Microglia P2X4 receptor contributes to central sensitization following recurrent nitroglycerin stimulation

Abstract

BackgroundThe mechanism underlying migraine chronification remains unclear. Central sensitization may account for this progression. The microglia P2X4 receptor (P2X4R) plays a pivotal role in the central sensitization of inflammatory and neuropathic pain, but there is no information about P2X4R in migraine. Therefore, the aim of this study was to identify the precise role of microglia P2X4R in chronic migraine (CM).MethodsWe used an animal model with recurrent intermittent administration of nitroglycerin (NTG), which closely mimics CM. NTG-induced basal and acute mechanical hypersensitivity were evaluated using the von Frey filament test. Then, we detected Iba1 immunoreactivity (Iba1-IR) and P2X4R expression in the trigeminal nucleus caudalis (TNC). To understand the effect of microglia and P2X4R on central sensitization of CM, we examined whether minocycline, an inhibitor of microglia activation, and 5-BDBD, a P2X4R antagonist, altered NTG-induced mechanical hyperalgesia. In addition, we also evaluated the effect of 5-BDBD on c-Fos and calcitonin gene-related peptide (CGRP) expression within the TNC.ResultsChronic intermittent administration of NTG resulted in acute and chronic basal mechanical hyperalgesia, accompanied with microglia activation and upregulation of P2X4R expression. Minocycline significantly decreased basal pain hypersensitivity but did not alter acute NTG-induced hyperalgesia. Minocycline also reduced microglia activation. 5-BDBD completely blocked the basal and acute hyperalgesia induced by NTG. This effect was associated with a significant inhibition of the NTG-induced increase in c-Fos protein and CGRP release in the TNC.ConclusionsOur results indicate that blocking microglia activation may have an effect on the prevention of migraine chronification. Moreover, we speculate that the P2X4R may be implicated in the microglia-neuronal signal in the TNC, which contributes to the central sensitization of CM.Electronic supplementary materialThe online version of this article (10.1186/s12974-018-1285-3) contains supplementary material, which is available to authorized users.

Microglia P2X4R-BDNF signalling contributes to central sensitization in a recurrent nitroglycerin-induced chronic migraine model

“…Recent evidence suggests that microglia surrounding TNC neurons directly or indirectly influence the establishment of central sensitization. Previous results from our team have indicated that microglial activation was correlated with NTG-induced hypersensitivity in C57BL/6 mice and also had an effect on central sensitization induced by chronic intermittent nitroglycerin (NTG) [4]. However, the molecular mechanism that underlies the crosstalk between microglia and neurons of the TNC needs further study.…”

“…However, the exact roles of activated microglia and P2X4Rs are not fully understood in migraine. In our previous studies, we found that the expression of P2X4Rs was increased in the TNC after repeated NTG stimulation [4]. P2X4Rs were associated with NTG-induced hyperalgesia and the changes in neurochemical signs accompanying migraine in the TNC, such as the signalling of c-Fos and calcitonin gene related peptide (CGRP).…”

P2X7R-mediated Autophagic Impairment Contributes to Central Sensitization in a chronic Migraine Model with Recurrent Nitroglycerin Stimulation in Mice

“…The theory that purinergic signaling participats in the pathophysiology of migraine was proposed by Geoffrey Burnstock in the 1980 [20,21]. The purinergic receptors, P2 × 4R and P2Y12R, were con rmed to contribute to the pathogenesis of CM according to our previous works [16,18]. P2 × 7R, an ionotropic purinergic receptor that is widely expressed in the microglia [22,23], has been reported to be involved in the cancer pain, neuropathic pain and in ammatory pain by mediating the microglial activation and the in ammatory response [24][25][26].…”

“…The mechanical withdrawal threshold of the hind paw and periorbit was assessed every other day before and 2 hours after NTG injection. We used Von Frey laments with the up-down method to determine the withdrawal threshold to mechanical stimulation as previously described [16]. Brie y, a series of Von Frey laments (range from 0.01 g to 2 g) were applied to the hind paw or periorbit, with an initial stimulation strength of 0.4 g. If there was no response to the stimulation, the lament strength was increased; Otherwise, the lament strength was decreased until there was a positive reaction.…”

“…Previous research associated with the mechanism underlying central sensitization has mainly focusd on neurons, while recent studies con rm that microglia in the central nervous system (CNS) are also involved in this process [11][12][13][14][15]. Our previous works have shown that the activated microglia in the trigeminal nucleus caudalis (TNC) area contribute to central sensitization in the CM by releasing in ammatory mediators and neurotrophic factors and subsequent microglia-neuron interactions [16][17][18][19].…”