OBJECTIVE

Fibroproliferative lesions of the conjunctiva known as giant papillae are a characteristic of vernal keratoconjunctivitis (VKC). The abundance of T helper 2 (Th2) cells and cytokines is increased in the giant papillae and tear fluid of individuals with VKC, and the Th2 cytokines interleukin (IL)-4 and IL-13 each stimulate the production of extracellular matrix (ECM) proteins by conjunctival fibroblasts. The role of Th2 cytokines in the development of giant papillae was further examined by determination of the effects of these molecules on the production by conjunctival fibroblasts of matrix metalloproteinase (MMP)-3, a key enzyme in ECM degradation.

METHODS

The amount of MMP-3 released into the culture medium by human conjunctival fibroblasts was determined by enzyme-linked immunosorbent assay, and the intracellular abundance of MMP-3 mRNA was quantitated by reverse transcription and real-time polymerase chain reaction analysis. Signaling by the transcription factors NF-kappaB and AP-1 was evaluated by immunoblot and immunofluorescence analyses.

RESULTS

Of the Th2 cytokines tested, only IL-4 and -13 inhibited both the basal and IL-1beta-induced release of MMP-3 by conjunctival fibroblasts. These effects of IL-4 and -13 were inhibited by neutralizing antibodies to the IL-4 receptor complex. IL-4 and -13 also each reduced the basal abundance, as well as inhibited the IL-1beta-induced upregulation, of MMP-3 mRNA in these cells. Neither IL-4 nor -13 affected the IL-1beta-induced activation of NF-kappaB or the AP-1 component c-Jun.

CONCLUSIONS

IL-4 and -13 each inhibit MMP-3 synthesis in human conjunctival fibroblasts, suggesting that these Th2 cytokines may contribute to the excessive deposition of ECM in giant papillae by preventing matrix degradation mediated by this enzyme.