Dipeptidyl peptidase-4（DPP-4） inhibitors exert their antihyperglycemic effects through repressing inactivation of certain incretin hormones and thus increasing insulin secretion and controlling glucose level. In thi...Dipeptidyl peptidase-4（DPP-4） inhibitors exert their antihyperglycemic effects through repressing inactivation of certain incretin hormones and thus increasing insulin secretion and controlling glucose level. In this study, the plasma concentrations of sitagliptin, a potent DPP-4 inhibitor, after a single oral dose of 300 mg/kg in streptozotocin-induced type 2 diabetic rats were determined by HPLC. A one-compartment pharmacokinetic（PK） model with first order absorption was developed to describe the PK profile of sitagliptin, and the drug concentrations at the doses given in the pharmacodynamic（PD） study were simulated accordingly. The dynamic changes in DPP-4 activity, insulin concentration and blood glucose level in diabetic rats at doses of 1, 5 and 10 mg/kg were measured, and a mechanism-based PK/PD model was established subsequently. In this model, the inhibitory effect of sitagliptin on DPP-4 activity was demonstrated using the Hill＇s function with direct link, and the downstream increase in insulin secretion and inhibition of glucose production were characterized using indirect response（IDR） models. This model interpreted the mechanism of antihyperglycemic action of sitagliptin, and may be modified and applied to other species or other agents in this class.展开更多
Apoptosis and hypertrophy of cardiomyocytes are the primary causes of heart failure （HF）, a global leading cause of death, and are regulated through the complicated intracellular signaling network, limiting the deve...Apoptosis and hypertrophy of cardiomyocytes are the primary causes of heart failure （HF）, a global leading cause of death, and are regulated through the complicated intracellular signaling network, limiting the development of effective treatments due to its complexity. To identify effective therapeutic strategies for HF at a system level, we develop a large-scale comprehensive mathematical model of the cardiac signaling network by integrating all available experimental evidence. Attractor landscape analysis of the network model identifies distinct sets of control nodes that effectively suppress apoptosis and hypertrophy of cardiomyocytes under ischemic or pressure overload-induced HF, the two major types of HF. Intriguingly, our system-level analysis suggests that intervention of these control nodes may increase the efficacy of clinical drugs for HF and, of most importance, different combinations of control nodes are suggested as potentially effective candidate drug targets depending on the types of HF. Our study provides a systematic way of developing mechanism-based therapeutic strategies for HF.展开更多
In this paper, the averaged value of the strain energy density （SED） over a control volume is used to predict the critical load of V-notched specimens made of functionally graded steels （FGSs） under mixed-mode loa...In this paper, the averaged value of the strain energy density （SED） over a control volume is used to predict the critical load of V-notched specimens made of functionally graded steels （FGSs） under mixed-mode loading. The studied FGSs contain ferritic and austenite phases in addition to bainitic layer produced by electroslag remelting. The mechanism- based strain gradient plasticity theory is used to determine the flow stress （yield stress or ultimate stress） of each layer. The Young＇s modulus and the Poisson＇s ratio have been assumed to be constant, while other mechanical properties vary exponentially along the specimen width. The control volume is centered in relation to the maximum principal stress present on the notch edge and assumes a crescent shape. The points belonging to the volume perimeter are obtained numerically. In the present contribution, the effects of notch radius and notch depth on the SED and the critical load are studied. The notch radius varies from 0.2 to 2.0 mm, and the notch depth varies from 5 to 7 ram. By using the SED approach and finite element simulations, the critical load is determined, and the obtained results show a sound agreement with the experimental results.展开更多
