Silybin regulates P450s activity by attenuating endoplasmic reticulum stress in mouse nonalcoholic fatty liver disease

Cytochrome P450s are important phase I metabolic enzymes located on endoplasmic reticulum (ER) involved in the metabolism of endogenous and exogenous substances. Our previous study showed that a hepatoprotective agent silybin restored CYP3A expression in mouse nonalcoholic fatty liver disease (NAFLD). In this study we investigated how silybin regulated P450s activity during NAFLD. C57BL/6 mice were fed a high-fat-diet (HFD) for 8 weeks to induce NAFLD, and were administered silybin (50, 100 mg ·kg^-1 ·d^-1, i.g.) in the last 4 weeks. We showed that HFD intake induced hepatic steatosis and ER stress, leading to significant inhibition on the activity of five primary P450s including CYP1A2, CYP2B6, CYP2C19, CYP2D6, and CYP3A in liver microsomes. These changes were dose-dependently reversed by silybin administration. The beneficial effects of silybin were also observed in TG-stimulated HepG2 cells in vitro. To clarify the underlying mechanism, we examined the components involved in the P450 catalytic system, membrane phospholipids and ER membrane fluidity, and found that cytochrome b5 (cyt b5) was significantly downregulated during ER stress, and ER membrane fluidity was also reduced evidenced by DPH polarization and lower polyunsaturated phospholipids levels. The increased ratios of NADP⁺/NADPH and PC/PE implied Ca²⁺ release and disruption of cellular Ca²⁺ homeostasis resulted from mitochondria dysfunction and cytochrome c (cyt c) release. The interaction between cyt c and cyt b5 under ER stress was an important reason for P450s activity inhibition. The effect of silybin throughout the whole course suggested that it regulated P450s activity through its anti-ER stress effect in NAFLD. Our results suggest that ER stress may be crucial for the inhibition of P450s activity in mouse NAFLD and silybin regulates P450s activity by attenuating ER stress.

Cystine supplementation rebalances the redox homeostasis of microenvironment in non-small cell lung cancer cells and reverses their resistance to docetaxel

Continuous docetaxel (DTX) treatment of non-small cell lung cancer induces development of drug resistance, but the mechanism is poorly understood. In this study we performed metabolomics analysis to characterize the metabolic patterns of sensitive and resistant A549 non-small cell lung cancer cells (A549/DTX cells). We showed that the sensitive and resistant A549 cells exhibited distinct metabolic phenotypes: the resistant cells were characterized by an altered microenvironment of redox homeostasis with reduced glutathione and elevated reactive oxygen species (ROS). DTX induction reprogrammed the metabolic phenotype of the sensitive cells, which acquired a phenotype similar to that of the resistant cells: it reduced cystine influx, inhibited glutathione biosynthesis, increased ROS and decreased glutathione/glutathione disulfide (GSH/GSSG); the genes involved in glutathione biosynthesis were dramatically depressed. Addition of the ROS-inducing agent Rosup (25, 50 μg/mL) significantly increased P-glycoprotein expression and reduced intracellular DTX in the sensitive A549 cells, which ultimately acquired a phenotype similar to that of the resistant cells. Supplementation of cystine (1.0 mM) significantly increased GSH synthesis, rebalanced the redox homeostasis of A549/DTX cells, and reversed DTX-induced upregulation of P-glycoprotein, and it markedly improved the effects of DTX and inhibited the growth of A549/DTX in vitro and in vivo. These results suggest that microenvironmental redox homeostasis plays a key role in the acquired resistance of A549 cancer cells to DTX. The enhancement of GSH synthesis by supplementary cystine is a promising strategy to reverse the resistance of tumor cells and has potential for translation in the clinic.

Compound danshen dripping pills normalize a reprogrammed metabolism of myocardial ischemia rats to interpret its time-dependent efficacy in clinic trials: a metabolomic study

INTRODUCTION

Clinical trials of Compound danshen dripping pills (CDDP) indicated distinct improvement in patients with chronic stable angina. Daily fluctuation of therapeutic effect agreed with a peak-valley PK profile during a 4-week CDDP regimen, but stabilized after 8-week treatment.

OBJECTIVES

This article aims to explore the underlying mechanism for the time-dependent drug efficacy of the up-down fluctuation or stabilization in clinic trials.

METHODS

A rat model of myocardial ischemia was established via isoproterenol induction. Metabolomics was employed to analyze the energy-related substances both in circulatory system and myocardium in the myocardial ischemia model.

RESULTS

CDDP treatment ameliorated myocardial ischemia, reversed the reprogramming of the metabolism induced by ISO and normalized the level of most myocardial substrates and the genes/enzymes associated with those metabolic changes. After 1- or 2-week treatment, CDDP regulated plasma and myocardial metabolome in an analogous, time-dependent way, and modulated metabolic patterns of ischemic rats that perfectly matched with the fluctuated or stabilized effects observed in clinical trials with 4 or 8-week treatment, respectively.

