Hydrochloride Iptakalim Neuroprotective Role In Its Pharmacological Mechanism

Stroke is the common disease that harms public health seriously. At present, there is no ideal agent to treat this disease clinically. Neuronal ATP-sensitive potassium channel (KATP), which couples the energy metabolism with electrical activity of neuron, is the one of the targets of neuroprotective agents. Iptakalim hydrochloride (Ipt), a compound with low molecular weight, can pass the blood-brain barrier, active KATP and possess anti-ischemic effects. Based on previous findings, we investigated the neuropretectve effects of Ipt and possible pharmacological mechanism in the present study.I. Neuroprotective effects of iptakalim hydrochlorideIptakalim hydrochloride 0.1nmol.L-1-100umol.L-1 protected cultured PC12 cells from glutamate-induced cycotoxity dose-dependently, increased the cellular survival and decreased the LDH release. This effect could be antagonized by 10p.mol.L-1 glibenclamide, the KATP channels blocker.The primary cultured cortical neurons subjected to hypoxia were used to investigate the protective effect of iptakalim hydrochloride. The results showed that hypoxia and reoxygenation medium induced apoptosis in primary culture cortical neurons. The damage also caused a decrease of Bcl-2 expression and an increase of Bax expression in rat hippocampus neurons with immunocellular chemistry technique. Iptakalim hydrochloride resulted in increasing the cellular survival, decreasing chromatin condensation, up-regulating Bcl-2 expression, this suggests that iptakalim hydrochloride exerts certain neuroprotective effects through activating KATP and regulating the Bcl-2 expression.II. Effects of iptakalim hydrochloride on Na+, Ca2+, K+ channels in cultured primary rat hippocampus neurons.Iptakalim hydrochloride had no significant effect on Na+, Ca2+ currents, but significantly increased the outward K+ currents. This enhancement of iptakalim hydrochloride was inhibited by synchronously application of glibenclamide. These data suggested iptakalim hydrochloride could active KATP selectively.III.Effects of iptakalim hydrochloride on glutamate systemIptakalim hydrochloride was shown to inhibit glutamate release from PC 12 cells in a concentration-dependent manner and increase glutamate uptake. The effects could be antagonized by glibenclamide, the KATP channels blocker.Iptakalim hydrochloride suppressed the glutamate-evoke currents and NMDA-evoke currents on cultured hippocampus neurons, which effects were antagonized by 30 umol.L-1 glibenclamide.Iptakalim hydrochloride resulted in inhibiting the sEPSCs in cultured rat hippocampus neurons, decreased both the frequency and amplitude in a concentration-dependent manner, but had no effect on mEPSCs.The results suggested iptakalim hydrochloride, through activing KATP, could inhibit glutamate release, improve glutamate reuptake, block the function of glutamate receptor, and thus attenuate the glutamatergic transmission in cerebral neurons and exerting anti-excitotoxic effect.In conclusion:1. Iptakalim hydrochloride possesses neuroprotective effects on glutamate-induced excitotoxicity in PC 12 cell and hypoxic injuring in cultured cortical neurons.2. Activating neuronal ATP-sensitive potassium channels and thus inhibiting glutamate-induced excitotoxicity is the key pharmacological mechanism for neuroproective effects of iptakalim hydrochloride.3. Iptakalim hydrochloride exerts certain protective effects on the neuronal apoptosis by hypoxic injury through regulating the Bcl-2 expression, which could be decreased by hypoxic insults.4. Iptakalim hydrochloride, with no significant effects on sodium and calcium channels, could activate ATP-sensitive potassium channels selectively.5. The anti-excitotoxic effect of iptakalim hydrochloride is related to activation of ATP-sensitive potassium channels. Its pharmacological property includes inhibiting glutamate release, improving glutamate reuptake, blocking the function of glutamate receptor, thus attenuating the glutamatergi...