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

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.

Teneligliptin Exerts Antinociceptive Effects in Rat Model of Partial Sciatic Nerve Transection Induced Neuropathic Pain

“…Recent evidence suggests that TEN enhances the positive effects of GLP-1 [18]. Several previous studies have concluded that activation of GLP-1R can effectively suppress neuroinflammation and central sensitization, thereby alleviating neuropathic pain in various animal models [19][20][21][22][23][24][25]. Furthermore, in the CNS, GLP-1R is confined to microglial cells of the spinal dorsal horn and greatly decreased after nerve injury and has been found to play a key role in microglial cell activation [19,26].…”

Temporal characteristics of astrocytic activation in the TNC in a mice model of pain induced by recurrent dural infusion of inflammatory soup

“…The results suggested that the astrocytes in the TNC were activated from 20 d to at least 47 d. We also detected Iba1 in the TNC, a biomarker of microglial activation, at transcription level through RNAscope ISH, and the results suggested that the microglia were activated at the same time with astrocytes. Microglia may contribute to the central sensitization through modulating cytokine signals communication among the astrocytes, microglia, and neurons [12,[24][25][26][27]. The duration of astrocytic and microglial activation is consistent with the sensitization of the trigeminovascular system.…”

“…GFAP is thought to be an important biomarker of astrocytic activation. Altered levels of proinflammation cytokines in plasma and serum, such as interleukin 1 beta (IL-1β), interleukin 6 (IL-6), and tumor necrosis factor alpha (TNF-α), has been demonstrated the correlation to migraine in both patients and animals [9][10][11][12]. But it remains unclear whether the levels change of cytokines in the TNC tissue and serum are correlated to the central sensitization and astrocytic activation in the TNC region in CM.…”

Identification of Constituents and Exploring the Mechanism for Toutongning Capsule in the Treatment of Migraine

“…Amounts of evidences supported the significance role of the PI3K-Akt signaling pathway in migraine [ 45 , 56 ]. A study has confirmed that glucagon-like peptide-1 receptor (GLP-1R) agonist inhibited the upregulation of PI3K/p-Akt in the trigeminal nucleus caudalis (TNC) via Western blotting, which indicated that microglial GLP-1R activation in TNC may suppress the central sensitization of chronic migraine by regulating TNC microglial activation via the PI3K/Akt pathway [ 57 ]. Furthermore, PRKCA, as a core target of our research in both the P13K-AKT pathway and MAPK signaling pathway, is calcium-activated and phospholipid and diacylglycerol (DAG)-dependent serine/threonine-protein kinase activating signaling cascade involving MAPK1/3 (ERK1/2) and RAP1GAP, thus promoting cell growth by phosphorylating and activating RAF1.…”