Sulfation of chondroitin and bile acids converges to antagonize Wnt/ß-catenin signaling and inhibit APC deficiency-induced gut tumorigenesis.

Sulfation is a crucial and prevalent conjugation reaction involved in cellular processes and mammalian physiology. 3'-Phosphoadenosine 5'-phosphosulfate (PAPS) synthase 2 (PAPSS2) is the primary enzyme to generate the universal sulfonate donor PAPS. The involvement of PAPSS2-mediated sulfation in adenomatous polyposis coli (APC) mutation-promoted colonic carcinogenesis has not been reported. Here, we showed that the expression of PAPSS2 was decreased in human colon tumors along with cancer stages, and the lower expression of PAPSS2 was correlated with poor prognosis in advanced colon cancer. Gut epithelial-specific heterozygous Apc deficient and Papss2-knockout (ApcΔgut-HetPapss2Δgut) mice were created, and the phenotypes were compared to the spontaneous intestinal tumorigenesis of ApcΔgut-Het mice. ApcΔgut-HetPapss2Δgut mice were more sensitive to gut tumorigenesis, which was mechanistically accounted for by the activation of Wnt/ß-catenin signaling pathway due to the suppression of chondroitin sulfation and inhibition of the farnesoid X receptor (FXR)-transducin-like enhancer of split 3 (TLE3) gene regulatory axis. Chondroitin sulfate supplementation in ApcΔgut-HetPapss2Δgut mice alleviated intestinal tumorigenesis. In summary, we have uncovered the protective role of PAPSS2-mediated chondroitin sulfation and bile acids-FXR-TLE3 activation in the prevention of gut carcinogenesis via the antagonization of Wnt/ß-catenin signaling. Chondroitin sulfate may be explored as a therapeutic agent for Papss2 deficiency-associated colonic carcinogenesis.

Activation of PXR causes drug interactions with Paxlovid in transgenic mice.

Paxlovid is a nirmatrelvir (NMV) and ritonavir (RTV) co-packaged medication used for the treatment of coronavirus disease 2019 (COVID-19). The active component of Paxlovid is NMV and RTV is a pharmacokinetic booster. Our work aimed to investigate the drug/herb-drug interactions associated with Paxlovid and provide mechanism-based guidance for the clinical use of Paxlovid. By using recombinant human cytochrome P450s (CYPs), we confirmed that CYP3A4 and 3A5 are the major enzymes responsible for NMV metabolism. The role of CYP3A in Paxlovid metabolism were further verified in Cyp3a-null mice, which showed that the deficiency of CYP3A significantly suppressed the metabolism of NMV and RTV. Pregnane X receptor (PXR) is a ligand-dependent transcription factor that upregulates CYP3A4/5 expression. We next explored the impact of drug- and herb-mediated PXR activation on Paxlovid metabolism in a transgenic mouse model expressing human PXR and CYP3A4/5. We found that PXR activation increased CYP3A4/5 expression, accelerated NMV metabolism, and reduced the systemic exposure of NMV. In summary, our work demonstrated that PXR activation can cause drug interactions with Paxlovid, suggesting that PXR-activating drugs and herbs should be used cautiously in COVID-19 patients receiving Paxlovid.

Protoporphyrin IX-induced phototoxicity: Mechanisms and therapeutics.

Protoporphyrin IX (PPIX) is an intermediate in the heme biosynthesis pathway. Abnormal accumulation of PPIX due to certain pathological conditions such as erythropoietic protoporphyria and X-linked protoporphyria causes painful phototoxic reactions of the skin, which can significantly impact daily life. Endothelial cells in the skin have been proposed as the primary target for PPIX-induced phototoxicity through light-triggered generation of reactive oxygen species. Current approaches for the management of PPIX-induced phototoxicity include opaque clothing, sunscreens, phototherapy, blood therapy, antioxidants, bone marrow transplantation, and drugs that increase skin pigmentation. In this review, we discuss the present understanding of PPIX-induced phototoxicity including PPIX production and disposition, conditions that lead to PPIX accumulation, symptoms and individual differences, mechanisms, and therapeutics.

Potential pharmacokinetic interactions with concurrent use of herbal medicines and a ritonavir-boosted COVID-19 protease inhibitor in low and middle-income countries.

