Human PXR modulates hepatotoxicity associated with rifampicin and isoniazid co-therapy

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.

Association of DNA methylation, polymorphism and mRNA level of ALAS1 with antituberculosis drug-induced liver injury

Aim: To investigate the association of DNA methylation, genetic polymorphisms and mRNA level of aminolevulinate synthase 1 (ALAS1) with antituberculosis drug-induced liver injury (AT-DILI) risk.Methods: Based on a 1:1 matched case-control study with 182 cases and 182 controls, one CpG island and three single nucleotide polymorphisms (SNPs) were detected. ALAS1 mRNA level was detected in 34 samples.Results: Patients with methylation status were at high risk of AT-DILI (odds ratio: 1.567, 95% CI: 1.015-2.421, p = 0.043) and SNP rs352169 was associated with AT-DILI risk (GA vs. GG, odds ratio: 1.770, 95% CI: 1.101-2.847, p = 0.019). ALAS1 mRNA level in the cases was significantly lower than that in the controls (0.75 ± 0.34 vs. 1.00 ± 0.42, p = 0.021).Conclusion: The methylation status and SNP rs352169 of ALAS1 were associated with AT-DILI risk.

Diagnosis, prevention and risk-management of drug-induced liver injury due to medications used to treat mycobacterium tuberculosis

INTRODUCTION

Many of the first line medications for the treatment of active and latent M. tuberculosis are hepatoxic and cause a spectrum of anti-tuberculosis drug induced liver injury (ATLI), including acute liver failure (ALF). Despite advances in recognition of and prevention of ATLI, isoniazid remains one of the leading causes of DILI as well as drug-induced ALF.

AREAS COVERED

A literature search of the incidence, risk factors, current societal guidelines, monitoring, and prophylactic medication usage in ATLI was performed using PubMed and institutional websites. Relevant articles from 1972 to 2024 were included in this review.

EXPERT OPINION

Current societal guidelines regarding ATLI monitoring are mixed, but many recommend liver enzyme testing of high-risk populations. We recommend liver test monitoring for all patients on multi-drug therapy as well as those on isoniazid therapy. Precision medicine practices, such as N-acetyltransferase-2 polymorphism genotyping, are thought to be beneficial in reducing the incidence of ATLI in high-risk populations. However, broader implementation is currently cost prohibitive. Hepatoprotective drugs are not currently recommended, although we do recognize their potential. In patients who develop ATLI but require ongoing anti-TB treatment, strategies to restart the same or less hepatotoxic regimens are currently being followed.

KLF15-Cyp3a11 Axis Regulates Rifampicin-Induced Liver Injury

Rifampicin (RFP) has demonstrated potent antibacterial effects in the treatment of pulmonary tuberculosis. However, the serious adverse effects on the liver intensively limit the clinical usage of the drug. Deacetylation greatly reduces the toxicity of RFP but also retains its curative activity. Here, we found that Krüppel-like factor 15 (KLF15) repressed the expression of the major RFP detoxification enzyme Cyp3a11 in mice via both direct and indirect mechanisms. Knockout of hepatocyte KLF15 induced the expression of Cyp3a11 and robustly attenuated the hepatotoxicity of RFP in mice. In contrast, overexpression of hepatic KLF15 exacerbated RFP-induced liver injury as well as mortality. More importantly, the suppression of hepatic KLF15 expression strikingly restored liver functions in mice even after being pretreated with overdosed RFP. Therefore, this study identified the KLF15-Cyp3a11 axis as a novel regulatory pathway that may play an essential role in the detoxification of RFP and associated liver injury. SIGNIFICANCE STATEMENT: Rifampicin has demonstrated antibacterial effects in the treatment of pulmonary tuberculosis. However, the serious adverse effects on the liver limit the clinical usage of the drug. Permanent depletion and transient inhibition of hepatic KLF15 expression significantly induced the expression of Cyp3a11 and robustly attenuated mouse hepatotoxicity induced by RFP. Overall, our studies show the KLF15-Cyp3a11 axis was identified as a novel regulatory pathway that may play an essential role in the detoxification of RFP and associated liver injury.

Integrating the gut microbiome and pharmacology

The gut microbiome harbors trillions of organisms that contribute to human health and disease. These bacteria can also affect the properties of medical drugs used to treat these diseases, and drugs, in turn, can reshape the microbiome. Research addressing interdependent microbiome-host-drug interactions thus has broad impact. In this Review, we discuss these interactions from the perspective of drug bioavailability, absorption, metabolism, excretion, toxicity, and drug-mediated microbiome modulation. We survey approaches that aim to uncover the mechanisms underlying these effects and opportunities to translate this knowledge into new strategies to improve the development, administration, and monitoring of medical drugs.

Genetic Polymorphisms of UDP-Glucuronosyltransferases and Susceptibility to Antituberculosis Drug-Induced Liver Injury: A Systematic Review and Meta-Analysis

Methods

The PRISMA statement was strictly followed, and the protocol was registered in PROSPERO (CRD42022339317). The PICOS framework was used: patients received antituberculosis treatment, UGTs polymorphisms (mutants), UGTs polymorphisms (wild), AT-DILI, and case-control studies. Eligible studies were searched through nine databases up to April 27, 2022. The study's qualities were assessed by the revised Little's recommendations. Meta-analysis was conducted with a random-effects model using odds ratios (ORs) with 95% confidence intervals (95% CIs) as the effect size.

Results

Twelve case-control studies with 2128 cases and 4338 controls were included, and 32 single nucleotide polymorphisms (SNPs) in the seven UGT genes have been reported in Chinese and Korean. All studies were judged as high quality. The pooled results indicated that UGT1A1 rs3755319 (AC vs. AA, OR = 1.454, 95% CI: 1.100-1.921, P = 0.009), UGT2B7 rs7662029 (G vs. A, OR = 1.547, 95% CI: 1.249-1.917, P < 0.0001; GG + AG vs. AA, OR = 2.371, 95% CI: 1.779-3.160, P < 0.0001; AG vs. AA, OR = 2.686, 95% CI: 1.988-3.627, P < 0.0001), and UGT2B7 rs7439366 (C vs. T, OR = 0.585, 95% CI: 0.477-0.717, P < 0.0001; CC + TC vs. TT, OR = 0.347, 95% CI: 0.238-0.506, P < 0.0001; CC vs. TC + TT, OR = 0.675, 95% CI: 0.507-0.898, P = 0.007) might be associated with the risk of AT-DILI.

Conclusions

The polymorphisms of UGT1A1 rs3755319, UGT2B7 rs7662029, and UGT2B7 rs7439366 were significantly associated with AT-DILI susceptibility. However, this conclusion should be interpreted with caution due to the low number of studies and the relatively small sample size.

