Cytochalasins protect hippocampal neurons against amyloid beta-peptide toxicity: evidence that actin depolymerization suppresses Ca2+ influx.

Increasing data suggest that the amyloid beta-peptide (A beta), which accumulates in the brains of Alzheimer's victims, plays a role in promoting neuronal degeneration. Cell culture studies have shown that A beta can be neurotoxic and recent findings suggest that the mechanism involves destabilization of cellular calcium homeostasis. We now report that cytochalasin D, a compound that depolymerizes actin microfilaments selectively, protects cultured rat hippocampal neurons against A beta neurotoxicity. Cytochalasin D was effective at concentrations that depolymerized actin (10-100 nM). The elevation of [Ca2+]i induced by A beta, and the enhancement of [Ca2+]i responses to glutamate in neurons exposed to A beta, were markedly attenuated in neurons pretreated with cytochalasin D. The protective effect of cytochalasin D appeared to result from a specific effect on actin filaments and reduction in calcium influx, because cytochalasin E, another actin filament-disrupting agent, also protected neurons against A beta toxicity; the microtubule-disrupting agent colchicine was ineffective; cytochalasin D did not protect neurons against the toxicity of hydrogen peroxide. These findings suggest that actin filaments play a role in modulating [Ca2+]i responses to neurotoxic insults and that depolymerization of actin can protect neurons against insults relevant to the pathogenesis of Alzheimer's disease.