Increased expression of β-defensins during development of sialoadenitis in MRL/lpr-mice

Objective: The expression of β-defensin(BD)-1, -2 and -3 has been detected in the salivary gland. However there is little information on the expression profiles of these BDs in the salivary gland under inflammatory conditions. MRL-Mp-lpr/lpr (MRL/lpr) autoimmune mice spontaneously develop lymphocytic infiltration of the salivary gland, producing a condition that resembled Sjogren's syndrome. In the present, we analyzed the expression patterns of BD-1, -2 and -3 during the development of sialoadenitis in MRL/lpr mice. Methods: Submandibular glands of female MRL/lpr mice were dissected at 4, 8, 10, 12, 14 and16 weeks of age (n=4 in each group). Submandibular glands of each sample were fixed, embedded and stained with H.E. staining. The immunohistochemical staining for b-defensins were employed anti-human b-defensin 2 antibody (Peptide Institute, Inc.) and anti-human b-defensin 3 antibody (Novus Biologicals Inc.) Total RNA was extracted from submandibular glands of each group. A quantitative RT-PCR assay was performed by quantitative RT-PCR using TagMan probes (Applied Biosystems) in order to observe the mRNA level of mouse BD-1, -2 and -3. The statistical significance of the difference was analyzed using Scheffe's test. Results: A mild, a moderate, and a severe inflammatory infiltrations are found in the submandibular glands at 12, 14, and 16 weeks-old MRL/lpr mice, respectively. The immunohistochemical staining for b-defensin 3 is detected in the ductal cell. Mouse BD-1 mRNA was expressed same levels among the ages. The expression level of BD-2 mRNA is significantly higher in 16 weeks than 4 or 8-weeks-old (p<0.01). The expression level of BD-3 mRNA is a highest in the 14-weeks-old, and the level is significantly higher than in 4-week or 16-week-old (p<0.05). Conclusion: The results indicate that BD-2 and -3 may mainly contribute to protection against microbial infection in the salivary duct during sialoadenitis before the ducts are destroyed by the autoimmune disease.