Effect of aspirin on a subtoxic dose of 14C-acetaminophen in mice

Sex-specific neurobehavioral and prefrontal cortex gene expression alterations following developmental acetaminophen exposure in mice

Acetaminophen (N-acetyl-p-aminophenol (APAP), also known as paracetamol) is one of the most common medications used by the general population, including pregnant people. Although many human observational and animal model studies have shown associations between prenatal and early postnatal APAP exposure and attention deficit hyperactivity disorder, autism spectrum disorders, and altered neurodevelopment, the existing literature is limited. In particular, no mouse studies of prenatal APAP exposure have investigated offspring attention deficits in behavioral tasks specifically designed to measure attention, and no prior rodent studies have utilized 'omics' technologies, such as transcriptomics, for an untargeted exploration of potential mechanisms. We randomly assigned pregnant mice (starting embryonic day 4-10) to receive APAP (150 mg/kg/day) or vehicle control through postnatal day 14. We evaluated 111 mouse offspring in a battery of behavioral tests, including pup ultrasonic vocalizations, elevated plus-maze, open field test, CatWalk (gait), pre-pulse inhibition, and the automated 5-choice serial reaction time task. Prefrontal cortex was collected at birth from 24 pups for RNA sequencing. Developmental APAP treatment resulted in increased and hastened separation-induced pup vocalizations between postnatal days 2 and 11, as well as decreased ambulation and vertical rearings in the open field in male but not female adult offspring. APAP treatment was also associated with altered sex-specific prefrontal cortex gene expression relating to glutathione and cytochrome p450 metabolism, DNA damage, and the endocrine and immune systems. This study provides additional evidence for the neurodevelopmental harm of prenatal APAP exposure and generates hypotheses for underlying molecular pathways via RNA sequencing.

Ginsenoside Rg1 prevents acetaminophen-induced oxidative stress and apoptosis via Nrf2/ARE signaling pathway

Inappropriate use of acetaminophen (APAP) can lead to morbidity and mortality secondary to hepatic necrosis. Ginsenoside Rg1 is a major active ingredient in processed Panax ginseng, which is proved to elicit biological effects. We hypothesized the beneficial effect of Rg1 on APAP-mediated hepatotoxicity was through Nrf2/ARE pathway. The study was conducted in cells and mice, comparing the actions of Rg1. Rg1 significantly improved cell survival rates and promoted the expression of antioxidant proteins. Meanwhile, Rg1 reduced the excessive ROS and the occurrence of cell apoptosis, which were related to Nrf2/ARE pathway. Expression of Nrf2 has a certain cell specificity.

The NSAID allosteric site of human cytosolic sulfotransferases

Non-steroidal anti-inflammatory drugs (NSAIDs) are among the most commonly prescribed drugs worldwide-more than 111 million prescriptions were written in the United States in 2014. NSAIDs allosterically inhibit cytosolic sulfotransferases (SULTs) with high specificity and therapeutically relevant affinities. This study focuses on the interactions of SULT1A1 and mefenamic acid (MEF)-a potent, highly specific NSAID inhibitor of 1A1. Here, the first structure of an NSAID allosteric site-the MEF-binding site of SULT1A1-is determined using spin-label triangulation NMR. The structure is confirmed by site-directed mutagenesis and provides a molecular framework for understanding NSAID binding and isoform specificity. The mechanism of NSAID inhibition is explored using molecular dynamics and equilibrium and pre-steady-state ligand-binding studies. MEF inhibits SULT1A1 turnover through an indirect (helix-mediated) stabilization of the closed form of the active-site cap of the enzyme, which traps the nucleotide and slows its release. Using the NSAID-binding site structure of SULT1A1 as a comparative model, it appears that 11 of the 13 human SULT isoforms harbor an NSAID-binding site. We hypothesize that these sites evolved to enable SULT isoforms to respond to metabolites that lie within their metabolic domains. Finally, the NSAID-binding site structure offers a template for developing isozyme-specific allosteric inhibitors that can be used to regulate specific areas of sulfuryl-transfer metabolism.

A Predictive 3D Multi-Scale Model of Biliary Fluid Dynamics in the Liver Lobule

Bile, the central metabolic product of the liver, is transported by the bile canaliculi network. The impairment of bile flow in cholestatic liver diseases has urged a demand for insights into its regulation. Here, we developed a predictive 3D multi-scale model that simulates fluid dynamic properties successively from the subcellular to the tissue level. The model integrates the structure of the bile canalicular network in the mouse liver lobule, as determined by high-resolution confocal and serial block-face scanning electron microscopy, with measurements of bile transport by intravital microscopy. The combined experiment-theory approach revealed spatial heterogeneities of biliary geometry and hepatocyte transport activity. Based on this, our model predicts gradients of bile velocity and pressure in the liver lobule. Validation of the model predictions by pharmacological inhibition of Rho kinase demonstrated a requirement of canaliculi contractility for bile flow in vivo. Our model can be applied to functionally characterize liver diseases and quantitatively estimate biliary transport upon drug-induced liver injury.

