Response to lipopolysaccharide in salivary components and the submandibular gland of pigs

The diagnostic use of saliva for disease detection and health monitoring is increasing in recent years. To investigate whether the components of saliva change with lipopolysaccharide (LPS) challenge and clarify whether these changes directly relate to the submandibular gland (SMG), 12 pigs were employed in the present study. At 6 h after LPS intramuscular injection, samples including saliva, plasma and SMG were taken. The amylase, cortisol, Immunoglobulin A (IgA), tumor necrosis factor alpha (TNF-α) and interleukin 1 beta (IL-1β) contents were analyzed by colorimetry, radioimmunoassay or ELISA, respectively. Chromogranin A (CgA) and lactoferrin protein concentrations were detected by western blot. Adenosine triphosphate (ATP) was measured by high-pressure liquid chromatography (HPLC) and the related gene expression was analyzed by reverse transcription polymerase chain reaction (RT-PCR) in SMG. The results showed that LPS treatment increased amylase activity and cortisol concentrations, whereas IL-1β, CgA and lactoferrin concentrations showed a decrease in saliva. Toll-like receptor 2 (TLR2), IL-1β and TNF-α gene expression in SMG increased. Decreased ATP concentration in SMG may be the reason for the opposite changes of IL-1β, lactoferrin and CgA content in the saliva and the SMG. The present study for the first time comprehensively demonstrates that the altered parameters in saliva can indicate the body inflammation in pigs, and they may become useful, noninvasive biomarkers for the evaluation of body state.