Abstract

The effect of the newly synthesized compound 2-[4-[(2,5-difluorophenyl)methoxy]phenoxy]-5-ethoxyaniline (SEA0400) on the Na⁺-Ca²⁺ exchanger (NCX) was investigated and compared against that of 2-[2-[4-(4-nitrobenzyloxy)phenyl]ethyl]isothiourea (KB-R7943). In addition, the effects of SEA0400 on reperfusion injury in vitro and in vivo were examined. SEA0400 was extremely more potent than KB-R7943 in inhibiting Na⁺-dependent Ca²⁺uptake in cultured neurons, astrocytes, and microglia: IC₅₀s of SEA0400 and KB-R7943 were 5 to 33 nM and 2 to 4 μM, respectively. SEA0400 at the concentration range that inhibited NCX exhibited negligible affinities for the Ca²⁺ channels, Na⁺ 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 store-operated Ca²⁺ entry in cultured astrocytes. SEA0400 attenuated dose- dependently paradoxical Ca²⁺challenge-induced production of reactive oxygen species, DNA ladder formation, and nuclear condensation in cultured astrocytes, whereas it did not affect thapsigargin-induced cell injury. Furthermore, administration of SEA0400 reduced infarct volumes after a transient middle cerebral artery occlusion in rat cerebral cortex and striatum. These results indicate that SEA0400 is the most potent and selective inhibitor of NCX, and suggest that the compound may exert protective effects on postischemic brain damage.