Uridine adenosine tetraphosphate acts as a pro-angiogenic factor in vitrothrough purinergic P2Y receptors

OBJECTIVE Uridine adenosine tetraphosphate(Up4A),a dinucleotide,contains both purine and pyrimidine moieties,and exerts its vascular influence via activation of purinergic receptors.Here,we aimed to investigate the effects of Up4 A on angiogenesis and the putative purinergic receptors(PR)involved in this process.METHODS Tubule formation assay was performed in 3D matrix system.In this assay,human umbilical vein endothelial cells(HUVECs)were co-cultured with pericytes with various Up4 A doses(0,1,2.5,5,10 and 20μmol·L-1)in the absence and presence of P2Y6 R antagonist MRS2578(10μmol·L-1)for 5d.Expression profile of PR subtypes and angiogenic factors was assessed in HUVECs by q-PCR with and without P2Y6 R antagonist.RESULTS No difference in initial tubule formation was detected between Up4 A stimulation and control conditions at day 2.In contrast,a significant increase in vascular density in response to Up4 A was observed at day 5.Up4 A at a dose of 2.5and 5μmol·L-1 promoted total tubule length(by-1.89 fold and-2.23fold),number of tubules(by-1.71 fold and-1.89fold)as well as number of junctions(by-2.24 fold and-2.80fold),all of which were inhibited by MRS2578.Further increase in Up4 A dose to10 and 20μmol·L-1 did not induce an increase in these vascular parameters as compared to non-treated controls.Moreover,Up4 A increased mRNA level of P2YRs(P2Y2R,P2Y4 R and P2Y6R)but not P2XR(P2X4R and P2X7R)or P1R(A2AR and A2BR),while Up4 A upregulated VEGFA and ANGPT1 but not VEGFR2,ANGPT2,Tie1 and Tie2at mRNA level.Transcriptional upregulation of P2 YRs and angiogenic factors by Up4 A was inhibited by MRS2578.CONCLUSION Up4 A is functionally capable of promoting tubule formation in vitro co-culture system.This process is likely mediated by activation of pyrimidine-favored P2 YRs but not P2 XR or P1 Rs,and involves stimulation of well known angiogenic factors.

Overexpression of Purinergic P2X4 Receptors in Hippocampus Rescues Memory Impairment in Rats with Type 2 Diabetes

Purinergic receptors have been reported to be involved in brain disorders.In this study,we explored their roles and mechanisms underlying the memory impairment in rats with type 2 diabetes mellitus(T2 DM).T2 DM rats exhibited a worse performance in the T-maze and Morris water maze(MWM) than controls.Microglia positive for P2 X purinoceptor 4(P2 X4 R) in the hippocampus were reduced and activated microglia were increased in T2 DM rats.Long Amplicon PCR(LA-PCR) showed that DNA amplification of the p2 x4 r gene in the hippocampus was lower in T2 DM rats.Minocycline significantly reduced the number of activated microglia and the mean distance traveled by T2 DM rats in the MWM.Most importantly,P2 X4 R overexpression suppressed the activated microglia and rescued the memory impairment of T2 DM rats.Overall,T2 DM led to excessive activation of microglia in the hippocampus,partly through the DNA damagemediated downregulation of P2 X4 Rs,thus contributing to memory impairment.

Nuclear receptors and pathogenesis of pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) is a devastating disease with a median overall survival time of 5 mo and the five years survival less than 5%, a rate essentially unchanged over the course of the years. A well defined progression model of accumulation of genetic alterations ranging from single point mutations to gross chromosomal abnormalities has been introduced to describe the origin of this disease. However, due to the its subtle nature and concurring events PDAC cure remains elusive. Nuclear receptors (NR) are members of a large superfamily of evolutionarily conserved ligand-regulated DNA-binding transcription factors functionally involved in important cellular functions ranging from regulation of metabolism, to growth and development. Given the nature of their ligands, NR are very tempting drug targets and their pharmacological modulation has been widely exploited for the treatment of metabolic and inflammatory diseases. There are now clear evidences that both classical ligand-activated and orphan NR are involved in the pathogenesis of PDAC from its very early stages; nonetheless many aspects of their role are not fully understood. The purpose of this review is to highlight the striking connections that link peroxisome proliferator activated receptors, retinoic acid receptors, retinoid X receptor, androgen receptor, estrogen receptors and the orphan NR Nur, chicken ovalbumin upstream promoter transcription factor II and the liver receptor homologue-1 receptor to PDAC development, connections that could lead to the identification of novel therapies for this disease.

