The activation of monocyte and T cell networks in patients with bipolar disorder

https://doi.org/10.1016/j.bbi.2011.03.013Get rights and content

Abstract

Objectives

We recently described a monocyte pro-inflammatory state in patients with bipolar disorder (BD). We hypothesized that the CD4+T cell system is also activated and determined percentages of Th1, Th2, Th17 and CD4+CD25highFoxP3+ regulatory T cells.

Methods

We carried out a detailed FACS analysis to determine the various T cell subsets and used frozen stored peripheral blood mononuclear cells (PBMC) of 38 BD patients (of whom we previously had tested monocytes for pro-inflammatory gene expression (Drexhage et al., 2010a, Padmos et al., 2008)) and of 22 age/gender matched healthy controls (HC). In addition the cytokines CCL2, IL-1β, IL-6, TNF-α, PTX3, IL-10, IFN-γ, IL-17A, IL-4, IL-5 and IL-22 were measured in serum.

Results

(a) Serum sCD25 levels and percentages of anti-inflammatory CD4+CD25highFoxP3+ regulatory T cells were higher, the latter in BD patients <40 years of age. Percentages of Th1, Th2 and Th17 cells were normal.

(b) Of the pro-inflammatory monocyte cytokines CCL2 and PTX3 were raised in serum.

(c) The monocyte pro-inflammatory state and the raised percentages of CD4+CD25highFoxP3+ regulatory T cells occurred independently from each other.

(d) In BD patients positive for thyroid autoimmune disease a significantly reduced percentage of CD4+CD25highFoxP3+ regulatory T cells was found as compared to BD patients without AITD.

Conclusion

Our data show an enhancement of pro-inflammatory monocyte and anti-inflammatory T cell forces in BD patients. A lack of anti-inflammatory T cell forces co-occurred with AITD in BD patients.

Highlights

► This manuscript describes the newest T lymphocyte subsets in patients with bipolar disorder and relate these to the classical subsets of the T cell network and to the monocyte inflammatory state.

Introduction

There is accumulating evidence that activation of the immune system plays an important role in the pathogenesis of bipolar disorder (BD). In support of this view we recently described a higher expression of a coherent set of 34 inflammatory genes, an inflammatory gene expression “signature”, in the circulating monocytes of 60–70% of BD patients (Drexhage et al., 2010a, Padmos et al., 2008). Apart from cells of the monocyte lineage, T cells are important contributors to the immune response, but literature on T cell numbers and cytokines in BD is scarce and the aim of the present study is to evaluate T cell related inflammatory networks in relation to monocyte activation state in patients with BD.

Previously we reported on higher numbers of CD25+ and CD71+ (“activated”) T cells in the circulation of BD patients (Breunis et al., 2003), but at present there are no data on the circulating numbers of the various CD4+T helper cell subsets in BD, such as CD4+T helper(h)1 and Th2 cells, though there are data on the serum levels of IFN-γ and IL-4, the hallmark cytokines of these two T cell subsets (Brietzke et al., 2009, Drexhage et al., 2010a, Ortiz-Dominguez et al., 2007). Both higher and unaltered levels of the cytokines have been described.

In recent years a new T helper subset has been discovered, the so-called CD4+ “Th17 cells”, which produce the pro-inflammatory cytokine IL-17 (Bettelli et al., 2008). Th17 cells protect the host against bacteria and fungi by activating macrophages via the production of IL-17 (but also IL-21 and IL-22). In addition Th17 cells play a role in the pathogenesis of autoimmune diseases such as psoriasis and rheumatoid arthritis (Bettelli et al., 2008). Functions of Th17 cells are thus very similar to those of Th1 cells. The inflammation inducing effects of Th1 cells, Th17 cells and of monocytes and macrophages are controlled by a special class of T cells, the regulatory CD4+CD25highFoxP3+ T cells (Hori et al., 2003, Wing and Sakaguchi, 2010). The main function of these natural, inborn, thymus-derived regulatory T cells is tempering the inflammatory response thereby maintaining homeostasis and tolerance to self-antigens. The cytokines involved in this anti-inflammatory action are thought to be TGF-β and IL-10 (though these cytokines are also produced by monocytes/macrophages). Patients lacking CD4+CD25highFoxP3+ natural T regulatory (reg) cells due to a genetic mutation in the gene coding for FoxP3, suffer from a severe and rapidly lethal poly-endocrine auto-immune syndrome (IPEX, Immune dysregulation, Polyendocrinopathy, Enteropathy X-linked syndrome) (Wildin et al., 2002).

