Objective To explore the effects of exposure to aluminum （AI） on long-term potentiation （LTP） and AMPA receptor subunits in rats in vivo. Methods Different dosages of aluminum-maltolate complex [Al（mal）3] were g...Objective To explore the effects of exposure to aluminum （AI） on long-term potentiation （LTP） and AMPA receptor subunits in rats in vivo. Methods Different dosages of aluminum-maltolate complex [Al（mal）3] were given to rats via acute intracerebroventricular （i.c.v.） injection and subchronic intraperitoneal （i.p.） injection. Following AI exposure, the hippocampal LTP were recorded by field potentiation technique in vivo and the expression of AMPAR subunit proteins （GluR1 and GluR2） in both total and membrane-enriched extracts from the CA1 area of rat hippocampus were detected by Western blot assay. Results Acute AI treatment produced dose-dependent suppression of LTP in the rat hippocampus and dose-dependent decreases of GluRz and GluR2 in membrane extracts; however, no similar changes were found in the total cell extracts, which suggests decreased trafficking of AMPA receptor subunits from intracellular pools to synaptic sites in the hippocampus. The dose-dependent suppressive effects on LTP and the expression of AMPA receptor subunits both in the membrane and in total extracts were found after subchronic AI treatment, indicating a decrease in AMPA receptor subunit trafficking from intracellular pools to synaptic sites and an additional reduction in the expression of the subunits. Conclusion Al（mal）3 obviously and dose-dependently suppressed LTP in the rat hippocampal CA1 region in vivo, and this suppression may be related to both trafficking and decreases in the expression of AMPA receptor subunit proteins. However, the mechanisms underlying these observations need further investigation.展开更多
To study the effect of glutamate on the intracellular calcium signal of pure cultured rat astrocytes and the role of NMDA and AMPA receptors in the procedure, the change of calcium signal was investigated by monitorin...To study the effect of glutamate on the intracellular calcium signal of pure cultured rat astrocytes and the role of NMDA and AMPA receptors in the procedure, the change of calcium signal was investigated by monitoring the fluctuation of intracellular Ca 2+ concentration ([Ca 2+ ] i) on the basis of Fura-2 single cell fluorescent ratio (F345/F380). The changes in the effect of glutamate on the intracellular calcium signal were observed after blockage of NMDA and(or) AMPA receptors. It was found that L-glutamate could induce an increased [Ca 2+ ] i in most of the cells in concentration- and time-dependent manner. D-(-)-2-amino-5-phosphonopentanoic acid (D-AP-5, a selective antagonist of the NMDA receptor) and 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX, a selective antagonist of the AMPA receptor) could abolish the effects of NMDA and AMPA respectively. The treatment of D-AP-5 and CNQX simultaneously or respectively could attenuate the effect of L-glutamate at varying degrees. All these indicated that glutamate could modulate intracellular Ca 2+ of pure cultured rat astrocytes through different pathways. The activation of NMDA and AMPA receptors took part in the complex mechanisms.展开更多
OBJECTIVE Respiratory depression hinders the use of anaesthetics and sedative hyp.notics.To explore the mechanism of LCX001 on protection against respiratory depression,a novel AMPA receptor modulator LCX001,synthesiz...OBJECTIVE Respiratory depression hinders the use of anaesthetics and sedative hyp.notics.To explore the mechanism of LCX001 on protection against respiratory depression,a novel AMPA receptor modulator LCX001,synthesized by our Institute of Medicinal Chemistry,is expected to relieve suppressed respiration.METHODS LCX001 was tested to alleviate respiratory depression triggered by opioid(fentanyl and TH-030418),propofol and pentobarbital in the plethysmography recording.The acetic acid writhing and hot-plate tests were conducted to evaluate analgesic effect of LCX001.Binding assay and whole-cell recording were used to analyze the property of LCX001 on positive modulation.The function of AMPA receptors were determined by location of receptors in the membrane and state of channel opening,and both processes were impressed by AMPA receptor regulatory proteins.Ac.cording to the theory,the effect of LCX001 on the expression of stargazin was measured firstly by west.ern blotting.The variation of receptor surface location was observed by live cell imaging.The regula.tion on neuronal Ca^(2+) and cell function was investigated intensively by Ca^(2+) imaging to clarify mecha.nism of