Analysis of the Vitamin D Receptor in Salivary Tissue in Sjögren’s Syndrome

Objectives: Sjögren’s Syndrome (SS) is an autoimmune disease in which the immune system targets the lacrimal and salivary glands, often leading to loss of tears and saliva. While the cause of SS is poorly understood, environmental factors likely contribute to disease. Vitamin D deficiency is implicated in SS, although the role of vitamin D in SS initiation and progression is unclear at present. Vitamin D binds the vitamin D receptor (VDR), and has potent innate immunosuppressive properties. The objective of this study was to determine whether the VDR is expressed in human salivary gland cells, and to assess VDR expression in the salivary tissue of the SS mouse model NOD/ShiLtJ (NOD).
Methods: To assess VDR expression in human salivary cells, we used the submandibular salivary gland (SMG) cell line A253. We analyzed constitutive VDR expression by real time PCR (RT-PCR) and western blot analysis. Then, we isolated SMG tissue from female NOD mice with clinical disease (n = 5) and age and sex matched BALB/c controls (n = 5), and quantified VDR levels using RT-PCR.
Results: We found A253 cells expressed VDR constitutively. Moreover, both NOD and BALB/c SMG tissue expressed VDR, and VDR expression was significantly reduced in NOD SMG tissue as compared to that derived from BALB/c (p = 0.029).
Conclusions: VDR is expressed in both murine and human salivary cells. Preliminary data suggest that reduced VDR levels may contribute to salivary gland inflammation in NOD mice.