Involvement of Endoplasmic Reticulum Stress in Uremic Cardiomyopathy: Protective Effects of Tauroursodeoxycholic Acid

Abstract

Background/Aims: Uremic cardiomyopathy (UCM) is a complication in chronic kidney disease. We investigated if endoplasmic reticulum stress (ERS) is involved in UCM, and determined the efficacy of tauroursodeoxycholic acid (TUDCA) in UCM prevention. Methods: Mice were divided randomly into three groups: sham (saline, i.p), 5/6 nephrectomized (Nx) (saline, i.p) and Nx+TUDCA (250 mg/kg/day, i.p.). Renal function was assessed by measuring serum creatinine, blood urea nitrogen and by periodic acid-Schiff reagent staining. Histologic examination of cardiac fibrosis and apoptosis was determined by Masson's trichrome and TUNEL assay. Cardiac function was evaluated by echocardiography. Fibrotic factors (transforming growth factor-β, fibronectin, collagen I/IV) were evaluated by real-time PCR. ERS-related proteins were measured by western blotting. Results: Impaired renal function and cardiac dysfunction were shown in 5/6 nephrectomy mice but were improved significantly by TUDCA. 5/6 nephrectomy mice exhibited marked cardiomyocyte apoptosis, cardiac fibrosis and elevated pro-fibrotic factors. ERS markers (GRP78, GRP94, P-PERK, P-eIF2a) and ERS-induced apoptosis pathways (activation of CHOP and caspase-12) were increased significantly in 5/6 nephrectomy mice, and TUDCA treatment blunted these changes. Conclusions: ERS has a key role in UCM, and the cardioprotective role of TUDCA is related to inhibition of ERS-induced apoptosis by inhibition of CHOP and caspase-12 pathways.