Effect of Psychologic Stress on Peroxidase and Thiocyanate Levels in Human Saliva Detected by Ultraweak Chemiluminescence

Abstract

Saliva sampling has the advantage of being noninvasive and stress free. Based on a recent study, salivary ultraweak chemiluminescence (UCL) is a new biomarker of psychologic stress. However, it is not clear what causes changes in the UCL level and whether the change is biologically significant. We investigated the candidates for salivary UCL induced by psychological stressors and discuss the physiologic function of these candidates. Volunteers completed a questionnaire and then performed the Kraepelin test. Saliva was sampled just before, immediately after, and 30 min after the stress exposure. The UCL of saliva significantly increased just after stress exposure (1.56-fold) and returned to prestress levels after 30 min. The concentration of secretory immunoglobulin A also increased significantly and the change in both biomarkers was rapid. Similar significant changes were observed in salivary peroxidase activity and the concentration of thiocyanate (SCN^-). On the other hand, the levels of amylase activity did not significantly increase and the concentration of cortisol increased slowly. Moreover, in the reconstitution experiment, UCL was generated at the same level by a mixture of peroxidase and SCN^- at physiologic concentrations. In conclusion, we determined that the Kraepelin test as a mental arithmetic task elicited a significant response in the body and this response can be calculated using salivary UCL. Furthermore, SCN^- and peroxidase in the saliva play a key role in salivary UCL.