Repeated acetaminophen dosing in rats: adaptation of hepatic antioxidant system

PIWI-interacting RNA-23210 protects against acetaminophen-induced liver injury by targeting HNF1A and HNF4A

Acetaminophen (APAP) overdose is one of the leading causes of acute liver failure in the US and other developed countries, the molecular mechanisms of APAP-induced hepatotoxicity remain speculative. PIWI-interacting RNAs (piRNAs), a novel class of small non-coding RNAs, have been identified as epigenetic regulators of transposon silencing, mRNA deadenylation, and elimination. However, the functional role of piRNAs in APAP-induced liver injury remains unclear. In the current study, the piRNA profiles were constructed in HepaRG cells after APAP exposure, and the roles of piR-23210 in regulating nuclear receptors (NRs) expression, metabolizing enzymes expression, and consequently APAP-induced liver injury were systematically investigated. As a result, 57 upregulated piRNAs were identified after APAP exposure, indicating the stress-response characteristic of piRNA molecules. Subsequent in vitro and in vivo experiments proved that piR-23210 is a novel self-protective molecule that targets HNF1A and HNF4A transcripts by interacting with RNA binding protein Nucleolin (NCL), suppresses downstream CYPs (CYP2E1, CYP3A4, and CYP1A2) expression, and protects against APAP-induced liver injury. In conclusion, our findings provided new mechanistic clues revealing potential protective role of a piRNA against the hepatoxicity of APAP.

Mechanistic insights into the protective effect of paracetamol against rotenone-induced Parkinson's disease in rats: Possible role of endocannabinoid system modulation

Parkinson's disease (PD) is a disabling progressive neurodegenerative disease. So far, PD's treatment remains symptomatic with no curative effects. Aside from its blatant analgesic and antipyretic efficacy, recent studies highlighted the endowed neuroprotective potentials of paracetamol (PCM). To this end: the present study investigated: (1) Possible protective role of PCM against rotenone-induced PD-like neurotoxicity in rats, and (2) the mechanisms underlying its neuroprotective actions including cannabinoid receptors' modulation. A dose-response study was conducted using three doses of PCM (25, 50, and 100 mg/kg/day, i.p.) and their effects on body weight changes, spontaneous locomotor activity, rotarod test, tyrosine hydroxylase (TH) and α-synuclein expression, and striatal dopamine (DA) content were evaluated. Results revealed that PCM (100 mg/kg/day, i.p.) halted PD motor impairment, prevented rotenone-induced weight loss, restored normal histological tissue structure, reversed rotenone-induced reduction in TH expression and striatal DA content, and markedly decreased midbrain and striatal α-synuclein expression in rotenone-treated rats. Accordingly, PCM (100 mg/kg/day, i.p.) was selected for further mechanistic investigations, where it ameliorated rotenone-induced oxidative stress, neuro-inflammation, apoptosis, and disturbed cannabinoid receptors' expression. In conclusion, our findings imply a multi-target neuroprotective effect of PCM in PD which could be attributed to its antioxidant, anti-inflammatory and anti-apoptotic activities, in addition to cannabinoid receptors' modulation.

Altered expressions of circulating microRNAs 122 and 192 during antitubercular drug induced liver injury indicating their role as potential biomarkers

Drug induced liver toxicity is a serious health complication leading to high mortality rates and post marketing withdrawal of drugs. Although considered to be the gold standard biomarkers; aspartate aminotransferase, alanine aminotransferase, total bilirubin and alkaline phosphatase have been found to have specificities beyond liver, therefore more specific and predictive markers for the detection of antitubercular drug mediated liver damage are required. Unfortunately, the effectiveness of currently used first line antitubercular drugs namely isoniazid, rifampicin, pyrazinamide is often accompanied with liver injury, impeding the cure of patients. Keeping in view, the prognostic and diagnostic applications of microRNAs in various diseases, we tried to assess the importance of microRNAs 122 and 192 in antitubercular drug associated liver injuries. The study included subjects having tuberculosis of any type with antitubercular drug induced liver injury; naïve or newly diagnosed tuberculosis patients, tuberculosis patients on drugs not having toxicity and healthy controls. Observations from this study revealed that expression levels of miR-122 and miR-192 were significantly decreased in the serum of antitubercular drug induced liver injury patients only. Therefore, these microRNAs or the pathways associated with them can be used as a tool to predict or cure antitubercular drug associated liver injury in future.

Effect of hydro-methanol stem bark extract of Burkea africana on erythrocyte osmotic fragility and haematological parameters in acetaminophen-poisoned rats

Background

Burkea africana is a widely used medicinal plant in folkloric medicine in many developing countries of the world. It is useful in the treatment of various ailments including hepatitis, jaundice, diarrhea, stomach aches, abscesses, oedema, epilepsy, bloody diarrhea, gonorrhea, syphilis, toothaches and poisoning. Nevertheless, there are little or no scientific evidence to substantiate this medicinal claim by traditional healers. Burkea africana stem bark was therefore, investigated for its protective or stabilizing effect on erythrocyte membrane in acetaminophen-treated rats. B. africana stem bark was extracted using 80% methanol. Erythrocyte stabilizing effect was studied using erythrocyte osmotic fragility (EOF) test. Thirty (30) male rats were randomly assigned into five (5) groups of six (6) rats each. Groups 1 and 2 served as normal control and negative control (acetaminophen-treated group) respectively. Groups 3, 4 and 5 were pretreated with methanol stem bark extract of Burkea africana (MSBEBA) at doses of 200, 400 and 600 mg/kg body weight respectively once daily for seven (7) days. Blood samples were collected from the animals in all the groups on the 8 day for evaluation of packed cell volume, haemoglobin, red blood cell, white blood cell counts, and differential white blood cell count as well as erythrocyte osmotic fragility.

Results

The erythrocyte osmotic fragility test showed that there was a significantly (p < 0.05) low percentage hemolysis in the groups pre-treated with the extract when compared with the negative control. The percentage hemolysis was least at 600 mg/kg body weight of the extract. There was also a significant (p < 0.05) increase in the packed cell volume, haemoglobin, red blood cell count at all the doses of the extract used. Neutrophils were significantly (p < 0.05) decreased while lymphocytes were significantly increased in the groups administered MSBEBA 400 and 600 mg/kg body weight.

Conclusion

Methanol stem bark extract of Burkea africana had protective effect on the red blood cells and also improved haematological parameters. This indicates that Burkea africana may be useful in the treatment of disease conditions that results in hemolytic anemia by stabilizing red erythrocyte membranes and enhancing erythropoiesis.

Specificity of transaminase activities in the prediction of drug-induced hepatotoxicity

The activities of the transaminases (aminotransferases) alanine aminotransferase and aspartate aminotransferase in the blood (serum or plasma) are widely used as sensitive markers of possible tissue damage and, in particular for liver toxicity. On the other hand, an increase in transaminase activities is not always accompanied by findings suggestive of hepatotoxicity. Transaminases are some of the key enzymes in the gluconeogenesis and glycolysis pathways and exist in many organs and tissues which have high activities of the gluconeogenesis and glycolysis. The activities of transaminases are altered not only in the liver but also in other organs by modification of gluconeogenesis by nutritional or hormonal factors and this phenomenon leads to alteration of transaminase activity in the blood. Drugs, which are considered to directly or secondarily modify gluconeogenesis through lowering blood glucose levels or activating lipid metabolism, such as α-glucosidase inhibitors and fibrates, slightly increase transaminase activities in the blood but there is little evidence that the phenomenon is related to drug-induced liver injury (DILI). This type of elevations can be called pharmacology-related elevation. The pharmacology-related elevation of transaminase activities sometimes makes it difficult to assess precisely the potential hepatotoxicity of new investigational drugs. Considering the characteristic of transaminases, concomitant use of new biomarkers more specific to hepatic injury is needed in the assessment of DILI both in non-clinical and clinical studies. In this review, we will discuss the specificity of transaminases to DILI and future perspectives for transaminases in the estimation of risk of DILI.