From dolphins to dogs:new opportunities to understand the role of P2X4 receptors in spinal cord injury and neuropathic pain

The P2X4 receptor belongs to the P2X receptor family of trimeric ligand-gated ion channels and was the first member of this family for which a crystal structure was obtained(Kawate et al.,2009).This structure confirmed the trimeric stoichiometry of P2X receptors and subsequent studies from the same group revealed the orthosteric binding site of the natural ligand adenosine 5′-triphosphate(ATP)in a cleft between each adjacent subunit(Hattori and Gouaux,2012).Now synonymous with structural descriptions of P2X receptors,these original studies described the structure of each P2X4 receptor subunit as that resembling a dolphin.

Genomic Organization of Purinergic P2X Receptors

Purinergic P2X receptors are a family of ligand-gated cationic channels activated by extracellular ATP. P2X subunit protein sequences are highly conserved between vertebrate species. However, they can generate a great diversity of coding splicing variants to fulfill several roles in mammalian physiology. Despite intensive research in P2X expression in both central and peripheral nervous system, there is little information about their homology, genomic structure and other key features that can help to develop selective drugs or regulatory strategies of pharmacological value which are lacking today. In order to obtain clues on mammalian P2X diversity, we have performed a bioinformatics analysis of the coding regions and introns of the seven P2X subunits present in human, simian, dog, mouse, rat and zebrafish. Here we report the arrangements of exon and intron sequences, considering its number, size, phase and placement;proposing some ideas about the gain and loss of exons and retention of introns. Taken together, these evidences show traits that can be used to gain insight into the evolutionary history of vertebrate P2X receptors and better understand the diversity of subunits coding the purinergic signaling in mammals.

Expression of BMP Receptors in Porcine Granulosa Cells (GCs) and Their Regulation by Luteinizing Hormone (LH)

Bone morphogenetic proteins（BMPs） play critical roles in follicle growth and development.BMPs initiate signaling by assembling BMP receptors and activating Smads,which in turn alter expression of target genes.The mechanism underlying the regulation of the expression of BMP receptors and Smads during follicle development in pigs is still unknown.By quantitative real-time PCR,the mRNA expression of BMP receptors and Smads in granulosa cells（GC） was investigated.Cells were obtained from small porcine follicles（SF;3 mm diameter） and dominant follicles（DF;6 mm diameter）;ActR1A and BMPR2 mRNA levels in DF were significantly higher（P0.05） than that in SF,whereas BMPR1B,Smad4 and Smad7 expression tended to decrease（P0.05）.The levels of BMPR1A,ActR2,Smad1,Smad5,and Smad8 mRNA did not differ between DFs and SFs.To investigate the effect of LH on BMP receptors in GC,cells obtained from porcine DFs were cultured in medium supplemented with different doses of luteinizing hormone（LH）.High doses of LH（4 IU mL-1） significantly decreased the concentration of estradiol（E2） and progesterone（P4） in medium and the expression of Cyp19a1（P450 aromatase,P450arom） and Cyp11a1（cholesterol side-chain cleavage enzyme P450,P450scc）,while significantly increased viable cell numbers and up-regulated expression of cyclin dependent kinase-4（CDK4） and cyclin D2.However,LH had no effect on the expression of BMP receptor genes.Thus,the present study indicates that the expression of members of the BMP signaling pathway in porcine GC is regulated during follicle development and the expression of BMP receptors are not regulated by LH in porcine GCs.

Role of P2X_7 receptors in neuronal death in the retina

Acknowledgments： I would like to express my appreciation to Professor Puro DG for leading me to this research topic during my stay as a research fellow in his laboratory at the University of Michigan in 2001, and also to Professor Ikeda T forgiving me the opportunity to study abroad and then to continue to investigate this topic in the Department of Ophthalmology at Osaka Medical College, lapan.

P2X receptors in maintenance and differentiation of neural progenitor cells

Purinergic receptors are among the first cell surface receptors expressed during embryonic development （Burnstock and Ulrich, 2011）. These are characterized based on their pharmacological properties of being activated by adenosine or purine/pyrimidine nucleotides as P1 and P2 receptors. P2 receptors are further classified by their structure as P2Y metabotropic and P2X ionotropic receptors.

Regulation of neural stem/progenitor cell functions by P2X and P2Y receptors

Neural stem/progenitor cells：Radial glial cells constitute multipotent cells in the ventricular zone,lining the wall of the lateral ventricle of the embryonic brain.They have the capacity to give rise to cells belonging to all three major linages（neurons,astrocytes and oligodendrocytes）of the nervous system（Tang and Illes,2017）.

