Eugene Bosmans

Increased plasma concentrations of interleukin-6, soluble interleukin-6, soluble interleukin-2 and transferrin receptor in major depression

Recently, it was found that major depression may be accompanied by significant changes in cell-mediated and humoral immunity. The purpose of this study was to investigate the plasma concentrations of interleukin (IL)-6, soluble IL-6 receptor (sIL-6R), sIL-2R and transferrin receptor (TfR) in patients with major depression in an acute phase of illness, in remission and during antidepressive treatment. Plasma concentrations of IL-6, sIL-6R, sIL-2R and TfR were significantly higher in major depressed subjects than in healthy controls. In major depressed subjects, but not in normal controls, there were significant positive correlations between the plasma concentrations of IL-6 and sIL-6R, IL-6 and sIL-2R, IL-6 and TfR, and between sIL-2R and TfR. Subchronic treatment with antidepressive drugs, such as fluoxetine or tricyclic antidepressants, did not significantly affect plasma IL-6, sIL-6R, sIL-2R or TfR. The latter did not significantly differ between major depressed patients in an acute phase of illness or in complete clinical remission. It is suggested that: (1) a coordinated and upregulated production of IL-6, sIL-6R, sIL-2R and TfR may constitute a trait marker of major depression; and that (2) an upregulated production of IL-6 may represent a contributing factor to the various immune disorders encountered in major depression and maybe to the pathophysiology or pathogenesis of that illness.

Relationships between interleukin-6 activity, acute phase proteins, and function of the hypothalamic-pituitary-adrenal axis in severe depression

Recent studies from this laboratory have provided some evidence that major depression, in particular melancholia, may be accompanied by an immune response. The present study was designed to investigate whether severe depression is characterized by increased interleukin-6 (Il-6) activity and whether Il-6 production is related to altered levels of acute phase reactants and to abnormal function of the hypothalamic-pituitary-adrenal (HPA) axis. Measurements were made in 8 healthy control subjects and 24 depressed inpatients of Il-6 production in culture supernatants of mitogen-stimulated peripheral leukocytes and plasma levels of haptoglobin (Hp), transferrin (Tf), and postdexamethasone cortisol. Il-6 activity was significantly higher in melancholic subjects than in healthy control subjects and in patients with minor depression or nonmelancholic major depression. Il-6 production was significantly correlated with Hp (positively) and Tf (negatively) plasma levels. There were significant and positive correlations between Il-6 activity and postdexamethasone cortisol values. The findings may suggest that increased Il-6 activity in severe depression is related to hypotransferrinemia, hyperhaptoglobinemia, and hyperactivity of the HPA axis.

Indicators of immune activation in major depression

Immune-inflammatory markers and their correlations were examined in patients with major depression. Plasma concentrations of interleukin-6 (IL-6), soluble IL-6 receptor (sIL-6R), soluble interleukin-2 receptor (sIL-2R), transferrin receptor (TfR), C-reactive protein (CRP), and alpha 1-acid glycoprotein (AGP), as well as the microheterogeneity of AGP, were measured in 49 major depressed patients during an acute phase of the illness and compared with concentrations in 15 normal control subjects. Plasma concentrations of IL-6, sIL-6, sIL-2R, TfR, CRP, and AGP were significantly higher in major depressed patients than in healthy control subjects. Patients with higher values of AGP microheterogeneity coefficient (AGP-RC > 1.5) had significantly higher concentrations of AGP, IL-6, and TfR. The correlations between cytokines and acute phase proteins studied point to a significant role of elevated IL-6 secretion in the induction of Type I AGP microheterogeneity changes that are characteristic of some inflammatory conditions.

Interleukin-2 and interleukin-6 in schizophrenia and mania: Effects of neuroleptics and mood stabilizers

There is some evidence that schizophrenia may be accompanied by alterations in cell-mediated immunity (CMI) and that antipsychotic agents may modulate CMI. The purpose of this study was to investigate the plasma levels of interleukin-6 (IL-6), soluble IL-6 receptor (sIL-6R), sIL-2R, and transferrin-receptor (TfR) in schizophrenia and mania, and the effects of treatment with neuroleptics or mood stabilizers on these variables. The subjects were 14 schizophrenic patients, 10 manic patients and 21 healthy volunteers. The above immune variables were measured in baseline conditions and after treatment with neuroleptics in schizophrenic patients and valproate in manic patients. Plasma concentrations of IL-6, sIL-6R, sIL-2R and TfR were significantly higher in the combined group of psychotic patients than in healthy volunteers. Plasma IL-6 was significantly higher in schizophrenic patients, while plasma sIL-6R and sIL-2R were significantly higher in mania than in normal controls. In schizophrenic patients, plasma levels of IL-6, sIL-6R and TfR were significantly lower after treatment with neuroleptics than before treatment. No significant effects of valproate on the immune-inflammatory markers could be found in the manic patients. It is suggested that activation of CMI may occur in both schizophrenia and mania and that neuroleptics may have immunosuppressive effects through suppression of IL-6 or IL-6R-related mechanisms.

