Background and aims: Scavenger receptors form a superfamily of membrane-bound receptors that bind and internalize different types of ligands, including pro-atherogenic oxidized low-density lipoproteins (oxLDLs). In vitro studies have indicated a role for the liver sinusoidal endothelial cell receptors stabilin 1 (stab1) and 2 (stab2) in oxLDL clearance. In this study, we evaluated the potential role of stab1 and stab2 in lipoprotein uptake in zebrafish, an upcoming model for studying cholesterol metabolism and atherosclerosis.
Methods: Lipoproteins were injected in the duct of Cuvier of wild-type (ABTL) or stab1 and stab2 mutant (stab1-/-stab2-/-) zebrafish larvae at 3 days post-fertilization. To examine the effect of stabilin deficiency on lipoprotein and cholesterol metabolism, zebrafish larvae were challenged with a high cholesterol diet (HCD; 4% w/w) for 10 days.
Results: Lipoprotein injections showed impaired uptake of both LDL and oxLDL into the vessel wall of caudal veins of stab1-/-stab2-/- zebrafish, which was paralleled by redistribution to tissue macrophages. Total body cholesterol levels did not differ between HCD-fed stab1-/-stab2-/- and ABTL zebrafish. However, stab1-/-stab2-/- larvae exhibited 1.4-fold higher mRNA expression levels of ldlra involved in (modified) LDL uptake, whereas the expression levels of scavenger receptors scarb1 and cd36 were significantly decreased.
Conclusions: We have shown that stabilins 1 and 2 have an important scavenging function for apolipoprotein B-containing lipoproteins in zebrafish and that combined deficiency of these two proteins strongly upregulates the clearance of lipoproteins by macrophages within the caudal vein. Our current study highlights the use of zebrafish as model to study lipoprotein metabolism and liver sinusoidal endothelial cell function.
Keywords: Foam cells; Macrophages; Scavenger receptors; Stabilins; Zebrafish.
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