title: Melatonin inhibits human fibroblast-like synoviocyte proliferation via extracellular signal-regulated protein kinase/P21(CIP1)/P27(KIP1) pathways.
abstract: The excessive proliferation and migration of synoviocytes are well-characterized phenomena that play key roles in the pathophysiology of rheumatoid arthritis (RA). Melatonin has been shown to have potent anti-proliferative effect in various cancer cells such as breast and prostate cancer cells. In this study, we examined the role of melatonin on synoviocyte proliferation in primary cultured human fibroblast-like synoviocytes (FLSs) by analyzing protein expression of P21(CIP1) (P21) and P27(KIP1) (P27), the cyclin-dependent kinase inhibitors that are important in cell cycle control, and the phosphorylation of mitogen-activated protein kinases (MAPKs). RA-FLS proliferation was determined by a [(3)H]-thymidine incorporation assay. Western blot analysis was applied to examine the underlying mechanisms of melatonin's effect. Melatonin inhibited RA-FLS proliferation in a dose-dependent manner. It reduced proliferation of passage 2 FLSs by 25% at 10 microm and by nearly 40% at 100 microm concentrations. The inhibitory effect of melatonin on RA-FLS proliferation was also observed in passages 4 and 6. Melatonin upregulated the expression levels of P21 and P27 dose-dependently (24 hr), induced the phosphorylation of extracellular signal-regulated protein kinase (ERK) time-dependently (10 microm), but did not affect phosphorylation of P38 in RA-FLSs. In addition, the expression of P21 and P27 triggered by melatonin was inhibited by the pretreatment of the ERK inhibitor, PD98059 (10 microm). The anti-proliferative action of melatonin in RA-FLSs was also blocked by PD98059. Taken together, these results suggest that melatonin exerts the inhibitory effect of the proliferation of RA-FLSs through the activation of P21 and P27 mediated by ERK. Hence we suggest that melatonin could be used as a therapeutic agent for the treatment of RA.
authors.affiliation: Division of Rheumatology, Department of Internal Medicine, Soonchunhyang University, College of Medicine, Choenan, Korea.
authors.forename: Seong-Su
authors.initials: SS
authors.lastname: Nah
authors.forename: Hye-Jin
authors.initials: HJ
authors.lastname: Won
authors.forename: Hae Jeong
authors.initials: HJ
authors.lastname: Park
authors.forename: Eunyoung
authors.initials: E
authors.lastname: Ha
authors.forename: Joo-Ho
authors.initials: JH
authors.lastname: Chung
authors.forename: Hong Yon
authors.initials: HY
authors.lastname: Cho
authors.forename: Hyung Hwan
authors.initials: HH
authors.lastname: Baik
mesh_terms: D000368:Aged; D001172:Arthritis, Rheumatoid / Q000201:enzymology / Q000378:metabolism / Q000473:pathology; D049109:Cell Proliferation / Q000187:drug effects; D002478:Cells, Cultured; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000378:metabolism*; D050760:Cyclin-Dependent Kinase Inhibitor p27 / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D048049:Extracellular Signal-Regulated MAP Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D005347:Fibroblasts / Q000166:cytology / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism; D005419:Flavonoids / Q000494:pharmacology; D006801:Humans; D008550:Melatonin / Q000494:pharmacology*; D008875:Middle Aged; D015398:Signal Transduction / Q000187:drug effects; D013583:Synovial Membrane / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism
chemical_list: C493956:CDKN1A protein, human; D050759:Cyclin-Dependent Kinase Inhibitor p21; D005419:Flavonoids; D050760:Cyclin-Dependent Kinase Inhibitor p27; D048049:Extracellular Signal-Regulated MAP Kinases; D008550:Melatonin; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one