Reduction of renal tubular GRP78 expression and induction of HO-1 and thioredoxin by losartan through up-regulation of SIRT1 in a mouse model of tunicamycin-induced ER stress. Tunicamycin-induced ER stress mouse model was induced by a single intraperitoneal injection of tunicamycin (TM, 2 mg/kg). Mice were randomly divided into four groups: control mice (n = 4), mice with TM injection (TM mouse, n = 4), TM mice with losartan (n = 4), and TM mice with losartan plus sirtinol (SIRT1 inhibitor, 5 mg/kg intraperitoneally). (n = 4). Losartan was administered by gavage at 10 mg/kg/day. Immunohistochemical staining (A) and Western blot of renal cortical tissue (B) for GRP78, heme oxygenase-1 (HO-1), thioredoxin, and SIRT1 were performed. Representative microscopic scans and quantitative analysis were shown. #: p < 0.05 vs. con (control); ##: p < 0.05 vs. TM; ###: p < 0.05 vs. TM + losartan (losar); scale bars = 20 µm.