Sex-related differences in NADPH-dependent lipid peroxidation induced by cadmium

Male and female rats were dosed once a day for 2 days with injections of 1.5 mg Cd/kg. Formation of thiobarbituric acid reactive substances (TBA-RS) was significantly increased in male rat liver but not in the females. NADPH-dependent lipid peroxidation in vitro in microsomes derived from untreated rat liver was greater in males than in females. Furthermore, addition of cadmium (Cd) to microsomes isolated from male rat liver produced a dose-dependent potentiation of NADPH-dependent lipid peroxidation from low concentrations of Cd. In microsomes derived from females a significant increase in lipid peroxidation was observed only at high Cd concentrations. NADPH-dependent lipid peroxidation enhanced by Cd was greater in the males than in the females. These data suggest that a sex-related difference in the ability of Cd to induce lipid peroxidation in vivo in rat liver appears to be mediated partly through differences in hepatic microsomal NADPH-dependent lipid peroxidation.     

镉所致肾损害与脂质过氧化的实验

每天以２ｍｇ／ｋｇ氯化镉生理盐水溶液给大鼠腹腔注射１５天，结果显示：氯化镉可引起肾功能的改变和脂质过氧化指标ＭＤＡ的升高及ＳＯＤ的下降，说明镉可诱发肾脏的脂质过氧化。亚细胞组分分析表明镉诱导的脂质过氧化主要发生在线粒体及微粒体中。比较脂质过氧化与肾损害出现的时间，可见染镉动物肾皮质及亚细胞组分ＭＤＡ的升高及ＳＯＤ的下降的时间均晚于肾功能异常。可以认为肾脏脂质过氧化并非镉引起肾损害的直接原因     

Effect of cadmium chloride on hepatic lipid peroxidation in mice

Intraperitoneal administration of cadmium chloride to 8-12 weeks old CBA-mice enhanced hepatic lipid peroxidation. A positive correlation between cadmium chloride dose and level of peroxidation was observed in both male and female mice. A sex-related difference in mortality was not observed but at a dose of 25 mumol CdCl2/kg the level of hepatic lipid peroxidation was higher in male mice than in female mice. The hepatic lipid peroxidation was not increased above the control level in 3 weeks old mice, while 6 weeks old mice responded with increased peroxidation as did 8-12 weeks old mice. The mortality after an acute toxic dose of cadmium chloride was the same in the three age groups. Pretreatment of mice with several low intraperitoneal doses of cadmium chloride alleviated cadmium induced mortality and lipid peroxidation. The results demonstrate both age dependency and a protective effect of metallothionein induction on cadmium chloride induced hepatic lipid peroxidation.     

Palm oil induced changes in ocular tissue lipid peroxidation, antioxidant enzymes and ATPases of rabbits in cadmium toxicity

This study determined the effect of supplementing rabbit diet with palm oil (PO) on lipid peroxidation, antioxidant enzymes and ATPases of different sections of the eyes in ocular cadmium toxicity. Twenty male New Zealand rabbits were randomly assigned to 4 groups of 5 rabbits in a study that lasted for 4 weeks. The control was given deionised water as eye drops and the other groups of rabbits were given eye drops of solution of 2mgkg(-1) body wt cadmium (as 3CdSO(4).8H(2)O). One test group was fed with the normal chow alone and the other test groups were fed with the chow fortified with either 5% or 10% palm oil. Ocular treatment of rabbit with cadmium significantly (P<0.05) reduced their weight compared with the control. Feeding the animals with palm oil (PO) improved the weights of the animals and decreased cadmium accumulation in the eye tissues. Lipid peroxidation level was raised by cadmium in the cornea, lens and retina with palm oil supplementation of the animal diet significantly (P<0.05) reducing the level of lipid peroxidation of the retina. Cadmium significantly (P<0.05) reduced antioxidant enzymes and ATPases in the eye tissues compared with the control. Feeding the rabbits with PO significantly (P<0.05) increased the activities of these enzymes in the retina to levels comparable with the control, with the 10% supplementation producing a more pronounced effect. The study shows that PO can alter cadmium accumulation, antioxidant enzymes and ATPases in ways which suggest that it offers protection of the eyes from ocular exposure to cadmium.     

