腺苷A1受体敲除小鼠戊四氮点燃后脑组织病理形态学变化

目的:通过观察腺苷A1受体敲除小鼠戊四氮点燃后脑组织病理形态学变化,探讨腺苷A1受体的神经保护作用。方法:腺苷A1受体基因敲除纯合型(-/-)小鼠20只纳入敲除鼠组,腺苷A1受体基因敲除野生型小鼠20只纳入野生型组,C57BL/6小鼠10只纳入对照组。敲除鼠组和野生型组小鼠制作戊四氮点燃癫痫模型,于点燃成功后24 h、30 d采用尼氏染色观察各组小鼠海马及皮质神经元的形态结构变化。结果:野生型组小鼠点燃后皮质和海马神经元损伤较敲除鼠组出现晚、范围小,损伤程度轻。结论:腺苷A1受体对癫痫发作小鼠具有神经保护作用。     

腺苷A2A受体敲除小鼠的福尔马林反应减弱同时脊髓NMDA受体结合能力也下降

腺苷是痛觉通路中疼痛反应的调节因子之一。在四种腺苷受体(A1、A2A、A2B、A3)中,腺苷作用于A2A受体被认为有致痛作用,这种作用被认为是刺激了感觉神经末梢的腺苷酸环化酶增加了cAMP水平所致。而腺苷A2A受体缺失的小鼠对热伤害性刺激的反应明显减弱。另外有报道A2A受体的选择性     

腺苷A2A受体基因敲除小鼠瘢痕胶原亚型的变化

背景：作者前期研究发现腺苷受体激动剂可以刺激胶原合成,腺苷受体拮抗剂可以抑制胶原合成,并且可以减轻皮肤胶原纤维增生。腺苷A2A受体基因敲除小鼠瘢痕转化生长因子β表达降低。目的：利用苦味酸-天狼星红偏振光法观察腺苷A2A受体基因敲除小鼠瘢痕胶原亚型的变化并探讨其机制。方法：腺苷A2A受体基因敲除小鼠和野生型小鼠制作瘢痕模型,采用苦味酸-天狼星红偏振光法对瘢痕组织中胶原的性质及分布特点进行观察、确定瘢痕组织胶原类型、分布、排列与水平。结果与结论：偏振光显微镜下可见野生型组小鼠增生性瘢痕组织中含有大量的嗜酸性胶原蛋白纤维束,Ⅰ型胶原纤维为红色,呈致密的条束状,显示很强的双折光性,腺苷A2A受体基因敲除小鼠瘢痕缺乏粗大胶原束,呈稀疏的条束状,排列相对整齐、密度较为均匀,Ⅰ型胶原纤维水平减少（P〈0.01）,瘢痕增生显著减轻。提示腺苷A2A受体参与瘢痕增生,对预防瘢痕增生有积极意义。     

腺苷A2A受体基因敲除小鼠瘢痕胶原亚型的变化

背景:作者前期研究发现腺苷受体激动剂可以刺激胶原合成,腺苷受体拮抗剂可以抑制胶原合成,并且可以减轻皮肤胶原纤维增生.腺苷A2A 受体基因敲除小鼠瘢痕转化生长因子β表达降低.目的:利用苦味酸-天狼星红偏振光法观察腺苷A2A 受体基因敲除小鼠瘢痕胶原亚型的变化并探讨其机制.方法:腺苷A2A受体基因敲除小鼠和野生型小鼠制作瘢痕模型,采用苦味酸-天狼星红偏振光法对瘢痕组织中胶原的性质及分布特点进行观察、确定瘢痕组织胶原类型、分布、排列与水平.结果与结论:偏振光显微镜下可见野生型组小鼠增生性瘢痕组织中含有大量的嗜酸性胶原蛋白纤维束,Ⅰ型胶原纤维为红色,呈致密的条束状,显示很强的双折光性,腺苷A2A 受体基因敲除小鼠瘢痕缺乏粗大胶原束,呈稀疏的条束状,排列相对整齐、密度较为均匀,Ⅰ型胶原纤维水平减少(P < 0.01),瘢痕增生显著减轻.提示腺苷A2A 受体参与瘢痕增生,对预防瘢痕增生有积极意义.     

