谷氨酸及其N-甲基-D-天冬氨酸受体在肺损伤中的作用

谷氨酸是哺乳动物中枢神经系统兴奋性氨基酸神经递质,N-甲基-D-天冬氨酸（N—methyl—D-aspartate,NMDA）受体是谷氨酸重要的离子型受体。多种外周非神经组织也发现NMDA受体在维持组织正常的生理功能、参与组织细胞的损伤与修复等方面发挥重要作用。近年来发现在肺组织同样存在NMDA受体的表达,后者参与多种肺部疾病的发生与发展。     

凝血酶增高NMDA受体敏感性与组织型谷氨酰胺转移酶的关系

目的探讨凝血酶增高大鼠的小脑颗粒细胞N-甲基-D-天冬氨酸受体(NMDA)敏感性是否与细胞内组织型谷氨酰胺转移酶(tTG)变化有关。方法以0·01U/ml浓度凝血酶单独或与tTG抑制剂单丹磺酰尸胺(MDC)0·5×10-4mol/L处理原代培养的Wistar大鼠小脑颗粒细胞30min后,以0·1×10-4mol/L、0·25×10-4mol/L和0·5×10-4mol/L3种浓度NMDA作用3h诱导上述处理的细胞凋亡,比较流式细胞仪检测到的细胞凋亡率差异以判断NMDA受体敏感性的变化;RT-PCR和Gelpro图像分析软件检测各NMDA浓度有/无凝血酶预处理的细胞内tTG mRNA变化差异。结果凝血酶预处理细胞后上述3种浓度NMDA诱导的细胞凋亡率均升高[(8·3±0·5~15·1±0·8)%,(14·1±1·1~23·8±0·7)%,(26·8±1·9~33·7±2·1)%]。预处理细胞时加入MDC可阻断凝血酶对NMDA受体的这种影响,细胞凋亡率降至(5·8±1·2)%、(11·5±1·5)%和(19·0±1·7)%;凝血酶预处理后各浓度NMDA处理细胞内tTG mRNA量均同一浓度单独NMDA处理的细胞高。结论凝血酶通过增高细胞内tTG使小脑颗粒细胞NMDA受体敏感性增高。     

N-甲基-D-天冬氨酸受体与疼痛

谷氨酸是中枢神经系统中重要的兴奋性神经递质,又称为兴奋性氨基酸（EAA）。其主要通过离子型和代谢型细胞膜受体发挥作用。离子型受体是直接的离子通道,分为3个主要类型（分别以其激动剂命名）：α氨基-3-羧基-5-甲基异噁唑-4-丙酸（AMPA）,海人藻酸（KA）和N-甲基-D-天冬氨酸（NMDA）。大量证据表明,NMDA受体在疼痛中枢敏化的产生和维持中起重要作用,也可能介导周围神经敏化及内脏疼痛。     

NMDA受体参与β淀粉样蛋白介导的突触可塑性损伤研究进展

阿尔茨海默症(AD)已成为继心脏病、癌症以及脑卒中之后导致人类死亡的主要疾病.目前AD的具体发病机制仍然没有被完全阐述清楚,越来越多的研究证据显示,与学习认知功能相关的神经元突触可塑性异常在AD发病过程中扮演着重要的角色.其中以N-甲基-D-天冬氨酸(NMDA)受体发挥的作用最为关键,其亚单位在AD病理过程中的作用在医学界引起了广泛关注.故研究NMDA受体介导的突触可塑性损伤机制对阐明AD发病机制具有重要意义.     

