Erratum to: Kinetic Characterization of Tyrosinase-catalyzed Oxidation of Four Polyphenols.

The article "Kinetic Characterization of Tyrosinase-catalyzed Oxidation of Four Polyphenols", written by Wan-yu LIU, Congming ZOU, Jian-hua HU, Zi-jun XU, Lu-qin SI, Jun-jun LIU, Jian-geng HUANG, was originally published electronically on the publisher's internet portal on May 2020 without open access. With the author(s)' decision to opt for Open Choice, the copyright of the article is changed to © The Author(s) 2020 and the article is forthwith distributed under a Creative Commons Attribution 4.0 International License ( https://creativecommons.org/licenses/by/4.0/ ), which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.The original article has been corrected.

Kinetic Characterization of Tyrosinase-catalyzed Oxidation of Four Polyphenols.

Phenolic compounds such as chlorogenic acid, cryptochlorogenic acid, neochlorogenic acid and caffeic acid are widely distributed in fruits, vegetables and traditional Chinese medicines with a wide range of biological activities. Tyrosinase plays a critical role in the food industry, but recent studies have proposed unexplored aspects of clinical application. Tyrosinase-catalyzed oxidation of four polyphenols as well as its underlying mechanism remains unclear. In the current work, we investigated the kinetic properties of tyrosinase-catalyzed oxidation of the four polyphenols of interest. To measure the unstable o-quinone products, an analytical method using 3-methyl-2-benzothiazolinone hydrazone (MBTH) was established. The optimal incubation time, buffer pH, temperature and enzyme concentration for the enzyme activity in the presence of each polyphenol of interest were investigated. Under the final optimized conditions, the kinetics and substrate specificity of four polyphenols were examined. Kinetic data showed that tyrosinase had the greatest substrate affnity to chlorogenic acid compared with its isomers and caffeic acid. The catalytic effciency with chlorogenic acid was 8- to 15-fold higher than that with the other 3 polyphenols. Molecular docking study demonstrated that the tight binding of chlorogenic acid at the peripheral site should be the major reason for the specifcity to chlorogenic acid. In light of this, the rational design of high-affnity inhibitors against tyrosinase may focus on the binding of both the Cu site and peripheral site. This study will supply a basis for the selection of phenolic acids in food industry and health care.

Angiotensin-Converting Enzyme Inhibitor Rapidly Ameliorates Depressive-Type Behaviors via Bradykinin-Dependent Activation of Mammalian Target of Rapamycin Complex 1.

BACKGROUND: Angiotensin-converting enzyme inhibitors (ACEIs) are widely prescribed antihypertensive agents. Intriguingly, case reports and clinical trials have indicated that ACEIs, including captopril and lisinopril, may have a rapid mood-elevating effect in certain patients, but few experimental studies have investigated their value as fast-onset antidepressants. METHODS: The present study consisted of a series of experiments using biochemical assays, immunohistochemistry, and behavioral techniques to examine the effect and mechanism of captopril on depressive-like behavior in 2 animal models, the chronic unpredictable stress model and the chronic social defeat stress model. RESULTS: Captopril (19.5 or 39 mg/kg, intraperitoneal injection) exerted rapid antidepressant activity in mice treated under the chronic unpredictable stress model and mice treated under the chronic social defeat stress model. Pharmacokinetic analysis revealed that captopril crossed the blood-brain barrier and that lisinopril, another ACEI with better blood-brain barrier permeability, exerted a faster and longer-lasting effect at a same molar equivalent dose. This antidepressant effect seemed to be independent of the renin-angiotensin system, but dependent on the bradykinin (BK) system, since the decreased BK detected in the stressed mice could be reversed by captopril. The hypofunction of the downstream effector of BK, Cdc42 (cell division control protein 42) homolog, contributed to the stress-induced loss of dendritic spines, which was rapidly reversed by captopril via activating the mTORC1 (mammalian target of rapamycin complex 1) pathway. CONCLUSIONS: Our findings indicate that the BK-dependent activation of mTORC1 may represent a promising mechanism underlying antidepressant pharmacology. Considering their affordability and availability, ACEIs may emerge as a novel fast-onset antidepressant, especially for patients with comorbid depression and hypertension.