The COVID-19 pandemic sparked the development of novel anti-viral drugs that have shown to be effective in reducing both fatality and hospitalization rates in patients with elevated risk for COVID-19 related morbidity or mortality. Currently, nirmatrelvir/ritonavir (Paxlovid™) fixed-dose combination is recommended by the World Health Organization for treatment of COVID-19. The ritonavir component is an inhibitor of cytochrome P450 (CYP) 3A, which is used in this combination to achieve needed therapeutic concentrations of nirmatrelvir. Because of the critical pharmacokinetic effect of this mechanism of action for Paxlovid™, co-administration with needed medications that inhibit or induce CYP3A is contraindicated, reflecting concern for interactions with the potential to alter the efficacy or safety of co-administered drugs that are also metabolized by CYP3A. Some herbal medicines are known to interact with drug metabolizing enzymes and transporters, including but not limited to inhibition or induction of CYP3A and P-glycoprotein. As access to these COVID-19 medications has increased in low- and middle-income countries (LMICs), understanding the potential for herb-drug interactions within these regions is important. Many studies have evaluated the utility of herbal medicines for COVID-19 treatments, yet information on potential herb-drug interactions involving Paxlovid™, specifically with herbal medicines commonly used in LMICs, is lacking. This review presents data on regionally-relevant herbal medicine use (particularly those promoted as treatments for COVID-19) and mechanism of action data on herbal medicines to highlight the potential for herbal medicine interaction Herb-drug interaction mediated by ritonavir-boosted antiviral protease inhibitors This work highlights potential areas for future experimental studies and data collection, identifies herbal medicines for inclusion in future listings of regionally diverse potential HDIs and underscores areas for LMIC-focused provider-patient communication. This overview is presented to support governments and health protection entities as they prepare for an increase of availability and use of Paxlovid™.

Identification of PXR Activators from Uncaria Rhynchophylla (Gou Teng) and Uncaria Tomentosa (Cat's Claw).

Uncaria rhynchophylla (Gou Teng) and Uncaria tomentosa (cat's claw) are frequently used herbal supplements in Asia and America, respectively. Despite their common usage, information is limited regarding potential herb-drug interactions associated with Gou Teng and cat's claw. The pregnane X receptor (PXR) is a ligand-dependent transcription factor that regulates cytochrome P450 3A4 (CYP3A4) expression and contributes to some known herb-drug interactions. A recent study found that Gou Teng induces CYP3A4 expression, but its mechanism is unknown. Cat's claw has been determined as a PXR-activating herb, but the PXR activators in cat's claw have not been identified. Using a genetically engineered PXR cell line, we found that the extracts of Gou Teng and cat's claw can dose-dependently activate PXR and induce CYP3A4 expression. We next used a metabolomic approach to profile the chemical components in the extracts of Gou Teng and cat's claw followed by screening for PXR activators. Four compounds, isocorynoxeine, rhynchophylline, isorhynchophylline, and corynoxeine, were identified as PXR activators from both Gou Teng and cat's claw extracts. In addition, three more PXR activators were identified from the extracts of cat's claw, including isopteropodine, pteropodine, and mitraphylline. All seven of these compounds showed the half-maximal effective concentration <10 µM for PXR activation. In summary, our work determined Gou Teng as a PXR-activating herb and discovered novel PXR activators from Gou Teng as well as cat's claw. SIGNIFICANCE STATEMENT: This study's data can be used to guide the safe use of Gou Teng and cat's claw by avoiding PXR-mediated herb-drug interactions.

Enzymes and Pathways of Kavain Bioactivation and Biotransformation.

Kavain is an active and major component in Piper methysticum Forst. (kava), which is a widely used dietary supplement for the treatment of anxiety, insomnia, and stress. However, kava-containing products can cause liver toxicity, and its underlying mechanisms are understudied. Cytochrome P450s (CYPs)-mediated bioactivation and biotransformation are highly associated with drug toxicity. In the current study, we profiled the metabolic pathways of kavain in mouse liver, urine, and feces. Overall, 28 kavain metabolites were identified including 17 new ones. The metabolic pathways of kavain include glutathione (GSH) conjugation, oxidation, dehydrogenation, O-demethylation, sulfation, and glucuronidation. The identification of kavain-GSH adducts suggests the formation of reactive metabolites of kavain in the liver. We further illustrated that CYP2C19, a highly polymorphic and inducible enzyme, was the major enzyme contributing to kavain biotransformation and bioactivation. Our data can be used to guide the safe use of kava products by preventing potential herb-drug interactions and hepatotoxicity.

