Corneal epithelial cells covered with contact lenses demonstrate a reduced innate defense response to bacterial exposure

Abstract

Abstract: : Purpose: The ocular surface epithelia secrete defensins as part of the innate immunity against infection. The expression of one of the defensins, human beta defensin–2 (hbd–2) is up–regulated by exposure to Gram–negative bacteria via an NF–ΚB–dependent pathway. Extended contact lens wear predisposes patients to bacterial corneal ulcers. The aim of this study was to examine the affects of contact lenses on hbd–2 gene expression and NF–ΚB activation. Method: Intact or fenestrated soft contact lenses(SCLs) were placed on human corneal epithelial cells (HCE) grown in a 24–well plate to 50% confluency. Cells grown without SCLs served as a control. After 3.5 days of the exposure, SCLs were removed and cells were inoculated with Pseudomonas aeruginosa supernatant for either 30 minutes or 6 hours. Cells were lysed in SDS sample buffer for Western blot analysis, or in TRIZOL for RT–PCR Results: The induction of hbd–2 gene expression in response to bacteria was abrogated in HCE cells exposed to undamaged SCL as compared to cells grown without an SCL. The effect was restored in cells exposed to SCL with holes. Western blot analysis suggested that exposure to SCL decreases IΚ–Bα phosphorylation in response to bacterial supernatant as compared to the control. Conclusion: Extended exposure to a SCL decreased hbd–2 up–regulation in response to bacteria in vitro. This decrease was partially restored with a fenestrated SCL that should cause less hypoxia. These findings suggest a mechanism by which SCL–induced hypoxia could influence the abiltiy of the cornea to defend itself against bacteria.

Keywords: contact lens • cornea: epithelium • cornea: basic science