Abstract 3921: Ecto-5′Nucleotidase (cd73) Derived From Endothelium Regulates Macrophage Trafficking In The Ischemic Brain
5′ ecto-nucleotidase (CD73) is a surface enzyme which lines the vascular lumen where it significantly tempers inflammation at the blood-vessel interface by catalyzing the terminal phosphohydrolysis of 5′ adenosine monophosphate to generate adenosine. Given the expression of CD73 on the endothelium and subpopulations of leukocytes, we designed a series of bone marrow transplantations between CD73−/− (KO) and wild type (WT) mice to evaluate the influence of both circulating and vascular CD73 as a modulator of ischemia-driven inflammation. Following myeloablation and marrow reconstitution, the middle cerebral artery was occluded to create cerebral ischemia. Chimeric mice lacking endothelial CD73 (WT–>KO) exhibited larger cerebral infarcts and impaired locomotor activity versus chimeras that lacked leukocyte CD73 (KO–>WT) (Table 1⇓). This suggests that ischemic cerebral protection is conferred by CD73 on vascular endothelium. Flow cytometric analyses demonstrated a significant increase (28%) in the infiltrating CD45hiF4/80hi macrophage populations in ischemic hemispheres of mice lacking endothelial CD73 (WT–>KO), compared to mice lacking leukocyte CD73 only (KO–>WT), and a 37% increase of macrophages versus control chimeras in which CD73 is present in both endothelium and leukocytes (WT–>WT) (Table 1⇓). Macrophages in ischemic hemispheres of chimeras with global lack of CD73 (KO–>KO) demonstrated greater activation when compared to control chimeras (WT–>WT) ( 60% greater CD80 mean fluorescence intensity ( MFI) and 26% greater CD86 MFI ) (Table 1⇓). Presence of CD73 on endothelium only (KO–>WT) greatly diminished the expression of both CD80 and CD86 versus chimeras with global lack of CD73 (KO–>KO) (Table 1⇓). Taken together, these experiments provide, for the first time, evidence of a role for tissue-derived CD73 in cerebroprotection, and suggest its potential role in modulation of inflammation and brain immune system function.