Grenz Almut, Zhang Hua, Weingart Jochen, von Wietersheim Simone, Eckle Tobias, Schnermann Juergen, Köhle Christoph, Kloor Doris, Gleiter Christoph H, Vallon Volker, Eltzschig Holger K, Osswald Hartmut
Dept. of Pharmacology and Toxicology, Tübingen Univ. Hospital, Wilhelmstr. 56, D-72074 Tübingen, Germany.
Am J Physiol Renal Physiol. 2007 Nov;293(5):F1501-11. doi: 10.1152/ajprenal.00243.2007. Epub 2007 Sep 12.
Previous studies have yielded conflicting results as to whether extracellular adenosine generation and signaling contributes to hypoxia-induced increases in renal erythropoietin (EPO) secretion. In this study, we combined pharmacological and genetic approaches to elucidate a potential contribution of extracellular adenosine to renal EPO release in mice. To stimulate EPO secretion, we used murine carbon monoxide exposure (400 and 750 parts per million CO, 4 h), ambient hypoxia (8% oxygen, 4 h), or arterial hemodilution. Because the ecto-5-nucleotidase (CD73, conversion of AMP to adenosine) is considered the pacemaker of extracellular adenosine generation, we first tested the effect of blocking extracellular adenosine generation with the specific CD73-inhibitor adenosine 5'-(alpha,beta-methylene) diphosphate (APCP) or by gene-targeted deletion of cd73. These studies showed that neither APCP-treatment nor targeted deletion of cd73 resulted in changes of stimulated EPO mRNA or serum levels, although the increases of adenosine levels in the kidney following CO exposure were attenuated in mice with APCP treatment or in cd73(-/-) mice. Moreover, pharmacological studies using specific inhibitors of individual adenosine receptors (A1 AR, DPCPX; A 2A AR, DMPX; A 2B AR, PSB 1115; A3AR, MRS 1191) showed no effect on stimulated increases of EPO mRNA or serum levels. Finally, stimulated EPO secretion was not attenuated in gene-targeted mice lacking A1A(-/-, A2A AR-/-, A2BAR(-/-), or A3AR-/-. Together, these studies combine genetic and pharmacological in vivo evidence that increases of EPO secretion during limited oxygen availability are not affected by extracellular adenosine generation or signaling.
关于细胞外腺苷的生成及信号传导是否促成缺氧诱导的肾脏促红细胞生成素（EPO）分泌增加，以往的研究结果相互矛盾。在本研究中，我们结合药理学和遗传学方法，以阐明细胞外腺苷对小鼠肾脏EPO释放的潜在作用。为刺激EPO分泌，我们采用了小鼠一氧化碳暴露（400和750 ppm CO，4小时）、环境低氧（8%氧气，4小时）或动脉血液稀释。由于胞外5'-核苷酸酶（CD73，将AMP转化为腺苷）被认为是细胞外腺苷生成的起搏器，我们首先测试了用特异性CD73抑制剂5'-（α，β-亚甲基）二磷酸腺苷（APCP）阻断细胞外腺苷生成的效果，或通过基因靶向敲除cd73来进行测试。这些研究表明，无论是APCP处理还是cd73的靶向敲除，均未导致刺激后的EPO mRNA或血清水平发生变化，尽管在APCP处理的小鼠或cd73基因敲除（cd73(-/-)）小鼠中，一氧化碳暴露后肾脏中腺苷水平的升高有所减弱。此外，使用单个腺苷受体特异性抑制剂（A1 AR，DPCPX；A 2A AR，DMPX；A 2B AR，PSB 1115；A3AR，MRS 1191）的药理学研究表明，这些抑制剂对刺激后EPO mRNA或血清水平的升高没有影响。最后，在缺乏A1A（A1A(-/-)）、A2A AR（A2A AR-/-）、A2B AR（A2B AR(-/-)）或A3AR（A3AR-/-）的基因靶向小鼠中，刺激后的EPO分泌并未减弱。总之，这些研究结合了遗传学和药理学体内证据，表明在氧供应受限期间EPO分泌的增加不受细胞外腺苷生成或信号传导的影响。
