Background

The transition from steatosis to non-alcoholic steatohepatitis (NASH) is a key issue in non-alcoholic fatty liver disease (NAFLD). Observations in patients with obstructive sleep apnea syndrome (OSAS) suggest that hypoxia contributes to progression to NASH and liver fibrosis, and the release of extracellular vesicles (EVs) by injured hepatocytes has been implicated in NAFLD progression.

Aim

To evaluate the effects of hypoxia on hepatic pro-fibrotic response and EV release in experimental NAFLD and to assess cellular crosstalk between hepatocytes and human hepatic stellate cells (LX-2).

Methods

HepG2 cells were treated with fatty acids and subjected to chemically induced hypoxia using the hypoxia-inducible factor 1 alpha (HIF-1α) stabilizer cobalt chloride (CoCl2). Lipid droplets, oxidative stress, apoptosis and pro-inflammatory and pro-fibrotic-associated genes were assessed. EVs were isolated by ultracentrifugation. LX-2 cells were treated with EVs from hepatocytes. The CDAA-fed mouse model was used to assess the effects of intermittent hypoxia (IH) in experimental NASH.

Results

Chemical hypoxia increased steatosis, oxidative stress, apoptosis and pro-inflammatory and pro-fibrotic gene expressions in fat-laden HepG2 cells. Chemical hypoxia also increased the release of EVs from HepG2 cells. Treatment of LX2 cells with EVs from fat-laden HepG2 cells undergoing chemical hypoxia increased expression pro-fibrotic markers. CDAA-fed animals exposed to IH exhibited increased portal inflammation and fibrosis that correlated with an increase in circulating EVs.

Conclusion

Chemical hypoxia promotes hepatocellular damage and pro-inflammatory and pro-fibrotic signaling in steatotic hepatocytes both in vitro and in vivo. EVs from fat-laden hepatocytes undergoing chemical hypoxia evoke pro-fibrotic responses in LX-2 cells.

中文翻译：

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源自经历化学低氧的载脂肝细胞的细胞外囊泡可促进肝星状细胞的纤维化前表型。

背景

从脂肪变性到非酒精性脂肪性肝炎（NASH）的转变是非酒精性脂肪肝疾病（NAFLD）的关键问题。对阻塞性睡眠呼吸暂停综合症（OSAS）患者的观察表明，低氧有助于NASH和肝纤维化的发展，并且受损的肝细胞释放胞外囊泡（EVs）与NAFLD的发展有关。

目标

评估缺氧对实验性NAFLD中肝促纤维化反应和EV释放的影响，并评估肝细胞与人肝星状细胞（LX-2）之间的细胞串扰。

方法

HepG2细胞用脂肪酸处理，并使用缺氧诱导因子1α（HIF-1α）稳定剂氯化钴（CoCl2）进行化学诱导的缺氧。评估了脂质滴，氧化应激，细胞凋亡以及促炎和纤维化相关基因。电动汽车通过超速离心分离。LX-2细胞用来自肝细胞的EV进行处理。用CDAA喂养的小鼠模型评估实验性NASH中间歇性缺氧（IH）的作用。

结果

化学性缺氧增加了载脂HepG2细胞中的脂肪变性，氧化应激，细胞凋亡以及促炎和促纤维化基因表达。化学性缺氧还增加了HepG2细胞中EV的释放。用经历化学缺氧的载脂HepG2细胞的EV电动车处理LX2细胞可增加表达前纤维化标记物。暴露于IH的CDAA喂养的动物表现出门静脉炎症和纤维化增加，这与循环EV的增加相关。

结论

化学性缺氧在体外和体内均会促进脂肪变性肝细胞的肝细胞损伤以及促炎和促纤维化信号传导。来自经受化学低氧作用的载脂肝细胞的电动汽车在LX-2细胞中引起促纤维化反应。