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Updated: Jun 15, 2025
Three-dimensional Confocal Analysis of Microglia/macrophage Markers of Polarization in Experimental Brain Injury
Published on: September 4, 2013
PD-1 mediates microglia polarization via the MAPK signaling pathway to protect blood-brain barrier function during
Linqiang Huang1, Xinping Li2, Zhuo Li1
1Department of Critical Care Medicine, Guangdong Provincial People's Hospital (Guangdong Academy of Medical Sciences), Southern Medical University, China.
Background:
Cerebral ischemia is characterized by its rapid onset and high rates of recurrence, morbidity, and mortality, with blood-brain barrier (BBB) permeability playing a vital role in brain injury. Therefore, it is important to understand the molecular mechanism which regulates the BBB during cerebral ischemia.
Materials And Methods:
An in vitro model of oxygen-glucose deprivation (OGD) and an in vivo model of cerebral ischemia/reperfusion (I/R) were constructed. PD-1 overexpression vectors and vectors containing si-RNA were transfected and injected into in vitro and in vivo models. Western blotting, real-time quantitative PCR (qPCR), immunofluorescence (IF) analysis, and immunohistochemical staining were employed to evaluate the expression levels of programmed cell death-1 (PD-1), microglia M1 and M2 biomarkers, and tight junction proteins. Flow cytometry and ELISA were used to measure the levels of pro-inflammatory cytokines. The BBB permeability of brain tissues was evaluated by Evans blue dye (EBD) extravasation and transendothelial electrical resistance (TEER). Brain water content was measured to assess the extent of inflammatory exudation. The infarct volume and neurological severity score (NSS) were used to assess the severity of brain injury. Brain cell apoptosis was assessed by the TUNEL assay and hematoxylin-eosin (H&E) staining.
Results:
PD-1 helped to convert the microglia M1 phenotype to the M2 phenotype and to reduce BBB permeability both in vitro and in vivo. Overexpression of PD-1 promoted a shift of the M1 phenotype to the M2 phenotype and reduced BBB permeability via the ERK and p38 MAPK signaling pathways. PD-1 reduced inflammatory exudation, BBB permeability, cell apoptosis, and brain injury in vivo.
Conclusion:
Our present study verified that PD-1 exerts an anti-inflammatory effect by converting the microglia M1 phenotype to the M2 phenotype, reducing BBB permeability, and thereby relieves brain injury caused by cerebral ischemia. PD-1 is potential therapeutic target for brain injury caused by cerebral ischemia.
Insights
Programmed cell death-1 (PD-1) reduces brain injury from cerebral ischemia by converting microglia to an anti-inflammatory M2 state and decreasing blood-brain barrier permeability. PD-1 shows potential as a therapeutic target for ischemic brain damage.
Area of Science:
- Neuroscience
- Immunology
- Molecular Biology
Background:
- Cerebral ischemia causes rapid brain injury, with blood-brain barrier (BBB) permeability being a key factor.
- Understanding the molecular mechanisms regulating BBB integrity during ischemia is crucial for developing effective treatments.
Purpose of the Study:
- To investigate the role of programmed cell death-1 (PD-1) in regulating BBB permeability and neuroinflammation during cerebral ischemia.
- To explore the potential of PD-1 as a therapeutic target for ischemic brain injury.
Main Methods:
- Established in vitro (oxygen-glucose deprivation) and in vivo (ischemia/reperfusion) models of cerebral ischemia.
- Utilized PD-1 overexpression and knockdown techniques.
- Assessed microglia phenotype, BBB integrity (Evans blue dye, TEER), inflammation (cytokines), apoptosis, and infarct volume using molecular and histological techniques.
Main Results:
- PD-1 promoted the conversion of microglia from M1 to M2 phenotypes, reducing inflammation.
- Overexpression of PD-1 decreased BBB permeability via ERK and p38 MAPK signaling pathways.
- PD-1 administration reduced inflammatory exudation, BBB permeability, apoptosis, and overall brain injury in vivo.
Conclusions:
- PD-1 exerts neuroprotective effects by modulating microglia polarization and enhancing BBB integrity.
- PD-1 represents a promising therapeutic target for mitigating brain damage in cerebral ischemia.
