Upregulation of Neuronal Cylindromatosis Expression is Essential for Electroacupuncture-Mediated Alleviation of Neuroinflammatory Injury by Regulating Microglial Polarization in Rats Subjected to Focal Cerebral Ischemia/Reperfusion

Xing Lin; Jian Zhan; Jin Jiang; Yikun Ren

doi:10.2147/JIR.S307841

Upregulation of Neuronal Cylindromatosis Expression is Essential for Electroacupuncture-Mediated Alleviation of Neuroinflammatory Injury by Regulating Microglial Polarization in Rats Subjected to Focal Cerebral Ischemia/Reperfusion

J Inflamm Res. 2021 May 20:14:2061-2078. doi: 10.2147/JIR.S307841. eCollection 2021.

Authors

Xing Lin¹, Jian Zhan², Jin Jiang³, Yikun Ren³

Affiliations

¹ Department of Biological Immunotherapy, Chongqing University Cancer Hospital, Chongqing Cancer Institute, Chongqing Cancer Hospital, Shapingba District, Chongqing, 400030, People's Republic of China.
² Department of Neurology, The Second Affiliated Hospital of Zunyi Medical College, Zunyi, Guizhou Province, 563000, People's Republic of China.
³ Department of Neurology, The First Affiliated Hospital of Chongqing Medical University, Chongqing, 400016, People's Republic of China.

Abstract

Background: Activated microglia are polarized into the M1 or M2 phenotype. We previously reported that electroacupuncture (EA) effectively prevented nuclear factor-κB (NF-κB) nuclear translocation and improved neuronal C-X-C motif 3 chemokine ligand 1 (CX3CL1) expression, repressing microglial activation by upregulating neuronal cylindromatosis (CYLD) expression in the periischemic cortex. However, the potential mechanisms are unclear. Therefore, we explored whether EA improved CYLD protein expression to regulate microglial polarization-mediated neuroinflammation and the potential mechanisms in an ischemic stroke model.

Methods: A middle cerebral artery occlusion/reperfusion (MCAO/R) model was established in male Sprague-Dawley (SD) rats. The rats were treated with EA at the Baihui, Hegu and Taichong acupoints once daily beginning 2 h after focal cerebral ischemia. CYLD gene interference was used to investigate the role of CYLD in microglial polarization. We used neurobehavioral evaluations and TTC staining to examine the neuroprotective effect of EA via CYLD upregulation. Immunofluorescence and RT-qPCR were used to measure NLRP3 activation, M1/M2 microglial activation, pro-/anti-inflammatory gene mRNA expression and crosstalk (CX3CL1/CX3CR1 axis) between neurons and microglia. Western blotting was used to assess the underlying molecular mechanism.

Results: CYLD inhibited M1 microglial activation and improved M2 microglial activation after 72 h of reperfusion. CYLD overexpression decreased the NLRP3 mRNA level. CYLD suppressed microglial overactivation by inhibiting NLRP3 activation. CYLD gene silencing partially weakened EA improvement of neurological function deficits and reduction of infarct volumes after 72 h reperfusion. In addition, EA inhibited M1-like phenotypic microglial activation and promoted M2-like phenotypic microglia through upregulating CYLD expression. Finally, EA-mediated modulation of the CX3CL1/CX3CR1 axis and NLRP3 inflammasome was reversed by CYLD gene silencing in the periischemic cortex.

Conclusion: EA-induced upregulation of neuronal CYLD expression plays anti-inflammatory and neuroprotective roles and regulates the interaction between neurons and microglia, thereby suppressing M1 and improving M2 microglial activation in the periischemic cortex.

Keywords: CX3CL1/CX3CR1 axis; CYLD; NLRP3 inflammasome; cerebral ischemia; electroacupuncture; microglial polarization; neuroinflammation.

Grants and funding

The study was supported by the Natural Science Foundation of Chongqing, Grand NO. cstc2019jcyj-msxmX0630, to JJ; the Natural Science Foundation of Chongqing, Grand NO. cstc2020jcyj-msxmX0325, to XL; the Chinese Medicine Science and Technology project of Chongqing Municipal Health committee, Grand NO. 2021ZY3794, to XL.