Chronic Mild Stress in Mice Decreases Peripheral Cytokine and Increases Central Cytokine Expression Independently of IL-10 Regulation of the Cytokine Network

OBJECTIVES: Accumulating evidence indicates that stress leads to an increased expression of pro-inflammatory cytokines such as interleukin (IL)-6. The production and action of pro-inflammatory cytokines are down-regulated by anti-inflammatory cytokines such as IL-10. This makes IL-10-deficient mice a potentially useful model to assess the effects of stress on cytokine production. METHODS: In the present study, IL-10-deficient mice were compared to wild-type mice in their behavioural and cytokine response to a chronic mild stress procedure. RESULTS: The 3-week chronic mild stress decreased body weight gain and sucrose consumption. It also resulted in a decreased expression of peripheral IL-1beta and IL-6 and an increased expression of brain IL-6. This last change in IL-6 was correlated to body weight loss in stressed mice. However, IL-10-deficient mice did not differ from wild-type mice in their response to the chronic mild stress procedure, despite substantial differences in functioning of the cytokine network. CONCLUSION: These results are interpreted in the context of the relationship between cytokines and behaviour.