Dibenzocyclooctadiene lignans from Kadsura coccinea alleviate APAP-induced hepatotoxicity via oxidative stress inhibition and activating the Nrf2 pathway in vitro.

Phytochemical investigation on the roots of Kadsura coccinea led to the isolation five previously unknown dibenzocyclooctadiene lignans, named heilaohusuins A-E (1-5). Their structures determined by NMR spectroscopy, HR-ESI-MS, and ECD spectra. Hepatoprotection effects of a series of dibenzocyclooctadiene derivatives (1-68) were investigated against acetaminophen (APAP) induced HepG2 cells. Compounds 2, 10, 13, 21, 32, 41, 46, and 49 showed remarkable protective effects, increasing the viabilities to > 52.2% (bicyclol, 52.1 ± 1.3%) at 10 µM. The structure-activity relationships (SAR) for hepatoprotective activity were summarized, according to the activity results of dibenzocyclooctadiene derivatives. Furthermore, we found that one new dibenzocyclooctadiene lignan heilaohusuin B attenuates hepatotoxicity, the mechanism might be closely correlated with oxidative stress inhibition via activating the Nrf2 pathway.

Protective Effect of Phoenix dactylifera L. Seeds against Paracetamol-Induced Hepatotoxicity in Rats: A Comparison with Vitamin C.

Phoenix dactylifera L. (date palm) seeds have been mentioned in the Moroccan pharmacopoeia as efficient remedies against a wide range of diseases including hepatic and gastrointestinal disorders and countless infections. The current work was performed to assess the phenolic profile and hepatoprotective potential of two date seed varieties, locally known as Jihl and Majhoul, aqueous extracts against paracetamol- (PCM-) driven liver toxicity in 42 Wistar rats. The polyphenol profile was built by means of an HPLC analysis. Hepatic damage was provoked by exposing rats to PCM at a dose of 1.5 g/kg once a week. Besides PCM, Jihl and Majhoul date seed extracts (200 and 400 mg/kg) were administered orally in a day-to-day routine. Our findings showed that among the examined polyphenol compounds, p-coumaric acid, quercetin, caffeic acid, and rutin were the most abundant phytochemicals. Date pits significantly (p < 0.001) stabilized the PCM-driven alterations in liver function parameters (AST, ALT, ALP, LDH, total protein, direct bilirubin, and total bilirubin). Moreover, Phoenix dactylifera pits enhanced considerably (p < 0.001) the activities of antioxidant enzymes (SOD, CAT, and GPx) as well as the level of reduced glutathione (GSH). The established hepatoprotective effect may be due to the date seeds antioxidant effect and their ability to trap free radicals. The main outcomes of the present study could validate the traditional use of these date seeds to manage various health conditions.

Therapeutic role of Typha elephantina leaves aqueous extract in paracetamol intoxicated rabbits.

Present study is aimed to investigate the hepatoprotective and hematopoietic effect of Typha elephantina leaves aqueous (T.E.AQ), extract in paracetamol (PCM) intoxicated rabbits. Experimental animals were divided into various groups. The blood was taken on day 7th (W1=Week 1), day 14th (W2 = week 2) and day 21st (W3 = week 3) of treatments and was analyzed for all hematological and serum biochemical markers. PCM administration caused marked increase in the levels of serum biochemical and hematological parameters. The leaves of T.E.AQ extract at dose rate 300mg/kg body weight significantly (P<0.05) reduced the elevated levels of serum biochemical and hematological indices towards normal values on third week (day 21st) of treatment while treatment in the first two weeks revealed non-significant effects even at all doses of extract. The levels of glutathione (GSH) and radical scavenging activity (RSA) were reduced and thiobarbituric acid reactive substances (TBARS) levels was high in the PCM feed animals. Administration of (T.E.AQ) extract at high dose (300mg/kg) significantly regulated and normalized these antioxidant values. The antioxidant capacity of (TE.AQ) extract, showed increase inhibition against various extract concentrations on the basis of percent scavenging of (DPPH) free radical. The histological sections of liver further supported the hepatoprotective activity of extract.

Protective effect of Heliotropium strigosum 70% aqueous methanolic extract against paracetamol induced hepatotoxicity in mice.

