Jackson Edwin K, Gillespie Delbert G, Mi Zaichuan, Cheng Dongmei, Bansal Rashmi, Janesko-Feldman Keri, Kochanek Patrick M
Department of Pharmacology and Chemical Biology, University of Pittsburgh, Pittsburgh, Pennsylvania;
Department of Neuroscience, University of Connecticut School of Medicine, Farmington, Connecticut;
Am J Physiol Renal Physiol. 2014 Jul 1;307(1):F14-24. doi: 10.1152/ajprenal.00134.2014. Epub 2014 May 7.
Energy depletion increases the renal production of 2',3'-cAMP (a positional isomer of 3',5'-cAMP that opens mitochondrial permeability transition pores) and 2',3'-cAMP is converted to 2'-AMP and 3'-AMP, which in turn are metabolized to adenosine. Because the enzymes involved in this "2',3'-cAMP-adenosine pathway" are unknown, we examined whether 2',3'-cyclic nucleotide 3'-phosphodiesterase (CNPase) participates in the renal metabolism of 2',3'-cAMP. Western blotting and real-time PCR demonstrated expression of CNPase in rat glomerular mesangial, preglomerular vascular smooth muscle and endothelial, proximal tubular, thick ascending limb and collecting duct cells. Real-time PCR established the expression of CNPase in human glomerular mesangial, proximal tubular and vascular smooth muscle cells; and the level of expression of CNPase was greater than that for phosphodiesterase 4 (major enzyme for the metabolism of 3',5'-cAMP). Overexpression of CNPase in rat preglomerular vascular smooth muscle cells increased the metabolism of exogenous 2',3'-cAMP to 2'-AMP. Infusions of 2',3'-cAMP into isolated CNPase wild-type (+/+) kidneys increased renal venous 2'-AMP, and this response was diminished by 63% in CNPase knockout (-/-) kidneys, whereas the conversion of 3',5'-cAMP to 5'-AMP was similar in CNPase +/+ vs. -/- kidneys. In CNPase +/+ kidneys, energy depletion (metabolic poisons) increased kidney tissue levels of adenosine and its metabolites (inosine, hypoxanthine, xanthine, and uric acid) without accumulation of 2',3'-cAMP. In contrast, in CNPase -/- kidneys, energy depletion increased kidney tissue levels of 2',3'-cAMP and abolished the increase in adenosine and its metabolites. In conclusion, kidneys express CNPase, and renal CNPase mediates in part the renal 2',3'-cAMP-adenosine pathway.
能量耗竭会增加肾脏中2',3'-环磷酸腺苷（3',5'-环磷酸腺苷的一种位置异构体，可打开线粒体通透性转换孔）的生成，且2',3'-环磷酸腺苷会转化为2'-单磷酸腺苷和3'-单磷酸腺苷，进而代谢为腺苷。由于参与此“2',3'-环磷酸腺苷-腺苷途径”的酶尚不清楚，我们研究了2',3'-环核苷酸3'-磷酸二酯酶（CNPase）是否参与2',3'-环磷酸腺苷的肾脏代谢。蛋白质免疫印迹法和实时定量聚合酶链反应证明CNPase在大鼠肾小球系膜细胞、球前血管平滑肌细胞、内皮细胞、近端肾小管细胞、髓袢升支粗段细胞和集合管细胞中均有表达。实时定量聚合酶链反应确定了CNPase在人肾小球系膜细胞、近端肾小管细胞和血管平滑肌细胞中的表达；且CNPase的表达水平高于磷酸二酯酶4（3',5'-环磷酸腺苷代谢的主要酶）。在大鼠球前血管平滑肌细胞中过表达CNPase可增加外源性2',3'-环磷酸腺苷向2'-单磷酸腺苷的代谢。向分离的CNPase野生型（+/+）肾脏中输注2',3'-环磷酸腺苷会增加肾静脉中的2'-单磷酸腺苷，而在CNPase基因敲除（-/-）的肾脏中这种反应减少了63%，而在CNPase +/+和 -/-肾脏中3',5'-环磷酸腺苷向5'-单磷酸腺苷的转化相似。在CNPase +/+肾脏中，能量耗竭（代谢毒物）会增加肾脏组织中腺苷及其代谢产物（肌苷、次黄嘌呤、黄嘌呤和尿酸）的水平，而不会积累2',3'-环磷酸腺苷。相反，在CNPase -/-肾脏中，能量耗竭会增加肾脏组织中2',3'-环磷酸腺苷的水平，并消除腺苷及其代谢产物的增加。总之，肾脏表达CNPase，且肾脏中的CNPase部分介导了肾脏的2',3'-环磷酸腺苷-腺苷途径。
