MMP9 and dry eye syndrome: It has been reported that selenium-binding lactoferrin (Se-lactoferrin) eye drops suppress the upregulated expression of heme oxygenase-1, cyclooxygenase-2, matrix metallopeptidase-9, and interleukin-6, and also suppress 8-OHdG production in a murine dry eye model induced by surgical removal of the lacrimal glands (Higuchi et al., 2012).