Asiatic acid ameliorates rifampicin- and isoniazid-induced liver injury in vivo by regulating sphingolipid metabolism and mitogen-activated protein kinase signalling pathways

In this study, we aimed to determine whether asiatic acid (AA) exerts any therapeutic effects on rifampicin (RFP)- and isoniazid (INH)-induced liver injury and elucidate the underlying mechanisms. Briefly, liver injury in mice was induced via RFP and INH administration. We investigated the effects and potential action mechanisms of AA on liver injury using transcriptomics, metabolomics and various examinations. We found that AA significantly ameliorated the pathological changes in liver tissues and decreased the transaminase activity, inflammation and oxidative stress damage. Transcriptomics revealed 147 differentially expressed genes (DEGs) between the AA and model groups that were enriched in metabolic and mitogen-activated protein kinase (MAPK) signalling pathways. Metabolomics revealed 778 differentially expressed metabolites between the AA and model groups. Furthermore, integrated transcriptomics and metabolomics analyses revealed strong correlations between DEGs and differentially expressed metabolites and indicated that AA regulates the sphingolipid metabolism by inhibiting the expression of delta 4-desaturase, sphingolipid 1. Experimental results confirmed that AA inhibited the MAPK signalling pathway. In summary, AA inhibits inflammation and oxidative stress damage by regulating the sphingolipid metabolism pathway and blocking the MAPK signalling pathway, thereby relieving the RFP/INH-induced liver injury.

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.

Effects of rifampicin on porphyrin metabolism in healthy volunteers

Pregnane X receptor (PXR) is known to stimulate haem synthesis, but detailed knowledge on the effects of PXR activation on porphyrin metabolism in humans is lacking. We utilized a randomized, crossover, open (blinded laboratory) and placebo-controlled trial with 600-mg rifampicin or placebo dosed for a week to investigate the effects of PXR activation on erythrocyte, plasma, faecal and urine porphyrins. Sixteen healthy volunteers participated on the trial, but the number of volunteers for blood and urine porphyrin analyses was 15 while the number of samples for faecal analyses was 14. Rifampicin increased urine pentaporphyrin concentration 3.7-fold (mean 1.80 ± 0.6 vs. 6.73 ± 4.4 nmol/L, p = 0.003) in comparison with placebo. Urine coproporphyrin I increased 23% (p = 0.036). Faecal protoporphyrin IX decreased (mean 31.6 ± 23.5 vs. 19.2 ± 27.8 nmol/g, p = 0.023). The number of blood erythrocytes was slightly elevated, and plasma bilirubin, catabolic metabolite of haem, was decreased. In conclusion, rifampicin dosing elevated the excretion of certain urinary porphyrin metabolites and decreased faecal protoporphyrin IX excretion. As urine pentaporphyrin and coproporphyrin I are not precursors in haem biosynthesis, increased excretion may serve as a hepatoprotective shunt when haem synthesis or porphyrin levels are increased.

Polymorphisms in drug metabolism genes as a risk factor for first-line anti-tuberculosis drug-induced liver injury

BACKGROUND

Anti-tuberculosis drug-induced liver injury (AT-DILI) is one of the most common side effects in TB patients during treatment. The prime cause of liver injury during TB treatment is reported to be isoniazid and its metabolites. Different factors influenced the development of AT-DILI, and genetic factors are one of the major factors.

METHODS AND RESULTS

Polymorphisms in drug metabolism genes like NAT2, CYP2E1, PXR, and GST have been reported to be associated with AT-DILI, and they are one of the major areas of focus at present. Attempts are met in this review to analyse the different markers in these drug metabolism genes for their association with AT-DILI.

CONCLUSION

A better understanding of the polymorphisms in these genes and their functional effects will give better insights into the development of AT-DILI, and it could facilitate in designing and developing more effective personalized treatment for TB.

Folic acid protects against tuberculosis-drug-induced liver injury in rats and its potential mechanism by metabolomics

Observational study indicated that folic acid (FA) supplementation may protect against tuberculosis-drug-induced liver injury (TBLI). The aim is to investigate the effect and mechanism of FA on TBLI in rats. Liver injury was induced by a daily gavage of isoniazid (INH) and rifampicin (RIF) in the model and FA groups. Rats in the FA group were also treated with 2.5 mg/kg body weight FA. Rats in the control group were not treated. Eight rats were used in each group. The severity of liver injury was measured by the serum levels of hepatic enzymes and histological score. The metabolites in serum and liver tissues were analyzed by HPLC-Q-TOF-MS/MS. FA treatment significantly reduced alanine aminotransferase and liver necrosis. Seventy-nine differential metabolites in the serum and liver tissues were identified among the three groups. N-acylethanolamines, INH and RIF metabolites, phosphatidylcholines, lysophosphatidylcholines, monoglycerides, diglycerides and bile acids were regulated by FA treatment, involving key metabolic pathways, such as N-acylethanolamine metabolism, INH and RIF metabolism, liver regeneration, inflammation alleviation and bile acid metabolism. RT-PCR and western blotting results confirmed the altered N-acylethanolamine metabolism and improved drug metabolism by FA. In conclusion, FA was protective against TBLI, which may be related to the regulation of N-acylethanolamine metabolism and drug detoxification by FA.

Microbial Metabolites as Ligands to Xenobiotic Receptors: Chemical Mimicry as Potential Drugs of the Future

Xenobiotic receptors, such as the pregnane X receptor, regulate multiple host physiologic pathways including xenobiotic metabolism, certain aspects of cellular metabolism, and innate immunity. These ligand-dependent nuclear factors regulate gene expression via genomic recognition of specific promoters and transcriptional activation of the gene. Natural or endogenous ligands are not commonly associated with this class of receptors; however, since these receptors are expressed in a cell-type specific manner in the liver and intestines, there has been significant recent effort to characterize microbially derived metabolites as ligands for these receptors. In general, these metabolites are thought to be weak micromolar affinity ligands. This journal anniversary minireview focuses on recent efforts to derive potentially nontoxic microbial metabolite chemical mimics that could one day be developed as drugs combating xenobiotic receptor-modifying pathophysiology. The review will include our perspective on the field and recommend certain directions for future research. SIGNIFICANCE STATEMENT: Xenobiotic receptors (XRs) regulate host drug metabolism, cellular metabolism, and immunity. Their presence in host intestines allows them to function not only as xenosensors but also as a response to the complex metabolic environment present in the intestines. Specifically, this review focuses on describing microbial metabolite-XR interactions and the translation of these findings toward discovery of novel chemical mimics as potential drugs of the future for diseases such as inflammatory bowel disease.

Plasma metabolomic and lipidomic alterations associated with anti-tuberculosis drug-induced liver injury

Background: Anti-tuberculosis drug-induced liver injury (ATB-DILI) is an adverse reaction with a high incidence and the greatest impact on tuberculosis treatment. However, there is a lack of effective biomarkers for the early prediction of ATB-DILI. Herein, this study uses UPLC‒MS/MS to reveal the plasma metabolic profile and lipid profile of ATB-DILI patients before drug administration and screen new biomarkers for predicting ATB-DILI. Methods: A total of 60 TB patients were enrolled, and plasma was collected before antituberculosis drug administration. The untargeted metabolomics and lipidomics analyses were performed using UPLC‒MS/MS, and the high-resolution mass spectrometer Q Exactive was used for data acquisition in both positive and negative ion modes. The random forest package of R software was used for data screening and model building. Results: A total of 60 TB patients, including 30 ATB-DILI patients and 30 non-ATB-DILI subjects, were enrolled. There were no significant differences between the ATB-DILI and control groups in age, sex, smoking, drinking or body mass index (p > 0.05). Twenty-two differential metabolites were selected. According to KEGG pathway analysis, 9 significantly enriched metabolic pathways were found, and both drug metabolism-other enzymes and niacin and nicotinamide metabolic pathways were found in both positive and negative ion models. A total of 7 differential lipid molecules were identified between the two groups. Ferroptosis and biosynthesis of unsaturated fatty acids were involved in the occurrence of ATB-DILI. Random forest analysis showed that the model built with the top 30 important variables had an area under the ROC curve of 0.79 (0.65-0.93) for the training set and 0.79 (0.55-1.00) for the validation set. Conclusion: This study demonstrated that potential markers for the early prediction of ATB-DILI can be found through plasma metabolomics and lipidomics. The random forest model showed good clinical predictive value for ATB-DILI.

