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.
Acetaminophen/toxicity* ; Acetaminophen/metabolism ; Acetaminophen/antagonists & inhibitors ; Analgesics, Non-Narcotic/toxicity* ; Analgesics, Non-Narcotic/metabolism ; Analgesics, Non-Narcotic/antagonists & inhibitors ; Animal ; Chlormethiazole/pharmacology* ; Cytochrome P-450 CYP2E1/antagonists & inhibitors ; Enzyme Inhibitors/pharmacology ; Female ; Human ; Liver/metabolism ; Liver/injuries* ; Liver/drug effects* ; Mice ; Mice, Inbred C57BL ; Sedatives, Nonbarbiturate/pharmacology* ; Support, Non-U.S. Gov't

To explore novel non-opioid analgesic agents, 16 compounds were synthesized and their structures were confirmed by 1H NMR and HR-MS. YX0611-1 was treated as the leading compound. The results of mice writhing model and hot plate model showed that compounds 2, 7, 8, 9, 11 and 15 had obvious analgesic activities in vivo. The test of affinity to mu, delta, kappa receptor displayed that active compounds didn't act on opioid receptor. The results of preliminary toxicity and pharmacokinetic tests showed that compound 7 had better safety and pharmacokinetic properties than that of YX0611-1, and it deserved further development.
Analgesics, Non-Narcotic ; chemical synthesis ; chemistry ; pharmacokinetics ; pharmacology ; toxicity ; Animals ; Female ; Male ; Mice ; Pain Measurement ; Piperazines ; chemical synthesis ; chemistry ; pharmacokinetics ; pharmacology ; toxicity ; Random Allocation ; Receptors, Opioid ; metabolism ; Structure-Activity Relationship

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.
Acetaminophen/*toxicity ; Administration, Oral ; Analgesics, Non-Narcotic/*toxicity ; Animals ; Drug-Induced Liver Injury/pathology/*physiopathology ; Gene Expression Profiling ; Heart/*physiology ; Liver/pathology/physiology ; Male ; Myocardium/pathology ; Rats ; Transcriptome/*drug effects

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.
Acetaminophen/toxicity* ; Analgesics, Non-Narcotic/toxicity* ; Animals ; Chemical and Drug Induced Liver Injury/pathology* ; Chemical and Drug Induced Liver Injury, Chronic/pathology* ; Humans ; Inflammation/metabolism* ; Liver/pathology* ; Mice ; Mice, Inbred C57BL ; Necrosis/pathology*