals.

Protective effect of Antigonon leptopus (Hook et. Arn) in cadmium induced hepatotoxicity and nephrotoxicity in rats

Background

Antigonon leptopus is a medicinal plant its leaves has not been reported for protective effects against cadmium induced hepatorenal toxicity. Cadmium (Cd) is a non-essential toxic metal used in industrial process, causes severe risk to human health with high levels. It is accumulated primarily in liver and kidney.

Methods

Male Wistar albino rats (200-250 g) were divided into 6 groups (n = 6) and had free access to diet and water. Cadmium chloride (5 mg/kg b.w/day) was administered orally for 21 days and methanolic extract of Antigonon leptopus (ALME) was administered to groups of cadmium treated rats at daily doses of 100, 200 and 400 mg/kg b.w;p.o. for 21 days. At the end, liver and kidney markers along with antioxidant parameters are evaluated.

Results

The results indicated that, administration of cadmium significantly (p < 0.05) increased the levels liver enzymes in serum and bilirubin levels, decreases in total proteins and albumin; in addition to the levels of uric acid, urea and creatinine were increased in the serum. Glutathione (GSH) levels and the enzyme catalase activities were significantly(p < 0.05) decreased while lipid peroxidation was increased in hepatic and renal tissues of cadmium treated rats. The pre-administration of ALME at all the three test doses, alleviated hepatorenal toxicity in cadmium treated rats, used Silymarin (100 mg/kg) as standard. Moreover, ALME treatment was able to reverse the histopathological changes in liver and kidney tissues, and increased the red blood cells, hemoglobin content and decreased prothrombin time and white blood cells.

Conclusion

Among all the three test doses, ALME at 200 mg/kg have shown significant antioxidant effect and also exerts beneficial effect against cadmium induced hepatorenal toxicity.

Protective effects of selenium against cadmium induced hematological disturbances, immunosuppressive, oxidative stress and hepatorenal damage in rats

Cadmium is a non-essential toxic metal used in industrial process, causes severe risk to human health. Selenium (Se) is an essential trace mineral of fundamental importance for human health. Selenium has antioxidant enzymes roles and is needed for the proper function of the immune system. In this study, the protective effects of selenium against cadmium intoxication in rats have been investigated by monitoring some selective cytokines (IL-1β, TNF α, IL-6, IL-10 and IFN-γ), antioxidant enzymes reduced glutathione (GSH), superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) and lipid peroxidation malondialdehyde (MDA) as well as some selective biochemical markers of liver and kidney functions. Thirty-two rats were divided into four equal groups; the first group was used as a control. Groups 2-4 were treated with selenium (Se; 0.1mg/kg BW), cadmium (Cd; 40mg/L drinking water) and selenium plus cadmium, respectively. Rats were orally administered their relevant doses daily for 30 days. Blood samples were collected from heart puncture at the end of the experiment (30 days) for complete blood picture (CBC) and serum was separated to evaluate the different immunological parameters and biochemical parameters, as well as liver specimens for Cd and Se estimation. Rats in the Cd treated group have a significantly higher hepatic concentration of Cd than in other treated groups. Results revealed that cadmium significantly increased IL-1β, TNF α, IL-6 and IL-10, beside peripheral neutrophils count, while the IFN-γ and lymphocytes were decreased in rat sera. In addition, GSH level, CAT, SOD and GPx activities were significantly decreased while lipid peroxidation (MDA) was increased. Regarding, liver and renal markers, they were significantly increased in the activities of aminotransferases (AST, ALT), urea and creatinine, while total plasma proteins and albumin were significantly decreased. On the other hand, selenium treated group, showed significantly increased IFN-γ, GSH level, CAT, and GPx activities, as well as lymphocyte count while IL-10 was decreased. Selenium in combination with cadmium, significantly improved the elevation of serum IL-1β, IL-6, TNF α, IL-10 and malondialdehyde in addition to enhancing the antioxidant enzyme activities of GSH, CAT, GPx and SOD. Moreover, selenium has ameliorated the cadmium-induced liver and kidney damage by improving hepatic and renal markers. The results of this investigation demonstrated that selenium has the potential to countermeasure the immunosuppressive as well as hepatic and renal oxidative damage induced by cadmium in rats; selenium has shown promising effects against Cd toxicity.