Since BD patients have a higher risk to develop endocrine autoimmune diseases, including autoimmune thyroid disease (AITD) (Kupka et al., 2002, Padmos et al., 2004), we had as second aim of this study to investigate whether BD patients with AITD have an imbalanced interplay between inflammation-prone monocytes and an abnormal tuned T cell system, notably abnormal numbers of natural T reg cells.

For this study we were able to use deep frozen leukocytes of 38 BD patients of the previously reported series of 56 BD patients tested for monocyte gene expression (Drexhage et al., 2010b, Padmos et al., 2008, van der Heul-Nieuwenhuijsen et al., 2010) and 22 age and gender matched healthy controls. This enabled us to relate the T cell state to the pro-inflammatory state of the monocytes of the BD patients. TPO-Abs were positive in 11 of the 38 cases (29%).

We determined the percentages of IFN-γ+Th1, IL-4+Th2, IL-17A+Th17 and of CD4+CD25highFoxP3+ regulatory T cells using FACS analysis. Next to these cellular analyses we evaluated the serum levels of the monocyte cytokines PTX3, CCL2, TNF-α, IL-1β IL-6, IL-8, and IL-10, of the shed sCD25 (the IL-2 Receptor, highly expressed on CD4+CD25highFoxP3+ regulatory T cells) and of the T cell cytokines IFN-γ, IL-4, IL-5, IL-17A and IL-22.

Section snippets

Patients with bipolar disorder and controls

The 38 BD subjects tested were the index cases of twin-pairs, which we had used in a previous study, aged 18–60 years, suffering from bipolar I or bipolar II disorder according to DSM-IV criteria (Padmos et al., 2009) (we tested these index BD cases, since we had frozen samples left in store of only these individuals). Material of the co-twins was not used in this study. The recruitment procedure and inclusion criteria have previously been described in (Vonk et al., 2007). In short the BD

Th1. (CD4+IFNγ+), Th2 (CD4+IL4+) and Th17 (CD4+IL17A+) cells in BD patients and HC

We first analyzed by forward and side scatter in FACS (for gating strategy, see Fig. 1) the percentages of total lymphocytes and monocytes in the PBMC preparations of the BD patients and healthy controls (HC). There were no differences in the percentages of monocytes and lymphocytes between BD and HC (data not shown).

Subsequently, we quantified after stimulation with PMA and ionomycin for 4 h (a procedure to activate lymphocytes) the percentages of the Th1, Th2 and Th17 cells. There were no

Discussion

This study shows significantly higher levels of sCD25 and higher percentages of circulating CD4+CD25highFoxP3+ regulatory T cells in the circulation of BD patients, the latter only in BD patients less than 40 years of age and in BD patients without signs of AITD.

The BD patients with AITD lacked the increase in CD4+CD25highFoxP3+ regulatory T cells and were additionally characterized by high circulating percentages of Th1 cells (though the latter not significant). Although in this relatively

Conflict of interest

H.A. Drexhage has received grants from the Netherlands Organisation for Health Research and Development, the European Union, the Stanley Medical Research Institute, the Dutch Diabetic Foundation and the JDRF; he has received speaker’s fees from Astra Zenica and he serves/has served in advisory boards of the Netherlands Organisation for Health Research and Development, the European Union and the JDRF.

W.A. Nolen has received grants from the Netherlands Organisation for Health Research and

Acknowledgments

We thank Alberto Mantovani for providing the PTX3 ELISA, Harm de Wit and Annemarie Wijkhuijs for their excellent technical assistance, Caspar Looman for statistical advice and Sandra de Bruin for help with designing the figures.

References (30)

  • M. Tohmi et al.

    Perinatal inflammatory cytokine challenge results in distinct neurobehavioral alterations in rats: implication in psychiatric disorders of developmental origin

    Neurosci. Res.

    (2004)
  • S.Y. Tsai et al.

    Effects of symptomatic severity on elevation of plasma soluble interleukin-2 receptor in bipolar mania

    J. Affect. Disord.

    (2001)
  • R. Vonk et al.

    Is autoimmune thyroiditis part of the genetic vulnerability (or an endophenotype) for bipolar disorder?

    Biol. Psychiatry

    (2007)
  • E. Bettelli et al.

    Induction and effector functions of T(H)17 cells

    Nature

    (2008)
  • S.Q. Crome et al.

    Translational mini-review series on Th17 cells: function and regulation of human T helper 17 cells in health and disease

    Clin. Exp. Immunol.

    (2010)
  • Cited by (0)

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