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Microglia P2Y13 Receptors Prevent Astrocyte Proliferation Mediated by P2Y1 Receptors.

ABSTRACT: Cerebral inflammation is a common feature of several neurodegenerative diseases that requires a fine interplay between astrocytes and microglia to acquire appropriate phenotypes for an efficient response to neuronal damage. During brain inflammation, ATP is massively released into the extracellular medium and converted into ADP. Both nucleotides acting on P2 receptors, modulate astrogliosis through mechanisms involving microglia-astrocytes communication. In previous studies, primary cultures of astrocytes and co-cultures of astrocytes and microglia were used to investigate the influence of microglia on astroglial proliferation induced by ADP?S, a stable ADP analog. In astrocyte cultures, ADP?S increased cell proliferation through activation of P2Y1 and P2Y12 receptors, an effect abolished in co-cultures (of astrocytes with ?12.5% microglia). The possibility that the loss of the ADP?S-mediated effect could have been caused by a microglia-induced degradation of ADP?S or by a preferential microglial localization of P2Y1 or P2Y12 receptors was excluded. Since ADP?S also activates P2Y13 receptors, the contribution of microglial P2Y13 receptors to prevent the proliferative effect of ADP?S in co-cultures was investigated. The results obtained indicate that P2Y13 receptors are low expressed in astrocytes and mainly expressed in microglia. Furthermore, in co-cultures, ADP?S induced astroglial proliferation in the presence of the selective P2Y13 antagonist MRS 2211 (3 ?M) and of the selective P2Y12 antagonist AR-C66096 (0.1 ?M), suggesting that activation of microglial P2Y12 and P2Y13 receptors may induce the release of messengers that inhibit astroglial proliferation mediated by P2Y1,12 receptors. In this microglia-astrocyte paracrine communication, P2Y12 receptors exert opposite effects in astroglial proliferation as a result of its cellular localization: cooperating in astrocytes with P2Y1 receptors to directly stimulate proliferation and in microglia with P2Y13 receptors to prevent proliferation. IL-1? also attenuated the proliferative effect of ADP?S in astrocyte cultures. However, in co-cultures, the anti-IL-1? antibody was unable to recover the ADP?S-proliferative effect, an effect that was achieved by the anti-IL-1? and anti-TNF-? antibodies. It is concluded that microglia control the P2Y1,12 receptor-mediated astroglial proliferation through a P2Y12,13 receptor-mediated mechanism alternative to the IL-1? suppressive pathway that may involve the contribution of the cytokines IL-1? and TNF-?.

SUBMITTER: Quintas C

PROVIDER: S-EPMC5943495 | biostudies-literature | 2018

REPOSITORIES: biostudies-literature

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Microglia P2Y<sub>13</sub> Receptors Prevent Astrocyte Proliferation Mediated by P2Y<sub>1</sub> Receptors.

Quintas Clara C Vale Nuno N Gonçalves Jorge J Queiroz Glória G

Frontiers in pharmacology 20180503

Cerebral inflammation is a common feature of several neurodegenerative diseases that requires a fine interplay between astrocytes and microglia to acquire appropriate phenotypes for an efficient response to neuronal damage. During brain inflammation, ATP is massively released into the extracellular medium and converted into ADP. Both nucleotides acting on P2 receptors, modulate astrogliosis through mechanisms involving microglia-astrocytes communication. In previous studies, primary cultures of ...[more]