Metformin produces anxiolytic-like effects in rats by facilitating GABAA receptor trafficking to membrane.

BACKGROUND AND PURPOSE: Altered function or expression of GABAA receptors contributes to anxiety disorders. Benzodiazepines are widely prescribed for the treatment of anxiety. However, the long-term use of benzodiazepines increases the risk of developing drug dependence and tolerance. Thus, it is urgent to explore new therapeutic approaches. Metformin is widely used to treat Type 2 diabetes and other metabolic syndromes. However, the role of metformin in psychiatric disorders, especially anxiety, remains largely unknown. EXPERIMENTAL APPROACH: We examined the effects of metformin on anxiety-like behaviour of rats in open field test and elevated plus maze test. We also observed the effect of metformin (10 µM, in vitro; 100 mg·kg-1 , in vivo) on the trafficking of GABAA receptors, as mechanisms underlying the anxiolytic effects of metformin. KEY RESULTS: Metformin (100 mg·kg-1 , i.p. 30 min) displayed a robust and rapid anxiolytic effect, without tolerance. Metformin up-regulated the surface expression of GABAA receptors and increased miniature inhibitory postsynaptic currents (mIPSCs). AMP-activated protein kinase (AMPK) activated by metformin-induced stimulation of forkhead box O3a (FoxO3a) transcriptional activity, followed by increased expression of GABAA receptor-associated protein (GABARAP) and its binding to GABAA receptors finally resulted in the membrane insertion of GABAA receptors. CONCLUSIONS AND IMPLICATIONS: Metformin increased mIPSCs by up-regulating the membrane insertion of GABAA receptors, via a pathway involving AMPK, FoxO3a, and the GABAA receptor-associated protein. Thus metformin has a potential new use in the treatment of anxiety disorders.

Pharmacokinetics and tolerability of oral dosage forms of huperzine a in healthy Chinese male volunteers: a randomized, single dose, three-period, six-sequence crossover study.

Huperzine A is a potent, reversible, and blood-brain barrier permeable acetylcholinesterase inhibitor. The aim of this study was to compare the pharmacokinetics, tolerability, and bioavailability of two formulations with the established reference formulation of huperzine A in a fasting, healthy Chinese male population. This was a randomized, single-dose, 3-period, 6-sequence crossover study. The plasma concentrations of huperzine A were determined by liquid chromatography tandem mass spectrometry. Tolerability was assessed based on subject interview, vital sign monitoring, physical examination, and routine blood and urine tests. The mean (SD) pharmacokinetic parameters of the reference drug were Cmax, 1.550 (0.528) ng/mL; t1/2, 12.092 (1.898) h; AUC0-72h, 17.550 (3.794) ng·h/mL. Those of the test formulation A and test formulation B were Cmax, 1.412 (0.467), 1.521 (0.608) ng/mL; t1/2, 12.073 (2.068), 12.271 (1.678) h; AUC0-72h, 15.286 (3.434) ng·h/mL, 15.673 (3.586) ng·h/mL. The 90% confidence intervals for the AUC0-72h and Cmax were between 0.80 and 1.25. No adverse events were reported by the subjects or found with results of clinical laboratory test. The test and reference products met the regulatory criteria for bioequivalence in these fasting, healthy Chinese male volunteers. All three formulations appeared to be well tolerated.

Activity-Dependent Sulfhydration Signal Controls N-Methyl-D-Aspartate Subtype Glutamate Receptor-Dependent Synaptic Plasticity via Increasing d-Serine Availability.

AIMS: Reactive sulfur species, including hydrogen sulfide (H2S) and its oxydates, have been raised as novel redox signaling molecules. The present study aimed at examining whether endogenous sulfhydration signal is required for long-term potentiation (LTP), a cellular model for memory. RESULTS: In this study, we found that increased synaptic activity triggered sulfide generation and protein sulfhydration. Activity-triggered sulfide production was essential for N-methyl-D-aspartate subtype glutamate receptor (NMDAR)-dependent LTP via maintaining the availability of d-serine, a primary coagonist for synaptic NMDARs. Genetic knockdown of cystathionine ß-synthase, not cystathionine γ-lyase, impaired LTP. H2S increased NMDAR-dependent LTP via sulfhydration and disinhibition of serine racemase (SR), a main synthetase of d-serine. We found that polysulfides also increased NMDAR-dependent LTP and NMDAR activity. In aged rats, the level of H2S and SR sulfhydration decreased significantly. Exogenous supplement of H2S restored the sulfhydration of SR, followed by the improvement of age-related deficits in LTP. Furthermore, boost of H2S signal in vivo improves hippocampus-dependent memory. Innovation and Conclusion: Our results provide a direct evidence for the biological significance of endogenous sulfhydration signal in synaptic plasticity. Exogenous supplement of H2S could be considered as the new therapeutic approach for the treatment of neurocognitive dysfunction after aging. Antioxid. Redox Signal. 27, 398-414.

