title: Mannan binding lectin-associated serine protease-2 (MASP-2) critically contributes to post-ischemic brain injury independent of MASP-1.
abstract: Complement activation via the lectin activation pathway (LP) has been identified as the key mechanism behind post-ischemic tissue inflammation causing ischemia-reperfusion injury (IRI) which can significantly impact the clinical outcome of ischemic disease. This work defines the contributions of each of the three LP-associated enzymes-mannan-binding lectin-associated serine protease (MASP)-1, MASP-2, and MASP-3-to ischemic brain injury in experimental mouse models of stroke.
  
  
  
  Focal cerebral ischemia was induced in wild-type (WT) mice or mice deficient for defined complement components by transient middle cerebral artery occlusion (tMCAO) or three-vessel occlusion (3VO). The inhibitory MASP-2 antibody was administered systemically 7 and 3.5 days before and at reperfusion in WT mice in order to assure an effective MASP-2 inhibition throughout the study. Forty-eight hours after ischemia, neurological deficits and infarct volumes were assessed. C3 deposition and microglia/macrophage morphology were detected by immunohistochemical, immunofluorescence, and confocal analyses.
  
  
  
  MASP-2-deficient mice (MASP-2(-/-)) and WT mice treated with an antibody that blocks MASP-2 activity had significantly reduced neurological deficits and histopathological damage after transient ischemia and reperfusion compared to WT or control-treated mice. Surprisingly, MASP-1/3(-/-) mice were not protected, while mice deficient in factor B (fB(-/-)) showed reduced neurological deficits compared to WT mice. Consistent with behavioral and histological data, MASP-2(-/-) had attenuated C3 deposition and presented with a significantly higher proportion of ramified, surveying microglia in contrast to the hypertrophic pro-inflammatory microglia/macrophage phenotype seen in the ischemic brain tissue of WT mice.
  
  
  
  This work demonstrates the essential role of the low-abundant MASP-2 in the mediation of cerebral ischemia-reperfusion injury and demonstrates that targeting MASP-2 by an inhibitory therapeutic antibody markedly improved the neurological and histopathological outcome after focal cerebral ischemia. These results contribute to identifying the key lectin pathway component driving brain tissue injury following cerebral ischemia and call for a revision of the presently widely accepted view that MASP-1 is an essential activator of the lectin pathway effector component MASP-2.
authors: Department of Neuroscience, IRCCS-Istituto di Ricerche Farmacologiche Mario Negri, via La Masa, 19-20156, Milan, Italy.
authors: Franca
authors: F
authors: Orsini
authors: Department of Neuroscience, IRCCS-Istituto di Ricerche Farmacologiche Mario Negri, via La Masa, 19-20156, Milan, Italy.|Department of Infection, Immunity and Inflammation, University of Leicester, MSB, University Road, Leicester, LE1 9HN, UK.|MRC Toxicology Unit, Leicester, LE1 9HN, UK.
authors: Elvina
authors: E
authors: Chrysanthou
authors: OMEROS Corporation, 201 Elliott Ave W, Seattle, WA, 98119, USA.
authors: Thomas
authors: T
authors: Dudler
authors: OMEROS Corporation, 201 Elliott Ave W, Seattle, WA, 98119, USA.
authors: W Jason
authors: WJ
authors: Cummings
authors: Fukushima Prefectural General Hygiene Institute and Department of Immunology, Fukushima Medical University, 1 Hikariga-oka, Fukushima City, 960-1295, Japan.
authors: Minoru
authors: M
authors: Takahashi
authors: Fukushima Prefectural General Hygiene Institute and Department of Immunology, Fukushima Medical University, 1 Hikariga-oka, Fukushima City, 960-1295, Japan.
authors: Teizo
authors: T
authors: Fujita
authors: OMEROS Corporation, 201 Elliott Ave W, Seattle, WA, 98119, USA.
authors: Gregory
authors: G
authors: Demopulos
authors: Department of Neuroscience, IRCCS-Istituto di Ricerche Farmacologiche Mario Negri, via La Masa, 19-20156, Milan, Italy. desimoni@marionegri.it.
authors: Maria-Grazia
authors: MG
authors: De Simoni
authors: Department of Infection, Immunity and Inflammation, University of Leicester, MSB, University Road, Leicester, LE1 9HN, UK. ws5@le.ac.uk.
authors: Wilhelm
authors: W
authors: Schwaeble
mesh_terms: D000818:Animals; D001930:Brain Injuries / Q000201:enzymology* / Q000473:pathology; D002545:Brain Ischemia / Q000201:enzymology* / Q000473:pathology; D008297:Male; D050606:Mannose-Binding Protein-Associated Serine Proteases / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout
chemical_list: C577328:MASP-1 protein, mouse; C491340:MASP-2 protein, mouse; D050606:Mannose-Binding Protein-Associated Serine Proteases
keywords: Cerebral ischemia; Complement system; Inflammation; Lectin pathway; Stroke