The study was carried out to evaluate the hepatoprotective potential of aqueous methanolic extract of Heliotropium strigosum (HSME) against paracetamol induced hepatotoxicity in Swiss albino mice. The plant powder (1.5Kg) was macerated in aqueous methanol (30:70) for 7 days. The extract was evaluated for the presence of different phytochemicals and High-performance liquid chromatography (HPLC) analysis. HSME was orally administered to mice at 125, 250 and 500mg/kg for 8 days followed by paracetamol intoxication (500mg/kg orally) on the 8th day using silymarin as standard control. All the therapy was administered by oral gavage. The liver biochemical parameters and histopathological evaluation were carried out to assess changes in liver function and histology. HPLC analysis confirmed the presence of quercetin, kaempferol, and other phenolic compounds. Treatment with the extract resulted in notable (p<0.05) reduction in liver parameters in dose dependent manner. The action of HSME 500mg/kg dose was comparable to silymarin. The effect of HSME against paracetamol induced hepatotoxicity was demonstrated by protective changes in the liver histopathological which proved the traditional uses of the plant.

Bioactive phenolic acid-substituted glycoses and glycosides from rhizomes of Cibotium barometz.

Two rarely phenolic acid-substituted alloses (1, 2) and one new glucoside (3), as well as nine known compounds (4-12) were isolated from rhizomes of Cibotium barometz (L.) J. Sm. Structures of 1-3 were established by extensively spectroscopic analyses (NMR, MS, etc.) and acid hydrolysis. All compounds were evaluated for the hepatoprotective activities against APAP-induced HepG2 cell damage. Compounds 1, 4-7, 10 exhibited significant hepatoprotective activities, even more strongly than positive control, bicycol. In addition, compounds 1 and 9 could reduce PC12 cell death induced by serum deprivation.

New Phenylpropanoid and Coumarin Glycosides from the Stems of Hydrangea paniculata Sieb.

A new phenylpropanoid glycoside (1), and two new coumarin glycosides (2, 3), together with two known compounds (4, 5), have been isolated from the stems of Hydrangea paniculata Sieb. Their structures have been determined by spectroscopic and chemical methods. Furthermore, compound 1 (50 µM) exhibited significant hepatoprotective activity against N-acetyl-p-aminophenol (APAP)-induced HepG2 cell damage in vitro assays.

Hepatoprotective action of various partitions of methanol extract of Bauhinia purpurea leaves against paracetamol-induced liver toxicity: involvement of the antioxidant mechanisms.

BACKGROUND: Methanol extract of Bauhinia purpurea L. (family Fabaceae) (MEBP) possesses high antioxidant and anti-inflammatory activities and recently reported to exert hepatoprotection against paracetamol (PCM)-induced liver injury in rats. In an attempt to identify the hepatoprotective bioactive compounds in MEBP, the extract was prepared in different partitions and subjected to the PCM-induced liver injury model in rats. METHODS: Dried MEBP was partitioned successively to obtain petroleum ether (PEBP), ethylacetate (EABP) and aqueous (AQBP) partitions, respectively. All partitions were subjected to in vitro antioxidant (i.e. total phenolic content (TPC), 2,2-diphenyl-1-picrylhydrazyl (DPPH)- and superoxide-radicals scavenging assay, and oxygen radical absorbance capacity (ORAC) assay) and anti-inflammatory (i.e. lipooxygenase (LOX) and xanthine oxidase (XO) assay) analysis. The partitions, prepared in the dose range of 50, 250 and 500 mg/kg, together with a vehicle (10 % DMSO) and standard drug (200 mg/kg silymarin) were administered orally for 7 consecutive days prior to subjection to the 3 mg/kg PCM-induced liver injury model in rats. Following the hepatic injury induction, blood samples and liver were collected for the respective biochemical parameter and histopathological studies. Body weight changes and liver weight were also recorded. The partitions were also subjected to the phytochemical screening and HPLC analysis. RESULTS: Of all partitions, EABP possessed high TPC value and demonstrated remarkable antioxidant activity when assessed using the DPPH- and superoxide-radical scavenging assay, as well as ORAC assay, which was followed by AQBP and PEBP. All partitions also showed low anti-inflammatory activity via the LOX and XO pathways. In the hepatoprotective study, the effectiveness of the partitions is in the order of EABP>AQBP>PEBP, which is supported by the microscopic analysis and histopathological scoring. In the biochemical analysis, EABP also exerted the most effective effect by reducing the serum level of alanine transaminase (ALT) and aspartate transaminase (AST) at all doses tested in comparison to the other partitions. Phytochemical screening and HPLC analysis suggested the presence of: flavonoids, condensed tannins and triterpenes in EABP; flavonoids, condensed tannins and saponins in PEBP and; only saponins in AQBP. CONCLUSION: EABP demonstrates the most effective hepatoprotection against PCM-induced liver injury in rats. This observation could be attributed to its remarkable antioxidant activity and the presence of flavonoids that might probably act synergistically with other biocompounds to cause the hepatoprotection.