Pharmacokinetics and Tolerability of Oral Dosage Forms of Huperzine A in Healthy Chinese Male Volunteers: a Randomized,Single Dose, Three-period, Six-sequence Crossover Study / 华中科技大学学报（医学）（英德文版）

Huperzine A is a potent,reversible,and blood-brain barrier permeable acetylcholinesterase irhibitor.The aim of this study was to compare the pharmacokinetics,tolerability,and bioavailability of two formulations with the established reference formulation of huperzine A in a fasting,healthy Chinese male population.This was a randomized,single-dose,3-period,6-sequence crossover study.The plasma concentrations of huperzine A were determined by liquid chromatography tandem mass spectrometry.Tolerability was assessed based on subject interview,vital sign monitoring,physical examination,and routine blood and urine tests.The mean (SD) pharmacokinetic parameters of the reference drug were Cmax,1.550 (0.528) ng/mL;t1/2,12.092 (1.898) h;AUC0-72h,17.550 (3.794) ng.h/mL.Those of the test formulation A and test formulation B were Cmax,1.412 (0.467),1.521 (0.608) ng/mL;t1/2,12.073 (2.068),12.271 (1.678) h;AUC0-72h,15.286 (3.434) ng.h/mL,15.673 (3.586) ng.h/mL.The 90％ confidence intervals for the AUC0-72h and Cmax were between 0.80 and 1.25.No adverse events were reported by the subjects or found with results of clinical laboratory test.The test and reference products met the regulatory criteria for bioequivalence in these fasting,healthy Chinese male volunteers.All three formulations appeared to be well tolerated.

ST09, a Novel Thioester Derivative of Tacrine, Alleviates Cognitive Deficits and Enhances Glucose Metabolism in Vascular Dementia Rats.

AIMS: Chemical entities containing mercapto group have been increasingly attractive in the therapy of central nerve system (CNS) diseases. In the recent study, we screened a series of mercapto-tacrine derivatives with synergistic neuropharmacological profiles in vitro. METHODS: We investigated the effect and mechanism of ST09, a thioester derivative of tacrine containing a potential mercapto group, on the vascular dementia (VaD) model of rat induced by bilateral common carotid arteries occlusion (2-VO). RESULTS: ST09 and its active metabolite ST10 retained excellent inhibition on acetylcholinesterase (AChE) activity. ST09 significantly attenuated the 2-VO-induced impairment in spatial acquisition performance and inhibited the 2-VO-induced rise of AChE activity. In the VaD model, ST09 attenuated the oxidative stress and decreased the apoptosis in the cortex and hippocampus. Compared with donepezil, ST09 exhibited a better effect on the regeneration of free thiols in 2-VO rats. Interestingly, ST09, not donepezil, greatly improved glucose metabolism in various brain regions of 2-VO rats using functional imaging of (18) F-labeled fluoro-deoxyglucose (FDG) positron emission tomography (PET). CONCLUSIONS: ST09 may serve as a more promising agent for the therapy of VaD than tacrine owing to the introduction of a potential mercapto group into the parent skeleton.

[Quantification of amlodipine in human plasma by LC-MS/MS method: elimination of matrix effects by improving chromatographic conditions].

A liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed and validated for the quantification of amlodipine in human plasma. The influence of alkalizer, extraction solvent and the chromatographic conditions on the matrix effects was investigated. The stable isotope-labeled amlodipine (amlodipine-d(4)) was used as an internal standard. Sample preparation involved simple liquid-liquid extraction procedure using methyl tertiary butyl ether. Chromatographic separation was achieved on a Welch Ultimate XB-C18 (100 mm × 2.1 mm, 3 µm) column with acetonitrile/2 mmol·L(-1) ammonium formate (p H 3.0） under gradient condition at a flow rate of 0.6 m L·min(-1). Detection was performed using electrospray ionization (ESI) in positive ion multiple reaction monitoring (MRM) mode. The linear range of the analyte was 0.1-20.0 µg·L(-1), with the lower limit of quantitation (LLOQ) of 0.1 µg·L(-1). The matrix factor for low, medium, high concentration quality control samples and internal standard was (93.9 ± 1.8)%, (95.8 ± 4.9)%, (93.9 ± 1.5)% and (97.9 ± 5.3)%, respectively. The method showed excellent specificity, linearity, intra-day and inter-day accuracy and precision, extraction recovery and stability, according to the CFDA guidance for bioanalytical method validation. The matrix effect was significantly improved through optimizing the chromatographic conditions. This economical, simple, robust, sensitive and specific method is entirely able to meet the requirement of the determination of amlodipine in human plasma samples obtained from bioequivalence studies.

Fast profiling ecotoxicity and skin permeability of benzophenone ultraviolet filters using biopartitioning micellar chromatography based on penetrable silica spheres.

Penetrable silica possesses hierarchical pores, mesopores and penetrable macropores, offering fast mass transfer, satisfactory mechanical strength as well as low column pressure. In the present study, penetrable octadecyl-bonded silica (ODS) was for the first time used as biopartitioning micellar chromatography (BMC) stationary phase to profile ecotoxicity and skin permeability of benzophenone UV-filters. Mobile phase (MP) pH and concentration of polyoxyethylene(23)lauryl ether in the MP were systematically studied. Quantitative retention-activity relationships (QRARs) model was established to correlate retention factors (k) on BMC with bioconcentration factor (BCF) and transdermal rate (TR) of UV-filters. Coefficient of determination (r(2)) of the QRARs model between log BCF and log k were 0.9398-0.9753, while r(2) between TR and log k were 0.7569-0.8434, which demonstrated satisfactory predictive ability of the methodology. It was a powerful tool for fast screening by combining penetrable ODS with BMC, and avoiding column blockage often occurring in BMC.

Pharmacokinetic and biodistribution studies of N-(2-hydroxypropyl)methacrylamide copolymer-dexamethasone conjugates in adjuvant-induced arthritis rat model.

N-(2-Hydroxypropyl)methacrylamide (HPMA) copolymer has been found to be arthrotropic (joint-targeting) in the adjuvant-induced arthritis (AA) rat model using magnetic resonance imaging (MRI). In this manuscript, we report the quantitative pharmacokinetics and biodistribution (PK/BD) of (125)I-labeled HPMA copolymer-dexamethasone conjugate (P-Dex) in AA rats. Structural parameters of the prodrug such as the molecular weight (MW) and Dex content were found to have strong impact on the PK/BD profiles of P-Dex. The increase of MW (14,000, 24,000, and 42,000 g/mol) and Dex content (0, 151, and 313 micromol/g) enhances the arthrotropism of P-Dex. For the conjugate with highest MW and Dex content (P-H-M(W)/Dex), the percentage of injected doses per gram (ID/g) of ankle synovial tissue at day seventh postadministration is 1% g(-1), which confirms P-Dex as an arthrotropic macromolecular prodrug. For liver and spleen, the ID/g values are 0.51 and 3.64% g(-1), respectively. As an antigen-presenting organ, the sequestration of the prodrug by spleen may be explained by its abnormal enlargement associated with the systemic inflammatory disease model. Gradual reduction of spleen weight due to the inflammation resolution effect of P-Dex may also contribute to the high ID/g values. Increase of Dex content and reduction of MW would increase P-Dex distribution to kidney. The highest ID/g value for kidney at day seventh postadministration (0.91% g(-1)) was found with P-L-M(w) (MW = 14,000 g/mol, Dex content =288 micromol/g), which may suggest kidney tubuli reabsorption of the conjugates. The P-Dex's distribution to heart and lung is minimum.

Comparison of self-microemulsifying drug delivery system versus solid dispersion technology used in the improvement of dissolution rate and bioavailability of vinpocetine.

