Relationship between a pro- and anti-inflammatory cytokine imbalance and depression in haemodialysis patients

Depression represents the most frequent psychiatric disorder in patients on maintenance haemodialysis (HD), and it might be associated with secretion of inflammatory cytokines. In this study, we explore the possible correlations between depression and pro-inflammatory (IL-1β, IL-6, and TNF-α), anti-inflammatory (IL-10) cytokines, as well as high-sensitivity C-reactive protein (hs-CRP) serum levels. Eighty three HD patients were enrolled in this cross-sectional study. Depressive symptoms were measured with the Beck Depression Inventory (BDI), and 'elevated symptoms of depression' were defined as a BDI score of ≥16. Biochemical parameters (serum albumin, haemoglobin, ferritin, etc.) and dialysis dosage delivery (kt/v) were assessed. Serum IL-1β, IL-6, IL-10, TNF-α, and hs-CRP levels were measured using an ELISA method. Thirty two, healthy, age- and sex-matched individuals were included as the control group. The prevalence of depression in HD patients was 61.4%. HD Patients with symptoms of depression had lower educational levels compared to non-depressed ones (P = 0.02), but did not differ with respect to age, gender, time on dialysis program, marital status, or smoking habits. Depressed patients also had significantly higher serum levels of IL-6, the IL-6-to-IL-10 ratio, as well as lower haemoglobin levels (P = 0.003, P = 0.002, and P = 0.02 respectively). No differences in mean serum IL-1β, IL-10, TNF-α, or hs-CRP concentrations were noted between the two groups. The BDI scores showed a significant, positive correlation with serum levels of IL-1β (P = 0.03), IL-6 (P = 0.001), TNF-α (P = 0.02), the IL-6-to-IL-10 ratio (P = 0.001), and a negative correlation with haemoglobin levels (P = 0.02). Maintenance HD patients with symptoms of depression may have higher serum levels of IL-6, a IL-6-to-IL-10 ratio, and lower haemoglobin concentrations. An imbalance between pro- and anti-inflammatory cytokines may play an important role in the pathogenesis of depression in HD patients.