P2X receptors: New players in cancer pain

Pain is unfortunately a quite common symptom for cancer patients. Normally pain starts as an episodic experience at early cancer phases to become chronic in later stages. In order to improve the quality of life of oncological patients, anti-cancer treatments are often accompanied by analgesic therapies. The P2 X receptor are adenosine triphosphate(ATP) gated ion channels expressed by several cells including neurons, cancer and immune cells. Purinergic signaling through P2 X receptors recently emerged as possible common pathway for cancer onset/growth and pain sensitivity. Indeed, tumor microenvironment is rich in extracellular ATP, which has a role in both tumor development and pain sensation. The study of the different mechanisms by which P2 X receptors favor cancer progression and relative pain, represents an interesting challenge to design integrated therapeutic strategies for oncological patients. This review summarizes recent findings linking P2 X receptors and ATP to cancer growth, progression and related pain. Special attention has been paid to the role of P2X2, P2X3, P2X4 and P2X7 in the genesisof cancer pain and to the function of P2X7 in tumor growth and metastasis. Therapeutic implications of the administration of different P2 X receptor blockers to alleviate cancer-associated pain sensations contemporarily reducing tumor progression are also discussed.

Role of P2X_7 receptors in the development of diabetic retinopathy

The P2X7 receptor is one of the members of the family of purinoceptors which are ligand-gated membrane ion channels activated by extracellular adenosine 5'-triphosphate. A unique feature of the P2X7 receptor is that its activation can result in the formation of large plasma membrane pores that allow not only the flux of ions but also of hydrophilic molecules of up to 900 Da. Recent studies indicate that P2X7-mediated signaling can trigger apoptotic cell death after ischemia and during the course of certain neurodegenerative disorders. Expression of the P2X7 receptor has been demonstrated in most types of cells in the retina. This purinoceptor mediates the contraction of pericytes and regulates the spatial and temporal dynamics of the vasomotor response through cell-to-cell electrotonic transmission within the microvascular networks. Of potential clinical significance, investigators have found that diabetes markedly boosts the vulnerability of retinal microvessels to the lethal effect of P2X7 receptor activation. This purinergic vasotoxicity may result in reduced retinal blood flow and disrupted vascular function in the diabetic retina. With recent reports indicating an association between P2X7 receptor activation and inflammatory cytokine expression in the retina, this receptor may also exacerbate the development of diabetic retinopathy by a mechanism involving inflammation.

Implication of Neuronal Versus Microglial P2X4 Receptors in Central Nervous System Disorders

The P2X4 receptor(P2X4)is an ATP-gated cation channel that is highly permeable to Ca2+and widely expressed in neuronal and glial cell types throughout the central nervous system(CNS).A growing body of evidence indicates that P2X4 plays key roles in numerous central disorders.P2X4 trafficking is highly regulated and consequently in normal situations,P2X4 is present on the plasma membrane at low density and found mostly within intracellular endosomal/lysosomal compartments.An increase in the de novo expression and/or surface density of P2X4 has been observed in microglia and/or neurons during pathological states.This review aims to summarize knowledge on P2X4 functions in CNS disorders and provide some insights into the relative contributions of neuronal and glial P2X4 in pathological contexts.However,determination of the cell-specific functions of P2X4 along with its intracellular and cell surface roles remain to be elucidated before its potential as a therapeutic target in multiple disorders can be defined.

P2X7/P2X4 Receptors Mediate Proliferation and Migration of Retinal Microglia in Experimental Glaucoma in Mice

Microglia are involved in the inflammatory response and retinal ganglion cell damage in glaucoma.Here,we investigated how microglia proliferate and migrate in a mouse model of chronic ocular hypertension(COH).In COH retinas,the microglial proliferation that occurred was inhibited by the P2X7 receptor(P2X7R)blocker BBG or P2X7R knockout,but not by the P2X4R blocker 5-BDBD.Treatment of primary cultured microglia with BzATP,a P2X7R agonist,mimicked the effects of cell proliferation and migration in COH retinas through the intracellular MEK/ERK signaling pathway.Transwell migration assays showed that the P2X4R agonist CTP induced microglial migration,which was completely blocked by 5-BDBD.In vivo and in vitro experiments demonstrated that ATP,released from activated Müller cells through connexin43 hemichannels,acted on P2X7R to induce microglial proliferation,and acted on P2X4R/P2X7R(mainly P2X4R)to induce microglial migration.Our results suggest that inhibiting the interaction of Müller cells and microglia may attenuate microglial proliferation and migration in glaucoma.

