Hepatotoxicity of mild analgesics

Paracetamol use and lowered risk of acute kidney injury in patients with rhabdomyolysis

BACKGROUND

Mortality with rhabdomyolysis-associated acute kidney injury can be as high as 80%. Experimental data from mouse models of rhabdomyolysis showed that paracetamol reduces the expected increase in serum creatinine level. We aimed to assess the association between paracetamol use and the need for starting renal replacement therapy (RRT).

METHODS

We conducted a propensity score-matched cohort study in Orléans Hospital, France (a 1136-bed, public, university-affiliated and teaching hospital). All patients with serum creatine phosphokinase (CK) level > 5000 IU/L between January 1st, 2008 and December 31st, 2017 were included. A propensity score was calculated for each included patient by using multivariable logistic regression and all available baseline characteristics. The main outcome was the incidence of RRT initiation from day 1 to day 28 in the propensity score-matched cohort between patients exposed and unexposed to paracetamol.

RESULTS

Over the study period, 1065 patients with at least one CK level measurement > 5000 IU/L were included; 40 (3.8%) had at least one RRT session. Among the 343 matched pairs, 10 (2.9%) exposed and 24 (7.0%) unexposed patients underwent RRT before day 28 (P = 0.021). Primary time-to-event analysis showed that exposure to paracetamol was significantly associated with reduced absolute risk of RRT: absolute risk difference = - 3.18% (95% CI - 5.23 to - 1.20, P = 0.001). All secondary analyses showed a significantly reduced absolute risk of RRT in patients exposed to paracetamol.

CONCLUSION

Our study showed a significant association between paracetamol exposure and reduced incidence of RRT among patients with rhabdomyolysis.

PYP1-4 peptide from Pyropia yezoensis protects against acetaminophen-induced hepatotoxicity in HepG2 cells

Acetaminophen (APAP) is a widely used analgesic and antipyretic. It is safe at normal treatment doses; however, APAP overdose is a major cause of acute liver and kidney failure. A variety of methods to reduce the damage caused by APAP overdose have previously been evaluated. The protein-rich seaweed Pyropia yezoensis has antioxidant, antitumor and anti-inflammatory activities, and protects against cytotoxicity. However, little is known regarding the protective effects of P. yezoensis peptide against APAP-induced hepatotoxicity. The present study investigated the ability of P. yezoensis peptide (PYP1-4) to ameliorate the damage caused by APAP-induced hepatotoxicity using HepG2 as the model cell line in addition to the signaling pathways involved. Briefly, cell viability, nitric oxide, reactive oxygen species and apoptosis assays were performed in conjunction with western blot analysis and reverse transcription-quantitative PCR. First, the present study revealed the minimum toxic concentration of APAP (15 mM) and the resting concentration of PYP1-4 (0–500 ng/ml). Administration of PYP1-4 to APAP-induced cells decreased the nitric oxide and reactive oxygen species levels, and restored the levels of antioxidant-associated proteins (catalase, heme oxygenase 1, superoxide dismutase 2 and quinone oxidoreductase 1). PYP1-4 increased the translocation of nuclear factor, erythroid 2 like 2 to the nucleus and the activities of glycogen synthase kinase-3β, Akt and AMP-activated protein kinase. In addition, APAP induced apoptosis; however, PYP1-4 inhibited apoptosis by modulating the levels of pro-apoptotic markers (Bad), anti-apoptotic markers (Bcl-2 and BH3 interacting domain death agonist), caspases and poly (ADP-ribose) polymerase 1. Subsequently, the insulin-like growth factor 1 receptor signaling pathway was investigated to determine whether PYP1-4 treatment restored the levels of cell growth-associated factors during APAP-induced hepatotoxicity. PYP1-4 treatment impacted the levels of components of the insulin receptor substrate 1/PI3K/Akt and Ras/Raf/ERK signaling pathways, and promoted cell survival. Therefore, the P. yezoensis peptide PYP1-4 may be useful for preventing APAP-induced hepatotoxicity.

Mechanistic identification of biofluid metabolite changes as markers of acetaminophen-induced liver toxicity in rats

Acetaminophen (APAP) is the most commonly used analgesic and antipyretic drug in the world. Yet, it poses a major risk of liver injury when taken in excess of the therapeutic dose. Current clinical markers do not detect the early onset of liver injury associated with excess APAP-information that is vital to reverse injury progression through available therapeutic interventions. Hence, several studies have used transcriptomics, proteomics, and metabolomics technologies, both independently and in combination, in an attempt to discover potential early markers of liver injury. However, the casual relationship between these observations and their relation to the APAP mechanism of liver toxicity are not clearly understood. Here, we used Sprague-Dawley rats orally gavaged with a single dose of 2 g/kg of APAP to collect tissue samples from the liver and kidney for transcriptomic analysis and plasma and urine samples for metabolomic analysis. We developed and used a multi-tissue, metabolism-based modeling approach to integrate these data, characterize the effect of excess APAP levels on liver metabolism, and identify a panel of plasma and urine metabolites that are associated with APAP-induced liver toxicity. Our analyses, which indicated that pathways involved in nucleotide-, lipid-, and amino acid-related metabolism in the liver were most strongly affected within 10 h following APAP treatment, identified a list of potential metabolites in these pathways that could serve as plausible markers of APAP-induced liver injury. Our approach identifies toxicant-induced changes in endogenous metabolism, is applicable to other toxicants based on transcriptomic data, and provides a mechanistic framework for interpreting metabolite alterations.

