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BACKGROUND:Previous studies have indicated that resistin stimulates a large set of chemokines in chondrocytes that are known to be important in inflammatory joint lesions. OBJECTIVE:To further investigate the mechanism of co-regulation roles of transcription and post-transcription in the up-regulation of two chemokine genes CCL3 and CCL4 in chondrocytes in response to resistin. METHODS:Human chondrocytes, T/C-28a2 and ATDC5 cels were cultured. The function of resistin on the chemokine genes, and the expression of C/EBPβ, nuclear factor-κB isoforms and chondrogenic specific miRNAs were tested by qPCR. The co-regulation of C/EBPβ and nuclear factor-κB was investigated by nuclear factor-κB inhibitor (IKK-NBD) and C/EBPβ inhibitor (SB303580) treatments, and subcelular localization was detected with or without resistin stimulation. RESULTS AND CONCLUSION:Resistin could increase the expression of chemokine genes independently. Chondrocytes reacted in a non-restrictedly cel-specific manner to resistin; C/EBPβ inhibitor, nuclear factor-κB and some chondrogenic specific miRNAs in a combinatorial manner regulated chemokine gene expression. The activity of C/EBPβ was augmented by a transient increase in activity of nuclear factor-κB, and both transcription factors acted independently on the chemokine genes, CCL3 and CCL4.
RESUMO
BACKGROUND:Pyrroloquinoline quinone is found to accelerate Schwann cel proliferation and growth factor secretion, but there is no report addressing its role in articular cartilage and chondrocytes. OBJECTIVE: To investigate the role of pyrroloquinoline quinone in chondrocyte proliferation and interleukin-1β-induced chondrocyte apoptosis in the articular cartilage of knee joints and to verify the protective mechanism involved. METHODS: Chondrocytes were isolated from New Zealand white rabbits (1 month of age), digested under aseptic conditions, and cultured in DMEM/F12 in the presence of 10% fetal bovine serum to alow for proliferation until passage 2. Adherent chondrocytes were cultured in serum-free DMEM/F12 medium with 0, 6.25, 12.5, 25.0, 50.0 and 100.0 μmol/L pyrroloquinoline quinone, separately. Proliferation activity was determined by MTT at 48 hours of pyrroloquinoline quinone administration. Cel cycle was determined by flow cytometry at 30 hours after pyrroloquinoline quinone administration. Apoptosis was determined by flow cytometry folowing 24 hours of pyrroloquinoline quinone pretreatment and 15 hours of interleukin-1β induction. RESULTS AND CONCLUSION: Pyrroloquinoline quinone enhanced chondrocyte proliferation activity, increased percentage of S phase and G2/M phase in a dose dependent manner and reached the peak when the concentration of pyrroloquinoline quinone was 12.5-25.0 μmol/L (P< 0.05). Pyrroloquinoline quinone also inhibited interleukin-1β-induced chondrocyte apoptosis in early and late stage, and 25.0 μmol/L pyrroloquinoline quinone had the best effects (P < 0.05). These findings suggest pyrroloquinoline quinone can promote chondrocyte division and proliferation, and protect the cels from interleukin-1β-induced apoptosis.