Paracetamol (acetaminophen)-induced toxicity: molecular and biochemical mechanisms, analogues and protective approaches

Protective effect of 5-HT7 receptor activation against glutamate-induced neurotoxicity in human neuroblastoma SH-SY5Y cells via antioxidative and antiapoptotic pathways

Serotonin exerts anti-inflammatory, antioxidant and antiapoptotic effects through 5-HT7 receptors. The present study determined the role of 5-HT7 receptors in glutamate-induced neurotoxicity by using human SH-SY5Y neuroblastoma cells. The cells were pretreated with different concentrations of 5-HT7 receptor agonist LP44 and antagonist SB269970 for 60 min, followed by treatment with glutamate. Cell proliferation was measured using xCELLigence system. Treatment with all the concentrations of LP44 significantly protected the cells from the toxic effects of glutamate after 24, 48 and 72 h. Although 5-HT7 receptor expression was significantly upregulated in glutamate-treated cells, it was downregulated in LP44-pretreated cells. Furthermore, LP44 treatment significantly decreased malondialdehyde levels and increased superoxide dismutase activities and glutathione levels. Moreover, LP44 treatment significantly decreased tumor necrosis factor alpha (TNF-α) levels and inhibited caspase 3 and caspase 9 mRNA expression. In contrast, SB269970 treatment exerted an insignificant effect on oxidative stress, inflammation and apoptosis. These findings suggest that exogenous stimulation of the 5-HT7 receptors may be protective in glutamate-induced neurotoxicity and that 5-HT7 receptor agonists can be used as therapeutic agents for preventing glutamate-induced neurological disorders.

Effects of hydrogen sulfide on acetaminophen-induced acute renal toxicity in rats

INTRODUCTION AND AIM

Hydrogen sulfide (H₂S) is an endogenously produced gas-structure mediator. It is proposed to have antioxidant, anti-inflammatory and antiapoptotic effects. Acetaminophen (N-acetyl-P-aminophenol; APAP) is an antipyretic and analgesic medication known as paracetamol. When taken at therapeutic doses there are few side-effects, but at high doses APAP can cause clear liver and kidney damage in humans and experimental animals. In this study, the effects of the H₂S donor of sodium hydrosulfide (NaHS) on acute renal toxicity induced by APAP in rats were researched in comparison with N-acetyl cysteine (NAC).

METHOD

Rats were divided into six groups (n = 7) as control. APAP, APAP + NAC, APAP + NaHS 25 µmol/kg, NaHS 50 µmol/kg and NaHS 100 µmol/kg. After oral dose of 2 g/kg APAP, NAC and NaHS were administered via the i.p. route for 7 days. In renal homogenates, KIM-1 (Kidney Injury Molecule-1), NGAL (neutrophil gelatinase-associated lipocalin), TNF-α and TGFβ levels were measured with the ELISA method for tissue injury and inflammation. In renal tissue, oxidative stress levels were identified by spectrophotometric measurement of TAS and TOS. Histopathologic investigation of renal tissue used caspase 3 staining for apoptotic changes, Masson trichrome and H&E staining for variations occurring in glomerular and tubular systems.

RESULTS

NaHS lowered KIM-1, NGAL, TNF-α, TGF-β and TOS levels elevated in renal tissue linked to APAP and increased TAS values. NaHS prevented apoptosis in the kidney and was identified to ensure histologic amelioration in glomerular and tubular structures. NaHS at 50 µmol/kg dose was more effective, with the effect reduced with 100 µmol/kg dose.

CONCLUSION

H₂S shows protective effect against acute renal injury linked to APAP. This protective effect reduces with high doses of H₂S. The anti-inflammatory and antioxidant activity of H₂S may play a role in the renoprotective effect.

Transformation of acetaminophen in natural surface water and the change of aquatic microbes

The kinetics and transformation pathway of acetaminophen (APAP) in natural surface water (one sample from the Yangtze River and three others from different lakes), and the changes of aquatic microbes in surface water were revealed in this study. Both photochemical and microbial reactions contributed to the transformation of APAP under irradiance of 1.0-250 mW/cm². Microbial compositions were significantly different among surface water, and same microbial transformation product (1,4-bezoquinone) was detected as the predominant biotransformation intermediate in four studied surface water, but the lag phase (12-50-h) for the transformation was highly dependent on the aquatic microbial abundance and composition. The lag phase no longer existed with irradiance increased to 5.9 mW/cm². Aquatic microbial abundance and composition were influenced by the presence of APAP and radiation, and the influence extent was dependent on microbial species. The findings demonstrated that the individual contribution of biotic and abiotic process to the overall transformation of APAP and maybe other phenol in surface water varied as the background composition of surface water and the external environment changed, and biotransformation dominated (>73%) the overall transformation of APAP in surface water.

Ameliorative and protective effects of ginger and its main constituents against natural, chemical and radiation-induced toxicities: A comprehensive review

Fatal unintentional poisoning is widespread upon human exposure to toxic agents such as pesticides, heavy metals, environmental pollutants, bacterial and fungal toxins or even some medications and cosmetic products. In this regards, the application of the natural dietary agents as antidotes has engrossed a substantial attention. One of the ancient known traditional medicines and spices with an arsenal of metabolites of several reported health benefits is ginger. This extended literature review serves to demonstrate the protective effects and mechanisms of ginger and its phytochemicals against natural, chemical and radiation-induced toxicities. Collected data obtained from the in-vivo and in-vitro experimental studies in this overview detail the designation of the protective effects to ginger's antioxidant, anti-inflammatory, and anti-apoptotic properties. Ginger's armoury of phytochemicals exerted its protective function via different mechanisms and cell signalling pathways, including Nrf2/ARE, MAPK, NF-ƙB, Wnt/β-catenin, TGF-β1/Smad3, and ERK/CREB. The outcomes of this review could encourage further clinical trials of ginger applications in radiotherapy and chemotherapy regime for cancer treatments or its implementation to counteract the chemical toxicity induced by industrial pollutants, alcohol, smoking or administered drugs.