Relation between lipid peroxidation and inflammation in the pulmonary toxicity of cadmium

Lipid peroxidation (LPO), measured as thiobarbituric acid reactive substances (TBARS), was evaluated in lungs of rats 24 h after intraperitoneal injection of 50, 250, and 1000 μg Cd/kg body weight as CdCl₂. In order to gain some insight into possible causative factors responsible for these oxidative phenomena, the redox-active elements iron (Fe) and copper (Cu), and total lung protein content (an indication of pulmonary inflammatory processes) were also measured. Results obtained demonstrate a similar dose-related, non-linear evolution of total lung TBARS and total lung protein as a function of increasing lung Cd concentrations. Standardization of total lung TBARS to lung protein content further resulted in a linear relationship with lung Cd concentrations, thus suggesting a possible cause-effect relationship between these parameters. No statistically significant association was observed between the dose-related evolution of lung TBARS, and iron (Fe) and copper (Cu) after Cd exposure. The results obtained provide support for the possible involvement of inflammatory phenomena as the most likely events responsible for the generation of LPO in lung tissue following acute exposure to Cd salts.     

Brain regional lipid peroxidation and metallothionein levels of developing rats exposed to cadmium and dexamethasone

Cadmium (Cd) is neurotoxic metal which induces histopathological damage and oxidative stress through free radicals over production. Metallothionein (MT) is a protein able to scavenge free radicals and to chelate metals. In this study we describe the lipid peroxidation (LPO) and MT content in the brain of developing rats exposed at Cd 1 mg/kg/day intra peritoneally (i.p.) and dexamethasone (Dx) 2 mg/kg/day (i.p.) alone and combined during 5 days. At those doses, cadmium significantly increases the levels of LPO in parietal cortex, striatum and cerebellum as compared to a control group while, in the hippocampus no modifications in the LPO levels were observed. In the group treated with Cd+Dx, Dx significantly diminished the levels of LPO in parietal cortex, striatum and cerebellum. On the other hand, the MT levels showed a significant increase in all regions of the groups treated with Dx and Cd+Dx as compared with the control group. These results show that Dx treatment prevented the increase in LPO levels associated to Cd exposure, probably through the increase in MT content.     

The role of stimulated lipid peroxidation and impaired calcium sequestration in the enhancement of cocaine induced hepatotoxicity by ethanol

The purpose of this study was to investigate possible mechanism of cocaine-induced hepatotoxicity and its potentiation by ethanol in mice. Ethanol (2 g/kg) and/or cocaine (25 mg/kg) injections were given as binge model (five injections in 3 days). Cocaine administration with or without ethanol caused an increase in lipid peroxidation in liver homogenate and its subcellular fractions. The greatest increases were observed in mitochondrial fraction following cocaine plus ethanol treatment. Also, glutathione (GSH) levels were increased in liver homogenate and its mitochondrial fractions after cocaine and cocaine plus ethanol treatment. Microsomal calcium sequestration was found to decrease in all treatments. These results suggest that increased lipid peroxidation and decreased microsomal calcium sequestration in the liver may play a possible role cocaine-induced hepatotoxicity and its potentiation by ethanol.     

Consequences of cadmium toxicity in rat hepatocytes: Mitochondrial dysfunction and lipid peroxidation

Cadmium (Cd) (10–100 μM) decreased the ATP/ADP ratio and enhanced lipid peroxidation (LPO) (measured as thiobarbituric acid reactants) in incubated rat hepatocytes. Analysis of the subcellular distribution of Cd indicated its preferential attachment to the inner membranes of mitochondria. Incubation of isolated mitochondria with 0.005–0.05 μM Cd resulted in increased formation of formazans from nitroblue tetrazolium salts, indicating enhanced membrane permeability to succinate. These Cd-concentrations also diminished mitochondrial ATP. LPO in mitochondria strongly increased only after Cd-exposures above 1 μM Cd. Similarly, in Cd-treated hepatocytes decreases in ATP/ADP ratios corresponded to increases in LPO stimulation only at 30 and 60 min but not at 15 min of incubation when ATP/ADP ratios were already affected. Moreover, neither hepatocellular ATP/ADP decrease nor mitochondrial formazan formation due to Cd were prevented by (+)-cyanidanol-3, an effective inhibitor of Cd-induced LPO. These data suggest that even low Cd-concentrations in the hepatocyte disturb the integrity of its mitochondrial membranes concomitantly impairing the hepatocellular energy supply. LPO, only observed at higher Cd-concentrations, is not responsible for these adverse Cd-effects.     

