Cyclic tensile stress of XXXX annulus fibrosus cells induces MAPK activation: involvement in proinflammatory gene expression.

@entity1 @entity650 @entity687 @entity1346 @entity1014 @entity1435 @entity1521 @entity2247 @entity1642
OBJECTIVE: To study the role of mitogen-activated protein kinases (MAPKs) in @entity1 annulus fibrosus (AF) cells subjected to @entity1642 ( @entity1642 ). DESIGN: An in  vitro system for @entity1642 studies was established using AF cultures on fibronectin-coated @entity1346 dishes. MAPK phosphorylation was studied by western analysis, while gene expression was followed by qRT-PCR. DNA synthesis was assessed by both tritiated @entity1014 incorporation and flow cytometry, and collagen synthesis using tritiated @entity1521 incorporation and the protease-free collagenase method. RESULTS: All three MAPKs studied, i.e., ERK, SAPK/JNK, and @entity1435 were found to be phosphorylated immediately after @entity1642 application within physiological range. A second wave of phosphorylation appeared at later time points. MAPK activation was elevated at higher @entity1642 magnitudes, but independent of the frequency. @entity1642 did not stimulate DNA synthesis neither extracellular matrix turnover, but it stimulated the proinflammatory genes, @entity2247 , @entity650 , and @entity687 . This stimulation was more intense at the highest magnitude (8%) tested  and at the median frequency (1  Hz) and time interval (12  h). Blocking of ERK, SAPK/JNK, and @entity1435 MAPK inhibited the @entity1642 -induced stimulation of @entity2247 and @entity687 , while @entity650 expression was mediated only by SAPK/JNK and @entity1435 MAPK. CONCLUSIONS: We have described for the first time the activation of MAPKs in @entity1 AF cells in response to @entity1642  and showed that it drives an inflammatory reaction. These observations shed light on the mechanisms of intervertebral disc (IVD) cell responses to mechanical stress, contributing to the understanding of disc pathophysiology  and possibly to the design of novel therapeutic interventions.
