Current Drug Metabolism - Volume 23, Issue 7, 2022

Background: The outbreak of coronavirus disease 19 (COVID-19) has caused great concern to public health. Convincing clinical experiences showed that traditional Chinese medicine (TCM) has exhibited remarkable efficacy in the prevention, treatment and rehabilitation of COVID-19. The research on the treatment of COVID-19 disease with TCM mainly focused on the pharmacological effects and mechanistic analysis. However, the TCM’s pharmacokinetics and potential herb-drug interaction in the treatment of COVID-19 are currently unclear. Methods: This review summarizes the pharmacokinetics and characteristics of cytochrome P450 enzyme (CYP450) metabolism of TCM recommended in the Guidelines for diagnosis and treatment of coronavirus disease 2019 (trial version eighth), and meanwhile analyzes the potential interactions between TCM and western medicine. Results: The pharmacokinetics of TCM mainly focused on preclinical pharmacokinetics, and fewer clinical pharmacokinetics research was reported. When TCM and western are both metabolized by CYP450 and coadministered, a potential herb-drug interaction might occur. Conclusion: Knowledge of the pharmacokinetics and metabolism of TCM is key to understanding rational TCM use of COVID-19 and developing antiviral TCM.

Background: Aflatoxin B1 is a harmful hepatocarcinogen which is metabolized in our body by Cytochrome P450 enzymes, namely CYP1A2, CYP3A4, CYP3A5, and CYP3A7, into toxic (exo-8, 9-epoxide) and nontoxic (AFQ1, endo-epoxide) products. We have found from the literature that due to cooperativity, the rate of metabolic reactions increases in CYP1A2 and CYP3A4 involving more than one site of proteins to form two products at a given time, whereas the interaction of CYP3A5 and CYP3A7 is still unknown. Our work aims to study these four enzymes with AFB1 based on binding site pocket characterization and to find the probable resultant products at each binding site. Methods: We used computational approaches like homology modeling, molecular docking to form mono and double ligated systems, molecular dynamic simulations to analyze the potential energies (vdW & electrostatic), PCA, RMSF, and residue-wise interactions at the active as well as allosteric sites of these four enzymes. Results: We found that CYP1A2, CYP3A4, and CYP3A5 were more hydrophobic at the first site and may induce epoxidation reaction to form toxic products, whereas the second site would be expected to be more polar and comprising charged interactions, thus enhancing non-toxic hydroxylated products. However, in CYP3A7, the first site favors hydroxylation, whereas the second site is involved in higher hydrophobic interactions. Conclusion: Thus, in the fetus where AFB1 is metabolized only by CYP3A7, a lower concentration of toxic metabolites will be expected, while in adults exhibiting CYP1A2, CYP3A4 and CYP3A5 may increase the concentration of the toxic metabolites due to the combined effect of these enzymes, consequently increasing liver toxicity. We believe that AFB1 binding characteristics will be helpful for medicinal chemists in the process of designing a new drug.

Background: Andrographolide has a potent antiviral effect in the treatment of coronavirus disease (COVID-19). However, there are no in vivo studies of andrographolide as an anti-COVID-19 treatment. Objective: The study aims to develop a physiologically based pharmacokinetic (PBPK) animal model and scale it up to a human model to predict andrographolide concentrations in the lungs. Methods: ADAPT5 (version 5.0.58) was used to establish the PBPK model based on 24 enrolled pharmacokinetic studies. Results: The perfusion-limited PBPK model was developed in mice and extrapolated to rats, dogs, and humans. The metabolism of andrographolide in humans was described by the Michaelis-Menten equation. The saturation of the metabolism occurred at a high dose (12 g), which could not be used therapeutically. The optimized oral bioavailability in humans was 6.3%. Due to the limit of solubility, the dose-dependent absorption between 20-1000 mg was predicted by GastroPlus®. Using the extrapolated human PBPK model together with the predicted dose-dependent fraction of the dose absorbed that enters the enterocytes by GastroPlus®, the oral dosage of 200 mg q8h of andrographolide would provide a trough level of free andrographolide at a steady state over the reported IC50 value against SARS-CoV-2 in the lungs for the majority of healthy humans. Based on the reported CC50 value, toxicity might not occur at the therapeutic dosage. Conclusion: The PBPK model of andrographolide in animals and humans was successfully constructed. Once additional data is available, the model would be needed to recalibrate to gain an understanding of a dose-response relationship and optimization of dosage regimens of andrographolide.