LCX001.RESULTS LCX001 effectively rescued and prevented opioid(fentanyl and TH-030418),propofol,and pentobarbital-induced respiratory depression by strengthening respiratory fre.quency and minute ventilation in rats.The acetic acid writhing test and hot-plate test revealed potent anti-nociceptive efficacy of LCX001,in contrast to some ampakines that did not affect analgesia.Fur.thermore,LCX001 potentiated [3 H]AMPA and L-glutamate binding affinity to AMPA receptors,and facili.tated glutamate-evoked inward currents in HEK293 cells stably expressing GluA2(R).Importantly,appli.cation of LCX001 generated a significant increase in GluA2(R) surface expression in a mechanism of stargazin up-regulation,and restrained opioid-induced abnormal intracellular Ca^(2+) load,which might par.ticipate in breathing modulation.CONCLUSION The novel pharmacological effect and potential new mechanism of LCX001 might promote ampakines to be a therapeutic option for protection against respi.ratory depression.展开更多
OBJECTIVE Respiratory depression hinders the use of anaesthetics and sedative hypnotics.For emergency use,specific antagonists are currently administered to counteract respiratory depression.However,antagonists are of...OBJECTIVE Respiratory depression hinders the use of anaesthetics and sedative hypnotics.For emergency use,specific antagonists are currently administered to counteract respiratory depression.However,antagonists are often short-lasting and can have multiple unexpected side effects.A novel AMPA receptor modulator LCX001,synthesized by our Institute of Medicinal Chemistry,is expected to relieve suppressed respiration.To explore the mechanism and impact of LCX001 on protection against respiratory depression.METHODS LCX001 was tested to alleviate respiratory depression triggered by opioid,propofol and pentobarbital in the plethysmography recording.The acetic acid writhing and hot-plate tests were conducted to evaluate potential analgesic effect of LCX001.Binding assay and whole-cell recording were used to analyze the property of LCX001 on positive modulation.The function of AMPA receptors were determined by location of receptors inthe membrane and state of channel opening,and both processes were impressed by AMPA receptor regulatory proteins.According to the theory,the effect of LCX001 on the expression of stargazin was measured firstly by Western blotting.The variation of receptor surface location were observed by live cell imaging.The regulation on neuronal Ca2+and cell function was investigated intensively by Ca2+imaging to clarify mechanism of LCX001.RESULTS LCX001 effectively rescued and prevented opioid(fentanyl and TH-030418),propofol,and pentobarbitalinduced respiratory depression by strengthening respiratory frequency and minute ventilation by 30%-50% in rats.The acetic acid writhing test and hot-plate test revealed potent anti-nociceptive efficacy of LCX001 on increasing the inhibition rate and %MPE to 80% and 65% respectively,in contrast to some ampakines that did not affect analgesia.Furthermore,LCX001 potentiated[3 H]AMPA and L-glutamate binding affinity to AMPA receptors,and facilitated glutamateevoked inward currents in HEK293 cells stably expressing GluA2(R).At 10 mmol·L^(-1) glutamate evoked amplitudes,LCX001 at 100 μmol·L^(-1) increased the potency of glutamate induced currents by(1120 ± 60) pA,compared with that of(752 ± 35) pA in the control group.LCX001 also prominently promoted steady state/peak amplitude ratio.LCX001 significantly slowed down the desensitization rates of the AMPA ion channel,and inhibited current decay.Importantly,application of LCX001 generated a significant increase in GluA2(R) surface expression in a mechanism of stargazin up-regulation,and restrained opioidinduced abnormal intracel ular Ca2+load,which might participate in breathing modulation.CONCLUSION The typical positive modulatory impact and potential new mechanism of LCX001 might promote ampakines to be a therapeutic option for protection against respiratory depression.展开更多
Glutamate acting on AMPA-type ionotropic glutamate receptor(AMPAR) mediates the majority of fast excitatory synaptic transmission in the mammalian central nervous system. Dynamic regulation of AMPAR by post-translatio...Glutamate acting on AMPA-type ionotropic glutamate receptor(AMPAR) mediates the majority of fast excitatory synaptic transmission in the mammalian central nervous system. Dynamic regulation of AMPAR by post-translational modifications is one of the key elements that allow the nervous system to adapt to environment stimulations. S-palmitoylation, an important lipid modification by post-translational addition of a long-chain fatty acid to a cysteine residue, regulates AMPA receptor trafficking, which dynamically affects multiple fundamental brain functions, such as learning and memory. In vivo, S-palmitoylation is controlled by palmitoyl acyl transferases and palmitoyl thioesterases.In this review, we highlight advances in the mechanisms for dynamic AMPA receptors palmitoylation,and discuss how palmitoylation affects AMPA receptors function at synapses in recent years.Pharmacological regulation of S-palmitoylation may serve as a novel therapeutic strategy for neurobiological diseases.展开更多
