Salivary proteome changes in response to stress and sensory stimuli

Stress is a physiological condition in which the psychophysical balance is altered and the body reacts to adapt. This adaptation occurs through the activation of different neuronal pathways, including the hypothalamic-pituitary axis and the autonomous system. The aim of this study was to highlight the variations of the salivary proteome in an acute stress model. The study was carried out on a group of 21 students aged between 18 and 30, carefully selected through the use of questionnaires. The students underwent an initial relaxation phase through sensory stimuli followed by a stress phase through an unexpected simulate oral examination in the presence of a professor. During the stress test, electrocardiogram, electroencephalogram, and skin conductance were constantly monitored. Whole saliva samples were collected both at the end of the relaxation phase and the stress phase, immediately processed and stored at -80°C until use. Salivary proteins (250 g) were separated by two-dimensional electrophoresis, resulting gels stained with the ruthenium complex (RuBP), images captured by ImageLAS4010 and analyzed with the Same Spot software. The differentially expressed protein spots were trypsin digested and analyzed by LC-MS/MS for protein identification. The proteomic results showed a significant differential expression of 29 spots in overall comparisons. In particular, an increase in -amylase secretion and variations in various kind of immunoglobulin chains and polymeric immunoglobulin receptor were observed. Moreover, other proteins resulted differentially secreted as a consequence of acute stress such as calgranulin B, cystatin S precursor and 14-3-3 proteins. Thus, the proteomic analysis of saliva can be an useful approach to evaluate the rapid responses induced by an acute stress such as the psychosensory one resulting from an exam. Overall, our results allow to better understand the salivary molecular changes induced by variations related to the psycho-sensory area which until now are mainly assessed by recording the autonomic nervous and cardiovascular systems