丹皮酚对缺糖缺氧再灌注损伤大鼠海马神经元EAA、NMDA受体表达的影响及机制探讨

目的观察丹皮酚对缺糖缺氧（OGD）再灌注损伤大鼠海马神经元兴奋性氨基酸（EAA）、N．甲基．D．天门冬氨酸（NMDA）受体表达的影响,探讨该药的神经保护作用机制。方法原代培养新生大鼠海马神经元8～12d后随机分为4组,其中对照组正常换液培养;模型组、丹皮酚组、地佐环平（MK-801）组均制备OGD再灌注损伤模型,在此基础上丹皮酚组于每个再灌注时间点前分别加入丹皮酚,MK-801组则加入MK-801溶液;倒置相差显微镜下观察神经元一般形态学变化,用MTr法测定神经元存活率,分别采用放射配基结合实验及RT-PCR法测定NMDA受体结合力、NR1亚基mRNA表达,以氨基酸分析仪检测EAA含量。结果模型组神经元肿胀或变形,突起缩短并逐渐消失,胞质内颗粒变性明显、甚至完全崩解;丹皮酚组及MK-801组神经元形态改变均较模型组减轻,胞体完整,突起较清楚,基本保持完整。与对照组比较,模型组神经元存活率明显降低,NMDA受体结合力、NR1亚基mRNA表达及E从含量明显升高,而丹皮酚组及MK_801组上述指标均较模型组明显改善（P均〈0．05）。结论丹皮酚对离体培养的大鼠海马神经元OGD再灌注损伤具有保护作用,其作用机制可能与抑制EAA及NMDA受体表达有关。     

同型半胱氨酸与N-甲基-D-天冬氨酸受体的研究进展

同型半胱氨酸(homocysteine,Hcy)是心血管疾病的独立危险因子,作用机制涉及损伤血管功能、活化炎症细胞和血小板、促进凝血及心肌肥大等方面。N-甲基-D-天冬氨酸(N-methyl-D-aspartic acid,NMDA)受体是兴奋性氨基酸受体的一种亚型,传统观点认为其主要分布在中枢神经系统,在神经元回路的形成及学习、记忆过程中起关键作用,并与神经退行性疾病密切相关。近年来,NMDA受体在心血管疾病中的作用得到人们的关注。现就NMDA受体在Hcy致心血管细胞功能损伤中的作用方面的研究进展作一综述。     

N-甲基-D-天门冬氨酸受体和活性氧对血管平滑肌细胞活性的影响

目的研究N-甲基-D-天门冬氨酸(N-methy-D-aspartate,NMDA)受体和活性氧(reactive oxygen species,ROS)是否参与同型半胱氨酸(homocysteine,Hcy)诱导血管平滑肌细胞活性的增强。方法采用5-溴脱氧尿嘧啶(BrdU)合成实验观察细胞的增殖活性,Trans well方法观察细胞的迁移活性,二乙酰二氯氢化荧光素检测平滑肌细胞中ROS水平。结果随Hcy浓度增加,Hcy诱导血管平滑肌细胞增殖、迁移活性增强,呈剂量依赖性,NMDA受体拮抗剂MK801、NAD(P)H氧化酶抑制剂二苯基碘(DPI)、自由基清除剂N-2酰半胱氨酸(NAC)能抑制Hcy诱导的增殖、迁移活性的增强。Hcy刺激后平滑肌细胞ROS水平升高作用能够被MK801、DPI、NAC抑制。结论ROS参与了Hcy诱导的血管平滑肌细胞增殖和迁移活性的增强,并且该途径是通过NMDA受体介导的。     

氯胺酮对乳鼠海马CA3区神经元凋亡及NMDAR-2B表达的影响

目的探讨氯胺酮对新生大鼠海马CA3区海马神经元凋亡及N-甲基-D-天冬氨酸受体(NMDAR)-2B表达的影响。方法将12只新生7 d的SD大鼠随机分为对照组和氯胺酮组,每组6只。氯胺酮组腹腔注射氯胺酮20 mg/kg,间隔90 min再次注射,共计5次;对照组于相应时间点腹腔注射等体积的生理盐水。24 h后灌注固定,断头取脑;TUNNEL法检测海马神经元凋亡情况;免疫组化法检测海马神经元CA3区NMDAR-2B表达。结果氯胺酮组凋亡细胞密度和NMDAR-2B表达均明显高于对照组(P均<0.05)。结论氯胺酮可引起新生大鼠海马神经元凋亡增加,其机制可能与NMDA受体表达上调有关。     