Reduction of adverse effects from intravenous acetylcysteine treatment for paracetamol poisoning: a randomised controlled trial.

BACKGROUND: Paracetamol poisoning is common worldwide. It is treated with intravenous acetylcysteine, but the standard regimen is complex and associated with frequent adverse effects related to concentration, which can cause treatment interruption. We aimed to ascertain whether adverse effects could be reduced with either a shorter modified acetylcysteine schedule, antiemetic pretreatment, or both. METHODS: We undertook a double-blind, randomised factorial study at three UK hospitals, between Sept 6, 2010, and Dec 31, 2012. We randomly allocated patients with acute paracetamol overdose to either the standard intravenous acetylcysteine regimen (duration 20·25 h) or a shorter (12 h) modified protocol, with or without intravenous ondansetron pretreatment (4 mg). Masking was achieved by infusion of 5% dextrose (during acetylcysteine delivery) or saline (for antiemetic pretreatment). Randomisation was done via the internet and included a minimisation procedure by prognostic factors. The primary outcome was absence of vomiting, retching, or need for rescue antiemetic treatment at 2 h. Prespecified secondary outcomes included a greater than 50% increase in alanine aminotransferase activity over the admission value. Analysis was by intention to treat. This trial is registered with ClinicalTrials.gov (identifier NCT01050270). FINDINGS: Of 222 patients who underwent randomisation, 217 were assessable 2 h after the start of acetylcysteine treatment. Vomiting, retching, or need for rescue antiemetic treatment at 2 h was reported in 39 of 108 patients assigned to the shorter modified protocol compared with 71 of 109 allocated to the standard acetylcysteine regimen (adjusted odds ratio 0·26, 97·5% CI 0·13-0·52; p<0·0001), and in 45 of 109 patients who received ondansetron compared with 65 of 108 allocated placebo (0·41, 0·20-0·80; p=0·003). Severe anaphylactoid reactions were recorded in five patients assigned to the shorter modified acetylcysteine regimen versus 31 who were allocated to the standard protocol (adjusted common odds ratio 0·23, 97·5% CI 0·12-0·43; p<0·0001). The proportion of patients with a 50% increase in alanine aminotransferase activity did not differ between the standard (9/110) and shorter modified (13/112) regimens (adjusted odds ratio 0·60, 97·5% CI 0·20-1·83); however, the proportion was higher with ondansetron (16/111) than with placebo (6/111; 3·30, 1·01-10·72; p=0·024). INTERPRETATION: In patients with paracetamol poisoning, a 12 h modified acetylcysteine regimen resulted in less vomiting, fewer anaphylactoid reactions, and reduced need for treatment interruption. This study was not powered to detect non-inferiority of the shorter protocol versus the standard approach; therefore, further research is needed to confirm the efficacy of the 12 h modified acetylcysteine regimen. FUNDING: Chief Scientist Office of the Scottish Government.

Mechanisms of acetaminophen-induced cell death in primary human hepatocytes.