Mechanisms of isoniazid and rifampicin-induced liver injury and the effects of natural medicinal ingredients: A review

Isoniazid (INH) and rifampicin (RFP) are the first-line medications for tuberculosis treatment, and liver injury is the major adverse effect. Natural medicinal ingredients provide distinct benefits in alleviating patients’ symptoms, lowering the liver injury risk, delaying disease progression, and strengthening the body’s ability to heal. This paper summarises the recent research on the mechanisms of INH and RFP-induced liver injury and the effects of natural medicinal ingredients. It is believed that INH-induced liver injury may be attributed to oxidative stress, mitochondrial dysfunction, drug metabolic enzymes, protoporphyrin IX accumulation, endoplasmic reticulum stress, bile transport imbalance, and immune response. RFP-induced liver injury is mainly related to cholestasis, endoplasmic reticulum stress, and liver lipid accumulation. However, the combined effect of INH and RFP on liver injury risk is still uncertain. RFP can increase INH-induced hepatotoxicity by regulating the expression of drug-metabolizing enzymes and transporters. In contrast, INH can antagonize RFP-induced liver injury by reducing the total bilirubin level in the blood. Sagittaria sagittifolia polysaccharide, quercetin, gallic acid, and other natural medicinal ingredients play protective roles on INH and RFP-induced liver injury by enhancing the body’s antioxidant capacity, regulating metabolism, inhibiting cell apoptosis, and reducing the inflammatory response. There are still many gaps in the literature on INH and RFP-induced liver injury mechanisms and the effects of natural medicinal ingredients. Thus, further research should be carried out from the perspectives of liver injury phenotype, injury markers, in vitro and in vivo liver injury model construction, and liver-gut axis. This paper comprehensively reviewed the literature on mechanisms involved in INH and RFP-induced liver injury and the status of developing new drugs against INH and RFP-induced liver injury. In addition, this review also highlighted the uses and advantages of natural medicinal ingredients in treating drug-induced liver injury.

Recent advances in research of modes of hepatocyte death in anti-tuberculosis drug-induced liver injury

Antituberculosis drug-induced liver injury (ATB-DILI) is the most common and most serious side effect of antituberculous drug therapy, which brings great challenges to drug treatment of tuberculosis. Isoniazid and rifampicin as first-line anti-tuberculosis drugs produce a variety of toxic metabolites that directly cause liver cell necrosis, and a large amount of free radicals that induce oxidative stress, leading to programmed death of liver cells such as apoptosis, ferroptosis, and autophagy. Iron death is a recently discovered mode of cell death, and its role in ATB-DILI has not been fully elucidated. Blocking the pathway of hepatocyte death is an important means to treat ATB-DILI. In this paper, we discuss the mechanism and characteristics of different cell death modes in order to help identify new diagnostic markers and therapeutic drug targets.

Relevance of gene polymorphisms of NAT2 and NR1I2 to anti-tuberculosis drug-induced hepatotoxicity

The recommended treatment regimen for tuberculosis is a combination of agents with antitubercular activity, during which hepatotoxicity is one of the most common side effects. In addition to the N-acetyltransferase 2 (NAT2) genotype, rs3814055 in nuclear receptor subfamily 1, group I, member 2 (NR1I2) has been demonstrated to be associated with anti-tuberculosis drug-induced hepatotoxicity (ATDH), but previous results have been inconsistent.A retrospective nested hospital-based case-control study was performed to investigate the association between genetic polymorphisms and the risk of ATDH. Fifteen genetic variants (13 SNPs and two null genotypes) in cytochrome P450 2E1, NR1I2, UDP-glucuronosyltransferase 1A1, NAT2, superoxide dismutase 1, superoxide dismutase 2, and glutathione S-transferases (GSTT1, GSTM1, GSTP1) were genotyped. Odds ratios with 95% confidence intervals were calculated with drug doses, body mass index comorbidity of diabetes mellitus, and baseline alanine transaminase value as covariates.Conditional logistic regression demonstrated that the NAT2 slow acetylation genotype and the T allele of rs3814055 in NR1I2 may contribute to susceptibility to ATDH.Stratified association analysis demonstrated that in NAT2 non-slow acetylators, the T allele of rs3814055 was a risk factor for ATDH, whereas the T allele did not increase the susceptibility to ATDH in slow acetylators.

Association of ABCG2 polymorphisms with susceptibility to anti-tuberculosis drug-induced hepatotoxicity in the Chinese population

Background The accumulation of endogenous hepatotoxin protoporphyrin IX (PPIX) in the liver was proposed to be a novel mechanism of anti-tuberculosis drug-induced hepatotoxicity (ATDH). ATP-binding cassette transporter G2 (ABCG2) plays an important role in modulating PPIX concentrations. This study aimed to explore the role of ABCG2 genetic polymorphisms in the risk of ATDH in Chinese patients.Methods A 1:4 matched case-control study was performed among 202 ATDH cases and 808 controls. Conditional logistic regression model was used to estimate the association between genotypes and the risk of ATDH by odds ratios (ORs) with 95% confidence intervals (CIs).Results Male patients with CC genotype of rs2622605 had an increased risk of ATDH (adjusted OR =1.615, 95% CI: 1.119-2.332, P = 0.011). The peak value of alkaline phosphatase was significantly higher in male patients with CC genotype of rs2622605 than in those with TT + TC genotype during antituberculosis treatment (102.0 U/L vs. 98.0 U/L, P = 0.029).Conclusions This is the first attempt to evaluate the association between ABCG2 genetic variants and the risk of ATDH. Based on the 1:4 matched case-control study, the polymorphism at rs2622605 in the ABCG2 gene may be associated with the susceptibility to ATDH in Chinese male patients.

The role of the genetic variant FECH rs11660001 in the occurrence of anti-tuberculosis drug-induced liver injury

WHAT IS KNOWN AND OBJECTIVE

The pathogenic mechanism of anti-tuberculosis drug-induced liver injury (AT-DILI) is still largely unknown. Recent studies have indicated that rifampicin and isoniazid cotreatment causes the accumulation of endogenous protoporphyrin IX in the liver through the haem biosynthesis pathway. Alanine synthase 1 (ALAS1) and ferrochelatase (FECH) are the rate-limiting enzymes in the production of haem. The present study aimed to investigate the genetic contribution of the ALAS1 and FECH genes to the risk of AT-DILI in an Eastern Chinese Han population.

