Dexamethasone induces human glutathione S transferase alpha 1 (hGSTA1) expression through the activation of glucocorticoid receptor (hGR)

Busulfan induces steatosis in HepaRG cells but not in primary human hepatocytes: Possible explanations and implication for the prediction of drug-induced liver injury

BACKGROUND

The antineoplastic drug busulfan can induce different hepatic lesions including cholestasis and sinusoidal obstruction syndrome. However, hepatic steatosis has never been reported in patients.

OBJECTIVES

This study aimed to determine whether busulfan could induce steatosis in primary human hepatocytes (PHH) and differentiated HepaRG cells.

METHODS

Neutral lipids were determined in PHH and HepaRG cells. Mechanistic investigations were performed in HepaRG cells by measuring metabolic fluxes linked to lipid homeostasis, reduced glutathione (GSH) levels, and expression of genes involved in lipid metabolism and endoplasmic reticulum (ER) stress. Analysis of two previous transcriptomic datasets was carried out.

RESULTS

Busulfan induced lipid accumulation in HepaRG cells but not in six different batches of PHH. In HepaRG cells, busulfan impaired VLDL secretion, increased fatty acid uptake, and induced ER stress. Transcriptomic data analysis and decreased GSH levels suggested that busulfan-induced steatosis might be linked to the high expression of glutathione S-transferase (GST) isoenzyme A1, which is responsible for the formation of the hepatotoxic sulfonium cation conjugate. In keeping with this, the GST inhibitor ethacrynic acid and the chemical chaperone tauroursodeoxycholic acid alleviated busulfan-induced lipid accumulation in HepaRG cells supporting the role of the sulfonium cation conjugate and ER stress in steatosis.

CONCLUSION

While the HepaRG cell line is an invaluable tool for pharmacotoxicological studies, it might not be always an appropriate model to predict and mechanistically investigate drug-induced liver injury. Hence, we recommend carrying out toxicological investigations in both HepaRG cells and PHH to avoid drawing wrong conclusions on the potential hepatotoxicity of drugs and other xenobiotics.

Drug-Drug Interactions Involving Dexamethasone in Clinical Practice: Myth or Reality?

Concomitant administration of multiple drugs frequently causes severe pharmacokinetic or pharmacodynamic drug-drug interactions (DDIs) resulting in the possibility of enhanced toxicity and/or treatment failure. The activity of cytochrome P450 (CYP) 3A4 and P-glycoprotein (P-gp), a drug efflux pump sharing localization and substrate affinities with CYP3A4, is a critical determinant of drug clearance, interindividual variability in drug disposition and clinical efficacy, and appears to be involved in the mechanism of numerous clinically relevant DDIs, including those involving dexamethasone. The recent increase in the use of high doses of dexamethasone during the COVID-19 pandemic have emphasized the need for better knowledge of the clinical significance of drug-drug interactions involving dexamethasone in the clinical setting. We therefore aimed to review the already published evidence for various DDIs involving dexamethasone in vitro in cell culture systems and in vivo in animal models and humans.

Activation of the Aryl Hydrocarbon Receptor (AHR) induces human glutathione S transferase alpha 1 (hGSTA1) expression

Glutathione S-transferases (GSTs) are a key enzyme superfamily involved in the detoxification and cytoprotection of a wide variety of xenobiotics, such as carcinogens, anticancer drugs, environmental toxicants, and endogenously produced free radicals. In the liver, the hGSTA1 isoenzyme is the most abundant and catalyzes the glutathione conjugation of a wide range of electrophiles and has been the principal GST responsible for xenobiotic detoxification. Given the critical role of this enzyme in several cellular processes, particularly cell detoxification, understanding the molecular mechanisms underlying the regulation of hGSTA1 expression is critical. Therefore, the aim of the present study was to investigate whether AHR is involved in the modulation of hGSTA1 gene expression and to characterize the molecular mechanism through which AHR exerts this regulation. Two xenobiotic response elements (XREs) were located at -602 bp and -1030 bp from the transcription start site at the hGSTA1 gene promoter. After treatment of HepG2 cells with beta-naphthoflavone (β-NF), an AHR agonist, induction of hGSTA1 mRNA was observed. This effect was mediated by the recruitment of AHR to the hGSTA1 gene promoter and its transactivation, as indicated by the ChIP, EMSA and luciferase activity assays. The increase in hGSTA1 transcription regulated by AHR also resulted in enhanced levels of hGSTA1 protein and activity. Taken together, our data suggest that AHR ligands have the potential to modify xenobiotic and endobiotic metabolism mediated by hGSTA1, thereby altering the detoxification of xenobiotics, steroidogenesis and the efficacy of chemotherapeutic agents.