UNLABELLED: Acetaminophen (APAP) overdose is the most prevalent cause of drug-induced liver injury in western countries. Numerous studies have been conducted to investigate the mechanisms of injury after APAP overdose in various animal models; however, the importance of these mechanisms for humans remains unclear. Here we investigated APAP hepatotoxicity using freshly isolated primary human hepatocytes (PHH) from either donor livers or liver resections. PHH were exposed to 5mM, 10mM or 20mM APAP over a period of 48 h and multiple parameters were assessed. APAP dose-dependently induced significant hepatocyte necrosis starting from 24h, which correlated with the clinical onset of human liver injury after APAP overdose. Interestingly, cellular glutathione was depleted rapidly during the first 3h. APAP also resulted in early formation of APAP-protein adducts (measured in whole cell lysate and in mitochondria) and mitochondrial dysfunction, indicated by the loss of mitochondrial membrane potential after 12h. Furthermore, APAP time-dependently triggered c-Jun N-terminal kinase (JNK) activation in the cytosol and translocation of phospho-JNK to the mitochondria. Both co-treatment and post-treatment (3h) with the JNK inhibitor SP600125 reduced JNK activation and significantly attenuated cell death at 24h and 48h after APAP. The clinical antidote N-acetylcysteine offered almost complete protection even if administered 6h after APAP and a partial protection when given at 15 h. CONCLUSION: These data highlight important mechanistic events in APAP toxicity in PHH and indicate a critical role of JNK in the progression of injury after APAP in humans. The JNK pathway may represent a therapeutic target in the clinic.

Evaluation of three-dimensional cultured HepG2 cells in a nano culture plate system: an in vitro human model of acetaminophen hepatotoxicity.

Overdoses of acetaminophen (paracetamol, N-acetyl-p-aminophenol; APAP) cause severe liver injury, yet there is no common or high throughput in vitro human APAP model. This study examined the characteristics and usefulness of HepG2 cells grown in a nano culture plate (NCP) system, a three-dimensional culture method, as an in vitro human model for APAP-induced hepatotoxicity. The NCP-cultured HepG2 cells showed higher expression of mRNA and protein levels of cytochrome P450 2E1, which metabolizes APAP to a toxic metabolite, APAP-cysteine adduct formation, and higher sensitivity against APAP-induced cell injury compared with conventionally cultured cells. We demonstrated that treatment of APAP in NCP-cultured HepG2 cells shows key mechanistic features of APAP-induced hepatotoxicity, such as decreases in intracellular glutathione and mitochondrial membrane potential, activation of JNK, and cellular injury; and pharmacological agents, such as Cyclosporine A (a mitochondrial permeability transition inhibitor) and SP600125 (a JNK inhibitor), prevented cell injury induced by APAP exposure. In addition, the antidote of APAP-induced hepatotoxicity, N-acetylcysteine, could attenuate cellular injury induced by APAP in NCP-cultured HepG2 cells. We suggest that cellular injury induced by APAP treatment using an NCP-HepG2 system is a useful human model to study mechanisms and screen drug candidates of APAP-induced hepatotoxicity.

Mouse liver protein sulfhydryl depletion after acetaminophen exposure.

Acetaminophen (APAP)-induced liver injury is the leading cause of acute liver failure in many countries. This study determined the extent of liver protein sulfhydryl depletion not only in whole liver homogenate but also in the zonal pattern of sulfhydryl depletion within the liver lobule. A single oral gavage dose of 150 or 300 mg/kg APAP in B6C3F1 mice produced increased serum alanine aminotransferase levels, liver necrosis, and glutathione depletion in a dose-dependent manner. Free protein sulfhydryls were measured in liver protein homogenates by labeling with maleimide linked to a near infrared fluorescent dye followed by SDS-polyacrylamide gel electrophoresis. Global protein sulfhydryl levels were decreased significantly (48.4%) starting at 1 hour after the APAP dose and maintained at this reduced level through 24 hours. To visualize the specific hepatocytes that had reduced protein sulfhydryl levels, frozen liver sections were labeled with maleimide linked to horseradish peroxidase. The centrilobular areas exhibited dramatic decreases in free protein sulfhydryls while the periportal regions were essentially spared. These protein sulfhydryl-depleted regions correlated with areas exhibiting histopathologic injury and APAP binding to protein. The majority of protein sulfhydryl depletion was due to reversible oxidation since the global- and lobule-specific effects were essentially reversed when the samples were reduced with tris(2-carboxyethy)phosphine before maleimide labeling. These temporal and zonal pattern changes in protein sulfhydryl oxidation shed new light on the importance that changes in protein redox status might play in the pathogenesis of APAP hepatotoxicity.

Ameliorative potential of whey protein hydrolysate against paracetamol-induced oxidative stress.

