Abstract T P237: Alpha-4 Integrin Mediates Inflammatory Monocyte Trafficking to the Brain After Intracerebral Hemorrhage
Background: Intracerebral hemorrhage (ICH) triggers an immune response leading to leukocyte recruitment to the brain and secondary injury. Inflammatory monocytes traffic to the brain over the first 3 days after ICH in murine models, and genetic knock-outs that lack these cells have improved functional outcomes. The aim of this study was to determine the adhesion molecules used by monocytes to enter the brain, and whether antagonism of candidate adhesion molecules could be a new therapeutic target.
Methods: ICH was modeled via injection of collagenase into the right striatum of wild type mice. Mice were sacrificed 1 and 3 days post-ICH. Brain and blood were harvested for leukocyte quantification by flow cytometry. Cells were stained with antibodies for CD45, CD3, Ly6G, Ly6C, CD11b, CD49d (alpha-4 integrin), CD11a/CD18 (LFA-1), and CD31 (PECAM). Inflammatory monocytes were identified as CD45high+CD3-Ly6G-CD11b+Ly6C+. Adhesion molecule expression on inflammatory monocytes in brain and blood were compared by t-test. To block leukocyte trafficking, anti-mouse alpha-4 integrin blocking antibody (or IgG control) was administered intraperitoneally 4 hours prior to ICH. Blinded behavioral testing using the cylinder and beam walking tests were used to quantify neurological deficit.
Results: Alpha-4 integrin is significantly increased on inflammatory monocytes in the brain after ICH compared to blood on days 1 and 3 (Day 1: 22.7 ±3.4% vs 0.9±0.5%, p<0.001, n=3/group, Day 3: 19.1±4.9% vs 2.9±0.5%, p<0.001, n=5/group). On days 1 and 3 after ICH, the majority of mice could not perform behavioral testing. However, on day 3 mice treated with anti-alpha-4 integrin antibody were more likely to be able to complete 20 rears in the cylinder within 15 minutes compared to controls (50% vs. 0%, p<0.05, n=6/group).
Conclusions: Alpha-4 integrin appears to be important for inflammatory monocyte trafficking into the brain after ICH and may be a new potential therapeutic target to prevent the early phase of immune-mediated injury. Importantly, there is a monoclonal antibody therapy approved for use in humans, which could be studied for ICH if further experimental work supports a benefit.
Author Disclosures: W. Ambler: None. M. Hammond: None. R. Taylor: None. L. Sansing: None. Y. Ai: None.
This research has received full or partial funding support from the American Heart Association, Founders - Connecticut, Maine, Massachusetts, New Hampshire, New Jersey, New York, Rhode Island, Vermont.
- © 2014 by American Heart Association, Inc.