Possible role of glutathione in prevention of acetaminophen-induced hepatotoxicity enhanced by fish oil in male Wistar rats

Paracetamol-induced nephrotoxicity and oxidative stress in rats: the protective role of Nigella sativa

Context Nigella sativa L. (Ranunculaceae) (NS) is traditionally used to treat many conditions such as inflammation. Objective This study evaluates the effects of NS seeds ethanol extract in paracetamol-induced acute nephrotoxicity in rats. Materials and methods Forty-eight female Wistar Albino rats were divided into eight groups: I = sham; II = sham + 1000 mg/kg NS; III = sham + 140 mg/kg (N-acetyl cysteine) NAC; IV = 2 g/kg paracetamol; V = 2 g/kg paracetamol + 140 mg/kg NAC; VI, VII and VIII = 2 g/kg paracetamol + 250, 500 and 1000 mg/kg NS, respectively. Paracetamol administration (oral) was carried out 1 h after NS and NAC administrations (oral), and all animals were sacrificed 24 h later. Results Paracetamol administration significantly increased serum urea (88.05 U/L) and creatinine (0.80 U/L) when compared with the sham group (49.80 and 0.31 U/L, respectively). However, serum urea level was reduced to 65.60, 56.00 and 54.18 U/L, with 250, 500 and 1000 mg/kg doses of the extract, respectively. Also, serum creatinine level was reduced to 0.64, 0.57 and 0.52 U/L with 250, 500 and 1000 mg/kg doses of the extract, respectively. NS administration increased superoxide dismutase and glutathione, and decreased malondialdehyde levels in the kidneys. Kidney histopathological examinations showed that NS administration antagonized paracetamol-induced kidney pathological damage. Discussion and conclusions The results suggest NS has a significant nephroprotective activity on paracetamol-induced nephrotoxicity. It may be suggested that the antiinflammatory and antioxidant effects of NS ethanolic extract originated from different compounds of its black seeds.

Dietary fish oil aggravates paracetamol-induced liver injury in mice

BACKGROUND

Paracetamol (APAP) hepatotoxicity remains the leading cause of drug-induced liver failure. Fish oil, which contains ω-3 fatty acids, has demonstrated therapeutic efficacy in several models of liver disease. Evidence for its use in APAP intoxication, however, is conflicting. The effects of fish oil supplementation on APAP-induced liver failure were investigated.

METHODS

Ten C57BL6/J mice were fed a diet based on menhaden fish oil (MEN) or soybean oil (SOY) for 3 weeks followed by APAP intoxication. In a second experiment, the prefeeding period was reduced to 5 days. In a third experiment, 10 mice received the study diets for 3 weeks, after which they received chronic, low-dose APAP administration for another 4 weeks. Finally, 10 mice received oral parenteral nutrition supplemented with either intravenous (IV) soybean-based or fish oil-based lipid emulsion for 19 days, followed by APAP intoxication.

RESULTS

The extent of hepatocellular necrosis (3.8 ± 0.2 vs 2.8 ± 0.2; P = .021) and serum alanine aminotransferase values (2807 ± 785 vs 554 ± 141 IU/L; P = .048) were significantly elevated in mice fed a MEN diet compared with SOY-diet fed controls. Long-term, low-dose APAP administration did not lead to liver injury irrespective of study diet. Pretreatment with soybean- or fish oil-based IV lipid emulsions followed by APAP intoxication demonstrated no significant differences in hepatic injury between groups.

CONCLUSION

Within therapeutic ranges, APAP is harmless to the liver irrespective of dietary fat composition. IV use of fish oil did not increase APAP-induced hepatotoxicity, but animals fed a fish oil-based diet were more susceptible, rather than resistant, to APAP-induced hepatotoxicity.

Dietary saturated and monounsaturated fats protect against acute acetaminophen hepatotoxicity by altering fatty acid composition of liver microsomal membrane in rats

Background

Dietary polyunsaturated fats increase liver injury in response to ethanol feeding. We evaluated the effect of dietary corn oil (CO), olive oil (OO), and beef tallow (BT) on fatty acid composition of liver microsomal membrane and acute acetaminophen hepatotoxicity.

