STAMBP and Keratoconjunctivitis sicca: As for the mechanisms, α-MSH activated PKA and Erk pathways in the dry eye ocular surface tissues (Fig. 7), and blockade of either pathway by the specific pharmacological blocker abolished the beneficial effects of α-MSH (Figs 3, 4, 5, 6), suggesting that α-MSH exerts its protection via both pathways.