Effect of prostaglandin analogues on tear proteomics and expression of cytokines and matrix metalloproteinases in the conjunctiva and cornea.

The purpose of this work was to identify potential tear-film-based proteins and their effect on changes in the conjunctiva and cornea in eyes using prostaglandin (PG) analogues. Recruited subjects were individuals who had used PG for at least 1 year and comparison with eyes of normal controls and timolol using patients were done. Approximately 3-5 μL of tears were sampled from both eyes of each subject using glass microcapillaries. Proteomic analysis was done to compare the pooled tear samples from each group by Bradford assay and cytokine arrays. Impression cytology was used to gather mRNA from conjunctival epithelial cells, and target protein mRNA was quantified by PCR. Rabbits treated with PG were scarified, and changes in the corneal stroma were evaluated by immunohistochemical staining and western blot analysis. There were increased levels of IL-1β, IL-6, MMP-1, MMP-3, and MMP-9 and decreased levels of TIMP-1 and TIMP-2 in the tears of PG-treated patients. The mRNA of IL-1β, MMP-1, MMP-3, and MMP-9 was elevated and mRNA of TIMP-1 and TIMP-2 was decreased in the conjunctival epithelial cells. Rabbits treated with PG showed corneal thinning with decreased collagen type I expression. The protein of MMP-1 and MMP-9 was elevated and protein of TIMP-1 was decreased in the rabbit cornea by western blot analysis. Immunohistochemical staining showed elevated expression of MMP-1 and MMP-9 and the decreased expression of TIMP-1 in the corneal stroma. The topical use of PG analogues results in an altered balance between MMPs and TIMPs, which may be triggered by inflammatory cytokines. This results in an increase of matrix degradation and decrease of stromal collagens in the cornea by PG treatments.