Methods

Male Sprague-Dawley rats were fed 15% (wt/wt) CO, OO or BT for 6 weeks. After treatment with acetaminophen (600 mg/kg), samples of plasma and liver were taken for analyses of the fatty acid composition and toxicity.

Results

Treatment with acetaminophen significantly elevated levels of plasma GOT and GPT as well as hepatic TBARS but reduced hepatic GSH levels in CO compared to OO and BT groups. Acetaminophen significantly induced protein expression of cytochrome P450 2E1 in the CO group. In comparison with the CO diet, lower levels of linoleic acid, higher levels of oleic acids and therefore much lower ratios of linoleic to oleic acid were detected in rats fed OO and BT diets.

Conclusions

Dietary OO and BT produces similar liver microsomal fatty acid composition and may account for less severe liver injury after acetaminophen treatment compared to animals fed diets with CO rich in linoleic acid. These findings imply that types of dietary fat may be important in the nutritional management of drug-induced hepatotoxicity.

Chelidonium majus is not hepatotoxic in Wistar rats, in a 4 weeks feeding experiment

AIM OF THE STUDY

Aerial parts of Chelidonium majus L. (Papaveraceae family) are traditionally used in the treatment of gallstones and dyspepsia, however several cases of hepatotoxicity are reported. In this work we evaluated the effects on liver function of a C. majus extract, obtained from the herbal material responsible for one case of hepatotoxicity.

MATERIALS AND METHODS

Experiments were performed in Wistar rats, after oral administration of doses corresponding to 1.5 and 3g/(kg day) of herbal drug, for 2 or 4 weeks. Blood samples were collected to perform biochemical analysis, whereas liver samples were used for histomorphological and immunohistochemical examination along with the determination of oxidative stress parameters.

RESULTS

No significant modification in animal body weight, food consumption, enzyme activities, hepatic histomorphology and MDA formation, at either time or dosage level. Conversely, C. majus induced a slight but significant decrease of GSH levels and SOD activity, especially at the high dose.

CONCLUSIONS

Our study suggests that C. majus, at doses about 50 and 100 times higher than those generally used in humans, does not alter hepatic function. However, the reduction in GSH levels and SOD activity suggests particular attention in use of C. majus or its preparations in situations (pharmacological treatments, physio-pathological conditions, etc.) that can compromise liver function.

Diets with corn oil and/or low protein increase acute acetaminophen hepatotoxicity compared to diets with beef tallow in a rat model

It has been reported that dietary polyunsaturated fats (PUFA) increase liver injury in response to ethanol feeding. We tested the hypothesis that diets rich in linoleic acid (18:2n-6) would affect acute liver injury after acetaminophen injection and that protein restriction might exacerbate the liver injury. We examined effects of feeding diets with either 15% (wt/wt) corn oil or 14% beef tallow and 1% corn oil for six weeks with either 6 or 20 g/100 g protein on acute hepatotoxicity. After the feeding period, liver injury was induced by injecting either with 600 mg/kg body weight acetaminophen suspended in gum arabic-based vehicle, or with vehicle alone during fasting status. Samples of liver and plasma were taken for analyses of hepatic glutathione (GSH) levels and liver-specific enzymes [(Glutamate-pyruvate transaminase (GPT) and glutamate-oxaloacetate transaminase (GOT)], respectively. Whereas GSH level was significantly lower in only group fed 15% corn oil with 6 g/100 g protein among acetaminophen-treated groups, activities of GPT and GOT were significantly elevated in all groups except the one fed beef tallow with 20 g/100 g protein, suggesting low protein might exacerbate drug-induced hepatotoxicity. The feeding regimens changed the ratio of 18:2n-6 to oleic acid (18:1n-9) in total liver lipids approximately five-fold, and produced modest changes in arachidonic acid (20:4n-6). We conclude that diets with high 18:2n-6 promote acetaminophen-induced liver injury compared to diets with more saturated fatty acids (SFA). In addition, protein restriction appeared to exacerbate the liver injury.