Protective effect of cinnamon against acetaminophen-mediated cellular damage and apoptosis in renal tissue

Acetaminophen, APAP, is a common over-the-counter drug with antipyretic-analgesic action. When APAP is used in large doses, it causes hepatotoxicity and nephrotoxicity but safe at therapeutic doses. Cinnamon (Cinnamomum zeylanicum) is extensively used in folk medicine due to its high content of natural antioxidants. The current investigation was planned to study the possible ameliorative effect of cinnamon toward induced APAP-apoptosis and cellular damage in renal cells. Four groups (nine rats each) were used; negative control group administrated distilled water for 15 days; positive control APAP group administrated a single dose of APAP (1 g/kg) orally on the last day; APAP+Cin L (200 mg/kg) and APAP+Cin H (400 mg/kg) aqueous extract of cinnamon orally once a day for 15 days. An hour after the last dose of cinnamon, all rats in the third and fourth group were administrated a single dose of APAP (1 g/kg) orally. GC/MS analysis was performed to identify the plant used in the study. APAP markedly increased serum levels of creatinine, BUN, and glucose and decreased levels of albumin and total protein. In addition, APAP could also exert severe alteration in the kidney histopathology along with upregulation of caspase-3 and PCNA. However, pre-treatment with cinnamon ameliorated the APAP-induced cellular alterations and apoptosis, possibly through its high content of antioxidants.

Hepatoprotective Effect of Eriobotrya japonica Leaf Extract and Its Various Fractions against Carbon Tetra Chloride Induced Hepatotoxicity in Rats

Eriobotrya japonica is traditionally used as an antipyretic, digestive, and diuretic agent. Its flowers possess free radical-scavenging, antioxidative, and hepatoprotective effects. We investigated the hepatoprotective potential of E. japonica leaf extract and its various fractions against hepatotoxicity in rats. Liver injury was stimulated by the oral administration of carbon tetrachloride (CCl₄; 2.5 mL/kg b.wt.). Male albino rats (n = 55) were distributed arbitrarily into 11 groups: Group I, normal control group; Group II, CCl₄ (positive control group); Group III, CCl₄ + silymarin; Groups IV and V, CCl₄ + two doses of 250 and 500 mg/kg of the 80% methanolic extract of E. japonica leaves, respectively; Groups VI and VII, CCl₄ + 250 mg/kg and 500 mg/kg of the ethyl acetate fraction, respectively; Groups VIII and IX, CCl₄ + 250 and 500 mg/kg of the butanol fraction, respectively; and Groups X and XI, CCl₄ + 250 and 500 mg/kg of the aqueous fraction of E. Japonica leaves, respectively. CCl₄-treated rats that were given 250 or 500 mg/kg of the methanol extract of E. Japonica leaves, or its ethyl acetate, butanol, or aqueous fractions, had significantly lower levels of biochemical parameters such as alanine aminotransferase, aspartate transaminase, alkaline phosphate, total protein, gamma-glutamyl transferase, and bilirubin levels than those of the CCl₄ positive group. However, the extract and fractions did not significantly affect lipid profiles. Thus, we conclude that Eriobotrya leaf extract and its fractions have a hepatoprotective effect against CCl₄-induced hepatotoxicity in rats.

Therapeutic Potential of Plants and Plant Derived Phytochemicals against Acetaminophen-Induced Liver Injury

Acetaminophen (APAP), which is also known as paracetamol or N-acetyl-p-aminophenol is a safe and potent drug for fever, pain and inflammation when used at its normal therapeutic doses. It is available as over-the-counter drug and used by all the age groups. The overdose results in acute liver failure that often requires liver transplantation. Current clinical therapy for APAP-induced liver toxicity is the administration of N-acetyl-cysteine (NAC), a sulphydryl compound an approved drug which acts by replenishing cellular glutathione (GSH) stores in the liver. Over the past five decades, several studies indicate that the safety and efficacy of herbal extracts or plant derived compounds that are used either as monotherapy or as an adjunct therapy along with conventional medicines for hepatotoxicity have shown favorable responses. Phytochemicals mitigate necrotic cell death and protect against APAP-induced liver toxicityby restoring cellular antioxidant defense system, limiting oxidative stress and subsequently protecting mitochondrial dysfunction and inflammation. Recent experimental evidences indicat that these phytochemicals also regulate differential gene expression to modulate various cellular pathways that are implicated in cellular protection. Therefore, in this review, we highlight the role of the phytochemicals, which are shown to be efficacious in clinically relevant APAP-induced hepatotoxicity experimental models. In this review, we have made comprehensive attempt to delineate the molecular mechanism and the cellular targets that are modulated by the phytochemicals to mediate the cytoprotective effect against APAP-induced hepatotoxicity. In this review, we have also defined the challenges and scope of phytochemicals to be developed as drugs to target APAP-induced hepatotoxicity.

Evaluation of antiproteinuric and hepato-renal protective activities of propolis in paracetamol toxicity in rats

BACKGROUND/OBJECTIVES

Propolis has a rich source of bioactive compounds and has renal and hepatic protective properties. The purpose of this study was to investigate the beneficial effect of hydro-ethanolic extract of propolis against paracetamol-induced liver damage and impairment of kidney function, as well as hematological changes in rats.