Elevated serum interleukin-6 (IL-6) and IL-6 receptor concentrations in posttraumatic stress disorder following accidental man-made traumatic events

BACKGROUND Recently, it has been reported that serum interleukin-1 beta (IL-1 beta), but not soluble IL-2 receptor (sIL-2R), concentrations were significantly higher in patients with posttraumatic stress disorder (PTSD) than in normal volunteers, and that psychological stress in humans is associated with increased secretion of proinflammatory cytokines, such as IL-6. METHODS The aim of the present study was to examine the inflammatory response system in patients with PTSD through measurements of serum IL-6, sIL-6R, sgp130 (the IL-6 signal transducing protein), sIL-1R antagonist (sIL-1RA; an endogenous IL-1 receptor antagonist), CC16 (an endogenous anticytokine), and sCD8 (the T suppressor-cytotoxic antigen). RESULTS Serum IL-6 and sIL-6R, but not sgp130, sIL-RA, CC16, or sCD8, concentrations were significantly higher in PTSD patients than in normal volunteers. Serum sIL-6R concentrations were significantly higher in PTSD patients with concurrent major depression than in PTSD patients without major depression and normal volunteers. There were no significant relationships between serum IL-6 or sIL-6R and severity measures of PTSD. CONCLUSIONS The results suggest that PTSD is associated with increased IL-6 signaling. It is hypothesized that stress-induced secretion of proinflammatory cytokines is involved in the catecholaminergic modulation of anxiety reactions.

Negative Immunoregulatory Effects of Antidepressants: Inhibition of Interferon-γ and Stimulation of Interleukin-10 Secretion

There is now some evidence that major depression is accompanied by activation of the inflammatory response system. There is also some evidence that antidepressants may suppress the release of cytokines, such as interleukin-1β (IL-1β) and IL-6 by activated monocytes and IL-2 and interferon-γ (IFNγ) by activated T cells. This study was carried out to examine the effects of clomipramine, sertraline, and trazodone on the stimulated production of IFNγ, a pro-inflammatory cytokine, and IL-10, a negative immunoregulatory cytokine. Whole blood of nine healthy volunteers was stimulated with PHA, 5 μg/mL and LPS, 25 μg/mL for 72 hr with and without incubation with clomipramine, 10−6 and 10−9 M, sertraline, 10−6 and 10−8 M, and trazodone, 10−6 and 10−8 M. All three antidepressants significantly reduced IFNγ secretion, whereas clomipramine and sertraline significantly increased IL-10 secretion in culture supernatant. All three antidepressants significantly reduced the IFNγ/IL-10 ratio. The results suggest that antidepressants, at concentrations in the therapeutical range, have negative immunoregulatory effects through inhibition of IFNγ and stimulation of IL-10 release.

Anti-inflammatory Effects of Antidepressants Through Suppression of the Interferon-γ/interleukin-10 Production Ratio

There is some evidence that major depression-in particular, treatment-resistant depression (TRD)-is accompanied by activation of the inflammatory response system and that proinflammatory cytokines may play a role in the etiology of depression. This study was carried out to examine the effects of antidepressive agents, i.e., imipramine, venlafaxine, L-5-hydroxytryptophan, and fluoxetine on the production of interferon-γ (IFN-γ), a proinflammatory cytokine, and interleukin-10 (IL-10), a negative immunoregulatory cytokine. Diluted whole blood of fluoxetine-treated patients with TRD (mean age, 50.6 ± 3.9 years) and age-matched healthy controls (mean age, 51.6 ± 1.7 years) and younger healthy volunteers (mean age, 35.4 ± 9.6 years) was stimulated with phytohemagglutinin (1 μg/mL) and lipopolysaccharide (5 μg/mL) for 48 hours with and without incubation with the antidepressants at 10−6 M and 10−5 M. IFN-γ and IL-10 were quantified by means of enzyme-linked immunoassays. The ratio of IFN-γ to IL-10 production by immunocytes was computed because this ratio is of critical importance in determining the capacity of immunocytes to activate or inhibit monocytic and T-lymphocytic functions. All four antidepressive drugs significantly increased the production of IL-10. Fluoxetine significantly decreased the production of IFN-γ. All four antidepressants significantly reduced the IFN-γ/IL-10 ratio. There were no significant differences in the antidepressant-induced changes in IFN-γ or IL-10 between younger and older healthy volunteers and TRD patients. Tricyclic antidepressants, selective serotonin reuptake inhibitors, and serotonin-noradrenaline reuptake inhibitors, as well as the immediate precursor of serotonin, have a common, negative immunoregulatory effect by suppressing the IFN-γ/IL-10 production ratio. It is suggested that the therapeutic efficacy of antidepressants may be related to their negative immunoregulatory effects.

