Inhibitory effects of quercetin and its major metabolite quercetin-3-O-ß-D-glucoside on human UDP-glucuronosyltransferase 1A isoforms by liquid chromatography-tandem mass spectrometry.

Quercetin is a flavonoid that is widely present in plant-derived food. Quercetin-3-O-ß-D-glucoside (Q3GA) is a predominant metabolite of quercetin in animal and human plasma. The inhibitory effects of the UDP-glucuronosyl transferases (UGTs) caused by herbal components may be a key factor for the clinical assessment of herb-drug interactions (HDIs). The present study aimed to investigate the inhibitory profile of quercetin and Q3GA on recombinant UGT1A isoforms in vitro. The metabolism of the nonspecific substrate 4-methylumbelliferone (4-MU) by the UGT1A isoforms was assessed by liquid chromatography-tandem mass spectrometry. Preliminary screening experiments indicated that quercetin exhibited stronger inhibitory effects on UGT1A1, UGT1A3, UGT1A6 and UGT1A9 enzymes than Q3GA. Kinetic experiments were performed to characterize the type of inhibition caused by quercetin and Q3GA towards these UGT isoforms. Quercetin exerted non-competitive inhibition on UGT1A1 and UGT1A6, with half maximal inhibitory concentration (IC50) values of 7.47 and 7.07 µM and inhibition kinetic parameter (Ki) values of 2.18 and 28.87 µM, respectively. Quercetin also exhibited competitive inhibition on UGT1A3 and UGT1A9, with IC50 values of 10.58 and 2.81 µM and Ki values of 1.60 and 0.51 µM, respectively. However, Q3GA displayed weak inhibition on UGT1A1, UGT1A3 and UGT1A6 enzymes with IC50 values of 45.21, 106.5 and 51.37 µM, respectively. In the present study, quercetin was a moderate inhibitor of UGT1A1 and UGT1A3, a weak inhibitor of UGT1A6, and a strong inhibitor on UGT1A9. The results of the present study suggested potential HDIs that may occur following quercetin co-administration with drugs that are mainly metabolized by UGT1A1, UGT1A3 and UGT1A9 enzymes.

Activation of Neuronal Voltage-Gated Potassium Kv7/KCNQ/M-Current by a Novel Channel Opener SCR2682 for Alleviation of Chronic Pain.

Treatment of chronic pain remains an unmet medical need. The neuronal voltage-gated potassium Kv7/KCNQ/M channel has been implicated as a therapeutic target for chronic pain. However, whether pharmacological activation of the Kv7 channel can alleviate pain remains elusive. In this study, we show that selective activation of native M-currents by a novel channel opener SCR2682 reduces repetitive firings of dorsal root ganglia (DRG) sensory neurons. Intraperitoneal administration of SCR2682 relieves mechanical allodynia and thermal hyperalgesia in rat models of pain induced by complete Freund's adjuvant (CFA) or spared nerve injury (SNI) in a dose-dependent manner without affecting locomotor activity. The antinociceptive efficacy of SCR2682 can be reversed by the channel-specific blocker XE991. Furthermore, SCR2682 increases Kv7.2/KCNQ2 mRNA and protein expression in DRG neurons from rats in the SNI model of neuropathic pain. Taken together, pharmacological activation of neuronal Kv7 channels by opener SCR2682 can alleviate pain in rats, thus possessing therapeutic potential for chronic pain or hyperexcitability-related neurologic disorders. SIGNIFICANCE STATEMENT: A novel voltage-gated potassium Kv7 channel opener SCR2682 inhibits action potential firings in dorsal root ganglia sensory neurons and exhibits efficacy in antinociception, thus possessing a developmental potential for treatment of chronic pain or epilepsy.

Inhibition effect of epigallocatechin-3-gallate on the pharmacokinetics of calcineurin inhibitors, tacrolimus, and cyclosporine A, in rats.

BACKGROUND: Epigallocatechin-3-gallate (EGCG) is the most biologically active catechin of green tea. Tacrolimus (TAC) and cyclosporine A (CsA) are immunosuppressive agents commonly used in clinical organ transplantation. The present study investigated the effect of EGCG on the pharmacokinetics of TAC and CsA in rats and its underlying mechanisms. RESEARCH DESIGN AND METHODS: Either TAC or CsA was administered to rats intravenously or orally with or without concomitant EGCG. Polymerase Chain Reaction and Western Blot were used to determine the effect of EGCG on drug-metabolizing enzymes (DMEs), drug transporters (DTs) and nuclear receptors (NRs). RESULTS: The Cmax and AUC of TAC were reduced, and V/F and CL/F of TAC were enhanced after co-administration of EGCG. EGCG increased the Cmax, AUC of CsA at 3 ~ 30 mg∙kg-1 dosages, while decreased those parameters at the dosage of 100 mg∙kg-1. EGCG inhibited the mRNA and protein expressions of DMEs and DTs, such as CYP3A1, A2, UGT1A1, Mdr1 and Mrp2, but upregulated the expressions of Car, Pxr and Fxr. CONCLUSIONS: These results revealed consumption of high dose EGCG may cause a significant alteration in pharmacokinetics of TAC and distribution/elimination profiles of CsA through the regulation of DMEs, DTs and NRs.

Suppression of KCNQ/M Potassium Channel in Dorsal Root Ganglia Neurons Contributes to the Development of Osteoarthritic Pain.