METHODS

A 1:4 matched case-control study was conducted, and eight SNPs in the ALAS1 and FECH genes were detected and assessed. A multivariate conditional logistic regression model was used to estimate the association between genotypes and the risk of AT-DILI by the odds ratios (ORs) with 95% confidence intervals (CIs), with liver disease history, hepatoprotectant use, smoking and drinking history as covariates.

RESULTS AND DISCUSSION

Overall, 202 AT-DILI cases and 808 controls were included in this study. The female patients carrying polymorphisms of rs11660001 in FECH had an increased risk of AT-DILI under the dominant and additive models (OR = 1.831, 95% CI: 1.014-3.307, p = 0.045; OR = 1.673, 95% CI: 1.015-2.760, p = 0.044, respectively). The peak aspartate transaminase level was significantly higher in female patients carrying the GA+AA genotype of rs11660001 than in those with the GG genotype during anti-TB treatment (p = 0.032).

WHAT IS NEW AND CONCLUSION

Based on this 1:4 individual matched case-control study, SNP rs11660001 in the FECH gene may be associated with susceptibility to AT-DILI in Chinese female anti-TB treatment patients. Further studies in larger varied populations are needed to validate our findings.

Metabolism of a Selective Serotonin and Norepinephrine Reuptake Inhibitor Duloxetine in Liver Microsomes and Mice

Duloxetine (DLX) is a dual serotonin and norepinephrine reuptake inhibitor, widely used for the treatment of major depressive disorder. Although DLX has shown good efficacy and safety, serious adverse effects (e.g., liver injury) have been reported. The mechanisms associated with DLX-induced toxicity remain elusive. Drug metabolism plays critical roles in drug safety and efficacy. However, the metabolic profile of DLX in mice is not available, although mice serve as commonly used animal models for mechanistic studies of drug-induced adverse effects. Our study revealed 39 DLX metabolites in human/mouse liver microsomes and mice. Of note, 13 metabolites are novel, including five N-acetyl cysteine adducts and one reduced glutathione (GSH) adduct associated with DLX. Additionally, the species differences of certain metabolites were observed between human and mouse liver microsomes. CYP1A2 and CYP2D6 are primary enzymes responsible for the formation of DLX metabolites in liver microsomes, including DLX-GSH adducts. In summary, a total of 39 DLX metabolites were identified, and species differences were noticed in vitro. The roles of CYP450s in DLX metabolite formation were also verified using human recombinant cytochrome P450 (P450) enzymes and corresponding chemical inhibitors. Further studies are warranted to address the exact role of DLX metabolism in its adverse effects in vitro (e.g., human primary hepatocytes) and in vivo (e.g., Cyp1a2-null mice). SIGNIFICANCE STATEMENT: This current study systematically investigated Duloxetine (DLX) metabolism and bioactivation in liver microsomes and mice. This study provided a global view of DLX metabolism and bioactivation in liver microsomes and mice, which are very valuable to further elucidate the mechanistic study of DLX-related adverse effects and drug-drug interaction from metabolic aspects.

Non-Clinical Investigation of Tuberculosis Drugs: Conjugated Norbornene- Based Nanocarriers Toxic Impacts on Zebrafish

INTRODUCTION:

Rifampicin conjugated (R-CP), and rifampicin -isoniazid dual conjugated (RI-CP) norbornene-derived nanocarriers are newly designed for pH stimuli-responsive delivery of tuberculosis (TB) drugs. Its biosafety level is yet to be well established.

OBJECTIVES:

To assess the impacts of the nanocarriers on liver cells using zebrafish animal model and human liver cell line model (HepG2).

METHODS:

Initially, lethal dose concentration for the norbornene-derived nanocarrier systems in zebrafish was determined. The toxic effects were analysed at the sub-lethal drug concentration by histopathological study, total GSH level, gene expression and DNA damage in zebrafish liver cells. Fish erythrocyte nuclear abnormalities were also evaluated. Cell viability and oxidative stress level (ROS generation) after exposure to the nanoconjugates was determined using HepG2 cell in the in vitro study.

RESULTS:

In vivo studies of both R-CP and RI-CP showed 100% mortality at 96 hours for exposure concentration >100mg/l and showed toxic changes in zebrafish liver histology, GSH, and DNA damage levels. A noticeable upregulated PXR, CYP3A and cyp2p6 genes was observed in RI-CP exposure than in RIF or R-CP molecules. The in vitro study revealed a dose-dependent effect on cell viability and ROS generation for RIF, R-CP and RI-CP exposures in HepG2 cells.

CONCLUSION:

The current study reports that the rifampicin conjugated (R-CP) and rifampicin-isoniazid conjugated (RI-CP) norbornene derived nanocarriers exhibit enhanced toxic responses in both adult zebrafish and HepG2 cells. The pH-sensitive norbornene derived nanocarriers on conjugation with different drugs exhibited varied impacts on hepatic cells. Hence the present investigation recommends a complete metabolomics analysis and norbornene carrier-drug interaction study to be performed for each drug conjugated norbornene nanocarrier to ensure its biosafety.

Preclinical models of idiosyncratic drug-induced liver injury (iDILI): Moving towards prediction

Idiosyncratic drug-induced liver injury (iDILI) encompasses the unexpected harms that prescription and non-prescription drugs, herbal and dietary supplements can cause to the liver. iDILI remains a major public health problem and a major cause of drug attrition. Given the lack of biomarkers for iDILI prediction, diagnosis and prognosis, searching new models to predict and study mechanisms of iDILI is necessary. One of the major limitations of iDILI preclinical assessment has been the lack of correlation between the markers of hepatotoxicity in animal toxicological studies and clinically significant iDILI. Thus, major advances in the understanding of iDILI susceptibility and pathogenesis have come from the study of well-phenotyped iDILI patients. However, there are many gaps for explaining all the complexity of iDILI susceptibility and mechanisms. Therefore, there is a need to optimize preclinical human in vitro models to reduce the risk of iDILI during drug development. Here, the current experimental models and the future directions in iDILI modelling are thoroughly discussed, focusing on the human cellular models available to study the pathophysiological mechanisms of the disease and the most used in vivo animal iDILI models. We also comment about in silico approaches and the increasing relevance of patient-derived cellular models.

St. John's Wort alleviates dextran sodium sulfate-induced colitis through pregnane X receptor-dependent NFκB antagonism

St. John's wort (SJW), from traditional herbs, activates the pregnane X receptor (PXR), a potential drug target for treating inflammatory bowel disease (IBD). However, how SJW alleviates dextran sodium sulfate (DSS)-induced experimental IBD by activating PXR is unknown. To test this, PXR-humanized, wild-type (WT) and Pxr-null mice, primary intestinal organoids cultures, and the luciferase reporter gene assays were employed. In vivo, a diet supplemented with SJW was found to activate intestinal PXR both in WT and PXR-humanized mice, but not in Pxr-null mice. SJW prevented DSS-induced IBD in PXR-humanized and WT mice, but not in Pxr-null mice. In vitro, hyperforin, a major component of SJW, activated PXR and suppressed tumor necrosis factor (TNF)α-induced nuclear factor (NF) κB translocation in primary intestinal organoids from PXR-humanized mice, but not Pxr-null mice. Luciferase reporter gene assays showed that hyperforin dose-dependently alleviated TNFα-induced NFκB transactivation by activating human PXR in Caco2 cells. Furthermore, SJW therapeutically attenuated DSS-induced IBD in PXR-humanized mice. These data indicate the therapeutic potential of SJW in alleviating DSS-induced IBD in vivo, and TNFα-induced NFκB activation in vitro, dependent on PXR activation, which may have clinical implications for using SJW as a herbal drug anti-IBD treatment.