Ly49A转基因小鼠脾细胞对半相合异基因骨髓移植后GVHD和GVL的作用

目的　观察Ly4 9A基因转染的C5 7BL 6小鼠脾细胞对半相合异基因骨髓移植 (allo BMT)后移植物抗宿主病 (GVHD)和移植物抗白血病效应 (GVL)的影响。方法　经由逆转录病毒介导将Ly4 9A基因转染至C5 7BL 6小鼠的脾细胞 ;流式细胞仪检测Ly4 9A受体在转染后脾细胞上的表达率 ;以亲代C5 7BL 6H 2 b 小鼠为供者 ,以接种EL96 11红白血病细胞的 (BALB c×C5 7BL 6 )F1H 2 d b(CB6F1)小鼠为受者 ,预处理条件为全身照射 (TBI,6 0 Co照射 10 .5Gy) ,进行脾细胞混合骨髓细胞移植 ,建立半相合异基因急性GVHD模型并在该模型基础上观察Ly4 9A基因转染的脾细胞对GVHD和GVL的作用。结果　Ly4 9A基因转染的C5 7BL 6小鼠的脾细胞 2 4h后蛋白表达率为 (42 .2 0± 4 .87) % ,空载体转染组为(18.6 7± 2 4 8) % ,未转染对照组为 (18.73± 3.82 ) % ,在半相合异基因移植中 (C5 7BL 6 H 2b →CB6F1H 2d b) ,未进行移植的单纯照射组生存期为 (7.80± 3.36 )d ;环磷酰胺治疗组生存期为 (2 1.70±2 87)d ;脾细胞混合骨髓细胞移植组生存期为 (2 9.4 0± 6 .4 3)d ;空载体转染的脾细胞混合骨髓细胞移植组生存期为 (2 9.10± 7.39)d ;Ly4 9A转染的脾细胞混合骨髓细胞移植组生存期为 (45 .0 0± 12 .38)d ,较上述各组生存期明显延长 (P     

同基因造血干细胞移植免疫重建诱导小鼠皮肤移植耐受

背景：器官移植耐受的最佳效果是能够诱导对移植抗原的特异性免疫耐受。目的：探讨小鼠异基因皮肤移植后,通过受体同基因造血干细胞移植重建免疫系统诱导移植皮肤免疫耐受的可行性。方法：取BALB/c小鼠骨髓。以C57BL/6小鼠为供体,BALB/c小鼠为受体,进行异基因皮肤移植;32只受体鼠随机均分为4组：移植对照组、环孢素A组、照射组和骨髓移植组。结果与结论：照射组小鼠10d内全部死亡,外周血白细胞数呈持续性降低;而骨髓移植组小鼠长期存活,白细胞数全身照射后6d降到最低,之后持续性增高,照射后21d与环孢素A组比较差异无显著性意义（P〉0.05）,移植皮肤存活时间显著长于其他各组（P〈0.01）,其淋巴细胞浸润及组织结构破坏明显减少,小鼠脾细胞对供体小鼠脾细胞增殖反应显著降低。说明同基因骨髓细胞移植重建免疫系统可显著延长小鼠移植皮肤存活时间,可诱导供者特异性免疫耐受。     