Enhancement of acetaminophen-induced chronic hepatotoxicity in spontaneously diabetic torii (SDT) rats

Some patients encounter hepatotoxicity after repeated acetaminophen (APAP) dosing even at therapeutic doses. In the present study, we focused on the diabetic state as one of the suggested risk factors of drug-induced liver injury in humans and investigated the contribution of accelerated gluconeogenesis to the susceptibility to APAP-induced hepatotoxicity using an animal model of type 2 diabetes patients. Sprague-Dawley (SD) rats and spontaneously diabetic torii (SDT) rats were each given APAP at 0 mg/kg, 300 and 500 mg/kg for 35 days by oral gavage. Plasma and urinary glutathione-related metabolites, liver function parameters, and hepatic glutathione levels were compared between the non-APAP-treated SDT and SD rats and between the APAP-treated SDT and SD rats. Hepatic function parameters were not increased at either dose level in the APAP-treated SD rats, but were increased at both dose levels in the APAP-treated SDT rats. Increases in hepatic glutathione levels attributable to the treatment of APAP were noted only in the APAP-treated SD rats. There were differences in the profiles of plasma and urinary glutathione-related metabolites between the non-APAP-treated SD and SDT rats and the plasma/urinary endogenous metabolite profile after treatment with APAP in the SDT rats indicated that hepatic glutathione synthesis was decreased due to accelerated gluconeogenesis. In conclusion, SDT rats were more sensitive to APAP-induced chronic hepatotoxicity than SD rats and the high susceptibility of SDT rats was considered to be attributable to lowered hepatic glutathione levels induced by accelerated gluconeogenesis.

Serum glutamate dehydrogenase activity enables early detection of liver injury in subjects with underlying muscle impairments

Serum activities of alanine and aspartate aminotransferases (ALT and AST) are used as gold standard biomarkers for the diagnosis of hepatocellular injury. Since ALT and AST lack liver specificity, the diagnosis of the onset of hepatocellular injury in patients with underlying muscle impairments is severely limited. Thus, we evaluated the potential of glutamate dehydrogenase (GLDH) as a liver specific alternative biomarker of hepatocellular injury. In our study, serum GLDH in subjects with Duchene muscular dystrophy (DMD) was equivalent to serum GLDH in age matched healthy subjects, while serum ALT was increased 20-fold in DMD subjects. Furthermore, serum GLDH in 131 subjects with variety of muscle impairments was similar to serum GLDH of healthy subjects while serum ALT corelated with serum creatine kinase, a widely accepted biomarker of muscle impairment. In addition, significant elevations of ALT, AST, and CK were observed in a case of a patient with rhabdomyolysis, while serum GLDH stayed within the normal range until the onset of hypoxia-induced liver injury. In a mouse model of DMD (DMD^mdx), serum GLDH but not serum ALT clearly correlated with the degree of acetaminophen-induced liver injury. Taken together, our data support the utility of serum GLDH as a liver-specific biomarker of liver injury that has a potential to improve diagnosis of hepatocellular injury in patients with underlying muscle impairments. In drug development, GLDH may have utility as a biomarker of drug induced liver injury in clinical trials of new therapies to treat muscle diseases such as DMD.

Silkworm pupa oil attenuates acetaminophen-induced acute liver injury by inhibiting oxidative stress-mediated NF-κB signaling

Acetaminophen (APAP) overdose causes severe hepatotoxicity and acute liver failure. The current study aims to investigate the protection effects of silkworm pupa oil (SPO) against acute hepatic injury in APAP-exposed Kunming mice. Our results showed that the liver index and the levels of serum alanine transaminase (ALT) and aspartate transaminase (AST) in mice subjected to APAP treatment were decreased by SPO. Supplement of SPO also restored hepatic histopathological alterations induced by APAP. The APAP-induced increase in proinflammatory cytokines, including TNF-α, IL-6, and IL-12, was reversed by SPO, which was mediated by the reduction of nuclear factor (NF)-κB p65 expression and the increase in the expression of IκB-α in liver tissue. Moreover, SPO inhibited APAP-triggered oxidative stress by decreasing MDA level and increasing the activities of SOD and GSH-Px. Collectively, SPO attenuated hepatic injury induced by APAP, which attributed to the suppression of oxidative stress-mediated NF-κB signaling. Our findings suggest that SPO supplementation may be potential strategy against acute hepatic injury.

Estimation of potential risk of allyl alcohol induced liver injury in diabetic patients using type 2 diabetes spontaneously diabetic Torii-Leprfa (SDT fatty) rats

In order to estimate the potential risk of chemicals including drug in patients with type 2 diabetes mellitus (T2DM), we investigated allyl alcohol induced liver injury using SD rats and Spontaneously Diabetic Torii-Lepr^fa (SDT fatty) rats as a model for human T2DM. The diabetic state is one of the risk factors for chemically induced liver injury because of lower levels of glutathione for detoxification by conjugation with chemicals and environmental pollutants and their reactive metabolites. Allyl alcohol is metabolized to a highly reactive unsaturated aldehyde, acrolein, which is detoxified by conjugation with glutathione. Therefore, we used allyl alcohol as a model compound. Our investigations showed that SDT fatty rats appropriately mimic the diabetic state in humans. The profiles of glucose metabolism, hepatic function tests and glutathione synthesis in the SDT fatty rats were similar to those in patients with T2DM. Five-week oral dosing with allyl alcohol to the SDT fatty rats revealed that the allyl alcohol induced liver injury was markedly enhanced in the SDT fatty rats when compared with the SD rats and the difference was considered to be due to lower hepatic detoxification of acrolein, the reactive metabolite of allyl alcohol, by depleted hepatic glutathione synthesis. Taking all the results of the present study into consideration, the potential for allyl alcohol to induce liver injury is considered to be higher in diabetic patients than in healthy humans.

Transport Stress Changes Blood Biochemistry, Antioxidant Defense System, and Hepatic HSPs mRNA Expressions of Channel Catfish Ictalurus punctatus

Transport procedures usually cause fish stress. The purpose of this study was to investigate the effect of transport stress on blood biochemical profiles, oxidative stress biomarkers, and hepatic heat shock proteins (HSPs) of channel catfish (Ictalurus punctatus). Fish (body weight 55.57 ± 5.13 g) were randomly distributed to two groups, the control, and the treatment. The control group was kept under the normal culture conditions. The treatment group was exposed to the process of transport (3.5 h). Fish samples were collected before transport, after packing and at 0, 1, 6, 24, 72, and 168 h after transport, respectively. Transport caused a significant increase in the serum concentrations of cortisol, glucose, total cholesterol, and triglyceride, as well as, the activity of aspartate aminotransferase at 0 and 1 h after transport compared with non-transported fish and the basal level. Blood total protein content significantly declined in the transported fish. Total antioxidant capacity (T-AOC), malonaldehyde content, and the activities of both glutathione peroxidase and catalase significantly increased in fish within 6 h after transport. The transported fish exhibited a significant higher level in either the concentration of nitric oxide or the mRNA expressions of both hepatic HSP70 and HSP90. It is concluded that transport triggers stress response of I. punctatus, leading to the obvious change in antioxidant capacity. I. punctatus need to be more care after transport to recover from transport stress.

