Involvement of interleukin 18 in cataract development in hereditary cataract UPL rats

Our previous studies have demonstrated that lens epithelial damage by excessive nitric oxide causes an elevation in lens opacification in UPL rats, and it has been reported that interferon-gamma production in lens epithelial cells is involved in cataract development. In this study, we investigated the involvement of interleukin (IL)-18, which leads to interferon-gamma, in UPL rat lenses. The opacification of UPL rat lenses starts at 39 days of age. The gene expression levels causing IL-18 activation (IL-18, IL-18 receptor and caspase-1) are increased at 32 days of age, and the expression of mature IL-18 protein in the UPL rat lenses also increases with ageing. On the other hand, the interferon-gamma levels in UPL rat lenses are increased, and the increase in interferon-gamma levels in UPL rat lenses reaches a maximum at 39 days of age. Mature IL-18 expression and interferon-gamma production are achieved prior to the onset of lens opacification. In conclusion, the expression levels of IL-18 in the lenses of UPL rats are increased with aging. In addition, interferon-gamma levels in the lenses of UPL rats are also increased. It is possible that interferon-gamma generated by the activated IL-18 may induce cataract development in UPL rats.