MATERIALS AND METHODS

Six groups of rats were used; the first group was served as a control; the second and third groups were treated by propolis extract at a dose of 50 and 100 mg/kg.B.WT. respectively; the fourth group was treated by paracetamol (200 mg/kg.B.WT.); the fifth group was treated by propolis (50 mg/kg.B.WT.) for eight days and then received similar dose of propolis for following seven days with paracetamol at a dose of 200 mg/kg.B.WT. daily for the seven days; and the sixth group was treated with propolis (100 mg/kg.B.WT.) for eight days and then received similar dose of propolis for following seven days with paracetamol at a dose of 200 mg/kg.B.WT. daily for the seven days. All the animals were treated for a period of 15 days. At the end of the experimental period, blood samples were collected for measurement of the liver enzymes, serum albumin, protein and creatinine, blood urea nitrogen, hematological parameters, and urine volume, protein and albumin.

RESULTS

Paracetamol over dose significantly lowered hemoglobin, serum total protein, albumin, and uric acid, while it significantly increased blood creatinine, blood urea nitrogen, alanine aminotransferase, aspartate aminotransferase and lactate dehydrogenase activities, white blood cells, and platelet count as compared to the control. However, these alterations were significantly attenuated by the use of propolis extract and the effect was dose dependent. Interestingly, propolis prevented paracetamol induced proteinuria, low hemoglobin and body weight loss.

CONCLUSIONS

Propolis significantly prevented paracetamol induced renal, hepatic and hematological toxicity and might be useful in the management of liver and renal diseases particularly proteinuria.

Development of a microcomposite with single-walled carbon nanotubes and Nd2O3 for determination of paracetamol in pharmaceutical dosage by adsorptive voltammetry

This study presents for the first time a new composite of carbon paste (CP), single-walled carbon nanotubes (SWCNTs) and Nd₂O₃ (Nd_OX). This versatile composite (Nd_OX-SWCNT/CPE) was applied to the oxidation of paracetamol (PCM). The newly formed surface was characterized by scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The results showed greater conductivity and a higher surface area for the composite than those of the carbon paste alone. Moreover, the anodic peak currents for PCM increased from 1.6 to 3.6 µA with CPE and Nd_OX-SWCNT/CPE, indicating an increase of nearly 51.0% for the anodic peak current. On the other hand, the anodic peak potentials shifted from 0.67 to 0.57 V. The detection limits were 0.05 µmol/L with Nd_OX-SWCNT/CPE and 0.50 µmol/L with SWCNT/CPE. The relative standard deviations (RSDs) were 1.5% (n = 7). The accuracy and interference of the methods were evaluated with a urine chemistry control spiked with known quantities of PCM, uric acid, dopamine, ascorbic acid, caffeine, acetylsalicylic acid, tartrazine, sunset yellow, allure red, rutin, morin and metal ions. Finally, the novelty and usefulness of the composite were evaluated to quantify PCM in pharmaceutical dosage forms such as tablets, powders and syrups for children.

Long-term adverse effects of paracetamol - a review

Paracetamol (acetaminophen) is the most commonly used drug in the world, with a long record of use in acute and chronic pain. In recent years, the benefits of paracetamol use in chronic conditions has been questioned, notably in the areas of osteoarthritis and lower back pain. Over the same period, concerns over the long-term adverse effects of paracetamol use have increased, initially in the field of hypertension, but more recently in other areas as well. The evidence base for the adverse effects of chronic paracetamol use consists of many cohort and observational studies, with few randomized controlled trials, many of which contradict each other, so these studies must be interpreted with caution. Nevertheless, there are some areas where the evidence for harm is more robust, and if a clinician is starting paracetamol with the expectation of chronic use it might be advisable to discuss these side effects with patients beforehand. In particular, an increased risk of gastrointestinal bleeding and a small (~4 mmHg) increase in systolic blood pressure are adverse effects for which the evidence is particularly strong, and which show a degree of dose dependence. As our estimation of the benefits decreases, an accurate assessment of the harms is ever more important. The present review summarizes the current evidence on the harms associated with chronic paracetamol use, focusing on cardiovascular disease, asthma and renal injury, and the effects of in utero exposure.

Formation of a Toxic Quinoneimine Metabolite from Diclofenac: A Quantum Chemical Study

BACKGROUND

Diclofenac is a non-steroidal antiinflammatory drug. It is predominantly metabolized by CYP2C9. 4'-hydroxydiclofenac and its quinoneimine are the metabolites of diclofenac. However, few numbers of serious cases of idiosyncratic hepatotoxicity due to diclofenac metabolism were reported. The formation of the quinoneimine metabolite was found to be responsible for this idiosyncratic toxicity. Quinoneimine is an over-oxidized metabolite of diclofenac.

METHOD

In this work, computational studies were conducted to detail the formation of a quinoneimine metabolite from diclofenac. Further, the idiosyncratic toxicity of quinoneimine due to its reactivity was also investigated by quantum chemical analysis.

RESULTS & CONCLUSION

The results demonstrate the possibility of formation of quinoneimine metabolite due to various factors that are involved in the metabolism of diclofenac. The present study may provide the structural in-sights during the drug development processes to avoid the metabolism directed idiosyncratic toxicity.

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.

