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.

Roles of the ABCG2 transporter in protoporphyrin IX distribution and toxicity.

ATP-binding cassette transporter subfamily G member 2 (ABCG2) is a membrane-bound transporter responsible for the efflux of various xenobiotics and endobiotics, including protoporphyrin IX (PPIX), an intermediate in the heme biosynthesis pathway. Certain genetic mutations and chemicals impair the conversion of PPIX to heme and/or increase PPIX production, leading to PPIX accumulation and toxicity. In mice, deficiency of ABCG2 protects against PPIX-mediated phototoxicity and hepatotoxicity by modulating PPIX distribution. In addition, in vitro studies revealed that ABCG2 inhibition increases the efficacy of PPIX-based photodynamic therapy by retaining PPIX inside target cells. In this review, we discuss the roles of ABCG2 in modulating the tissue distribution of PPIX, PPIX-mediated toxicity, and PPIX-based photodynamic therapy. Significance Statement This review summarized the roles of ABCG2 in modulating PPIX distribution and highlighted the therapeutic potential of ABCG2 inhibitors for the management of PPIX-mediated toxicity.

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.

Loss of TAZ after YAP deletion severely impairs foregut development and worsens cholestatic hepatocellular injury.

BACKGROUND: We previously showed that loss of yes-associated protein 1 (YAP) in early liver development (YAPKO) leads to an Alagille syndrome-like phenotype, with failure of intrahepatic bile duct development, severe cholestasis, and chronic hepatocyte adaptations to reduce liver injury. TAZ, a paralog of YAP, was significantly upregulated in YAPKO hepatocytes and interacted with TEA domain family member (TEAD) transcription factors, suggesting possible compensatory activity. METHODS: We deleted both Yap1 and Wwtr1 (which encodes TAZ) during early liver development using the Foxa3 promoter to drive Cre expression, similar to YAPKO mice, resulting in YAP/TAZ double knockout (DKO) and YAPKO with TAZ heterozygosity (YAPKO TAZHET). We evaluated these mice using immunohistochemistry, serum biochemistry, bile acid profiling, and RNA sequencing. RESULTS: DKO mice were embryonic lethal, but their livers were similar to YAPKO, suggesting an extrahepatic cause of death. Male YAPKO TAZHET mice were also embryonic lethal, with insufficient samples to determine the cause. However, YAPKO TAZHET females survived and were phenotypically similar to YAPKO mice, with increased bile acid hydrophilicity and similar global gene expression adaptations but worsened the hepatocellular injury. TAZ heterozygosity in YAPKO impacted the expression of canonical YAP targets Ctgf and Cyr61, and we found changes in pathways regulating cell division and inflammatory signaling correlating with an increase in hepatocyte cell death, cell cycling, and macrophage recruitment. CONCLUSIONS: YAP loss (with or without TAZ loss) aborts biliary development. YAP and TAZ play a codependent critical role in foregut endoderm development outside the liver, but they are not essential for hepatocyte development. TAZ heterozygosity in YAPKO livers increased cell cycling and inflammatory signaling in the setting of chronic injury, highlighting genes that are especially sensitive to TAZ regulation.

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.

Metabolism-guided development of Ko143 analogs as ABCG2 inhibitors.

ATP-binding cassette subfamily G member 2 (ABCG2), an efflux transporter, is involved in multiple pathological processes. Ko143 is a potent ABCG2 inhibitor; however, it is quickly metabolized through carboxylesterase 1-mediated hydrolysis of its t-butyl ester moiety. The current work aimed to develop more metabolically stable ABCG2 inhibitors. Novel Ko143 analogs were designed and synthesized by replacing the unstable t-butyl ester moiety in Ko143 with an amide group. The synthesized Ko143 analogs were evaluated for their ABCG2 inhibitory activity, binding mode with ABCG2, cytotoxicity, and metabolic stability. We found that the amide modification of Ko143 led to metabolically stable ABCG2 inhibitors. Among these Ko143 analogs, K2 and K34 are promising candidates with favorable oral pharmacokinetic profiles in mice. In summary, we synthesized novel Ko143 analogs with improved metabolic stability, which can potentially be used as lead compounds for the future development of ABCG2 inhibitors.

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™.

Analysis of pulmonary artery variation based on 3D reconstruction of CT angiography.