Effect of geraniol against arecoline induced toxicity in the third instar larvae of transgenic Drosophila melanogaster (hsp70-lacZ) Bg9

In the present study geraniol at the final concentration of 10, 20, 30, and 40 µM was mixed in the diet along with 80 µM of arecoline and the third instar larvae of transgenic Drosophila melanogaster (hsp70-lacZ) Bg⁹ were allowed to feed on it for 24 hrs. After the exposure of 24 hrs the larvae were subjected to ONPG, X-gal, trypan blue exclusion test, oxidative stress markers and apoptotic and comet assays. The exposure of larvae to geraniol showed a dose dependent decrease in the activity of β-galactosidase, tissue damage and oxidative stress markers. A dose dependent decrease in apoptosis and DNA damage was also observed. Molecular docking studies also support the protective role of geraniol against the arecoline induced toxicity. The results suggest that geraniol is potent in reducing the toxicity induced by arecoline in the third instar larvae of transgenic Drosophila melanogaster (hsp70-lacZ) Bg⁹.

The effects of colostrum on some biochemical parameters in the experimental intoxication of rats with paracetamol

In the current study, the possible prophylactic and therapeutic effects of colostrum (COL) on acute organ injury caused by paracetamol (PAR) in rats were evaluated. Within the scope of this study, a 2-month-old male (150-200 g) 70 Wistar Albino rat was used and a total of seven groups were designed. The first group (CNT) was maintained for control purposes. The second group (COL-1) was given COL for 1 day, at a dose of 500 mg/kg at 6-h intervals, and blood and tissue sampling was performed at 24 h. The third group (COL-7) received COL for 7 days, at a dose of 500 mg/kg at 6-h intervals on day 1 and at a daily dose of 500 mg/kg on the following days, and blood and tissue samples were taken at the end of seventh day. The fourth group (PAR-1) was administered with PAR at a dose of 1.0 g/kg bw and was blood and tissue sampled at 24 h. The fifth group (PAR-7) received PAR at a dose of 1.0 g/kg bw on day 1 and was blood and tissue was removed at the end of day 7. The sixth group (PAR+COL-1) was administered with a combination of PAR (1 g/kg bw) and COL (500 mg/kg at 6-h intervals), and blood and tissue samples were collected at 24 h. The seventh group (PAR+COL-7) received 1.0 g/kg bw of PAR on day 1 and was given COL throughout the 7-day study period (at a dose of 500 mg/kg at 6-h intervals on day 1 and at a daily dose of 500 mg/kg on the following days). In the seventh group, blood and tissue samples were taken at the end of seventh day. Alkaline phosphatase (ALP), alanine aminotransferase (ALT), aspartate aminotransferase (AST), blood urea nitrogen (BUN), glucose, creatinine, triglyceride, total bilirubin, total protein and albumin levels/activities were analysed in the serum samples. The malondialdehyde (MDA), nitric oxide (NO), superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GSH-Px) levels/activities, known as oxidative stress parameters, were assayed for tissue homogenates and blood (erythrocytes/plasma); in addition, enzyme activities of GSH S-transferase (GST), cytochrome P4502E1 (CYP2E1), NADH-cytochrome b5 reductase (CYTB5), glucose-6-phosphate dehydrogenase (G6PD), NADPH-cytochrome P450 C reductase (CYTC) and glutathione (GSH) levels/activities defined as drug metabolising parameters were measured in liver homogenates. In result, it was determined that PAR caused significant alterations in some biochemical and lipid peroxidation parameters and the activities/levels of drug metabolising parameters in the liver and that COL normalised some of these parameters and reduced PAR-induced tissue damage.

Multiple microRNAs function as self-protective modules in acetaminophen-induced hepatotoxicity in humans

Acetaminophen (APAP) overdose is the leading cause of acute liver failure. Yet the mechanisms underlying adaptive tolerance toward APAP-induced liver injury are not fully understood. To better understand molecular mechanisms contributing to adaptive tolerance to APAP is an underpinning foundation for APAP-related precision medicine. In the current study, the mRNA and microRNA (miRNA) expression profiles derived from next generation sequencing data for APAP-treated (5 and 10 mM) HepaRG cells and controls were analyzed systematically. Putative miRNAs targeting key dysregulated genes involved in APAP hepatotoxicity were selected using in silico prediction algorithms, un-biased gene ontology, and network analyses. Luciferase reporter assays, RNA electrophoresis mobility shift assays, and miRNA pull-down assays were performed to investigate the role of miRNAs affecting the expression of dysregulated genes. Levels of selected miRNAs were measured in serum samples obtained from children with APAP overdose (58.6-559.4 mg/kg) and from healthy controls. As results, 2758 differentially expressed genes and 47 miRNAs were identified. Four of these miRNAs (hsa-miR-224-5p, hsa-miR-320a, hsa-miR-449a, and hsa-miR-877-5p) suppressed drug metabolizing enzyme (DME) levels involved in APAP-induced liver injury by downregulating HNF1A, HNF4A and NR1I2 expression. Exogenous transfection of these miRNAs into HepaRG cells effectively rescued them from APAP toxicity, as indicated by decreased alanine aminotransferase levels. Importantly, hsa-miR-320a and hsa-miR-877-5p levels were significantly elevated in serum samples obtained from children with APAP overdose compared to health controls. Collectively, these data indicate that hsa-miR-224-5p, hsa-miR-320a, hsa-miR-449a, and hsa-miR-877-5p suppress DME expression involved in APAP-induced hepatotoxicity and they contribute to an adaptive response in hepatocytes.

N-Acetyl cysteine does not prevent liver toxicity from chronic low-dose plus subacute high-dose paracetamol exposure in young or old mice

Paracetamol is an analgesic commonly used by people of all ages, which is well documented to cause severe hepatotoxicity with acute overexposures. The risk of hepatotoxicity from nonacute paracetamol exposures is less extensively studied, and this is the exposure most common in older adults. Evidence on the effectiveness of N-acetyl cysteine (NAC) for nonacute paracetamol exposures, in any age group, is lacking. This study aimed to examine the effect of long-term exposure to therapeutic doses of paracetamol and subacute paracetamol overexposure, in young and old mice, and to investigate whether NAC was effective at preventing paracetamol hepatotoxicity induced by these exposures. Young and old male C57BL/6 mice were fed a paracetamol-containing (1.33 g/kg food) or control diet for 6 weeks. Mice were then dosed orally eight times over 3 days with additional paracetamol (250 mg/kg) or saline, followed by either one or two doses of oral NAC (1200 mg/kg) or saline. Chronic low-dose paracetamol exposure did not cause hepatotoxicity in young or old mice, measured by serum alanine aminotransferase (ALT) elevation, and confirmed by histology and a DNA fragmentation assay. Subacute paracetamol exposure caused significant hepatotoxicity in young and old mice, measured by biochemistry (ALT) and histology. Neither a single nor double dose of NAC protected against this toxicity from subacute paracetamol in young or old mice. This finding has important clinical implications for treating toxicity due to different paracetamol exposure types in patients of all ages, and implies a need to develop new treatments for subacute paracetamol toxicity.