Comparison of base-line and chemical-induced transcriptomic responses in HepaRG and RPTEC/TERT1 cells using TempO-Seq

The utilisation of genome-wide transcriptomics has played a pivotal role in advancing the field of toxicology, allowing the mapping of transcriptional signatures to chemical exposures. These activities have uncovered several transcriptionally regulated pathways that can be utilised for assessing the perturbation impact of a chemical and also the identification of toxic mode of action. However, current transcriptomic platforms are not very amenable to high-throughput workflows due to, high cost, complexities in sample preparation and relatively complex bioinformatic analysis. Thus, transcriptomic investigations are usually limited in dose and time dimensions and are, therefore, not optimal for implementation in risk assessment workflows. In this study, we investigated a new cost-effective, transcriptomic assay, TempO-Seq, which alleviates the aforementioned limitations. This technique was evaluated in a 6-compound screen, utilising differentiated kidney (RPTEC/TERT1) and liver (HepaRG) cells and compared to non-transcriptomic label-free sensitive endpoints of chemical-induced disturbances, namely phase contrast morphology, xCELLigence and glycolysis. Non-proliferating cell monolayers were exposed to six sub-lethal concentrations of each compound for 24 h. The results show that utilising a 2839 gene panel, it is possible to discriminate basal tissue-specific signatures, generate dose-response relationships and to discriminate compound-specific and cell type-specific responses. This study also reiterates previous findings that chemical-induced transcriptomic alterations occur prior to cytotoxicity and that transcriptomics provides in depth mechanistic information of the effects of chemicals on cellular transcriptional responses. TempO-Seq is a robust transcriptomic platform that is well suited for in vitro toxicity experiments.

Acetaminophen reduces the protein levels of high affinity amino acid permeases and causes tryptophan depletion

In yeast, toxicity of acetaminophen (APAP), a frequently used analgesic and antipyretic drug, depends on ubiquitin-controlled processes. Previously, we showed a remarkable overlap in toxicity profiles between APAP and tyrosine, and a similarity with drugs like rapamycin and quinine, which induce degradation of the amino acid permease Tat2. Therefore, we investigated in yeast whether APAP reduced the expression levels of amino acid permeases. The protein levels of Tat2, Tat1, Mup1 and Hip1 were reduced, while the expression of the general permease Gap1 was increased, consistent with a nutrient starvation response. Overexpression of Tat1 and Tat2, but not Mup1, Hip1 and Gap1 conferred resistance to APAP. A tryptophan auxotrophic strain trp1Δ was more sensitive to APAP than wild-type and addition of tryptophan completely restored the growth restriction of trp1∆ upon APAP exposure, while tyrosine had an additive effect on APAP toxicity. Furthermore, intracellular aromatic amino acid concentrations were reduced upon APAP exposure. This effect was less prominent in ubiquitin-deficient yeast strains that were APAP resistant and showed a reduced degradation of high affinity amino acid permeases. APAP-induced changes in intracellular amino acid concentrations were also detected in hepatoma HepG2 cells indicating significance for humans.

Inter-individual and inter-organ variability in the bioactivation of paracetamol by human liver and kidney tissues

Paracetamol (PAR) overdose is associated with massive hepatic injury; it may induce kidney toxicity as well. It is essential to measure organ-specific activities of related CYPs for evaluating the overdose cases. Available HPLC-based methods require high amounts of tissue samples. In order to develop liquid chromatography mass spectrometry (LC-MS)-based methods to process small amounts of human tissues, liver and kidney samples were obtained. Individual microsomes were prepared and incubated with PAR (for quantifying bioactivation), with nifedipine (for measuring CYP3A4 activity) and with p-nitrophenol (for measuring CYP2E1 activity). The small amount of tissue microsomes was sufficient to measure both the formation of NAPQI and the activities of CYP enzymes. Although the sample size in group was relatively low, both NAPQI formation and activity of CYP2E1 were significantly higher in males compared to females in kidney. Considerable variations in the metabolic capacity of individuals were observed for both organs.

The Effects of Chronic Iron Overload in Rats with Acute Acetaminophen Overdose

BACKGROUND AND AIMS

Rats are resistant to acetaminophen (APAP) hepatotoxicity. In this study, we evaluated whether by augmentation of the hepatic oxidative stress, through the induction of hepatic iron overload (IO), it will be feasible to overcome the resistance of rats to the toxic effects of APAP.

METHOD

Rats with no or increased hepatic IO.

RESULTS

Providing iron by diet induced hepatocellular IO, while parenteral iron administration induced combined hepatocellular and sinusoidal cell IO. APAP administration to rats with no IO caused an increase in hepatic oxidative stress and a decrease in the hepatic antioxidative markers but no hepatic cell damage. APAP administration to rats with hepatocellular IO further amplified the hepatic oxidative stress but induced only hepatocyte feathery degeneration without any increase in serum aminotransaminases. APAP administration to rats with combined hepatocellular and sinusoidal cell IO caused an unexpected decrease in hepatic oxidative stress and increase in the hepatic antioxidative markers and no hepatic cell damage. No hepatic expression of activated c-jun-N-terminal kinase was detected in any of the rats.

CONCLUSIONS

The hepatic distribution of iron may affect its oxidative/antioxidative milieu. Augmentation of hepatic oxidative stress did not increase the rats' vulnerability to APAP.

Potentiating effect of acetaminophen and carbon tetrachloride-induced hepatotoxicity is mediated by activation of receptor interaction protein in mice

When multiple drugs or chemicals are used in combination, it is important to understand the risk of their interactions and predict potential additive effects. The aim of the current study was to investigate the molecular mechanism(s) accounting for the additive/synergistic effect of combination treatment with acetaminophen (APAP) and carbon tetrachloride (CCl₄). Mice were intraperitoneally administered vehicle or 100 mg/kg (5 mL/kg) APAP and 30 min after vehicle or 15 mg/kg (5 mL/kg) CCl₄. Sixteen hours after treatment, mice from each group were sacrificed and the livers were removed. CCl₄ administration caused slight glycogen depletion; this effect was more pronounced following co-administration of APAP and CCl₄. ATP and NADPH levels showed the same trend as glycogen levels. The levels of receptor interacting protein 1 and 3 increased following combination treatment with APAP and CCl₄. In contrast, levels of the glutamate cysteine ligase catalytic subunit and glutamate cysteine ligase modifier subunits were not significantly affected by combination treatment. APAP and CCl₄ co-administration potentiated the phosphorylation of c-Jun N-terminal kinase and p38 kinases, although phosphorylated activation of extracellular signal-regulated kinase was not changed. Our results suggest that APAP and CCl₄ co-administration potentiates hepatotoxicity in an additive/synergistic manner via receptor interacting protein activation.

