Dry eye and associated ocular surface diseases affect over 40 million Americans and are the primary reason for visits to ophthalmologists. Unfortunately, treatments for dry eye are either palliative or treat inflammation and ocular surface apoptosis, but they are not cures and do not target the main cause of the disease, abnormal tear production. The present proposal focuses on the lacrimal gland secretion of the aqueous layer of tears and its dysfunction that causes aqueous deficiency dry eye (ADDE). The overall goal of this research is to understand the underlying cause of ADDE, the dysfunction of the lacrimal gland and to provide a broader base for the development of dry eye therapeutics beyond targeting inflammation that amplifies the original cause. In the present proposal the neurally-activated signaling mechanisms that regulate lacrimal gland secretion of proteins, electrolytes, and water will be compared in healthy and diseased lacrimal glands. The disease model to be used is the thrombospondin-1 (TSP-1)-/- mouse that mimics the chronic development of human ADDE. TSP-1 is a master regulator of cellular signaling and is best known for activation of TGF-b to prevent inflammation. TSP-1 additionally has multiple signaling domains and can function both extra- and intra-cellularly. Unlike other murine models of dry eye where inflammation remains indistinguishable as a cause or effect, in TSP-1-/- mouse lacrimal glands distinct secretory dysfunction is followed by destructive inflammatory responses. To date aberrant Ca2+ signaling and protein secretion induced by neurotransmitter activation of a1D- adrenergic and M3-muscarinic receptors has been documented in TSP-1 null mouse lacrimal glands. These abnormalities are consistent with abnormal tear secretion and impaired lacrimal gland cell proliferation in TSP-1-/- mice. Together these functional changes lead to dry eye disease. The goal of the present proposal is to identify the signaling mechanisms responsible for the alterations in TSP-1-/- mouse lacrimal glands thereby generating new targets for treatment of ADDE. The following specific aims are proposed: 1. Determine the signaling pathway components targeted in TSP-1-/- compared to wild type (WT) mouse lacrimal glands that cause the differential changes in a1D-adrenergic and M3-muscarinic receptor-induced changes in protein secretion that lead to secretion of abnormal tears, 2. Investigate the cellular mechanisms that lead to decreased cell proliferation and alteration of the progenitor cells in TSP-1-/- mouse lacrimal glands preventing repair, and 3. Investigate if replacement of TSP-1 in the lacrimal gland can restore lacrimal gland function and improve the signs of ADDE in TSP-1-/- mice. TSP-1-/- mouse lacrimal glands will be compared with WT glands at three ages: 1. no inflammation or secretory deficit, 2. secretory deficit and no inflammation, and 3. secretory deficit and inflammation. For in vitro studies peroxidase activity, FACS analysis, western blotting, ELISA, immunoprecipitation, single cell Ca2+, WST-8, and immunofluorescence microscopy will be used. For in vivo studies, corneal fluorescein staining and tear volume will be evaluated after treatment.
Millions of Americans suffer from dry eye disease. The causes are varied and include aging, refractive surgery, menopause, autoimmune disease, and trauma causing damage to the ocular surface resulting in pain, inflammation, and irritation. There is no cure for dry eye and as the lacrimal gland is the primary contributor to the aqueous layer of the tear film, identification of the defective cellular mechanisms of a diseased lacrimal gland could lead to treatments for dry eye disease.
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