| Objective The goals of this study is to investigate the role of lipid-induced endoplasmic reticulum stress(ERS) in podocyte injury under inflammatory condition and to explore whether it is related to intracellular cholesterol transportersNiemann-pick C1protein(NPC1).Methods Podocytes were cultured and divided into controlgroup, low-densitylipoprotein(LDL)group,IL-1β+LDLgroup,tunicamycingroup(T M),4-phenylbutyric acid(4-PBA)groupandstatingroup.The apoptosis of podocytes was measured by flow cytometry. The accumulation of lipid droplet in the cells was detected by oil red O staining. Enzymatic was used to caculate the total cholesterol of endoplasmic reticulum.ThemRNA leves ofNPC1,protein kinase R-like endoplasmic reticulum kinase(PERK),gluco se-regulatedprotein78(GRP78), and activating transcription factor 6(ATF6)were determined by real-time PCR.GRP78 protein level was detected by immunofluorescence assay.Results(1) Compared with the control group and high-Lipid group, Co-treatment of cells with high levels of lipid and IL-1β significantly increased the cell apoptosis rate(p<0.05), intracellular lipid accumulation, endoplasmic reticulum lipid content(p<0.001), and the levels of GRP78, PERK, ATF6, NPC1 mRNA(p<0.05 respectively);(2)Compared with Lipid+IL-1β group, Pretreatment of cells with low concentrations of TM and 4-PBA significantly decreased the apoptosis rate(p<0.05), down-regulated GRP78, PERK, ATF6 expression(p<0.05 respectively), while statin and 4-PBA treatment can reduce NPC1 expression and intracellular lipid accumulation(p<0.05). And they all reduce endoplasmic reticulum lipid content in different degrees(p<0.05).Conclusion These results suggest that lipid may be transported to ER by NPC1 and its accumulation in ER promotes podocyte injury through activating ERS under inflammatory conditions. Reduction of ERS and the intacellular accumulation of lipid droplet can alleviate the damages on podocytes. |
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