The TSPO ligand XBD173 increases pregnenolone levels and CYP11A1 inhibition prevents XBD173-induced phagocytosis. (A) Pregnenolone levels in cell culture supernatants of BV-2 cells treated with 20 μM XBD173, 50 ng/ml LPS, or 20 μM XBD173 + 50 ng/ml LPS for 24 hours. Data show mean ± SD (n = 3/group) ***P <0.001 XBD173 versus vehicle-treated cells, **P <0.01 XBD173 + LPS versus LPS-treated cells. (B) Quantification of latex bead phagocytosis of BV-2 cells treated with 20 μM XBD173 or 20 μM XBD173 + 100 μM aminoglutethimide for 24 hours. Data show mean ± SEM (n = 30/group) ***P <0.0001 XBD173 versus control cells. LPS, lipopolysaccharide; TSPO, translocator protein (18 kDa).