Flurazepam inhibits the P-glycoprotein transport function: an insight to revert multidrug-resistance phenotype

The regulatory effects of mitragynine on P-glycoprotein transporter

OBJECTIVES

Kratom preparation containing Mitragyna speciosa Korth plant is frequently used as a recreational drug. Mitragynine, a major alkaloid isolated from M. speciosa, is often detected concurrently with other drugs during forensic analysis, indicating a safety concern. P-glycoprotein (P-gp) is a multidrug transporter. Modulation of P-gp transport activity by drugs or herbal compounds in the brain may lead to drug-herb interactions, resulting in neurotoxicity. We aim to determine the effects of mitragynine on the P-gp regulation and possible neurotoxicity.

METHODS

The effects of mitragynine on the P-gp regulation were investigated in human brain capillary endothelial cells (hCMEC/D3) using molecular docking and dynamic simulation and an optimized bidirectional transport assay, respectively. Repeated-dose treatment and neurotoxicity assessment were carried out using a blood-brain barrier model and polimerase chain reaction (PCR) array.

KEY FINDINGS

Mitragynine inhibits the P-gp transport activity via binding onto the nucleotide-binding domain site and forms a stable interaction with the P-gp protein complex. Nontoxic concentrations of mitragynine (<4 μM) and substrate drugs (0.001 μM) in the cells significantly enhanced endothelial cell permeability and elicited signs of neurotoxicity in PC-12 cells.

CONCLUSIONS

Mitragynine is likely a P-gp inhibitor, hence concurrent administration of kratom products with P-gp substrates may lead to clinically significant interactions and neurotoxicity.

Diabetes and hypertension increase the placental and transcellular permeation of the lipophilic drug diazepam in pregnant women

Background

Previous studies carried out in our laboratories have demonstrated impaired drug permeation in diabetic animals. In this study the permeation of diazepam (after a single dose of 5 mg/day, administered intramuscularly) will be investigated in diabetic and hypertensive pregnant women.

Methods

A total 75 pregnant women were divided into three groups: group 1 (healthy control, n = 31), group 2 (diabetic, n = 14) and group 3 (hypertensive, n = 30). Two sets of diazepam plasma concentrations were collected and measured (after the administration of the same dose of diazepam), before, during and after delivery. The first set of blood samples was taken from the mother (maternal venous plasma). The second set of samples was taken from the fetus (fetal umbilical venous and arterial plasma). In order to assess the effect of diabetes and hypertension on diazepam placental-permeation, the ratios of fetal to maternal blood concentrations were determined. Differences were considered statistically significant if p ≤ 0.05.

Results

The diabetes and hypertension groups have 2-fold increase in the fetal umbilical-venous concentrations, compared to the maternal venous concentrations. Feto: maternal plasma-concentrations ratios were higher in diabetes (2.01 ± 1.10) and hypertension (2.26 ± 1.23) groups compared with control (1.30 ± 0.48) while, there was no difference in ratios between the diabetes and hypertension groups. Umbilical-cord arterial: venous ratios (within each group) were similar among all groups (control: 0.97 ± 0.32; hypertension: 1.08 ± 0.60 and diabetes: 1.02 ± 0.77).

Conclusions

On line with our previous findings which demonstrate disturbed transcellular trafficking of lipophilic drugs in diabetes, this study shows significant increase in diazepam placental-permeation in diabetic and hypertensive pregnant women suggesting poor transcellular control of drug permeation and flux, and bigger exposure of the fetus to drug-placental transport.

Sucralose, a synthetic organochlorine sweetener: overview of biological issues

Sucralose is a synthetic organochlorine sweetener (OC) that is a common ingredient in the world's food supply. Sucralose interacts with chemosensors in the alimentary tract that play a role in sweet taste sensation and hormone secretion. In rats, sucralose ingestion was shown to increase the expression of the efflux transporter P-glycoprotein (P-gp) and two cytochrome P-450 (CYP) isozymes in the intestine. P-gp and CYP are key components of the presystemic detoxification system involved in first-pass drug metabolism. The effect of sucralose on first-pass drug metabolism in humans, however, has not yet been determined. In rats, sucralose alters the microbial composition in the gastrointestinal tract (GIT), with relatively greater reduction in beneficial bacteria. Although early studies asserted that sucralose passes through the GIT unchanged, subsequent analysis suggested that some of the ingested sweetener is metabolized in the GIT, as indicated by multiple peaks found in thin-layer radiochromatographic profiles of methanolic fecal extracts after oral sucralose administration. The identity and safety profile of these putative sucralose metabolites are not known at this time. Sucralose and one of its hydrolysis products were found to be mutagenic at elevated concentrations in several testing methods. Cooking with sucralose at high temperatures was reported to generate chloropropanols, a potentially toxic class of compounds. Both human and rodent studies demonstrated that sucralose may alter glucose, insulin, and glucagon-like peptide 1 (GLP-1) levels. Taken together, these findings indicate that sucralose is not a biologically inert compound.