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Ecto-5'-nucleotidase (CD73) attenuates inflammation after spinal cord injury by promoting macrophages/microglia M2
Shun Xu1, Wei Zhu1, Minghao Shao1
1Department of Orthopedics, Huashan Hospital, Fudan University, No.12, Wulumuqi middle Road, Jingan District, Shanghai, 200040, China.
Background:
Immune activation, specifically activation of macrophages and resident microglia, leading to inflammation is a key component in the progression of spinal cord injury (SCI). Macrophages/microglia exist in two states-the classically activated M1 phenotype that confers pro-inflammatory effects or the alternatively activated M2 phenotype that confers anti-inflammatory effects. Ecto-5'-nucleotidase (CD73) is an immunosuppressive molecule intricately involved in adaptive and innate immune responses and is able to dephosphorylate AMP to adenosine. However, it is not known if CD73 is able to modulate the macrophages/microglia transformation between the M1 and M2 phenotypes.
Methods:
We used gene-deficient mice to determine the role of CD73 in macrophages/microglia polarization post-SCI in vivo. We used small interference RNA (siRNA) or pcDNA3.1 to inhibit or overexpress CD73 in BV2 cells to verify anterior discovery in vitro. A combination of molecular and histological methods was used to detect the macrophages/microglia polarization and explore the mechanism both in vivo and in vitro.
Results:
We found that SCI induced the upregulation of CD73 expression. CD73 deficient mice were noted to demonstrate overwhelming immune responses, few anti-inflammatory phenotype macrophages/microglia, and had a poorer locomotor recovery in comparison to wild-type mice that were also inflicted with SCI. In vitro studies found that CD73 suppression inhibited the expression of characteristic microglial anti-inflammatory polarization markers in BV2 cells, while the converse was noted in CD73 overexpression. Subsequent experiments confirmed that CD73 promoted microglia alternative activation by stimulating p38 MAPK.
Conclusion:
We were able to conclude that CD73 imparts neuroprotective effects by mediating macrophages/microglia polarization. These findings allow for better understanding of the modulatory factors involved in triggering the change in macrophages/microglia phenotypes, therefore uncovering additional molecules and pathways that may be targeted in the innovation of novel SCI therapies.
Insights
Ecto-5'-nucleotidase (CD73) plays a crucial role in spinal cord injury (SCI) recovery by promoting anti-inflammatory macrophage and microglia polarization, which is essential for neuroprotection.
Area of Science:
- Immunology
- Neuroscience
- Cell Biology
Background:
- Spinal cord injury (SCI) involves immune activation, particularly of macrophages and microglia, leading to inflammation.
- Macrophages/microglia exist as pro-inflammatory M1 or anti-inflammatory M2 phenotypes.
- Ecto-5'-nucleotidase (CD73) is an immunosuppressive enzyme, but its role in macrophage/microglia polarization post-SCI is unknown.
Purpose of the Study:
- To investigate the role of CD73 in modulating macrophage/microglia polarization following SCI.
- To determine if CD73 influences the M1/M2 phenotype switch in immune cells after SCI.
Main Methods:
- Utilized gene-deficient mice to study CD73's in vivo function post-SCI.
- Employed siRNA and pcDNA3.1 in BV2 cells for in vitro CD73 inhibition or overexpression.
- Combined molecular and histological techniques to assess immune cell polarization and underlying mechanisms.
Main Results:
- SCI increased CD73 expression.
- CD73-deficient mice showed heightened inflammation, reduced M2 macrophages/microglia, and impaired locomotor recovery.
- In vitro, CD73 suppression decreased M2 markers, while overexpression increased them.
- CD73 was found to promote M2 polarization via p38 MAPK signaling.
Conclusions:
- CD73 confers neuroprotection by mediating macrophage/microglia polarization towards an anti-inflammatory M2 phenotype.
- Understanding CD73's modulatory role offers potential therapeutic targets for novel SCI treatments.