Molecular pathogenesis of acetaminophen-induced liver injury and its treatment options / 浙江大学学报（英文版）（B辑：生物医学和生物技术）

Acetaminophen, also known as N-acetyl-p-aminophenol (APAP), is commonly used as an antipyretic and analgesic agent. APAP overdose can induce hepatic toxicity, known as acetaminophen-induced liver injury (AILI). However, therapeutic doses of APAP can also induce AILI in patients with excessive alcohol intake or who are fasting. Hence, there is a need to understand the potential pathological mechanisms underlying AILI. In this review, we summarize three main mechanisms involved in the pathogenesis of AILI: hepatocyte necrosis, sterile inflammation, and hepatocyte regeneration. The relevant factors are elucidated and discussed. For instance, N-acetyl-p-benzoquinone imine (NAPQI) protein adducts trigger mitochondrial oxidative/nitrosative stress during hepatocyte necrosis, danger-associated molecular patterns (DAMPs) are released to elicit sterile inflammation, and certain growth factors contribute to liver regeneration. Finally, we describe the current potential treatment options for AILI patients and promising novel strategies available to researchers and pharmacists. This review provides a clearer understanding of AILI-related mechanisms to guide drug screening and selection for the clinical treatment of AILI patients in the future.

Eficácia hepatoprotetora do extrato metanólico de Indigofera suffruticosa (Mill) em lesão hepática induzido por paracetamol em camundongos / Hepatoprotective efficacy of methanolic extract of indigofera suffruticosa (mill) on paracetamol-induced liver damage in mice

ABSTRACT BACKGROUND: Indigofera suffruticosa Mill (Fabaceae) is abundant in northeastern Brazil and popularly used in the treatment of infectious and inflammatory processes. Several biological properties, such as anti-inflammatory, anticancer, antitumor, hepatoprotective and low toxicity, are reported for this plant. OBJECTIVE: This study investigated hepatoprotective activity and the antioxidant effect of methanolic extract of I. suffruticosa leaves (MEIS) on Swiss albino mice submitted to experimental models of acetaminophen-induced liver injury. METHODS: MEIS (50 mg/kg; p.o.) was standardized according to the LD50 and its hepatoprotective property on Swiss albino mice evaluated during a 7-day period. On the eighth day, the acetaminophen-induced hepatic injury was performed. Histomorphometric analysis of liver tissue, antioxidant activity and serum levels of alanine aminotransferase (AST), aspartate aminotransferase (ALT) and bilirubin were measured. RESULTS: MEIS (50 mg/kg; p.o.) restored serum enzyme levels and results were close to those of positive control (silymarin) when compared to the negative control. Histopathological and histomorphometric analyzes confirmed MEIS hepatoprotective activity, showing reorganization of structural units of cells, nuclei and sinusoidal capillaries of hepatocytes, reducing the damage on liver tissue and increasing organ regeneration rate. MEIS showed high antioxidant potential at concentrations of 1000 and 500 µg/mL. CONCLUSION: This study suggests that MEIS has hepatoprotective activity and high antioxidant potential.

RESUMO CONTEXTO: Indigofera suffruticosa Mill (Fabaceae) é abundante no nordeste do Brasil e popularmente utilizada no tratamento de processos infecciosos e inflamatórios. Várias propriedades biológicas, como anti-inflamatório, anticâncer, antitumoral, hepatoprotetor e baixa toxicidade, são relatadas para esta planta. OBJETIVO: Este estudo investigou a atividade hepatoprotetora e o efeito antioxidante do extrato metanólico de folhas de I. suffruticosa (MEIS) em camundongos albinos suíços submetidos a modelos experimentais de lesão hepática induzida por paracetamol. MÉTODOS: O MEIS na dose de 50 mg/kg (via oral) foi padronizado de acordo com a LD50 e sua propriedade hepatoprotetora em camundongos albinos Swiss avaliados durante um período de sete dias. No oitavo dia, a lesão hepática foi induzida por paracetamol em todos grupos pre-tratados. Foram medidos os níveis sericos enzimaticos, alanina aminotransferase, aspartato aminotransferase e bilirrubina, análise histomorfométrica do tecido hepático e atividade antioxidante. RESULTADOS: O MEIS restaurou os níveis séricos de enzimas e os resultados foram próximos aos do controle positivo (silimarina) quando comparados ao controle negativo. As análises histopatológicas e histomorfométricas confirmaram a atividade hepatoprotetora do MEIS, mostrando reorganização das unidades estruturais das células, núcleos e capilares sinusoidais dos hepatócitos, reduzindo os danos no tecido hepático e aumentando a taxa de regeneração de órgãos. O MEIS apresentou alto potencial antioxidante nas concentrações de 1000 e 500 µg/mL. CONCLUSÃO: Este estudo sugere que I. suffruticosa tem atividade hepatoprotetora e alto potencial antioxidante.