Silibinin ameliorates oxidative stress induced aberrant crypt foci and lipid peroxidation in 1, 2 dimethylhydrazine induced rat colon cancer

Pharmacological intervention to reduce CRC mortality entails the use of oral agents that can avert carcinogenesis. Silibinin, a major component of silymarin isolated from Silybum marianum (L.) was found to possess attractive remedial features. An in vivo study was designed to elucidate the effect of silibinin on the formation of 1, 2 dimethylhydrazine (DMH) induced aberrant crypt foci (ACF), tissue lipid peroxidation (LPO) and enzymic antioxidants status during different phases of experimental colon cancer. DMH alone treated rats showed significantly (p < 0.05) increased size and number of ACF, accompanied by decreased LPO and enzymic antioxidant activities. Administration of silibinin to DMH treated rats inhibited mean colonic ACF and multi-crypt AC/foci and also improved the levels of enzymic antioxidants in a time dependent manner. Histologically no obvious sign of neoplasia was observed in silibinin supplemented DMH treated rats during the various stages of carcinogenesis. Our results show that silibinin possesses potent chemopreventive activity against colon carcinogenesis.     

Glutathione depletion, lipid peroxidation and mitochondrial dysfunction are induced by chronic stress in rat brain.

Damage to the mitochondrial electron transport chain has been suggested to be an important factor in the pathogenesis of a range of neurodegenerative disorders. We have previously demonstrated that chronic stress induced an increase in nitric oxide (NO) production via an expression of inducible NO synthase (iNOS) in brain. Since it has been demonstrated that NO regulates mitochondrial function, we sought to study the susceptibility of the mitochondrial respiratory chain complexes to chronic restrain stress exposure in brain cortex. In adult male rats, stress (immobilization for six hours during 21 days) inhibits the activities of the first complexes of the mitochondrial respiratory chain (inhibition of 69% in complex I-III and of 67% in complex II-III), without affecting complex IV activity, ATP production and oxygen consumption. The mitochondrial marker citrate synthase is not significantly affected by stress after 21 days, indicating that at this time the mitochondrial structure is still intact. Moreover, the administration of the preferred inducible nitric oxide synthase (iNOS) inhibitor aminoguanidine (400 mg/kg i.p. daily from days 7 to 21 of stress) protects against the inhibition of the activity of complexes of the mitochondrial respiratory chain as well as prevents NO(x)(-) accumulation, lipid peroxidation and glutathione depletion induced by stress. These results suggest that a sustained overproduction of NO via iNOS is responsible, at least in part, of the inhibition of mitochondrial respiratory chain caused by stress and that this pathway also accounts for the oxidative stress found in this situation.     

Copper-induced lipid peroxidation and hemolysis in whole blood: evidence for a lack of correlation

In order to establish a possible relationship between hemolytic and peroxidant activities of copper ions, lipid peroxidation was studied in plasma and whole blood incubated for 24 h with different concentrations of copper. The lipid peroxidation was investigated by the determination of thiobarbituric acid-reactive species, conjugated dienes and fluorescent lipid chromophores. The copper-induced lipoperoxidation was clearly demonstrated in plasma incubated with high concentrations of copper (12.10(-4) and 20.10(-4) M); in whole blood, all the lipoperoxidation products were increased in the plasma, while the fluorescent lipid chromophores remained unchanged in red cells. With a copper concentration similar to that found in acute copper intoxication (4.10(-4) M) no lipoperoxidation was observed and yet hemolysis occurred, reduced glutathione (GSH) decreased dramatically and methemoglobin (MetHb) increased. From these results, we assume that, despite its prooxidant activity and its capacity to produce lipoperoxidation, it has not been proven that copper ions at pathophysiological concentrations induce hemolysis by an oxidative mechanism.     

Antioxidant enzymes activity and lipid peroxidation in liver and kidney of rats exposed to cadmium and ethanol.