嘌呤受体P2X4介导慢性疼痛的研究进展

慢性疼痛是一种临床常见病症,其发病机制复杂,目前临床上尚缺乏效佳、毒副作用少、针对性强的治疗方法,因此慢性疼痛的病理机制研究仍然是目前疼痛研究领域的热点。嘌呤受体激活与疼痛调制机制密切相关,嘌呤受体P2X配体门控离子通道4(purinergicreceptor P2X ligand-gated ion channel 4,P2X4R)作为嘌呤受体家族的重要成员之一,在慢性疼痛的发生发展中发挥着重要作用。研究发现,P2X4R在神经病理痛、炎性痛、癌性痛及内脏痛等慢性疼痛的形成、传导和调节中均发挥关键作用。本文就有关P2X4R在不同类型慢性疼痛中的作用及相关研究进展做一综述。

The bumpy road of purinergic inhibitors to clinical application in immune-mediated diseases

Purinergic signaling plays important roles throughout the body in the regulation of organ functions during and following the disruption of homeostasis.This is also reflected by the widespread expression of two families of purinergic receptors(P1 and P2)with numerous subtypes.In the last few decades,there has been increasing evidence that purinergic signaling plays an important role in the regulation of immune functions.Mainly,signals mediated by P2 receptors have been shown to contribute to immune system-mediated pathologies.Thus,interference with P2 receptors may be a promising strategy for the modulation of immune responses.Although only a few clinical studies have been conducted in isolated entities with limited success,preclinical work suggests that the use of P2 receptor inhibitors may bear some promise in various autoimmune diseases.Despite the association of P2 receptors with several disorders from this field,the use of P2 receptor antagonists in clinical therapy is still very scarce.In this narrative review,we briefly review the involvement of the purinergic system in immunological responses and clinical studies on the effect of purinergic inhibition on autoimmune processes.We then open the aperture a bit and show some preclinical studies demonstrating a potential effect of purinergic blockade on autoimmune events.Using suramin,a non-specific purinergic inhibitor,as an example,we further show that off-target effects could be responsible for observed effects in immunological settings,which may have interesting implications.Overall,we believe that it is worthwhile to further investigate this hitherto underexplored area.

神经病理性疼痛大鼠脊髓背角小胶质细胞P2X4受体的表达及意义

目的探讨神经病理性疼痛大鼠脊髓背角小胶质细胞离子型嘌呤受体(ionotropic purinoceptor,P2X)P2X4的表达及其意义。方法雌性SD大鼠20只,随机分为坐骨神经保留性损伤(SNI)组和对照组。SNI组大鼠于左后肢制备SNI模型,对照组大鼠仅暴露坐骨神经后立即缝合手术切口。术后观测机械疼痛阈值的变化,于术后第7天断头处死大鼠,截取L4～6段脊髓,分离左右侧脊髓。采用免疫组化法检测脊髓背角P2X4受体及蛋白激酶p38MAPK的表达。结果与对照组相比,SNI模型组大鼠机械刺激50%缩爪阈值显著降低(P<0.01)。SNI模型组大鼠手术侧脊髓背角活化的小胶质细胞表面P2X4受体的表达水平(456.86±32.21)较非手术侧(106.27±12.16)明显增高(P<0.01),同时SNI模型组大鼠手术侧脊髓背角p38MAPK表达水平(399.95±32.42)较非手术侧(123.63±15.47)明显增高(P<0.01)。结论神经病理性疼痛大鼠模型脊髓背角活化小胶质细胞P2X4受体表达增加,可能通过激活p38MAPK促进了疼痛的发生。

结肠扩张刺激对P2X4受体在IBS大鼠神经中枢中表达的影响

目的观察P2X4受体在结肠扩张刺激引起的IBS大鼠骶髓后连合核(DCN)和骶髓后角中表达的变化,为探讨IBS的神经作用机制提供理论依据。方法采用免疫组织荧光化学的方法,通过对P2X4受体和小胶质细胞的标志物OX42的荧光双标记,观察其在小胶质细胞和神经元上的反应;通过免疫电镜同步观察P2X4受体与小胶质细胞和神经元的相互关系。结果对照组大鼠的DCN和骶髓后角中几乎没有发现P2X4的表达。而在IBS大鼠组,P2X4在DCN和骶髓后角神经元和小胶质细胞中表达明显增高。电镜下,在对照组的DCN和骶髓后角,少数P2X4-LI产物表达在胶质细胞突起上,此突起可与神经元胞体、轴突、树突或另外的胶质细胞突起接触。而在IBS大鼠的DCN和骶髓后角中,P2X4在抑制性突触上的表达明显增加。有的表达在突触复合体上,并且在神经元上也有发现。然而P2X4阳性产物更多的表达在胶质细胞的突起上。结论P2X4是小胶质细胞活化的启动因素,可能是IBS内脏敏感性增高的重要因素。