The aim of the present study was to validate the antioxidant effect of whey protein hydrolysate (WPH) using a small animal model. Paracetamol is common drug that is safe at therapeutic levels; however, an overdose causes oxidative stress, which may lead to potential hepatic and renal necrosis. The protective effect of WPH against paracetamol-induced hepato-nephrotoxicity in mice was investigated in this study. The WPH was prepared by hydrolyzing ultrafiltered retentate of mozzarella cheese whey with commercial food-grade alcalase; the resulting WPH had substantial in vitro antioxidant activity. Male albino mice were treated with WPH for 4 d [intraperitoneally at 4 mg/kg of body weight (BW) per day or orally at 8 mg/kg of BW per day] before or after oral administration of paracetamol (300 mg/kg of BW) for 2 d. Two control groups were used; the negative control mice were administered water only; the paracetamol group was administered paracetamol at 300 mg/kg of BW but received no WPH. Levels of different marker enzymes (glutamate pyruvate transaminase and alkaline phosphatase), creatinine, and blood urea nitrogen were measured in the experimental animal blood sera. The WPH successfully mitigated the increase in the concentration of oxidative biomarkers such as glutathione pyruvate transaminase, alkaline phosphatase, and creatinine, and restored the level of blood urea nitrogen to normal in sera of mice in which oxidative stress was induced with an overdose of paracetamol. Furthermore, the indices of different antioxidant enzymes, such as catalase, superoxide dismutase, and glutathione peroxidase, and lipid peroxidation end-products were determined in liver homogenate. The mice that were given WPH, either intraperitoneally or orally, showed increased activities of antioxidant enzymes and a reduction in thiobarbituric acid reactive substances (TBARS) compared with the paracetamol control group. The protective effect of WPH was less when administered orally than intraperitoneally. We concluded that WPH is the potential protector against paracetamol-induced hepato-nephrotoxicity and can be effectively used in health-promoting foods as a biofunctional ingredient.

A new flavonoid C-glycoside from Solanum elaeagnifolium with hepatoprotective and curative activities against paracetamol-induced liver injury in mice.

A new flavonoid C-glycoside, kaempferol 8-C-beta-galactoside, along with twelve known glycosidic flavonoids was isolated from the aqueous methanolic extract of Solanum elaeagnifolium Cav. (Solanaceae), by conventional chromatographic methods; their structure elucidation was achieved using UV, ESI-MS, and NMR spectral analyses. Groups of six mice were administered S. elaeagnifolium extracts at 25, 50, and 75 mg/kg body weight (BW) prior to or post administration of a single dose of paracetamol (500 mg/kg BW). The extract showed significant hepatoprotective and curative effects against histopathological and histochemical damage induced by paracetamol in liver. The extract also ameliorated the elevation in glutamate oxaloacetate transaminase (GOT), glutamate pyruvate transaminase (GPT), and alkaline phosphatase (ALP) levels. These findings were accompanied by a nearly normal architecture of the liver in the treated groups, compared to the paracetamol control group. As a positive control, silymarin was used, an established hepatoprotective drug against paracetamol-induced liver injury. This study provides the first validation of the hepatoprotective activity of S. elaeagnifolium.

P2X7 receptor-mediated purinergic signaling promotes liver injury in acetaminophen hepatotoxicity in mice.

Inflammation contributes to liver injury in acetaminophen (APAP) hepatotoxicity in mice and is triggered by stimulation of immune cells. The purinergic receptor P2X7 is upstream of the nod-like receptor family, pryin domain containing-3 (NLRP3) inflammasome in immune cells and is activated by ATP and NAD that serve as damage-associated molecular patterns. APAP hepatotoxicity was assessed in mice genetically deficient in P2X7, the key inflammatory receptor for nucleotides (P2X7-/-), and in wild-type mice. P2X7-/- mice had significantly decreased APAP-induced liver necrosis. In addition, APAP-poisoned mice were treated with the specific P2X7 antagonist A438079 or etheno-NAD, a competitive antagonist of NAD. Pre- or posttreatment with A438079 significantly decreased APAP-induced necrosis and hemorrhage in APAP liver injury in wild-type but not P2X7-/- mice. Pretreatment with etheno-NAD also significantly decreased APAP-induced necrosis and hemorrhage in APAP liver injury. In addition, APAP toxicity in mice lacking the plasma membrane ecto-NTPDase CD39 (CD39-/-) that metabolizes ATP was examined in parallel with the use of soluble apyrase to deplete extracellular ATP in wild-type mice. CD39-/- mice had increased APAP-induced hemorrhage and mortality, whereas apyrase also decreased APAP-induced mortality. Kupffer cells were treated with extracellular ATP to assess P2X7-dependent inflammasome activation. P2X7 was required for ATP-stimulated IL-1ß release. In conclusion, P2X7 and exposure to the ligands ATP and NAD are required for manifestations of APAP-induced hepatotoxicity.

