1α,25-（OH）₂D₃Facilitates Uptake Of Aβ In HepG2Cells By Up-regulating LRP1

Objective:The purpose of this research were to study the effect of la,25-(OH)2D3on Low-density lipoprotein receptor-related protein1(LRP1) and vitamin D receptor (VDR) expression and uptake of β-amyloid (Aβ) in HepG2cells.Methods:The HepG2cells were cultured in vitro, the optimal concentration and action time were determined by MTT assay. The expression of LRP1and VDR were determined by western blot technique and Real-Time PCR; The uptake of AP in HepG2cells were analyzed by enzyme linked immunosorbent assay (ELISA). The role of LRP1in mediating the uptake of Aβ in HepG2cells was assessed using receptor associated protein (RAP), a competitive inhibitor ofLRP1.Results:1. Combined the results of MTT assay with reported researches, we chose1nM,10nM,50nM,100nM as intervention concentrations,6h and24h as intervention time.2. HepG2cells were treated with1α,25-(OH)2D3for6h,50nM,100nM1α,25-(OH)2D3significantly increased the expression of LRP1protein (p<0.05),1nM、10nM1α,25-(OH)2D3had no effect;10nM,50nM,100nM la,25-(OH)2D3significantly increased the expression of VDR protein (p<0.05),1nM1α,25-(OH)2D3had no effect. HepG2cells were treated with1α,25-(OH)2D3for24h,10nM,50nM,100nM la,25-(OH)2D3significantly increased the expression of LRP1protein (p<0.05), the up-regulation trend of the expression of LRP1protein was observed in1nM, but there were not statistical differences.1nM,10nM la,25-(OH)2D3significantly increased the expression of VDR protein (p<0.05), the up-regulation trend of the expression of VDR protein were observed in50nM,100nM groups, but there were not statistical differences.3. HepG2cells were treated with1α,25-(OH)2D3for6h, significant up-regulation of the expression of LRP1mRNA were observed in10nM,50nM,100nM groups (p<0.05),1nM group had no effect. Significant up-regulation of the expression of VDR mRNA were observed in50nM,100nM groups (p<0.01),1nM,10nM groups had no effect. HepG2cell were incubated with la,25-(OH)2D3for24h, All1α,25-(OH)2D3groups significantly enhanced the expression of LRP1and VDR mRNA (p<0.05).4. HepG2cells were treated with1α,25-(OH)2D3for6h, significant up-regulation of uptake Aβ1-40were discovered in10nM,50nM,100nM groups(p<0.05) and no difference was discovered in1nM group. RAP significantly reduced the uptake Aβ1-40in HepG2cells (p<0.05), and abolished the up-regulation of1α,25-(OH)2D3on uptake AP1-40in HepG2cells (p<0.05).Conclusions:la,25-(OH)2D3could induce the expression of LRP1and VDR protein and mRNA in HepG2cells, up-regulate the uptake of Aβ mediated by LRP1.