Comparative Protective Effects of N-Acetylcysteine, N-Acetyl Methionine, and N-Acetyl Glucosamine against Paracetamol and Phenacetin Therapeutic Doses-Induced Hepatotoxicity in Rats

BACKGROUND AND AIMS

Both paracetamol (PA) and phenacetin (PH) are analgesic and antipyretic agents. Part of phenacetin therapeutic activity is attributed to its metabolism into paracetamol. Paracetamol causes direct hepatic oxidative stress damage. The present study aimed to investigate the possible damaging effects of both PA and PH, when used in therapeutic doses, on rat liver and to compare the antioxidant and hepatoprotective effects of N-acetylcysteine (NAC), N-acetyl-methionine (NAM), and N-acetylglucosamine (NAG) against PA- or PH-induced hepatic damage.

METHODS

90 male Wistar albino rats (120-140 gm) were undertaken, categorized randomly into 9 groups of 10 rats each, and administered by gavage for 2 weeks with DMSO 1% (controls), PA, PA+NAC, PA+NAM, PA+NAG, PH, PH+NAC, PH+NAM, and PH+NAG. Biochemical assays of malondialdehyde (MDA), nitric oxide (NO), reduced glutathione (GSH), total thiols, and alpha-fetoprotein (AFP) in liver homogenates and serum assays of ALT, AST, 8-hydroxy guanine (8-OH-Gua), and AFP were done. Also histopathological examinations of liver tissues in various groups were done.

RESULTS

PA and PH cause significant increase in hepatic levels of MDA, NO, and AFP and serum ALT, AST, and 8-OH-Gua levels, with significant decrease in hepatic GSH and total thiols. NAG and NAC significantly improve the PA- and PH-induced hepatic and blood, biochemical, and histopathological disturbances, respectively.

CONCLUSIONS

Both PA and PH induce oxidative stress in rat liver within their therapeutic doses. NAG and NAC in pharmacological doses can antagonize the oxidative damaging effect of both PA and PH.

Silymarin prevents acetaminophen-induced hepatotoxicity in mice

Acetaminophen or paracetamol (APAP) overdose is a common cause of liver injury. Silymarin (SLM) is a hepatoprotective agent widely used for treating liver injury of different origin. In order to evaluate the possible beneficial effects of SLM, Balb/c mice were pretreated with SLM (100 mg/kg b.wt. per os) once daily for three days. Two hours after the last SLM dose, the mice were administered APAP (300 mg/kg b.wt. i.p.) and killed 6 (T₆), 12 (T₁₂) and 24 (T₂₄) hours later. SLM-treated mice exhibited a significant reduction in APAP-induced liver injury, assessed according to AST and ALT release and histological examination. SLM treatment significantly reduced superoxide production, as indicated by lower GSSG content, lower HO-1 induction, alleviated nitrosative stress, decreased p-JNK activation and direct measurement of mitochondrial superoxide production in vitro. SLM did not affect the APAP-induced decrease in CYP2E1 activity and expression during the first 12 hrs. Neutrophil infiltration and enhanced expression of inflammatory markers were first detected at T₁₂ in both groups. Inflammation progressed in the APAP group at T₂₄ but became attenuated in SLM-treated animals. Histological examination suggests that necrosis the dominant cell death pathway in APAP intoxication, which is partially preventable by SLM pretreatment. We demonstrate that SLM significantly protects against APAP-induced liver damage through the scavenger activity of SLM and the reduction of superoxide and peroxynitrite content. Neutrophil-induced damage is probably secondary to necrosis development.

Fine-tuning the expression of microRNA-155 controls acetaminophen-induced liver inflammation

Treatment of acetaminophen (APAP) in overdose can cause a potentially serious and fatal liver injury. MicroRNA-155 (miR-155), a multifunctional microRNA, is known to mediate inflammatory responses via regulating various target genes. In this study, we aimed to study the role of miR-155 in APAP-induced liver injury, using miR-155-/- mice and miR-155 in vivo intervention. We noted that miR-155 expression was significantly increased in liver and blood after APAP treatment. Knockout of miR-155 deteriorated APAP-induced liver damage, with the elevated serum levels of AST and ALT. The levels of various inflammatory mediators, such as TNF-α and IL-6, were markedly augmented in livers in the absence of miR-155. Moreover, miR-155 deficiency aberrantly activated NF-kappa-B signaling via enhancing p65 and IKKε expression. Finally, in vivo administration of miR-155 agomir attenuated APAP-induced liver damage, reduced the serum levels of AST and ALT, and dampened the NF-kB signaling. In conclusion, our data demonstrated that miR-155 protects the mice against APAP-induced liver damage via mediating NF-KB signaling pathway, suggesting that miR-155 might be a potential pharmaceutic target for treatment of APAP-induced liver inflammation.

