It is interesting to note that the overexpression of TSP1, whether induced by TGFb and PDGF in normal fibroblasts or basally in SSc lesional dermal fibroblasts, was inhibited by the MEK/ ERK inhibitor. All these results indicate that, as an endogenous activator of TGFb, TSP1 contributes to the pathological contractile http://www.selleckchem.com/products/AP24534.html activity of SSc fibroblasts. Moreover, TSP1 may also potentially mediate responses to PDGF in the pathogenesis of SSc. Our results are consistent with a previous suggestion that constitutive overexpression of TSP1 in SSc fibroblasts depends on autocrine TGFb signalling. Lesional SSc dermal fibroblasts overexpress syndecan 4, CCN2 and TSP1. CCN2 is expressed by mesenchymal cells undergoing active tissue remodelling, and is characteristically overexpressed in connective tis sue pathologies such as fibrosis and cancer.

Heparan sulfate chains of syndecan 4 mediate response to growth and differentiation factors such as TGFb. Syndecan 4 also binds CCN and acts as a coreceptor for CCN2. Although the precise nature of the interac tions among syndecan 4, CCN2 and TSP1 is still unclear, our previous investigations found low expres sion of TSP1 in fibroblasts isolated from syndecan 4 or CCN2 mice. In our current study, TSP1 knockdown with siRNA did not alter expression of syn decan 4 and CCN2. Collectively, these results suggest expression of TSP1 in fibroblast culture is downstream of both syndecan 4 and CCN2. It has been reported that, in a mouse model of arthritis, injection of TSP1 blocking peptides for 16 days reduced joint infiltration and inflammation and CCN2 message and protein levels.

However, this reduced CCN2 could result indirectly due to the ability of TSP1 to activate latent TGFb. Alternatively, a mechanism involving activation of cell types other than fibroblasts might be involved. There fore, whether TSP1 directly affects CCN2 expression in vivo in SSc still needs to be investigated. We have previously shown that Drug_discovery the ras/MEK/ERK classical MAP kinase cascade is important for several features of fibrogenesis. For example, MEK/ERK med iates the induction of CCN2 expression in normal mesenchymal cells. In addition, MEK/ERK is required for a SMA stress fibre assembly, via a synde can 4 dependent mechanism. Moreover, the enhanced constitutive ERK activation in lesional SSc fibroblasts is due to an increase in syndecan 4 expres sion.

The MEK ERK pathway and HSPGs contri bute to the overexpression of profibrotic proteins and enhanced contractile forces in SSc dermal fibroblasts, and the procontractile signals from TGFb are integrated through syndecan selleck compound 4 and MEK/ERK. TGFb has long been hypothesised to be a major contributor to patho logical fibrotic diseases. In this investigation we showed that TSP1 mediated TGFb activation con tributes to the pathological contractile activity of SSc fibroblasts via an ERK dependent mechanism.