Is There a Causal Relation between Maternal Acetaminophen Administration and ADHD?

Objective

Recent epidemiological studies reported an association between maternal intake of acetaminophen (APAP) and attention deficit hyperactivity disorder (ADHD) in their children. However, none of these studies demonstrated causality. Our objective was to determine whether exposure to APAP during pregnancy result in hyperkinetic dysfunctions in offspring, using a murine model.

Material and Methods

Pregnant CD1 mice (N = 8/group) were allocated to receive by gavage either APAP (150 mg/kg/day, equivalent to the FDA-approved maximum human clinical dose), or 0.5% carboxymethylcellulose (control group), starting on embryonic day 7 until delivery. Maternal serum APAP and alanine transaminase (ALT) concentrations were determined by ELISA and kinetic colorimetric assays, respectively. Open field locomotor activity (LMA) in the 30-day old mouse offspring was quantified using Photobeam Activity System. Mouse offspring were then sacrificed, whole brains processed for magnetic resonance imaging (MRI; 11.7 Tesla magnet) and for neuronal quantification using Nissl stain. The association between APAP exposure and LMA in mouse offspring was analyzed using a mixed effects Poisson regression model that accounted for mouse offspring weight, gender, random selection, and testing time and day. We corrected for multiple comparisons and considered P<0.008 as statistically significant.

Results

Maternal serum APAP concentration peaked 30 minutes after gavage, reaching the expected mean of 117 μg/ml. Serum ALT concentrations were not different between groups. There were no significant differences in vertical (rearing), horizontal, or total locomotor activity between the two rodent offspring groups at the P level fixed to adjust for multiple testing. In addition, no differences were found in volumes of 29 brain areas of interest on MRI or in neuronal quantifications between the two groups.

Conclusion

This study refutes that hypothesis that prenatal exposure to APAP causes hyperkinetic dysfunction in mouse offspring. Due to lack of accurate assessment of ADHD in murine models, our results should be taken with caution when compared to the reported clinical data.

Korean red ginseng extract prevents APAP-induced hepatotoxicity through metabolic enzyme regulation: the role of ginsenoside Rg3, a protopanaxadiol

BACKGROUND

Inappropriate use of acetaminophen (APAP) can lead to morbidity and mortality secondary to hepatic necrosis.

AIMS

We evaluated the beneficial effect and molecular mechanism of Korean red ginseng (KRG) on the APAP-mediated hepatotoxicity and identified a major component of KRG for hepatoprotection.

METHODS

Survival test, liver function test, histopathological study, APAP-metabolic profiling and gene expression were examined in mice. We determined the enzyme expression and upstream signalling in H4IIE cells analysed by RT-PCR, immunoblotting, siRNA gene knockdown and promoter-luciferase assay.

RESULTS

High doses of KRG reduced mortality at the LD50 of APAP. APAP increased AST and ALT activities, which were abrogated by low doses of KRG. These protective effects were consistent with the results from histopathological examinations. KRG altered APAP metabolic profiles through inhibition of cytochrome P450 2E1 and induction of glutathione S-transferase A2 (GSTA2). Knockdown of GSTA2 catalyses the conjugation of glutathione reversed KRG-mediated protection against N-acetyl-p-benzoquinone imine in H4IIE cells. The nuclear Nrf2 and C/EBPβ, which are essential transcriptional factors for GSTA2 were increased by KRG. These effects were downstream of multiple signalling, including PI3K, JNK or PKA. Ginsenoside Rg3 but not Rb1, Rc and Rg1 significantly increased GSTA2 protein expression. Rg3 resulted in the transcriptional activation of GSTA2 downstream of the multiple cellular signalling.

CONCLUSIONS

These results demonstrate that KRG is efficacious in protection against APAP-induced hepatotoxicity and mortality through metabolic regulation and that Rg3 is a major component of KRG for the GST induction, implying that Rg3 should be considered to be a potential hepatoprotective agent.

Uncertainty factors for chemical risk assessment: interspecies differences in glucuronidation

For the risk assessment of effects other than cancer, a safe daily intake in humans is generally derived from a surrogate threshold dose (e.g. NOAEL) in an animal species to which an uncertainty factor of 100 is usually applied. This 100-fold is to allow for possible interspecies (10-fold) and interindividual (10-fold) differences in response to a toxicant, and incorporates toxicodynamic and toxicokinetic aspects of variability. The current study determined the magnitude of the interspecies differences in the internal dose of compounds for which glucuronidation is the major pathway of metabolism in either humans or in the test species. The results showed that there are major interspecies differences in the nature of the biological processes which influence the internal dose, including the route of metabolism, the extent of presystemic metabolism and enterohepatic recirculation. The work presented does not support the refinement of the interspecies toxicokinetic default to species- and pathway-specific values, but demonstrates the necessity for risk assessments to be carried out using quantitative chemical-specific data which define the fundamental processes which will influence the internal dose of a chemical (toxicokinetics), or the interaction of toxicant with its target site (toxicodynamics).

