Saliva is vital for oral health. It is essential for the hydration of the oral mucosa;it provides lubrication, begins nutrient digestion and imparts antimicrobial and mechanical protection for the mouth and upper gastrointestinal tract. Reduced flow of saliva results in "dry mouth" (xerostomia) and greatly impacts the quality of life of sufferers. A major cause of salivary gland hypofunction is Sjogrens syndrome (SS), a relatively common autoimmune exocrinopathy affecting the salivary and lacrimal glands. SS results in progressively worsening dry mouth and dry eye (xerophthalmia) as significant glandular tissue is ultimately destroyed following lymphocyte infiltration. Significantly, in established animal models of SS, such as the IL14a B cell "knock-in" mouse, or the C57BL/6.NOD-Aec1Aec2 mouse, signaling events and fluid flow are markedly decreased prior to any evidence of destruction of glandular tissue. Moreover, morphologically intact tissue is often retained in SS patients, but paradoxically, is apparently refractory to stimulation. Given this information, this project will tst the hypothesis that defects in stimulus-secretion coupling are responsible for decreased saliva formation early in the disease and in remaining functional tissue as the disease progresses. The proposal will utilize mouse models of SS to probe the underlying defects in pathways leading to fluid and protein secretion from salivary and lacrimal glands as the disease develops. Important findings in mouse models will be validated by performing similar experiments in labial gland biopsies from SS patients.
In specific aim 1, experiments will be performed to ascertain why intracellular Ca2+ signaling, the primary stimulus for fluid secretion is compromised in SS mouse models. Experiments will determine whether the production of second-messengers is compromised in SS. Multi-photon imaging in gland lobules together with high-speed wide-field imaging, combined with focal flash photolysis in isolated acini, will question if the machinery responsible for Ca2+ release, Ca2+ influx or Ca2+ clearance is altered in SS.
In specific aim 2, experiments will be performed to elucidate why the exocytosis of protein is attenuated in SS models and if the function of ion channels necessary for fluid secretion is altered. Multi-photon imaging of fluid phase markers together with capacitance measurements of cell membrane surface area will be used to monitor exocytosis. We will determine whether signaling, or the exocytotic machinery in SS is disrupted. Finally, we will evaluate if the function of Ca2+- activated Cl- and K+ channels are altered in SS. These studies are designed to provide fundamental information regarding the functional changes occurring in stimulus-secretion coupling in SS. The ultimate goal of this project is to use this knowledge to rationale design and test strategies for the rescue and maintenance of secretion based on exploiting the physiology of remaining functional secretory tissue in SS.
Saliva and tears are fluids which are essential for maintaining a healthy mouth and eyes. Sjogrens syndrome is a common disease where the secretion of these fluids is decreased resulting in major health problems for the afflicted. This study is designed to define the reasons why outwardly healthy tissue which remains in these patients does not adequately secrete these fluids. Ultimately this information may be used to design therapies for this serious health issue.
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