Cholesterol deficiency increases the vulnerability of hippocampal glia in primary culture to glutamate-induced excitotoxicity.

Cholesterol, a molecule critical for cellular function, is found in particular high concentration in the brain and has been implicated to synaptic plasticity and neuronal regeneration. This study was undertaken to investigate the mechanism by which cholesterol shortage modulates glutamate (Glu)-induced excitotoxicity in hippocampal cell cultures. A combined treatment of lovastatin and beta-cyclodextrin reduced cellular content of cholesterol while having no significant effect on cell viability in neuron/glia mixed cultures. The experimental manipulation, nonetheless, exacerbated Glu-induced membrane damage and loss of mitochondrial activity in mixed cultures. Analysis of [3H]thymidine incorporation revealed cholesterol deficiency impaired cell proliferation in mixed cultures after Glu exposure, indicating considerable loss of glia. Indeed, it was found that cholesterol deprivation potentiated the release of lactate dehydrogenase (LDH) and the impairment in mitochondrial reduction of WST-1 reagent in astrocyte-enriched cultures subjected to Glu exposure. The detrimental effect of cholesterol shortage, nevertheless, was not observed in cultured neurons. Notably, the pretreatment of lovastatin and beta-cyclodextrin caused a decrease in the content of cellular LDH while having no effect on cell cycle profile and cellular activity of WST-1 reduction in astrocyte-enriched cultures. In contrast, removal of cholesterol had no effect on LDH content in neuron-enriched cultures. It is concluded that the differential vulnerability of cholesterol-depleted neural cells to excitotoxic damage may, in part, be ascribed to cholesterol shortage destabilizing the plasma membrane of astrocytes, thus rendering them less capable of withstanding Glu insult.