Background: Recent technological advances offer an opportunity to further elucidate the complex cytokine network in Major Depressive Disorder (MDD). The objective of this study was to investigate the role of pro-inflammatory and anti-inflammatory cytokines in the mechanism of depressive disorders. Given the activating role of cytokines on the hypothalamic-pituitary-adrenal (HPA) axis, and the relevance of its regulation in MDD, we also analyzed the relationships between several cytokines and cortisol levels.
Methods: Twenty-five unipolar depressive patients and 20 healthy controls were recruited in this study. Flow cytometric bead array system (FCM-CBA) was used to examine the concentration of cytokines (IL-2, IL-4, IL-6, IL-10, TNF, INF-α) in peripheral blood. Plasma Adrenocorticotropic Hormone (ACTH) and serum cortisol concentrations were detected.
Results: Compared with the controls, depressive patients had a significant increase in concentration of IL-2, TNF, serum cortisol, and TNF/IL-4 (p < 0.05). There was a significant positive correlation between serum cortisol and IL-2, as well as ACTH and IL-2 (p < 0.05) in depressive patients. There was a significant positive correlation between IL-2 and the Hamilton depression rating scale (HAMD) total scores in depressive patients, and also with TNF (p < 0.05). There was no significant difference in concentration of IL-4, IL-6, IL-10, and INF-α between two groups (p > 0.05).
Conclusions: The present results suggest that depressive patients had an increase in concentration of some pro-inflammatory cytokines. Both IL-2 and TNF play important roles in the development of depressive disorders, and their concentration in peripheral blood may be used to evaluate the severity of depressive disorders.