Effects of Experimental Dry Eye on Tear Cytokine Profiles in Two Strains of Mice

Abstract

Abstract: : Purpose: To evaluate the effect of dry eye on inflammatory cytokines in tears obtained from 2 strains of mice: the BALB/c and the C57BL6. Methods: BALB/c and C57BL6 mice were treated with systemic scopolamine and exposure to a continuous air draft for up to 8 days to induce experimental dry eye (EDE). Tear fluid was collected 1 day prior to and at days 2, 4, 6, and 8 after EDE. The concentrations of IL–1α, IL–1ß, IL–2, IL–4, IL–10, IL–13, IFN–γ and TNF–α in tear fluid washings were measured by the Beadlyte® Luminex Multiplex Assay. Results were normalized using tear protein concentration. Results: EDE increased tear IL–1α concentration in both strains of mice: the BALB/c strain peaked at day 6 (108.8 ng/µg protein) while the C57BL6 group peaked at day 8, with a higher concentration (238.6 ng/µg protein). Similar results were obtained for IL–ß. BALB/c mice peaked at day 6 (15.2 ng/µg protein) while the C57BL6 group peaked at day 8 (26.5 ng/µg protein). IL–10 was detected at low levels, peaking at day 6 (16.2 ng/µg protein) in the BALB/c strain, while it was first detected in C57BL6 mice at day 6, peaking at day 8 (152.2 ng/µg protein). IL–13 peaked at day 2 (17.9 ng/µg protein) then decreased to barely detectable levels in BALB/c mice, while C57BL6 mice also showed a gradual decrease from baseline, but peaked later at day 8 (22.3 ng/µg protein). IFN–γ was markedly higher in C57BL6 mice than BALB/c mice on days 6 and 8 (56.2 ng/µg protein vs. 1.2 ng/µg protein for day 8). TNF–α was detected in a higher level in C57BL6 mice than BALB/c mice on days 2 and 8 (50.9 ng/µg protein vs. 8.0 ng/µg protein for day 2). IL–4 was not detected in tears from C57BL6 mice, while it was detected at a consistently low concentration throughout the treatment (0 ∼ 1.1 ng/µg protein) in BALB/c mice. IL–2 was not detected in either strain. Conclusions: EDE increases the concentration of inflammatory cytokines in tears, including IL–1α, IL–1ß, IL–10, IL–13, IFN–γ and TNF–α in BALB/c and C57BL6 mice. The absence of IL–4 and a higher IFN–γ concentration in C57BL6 tears are consistent with previous observations that this strain is predominantly a Th1 responder to proinflammatory stress.

Keywords: cornea: tears/tear film/dry eye • cytokines/chemokines