Objective To investigate the effects ofamiodarone （AMD） on simvastatin （SV） in human liver microsomes and the possible underlying mechanisms. Methods Time-, NADPH- and concentration-dependent inhibitions were test...Objective To investigate the effects ofamiodarone （AMD） on simvastatin （SV） in human liver microsomes and the possible underlying mechanisms. Methods Time-, NADPH- and concentration-dependent inhibitions were tested in HLM. The logarithm of relative inhibition values was plotted versus preincubation time （0, 5, 10, 15, 20min） for a series concentration of AMD used （0, 2, 5, 25, 50 umol/L）, and the slopes determined by linear regression. These slope values represente the observed inactivation rate constants （kobs ）. A double-reciprocal plot was then constructed using the reciprocal of the kobs （y-axis） and the reciprocal of the associated inhibitor concentration （x-axis） to estimate the values of kinact and K1, which were two principal kinetic constants that were specific for mechanism-based inhibition （MBI）.drug-drug interactions （DDI） potential was predicted based on in vitro data and by using the in vitro-in vivo extrapolation. Results The time-, concentration- and NADPH-dependent characteristics confirmed that when SV was the substrate of CYP3A4, the inhibition of AMD to CYP3A4 is MBI. KI and kinact value were calculated to be 5.1umol/L and 0.018minL The CLant of SV was reduced 2.96-5.63 fold when it was administrated with AMD. Conclusion Based on the results, AMD would inhibit SV metabolism via the mechanism-based manner, which would lead to DDI when they are taken together. Careful clinical observation is recommended when AMD and SV have to be simultaneously prescribed.展开更多
There are two general approaches to drug discovery. The oldest is the empirically-driven in vivo identification of a drug candidate, with little or no consideration given to identifying the active constituent. The alt...There are two general approaches to drug discovery. The oldest is the empirically-driven in vivo identification of a drug candidate, with little or no consideration given to identifying the active constituent. The alternative is mechanism-based, a process that entails the in vitro screening of purified chemical compounds to identify those that interact specifically with a selected biological target, after which they are tested for therapeutic potential. A major difference between these approaches is the extent to which the principles of pharmacology are employed to demonstrate safety and efficacy and to enable improvements in the therapeutic properties of the product. As a thorough pharmacological analysis of the pharmacokinetics and pharmacodynamics of a test agent requires that it be a stable, single, purified substance, such testing is more difficult with unpurified samples containing multiple compounds as compared to single agents. A lack of pharmacological information compromises the clinical utility of a test substance by leaving open questions about its bioavailability, metabolism, and mechanisms of therapeutic actions and toxicities. Although drug discovery success has be achieved with both the empirically-driven and mechanism-based approaches, the proper application of pharmacological techniques in the drug discovery process maximizes efficacy, safety and the chance for regulatory approval. In addition, pharmacological data provides information needed for improving the therapeutic properties of an agent, enhancing its clinical utility, and extending the product lifespan.展开更多
Royal palm tree peroxidase (RPTP) has been isolated to homogeneity from leaves of Roystonea regia palm trees. The enzyme purification steps included homogenization, (NH4)SO4 precipitation, extraction of palm leaf colo...Royal palm tree peroxidase (RPTP) has been isolated to homogeneity from leaves of Roystonea regia palm trees. The enzyme purification steps included homogenization, (NH4)SO4 precipitation, extraction of palm leaf colored compounds and consecutive chromatography on Phenyl-Sepharose, TSK-Gel DEAE-5PW and Superdex-200. The novel peroxidase was characterized as having a molecular weight of 48.2 ± 3.0 kDa and an isoelectric point pI 5.4 ± 0.1. The enzyme forms dimers in solution with approximate molecular weight of 92 ± 2 kDa. Here we investigated the steady-state kinetic mechanism of the H2O2-supported oxidation of different organic substrates by RPTP. The results of the analysis of the initial rates vs. H2O2 and reducing substrate concentrations were seen to be consistent with a substrate-inhibited Ping-Pong Bi-Bi reaction mechanism. The phenomenological approach used expresses the peroxidase Ping-Pong mechanism in the form of the Michaelis-Menten equation and affords an interpretation of the effects in terms of the kinetic parameters KmH2O2, KmAH2, kcat, KSIH2O2, KSIAH2 and of the microscopic rate constants k1 and k3 of the shared three-step peroxidase catalytic cycle. Furthermore, the concentration and time-dependences and the mechanism of the suicide inactivation of RPTP by hydrogen peroxide were studied kinetically with guaiacol as co-substrate. The turnover number (r) of H2O2 required to complete the inactivation of the enzyme was 2154 ± 100 and the apparent rate constants of catalysis 185 s–1 and 18 s–1.展开更多