Genetic and Functional Evaluation of the Role of FOXO1 in Antituberculosis Drug-Induced Hepatotoxicity

Background

The accumulation of the hepatotoxic substance protoporphyrin IX (PPIX) induced by aminolevulinate synthase 1 (ALAS1) activation is one of the important mechanisms of antituberculosis drug-induced hepatotoxicity (ATDH). Forkhead box protein O1 (FOXO1) may activate ALAS1 transcription. However, little is known about their roles in ATDH; we performed a study to determine the association between polymorphisms in the two genes and ATDH susceptibility. Then, we verified this possible association by cellular functional experiments.

Materials and Methods

Tag single-nucleotide polymorphisms (TagSNPs) in the two genes were genotyped in 746 tuberculosis patients. The frequencies of the alleles, genotypes, genetic models, and haplotype distribution of the variants were compared between the case and control groups. L-02 cells and HepG2 cells were incubated with the indicated concentration of isoniazid (INH) and rifampicin (RIF) for the desired times, and then the expression levels of ALAS1 and FOXO1 mRNAs and proteins were detected. HepG2 cells were transiently transfected with FOXO1 siRNA to observe the effect of changes in the FOXO1 expression on the cell survival rate and ALAS1 expression.

Results

The C allele at rs2755237 and the T allele at rs4435111 in the FOXO1 gene were associated with a decreased risk of ATDH. The expression of ALAS1 in both L-02 cells and HepG2 cells was increased by the coadministration of INH/RIF (600/200 μM) for 24 h. Although FOXO1 expression was reduced slightly by the same treatment, its content in the nucleus was significantly increased. However, the cell survival rate and ALAS1 expression level were not significantly altered by the downregulation of FOXO1 in HepG2 cells.

Conclusions

Variants of the rs4435111 and rs2755237 loci in the FOXO1 gene were associated with susceptibility to ATDH. Coadministration of INH/RIF promoted the transfer of FOXO1 from the cytoplasm to the nucleus, but the functional significance of its nuclear translocation requires further verification.

The impact of cytochrome P450 3A genetic polymorphisms on tacrolimus pharmacokinetics in ulcerative colitis patients

Tacrolimus (Tac) is an effective remission inducer of refractory ulcerative colitis (UC). Gene polymorphisms result in interindividual variability in Tac pharmacokinetics. In this study, we aimed to examine the relationships between gene polymorphisms and the metabolism, pharmacokinetics, and therapeutic effects of Tac in patients with UC. Forty-five patients with moderate-to-severe refractory UC treated with Tac were retrospectively enrolled. Genotyping for cytochrome P450 (CYP) 3A4*1G, CYP3A5*3, CYP2C19*2, CYP2C19*3, nuclear receptor subfamily 1 group I member 2 (NR1I2)–25385C>T, ATP-binding cassette subfamily C member 2 (ABCC2)–24C>T, ABCC2 1249G>A, and ABCC2 3972C>T was performed. Concentration/dose (C/D) ratio, clinical therapeutic effects, and adverse events were evaluated. The C/D ratio of Tac in UC patients with the CYP3A4*1G allele was statistically lower than in those with the CYP3A4*1/*1 allele (P = 0.005) and significantly lower in patients with CYP3A5*3/*3 than in those with CYP3A5*1 (P < 0.001). Among patients with the CYP3A4*1G allele, the C/D ratio was significantly lower in patients with CYP3A5*1 than in those with CYP3A5*3/*3 (P = 0.001). Patients with the NR1I2–25385C/C genotype presented significantly more overall adverse events than those with the C/T or T/T genotype (P = 0.03). Although CYP3A4*1G and CYP3A5*3 polymorphisms were related to Tac pharmacokinetics, CYP3A5 presented a stronger effect than CYP3A4. The NR1I2–25385C/C genotype was related to the overall adverse events. The evaluation of these polymorphisms could be useful in the treatment of UC with Tac.

Schisandrol B promotes liver enlargement via activation of PXR and YAP pathways in mice

BACKGROUND

Schisandrol B (SolB) is one of the bioactive components from a traditional Chinese medicine Schisandra chinensis or Schisandra sphenanthera. It has been demonstrated that SolB exerts hepatoprotective effects against drug-induced liver injury and promotes liver regeneration. It was found that SolB can induce hepatomegaly but the involved mechanisms remain unknown.

PURPOSE

This study aimed to explore the mechanisms involved in SolB-induced hepatomegaly.

METHODS

Male C57BL/6 mice were injected intraperitoneally with SolB (100 mg/kg) for 5 days. Serum and liver samples were collected for biochemical and histological analyses. The mechanisms of SolB were investigated by qRT-PCR and western blot analyses, luciferase reporter gene assays and immunofluorescence.

RESULTS

SolB significantly increased hepatocyte size and proliferation, and then promoted liver enlargement without liver injury and inflammation. SolB transactivated human PXR, activated PXR in mice and upregulated hepatic expression of its downstream proteins, such as CYP3A11, CYP2B10 and UGT1A1. SolB also significantly enhanced nuclear translocation of PXR and YAP in human cell lines. YAP signal pathway was activated by SolB in mice.

CONCLUSION

These findings demonstrated that SolB can significantly induce liver enlargement, which is associated with the activation of PXR and YAP pathways.

The xenobiotic receptors PXR and CAR in liver physiology, an update

Pregnane X receptor (PXR) and constitutive androstane receptor (CAR) are two nuclear receptors that are well-known for their roles in xenobiotic detoxification by regulating the expression of drug-metabolizing enzymes and transporters. In addition to metabolizing drugs and other xenobiotics, the same enzymes and transporters are also responsible for the production and elimination of numerous endogenous chemicals, or endobiotics. Moreover, both PXR and CAR are highly expressed in the liver. As such, it is conceivable that PXR and CAR have major potentials to affect the pathophysiology of the liver by regulating the homeostasis of endobiotics. In recent years, the physiological functions of PXR and CAR in the liver have been extensively studied. Emerging evidence has suggested the roles of PXR and CAR in energy metabolism, bile acid homeostasis, cell proliferation, to name a few. This review summarizes the recent progress in our understanding of the roles of PXR and CAR in liver physiology.

Probiotics mixture reinforces barrier function to ameliorate necrotizing enterocolitis by regulating PXR-JNK pathway

Background

Intestinal dysbiosis is believed to be one of the factors inducing neonatal necrotizing enterocolitis (NEC). Probiotics have been employed to treat NEC in a number of animal experiments and clinical trials, and some significant benefits of utilizing probiotics for the prevention or alleviation of NEC have been confirmed. However, the mechanism underlying the efficacy of probiotics in treating NEC has not been elucidated.

