An Na+/H+ exchanger inhibitor suppresses cellular swelling and neuronal death induced by glutamate in cultured cortical neurons

Abstract

We examined the effects of a selective Na⁺/H⁺ exchanger inhibitor, SM-20220 (N-(aminoiminomethyl)-1-methyl-1H-indole-2-carboxamide methanesulfonate), on neuronal death induced by glutamate in rat cortical neurons. Morphological changes in neurons were observed with a differential interference contrast microscope, and cellular swelling was analysed. Neuronal death was assessed by staining the cell with propidium iodide. The intracellular calcium concentration ([Ca²⁺]_i) and the intracellular pH were measured by fluorescence imaging with fluo-3/AM as an indicator for [Ca²⁺]_i and BCECF/AM for pH, respectively. SM-20220 (0.3 to 30 nM) dose-dependently attenuated glutamate (300 μM)-induced neuronal death in a dose-dependent fashion over 6 hours, and inhibited acute cellular swelling following glutamate (100 μM) exposure. SM-20220 suppressed the persistent [Ca²⁺]_i increase following glutamate (500 μM) exposure, and inhibited intracellular acidification induced by glutamate (1 mM). The activation of the Na⁺/H⁺ exchanger system may enhance the progress of cerebral damage and oedema following glutamate exposure. SM-20220, a Na⁺/H⁺ exchanger inhibitor, suppressed neuronal death and cellular swelling induced by glutamate through inhibition of both Ca²⁺ influx and acidification in neurons.