Background: There is increasing evidence that chaperones are also present outside the cell, exerting cytokine-like effects and influencing immune recognition. Hsp70 has been found to be present in human blood sera. Chaperonins Cpn10 and Cpn60 are present in pancreatic juice, but Hsp70 is not. These observations raise the possibility that molecular chaperones may be present in other secretory fluids, such as human saliva.
Material/methods: Human whole saliva was collected from six participants under resting conditions and secretory stimulation. The samples were precleared by centrifugation and sterile filtered. Salivary volume, protein concentration and amylase activity were determined. For detection of Hsp70 saliva proteins were separated on a 12.5% SDS-PAGE. Semi-dry Western blot analysis was used with a primary antibody against the inducible form of Hsp70. Hsp70 bands were detected with a horseradish peroxidase-linked secondary antibody and ECL-Western blotting analysis.
Results: A single band was recognized around 70 kDa in the saliva of all the participants. There was a significant decrease of Hsp70, and a non-significant decrease of total protein concentration during stimulation, whereas the activity of salivary amylase increased significantly. Stimulation significantly increased the Hsp70, total protein and amylase outputs as well as the amylase/protein ratio, and decreased the Hsp70/amylase and Hsp70/protein ratios.
Conclusions: Hsp70 is secreted to saliva, but unlike amylase is not transported by the exocytotic secretory mechanisms of acinar cells. Passive transport mechanisms of Hsp70 from blood serum or from salivary gland cells may be major routes of salivary Hsp70 secretion.