Exploratory Application of Neuropharmacometabolomics in Severe Childhood Traumatic Brain Injury.

OBJECTIVES: To employ metabolomics-based pathway and network analyses to evaluate the cerebrospinal fluid metabolome after severe traumatic brain injury in children and the capacity of combination therapy with probenecid and N-acetylcysteine to impact glutathione-related and other pathways and networks, relative to placebo treatment. DESIGN: Analysis of cerebrospinal fluid obtained from children enrolled in an Institutional Review Board-approved, randomized, placebo-controlled trial of a combination of probenecid and N-acetylcysteine after severe traumatic brain injury (Trial Registration NCT01322009). SETTING: Thirty-six-bed PICU in a university-affiliated children's hospital. PATIENTS AND SUBJECTS: Twelve children 2-18 years old after severe traumatic brain injury and five age-matched control subjects. INTERVENTION: Probenecid (25 mg/kg) and N-acetylcysteine (140 mg/kg) or placebo administered via naso/orogastric tube. MEASUREMENTS AND MAIN RESULTS: The cerebrospinal fluid metabolome was analyzed in samples from traumatic brain injury patients 24 hours after the first dose of drugs or placebo and control subjects. Feature detection, retention time, alignment, annotation, and principal component analysis and statistical analysis were conducted using XCMS-online. The software "mummichog" was used for pathway and network analyses. A two-component principal component analysis revealed clustering of each of the groups, with distinct metabolomics signatures. Several novel pathways with plausible mechanistic involvement in traumatic brain injury were identified. A combination of metabolomics and pathway/network analyses showed that seven glutathione-centered pathways and two networks were enriched in the cerebrospinal fluid of traumatic brain injury patients treated with probenecid and N-acetylcysteine versus placebo-treated patients. Several additional pathways/networks consisting of components that are known substrates of probenecid-inhibitable transporters were also identified, providing additional mechanistic validation. CONCLUSIONS: This proof-of-concept neuropharmacometabolomics assessment reveals alterations in known and previously unidentified metabolic pathways and supports therapeutic target engagement of the combination of probenecid and N-acetylcysteine treatment after severe traumatic brain injury in children.

A High Dose of Isoniazid Disturbs Endobiotic Homeostasis in Mouse Liver.

Overdose of isoniazid (INH), an antituberculosis drug, can be life-threatening because of neurotoxicity. In clinical practice for management of INH overdose and acute toxicity, the potential of INH-induced hepatotoxicity is also considered. However, the biochemical basis of acute INH toxicity in the liver remains elusive. In the current study, we used an untargeted metabolomic approach to explore the acute effects of INH on endobiotic homeostasis in mouse liver. We found that overdose of INH resulted in accumulation of oleoyl-l-carnitine and linoleoyl-l-carnitine in the liver, indicating mitochondrial dysfunction. We also revealed the interactions between INH and fatty acyl-CoAs by identifying INH-fatty acid amides. In addition, we found that overdose of INH led to the accumulation of heme and oxidized NAD in the liver. We also identified an INH and NAD adduct in the liver. In this adduct, the nicotinamide moiety in NAD was replaced by INH. Furthermore, we illustrated that overdose of INH depleted vitamin B6 in the liver and blocked vitamin B6-dependent cystathionine degradation. These data suggest that INH interacts with multiple biochemical pathways in the liver during acute poisoning caused by INH overdose.

Nuclear receptors in herb-drug interactions.

Widespread usage of herbs as supplements or medicines raises the potential of herb-drug interactions (HDIs). Basically, HDIs occur by pharmacokinetic and/or pharmacodynamic pathways. Nuclear receptors (NRs) are a class of transcription factors whose role in drug interactions has been defined. A large number of herbs activate NRs, resulting in HDIs. NR-mediated HDIs are similar to drug-drug interactions, but are more complicated because of the presence of multiple compounds in herbs. Dosage and therapeutic sequence as well as various other factors, including the patient's gender, age, and genetic makeup, may affect outcomes of NR-mediated HDIs.