小鼠异基因骨髓移植γ线清髓性照射对骨髓内皮龛的损伤研究

本研究探索异基因骨髓移植清髓性γ线照射预处理对受鼠骨髓内皮的损伤程度。体外培养小鼠骨髓单个核细胞,经5-7天检测其表面标记、吞噬Dil-Ac-LDL和结合FITC-UEA-1鉴定,并行CFSE标记。分析正常组、清髓性照射组、内皮祖细胞（endothelial progenitor cells,EPC）移植组及照射联合EPC移植组小鼠外周血中白细胞变化、骨髓内皮的改变及CFSE标记EPC的骨髓内分布。结果发现,培养细胞鉴定证实为CD31＋CD133＋CD45low/-,且具有吞噬Dil-Ac-LDL和结合FITC-UEA-1能力。小鼠清髓照射后外周血白细胞迅速减少,与正常组相比,有显著差异（p〈0.05）。照射后3天,骨髓中大量出血,内皮细胞和基底膜间连接被损坏。清髓照射后输注CFSE标记EPC,18小时后小鼠骨髓中可见CFSE＋细胞,其细胞量是正常小鼠单纯EPC输注组的58倍（p〈0.05）。结论：移植清髓照射预处理引起严重骨髓内皮龛损伤,该损伤驱动外源性EPC的归巢。     

敲除腺苷A2A受体基因对慢性低O2高CO2模型小鼠前额叶皮质细胞凋亡及磷酸化p38MAPK蛋白的影响

目的 观察敲除腺苷A2A受体基因对慢性低O2高CO2模型小鼠前额叶皮质细胞凋亡以及磷酸化p38丝裂原活性蛋白激酶（p-p38MAPK）蛋白表达的影响。 方法 采用随机数字表法将16只腺苷A2A受体野生型（+/+）小鼠和16只腺苷A2A受体基因敲除型（-/-）小鼠各分为2个亚组,分别是对照-野生基因组、4周低O2高CO2-野生基因组（简称模型-野生基因组）、对照-基因敲除组、4周低O2高CO2-基因敲除组（简称模型-基因敲除组）,每组各8只小鼠。将模型-野生基因组、模型-基因敲除组小鼠置于常压低O2高CO2动物舱内,舱内O2浓度维持在9%~11%水平,CO2浓度维持在5.5%~6.5%水平,每天干预8 h,每周干预6 d,持续干预4周。于4周制模结束后采用原位末端标记法(TUNEL)检测各组小鼠前额叶皮质细胞凋亡情况,采用蛋白免疫印迹法检测各组小鼠前额叶皮质磷酸化p38MAPK蛋白表达水平。 结果 两模型亚组前额叶皮质凋亡细胞数量均较相应的对照亚组明显增加(P<0.05),并且模型-野生基因组皮质凋亡情况较模型-基因敲除组更显著(P<0.05);两模型亚组前额叶皮质p-p38MAPK蛋白表达均较相应的对照亚组明显上调(P<0.05),并且模型-野生基因组p-p38MAPK蛋白表达上调幅度较模型-基因敲除组更显著(P<0.05)。 结论 敲除腺苷A2A受体基因能抑制慢性低O2高CO2模型小鼠前额叶皮质p38MAPK信号转导通路活化,减少前额叶皮质神经细胞凋亡,为改善慢性阻塞性肺疾病（COPD）患者认知功能提供更多实验依据。     

腺苷A1受体基因敲除小鼠致痫后海马神经细胞线粒体功能损伤的研究

目的:观察腺苷A1受体基因敲除小鼠戊四氮致痫后海马神经细胞线粒体功能的损伤。方法:腺苷A1受体基因敲除小鼠和野生型小鼠各30只,各随机分为对照组、致痫后6h、24h、7d、30d组,每组6只;戊四氮点燃制作癫痫模型;于各时间点取小鼠海马,流式细胞仪测线粒体膜电位,免疫荧光测细胞色素C(cyt C)的表达。结果:基因敲除小鼠和野生型小鼠致痫后6h、24h、7d及30d组的线粒体膜电位均低于对照组(P<0.05),cyt C释放量均高于对照组(P<0.05);除对照组外,基因敲除小鼠致痫后6h、24h、7d及30d组的线粒体膜电位均低于野生型小鼠(P<0.05),cyt C释放量均高于野生型小鼠(P<0.05)。结论:癫痫早期即可出现海马线粒体功能损伤,腺苷A1受体有助于减轻癫痫小鼠海马线粒体损伤。     

