Modulation of Corneal Endothelial Mitochondrial Activity and Dysfunction by Estrogen

“Modulation of Corneal Endothelial Mitochondrial Activity and Dysfunction by Estrogen” ABSTRACT The broad long-term objective of this project is to determine if estrogen is protective or detrimental to the health of corneal endothelial cells. Estrogen has been shown to be protective of many tissues and this protection is lost during menopause. Estrogen has many cellular effects including modulation of mitochondrial activity and antioxidant status. The corneal endothelium, responsible for maintaining the transparency of the cornea, is metabolically very active and has a very high density of mitochondria. Fuchs Endothelial Corneal Dystrophy (FECD) is characterized by an accelerated loss of endothelial cells, basement membrane deposits (guttae), and corneal edema. FECD specimens show dysfunctional mitochondria, reduced mitochondrial density, and high levels of oxidative damage to DNA, protein, and lipids. Two-thirds to three-quarters of FECD patients are postmenopausal women, suggesting that like glaucoma, macular degeneration, dry eye, and cataract, estrogen is protective. Conversely, an alternate hypothesis that premenopausal estrogen exposure is toxic to the endothelium via UV-light facilitated formation of nuclear and mitochondrial Estrogen-DNA adducts has been put forth. Studies examining estrogenic effects on corneal endothelium have been done with cultured cells or an acute damage model in mice. FECD however develops slowly over many years. Therefore, mouse models that provide a slower development of endothelial dysfunction will be best for determining if estrogen modulates dysfunction. To test the hypothesis that estrogen influences endothelial function, mitochondrial activity, or antioxidant capacity, in Specific Aim 1 corneal thickness, Endothelial Cell Density and morphology will be measured in an equal number of male and female estrogen receptor knockouts (KO) over one year. At that time endothelial explants will be examined for levels of mitochondrial activity and density; reactive oxygen species; oxidative damage and gene expression changes. Using the same methods, in Specific Aim 2, to test if estrogen protects the corneal endothelium, we ask if sex is a factor in oxidative stress models of endothelial dysfunction. Lastly, in Specific Aim 3, using a relatively new mouse menopause approach, we ask if corneal endothelial function is better, worse or the same in oxidative stress models following menopause. Together, completion of the aims will determine unequivocally whether the corneal endothelium is protected by estrogen, damaged by estrogen, or neutral. If protective, estrogen receptor agonists could delay progression of FECD and extend the useful life of endothelial grafts. If estrogen receptor agonists are going to be used to treat dry eye disease, lower IOP, or protect retinal ganglion cells in glaucoma or other eye disorders, it is essential to know if estrogen is protective or toxic to the corneal endothelium.