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Brain Behav Immun. 2018 Feb;68:146-157. doi: 10.1016/j.bbi.2017.10.013. Epub 2017 Oct 18.

Evidence of fatigue, disordered sleep and peripheral inflammation, but not increased brain TSPO expression, in seasonal allergy: A [11C]PBR28 PET study.

Author information

1
Department of Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden; Stress Research Institute, Stockholm University, Stockholm, Sweden. Electronic address: sandra.tamm@ki.se.
2
Centre for Psychiatry Research, Department of Clinical Neuroscience, Karolinska Institutet & Stockholm Health Care Services, Stockholm County Council, Stockholm, Sweden.
3
Department of Medicine and Center for Molecular Medicine, Karolinska Institutet, Karolinska University Hospital, Stockholm, Sweden.
4
Asthma & Allergy Clinic, S:t Görans Hospital, Stockholm, Sweden.
5
Stress Research Institute, Stockholm University, Stockholm, Sweden.
6
Department of Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden; Stockholm Spine Center, Stockholm, Sweden.
7
Department of Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden.
8
Department of Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden; Stress Research Institute, Stockholm University, Stockholm, Sweden.
9
Department of Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden; Department of Medicine and Center for Molecular Medicine, Karolinska Institutet, Karolinska University Hospital, Stockholm, Sweden; Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden.

Abstract

Allergy is associated with non-specific symptoms such as fatigue, sleep problems and impaired cognition. One explanation could be that the allergic inflammatory state includes activation of immune cells in the brain, but this hypothesis has not been tested in humans. The aim of the present study was therefore to investigate seasonal changes in the glial cell marker translocator protein (TSPO), and to relate this to peripheral inflammation, fatigue and sleep, in allergy. We examined 18 patients with severe seasonal allergy, and 13 healthy subjects in and out-of pollen season using positron emission tomography (n = 15/13) and the TSPO radioligand [11C]PBR28. In addition, TNF-α, IL-5, IL-6, IL-8 and IFN-γ were measured in peripheral blood, and subjective ratings of fatigue and sleepiness as well as objective and subjective sleep were investigated. No difference in levels of TSPO was seen between patients and healthy subjects, nor in relation to pollen season. However, allergic subjects displayed both increased fatigue, sleepiness and increased percentage of deep sleep, as well as increased levels of IL-5 and TNF-α during pollen season, compared to healthy subjects. Allergic subjects also had shorter total sleep time, regardless of season. In conclusion, allergic subjects are indicated to respond to allergen exposure during pollen season with a clear pattern of behavioral disruption and peripheral inflammatory activation, but not with changes in brain TSPO levels. This underscores a need for development and use of more specific markers to understand brain consequences of peripheral inflammation that will be applicable in human subjects.

KEYWORDS:

Allergy; Cytokines; Fatigue; Immune-to-brain signaling; Positron emission tomography; Sickness behavior; Sleep

PMID:
29054675
DOI:
10.1016/j.bbi.2017.10.013
[Indexed for MEDLINE]
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