混合骨髓移植后过继免疫治疗小鼠白血病

背景：急性白血病自体造血干细胞移植后复发率高,异基因造血干细胞移植后移植相关病死率高,混合造血干细胞移植及移植后过继免疫治疗有可能取长补短,提高疗效。目的：观察自体骨髓混合H-2半相合异体骨髓移植后供体淋巴细胞输注＋白细胞介素2治疗对小鼠白血病的疗效。方法：将Balb/c小鼠经直线加速器照射3Gy后分为白血病模型组、白血病模型照射组、混合移植组、自体骨髓移植组,均尾静脉注射5×10^5K562（GFP＋/NeoR＋）或K562（GFP-/NeoR-）细胞。7d后6Gy照射,自体骨髓移植组移植自体骨髓细胞或联合白细胞介素2治疗;混合移植组移植小鼠自体骨髓细胞混合1/10的H-2半相合异体骨髓细胞后应用白细胞介素2或联合供体淋巴细胞输注治疗。4周后行小鼠外周血及骨髓细胞形态检查,外周血细胞亚群、GFP及NeoR基因测定,肝、脾匀浆细胞GFP和NeoR基因测定。结果与结论：白血病模型组小鼠因骨髓造血功能衰竭于20d内全部死亡,白血病模型照射组小鼠因造血功能衰竭于14d内全部死亡;自体骨髓移植组、混合移植组均有多少不等小鼠无白血病存活超过28d,且混合骨髓移植后及自体骨髓移植后应用白细胞介素2治疗可提高白血病小鼠长期无病生存率,在此基础上联合供体淋巴细胞输注可更进一步提高白血病小鼠长期无病生存率。     

Renal protection from ischemia mediated by A2A adenosine receptors on bone marrow-derived cells

Activation of A2A adenosine receptors (A2ARs) protects kidneys from ischemia-reperfusion injury (IRI). A2ARs are expressed on bone marrow-derived (BM-derived) cells and renal smooth muscle, epithelial, and endothelial cells. To measure the contribution of A2ARs on BM-derived cells in suppressing renal IRI, we examined the effects of a selective agonist of A2ARs, ATL146e, in chimeric mice in which BM was ablated by lethal radiation and reconstituted with donor BM cells derived from GFP, A2AR-KO, or WT mice to produce GFP-->WT, A2A-KO-->WT, or WT-->WT mouse chimera. We found little or no repopulation of renal vascular endothelial cells by donor BM with or without renal IRI. ATL146e had no effect on IRI in A2A-KO mice or A2A-KO-->WT chimera, but reduced the rise in plasma creatinine from IRI by 75% in WT mice and by 60% in WT-->WT chimera. ATL146e reduced the induction of IL-6, IL-1beta, IL-1ra, and TGF-alpha mRNA in WT-->WT mice but not in A2A-KO-->WT mice. Plasma creatinine was significantly greater in A2A-KO than in WT mice after IRI, suggesting some renal protection by endogenous adenosine. We conclude that protection from renal IRI by A2AR agonists or endogenous adenosine requires activation of receptors expressed on BM-derived cells.     

Adenosine inhibits tumor necrosis factor-alpha release from mouse peritoneal macrophages via A2A and A2B but not the A3 adenosine receptor