Acetaminophen hepatotoxicity in mice: Effect of age, frailty and exposure type

Acetaminophen is a commonly used analgesic that can cause severe hepatotoxicity in overdose. Despite old age and frailty being associated with extensive and long-term utilization of acetaminophen and a high prevalence of adverse drug reactions, there is limited information on the risks of toxicity from acetaminophen in old age and frailty. This study aimed to assess changes in the risk and mechanisms of hepatotoxicity from acute, chronic and sub-acute acetaminophen exposure with old age and frailty in mice. Young and old male C57BL/6 mice were exposed to either acute (300 mg/kg via oral gavage), chronic (100 mg/kg/day in diet for six weeks) or sub-acute (250 mg/kg, t.i.d., for three days) acetaminophen, or saline control. Pre-dosing mice were scored for the mouse clinical frailty index, and after dosing serum and liver tissue were collected for assessment of toxicity and mechanisms. There were no differences with old age or frailty in the degree of hepatotoxicity induced by acute, chronic or subacute acetaminophen exposure as assessed by serum liver enzymes and histology. Age-related changes in the acetaminophen toxicity pathways included increased liver GSH concentrations, increased NQO1 activity and an increased pro- and anti-inflammatory response to acetaminophen in old age. Frailty-related changes included a negative correlation between frailty index and serum protein, albumin and ALP concentrations for some mouse groups. In conclusion, although there were changes in some pathways that would be expected to influence susceptibility to acetaminophen toxicity, there was no overall increase in acetaminophen hepatotoxicity with old age or frailty in mice.

Bazhen decoction protects against acetaminophen induced acute liver injury by inhibiting oxidative stress, inflammation and apoptosis in mice

Bazhen decoction is a widely used traditional Chinese medicinal decoction, but the scientific validation of its therapeutic potential is lacking. The objective of this study was to investigate corresponding anti-oxidative, anti-inflammatory and anti-apoptosis activities of Bazhen decoction, using acetaminophen-treated mice as a model system. A total of 48 mice were divided into four groups. Group I, negative control, treated with vehicle only. Group II, fed with 500 mg/kg/day Bazhen decoction for 10 continuous days. Group III, received a single dose of 900 mg/kg acetaminophen. Group IV, fed with 500 mg/kg/day Bazhen decoction for 10 continuous days and a single dose of 900 mg/kg acetaminophen 30 min before last Bazhen decoction administration. Bazhen decoction administration significantly decrease acetaminophen-induced serum ALT, AST, ALP, LDH, TNF-α, IL-1β, ROS, TBARS and protein carbonyl group levels, as well as GSH depletion and loss of MMP. Bazhen decoction restore SOD, CAT, GR and GPx activities and depress the expression of pro-inflammatory factors, such as iNOS, COX-2, TNF-α, NF-κB, IL-1β and IL-6, respectively. Moreover, Bazhen decoction down-regulate acetaminophen-induced Bax/Bcl-2 ratio, caspase 3, caspase 8 and caspase 9. These results suggest the anti-oxidative, anti-inflammatory and anti-apoptosis properties of Bazhen decoction towards acetaminophen-induced liver injury in mice.

Effect of acetaminophen exposure in Oncorhynchus mykiss gills and liver: detoxification mechanisms, oxidative defence system and peroxidative damage

The increasing presence of pharmaceutical drugs in nature is cause of concern due to the occurrence of oxidative stress in non-target species. Acetaminophen is widely used in human medicine as an analgesic and antipyretic drug, and it is one of the most sold non-prescription drugs. The present study aimed to assess the toxic effects of acetaminophen (APAP) in Oncorhynchus mykiss following acute and chronic exposures in realistic levels. In order to evaluate the APAP effects in the rainbow trout, gills and liver were analyzed with biochemical biomarkers, such as catalase (CAT), total and selenium-dependent glutathione peroxidase (GPx), glutathione reductase (GRed) and glutathione-S-transferases (GSTs) activity and also lipid peroxidation levels (TBARS). The results obtained in all tests indicate that a significant response of oxidative stress was established, along with the increase of APAP concentrations. The establishment of an oxidative stress scenario occurred with the involvement of all tested biomarkers, sustaining a generalized set of pro-oxidative effects elicited by APAP. Additionally, the occurrence of oxidative damage strongly suggests the impairment of the antioxidant defense mechanism of O. mykiss. It is important to note that the occurrence of oxidative deleterious effects and peroxidative damages occurred for concentrations similar to those already reported for several freshwater ecosystems. The importance of these assumptions is further discussed under the scope of ecological relevance of the assessment of effects caused by pharmaceuticals in non-target organisms.

Perturbation of bile acid homeostasis is an early pathogenesis event of drug induced liver injury in rats

Drug-induced liver injury (DILI) is a significant consideration for drug development. Current preclinical DILI assessment relying on histopathology and clinical chemistry has limitations in sensitivity and discordance with human. To gain insights on DILI pathogenesis and identify potential biomarkers for improved DILI detection, we performed untargeted metabolomic analyses on rats treated with thirteen known hepatotoxins causing various types of DILI: necrosis (acetaminophen, bendazac, cyclosporine A, carbon tetrachloride, ethionine), cholestasis (methapyrilene and naphthylisothiocyanate), steatosis (tetracycline and ticlopidine), and idiosyncratic (carbamazepine, chlorzoxasone, flutamide, and nimesulide) at two doses and two time points. Statistical analysis and pathway mapping of the nearly 1900 metabolites profiled in the plasma, urine, and liver revealed diverse time and dose dependent metabolic cascades leading to DILI by the hepatotoxins. The most consistent change induced by the hepatotoxins, detectable even at the early time point/low dose, was the significant elevations of a panel of bile acids in the plasma and urine, suggesting that DILI impaired hepatic bile acid uptake from the circulation. Furthermore, bile acid amidation in the hepatocytes was altered depending on the severity of the hepatotoxin-induced oxidative stress. The alteration of the bile acids was most evident by the necrosis and cholestasis hepatotoxins, with more subtle effects by the steatosis and idiosyncratic hepatotoxins. Taking together, our data suggest that the perturbation of bile acid homeostasis is an early event of DILI. Upon further validation, selected bile acids in the circulation could be potentially used as sensitive and early DILI preclinical biomarkers.

Evaluation of paracetamol distribution and stability in case of acute intoxication in rats

Effects of different storing conditions on paracetamol concentration in biological samples of acute intoxicated rats were investigated. The stability and distribution of paracetamol was observed in postmortem serum, liver, kidney and brain tissues. The serum samples were stored for 30 days and daily changes were evaluated for paracetamol. A significant difference ( p = 0.05) was noticed on the 30th experimental day. Paracetamol serum levels changed as much as 66.30% and 33.78% for 4°C and −20°C, respectively. The stability of paracetamol in liver stored at −20°C was also evaluated for 30 days. The paracetamol concentration levels taken from liver samples dramatically decreased from 30.36% on the 1st day to 94.97% on the 30th day. The paracetamol distribution in organs was as 2.68 , 1.11 and 0.68 mg/g in liver, kidney and brain samples, respectively. Meaningful difference in paracetamol in serum and liver samples was in observed in 30th day values ( p = 0.05).

