Hydroxysafflor yellow A protects neurons from excitotoxic death through inhibition of NMDA receptors
摘要：Excessive glutamate release causes over-activation of NMDARs, leading to excitatory neuronal damage in cerebral ischemia. HSYA, a compound extracted from Carthamus tinctorius L., has been reported to exert a neuroprotective effect in many pathological conditions, including brain ischemia. However, the underlying mechanism of HSYA’s effect on neurons remains elusive. In the present study we conducted experiments using patch-clamp recording of mouse hippocampal slices. In addition, we performed Ca2+ imaging, western blots, as well as mt-cp YFP transfection into cultured hippocampal neurons in order to decipher the physiological mechanism underlying HSYA’s neuroprotective effect. Through the electrophysiology experiments, we found that HSYA inhibited NMDAR-mediated excitatory postsynaptic currents（NMDAR EPSCs） without affecting AMPA and GABAA receptormediated currents. This inhibitory effect of HSYA on NMDARs was concentration-dependent. HSYA did not show any preferential inhibition of either NR2A- or NR2B- subunit-containing NMDARs. Additionally, HSYA exhibits a facilitatory effect on paired NMDAR EPSCs. Furthermore, HSYA reduced the magnitude of NMDAR-mediated membrane depolarization currents evoked by oxygen-glucose-deprivation（OGD）, and suppressed OGD-induced and NMDAR-dependent ischemic long-term potentiation（i-LTP）, which is believed to cause severe reperfusion damage after ischemia. Through the molecular biology experiments, we found that HSYA inhibited the NMDA-induced and NMDAR-mediated intracellular Ca2+ concentration([Ca2+]i) increase in hippocampal cultures, reduced apoptotic and necrotic cell deaths, and prevented mitochondrial damage. Together, our data demonstrate for the first time that HSYA protects hippocampal neurons from excitotoxic damage through the inhibition of NMDARs. This novel finding indicates that HSYA may be a promising pharmacological candidate for the treatment of brain ischemia.