Three recent findings are leading to a mechanistic understanding of glandular destruction in Sjogren's syndrome: 1) identification of pro- inflammatory cytokines associated with autoimmune sialoadenitis, 2) recognition that salivary gland epithelial cells are co-participants in the immune response, and 3) characterization of new mouse models for autoimmune sialoadenitis in which B and T immune effector cells and/or certain cytokines are absent. Despite these gains, important questions remain regarding the role of cytokines in acinar cell destruction. The hypothesis underlying Aim 1 is that alterations in the production of certain inflammatory cytokines in parotid gland acinar cells initiate autoimmune sialoadenitis. Using five mouse models (NOD, NOD-scid, MRL/lpr, NOD-H.2b (diabetes-free phenotype), NODIllbctm1Chaplin (an IL-1beta knockout mouse)) and a control BALB/c strain, quantitative RT- PCR, and Southern blot confirmation, we will make quantitative determinations of three key inflammatory cytokines IL-1beta, IL-6, and TNF-alpha) mRNAs in dispersed parotid acinar cell preparations that are T-cell free. TUNEL analysis and in situ hybridization will examine apoptosis in the same cells showing altered cytokine expression. The studies in this aim explore several new questions important to our understanding autoimmune sialoadenitis: 1) what are the quantitative alterations of cytokine mRNAs in acinar cells from mouse models that precede phenotypic expression of autoimmune sialoadenitis?; 2) is increased acinar cell production of certain inflammatory cytokines independent of a lymphocytic infiltrate?; and 3) does increased acinar cell production of inflammatory cytokines occur in acinar cells involved in apoptosis? The experiments in Aim 2 are designed to test the hypothesis that inter- and/or intracellular storage and release of certain inflammatory cytokines are dysregulated in autoimmune sialoadenitis. Biochemical and ELISA experiments will show which of these key inflammatory cytokines are released by adrenergic and by cholinergic stimulation and in what time period following stimulation in early though late stages of autoimmune sialoadenitis. Morphologic and morphometric experiments will show whether or not a vesicular secretory process is capable of selective release of these cytokines and whether this process is dysregulated before disease onset. Immunoelectron microscopy experiments will test the hypothesis that cytoplasmic vesicles containing proinflammatory cytokines may be mistargeted basolaterally thereby releasing mediators capable of recruiting inflammatory cells or intracellularly thereby initiating an apoptotic pathway.
