Effects Of P38 MAPK Signal Pathway On Temporomandibular Joint Synovitis

Part one:Effect of p38MAPK on IL-1β and MMP3 expression in rat TMJ synovial fibroblasts induced by lipopolysaccharideObjectives:To investigate the effect of p38 MAPK on IL-1β and MMP3 expression in rat temporomandibular joint synovial fibroblasts induced by lipopolysaccharide.Methods:Synovial fibroblasts were separated from rat TMJ by enzyme digestion then subcultured and the phenotypes were analyzed with cell surface markers vimentin and CD68.SFs were respectively treated with LPS for 24 hours or pretreated with SB203580 before LPS. The expressions of IL-1β, MMP3, p-p38, p-ATF2 were detected by immunochemical staining, expressions of IL-1β and MMP3 mRNA were detected by RT-PCR to evaluated the activation level of p38 signal and gene and protein expressions of inflammatory factor. The non-treated cells were used as control.Results:The synovial cells were observed spindle shaped and cytoplasm rich, in accordance with morphological characteristics of synovial fibroblasts. The immunochemical staining showed positive expression of vimentin and negative expression of CD68. The expression of IL-1β and MMP3 mRNA and protein increased significantly under LPS stimulation, compared with the control (p<0.05). In addition, the p-p38 and p-ATF2 expressions were also enhanced after LPS stimulation (p<0.05 compared with the control). In the SFs pretreated with p38 inhibitor SB203580, the enhanced expressions of IL-1β and MMP3 mRNA and protein were down-regulated (p<0.05 compared with LPS without SB203580 group).Conclusions:LPS can enhance the expressions of IL-1β and MMP3 in SFs and also activate the p38 MAPK signal. The pretreatment with p38 MAPK inhibitor SB203580 can significantly inhibit the overexpression of IL-1β and MMP3 at mRNA and protein levels. P38 MAPK plays an important role in the expression of IL-1β and MMP3 in SFs induced by LPS and it may participate in the process of the temporomandibular joint synovitis.Part two:Effect of p38 MAPK on inflammatory response in rat temporomandibular joint synoviumObjectives:To investigate the effect of p38 MAPK on inflammatory response in rat temporomandibular joint synovium.Methods:Thirty-six rats were randomly divided into three groups:the control+ NS group (served as control), the increased occlusal vertical dimension (iOVD)+NS group and the iOVD+SB203580 group.In the second and third groups, we increased the occlusal vertical dimension for 2 weeks by cementing occlusal splints to the maxillary molars. In the third group, rats received intra-articular injections of SB203580 during the procedure, while the rats in the other groups received injections of isotonic NS. Morphologic changes of synovial tissues were observed and scored. Activation levels of p38 MAPK and ATF2 were detected by immunohistochemistry. Expression of IL-1β and MMP3 mRNA and protein were measured by real-time quantitative polymerase chain reaction and immunohistochemistry respectively.Results:HE staining showed inflammatory changes in synovium of iOVD rats and the pathology score of iOVD+NS group significantly increased compared with control. IL-1β and MMP3 mRNA and protein expressions in synovium of iOVD rats were enhanced, as well as p-p38 and p-ATF2 expressions (p<0.05 compared with the control). The treatment of SB203580 relieved inflammatory response in the synovium and also reduced the expression of IL-1β and MMP3 mRNA and protein (p<0.05 compared with the iOVD+NS group).Conclusions:P38 MAPK signal may participate in the initiation and progression process of the TMJ synovitis. P38 inhibitor SB203580 can inhibit the overexpression of IL-1 β and MMP3 at mRNA and protein levels and relieve the synovial inflammatory in rats induced by increased occlusal vertical dimension.