Evaluación del potencial hepatoprotector de la Mentha piperita L previo a la inducción de hepatotoxicidad con acetaminofen / Evaluation of hepatoprotective potential of Mentha piperita L before induction of hepatotoxicity with acetaminophen

A preclinical pharmacological study was conducted to evaluate the hepatoprotective effect of Mentha piperita L. against paracetamol induced toxicity. Adult male NMRI mice who were administered orally soft plant extracts in doses of 200mg/kg and 400mg/kg, three consecutive days prior to the induction of hepatotoxicity were used. Clinical signs of toxicity, hepatic biochemical parameters and morphological analysis of the liver was evaluated. The biochemical parameters analyzed showed significant differences, but none of the two groups showed a similar untreated control group behavior. No macroscopic changes in the liver were confirmed. Microscopically, the study groups with Mentha piperita L. showed mild to moderate damage with significant differences from the untreated control group. The evaluation of hepatoprotective potential on the M. piperita L. extract at doses studied did not behave as hepatoprotective agent...

Se realizó un estudio farmacológico preclínico para evaluar el efecto hepatoprotector de Mentha piperita L. frente a la toxicidad inducida por el paracetamol. Se emplearon ratones adultos machos NMRI a los que se administró por vía oral extractos blandos de la planta a dosis de 200 mg/kg y 400 mg/kg, tres días consecutivos previos a la inducción de la hepatotoxicidad. Se evaluaron los signos clínicos de toxicidad, parámetros bioquímicos hepáticos y el análisis morfológico del hígado. Los parámetros bioquímicos analizados mostraron diferencias altamente significativas, pero ninguno de los dos grupos presentaron un comportamiento similar al grupo control no tratado. No se confirmaron alteraciones macroscópicas del hígado. A nivel Microscópico, los grupos en estudio con Mentha piperita L. presentaron daños de leves a moderados con diferencias significativas respecto al grupo control no tratado. Se puede afirmar que según la evaluación del potencial hepatoprotector del extracto de M. piperita L. a las dosis estudiadas no se comportó como agente hepatoprotector...

Freshly isolated hepatocyte transplantation in acetaminophen-induced hepatotoxicity model in rats / Transplante de hepatócitos recém-isolados em um modelo de hepatotoxicidade induzida por acetaminofeno em ratos

CONTEXT: Hepatocyte transplantation is an attractive therapeutic modality for liver disease as an alternative for orthotopic liver transplantation. OBJECTIVE: The aim of the current study was to investigate the feasibility of freshly isolated rat hepatocyte transplantation in acetaminophen-induced hepatotoxicity model. METHODS: Hepatocytes were isolated from male Wistar rats and transplanted 24 hours after acetaminophen administration in female recipients. Female rats received either 1x10(7) hepatocytes or phosphate buffered saline through the portal vein or into the spleen and were sacrificed after 48 hours. RESULTS: Alanine aminotransferase levels measured within the experiment did not differ between groups at any time point. Molecular analysis and histology showed presence of hepatocytes in liver of transplanted animals injected either through portal vein or spleen. CONCLUSION: These data demonstrate the feasibility and efficacy of hepatocyte transplantation in the liver or spleen in a mild acetaminophen-induced hepatotoxicity model.

