Salivary proteome changes in response to acute stress in students performing an exam simulation with and without olfactory stimulation

The autonomic nervous system (ANS) plays a crucial role both in acute and chronic psychological (mental) stress eliciting changes in many local and systemic physiological and biochemical processes. Salivary secretion is regulated by ANS. In this study we explored salivary proteome changes produced in 34 students by a test stress, which simulated an “oral exam”. Students underwent a relaxation phase followed by the stress test, during which electrocardiogram was recorded. To evaluate the effect of the olfactory stimulus, 16 students experienced a pleasant odor diffused throughout the whole session in the room. Saliva samples were collected after the relaxation (T0) and the stress test (T1). State anxiety was also evaluated at T0 and T1. Salivary proteins were separated by two-dimensional electrophoresis and the T1 protein pattern was compared to the T0 one. Spots differentially expressed were trypsin digested and identified by LC-MS/MS. Western blot analysis was used to validate results. Anxiety scores and heart rate changes indicated that the fake exam induced anxiety. Significant changes of -amylase, polymeric immunoglobulin receptor, and IgA secretion were observed after stress test in both conditions. Moreover, the presence of a pleasant odor reduced the acute social stress also affecting the salivary proteome changes and suggested potential differences in gender responses particularly for IgA secretion. Therefore, saliva proteomic analysis was useful to evaluate the rapid responses associated to an acute stress test also highlighting known biomarkers.