Osteoarthritic pain has a strong impact on patients' quality of life. Understanding the pathogenic mechanisms underlying osteoarthritic pain will likely lead to the development of more effective treatments. In the present study of osteoarthritic model rats, we observed a reduction of M-current density and a remarkable decrease in the levels of KCNQ2 and KCNQ3 proteins and mRNAs in dorsal root ganglia (DRG) neurons, which were associated with hyperalgesic behaviors. The activation of KCNQ/M channels with flupirtine significantly increased the mechanical threshold and prolonged the withdrawal latency of osteoarthritic model rats at 3-14 days after model induction, and all effects of flupirtine were blocked by KCNQ/M-channel antagonist, XE-991. Together, these results indicate that suppression of KCNQ/M channels in primary DRG neurons plays a crucial role in the development of osteoarthritic pain.

Self-powered photoelectrochemical aptasensor based on phosphorus doped porous ultrathin g-C3N4 nanosheets enhanced by surface plasmon resonance effect.

This work reports a facile and sensitive self-powered cathodic photoelectrochemical (PEC) aptasensor for the detection of oxytetracycline (OTC) based on Au nanoparticles-decorated phosphorus-doped porous ultrathin g-C3N4 nanosheets (Au/PCN-S). The prepared PCN-S possesses large specific surface area with abundant in-plane pores on its surface, ideal biocompatibility, and excellent visible light response. The in situ photo-reduced Au nanoparticles further enhanced the PEC performance owing to its unique surface plasmon resonance (SPR) effect. Under visible light irradiation, the photocurrent of Au/PCN-S composites was significantly enhanced, which was about 22 times higher than that of pure g-C3N4. In the self-powered PEC biosensing of OTC, the device exhibited high sensitivity toward the presence of dissolved oxygen in the electrolyte and presented a wide detection range from 0.5 to 200 nM and a detection limit of 0.34 nM, as well as certain selectivity, reproducibility and stability. The proposed Au/PCN-S nanocomposites would be considered as a promising visible light-responsive photoactive material for fabrication of PEC biosensors with high performance.

Construction of plasmonic Ag modified phosphorous-doped ultrathin g-C3N4 nanosheets/BiVO4 photocatalyst with enhanced visible-near-infrared response ability for ciprofloxacin degradation.

To realize the full utilization of solar energy, the design of highly efficient photocatalyst with improved visible-near-infrared photocatalysis performance has attracted great attentions for environment pollutant removal. In this work, we rationally employed the surface plasmon resonance effect of metallic Ag in the phosphorus doped ultrathin g-C3N4 nanosheets (PCNS) and BiVO4 composites to construct a ternary Ag@PCNS/BiVO4 photocatalyst. It was applied for the photodegradation of ciprofloxacin (CIP), exhibiting 92.6% removal efficiency under visible light irradiation (λ>420nm) for 10mg/L CIP, and presenting enhanced photocatalytic ability than that of single component or binary nanocomposites under near-infrared light irradiation (λ>760nm). The improved photocatalytic activity of the prepared Ag@PCNS/BiVO4 nanocomposite can be attributed to the synergistic effect among the PCNS, BiVO4 and Ag, which not only improves the visible light response ability and hinders the recombination efficiency of the photogenerated electrons and holes, but also retains the strong the redox ability of the photogenerated charges. According to the trapping experiment and ESR measurements results, OH, h+ and O2- all participated in the photocatalytic degradation process. Considering the SPR effect of metallic Ag and the established local electric field around the interfaces, a dual Z-scheme electrons transfer mechanism was proposed.

Development and validation of HTS assay for screening the calcium-activated chloride channel modulators in TMEM16A stably expressed CHO cells.

Calcium-activated chloride channels (CaCCs), for example TMEM16A, are widely expressed in a variety of tissues and are involved in many important physiological functions. We developed and validated an atomic absorption spectroscopy (AAS)-based detection system for high-throughput screening (HTS) of CaCC modulators. With this assay, Cl(-) flux from CHO cells stably transfected with TMEM16A is assayed indirectly, by measuring excess silver ions (Ag(+)) in the supernatant of AgCl precipitates. The screening process involved four steps: (1) TMEM16A CHO cells were incubated in high-K(+) and high-Cl(-) buffer with test compounds, and with ionomycin as Ca(2+) ionophore, for 12 min; (2) cells were washed with a low-K(+), Cl(-)-free and Ca(2+)-free buffer; (3) CaCC/TMEM16A were activated in high-K(+), Cl(-)-free buffer with ionomycin (10 µmol L(-1)) for 12 min; and (4) excess Ag(+) concentration was measured using an ion channel reader (ICR, an AAS system). The assay can be used to screen CaCC activators and inhibitors at the same time. With this assay, positive control drugs, including NPPB, CaCCinh-A01, flufenamic acid (Flu) and Eact, all had good concentration-dependent effects on CaCC/TMEM16A. NPPB and CaCCinh-A01 inhibited the CaCC/TMEM16A currents completely at 300 µmol L(-1), with IC50 values of 39.35 ± 4.72 µmol L(-1) and 6.35 ± 0.27 µmol L(-1), respectively; and Eact, activated CaCC/TMEM16A, with an EC50 value of 3.92 ± 0.87 µmol L(-1).