电针对神经病理性痛大鼠脊髓背角P2X4受体表达的影响

目的:通过观察电针干预慢性坐骨神经压迫性损伤(chronic constrictive injury,CCI)大鼠痛阈变化及脊髓背角P2X4受体的表达情况,探讨P2X4受体在电针镇痛效应中的作用。方法:18只SD大鼠随机分为3组:假模组(Sham Group)、模型对照组(CCI Group)和电针干预组(EA Group),CCI组及EA组结扎坐骨神经造成CCI疼痛模型,各组于术前(0 d)及术后20 d分别测量患侧足机械缩足反射阈值(MWT)和热缩足反射潜伏期(TWL),EA组于术后第5天电针"足三里"-"阳陵泉"连续14 d,1次/d。术后20 d取各组大鼠L4~6脊髓段用免疫荧光检测P2X4受体表达情况。结果:与术前比较,CCI大鼠痛阈明显降低,出现痛觉过敏(P<0.01),而电针干预后EA组较CCI模型组痛阈明显增加(P<0.05)但仍低于假模组。术后20 d EA组较CCI组脊髓背角中P2X4受体表达显著减少(P<0.05)。结论:脊髓背角P2X4受体参与了大鼠神经病理性疼痛的发生发展,电针可能通过抑制大鼠脊髓中P2X4受体的表达而产生镇痛作用。

P2X4受体在大鼠胫骨癌痛中的变化及可能机制

目的:观察骨癌痛大鼠脊髓P2X4受体表达的变化,并探讨其可能机制。方法:72只SD大鼠随机分为两部分(6组),第一部分:空白对照组(K组,n=14)、假手术组(J组,n=14)、模型组(M组,n=20)。K组不给予任何处理,J组和M组分别在左胫骨上端注射PBS液和Walker256乳腺癌细胞5μl(2×107/ml)。各组分别于术前1天,术后3、6、9、12、15、18天时随机各取8只大鼠测定左后肢机械缩足反射阈值(MWT)。K组和J组于术后12天,M组于术后6、12、18天时各处死6只大鼠,取L4～6脊髓组织,用免疫组化法检测P2X4受体表达;第二部分:溶媒对照组、TNP-ATP组、PPADS组,每组8只。各组从骨癌痛造模术后第7天起,连续5天分别鞘内给予双蒸水(ddH2O)、PPADS(100nmol)、TNP-ATP(30nmol)各10μl,并于建模后第12天取L4～6脊髓,用免疫组织化学方法检测脊髓P2X4受体及p-ERK的表达。结果:与K组和J组比较,M组大鼠术后第6～18天,左后肢MWT进行性下降,P2X4受体(P2X4R)阳性细胞数明显增加(P<0.01)。连续5天鞘内注射TNP-ATP可抑制由胫骨癌痛引起的脊髓P2X4受体及p-ERK表达增加(P<0.05),而PPADS组和ddH2O溶剂组却没有此种效应(P>0.05)。结论:脊髓P2X4受体表达上调可能参与了大鼠胫骨癌痛的产生和维持,其机制可能与激活下游ERK通路有关。

乙酸致内脏痛大鼠孤束核及胸髓中P2X4受体表达的变化

本文探讨了乙酸致内脏痛模型大鼠孤束核及胸髓背角内P2X4受体表达的时程变化。将SD大鼠随机分为6组:空白对照组、内脏痛10、30、60、90和180min组,分别检测各组大鼠行为学以及孤束核、胸髓背角浅层内P2X4受体的表达变化。结果表明,乙酸致内脏痛后各组大鼠均出现典型的扭体行为,内脏痛指数在60、90和180min组最高,30min组其次,10min组最低,各组之间的差别有统计学意义(P<0.01);各内脏痛组P2X4阳性产物在孤束核及胸髓背角浅层表达明显增高,产物呈绿色点状,见于细胞胞膜、突起、胞浆,其时程变化是10min出现表达,30min进一步增高,60min达到顶峰,90min开始下降,至180min进一步降低。此结果表明延髓孤束核及胸髓背角浅层内的P2X4受体在内脏伤害性刺激后表达增加,60min达到高峰。