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PET studies of the glial cell marker TSPO in psychosis patients - a meta-analysis using individual participant data

Research output: Contribution to journalArticle

Pontus Plavén-Sigray, Granville J. Matheson, Karin Collste, Abhishekh H. Ashok, Jennifer M. Coughlin, Oliver D. Howes, Romina Mizrahi, Martin G. Pomper, Pablo Rusjan, Mattia Veronese, Yuchuan Wang, Simon Cervenka

Original languageEnglish
JournalBiological Psychiatry
Early online date6 Mar 2018
DOIs
StateE-pub ahead of print - 6 Mar 2018

King's Authors

Abstract

Background Accumulating evidence suggests that the immune system may be an important target for new treatment approaches in schizophrenia. Positron emission tomography (PET) and radioligands binding to the translocator protein (TSPO), which is expressed in glial cells in brain including immune cells, represents a potential method for patient stratification and treatment monitoring. This study examined if patients with first episode psychosis and schizophrenia had altered TSPO levels compared to healthy control subjects. Methods PubMed was searched for studies comparing patients with psychosis to healthy controls using second-generation TSPO radioligands. The outcome measure was distribution volume (VT), an index of TSPO levels, in frontal cortex (FC), temporal cortex (TC) and hippocampus (HIP). Bayes factors (BF) were applied to examine the relative support for higher, lower or no difference in patients’ TSPO levels compared to healthy controls. Results Five studies, with 75 participants with first-episode psychosis or schizophrenia and 77 healthy controls were included. BF showed strong support for lower VT in patients relative to no difference (all BF>32), or relative to higher VT (all BF>422), in all brain regions. From the posterior distributions, mean patient-control differences in standardized VT values were -0.48 for FC (95% credible interval (CredInt)=-0.88 to -0.09), -0.47 for TC (CredInt=-0.87 to -0.07) and -0.63 for HIP (CredInt=-1.00 to -0.25). Conclusion The lower levels of TSPO observed in patients may correspond to altered function or lower density of brain immune cells. Future studies should focus on investigating the underlying biological mechanisms and their relevance for treatment.

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