Adenosine is elaborated in injured tissues where it suppresses inflammatory responses of essentially all immune cells, including production of proinflammatory cytokines such as tumor necrosis factor-alpha (TNF-alpha). Most of the anti-inflammatory actions of adenosine have been attributed to signaling through the A(2A) adenosine receptor (A(2A)AR). Previously, however, it has been shown that the A(3)AR agonist N(6)-(3-iodobenzyl)adenosine-5'-N-methylcarboxamide (IB-MECA) potently inhibited TNF-alpha release from macrophages obtained from A(2A)AR "knockout" (A(2A)KO) mice, suggesting that the A(3)AR may also regulate cytokine expression. Here, we confirmed that the A(2A)AR is the primary AR subtype that suppresses TNF-alpha release from thioglycollate-elicited mouse peritoneal macrophages induced by both Toll-like receptor-dependent (TLR) and TLR-independent stimuli, but we determined that the A(2B)AR rather than the A(3)AR mediates the non-A(2A)AR actions of adenosine since 1) the ability of IB-MECA to inhibit TNF-alpha release was not altered in macrophages isolated from A(3)KO mice, and 2) the A(2B)AR antagonist 1,3-dipropyl-8-[4-[((4-cyanophenyl)carbamoylmethyl)oxy]phenyl]xanthine (MRS 1754) blocked the ability of the nonselective AR agonist adenosine-5'-N-ethylcarboxamide (NECA) to inhibit TNF-alpha release from macrophages isolated from A(2A)KO mice. Although A(2B)ARs seem capable of inhibiting TNF-alpha release, the A(2A)AR plays a dominant suppressive role since MRS 1754 did not block the ability of NECA to inhibit TNF-alpha release from macrophages isolated from wild-type (WT) mice. Furthermore, the potency and efficacy of adenosine to inhibit TNF-alpha release from WT macrophages were not influenced by blocking A(2B)ARs with MRS 1754. The data indicate that adenosine suppresses TNF-alpha release from macrophages primarily via A(2A)ARs, although the A(2B)AR seems to play an underlying inhibitory role that may contribute to the anti-inflammatory actions of adenosine under select circumstances.     

Adenosine negative feedback on A2A adenosine receptors mediates hyporesponsiveness in chronically septic mice

Strategies are needed to reverse the immune cell hyporesponsiveness and prevent bacterial overgrowth associated with high mortality rates in septic patients. Adenosine signaling may be mediating immunosuppressive signals within the inflammatory microenvironment that are safeguarding bacteria by rendering immune cells hyporesponsive. We examined A2A adenosine receptor (A2AR)-mediated immune responses in a chronic model of cecal ligation and puncture (CLP)-induced sepsis using both wild-type (WT) and A2AR knockout (KO) mice. In this model, chronic bacterial peritonitis was established that results in the first death on day 4. A2A adenosine receptors promoted bacterial overgrowth that was associated with a high 28-day sepsis mortality (WT 87% vs. A2AR KO 13%; P < 0.0001). Chronic bacteremia persisted in both WT and A2AR KO mice over the 28-day study period. Bacteremia was significantly decreased in A2AR KO mice 2 days after antibiotic therapy cessation (day 6 after CLP; P < 0.005). Local and disseminated bacteria levels were compared at the end of the 28-day study period or from moribund mice. A2A adenosine receptor deficiency dramatically decreased peritoneal (P < 0.05), splenic (P < 0.05), and blood (P < 0.01) bacterial levels. A2A adenosine receptor deficiency caused an early reduction in inflammatory mediators IL-6, macrophage inflammatory protein 2, TNF-srI, and TNF-srII (P < 0.05), but not in TNF-α, IL-1β, IL-10, or monocyte chemotactic protein 1 within 24 h after CLP. In response to an intravenous lipopolysaccharide (day 5 after CLP) challenge, A2AR KO mice showed enhanced secretion of TNF-α (2 h), IFN-γ, IL-6, monocyte chemotactic protein 1, IL-10, and macrophage inflammatory protein 2 (9 h) (P < 0.05), suggesting that A2ARs attenuate inflammatory responses to repeat infectious insults. These data demonstrate that A2AR blockade may be an effective immunotherapy treatment to prevent bacterial overgrowth and reduce mortality secondary to immunosuppression in septic patients.     