Paracetamol toxicity: What would be the implications of a change in UK treatment guidelines?

BACKGROUND: Treatment of single-time-point ingestion acute paracetamol (acetaminophen) poisoning with N-acetylcysteine (NAC) is guided by plotting a timed plasma paracetamol concentration on established nomograms. Guidelines in the UK differ from those in the U.S. and Australasia by having two treatment lines on the nomogram. Patients deemed to be at 'normal' risk of hepatotoxicity are treated using the treatment line starting at 200 mg/L at 4 h post-ingestion; those at higher risk are treated using the 'high risk' treatment line starting at 100 mg/L at 4 h post-ingestion. AIM: To examine the effect on treatment numbers if UK guidelines were to adopt a single treatment line nomogram or lower, risk-stratified treatment lines. METHODS: We undertook a retrospective analysis of a series of acute single-time-point paracetamol poisonings presenting to our inner city emergency department. Treatment numbers and effect on treatment costs were modelled for three alternative scenarios: a 150 line-a combined single treatment line starting at a 4 h concentration of 150 mg/L, a 100 line-a combined single treatment line starting at a 4 h concentration of 100 mg/L, and a 150/75 line-a double treatment line at the lower concentrations of 150 mg/L for normal risk and 75 mg/L for high risk patients. RESULTS: A total of 1,214 cases were identified. Under current UK guidance, 133 (11.0%) high risk cases and 98 (8.1%) normal risk cases needed treatment (total 231, 19.0%). A 150 line would result in 87 (7.2%) high risk cases and 155 (12.8%) normal risk cases needing treatment (total 242, 19.9%). A 100 line would result in 133 (11.0%) high risk and 251 (20.7%) normal risk cases needing treatment (total 384, 31.6%). A 150/75 line would result in 153 (12.6%) high risk and 155 (12.8%) normal risk cases needing treatment (total 308, 25.4%). CONCLUSIONS: Both a 100 line and a 150/75 line would result in a large increase in the number of patients being treated and an associated increase in the costs of treatment. A single 150 mg/L treatment line would simplify treatment algorithms and lead to a similar number of patients being treated with NAC overall. A potential concern however is whether any of the high risk cases that would no longer be treated might develop significant hepatotoxicity. After consideration of the evidence for dual treatment lines, we feel that these risks are small and that it is worth reconsidering a change of treatment recommendations to a single 150 line.

The effect of different doses of flumazenil on acetaminophen toxicity in rats.

BACKGROUND: Acetaminophen is an analgesic drug that is used safely in therapeutic doses. At high doses, it causes hepatotoxicity, resulting in hepatic necrosis. Some medications and methods are available for treatment of acetaminophen overdose. However, results are inconsistent, and sufficient outcomes cannot always be obtained. OBJECTIVE: The mechanism of action of acetaminophen has not been fully understood. It has been suggested that it exerts its effects on GABA receptors. Flumazenil has been experimentally proven to produce an antagonism on acetaminophen's analgesic effect.The purpose of this study was to determine whether flumazenil antagonized the toxic effects of acetaminophen overdose in rats. METHODS: A total of 49 Wistar albino rats weighing between 250 - 350 g were used in the study. Nine rats were examined for a preliminary study, and the other rats were randomly divided into five groups with eight subjects in each. CONTROL GROUP: Saline; Acetaminophen group: 3 g/kg acetaminophen; Experimental Group F1: 3 g/kg acetaminophen + 0.1 mg/kg flumazenil; Experimental group F2: 3 g/kg acetaminophen + 1 mg/kg flumazenil; Experimental group F3: 3 g/kg acetaminophen + 10 mg/kg flumazenil. Acetaminophen was administered in a 3 ml saline solution by way of gastric catheter. Flumazenil was administered by way of intraperitoneal injections. Serum levels of acetaminophen, AST, ALT, LDH, ALP and bilirubin were recorded over a 24-hour period. RESULTS: Serum acetaminophen levels were similar between the groups. The AST, ALT, ALP, LDH, total bilirubin and direct bilirubin levels of Group A were significantly higher compared with the Group C, Group F1, Group F2 and Group F3. There was not a statistically significant difference in the AST, ALT, ALP, LDH, total bilirubin or direct bilirubin levels of the flumazenil-administered groups. CONCLUSION: Flumazenil's prevention of the acetaminophen-induced increase in liver enzymes is promising. There is some indication that flumazenil could be used in treatment of acetaminophen intoxication (Tab. 2, Ref. 25).