Objective: The aim of this study is to acquire pulmonary CT (Computed tomography) angiographic data for the purpose of creating a three-dimensional reconstruction. Additionally, we aim to analyze the features and deviations of the branches in both pulmonary lobes. This information is intended to serve as a more comprehensive and detailed reference for medical professionals when conducting preoperative evaluations and devising surgical plans. Method: Between August 2019 and December 2021, 420 patients were selected from the thoracic surgery department at the First Hospital of Jilin University, and underwent pulmonary 64 channel contrast enhanced CT examinations (Philips ICT 256). The images were acquired at a 1.5 mm slice thickness, and the DCM files that complied with DICOM (Digital Imaging and Communications in Medicine) standards were analysed for 3D (three dimensional) reconstruction using Mimics 22.0 software. The reconstructed pulmonary artery models were assessed by attending chest surgeons and radiologists with over 10 years of clinical experience. The two-dimensional image planes, as well as the coronary and sagittal planes, were utilized to evaluate the arteries. The study analyzed the characteristics and variations of the branches and courses of pulmonary arteries in each lobe of the lungs, with the exception of the subsegmental arterial system. Two chest surgeons and two radiologists with professional titles-all of whom had over a decade of clinical experience-jointly evaluated the 3D models of the pulmonary artery and similarly assessed the characteristics and variations of the branches and courses in each lobe of the lungs. Results: Significant variations were observed in the left superior pulmonary artery across the 420 subjects studied. In the left upper lobe, the blood supply of 4 arteries accounted for 50.5% (n = 212), while the blood supply of 2 arteries in the left lower lobe was the most common, accounting for 79.5% (n = 334). The greatest variation in the right pulmonary artery was observed in the branch supply of the right upper lobe mediastinal artery. In the majority of cases (77.9%), there were two arteries present, which was the most common configuration observed accounting for 64% (n = 269). In the right inferior lobe of the lung, there were typically 2-4 arteries, with 2 arteries being the most common configuration (observed in 79% of cases, n = 332). Conclusion: The three-dimensional reconstruction of pulmonary artery CT angiography enables clear observation of the branches and distribution of the pulmonary artery while also highlighting any variations. This technique holds significant clinical value for preoperative assessments regarding lesions and blood vessels.

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.

N-Methyl Protoporphyrin IX: An Understudied Porphyrin.

N-Methyl protoporphyrin IX (NmePPIX) is a derivative of protoporphyrin IX (PPIX) and the lattice of heme. Certain xenobiotics strongly induce NmePPIX production in the liver. The existence of endogenous NmePPIX in untreated animal liver has also been reported. The detailed mechanisms of NmePPIX biosynthesis remain unclear, but cytochrome P450 enzymes are thought to be critical in xenobiotic-induced NmePPIX production. High levels of NmePPIX cause PPIX accumulation because NmePPIX is a potent inhibitor (Ki = 7 nM) of ferrochelatase, the last enzyme in the heme biosynthesis pathway that converts PPIX to heme. NmePPIX is also involved in several other physiological processes, including inhibition of nitric oxide production and promotion of lamin aggregation. Compared to the two well-characterized porphyrins, PPIX and heme, NmePPIX is understudied regarding the mechanism of formation, fate, and physiological functions. This Review summarizes the current understanding of NmePPIX and provides perspectives on areas of future research on NmePPIX.

Circular_0086414 induces SPARC like 1 (SPARCL1) production to inhibit esophageal cancer cell proliferation, invasion and glycolysis and induce cell apoptosis by sponging miR-1290.

Circular RNA (circRNA) plays an important role in cancer progression. Here, we investigated the function of circ_0086414 in the malignant progression of esophageal cancer (EC). RNA expression of circ_0086414, microRNA-1290 (miR-1290), and SPARC like 1 (SPARCL1) was detected by quantitative real-time polymerase chain reaction. The protein levels of N-cadherin, E-cadherin, and SPARCL1 were checked by Western blotting analysis. Cell proliferation was investigated by 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), 5-Ethynyl-29-deoxyuridine (EdU), and cell colony formation assays. Cell invasion and apoptosis were analyzed by transwell invasion assay and flow cytometry analysis, respectively. Glycolysis was evaluated by analyzing glucose consumption and lactate production. In an xenograft mouse model, the effect of circ_0086414 on tumor tumorigenesis was investigated. The interactions among circ_0086414, miR-1290, and SPARCL1 were identified by dual-luciferase reporter and RNA pull-down assays. Results showed that circ_0086414 and SPARCL1 expression were significantly downregulated, while miR-1290 was upregulated in EC tissues and cells. EC patients with low circ_0086414 expression had a poor prognosis. Increasing circ_0086414 expression led to decreased EC cell proliferation, invasion and glycolysis and increased cell apoptosis, accompanied by a decrease of N-cadherin expression and an increase of E-cadherin expression. Also, the enforced expression of circ_0086414 delayed tumor tumorigenesis. Besides, circ_0086414 acted as a miR-1290 sponge and regulated EC cell processes by binding to the miRNA. MiR-1290 also participated in EC malignant progression through SPARCL1. Further, circ_0086414 stimulated SPARCL1 production by negatively regulating miR-1290. Thus, circ_0086414 inhibited EC cell malignancy through the miR-1290/SPARCL1 pathway, providing a reliable target for the therapy of EC.