Protective Activity of Total Polyphenols from Genista quadriflora Munby and Teucrium polium geyrii Maire in Acetaminophen-Induced Hepatotoxicity in Rats

Oxidative stress is a major cause of drug-induced hepatic diseases and several studies have demonstrated that diet supplementation with plants rich in antioxidant compounds provides a variety of health benefits in these circumstances. Genista quadriflora Munby (Gq) and Teucrium polium geyrii Maire (Tp) are known to possess antioxidant and numerous biological properties and these endemic plants are often used for dietary or medicinal applications. Herein, we evaluated the beneficial effect of rich-polyphenol fractions of Gq and Tp to prevent Acetaminophen-induced liver injury and investigated the mechanisms involved in this protective action. Rats were orally administered polyphenolic extracts from Gq or Tp (300 mg/kg) or N-acetylcysteine (NAC: 200 mg/kg) once daily for ten days prior to the single oral administration of Acetaminophen (APAP: 1 g/kg). The results show that preventive administration of polyphenolic extracts from Gq or Tp exerts a hepatoprotective influence during APAP treatment by improving transaminases leakage and liver histology and stimulating antioxidant defenses. Besides, suppression of liver CYP2E1, GSTpi and TNF-α mRNA levels, with enhancement of mitochondrial bioenergetics may contribute to the observed hepatoprotection induced by Gq and Tp extracts. The effect of Tp extract is significantly higher (1.5–2 fold) than that of Gq extract and NAC regarding the enhancement of mitochondrial functionality. Overall, this study brings the first evidence that pretreatment with these natural extracts display in vivo protective activity against APAP hepatotoxicity through improving mitochondrial bioenergetics, oxidant status, phase I and II enzymes expression and inflammatory processes probably by virtue of their high total polyphenols content.

Some biochemical and haematological changes in rats pretreated with aqueous stem bark extract of Lophira lanceolata and intoxicated with paracetamol (acetaminophen)

BACKGROUND

This study investigated the acute toxicity effect of aqueous stem bark extract of Lophira lanceolata and the activities of liver enzymes and other markers of organ damage in rats pretreated with aqueous stem bark extract of L. lanceolata extract and subsequently intoxicated with paracetamol (PCM).

METHODS

A total of 30 rats were used to determine the acute toxicity of aqueous extract of L. lanceolata stem. They were divided into six groups consisting of five rats each. The groups (A-F) were administered the increasing doses of the extract (500 mg/kg, 1,000 mg/kg, 2,000 mg/kg, 3,200 mg/kg, 4,000 mg/kg and 5,000 mg/kg) orally. The rats were observed over a period of 24 h for acute toxicity signs such as dullness, anorexia, morbidity and death. Thirty rats of mixed sexes randomly assigned to six groups (A-F) of five rats each were used for the study on the effects of L. lanceolata extract on the haematology, liver enzymes and markers of organ damage of extract-pretreated PCM-intoxicated rats. The rats in groups A-D were pretreated with 100 mg/kg, 200 mg/kg, 300 mg/kg of L. lanceolata extract and 100 mg/kg Silymarin, respectively, twice a day for 7 days. On the seventh day, all the rats in groups A-E received 1,000 mg/kg PCM (per os). Group E rats served as negative control while group F rats were neither intoxicated nor treated with the extract and served as positive control. Eighteen hours after PCM intoxication, blood samples were collected for biochemical analyses. The serum activities of these enzymes (aspartate aminotransferase [AST], alanine aminotransferase [ALT], alkaline phosphatase [ALP]) and other markers of organ damages (bilirubin and total protein) were investigated. Haematologic parameters such as packed cell volume, red blood cell count, white blood cell count and haemoglobin concentration were also determined.

RESULTS

The extract did not cause any death in all the groups even at the highest dose (5,000 mg/kg body weight). The results also showed varying degrees in the activity of the enzymes in the serum in comparison with the negative control. The mean serum ALP, ALT and AST activity of group C (rats pretreated with 300 mg/kg of the extract and 1,000 mg/kg PCM) were significantly (p<0.05) lower than that of the group E (rats intoxicated with 1,000 mg/kg PCM only). The AST and ALP activities of groups C-E rats) were statistically comparable. The serum ALT activities of group C rats were significantly (p<0.05) lower than that of group E rats but were statistically comparable (p>0.05) with the group F counterpart. The bilirubin levels were significantly (p<0.05) lower in the groups pretreated with the extract and Silymarin in comparison with the D group. The total protein and the haematologic indices were not significantly different (p>0.05) across the groups.

CONCLUSIONS

This study therefore showed that the aqueous stem bark extract of L. lanceolata possesses some active constituents that have antihepatotoxic potentials.

Roles of lipoxin A4 in preventing paracetamol-induced acute hepatic injury in a rabbit model

The objective of this research is to investigate the potential role of lipoxin A4 in preventing paracetamol (PCM)-induced hepatic injury. One hundred male New Zealand white rabbits were randomly divided into control group, PCM group, N-acetylcysteine (NAC) group, lipoxin A4 (LXA4) group, and LXA4 + NAC group. The rabbits were assigned to receive 300 mg/kg weight PCM in 0.9 % saline or equivalent volume of saline via gastric lavage. LXA4 (1.5 μg/kg) and equivalent volume of 2 % ethanol were separately given to the rabbits in LXA4-treated and PCM groups 24 h after PCM administration. Meanwhile, the rabbits in the NAC-treated groups received a loading dose of 140 mg/kg of N-acetylcysteine. The blood samples and liver tissue were collected for biochemical and histological evaluation 36 h after paracetamol administration. The administration of LXA4 24 h after paracetamol poisoning resulted in significant improvement in hepatic injury as represented by decrease of hepatocellular enzyme release and attenuation of hepatocyte apoptosis and necrosis. In LXA4-treated groups, the expression of TNF-α was significantly lower than those in PCM and NAC groups (p < 0.05). In contrast, the level of IL-10 was significantly higher than PCM and NAC groups (p < 0.05). Moreover, the expressions of NF-κB p65 in PCM and NAC groups were significantly increased compared with those of LXA4-treated groups and control group (respectively, p < 0.05 and p < 0.01). LXA4-treated groups also showed significantly higher survival rates. Lipoxin A4 significantly mitigates paracetamol-induced hepatic injury, in which anti-inflammation effect may play an important role, leading to hepatic apoptosis and necrosis.