Adenosine A2A receptor activation reduces hepatic ischemia reperfusion injury by inhibiting CD1d-dependent NKT cell activation

Ischemia reperfusion injury results from tissue damage during ischemia and ongoing inflammation and injury during reperfusion. Liver reperfusion injury is reduced by lymphocyte depletion or activation of adenosine A2A receptors (A2ARs) with the selective agonist 4-{3-[6-amino-9-(5-ethylcarbamoyl-3,4-dihydroxy-tetrahydro-furan-2-yl)-9H-purin-2-yl]- prop-2-ynyl}-cyclohexanecarboxylic acid methyl ester (ATL146e). We show that NKT cells are stimulated to produce interferon (IFN)-gamma by 2 h after the initiation of reperfusion, and the use of antibodies to deplete NK1.1-positive cells (NK and NKT) or to block CD1d-mediated glycolipid presentation to NKT cells replicates, but is not additive to, the protection afforded by ATL146e, as assessed by serum alanine aminotransferase elevation, histological necrosis, neutrophil accumulation, and serum IFN-gamma elevation. Reduced reperfusion injury observed in RAG-1 knockout (KO) mice is restored to the wild-type (WT) level by adoptive transfer of NKT cells purified from WT or A2AR KO mice but not IFN-gamma KO mice. Additionally, animals with transferred A2AR-/- NKT cells are not protected from hepatic reperfusion injury by ATL146e. In vitro, ATL146e potently inhibits both anti-CD3 and alpha-galactosylceramide-triggered production of IFN-gamma by NKT cells. These findings suggest that hepatic reperfusion injury is initiated by the CD1d-dependent activation of NKT cells, and the activation of these cells is inhibited by A2AR activation.     

The A3 adenosine receptor agonist CP-532,903 [N6-(2,5-dichlorobenzyl)-3'-aminoadenosine-5'-N-methylcarboxamide] protects against myocardial ischemia/reperfusion injury via the sarcolemmal ATP-sensitive potassium channel

We examined the cardioprotective profile of the new A(3) adenosine receptor (AR) agonist CP-532,903 [N(6)-(2,5-dichlorobenzyl)-3'-aminoadenosine-5'-N-methylcarboxamide] in an in vivo mouse model of infarction and an isolated heart model of global ischemia/reperfusion injury. In radioligand binding and cAMP accumulation assays using human embryonic kidney 293 cells expressing recombinant mouse ARs, CP-532,903 was found to bind with high affinity to mouse A(3)ARs (K(i) = 9.0 +/- 2.5 nM) and with high selectivity versus mouse A(1)AR (100-fold) and A(2A)ARs (1000-fold). In in vivo ischemia/reperfusion experiments, pretreating mice with 30 or 100 microg/kg CP-532,903 reduced infarct size from 59.2 +/- 2.1% of the risk region in vehicle-treated mice to 42.5 +/- 2.3 and 39.0 +/- 2.9%, respectively. Likewise, treating isolated mouse hearts with CP-532,903 (10, 30, or 100 nM) concentration dependently improved recovery of contractile function after 20 min of global ischemia and 45 min of reperfusion, including developed pressure and maximal rate of contraction/relaxation. In both models of ischemia/reperfusion injury, CP-532,903 provided no benefit in studies using mice with genetic disruption of the A(3)AR gene, A(3) knockout (KO) mice. In isolated heart studies, protection provided by CP-532,903 and ischemic preconditioning induced by three brief ischemia/reperfusion cycles were lost in Kir6.2 KO mice lacking expression of the pore-forming subunit of the sarcolemmal ATP-sensitive potassium (K(ATP)) channel. Whole-cell patch-clamp recordings provided evidence that the A(3)AR is functionally coupled to the sarcolemmal K(ATP) channel in murine cardiomyocytes. We conclude that CP-532,903 is a highly selective agonist of the mouse A(3)AR that protects against ischemia/reperfusion injury by activating sarcolemmal K(ATP) channels.     

