Expression of Human β-Defensins in Conjunctival Epithelium: Relevance to Dry Eye Disease

Purpose - The goals of this study were to investigate whether β-defensins are differentially expressed in the conjunctival epithelium of patients with moderate dry eye when compared with normal subjects and whether proinflammatory cytokines or bacteria can modulate the expression of human β-defensins (hBDs)-1, -2, and -3 by conjunctival epithelial cells. Methods - RNA extracted from conjunctival impression cytology specimens of eight normal subjects and nine patients with moderate dry eye was used in RT-PCR to detect mRNA for hBDs-1, -2, and -3. Two conjunctival epithelial cell lines and primary cultured conjunctival epithelial cells were treated with proinflammatory cytokines or heat-killed Pseudomonas aeruginosa. RT-PCR and immunoblot analysis were used to detect mRNA for hBD-1, -2, and -3 and protein secretion of hBD-2, respectively. Results - hBD-2 message was detected in RNA samples of eight of nine patients with dry eye, but not in any of the normal subjects’ samples, whereas hBD-1 and -3 were detected in all subjects tested. RT-PCR revealed an upregulation of hBD-2 but no difference in expression of hBD-1 and -3 in cultured conjunctival cells after a 24-hour treatment with 10 ng/mL interleukin (IL)-1β, IL-1β and tumor necrosis factor-α (10 ng/mL) or heat-killed Pseudomonas aeruginosa (1 million colony-forming units; n = 3). hBD-2 expression was upregulated from 4 hours of treatment with IL-1β (at 10 ng/mL; (n = 2–3) and at a concentration of 0.1 ng/mL IL-1β (24-hour treatment; n = 2–3). Immunoblots demonstrated protein secretion results corresponding to the RT-PCR data. Conclusions - hBD-2 was expressed only in the conjunctival epithelium of patients with moderate dry eye. Because cytokines such as IL-1β and TNF-α induced the expression of hBD-2 by conjunctival epithelial cells and because increased proinflammatory cytokine activity is a feature of dry eye disease, it can be speculated that the hBD-2 upregulation observed in subjects with moderate dry eye is mediated by proinflammatory cytokine activity.