Bi-allelic hydroxymethylbilane synthase inactivation defines a homogenous clinico-molecular subtype of hepatocellular carcinoma.

BACKGROUND & AIMS: Acute intermittent porphyria (AIP), caused by heterozygous germline mutations of the heme synthesis pathway enzyme HMBS (hydroxymethylbilane synthase), confers a high risk of hepatocellular carcinoma (HCC) development. Yet, the role of HMBS in liver tumorigenesis remains unclear. METHODS: Herein, we explore HMBS alterations in a large series of 758 HCC cases, including 4 patients with AIP. We quantify the impact of HMBS mutations on heme biosynthesis pathway intermediates and we investigate the molecular and clinical features of HMBS-mutated tumors. RESULTS: We identify recurrent bi-allelic HMBS inactivation, both in patients with AIP acquiring a second somatic HMBS mutation and in sporadic HCC with 2 somatic hits. HMBS alterations are enriched in truncating mutations, in particular in splice regions, leading to abnormal transcript structures. Bi-allelic HMBS inactivation results in a massive accumulation of its toxic substrate porphobilinogen and synergizes with CTNNB1-activating mutations, leading to the development of well-differentiated tumors with a transcriptomic signature of Wnt/ß-catenin pathway activation and a DNA methylation signature related to ageing. HMBS-inactivated HCC mostly affects females, in the absence of fibrosis and classical HCC risk factors. CONCLUSIONS: These data identify HMBS as a tumor suppressor gene whose bi-allelic inactivation defines a homogenous clinical and molecular HCC subtype. LAY SUMMARY: Heme (the precursor to hemoglobin, which plays a key role in oxygen transport around the body) synthesis occurs in the liver and involves several enzymes including hydroxymethylbilane synthase (HMBS). HMBS mutations cause acute intermittent porphyria, a disease caused by the accumulation of toxic porphyrin precursors. Herein, we show that HMBS inactivation is also involved in the development of liver cancers with distinct clinical and molecular characteristics.

Roles of Cofactors in Drug-Induced Liver Injury: Drug Metabolism and Beyond.

Drug-induced liver injury (DILI) remains one of the major concerns for healthcare providers and patients. Unfortunately, it is difficult to predict and prevent DILI in the clinic because detailed mechanisms of DILI are largely unknown. Many risk factors have been identified for both "intrinsic" and "idiosyncratic" DILI, suggesting that cofactors are an important aspect in understanding DILI. This review outlines the cofactors that potentiate DILI and categorizes them into two types: (1) the specific cofactors that target metabolic enzymes, transporters, antioxidation defense, immune response, and liver regeneration; and (2) the general cofactors that include inflammation, age, gender, comorbidity, gut microbiota, and lifestyle. The underlying mechanisms by which cofactors potentiate DILI are also discussed. SIGNIFICANCE STATEMENT: This review summarizes the risk factors for DILI, which can be used to predict and prevent DILI in the clinic. This work also highlights the gaps in the DILI field and provides future perspectives on the roles of cofactors in DILI.

Chronic Activation of LXRα Sensitizes Mice to Hepatocellular Carcinoma.