Rapid stimulation of presynaptic serotonin transport by A(3) adenosine receptors

The inactivation of synaptic serotonin (5-hydroxytryptamine, 5-HT) is largely established through the actions of the presynaptic, antidepressant-sensitive 5-HT transporter (SERT, SLC6A4). Recent studies have demonstrated post-translational regulation of SERT mediated by multiple Ser/Thr kinases, including protein kinases C and G (PKC and PKG) and p38 mitogen-activated protein kinase (MAPK), as well as the Ser/Thr phosphatase PP2A. Less well studied are specific surface receptors that target these signaling pathways to control SERT surface expression and/or catalytic rates. Using rat basophilic leukemia 2H3 cell line (RBL-2H3), we previously established that activation of A(3) adenosine receptors (A(3)AR) stimulates SERT activity via both PKG and p38 MAPK (Zhu et al., 2004a). Whether A(3)ARs regulate SERT in the central nervous system (CNS) is unknown. Here we report that the A(3)AR agonist N(6)-(3-iodobenzyl)-N-methyl-5'carbamoyladenosine (IB-MECA) rapidly (10 min) and selectively stimulates 5-HT transport in mouse midbrain, hippocampal, and cortical synaptosomes. IB-MECA-induced stimulation of 5-HT uptake is blocked by the selective A(3)AR antagonist 3-ethyl-5-benzyl-2-methyl-phenylethynyl-6-phenyl-1,4(+/-)dihydropyridine-3,5-dicarboxylate (MRS1191) and is absent from synaptosomes prepared from A(3)AR knockout mice. Kinetic analyses demonstrate that IB-MECA induces an increase of 5-HT transport V(max) with no significant change in K(m). As in RBL-2H3 cells, IB-MECA stimulation of synaptosomal 5-HT uptake can be blocked by preincubation with PKG antagonists N-[2-(methylamino)ethy]-5-isoquinoline-sulfonamide (H8) and DT-2 (YGRKKRRQRRRPPLRK(5)H), as well as by the p38 MAPK inhibitor SB203580 [4-(4-fluorophenyl)-2-(4-methylsulfinylphenyl)-5-(4-pyridyl)-1H-imidazole]. Chronoamperometry studies in the anesthetized rat hippocampus support a role for A(3)ARs in SERT regulation in vivo. Together, these results identify a novel, region-specific action of CNS A(3)ARs in the modulation of SERT-mediated 5-HT transport that may be relevant for the etiology and/or therapy of 5-HT-linked brain disorders.     

Inosine binds to A3 adenosine receptors and stimulates mast cell degranulation.

We investigated the mechanism by which inosine, a metabolite of adenosine that accumulates to > 1 mM levels in ischemic tissues, triggers mast cell degranulation. Inosine was found to do the following: (a) compete for [125I]N6-aminobenzyladenosine binding to recombinant rat A3 adenosine receptors (A3AR) with an IC50 of 25+/-6 microM; (b) not bind to A1 or A2A ARs; (c) bind to newly identified A3ARs in guinea pig lung (IC50 = 15+/-4 microM); (d) lower cyclic AMP in HEK-293 cells expressing rat A3ARs (ED50 = 12+/-5 microM); (e) stimulate RBL-2H3 rat mast-like cell degranulation (ED50 = 2.3+/-0.9 microM); and (f) cause mast cell-dependent constriction of hamster cheek pouch arterioles that is attenuated by A3AR blockade. Inosine differs from adenosine in not activating A2AARs that dilate vascular smooth muscle and inhibit mast cell degranulation. The A3 selectivity of inosine may explain why it elicits a monophasic arteriolar constrictor response distinct from the multiphasic dilator/constrictor response to adenosine. Nucleoside accumulation and an increase in the ratio of inosine to adenosine may provide a physiologic stimulus for mast cell degranulation in ischemic or inflamed tissues.     

