Sjogren's syndrome (SS) is an autoimmune disorder characterized by inflammation and destruction of lacrimal and salivary glands leading to xerostomia. The diminished function of exocrine glands in SS is often associated with lymphocytic infiltration of the tissue and increased production of pro- inflammatory cytokines such as interleukin-1beta (IL-1beta), interleukin-6 (IL-6), tumor necrosis factor-alpha (TNFalpha) and interferon-gamma (IFNgamma). We have shown that the G protein-coupled P2Y2 nucleotide receptor (P2Y2R) is up-regulated in response to damage or stress in salivary gland epithelium. The role of the P2Y2R in stressed salivary epithelium has not been determined, however, studies in our lab have shown that in vascular endothelium the activation of up-regulated P2Y2Rs increases the expression of VCAM-1 and promotes the binding and transendothelial migration of monocytes. Preliminary results indicate that activation of P2Y2Rs in salivary epithelium up-regulates VCAM-1 expression and stimulates lymphocyte adherence, a source of cytokine release. Moreover, we have obtained evidence that P2Y2R activation in salivary glands enhances activity of metalloproteases that are involved in the release of soluble cytokines from the salivary epithelium. These data strongly support a hypothesis that P2Y2R expression and activation in salivary gland cells contributes to epithelial dysfunction in SS by regulating the expression of adhesion molecules that promote the binding of immune cells to salivary epithelium and by activating metalloproteases involved in the release of cytokines that compromise epithelial integrity. Therefore, proposed studies will utilize polarized rat parotid (Par-C10) monolayers to evaluate the role of P2Y2Rs in the expression of specific adhesion molecules that promote lymphocyte adherence (Specific Aim 1) and to the activation of metalloproteases that generate pro-inflammatory cytokines (Specific Aim 2). Then, the effects of relevant cytokines will be evaluated with respect to transepithelial anion secretion (l(sc)) and the expression and phosphorylation of epithelial cell tight junction proteins that regulate ion transport and epithelial integrity in salivary glands (Specific Aim 3). These studies may lead to better therapeutic strategies for minimizing autoimmune-associated dysfunction of salivary gland that contributes to xerostomia in patients with SS.
