Expression of Toll-like Receptors during Development of Sialoadenitis in Mice

Objectives: Toll-like receptors (TLR) play a fundamental role in the activation of the innate immune system during infection. Although expression of TLRs has been detected in the salivary gland, there is little information on the expression profiles in the salioadenitis. Non-obese diabetic (NOD) mice spontaneously develop sialoadenitis, producing a condition that resembles Sjogren's syndrome. The present study analyzed the expression patterns of TLR-2,-3,-4,-7,-8 and -9 during the development of sialoadenitis in NOD mice. Method: Female NOD mice (ClEAJapan) were used in the present study. Submandibular glands were dissected from the mice at 4,8,10,12,14 and 16 weeks of age (n=5 in each group). Expression of and TLR-2,-3,-4,-7,-8 and -9, and myeloid differentiation factor 88 (MyD88) was observed by RT-PCR and quantitative RT-PCR using TaqMan probes (Applied Biosystem, CA). Several experiments were performed, each in triplicate. The relative expression of each mRNA was calculated as the ΔΔCt using the formula described by Saitoh et al.(Med Mol Morphol 2007). The data was analyzed using one-way ANOVA. Differences between experimental groups were considered statistically significant at the p<0.05 levels. Immunohistochemical staining for TRL-7 and -9 was carried out using anti-TLR-7 and -TLR-9 antibodies (Hycult Biotech.) Results: The submandibular glands show no indication of inflammatory reactions in 4- and 8-week-old mice. Ten-week-old mice generally had one focus of lymphatic infiltration per lobule. Expression levels of TLR-7 and-9 at 14 and 16 weeks were significantly higher than at 4 or 8 weeks (p<0.01). Immunohistochemical positives for TLR-7 and -9 were observed in the foci of lymphatic infiltration. Conclusion: The results indicate that TRL-7 and -9 may be upregulated during the development of autoimmune sialoadenitis.