ABSTRACT
Analgesics and sedative hypnotics in clinical use often give rise to significant side effects, particularly respiratory depression. For emergency use, specific antagonists are currently administered to counteract respiratory depression. However, antagonists are often short-lasting and eliminate drug generated analgesia. To resolve this issue, novel positive AMPA modulators, LCX001, was tested to alleviate respiratory depression triggered by different drugs. The acetic acid writhing and hot-plate test were conducted to evaluate analgesic effect of LCX001. Binding assay, whole-cell recording, live cell imaging, and Ca2+ imaging were used to clarify mechanism and impact of LCX001 on respiratory protection. Results showed that LCX001 effectively rescued and prevented opioid (fentanyl and TH-030418), propofol, and pentobarbital-induced respiratory depression by strengthening respiratory frequency and minute ventilation. The acetic acid writhing test and hot-plate test revealed potent anti-nociceptive efficacy of LCX001, in contrast to other typical ampakines that did not affect analgesia. Furthermore, LCX001 potentiated [3H]AMPA and L-glutamate binding affinity to AMPA receptors, and facilitated glutamate-evoked inward currents in HEK293 cells stably expressing GluA2(R). LCX001 had a typical positive modulatory impact on AMPAR-mediated function. Importantly, application of LCX001 generated a significant increase in GluA2(R) surface expression, and restrained opioid-induced abnormal intracellular Ca2+ load, which might participate in breathing modulation. Our study improves therapeutic interventions for the treatment of drug induced respiratory depression, and increases understanding of potential mechanism of AMPA receptor modulators.
ABSTRACT
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 Ca2+and cell function was investigated intensively by Ca2+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[3H]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 Ca2+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.