Results

Impairment of the intestinal barrier, which was characterized by the decreased expression of tight junction components, was observed in the pathogenesis of NEC. The probiotic mixture alleviated this intestinal damage by enhancing the function of the barrier. Meanwhile, the probiotics remodeled the composition of the intestinal microbiota in NEC mice. Furthermore, increased expression of the pregnane X receptor (PXR) was observed after treatment with the probiotic mixture, and PXR overexpression in Caco-2 cells protected the barrier from lipopolysaccharide (LPS) damage. Further research showed that PXR could inhibit the phosphorylation of c-Jun N-terminal kinase (JNK) and could increase the expression of tight junction components.

Conclusions

Our study confirmed that probiotics could ameliorate intestinal lesions by enhancing the function of the mucosal barrier. Specifically, probiotics may target PXR, which may subsequently enhance the expression of tight junction components by inhibiting the phosphorylation of JNK and enhance the function of the barrier.

Dysregulation of Endobiotic Homeostasis Mechanisms: Novel Insights into Adverse Pharmacokinetic Interactions between Illicit Substances and Clinical Drugs

Many patients with a variety of medical conditions take illicit substances concomitantly with clinical drugs. This concomitant usage can lead to life-threatening adverse events. Despite the evidence that these adverse events can be caused by pharmacokinetic interactions, the underlying mechanisms are poorly understood. Investigation of mechanisms involved in dysregulation of endobiotic homeostasis during the concomitant usage of illicit substances with clinical drugs could provide novel insights into pharmacokinetic mechanisms of adverse interactions between illicit substances and clinical drugs.

NR1I2 genetic polymorphisms and the risk of anti-tuberculosis drug-induced hepatotoxicity: A systematic review and meta-analysis

Anti-tuberculosis drug-induced hepatotoxicity (ATDH) is a serious adverse drug reaction. Conflicting results have been obtained regarding the associations of nuclear receptor subfamily 1 group I member 2 (NR1I2) gene polymorphisms on susceptibility to ATDH. Therefore, we aimed to evaluate the associations using a systematic review/meta-analysis approach. PubMed, Medline, Cochrane Library, Web of Science and SinoMed databases were searched for all eligible studies from inception to June 10, 2020. Pooled adjusted odds ratios (ORs) with 95% confidence intervals (CIs) were employed to evaluate the strength of the association between the NR1I2 polymorphisms and the risk of ATDH. Subgroup analysis was performed by region of origin, and meta-regression were performed to detect potential sources of heterogeneity. A total of five case-control studies involving 572 cases and 1867 controls were identified. Fourteen SNPs in the NR1I2 gene have been reported, and the most heavily studied SNPs were rs3814055 and rs7643645. The pooled estimates did not exhibit any significant associations between SNPs rs3814055 and rs7643645 and the risk of ATDH (rs3814055: dominant model, OR = 1.00, 95% CI: 0.82-1.22, P = 1.00; recessive model, OR = 1.17, 95% CI: 0.76-1.78, P = .48; rs7643645: dominant model, OR = 1.04, 95% CI: 0.64-1.68, P = .89; recessive model, OR = 0.98, 95% CI: 0.65-1.49, P = .93). Subgroup analysis obtained similar negative results in Chinese patients, and the diagnostic criteria of ATDH may be the source of heterogeneity. Based on the meta-analysis described in this report, we did not observe any association between NR1I2 gene polymorphisms and ATDH susceptibility. However, this conclusion should be interpreted with caution due to the low number of studies and the relatively small sample size.

Metabolic profiling of norepinephrine reuptake inhibitor atomoxetine

Atomoxetine (ATX), a selective and potent inhibitor of the presynaptic norepinephrine transporter, is used mainly to treat attention-deficit hyperactivity disorder. Although multiple adverse effects associated with ATX have been reported including severe liver injuries, the mechanisms of ATX-related toxicity remain largely unknown. Metabolism frequently contributes to adverse effects of a drug through reactive metabolites, and the bioactivation status of ATX is still not investigated yet. Here, we systematically investigated ATX metabolism, bioactivation, species difference in human, mouse, and rat liver microsomes (HLM, MLM, and RLM) and in mice using metabolomic approaches as mice and rats are commonly used animal models for the studies of drug toxicity. We identified thirty one ATX metabolites and adducts in LMs and mice, 16 of which are novel. In LMs, we uncovered two methoxyamine-trapped aldehydes, two cyclization metabolites, detoluene-ATX, and ATX-N-hydroxylation for the first time. Detoluene-ATX and one cyclization metabolite were also observed in mice. Using chemical inhibitors and recombinant CYP enzymes, we demonstrated that CYP2C8 and CYP2B6 mainly contribute to the formation of aldehyde; CYP2D6 is the dominant enzyme for the formation of ATX cyclization and detoluene-ATX; CYP3A4 is major enzyme responsible for the hydroxylamine formation. The findings concerning aldehydes should be very useful to further elucidate the mechanistic aspects of adverse effects associated with ATX from metabolic angles. Additionally, the species differences for each metabolite should be helpful to investigate the contribution of specific metabolites to ATX toxicity and possible drug-drug interactions in suitable models.

Current progress in identifying endogenous biomarker candidates for drug transporter phenotyping and their potential application to drug development

Drug transporters play important roles in the elimination of various compounds from the blood. Genetic variation and drug-drug interactions underlie the pharmacokinetic differences for the substrates of drug transporters. Some endogenous substrates of drug transporters have emerged as biomarkers to assess differences in drug transporter activity-not only in animals, but also in humans. Metabolomic analysis is a promising approach for identifying such endogenous substrates through their metabolites. The appropriateness of metabolites is supported by studies in vitro and in vivo, both in animals and through pharmacogenomic or drug-drug interaction studies in humans. This review summarizes current progress in identifying such endogenous biomarkers and applying them to drug transporter phenotyping.

Mechanism of Hydrophobic Bile Acid-Induced Hepatocyte Injury and Drug Discovery

Cholestatic liver disease is caused by the obstruction of bile synthesis, transport, and excretion in or outside the liver by a variety of reasons. Long-term persistent cholestasis in the liver can trigger inflammation, necrosis, or apoptosis of hepatocytes. Bile acid nuclear receptors have received the most attention for the treatment of cholestasis, while the drug development for bile acid nuclear receptors has made considerable progress. However, the targets regulated by bile acid receptor drugs are limited. Thus, as anticipated, intervention in the expression of bile acid nuclear receptors alone will not yield satisfactory clinical results. Therefore, this review comprehensively summarized the literature related to cholestasis, analyzed the molecular mechanism that bile acid damages cells, and status of drug development. It is hoped that this review will provide some reference for the research and development of drugs for cholestasis treatment in the future.

