Abstract: Heat shock proteins (HSP) represent a very conservative family of cytoprotective proteins that are specifically induced in response to several environmental stresses at the cellular level (heat shock, cellular energy depletion, oxidative stress, or inflammation). Among these proteins, the inducible form of the 70 kDa family, i.e., Hsp72, plays an important role in cytoprotection by preventing the abnormal folding of newly synthesized polypeptides, or by assisting in the repair of damaged proteins or in the degradation of irreversibly damaged proteins. An adapted stress response in terms of transcription and translation of Hsp70 is necessary to ensure cell survival under stressful conditions. Lymphocytes apoptosis plays an important role in the immune function. It is now well documented that acute psychological stress, particularly when it reaches high intensity, leads to high Hsp70 expression and lymphocytes apoptosis. Relatively fewer studies have been conducted on the effects induced by chronic psychological stress on Hsp70 expression in lymphocytes, and the relation between Hsp70 expression and lymphocytes apoptosis. The aim of this study is to investigate the effect of psychological stress on Hsp70 expression, lymphocytes apoptosis, and the relationship between them.
Twenty-four SD rats were randomly divided into three groups of eight as follows: control group (C), high intensity psychological stress group (H), and moderate intensity psychological stress group (M). A flow cytometer detected the extent of apoptosis and hsp70 expression in the peripheral blood lymphocytes of rats under psychological stress of varying intensity. One-way ANOVA and correlation analysis were used for the statistical analysis.
In comparison with group C, the Hsp70 expression in lymphocytes groups H and M was significantly higher. The extent of apoptosis in group H increased significantly, while the extent of apoptosis in group M did increase, but not significantly. The positive correlation between the changes of Hsp70 expression and the lymphocytes apoptosis in group M was significant, while the correlation for group H was positive, but not significantly.
This study suggested that chronic psychological stress, especially that of high intensity, increased the Hsp70 expression and the lymphocytes apoptosis in peripheral blood lymphocytes. Furthermore, as the intensity of psychological stress increases, the Hsp70 expression in lymphocytes increased slowly while the extent of apoptosis increased rapidly. As a result, the immune function kept deteriorating

Key words: psychological stress, lymphocytes, Hsp70, apoptosis