Abstract T P200: CD13 is an Immune Regulator in the CNS Following Ischemic Stroke
Background: Focal cerebral ischemia results in marked inflammatory response initiated by microglia and astrocyte activation, upregulation of pro-inflammatory cytokines, and disruption of the blood brain barrier leading to invasion of peripheral immune cells. CD13 (Aminopeptidase N), a 150 kD type II transmembrane metalloprotease highly expressed on myeloid cells, has recently been shown to possess several non-enzymatic functions involving the regulation of processes related to inflammation including antigen presentation and cell trafficking into sites of inflammation. We hypothesized that deletion of CD13 would alter the innate immune response after stroke leading to smaller infarcts and neuroprotection.
Methods: C57BL/6 WT and CD13 KO male mice were subjected to transient focal ischemia by middle cerebral artery occlusion for 90 minutes. Motor and sensory deficits were assessed using the Benderson neurological deficit score and open field analysis. Mice were sacrificed at 48hrs and brain slices stained with Cresyl Violet for infarct analysis. Immunohistochemistry was performed on fresh frozen slices to visualize microglial activation.
Results: There was significant reduction in total hemispheric and cortical infarct in KO compared to WT at 48 hours post stroke (Hemispheric 50.8 ± 2.0 WT vs. 40.7 ± 3.8 KO p=.04, Cortical 56.5 ± 4.0 WT vs. 40.1 ± 5.8 KO p=.04, n=6-10). Behaviorally, CD13 KO mice performed better in the open field test than WT, displaying less motor dysfunction (p=.047). 48hrs post stroke. CD13 KO mice had lower neurological deficit scores (3 WT vs. 2 KO, IQR=0, U=0, n=6-10). CD13 mice had less mortality at all time-points. IHC revealed increased microglia activation in the infarct hemisphere of KO mice when compared to WT.
Conclusions: CD13 KO mice had smaller infarct sizes and better acute behavioral outcomes than WT mice. Furthermore, initial IHC results displayed a phenotypically different immune response in KO animals. Flow cytometry is characterizing the differences in the immune response between the groups and microglial phenotypes. Further identifying and targeting of the non-enzymatic functions of CD13 in the CNS may lead to novel therapeutic clinical treatments to reduce morbidity and mortality from ischemic stroke.
Author Disclosures: S. Tarabishy: None. A. Patrizz III: None. N.S. Mancini: None. L. Shapiro: None. L.D. McCullough: None.
- © 2014 by American Heart Association, Inc.