Acute phase protein induction by experimental inflammation in the salivary gland.

BACKGROUND: The submandibular gland (SMG) is a major salivary gland, which plays an important role in maintenance the oral health. In this study, we intended to explore the role of the SMG's defense system of the animals in which experimental inflammation is induced.

METHODS: The levels of mRNAs for inflammation cytokines and acute phase proteins were detected by reverse transcriptase-polymerase chain reaction (RT-PCR).

RESULTS: The mRNAs for acute phase proteins were found to be increased in the SMG and extraorbital and intraorbital lacrimal gland (ELG and ILG) of rats at 24 h after subcutaneous injection of turpentine oil. The induction of mRNA for these inflammatory proteins by turpentine oil was preceded by a transient increase in the level of mRNAs for IL-1beta, IL-6 and TNF-alpha at 6 h after subcutaneous injection of the oil. Such cytokine induction was similarly seen by lipopolysaccharide (LPS) injection, and involvement of Toll-like receptor 4 (TLR4) was strongly suggested from experiment using C3H/HeJ mice, a TLR4-deficient mutant strain.

CONCLUSION: The up-regulation of acute phase proteins and inflammation cytokines in the SMG, ELG and ILG by experimental inflammation suggests the existence of a strict defense system via the innate immune system in the SMG and other exocrine gland.