Steroid-resistant nephrotic syndrome: pharmacogenetics and epigenetic points and views

Introduction: Glucocorticoids (GCs) are the first-line therapy for patients with nephrotic syndrome (NS), a common glomerular disease, that cause complete remission in most of the cases. In response to the treatment, NS patients are divided into glucocorticoid-sensitive and -resistant. This variation is due to the differences in pharmacokinetics and pharmacodynamics of GCs in each patient that affect the response to the treatment modality. Since the genetic variations in drug-metabolizing enzymes and transporter proteins significantly impact the pharmacokinetics, efficacy and safety of the applied medications, this review highlights the basic mechanisms of genetic variations involved in GCs metabolism in drug-resistant NS patients.Areas covered: This review explains the pharmacogenetic variations that influence the profile of GCs responses and their pharmacokinetics in NS patients. Moreover, the epigenetic variations including histone modifications and miRNA gene regulation that have an influence on GCs responses will review. A comprehensive literature search was performed using different keywords to the reviewed topics.Expert opinion: The accumulative data suggest the importance of pharmacogenetic studies to develop personalized therapies and increase the GCs responsiveness in these patients. It is imperative to know that genetic testing does not give absolute answers to all existing questions in steroid resistance.

Hepatic transcriptome profile of sheep (Ovis aries) in response to overgrazing: novel genes and pathways revealed

BACKGROUND

Overgrazing is a major factor that causes steppe degradation in Inner Mongolian, resulting in extensive ecosystem damage. Scarcity of grass means sheep are smaller and therefore mutton and cashmere production is greatly reduced, which has resulted in massive annual economic losses. Liver is the primary metabolic organ in mammals. It is also the key source of energy supply and detoxification of metabolites in animals, has a close relationship with animal growth. However, investigations on the responses of sheep induced by consequence of overgrazing, particularly those relating to liver-related molecular mechanisms and related metabolic pathways, remain elusive.

RESULTS

The body weight daily gain of sheep, immune organ indices (liver and spleen), and serum parameters related to immune response, protein synthesis and energy supply (IgG, albumin, glucose and non-esterified fatty acid) were significantly lower in the overgrazing group. Other serum parameters including alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase, total bilirubin, blood urea nitrogen and interleukin-6 were significantly higher in the overgrazing group. For the RNA-Seq results, we identified approximately 50 differentially expressed genes, of which half of were up-regulated and the other half were down-regulated (overgrazing group versus light grazing group). Bioinformatics analysis identified two enriched KEGG pathways including peroxisome proliferator-activated receptor (PPAR) signaling pathway (related to lipolysis) and ECM-receptor interaction (related to liver injury and apoptosis). Additionally, several of the down-regulated genes were related to detoxification and immune response.

CONCLUSIONS

Overall, based on the high-throughput RNA sequencing profile integrated with the results of serum biochemical analyses, consequences of lower forage availability and quality under overgrazing condition induced altered expression levels of genes participating in energy metabolism (particularly lipid metabolism) and detoxification and immune responses, causing lipolysis and impaired health status, which might be key reasons for the reduced growth performance of sheep. This investigation provides a novel foundation for the development of sheep hepatic gene interactive networks that are a response to the degraded forage availability under overgrazing condition.

High throughput metabolomics-proteomics investigation on metabolic phenotype changes in rats caused by Radix Scrophulariae using ultra-performance liquid chromatography with mass spectrometry

Radix Scrophulariae, a traditional Chinese herb, is used to treat various diseases, including H₂O₂-induced apoptosis in cardiomyocytes, HaCaT cells, hyperuricaemia, and depression. This study screened metabolites, proteins and common pathways to better understand both the therapeutic effects and side effects of this herb. Methods: Untargeted metabolomics based on UPLC-TOF-MS, coupled with proteomics based on nano-UPLC-Q-Exactive-MS/MS, were used to investigate the effects of R. Scrophulariae in rats. Fifty-one identified metabolites in urine samples and 76 modulated proteins in liver tissue were potential biomarkers for R. Scrophulariae treatment. The biomarkers and common pathways involved were steroid hormone biosynthesis, drug metabolism-cytochrome p450, drug metabolism-other enzymes, pentose and glucuronate interconversions, and starch and sucrose metabolism. Some biomarkers were beneficial for treating diseases such as cancer, tuberculosis and isovaleric acidaemia, while other biomarkers caused side effects. Metabolomic and proteomic analyses of R. Scrophulariae-treated rats provided valuable information on the biological safety and efficacy of using R. Scrophulariae clinically.

Radix Scrophulariae, a traditional Chinese herb, is used to treat various diseases, including H₂O₂-induced apoptosis in cardiomyocytes, HaCaT cells, hyperuricaemia, and depression.