Conclusions
Binding of RA-SF to LM-111 in the presence of TGF-beta(1) triggers a significant IL16 response and thus may contribute to the infiltration of CD4+ lymphocytes into synovial tissues. This mode of IL16 induction represents a novel pathway leading to IL16 production in RA-SF but not in OA-SF, which operates independently of NFkappaB signalling.
Methods
SF were seeded in laminin-coated flasks and activated by the addition of cytokines. The expression of IL16 was investigated by quantitative RT-PCR, immunoblotting and ELISA; its biological activity was determined by a cell migration assay. Cell-matrix interactions were investigated by cell binding and attachment assays. Relevant intracellular signalling pathways were studied by immunoblotting and with pharmacological blocking reagents.
Results
Stimulation of SF with transforming growth factor beta(1)(TGF-beta(1)) and growth on laminin-111 (LM-111) significantly increased the expression of IL16. Binding to LM-111 induced significantly more IL16 mRNA in RA-SF than in OA-SF (p<0.05). The IL16 cytokine was detected in supernatants of TGF-beta(1)-activated and in LM-111+TGF-beta(1)-activated RA-SF (38 to 62 pg/ml), but not in supernatants of OA-SF. This IL16 regulation involved p38MAPK, ERK1/2 and SMAD2 signalling, but not NFkappaB. Conclusions: Binding of RA-SF to LM-111 in the presence of TGF-beta(1) triggers a significant IL16 response and thus may contribute to the infiltration of CD4+ lymphocytes into synovial tissues. This mode of IL16 induction represents a novel pathway leading to IL16 production in RA-SF but not in OA-SF, which operates independently of NFkappaB signalling.