Effects of interleukin-6 on depression risk in dialysis patients

Depression represents the most frequent psychiatric disorder in nephrology. Cytokines, and especially IL-6, were found to be elevated in depressed patients with normal renal function. The objective of this pilot study was to examine the relationship between depression and cytokines (IL-6, TNF-alpha, and IL-10) in patients with end-stage kidney disease (ESKD).

We studied 44 stable patients with ESKD for 71 +/- 66 months (32 males; 64 +/- 13 years; 27 on hemodialysis and 17 on peritoneal dialysis). The control group included 20 healthy age- and gender-matched individuals (12 males; 60 +/- 12 years). Depression was assessed by the Zung Self-Rating Depression Scale (ZS). Nephelometry for high-sensitivity CRP and ELISA kits for IL-6, IL-10 and TNF-alpha were used.

Compared to controls, patients with ESKD had higher ZS scores (56.8 +/- 16.8 vs. 44 +/- 12.7, p < 0.01), WBC (7,987 +/- 2,347 vs. 6,413 +/- 870/mm(3), p < 0.01), ESR (36.3 +/- 15.8 vs. 9.4 +/- 3.3 mm, p < 0.001), TNF-alpha (52 +/- 18.4 vs. 10.7 +/- 2.8 pg/ml, p < 0.001) and IL-6 (6.3 +/- 4 vs. 1.8 +/- 0.4 pg/ml, p < 0.001). No differences in high-sensitivity CRP and IL-10 were noted between the ESKD and control groups. Serum IL-6 levels were the only parameter positively correlated with the values of the ZS score in ESKD patients (r = 0.34, p < 0.02).

IL-6 may play a role in the pathogenesis of depression in patients with ESKD.