甲状腺素对大鼠海马细胞凋亡和AMPA、NMDA受体的影响

目的观察甲状腺素对大鼠海马细胞凋亡和α-氨基-3-羧基-5-甲基-4-异恶唑丙酸(AMPA)、N-甲基-D-天冬氨酸(NMDA)受体表达的影响。方法选取健康SD大鼠20只,随机分为对照组、甲状腺功能亢进症(甲亢)组各10只,腹腔注射L-甲状腺素35 d建立大鼠甲亢模型。检测两组大鼠血清三碘甲腺原氨酸(T3)、血清总甲状腺素(T4)水平;水迷宫检测大鼠学习记忆力;免疫组化检测两组大鼠海马细胞Bax、Bcl-2蛋白及AMPA及NMDA受体变化。结果与对照组比较,甲亢组血清T3、T4水平明显升高(P0.01),逃避潜伏期明显延长(P0.05);Bax蛋白表达明显升高(P0.01);Bcl-2蛋白及AMPA、NMDA受体表达均显著减少(P0.01)。结论甲状腺素可促进海马细胞Bax蛋白表达;降低Bcl-2蛋白、AMPA、NMDA受体的表达;这可能是甲亢大鼠学习记忆力降低的分子生物学机制之一。     

抗N-甲基-D-天冬氨酸受体脑炎精神行为异常的研究

摘要 抗N-甲基-D-天冬氨酸受体(NMDAR)脑炎是自身免疫性脑炎(AE)的最主要类型,精神行为异常是其常见、有时甚至是首发的临床症状,会造成患者首诊于精神科,极易导致漏诊、误诊和误治。因此,正确认识和识别抗NMDAR脑炎的精神行为异常有助于及早明确诊断、及时给予恰当的治疗、进而改善患者的预后。本文拟对抗NMDAR脑炎精神行为异常的发病机制、临床特点、辅助检查、治疗及预后等进行综述,为提高临床医生对抗NMDAR脑炎精神行为异常的认识和识别能力而提供帮助。     

阻塞性睡眠呼吸暂停导致认知功能障碍的机制及与孤束核病变的关系

阻塞性睡眠呼吸暂停（OSA）是近年来较为常见的一种疾病,可以引起多系统病变.OSA导致的认知功能障碍也越来越受到重视.低氧血症和睡眠结构紊乱诱导的氧化应激和炎症反应等被认为是OSA患者发生认知功能障碍的主要机制.目前一个新的假说强调,在OSA的患者中孤束核的炎症和结构异常在触发记忆和认知功能障碍亦可能发挥举足轻重的作用.因此,进一步研究OSA导致认知功能障碍的病理机制及与孤束核病变的关系,将为OSA患者并发认知功能障碍的防治提供一新视角.     

Modulation of the baroreflex control of heart rate by angiotensin-(1-7) at the nucleus tractus solitarii of normotensive and spontaneously hypertensive rats