CONTEXTO: O transplante de hepatócitos é uma modalidade terapêutica atrativa para doenças hepáticas como alternativa ao transplante hepático ortotópico. OBJETIVO: Investigar a factibilidade do uso de hepatócitos frescos isolados de ratos em um modelo de hepatotoxicidade induzida por paracetamol. MÉTODOS: Hepatócitos foram isolados de ratos Wistar machos e transplantados 24 horas após a administração de paracetamol em receptores fêmeas. As ratas receberam 1x10(7) hepatócitos ou tampão salina fosfato pela veia porta ou no baço e foram sacrificadas após 48 horas. RESULTADOS: Os níveis de alanina aminotransferase medidos durante o experimento não diferiram entre os grupos em nenhum momento. Análises moleculares e histológicas demonstraram a presença de hepatócitos no fígado dos animais transplantados pelo baço ou pela veia porta. CONCLUSÃO: Os dados indicam a factibilidade e eficácia do transplante de hepatócitos no fígado ou baço em um modelo de hepatotoxicidade leve induzida por paracetamol.

Gene Expression in Rat Hearts Following Oral Administration of a Single Hepatotoxic Dose of Acetaminophen

PURPOSE: Toxicity caused by acetaminophen and its toxic mechanisms in the liver have been widely studied, including effects involving metabolism and oxidative stress. However, its adverse effects on heart have not been sufficiently investigated. This study evaluated the cardiac influence and molecular events occurring within the myocardium in rats treated with a dose of acetaminophen large enough to induce conventional liver damage. MATERIALS AND METHODS: Male rats were orally administered a single dose of acetaminophen at 1,000 mg/kg-body weight, and subsequently examined for conventional toxicological parameters and for gene expression alterations to both the heart and liver 24 hours after administration. RESULTS: Following treatment, serum biochemical parameters including aspartate aminotransferase and alanine aminotransferase were elevated. Histopathological alterations of necrosis were observed in the liver, but not in the heart. However, alterations in gene expression were observed in both the liver and heart 24 hours after dosing. Transcriptional profiling revealed that acetaminophen changed the expression of genes implicated in oxidative stress, inflammatory processes, and apoptosis in the heart as well as in the liver. The numbers of up-regulated and down-regulated genes in the heart were 271 and 81, respectively, based on a two-fold criterion. CONCLUSION: The induced expression of genes implicated in oxidative stress and inflammatory processes in the myocardium reflects molecular levels of injury caused by acetaminophen (APAP), which could not be identified by conventional histopathology.

Antihepatotoxic effect of beta-carotene on paracetamol induced hepatic damage in rats.

Enzyme levels of serum glutamate oxaloacetate transaminase (SGOT), serum glutamate pyruvate transaminase (SGPT) and alkaline phosphatase (ALP) increased following paracetamol induction were significantly lowered due to pretreatment with the beta-carotene (BC). This supplementation reversed the trend inducing a significant decrease in bilirubin and urea levels. Paracetamol administration significantly reduced hepatic glycogen, glutathione (GSH), glutathione-S-transferase (GST), glutathione peroxidase (GPX) and glutathione reductase (GSH-R). Pretreatment of rats with BC significantly increased the enzyme activities. The results suggest hepatoprotective activity of BC.

¿Contribuye el TNF-alfa a la fisiopatolog'ia de las hepatopatias? / Does TNF-alpha contribute to liver disease physiopathology?

The aim of the present paper is to establish the possible role of serum TNF in the pathophysiology of three experimental models of liver injury: paracetamol intoxication, cholestasis followed by paracetamol intoxication and cholestasis. We concluded that under our experimental conditions the serum TNF-alpha levels were not responsible for the inflammatory phenomena described in our previous paper as apopt.

Metabolismo de benzodiacepinas en distintos modelos de hepatopatías experimentales / Benzodiazepines metabolism in different models of experimental liver diseases

El objetivo de este trabajo es estabelecer posibles alteraciones en la glucuronización de benzodizcepinas en dos modelos experimentales de injuria hepática: La intoxicación aguda con paracetamol y la colestasis seguida de una intoxicación aguda con paracetamol. Por el contrario, los animales colestáticos seguidos de una intoxicación con paracetamol, mostraron un incremento en la glucuronización de los sustratos ensayados.