Background Activation of N-methyl-D-aspartate （NMDA） receptors and alpha-amino-3-hydroxy-5-methyl- 4-isoxazole-propionic acid （AMPA） receptors play an important role in the neurons death induced by ischemia. The m...Background Activation of N-methyl-D-aspartate （NMDA） receptors and alpha-amino-3-hydroxy-5-methyl- 4-isoxazole-propionic acid （AMPA） receptors play an important role in the neurons death induced by ischemia. The mitigating effect of intravenous anesthetics on ischemic neuron injury is related to their influence on NMDA receptors. This study was performed to investigate the effect of ketamine-midazolam anesthesia on the NMDA and AMPA receptor subunits expression in the peri-infarction of ischemic rat brain and explore its potential mechanism of neuroprotection. Methods Thirty Sprague Dawley （SD） rats were subjected to permanent middle cerebral artery occlusion under ketamine/atropine （100/0.05 mg/kg） or ketamine-midazolam/atropine （60/50/0.05 mg/kg） intraperitoneal anesthesia （n=15 each）. Twenty-four hours after ischemia, five rats in each group were killed by injecting the above dosage of ketamine or ketamine-midazolam intraperitoneally and infarct size was measured. Twenty-four and 72 hours after ischemia, four rats in each group were killed by injecting the above dosage of ketamine or ketamine-midazolam intraperitoneally. After staining the brain tissue slices with toluidine blue, the survived neurons in the peri-infarction were observed. Also, the expression level of NMDA receptors 1 （NR1）, NMDA receptors 2A （NR2A）, NMDA receptors 2B （NR2B） and AMPA （GluR1 subunit） were determined by grayscale analysis in immunohistochemical stained slices. Results Compared with ketamine anesthesia, ketamine-midazolam anesthesia produced not only smaller infarct size [（24.1±4.6）% vs （38.4±4.2）%, P〈0.05], but also higher neuron density （24 hours： 846±16 vs 756±24, P〈0.05; 72 hours： 882±22 vs 785± 18, P〈0.05） and lower NR2A （24 hours： 123.0±4.9 vs 95.0±2.5, P〈 0.05; 72 hours： 77.8±4.1 vs 54.2±3.9, P〈0.05） and NR2B （24 hours： 98.5±2.7 vs 76.3±2.4, P〈0.05; 72 hours： 67.2±7.5 vs 22.2± 2.6, P〈0.05） expression level in the peri-infarction following ischemia. Conclusion The protective effects of ketamine-midazolam anesthesia on ischemic brain injury may relate to decreasing NR2A and NR2B expression.展开更多
2,3-Benzodiazepine(2,3-BDZ) compounds represent a group of structurally diverse,smallmolecule antagonists of(R,S)-2-amino-3-(3-hydroxy-5-methyl-4-isoxazolyl)propionic acid(AMPA)receptors.Antagonists of AMPA receptors ...2,3-Benzodiazepine(2,3-BDZ) compounds represent a group of structurally diverse,smallmolecule antagonists of(R,S)-2-amino-3-(3-hydroxy-5-methyl-4-isoxazolyl)propionic acid(AMPA)receptors.Antagonists of AMPA receptors are drug candidates for potential treatment of a number of neurological disorders such as epilepsy,stroke and amyotrophic lateral sclerosis(ALS).How to make better inhibitors,such as 2,3-BDZs,has been an enduring quest in drug discovery.Among a few available tools to address this specific question for making better 2,3-BDZs,perhaps the best one is to use mechanistic clues from studies of the existing antagonists to design and discover more selective and more potent antagonists.Here I review recent work in this area,and propose some ideas in the continuing effort of developing newer 2,3-BDZs for tighter control of AMPA receptor activities in vivo.展开更多
基金supported by the Natural Science Foundation of China(NSFC,30972512 and 81202182)the Research Foundation for the Doctoral Program of Higher Education(20121417110002)
