Platelet-Derived Growth Factor-BB: A Stimulus for Cytokine Production by Orbital Fibroblasts in Graves' Ophthalmopathy

PURPOSE. Graves' ophthalmopathy (GO) is characterized by the infiltration of immune cells into the orbit, a process in which cytokines play a central role. Orbital fibroblasts are potent producers of cytokines on different stimuli. Recently, the authors showed increased expression of the PDGF-B chain in GO orbital tissue. The dimeric PDGF-BB molecule has been described to activate the NF-kappa B pathway, which is well recognized for its role in regulating cytokine production. This study was conducted to determine the role of PDGF-BB in the production of proinflammatory cytokines by orbital fibroblasts in GO. METHODS. Orbital, lung, and skin fibroblasts were stimulated with PDGF-BB, and cytokine (IL-1 beta, IL-6, IL-8, IL-16, CCL2, CCL5, CCL7, TNF-alpha) production was measured by ELISA. Involvement of NF-kappa B activation through PDGF signaling was investigated by electrophoretic mobility shift assay, specific NF-kappa B inhibitors, and the PDGF-receptor kinase inhibitor imatinib mesylate. RESULTS. IL-6, IL-8, CCL2, CCL5, and CCL7 production by orbital fibroblasts was increased by PDGF-BB stimulation, whereas IL-16, IL-1 beta, and TNF-alpha production was not affected. PDGF-BB induced NF-kappa B activity in orbital fibroblasts, and both NF-kappa B inhibitors and imatinib mesylate reduced PDGF-BB-induced cytokine production. Similar, but less vigorous, effects of PDGF-BB on cytokine production were observed in lung and skin fibroblasts. CONCLUSIONS. PDGF-BB is a potent inducer of proinflammatory cytokines via the NF-kappa B pathway in orbital fibroblasts, whereas cytokine production by fibroblasts from other anatomic locations showed a moderate response. These data suggest a possible role for PDGF-BB in regulating orbital inflammation in GO and identify the PDGF signaling cascade as a therapeutic target in GO. (Invest Ophthalmol Vis Sci. 2010;51:1002-1007) DOI:10.1167/iovs.09-433