Strain difference of cadmium-induced testicular toxicity in inbred Wistar-Imamichi and Fischer 344 rats

Previously, we reported that Wistar-Imamichi (WI) rats are highly resistant to cadmium (Cd)-induced lethality and hepatotoxicity compared to Fischer 344 (F344) rats. Since the testes are one of the most sensitive organs to acute Cd toxicity, we examined possible strain-related differences in Cd-induced testicular toxicity between inbred WI and F344 rats. Rats were treated with a single dose of 0.5, 1.0 or 2.0 mg Cd/kg, as CdCl(2), sc and killed 24 h later. Cd at doses of 1.0 and 2.0 mg/kg induced severe testicular hemorrhage, as assessed by pathological and testis hemoglobin content, in F344 rats, but not WI rats. After Cd treatment (2.0 mg/kg), the testicular Cd content was significantly lower in WI rats than in the F344 rats, indicating a toxiokinetic mechanism for the observed strain difference. Thus, the remarkable resistance to Cd-induced testicular toxicity in WI rats is associated, at least in part, with lower testicular accumulation of Cd. When zinc (Zn; 10 mg/kg, sc) was administered in combination with Cd (2.0 mg/kg) to F344 rats, the Cd-induced increase in testicular hemoglobin content, indicative of hemorrhage, was significantly reduced. Similarly, the testicular Cd content was significantly decreased with Zn co-treatment compared to Cd treatment alone. Thus, it can be concluded that the testicular Cd accumulation partly competes with Zn transport systems and that these systems may play an important role in the strain-related differences in Cd-induced testicular toxicity between WI and F344 rats.

Changes in antioxidant status and biochemical parameters after orally cadmium administration in females rats

The research was conducted to investigate the toxic effects of cadmium chloride (CdCl2), administered during gestation period on female Wistar rats. Pregnant rats received CdCl2 (20 mg/l, orally) from Day 6 to Day 19 of pregnancy. Results showed that Cd treatment induced a decrease in body weight gain. The relative liver weight increased significantly, with a marked decrease of glycogen and total lipids content. The administration of Cd induced hepatotoxicity as indicated by elevations in plasma alanine aminotransferase (ALT), aspartate aminotransferase and lactate dehydrogenase (LDH) activities (p < 0.05). Treatment with CdCl2 caused a significant (p < 0.05) increase in glucose. A significant increase was observed in the level of MDA and 8-oxodGuo tissues in the cadmium-exposed group compared to the control group (p < 0.05). Results showed that cadmium given to dams led to an oxidative stress and DNA damage in tissues of pregnant rats.

The hepatoprotective effects of selenium against cadmium toxicity in rats

Exposure to cadmium and other pollutants is a major environmental problem. Cadmium is causing acute liver injury but the mechanism of hepatotoxicity is poorly understood. The present study aimed to assess the possible reasons by which cadmium causes liver toxicity. Furthermore, the protective role of selenium against this toxicity was investigated. The hepatic level of lipid peroxidation (malondialdehyde, MDA), the antioxidant system (reduced glutathione, glutathione peroxidase, and thioredoxin reductase), as well as the levels of different lipid classes and the fatty acids pattern were determined in three groups of rats of 15 each. The first group (control group) received saline solution intraperitoneal (i.p.) daily for 10 days. The second group (cadmium chloride-treated group) received 2 mg/kg body weight cadmium chloride solution i.p. for a period of 10 days. The third group (cadmium chloride/sodium selenite-treated group) received cadmium chloride as in the second group and received i.p. sodium selenite (1 mg/kg body weight) at the first and sixth day of treatment (two separate injections within 10 days). The results showed that cadmium treatment increased the hepatic level of malondialdehyde (MDA) and the mean percent of total saturated fatty acid in all lipid classes, whereas the levels of antioxidant system, the levels of hepatic cholesterol esters, triglycerides, total phospholipids, mono- and polyunsaturated fatty acids in all lipid classes were decreased compared to control rats. These changes resulting from Cd-treatment were prevented due to treatment of rats with selenium since the levels of reduced glutathione, glutathione peroxidase, and thioredoxin reductase were induced in Se/Cd-treated group compared with either Cd-treated or control group. In addition, selenium maintained the low levels of cholesterol esters, triglycerides, total phospholipids, mono- and polyunsaturated fatty acids in all lipid classes caused by cadmium to their normal levels. It is concluded that cadmium-induced oxidative stress by increasing the levels of free radicals and by decreasing antioxidants level. This oxidative stress could be the primary cause of Cd-induced hepatotoxicity. Also, selenium can be used as a protective agent against Cd-toxicity. This study could provide a possible explanation to hepatotoxicity resulting from exposure to cadmium in the environment. In addition, selenium could ameliorate cadmium-induced hepatotoxicity since it reduced MDA levels and increased the activities of antioxidant enzymes in this tissue.

