Neurosteroids and Translocator Protein (TSPO) in neuroinflammation.

Neurosteroids have a crucial role in physiological intrinsic regulations of the Central Nervous System functions. They are derived from peripheral steroidogenic sources and from the de novo neurosteroidogenic capacity of brain cells. Significant alterations of neurosteroid levels have been frequently observed in neuroinflammation and neurodegenerative diseases.

Human oligodendrocyte-like cell differentiation is promoted by TSPO-mediated endogenous steroidogenesis.

Mature oligodendrocytes (OLs) arise from oligodendrocyte precursor cells that, in case of demyelination, are recruited at the lesion site to remyelinate the axons and therefore restore the transmission of nerve impulses. It has been widely documented that exogenously administered steroid molecules are potent inducers of myelination. However, little is known about how neurosteroids produced de novo by OLs can impact this process.

The human microglial surveillant phenotype is preserved by de novo neurosteroidogenesis through the control of cholesterol homeostasis: Crucial role of 18 kDa Translocator Protein.

Neurodegenerative disease-associated microglia commonly exhibit harmful cholesterol accumulation that impairs their ability to resolve the neuroinflammatory response, contributing to disease onset and progression. Neurosteroids, whose levels have been often found significantly altered in brain diseases, are the most potent endogenous anti-inflammatory molecules exerting beneficial effects on activities of brain cells, including microglia. For the first time, the impact of neurosteroidogenesis on cholesterol homeostasis for the immune surveillance phenotype maintenance was investigated in a human microglia in vitro model.