文摘Objective To explore the effects of exposure to aluminum （AI） on long-term potentiation （LTP） and AMPA receptor subunits in rats in vivo. Methods Different dosages of aluminum-maltolate complex [Al（mal）3] were given to rats via acute intracerebroventricular （i.c.v.） injection and subchronic intraperitoneal （i.p.） injection. Following AI exposure, the hippocampal LTP were recorded by field potentiation technique in vivo and the expression of AMPAR subunit proteins （GluR1 and GluR2） in both total and membrane-enriched extracts from the CA1 area of rat hippocampus were detected by Western blot assay. Results Acute AI treatment produced dose-dependent suppression of LTP in the rat hippocampus and dose-dependent decreases of GluRz and GluR2 in membrane extracts; however, no similar changes were found in the total cell extracts, which suggests decreased trafficking of AMPA receptor subunits from intracellular pools to synaptic sites in the hippocampus. The dose-dependent suppressive effects on LTP and the expression of AMPA receptor subunits both in the membrane and in total extracts were found after subchronic AI treatment, indicating a decrease in AMPA receptor subunit trafficking from intracellular pools to synaptic sites and an additional reduction in the expression of the subunits. Conclusion Al（mal）3 obviously and dose-dependently suppressed LTP in the rat hippocampal CA1 region in vivo, and this suppression may be related to both trafficking and decreases in the expression of AMPA receptor subunit proteins. However, the mechanisms underlying these observations need further investigation.
基金ThisprojectwassupportedbyagrantfromNationalNaturalSciencesFoundationofChina (No .30 0 4 0 0 37)
文摘To study the effect of glutamate on the intracellular calcium signal of pure cultured rat astrocytes and the role of NMDA and AMPA receptors in the procedure, the change of calcium signal was investigated by monitoring the fluctuation of intracellular Ca 2+ concentration ([Ca 2+ ] i) on the basis of Fura-2 single cell fluorescent ratio (F345/F380). The changes in the effect of glutamate on the intracellular calcium signal were observed after blockage of NMDA and(or) AMPA receptors. It was found that L-glutamate could induce an increased [Ca 2+ ] i in most of the cells in concentration- and time-dependent manner. D-(-)-2-amino-5-phosphonopentanoic acid (D-AP-5, a selective antagonist of the NMDA receptor) and 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX, a selective antagonist of the AMPA receptor) could abolish the effects of NMDA and AMPA respectively. The treatment of D-AP-5 and CNQX simultaneously or respectively could attenuate the effect of L-glutamate at varying degrees. All these indicated that glutamate could modulate intracellular Ca 2+ of pure cultured rat astrocytes through different pathways. The activation of NMDA and AMPA receptors took part in the complex mechanisms.
基金supported by Major Science and Technology Project of China(2015ZX09501003)
文摘OBJECTIVE Respiratory depression hinders the use of anaesthetics and sedative hyp.notics.To explore the mechanism of LCX001 on protection against respiratory depression,a novel AMPA receptor modulator LCX001,synthesized by our Institute of Medicinal Chemistry,is expected to relieve suppressed respiration.METHODS LCX001 was tested to alleviate respiratory depression triggered by opioid(fentanyl and TH-030418),propofol and pentobarbital in the plethysmography recording.The acetic acid writhing and hot-plate tests were conducted to evaluate analgesic effect of LCX001.Binding assay and whole-cell recording were used to analyze the property of LCX001 on positive modulation.The function of AMPA receptors were determined by location of receptors in the membrane and state of channel opening,and both processes were impressed by AMPA receptor regulatory proteins.Ac.cording to the theory,the effect of LCX001 on the expression of stargazin was measured firstly by west.ern blotting.The variation of receptor surface location was observed by live cell imaging.The regula.tion on neuronal Ca^(2+) and cell function was investigated intensively by Ca^(2+) imaging to clarify mecha.nism of LCX001.RESULTS LCX001 effectively rescued and prevented opioid(fentanyl and TH-030418),propofol,and pentobarbital-induced respiratory depression by strengthening respiratory fre.quency and minute ventilation in rats.The acetic acid writhing test and hot-plate test revealed potent anti-nociceptive efficacy of LCX001,in contrast to some ampakines that did not affect analgesia.Fur.thermore,LCX001 potentiated [3 H]AMPA and L-glutamate binding affinity to AMPA receptors,and facili.tated glutamate-evoked inward currents in HEK293 cells stably expressing GluA2(R).Importantly,appli.cation of LCX001 generated a significant increase in GluA2(R) surface expression in a mechanism of stargazin up-regulation,and restrained opioid-induced abnormal intracellular Ca^(2+) load,which might par.ticipate in breathing modulation.CONCLUSION The novel pharmacological effect and potential new mechanism of LCX001 might promote ampakines to be a therapeutic option for protection against respi.ratory depression.