Celastrol ameliorates acute liver injury through modulation of PPARα

Celastrol, derived from the roots of the Tripterygium Wilfordi, has attracted interest for its potential anti-inflammatory and lipid-lowering activities. In the present study, the protective effect of celastrol on carbon tetrachloride (CCl4)-induced acute liver injury was investigated. Celastrol improved the increased transaminase activity, inflammation, and oxidative stress induced by CCl4, resulting in improved metabolic disorders found in mice with liver injury. Dual-luciferase reporter assays and primary hepatocyte studies demonstrated that the peroxisome proliferator-activated receptor α (PPARα) signaling mediated the protective effect of celastrol, which was not observed in Ppara-null mice, and co-treatment of wild-type mice with the PPARα antagonist GW6471. Mechanistically, PPARα deficiency potentiated CCl4-induced liver injury through a deoxycholic acid (DCA)-EGR1-inflammatory factor axis. These data demonstrate a novel role for celastrol in protection against acute liver injury through modulating PPARα signaling.

PXR-mediated idiosyncratic drug-induced liver injury: mechanistic insights and targeting approaches

INTRODUCTION

The human liver is the center for drug metabolism and detoxification and is, therefore, constantly exposed to toxic chemicals. The loss of liver function as a result of this exposure is referred to as drug-induced liver injury (DILI). The pregnane X receptor (PXR) is the primary regulator of the hepatic drug-clearance system, which plays a critical role in mediating idiosyncratic DILI.

AREAS COVERED

This review is focused on common mechanisms of PXR-mediated DILI and on in vitro and in vivo models developed to predict and assess DILI. It also provides an update on the development of PXR antagonists that may manage PXR-mediated DILI.

EXPERT OPINION

DILI can be caused by many factors, and PXR is clearly linked to DILI. Although emerging data illustrate how PXR mediates DILI and how PXR activity can be modulated, many questions concerning the development of effective PXR modulators remain. Future research should be focused on determining the mechanisms regulating PXR functions in different cellular contexts.

Toxicoproteomic Profiling of hPXR Transgenic Mice Treated with Rifampicin and Isoniazid

Tuberculosis is a global health threat that affects millions of people every year, and treatment-limiting toxicity remains a considerable source of treatment failure. Recent reports have characterized the nature of hPXR-mediated hepatotoxicity and the systemic toxicity of antitubercular drugs. The antitubercular drug isoniazid plays a role in such pathologic states as acute intermittent porphyria, anemia, hepatotoxicity, hypercoagulable states (deep vein thrombosis, pulmonary embolism, or ischemic stroke), pellagra (vitamin B₃ deficiency), peripheral neuropathy, and vitamin B₆ deficiency. However, the mechanisms by which isoniazid administration leads to these states are unclear. To elucidate the mechanism of rifampicin- and isoniazid-induced liver and systemic injury, we performed tandem mass tag mass spectrometry-based proteomic screening of mPxr^-/- and hPXR mice treated with combinations of rifampicin and isoniazid. Proteomic profiling analysis suggested that the hPXR liver proteome is affected by antitubercular therapy to disrupt [Fe-S] cluster assembly machinery, [2Fe-2S] cluster-containing proteins, cytochrome P450 enzymes, heme biosynthesis, homocysteine catabolism, oxidative stress responses, vitamin B₃ metabolism, and vitamin B₆ metabolism. These novel findings provide insight into the etiology of some of these processes and potential targets for subsequent investigations. Data are available via ProteomeXchange with identifier PXD019505.

Bile acids, lipid and purine metabolism involved in hepatotoxicity of first-line anti-tuberculosis drugs

OBJECTIVES

Rifampin (RIF), isoniazid (INH) and pyrazinamide (PZA) are essential components of the short-term first-line anti-tuberculosis (anti-TB) chemotherapy regimen and can cause hepatotoxicity. However, the mechanism of anti-TB drug-induced hepatotoxicity (ATDH) is currently unclear. We investigate the relevant contributions to liver injury and the pathway of the above-mentioned drugs administered alone or in combination.

METHODS

UPLC-Q-TOF/MS-based metabolomics, bile acids (BAs) analysis and FXR/SHP detection were used to evaluate the toxicity of these drugs and clarify the underlying metabolism-related pathway.

RESULTS

In C57BL/6 mice administered the corrected clinical doses, RIF, INH and PZA could induced hepatotoxicity; with less toxicity in the combination therapy than RIF. The pathological biochemistry, BAs concentration and metabolically regulated FXR/SHP gene expression analyzes in mice were consistent with the metabolomics results. FXR played a role in the hepatotoxicity of anti-tuberculosis drugs in the obeticholic acid treated and FXR^-/- mice. Additionally, the purine and lipid metabolic pathways were involved in ATDH.

CONCLUSION

ATDH was involved in bile acids and lipid and purine metabolism. The BAs metabolic pathway involvement in mice was validated in TB patients. The noninvasive metabolomics approach is more systemic than routine toxicity evaluation and can be used to assess compound toxicity and the underlying mechanism.

Metabolism of JQ1, an inhibitor of bromodomain and extra terminal bromodomain proteins, in human and mouse liver microsomes†

JQ1 is a small-molecule inhibitor of the bromodomain and extra terminal (BET) protein family that potently inhibits the bromodomain testis-specific protein (BRDT), which is essential for spermatogenesis. JQ1 treatment produces a reversible contraceptive effect by targeting the activity of BRDT in mouse male germ cells, validating BRDT as a male contraceptive target. Although JQ1 possesses favourable physical properties, it exhibits a short half-life. Because the details of xenobiotic metabolism play important roles in the optimization of drug candidates and in determining the role of metabolism in drug efficacy, we investigated the metabolism of JQ1 in human and mouse liver microsomes. We present the first comprehensive view of JQ1 metabolism in liver microsomes, distinguishing nine JQ1 metabolites, including three monohydroxylated, one de-tert-butylated, two dihydroxylated, one monohydroxylated/dehydrogenated, one monohydroxylated-de-tert-butylated and one dihydroxylated/dehydrogenated variant of JQ1. The dominant metabolite (M1) in both human and mouse liver microsomes is monohydroxylated on the fused three-ring core. Using recombinant cytochrome P450 (CYP) enzymes, chemical inhibitors and the liver S9 fraction of Cyp3a-null mice, we identify enzymes that contribute to the formation of these metabolites. Cytochrome P450 family 3 subfamily A member 4 (CYP3A4) is the main contributor to the production of JQ1 metabolites in vitro, and the CYP3A4/5 inhibitor ketoconazole strongly inhibits JQ1 metabolism in both human and mouse liver microsomes. Our findings suggest that JQ1 half-life and efficacy might be improved in vivo by co-administration of a selective CYP inhibitor, thereby impacting the use of JQ1 as a probe for BRDT activity in spermatogenesis and as a probe or therapeutic in other systems.

PXR: a center of transcriptional regulation in cancer

Pregnane X receptor (PXR, NR1I2) is a prototypical member of the nuclear receptor superfamily. PXR can be activated by both endobiotics and xenobiotics. As a key xenobiotic receptor, the cellular function of PXR is mostly exerted by its binding to the regulatory gene sequences in a ligand-dependent manner. Classical downstream target genes of PXR participate in xenobiotic responses, such as detoxification, metabolism and inflammation. Emerging evidence also implicates PXR signaling in the processes of apoptosis, cell cycle arrest, proliferation, angiogenesis and oxidative stress, which are closely related to cancer. Here, we discussed, in addition to the characterization of PXR per se, the biological function and regulatory mechanism of PXR signaling in cancer, and its potential for the targeted prevention and therapeutics.

