Beta-endorphin ameliorates synovial cell hyperfunction in the collagen-induced arthritis rat model by specific downregulation of NF-kappa B activity.
OBJECTIVE
To observe the multiple immunoregulating effects of beta-endorphin (beta-END) on synovium cells of collagen-induced arthritis (CIA) in rats and to determine whether the regulation involves the transcriptional factor-kappaB (NF-kappaB) signal pathway.


METHODS
CIA was induced in female Wistar rats by immunization with native bovine type-II collagen emulsified with complete Freund's adjuvant. Synovial cells in the knees of the CIA rats were cultivated, and the effects of beta-END, beta-END receptor inhibitor (naloxone, Nal) in proliferation and apoptosis of the synovial cells were assayed by 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium, flow cytometry, and DNA integrity, respectively. The effects of beta-END and Nal on mRNA expression of several cytokines in the synovial cells, including tumor necrosis factor-alpha (TNF-alpha), interleukin-1beta (IL-1beta), IL-6, regulated upon activation normal T-cell expressed and secreted (RANTES), inducible nitric oxide synthase (iNOS), matrix metalloproteinase-2 (MMP-2) and MMP-9 were estimated by quantitative reverse transcription-polymerase chain reaction. Effects of beta-END and Nal on NF-kappaB activity were analyzed using luciferase gene reporter assays. The effects of beta-END and Nal on p65NF-kappaB expression of the synovial cells were examined using Western blot.


RESULTS
75% of the rats were demonstrated to have established the CIA model successfully. beta-END was shown to exert multiple effects on synovial cells of CIA rats including decreased proliferation, induced apoptosis, and downregulation of TNF-alpha, IL-1beta, IL-6, RANTES, iNOS, MMP-2 and MMP-9 mRNA expression. beta-END seemed to play an immunoregulating role by downregulating the activity and expression of NF-kappaB. It was found that the beta-END receptor blockage could counteract all the effects.


CONCLUSIONS
beta-END ameliorates synovial cell functions of CIA rats through binding with receptors and downregulating the NF-kappaB signal pathway. This suggests that beta-END, by blocking the activity and expression of NF-kappaB, is a potential anti-inflammatory and anti-rheumatic agent against CIA.
Yin
Hongen
H
Department of Rheumatology and Clinical Immunology, Peking Union Medical College Hospital, Beijing, PR China. yinhongen@sohu.com
Zhang
Fengchun
F
Yu
Mengxue
M
Cheng
Hong
H
Lin
Jiayou
J
Gao
Yang
Y
Han
Bing
B
Zhu
Liping
L
D000704:Analysis of Variance; D000818:Animals; D017209:Apoptosis; D001168:Arthritis / Q000139:chemically induced / Q000378:metabolism* / Q000473:pathology; D001169:Arthritis, Experimental / Q000473:pathology*; D049109:Cell Proliferation / Q000187:drug effects; D002478:Cells, Cultured; D018946:Chemokine CCL5 / Q000235:genetics / Q000378:metabolism; D024061:Collagen Type III; D016207:Cytokines / Q000235:genetics / Q000378:metabolism; D053938:DNA Fragmentation / Q000187:drug effects; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D015536:Down-Regulation / Q000187:drug effects*; D004347:Drug Interactions; D005260:Female; D005434:Flow Cytometry / Q000379:methods; D016328:NF-kappa B / Q000378:metabolism*; D009270:Naloxone / Q000494:pharmacology; D012333:RNA, Messenger / Q000096:biosynthesis; D051381:Rats; D017208:Rats, Wistar; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods; D015398:Signal Transduction / Q000187:drug effects*; D013583:Synovial Membrane / Q000166:cytology / Q000187:drug effects*; D014057:Tomography, X-Ray Computed / Q000379:methods; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology; D001615:beta-Endorphin / Q000494:pharmacology*
D018946:Chemokine CCL5; D024061:Collagen Type III; D016207:Cytokines; D016328:NF-kappa B; D012333:RNA, Messenger; D014409:Tumor Necrosis Factor-alpha; D009270:Naloxone; D001615:beta-Endorphin