Background Central sensitization is an important mechanism of chronic migraine (CM) and is related to the inflammatory response of microglia. The NOD-like receptor protein 3 (NLRP3) inflammasome may regulate the inflammatory process of microglia in several neurological diseases, but its role in CM is largely unknown. Therefore, the aim of this study was to identify the precise role of microglial NLRP3 in CM. Methods An experimental CM mouse model was established by repeated intraperitoneal (i.p) injection with nitroglycerin (NTG). We evaluated the expression levels of NLRP3 and its downstream interleukin (IL)-1β protein in the trigeminal nucleus caudalis (TNC; which is a central area relevant to migraine pain) at different time points. To further examine the effects of the NLRP3 inflammasome pathway on central sensitization of CM, we examined MCC950, an NLRP3 inflammasome-specific inhibitor, and IL-1ra, an IL-1β antagonist, whether altered NTG-induced mechanical hyperalgesia of the periorbital area and hind paw. The effect of MCC950 and IL-1ra on c-Fos, phosphorylated extracellular signal-regulated kinase (p-ERK) and calcitonin gene-related peptide (CGRP) expression in the TNC were also analyzed. The cell localization of NLRP3 and IL-1β in the TNC was evaluated by immunofluorescence staining. Results Repeated NTG administration induced acute and chronic mechanical hyperalgesia and increased expression of NLRP3 and IL-1β. Blockade of NLRP3 or IL-1β reduced NTG-induced hyperalgesia, and this effect was accompanied by a significant inhibition of the NTG-induced increase in p-ERK, c-Fos and CGRP levels in the TNC. Immunofluorescence staining revealed that NLRP3 and IL-1β were mainly expressed in microglia in the TNC, and the IL-1β receptor, IL-1R, was mainly expressed in neurons in the TNC. Conclusions These results indicate that NLRP3 activation in the TNC participates in the microglial-neuronal signal by mediating the inflammatory response. This process contributes to the central sensitization observed in CM. Electronic supplementary material The online version of this article (10.1186/s12974-019-1459-7) contains supplementary material, which is available to authorized users.

Our study showed that the clinical features of vestibular migraine in China were similar to those of Western studies. The definition of vertigo episodes and migraine subtypes of vestibular migraine in International Classification of Headache Disorders 3rd edition beta version might be modified further. More than five vertigo attacks per day within 72 hours might be helpful as far as identifying vestibular migraine patients with short-lasting attacks.

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.

BackgroundMicroglial activation contributes to the development of chronic migraine (CM). The P2Y12 receptor (P2Y12R), a metabolic purinoceptor that is expressed on microglia in the central nervous system (CNS), has been indicated to play a critical role in the pathogenesis of chronic pain. However, whether it contributes to the mechanism of CM remains unknown. Thus, the present study investigated the precise details of microglial P2Y12R involvement in CM.MethodsMice subjected to recurrent nitroglycerin (NTG) treatment were used as the CM model. Hyperalgesia were assessed by mechanical withdrawal threshold to electronic von Frey and thermal withdrawal latency to radiant heat. Western blot and immunohistochemical analyses were employed to detect the expression of P2Y12R, Iba-1, RhoA, and ROCK2 in the trigeminal nucleus caudalis (TNC). To confirm the role of P2Y12R and RhoA/ROCK in CM, we systemically administered P2Y12R antagonists (MRS2395 and clopidogrel) and a ROCK2 inhibitor (fasudil) and investigated their effects on microglial activation, c-fos, and calcitonin gene-related peptide (CGRP) expression in the TNC. To further confirm the effect of P2Y12R on microglial activation, we preincubated lipopolysaccharide (LPS)-treated BV-2 microglia with MRS2395 and clopidogrel. ELISA was used to evaluate the levels of inflammatory cytokines.ResultsThe protein levels of P2Y12R, GTP-RhoA, ROCK2, CGRP, c-fos, and inducible nitric oxide synthase (iNOS) in the TNC were increased after recurrent NTG injection. A double labeling study showed that P2Y12R was restricted to microglia in the TNC. MRS2395 and clopidogrel attenuated the development of tactile allodynia and suppressed the expression of CGRP, c-fos, and GTP-RhoA/ROCK2 in the TNC. Furthermore, fasudil also prevented hyperalgesia and suppressed the expression of CGRP in the TNC. In addition, inhibiting P2Y12R and ROCK2 activities suppressed NTG-induced microglial morphological changes (process retraction) and iNOS production in the TNC. In vitro, a double labeling study showed that P2Y12R was colocalized with BV-2 cells, and the levels of iNOS, IL-1β, and TNF-α in LPS-stimulated BV-2 microglia were reduced by P2Y12R inhibitors.ConclusionsThese data demonstrate that microglial P2Y12R in the TNC plays a critical role in the pathogenesis of CM by regulating microglial activation in the TNC via RhoA/ROCK pathway.

No abstract