Adenosine 5'-monophosphate blocks acetaminophen toxicity by increasing ubiquitination-mediated ASK1 degradation

Acetaminophen (APAP) overdose is the most frequent cause of drug-induced liver failure in the world. Hepatic c-jun NH2-terminal protein kinase (JNK) activation is thought to be a consequence of oxidative stress produced during APAP metabolism. Activation of JNK signals causes hepatocellular damage with necrotic and apoptotic cell death. Here we found that APAP caused a feedback increase in plasma adenosine 5′-monophsphate (5′-AMP). We demonstrated that co-administration of APAP and 5′-AMP significantly ameliorated APAP-induced hepatotoxicity in mice, without influences on APAP metabolism and its analgesic function. The mechanism of protection by 5′-AMP was through inhibiting APAP-induced activation of JNK, and attenuating downstream c-jun and c-fos gene expression. This was triggered by attenuating apoptosis signal-regulated kinase 1(ASK1) methylation and increasing ubiquitination-mediated ASK1 protein degradation. Our findings indicate that replacing the current APAP with a safe and functional APAP/5′-AMP formulation could prevent APAP-induced hepatotoxicity.

Protective effect of an L-type calcium channel blocker, amlodipine, on paracetamol-induced hepatotoxicity in rats

Paracetamol (P), one of the most popular and commonly used analgesic and antipyretic agents, causes hepatotoxicity in overdoses. Amlodipine (AML), an L-type calcium channel blocker, has been shown to have anti-inflammatory activity by reversing the effect of calcium in the inflammation pathogenesis. In this study, the hepatoprotective activity of AML on P-induced hepatotoxicity was evaluated. Thirty male albino Wistar rats were divided into five groups: (1) control, (2) 2 g/kg of P, (3) 2 g/kg of P + 5 mg/kg of AML, (4) 2 g/kg of P + 10 mg/kg of AML, and (5) 10 mg/kg of AML. Some liver enzymes, oxidative parameters, cytokine mRNA expressions, histopathology, and immunohistochemical studies were performed in liver and blood samples. The serum levels of alanine aminotransferase and aspartate aminotransferase and the mRNA expression of tumor necrosis factor-alpha (TNF-α) and transforming growth factor-beta in the liver tissues were significantly increased in the group treated with P. The superoxide dismutase and glutathione parameters decreased and malondialdehyde levels increased in the livers of the rats treated with P. All these parameters were increased with both doses of the AML similar to the control group. A histopathological examination of the liver showed that AML administration ameliorated the P-induced inflammatory liver damage. In immunohistochemical staining, the expression of TNF-α in the cytoplasm of the hepatocytes was increased in the P group but not in other treatment groups when compared to the control. In conclusion, AML treatment showed significant protective effects against P-induced hepatotoxicity by increasing the activity of antioxidants and reducing inflammatory cytokines.

Extrahepatic toxicity of acetaminophen: critical evaluation of the evidence and proposed mechanisms

Research on acetaminophen (APAP) toxicity over the last several decades has focused on the pathophysiology of liver injury, but increasingly attention is paid to other known and possible adverse effects. It has been known for decades that APAP causes acute kidney injury, but confusion exists regarding prevalence, and the mechanisms have not been well investigated. More recently, evidence for pulmonary, endocrine, neurological, and neurodevelopmental toxicity has been reported in a number of published experimental, clinical, and epidemiological studies, but the quality of those studies has varied. It is important to view those data critically due to implications for regulation and clinical practice. Here, we review evidence and proposed mechanisms for extrahepatic adverse effects of APAP and weigh weaknesses and strengths in the available data.

Increased risk of congestive heart failure in patients with acetaminophen poisoning: A nationwide cohort study

Acetaminophen poisoning increases cytochrome P450 2E1 expression and reactive oxygen species production, which may lead to maladaptive myocardial remodeling and congestive heart failure (CHF). We conducted a nationwide cohort study to investigate the incidence and risk of CHF in patients with acetaminophen poisoning. We identified a cohort of adult patients with newly diagnosed acetaminophen poisoning in the inpatient claims of the Taiwan National Health Insurance Research Database for the 1998-2011 period. A comparison cohort was frequency matched at a 4:1 ratio for sex, age and index year. All patients were followed up until the occurrence of CHF, withdrawal from the National Health Insurance program, or December 31, 2011. Cox proportional hazards models were employed to calculate the risk of CHF in the acetaminophen poisoning cohort compared with the comparison cohort, and the hazard ratios with 95% confidence intervals are presented. A total of 3546 and 14 184 patients with and without acetaminophen poisoning were followed up for a total of 25 856 and 102 119 person-years, respectively. The overall incidence of CHF was higher in the acetaminophen poisoning cohort than in the comparison cohort (8.12 vs. 5.19 per 10 000 person-years). After adjustment for covariates, the acetaminophen poisoning cohort exhibited a 1.59-fold higher risk of CHF (adjusted hazard ratio = 1.59; 95% confidence interval = 1.43-1.75) than did the comparison cohort. Patients with acetaminophen poisoning exhibited a significantly higher risk of CHF compared with the comparison cohort. Clinicians should follow up heart function in patients with acetaminophen poisoning.