Signalling pathways involved in paracetamol-induced hepatotoxicity: new insights on the role of protein tyrosine phosphatase 1B

Acute hepatic failure secondary to paracetamol poisoning is associated with high mortality. Paracetamol-induced hepatotoxicity causes oxidative stress that triggers signalling pathways and ultimately leads to lethal hepatocyte injury. We will review the signalling pathways activated by paracetamol in the liver emphasizing the role of protein tyrosine phosphatase 1B (PTP1B) in the balance between cell death and survival in hepatocytes. PTP1B has emerged as a key modulator of the antioxidant system mediated by the nuclear factor erythroid-2-related factor 2 (Nrf2) in hepatic cells in response to paracetamol overdose. Also, this phosphatase modulates the classical survival pathways triggered by the activation of the insulin-like growth factor-I (IGF-I) signalling cascade. Therefore, PTP1B is a novel therapeutic target against paracetamol-induced liver failure.

Attenuation of Acetaminophen-Induced Hepatotoxicity In Vivo and In Vitro by a 43-kD Protein Isolated from the Herb Cajanus indicus L

ABSTRACT The aim of this study was to evaluate the hepatoprotective role of a 43-kD protein (Hp-P) isolated from the leaves of Cajanus indicus L. against acetaminophen (APAP)-induced toxicity in mouse liver and in isolated hepatocytes. The hepatotoxicity of APAP and the hepatoprotective activity of Hp-P in vivo were determined by measuring the liver-specific serum marker enzymes alanine amino transferase (ALT) and alkaline phosphatase (ALP) in murine sera and observing the histological changes in the mice liver treated with the protein before and after (2 mg/kg body weight for 5 days) APAP (at a dose of 300 mg/kg body weight for 2 days) administration. The cell viability, LDH leakage, GSH level, and lipid peroxidation were measured in isolated hepatocytes to evaluate the cytotoxic effect of APAP and the protective role of Hp-P in vitro. Experimental results showed that APAP induced hepatotoxicity in vivo as revealed from the changes in serum-specific marker enzyme levels and histology of liver. It also induced cytotoxicity in hepatocytes as observed from the changes in cell viability and LDH leakage. Pretreatment with Hp-P prevented the APAP-induced elevation of ALT and ALP in murine sera. In addition, posttreatment with Hp-P significantly altered most of the changes induced by APAP. Although some natural recovery has been observed in toxin controls, the Hp-P-induced recovering process is more rapid than the natural ones. In histological studies, less centrilobular necrosis was found in the liver treated with Hp-P before and after APAP intoxication compared to the liver treated with APAP alone. Radical scavenging experiment showed that Hp-P scavenges DPPH radicals directly. Studies also showed that APAP-induced reduced cell viability and cellular LDH leakage could be prevented by the combinatorial effect of Hp-P. Besides, treatment of hepatocytes with Hp-P and APAP together maintained the normal GSH level. APAP-induced enhanced lipid peroxidation was also decreased when cells were treated with APAP and Hp-P together. Hp-P alone, on the other hand, did not induce any alterations of the studied parameters. Results of this study have been compared with a known antioxidant, alpha-tocopherol. Data from both the in vivo (before and after APAP administration) and in vitro studies suggest that Hp-P has potent hepato- and cytoprotective properties against APAP-induced toxicity.

Discovery of common urinary biomarkers for hepatotoxicity induced by carbon tetrachloride, acetaminophen and methotrexate by mass spectrometry-based metabolomics

Liver toxicity represents an important healthcare issue because it causes significant morbidity and mortality and can be difficult to predict before symptoms appear owing to drug therapy or exposure to toxicants. Using metabolomic techniques, we discovered common biomarkers for the prediction of hepatotoxicity in rat urine using mass spectrometry. For this purpose, liver toxicity was induced by 5 days of oral administration of carbon tetrachloride (1 ml kg(-1) per day), acetaminophen (1000 mg kg(-1) per day) and methotrexate (50 mg kg(-1) per day). Serum levels of alkaline phosphatase aspartate aminotransferase, alanine aminotransferase and histopathology in liver tissue were then checked to demonstrate liver toxicity. Global metabolic profiling with UPLC-TOF-MS (ultraperformance liquid chromatography-mass spectrometry), multivariate analysis (partial least square-discriminant analysis, hierarchical analysis) and database searching were performed to discover common biomarkers for liver toxicity induced by these three compounds. Urinary concentrations of the newly discovered biomarkers were then quantified to confirm them as biomarkers of hepatotoxicity with targeted metabolic profiling using GC (gas chromatography)-MS and CE (capillary electrophoresis)-MS. In the results, steroids, amino acids and bile acids were metabolically changed between the control and drug-treated groups in global metabolic profiling; 11β-hydroxyandrosterone, epiandrosterone, estrone, 11-dehydrocorticosterone, glycine, alanine, valine, leucine, dl-ornithine, 3-methylhistidine, cholic acid and lithocholic acid were selected as liver toxicity biomarkers after performing targeted metabolic profiling. In conclusion, we discovered metabolite biomarkers belonging to three different metabolic pathways to check for liver toxicity with mass spectrometry from a metabolomics study that could be used to evaluate hepatotoxicity induced by drugs or other toxic compounds.

Protective effects of 2,4-dihydroxybenzophenone against acetaminophen-induced hepatotoxicity in mice

AIM: To examine the effects of 2,4-dihydroxybenzophenone (BP-1), a benzophenone derivative used as an ultraviolet light absorbent, on acetaminophen (APAP)-induced hepatotoxicity in C57BL/6J mice.

