SEA0400, a novel and selective inhibitor of the Na+-Ca2+ exchanger, attenuates reperfusion injury in the in vitro and in vivo cerebral ischemic models

The effect of the newly synthesized compound 2-[4-[(2,5-difluorophenyl)meth oxy] phenoxy]-5-ethoxyaniline (SEA0400) on the Na+-Ca2+ exchanger (NCX) was investigated and compared against that of 2-[2-[4-(4-nitrobenzyloxy)phenyl ]ethyl]iso thiourea (KB-R7943). In addition, the effects of SEA0400 on repe rfusion injury in vitro and in vivo were examined. SEA0400 was extremely mo re potent than KB-R7943 in inhibiting Nat dependent Ca2+ uptake in cultured neurons, astrocytes, and microglia: IC(50)s of SEA0400 and KB-R7943 were 5 to 33 nM and 2 to 4 muM, respectively. SEA0400 at the concentration range that inhibited NCX exhibited negligible affinities for the Ca2+ channels, N a+ channels, K+ channels, norepinephrine transporter, and 14 receptors, and did not affect the activities of the Na+/H+ exchanger, Na+,K+-ATPase, Ca2-ATPase, and five enzymes. SEA0400, unlike KB-R7943, did not inhibit the st ore-operated Ca2+ entry in cultured astrocytes. SEA0400 attenuated dose-dep endently paradoxical Ca2+ challenge-induced production of reactive oxygen s pecies, DNA ladder formation, and nuclear condensation in cultured astrocyt es, whereas it did not affect thapsigargin-induced cell injury. Furthermore , administration of SEA0400 reduced infarct volumes after a transient middl e cerebral artery occlusion in rat cerebral cortex and striatum. These resu lts indicate that SEA0400 is the most potent and selective inhibitor of NCX , and suggest that the compound may exert protective effects on postischemi c brain damage.