PMID: 29773988

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Project description:Extracellular ATP and ADP have been shown to exhibit potent angiogenic effects on pulmonary artery adventitial vasa vasorum endothelial cells (VVEC). However, the molecular signaling mechanisms of extracellular nucleotide-mediated angiogenesis remain not fully elucidated. Since elevation of intracellular Ca(2+) concentration ([Ca(2+)](i)) is required for cell proliferation and occurs in response to extracellular nucleotides, this study was undertaken to delineate the purinergic receptor subtypes involved in Ca(2+) signaling and extracellular nucleotide-mediated mitogenic responses in VVEC. Our data indicate that stimulation of VVEC with extracellular ATP resulted in the elevation of [Ca(2+)](i) via Ca(2+) influx through plasma membrane channels as well as Ca(2+) mobilization from intracellular stores. Moreover, extracellular ATP induced simultaneous Ca(2+) responses in both cytosolic and nuclear compartments. An increase in [Ca(2+)](i) was observed in response to a wide range of purinergic receptor agonists, including ATP, ADP, ATP?S, ADP?S, UTP, UDP, 2-methylthio-ATP (MeSATP), 2-methylthio-ADP (MeSADP), and BzATP, but not adenosine, AMP, diadenosine tetraphosphate, ??MeATP, and ??MeATP. Using RT-PCR, we identified mRNA for the P2Y1, P2Y2, P2Y4, P2Y13, P2Y14, P2X2, P2X5, P2X7, A1, A2b, and A3 purinergic receptors in VVEC. Preincubation of VVEC with the P2Y1 selective antagonist MRS2179 and the P2Y13 selective antagonist MRS2211, as well as with pertussis toxin, attenuated at varying degrees agonist-induced intracellular Ca(2+) responses and activation of ERK1/2, Akt, and S6 ribosomal protein, indicating that P2Y1 and P2Y13 receptors play a major role in VVEC growth responses. Considering the broad physiological implications of purinergic signaling in the regulation of angiogenesis and vascular homeostasis, our findings suggest that P2Y1 and P2Y13 receptors may represent novel and specific targets for treatment of pathological vascular remodeling involving vasa vasorum expansion.

Project description:Alexander disease (AxD) is an intractable neurodegenerative disorder caused by GFAP mutations. It is a primary astrocyte disease with a pathological hallmark of Rosenthal fibres within astrocytes. AxD astrocytes show several abnormal phenotypes. Our previous study showed that AxD astrocytes in model mice exhibit aberrant Ca2+ signals that induce AxD aetiology. Here, we show that microglia have unique phenotypes with morphological and functional alterations, which are related to the pathogenesis of AxD. Immunohistochemical studies of 60TM mice (AxD model) showed that AxD microglia exhibited highly ramified morphology. Functional changes in microglia were assessed by Ca2+ imaging using hippocampal brain slices from Iba1-GCaMP6-60TM mice and two-photon microscopy. We found that AxD microglia showed aberrant Ca2+ signals, with high frequency Ca2+ signals in both the processes and cell bodies. These microglial Ca2+ signals were inhibited by pharmacological blockade or genetic knockdown of P2Y12 receptors but not by tetrodotoxin, indicating that these signals are independent of neuronal activity but dependent on extracellular ATP from non-neuronal cells. Our single-cell RNA sequencing data showed that the expression level of Entpd2, an astrocyte-specific gene encoding the ATP-degrading enzyme NTPDase2, was lower in AxD astrocytes than in wild-type astrocytes. In situ ATP imaging using the adeno-associated virus vector GfaABC1D ATP1.0 showed that exogenously applied ATP was present longer in 60TM mice than in wild-type mice. Thus, the increased ATP level caused by the decrease in its metabolizing enzyme in astrocytes could be responsible for the enhancement of microglial Ca2+ signals. To determine whether these P2Y12 receptor-mediated Ca2+ signals in AxD microglia play a significant role in the pathological mechanism, a P2Y12 receptor antagonist, clopidogrel, was administered. Clopidogrel significantly exacerbated pathological markers in AxD model mice and attenuated the morphological features of microglia, suggesting that microglia play a protective role against AxD pathology via P2Y12 receptors. Taken together, we demonstrated that microglia sense AxD astrocyte dysfunction via P2Y12 receptors as an increase in extracellular ATP and alter their morphology and Ca2+ signalling, thereby protecting against AxD pathology. Although AxD is a primary astrocyte disease, our study may facilitate understanding of the role of microglia as a disease modifier, which may contribute to the clinical diversity of AxD.

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Dataset Information

Microglia P2Y13 Receptors Prevent Astrocyte Proliferation Mediated by P2Y1 Receptors.

Publications

Microglia P2Y<sub>13</sub> Receptors Prevent Astrocyte Proliferation Mediated by P2Y<sub>1</sub> Receptors.

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