Proteomic Analysis of Salivary Acinar Cells from EGCG-Treated NOD Mice

Autoimmune disorders, the third most common group of diseases in the United States, affect about 8% of the population. Sjogren's syndrome (SS), a major autoimmune disease, involves autoimmune-induced atrophy of salivary and lacrimal gland secretory acinar cells. This tissue destruction leads to xerostomia and xerophthalmia. At present, approximately 30% of American seniors experience xerostomia. Thus, identification of biomarkers for early detection and intervention would help the development of novel approaches to ameliorating SS. We previously reported that green tea polyphenols (GTPs) reduced the severity of autoimmune symptoms in NOD mice. The NOD mouse (derived from the BALB/c strain) develops an autoimmune-induced SS-like pathology, and is a suitable model to test the feasibility of identifying such markers, and to examine the effects of GTPs on autoimmunity. Objectives: To identify protein expression changes and disease markers of the salivary gland acinar cells in NOD mice either consumed water or EGCG (the most abundant GTP), by laser capture microscopic (LCM) dissection and proteomic analysis. Methods: Analysis of protein expression patterns in the salivary acinar cells of NOD mice was performed using advanced proteomic technology. Submandibular salivary acinar cells were dissected by LCM. Fluorescent dye-labeled proteins were subjected to 2-dimensional gel electrophoresis and protein expression levels were quantified. Results: EGCG modulated protein expression in NOD mice, and some proteins had over a 10-fold change in expression level. Changes were also found between EGCG-fed NOD and Balb/c normal mice. Collectively, EGCG treatment of NOD mice was found to shift protein expression in acinar cells towards the normal (BALB/c) pattern. This may account in part for the protective properties of EGCG against autoimmune diseases. Conclusion: proteomic technology is potentially useful for the identification of candidate biomarkers for either early detection or therapeutic-response of autoimmune diseases.