History and Perspectives of A2A Adenosine Receptor Antagonists as Potential Therapeutic Agents

Growing evidence emphasizes that the purine nucleoside adenosine plays an active role as a local regulator in different pathologies. Adenosine is a ubiquitous nucleoside involved in various physiological and pathological functions by stimulating A₁, A_2A, A_2B, and A₃ adenosine receptors (ARs). At the present time, the role of A_2AARs is well known in physiological conditions and in a variety of pathologies, including inflammatory tissue damage and neurodegenerative disorders. In particular, the use of selective A_2A antagonists has been reported to be potentially useful in the treatment of Parkinson's disease (PD). In this review, A_2AAR signal transduction pathways, together with an analysis of the structure–activity relationships of A_2A antagonists, and their corresponding pharmacological roles and therapeutic potential have been presented. The initial results from an emerging polypharmacological approach are also analyzed. This approach is based on the optimization of the affinity and/or functional activity of the examined compounds toward multiple targets, such as A₁/A_2AARs and monoamine oxidase‐B (MAO‐B), both closely implicated in the pathogenesis of PD.     

Adenosine A3 agonists reverse neuropathic pain via T cell–mediated production of IL-10

The A₃ adenosine receptor (A₃AR) has emerged as a therapeutic target with A₃AR agonists to tackle the global challenge of neuropathic pain, and investigation into its mode of action is essential for ongoing clinical development. Immune cell A₃ARs, and their activation during pathology, modulate cytokine release. Thus, the use of immune cells as a cellular substrate for the pharmacological action of A₃AR agonists is enticing, but unknown. The present study discovered that Rag-KO mice lacking T and B cells, as compared with WT mice, are insensitive to the anti-allodynic effects of A₃AR agonists. Similar findings were observed in interleukin-10 and interleukin-10 receptor knockout mice. Adoptive transfer of CD4⁺ T cells from WT mice infiltrated the dorsal root ganglion (DRG) and restored A₃AR agonist-mediated anti-allodynia in Rag-KO mice. CD4⁺ T cells from Adora3-KO or Il10-KO mice did not. Transfer of CD4⁺ T cells from WT mice, but not Il10-KO mice, into Il10-KO mice or Adora3-KO mice fully reinstated the anti-allodynic effects of A₃AR activation. Notably, A₃AR agonism reduced DRG neuron excitability when cocultured with CD4⁺ T cells in an IL-10–dependent manner. A₃AR action on CD4⁺ T cells infiltrated in the DRG decreased phosphorylation of GluN2B-containing N-methyl-D-aspartate receptors at Tyr1472, a modification associated with regulating neuronal hypersensitivity. Our findings establish that activation of A₃AR on CD4⁺ T cells to release IL-10 is required and sufficient evidence for the use of A₃AR agonists as therapeutics.     

Transcutaneous electrical nerve stimulation activates peripherally located alpha-2A adrenergic receptors

The alpha2A and alpha2C adrenergic receptor (AR) subtypes mediate antinociception when activated by the endogenous ligand norepinephrine. These receptors also produce antinociceptive synergy when activated concurrently with opioid receptor activation. The involvement of the opioid receptors in the mechanisms governing transcutaneous electrical nerve stimulation (TENS) has been well described. While spinal alpha-2 ARs do not appear to be involved in TENS antihyperalgesia in rats, the noradrenergic analgesic system also involves supraspinal and peripheral sites. Thus, a broader evaluation of the potential contribution of alpha-2 AR to TENS is warranted. The current study compared the antihyperalgesic efficacy of high (100 Hz) and low (4 Hz) frequency TENS in mutant mice lacking a functional alpha2A AR against their respective wildtype counterparts. The degree of secondary heat hyperalgesia induced by intra-articular injection of carrageenan/kaolin (3%) mixture did not differ among the experimental groups. However, the antihyperalgesia induced by both low and high frequency TENS was significantly diminished in alpha2A mutant mice compared to controls. The alpha2 adrenergic receptor selective antagonist, SK&F 86466, reversed TENS-mediated antihyperalgesia when delivered intra-articularly, but not when delivered intrathecally or intracerebroventricularly. These data suggest that peripheral alpha2 ARs contribute, in part, to TENS antihyperalgesia. This pharmacodynamic response is consistent with previous anatomical observations that alpha2A ARs are expressed on primary afferent neurons and macrophages near injured tissue.