Role of Mitochondrial Protein, mitoNEET, in Impaired Intracellular Cholesterol Metabolism-Induced Neuronal Cell Death.

Parkinson's disease (PD) is a progressive neurological disorder with an unclear etiology. Nonetheless, abnormal cholesterol metabolism is considered an environmental risk factor. MitoNEET (mNT) is an iron-sulfur cluster protein located in the outer mitochondrial membrane. mNT dysfunction is involved in the pathology of several diseases, including PD. However, the cause of mNT dysfunction remains unclear. Therefore, we hypothesized that increased intracellular cholesterol levels may reduce mNT function and increase reactive oxygen species (ROS) levels, resulting in neuronal cell death and PD progression. In this study, we investigated the effects of cholesterol on cell viability and mNT levels in human neuroblastoma (SH-SY5Y) cells. Cholesterol reduced cell viability and mNT protein levels and increased ROS generation. Pioglitazone, an mNT activator, decreased cholesterol-induced ROS generation but did not rescue cell viability, suggesting that reduced mNT levels may be involved but are not the sole cause of cholesterol-induced cell death. Additionally, the viability of cells treated with rotenone, 6-hydroxydopamine, and 1-methyl-4-phenylpyridinium in the presence of cholesterol was measured. However, no significant enhancement in cell death was observed. Moreover, the toxic compounds did not reduce mNT levels, indicating that mNT is not involved in toxic compound-induced cell death. In summary, these results indicate that cholesterol induces cell death, reduces mNT protein levels without suppressing transcription, and increases ROS generation, which may affect PD development. Further assessment of the mechanisms associated with abnormal intracellular cholesterol metabolism, reduced mNT levels, and cell death may lead to the discovery of novel treatments for PD.