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Updated: May 21, 2026
Three-dimensional Confocal Analysis of Microglia/macrophage Markers of Polarization in Experimental Brain Injury
Published on: September 4, 2013
Class A scavenger receptor promotes cerebral ischemic injury by pivoting microglia/macrophage polarization
Y Xu1, Lingling Qian, Guijuan Zong
1Atherosclerosis Research Center, Key Laboratory of Cardiovascular Disease and Molecular Intervention, Nanjing Medical University, Nanjing 210029, China.
Abstract:
Class A scavenger receptor (SR-A) is primarily expressed in microglia/macrophages and plays an important role in immune responses. However, whether SR-A can influence microglia/macrophage polarization in cerebral ischemic injury is not known. To this end we monitored the phenotypic alteration of microglia/macrophages in an animal model of cerebral ischemia injury. SR-A was up-regulated in mouse brains 24h after permanent occlusion of middle cerebral artery (MCAO). SR-A-deficient mice displayed reduced infarct size and improved neurological function compared with wild-type mice littermate controls. Furthermore, a decrease in inflammatory F4/80(+)CD11b(+)CD45(high)CD11c(+) microglia/macrophages and attenuated nuclear factor-kappaB (NF-κB) activation was found in ischemic brains in the SR-A null mice. This was accompanied by alleviation of classically activated M1 macrophage markers and preservation of alternatively activated M2 macrophage markers. These data suggest that SR-A contributes to cerebral ischemic injury by pivoting the phenotype of microglia/macrophages to a skewed M1 polarization.
Insights
Scavenger receptor A (SR-A) promotes brain damage after stroke by skewing microglia/macrophages toward an inflammatory M1 state. SR-A deficiency reduces stroke injury and improves neurological function.
Area of Science:
- Neuroscience
- Immunology
- Cell Biology
Background:
- Class A scavenger receptor (SR-A) is crucial for immune responses, primarily in microglia and macrophages.
- The role of SR-A in microglia/macrophage polarization during cerebral ischemic injury remains unclear.
Purpose of the Study:
- To investigate the influence of SR-A on microglia/macrophage polarization in a mouse model of cerebral ischemia.
- To determine SR-A's contribution to brain injury following ischemic stroke.
Main Methods:
- Established a permanent middle cerebral artery occlusion (MCAO) model in mice.
- Compared wild-type and SR-A-deficient mice for infarct size and neurological function.
- Analyzed microglia/macrophage phenotypes (F4/80, CD11b, CD45, CD11c) and NF-κB activation in brain tissue.
Main Results:
- SR-A expression increased in mouse brains 24 hours post-MCAO.
- SR-A-deficient mice showed reduced infarct volume and better neurological outcomes.
- Ischemic brains in SR-A null mice had fewer inflammatory microglia/macrophages and reduced NF-κB activation.
- SR-A deficiency led to decreased M1 markers and preserved M2 markers in macrophages.
Conclusions:
- SR-A exacerbates cerebral ischemic injury.
- SR-A drives microglia/macrophage polarization towards a pro-inflammatory M1 phenotype.
- Targeting SR-A may offer a therapeutic strategy for ischemic stroke.