Acetaminophen Poisoning May Increase Coronary Artery Disease Risk: A Nationwide Cohort Study

The purpose of this nationwide cohort study was to investigate the incidence and risk of coronary artery disease (CAD) in patients with acetaminophen (APAP) poisoning. We identified the patients with APAP poisoning and randomly selected comparison patients according to a 1:4 ratio, matching them by age, sex, and the index year using data from the National Health Insurance Research Database from 2000 to 2010. We traced both cohorts until a diagnosis of CAD, loss to follow-up, or the end of 2011. In total, 2723 patients with APAP poisoning and 10,892 comparison patients have followed. The incidence rate of CAD was higher in the APAP poisoning cohort than in the non-APAP poisoning cohort (1.53 vs 0.87 per 1000 patient-years). The APAP poisoning cohort exhibited a 1.85-fold higher risk of CAD than did the non-APAP poisoning cohort (adjusted hazard ratio [aHR] 1.85; 95% confidence interval [CI] 1.16-2.94). Male sex, advanced age, and hypertension were independently associated with CAD risk. The risk of CAD was considerably higher within 3 years following APAP poisoning (aHR 2.73; 95% CI 1.31-5.69). This study indicated that APAP poisoning may increase risk of CAD development.

Polydatin protects against acetaminophen-induced hepatotoxicity in mice via anti-oxidative and anti-apoptotic activities

Polydatin protects against acetaminophen-induced hepatotoxicity in mice.

EDC IMPACT: Is exposure during pregnancy to acetaminophen/paracetamol disrupting female reproductive development?

Concern has been raised over chemical-induced disruption of ovary development during fetal life resulting in long-lasting consequences only manifesting themselves much later during adulthood. A growing body of evidence suggests that prenatal exposure to the mild analgesic acetaminophen/paracetamol can cause such a scenario. Therefore, in this review, we discuss three recent reports that collectively indicate that prenatal exposure in a period of 13.5 days post coitum in both rats and mouse can result in reduced female reproductive health. The combined data show that the exposure results in the reduction of primordial follicles, irregular menstrual cycle, premature absence of corpus luteum, as well as reduced fertility, resembling premature ovarian insufficiency syndrome in humans that is linked to premature menopause. This could especially affect the Western parts of the world, where the age for childbirth is continuously being increased and acetaminophen is recommended during pregnancy for pain and fever. We therefore highlight an urgent need for more studies to verify these data including both experimental and epidemiological approaches.

Drug toxicity profiling of a Saccharomyces cerevisiae deubiquitinase deletion panel shows that acetaminophen mimics tyrosine

Post-translational protein modification by addition or removal of the small polypeptide ubiquitin is involved in a range of critical cellular processes, like proteasomal protein degradation, DNA repair, gene expression, internalization of membrane proteins, and drug sensitivity. We recently identified genes important for acetaminophen (APAP) toxicity in a comprehensive screen and our findings suggested that a small set of yeast strains carrying deletions of ubiquitin-related genes can be informative for drug toxicity profiling. In yeast, approximately 20 different deubiquitinating enzymes (DUBs) have been identified, of which only one is essential for viability. We investigated whether the toxicity profile of DUB deletion yeast strains would be informative about the toxicological mode of action of APAP. A set of DUB deletion strains was tested for sensitivity and resistance to a diverse series of compounds, including APAP, quinine, ibuprofen, rapamycin, cycloheximide, cadmium, peroxide and amino acids and a cluster analysis was performed. Most DUB deletion strains showed an altered growth pattern when exposed to these compounds by being either more sensitive or more resistant than WT. Toxicity profiling of the DUB strains revealed a remarkable overlap between the amino acid tyrosine and acetaminophen (APAP), but not its stereoisomer AMAP. Furthermore, co-exposure of cells to both APAP and tyrosine showed an enhancement of the cellular growth inhibition, suggesting that APAP and tyrosine have a similar mode of action.

2,3,4',5-tetrahydroxystilbene-2-O-β-D-glucoside exacerbates acetaminophen-induced hepatotoxicity by inducing hepatic expression of CYP2E1, CYP3A4 and CYP1A2

Hepatotoxicity induced by medicinal herb Polygonum multiflorum Thunb. attracts wide attention in the world recently. 2,3,4',5-tetrahydroxystilbene-2-O-β-D-glucoside (TSG) is a main active compound in Polygonum multiflorum Thunb. This study aims to observe TSG-provided the aggravation on acetaminophen (APAP)-induced hepatotoxicity in mice by inducing hepatic expression of cytochrome P450 (CYP450) enzymes. Serum alanine/aspartate aminotransferase (ALT/AST) analysis and liver histological evaluation showed that TSG (200, 400, 800 mg/kg) exacerbated the hepatotoxicity induced by sub-toxic dose of APAP (200 mg/kg) in mice, but TSG alone had no hepatotoxicity. TSG aggravated hepatic reduced glutathione (GSH) depletion and APAP-cysteine adducts (APAP-CYS) formation induced by APAP in mice. TSG increased the expression of CYP2E1, CYP3A4 and CYP1A2 both in mice and in human normal liver L-02 hepatocytes. TSG also enhanced liver catalytic activity of CYP2E1, CYP3A4 and CYP1A2 in mice. TSG induced the nuclear translocation of aryl hydrocarbon receptor (AHR) and pregnane X receptor (PXR), and TSG-provided the aggravation on APAP-induced hepatotoxicity in mice was reversed by PXR or AHR inhibitors. In summary, our results demonstrate that TSG enhances hepatic expression of CYP3A4, CYP2E1 and CYP1A2, and thus exacerbates the hepatotoxicity induced by APAP in mice. PXR and AHR both play some important roles in this process.

