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
Department of Cell Death and Proliferation, IIBB-CSIC, Barcelona, Spain; Liver Unit, IDIBAPS Hospital Clinic de Barcelona and CIBEREHD, Barcelona, Spain.
Institute of Molecular Biology and Genetics CSIC, Medical School, University of Valladolid and CIBERDEM, Valladolid, Spain.
J Hepatol. 2014 Nov;61(5):1126-34. doi: 10.1016/j.jhep.2014.06.009. Epub 2014 Jun 16.
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.
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.
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.
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.
酸性鞘磷脂酶（ASMase）在非酒精性脂肪性肝炎（NASH）中被激活。然而，ASMase对NASH的作用了解甚少，且仅限于肝脂肪变性和葡萄糖代谢方面。在此，我们研究了ASMase在高脂饮食（HFD）诱导的NASH中的作用。
对喂食HFD的ASMase基因敲除（-/-）小鼠的自噬、内质网（ER）应激和溶酶体膜通透性（LMP）进行测定。在喂食HFD的野生型小鼠中分析ASMase药理学抑制对NASH的影响。
ASMase缺乏决定了对HFD或蛋氨酸-胆碱缺乏饮食介导的肝脂肪变性具有抗性。ASMase（-/-）小鼠对HFD诱导的肝脏ER应激具有抗性，但对衣霉素介导的ER应激敏感，这表明ASMase（-/-）小鼠对ER应激和脂肪变性的抗性具有选择性。在雷帕霉素和/或氯喹存在下测定的自噬通量，在ASMase（-/-）小鼠的原代小鼠肝细胞（PMH）中较低，并伴有p62水平升高，提示自噬受损。此外，氯喹和布雷菲德菌素A抑制自噬在ASMase（+/+）小鼠的PMH中引起ER应激，但在ASMase（-/-）小鼠中未引起。ASMase（-/-）的PMH表现出溶酶体胆固醇负载增加、LMP降低以及对盐酸O-甲基丝氨酸十二烷基酰胺或棕榈酸诱导的凋亡具有抗性，通过用氧甾醇25-羟基胆固醇降低胆固醇水平可逆转这些作用。在体内，广泛使用的三环类抗抑郁药阿米替林对ASMase的药理学抑制可保护野生型小鼠免受HFD诱导的肝脂肪变性、纤维化和肝损伤，这些作用表明处于NASH早期阶段。
这些发现强调了ASMase在饮食诱导的NASH中的关键作用，并提示阿米替林作为NASH患者治疗药物的潜力。