The oxidative status of liver and kidney of rats co-exposed to cadmium (50 mg Cd/l in drinking water) and ethanol (5 g EtOH/kg body weight/24 h, intragastrically) for 12 weeks was studied. The activities of antioxidant enzymes such as superoxide dismutase (SOD) and catalase (CAT) as well as the concentration of malondialdehyde (MDA), as an indicator of lipid peroxidation, were measured in homogenates of the liver and kidney. Concentrations of zinc (Zn), copper (Cu), iron (Fe) and Cd in the serum or blood, and their content in the liver and kidney as well as EtOH concentration in the whole blood were assayed. Daily Cd intake in the Cd and Cd+EtOH groups was similar and ranged from 2.39 to 4.88 mg/kg body weight/24 h and from 2.64 to 4.14 mg/kg body weight/24 h, respectively. After the administration of EtOH alone, the activity of SOD increased in the kidney and decreased in the liver, whereas the activity of CAT decreased in both these organs, and MDA concentration increased in the liver and was unchanged in the kidney. The exposure to 50 mg Cd/l led to a decrease in the activities of SOD in the liver and CAT in the liver and kidney, and an increase in the kidney activity of SOD and MDA concentration in both these organs. In the rats co-exposed to Cd and EtOH, the kidney activity of SOD and the liver concentration of MDA were lower, whereas the kidney activity of CAT was higher compared to the Cd group. The concentration of Fe in the serum and its content in the liver of rats treated with EtOH increased, whereas the concentrations of Zn and Cu in the serum and the content of Zn, Cu and Fe in the kidney and that of Zn and Cu in the liver were unchanged. In the liver and kidney of rats treated with Cd alone, the content of Fe was decreased and that of Zn and Cu was enhanced. After EtOH administration to Cd-exposed rats, a decrease in Cu serum concentration and its liver content and an increase in Fe concentration in the serum and its content in the liver and kidney, compared to the group exposed to Cd alone, were noted. Moreover, EtOH decreased the blood Cd concentration and its accumulation in the liver and kidney of these animals. EtOH alone decreased Cd content in the liver and increased in the kidney, however the whole content of Cd in these organs was unchanged compared with control. The results of this study indicate that despite the ability of Cd and EtOH to induce the oxidative stress the effect in the liver and kidney is not intensified at simultaneous exposure to both substances. The changes in the studied indicators of oxidative stress (SOD, CAT and MDA) observed in the kidney and especially in the liver of the rats co-exposed to Cd and EtOH may result from an independent effect of Cd and/or EtOH and also from their interaction. The interactive effect may involve, among others, changes in Cd accumulation and content of Zn, Cu and Fe in these organs and their concentration in serum. Since the rats treated with Cd and Cd+EtOH had reduced drinking fluids intake that might result in dehydratation, the effect of the both xenobiotics on the oxidative status of the body may be not solely due to Cd and/or EtOH, but also the modyfing influence of accompanying alterations such as reduced water intake and dehydratation. The results of the study allow us to hypothesize that Cd-exposed alcohol misusers are not at enhanced risk of liver and kidney damage due to lipid peroxidation.     

Effects of antioxidant vitamins on glutathione depletion and lipid peroxidation induced by restraint stress in the rat liver

BACKGROUND AND AIM: Stress as a cofactor has been reported to affect the progression and severity of several diseases. The influence of stress on the liver is of interest from the clinical point of view because stress plays a potential role in aggravating liver diseases in general and hepatic inflammation in particular, probably through generation of reactive oxygen species. The present study was undertaken to investigate the potential of the antioxidant vitamins A (retinol), E (tocopherol) and C (ascorbic acid) individually and in combination (vitamin E + C) to modulate restraint stress-induced oxidative changes. These effects were determined by measuring changes in hepatic levels of free radical scavenging enzymes such as superoxide dismutase (SOD), glutathione-S-transferase (GST) and catalase, as well as levels of total glutathione (GSH), malondialdehyde (MDA), aspartate aminotransferase (AST) and alanine aminotransferase (ALT). METHODS: Immobilisation was achieved by placing the animals in wire mesh cages of their size. The rats were orally administered vitamins A, E and C individually and in combination (E + C) prior to and after 6 hours of immobilisation stress exposure. The hepatic levels of SOD, GST, catalase, GSH and MDA were determined by spectrophotometric methods. Liver SOD activity was assayed by monitoring the amount of enzyme required to inhibit autoxidation of pyrogallol by 50%. Hepatic GST was monitored by following the increase in absorbance at 340 nm of CDNB-GSH conjugate generated due to GST catalysis between GSH and CDNB. Catalase activity in liver tissues was determined using peroxidase as the substrate. Lipid peroxidation was measured by determining the level of thiobarbituric acid reactive substances. ALT and AST were determined by commercial kits. RESULTS: Six hours of immobilisation stress caused a decrease in liver levels of SOD (p = 0.001), catalase (p = 0.031), GST (p = 0.021) and GSH (0.013), while levels of MDA (p = 0.0015), AST (p = 0.05) and ALT (p = 0.046) were increased compared with non-stressed control rats. Both pre-vitamin stress and post-vitamin stress treatments either alone or in combination were associated with increased normalisation of these parameters towards control values, with post-vitamin treatment being the more effective of the two. Vitamins E and C individually were found to be more effective in restoring the endogenous antioxidant system than vitamin A. The combined vitamin (E + C) post-stress treatment was found to be effective but not additive in combating hepatic oxidative stress. The beneficial effects of these vitamin treatments were also reflected in reversions of altered AST and ALT levels towards their control values. CONCLUSION: Vitamins E or C alone or in combination can be given as prophylactic/therapeutic supplements for combating scavenging free radicals generated in liver tissue. This approach may reduce oxidative stress caused by diseases such as cirrhosis.     

