Set-up and molecular characterization of an in vitro model of chronic stress in BV2 microglial cells

Chronic stress is a major risk factor for the development of neuropsychiatric disorders and is characterized by prolonged activation of the HPA axis and glucocorticoid release. While acute glucocorticoid signalling promotes adaptive responses through mineralocorticoid (MR) and glucocorticoid receptors (GR) balance, chronic exposure leads to a dysregulated GR-driven state. Microglia, sensitive to stress hormones, are involved in the pathophysiology of such conditions and their resulting alterations, namely redox imbalance. To understand how chronic glucocorticoid exposure affects microglial function and the core mechanisms underlying stress-related conditions in vitro, I established a model of chronic stress using BV2 murine microglial cell line, treated for 96h with corticosterone, a rodent glucocorticoid. I observed increased GR nuclear levels and GR/MR ratio, suggesting GR-dominated signalling. However, nuclear pGR, necessary for transcriptional activity, and pGR/GR ratio are significantly decreased, suggesting a dysfunctional state. Moreover, I found an increase in nuclear pro-oxidant TXNIP1,2 and in catalase mRNA levels to compensate for its significantly decreased antioxidant activity, as measured according to a validated enzymatic essay3. Lastly, I observed upregulation of activation marker CD11b, further confirmed by cytofluorimetry, which also revealed distinct expression patterns corresponding to two populations with differential responsiveness and morphology.