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Updated: Jul 2, 2025
Three-dimensional Confocal Analysis of Microglia/macrophage Markers of Polarization in Experimental Brain Injury
Published on: September 4, 2013
Sp1 Regulates the M1 Polarization of Microglia Through the HuR/NF-κB Axis after Spinal Cord Injury
Hangyu Guo1, Mingyu Du2, Yang Yang3
1Department of Orthopedic Surgery, The Second Affiliated Hospital of Harbin Medical University, Harbin 150081, PR China.
Abstract:
The M1 polarization of microglia, followed by the production of pro-inflammatory mediators, hinders functional recovery after spinal cord injury (SCI). Our previous study has illuminated that specificity protein 1 (Sp1) expression is increased following SCI, whereas the function and regulatory mechanism of Sp1 during M1 polarization of microglia following SCI remain unknown. RNA binding protein, HuR, has been shown to be up-regulated in the injured spinal cord through analysis of the GEO database. Further investigation using Chip-Atlas data suggests a binding between Sp1 and HuR. Emerging evidence indicates that HuR plays a pivotal role in neuroinflammation after SCI. In this research, Sp1 and HuR levels in mice with SCI and BV2 cells treated with lipopolysaccharide (LPS) was determined by using quantitative real-time polymerase chain reaction and Western blotting techniques. A series of in vitro assays were performed to investigate the function of Sp1 during M1 polarization of microglia. The association between Sp1 and its target gene HuR was confirmed through gene transfection and luciferase reporter assay. Enhanced expression of HuR was observed in both SCI mice and LPS-treated BV2 cells, while Sp1 knockdown restrained M1 polarization of microglia and its associated inflammation by inhibiting the NF-κB signaling pathway. Silencing Sp1 also suppressed microglia activation and its mediated inflammatory response, which could be reversed by overexpression of HuR. In conclusion, silencing Sp1 restrains M1 polarization of microglia through the HuR/NF-κB axis, leading to neuroprotection, and thus promotes functional restoration following SCI.
Insights
Specificity protein 1 (Sp1) silencing restrains microglial M1 polarization and inflammation after spinal cord injury (SCI). This neuroprotective effect is mediated by inhibiting the HuR/NF-κB axis, promoting functional recovery.
Area of Science:
- Neuroscience
- Immunology
- Cell Biology
Background:
- Microglial M1 polarization and pro-inflammatory mediator release impede functional recovery post-spinal cord injury (SCI).
- Specificity protein 1 (Sp1) expression increases after SCI, but its role in microglial M1 polarization remains unclear.
- RNA binding protein HuR is upregulated in injured spinal cords and implicated in neuroinflammation.
Purpose of the Study:
- To investigate the function and regulatory mechanism of Sp1 in microglial M1 polarization following SCI.
- To elucidate the relationship between Sp1 and HuR in the context of SCI-induced neuroinflammation.
- To determine if targeting Sp1 can mitigate SCI-induced inflammation and promote recovery.
Main Methods:
- Quantitative real-time PCR and Western blotting to assess Sp1 and HuR levels in SCI mice and LPS-treated BV2 cells.
- In vitro assays to evaluate Sp1's role in microglial M1 polarization.
- Gene transfection and luciferase reporter assays to confirm the Sp1-HuR association.
Main Results:
- Sp1 knockdown suppressed M1 polarization and inflammation by inhibiting the NF-κB signaling pathway.
- Silencing Sp1 reduced microglia activation and inflammatory response, effects reversed by HuR overexpression.
- Enhanced HuR expression was observed in both SCI mice and LPS-treated BV2 cells.
Conclusions:
- Silencing Sp1 restrains microglial M1 polarization via the HuR/NF-κB axis, offering neuroprotection.
- Targeting Sp1 presents a potential therapeutic strategy for promoting functional restoration after SCI.
- The Sp1-HuR interaction is a key mechanism in SCI-induced neuroinflammation.
