Protective Effects of EGCG on Salivary Gland of 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) is one of the major autoimmune disorders and leads to autoimmune-induced atrophy of salivary and lacrimal gland secretory acinar cells, causing xerostomia and xerophthalmia. There is no cure for SS and the pathogenesis of the disease is still largely unknown. Thus, protection of the acinar cells from autoimmune-induced destruction becomes essential for salivary function in SS patients, especially, by non-toxic, naturally-occurring phytochemicals needs to be investigated. We hypothesize that oral consumption of EGCG reduces severity of SS symptoms via its anti-apoptotic, anti-inflammatory, and autoantigen-inhibitory properties. Objectives: to investigate if EGCG, the most abundant green tea polyphenol, possesses protective effects against autoimmune-induced acinar cell destruction in the non-obese diabetic (NOD) mouse model for SS-like symptoms. Methods: animals were provided with either water or water containing 0.2% EGCG. At the age of 8, 16 and 22 weeks, samples were collected for pathological and serological autoantibody analysis. Results: Massive lymphocyte infiltration was observed in the salivary glands of the water-fed group at the age of 16 weeks, while the EGCG group showed significantly reduced lymphocyte infiltration. By 22 weeks of age, animals fed with water demonstrated high levels of apoptotic activity within the lymphocytic infiltrates, and high levels of serum total autoantibody, in comparison with the animals fed with EGCG. In addition, proliferating cell nuclear antigen (PCNA) and Ki-67 were significantly induced in the salivary glands of animals fed with water in comparison with that in the EGCG-fed animals. Conclusion: EGCG is able to protect the salivary acinar cells from autoimmune-induced inflammation, apoptosis, and autoantibody production in NOD mice. The results suggest that EGCG could ultimately be used to delay or manage SS-like autoimmune disorders.