Hepatic steatosis in response to acute alcohol exposure in zebrafish requires sterol regulatory element binding protein activation #

Abstract

Steatosis is the most common consequence of acute alcohol abuse and may predispose to more severe hepatic disease. Increased lipogenesis driven by the sterol response element binding protein (SREBP) transcription factors is essential for steatosis associated with chronic alcohol ingestion, but the mechanisms underlying steatosis following acute alcohol exposure are unknown. Zebrafish larvae represent an attractive vertebrate model for studying alcoholic liver disease (ALD), because they possess the pathways to metabolize alcohol, the liver is mature by 4 days post-fertilization (dpf), and alcohol can be simply added to their water. Exposing 4 dpf zebrafish larvae to 2% ethanol (EtOH) for 32 hours achieves ϳ80 mM intracellular EtOH and upregulation of hepatic cyp2e1, sod, and bip, indicating that EtOH is metabolized and provokes oxidant stress. EtOH-treated larvae develop hepatomegaly and steatosis accompanied by changes in the expression of genes required for hepatic lipid metabolism. Based on the importance of SREBPs in chronic ALD, we explored the role of Srebps in this model of acute ALD. Srebp activation was prevented in gonzo larvae, which harbor a mutation in the membrane-bound transcription factor protease 1 (mbtps1) gene, and in embryos injected with a morpholino to knock down Srebp cleavage activating protein (scap). Both gonzo mutants and scap morphants were resistant to steatosis in response to 2% EtOH, and the expression of many Srebp target genes are down-regulated in gonzo mutant livers. Conclusion: Zebrafish larvae develop signs of acute ALD, including steatosis. Srebp activation is required for steatosis in this model. The tractability of zebrafish genetics provides a valuable tool for dissecting the molecular pathogenesis of acute ALD. (HEPATOLOGY 2009;49:443-452.)

Cannabinoid receptor signaling regulates liver development and metabolism

“…This disruption in lipid metabolism suggests that Cnr activity is necessary not only for hepatobiliary development, but also affects physiological regulation of metabolic homeostasis. To examine whether abnormal lipid handling during larval development alters susceptibility to pathological lipid accumulation, we utilized an established alcohol-induced steatosis model (Passeri et al, 2009): zebrafish exposed to 2% ethanol from 96-120 hpf develop steatosis at an incidence of 30-60%, as visualized by whole-mount Oil Red O (ORO) staining. cnr1 −/− , but not cnr2 −/− , mutants are protected from steatosis, with hepatic ORO staining detectable in only 19% of ethanol-exposed cnr1 −/− larvae (Fig.…”

“…Whole-mount Oil Red O staining was conducted as previously described (Passeri et al, 2009). Embryos were scored based on the presence of red lipid droplets in the liver.…”

Characterization of SIGIRR/IL-1R8 Homolog from Zebrafish Provides New Insights into Its Inhibitory Role in Hepatic Inflammation

“…Aside from the widely used mouse models, the zebrafish model has attracted considerable interest from researchers because of its conserved innate immunity and numerous advantages for investigations, such as its high fecundity, rapid development, easy visualization, and genetic manipulation. The zebrafish has been extensively used in studies of developmental and comparative immunology and in modeling human diseases, such as T cell acute lymphoblastic leukemia (67), diabetes mellitus (68), Alagille syndrome, alcoholic liver disease (69), and hepatocellular carcinoma (70). In the present study, the zebrafish model showed its advantages for uncovering the involvement of SIGIRR in hepatic inflammation, which indicates a new function of SIGIRR in liver homeostasis.…”

In vivo cell biology in zebrafish – providing insights into vertebrate development and disease

“…For example, zebrafish are proving useful for alcohol research (Jang et al, 2012;Monk et al, 2013;North et al, 2010;Passeri et al, 2009;Tsedensodnom et al, 2013;Yin et al, 2012). By using transgenic zebrafish expressing a GFP-tagged secreted glycoprotein in hepatocytes Tsedensodnom et al, 2013;Xie et al, 2010), and zebrafish that express fluorescent protein markers of the hepatocyte secretory organelles and of other cells in the liver (Yin et al, 2012), the mechanisms by which alcohol and other drugs cause organ-specific and organelle-mediated toxicity can be uniquely addressed.…”