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-kappaB 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-1beta, IL-6, IL-8, IL-16, CCL2, CCL5, CCL7, TNF-alpha) production was measured by ELISA. Involvement of NF-kappaB activation through PDGF signaling was investigated by electrophoretic mobility shift assay, specific NF-kappaB 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-1beta, and TNF-alpha production was not affected. PDGF-BB induced NF-kappaB activity in orbital fibroblasts, and both NF-kappaB 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-kappaB 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.

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Investigative Ophthalmology & Visual Science
Erasmus MC: University Medical Center Rotterdam

van Steensel, L., Paridaens, D., Dingjan, G., van Daele, P., van Hagen, M., Kuijpers, R., … Dik, W. (2010). Platelet-derived growth factor-BB: a stimulus for cytokine production by orbital fibroblasts in Graves' ophthalmopathy. Investigative Ophthalmology & Visual Science, 51(2), 1002–1007. Retrieved from http://hdl.handle.net/1765/19308