Acetaminophen bioactivation by human cytochrome P450 enzymes and animal microsomes

Acetaminophen is a widely used analgesic antipyretic agent. When used at low doses, it is a safe drug, but at higher doses it can cause acute hepatic necrosis in humans and experimental animals. The key mechanism in the hepatotoxicity is cytochrome P450 (CYP)-catalysed formation of the reactive metabolite, N-acetyl-p-benzoquinone imine (NAPQI) that is capable of binding to cellular macromolecules and in that way an LC/MS liquid chromatography/mass spectrometry (LC/MS) method was developed to measure NAPQI formation by trapping it to reduced glutathione. This method was used to determine the bioactivation of acetaminophen at two concentrations: 50 microM therapeutic and 1 mM toxic by using nine human recombinant CYP enzymes: CYP1A1, CYP1A2, CYP2A6, CYP2B6, CYP2C9, CYP2C19, CYP2D6, CYP2E1, and CYP3A4; and with different microsomes from experimental animals. At the toxic concentration the formation of NAPQI-glutathione was highest with CYP3A4 followed by CYP2E1, CYP1A2, and CYP2D6. At the therapeutic concentration, CYP3A4 had also the highest bioactivation capacity. In a comparison of the enzyme kinetics, CYP3A4 was the most efficient CYP with the lowest K(m) value 130 microM (95% confidence interval = 63-210 microM). Dexamethasone-induced rat liver microsomes had the most effective bioactivation capacity at therapeutic and toxic acetaminophen concentrations. This study suggests that CYP3A4 is the major CYP enzyme form catalysing acetaminophen oxidation to NAPQI in human liver.

Effect of dietary fat on selected parameters of toxicity following 1- or 3-month exposure of rats to toluidine isomers

The aim of the study was to investigate the effect of the dietary fat on selected parameters of toluidines toxicity in rats during subchronic exposure. Three isomers of toluidine (ortho, meta, and para) were administered to rats in the diet for 1 and 3 months at levels 40, 80, 160 mg/kg/day in two kinds of diet containing either 4% or 14% fat. All doses of toluidine isomers produced a 1.5- to 9.8-fold increase in methemoglobin (MetHb) level during both treatment periods. A distinct dose-response relationship was observed, especially for o- and m-toluidine; the effect was generally greater in rats fed high-fat diet. Reduced glutathione level in liver was increased in all treated groups, 1.5- to 5.1-fold, irrespective of the kind of diet. An increase in hepatic lipid peroxidation (thiobarbituric acid reactive substances; TBARS), 1.5- to 4.5-fold, was noticed in the majority of the treated groups. Generally, there was no consistent effect of diet except for p-toluidine where the level of hepatic TBARS was lower in rats fed high-fat diet. Blood urea nitrogen (BUN) level in animals treated with all doses of o- and m-toluidine was 1.3- to 5.0-fold higher in comparison with respective controls. No clear relationship between BUN level and the kind of diet was found. No effect of toluidines on the activity of serum aspartate aminotransferase (AST) and sorbitol dehydrogenase (SDH) were observed. In the majority of groups treated for 30 and 90 days the amount of toluidines in 24-h urine was lower in rats fed high-fat diet. Final body weight gain in rats treated with o- and p-toluidine (80 and 160 mg/kg body weight [b.w.]) was lower as compared to controls. In summary the high-fat diet stimulated methemoglobin formation in rats treated with o- and m-toluidine and cause the decrease in the amount of toluidines in 24-h urine. The high content of fat did not affect consistently the other parameters tested.

The effect of food or water deprivation on paracetamol pharmacokinetics in calves

This study investigated the effect of food or water deprivation on the pharmacokinetics of paracetamol in 30 Holstein-Friesian preruminant calves (10 controls, 10 food withheld and 10 water-deprived) aged 24-25 days. Control calves were given paracetamol at 24-25 days and again at 28-29 days of age. In the food withheld and water-deprived calves paracetamol studies were performed before and after 4 days of food or water deprivation. In the control group there were no significant differences in pharmacokinetic parameters for paracetamol in 24-25 and 28-29-day-old calves. Witholding food for 4 days was associated with an increase in the mean residence time (MRT) of paracetamol (P < 0.01). When food was withheld total body clearance (ClB) of paracetamol was significantly decreased (P < 0.05). The volume of distribution (Vss) was not significantly altered. Similarly, water deprivation was associated with a significant increase in MRT and significant decrease in ClB of paracetamol (P < 0.01). The Vss was not significantly altered. Food or water deprivation also influenced the formation of major metabolites (glucuronide and sulphate) of paracetamol. It is concluded that food or water deprivation may impair the elimination drugs that undergo metabolism by UDP-glucuronyltransferase and sulphotransferase in cattle.

