Monocyte markers correlate with immune and neuronal brain changes in REM sleep behavior disorder

Kristine Farmen, Sara K Nissen, Morten G Stokholm, Alex Iranzo, Karen Østergaard, Mónica Serradell, Marit Otto, Kristina B Svendsen, Alicia Garrido, Dolores Vilas, Per Borghammer, Joan Santamaria, Arne Møller, Carles Gaig, David J Brooks, Eduardo Tolosa, Nicola Pavese, Marina Romero-Ramos

Research output: Contribution to journal/Conference contribution in journal/Contribution to newspaperJournal articleResearchpeer-review


Synucleinopathies are neurodegenerative diseases with both central and peripheral immune responses. However, whether the peripheral immune changes occur early in disease and their relation to brain events is yet unclear. Isolated rapid-eye-movement (REM) sleep behavior disorder (iRBD) can precede synucleinopathy-related parkinsonism and provides a prodromal phenotype to study early Parkinson's disease events. In this prospective case-control study, we describe monocytic markers in a cohort of iRBD patients that were associated with the brain-imaging markers of inflammation and neuronal dysfunction. Using 11C-PK11195 positron emission tomography (PET), we previously showed increased immune activation in the substantia nigra of iRBD patients, while 18F-DOPA PET detected reduced putaminal dopaminergic function. Here we describe that patients' blood monocytic cells showed increased expression of CD11b, while HLA-DR expression was decreased compared to healthy controls. The iRBD patients had increased classical monocytes and mature natural killer cells. Remarkably, the levels of expression of Toll-like receptor 4 (TLR4) on blood monocytes in iRBD patients were positively correlated with nigral immune activation measured by 11C-PK11195 PET and negatively correlated with putaminal 18F-DOPA uptake; the opposite was seen for the percentage of CD163+ myeloid cells. This suggesting a deleterious role for TLR4 and, conversely, a protective one for the CD163 expression. We show an association between peripheral blood monocytes and brain immune and dopaminergic changes in a synucleinopathy-related disorder, thus suggesting a cross-talk among periphery and brain during the disease.

Original languageEnglish
Article numbere2020858118
JournalProceedings of the National Academy of Sciences
Number of pages7
Publication statusPublished - Mar 2021


  • CD163
  • Monocytes
  • Neuroinflammation
  • Positron emission tomography
  • TLR4
  • monocytes
  • neuroinflammation
  • positron emission tomography


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