Toll-like receptor 4 contributes to poor outcome after intracerebral hemorrhage
Article first published online: 25 OCT 2011
Copyright © 2011 American Neurological Association
Annals of Neurology
Volume 70, Issue 4, pages 646–656, October 2011
How to Cite
Sansing, L. H., Harris, T. H., Welsh, F. A., Kasner, S. E., Hunter, C. A. and Kariko, K. (2011), Toll-like receptor 4 contributes to poor outcome after intracerebral hemorrhage. Ann Neurol., 70: 646–656. doi: 10.1002/ana.22528
- Issue published online: 25 OCT 2011
- Article first published online: 25 OCT 2011
- Accepted manuscript online: 28 JUN 2011 02:22PM EST
- Manuscript Accepted: 20 JUN 2011
- Manuscript Revised: 31 MAY 2011
- Manuscript Received: 22 NOV 2010
Intracerebral hemorrhage (ICH) is a devastating stroke subtype in which perihematomal inflammation contributes to neuronal injury and functional disability. Histologically, the region becomes infiltrated with neutrophils and activated microglia followed by neuronal loss, but little is known about the immune signals that coordinate these events. This study aimed to determine the role of Toll-like receptor 4 (TLR4) in the innate immune response after ICH and its impact on neurobehavioral outcome.
Transgenic mice incapable of TLR4 signaling and wild-type controls were subjected to striatal blood injection to model ICH. The perihematomal inflammatory response was then quantified by immunohistochemistry, whole brain flow cytometry, and polymerase chain reaction. The critical location of TLR4 signaling was determined by blood transfer experiments between genotypes. Functional outcomes were quantified in all cohorts using the cylinder and open field tests.
TLR4-deficient mice had markedly decreased perihematomal inflammation, associated with reduced recruitment of neutrophils and monocytes, fewer microglia, and improved functional outcome by day 3 after ICH. Moreover, blood transfer experiments revealed that TLR4 on leukocytes or platelets within the hemorrhage contributes to perihematomal leukocyte infiltration and the neurological deficit.
Together, these data identify a critical role for TLR4 signaling in perihematomal inflammation and injury and indicate this pathway may be a target for therapeutic intervention. ANN NEUROL 2011;70:646–656