Experiment of THP-1 macrophage foam-cell formation through mTOR signal pathway activation induced by inflammatory stress / 中国药理学通报

ABSTRACT

Aim To investigate if LPS increases the sterol regulatory element binding proteins ( SREBPs ) cleavage-activating protein ( SCAP )-SREBP2 expres-sion by activation of mTOR signal pathway in THP-1 macrophages , upgrading LDLr level , causing foam-cell formation .Methods THP-1 macrophages were incu-bated in serum free medium in the absence of 5 mg?L-1 LDL alone , or 5 mg? L-1 LDL plus 200 μg? L-1 LPS, or 5 mg? L-1 LDL plus 200 μg? L-1 LPS plus 10 μg? L-1 rapamycin .Morphological examination of macrophages was performed with Oil Red O staining . Expression changes of LDLr , SREBP2, SCAP, S6K1 and mTOR mRNA were detected by real time quantita-tive polymerase chain reaction ( PCR ) .Western blot was used to analyze protein expression changes of LD-Lr, S6K1 and mTOR.Translocation of SCAP-SREBP2 complex from the endoplasmic reticulum ( ER ) to the Golgi was determined by confocal microscopy .Results LPS enhanced transformation of THP-1 macrophages into foam cells by increased uptake of lipid as evi-denced by Oil Red O assay .LPS increased mRNA lev-els of LDLr, SREBP2, SCAP, S6K1 and mTOR ( P <0.05) .Rapamycin reduced the mRNA levels of LDLr , SREBP2,SCAP,S6K1 and mTOR induced by LPS ( P<0.05 ) .Western blot demonstrated that LPS also caused over-expression of protein of LDLr , S6K1 and mTOR(P<0.05).Rapamycin reduced the expression of protein of LDLr, S6K1 and mTOR induced by LPS ( P <0.05 ) .Confocal microscopy demonstrated LPS caused an escape of SCAP-SREBP2 complex from the ER to the Golgi .Rapamycin inhibited the translocation of SCAP-SREBP2 complex from the ER to the Golgi . Conclusions Inflammatory stress increases SCAP/SREBP2 expression by activation of mTOR signal path-way, resulting in an escape of SCAP-SREBP2 complex from the ER to the Golgi , furthermore elevating LDLr expression and causing foam-cell formation .Rapamy-cin reverses the activation of mTOR signal pathway and decreases lipid deposition in THP-1 macrophages in-duced by LPS .