The oxysterol receptor liver X receptor (LXR) is a nuclear receptor best known for its function in the regulation of lipid and cholesterol metabolism. LXRs, both the α and ß isoforms, have been suggested as potential therapeutic targets for several cancer types. However, there was a lack of report on whether and how LXRα plays a role in the development of hepatocellular carcinoma (HCC). In the current study, we found that systemic activation of LXRα in the VP-LXRα knock-in (LXRαKI) mice or hepatocyte-specific activation of LXRα in the VP-LXRα transgenic mice sensitized mice to liver tumorigenesis induced by the combined treatment of diethylnitrosamine (DEN) and 3,3',5,5'-tetrachloro-1,4-bis (pyridyloxy) benzene (TCPOBOP). Mechanistically, the LXRα-responsive up-regulation of interleukin-6 (IL-6)/signal transducer and activator of transcription 3 (STAT3) signaling pathway and the complement system, and down-regulation of bile acid metabolism, may have contributed to increased tumorigenesis. Accumulations of secondary bile acids and oxysterols were found in both the serum and liver tissue of LXRα activated mice. We also observed an induction of monocytic myeloid-derived suppressor cells accompanied by down-regulation of dendritic cells and cytotoxic T cells in DEN/TCPOBOP-induced liver tumors, indicating that chronic activation of LXRα may have led to the activation of innate immune suppression. The HCC sensitizing effect of LXRα activation was also observed in the c-MYC driven HCC model. Conclusion: Our results indicated that chronic activation of LXRα promotes HCC, at least in part, by promoting innate immune suppressor as a result of accumulation of oxysterols, as well as up-regulation of the IL-6/Janus kinase/STAT3 signaling and complement pathways.

Alterations of Cytochrome P450-Mediated Drug Metabolism during Liver Repair and Regeneration after Acetaminophen-Induced Liver Injury in Mice.

Acetaminophen (APAP)-induced liver injury (AILI) is the leading cause of acute liver failure in the United States, but its impact on metabolism, therapeutic efficacy, and adverse drug reactions (ADRs) of co- and/or subsequent administered drugs are not fully investigated. The current work explored this field with a focus on the AILI-mediated alterations of cytochrome P450-mediated drug metabolism. Various levels of liver injury were induced in mice by treatment with APAP at 0, 200, 400, and 600 mg/kg. Severity of liver damage was determined at 24, 48, 72, and 96 hours by plasma levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), microRNA miR122, and tissue staining. The expression and activities of CYP3A11, 1A2, 2B10, 2C29, and 2E1 were measured. Sedation efficacy and ADRs of midazolam, a CYP3A substrate, were monitored after APAP treatment. ALT, AST, and miR122 increased at 24 hours after APAP treatment with all APAP doses, whereas only groups treated with 200 and 400 mg/kg recovered back to normal levels at 72 and 96 hours. The expression and activity of the cytochromes P450 significantly decreased at 24 hours with all APAP doses but only recovered back to normal at 72 and 96 hours with 200 and 400, but not 600, mg/kg of APAP. The alterations of cytochrome P450 activities resulted in altered sedation efficacy and ADRs of midazolam, which were corrected by dose justification of midazolam. Overall, this work illustrated a low cytochrome P450 expression window after AILI, which can decrease drug metabolism and negatively impact drug efficacy and ADRs. SIGNIFICANCE STATEMENT: The data generated in the mouse model demonstrated that expression and activities of cytochrome P450 enzymes and correlated drug efficacy and ADRs are altered during the time course of liver repair and regeneration after liver is injured by treatment with APAP. Dose justifications based on predicted changes of cytochrome P450 activities can achieve desired therapeutic efficacy and avoid ADRs. The generated data provide fundamental knowledge for translational research to drug treatment for patients during liver recovery and regeneration who have experienced AILI.

Inhibition of p53 Sulfoconjugation Prevents Oxidative Hepatotoxicity and Acute Liver Failure.

BACKGROUND & AIMS: Sulfoconjugation of small molecules or protein peptides is a key mechanism to ensure biochemical and functional homeostasis in mammals. The PAPS synthase 2 (PAPSS2) is the primary enzyme to synthesize the universal sulfonate donor 3'-phosphoadenosine 5'-phosphosulfate (PAPS). Acetaminophen (APAP) overdose is the leading cause of acute liver failure (ALF), in which oxidative stress is a key pathogenic event, whereas sulfation of APAP contributes to its detoxification. The goal of this study was to determine whether and how PAPSS2 plays a role in APAP-induced ALF. METHODS: Gene expression was analyzed in APAP-induced ALF in patients and mice. Liver-specific Papss2-knockout mice using Alb-Cre (Papss2ΔHC) or AAV8-TBG-Cre (Papss2iΔHC) were created and subjected to APAP-induced ALF. Primary human and mouse hepatocytes were used for in vitro mechanistic analysis. RESULTS: The hepatic expression of PAPSS2 was decreased in APAP-induced ALF in patients and mice. Surprisingly, Papss2ΔHC mice were protected from APAP-induced hepatotoxicity despite having a decreased APAP sulfation, which was accompanied by increased hepatic antioxidative capacity through the activation of the p53-p2-Nrf2 axis. Treatment with a sulfation inhibitor also ameliorated APAP-induced hepatotoxicity. Gene knockdown experiments showed that the hepatoprotective effect of Papss2ΔHC was Nrf2, p53, and p21 dependent. Mechanistically, we identified p53 as a novel substrate of sulfation. Papss2 ablation led to p53 protein accumulation by preventing p53 sulfation, which disrupts p53-MDM2 interaction and p53 ubiquitination and increases p53 protein stability. CONCLUSIONS: We have uncovered a previously unrecognized and p53-mediated role of PAPSS2 in controlling oxidative response. Inhibition of p53 sulfation may be explored for the clinical management of APAP overdose.

