Complex components of Shengmai formula interact with organic cation transporter 2 (OCT2) in MDCK cells.

ETHNOPHARMACOLOGICAL RELEVANCE: Shengmai formula (SMF) is a well-known Chinese herbal compound preparation, which is utilized extensively for the treatment of myocardial ischemia, arrhythmia and other life-threatening conditions. Our previous researches have shown that some of the active ingredients in SMF can interact with organic anion transport polypeptide 1B1 (OATP1B1), breast cancer resistance protein (BCRP) and organic anion transporter 1 (OAT1), etc. Organic cation transporter 2 (OCT2) is a highly expressed uptake transporter in the kidney, and its interaction with the major active components in SMF remains unclear. AIM OF THE STUDY: We purposed to explore OCT2-mediated interactions and compatibility mechanisms of the main active compounds in SMF. MATERIALS AND METHODS: Fifteen active ingredients of SMF, including ginsenoside Rb1, Rd, Re, Rg1, Rf, Ro and Rc, methylophiopogonanone A and B, ophiopogonin D and D', schizandrin A and B, schizandrol A and B, were selected to investigate OCT2-mediated interactions in Madin-Darby cacine kidney (MDCK) cells stably expressing OCT2. RESULTS: Among the above 15 main active components, only ginsenosides Rd, Re and schizandrin B could significantly inhibit the uptake of 4-(4-(dimethylamino)styryl)-N-methyl pyridiniumiodide (ASP+), a classical substrate of OCT2. Ginsenoside Rb1 and methylophiopogonanone A can be transported by MDCK-OCT2 cells, and their uptake was significantly reduced when OCT2 inhibitor decynium-22 was added. Ginsenoside Rd could remarkably reduce the uptake of methylophiopogonanone A and ginsenoside Rb1 by OCT2, ginsenoside Re only decreased the uptake of ginsenoside Rb1, while schizandrin B had no effect on the uptake of both. CONCLUSIONS: OCT2 mediates the interaction of the major active components in SMF. Ginsenosides Rd, Re and schizandrin B are the potential inhibitors of OCT2, while ginsenosides Rb1 and methylophiopogonanone A are the potential substrates of OCT2. There is an OCT2-mediated compatibility mechanism among these active ingredients of SMF.

Monoacylglycerol lipase inhibitors: modulators for lipid metabolism in cancer malignancy, neurological and metabolic disorders.

Monoacylglycerol lipase (MAGL) is a serine hydrolase that plays a crucial role catalysing the hydrolysis of monoglycerides into glycerol and fatty acids. It links the endocannabinoid and eicosanoid systems together by degradation of the abundant endocannabinoid 2-arachidaoylglycerol into arachidonic acid, the precursor of prostaglandins and other inflammatory mediators. MAGL inhibitors have been considered as important agents in many therapeutic fields, including anti-nociceptive, anxiolytic, anti-inflammatory, and even anti-cancer. Currently, ABX-1431, a first-in-class inhibitor of MAGL, is entering clinical phase 2 studies for neurological disorders and other diseases. This review summarizes the diverse (patho)physiological roles of MAGL and will provide an overview on the development of MAGL inhibitors. Although a large number of MAGL inhibitors have been reported, novel inhibitors are still required, particularly reversible ones.

Impact of the organic cation transporter 2 inhibitor cimetidine on the single-dose pharmacokinetics of the glucosylceramide synthase inhibitor lucerastat in healthy subjects.