Celastrol ameliorates acetaminophen-induced oxidative stress and cytotoxicity in HepG2 cells

Acetaminophen (APAP) is the most commonly used analgesic and antipyretic drug in the world. However, hepatotoxicity caused by APAP overdose is the most frequent cause of acute liver failure worldwide and oxidative stress involved in the pathogenesis of APAP hepatotoxicity. Celastrol is a natural triterpenoid derived from Tripterygium wilfordii Hook F. that exhibits antioxidant, anti-inflammatory, and antitumor activities. In this study, we aimed to investigate the potential ameliorative effects of celastrol against APAP-induced cytotoxicity and oxidative stress. Human hepatocellular carcinoma cells (HepG2) were incubated with 20 mM of APAP for 24 h and posttreated with 50 nM, 100 nM, or 200 nM of celastrol for a further 24 h. The methylthiazolyldiphenyl-tetrazolium bromide, lactate dehydrogenase, and neutral red uptake assays showed celastrol posttreatments recovered cell viability and cell membrane integrity in a concentration-dependent manner. Celastrol posttreatments exerted a significant increase in the glutathione content and a decrease in the malondialdehyde and protein carbonylation levels. Also, celastrol posttreatments attenuated the APAP-induced oxidative stress by raising glutathione peroxidase, glutathione reductase, and catalase activities. However, superoxide dismutase activity did not change. In conclusion, celastrol treatment may improve cell viability and increase cellular antioxidant defense in HepG2 cells. These results suggest that celastrol may have the potential to ameliorate the APAP-induced oxidative stress and cytotoxicity.

The impact of vitamin C on the relationship among inflammation, lipid peroxidation and platelet activation during analgesic nephropathy in rats

BACKGROUND

Oxidative stress and inflammation are involved in the pathogenesis of paracetamol-induced renal damage. This study examines the relationship between 8-iso-prostaglandin F2α (8-iso-PGF2α) and platelet activation as well as the relative contribution of the pro-inflammatory markers interleukin (IL)-1β and tumor necrosis factor-α (TNF-α) in enhanced 8-iso-PGF2α biosynthesis, as a complementary onset during analgesic nephropathy induced by chronic treatment with paracetamol. The protective effects of vitamin C on the aforementioned settings are also investigated.

METHODS

Analgesic nephropathy was induced in Wistar rats. Renal function markers and the activity of antioxidant enzymes were determined spectrophotometrically. Immunoassays were used to measure the pro-inflammatory markers and the markers of lipid peroxidation and platelet activation.

RESULTS

The chronic treatment with paracetamol led to renal dysfunction, represented by the elevation of plasma urea and creatinine and the decline in the enzymatic antioxidant status, but did not cause a significant increase in TNF-α and IL-1β. The paracetamol-induced lipid peroxidation and enhanced production of 8-iso-PGF2α was not sufficient to cause changes in platelet activation represented by the level of 11-dehydro thromboxane B2.

CONCLUSIONS

Our results suggest that oxidative stress cannot circumvent the need of stimulation by circulatory cytokines in order to induce inflammatory response and changes in platelet activation during analgesic nephropathy. Vitamin C proved to be beneficial in restoring the renal function markers to normal, increasing the renal enzymatic antioxidant potential, inhibiting lipid peroxidation, and lowering cytokine production and 11-dehydro thromboxane B2 excretion. The observed effects of vitamin C offer support for its potential use as protective treatment in cases of chronic paracetamol overdose.

Drug-Induced Liver Injury in Children: Clinical Observations, Animal Models, and Regulatory Status

Drug-induced liver injury in children (cDILI) accounts for about 1% of all reported adverse drug reactions throughout all age groups, less than 10% of all clinical DILI cases, and around 20% of all acute liver failure cases in children. The overall DILI susceptibility in children has been assumed to be lower than in adults. Nevertheless, controversial evidence is emerging about children's sensitivity to DILI, with children's relative susceptibility to DILI appearing to be highly drug-specific. The culprit drugs in cDILI are similar but not identical to DILI in adults (aDILI). This is demonstrated by recent findings that a drug frequently associated with aDILI (amoxicillin/clavulanate) was rarely associated with cDILI and that the drug basiliximab caused only cDILI but not aDILI. The fatality in reported cDILI studies ranged from 4% to 31%. According to the US Food and Drug Administration-approved drugs labels, valproic acid, dactinomycin, and ampicillin appear more likely to cause cDILI. In contrast, deferasirox, isoniazid, dantrolene, and levofloxacin appear more likely to cause aDILI. Animal models have been explored to mimic children's increased susceptibility to valproic acid hepatotoxicity or decreased susceptibility to acetaminophen or halothane hepatotoxicity. However, for most drugs, animal models are not readily available, and the underlying mechanisms for the differential reactions to DILI between children and adults remain highly hypothetical. Diagnosis tools for cDILI are not yet available. A critical need exists to fill the knowledge gaps in cDILI. This review article provides an overview of cDILI and specific drugs associated with cDILI.

Toxic mechanisms of microcystins in mammals

Microcystins, such as microcystin-leucine arginine (MC-LR), are some of the most toxic and prevalent cyanotoxins produced by cyanobacteria in freshwater and saltwater algal blooms worldwide. Acute and chronic exposures to microcystins are primarily known to cause hepatotoxicity; cellular damage and genotoxicity within mammalian livers. However, in vivo studies indicate that similar damage may occur in other mammalian organs and tissues, such as the kidney, heart, reproductive systems, and lungs - particularly following chronic low-dose exposures. Mechanisms of toxicity of mycrocystins are reviewed herein; including cellular uptake, interaction with protein phosphatases PP1 and PP2A, cytoskeletal effects, formation of oxidative stress and induction of apoptosis. In general, the mode of action of toxicity by MCs in mammalian organs are similar to those that have been observed in liver tissues. A comprehensive understanding of the toxic mechanisms of microcystins in mammalian tissues and organs will assist in the development of risk assessment approaches to public health protection strategies and the development of robust drinking water policies.

