BACKGROUND Obstructive sleep apnea syndrome (OSAS) is associated to intermittent hypoxia (IH) and is an aggravating factor of non-alcoholic fatty liver disease (NAFLD). We investigated the effects of hypoxia in both in vitro and in vivo models of NAFLD. METHODS Primary rat hepatocytes treated with free fatty acids (FFA) were subjected to chemically induced hypoxia (CH) using the hypoxia-inducible factor-1 alpha (HIF-1α) stabilizer cobalt chloride (CoCl2). Triglyceride (TG) content, mitochondrial superoxide production, cell death rates, cytokine and inflammasome components gene expression and protein levels of cleaved caspase-1 were assessed. Also, Kupffer cells (KC) were treated with conditioned medium (CM) and extracellular vehicles (EVs) from hypoxic fat-laden hepatic cells. The choline deficient L-amino acid defined (CDAA)-feeding model used to assess the effects of IH on experimental NAFLD in vivo. RESULTS Hypoxia induced HIF-1α in cells and animals. Hepatocytes exposed to FFA and CoCl2 exhibited increased TG content and higher cell death rates as well as increased mitochondrial superoxide production and mRNA levels of pro-inflammatory cytokines and of inflammasome-components interleukin-1β, NLRP3 and ASC. Protein levels of cleaved caspase-1 increased in CH-exposed hepatocytes. CM and EVs from hypoxic fat-laden hepatic cells evoked a pro-inflammatory phenotype in KC. Livers from CDAA-fed mice exposed to IH exhibited increased mRNA levels of pro-inflammatory and inflammasome genes and increased levels of cleaved caspase-1. CONCLUSION Hypoxia promotes inflammatory signals including inflammasome/caspase-1 activation in fat-laden hepatocytes and contributes to cellular crosstalk with KC by release of EVs. These mechanisms may underlie the aggravating effect of OSAS on NAFLD. [Abstract word count: 257].

中文翻译：

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化学性缺氧会在富含脂肪的肝细胞中诱导促炎信号，并通过细胞外小泡与库普弗细胞发生细胞串扰。

背景技术阻塞性睡眠呼吸暂停综合症（OSAS）与间歇性缺氧（IH）相关，是非酒精性脂肪肝疾病（NAFLD）的加重因素。我们研究了NAFLD体外和体内模型中缺氧的影响。方法使用缺氧诱导因子-1α（HIF-1α）稳定剂氯化钴（CoCl2）对游离脂肪酸（FFA）处理的原代大鼠肝细胞进行化学诱导的缺氧（CH）。评估了甘油三酸酯（TG）含量，线粒体超氧化物生成，细胞死亡率，细胞因子和炎性体成分的基因表达以及裂解的caspase-1的蛋白水平。此外，用条件培养基（CM）和来自缺氧性脂肪过多肝细胞的细胞外载体（EV）处理库普弗细胞（KC）。胆碱缺乏L-氨基酸定义（CDAA）喂养模型，用于评估IH对体内实验性NAFLD的影响。结果低氧诱导细胞和动物体内的HIF-1α。暴露于FFA和CoCl2的肝细胞表现出增加的TG含量和更高的细胞死亡率，以及增加的线粒体超氧化物生成和促炎细胞因子以及炎性体成分白介素-1β，NLRP3和ASC的mRNA水平。在暴露于CH的肝细胞中，裂解的caspase-1的蛋白质水平增加。来自缺氧性脂肪肝细胞的CM和EV在KC中引起促炎表型。来自暴露于IH的CDAA喂养的小鼠的肝脏表现出促炎和炎性体基因的mRNA水平升高，并且裂解的caspase-1水平升高。结论缺氧促进脂肪载肝细胞中的炎性信号，包括炎性体/半胱天冬酶1活化，并通过释放EV促进与KC的细胞串扰。这些机制可能是OSAS对NAFLD加剧作用的基础。[抽象字数：257]。