Targeting metabotropic glutamate receptor 4 for cancer immunotherapy.

In this study, we report a novel role of metabotropic glutamate receptor 4 (GRM4) in suppressing antitumor immunity. We revealed in three murine syngeneic tumor models (B16, MC38, and 3LL) that either genetic knockout (Grm4−/−) or pharmacological inhibition led to significant delay in tumor growth. Mechanistically, perturbation of GRM4 resulted in a strong antitumor immunity by promoting natural killer (NK), CD4+, and CD8+ T cells toward an activated, proliferative, and functional phenotype. Single-cell RNA sequencing and T cell receptor profiling further defined the clonal expansion and immune landscape changes in CD8+ T cells. We further showed that Grm4−/− intrinsically activated interferon-γ production in CD8+ T cells through cyclic adenosine 3',5'-monophosphate (cAMP)/cAMP response element binding protein­mediated pathway. Our study appears to be of clinical significance as a signature of NKhigh-GRM4low and CD8high-GRM4low correlated with improved survival in patients with melanoma. Targeting GRM4 represents a new approach for cancer immunotherapy.

Role of CYP2A6 in Methimazole Bioactivation and Hepatotoxicity.

Methimazole (MMI) is a widely used antithyroid drug, but it can cause hepatotoxicity by unknown mechanisms. Previous studies showed that the hepatic metabolism of MMI produces N-methylthiourea, leading to liver damage. However, the specific enzyme responsible for the production of the toxic metabolite N-methylthiourea is still unclear. In this study, we screened cytochromes P450 (CYPs) in N-methylthiourea production from MMI. CYP2A6 was identified as the key enzyme in catalyzing MMI metabolism to produce N-methylthiourea. When mice were pretreated with a CYP2A6 inhibitor, formation of N-methylthiourea from MMI was remarkably reduced. Consistently, the CYP2A6 inhibitor prevented MMI-induced hepatotoxicity. These results demonstrated that CYP2A6 is essential in MMI bioactivation and hepatotoxicity.

Compensatory hepatic adaptation accompanies permanent absence of intrahepatic biliary network due to YAP1 loss in liver progenitors.

Yes-associated protein 1 (YAP1) regulates cell plasticity during liver injury, regeneration, and cancer, but its role in liver development is unknown. We detect YAP1 activity in biliary cells and in cells at the hepatobiliary bifurcation in single-cell RNA sequencing analysis of developing livers. Deletion of Yap1 in hepatoblasts does not impair Notch-driven SOX9+ ductal plate formation but does prevent the formation of the abutting second layer of SOX9+ ductal cells, blocking the formation of a patent intrahepatic biliary tree. Intriguingly, these mice survive for 8 months with severe cholestatic injury and without hepatocyte-to-biliary transdifferentiation. Ductular reaction in the perihilar region suggests extrahepatic biliary proliferation, likely seeking the missing intrahepatic biliary network. Long-term survival of these mice occurs through hepatocyte adaptation via reduced metabolic and synthetic function, including altered bile acid metabolism and transport. Overall, we show YAP1 as a key regulator of bile duct development while highlighting a profound adaptive capability of hepatocytes.

Metabolism and Hepatotoxicity of Pyrazinamide, an Antituberculosis Drug.

Pyrazinamide (PZA) is an important component of a standard combination therapy against tuberculosis. However, PZA is hepatotoxic, and the underlying mechanisms are poorly understood. Biotransformation of PZA in the liver was primarily suggested behind its hepatoxicity. This review summarizes the knowledge of the key enzymes involved in PZA metabolism and discusses their contributions to PZA hepatotoxicity. SIGNIFICANCE STATEMENT: This review outlines the current understanding of PZA metabolism and hepatotoxicity. This work also highlights the gaps in this field, which can be used to guide the future studies on PZA-induced liver injury.