Effect of butylated hydroxytoluene (E321) pretreatment versus L-arginine on liver injury after sub-lethal dose of endotoxin administration

Aim of this study was to compare the effects of L-arginine (L-arg) and food-antioxidant butylated hydroxytoluene (BHT) against oxidative stress of Escherichia coli endotoxin (LPS) in liver. Ninety Wistar albino rats were assigned in three groups. Rats received one of the following pre-treatment previous to 5mg/kg LPS intraperitoneally: saline, L-arg (NO donor, 100mg/kg) or BHT (250 mg/kg/day), for 3 days. At second, fourth and sixth hours, plasma nitrite-plus-nitrate, circulating liver enzymes, glutathione levels, superoxide dismutase, glutathione peroxidase activities were measured. The most remarkable liver injury was evident in BHT pre-treated animals at all time points compared to L-arg pre-treated rats. While BHT enhanced superoxide dismutase activities following LPS, glutathione decreased simultaneously compared to L-arg group. Although the risk associated with the use of BHT alone in subthreshold doses appeared to be low, higher risk of liver toxicity should be considered when over-consuming this food additive in endotoxemic settings.

Repeated preexposure or coexposure to arsenic differentially alters acetaminophen-induced oxidative stress in rat kidney

Acetaminophen (AP) is a widely used, cheap, and over-the-counter nonsteroidal anti-inflammatory drug. Its toxicity depends on the cytochrome P-450 (CYP)-mediated oxidation to the toxic metabolite N-acetyl-p-benzoquinoneimine. On the other hand, arsenic, a global groundwater and environmental contaminant of major public health concern, decreases hepatic CYP content and its dependent monoxygenase activities. We hypothesized that arsenic exposure would reduce the AP toxicity. Our aim was to evaluate the effects of repeated preexposure or coexposure to arsenic on the oxidative stress induced by a single or repeated oral administration of AP in rat kidney and its possible relationship with the effects of arsenic on certain antioxidants. Rats were exposed to arsenic through drinking water at 25 ppm for 28 days. The dosages of AP used for a single administration after arsenic preexposure for 28 days were 420 and 1000 mg kg(-1) , while for daily concurrent administration with arsenic for 28 days were 105 and 420 mg kg(-1) body weight. AP increased lipid peroxidation (LPO) in rat kidney where its acute administration caused more LPO than its subacute dosing. Repeated arsenic exposure differentially altered the AP-induced LPO. Arsenic preexposure antagonized LPO induced by the acute AP administration; in contrast, arsenic coexposure aggravated the repeated dose (AP)-mediated LPO. Arsenic-mediated alterations in renal sensitivity to LPO did not appear to be linked to the antioxidants such as reduced glutathione, superoxide dismutase, catalase, glutathione peroxidase, and glutathione reductase; nor could it be related to glutathione-S-transferase activity. The results indicated that repeated arsenic preexposure decreased susceptibility of rat kidney to acute AP-mediated oxidative stress; on the contrary, its coexposure rendered the rat kidney more vulnerable to oxidative stress induced by the repeated dosing of AP.

Comparison of the protective actions of N-acetylcysteine, hypotaurine and taurine against acetaminophen-induced hepatotoxicity in the rat

When used in overdoses, acetaminophen (APAP) is a common cause of morbidity and mortality in humans. At present, N-acetylcysteine (NAC) is the antidote of choice for acetaminophen overdoses. Prompt administration of NAC can prevent the deleterious actions of APAP in the liver. In view of the similarities in antioxidant effects demonstrated by NAC, hypotaurine (HYTAU) and taurine (TAU) in this and other our laboratories, the present study was undertaken to compare these compounds for the ability to attenuate plasma and liver biochemical changes associated with a toxic dose of APAP. For this purpose, fasted male Sprague-Dawley rats, 225-250 g in weight, were intraperitoneally treated with APAP (800 mg/kg), NAC, HYTAU or TAU (2.4 mM/kg) followed 30 min later by APAP, or 50% PEG 400 (the vehicle for APAP). At 6 hr after APAP administration, all animals were sacrificed by decapitation and their blood and livers collected. The plasma fractions were analyzed for indices of liver damage (alanine transaminase, aspartate transaminase, lactate dehydrogenase), levels of malondialdehyde (MDA), reduced (GSH) and oxidized (GSSG) glutathione, and activities of glutathione reductase (GR), glutathione S-transferase (GST) and gamma-glutamylcisteinyl synthetase (GCS). Suitable liver homogenates were analyzed for the same biochemical parameters as the plasma but indices of liver damage. By itself, APAP increased MDA formation and had a significant lowering influence on the levels of GSH and GSSG, the GSH/GSSH ratio, and the activities of GR, GST and GCS both in the plasma and liver. In addition, APAP promoted the leakage of transaminases and lactate dehydrogenase from the liver into the plasma. Without exceptions, a pretreatment with a sulfur-containing compound led to a significant attenuation of the liver injury and the biochemical changes induced by APAP. Within a narrow range of potency differences, HYTAU appeared to be the most protective and TAU the least. The present results suggest that, irrespective of the differences in structural features and in vitro antioxidant properties that may exist among NAC, TAU and HYTAU, these compounds demonstrate equivalent patterns of protection and, to a certain extent, equipotent protective actions against the toxic actions of APAP in the liver when tested in equimolar doses and under the same conditions in an animal model.

Free radical scavenging, antioxidant enzymes and wound healing activities of leaves extracts from Clerodendrum infortunatum L

Three successive extracts of Clerodendrum infortunatum L. leaves have been studied for their potential as antioxidants in 1,1-diphenyl-2-picrylhydrazyl (DPPH) model. The scavenging activity of ethanol extract was found to be high when compared to petroleum ether and chloroform extracts. Hence, it was selected to evaluate the beneficial properties using in vitro and in vivo models. The antioxidant and its protective effects against CCl(4) induced oxidative stress in rats were significantly high. Further, to validate the traditional therapeutic claim, wound healing activity of the plant extracts was also carried out. Among the three extracts tested the petroleum ether and ethanol extracts exhibited a significant response. The presence of high antioxidant and pharmacological properties correlates to the total phenolic contents in the plant Clerodendrum infortunatum L.

A comparative study of the antioxidant properties of two different species of Ocimum of southern Africa on alcohol-induced oxidative stress

The present study investigates the protective effect of methanol extract of Ocimum gratissimum (MOEG) and Ocimum canum (MOEC) from Southern Africa on the oxidative stress induced by alcohol consumption. Male Wistar rats weighing 200-250 g were divided into six groups of six rats each as follows: the normal control group was administered distilled water, the ethanol control was administered ethanol (5 g/kg), and experimental groups EX1 and EX3 were fed ethanol (5 g/kg) plus MOEG and MEOC (100 mg/kg), respectively. Two other experimental groups, EX2 and EX4, were administered MEOG and MEOC (100 mg/kg), respectively, for 30 days. At the end of the experiment, rats were sacrificed, and blood was collected to assay thiobarbituric acid-reactive substances (TBARS), reduced glutathione (GSH), catalase (CAT), superoxide dismutase (SOD), alanine aminotransferase (ALT), aspartate aminotransferase (AST), and vitamins E and C. Results indicated a significant reduction in the levels of TBARS, ALT, and AST and a significant increase in the levels of GSH and vitamins E and C. The level of vitamin E is greater with MOEG treatment, whereas the vitamin C level goes up with MOEC treatment. A marked improvement occurred in the activities of CAT and SOD in groups EX1 and EX3 compared to the levels with group EC. Thus the results indicated a significant protection by these extracts against ethanol-induced hepatotoxicity (P <or= .05). Again the groups that were treated with extracts only (EX2 and EX4) showed low levels of TBARS, ALT, and AST, which clearly indicates the extract had no toxic effects on hepatocytes. Comparison of results for these two Ocimum species showed no significant difference except in the levels of vitamins E and C with two treatments. Thus there is a possibility that O. canum might be participating through vitamin C and O. gratissimum through vitamin E.

