Depression, GABA and age correlate with the plasma levels of inflammatory markers.

Abstract

Immunomodulation is increasingly being recognised as a part of mental diseases. Here, we examined if levels of immunological protein markers altered with depression, age or by the inhibitory neurotransmitter gamma-aminobutyric acid (GABA). Analysis of plasma samples from patients with major depressive episode and control blood donors (CBD) revealed expression of 67 inflammatory markers. Thirteen of these markers had augmented levels in patients as compared to CBD. and 21 markers correlated with age of the patients, whereas 10 markers correlated with the age of CBD. Interestingly, CST5 and CDCP1 showed the strongest correlation with age in the patients and in the CBD, respectively. IL-18 was the only marker that correlated with the MADRS-S scores of the patients. Neuronal growth factors (NGFs) were significantly enhanced in plasma from the patients and so was the average plasma GABA concentration. GABA modulated release of seven cytokines in CD3+ stimulated peripheral blood mononuclear cells (PBMC) from the patients. The study reveals significant changes in plasma composition of small molecules during depression and identifies potential peripheral biomarkers of the disease.