Modulation of antioxidant defence system by dietary fat in rats intoxicated with o-toluidine

o-Toluidine was administered to rats in the diet for four weeks at levels approximately 40, 80 and 160 mg/kg b.w. per day. Two types of diet have been used, standard (4% fat) and high fat (14% fat). Activity of antioxidant enzymes, level of glutathione and thiobarbituric acid reactive substances were measured in liver. Glutathione peroxidase was significantly increased in all treated groups while glutathione S-transferase and glutathione reductase were elevated in rats fed high-fat diet. o-Toluidine slightly enhanced catalase activity regardless of the kind of diet. Superoxide dismutase was the only enzyme whose activity was lowered in almost all treated groups. Enzymatic and nonenzymatic microsomal lipid peroxidation was enhanced 2- to 3-fold in both diet groups. Reduced glutathione level in liver was 2.3- to 4.0-fold increased in all treated groups. Our findings indicate that free radical processes can be involved in the toxic effects of o-toluidine and dietary fat can modify the response of some antioxidant enzymes to this compound.

Effects of palm oil on lipid peroxidation, reduced glutathione, glutathione peroxidase, and vitamin A levels in the corpus uteri, cornu uteri and corpus luteum of young and adult female sheep

The aim of the current study was to determine whether a rumen protected palm oil based diet affect malondialdehyde (MDA), glutathione peroxidase (GSH-Px), reduced glutathione (rGSH) and vitamin A levels in the tissues of cornu uteri, corpus uteri and corpus luteum over the barley based isoenergetic and isonitrogenous diet, and whether the response is different between ewes and ewe-lambs. During the breeding season, half of Morkaraman ewes (2-4-year-old, n = 10) and ewe-lambs (7-8-months-old, n = 10) was offered a barley based diet and the other half was offered a protected palm oil based diet for 42 +/- 0.7 days. At the end of the experiment all animals were slaughtered and measurements carried out in the tissues collected. In all animals tested, cornu uteri had the highest MDA levels followed by corpus uteri and corpus luteum (P < 0.01) but no differences were between the tissues observed in GSH-Px and rGSH levels (P > 0.05). Vitamin A levels were, however, higher in corpus luteum than in cornu uteri and corpus uteri (P < 0.05). Corpus uteri MDA levels were not different (P > 0.05) but rGSH levels were higher for the palm oil fed groups (P < 0.05). GSH-Px and rGSH levels were higher for ewe-lambs than ewes (P < 0.05). In conclusion, it appears that MDA, rGSH, GSH-Px, and vitamin A work in a different fashion for corpus uteri, cornu uteri and corpus luteum, and for ewes and ewe-lambs. Dietary palm oil did not significantly affect the parameters studied except higher rGSH levels in corpus uteri. Levels of antioxidatively active substances, such as rGSH and GSH-Px were lower in ewes compared with those in ewe-lambs.

Effects of fish oil and vitamin E on the antioxidant defense system in diet-induced hypercholesterolemic rabbits

This study was designed to investigate the effects of fish oil and vitamin E on the antioxidant defense system in hypercholesterolemic rabbits. A high fat and cholesterol diet, with or without supplement by fish oil and/or a vitamin E supplement, was fed to rabbits for 6 weeks. Compared to the reference diet of regular laboratory rabbit chow, a high fat and cholesterol-enriched diet increased atheroma formation, plasma lipid and peroxide levels, decreased blood glutathione levels, and reduced plasma glutathione reductase, glutathione peroxidase, and catalase activities. Fish oil supplementation significantly reduced atheroma and increased glutathione reductase and glutathione peroxidase activities and blood glutathione levels, but increased plasma lipid peroxide levels. Vitamin E supplementation of the fish oil diet enhanced the beneficial effects by increasing glutathione reductase activity and decreasing peroxide levels. These results indicate that a high fat and cholesterol diet attenuates blood glutathione levels and plasma antioxidant enzyme activities, which may account for some of its atherogenic properties. Consumption of fish oil enhances antioxidative defenses against the oxidative stress imposed by hypercholesterolemia, and vitamin E further enhances these beneficial effects.