Leukoregulin induction of protein expression in human orbital fibroblasts: Evidence for anatomical site-restricted cytokine–target cell interactions

Abstract

The molecular basis for the profound inf lammatory response and the accumulation of hyaluronan in orbital connective tissues seen in thyroid-associated ophthalmopathy is unknown. Moreover, the link between the orbital manifestations of Graves' disease and those in the pretibial skin, localized dermopathy, has yet to be established. We have reported recently that leukoregulin, an activated T lymphocyte-derived cytokine, dramatically induces hyaluronan synthesis and prostaglandin-endoperoxide H synthase 2 in human orbital fibroblasts in culture. In the current studies, utilizing giant two-dimensional gel electrophoresis, we find that orbital fibroblasts express constitutively a protein profile that distinguishes them from skin fibroblasts derived from the abdominal wall and from the pretibium. We further demonstrate that leukoregulin, when present in culture medium for 16 hr, up-regulates a set of orbital fibroblast proteins not present in untreated cultures or in fibroblasts from the abdominal wall. However, some of the same protein inductions are present in the pretibial fibroblasts. These leukoregulininduced changes in protein expression are completely blocked by dexamethasone (10 nM). Our findings are the first to identify proteins that appear to be expressed and differentially regulated in an anatomical site-restricted manner in orbital and pretibial fibroblasts and seem to establish a molecular link between fibroblasts from the orbit and those in pretibial skin.

Igs from Patients with Graves’ Disease Induce the Expression of T Cell Chemoattractants in Their Fibroblasts

“…The particularly robust responses observed in fibroblasts from the orbit to T cellderived cytokines such as leukoregulin, IL-1, and CD154 and their expression and surface display of functional CD40 may underlie the susceptibility of orbital connective tissue to the anatomic siteselective manifestations associated with GD (7)(8)(9)(10)(11)(12). Supporting this concept is the distinct profile of proteins expressed by cytokine-activated orbital and pretibial fibroblasts (57). On the other hand, dermopathy can occur, on occasion, in areas of the skin distant from the shin, and these cases have often been associated with antecedent trauma (1).…”

Immunoglobulin Activation of T Cell Chemoattractant Expression in Fibroblasts from Patients with Graves’ Disease Is Mediated Through the Insulin-Like Growth Factor I Receptor Pathway

“…For instance, compared with cells from tissues irrelevant to GD, orbital fibroblasts exhibit exaggerated responses to proinflammatory cytokines (36,37). The profile of proteins they express following treatment with T cell-derived cytokines differs (38), and they display particularly high levels of CD40 (39). Ligation of that receptor on orbital fibroblasts with CD154 results in the robust up-regulation of key proinflammatory molecules, such as IL-6, IL-8, and PG endoperoxide H synthase-2, and the generation of hyaluronan (39,40).…”

Aberrant Expression of the Insulin-Like Growth Factor-1 Receptor by T Cells from Patients with Graves’ Disease May Carry Functional Consequences for Disease Pathogenesis

“…Cytokines and lipid mediators, synthesized by infiltrating T lymphocytes, monocytes, and mast cells, drive tissue remodeling, including the accumulation of hyaluronan, an abundant nonsulfated glycosaminoglycan (25,26). The unique phenotype of orbital fibroblasts and their exaggerated responses to cytokines such as IL-1␤ represent the basis for disease susceptibility of these tissues (25,(27)(28)(29)(30)(31). Why immunocompetent cells are recruited to the orbit in TAO remains uncertain.…”