In this study,we considered the wetting phenomenon on a general substrate from a new viewpoint of continuum mechanics.The analyses first show how the Wenzel and the Cassie models deviate the practical results in some ...In this study,we considered the wetting phenomenon on a general substrate from a new viewpoint of continuum mechanics.The analyses first show how the Wenzel and the Cassie models deviate the practical results in some special substrates,and then elucidate the mechanism of the triple contact line(TCL) moving.Based upon variational theory of the total free functional dealing with the movable boundary condition,we show that the macroscopic contact angle(MCA) expression is the corresponding transversality condition.It manifests that the MCA depends only on the chemical and geometric property at the TCL,and is not affected by the gravity of the droplet and the contact area beneath the liquid.Our continuum model also shows the exploration of the pinning effect on a sharp wedge or the interface between two different phases.This investigation will help designing super-hydrophobic materials for novel micro-fluidic devices.展开更多
Cytochrome P4502J2(CYP2J2)metabolizes arachidonic acid(AA)to cardioprotective epoxyeicosatrienoic acids(EETs).Dronedarone,an antiarrhythmic drug prescribed for treatment of atrial fibrillation(AF)induces cardiac adver...Cytochrome P4502J2(CYP2J2)metabolizes arachidonic acid(AA)to cardioprotective epoxyeicosatrienoic acids(EETs).Dronedarone,an antiarrhythmic drug prescribed for treatment of atrial fibrillation(AF)induces cardiac adverse effects(AEs)with poorly understood mechanisms.We previously demonstrated that dronedarone inactivates CYP2J2 potently and irreversibly,disrupts AA-EET pathway leading to cardiac mitochondrial toxicity rescuable via EET enrichment.In this study,we investigated if mitigation of CYP2J2 inhibition prevents dronedarone-induced cardiac AEs.We first synthesized a deuterated analogue of dronedarone(termed poyendarone)and demonstrated that it neither inactivates CYP2J2,disrupts AA-EETs metabolism nor causes cardiac mitochondrial toxicity in vitro.Our patch-clamp experiments demonstrated that pharmacoelectrophysiology of dronedarone is unaffected by deuteration.Next,we show that dronedarone treatment or CYP2J2 knockdown in spontaneously beating cardiomyocytes indicative of depleted CYP2J2 activity exacerbates beat-to-beat(BTB)variability reflective of proarrhythmic phenotype.In contrast,poyendarone treatment yields significantly lower BTB variability compared to dronedarone in cardiomyocytes indicative of preserved CYP2J2 activity.Importantly,poyendarone and dronedarone display similar antiarrhythmic properties in the canine model of persistent AF,while poyendarone substantially reduces beat-to-beat variability of repolarization duration suggestive of diminished proarrhythmic risk.Our findings prove that deuteration of dronedarone prevents CYP2J2 inactivation and mitigates dronedarone-induced cardiac AEs.展开更多
Background:Extensive research on fragile X mental retardation gene knockout mice and mutant Drosophila models has largely expanded our knowledge on mechanism-based treatment of fragile X syndrome(FXS).In light of thes...Background:Extensive research on fragile X mental retardation gene knockout mice and mutant Drosophila models has largely expanded our knowledge on mechanism-based treatment of fragile X syndrome(FXS).In light of these findings,several clinical trials are now underway for therapeutic translation to humans.Data sources:Electronic literature searches were conducted using the PubMed database and ClinicalTrials.gov.The search terms included"fragile X syndrome","FXS and medication","FXS and therapeutics"and"FXS and treatment".Based on the publications identified in this search,we reviewed the neuroanatomical abnormalities in FXS patients and the potential pathogenic mechanisms to monitor the progress of FXS research,from basic studies to clinical trials.Results:The pathological mechanisms of FXS were categorized on the basis of neuroanatomy,synaptic structure,synaptic transmission and fragile X mental retardation protein(FMRP)loss of function.The neuroanatomical abnormalities in FXS were described to motivate extensive research into the region-specific pathologies in the brain responsible for FXS behavioural manifestations.Mechanism-directed molecular medicines were classified according to their target pathological mechanisms,and the most recent progress in clinical trials was discussed.Conclusions:Current mechanism-based studies and clinical trials have greatly contributed to the development of FXS pharmacological therapeutics.Research examining the extent to which these treatments provided a rescue effect or FMRP compensation for the developmental impairments in FXS patients may help to improve the effi cacy of treatments.展开更多
基金sponsored by Department of Clinical Pharmacology and Pharmacometrics, Pfizer