METHODS: Mice were administered orally with BP-1 at doses of 200, 400 and 800 mg/kg body weight respectively every morning for 4 d before a hepatotoxic dose of APAP (350 mg/kg body weight) was given subcutaneously. Twenty four hours after APAP intoxication, the serum enzyme including serum alaine aminotransferase (ALT), aspartate aminotransferase (AST), lactate dehydrogenase (LDH) were measured and liver histopathologic changes were examined.

RESULTS: BP-1 administration dramatically reduced serum ALT, AST and LDH levels. Liver histopathological examination showed that BP-1 administration antagonized APAP-induced liver pathological damage in a dose-dependent manner. Further tests showed that APAP-induced hepatic lipid peroxidation was reduced significantly by BP-1 pretreatment, and glutathione depletion was ameliorated obviously.

CONCLUSION: BP-1 can effectively protect C57BL/6J mice from APAP-induced hepatotoxicity, and reduction of oxidative stress might be part of the protection mechanism.

Gap junction dysfunction reduces acetaminophen hepatotoxicity with impact on apoptotic signaling and connexin 43 protein induction in rat

Acetaminophen (APAP) is a widely used antipyretic and analgesic agent. However, overdosing and sometimes even a recommended dose can lead to serious and conceivably fatal liver toxicity. Therefore, it is important to clarify understand mechanisms of hepatotoxicity induced by APAP. Gap junctions, formed by connexin, have important roles in maintenance of tissue homeostasis and control of cell growth and differentiation. In the liver, Cx32 is a major gap junction protein whose expression is known to gradually decrease with chronic liver disease progression. In the present study, acute hepatotoxic effects of APAP were found to be reduced in Cx32 dominant negative transgenic rats lacking normal gap junctional intercellular communication in the liver. In littermate wild-type rats, the injured centrilobular hepatocytes were positive for TUNEL staining and featured elevated expre ssion of cleaved caspase-3 and Cx43, which is not expressed in normal hepatocytes. These results suggest that APAP hepatotoxicity involves apoptosis, and induction of Cx43 expression may play an important role in the apoptotic signaling. Moreover, gap junctional functions of Cx32 can play important roles in removing damaged hepatocytes by apoptosis for liver tissue homeostasis.

Investigation of long-term retention of unchanged (-)-N-{2-[(R)-3-(6,7-dimethoxy-1,2,3,4-tetrahydroisoquinoline-2-carbonyl)piperidino]ethyl}-4-fluorobenzamide, a novel "funny" If current channel inhibitor, and its metabolites in the eyeball and thoracic aorta of rats

(-)-N-{2-[(R)-3-(6,7-dimethoxy-1,2,3,4-tetrahydroisoquinoline-2-carbonyl)piperidino]ethyl}-4-fluorobenzamide (YM758), a novel "funny" If current channel inhibitor, was being developed as a treatment for stable angina and atrial fibrillation. After a single oral administration of (14)C-YM758, extensive accumulation and long-term retention of radioactivity were observed in the eyeballs of nonalbino rats and in the thoracic aorta of albino/nonalbino rats. Radioluminograms of the eyeballs of nonalbino rats indicated that the radioactivity was localized to the uveal tract, which suggests that the radioactivity may be positively charged and bound mainly to the melanins. Treatment with a mixture of 2 mol/l hydrochloric acid and methanol (5:95, v/v) allowed for the recovery of the major portion of radioactivity from the eyeball, which suggests reversible binding. The radioactive constituents in eyeballs consisted of the unchanged drug (YM758) and three metabolites [mainly 6,7-dimethoxy-2-[(3R)-piperidin-3-ylcarbonyl]-1,2,3,4-tetrahydroisoquinoline (YM-252124)]. Using the organic solvent mixture described above, almost all of the radioactivity was not collected from the thoracic aorta, and approximately 90% was recovered by treatment with elastase, which suggests that some metabolites covalently bind to the elastin fiber localized in the tunica media.

Intestinal glucose uptake protects liver from lipopolysaccharide and D-galactosamine, acetaminophen, and alpha-amanitin in mice

We have recently observed that oral administration of D-glucose saves animals from lipopolysaccharide (LPS)-induced death. This effect is the likely consequence of glucose-induced activation of the sodium-dependent glucose transporter-1. In this study, we investigated possible hepatoprotective effects of glucose-induced, sodium-dependent, glucose transporter-1 activation. We show that oral administration of D-glucose, but not of either D-fructose or sucrose, prevents LPS-induced liver injury, as well as liver injury and death induced by an overdose of acetaminophen. In both of these models, physiological liver morphology is maintained and organ protection is confirmed by unchanged levels of the circulating markers of hepatotoxicity, such as alanine transaminase or lactate dehydrogenase. In addition, D-glucose was found to protect the liver from alpha-amanitin-induced liver injury. In this case, in contrast to the previously described models, a second signal had to be present in addition to glucose to achieve protective efficacy. Toll-like receptor 4 stimulation that was induced by low doses of LPS was identified as such a second signal. Eventually, the protective effect of orally administered glucose on liver injury induced by LPS, overdose of acetaminophen, or alpha-amanitin was shown to be mediated by the anti-inflammatory cytokine interleukin-10. These findings, showing glucose-induced protective effects in several animal models of liver injury, might be relevant in view of possible therapeutic interventions against different forms of acute hepatic injury.