基金National Science and Technology Major Project of China (2015ZX09501003).
文摘OBJECTIVE Respiratory depression hinders the use of anaesthetics and sedative hypnotics.For emergency use,specific antagonists are currently administered to counteract respiratory depression.However,antagonists are often short-lasting and can have multiple unexpected side effects.A novel AMPA receptor modulator LCX001,synthesized by our Institute of Medicinal Chemistry,is expected to relieve suppressed respiration.To explore the mechanism and impact of LCX001 on protection against respiratory depression.METHODS LCX001 was tested to alleviate respiratory depression triggered by opioid,propofol and pentobarbital in the plethysmography recording.The acetic acid writhing and hot-plate tests were conducted to evaluate potential analgesic effect of LCX001.Binding assay and whole-cell recording were used to analyze the property of LCX001 on positive modulation.The function of AMPA receptors were determined by location of receptors inthe membrane and state of channel opening,and both processes were impressed by AMPA receptor regulatory proteins.According to the theory,the effect of LCX001 on the expression of stargazin was measured firstly by Western blotting.The variation of receptor surface location were observed by live cell imaging.The regulation on neuronal Ca2+and cell function was investigated intensively by Ca2+imaging to clarify mechanism of LCX001.RESULTS LCX001 effectively rescued and prevented opioid(fentanyl and TH-030418),propofol,and pentobarbitalinduced respiratory depression by strengthening respiratory frequency and minute ventilation by 30%-50% in rats.The acetic acid writhing test and hot-plate test revealed potent anti-nociceptive efficacy of LCX001 on increasing the inhibition rate and %MPE to 80% and 65% respectively,in contrast to some ampakines that did not affect analgesia.Furthermore,LCX001 potentiated[3 H]AMPA and L-glutamate binding affinity to AMPA receptors,and facilitated glutamateevoked inward currents in HEK293 cells stably expressing GluA2(R).At 10 mmol·L^(-1) glutamate evoked amplitudes,LCX001 at 100 μmol·L^(-1) increased the potency of glutamate induced currents by(1120 ± 60) pA,compared with that of(752 ± 35) pA in the control group.LCX001 also prominently promoted steady state/peak amplitude ratio.LCX001 significantly slowed down the desensitization rates of the AMPA ion channel,and inhibited current decay.Importantly,application of LCX001 generated a significant increase in GluA2(R) surface expression in a mechanism of stargazin up-regulation,and restrained opioidinduced abnormal intracel ular Ca2+load,which might participate in breathing modulation.CONCLUSION The typical positive modulatory impact and potential new mechanism of LCX001 might promote ampakines to be a therapeutic option for protection against respiratory depression.
