In vitro Assessment of the Effects of Silybin on CYP2B6-mediated Metabolism.

Silybin is a flavonol compound with a variety of physiological properties, such as hepatoprotective, anti-fibrogenic, and hypocholesterolemic effects. Although the in vivo and in vitro effects of silybin are frequently reported, studies on herb-drug interactions have yet to be performed. With the discovery of multiple important substrates of CYP2B6 recently, there is a growing body of evidence indicating that CYP2B6 plays a much larger role in human drug metabolism than previously thought.The purpose of this study is to determine how silybin affects the CYP2B6 enzyme's activity, as well as to clarify the molecular mechanisms for inhibition by silybin. The results showed that silybin inhibited CYP2B6 activity in liver microsomes in a non-competitive manner, with IC50 and Ki values of 13.9 µM and 38.4 µM, respectively. Further investigations revealed that silybin could down-regulate the expression of CYP2B6 protein in HepaRG cells. The hydrogen bond conformation of silybin in the active site of the CYP2B6 isoform was revealed by a molecular docking study. Collectively, our findings verify that silybin is an inhibitor of CYP2B6 and explain the molecular mechanism of inhibition. This can lead to a better understanding of the herb-drug interaction between silybin and the substrates of the CYP2B6 enzyme, as well as a more rational clinical use of silybin.

Silymarin Protects against Acute Liver Injury Induced by Acetaminophen by Downregulating the Expression and Activity of the CYP2E1 Enzyme.

Previous studies have shown that silymarin protects against various types of drug-induced liver injury, but whether the protective mechanism of silymarin against acetaminophen-induced liver injury is related to the CYP2E1 enzyme remains unclear. In this study, we investigated the effect of silymarin on the activity and expression of CYP2E1 in vitro and in vivo. The results of in vitro studies showed that silymarin not only inhibited the activity of CYP2E1 in human and rat liver microsomes but also reduced the expression of CYP2E1 in HepG2 cells. In vivo studies showed that silymarin pretreatment significantly reduced the conversion of chlorzoxazone to its metabolite 6-OH-CLX and significantly increased the t1/2, area under the curve (AUC) and mean residence time (MRT) of chlorzoxazone. In addition, silymarin pretreatment significantly inhibited the upregulation of Cyp2e1 expression, reduced the production of 3-cysteinylacetaminophen trifluoroacetic acid salt (APAP-CYS), and restored the liver glutathione level. The results of our study show that silymarin plays an important protective role in the early stage of acetaminophen-induced acute liver injury by reducing the activity and expression of CYP2E1, reducing the generation of toxic metabolites, and alleviating liver injury.

Targeted inhibition of FcRn reduces NET formation to ameliorate experimental ulcerative colitis by accelerating ANCA clearance.

Dysregulated immune responses have now been recognized as an essential stimulator of ulcerative colitis (UC). Neutrophil extracellular traps (NET) were reported as the potential factor in sustaining mucosal inflammation in UC. NET formation further induces antineutrophil cytoplasm autoantibodies (ANCA) that serve as a biomarker in determining the severity of UC, which have a long half-life due to neonatal Fc receptor (FcRn)-mediated recycling. This study aimed to explore the role of the ANCA-NET cycle in UC and evaluate the potential of targeting FcRn in UC treatment. Dextran sodium sulfate-induced mice and rat models were used in this study. anti-rat FcRn monoclonal antibodies were used to block FcRn function in vivo. Disease activity index (DAI) and histopathological score (HS) were estimated to characterize the inflammation severity of UC. Serum concentrations of IgG, ANCA, TNF-α, IL-1ß and CRP were measured using specific ELISA kits. Colonic NET-associated protein (NAP) expression was determined by western blotting. Serum ANCA and colonic NAPs showed a positive correlation that varied with changes in serum inflammation-related indexes (IRI; including TNF-α, IL-1ß, and CRP) and DAI and HS in mice with UC. Blockade of FcRn significantly reduced serum ANCA levels and colonic NAP expression and effectively decreased serum IRIs, DAI, and HS in rats with UC. Especially during the inflammation recurrence period, blockade of FcRn exerted even better therapeutic effects in rats with UC than salazosulfapyridine. Our results show that anti-FcRn therapy has benefits in UC treatment through reduced colonic NET formation by accelerating serum ANCA clearance.

Assessing CYP2C8-Mediated Pharmaceutical Excipient-Drug Interaction Potential: A Case Study of Tween 80 and Cremophor EL-35.

Pharmaceutical excipients (PEs) are substances included in drug formulations. Recent studies have revealed that some PEs can affect the activity of metabolic enzymes and drug transporters; however, the effects of PEs on CYP2C8 and its interaction potential with drugs remain unclear. In this study, we evaluated the effects of Tween 80 and EL-35 on CYP2C8 in vitro and further investigated their impacts on the PK of paclitaxel (PTX) in rats after single or multiple doses. The in vitro study indicated that Tween 80 and EL-35 inhibited CYP2C8 activity in human and rat liver microsomes. EL-35 also decreased the expression of CYP2C8 in HepG2 cells. In the in vivo study, Tween 80 did not alter the PK of PTX after single or multiple doses, whereas EL-35 administered for 14 days significantly increased the AUC and MRT of PTX. Further analysis indicated that multiple-dose EL-35 reduced the expression of Cyp2c22 and production of 6-OH-PTX in the rat liver. Our study suggested that short-term exposure to both PEs did not affect the PK of PTX in rats, but multiple doses of EL-35 increased the AUC and MRT of PTX by downregulating the hepatic expression of Cyp2c22. Such effects should be taken into consideration during drug formulation and administration.

Impacts of Cytochrome P450 2D6*10 Allele and a High-Fat Meal on the Pharmacokinetics of Dapoxetine in Healthy Chinese Men: A Single-Dose, Two-Treatment Study.

INTRODUCTION: Factors that impact the pharmacokinetics of dapoxetine, a 5-HT selective reuptake inhibitor used for the treatment of premature ejaculation, have not been clearly identified. This study aimed to evaluate the effects of consumption of a high-fat meal and cytochrome P450 (CYP) 2D6 polymorphisms on the pharmacokinetics of dapoxetine in healthy Chinese men. METHODS: Twenty-two healthy volunteers were enrolled and classified based on their CYP2D6 genotype. A single-dose, two-treatment (fasted and fed), two-period, one-sequence pharmacokinetic study was conducted. Plasma concentrations of the drug were determined using LC-MS. Pharmacokinetic parameters were calculated by a noncompartmental analysis. RESULTS: The consumption of food significantly prolonged the time required for dapoxetine to reach its peak concentration and area under the concentration-time curve (AUC0-48) (p < 0.01). Compared with that in *1/*10 and *2/*10 genotypes, the dapoxetine plasma exposure in *10/*10 individuals was notably increased. The AUC0-48 value for *10/*10 was significantly higher than that for *1/*10 and *2/*10 (p < 0.05). CONCLUSION: The obtained results demonstrated that a high-fat meal and the CYP2D6 *10/*10 genotype influence the pharmacokinetic properties of dapoxetine and may thus have potential clinical implications. Future studies focusing on safe dapoxetine dosing based on CYP2D6 genotyping are needed. FUNDING: This study was partially sponsored by Xiamen Fuman Pharmaceutical Co., Ltd. The article processing charges were funded by The People's Hospital of Dujiangyan City.