Effects of Oxidative Stress on the Conjunctiva in Cu, Zn-Superoxide Dismutase-1 (Sod1)-Knockout Mice

A healthy conjunctiva secreting mucins is essential for maintaining the integrity of the ocular surface epithelium. We used Cu, Zn-superoxide dismutase 1-deficient mice (Sod1-/- mice) and investigated the effect of oxidative stress on the tear function, conjunctival phenotype, and ocular surface mucin expression. Fifty-week-old C57/B6 wild-type (WT) and Sod1-/- mice were used for evaluations of the tear film breakup time and periodic acid Schiff staining of the conjunctival specimens to detect goblet cell densities in the conjunctiva. Immunohistochemistry stainings with anti-Muc5AC, anti-Muc1, anti-4-hydroxy-2-nonenal, and anti-8-hydroxy-2'-deoxyguanosine antibodies were also performed. The mRNA expression levels of Muc1, Muc5AC, Spdef, involcurin, and transglutaminase 1 were quantified with real-time RT-PCR. The mean goblet cell density in the aged Sod1-/- mice was significantly lower than the aged WT mice. The mean number of Muc5ac-positive cells was significantly lower in the aged Sod1-/- mice compared with the aged WT mice. The conjunctival epithelium in the aged Sod1-/- mice displayed marked staining with lipid and DNA oxidative stress markers. The mRNA expression of transglutaminase 1 and involcurin in the aged Sod1-/- mice was significantly higher than the aged WT mice. The Spdef mRNA expression in the aged Sod1-/- mice was also significantly lower than the aged WT mice. Elevated oxidative stress status appears to affect the conjunctival differentiation and alter the conjunctival epithelial phenotype with aging in the Sod1-/- mice.