The antipsychotropic drug Duloxetine rescues PAX6 haploinsufficiency of mutant limbal stem cells through inhibition of the MEK/ERK signaling pathway

Aniridia is a panocular disease causing progressive severe visual impairment and blindness due to PAX-6 haploinsufficiency. One of the most disabling ocular symptoms is aniridia-related keratopathy (ARK), a progressive corneal opacification due to epithelial impairment, vascular and conjunctival pathologies. There is currently no available treatment to prevent progressive visual loss. For this aim, we have used mutant limbal cells for phenotypic screening using FDA-approved and bio-actives drug library and found Duloxetine, a serotonin and norepinephrine reuptake inhibitor used against severe depression as able to enhance endogenous PAX6 expression and target genes, which returned fairly to amounts found in normal limbal cells. In addition, Duloxetine could restore cell migration of the mutant cells. Furthermore, we show that Duloxetine activates PAX6 through inhibition of the ERK pathway on limbal mutant cells. This observation fits the recent report that MEK inhibitors enhance PAX6 in vivo, partially rescuing aniridia developmental phenotype of Pax6(+/-) mice. The discovery of an unique compound able to enhance PAX6 activity and that could be locally administered using eye drops associated with drug repurposing is expected to lead to rapid development of applicable drugs for the topical (eye drops) treatment of aniridia.