EFFECTS OF ACUTE RESTRAINT STRESS ON TSPO EXPRESSION ACROSS DIFFERENT BRAIN CELL TYPES

Stress is a major public health issue linked to physical and mental disorders, and efficient treatment of stress-related disorders is still a major challenge. Accumulating evidence supports a critical role for the translocator protein (TSPO) in mediating stress-related responses, with its ligands emerging as promising alternative therapeutic options. TSPO is mainly located on the outer mitochondrial membrane. Under normal conditions, it is predominantly expressed in microglia and endothelial cells. Activation of TSPO through ligands such as etifoxine has been shown to stimulate the biosynthesis of endogenous neurosteroids, including allopregnanolone, which exert anxiolytic effects. Our goal is to elucidate the effects of stress on TSPO in brain regions susceptible to stress. 3-month-old wild-type mice underwent restraint stress for 3.5 hours, followed by a battery of behavioral tests: Y-maze, Zero maze, and Open field to evaluate memory, anxiety, and exploratory behavior. Additionally, to access potential anxiolytic effects, etifoxine was administered following restraint stress. These experiments were replicated in Slco1c1xTSPOcKO and Cx3cr1xTSPOcKO animals. Immunofluorescence and cell reconstruction were performed to assess TSPO expression across different cell types. Our data indicate that seven days after restraint, animals still exhibited an anxiogenic phenotype. TSPO levels were elevated in microglia but reduced in endothelial cells upon stress. Selective depletion of either microglia or endothelial TSPO abolished any anxiogenic effects upon restraint and potentially obliterates any link between microglia-endothelial TSPO regulation. Moreover, administration of etifoxine after restraint magnifies the TSPO expression effect, consistent with effects observed under acute stress, but did not produce a clear anxiolytic effect.