The novel findings of our present study are as follows, 1. Conditioned medium from peripheral blood macro phages increases uPA expression in human chondrocytes, two. This boost in uPA expression is particularly attri butable towards the paracrine effects with the cytokine IL 1b released by macrophages, three. Macrophage induced uPA expression in chondro cytes is mediated by means of JNK and Akt phosphorylation, and NF B activation, and four. Reduced shear stresses attenuate peripheral blood macrophage induced uPA expression. uPA is often a serine protease that converts plasminogen to plasmin. Plasmin can then degrade proteoglycans and transform MMPs into their active forms. The uPA itself also has a direct part inside the degradation of ECM pro teins. The PA plasmin system has a broad spectrum of activity.
In human OA and animal models of OA, exactly where enhanced bone remodeling may trigger cartilage damage, uPA plasmin is upregulated. selleck inhibitor Other reports also indicated a greater expression and activity of uPA in arthritis groups compared with typical controls. The improved levels of uPA in OA joints recommend that they play a role in this illness. It has been demonstrated that the transcript levels of uPA enhance drastically for the duration of the early and medium stages of OA. The capability of macrophages to stimulate uPA gene expression in chondrocytes may possibly, at least in element, cause the eleva tion of uPA inside the synovial fluid in the course of OA progression. The mechanism by which macrophages regulate uPA gene expression in chondrocytes, however, remains unclear. In our present study, we investigated the molecular mechanisms by which macrophages stimulate uPA expression in human chondrocytes.
We offer a number of lines of evidence from our current data that macro phage induced uPA expression in chondrocytes is mediated by means of NF B. First, we selleck chemicals identified that PB MCM sti mulates uPA expression and production by human chondrocytes in an in vitro culture technique. Second, TF ELISA and ChIP assays demonstrated a rise in NF B binding to the uPA gene promoter in chondro cytes. Third, the inhibition of NF B activation in chon drocytes by pretreatment with JNK and Akt inhibitors, transfection with particular siRNAs of JNK, or the expres sion of a dominant unfavorable mutant of Akt, abolishes macrophage induced uPA expression. The results of our present study also demonstrate for the very first time that macrophages not simply market the secretion of uPA, but additionally induce their gene expression in cultured human chondrocytes, and that macrophage induced uPA expression occurs at the transcriptional level. Evaluation of human uPA promoter activity with dif ferent plasmid constructs further revealed that NF B will be the main cis element for PB MCM responsiveness through JNK and Akt phosphorylation.