Effects of rapamycin on intracellular cholesterol homeostasis of glomerular mesangial cell in the presence of interleukin-1 beta.
OBJECTIVE
To investigate the effects of rapamycin on cholesterol homeostasis of glomerular mesangial cells and the underlying mechanisms.


METHODS
Intracellular cholesterol accumulation was measured by Oil Red O staining and high performance liquid chromatography. The effects of rapamycin on interleukin-1 beta (IL-1 beta)-induced mRNA and protein changes of low-density lipoprotein receptor (LDLR) and ATP-binding cassette transporter A1 (ABCA1) were assayed by quantitative real-time PCR and Western blot. Transient expressions of 3 types of mammalian target of rapamycin (mTOR), including mTOR-WT (wild type), mTOR-RR (rapamycin resistant, with kinase activity), and mTOR-RR-KD (rapamycin resistant, without kinase activity), were obtained by plasmid transfection.


RESULTS
Rapamycin had no significant influence on intracellular cholesterol concentration under normal condition, but it significantly decreased the intracellular cholesterol concentration in the presence of IL-1 beta. Rapamycin dose-dependently suppressed the increased expression of LDLR induced by IL-1 beta and up-regulated the suppressed expression of ABCA1 caused by IL-1 beta. Transient expression of 3 types of mTOR all reduced ABCA1 mRNA expression significantly, which all could be overroded by rapamycin.


CONCLUSIONS
Rapamycin may contribute to the maintaining of glomerular mesangial cell intracellular cholesterol homeostasis under inflammatory state by both reducing cholesterol uptake and increasing cholesterol efflux. And the effect may be not completely mediated by mTOR.
Zhang
Guo-juan
GJ
Department of Nephrology, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing 100730.
Li
Hang
H
Li
Xue-wang
XW
D064286:ATP Binding Cassette Transporter 1; D018528:ATP-Binding Cassette Transporters / Q000235:genetics / Q000378:metabolism; D000818:Animals; D002460:Cell Line; D002784:Cholesterol / Q000378:metabolism*; D006706:Homeostasis / Q000187:drug effects*; D006801:Humans; D007166:Immunosuppressive Agents / Q000494:pharmacology*; D053583:Interleukin-1beta / Q000378:metabolism*; D050527:Mesangial Cells / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*; D011973:Receptors, LDL / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology; D020123:Sirolimus / Q000494:pharmacology*
C577836:ABCA1 protein, human; D064286:ATP Binding Cassette Transporter 1; D018528:ATP-Binding Cassette Transporters; D007166:Immunosuppressive Agents; D053583:Interleukin-1beta; D011973:Receptors, LDL; D002784:Cholesterol; D020123:Sirolimus