Comparative bioavailability of aspirin and paracetamol following single dose administration of soluble and plain tablets

In this study, the bioavailability of aspirin and paracetamol was compared in plain and soluble combination formulations in fasting, healthy volunteers. Blood samples were taken and Cmax, Tmax and AUC measured at various times following administration of single doses of the two formulations in 12 subjects. The rapidity of uptake of aspirin following administration of a soluble formulation suggests significant absorption from the stomach. There was no significant difference in the pharmacokinetic parameters of paracetamol derived from a soluble or plain formulation. A comparison of the uptake of aspirin from the soluble aspirin formulation with paracetamol from either plain or soluble tablets showed that aspirin entered the plasma and achieved peak levels significantly more quickly. However, the half life of paracetamol was significantly longer than that of aspirin. These findings suggest that onset of analgesia should be more rapid following dosing with soluble aspirin, a conclusion supported by comparative efficacy studies conducted with differing formulations of aspirin.

Treatment of fever in 1982: a review

While there is room for questioning the need, or even advisability, of routine antipyretic therapy, the available data do not yet constitute any sort of a contraindication. There are reasons for individualizing the decision. However, having once decided, there is no compelling reason for selecting one antipyretic over any other, and aspirin remains the most satisfactory in light of the available evidence. Some serious theoretic questions persist about the safety of acetaminophen use in sick persons, and clearly there are some precautions that should be taken with regard to the doses of flavored preparations of this and any future products whose attractiveness to children is thus enhanced.

N-acetylcysteine-induced inhibition of gastric emptying: a mechanism affording protection to mice from the hepatotoxicity of concomitantly administered acetaminophen

Swiss Webster male mice, 22 +/- 3 g, killed 17-18 h following the concomitant oral administration of acetaminophen (350 mg/kg) and N-acetyl-cysteine (NAC, 100-500 mg/kg, treated) had statistically significant lower plasma transaminases (GOT and GPT) than control mice (acetaminophen + water). Possible mechanisms underlying this protective effect of NAC were examined. NAC (500 mg/kg) reduced [14C]acetaminophen-derived radioactivity in the blood and tissues but increased the percentage of the dose in the gastrointestinal tract. Depletion of hepatic sulphydryl compounds below 75% of the control value was prevented by NAC treatment, whereas urinary excretion of mercapturate and sulfate, metabolites derived from sulphydryls, were proportionally increased and excretion of unchanged drug was decreased by NAC. Absorption of acetaminophen from the small intestine was prevented by NAC and this was attributed to an inhibition in gastric emptying. Since all changes observed following NAC treatment could be attributed to inhibition of gastric emptying, it was considered the major mechanism responsible for affording in mice protection from acetaminophen-induced hepatocellular damage following concomitant oral administration.

Interactions of aspirin with acetaminophen and caffeine in rat stomach: pharmacokinetics of absorption and accumulation in gastric mucosa

To study the pharmacokinetic interactions between aspirin (250 mg/kg) and simultaneously administered oral acetaminophen (125 mg/kg) or caffeine (50 mg/kg) in male rats, noninterfering GLC assays for these drugs were developed. Acetaminophen and caffeine both retarded the appearance of salicylate in plasma. During the elimination phase, acetaminophen enhanced plasms salicylate levels whereas caffeine did not. Aspirin reduced the plasms levels of both acetaminophen and caffeine during absorption and elimination. Regardless of whether the drugs had been administered separately or in combination, higher concentrations of salicylate, acetaminophen, and caffeine were found in the glandular part of the stomach compared to the nonglandular part (rumen). In both parts, the absorption of acetaminophen increased in the presence of aspirin. Simultaneous administration of aspirin with caffeine did not influence the absorption of either drug in the glandular and ruminal parts. The inhibitory action of acetaminophen and the potentiating action of caffeine on the erosive activity of aspirin are not due to any effects of these drugs on salicylate accumulation in glandular tissue.

Effect of a concomitant single dose of ethanol on the hepatotoxicity and metabolism of acetaminophen in mice

A concomitant single dose of ethanol (1 g/kg) protected mice from hepatic injury induced by acetaminophen (250 mg/kg) as evidenced by the lowering of plasma transaminases. Pharmacokinetic studies with [14C]acetaminophen indicated that ethanol enhanced the initial blood concentrations of radiolabel and its rate of elimination. A tissue distribution study suggested that these effects were probably due to an ethanol-induced inhibition of the biliary clearance of acetaminophen from the blood. Examination of the urinary and biliary metabolites indicated that ethanol inhibited the excretion of the degradation products derived from the glutathione-deactivated hepatotoxic acetaminophen intermediate. The decrease in acetaminophen induced hepatotoxicity was therefore attributed to an inhibitory effect of ethanol on the biotransformation of acetaminophen to the toxic intermediate.