Cyclosporine inhibits apoptosis in experimental murine xerophthalamia conjunctival epithelium

Abstract

This study examined the inhibitory effect of topical cyclosporine (CsA) treatment on conjunctiva epithelial apoptosis in a murine model of xerophthalamia. Dry eye was induced in 3 groups of C57BL6 mice by subcutaneous injection of scopolamine (t.i.d) and exposure to an air draft and low-humidity environment for 16 h each day for 12 days. The dry eye control group received no topical treatment; another group received 1 microL of 0.05% CsA topically (t.i.d, dry eye+CsA); and the third group received 1 microL of the castor oil vehicle of CsA topically (t.i.d, dry eye + vehicle). Normal mice were used as untreated controls. Twelve days later, the mice were killed, and their conjunctivas were excised. The number of the conjunctival goblet cells was counted in tissue sections stained with periodic acid Schiff (PAS) reagent. Their conjunctiva epithelium had been investigated by immuno-histochemical staining to detect the goblet cells and the expression of Caspase-3, Bax and bcl-2. Our results showed that compared with dry eye control and dry eye mice + vehicle groups, the number of conjunctival epithelial goblet cells was significantly greater in the untreated controls and dry eye mice receiving CsA (P < 0.01 for both groups). There was no significant difference in the number of conjunctival epithelial goblet cells between the dry eye control and dry eye+vehicle group. It was also true of the number of conjunctival epithelial goblet cells when comparison was made between the normal group and the dry eye+CsA group. Expressions of Caspas-3 and Bax were increased and ex-pression of bcl-2 was decreased in conjunctival epithelial cells in dry eye control and dry eye mice+vehicle groups. There was a significant positive correlation between goblet cell number and the number of cells that expressed bcl-2, and a negative correlation between goblet cells and Caspase-3 and Bax expression. It is concluded that the topical use of CsA could significantly reduce conjunctival epithelial apoptosis and protect goblet cell against the loss in experimental murine xerophathalamia. Inhibition of apoptosis appears to be a key mechanism responsible for the therapeutic effect of CsA on xerophthalamia.