Toxicodynamics of subacute co-exposure to groundwater contaminant arsenic and analgesic-antipyretic drug acetaminophen in rats

Arsenic is an environmental contaminant, while acetaminophen is an extensively used nonsteroidal analgesic-antipyretic drug. We evaluated whether subacute co-exposure to arsenic and acetaminophen would produce more toxicity than that caused by exposure to either of the xenobiotics in rats. Toxicity was evaluated through changes in body weight, feed consumption, liver weight and microsomal drug-metabolizing enzymes, lipid peroxidation and antioxidants in liver. Arsenic had no effect on body weight and feed consumption. Acetaminophen-mediated decrease in body weight was attenuated in the co-exposed rats. Acetaminophen alone or its co-administration with arsenic decreased feed consumption. Arsenic reduced acetaminophen-mediated increase in the activities of drug-metabolizing enzymes. The co-exposure caused lesser lipid peroxidation than the individual exposure. Arsenic or acetaminophen given alone depleted GSH and decreased the activities of superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase and glutathione-S-transferase and these effects remained mostly unaffected after co-exposure. The results suggest that co-exposure to arsenic and acetaminophen may be less hazardous than their independent exposure in rats.

Mechanism-based bioanalysis and biomarkers for hepatic chemical stress

Adverse drug reactions, in particular drug-induced hepatotoxicity, represent a major challenge for clinicians and an impediment to safe drug development. Novel blood or urinary biomarkers of chemically-induced hepatic stress also hold great potential to provide information about pathways leading to cell death within tissues. The earlier pre-clinical identification of potential hepatotoxins and non-invasive diagnosis of susceptible patients, prior to overt liver disease is an important goal. Moreover, the identification, validation and qualification of biomarkers that have in vitro, in vivo and clinical transferability can assist bridging studies and accelerate the pace of drug development. Drug-induced chemical stress is a multi-factorial process, the kinetics of the interaction between the hepatotoxin and the cellular macromolecules are crucially important as different biomarkers will appear over time. The sensitivity of the bioanalytical techniques used to detect biological and chemical biomarkers underpins the usefulness of the marker in question. An integrated analysis of the biochemical, molecular and cellular events provides an understanding of biological (host) factors which ultimately determine the balance between xenobiotic detoxification, adaptation and liver injury. The aim of this review is to summarise the potential of novel mechanism-based biomarkers of hepatic stress which provide information to connect the intracellular events (drug metabolism, organelle, cell and whole organ) ultimately leading to tissue damage (apoptosis, necrosis and inflammation). These biomarkers can provide both the means to inform the pharmacologist and chemist with respect to safe drug design, and provide clinicians with valuable tools for patient monitoring.

Acetaminophen protects brain endothelial cells against oxidative stress

Increasing evidence suggests that acetaminophen has unappreciated anti-oxidant and anti-inflammatory properties. Drugs that affect oxidant and inflammatory stress in the brain are of interest because both processes are thought to contribute to the pathogenesis of neurodegenerative disease. The objective of this study is to determine whether acetaminophen affects the response of brain endothelial cells to oxidative stress. Cultured brain endothelial cells are pre-treated with acetaminophen and then exposed to the superoxide-generating compound menadione (25 microM). Cell survival, inflammatory protein expression, and anti-oxidant enzyme activity are measured. Menadione causes a significant (p<0.001) increase in endothelial cell death as well as an increase in RNA and protein levels of tumor necrosis factor alpha, interleukin-1, macrophage inflammatory protein alpha, and RANTES. Menadione also evokes a significant (p<0.001) increase in the activity of the anti-oxidant enzyme superoxide dismutase (SOD). Pre-treatment of endothelial cell cultures with acetaminophen (25-100 microM) increases endothelial cell survival and inhibits menadione-induced expression of inflammatory proteins and SOD activity. In addition, we document, for the first time, that acetaminophen increases expression of the anti-apoptotic protein Bcl2. Suppressing Bcl2 with siRNA blocks the pro-survival effect of acetaminophen. These data show that acetaminophen has anti-oxidant and anti-inflammatory effects on the cerebrovasculature and suggest a heretofore unappreciated therapeutic potential for this drug in neurodegenerative diseases such as Alzheimer's disease that are characterized by oxidant and inflammatory stress.

Proteomic Study of Hepatic Nuclear Extracts in an Adaptive Acetaminophen Tolerance Model

Introduction

Variability in response to acetaminophen (APAP)-induced aseptic inflammation and tolerance to the impending hepatic damage has been described. To understand the mechanism of adaptive tolerance, we investigated the proteomic profiles of crude nuclear lysates in a mouse model. We hypothesized that pretreatment with low doses of APAP prior to a toxic dose results in differential protein expression.

Materials and Methods

Mice (BALB/C) were separated into three groups: the pretreated (PT) group received incremental doses of APAP while the last dose only (LD) and naïve groups were given saline vehicle. A toxic dose of APAP was administered on the seventh day to the PT and LD animals only and all groups were euthanized 3 h postdose. Total protein from crude hepatic nuclear lysates were applied to protein arrays and analyzed by immunoaffinity mass spectrometry.

Results and Discussion

Comparative data analyses of protein peaks revealed a protein that was significantly increased at m/z of 60,030 (p60) in the LD animals vs the other two groups. The closest match for the preliminary identification of the p60 protein based on a Swiss-Prot/TagIdent database search using the approximate isoelectric point and molecular weight information was Ccr4–Not complex subunit-2. This protein is a subunit of a multiprotein complex and serves as a transcriptional suppressor involved in controlling mRNA synthesis and degradation. Preliminary identification was also supported by Western blot analysis using anti-CNOT2 antibody.

Conclusion

Considering the APAP tolerance model, we conclude that toxicogenomic approaches such as nuclear profiling are useful tools in assessing differential expression of transcriptional factors involved in inflammatory response and adaptive tolerance to toxins.

Quantitative rat liver function test by galactose single point method

Summary

The purpose of this study was to investigate the galactose single point (GSP) method, a residual liver function test recently recommended by the US Food and Drug Administration, which can be a useful tool for rat liver function measurement. Rats were treated either with carbon tetrachloride (CCl4) alone (1 mL/kg, intraperitoneally [i.p.]) for one day or with isoniazid (INH) alone (150 mg/kg, i.p.) or (in order to ameliorate the effects of INH) with a combination of INH and bis- p-nitrophenyl phosphate (BNPP) (25 mg/kg, i.p.) for 21 days. Hepatotoxicity was assayed by plasma aspartate aminotransferase (AST) and alanine aminotransferase (ALT) activities and scores of histological activity index-necroinflammation (HAI-NI) of the respective liver specimens. The GSP method in rats was defined by the galactose blood level after 60 min. Significant differences in GSP values were observed between controls and the CCl4-treated rats. After 21 days of treatment, no significant changes in AST and ALT values were observed among the control, INH and INH-BNPP groups. There were significant differences in average GSP values for controls ( P < 0.001) and INH-BNPP ( P < 0.001) compared with INH alone. Highly significant correlations ( P < 0.001) were obtained between GSP and scores of HAI-NI for all the groups. GSP was concluded to be a more sensitive biomarker of INH-induced hepatotoxicity than AST or ALT in the rats. The GSP method has been proved to be a simple and useful tool for the quantitative determination of liver function in rats, which can possibly be extended to other animals.