文摘Dipeptidyl peptidase-4（DPP-4） inhibitors exert their antihyperglycemic effects through repressing inactivation of certain incretin hormones and thus increasing insulin secretion and controlling glucose level. In this study, the plasma concentrations of sitagliptin, a potent DPP-4 inhibitor, after a single oral dose of 300 mg/kg in streptozotocin-induced type 2 diabetic rats were determined by HPLC. A one-compartment pharmacokinetic（PK） model with first order absorption was developed to describe the PK profile of sitagliptin, and the drug concentrations at the doses given in the pharmacodynamic（PD） study were simulated accordingly. The dynamic changes in DPP-4 activity, insulin concentration and blood glucose level in diabetic rats at doses of 1, 5 and 10 mg/kg were measured, and a mechanism-based PK/PD model was established subsequently. In this model, the inhibitory effect of sitagliptin on DPP-4 activity was demonstrated using the Hill＇s function with direct link, and the downstream increase in insulin secretion and inhibition of glucose production were characterized using indirect response（IDR） models. This model interpreted the mechanism of antihyperglycemic action of sitagliptin, and may be modified and applied to other species or other agents in this class.
文摘Apoptosis and hypertrophy of cardiomyocytes are the primary causes of heart failure （HF）, a global leading cause of death, and are regulated through the complicated intracellular signaling network, limiting the development of effective treatments due to its complexity. To identify effective therapeutic strategies for HF at a system level, we develop a large-scale comprehensive mathematical model of the cardiac signaling network by integrating all available experimental evidence. Attractor landscape analysis of the network model identifies distinct sets of control nodes that effectively suppress apoptosis and hypertrophy of cardiomyocytes under ischemic or pressure overload-induced HF, the two major types of HF. Intriguingly, our system-level analysis suggests that intervention of these control nodes may increase the efficacy of clinical drugs for HF and, of most importance, different combinations of control nodes are suggested as potentially effective candidate drug targets depending on the types of HF. Our study provides a systematic way of developing mechanism-based therapeutic strategies for HF.
文摘In this paper, the averaged value of the strain energy density （SED） over a control volume is used to predict the critical load of V-notched specimens made of functionally graded steels （FGSs） under mixed-mode loading. The studied FGSs contain ferritic and austenite phases in addition to bainitic layer produced by electroslag remelting. The mechanism- based strain gradient plasticity theory is used to determine the flow stress （yield stress or ultimate stress） of each layer. The Young＇s modulus and the Poisson＇s ratio have been assumed to be constant, while other mechanical properties vary exponentially along the specimen width. The control volume is centered in relation to the maximum principal stress present on the notch edge and assumes a crescent shape. The points belonging to the volume perimeter are obtained numerically. In the present contribution, the effects of notch radius and notch depth on the SED and the critical load are studied. The notch radius varies from 0.2 to 2.0 mm, and the notch depth varies from 5 to 7 ram. By using the SED approach and finite element simulations, the critical load is determined, and the obtained results show a sound agreement with the experimental results.
文摘Objective To investigate the effects ofamiodarone （AMD） on simvastatin （SV） in human liver microsomes and the possible underlying mechanisms. Methods Time-, NADPH- and concentration-dependent inhibitions were tested in HLM. The logarithm of relative inhibition values was plotted versus preincubation time （0, 5, 10, 15, 20min） for a series concentration of AMD used （0, 2, 5, 25, 50 umol/L）, and the slopes determined by linear regression. These slope values represente the observed inactivation rate constants （kobs ）. A double-reciprocal plot was then constructed using the reciprocal of the kobs （y-axis） and the reciprocal of the associated inhibitor concentration （x-axis） to estimate the values of kinact and K1, which were two principal kinetic constants that were specific for mechanism-based inhibition （MBI）.drug-drug interactions （DDI） potential was predicted based on in vitro data and by using the in vitro-in vivo extrapolation. Results The time-, concentration- and NADPH-dependent characteristics confirmed that when SV was the substrate of CYP3A4, the inhibition of AMD to CYP3A4 is MBI. KI and kinact value were calculated to be 5.1umol/L and 0.018minL The CLant of SV was reduced 2.96-5.63 fold when it was administrated with AMD. Conclusion Based on the results, AMD would inhibit SV metabolism via the mechanism-based manner, which would lead to DDI when they are taken together. Careful clinical observation is recommended when AMD and SV have to be simultaneously prescribed.