OBJECTIVES: In the present study, we evaluated the effect of angiotensin-(1-7) [Ang-(1-7)] and its selective antagonist, D-Ala7-Ang-(1-7) (A-779), at the nucleus tractus solitarii (nTS), in the modulation of the bradycardic component of the baroreceptor reflex. METHODS: Mean arterial pressure (MAP) and heart rate were continuously recorded. Reflex changes in heart rate elicited by bolus injection of graded doses of phenylephrine were evaluated before and after bilateral microinjection (glass micropipette) of Ang-(1-7) (10 pmol or 25 pmol), A-779 (50 pmol) or saline (vehicle) into the nTS of urethane anesthetized male Wistar rats or spontaneously hypertensive rats (SHR). The averaged ratio between reflex changes in heart rate and changes in MAP was used as index of baroreflex sensitivity. RESULTS: Microinjection of Ang-(1-7) into the nTS elicited significant decreases in MAP and heart rate in both Wistar and SHR. While the decrease in MAP was similar in both strains, the changes in heart rate were smaller in SHR. A-779 produced small changes in MAP and heart rate that were no different from those induced by saline. After microinjection of 10 pmol of Ang-(1-7) into the nTS of normotensive rats, there was a significant increase in baroreflex sensitivity. In SHR, only the microinjection of a higher dose (25 pmol) of Ang-(1-7) produced a significant increase in baroreflex sensitivity. A significant reduction inbaroreflex sensitivity was observed after microinjection of A-779 (50 pmol) in both strains. CONCLUSIONS: These results indicate that Ang-(1-7) exerts a tonic modulatory effect on the baroreflex control of heart rate at the nTS, probably through a non-AT1 non-AT2 receptor subtype. In addition, our data showed a reduced sensitivity to Ang-(1-7) at the nTS of SHR, that could be accounting, at least in part, for the decreased baroreflex sensitivity present in this model of hypertension.     

CNQX binding to non-NMDA glutamate receptors in canine cerebro-cortical crude synaptosomal membranes: Pharmacological characterization and comparison of binding parameters in dogs with congenital portosystemic encephalopathy and control dogs

The pharmacological profile and binding characteristics of the non-NMDA antagonist of glutamate receptors [³H]6-cyano-7-nitro-quinoxaline-2,3-dione (CNQX), were investigated in triton-washed crude synaptosomal membranes prepared from canine cerebral cortex. [³H]CNQX binding was inhibited by various glutamate agonists and antagonists, the rank order of potency being CNQX>-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)=quisqualate=kainate>glutamate. Two binding sites for [³H]CNQX were apparent when non-specific binding (NSB) was defined with unlabelled CNQX. In contrast, when NSB was defined with saturating concentrations of unlabelled AMPA and kainate, only one binding site was identified which corresponded to the high affinity site identified when CNQX was used to define NSB. No physiologically relevant differences were found in binding parameters for [³H]CNQX membranes from dogs with congenital portosystemic encephalopathy (PSE) when compared with control dogs. The affinity constant (K_i of AMPA displacement of [³H]CNQX binding was not significantly different in PSE dogs compared with control dogs. These results suggest that the antagonist site on cortical non-NMDA receptors is not perturbed in dogs with congenital PSE.     

A role for N-methyl-D-aspartate (NMDA) receptors in the control of LH secretion and initiation of female puberty

The physiological role of N-methyl-D-aspartate (NMDA) receptors in controlling LH secretion and the initiation of puberty was investigated using two specific antagonists, MK-801 and DL-2-amino-5-phosphono valeric acid (AP-5). Single daily sc injections of MK-801 (0.1-0.2 mg/kg BW), a noncompetitive NMDA receptor antagonist, given to prepubertal rats significantly delayed but did not prevent the timing of puberty, as determined by the age at vaginal opening and first ovulation. Infusion of MK-801 (5 micrograms/h) via osmotic minipumps for 4 days inhibited the postovariectomy rise of LH secretion in prepubertal rats. Both MK-801 (0.2 mg/kg BW, sc) and AP-5 (4 x 30 mg, iv), a competitive NMDA receptor antagonist, blocked the estradiol-induced LH surge in prepubertal ovariectomized rats. These results demonstrate that blockade of NMDA receptors can prevent the development of enhanced LH secretion in female rats undergoing sexual maturation. Moreover, they support the view that activation of NMDA receptors significantly contributes to the physiological initiation of the pubertal process.     

Neuronal activity of the cat supraoptic nucleus is influenced by muscle small-diameter afferent (groups III and IV) receptors.