Sasa veitchii extracts suppress acetaminophen-induced hepatotoxicity in mice

Background

The aim of this study was to investigate the therapeutic effects of a Sasa veitchii leaf extract (SE) on acetaminophen (APAP)-induced hepatotoxicity.

Methods

Seven-week-old male ddY mice were orally administered SE or saline (0.2 mL) once a day for a week. Twenty-four hours after the last pretreatment, the mice were intraperitoneally injected with 550 mg/kg APAP or saline under fasting conditions. The mice from each group were euthanized and bled for plasma analysis 2, 6, 24, and 72 h after the injection.

Results

We found that pretreatment with SE significantly decreased hepatic injury markers (i.e., alanine aminotransferase and aspartate aminotransferase), oxidative stress (malondialdehyde and glutathione level), inflammatory cytokines, histological damage, c-jun N-terminal kinase activation, and receptor-interacting protein-1 activation. Further, SE pretreatment decreased Cyp2e1 expression and increased total antioxidant capacity in the liver.

Conclusion

Our findings demonstrate that prophylactic SE treatment protects mice from APAP-induced hepatotoxicity through modulation of Cyp2e1 expression and antioxidant capacity.

Kinetics of the Acetaminophen-Based Oscillatory Chemical Reaction with and without Ferroin as Catalyst: An Inorganic Prototype Model for Acetaminophen–Ethanol Syndrome

This paper describes the nonlinear behaviour of the acetaminophen-based uncatalysed Belousov–Zhabotinsky oscillator and its dynamics in the presence of ferroin as catalyst. The role of free metal ions as catalysts was examined and the results compared with those of corresponding complexed catalysts. Free metal ions were found to be sluggish with respect to the evolution of the oscillatory regime as compared to complexed ones. The effect was monitored of change of the ligand moiety of the catalyst complex on the oscillatory parameters. Since ethanol potentiates the hepatotoxicity caused by acetaminophen in vivo, it is thought to understand this interaction by virtue of causing perturbation of the acetaminophen-based oscillator with different concentrations of ethanol with and without ferroin as catalyst. Another dimension to the ethanol effect was examined by perturbation of the system with ethanol at different stages of the reaction so as to get an idea as to whether it is acetaminophen or some reactive intermediate generated in the reaction system which reacts with ethanol. Further, the ferroin-catalysed oscillator is taken as a prototype inorganic model of the acetaminophen–ethanol syndrome, as ferroin and hypobromous acid (HOBr) act as inorganic replacements for cytochrome P450 and nicotinamide adenine dinucleotide phosphate (NADPH) in alcohol metabolism.

Suppressive effect of kamebakaurin on acetaminophen-induced hepatotoxicity by inhibiting lipid peroxidation and inflammatory response in mice

BACKGROUND

Kamebakaurin (KA) is an ent-kaurane diterpenoid known to have anti-inflammatory potential. In the current study, we investigated whether pretreatment with KA could ameliorate acetaminophen (APAP)-induced hepatotoxicity by inhibiting the anti-inflammatory response in mice.

METHODS

Seven-week-old C57BL/6J mice were orally administered KA or olive oil emulsion for seven days. Twenty-four hours after the last KA or olive oil administration, the mice were intraperitoneally injected with 400mg/kg APAP or saline under feed deprived condition. The mice from each group were euthanized and bled for plasma analysis 24h after the injection.

RESULT

APAP increased plasma levels of hepatic injury markers (i.e., alanine aminotransferase and aspartate aminotransferase), lipid peroxidation, and pro-inflammatory cytokines. Pretreatment with KA reduced the magnitude of APAP-induced increases in plasma levels of hepatic injury markers, lipid peroxidation, and inflammatory response. In addition, KA exhibited antioxidant capacity in a dose-dependent manner, with slight reactive oxygen species scavenging activity.

CONCLUSION

Our results indicate that KA has the ability to protect the liver from APAP-induced hepatotoxicity, presumably by both inhibiting the inflammatory response and oxidative stress.

Computational Approach to Structural Alerts: Furans, Phenols, Nitroaromatics, and Thiophenes

Structural alerts are commonly used in drug discovery to identify molecules likely to form reactive metabolites and thereby become toxic. Unfortunately, as useful as structural alerts are, they do not effectively model if, when, and why metabolism renders safe molecules toxic. Toxicity due to a specific structural alert is highly conditional, depending on the metabolism of the alert, the reactivity of its metabolites, dosage, and competing detoxification pathways. A systems approach, which explicitly models these pathways, could more effectively assess the toxicity risk of drug candidates. In this study, we demonstrated that mathematical models of P450 metabolism can predict the context-specific probability that a structural alert will be bioactivated in a given molecule. This study focuses on the furan, phenol, nitroaromatic, and thiophene alerts. Each of these structural alerts can produce reactive metabolites through certain metabolic pathways but not always. We tested whether our metabolism modeling approach, XenoSite, can predict when a given molecule's alerts will be bioactivated. Specifically, we used models of epoxidation, quinone formation, reduction, and sulfur-oxidation to predict the bioactivation of furan-, phenol-, nitroaromatic-, and thiophene-containing drugs. Our models separated bioactivated and not-bioactivated furan-, phenol-, nitroaromatic-, and thiophene-containing drugs with AUC performances of 100%, 73%, 93%, and 88%, respectively. Metabolism models accurately predict whether alerts are bioactivated and thus serve as a practical approach to improve the interpretability and usefulness of structural alerts. We expect that this same computational approach can be extended to most other structural alerts and later integrated into toxicity risk models. This advance is one necessary step toward our long-term goal of building comprehensive metabolic models of bioactivation and detoxification to guide assessment and design of new therapeutic molecules.