Distinct regulation by lipopolysaccharides of the expression of interleukin-1β by murine macrophages and salivary glands

The regulation of interleukin (IL)-1 expression and secretion by salivary glands and macrophages in response to lipopolysaccharides (LPS) was compared. In wild-type mice, injection of LPS significantly decreased the volume of saliva stimulated by pilocarpine and increased its protein and amylase concentration. It did not modify the salivary concentration of IL-1β. The cytokine was expressed by submandibular acini and ducts. Macrophages also expressed IL-1β but at lower concentration than salivary glands. The pre-incubation of macrophages with LPS increased the phosphorylation of IκB and the expression of IL-1β. Adenosine triphosphate also promoted the secretion of the cytokine by these cells. These responses were absent in submandibular gland cells. These glands expressed CD14, TLR4 and MyD88. P2X 7 -KO mice secreted a lower volume of saliva which contained less proteins and amylase. In conclusion, IL-1β is constitutively expressed by submandibular glands and its secretion is not regulated by a P2X 7 agonist. In these cells, LPS do not activate the nuclear factor-κB–pro-IL-1β axis in spite of the expression of the proteins involved in their recognition.