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Vasoactive Intestinal Peptide Ameliorates Synovial Cell Functions of Collagen-Induced Arthritis Rats by Down-Regulating NF-κB Activity

The objectives of this work were to observe the multiple immuno-regulating effects of vasoactive intestinal peptide (VIP) on synovial cells of collagen induced arthritis (CIA) rats and to determine whether the transcriptional factor-κB (NF-κB) signal pathway was involved. CIA was induced using female Wistar rats by native bovine type II collagen (C II) emulsified with complete Freund's adjuvant (CFA). Synovial cells from the knees of the CIA rats were cultivated, and the effects of VIP and VIP receptor inhibitor ([D-P-Cl-Phe(6), Leu(17)]-VIP, I) on proliferation and apoptosis of the synovial cells were assayed by 3-(4,5-dimethylthiazol-2-yl)-5-(3-carcoxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS), flow cytometry, and DNA integrity. The effects of VIP and [D-P-Cl-Phe(6), Leu(17)]-VIP on mRNA expression of several cytokines in the synovial cells including tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), interleukin-6 (IL-6), regulated upon activation, normal T-cell expressed and secreted (RANTES), inducible NO synthase (iNOS), matrix metalloproteinase-2 (MMP-2) and MMP-9 were estimated by quantitative reverse transcription-polymerase chain reaction (RT-PCR). Effects of VIP and [D-P-Cl-Phe(6), Leu(17)]-VIP on NF-κB activity were analyzed using luciferase gene reporter assays. Effects of VIP and [D-P-Cl-Phe(6), Leu(17)]-VIP on p65NF-κB expression of the synovial cells were examined by Western blot. Seventy-five percent of the induced rats developed CIA. VIP has multiple effects on synovial cells of CIA rats including decreasing proliferation, inducing apoptosis, and down-regulating mRNA expression of several inflammatory factors. VIP was found to play immuno-regulating roles through the down-regulation of the activity and expression of NF-κB, whereas VIP receptor blockade was found to counteract all the effects. In conclusion, VIP was found to ameliorate synovial cell functions of CIA rats through binding with receptors and further down-regulating NF-κB signal pathway, suggesting VIP is a potential anti-inflammatory and anti-rheumatic agent of CIA by blocking NF-κB.