Journal
BRAIN BEHAVIOR AND IMMUNITY
Volume 58, Issue -, Pages 218-227Publisher
ACADEMIC PRESS INC ELSEVIER SCIENCE
DOI: 10.1016/j.bbi.2016.07.150
Keywords
Fibromyalgia; Translocator protein; Serotonin; Genetic polymorfisms; Functional magnetic resonance imaging; Serotonin transporter; SCL6A4; rs6971; 5-HTTLPR; Gene-to-gene interactions
Categories
Funding
- Swedish Rheumatism Association
- Stockholm County Council
- Swedish Foundation for Strategic Research [2012-0179]
- Swedish Research Council [K2013-52X-22199-01-3, K2015-99x-21874-05-4, 2011-4807, K2009-52P-20943-03-2]
- AFA insurance
- Karolinska Institutet Foundation
- Karolinska Institutet
- European Union [602919]
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The translocator protein (TSPO) is upregulated during glia activation in chronic pain patients. TSPO constitutes the rate-limiting step in neurosteroid synthesis, thus modulating synaptic transmission. Related serotonergic mechanisms influence if pro- or anti-nociceptive neurosteroids are produced. This study investigated the effects of a functional genetic polymorphism regulating the binding affinity to the TSPO, thus affecting symptom severity and cerebral pain processing in fibromyalgia patients. Gene-to-gene interactions with a functional polymorphism of the serotonin transporter gene were assessed. Fibromyalgia patients (n = 126) were genotyped regarding the polymorphisms of the TSPO (rs6971) and the serotonin transporter (5-HTTLPR/rs25531). Functional magnetic resonance imaging (n = 24) was used to study brain activation during individually calibrated pressure pain. Compared to mixed/low TSPO affinity binders, the high TSPO affinity binders rated more severe pain (p = 0.016) and fibromyalgia symptoms (p = 0.02). A significant interaction was found between the TSPO and the serotonin transporter polymorphisms regarding pain severity (p < 0.0001). Functional connectivity analyses revealed that the TSPO high affinity binding group had more pronounced pain-evoked functional connectivity in the right frontoparietal network, between the dorsolateral prefrontal area and the parietal cortex. In conclusion, fibromyalgia patients with the TSPO high affinity binding genotype reported a higher pain intensity and more severe fibromyalgia symptoms compared to mixed/low affinity binders, and this was modulated by interaction with the serotonin transporter gene. To our knowledge this is the first evidence of functional genetic polymorphisms affecting pain severity in FM and our findings are in line with proposed glia-related mechanisms. Furthermore, the functional magnetic resonance findings indicated an effect of translocator protein on the affective-motivational components of pain perception. (C) 2016 The Authors. Published by Elsevier Inc.
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