Cadmium accumulation and subcellular distribution in relation to cadmium chloride induced cytotoxicity in vitro

A bovine kidney cell culture system was used to assess what relationship cadmium (Cd) uptake and subcellular distribution had to cadmium chloride induced cytotoxicity. Twenty-four hour incubation with 0.1–10 μM Cd elicited 0–90% cytotoxicity. Fifty percent cytotoxicity was estimated to result from 0.8 μM Cd. A concentration-related Cd accumulation paralleled the cytotoxicity profile. The time-course for Cd accumulation was linear for the first 6 h of exposure and plateaued by 18 h post-exposure. When the degree of cytotoxicity was compared with the cellular Cd burden at 24 h post-treatment a least-squares linear regression analysis (r = 0.93) indicated a direct relationship. Subcellular distribution studies indicated greater than 90% Cd recovery from the soluble supernatant (105 000 g) at all levels of cytotoxicity studied. Metallothionein sequestered less than 25% of the cellular Cd. As a result of the correlation of the degree of cytotoxicity with the cellular Cd burden and the independence of subcellular distribution from cytotoxicity, a cumulative mechanism of toxicity for Cd in MDBK cells was suggested.     

Effect of cadmium on lipid peroxidation and antioxidant enzymes in undernourished weanling rat brain

The effect of early postnatal cadmium exposure on lipid peroxidation and antioxidant enzymes in undernourished weanling rat brain has been studied. The results suggest that undernutrition makes the weanling rat brain more susceptible to the neurotoxic effects of cadmium. Cadmium at a low dose of 1 mg/kg body weight did not produce any changes in lipid peroxidation and antioxidant enzymes in normal weanling rat brain, but caused a significant increase in lipid peroxidation and markedly decreased the activities of antioxidant enzymes like glutathione peroxidase, superoxide dismutase and catalase when subjected to undernutrition.     

Prevention of cadmium induced lipid peroxidation, depletion of some antioxidative enzymes and glutathione by a series of novel organoselenocyanates

A series of organoselenocyanate compounds 4a–d were synthesized utilizing 1,8-naphthalic anhydride as the building unit. To evaluate the preventive potential of the Se compounds against Cd induced hepatic lipid peroxidation and oxidative stress, female Swiss Albino mice were exposed to Cd (as CdCl₂) during 20 days at a dose of 1 or 2 mg/kg bw given ip and the selenium compounds were given at the dose of 3 mg/kg bw orally in a pretreatment and concomitant treatment schedule. Hepatic lipid peroxidation level was increased significantly by Cd, whereas the glutathione-S-transferase (GST), superoxide dismutase(SOD), reduced glutathione(GSH) and catalase(CAT) levels were decreased. The selenium compounds effectively decreased the hepatic lipid peroxidation level of the animals treated with Cd. The compounds were also effective in restoring the GST, SOD, and GSH as well as CAT level towards normal. Cadmium induced enhanced Serum alanine aminotransferase (ALT) and aspertate aminotransferase (AST) level were also decreased by the selenium compounds. The study evidences the preventive effects of organoselenocyanates 4a–d (Scheme 1) against Cd induced lipid peroxidation and oxidative stress, 4d showing the highest activity.