Orbital fibroblast chemokine modulation: eVects of dexamethasone and cyclosporin A

Aim—Orbital inflammation is common, but the mechanisms underlying leucocytic infiltration of orbital tissue are poorly understood. Human orbital fibroblasts (OF) express chemokines, interleukin 8 (IL-8) and monocyte chemotactic protein 1 (MCP-1), when exposed to proinflammatory cytokines. The eVects of dexamethasone (DEX) and cyclosporin A (CSA) on OF IL-8 and MCP-1 were examined. Methods—Cultured humanOFwere incubated with recombinant interleukin 1â (rIL-1â; 0.2, 2.0, 20 ng/ml) alone or incubated with rIL-1â and DEX (10, 10, 10 M) or CSA (3, 30, 300 ng/ml) for 24 hours. ELISA and northern blot analyses were performed to determine OF IL-8 and MCP-1 protein secretion and mRNA expression, respectively. Results—OF lacked constitutive IL-8 or MCP-1 expression, but secreted significant amounts of these chemokines and expressed substantial steady state mRNA for both chemokines upon rIL-1â stimulation. DEX caused dose dependent inhibition of IL-1 induced IL-8 (p<0.001) and MCP-1 (p<0.05) secretion and mRNA expression at all concentrations of rIL-1â. CSA enhanced IL-1 induced OF IL-8 (p<0.001) and suppressed rIL-1â induced OF MCP-1 (p<0.05) secretion when lower doses of rIL-1â were used. These eVects on secreted chemokines at diVerent concentrations of rIL-1â and immunomodulating agents were corroborated by steady state OF IL-8 and MCP-1 mRNA expression. Conclusions—DEX is a potent inhibitor of OF IL-8 and MCP-1. In contrast, CSA enhances IL-1 induced OF IL-8 and suppresses OF MCP-1. These observations may explain the relative lack of CSA eVectiveness in human orbital diseases that respond to corticosteroids. (Br J Ophthalmol 1998;82:318–322) Orbital inflammation accounts for approximately 57% of all orbital disorders. These disorders, characterised by inflammatory cell infiltrates, include orbital cellulitis, orbital myositis, Graves’ eye disease, idiopathic orbital inflammation (orbital pseudotumour), as well as inflammation associated with systemic diseases. The mechanisms mediating orbital inflammation, however, remain poorly understood. Infiltration of leucocytes into inflamed tissue is a complex phenomenon, probably orchestrated by chemotactic gradients expressed via cytokine cascades. We believe that resident orbital cells may participate in the initiation and perpetuation of many orbital inflammatory disease processes. We have shown that orbital fibroblasts (OF) secrete mediators that may be crucial to orchestrating orbital immune and inflammatory responses. Specifically, stimulation with lipopolysaccharide (LPS) or recombinant (r) proinflammatory cytokines (interleukin 1â (rIL-1â), tumour necrosis factor á (rTNF-á), or interferon ã (rIFN-ã)) induces secretion of diVerent OF chemokines, low molecular weight, proinflammatory cytokines that (1) chemoattract and activate distinct leucocyte subsets and (2) participate in the upregulation of inflammatory responses. Interleukin 8 (IL-8) and monocyte chemotactic protein 1 (MCP-1) are the two most potent and best characterised members of the superfamily of low molecular weight CXC and CC leucocyte chemokines, respectively. Induced principally by IL-1, TNF, and LPS, IL-8 preferentially chemoattracts and activates neutrophils, while MCP-1 attracts and stimulates monocytes and lymphocytes. Thus, OF are anatomically well positioned and are functionally able to participate in the regulation of leucocyte movement and activation in diseased orbital tissue when exposed to ambient proinflammatory cytokines. The production of novel chemotactic cytokines by OF is noteworthy because coordinating communication between the interstitium and vascular bed may dictate the initiation, maintenance, and resolution phases of orbital inflammation. Strategies aimed at modulating these potent leucocyte chemoattractant and activating agents may be helpful in the control of orbital inflammatory disease. To examine the eVects of the immunosuppressive agents dexamethasone (DEX) and cyclosporin A (CSA), cultured human OF were co-incubated with these immunosuppressive agents and rIL1â, a known inducer of IL-8 and MCP-1. OF IL-8 and MCP-1 protein secretion was measured and steady state mRNA expression was analysed.