TProtective effect of chlormethiazole, a sedative, against acetaminophen-induced liver injury in mice

OBJECTIVES: The hepatotoxicity of acetaminophen is not a result of the parent compound but is mediated by its reactive metabolite N-acetyl-p-benzoquinone imine. Cytochrome P4502E1 (CYP2E1) is the principal enzyme of this biotransformation, which accounts for approximately 52% of the bioactivation in human microsomes. Recently, chlormethiazole a sedative drug, is reported to be an efficient inhibitor of CYP2E1 activity in human beings. In this study we wished to evaluate whether chlormethiazole, an inhibitor of CYP2E1, could prevent acetaminophen-induced liver injury in mice. METHODS: Acetaminophen, at doses ranging from 200 to 600 mg/kg, was injected into the peritoneum of female C57BL/6 inbred mice fasted for four hours. Chlormethiazole (60 mg/kg) or 5% dextrose water was given 30 min before or 2 h after acetaminophen. Serum aminotransferase activities, histologic index score, survival rate and hepatic malondialdehyde levels were compared. RESULTS: Pretreatment with chlormethiazole 30 min before 400 mg/kg of acetaminophen completely inhibited acetaminophen-induced liver injury (median 118.5 U/L, range 75 to 142 vs. 14,070 U/L, range 5980 to 27,680 for AST; 49 U/L, range 41 to 64 vs. 15,330 U/L, range 13,920 to 15,940 for ALT). In mice receiving chlormethiazole 2 h after acetaminophen, the mean AST and ALT levels were also less elevated, reaching only 20% of the value of acetaminophen-only group. These protective effects were confirmed histologically. Whereas more than 50% of mice died at 500 mg/kg of acetaminophen, all the mice pretreated with chlormethiazole survived at the same dose. CONCLUSION: Chlormethiazole effectively reduces acetaminophen-induced liver injury in mice. Further studies are needed to assess its role in humans.

Gastric emptying in rats with acetaminophen-induced hepatitis

The objective of this work was to study the gastric emptying (GE) of liquids in fasted and sucrose-fed rats with toxic hepatitis induced by acetaminophen. The GE of three test meals (saline, glucose and mayonnaise) was evaluated in Wistar rats. For each meal, the animals were divided into two groups (N = 24 each). Group I was fed a sucrose diet throughout the experiment (66 h) while group II was fasted. Forty-two hours after the start of the experiment, each group was divided into two subgroups (N = 12 each). Subgroup A received a placebo and subgroup B was given acetaminophen (1 g/kg). Twenty-four hours later, the GE of the three test meals was assessed and blood samples were collected to measure the serum levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST) and acetaminophen. In group IB, the mean AST and ALT values were 515 and 263 IU/l, respectively, while for group IIB they were 4014 and 2472 IU/l, respectively. The mean serum acetaminophen levels were higher in group IIB (120 µg/ml) than in group IB (87 µg/ml). The gastric retention values were significantly higher in group IIB than in group IIA for all three test meals: saline, 51 vs 35 percent; glucose, 52 vs 38 percent and mayonnaise, 51 vs 29 percent(median values). The correlation between gastric retention and AST levels was significant (P<0.05) for group IIB for the three test meals: r = 0.73, 0.67 and 0.68 for saline, glucose and mayonnaise, respectively. We conclude that GE is altered in rats with hepatic lesions induced by acetaminophen, and that these alterations may be related to the liver cell necrosis caused by the drug

Silymarin mediated differential modulation of toxicity induced by carbon tetrachloride, paracetamol and D-galactosamine in freshly isolated rat hepatocytes.

Influence of silymarin on the modulation of hepatotoxicity induced by carbon tetrachloride (CCl4), paracetamol (AAP) and D-galactosamine (GalN) was examined in freshly isolated rat hepatocytes in suspension culture. While the three hepatotoxicants produced differential biochemical response, the flavone was able to restore biochemical alterations only in hepatocytes exposed to CCl4 and AAP induced toxicity. Silymarin at 0.4 mM was able to counteract lipid peroxidation and enzyme leakage induced by 3 mM CCl4 The flavone also offered protection by more than 60% in hepatocytes isolated from PB pre-treated rats where CCl4 at 2 mM produced enhanced toxicity over hepatocytes isolated from untreated control rats. Similarly, the flavone protected AAP-induced GSH depletion by more than 75% in hepatocytes isolated from untreated and 3-methylcholanthrene treated rats. However, instead of protecting GalN-induced depletion of UDP-glucuronic acid in hepatocytes, the flavone itself reduced the nucleotide content very rapidly compared to GalN, the later exerted time dependent effect. Silymarin at 0.4 mM reduced UDPGA by more than 60%. The results suggested that freshly isolated hepatocytes in suspension culture offer a simple and convenient method for evaluation of pharmaceutical agents of antihepatotxic potentials against various hepatotoxicants.