Increased serum tumor necrosis factor alpha concentrations in major depression and multiple sclerosis

There is now evidence that major depression is accompanied by activation of the inflammatory response system (IRS) as indicated by an increased production of pro-inflammatory cytokines. There is circumstantial evidence implicating pro-inflammatory cytokines, such as tumor necrosis factor-alpha (TNFalpha) in the pathogenesis of multiple sclerosis (MS). The aims of the present study were to examine (i) the serum concentrations of interleukin-6 (IL-6), IL-8, TNFalpha, IL-2 receptor (IL-2R) and CC16 (uteroglobulin), an endogenous anti-cytokine, in depressed and MS patients compared to normal controls, and (ii) the effects of treatment with antidepressants on the above IRS variables in depressed patients. Serum TNFalpha was significantly higher in depressed and MS patients than in normal controls. Serum IL-8 was significantly higher in depressed patients than in patients with MS. Serum CC16 was significantly higher in patients with MS than in normal controls and depressed patients. Nonresponders to treatment with antidepressants had significantly higher serum IL-2R and lower serum CC16 concentrations than responders to treatment. The results show that (i) depression is accompanied by activation of the IRS and that this activation is more pronounced in depression than in MS, and (ii) IRS activation in depressed patients is related to a nonresponse to treatment with antidepressants.

Increased neopterin and interferon-gamma secretion and lower availability of L-tryptophan in major depression: further evidence for an immune response.

There is now some evidence that major depression may be accompanied by an immune response. The latter condition is suggested by elevated secretion of neopterin and interferon-gamma (IFN gamma) and by lower L-tryptophan (L-TRP) plasma levels. This study investigated the plasma levels of neopterin, L-TRP, and the L-TRP/competing amino acids (CAA) ratio in 30 normal control subjects and 47 depressed subjects (16 minor depressed, 13 simple major depressed, and 18 melancholic subjects), and IFN gamma secretion by mitogen-stimulated peripheral blood mononuclear cells in 7 normal control subjects and 13 major depressed subjects. Plasma neopterin levels were significantly higher in depressed subjects than in normal controls; 61% of melancholic patients had increased neopterin levels (> or = 7 nmol/l) with a specificity of 90%. Patients with major depression had significantly lower L-TRP and L-TRP/CAA values compared with normal control subjects. The amino acid values were significantly and negatively correlated with plasma neopterin levels. Major depressed subjects exhibited significantly higher IFN gamma secretion than did normal control subjects. The results further support the hypothesis that major depression is accompanied by an immune response and that the lower L-TRP availability in that illness may be an epiphenomenon of immune activation.

Activation of the inflammatory response system in autism.

Background/Aim: There is now some evidence that autism may be accompanied by abnormalities in the inflammatory response system (IRS). Products of the IRS, such as proinflammatory cytokines, may induce some of the behavioral symptoms of autism, such as social withdrawal, resistance to novelty and sleep disturbances. The main aim of the present study was to examine whether autism is accompanied by an activation of the IRS. Methods: We measured the production of interleukin (IL)-6, IL-10, the IL-1 receptor antagonist (IL-1RA), interferon (IFN)-γ and tumor necrosis factor (TNF)-α by whole blood and the serum concentrations of IL-6, the IL-2 receptor (IL-2R) and IL-1RA. Results: This study showed a significantly increased production of IFN-γ and IL-1RA and a trend toward a significantly increased production of IL-6 and TNF-α by whole blood of autistic children. There were no significant differences in the serum concentrations of IL-6, IL-2R and IL-1RA between autistic and normal children. Conclusions: These results suggest that autism may be accompanied by an activation of the monocytic (increased IL-1RA) and Th-1-like (increased IFN-γ) arm of the IRS. It is hypothesized that increased production of proinflammatory cytokines could play a role in the pathophysiology of autism.