title: Neuromelanin activates proinflammatory microglia through a caspase-8-dependent mechanism.
abstract: BACKGROUND
  We have uncovered a caspase-dependent (caspase-8/caspase-3/7) signaling governing microglia activation and associated neurotoxicity. Importantly, a profuse non-nuclear activation of cleaved caspases 8 and 3 was found in reactive microglia in the ventral mesencephalon from subjects with Parkinson's disease, thus supporting the existence of endogenous factors activating microglia through a caspase-dependent mechanism. One obvious candidate is neuromelanin, which is an efficient proinflammogen in vivo and in vitro and has been shown to have a role in the pathogenesis of Parkinson's disease. Consequently, the goal of this study is to test whether synthetic neuromelanin activates microglia in a caspase-dependent manner.
  
  
  RESULTS
  We found an in-vivo upregulation of CD16/32 (M1 marker) in Iba1-immunolabeled microglia in the ventral mesencephalon after neuromelanin injection. In vitro experiments using BV2 cells, a microglia-derived cell line, demonstrated that synthetic neuromelanin induced a significant chemotactic response to BV2 microglial cells, along with typical morphological features of microglia activation, increased oxidative stress and induction of pattern-recognition receptors including Toll-like receptor 2, NOD2, and CD14. Analysis of IETDase (caspase-8) and DEVDase (caspase-3/7) activities in BV2 cells demonstrated a modest but significant increase of both activities in response to neuromelanin treatment, in the absence of cell death.
  
  
  CONCLUSIONS
  Caspase-8 inhibition prevented typical features of microglia activation, including morphological changes, a high rate of oxidative stress and expression of key proinflammatory cytokines and iNOS.
authors.affiliation: Department of Biochemistry and Molecular Biology, Faculty of Pharmacy, University of Sevilla, 41012, Sevilla, Spain. nikenza.viceconte@yahoo.it.|Instituto de Biomedicina de Sevilla, Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla, 41013, Sevilla, Spain. nikenza.viceconte@yahoo.it.|Present address: Department of Biosciences and Nutrition, Karolinska Institutet, 17177, Stockholm, Sweden. nikenza.viceconte@yahoo.it.
authors.forename: Nikenza
authors.initials: N
authors.lastname: Viceconte
authors.affiliation: Centre for Neuroscience and Trauma, Blizard Institute, Queen Mary University of London, E1 2AT, London, United Kingdom. m.burguillos@qmul.ac.uk.
authors.forename: Miguel A
authors.initials: MA
authors.lastname: Burguillos
authors.affiliation: Department of Biochemistry and Molecular Biology, Faculty of Pharmacy, University of Sevilla, 41012, Sevilla, Spain. ajherrera@us.es.|Instituto de Biomedicina de Sevilla, Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla, 41013, Sevilla, Spain. ajherrera@us.es.
authors.forename: Antonio J
authors.initials: AJ
authors.lastname: Herrera
authors.affiliation: Department of Biochemistry and Molecular Biology, Faculty of Pharmacy, University of Sevilla, 41012, Sevilla, Spain. depablos@us.es.|Instituto de Biomedicina de Sevilla, Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla, 41013, Sevilla, Spain. depablos@us.es.
authors.forename: Rocío M
authors.initials: RM
authors.lastname: De Pablos
authors.affiliation: Department of Oncology-Pathology, Karolinska Institutet, Cancer Centrum Karolinska, 17176, Stockholm, Sweden. Bertrand.Joseph@ki.se.
authors.forename: Bertrand
authors.initials: B
authors.lastname: Joseph
authors.affiliation: Department of Biochemistry and Molecular Biology, Faculty of Pharmacy, University of Sevilla, 41012, Sevilla, Spain. jlvenero@us.es.|Instituto de Biomedicina de Sevilla, Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla, 41013, Sevilla, Spain. jlvenero@us.es.
authors.forename: José L
authors.initials: JL
authors.lastname: Venero
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D001921:Brain / Q000166:cytology; D053148:Caspase 3 / Q000378:metabolism; D053181:Caspase 8 / Q000378:metabolism*; D002461:Cell Line, Transformed; D016207:Cytokines / Q000235:genetics / Q000378:metabolism*; D008070:Lipopolysaccharides / Q000494:pharmacology; D008543:Melanins / Q000494:pharmacology*; D051379:Mice; D008810:Mice, Inbred C57BL; D017628:Microglia / Q000187:drug effects*; D009569:Nitric Oxide / Q000378:metabolism; D053474:Nod1 Signaling Adaptor Protein / Q000235:genetics / Q000378:metabolism; D053473:Nod2 Signaling Adaptor Protein / Q000235:genetics / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D000067759:Receptor for Advanced Glycation End Products / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D051195:Toll-Like Receptor 2 / Q000235:genetics / Q000378:metabolism; D051197:Toll-Like Receptor 4 / Q000235:genetics / Q000378:metabolism
chemical_list: C000593871:AGER protein, human; D016207:Cytokines; D008070:Lipopolysaccharides; D008543:Melanins; C119067:NOD1 protein, human; C429018:NOD2 protein, human; D053474:Nod1 Signaling Adaptor Protein; D053473:Nod2 Signaling Adaptor Protein; D017382:Reactive Oxygen Species; D000067759:Receptor for Advanced Glycation End Products; C495342:TLR2 protein, human; D051195:Toll-Like Receptor 2; D051197:Toll-Like Receptor 4; C014121:neuromelanin; D009569:Nitric Oxide; D053148:Caspase 3; D053181:Caspase 8