Differential biochemical response of freshly isolated rat hepatocytes to paracetamol, carbon tetrachloride and D-galactosamine toxicity.

Differential response of freshly isolated rat hepatocytes to paracetamol (acetaminophen, AAP), carbon tetrachloride (CCl4) and D-galactosamine (GalN) was examined. The viability of the cells in suspension culture was not altered for 4 hr when incubated in Hank's balanced salt solution (HBSS) supplemented with 4.2 mM NaHCO3, 10 mM HEPES buffer and 0.5% bovine serum albumin. AAP induced time and dose dependent depletion of GSH as an early manifestation of AAP toxicity. Hepatocytes exposed to AAP exhibited lower lactate dehydrogenase (LDH) activity released into the medium than in controls. This was due to the interaction of a reactive metabolite of AAP, i. e. N-acetyl p-benzoquinoneimine (NAPQI) with cell proteins. Hepatocytes isolated from rats pretreated with 3-methylcholanthrene expressed higher sensitivity to AAP toxicity at least by a factor of 5. Furthermore, AAP-induced toxicity was not found to be related to any lipoperoxidative stress. CCl4 on the other hand elicited a highly lipoperoxidative response in hepatocytes and consequent leakage of cellular enzymes with lengths of incubation. Again the sensitivity of the response to CCl4 was enhanced remarkably in hepatocytes isolated from phenobarbital- pretreated rats; LDH leakage increased by 3-fold and thio-barbituric acid reactive substances by 25-fold. Unlike the two toxicants, galactosamine depleted UDP-glucuronic acid in a concentration and time-related manners. The differential biochemical response of hepatocytes to three hepatotoxicants investigated may prove useful as rapid in vitro screen for selection of compounds of hepatoprotective potentials.

Respiratory functions in kidney mitochondria following paracetamol administration to young-adult & old rats.

Effects of paracetamol treatment in vivo to young-adult (2-3 months) and old (22-24 months) rats at subtoxic (375 mg/kg) and toxic (750 mg/kg) doses on kidney mitochondrial energy metabolism were examined. Administration of paracetamol (both doses) to young-adult animals did not, in general, affect the respiratory functions of kidney mitochondria. On the other hand, treatment of toxic doses to aged animals resulted in decrease in the state 3 respiration rates with glutamate, pyruvate + malate and succinate as substrates. Succinoxidase activity was also impaired in this experimental group. With subtoxic doses, state 3 respiration rate was decreased only with pyruvate + malate as substrate. Results indicate that the in vivo administration of paracetamol impaired kidney mitochondrial energy metabolism in aged animals.

In vivo effects of acetaminophen on rat RBC and role of vitamin E.

Non-therapeutic toxic dose (250 mg/kg) of acetaminophen (paracetamol), in vivo to albino rats significantly decreased red cell reduced glutathione (GSH) content and activity of (Na+, K+)-ATPase enzyme, whereas osmotic fragility (O.F.) was increased. However, no change was observed in the activity of glutathione reductase (GR) after acetaminophen treatment, while acetaminophen plus vitamin E treated rats showed significant increase in GR activity. Supplementation of vitamin E to the drug treated rats effectively brought the GSH content, (Na+, K+)-ATPase activity and O.F. back to almost normal. The results suggest that acetaminophen toxic dose treatment induces metabolic and membranal alterations making red cells prone to hemolysis, while vitamin E which is an antioxidant shows its ameliorating role to these changes.

Intoxicación por analgésicos, antipiréticos y antiinflamatorios / Poisoning by analgesicos, antipireticos antiinflammatory

La intoxicación por analgésicos es una de las más comunes en cualquier parte del mundo, dentro de las intoxicaciones medicamentosas. Estas pueden ser iatrogénicas, accidentales o intencionales (suicidas). Este artículo incluye varios grupos de medicamentos con algunas características individuales desde el punto de vista de toxicidad, que vale la pena resaltar.