Inhibition of Matrix Metalloproteinase–3 Synthesis in Human Conjunctival Fibroblasts by IL–4 or IL–13

Abstract

Abstract: : Purpose: Fibroproliferative lesions known as giant papillae are a characteristic of vernal keratoconjunctivitis (VKC). The abundance of T helper 2 (Th2) cells and Th2 cytokines is increased in the giant papillae and tear fluid of individuals with VKC. We previously showed that the Th2 cytokines interleukin (IL)–4 and IL–13 each stimulate the synthesis of extracellular matrix (ECM) proteins in conjunctival fibroblasts. The role of Th2 cytokines in the development of giant papillae was examined further by determining the effects of IL–4 and IL–13 on the production by these cells of matrix metalloproteinase (MMP)–3, a key enzyme in ECM degradation. Methods: Human conjunctival fibroblasts were cultured with Th2 cytokines in the absence or presence of IL–1ß. The amount of MMP–3 released into the culture medium 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. The phosphorylation of IΚBα and c–Jun and the subcellular localization of NF–ΚB were evaluated by immunoblot and immunofluorescence analyses, respectively. Results: Of the Th2 cytokines tested, only IL–4 and IL–13 (not IL–5, IL–9, or IL–10) inhibited basal and IL–1ß–induced MMP–3 release by conjunctival fibroblasts. These effects of IL–4 and IL–13 were dose dependent and inhibited by neutralizing antibodies to the common IL–4Rα chain of both IL–4 and IL–13 receptors. IL–4 and IL–13 also each reduced the basal abundance of, as well as inhibited the IL–1ß–induced increase in, MMP–3 mRNA in conjunctival fibroblasts. IL–4 or IL–13 did not affect either the phosphorylation of IΚBα and c–Jun or the translocation of NF–ΚB to the nucleus induced in these cells by IL–1ß. Conclusions: IL–4 and IL–13 inhibit MMP–3 synthesis in human conjunctival fibroblasts, suggesting that these cytokines contribute to the excessive deposition of ECM in giant papillae by preventing ECM degradation by this enzyme.

Keywords: conjunctivitis • extracellular matrix • cytokines/chemokines