Pregnane X receptor- and CYP3A4-humanized mouse models and their applications.

Pregnane X receptor (PXR) is a pivotal nuclear receptor modulating xenobiotic metabolism primarily through its regulation of CYP3A4, the most important enzyme involved in drug metabolism in humans. Due to the marked species differences in ligand recognition by PXR, PXR-humanized (hPXR) mice, and mice expressing human PXR and CYP3A4 (Tg3A4/hPXR) were established. hPXR and Tg3A4/hPXR mice are valuable models for investigating the role of PXR in xenobiotic metabolism and toxicity, in lipid, bile acid and steroid hormone homeostasis, and in the control of inflammation.

The Chinese herbal medicine Sophora flavescens activates pregnane X receptor.

Sophora flavescens (SF) is an herbal medicine widely used for the treatment of viral hepatitis, cancer, viral myocarditis, gastrointestinal hemorrhage, and skin diseases. It was recently reported that SF up-regulates CYP3A expression. The mechanism of SF-induced CYP3A expression is unknown. In the current study, we tested the hypothesis that SF-induced CYP3A expression is mediated by the activation of pregnane X receptor (PXR). We used two cell lines, DPX2 and HepaRG, to investigate the role of PXR in SF-induced CYP3A expression. The DPX2 cell line is derived from HepG2 cells with the stable transfection of human PXR and a luciferase reporter gene linked with a human PXR response element identified in the CYP3A4 gene promoter. In DPX2 cells, SF activated PXR in a concentration-dependent manner. We used a metabolomic approach to identify the chemical constituents in SF, which were further analyzed for their effect on PXR activation and CYP3A regulation. One chemical in SF, N-methylcytisine, was identified as an individual chemical that activated PXR. HepaRG is a highly differentiated hepatoma cell line that mimics human hepatocytes. In HepaRG cells, N-methylcytisine significantly induced CYP3A4 expression, and this induction was suppressed by the PXR antagonist sulforaphane. These results suggest that SF induces CYP3A expression via the activation of PXR.

Metabolism of melatonin by human cytochromes p450.

In humans, the pineal hormone melatonin (MEL) is principally metabolized to 6-hydroxymelatonin (6-HMEL), which is further conjugated with sulfate and excreted in urine. MEL O-demethylation represents a minor reaction. The exact role of individual human cytochromes P450 (P450s) in these pathways has not been established. We used a panel of 11 recombinant human P450 isozymes to investigate for the first time the 6-hydroxylation and O-demethylation of MEL. CYP1A1, CYP1A2, and CYP1B1 all 6-hydroxylated MEL, with CYP2C19 playing a minor role. These reactions were NADPH-dependent. CYP2C19 and, to some extent CYP1A2, O-demethylated MEL. The K(m) (microM) and V(max) (k(cat), pmol min(-1) pmol(-1) P450) for 6-hydroxylation were estimated as 19.2 +/- 2.01 and 6.46 +/- 0.22 (CYP1A1), 25.9 +/- 2.47 and 10.6 +/- 0.32 (CYP1A2), and 30.9 +/- 3.76 and 5.31 +/- 0.21 (CYP1B1). These findings confirm the suggestion of others that CYP1A2 is probably the foremost hepatic P450 in the 6-hydroxylation of MEL and a single report that CYP1A1 is also able to mediate this reaction. However, this is the first time that CYP1B1 has been shown to 6-hydroxylate MEL. The IC50 for the CYP1B1-selective inhibitor (E)-2,4,3',5'-tetramethoxystilbene was estimated to be 30 nM for MEL 6-hydroxylation by recombinant human CYP1B1. Comparison of brain homogenates from wild-type and cyp1b1-null mice revealed that MEL 6-hydroxylation was clearly mediated to a significant degree by CYP1B1. CYP1B1 is not expressed in the liver but has a ubiquitous extrahepatic distribution, and is found at high levels in tissues that also accumulate either MEL or 6-HMEL, such as intestine and cerebral cortex, where it may assist in regulating levels of MEL and 6-HMEL.