文摘There are two general approaches to drug discovery. The oldest is the empirically-driven in vivo identification of a drug candidate, with little or no consideration given to identifying the active constituent. The alternative is mechanism-based, a process that entails the in vitro screening of purified chemical compounds to identify those that interact specifically with a selected biological target, after which they are tested for therapeutic potential. A major difference between these approaches is the extent to which the principles of pharmacology are employed to demonstrate safety and efficacy and to enable improvements in the therapeutic properties of the product. As a thorough pharmacological analysis of the pharmacokinetics and pharmacodynamics of a test agent requires that it be a stable, single, purified substance, such testing is more difficult with unpurified samples containing multiple compounds as compared to single agents. A lack of pharmacological information compromises the clinical utility of a test substance by leaving open questions about its bioavailability, metabolism, and mechanisms of therapeutic actions and toxicities. Although drug discovery success has be achieved with both the empirically-driven and mechanism-based approaches, the proper application of pharmacological techniques in the drug discovery process maximizes efficacy, safety and the chance for regulatory approval. In addition, pharmacological data provides information needed for improving the therapeutic properties of an agent, enhancing its clinical utility, and extending the product lifespan.
文摘Royal palm tree peroxidase (RPTP) has been isolated to homogeneity from leaves of Roystonea regia palm trees. The enzyme purification steps included homogenization, (NH4)SO4 precipitation, extraction of palm leaf colored compounds and consecutive chromatography on Phenyl-Sepharose, TSK-Gel DEAE-5PW and Superdex-200. The novel peroxidase was characterized as having a molecular weight of 48.2 ± 3.0 kDa and an isoelectric point pI 5.4 ± 0.1. The enzyme forms dimers in solution with approximate molecular weight of 92 ± 2 kDa. Here we investigated the steady-state kinetic mechanism of the H2O2-supported oxidation of different organic substrates by RPTP. The results of the analysis of the initial rates vs. H2O2 and reducing substrate concentrations were seen to be consistent with a substrate-inhibited Ping-Pong Bi-Bi reaction mechanism. The phenomenological approach used expresses the peroxidase Ping-Pong mechanism in the form of the Michaelis-Menten equation and affords an interpretation of the effects in terms of the kinetic parameters KmH2O2, KmAH2, kcat, KSIH2O2, KSIAH2 and of the microscopic rate constants k1 and k3 of the shared three-step peroxidase catalytic cycle. Furthermore, the concentration and time-dependences and the mechanism of the suicide inactivation of RPTP by hydrogen peroxide were studied kinetically with guaiacol as co-substrate. The turnover number (r) of H2O2 required to complete the inactivation of the enzyme was 2154 ± 100 and the apparent rate constants of catalysis 185 s–1 and 18 s–1.
基金supported by the National Natural Science Foundation of China(Grant Nos.10802099,11272357 and 11102140)the Doctoral Fund of Ministry of Education of China(Grant No.20110141120024)+2 种基金the Natural Science Foundation of Shandong Province(Grant No.ZR2009AQ006)the Opening Project of State Key Laboratory of Explosion Science and Technology(Beijing Institute of Technology)(Grant No. KFJJ12-11M)the support from the Brain Korea 21 Program at Seoul National University
文摘In this study,we considered the wetting phenomenon on a general substrate from a new viewpoint of continuum mechanics.The analyses first show how the Wenzel and the Cassie models deviate the practical results in some special substrates,and then elucidate the mechanism of the triple contact line(TCL) moving.Based upon variational theory of the total free functional dealing with the movable boundary condition,we show that the macroscopic contact angle(MCA) expression is the corresponding transversality condition.It manifests that the MCA depends only on the chemical and geometric property at the TCL,and is not affected by the gravity of the droplet and the contact area beneath the liquid.Our continuum model also shows the exploration of the pinning effect on a sharp wedge or the interface between two different phases.This investigation will help designing super-hydrophobic materials for novel micro-fluidic devices.