The objective of this study is to compare the differences between self-microemulsifying drug delivery system (SMEDDS) and solid dispersion (SD) technology used to improve the dissolution rate and bioavailability of vinpocetine (VIP). The formulation of VIP-SMEDDS was composed of Labrafac, oleic acid, Cremophor EL, Transcutol P, and gum acacia which was used as solid absorbent. VIP-SD was prepared using poloxamer F68 as the carrier. In the solubility test, the solubility of VIP in SMEDDS was 17.3 times as much as that in SD. In the dissolution test, SMEDDS had shown better enhancement and stability in dissolving VIP than SD. When compared to VIP crude powder, the bioavailability of VIP in SMEDDS (VIP-SMEDDS) was 1.89-fold higher, and was less affected by food intake. However, the bioavailability of VIP in SD (VIP-SD) was bioequivalent to that of VIP crude powder. The tissue uptake of VIP-SMEDDS in Peyer's patches, intestine and liver after administration for 2 hours was more favorable than that of VIP-SD, which was 3.7 times higher in Peyer's patches, 2.2 times higher in intestine and 1.5 times higher in liver. In Caco-2 tests, the apparent permeability (P(app)) of VIP-SMEDDS was 2.65 times of that of VIP-SD. The width of the cell tight junctions of Caco-2 cell monolayer treated with VIP-SMEDDS were 9.6-fold wider, but there was no significant change after treatment with VIP-SD, when compared to the blank control. In conclusion, SMEDDS was more efficient than the traditional SD technology in increasing solubility, dissolution, intestinal permeability, lymphatic absorption and bioavailability of the insoluble drugs such as VIP, which is less affected by food intake.

[Advances in the study of excipient inhibitors of intestinal P-glycoprotein].

P-glycoprotein (P-gp) located in the apicalmembranes of intestinal absorptive cells is an energy-dependent efflux pump which can reduce the bioavailability of a wide range of substrate drugs. There is increasingly interest in enhancing the bioavailability of these molecules by inhibiting intestinal P-gp. A classification of excipient inhibitors of intestinal P-gp nonionic surfactants, poly (ethylene glycol), derivates of beta-cyclodextrin and thiolated chitosan will be presented and then the inhibition mechanism will be discussed. Compared with traditional P-gp inhibitor, excipient inhibitors appear to have minimal nonspecific pharmacological activity, thus potential side effects can be mostly avoided. These excipient inhibitors, which hold the promise of replacing the traditional ones, will be extensively employed to significantly improve the intestinal absorption of poorly soluble and absorbed drugs as a result of P-gp inhibition, and thus to enhance the bioavailability of these drugs. However, the further studies of both the mechanism and clinical application are urgently needed.

[The inhibitory effect of pluronic on P-glycoprotein drug pump].

To investigate the inhibitory effect of Pluronic on P-glycoprotein (P-gp) drug efflux pump, Caco-2 cells and animal models were established to study the influence of Pluronic on celiprolol transport across Caco-2 cell monolayer and intestinal mucous membrane with verapamil set as a positive control. Drug concentration was measured by HPLC and the apparent permeability coefficient (P(app)), absorption rate constant (k(a)) and the effective permeability coefficient (P(eff)) were calculated. P(app) of basolateral to apical side and apical to basolateral side was (2.10 +/- 0.13) x 10(-6) and (0.333 +/- 0.018) x 10(-6) cm x s(-1), respectively. Transports of celiprolol across Caco-2 cell monolayer were influenced by both verapamil and Pluronic. The absorption constants (k(a)) of celiprolol at duodenum, jejunum, ileum, and colon were (0.09 +/- 0.03), (0.14 +/- 0.04), (0.11 +/- 0.03) and (0.05 +/- 0.02) h(-1), k(a) of celiprolol in verapamil group were (0.14 +/- 0.03), (0.24 +/- 0.02), (0.25 +/- 0.03) and (0.23 +/- 0.02) h(-1), and k(a) of celiprolol in Pluronic group were (0.13 +/- 0.02), (0.22 +/- 0.02), (0.22 +/- 0.03) and (0.20 +/- 0.03) h(-1), respectively. Pluronic showed significant effect on inhibiting P-gp of Caco-2 cell and intestinal mucosa in rats.