title: Rapamycin down-regulates inducible nitric oxide synthase by inducing proteasomal degradation.
abstract: We investigated the effect of rapamycin, a specific inhibitor of the mammalian serine/threonine kinase, mammalian target of rapamycin (mTOR), on the expression of inducible nitric oxide synthase (iNOS) in lipopolysaccharide (LPS)-stimulated RAW 264.7 cells. Pretreatment of cells with rapamycin significantly inhibited LPS-induced nitrite production and the expression of iNOS protein in a dose-dependent manner. However, LPS-induced mRNA expression of iNOS and its concomitant activation of nuclear factor (NF)-kappaB remained unchanged by rapamycin. Intriguingly, LPS-induced nitrite production and iNOS protein expression were partially blocked at nanomolar concentrations of rapamycin, whereas phosphorylation of both p70 S6 kinase and 4E-BP1 was completely abolished. The suppression of LPS-induced iNOS expression by rapamycin was reversed by the protease inhibitor lactacystin. Furthermore, rapamycin treatment stimulated 20S proteasome activity, which was slightly elevated by LPS. Taken together, our findings strongly suggest that rapamycin down-regulates LPS-induced iNOS protein expression via proteasomal activation, as well as through inhibition of the mTOR signaling pathway.
authors.affiliation: Department of Biochemistry and Molecular Biology, College of Pharmacy, Sungkyunkwan University, Suwon, Korea.
authors.forename: Hye Kyoung
authors.initials: HK
authors.lastname: Jin
authors.forename: Seong Hoon
authors.initials: SH
authors.lastname: Ahn
authors.forename: Jong Woo
authors.initials: JW
authors.lastname: Yoon
authors.forename: Jong Woo
authors.initials: JW
authors.lastname: Park
authors.forename: Eun Kyung
authors.initials: EK
authors.lastname: Lee
authors.forename: Jeong Soo
authors.initials: JS
authors.lastname: Yoo
authors.forename: Jae Cheol
authors.initials: JC
authors.lastname: Lee
authors.forename: Wahn Soo
authors.initials: WS
authors.lastname: Choi
authors.forename: Jeung-Whan
authors.initials: JW
authors.lastname: Han
mesh_terms: D000818:Animals; D015152:Blotting, Northern; D015153:Blotting, Western; D002460:Cell Line; D004305:Dose-Response Relationship, Drug; D015536:Down-Regulation; D024202:Electrophoretic Mobility Shift Assay; D008070:Lipopolysaccharides / Q000494:pharmacology; D008264:Macrophages / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism; D051379:Mice; D009569:Nitric Oxide / Q000096:biosynthesis; D052247:Nitric Oxide Synthase Type II / Q000037:antagonists & inhibitors* / Q000096:biosynthesis; D009573:Nitrites / Q000378:metabolism; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D061988:Proteasome Inhibitors; D011494:Protein Kinases / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D038762:Ribosomal Protein S6 Kinases, 70-kDa / Q000378:metabolism; D020123:Sirolimus / Q000494:pharmacology*; D058570:TOR Serine-Threonine Kinases
chemical_list: D008070:Lipopolysaccharides; D009573:Nitrites; D061988:Proteasome Inhibitors; D009569:Nitric Oxide; D052247:Nitric Oxide Synthase Type II; C496317:Nos2 protein, mouse; D011494:Protein Kinases; C546843:mTOR protein, mouse; D038762:Ribosomal Protein S6 Kinases, 70-kDa; D058570:TOR Serine-Threonine Kinases; D046988:Proteasome Endopeptidase Complex; D020123:Sirolimus