基金supported by the National University Heart Centre Singapore (NUHCS) Cardiovascular Research Institute (CVRI)Core Fund [Grant NUHSRO/2019/082/Core]SCEPTRE CG Seed Grant [Grant NMRC/CG/M008/2017, Singapore]+2 种基金Singapore Ministry of Education Tier 1 Academic Research Funding [Grant R-148-000-193-112]the National University of Singapore, Department of Pharmacy, Final Year Project Funding [Grant C148-000-003-001] provided to Eric Chun Yong Chanfrom Japan Society for the Promotion of Science (JSPS) KAKENHI [grant number 20K16136] provided to Ryuichi Kambayashi
文摘Cytochrome P4502J2(CYP2J2)metabolizes arachidonic acid(AA)to cardioprotective epoxyeicosatrienoic acids(EETs).Dronedarone,an antiarrhythmic drug prescribed for treatment of atrial fibrillation(AF)induces cardiac adverse effects(AEs)with poorly understood mechanisms.We previously demonstrated that dronedarone inactivates CYP2J2 potently and irreversibly,disrupts AA-EET pathway leading to cardiac mitochondrial toxicity rescuable via EET enrichment.In this study,we investigated if mitigation of CYP2J2 inhibition prevents dronedarone-induced cardiac AEs.We first synthesized a deuterated analogue of dronedarone(termed poyendarone)and demonstrated that it neither inactivates CYP2J2,disrupts AA-EETs metabolism nor causes cardiac mitochondrial toxicity in vitro.Our patch-clamp experiments demonstrated that pharmacoelectrophysiology of dronedarone is unaffected by deuteration.Next,we show that dronedarone treatment or CYP2J2 knockdown in spontaneously beating cardiomyocytes indicative of depleted CYP2J2 activity exacerbates beat-to-beat(BTB)variability reflective of proarrhythmic phenotype.In contrast,poyendarone treatment yields significantly lower BTB variability compared to dronedarone in cardiomyocytes indicative of preserved CYP2J2 activity.Importantly,poyendarone and dronedarone display similar antiarrhythmic properties in the canine model of persistent AF,while poyendarone substantially reduces beat-to-beat variability of repolarization duration suggestive of diminished proarrhythmic risk.Our findings prove that deuteration of dronedarone prevents CYP2J2 inactivation and mitigates dronedarone-induced cardiac AEs.
基金supported in part by grants from the National Key Basic Research Program of China(No.2012CB944600)National Natural Science Foundation of China(No.81071028,81172513)Program for New Century Excellent Talents in University(No.NCET-10-0832).
文摘Background:Extensive research on fragile X mental retardation gene knockout mice and mutant Drosophila models has largely expanded our knowledge on mechanism-based treatment of fragile X syndrome(FXS).In light of these findings,several clinical trials are now underway for therapeutic translation to humans.Data sources:Electronic literature searches were conducted using the PubMed database and ClinicalTrials.gov.The search terms included"fragile X syndrome","FXS and medication","FXS and therapeutics"and"FXS and treatment".Based on the publications identified in this search,we reviewed the neuroanatomical abnormalities in FXS patients and the potential pathogenic mechanisms to monitor the progress of FXS research,from basic studies to clinical trials.Results:The pathological mechanisms of FXS were categorized on the basis of neuroanatomy,synaptic structure,synaptic transmission and fragile X mental retardation protein(FMRP)loss of function.The neuroanatomical abnormalities in FXS were described to motivate extensive research into the region-specific pathologies in the brain responsible for FXS behavioural manifestations.Mechanism-directed molecular medicines were classified according to their target pathological mechanisms,and the most recent progress in clinical trials was discussed.Conclusions:Current mechanism-based studies and clinical trials have greatly contributed to the development of FXS pharmacological therapeutics.Research examining the extent to which these treatments provided a rescue effect or FMRP compensation for the developmental impairments in FXS patients may help to improve the effi cacy of treatments.