Recurrent acute liver failure and mitochondriopathy in a case of Wolcott-Rallison syndrome

A 10-year-old Arabic boy of consanguineous parents has suffered eight episodes of acute liver failure with haemolysis triggered by intercurrent febrile illnesses. The first crisis occurred at 9 months of age, after which diabetes mellitus developed. By the age of 6 years, short stature, mild myopathy and later skeletal epiphyseal dysplasia also became evident. His psychosocial development and educational achievements have remained within normal limits. While there were no clear biochemical indicators of a mitochondrial disorder, an almost complete deficiency of complex I of the respiratory chain was demonstrated in liver but not in fibroblast or muscle samples. Molecular analysis of the eukaryotic translation initiation factor 2alpha kinase gene (EIF2AK3) demonstrated a homozygous mutation, compatible with a diagnosis of Wolcott-Rallison syndrome (WRS). This patient's course adds a new perspective to the presentation of WRS caused by mutations in the EIF2AK3 gene linking it to mitochondrial disorders: recoverable and recurrent acute liver failure. The findings also illustrate the diagnostic difficulty of mitochondrial disease as it cannot be excluded by muscle or skin biopsy in patients presenting with liver disease. The case also further complicates the decision-making process for liver transplantation in cases of acute liver failure in the context of a possible mitochondrial disorder. Such patients may be more likely to recover spontaneously if a mitochondrial disorder underlies the liver failure, yet without neurological features liver transplantation remains an option.

Hepatoprotective potential of Aloe barbadensis Mill. against carbon tetrachloride induced hepatotoxicity

Aloe barbadensis Mill. Syn. Aloe vera Tourn. ex Linn.(Liliaceae) has been used in variety of diseases in traditional Indian system of medicine in India and its use for hepatic ailments is also documented. In the present study an attempt has been made to validate its hepatoprotective activity. The shade dried aerial parts of Aloe barbadensis were extracted with petroleum ether (AB-1), chloroform (AB-2) and methanol (AB-3). The plant marc was extracted with distilled water (AB-4). All the extracts were evaluated for hepatoprotective activity on limited test models as hexobarbitone sleep time, zoxazolamine paralysis time and marker biochemical parameters. AB-1 and AB-2 were observed to be devoid of any hepatoprotective activity. Out of two active extracts (AB-3 and AB-4), the most active AB-4 was studied in detail. AB-4 showed significant hepatoprotective activity against CCl4 induced hepatotoxicity as evident by restoration of serum transaminases, alkaline phosphatase, bilirubin and triglycerides. Hepatoprotective potential was confirmed by the restoration of lipid peroxidation, glutathione, glucose-6-phosphatase and microsomal aniline hydroxylase and amidopyrine N-demethylase towards near normal. Histopathology of the liver tissue further supports the biochemical findings confirming the hepatoprotective potential of AB-4. The present study shows that the aqueous extract of Aloe barbadensis is significantly capable of restoring integrity of hepatocytes indicated by improvement in physiological parameters, excretory capacity (BSP retention) of hepatocytes and also by stimulation of bile flow secretion. AB-4 did not show any sign of toxicity up to oral dose of 2 g/kg in mice.

Characterization of resistance to bromobenzene-induced hepatotoxicity by microarray

In our previous study, we demonstrated that the initial hepatic injury caused by bromobenzene (BB) was no longer detected in rats despite subsequent dosing, indicating that the liver acquired resistance to BB-induced hepatotoxicity. In this experiment, microarray analysis was conducted to characterize this resistance. The liver samples for the analysis utilized were obtained from previous experiments where F344 rats were treated intraperitoneally with BB (150 mg/kg). At 24 hr post-dose, hepatic injury was confirmed by monitoring the AST values and then the rats were maintained at the same dosing regimen for an additional 8 days. The gene expression profiles of the BB-treated rat livers were compared with a vehicle-treated group by Affymetrix RG_U34A arrays. As results, a decreased expression level of CYP3A9 and an increased expression level of GST Yc2 and glutathione peroxidase (GPX) were detected. These changes indicated suppression of the phase I reaction and induction of the phase II reaction (glutathione conjugation). Increased expression levels of epoxide hydrolase (EH) and NAD(P)H:quinone oxidoreductase (NQO1) also suggested the involvement of EH- and NQO1-mediated hydrolysis other than glutathione conjugation with resistance in the phase II reaction. Moreover, an increased expression level of abcc3 (multidrug resistance protein 3; Mrp3) was significantly noted. Based on the present findings, it was suggested that Mrp3 in the phase III reaction (drug elimination) contributed to the resistance to BB hepatotoxicity in addition to the suppression of the phase I reaction (metabolic activation) and the induction of the phase II reaction (detoxification). Among them, the factors which contributed most were considered to be the increased GST Yc2 and Mrp3, based on the degree of the gene expression changes.

Protective effect of silymarin on oxidative stress in rat brain

Brain is susceptible to oxidative stress and it is associated with age-related brain dysfunction. Previously, we have pointed out a dramatic decrease of glutathione levels in the rat brain after acetaminophen (APAP) oral administration overdose. Silymarin (SM) is a mixture of bioactive flavonolignans isolated from Silybum marianum (L.) Gaertn., employed usually in the treatment of alcoholic liver disease and as anti-hepatotoxic agent in humans. In this study, we have evaluated the effect of SM on enzymatic and non enzymatic antioxidant defensive systems in rat brain after APAP-induced damage. Male albino Wistar rats were treated with SM (200 mg/kg/die orally) for three days, or with APAP single oral administration (3 g/kg) or with SM (200 mg/kg/die orally) for 3 days and APAP single oral administration (3 g/kg) at third day. Successively the following parameters were measured: reduced and oxidized glutathione (GSH and GSSG), ascorbic acid (AA), enzymatic activity variations of superoxide dismutase (SOD) and malondialdehyde levels (MDA). Our results showed a significant decrease of GSH levels, AA levels and SOD activity and an increase of MDA and GSSG levels after APAP administration. After SM administration GSH and AA significantly increase and SOD activity was significantly enhanced. In the SM+APAP group, GSH values significantly increase and the others parameters remained unchanged respect to control values. These results suggest that SM may to protect the SNC by oxidative damage for its ability to prevent lipid peroxidation and replenishing the GSH levels.

Effect of multiple freeze-thaw cycles of cytoplasm samples on the activity of antioxidant enzymes

INTRODUCTION

In this paper the activity of cytoplasmatic antioxidant enzymes after multiple freeze-thaw cycles of samples of cytoplasm was assayed in order to characterise the limits that would be necessary to impose on experimental design.

METHODS

The activities of antioxidant enzymes in samples of rat liver cytoplasm were evaluated after 1, 2, 3, 4, 5, 10 and 15 freeze-thaw cycles. The activity of antioxidant enzymes was determined by standard methods developed for this purpose.

RESULTS

The most resistant against freeze-thaw stress was catalase; even 15 freeze-thaw cycles did not change its activity. The remaining enzymes tested revealed a significant loss in their activity after 4-5 freeze-thaw cycles. The most sensitive was glutathione S-tranferase; its activity was significantly decreased after 3 thaw cycles.

DISCUSSION

The data presented may be helpful in designing experiments in which assay of antioxidant enzymes is a part.