In anesthetized cats, responses of single neurosecretory neurons of the supraoptic nucleus to activation of muscle receptors were investigated. Electrical stimulation (1-3 pulses at 200 Hz) of group III and IV pure muscle afferents (gastrocnemius nerve) evoked excitation of greater than 50% of supraoptic nucleus neurons (n = 50), whereas stimulation of group Ia or Ib fibers was ineffective. Baroreceptor stimulation inhibited 95% of these supraoptic nucleus neurons that responded to activation of muscle afferents. Excitation of receptors in the gastrocnemius muscle by intra-arterial injection of chemicals (NaCl, KCl, and bradykinin) increased firing rates of most (84%, 74%, and 80%, respectively) neurosecretary neurons. The magnitude of the excitatory response was dose dependent--bradykinin being the most effective. The response disappeared after muscle denervation. When the gastrocnemius muscle alone was contracted phasically by ventral root stimulation, discharges of the supraoptic nucleus neurons increased, whereas quick stretch of the muscle had no effect. We conclude that activation of muscle receptors by chemical or mechanical stimulus can directly excite neurosecretory neurons in the supraoptic nucleus and that afferent impulses are carried by polymodal fibers of small diameter but not by the largest afferents (group I) from the muscle. The results may relate to increased concentrations of plasma vasopressin during exercise.     

电针改善血管性痴呆大鼠学习记忆及其与海马神经细胞谷氨酸、NMDAR表达的关系

目的 观察电针对血管性痴呆(VD)大鼠学习记忆功能和海马谷氨酸及其NMDA受体表达的影响,探讨电针的治疗作用机制.方法SD大鼠,随机分为正常对照组、假手术组、模型组、电针组.在建立VD大鼠模型后,电针“百会”、“大椎”穴,水迷宫观察大鼠学习记忆能力,免疫组织化学染色技术观察脑组织海马谷氨酸及其NMDA受体染色结果.结果 与模型组比较,经电针治疗后水迷宫潜伏期明显缩短(P＜0.01),相同时间内在原平台象限跨越相应平台次数明显增多(P＜0.01);谷氨酸及其NMDA受体免疫阳性细胞积分光密度显著增加(P＜0.01).结论 电针大鼠“白会”、“大椎”穴能改善大鼠学习记忆能力,其机制可能与提高海马谷氨酸及其NMDA受体表达有关.     

Circadian rhythms of dopamine, glutamate and GABA in the striatum and nucleus accumbens of the awake rat: modulation by light

Using microdialysis, we investigated the circadian rhythms of the extracellular concentrations of dopamine, glutamate and gamma-aminobutyric acid (GABA) in the striatum and nucleus accumbens of the awake rat. Wistar rats were maintained in a 12 hr dark:12 hr light (12:12) cycle for 2 wk before the experiment began. The neurotransmitter levels were measured every 30 min for 30 hr in control (maintaining the 12:12 cycle) or in experimental conditions under a 24-h light period (continuous light) or under a 24-h dark interval (continuous dark). The dopamine metabolites, DOPAC and HVA, and the main serotonin metabolite, 5-HIAA, were measured along with arginine and glutamine under all conditions. In 12:12 conditions, a circadian rhythm of dopamine, glutamate and GABA was found in both the striatum and nucleus accumbens. Again under 12:12 conditions, DOPAC, HVA, 5-HIAA, and arginine, but not glutamine, fluctuated in a circadian rhythm. In the striatum under constant light conditions, there was a circadian rhythm of dopamine, glutamate, GABA, DOPAC and HVA, but not 5-HIAA. By contrast, when the rats were kept under continuous dark, dopamine and its metabolites, DOPAC and HVA (but not glutamate and GABA), did not fluctuate in a circadian rhythm. In the nucleus accumbens, under both constant light or dark conditions, no changes were found in the circadian rhythm in any of the neurotransmitters and metabolites studied. These findings show that in the striatum, dopamine but not glutamate and GABA, seem to be influenced by light. In the nucleus accumbens, however, the three neurotransmitters had a circadian rhythm, which was independent of light.     

