Suppression of NF–Kappa B Signaling by SN50 Potentiates TNF–Alpha/JNK–Driven Cell Proliferation in Healing Corneal Epithelium and Has Therapeutic Effects on Corneal Alkali Burns in Mice

Abstract

Abstract: : Purpose: To evaluate the therapeutic efficacy of topical administration of SN50, an inhibitor of nuclear factor–kappa B (NF–kB), in a corneal alkali burn model in mice and to examine the role of NF–kB signal in epithelial cell proliferation. Methods: A central alkali burn was produced with 1N NaOH in right cornea of C57BL/6 mice (n=68) under general and topical anesthesia. SN50 (10 micro g/micro l) or vehicle was topically administered daily for up to 12 days. The eyes were processed for western blot, histology, immunohistochemistry after BrdU labeling and real–time RT–PCR. To elucidate the role of NF–kB in epithelial cell proliferation, mouse corneas were organ–cultured with either TNF–alpha, SN50, or an inhibitor of JNK and epithelial proliferation was evaluated. Examinations of cell proliferation in healing epithelium in TNF–alpha–null mice (n=8) treated with SN50 or vehicle were also conducted. Results: Western blot and immunostaining showed that SN50 suppressed NF–kB activation in tissue and reduced the incidence of epithelial defects/ulceration in healing corneas. Myofibroblast generation, inflammation, basement membrane destruction and mRNA expression of cytokines were all less in SN50–treated corneas as compared with control. Experiments using an organ–culture and TNF–alpha–null mice showed that acceleration of epithelial cell proliferation by SN50 treatment was found to depend on TNF–alpha/JNK signaling. Conclusions: Topical SN50 is effective in treating corneal alkali burns in mice. The mechanisms may include suppression of activation of stromal cells and invasion of inflammatory cells, as well as acceleration of epithelial cell proliferation by blocking NF–kB signaling.

Keywords: cornea: basic science • signal transduction: pharmacology/physiology • wound healing