Background: Cytochrome P450 1B1(CYP1B1) is an extrahepatic P450 isoenzyme that can participate in processes of undermining the effectiveness and safety of anti-cancer therapy. Ginsenosides are the main active ingredients in ginseng, which possesses rich pharmacological activities, including anti-cancer activity and organ protection. However, the effect of ginsenosides on the activity of CYP1B1 remains unclear. Objective: The present study aimed to investigate the inhibitory effect of ginsenosides on CYP1B1 and reveal the structure-inhibitory activity relationship. Methods: Firstly, recombinant CYP1B1 and EROD reactions were used to evaluate the inhibitory effect of ginsenosides. Secondly, molecular docking was used to simulate the interactions between ginsenosides and CYP1B1. Finally, the structure-inhibitory activity relationship was analyzed. Results: The ginsenosides, Rb2, Rd, and Rg3, significantly inhibited CYP1B1; the ginsenoside Rd showed the strongest inhibition effect, with a Ki value of 47.37 μM in non-competitive mode. Notably, ginsenoside Rd formed hydrogen bonds with two key amino acid residues of CYP1B1, and one bond was between the glycosyl in position 20 and ALA330, which also made ginsenoside Rd close to the heme iron of CYP1B1. In contrast, ginsenosides, Rb2 and Rg3, which showed weaker inhibition, interacted with only one CYP1B1 residue by the hydrogen bond, which was far away from the heme iron. Finally, the structure-inhibitory activity relationship analysis demonstrated that the number of glycosyls in position 20 and the type of sapogenins in the ginsenoside structure are the key factors determining inhibitory activity. Meanwhile, ALA330 was a vital amino acid in the potent inhibition of CYP1B1 by ginsenosides. Conclusion: A structure-dependent inhibitory effect on CYP1B1 was revealed for ginsenosides, among which ginsenoside Rd showed the strongest inhibition due to its mono-glycosyl in position 20 of the ginsenoside parent structure. These findings would provide evidence for the synthesis of novel CYP1B1 inhibitors to augment the anti-cancer therapeutic effect.

Background: Cytochrome P450 (P450) is the largest family of enzymatic proteins in the human liver, and its features have been studied in physiology, medicine, biotechnology, and phytoremediation. Objective: The aim of this study was to assess the catalytic activities of 28 human CYP3A4 alleles by using dronedarone as a probe drug in vitro, including 7 novel alleles recently found in the Han Chinese population. Methods: We expressed 28 CYP3A4 alleles in insect microsomes and incubated them with 1-100 μM of dronedarone at 37 °C for 40 minutes to obtain the metabolites of N-debutyl-dronedarone. Results: Compared with the wild type of CYP3A4, the 27 defective alleles can be classified into four categories. Three alleles had no detectable enzyme activity leading to a lack of kinetic parameters of N-debutyl-dronedarone; the other three alleles slightly despaired when it comes to intrinsic clearance values compared with the features of the wild type. Sixteen alleles exhibited 35.91%~79.70% relative values (in comparison to the wild-type) and could be defined as the “moderate decrease group”. The rest of the alleles showed a considerable decrease in intrinsic clearance values, ranging from 11.88%~23.34%. Therefore they were classified as a “significantly decreased group”. More specifically, 18 CYP3A4 alleles exhibited a substrate inhibition trend toward dronedarone when the concentration rises to 20 μM. Conclusion: The outcomes of this novel study on the metabolism of dronedarone by CYP3A4 alleles can be used as experimental data support for the individualized use of this modern drug.

Background: Diabetic peripheral neuropathy is the most common complication of diabetes mellitus. Epalrestat, an aldose reductase inhibitor, has been approved for clinical therapy for diabetic peripheral neuropathic pain. In the present study, solid lipid-based nanoparticles are used for oral administration of epalrestat (E-SLN) and evaluated against diabetic neuropathic pain in a rat model. Methods: Experimental diabetes in rats was induced by a single dose of streptozotocin (STZ) administration. The therapeutic efficiency of Epalrestat nanoparticles (0.25, 0.50, 1, and 5 mg/kg) in diabetic rats was studied. STZinduced diabetic rats were treated with different doses of E-SLN for 8 weeks. The nanoparticles were orally administered at a single dose in rats, and the various parameters related to peripheral neuropathy were evaluated and compared with the bare drug. The blood glucose level was estimated by standard glucometer, HbA1c, triglycerides, total cholesterol, and liver function test (ALT and AST) were analyzed by blood samples collected from retro-orbital plexus. Oxidative stress markers and Na+K+ATPase, TNF-α, and IL-1β levels were measured in the homogenate of sciatic nerves. Behavioral tests were also performed by the hot plate method and tail-flick method. Results: E-SLN synthesized by the micro-emulsification method was 281 ± 60 nm in size, and encapsulation efficacy was found to be 88 ± 2%. Optimized E-SLN were characterized and found to be optimum in size, spherical shape, decent encapsulation efficiency, stable at acidic gastric pH, and suitable for oral delivery. E-SLNs did not significantly reverse the STZ-induced elevated blood glucose level (FBS and PPBS), HbA1c, triglycerides, and total cholesterol but significantly improved TNF-α, IL-1β, and increased Na+K+ATPase levels, oxidative stress marker and ALT, AST in the treated rat group as compared with the diabetic group. Doses of E-SLN, i.e. 0.5, 1.0, 2.5, and 5 mg/kg, significantly increased the tail-flick latency time and hot plate response time in a dose-dependent manner compared with the diabetic group. Conclusion: Thus, it is suggested that E-SLN were equally effective and less hepatotoxic compared with the standard treatment of epalrestat. To the best of our knowledge, we, for the first time, propose the orally deliverable E-SLN that ameliorates STZ-induced diabetes neuropathic pain effectively as compared with conventional epalrestat.