Chemokine Expression during Adipogenesis and Inflammation in Orbital Fibroblasts from Patients with Graves' Orbitopathy

Abstract

Purpose: Chemokines are involved in the pathogenesis of various autoimmune diseases, including Graves' orbitopathy (GO), but comprehensive analyses of the dynamics of these cytokines and their receptors in such diseases remain lacking. In this study, we investigated the expressions of chemokines and their receptors during adipogenesis and inflammation in primary cultured orbital fibroblasts from patients with GO.

Methods: The messenger RNA (mRNA) expression levels of chemokines were compared between GO (n = 6) and non-GO (n = 5) orbital tissues by real-time polymerase chain reaction. After adipogenesis was induced in primary cultured orbital fibroblasts from patients with GO (n =5) and following stimulation with interleukin (IL)-1β and tumor necrosis factor (TNF)-α, the mRNA expression levels of chemokines and their receptors were analyzed.

Results: Chemokines were significantly downregulated in GO orbital tissues compared to non-GO orbital tissues (p < 0.05). Adipogenesis resulted in a strong increase in mRNA expression levels of chemokines and their receptors at an early stage (day 1); however, expression levels started to decrease thereafter and, eventually, decreased to below basal levels at the end of adipogenesis (day 10). Following stimulation with IL-1β and TNF-α, the mRNA expression levels of chemokines and their receptors increased, showing different responses to various proinflammatory cytokines.

Conclusions: Chemokines were strongly upregulated in the early phase of adipogenesis before decreasing continuously until the end of adipogenesis. Also, overt mature GO tissues showed reduced mRNA expression of chemokines compared to controls, which might indicate the existence of a shorter window for effective medical inflammatory treatment. The heightened levels of chemokines and their receptors observed after stimulation with IL-1β and TNF-α suggest a crucial role of proinflammatory cytokines in the pathogenesis of GO and, further, support the idea that chemokines could be used as biomarkers of GO activity.