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L. Luo, D. Li, A. Doshi, W. Farley, S. Pflugfelder; Experimental Dry Eye Induced Expression of Inflammatory Cytokines ( IL-1ß and TNF- ), MMP-9 and Activated MAPK by the Corneal Epithelium . Invest. Ophthalmol. Vis. Sci. 2003;44(13):1026.
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Purpose: To investigate the expression of inflammatory cytokines, Interleukin-1 ß (IL-ß) and tumor necrosis factor (TNF-α), matrix metalloproteinase 9 (MMP-9) and the activated mitogen-activated protein kinases (MAPK), c-jun N-terminal kinase (JNK) extracellular-regulated kinase (ERK) and p38, by ocular surface in experimental dry eye mice. Methods: 129SvEv/CD-1 mixed white mice aged 6-8 weeks were treated with systemic scopolamine and exposure to an air draft for 7 days, or treated with hypertonic saline drops (500 mOsm) 6 times/day for 2 days. Untreated mice were used as controls. Tears were collected for ELISA and zymography. Corneal epithelia were lysed in RIPA buffer for Western blot with phospho-MAPK antibodies, or lysed in 4M guanidium thiocyanate solution for total RNA extraction and subjected to semi-quantitative RT-PCR for gene expression with mouse specific primers for IL-1ß, TNF-α, MMP-9 and GAPDH, the latter as a loading control. Results: Compared with age matched controls, the concentrations of IL-1ß and TNF-α measured by ELISA and MMP-9 by zymography in the tear fluid were significantly increased in 7-day treated dry eye mice. Detected by RT-PCR, the expression of IL-1ß, TNF-α and MMP-9 mRNA by corneal epithelia were also significantly induced in 7-day treated dry eye mice. Western blots revealed that phosphorylated JNK1/2, ERK1/2 and p38 were markedly increased in corneal epithelia of these dry eye mice. Interestingly, two-day treatment with hypertonic saline also stimulated IL-1ß and MMP-9 proteins in tears and their mRNA in corneal epithelia, as well as activation of JNK1/2, ERK1/2 and p38 signaling pathways in corneal epithelia compared with untreated control mice. Conclusions: It was demonstrated that Experimental dry eye and exposure to hypertonic saline increases expression and production of IL-1ß, TNF-α and MMP-9 as well as MAPK signaling pathways in the corneal epithelia. These findings establish a link between the hyperosmolar tear film of dry eye and the induction of ocular surface inflammation in keratoconjunctivitis Sicca.
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