Ischemic Cerebroprotection Conferred by Myeloid Lineage-Restricted or Global CD39 Transgene Expression
Background—Cerebral tissue damage after an ischemic event can be exacerbated by inflammation and thrombosis. Elevated extracellular ATP and ADP levels are associated with cellular injury, inflammation and thrombosis. Ectonucleoside triphosphate diphosphohydrolase-1 (CD39), an enzyme expressed on the plasmalemma of leukocytes and endothelial cells, suppresses platelet activation and leukocyte infiltration by phosphohydrolyzing ATP/ADP. To investigate the effects of increased CD39 in an in vivo cerebral ischemia model, we developed a transgenic (TG) mouse expressing human CD39 (hCD39).
Methods—A floxed-stop sequence was inserted between the promoter and the hCD39 transcriptional start site, generating a mouse in which the expression of hCD39 can be controlled tissue-specifically, using Cre recombinase mice. We generated mice that express hCD39 globally or in myeloid-lineage cells only. Cerebral ischemia was induced by middle cerebral artery (MCA) occlusion. Infarct volumes were quantified by MRI after 48 hours.
Results—Both global and TG hCD39- and myeloid lineage (LysM) CD39-overexpressing mice (TG n=9, LysM n=6) demonstrated significantly smaller cerebral infarct volumes compared to wild type (WT) mice. Leukocytes from ischemic and contralateral hemispheres were analyzed by flow cytometry. While contralateral hemispheres had equal numbers of macrophages and neutrophils, ischemic hemispheres from TG mice had less infiltration (n=4). TG mice showed less neurologic deficit compared to WT mice (n=6).
Conclusions—This is the first report of transgenic overexpression of CD39 in mice imparting a protective phenotype following stroke, with reduced leukocyte infiltration, smaller infarct volumes, and decreased neurological deficit. CD39 overexpression, either globally or in myeloid lineage cells, quenches post-ischemic leukosequestration and reduces stroke-induced neurological injury.
- Received May 3, 2016.
- Revision received March 13, 2017.
- Accepted March 22, 2017.