Role of cytochrome P450 2E1 in protein nitration and ubiquitin-mediated degradation during acetaminophen toxicity

It is well established that following a toxic dose of acetaminophen (APAP), nitrotyrosine protein adducts (3-NT), a hallmark of peroxynitrite production, were colocalized with necrotic hepatic centrilobular regions where cytochrome P450 2E1 (CYP2E1) is highly expressed, suggesting that 3-NT formation may be essential in APAP-mediated toxicity. This study was aimed at investigating the relationship between CYP2E1 and nitration (3-NT formation) followed by ubiquitin-mediated degradation of proteins in wild-type and Cyp2e1-null mice exposed to APAP (200 and 400mg/kg) for 4 and 24h. Markedly increased centrilobular liver necrosis and 3-NT formation were only observed in APAP-exposed wild-type mice in a dose- and time-dependent manner, confirming an important role for CYP2E1 in APAP biotransformation and toxicity. However, the pattern of 3-NT protein adducts, not accompanied by concurrent activation of nitric oxide synthase (NOS), was similar to that of protein ubiquitination. Immunoblot analysis further revealed that immunoprecipitated nitrated proteins were ubiquitinated in APAP-exposed wild-type mice, confirming the fact that nitrated proteins are more susceptible than the native proteins for ubiquitin-dependent degradation, resulting in shorter half-lives. For instance, cytosolic superoxide dismutase (SOD1) levels were clearly decreased and immunoprecipitated SOD1 was nitrated and ubiquitinated, likely leading to its accelerated degradation in APAP-exposed wild-type mice. These data suggest that CYP2E1 appears to play a key role in 3-NT formation, protein degradation, and liver damage, which is independent of NOS, and that decreased levels of many proteins in the wild-type mice (compared with Cyp2e1-null mice) likely contribute to APAP-related toxicity.

Acute Hepatotoxicity: A Predictive Model Based on Focused Illumina Microarrays

Drug-induced hepatotoxicity is a major issue for drug development, and toxicogenomics has the potential to predict toxicity during early toxicity screening. A bead-based Illumina oligonucleotide microarray containing 550 liver specific genes has been developed. We have established a predictive screening system for acute hepatotoxicity by analyzing differential gene expression profiles of well-known hepatotoxic and nonhepatotoxic compounds. Low and high doses of tetracycline, carbon tetrachloride (CCL4), 1-naphthylisothiocyanate (ANIT), erythromycin estolate, acetaminophen (AAP), or chloroform as hepatotoxicants, clofibrate, theophylline, naloxone, estradiol, quinidine, or dexamethasone as nonhepatotoxic compounds, were administered as a single dose to male Sprague-Dawley rats. After 6, 24, and 72 h, livers were taken for histopathological evaluation and for analysis of gene expression alterations. All hepatotoxic compounds tested generated individual gene expression profiles. Based on leave-one-out cross-validation analysis, gene expression profiling allowed the accurate discrimination of all model compounds, 24 h after high dose treatment. Even during the regeneration phase, 72 h after treatment, CCL4, ANIT, and AAP were predicted to be hepatotoxic, and only these three compounds showed histopathological changes at this time. Furthermore, we identified 64 potential marker genes responsible for class prediction, which reflected typical hepatotoxicity responses. These genes and pathways, commonly deregulated by hepatotoxicants, may be indicative of the early characterization of hepatotoxicity and possibly predictive of later hepatotoxicity onset. Two unknown test compounds were used for prevalidating the screening test system, with both being correctly predicted. We conclude that focused gene microarrays are sufficient to classify compounds with respect to toxicity prediction.

ACETAMINOPHEN-INDUCED HEPATOTOXICITY

The analgesic acetaminophen causes a potentially fatal, hepatic centrilobular necrosis when taken in overdose. The initial phases of toxicity were described in Dr. Gillette's laboratory in the 1970s. These findings indicated that acetaminophen was metabolically activated by cytochrome P450 enzymes to a reactive metabolite that depleted glutathione (GSH) and covalently bound to protein. It was shown that repletion of GSH prevented the toxicity. This finding led to the development of the currently used antidote N-acetylcysteine. The reactive metabolite was subsequently identified to be N-acetyl-p-benzoquinone imine (NAPQI). Although covalent binding has been shown to be an excellent correlate of toxicity, a number of other events have been shown to occur and are likely important in the initiation and repair of toxicity. Recent data have shown that nitrated tyrosine residues as well as acetaminophen adducts occur in the necrotic cells following toxic doses of acetaminophen. Nitrotyrosine was postulated to be mediated by peroxynitrite, a reactive nitrogen species formed by the very rapid reaction of superoxide and nitric oxide (NO). Peroxynitrite is normally detoxified by GSH, which is depleted in acetaminophen toxicity. NO synthesis (serum nitrate plus nitrite) was dramatically increased following acetaminophen. In inducible nitric oxide synthase (iNOS) knockout mice, acetaminophen did not increase NO synthesis or tyrosine nitration; however, histological evidence indicated no difference in toxicity. Acetaminophen did not cause hepatic lipid peroxidation in wild-type mice but did cause lipid peroxidation in iNOS knockout mice. These data suggest that NO may play a role in controlling lipid peroxidation and that reactive nitrogen/oxygen species may be important in toxicity. The source of the superoxide has not been identified, but our recent finding that NADPH oxidase knockout mice were equally sensitive to acetaminophen and had equal nitration of tyrosine suggests that the superoxide is not from the activation of Kupffer cells. It was postulated that NAPQI-mediated mitochondrial injury may be the source of the superoxide. In addition, the significance of cytokines and chemokines in the development of toxicity and repair processes has been demonstrated by several recent studies. IL-1beta is increased early in acetaminophen toxicity and may be important in iNOS induction. Other cytokines, such as IL-10, macrophage inhibitory protein-2 (MIP-2), and monocyte chemoattractant protein-1 (MCP-1), appear to be involved in hepatocyte repair and the regulation of proinflammatory cytokines.

