Selective increase of cerebrospinal fluid IL-6 during experimental systemic inflammation in humans: association with depressive symptoms

• Published in: Molecular psychiatry Vol. 22; no. 10; pp. 1448 - 1454
• Main Authors: Engler, H, Brendt, P, Wischermann, J, Wegner, A, Röhling, R, Schoemberg, T, Meyer, U, Gold, R, Peters, J, Benson, S, Schedlowski, M
• Format: Journal Article
• Language: English
• Published: England Nature Publishing Group 01.10.2017
• Subjects: Adult; Analysis; Anesthesiology; Blood; Body mass index; Body weight; Brain; Catheters; Cerebrospinal fluid; Cytokines; Cytokines - blood; Depression (Mood disorder); Depression - blood; Depression - cerebrospinal fluid; Depression - immunology; Depression - metabolism; Drug dosages; Emotional disorders; Endotoxins - administration & dosage; Hospitals; Humans; Immune system; Immunity, Innate; Inflammation; Inflammation - blood; Inflammation - cerebrospinal fluid; Inflammation - immunology; Inflammation - psychology; Innate immunity; Intensive care; Interleukin 10; Interleukin 6; Interleukin-6 - cerebrospinal fluid; Interleukin-6 - immunology; Intravenous administration; Latency; Male; Mental depression; Mood; Mood disorders; Pathogens; Peripheral blood; Therapeutic targets; Tumor necrosis factor-TNF; Tumor necrosis factor-α; Young Adult
• ISSN: 1359-4184; 1476-5578
• DOI: 10.1038/mp.2016.264

Systemic inflammation is accompanied by profound behavioral and mood changes that resemble symptoms of depression. Findings in animals suggest that pro-inflammatory cytokines released by activated immune cells in the periphery evoke these behavioral symptoms by driving inflammatory changes in the brain. However, experimental data in humans are lacking. Here we demonstrate in healthy male volunteers (10 endotoxin treated, 8 placebo treated) that intravenous administration of low-dose endotoxin (0.8 ng/kg body weight), a prototypical pathogen-associated molecular pattern that activates the innate immune system, not only induces a significant increase in peripheral blood cytokine concentrations (that is, tumor necrosis factor-α, interleukin (IL)-6, IL-10) but also results, with some latency, in a robust and selective increase of IL-6 in the cerebrospinal fluid (CSF). Moreover, we found a strong association between the endotoxin-induced increase of IL-6 in the CSF and the severity of mood impairment, with larger increases in CSF IL-6 concentration followed by a greater deterioration in mood. Taken together, these findings suggest that the appearance of depressive symptoms in inflammatory conditions might be primarily linked to an increase in central IL-6 concentration, identifying IL-6 as a potential therapeutic target in mood disorders.