Stress-induced cytokine changes in rats

Stress-induced cytokine changes may be the link between stress and the pathogenesis of psychiatric disorders such as depression, and organic diseases such as infections, autoimmune diseases and cancer. We tested the effect of stress on interleukin (IL)-2, IL-4, IL-6, IL-10, IL-22, tumour necrosis factor (TNF)-a and interferon (IFN)-y serum levels in male Wistar rats. Rats underwent either acute stress by forced swimming (N = 8), chronic restraint stress (N = 8), or were not subjected to any stress (N = 8). IL-2 serum levels were significantly higher in forced swimming, but not in restraint stress rats, compared to non-stressed rats. IL-4, IL-6, IL-10 and TNF-a levels were higher in both forced swimming and restraint stress compared to non-stressed rats. IFN-y production was significantly decreased by restraint stress, but not by forced swimming. IL-22 was not affected significantly by either stress condition. Alterations in the pro-inflammatory cytokines IL-6 and TNF-a may indicate a pathophysiological pathway from acute and chronic stress to the development of depression. Changes in IL-4 and IL-10 may link acute and chronic stress to autoimmune disorders, allergies or cancer. The reported changes in IFN-y could provide an explanation for the higher susceptibility to infection seen in life periods associated with sustained levels of stress.