Hypoxia upregulates glucose transport activity through an adenosine-mediated increase of GLUT1 expression in retinal capillary endothelial cells.
Hypoxia upregulates glucose transport activity through an adenosine-mediated increase of GLUT1 expression in retinal capillary endothelial cells.
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DOI：
10.2337/diabetes.47.9.1480
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发表时间：
1998-09
期刊：
影响因子：
7.7
通讯作者：
H. Takagi;G. King;L. P. Aiello
中科院分区：
文献类型：
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作者：
H. Takagi;G. King;L. P. Aiello
视网膜血管细胞内葡萄糖的升高被认为是糖尿病视网膜病变发生的重要原因。细胞内葡萄糖浓度既受葡萄糖代谢速率的调节，又受葡萄糖转运速率的调节。由于视网膜低氧常先于增殖性糖尿病视网膜病变，我们研究了低氧对培养的牛视网膜内皮细胞(BRECs)葡萄糖转运系统的调节。由于已知视网膜缺血会增加细胞内腺苷水平，从而调节缺氧诱导基因，如血管内皮生长因子和促红细胞生成素，因此腺苷及其受体介导的通路的作用也得到了评估。低氧(0.5%O2、5%CO2和94.5%N_2)以时间依赖的方式刺激BREC GLUT1 mRNA的表达，12 h后Glut1的表达增加8.9+/-1.5倍(P<；0.01)，12 h内Glut1的表达恢复到基础水平(1.4+/-0.3倍)。N6-环戊基腺苷(腺苷A1受体激动剂，Kd=1nmol/L)对GLUT1mRNA的表达无影响，而2-p-(2-carboxyethyl)-phenethyl-amino-5‘-N-ethylcarboxamidoadenosine和5’-(N-乙基钙酰胺)-腺苷(腺苷A2受体激动剂，Kd值分别为15和16nmol/L)在低浓度时使GLUT1mRNA表达增加，最大刺激倍数分别为2.3/-0.2倍和2.1+/-0.2倍(P<；0.01)。腺苷A2a受体拮抗剂8-(3-氯苯乙烯)咖啡因(对A2R的Kd=100nmol/L)在100nmo/L时抑制低氧刺激的GLUT1mRNA表达40+/-8%，缺氧12h后GLUT1蛋白表达上调3.0+/-0.3倍(P<；0.01)，但这种反应可被CSC减弱(P<；0.05)。缺氧12h后葡萄糖转运活性增加2.1/-0.3倍(P<；0.001)，CsC抑制65%(P<；0.01)。蛋白激酶A抑制剂(H89，20微克/L)可抑制低氧诱导的GLUT1mRNA表达42+/-9%(P<；0.01)。这些数据表明，BREC中的低氧通过增加GLUT1的表达来上调葡萄糖的转运活性，而GLUT1的表达部分由腺苷、A2R和cAMP-PKA途径介导。
Elevation of intracellular glucose within retinal vascular cells is believed to be an important causal factor in the development of diabetic retinopathy. The intracellular glucose concentration is regulated by both the rate of glucose metabolism and glucose transport. Because retinal hypoxia often precedes proliferative diabetic retinopathy, we have studied the regulation of the glucose transport system by hypoxia in cultured bovine retinal endothelial cells (BRECs). Because retinal ischemia is known to increase intracellular adenosine levels, which subsequently regulate hypoxia-inducible genes, such as vascular endothelial growth factor and erythropoietin, the role of adenosine and its receptor-mediated pathways has also been evaluated. Hypoxia (0.5% O2, 5% CO2, and 94.5% N2) stimulated GLUT1 mRNA expression in BRECs in a time-dependent manner with an 8.9 +/- 1.5-fold (P < 0.01) increase observed after 12 h. GLUT1 mRNA expression returned to baseline (1.4 +/- 0.3-fold of control) within 12 h after reinstitution of normoxia. N6-Cyclopentyl adenosine (adenosine A1 receptor agonist, Kd = 1 nmol/l) did not affect GLUT1 mRNA expression at concentrations up to 1 micromol/l, while 2-p-(2-carboxyethyl)-phenethyl-amino-5'-N-ethylcarboxamidoadenosine and 5'-(N-ethylcalboxamido)-adenosine (adenosine A2 receptor [A2R] agonists, Kd = 15 and 16 nmol/l, respectively) increased mRNA levels at concentrations as low as 10 nmol/l. Maximal stimulation was 2.3 +/- 0.2- and 2.1 +/- 0.2-fold, respectively (P < 0.01). The adenosine A2a receptor antagonist 8-(3-chlorostyryl)caffeine (CSC) (Kd = 100 nmol/l for A2R) inhibited hypoxia-stimulated GLUT1 mRNA expression by 40 +/- 8% at 100 nmo/l. Hypoxia upregulated GLUT1 protein expression by 3.0 +/- 0.3-fold after 12 h (P < 0.01), but this response was attenuated by CSC (P < 0.05). Hypoxia increased glucose transport activity by 2.1 +/- 0.3-fold (P < 0.001) after 12 h, a response inhibited 65% by CSC (P < 0.01). A protein kinase A (PKA) inhibitor (H89, 20 micromol/l) suppressed hypoxia-induced GLUT1 mRNA expression by 42 +/- 9% (P < 0.01). These data suggest that hypoxia in BRECs upregulates glucose transport activity through an increase of GLUT1 expression that is partially mediated by adenosine, A2R, and the cAMP-PKA pathway.