Activation of microglial GLP-1R in the trigeminal nucleus caudalis suppresses central sensitization of chronic migraine after recurrent nitroglycerin stimulation

  • J Headache Pain. 2021 Jul 29;22(1):86. doi: 10.1186/s10194-021-01302-x.
Feng Jing  1  2 ,  Qian Zou  3 ,  Yangyang Wang  3 ,  Zhiyou Cai  4  5 ,  Yong Tang  6
Affiliations
  • 1. Department of Histology and Embryology, Chongqing Medical University, No.1 Yixueyuan Road, Yuzhong District, 400016, Chongqing, China.
  • 2. Department of Neurology, Chongqing General Hospital, University of Chinese Academy of Sciences, No.118 Xingguang Avenue, Liangjiang New Area, 401147, Chongqing, China.
  • 3. Chongqing Key Laboratory of Neurodegenerative Diseases, No.312 Zhongshan First Road, Yuzhong District, 400013, Chongqing, China.
  • 4. Department of Neurology, Chongqing General Hospital, University of Chinese Academy of Sciences, No.118 Xingguang Avenue, Liangjiang New Area, 401147, Chongqing, China. [email protected].
  • 5. Chongqing Key Laboratory of Neurodegenerative Diseases, No.312 Zhongshan First Road, Yuzhong District, 400013, Chongqing, China. [email protected].
  • 6. Department of Histology and Embryology, Chongqing Medical University, No.1 Yixueyuan Road, Yuzhong District, 400016, Chongqing, China. [email protected].
PMID: 34325647 DOI: 10.1186/s10194-021-01302-x
Abstract

Background: Central sensitization is considered a critical pathogenic mechanism of chronic migraine (CM). Activation of microglia in the trigeminal nucleus caudalis (TNC) contributes to this progression. Microglial glucagon-like peptide-1 receptor (GLP-1R) activation can alleviate pain; however, whether it is involved in the mechanism of CM has not been determined. Thus, this study aims to investigate the precise role of GLP-1R in the central sensitization of CM.

Methods: Repeated nitroglycerin injection-treated mice were used as a CM animal model in the experiment. To identify the distribution and cell localization of GLP-1R in the TNC, we performed immunofluorescence staining. Changes in the expression of GLP-1R, Iba-1, PI3K and p-Akt in the TNC were examined by western blotting. To confirm the effect of GLP-1R and PI3K/Akt in CM, a GLP-1R selective agonist (liraglutide) and antagonist (exendin(9-39)) and a PI3K selective antagonist (LY294002) were administered. Mechanical hypersensitivity was measured through von Frey filaments. To investigate the role of GLP-1R in central sensitization, Calcitonin gene-related peptide (CGRP) and c-Fos were determined using western blotting and immunofluorescence. To determine the changes in microglial activation, IL-1β and TNF-α were examined by western blotting, and the number and morphology of microglia were measured by immunofluorescence. We also confirmed the effect of GLP-1R on microglial activation in lipopolysaccharide-treated BV-2 microglia.

Results: The protein expression of GLP-1R was increased in the TNC after nitroglycerin injection. GLP-1R was colocalized with microglia and astrocytes in the TNC and was fully expressed in BV-2 microglia. The GLP-1R agonist liraglutide alleviated basal allodynia and suppressed the upregulation of CGRP, c-Fos and PI3K/p-Akt in the TNC. Similarly, the PI3K Inhibitor LY294002 prevented nitroglycerin-induced hyperalgesia. In addition, activating GLP-1R reduced Iba-1, IL-1β and TNF-α release and inhibited TNC microglial number and morphological changes (process retraction) following nitroglycerin administration. In vitro, the protein levels of IL-1β and TNF-α in lipopolysaccharide-stimulated BV-2 microglia were also decreased by liraglutide.

Conclusions: These findings suggest that microglial GLP-1R activation in the TNC may suppress the central sensitization of CM by regulating TNC microglial activation via the PI3K/Akt pathway.

Keywords
Central sensitization; Chronic migraine; GLP-1 receptor; Microglia; Nitroglycerin; Trigeminal nucleus caudalis.
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