Figure 4

Role of activated MAP-kinases pp38 and pp42/44 in strain-induced expression of the active form of MMP-13. PDL cells were seeded on flexible bottom cell culture dishes, strained with averaged 2.5% and followed by westernblot analysis. The numerical expression values were denoted in relation to unstrained controls. The maximum inhibition was related to the respective strain-kinetic time points. (A) For strain-induced MMP-13 expression detection in a pp38-specific inhibition assay, PDL cells were pre-treated with 10 μM of a phosphorylation-specific inhibitor (SB202190) against pp38 and the MMP-13 down-regulation was compared versus untreated control. The numerical changes of the MMP13 protein expression status in consequence of strain application were visualised by arrows in the graph. Efficiency of pp38 inhibition yielded in a maximum inhibition of 62% after 6 hours strain and was visualised by the immunoblots (inset). (B) Strain-induced expression of MMP-13 in a pp42/44-specific inhibition assay was performed by pre-treating PDL cells with 10 μM of a phosphorylation-specific inhibitor (UO-126) against pp42/44 and the MMP-13 down-regulation was compared versus untreated control. The numerical changes of the MMP-13 protein expression status in consequence of strain application were visualised by arrows in the graph. Efficiency of pp42/44 inhibition yielded in a maximum inhibition of 16% after 6 hours strain and was visualised by the immunoblots (inset). Data of each graph represent the mean of three individual experiments (n = 3), mean +/- SD and means were subjected to the Students T-test. All compared mean values with p < 0.01 were considered as statistical significant and are marked with an asterisk. The depicted western blots exemplify the protein expression changes of one biological replicate.