Inflammatory cytokine expression on the ocular surface in the Botulium toxin B induced murine dry eye model

Purpose: Inflammation plays an important role in dry eye syndrome. In this study, inflammatory cytokine expression on the ocular surface in the Botulium toxin B (BTX-B) induced mouse dry eye model was investigated. Methods: CBA/J mice received an injection of saline or 20 milliunits (mU) of BTX-B into the lacrimal gland. Tear production and corneal fluorescein staining were evaluated in all groups before injection and at 3 time points after. The pro-inflammatory cytokines macrophage inhibitory factor (MIF), interleukin-1 beta (IL-1 beta), tumor necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6) in conjunctival and corneal epithelium were evaluated by real time quantitative PCR and immunohistochemistry. Results: BTX-B injected mice showed significantly decreased aqueous tear production and increased corneal fluorescein staining at the 1 week and 2 week time points compared with normal control and saline-injected mice. The BTX-B injected mice mRNA expression levels of TNF-alpha and IL-1 beta from conjunctival and corneal epithelial cells increased significantly at two early time points comparing with that of normal and saline injected mice, but IL-1 beta returned to normal levels at the 4 week time point. Saline injected mice showed no difference in mRNA expression of TNF-alpha, IL-1 beta, MIF, and IL-6 on the ocular surface tissue at all time points. Immunohistochemistry confirmed these findings. Conclusions: BTX-B induced mouse model showed decreased aqueous tear production, increased corneal fluorescein staining, and TNF-alpha and IL-1 beta increased expression on the ocular surface within one month. The patterns seen appeared to mimic those in humans with non-Sjogren's syndrome keratoconjunctivitis sicca (NS-KCS).