Expression of N-methyl-D-aspartate (NMDA) and alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) GluR2/3 receptors in the developing rat pineal gland

The expression of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) type glutamate (GluR2/3) receptors and N-methyl-D-aspartate receptor subtype 1 (NMDAR1) was carried out by immunohistochemistry, double immunofluorescence and real-time RT-PCR analysis in the pineal glands of 1-day to 6-wk-old rats in the present study. GluR2/3 immunopositive cells were distributed throughout the pineal gland and showed branching processes in all age groups. The NMDAR1 immunoreactivity, however, was observed in fewer branched cells. A constitutive mRNA expression of NMDAR1, GluR2 and GluR3 was detected in the pineal glands of various ages and showed no significant difference between the age groups studied. Immunohistochemical and double immunofluorescence results showed that the GluR2/3 were mainly expressed and co-localized with OX-42-positive microglia/macrophages and the glial fibrillary acidic protein (GFAP)-positive astrocytes. Co-localization of NMDAR1 with OX-42- and GFAP-positive cells was much less. The expression of these receptors on the glial cells suggests that they may be involved in the development and growth of the pineal gland in the early postnatal period (1 day to 3 wk) and subsequently in the regulation of melatonin synthesis.     

Structural basis for the specific recognition of dual receptors by the homopolymeric pH 6 antigen (Psa) fimbriae of Yersinia pestis

The pH 6 antigen (Psa) of Yersinia pestis consists of fimbriae that bind to two receptors: β1-linked galactosyl residues in glycosphingolipids and the phosphocholine group in phospholipids. Despite the ubiquitous presence of either moiety on the surface of many mammalian cells, Y. pestis appears to prefer interacting with certain types of human cells, such as macrophages and alveolar epithelial cells of the lung. The molecular mechanism of this apparent selectivity is not clear. Site-directed mutagenesis of the consensus choline-binding motif in the sequence of PsaA, the subunit of the Psa fimbrial homopolymer, identified residues that abolish galactosylceramide binding, phosphatidylcholine binding, or both. The crystal structure of PsaA in complex with both galactose and phosphocholine reveals separate receptor binding sites that share a common structural motif, thus suggesting a potential interaction between the two sites. Mutagenesis of this shared structural motif identified Tyr126, which is part of the choline-binding consensus sequence but is found in direct contact with the galactose in the structure of PsaA, important for both receptor binding. Thus, this structure depicts a fimbrial subunit that forms a polymeric adhesin with a unique arrangement of dual receptor binding sites. These findings move the field forward by providing insights into unique types of multiple receptor–ligand interactions and should steer research into the synthesis of dual receptor inhibitor molecules to slow down the rapid progression of plague.     

Expression and function of vascular endothelial growth factor receptors (Flt-1 and Flk-1) in vascular adventitial fibroblasts

Vascular endothelial growth factor receptors (VEGFRs) are previously considered to exist exclusively in endothelial cells. However, little is known if the receptors are expressed in other non-endothelial cells. In this study, we measured activation of two VEGFRs, Flk-1 and Flt-1, and their biological functions in cultured adventitial fibroblasts and injured rat carotid injury arteries induced by balloon angioplasty. Our results indicated that Flt-1, but not Flk-1, existed in adventitial fibroblasts. Angiotensin II increased Flt-1 protein expression in a time- and concentration-dependent manner. Adventitial fibroblast migration stimulated by vascular endothelial growth factor (VEGF) and placental growth factor (PIGF) required Flt-1 expression. The Flt-1-induced adventitial fibroblast migration was blocked by anti-Flt-1 neutralizing antibody and soluble VEGFR1 protein (sFlt-1). However, Flt-1 activation did not enhance cell proliferation. In addition, Flt-1 expression was significantly increased in the neointima and adventitia in injured rat carotid arteries. We concluded that functional expression of Flt-1 in adventitial fibroblasts might be an important mediator in the pathogenesis of vascular remodeling after arterial injury.