TY - JOUR
T1 - Dopamine signaling modulates microglial NLRP3 inflammasome activation
T2 - implications for Parkinson's disease
AU - Pike, Adrianne F
AU - Longhena, Francesca
AU - Faustini, Gaia
AU - van Eik, Jean-Marc
AU - Gombert, Iris
AU - Herrebout, Maaike A C
AU - Fayed, Mona M H E
AU - Sandre, Michele
AU - Varanita, Tatiana
AU - Teunissen, Charlotte E
AU - Hoozemans, Jeroen J M
AU - Bellucci, Arianna
AU - Veerhuis, Robert
AU - Bubacco, Luigi
N1 - Funding Information: The authors wish to thank the Netherlands Brain Bank for surgical and post mortem brain specimens, respectively, Michele Sandre (Department of Biology, University of Padua) for preparing and providing the α-synuclein fibrils used in these experiments, Prof. Dr. Martin Korte (Neuroinflammation and Neurodegeneration Group, Helmholtz Centre for Infection Research, Braunschweig, Germany) and Prof. Dr. Taco de Vries [Center for Neurogenomics and Cognitive Research (CNCR), Amsterdam UMC, Amsterdam, the Netherlands] for valuable mechanistic discussion and input, and Prof. Dr. Michael Heneka and Dr. Róisín McManus of the German Center for Neurodegenerative Diseases (DZNE, Bonn, Germany) for providing essential mouse microglial culture materials and protocols. Funding Information: The work presented is part of the EU Joint Programme-Neurodegenerative Disease Research (JPND) project “InCure” and was supported by the following funding organizations under the aegis of JPND: the Netherlands Organisation for Health Research and Development (ZonMw; funding code 733051051) (Netherlands), and the Ministry of Education, Universities and Research (Italy). The work was also supported by Progetto Dipartimenti di Eccellenza MIUR “Biological signals: from cells to ecosystems” funding through the Department of Biology, University of Padua and by the Italian MIUR PRIN 2017-1065 through the University of Padua and the University of Brescia. Publisher Copyright: © 2022, The Author(s).
PY - 2022/12
Y1 - 2022/12
N2 - BACKGROUND: Parkinson's disease (PD) is characterized by the loss of nigral dopaminergic neurons leading to impaired striatal dopamine signaling, α-synuclein- (α-syn-) rich inclusions, and neuroinflammation. Degenerating neurons are surrounded by activated microglia with increased secretion of interleukin-1β (IL-1β), driven largely by the NLRP3 inflammasome. A critical role for microglial NLRP3 inflammasome activation in the progression of both dopaminergic neurodegeneration and α-syn pathology has been demonstrated in parkinsonism mouse models. Fibrillar α-syn activates this inflammasome in mouse and human macrophages, and we have shown previously that the same holds true for primary human microglia. Dopamine blocks microglial NLRP3 inflammasome activation in the MPTP model, but its effects in this framework, highly relevant to PD, remain unexplored in primary human microglia and in other in vivo parkinsonism models. METHODS: Biochemical techniques including quantification of IL-1β secretion and confocal microscopy were employed to gain insight into dopamine signaling-mediated inhibition of the NLRP3 inflammasome mechanism in primary human microglia and the SYN120 transgenic mouse model. Dopamine and related metabolites were applied to human microglia together with various inflammasome activating stimuli. The involvement of the receptors through which these catecholamines were predicted to act were assessed with agonists in both species. RESULTS: We show in primary human microglia that dopamine, L-DOPA, and high extracellular K+, but not norepinephrine and epinephrine, block canonical, non-canonical, and α-syn-mediated NLRP3 inflammasome-driven IL-1β secretion. This suggests that dopamine acts as an inflammasome inhibitor in human microglia. Accordingly, we provide evidence that dopamine exerts its inhibitory effect through dopamine receptor D1 and D2 (DRD1 and DRD2) signaling. We also show that aged mice transgenic for human C-terminally truncated (1-120) α-syn (SYN120 tg mice) display increased NLRP3 inflammasome activation in comparison to WT mice that is diminished upon DRD1 agonism. CONCLUSIONS: Dopamine inhibits canonical, non-canonical, and α-syn-mediated activation of the NLRP3 inflammasome in primary human microglia, as does high extracellular K+. We suggest that dopamine serves as an endogenous repressor of the K+ efflux-dependent microglial NLRP3 inflammasome activation that contributes to dopaminergic neurodegeneration in PD, and that this reciprocation may account for the specific vulnerability of these neurons to disease pathology.
AB - BACKGROUND: Parkinson's disease (PD) is characterized by the loss of nigral dopaminergic neurons leading to impaired striatal dopamine signaling, α-synuclein- (α-syn-) rich inclusions, and neuroinflammation. Degenerating neurons are surrounded by activated microglia with increased secretion of interleukin-1β (IL-1β), driven largely by the NLRP3 inflammasome. A critical role for microglial NLRP3 inflammasome activation in the progression of both dopaminergic neurodegeneration and α-syn pathology has been demonstrated in parkinsonism mouse models. Fibrillar α-syn activates this inflammasome in mouse and human macrophages, and we have shown previously that the same holds true for primary human microglia. Dopamine blocks microglial NLRP3 inflammasome activation in the MPTP model, but its effects in this framework, highly relevant to PD, remain unexplored in primary human microglia and in other in vivo parkinsonism models. METHODS: Biochemical techniques including quantification of IL-1β secretion and confocal microscopy were employed to gain insight into dopamine signaling-mediated inhibition of the NLRP3 inflammasome mechanism in primary human microglia and the SYN120 transgenic mouse model. Dopamine and related metabolites were applied to human microglia together with various inflammasome activating stimuli. The involvement of the receptors through which these catecholamines were predicted to act were assessed with agonists in both species. RESULTS: We show in primary human microglia that dopamine, L-DOPA, and high extracellular K+, but not norepinephrine and epinephrine, block canonical, non-canonical, and α-syn-mediated NLRP3 inflammasome-driven IL-1β secretion. This suggests that dopamine acts as an inflammasome inhibitor in human microglia. Accordingly, we provide evidence that dopamine exerts its inhibitory effect through dopamine receptor D1 and D2 (DRD1 and DRD2) signaling. We also show that aged mice transgenic for human C-terminally truncated (1-120) α-syn (SYN120 tg mice) display increased NLRP3 inflammasome activation in comparison to WT mice that is diminished upon DRD1 agonism. CONCLUSIONS: Dopamine inhibits canonical, non-canonical, and α-syn-mediated activation of the NLRP3 inflammasome in primary human microglia, as does high extracellular K+. We suggest that dopamine serves as an endogenous repressor of the K+ efflux-dependent microglial NLRP3 inflammasome activation that contributes to dopaminergic neurodegeneration in PD, and that this reciprocation may account for the specific vulnerability of these neurons to disease pathology.
KW - Dopamine
KW - NLRP3 inflammasome
KW - Neuroinflammation
KW - Parkinson’s disease
KW - Potassium
KW - Primary human microglia
KW - α-Synuclein
UR - http://www.scopus.com/inward/record.url?scp=85124775268&partnerID=8YFLogxK
U2 - https://doi.org/10.1186/s12974-022-02410-4
DO - https://doi.org/10.1186/s12974-022-02410-4
M3 - Article
C2 - 35172843
SN - 1742-2094
VL - 19
SP - 50
JO - Journal of neuroinflammation
JF - Journal of neuroinflammation
IS - 1
M1 - 50
ER -