Metabolomics describes previously unknown toxicity mechanisms of isoniazid and rifampicin

Isoniazid and rifampicin are well-known anti-mycobacterial agents and are widely used to treat pulmonary tuberculosis (TB) as part of the combined therapy approach, recommended by the World Health Organization. The ingestion of these first-line TB drugs are, however, not free of side effects, and are toxic to the liver, kidney, and central nervous system. These side effects are associated with poor treatment compliance, resulting in TB treatment failure, relapse and drug resistant TB. This occurrence has subsequently led to the recent application of novel research technologies, towards a better understanding of the underlying toxicity mechanisms of TB drugs in humans, mostly focussing on the 2 most important TB drugs: isoniazid and rifampicin. In this review, we discuss the contribution that one such an approach, termed metabolomics has made toward this field, and also highlight the impact that this might have towards the development of improved TB treatment regimens.

Mechanism of Hydrophobic Bile Acid-Induced Hepatocyte Injury and Drug Discovery

Cholestatic liver disease is caused by the obstruction of bile synthesis, transport, and excretion in or outside the liver by a variety of reasons. Long-term persistent cholestasis in the liver can trigger inflammation, necrosis, or apoptosis of hepatocytes. Bile acid nuclear receptors have received the most attention for the treatment of cholestasis, while the drug development for bile acid nuclear receptors has made considerable progress. However, the targets regulated by bile acid receptor drugs are limited. Thus, as anticipated, intervention in the expression of bile acid nuclear receptors alone will not yield satisfactory clinical results. Therefore, this review comprehensively summarized the literature related to cholestasis, analyzed the molecular mechanism that bile acid damages cells, and status of drug development. It is hoped that this review will provide some reference for the research and development of drugs for cholestasis treatment in the future.

Adverse pharmacokinetic interactions between illicit substances and clinical drugs

Adverse pharmacokinetic interactions between illicit substances and clinical drugs are of a significant health concern. Illicit substances are taken by healthy individuals as well as by patients with medical conditions such as mental illnesses, acquired immunodeficiency syndrome, diabetes mellitus and cancer. Many individuals that use illicit substances simultaneously take clinical drugs meant for targeted treatment. This concomitant usage can lead to life-threatening pharmacokinetic interactions between illicit substances and clinical drugs. Optimal levels and activity of drug-metabolizing enzymes and drug-transporters are crucial for metabolism and disposition of illicit substances as well as clinical drugs. However, both illicit substances and clinical drugs can induce changes in the expression and/or activity of drug-metabolizing enzymes and drug-transporters. Consequently, with concomitant usage, illicit substances can adversely influence the therapeutic outcome of coadministered clinical drugs. Likewise, clinical drugs can adversely affect the response of coadministered illicit substances. While the interactions between illicit substances and clinical drugs pose a tremendous health and financial burden, they lack a similar level of attention as drug-drug, food-drug, supplement-drug, herb-drug, disease-drug, or other substance-drug interactions such as alcohol-drug and tobacco-drug interactions. This review highlights the clinical pharmacokinetic interactions between clinical drugs and commonly used illicit substances such as cannabis, cocaine and 3, 4-Methylenedioxymethamphetamine (MDMA). Rigorous efforts are warranted to further understand the underlying mechanisms responsible for these clinical pharmacokinetic interactions. It is also critical to extend the awareness of the life-threatening adverse interactions to both health care professionals and patients.

Mechanism, prevention, and treatment of drug-induced cholestasis

Drug-induced cholestasis (DIC) refers to the accumulation of bile acid in the liver or systemic circulation due to the obstruction of intrahepatic and extrahepatic bile flow caused by various prescription or non-prescription chemicals, biological agents, traditional Chinese medicines, natural drugs, and their metabolites. In recent years, the incidence of DIC, a common manifestation of drug-induced liver injury (DILI), has been increasing with the aging of the population, the increase of the variety of clinical medications, and the more common use of combined drugs. Therefore, DIC has attracted wide attention from medical professionals, including clinical pharmacists. Hepatic injury induced by DIC is a complex process, which is triggered by two types of biological reactions: the deteriorative response, caused by bile acid accumulation, and the adaptive response aiming at removing the accumulated bile acids. Current studies have shown that several factors can trigger DIC, including changes of functions or microstructures of membrane transporters, hepatocytes, and bile ducts. There is still a lack of specific effective treatment for DIC. Timely withdrawal of suspected liver-injuring drugs is the most important strategy for DIC, and appropriate drugs should be then chosen to relieve the condition based on the clinical type of DIC and symptoms such as itching. For very few patients with severe liver failure, liver transplantation should be considered to save their lives. As such, in-depth knowledge of the mechanism of DIC can help to optimize the prediction and pharmacovigillance model of DILI in vivo during drug development and afterwards marketing, and promote the improvement of prevention and treatment strategies and the development of related interventions. This article reviews the progress in the understanding of the pathogenesis, prevention, and treatment of DIC, with an aim to provide reference for further studies.

Genetic polymorphisms in PXR and NF-κB1 influence susceptibility to anti-tuberculosis drug-induced liver injury

BACKGROUND

Pregnane X receptor (PXR) regulates the expression of drug-metabolizing enzymes and transport enzymes. NF-κB not only plays a role in liver homeostasis and injury-healing processes by regulating inflammatory responses but may also regulate the transcription of PXR. Currently, genetic polymorphisms in PXR are associated with adverse drug effects. Because little is known about the association between NF-κB1 genetic polymorphisms and adverse drug reactions, we explored the association between PXR and NF-κB1 single nucleotide polymorphisms (SNPs) and susceptibility to anti-tuberculosis drug-induced liver injury (ATDILI).

MATERIALS AND METHODS

A total of 746 tuberculosis patients (118 with ATDILI and 628 without ATDILI) were prospectively enrolled at West China Hospital between December 2014 and April 2018. Nine selected SNPs (rs3814055, rs13059232, rs7643645 and rs3732360 in PXR and rs78872571, rs4647992, rs60371688, rs1598861 and rs3774959 in NF-κB1) were genotyped with a custom-designed 2x48-plex SNP Scan TM Kit. The frequencies of the alleles, genotypes and genetic models of the variants were compared between patients with or without ATDILI, while joint effect analysis of the SNP-SNP interactions was performed using multiplicative and additive models. The odds ratios (ORs) and the corresponding 95% confidence intervals (CIs) were calculated.

RESULTS

The T allele of rs3814055 in PXR was associated with a decreased risk for ATDILI (OR 0.61; 95% CI: 0.42-0.89, p = 0.0098). The T alleles of rs78872571 and rs4647992 in NF-κB1 were significantly associated with an increased risk for ATDILI (OR 1.91; 95% CI: 1.06-3.43, p = 0.028 and OR 1.81; 1.06-3.10, p = 0.029, respectively). The allele, genotype and genetic model frequencies were similar in the two groups for the other six SNPs (all P>0.05). There were no multiplicative or additive interactions between the SNPs.

CONCLUSION

Our study is the first to reveal that rs3814055 variants in PXR and rs78872571 and rs4647992 variants in NF-κB1 are associated with susceptibility to ATDILI caused by first-line anti-tuberculosis combination treatment in the Han Chinese population.