CONCLUSION

Metabolic modulation by CDDP contributes to the fluctuated or stabilized therapeutic outcome, and is a potential therapeutic approach for myocardial ischemia diseases.

Inhibitory Effects of Danshen components on CYP2C8 and CYP2J2

The use of Chinese herbal medicines and natural products has become increasingly popular in both China and Western societies as an alternative medicine for the treatment of diseases or as a health supplement. Danshen, the dried root of Salvia miltiorrhiza (Fam.Labiatae), which is rich in phenolic acids and tanshinones, is a widely used herbal medicine for the treatment of cardio-cerebrovascular diseases. The goal of this study was to examine the inhibitory effects of fifteen components derived from Danshen on CYP2C8 and CYP2J2, which are expressed both in human liver and cardiovascular systems. Recombinant CYP2C8 and CYP2J2 were used, and the mechanism, kinetics, and type of inhibition were determined. Taxol 6-hydroxylation and astemizole O-desmethyastemizole were determined as probe activities for CYP2C8 and CYP2J2, respectively. Metabolites formations were analyzed using liquid chromatography-tandem mass spectrometry (LC-MS/MS). The results demonstrated that salvianolic acid A was a competitive inhibitor of CYP2C8 (K_i = 2.5 μM) and mixed-type inhibitor of CYP2J2 (K_i = 7.44 μM). Salvianolic acid C had moderate noncompetitive and mixed-type inhibitions on CYP2C8 (K_i = 4.82 μM) and CYP2J2 (K_i = 5.75 μM), respectively. Tanshinone IIA was a moderate competitive inhibitor of CYP2C8 (K_i = 1.18 μM). Dihydrotanshinone I had moderate noncompetitive inhibition on CYP2J2 (K_i = 6.59 μM), but mechanism-based inhibition on CYP2C8 (K_I = 0.43 μM, k_inact = 0.097 min^-1). Tanshinone I was a moderate competitive inhibitor of CYP2C8 (K_i = 4.20 μM). These findings suggested that Danshen preparations appear not likely to pose a significant risk of drug interactions mediated by CYP2C8 after oral administration; but their inhibitory effects on intestinal CYP2J2 mediated drug metabolism should not be neglected when they are given orally in combination with other drugs. Additionally, this study provided novel insights into the underling pharmacological mechanisms of Danshen components from the perspective of CYP2C8 and CYP2J2 inhibition.

Exploring the neuroprotective effects of ginkgolides injection in a rodent model of cerebral ischemia-reperfusion injury by GC-MS based metabolomic profiling

Cerebral ischemia-reperfusion (I/R) injury usually contributes to mortality and disability after ischemic stroke. Ginkgolides injection (GIn), a standard preparation composed of ginkgo diterpene lactones extract, is clinically used for neuroprotective treatment on reconvalescents of cerebral infarction. However, the understanding about its therapeutic mechanism is still lacking. In this study, a gas chromatography-mass spectrometry (GC-MS) based metabolomic approach coupled with multivariate data analysis (MVDA) was applied to explore the neuroprotective effects of GIn in a rodent model of focal ischemic stroke induced by transient middle cerebral artery occlusion (tMCAO). Metabolomic profiling revealed a series of metabolic perturbations that underlie the cerebral I/R pathological events. GIn can reverse the I/R induced brain metabolic deviations by modulating multiple metabolic pathways, such as glycolysis, Krebs cycle, pentose phosphate pathway (PPP), γ-aminobutyrate (GABA) shunt and lipid metabolism. Moreover, the main bioactive components of GIn were distributed to brain tissue much more easily in tMCAO rats than in normal rats after an intravenous administration, suggesting that the increased cerebral exposure to ginkgolides in I/R pathological condition potentially facilitated the neuroprotective effects of GIn by directly targeting at brain. The present study provided valuable information for our understanding about metabolic changes of cerebral I/R injury and clinical application of GIn.

Metabolomics and its application to the evaluation of the efficacy and toxicity of traditional Chinese herb medicines

Traditional Chinese herb medicines (TCHMs) have been used in the treatment of a variety of diseases for thousands of years in Asian countries. The active components of TCHMs usually exert combined synergistic therapeutic effects on multiple targets, but with less potential therapeutic effect based on routine indices than Western drugs. These complex effects make the assessment of the efficacy of TCHMs and the clarification of their underlying mechanisms very challenging, and therefore hinder their wider application and acceptance. Metabolomics is a crucial part of systems biology. It allows the quantitative measurement of large numbers of the low-molecular endogenous metabolites involved in metabolic pathways, and thus reflects the fundamental metabolism status of the body. Recently, dozens of metabolomic studies have been devoted to prove the efficacy/safety, explore the underlying mechanisms, and identify the potential biomarkers to access the action targets of TCHMs, with fruitful results. This article presents an overview of these studies, focusing on the progress made in exploring the pharmacology and toxicology of various herbal medicines.