基金supported by grants from the National Basic Research Program of China (the 973 Program, No. 2013CB531303 to Dr. Jianguo Chen No. 2014CB744601 to Fang Wang)+3 种基金the National Natural Scientific Foundation of China (NSFC, No. 81222048 to Fang Wang No. 81302754 to Peng Fei Wu)supported by the International Science & Technology Cooperation Program of China (No. 2011DFA32670 to Jianguo Chen)PCSIRT (No. IRT13016)
文摘Glutamate acting on AMPA-type ionotropic glutamate receptor(AMPAR) mediates the majority of fast excitatory synaptic transmission in the mammalian central nervous system. Dynamic regulation of AMPAR by post-translational modifications is one of the key elements that allow the nervous system to adapt to environment stimulations. S-palmitoylation, an important lipid modification by post-translational addition of a long-chain fatty acid to a cysteine residue, regulates AMPA receptor trafficking, which dynamically affects multiple fundamental brain functions, such as learning and memory. In vivo, S-palmitoylation is controlled by palmitoyl acyl transferases and palmitoyl thioesterases.In this review, we highlight advances in the mechanisms for dynamic AMPA receptors palmitoylation,and discuss how palmitoylation affects AMPA receptors function at synapses in recent years.Pharmacological regulation of S-palmitoylation may serve as a novel therapeutic strategy for neurobiological diseases.
基金This study was supported by National Natural Science Foundation of China （NSFC） （No.30200291）.
文摘Background Activation of N-methyl-D-aspartate （NMDA） receptors and alpha-amino-3-hydroxy-5-methyl- 4-isoxazole-propionic acid （AMPA） receptors play an important role in the neurons death induced by ischemia. The mitigating effect of intravenous anesthetics on ischemic neuron injury is related to their influence on NMDA receptors. This study was performed to investigate the effect of ketamine-midazolam anesthesia on the NMDA and AMPA receptor subunits expression in the peri-infarction of ischemic rat brain and explore its potential mechanism of neuroprotection. Methods Thirty Sprague Dawley （SD） rats were subjected to permanent middle cerebral artery occlusion under ketamine/atropine （100/0.05 mg/kg） or ketamine-midazolam/atropine （60/50/0.05 mg/kg） intraperitoneal anesthesia （n=15 each）. Twenty-four hours after ischemia, five rats in each group were killed by injecting the above dosage of ketamine or ketamine-midazolam intraperitoneally and infarct size was measured. Twenty-four and 72 hours after ischemia, four rats in each group were killed by injecting the above dosage of ketamine or ketamine-midazolam intraperitoneally. After staining the brain tissue slices with toluidine blue, the survived neurons in the peri-infarction were observed. Also, the expression level of NMDA receptors 1 （NR1）, NMDA receptors 2A （NR2A）, NMDA receptors 2B （NR2B） and AMPA （GluR1 subunit） were determined by grayscale analysis in immunohistochemical stained slices. Results Compared with ketamine anesthesia, ketamine-midazolam anesthesia produced not only smaller infarct size [（24.1±4.6）% vs （38.4±4.2）%, P〈0.05], but also higher neuron density （24 hours： 846±16 vs 756±24, P〈0.05; 72 hours： 882±22 vs 785± 18, P〈0.05） and lower NR2A （24 hours： 123.0±4.9 vs 95.0±2.5, P〈 0.05; 72 hours： 77.8±4.1 vs 54.2±3.9, P〈0.05） and NR2B （24 hours： 98.5±2.7 vs 76.3±2.4, P〈0.05; 72 hours： 67.2±7.5 vs 22.2± 2.6, P〈0.05） expression level in the peri-infarction following ischemia. Conclusion The protective effects of ketamine-midazolam anesthesia on ischemic brain injury may relate to decreasing NR2A and NR2B expression.
基金supported by NIH/NINDS Grant R01 NS060812a grant from Muscular Dystrophy Association(MDA)
文摘2,3-Benzodiazepine(2,3-BDZ) compounds represent a group of structurally diverse,smallmolecule antagonists of(R,S)-2-amino-3-(3-hydroxy-5-methyl-4-isoxazolyl)propionic acid(AMPA)receptors.Antagonists of AMPA receptors are drug candidates for potential treatment of a number of neurological disorders such as epilepsy,stroke and amyotrophic lateral sclerosis(ALS).How to make better inhibitors,such as 2,3-BDZs,has been an enduring quest in drug discovery.Among a few available tools to address this specific question for making better 2,3-BDZs,perhaps the best one is to use mechanistic clues from studies of the existing antagonists to design and discover more selective and more potent antagonists.Here I review recent work in this area,and propose some ideas in the continuing effort of developing newer 2,3-BDZs for tighter control of AMPA receptor activities in vivo.
