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Role of eCIRP in Mediating Post-ischemia Microglial Phagocytosis via TREM-2 Receptor: Insights from Porcine and Mouse
Peijuan Li1,2, Zhangping Sun3, Yushu Chen4
1Gastrointestinal Surgery, Shandong Provincial Hospital Affiliated to, Shandong First Medical University, Jinan, Shandong, China.
Abstract:
Cerebral ischemia/reperfusion (I/R) injury triggers potent neuroinflammatory responses, in which microglial activation and dysregulated phagocytosis may contribute to neuronal damage. Extracellular cold-inducible RNA-binding protein (eCIRP), a damage-associated molecular pattern, has been implicated in postischemic inflammation; however, its role in regulating microglial phagocytosis remains poorly understood. This study employed a porcine model of cardiac arrest/reperfusion (CA/R) and a mouse cellular model of oxygen-glucose deprivation/reoxygenation (OGD/R) in BV2 microglia and N2a neuron to investigate the role of the eCIRP-TREM2 signaling in microglial activation. We evaluated protein expression and direct interaction between CIRP and TREM2 by Western blotting, immunofluorescence, co-immunoprecipitation, and surface plasmon resonance (SPR), while assessing phagocytic activity by fluorescent microsphere uptake and synaptic protein expression assays. Both CA/R and OGD/R conditions significantly elevated the levels of CIRP expression and activation of the TREM2-DAP12-Syk-ERK1/2 signaling. Treatment with recombinant human CIRP (rhCIRP) further increased the expression of microglial activation markers and enhanced phagocytic activity, accompanied by reducing the expression of synaptic proteins. These effects were partially mitigated by CIRBP or TREM2 silencing, or ERK inhibition. Our findings support a novel hypothesis that eCIRP may bind to TREM2 and activate downstream signaling in microglia, enhancing their phagocytic responses in the process of I/R-induced neuronal injury. The eCIRP-TREM2 axis may thus represent a potential therapeutic target for modulating neuroinflammation and preserving neuronal integrity.
Insights
Extracellular cold-inducible RNA-binding protein (eCIRP) enhances microglial phagocytosis via TREM2 signaling, contributing to brain injury after ischemia/reperfusion. Targeting this eCIRP-TREM2 axis may protect neurons.
Area of Science:
- Neuroscience
- Immunology
- Cell Biology
Background:
- Cerebral ischemia/reperfusion (I/R) injury causes neuroinflammation, involving microglial activation and altered phagocytosis.
- Extracellular cold-inducible RNA-binding protein (eCIRP) is linked to postischemic inflammation, but its role in microglial phagocytosis is unclear.
Purpose of the Study:
- To investigate the role of extracellular cold-inducible RNA-binding protein (eCIRP) and its signaling pathway with TREM2 in microglial activation and phagocytosis during cerebral I/R injury.
Main Methods:
- Utilized porcine cardiac arrest/reperfusion (CA/R) and mouse oxygen-glucose deprivation/reoxygenation (OGD/R) models.
- Assessed protein interactions (Western blotting, co-immunoprecipitation, SPR) and microglial phagocytic activity (microsphere uptake, synaptic protein assays).
- Investigated effects of recombinant human CIRP (rhCIRP), CIRBP/TREM2 silencing, and ERK inhibition.
Main Results:
- Both CA/R and OGD/R models increased eCIRP levels and activated the TREM2-DAP12-Syk-ERK1/2 pathway.
- rhCIRP treatment enhanced microglial activation and phagocytosis while decreasing synaptic proteins.
- Silencing CIRBP or TREM2, or inhibiting ERK, partially reversed these effects.
Conclusions:
- Extracellular cold-inducible RNA-binding protein (eCIRP) binds TREM2, activating downstream signaling in microglia.
- This eCIRP-TREM2 interaction enhances microglial phagocytosis, contributing to neuronal injury in I/R.
- The eCIRP-TREM2 axis is a potential therapeutic target for neuroinflammation and neuronal protection.