Strain difference of cadmium accumulation by liver slices of inbred Wistar-Imamichi and Fischer 344 rats

Strain difference in the accumulation of cadmium (Cd) by liver slices was examined in inbred Cd-resistant Wistar-Imamichi (WI) and Cd-sensitive Fischer 344 (F344) rats. The accumulation of Cd by liver slices of WI rats was significantly lower than that of F344 rats, suggesting strain-related differences in the transport of Cd into the liver cells of these two rat strains. In addition, a similar strain difference was observed in the accumulation of zinc (Zn) by liver slices from WI and F344 rats. Cd accumulation by F344 liver slices decreased when Zn was added to the medium in combination with Cd. Furthermore, in F344 liver slices, Zn accumulation was significantly decreased when Cd was added to the medium. These results suggest that the accumulation of Cd by the liver is probably mediated, at least in part, by Zn transport systems. However, we found no strain difference in hepatic ZnT3 or ZIP3 transcript levels between WI and F344 rats. Further work is in progress to identify the transporter that causes the strain differences in hepatic Cd accumulation seen with WI and F344 rats.

Impairments of hippocampal synaptic plasticity induced by aggregated beta-amyloid (25–35) are dependent on stimulation-protocol and genetic background

The aggregation of beta-amyloid to plaques in the brain is one of the hallmarks of Alzheimer disease (AD). Numerous studies have tried to elucidate to what degree amyloid peptides play a role in the neurodegenerative developments seen in AD. While most studies report an effect of amyloid on neural activity and cognitive abilities of rodents, there have been many inconsistencies in the results. This study investigated to what degree the different genetic backgrounds affect the outcome of beta-amyloid fragment (25-35) on synaptic plasticity in vivo in the rat hippocampus. Two strains, Wistar and Lister hooded rats, were tested. In addition, the effects of a strong (600 stimuli) and a weak stimulation protocol (100 stimuli) on impairments of LTP were analysed. Furthermore, since the state of amyloid aggregation appears to play a role in the induction of toxic processes, it was tested by dual polarisation interferometry to what degree and at what speed beta-amyloid (25-35) can aggregate in vitro. It was found that 100 nmol beta-amyloid (25-35) injected icv did impair LTP in Wistar rats when using the weak but not the strong stimulation protocol (P < 0.001). One-hundred nano mole of the reverse sequence amyloid (35-25) had no effect. LTP in Lister Hooded rats was not impaired by amyloid at any stimulation protocol. The aggregation studies showed that amyloid (25-35) aggregated within hours, while amyloid (35-25) did not. These results show that the genetic background and the stimulation protocol are important variables that greatly influence the experimental outcome. The fact that amyloid (25-35) aggregated quickly and showed neurophysiological effects, while amyloid (35-25) did not aggregate and did not show any effects indicates that the state of aggregation plays an important role in the physiological effects.

A possible mechanism of resistance to cadmium toxicity in male Long-Evans rats

The susceptibility to cadmium (Cd)-induced toxicity in male Long-Evans (LE) rats was compared with that in male Fischer 344 (Fischer) and Wistar-Imamichi (WI) rats, which are sensitive and resistant, respectively, to Cd toxicity. All rats of the LE and WI strains survived for 7 days after the treatment with a toxic dose of Cd (6.5mg/kg b.w.). However, all rats of the Fischer strain died by the following day. The strong resistance to Cd toxicity in the LE strain was confirmed to be independent of metallothionein synthesis induced by Cd. The hepatic and renal Cd contents after its administration were significantly lower in the LE strain than in the Fischer strain. Furthermore, the hepatic and renal zinc (Zn) contents after its administration were significantly lower in the LE strain than in the Fischer strain. These limited data suggest that the strong resistance to Cd toxicity in male LE rats results from, at least in part, the lower accumulation of the metal in the liver and kidney, in a similar mechanism as the lower Zn accumulation.