Over-the-counter analgesics: a toxicology perspective

The decision to use any analgesic is a balance of benefit and risk. In the case of analgesics, it is important to balance the therapeutic benefit against both the risk in therapeutic use and the risk (and ease of treatment) in overdose. Paracetamol in therapeutic dose carries little risk of adverse events. Less than 0.1% of the estimated 30 million paracetamol users in the United Kingdom attend hospital with a paracetamol overdose each year, and approximately 200 people die, most of whom presented late or did not receive antidote, N-acetylcysteine, within 12 hours. Nonsteriodal anti-inflammatory drugs (NSAIDs) have greater adverse effects in therapeutic use than paracetamol but also have a lower incidence of severe features or death in overdose. There is no antidote available for NSAID poisoning. Aspirin carries both significant adverse effects in therapeutic dose and a substantial risk in overdose, for which there is no antidote. Its risk-benefit profile is probably the poorest of all analgesics currently available over-the-counter (OTC); this is reflected in current trends both in analgesic use and overdose figures. Although a number of options to reduce deaths from poisoning by OTC analgesics have been considered, few are practical, and all must take account of the public health benefits provided by these drugs. A perspective should be retained that the vast majority of the population in Australia, the United States, the United Kingdom, and Denmark derive therapeutic benefit from OTC analgesics and do not take them in overdose. The majority of those who do take overdoses come to little or no harm. Management of serious poisoning by paracetamol, aspirin, or NSAIDs remains a medical challenge.

Acetaminophen hepatotoxicity and mechanisms of its protection by N-acetylcysteine: a study of Hep3B cells

Acetaminophen (AAP) hepatotoxicity, resulting in centrilobular necrosis, is frequently encountered following suicidal attempts, especially by adolescents, but also after its excessive use in infants. The subcellular and molecular sequences leading to hepatocellular cell death are not yet clear. We therefore investigated AAP hepatotoxicity by using cultured hepatoma-derived cells (Hep3B) exposed to AAP and N-acetylcysteine (NAC), used as a protective agent. Specifically, we studied the role of apoptosis and oxidative damage as putative mechanisms of AAP-associated cytotoxicity. Hep3B cells were exposed to AAP (5-25 mM) and NAC (5 mM) for different time periods. Cell viability was assessed by the Alamar Blue Reduction Test and LDH. Oxidative damage was evaluated by measuring reactive oxygen species (ROS) and glutathione. AAP-induced apoptosis was investigated by flow cytometry and transmission electron microscopy. We found that: 1. In Hep3B cells, AAP causes a time- and concentration-dependent cytotoxic effect, leading to oxidative stress, mitochondrial dysfunction, alterations of membrane permeability and apoptosis; 2. In the course of AAP cytotoxicity, the generation of ROS appears as an early event which precedes decrease of viability, LDH leakage, glutathione depletion and apoptosis; 3. NAC protects Hep3B cells from AAP-induced oxidative injury, but does not prevent apoptosis.

Primary changes in liver damage by aspirin in rats

BACKGROUND

It has been known that acetylsalicylic acid (ASA) causes liver cell damage, however, its mechanisms remain obscure.

METHODS AND RESULTS

To clarify the earliest change in the course of liver cell damage induced by oral administration of ASA, rats that had received ASA at 50 mg/kg and 150 mg/kg bodyweight orally for 7 days were investigated. Mitochondria were isolated for measurements of mitochondrial respiration, and for electron microscopic observations, small pieces of liver were excised and fixed. Uncoupling of oxidative phosphorylation was observed in mitochondria isolated from ASA-treated rats. Although no histological changes were evident, lamellar structures in bile canaliculi were ultrastructurally observed in all rats treated with ASA.

CONCLUSIONS

This laminar structure, which is negative for bilirubin staining, seems to be one of the most sensitive indicators of ASA-induced liver damage.

Antipyretic efficacy of tiaprofenic acid in febrile children

In children, tiaprofenic acid (TA), a non steroidal antiinflammatory drug, propionic-acid derivative, has been proven effective in the treatment of symptoms of tonsillitis and pharyngitis but not yet in the symptomatic treatment of fever. This double-blind, parallel group, placebo (Pl) controlled study was designed in order to demonstrate the antipyretic activity of TA. The co-prescription of other antipyretic medications in children may therefore be avoided. Two groups of children, 29 (TA group) and 26 (Pl group), were included and received either 4.2 +/- 0.5 mg/kg of TA given orally in a single dose or a Pl match. Rectal temperature was recorded just before and 1, 2, 4 and 6 hours after dosing. The maximum temperature decrease was significantly greater in the TA group (-1.3 degrees C +/- 0.7 degree C) than in the Pl group (-0.4 degree C +/- 0.8 degree C). The percentage of children who needed a rescue treatment during the study was 35% (10/29) and 62% (16/26) in the TA and Pl group, respectively. The rescue treatment was composed of a single oral acetaminophen dose in case of fever above 39.5 degrees C or if the temperature decrease was not at least equal to 0.6 degree C four hours after dosing. No major side effect was reported by the parents during the study period. In conclusion, TA at a single mean 4.2 mg/kg oral dose, is an effective antipyretic drug in febrile children. The duration of the antipyretic effect was estimated as at least four hours.

