ASMase regulates autophagy and lysosomal membrane permeabilization and its inhibition prevents early stage non-alcoholic steatohepatitis

• Published in: Journal of hepatology 2014-11, Vol.61 (5), p.1126-1134
• Main Authors: Fucho, Raquel, Martínez, Laura, Baulies, Anna, Torres, Sandra, Tarrats, Nuria, Fernandez, Anna, Ribas, Vicente, Astudillo, Alma M, Balsinde, Jesús, Garcia-Rovés, Pablo, Elena, Montserrat, Bergheim, Ina, Lotersztajn, Sophie, Trautwein, Christian, Appelqvist, Hanna, Paton, Adrienne W, Paton, James C, Czaja, Mark J, Kaplowitz, Neil, Fernandez-Checa, Jose C, García-Ruiz, Carmen
• Format: Article
• Language: English
• Subjects: Amitriptyline - pharmacology; Animals; Autophagy; Autophagy - physiology; Ceramide; Ceramides - metabolism; Cholesterol - metabolism; Choline Deficiency - complications; Diet, High-Fat - adverse effects; Disease Models, Animal; Endoplasmic Reticulum Stress; Fatty liver; Gastroenterology and Hepatology; Humans; Liver - metabolism; Liver - pathology; Lysosomal membrane permeabilization; Lysosomes - metabolism; Methionine - deficiency; Mice; Mice, Inbred C57BL; Mice, Knockout; Non-alcoholic Fatty Liver Disease - enzymology; Non-alcoholic Fatty Liver Disease - etiology; Non-alcoholic Fatty Liver Disease - prevention & control; Permeability; Sphingomyelin Phosphodiesterase - antagonists & inhibitors; Sphingomyelin Phosphodiesterase - deficiency; Sphingomyelin Phosphodiesterase - metabolism; Sphingomyelins - metabolism
• ISSN: 0168-8278; 1600-0641; 1600-0641
• DOI: 10.1016/j.jhep.2014.06.009

Background & Aims Acid sphingomyelinase (ASMase) is activated in non-alcoholic steatohepatitis (NASH). However, the contribution of ASMase to NASH is poorly understood and limited to hepatic steatosis and glucose metabolism. Here we examined the role of ASMase in high fat diet (HFD)-induced NASH. Methods Autophagy, endoplasmic reticulum (ER) stress and lysosomal membrane permeabilization (LMP) were determined in ASMase−/− mice fed a HFD. The impact of pharmacological ASMase inhibition on NASH was analyzed in wild type mice fed a HFD. Results ASMase deficiency determined resistance to hepatic steatosis mediated by a HFD or methionine-choline deficient diet. ASMase−/− mice were resistant to HFD-induced hepatic ER stress, but sensitive to tunicamycin-mediated ER stress, indicating selectivity in the resistance of ASMase−/− mice to ER stress and steatosis. Autophagic flux, determined in the presence of rapamycin and/or chloroquine, was lower in primary mouse hepatocytes (PMH) from ASMase−/− mice and accompanied by increased p62 levels, suggesting autophagic impairment. Moreover, autophagy suppression by chloroquine and brefeldin A caused ER stress in PMH from ASMase+/+ mice but not in ASMase−/− mice. ASMase−/− PMH exhibited increased lysosomal cholesterol loading, decreased LMP and apoptosis resistance induced by O-methyl-serine dodecylamide hydrochloride or palmitic acid, effects that were reversed by decreasing cholesterol levels by oxysterol 25-hydroxycholesterol. In vivo pharmacological ASMase inhibition by amitriptyline, a widely used tricyclic antidepressant, protected wild type mice against HFD-induced hepatic steatosis, fibrosis, and liver damage, effects indicative of early-stage NASH. Conclusions These findings underscore a critical role for ASMase in diet-induced NASH and suggest the potential of amitriptyline as a treatment for patients with NASH.