Abstract

BACKGROUND: The role of immune response dysregulation has been previously noticed in the pathogenesis of bipolar disorder (BD). METHODS: In the current investigation, we compared expression levels of eight cytokines and a chemokine (CXCL8) in the peripheral blood of BD patients and healthy subjects. All BD patients were in euthymic phase. RESULTS: We found higher expression of IL-1B, IL-10, IFN-G, TNF-a, TGF-B and IL-2 in male patients compared with male controls (ExR=3.44, P<0.0001, ExR=2.54, P<0.0001; ExR=2.39, P<0.0001; ExR=2.74, P<0.0001; ExR=2.32, P<0.0001; ExR=1.87, P=0.04 respectively). For these cytokines, no significant differences were found between female patients and female controls. While expression of IL-6 was higher in male patients compared with male controls (ExR=2.07, P=0.006), in female subjects the opposite trend was detected (ExR=0.44, P=0.02). However, no significant difference was detected between female subjects. Expression levels of IL-17 were not different between patients and controls or between any subgroups of them. We found significant correlations between expression of IFN-G and age at disease onset (R=0.25, P=0.04) as well as expression of CXCL8 and both age of patients and age at disease onset (R=0.26, P=0.03; R=0.25, P=0.04). Moreover, inverse correlation was detected between expression of TNF-a and age in control group (R=-0.34, P=0.008). CONCLUSION: Combination of transcript levels of six genes could differentiate BD patients from healthy subjects with diagnostic power of 0.85 (Sensitivity=78, Specificity=80 and P<0.0001). The current investigation highlights the role of cytokine coding genes in the pathogenesis of BD and potentiates them as diagnostic biomarkers.