PURPOSE: Lucerastat is an orally available glucosylceramide synthase inhibitor with a potential to provide substrate reduction therapy for Fabry patients independent of their α-galactosidase A genotype. In humans, lucerastat is mainly eliminated as unchanged parent compound through renal excretion both by active secretion and passive filtration. In vitro studies indicated that lucerastat is a substrate of human organic cation transporter 2 (OCT2) mainly expressed in the kidney. METHODS: Therefore, this clinical study, conducted in 14 healthy male subjects, investigated the effect of 800 mg twice-daily oral administration of the OCT2 inhibitor cimetidine at steady state on the single-dose pharmacokinetics (PK) of 500 mg lucerastat. The safety and tolerability of lucerastat administered alone and concomitantly with cimetidine were also evaluated. RESULTS: Exposure to lucerastat was slightly higher upon co-administration of cimetidine indicated by geometric mean area under the plasma concentration-time curve from zero to infinity (AUC0-∞) ratio of 1.22 (90% confidence interval [CI] 1.16-1.28). Cimetidine delayed the time to reach maximum lucerastat concentrations (tmax) by 1 h but did not affect its elimination half-life (t½) or maximum plasma concentration (Cmax) as geometric mean ratios were 1.00 (0.91-1.10) and 1.04 (0.92-1.17), respectively, at cimetidine steady state. Lucerastat was safe and well tolerated when given alone and in combination with cimetidine. CONCLUSION: These results indicate that the single-dose PK of lucerastat are not changed to a clinically relevant extent by cimetidine-mediated OCT2 inhibition, allowing the concomitant use of OCT2 inhibitors with lucerastat without any need for dose adjustment. TRIAL REGISTRATION: EudraCT: 2017-003725-14; ClinicalTrials.gov: NCT03380455.

Saikosaponin b2 enhances the hepatotargeting effect of anticancer drugs through inhibition of multidrug resistance-associated drug transporters.

AIMS: Vinegar-baked Radix Bupleuri (VBRB) potentiates the activity of anticancer drugs in the liver by increasing their hepatic distribution. However, this phenomenon may be associated with drug transporters. We investigated the effect of saikosaponin b2 (SSb2; the main component of VBRB) on the activity and expression of different drug transporters in both normal cells and those that overexpress the transporter. MAIN METHODS: The activities of transporters were analyzed by concentration of their cellular substrates. Concentrations of colchicine (substrate of Pgp and MRP1) and cisplatin (substrate of OCT2 and MRP2) were determined by high-performance liquid chromatography (HPLC). The concentration of rhodamine B was determined by flow cytometry. The expression of transporter gene and protein were determined by qRT-PCR and Western blotting analysis. KEY FINDINGS: SSb2 increased colchicine efflux in HEK293 cells by primarily increasing Mrp1 activity, independent of gene and protein expression. SSb2 enhanced Mrp2 function and increased cisplatin efflux in BRL3A cells by upregulating Mrp2 gene expression, with a marginal effect on Pgp in normal cells. SSb2 increased OCT2 activity in OCT2-HEK293 cells by increasing the expression of OCT2 protein and mRNA; however, SSb2 inhibited MRP2 activity in MRP2-HEK293 cells by decreasing MRP2 protein expression, and decreased Pgp and MRP1 activity in Pgp- and MRP1-HEK293 cells. SIGNIFICANCE: SSb2 might potentially be the key active component of VBRB that enhances the hepatotargeting of anticancer drugs through the inhibition of multidrug resistance-associated drug transporters (Pgp, MRP1, and MRP2) in an environment-dependent manner.

The synthesis of the rhamnogalacturonan II component 3-deoxy-D-manno-2-octulosonic acid (Kdo) is required for pollen tube growth and elongation.

Despite a very complex structure, the sugar composition of the rhamnogalacturonan II (RG-II) pectic fraction is extremely conserved. Among its constituting monosaccharides is the seldom-observed eight-carbon sugar 3-deoxy-D-manno-octulosonic acid (Kdo), whose phosphorylated precursor is synthesized by Kdo-8-P synthase. As an attempt to alter specifically the RG-II structure in its sugar composition and assess the consequences on the function of RG-II in cell wall and its relationship with growth, Arabidopsis null mutants were sought in the genes encoding Kdo-8-P synthase. Here, the isolation and characterization of one null mutant for the isoform 1 (AtkdsA1-S) and two distinct null mutants for the isoform 2 of Arabidopsis Kdo-8-P synthase (AtkdsA2-V and AtkdsA2-S) are described. Evidence is provided that AtkdsA2 gene expression is preferentially associated with plantlet organs displaying a meristematic activity, and that it accounts for 75% of the mRNAs to be translated into Kdo-8-P synthase. Furthermore, this predominant expression of AtKDSA2 over AtKDSA1 was confirmed by quantification of the cytosolic Kdo content in the mutants, in a variety of ecotypes. The inability to identify a double knockout mutant originated from pollen abortions, due to the inability of haploid pollen of the AtkdsA1- AtkdsA2- genotype to form an elongated pollen tube properly and perform fertilization.