Cellular Basis of Steroid Glaucoma

Glaucoma is a blinding disease affecting millions of Americans. In this disease, the pressure inside the eye becomes elevated and can destroy the optic nerve, resulting in permanent visual loss. Treatment of the eye with steroid eye drops can lead to increased pressure and in some individuals can actually cause glaucoma and loss of vision. The purpose of the research outlined in this grant proposal is to discover the reasons that steroid treatment can cause increased pressure, and to use this knowledge to develop potential new means to prevent and treat this disease. It is even possible that such new approaches may help us to develop new medications for other types of glaucoma. Our studies are based on the premise that steroid glaucoma has a cellular basis. There are two layers of cells through which the clear fluid in the eye, or aqueous humor, must pass as it drains from the eye to return to the circulation. Normally the aqueous can flow through small spaces which lie between the cells in these layers. Through study of human cells obtained from these layers and kept alive and healthy in culture, we are seeking to understand how the passage of fluid through them can be regulated. In earlier studies supported by the AHAF, we found that with steroid treatment causes the channels between the cells to become narrowed, and the flow is clearly reduced. Moreover, we found an increased synthesis of a protein associated with cell junctions. Then, it was also discovered that treating these cells with a molecule designed to block synthesis of that specific cell junction protein restored fluid flow to normal levels. This result demonstrated that the protein was an important element in maintenance of normal resistance to flow. These findings allowed us to formulate the hypothesis that in this form of glaucoma, steroids increase synthesis of proteins associated with cell junctions so that the junctions are altered to restrict flow through cell layers, resulting in an elevated pressure and glaucoma. We have developed three Specific Aims to test this hypothesis: In Specific Aim 1, we will use new molecular techniques to increase and decrease the junctional protein to see if these changes correlate with expected alterations in fluid flow and junctional proteins. In Specific Aim 2, changes in this junction-associated protein and flow will be examined in an animal model of steroid glaucoma we are developing. Tissues from patients with steroid glaucoma will also be studied to see if the same alterations in junctions and junctional proteins occur. If these studies show that our hypothesis is correct, it is possible that a new therapy based on decreasing this junction-associated protein may be effective for the treatment of steroid and other glaucomas, and we can begin to test it in the animal model, as planned in Specific Aim 3.