Chemical hypoxia induces pro-inflammatory signals in fat-laden hepatocytes and contributes to cellular crosstalk with Kupffer cells through extracellular vesicles

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. 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. 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. 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]. •Obstructive sleep apnea syndrome (OSAS) is an aggravating factor of non-alcoholic fatty liver disease (NAFLD).•The effects of cobalt chloride-induced chemical hypoxia on fat-laden hepatocytes were explored•Hypoxia amplified hepatocellular damage, promote inflammation and determine increased expression of inflammasome components.•Intermittent hypoxia in mice with steatohepatits also promoted a proinflammatory phenotype and inflammasome activation•Cellular crosstalk between hypoxic fat-laden hepatocytes and Kupffer cells is in part mediated by extracellular vesicles