Analgesic-associated nephropathy

Although the question of whether or not analgesic abuse leads to a certain type of nephropathy has been investigated since 1953, no conclusive answer has been forthcoming. Epidemiologic investigations on the correlation between analgesic abuse and renal function as well as experimental animal studies have given contradictory results concerning the possibility of analgesic-associated kidney damage. However, studies on the correlation between analgesic abuse and papillary necrosis have demonstrated that this lesion coincides in 69% of the cases with an analgesic history. Follow-up studies of patients with analgesic nephropathy have shown that renal function deteriorates in 60% of the patients with continued abuse and that it stabilizes in 80% of the patients after cessation of abuse. Studies on the legislative restriction of phenacetin/acetaminophen, carried out mostly in Scandinavian countries since 1965, show a 50%-90% decline in signs of analgesic nephropathy (papillary necrosis) following a reduction in the sale of these drugs. The prevalence of analgesic abuse may be underestimated, since up to 80% of the abusers tend to deny their analgesic intake. Obviously, only a small percentage of analgesic abusers (approximately 1%) finally develop nephropathy. Even though the results of epidemiologic and experimental studies are contradictory, the results of investigations on papillary necrosis and on legislative prevention as well as of patient follow-ups tend to indicate a correlation between analgesic abuse and a well-defined type of nephropathy.

Quinuronium induced hepatotoxicity in rats

Two groups of 6 rats each received subcutaneous injections of 2.3 mg/kg or 5.0 mg/kg of quinuronium, respectively, on two consecutive days, while 5 rats injected with physiological saline served as controls. Clinical signs of muscular tremors, jumps, enlarged and hyperemic eyeballs, lacrimation, depression and anorexia were observed following administration of quinuronium. One rat receiving 5 mg/kg died before termination of the study. When killed 48 h after the first injection, the quinuronium-treated rats had a higher liver weight/body weight ratio compared to the controls. Quinuronium resulted in hepatic centrilobular fatty degeneration, but no depletion of hepatic glutathione (GSH). The present findings suggest that glutathione depletion does not seem to be involved in quinuronium hepatotoxicity.

Comparison of a traditional paracetamol medication and a new paracetamol/paracetamol-methionine ester combination

The SUR 2647 combination is a sachet formulation containing free paracetamol and its N-acetyl-methionate ester (SUR 2647). In a randomized, single-blind, between-patient study the onset of analgesia, duration and efficacy of the SUR 2647 combination vs paracetamol was investigated in out-patients after oral surgery. One group (n = 27) received sachets of SUR 2647 combination 2 b.i.d. (equivalent to 2 g paracetamol X 2) on the day of operation, and one sachet b.i.d. (equivalent to 1 g paracetamol X 2) for the following two days. The other group (n = 26) received paracetamol tablets 2 q.i.d. on the day of operation (1 g X 4) and one tablet q.i.d. (0.5 g X 4) for the following two days. Several objective and subjective assessments, including pain score on a visual analogue scale, were recorded for comparison of the postoperative courses. Median onset of analgesia for both groups was less than or equal to 0.5 h. The duration after SUR 2647 combination was greater than or equal to 5.5 h as compared to greater than or equal to 2.5 h for paracetamol. Mean pain scores showed that the SUR 2647 combination regime reduced pain significantly more than the paracetamol regime from 0.5 to 3.0 h after initiation of medication. The mean pain scores did not show a significant difference during the remaining observation period. Mild to moderate drowsiness was reported in both treatment groups, but it was more common in subjects given SUR 2647 combination.

Use of antipyretic analgesics in the pediatric patient

Fever and pain are the most common issues in pediatric patient management. Acetaminophen, aspirin, and dipyrone are the most commonly used drugs and are equivalent in their efficacy. Dipyrone, used in many parts of the world, but not in the United States, is an effective agent; however, it has been implicated in producing agranulocytosis and anaphylactic shock. The salicylates have anti-inflammatory effects making them appropriate for the treatment of patients with juvenile rheumatoid arthritis, but they are gastric irritants, may impair clotting, and, because of saturable kinetics, may lead to accumulation and toxicity. Acetaminophen is an effective antipyretic and analgesic with few side effects that is toxic only in massive overdose.

Distribution of the acetyl compared with the salicyl moiety of acetylsalicylic acid. Acetylation of macromolecules in organs wherein side-effects are manifest

The distribution in rats of the acetyl group of aspirin has been compared with that of the salicyl moiety with the objective of establishing if: (1) there are differences in their biodisposition which might be important in the development of side- or therapeutic effects of aspirin, and (2) the range of organs and biomolecules therein which are acetylated by aspirin. Using whole-body autoradiography and liquid scintillation counting techniques it was found that the acetyl group of 3H- or 14C-acetyl-labelled aspirin became bound to a wide variety of proteins, glycoproteins and lipids of the glandular and non-glandular region of the stomach, kidney, liver and to a lesser extent bone marrow, i.e. organs in which side-effects are frequently encountered. It is suggested that: (1) the acetylation of biomolecules may be a major factor in the development of side-effects in these organs, and (2) in addition to acetylation of prostaglandin synthetase, the acetylation of enzymes and other biomolecules may have a much wider bearing on the biochemical changes underlying the development of these side-effects. Acetylation of the protein/macromolecular components was especially pronounced in inflamed (c.f. control) hindpaws of carrageenan-injected rats. This could be a result of acetylation of the drug-carrier protein, albumin, and other proteins carried into inflamed tissues and this acetylation could have marked consequences for the functions of these proteins.