Acetaminophen hepatotoxicity and HIF-1α induction in acetaminophen toxicity in mice occurs without hypoxia.

HIF-1α is a nuclear factor important in the transcription of genes controlling angiogenesis including vascular endothelial growth factor (VEGF). Both hypoxia and oxidative stress are known mechanisms for the induction of HIF-1α. Oxidative stress and mitochondrial permeability transition (MPT) are mechanistically important in acetaminophen (APAP) toxicity in the mouse. MPT may occur as a result of oxidative stress and leads to a large increase in oxidative stress. We previously reported the induction of HIF-1α in mice with APAP toxicity and have shown that VEGF is important in hepatocyte regeneration following APAP toxicity. The following study was performed to examine the relative contribution of hypoxia versus oxidative stress to the induction of HIF-1α in APAP toxicity in the mouse. Time course studies using the hypoxia marker pimonidazole showed no staining for pimonidazole at 1 or 2h in B6C3F1 mice treated with APAP. Staining for pimonidazole was present in the midzonal to periportal regions at 4, 8, 24 and 48h and no staining was observed in centrilobular hepatocytes, the sites of the toxicity. Subsequent studies with the MPT inhibitor cyclosporine A showed that cyclosporine A (CYC; 10mg/kg) reduced HIF-1α induction in APAP treated mice at 1 and 4h and did not inhibit the metabolism of APAP (depletion of hepatic non-protein sulfhydryls and hepatic protein adduct levels). The data suggest that HIF-1α induction in the early stages of APAP toxicity is secondary to oxidative stress via a mechanism involving MPT. In addition, APAP toxicity is not mediated by a hypoxia mechanism.

Ondansetron does not block paracetamol-induced analgesia in a mouse model of fracture pain.

BACKGROUND: The aim of this study was to assess any interaction between ondansetron and paracetamol on a model of post-fracture pain in mice. METHODS: In protocol A, after fracture of the tibia, mice were assigned to four groups: paracetamol 30 mg kg⁻¹, paracetamol 50 mg kg⁻¹, paracetamol 100 mg kg⁻¹, or a saline vehicle i.p. In protocol B, after fracture of the tibia, mice were randomized to receive either paracetamol (100 mg kg⁻¹) plus saline (vehicle), paracetamol (100 mg kg⁻¹) plus ondansetron (1 mg kg⁻¹), paracetamol (100 mg kg⁻¹) plus ondansetron (2 mg kg⁻¹), saline plus ondansetron (2 mg kg⁻¹), or saline plus saline i.p. Three tests were used to assess pain behaviour: von Frey filament application, hot-plate test, and a subjective pain scale. Rescue analgesia with morphine was administered as necessary. RESULTS: In protocol A, paracetamol (100 mg kg⁻¹)-treated animals had less mechanical nociception, thermal nociception, and a lower subjective pain scale rating, when compared with those receiving paracetamol at 30 or 50 mg kg⁻¹ or saline [ED50 paracetamol=46.3 (6.34) mg kg⁻¹]. No difference was found between paracetamol (30 mg kg⁻¹) and saline-treated animals. In protocol B, the mechanical withdrawal threshold, the thermal withdrawal latency, and the subjective pain scale were lower after injection of paracetamol (100 mg kg⁻¹)+saline, paracetamol (100 mg kg⁻¹)+ondansetron (1 mg kg⁻¹), and paracetamol (100 mg kg⁻¹)+ondansetron (2 mg kg⁻¹), whereas in mice receiving saline+ondansetron (2 mg kg⁻¹) or saline+saline, there was no difference. CONCLUSION: We found that paracetamol 100 mg kg⁻¹ blocked the development of hyperalgesia and allodynia after fracture pain and ondansetron did not modify the antinociceptive effect of paracetamol in this model.