THE INFLAMMATORY RESPONSE SYSTEM AND THE AVAILABILITY OF PLASMA TRYPTOPHAN IN PATIENTS WITH PRIMARY SLEEP DISORDERS AND MAJOR DEPRESSION

Background: It is now well established that major depression is accomp anied by an immune-inflammatory system response and that indicators of the latter are inversely correlated with lower availability of plasma tryptophan in depression. Inflammation and infection can alter sleep architecture, whereas sleep disturbances can impair immune functions. Aims and Methods: The aims of the present study were to examine: (i) i mmune-inflammatory markers, i.e. serum interleukin-6 (IL-6), IL-8, IL- 6 receptor (IL-BR), IL-1R antagonist (IL-IRA), gp130, and prostaglandi n E2 (PGE2) production by mitogen-stimulated whole blood and the avail ability of plasma tryptophan in patients with primary sleep disorders, major depression and healthy volunteers; and (ii) the relationships b etween the availability of tryptophan and indicators of the immune-inf lammatory response system. Results: Mitogen-stimulated release of PGE2 , and serum IL-6 and IL-8, were significantly increased in both depres sed and sleep disordered patients compared to normal controls. Serum I L-1RA was significantly higher in depressed patients than in normal co ntrols. Patients with depression and sleep disorders had a significant ly lower availability of tryptophan than normal controls. There were s ignificant and inverse relationships between the availability of plasm a tryptophan and serum IL-1RA, IL-6 and IL-8. Conclusions: The results suggest that (i) there is an activation of the immune-inflammatory re sponse system in primary sleep disorders and depression; and (ii) the decreased availability of plasma tryptophan may be related to the infl ammatory system response. (C) 1998 Elsevier Science B.V.