Investigation of proteomic biomarkers in in vivo hepatotoxicity study of rat liver: toxicity differentiation in hepatotoxicants

We investigated the overall protein expression profiles in the in vivo hepatotoxicity of rats induced by four well-recognized hepatotoxicants. Acetaminophen (APAP), amiodarone (AMD), tetracycline (TC) and carbon tetrachloride (CTC) were administered to male rats by gavages and the liver at 24 hr post-dosing was applied to the proteomic experiment. Blood biochemistry and histopathology were examined to identify specific changes related to the compounds given. Protein expression in the liver was investigated by 2-dimensional gel electrophoresis (2DE), and spots showing a significantly different expression in treated versus control group were excised from gels and identified by Q-Tof mass spectrometer. They were well characterized based on their functions related to the mechanisms of toxicity of the compounds. Among them, we focused on the 8 proteins that were affected by all 4 compounds examined. Proteins related to oxidative stress response such as carbonic anhydrase III (CA3) and 60kDa heat shock protein (HSP60), and energy metabolism such as adenylate kinase 4 (AK4) were found. Moreover, hierarchical clustering analysis using 2D-gel spots information revealed the possibility to differentiate the groups based on their toxicity levels such as severity of liver damage. These results suggested that assessing the effects of hepatotoxicants on protein expression is worth trying to screen candidate compounds at the developmental stage of drugs.

Biophotonic imaging in HO-1.luc transgenic mice: real-time demonstration of gender-specific chloroform induced renal toxicity

The metabolism of luciferin in mice transgenic for luciferase (luc) produces light that may be detected trans vivo by an intensified CCD camera (biophotonics). Thus, the generation of transgenic promoter-luciferase animals for genes regulated by specific toxic processes, coupled with real-time evaluation of site-specific gene expression may provide novel, non-invasive biomarkers which are predictive of developing toxicity in vivo. As part of a programme to evaluate the potential of biophotonics for predictive toxicology we have conducted a series of studies in HO-1.luc transgenic mice. Male and female animals were treated with chloroform (200 mg/kg, p.o., daily for 5 days) and imaged 2 and 6 h after dosing. During a 2-day washout period, female animals were treated daily with testosterone prior to repeat administration of chloroform for a further 5 days. Comparison of the in vivo response of the luciferase reporter with markers of toxicity measured ex vivo (differential gene expression of adaptive antioxidant response genes, clinical chemistry and microscopic examination) confirms the gender-specific difference in chloroform renal toxicity in HO-1.luc transgenic mice and its reversal following androgenisation of females and correlates with the expression of the endogenous haem oxygenase-1 (HO-1) gene. These studies demonstrate the capacity of biophotonics for real-time site-specific gene expression, which may be predictive of developing toxicity.

Applications of cytotoxicity assays and pre-lethal mechanistic assays for assessment of human hepatotoxicity potential

While drug toxicity (especially hepatotoxicity) is the most frequent reason cited for withdrawal of an approved drug, no simple solution exists to adequately predict such adverse events. Simple cytotoxicity assays in HepG2 cells are relatively insensitive to human hepatotoxic drugs in a retrospective analysis of marketed pharmaceuticals. In comparison, a panel of pre-lethal mechanistic cellular assays hold the promise to deliver a more sensitive approach to detect endpoint-specific drug toxicities. The panel of assays covered by this review includes steatosis, cholestasis, phospholipidosis, reactive intermediates, mitochondria membrane function, oxidative stress, and drug interactions. In addition, the use of metabolically competent cells or the introduction of major human hepatocytes in these in vitro studies allow a more complete picture of potential drug side effect. Since inter-individual therapeutic index (TI) may differ from patient to patient, the rational use of one or more of these cellular assay and targeted in vivo exposure data may allow pharmaceutical scientists to select drug candidates with a higher TI potential in the drug discovery phase.

Idiosyncratic toxicity: the role of toxicophores and bioactivation

Drugs and chemicals can undergo enzyme-catalyzed bioactivation reactions within cellular systems, with the formation of reactive chemical species. These reactive metabolites can lead to thiol depletion, reversible protein modification (glutathionylation and nitration), further irreversible protein adduct formation and subsequent irreversible protein damage. The incorporation of potentially reactive chemical moieties - toxicophores - within new therapeutic agents should be limited. However, this cannot always be prevented, particularly when the structural feature responsible for toxicity is also responsible for the pharmacological efficacy. The identification and further knowledge of critical levels of thiol depletion and/or covalent modification of protein will aid in the development of new drugs. Importantly, the identification of drug-thiol conjugation should provide a warning of potential problems, yet not hinder the development of a potentially therapeutically useful drug.

Antioxidants protect primary rat hepatocyte cultures against acetaminophen-induced DNA strand breaks but not against acetaminophen-induced cytotoxicity

Acetaminophen, a safe analgesic when dosed properly but hepatotoxic at overdoses, has been reported to induce DNA strand breaks but it is unclear whether this event preceeds hepatocyte toxicity or is only obvious in case of overt cytotoxicity. Moreover, it is not known whether the formation of reactive oxygen species (ROS) is involved in the formation of the DNA strand breaks. In the present study, the dose-response curves for cytotoxicity and DNA strand breaks and the response to antioxidant protection have been compared. In primary hepatocytes from untreated male rats, cytotoxicity as measured by the MTT test and by Neutral Red accumulation was obvious at 10 mM acetaminophen but DNA strand breaks as measured by the comet assay were only found at 25-30 mM acetaminophen. Non-cytotoxic concentrations of three compounds with antioxidant activity, the glutathione precursor N-acetylcysteine (100 micro M), the plant polyphenol silibin (25 micro M) and the antioxidant vitamin alpha-tocopherol (50 micro M), were not able to inhibit acetaminophen toxicity at any acetaminophen concentration, while they completely prevented the formation of DNA strand breaks at 25-30 mM acetaminophen. The occurrence of oxidative stress in our experiments was indicated by a slight increase of malondialdehyde formation at 40 mM acetaminophen and by an adaptive increase in catalase mRNA concentration. We conclude that in acetaminophen-treated hepatocytes ROS-independent cell death and ROS-dependent DNA strand breaks occur which appear not to be causally related as judged from their dose dependency and their response to antioxidants.

The impact of therapeutic doses of paracetamol on serum total antioxidant capacity

INTRODUCTION

A link between regular paracetamol intake and asthma in adults has recently been postulated. Detoxification of paracetamol may deplete stores of glutathione, which is one of the major antioxidants present in the lung. A reduced source of glutathione in the lung may lead to increased oxidative damage to the epithelium and hence increased frequency and severity of asthma attacks in susceptible individuals.

AIM OF STUDY

This study aimed to determine whether regular intake of maximum therapeutic doses of paracetamol reduced serum antioxidant capacity in healthy volunteers.

METHODS

Fifteen young healthy volunteers (nine men, six women, mean age 21.3 years, range 19-32) took maximum therapeutic doses of paracetamol (1 g four times a day) for 14 days. On days 0 and 14 blood samples were taken at baseline and hourly for a period of 4 h following ingestion of 1 g paracetamol. Single venous blood samples were collected 1 h after ingestion of 1 g paracetamol on days 4, 7 and 10. Blood samples were analysed for serum paracetamol concentration and total antioxidant capacity.

RESULTS

Mean total antioxidant capacity was significantly reduced over the 3-h post-dosing on both days 0 and 14 (P < 0.01). The results from days 4, 7 and 10 showed a trend towards reduced antioxidant activity over time. On day 14 values were consistently lower compared with the corresponding times on day 0 (P < 0.01 at 0, 1, 3 and 4 h, P < 0.05 at 2 h).

CONCLUSIONS

Chronic ingestion of maximum therapeutic doses of paracetamol depletes serum antioxidant capacity in healthy volunteers in as few as 14 days, possibly by a reduction in glutathione. This may have implications for analgesic use in asthmatic individuals. Further studies are now required to assess the impact of paracetamol on antioxidant defences in the lung.