Sortilin Inhibited ABCA1 Expression And The Cholesterol Efflux And Accelerated Atherosclerosis Development

Background:Sortilin,encoding by SORT1 gene,is one of the five vacuolar protein sorting 10 protein?VPS10P?domain family.Sortilin can bind and traffic intracellular targeting protein to the cell membrane or the lysosomal for degradation,including several lipid related proteins.It is well shown that sortilin involves in regulation of both the intracellular and plasma lipid metabolism,which is associated with the development of atherosclerosis.ABCA1,an important membrane transporter,can regulate the cellular cholesterol efflux and inhibit the formation of foam cell,which has an anti-atherosclerosis effect.While it is not clear if there are association n between sortilin and ABCA1.The purpose of this study is to determine the effect of macrophage sortilin expression on the ABCA1-mediated cholesterol efflux,foam cell formation,and atherosclerosis.Methods:THP-1 cell was incubated with ox-LDL and the expression of sortilin mRNA and sortilin protein were detected by western blot.After transfection with LV-sortilin and sortilin shRNA in THP-1 macrophage,cholesterol efflux was measured by liquid scintillation.The interaction between sortilin and ABCA1 was detected by co-immunoprecipitation.Cellular lipid contents were detected by high performance liquid chromatography?HPLC?.Intracellular lipid droplets were stained with oil red O.The artery plaque lesions in LDLR^-/-mice were observed by Sudan IV,HE,Masson,and Oil Red O staining.Results:Our results showed that macrophage sortilin expression was in manners of both dose-and time-dependent of ox-LDL treatment,reaching the peak level under the incubation with 50?g/mL ox-LDL for 24 h.Meanwhile,we found that the overexpression of macrophage sortilin resulted in inhibition of cholesterol efflux and down-regulation of ABCA1 level,but the sortilin mRNA level remained unchanged.Our also found that sortilin can bind ABCA1 protein,promoting the intracellular cholesterol efflux.Compared to LV-sortilin group,the ABCA1 level was increased with chloroquine treatment,but there is no obvious change with MG132 treatment.On the contrary,the ABCA1 protein level and ABCA1--mediated cholesterol efflux was increased when inhibiting sortilin expression using shRNA.Accordingly,aortic lipid deposition and plaque area were exacerbated,and ABCA1 expression was reduced in mice infected with LV-sortilin alone.However,it was partially reversed under the LV-sortilin infection supplemented with LV-ABCA1 or chloroquine.Conclusions:Macrophage sortilin reduces ABCA1 expression and apoA-I--dependent cholesterol efflux,facilitating the formation of foam cell and the development of atherosclerosis.