Functional role of sodium glucose transporter in high glucose-mediated angiotensin type 1 receptor downregulation in human proximal tubule cells.
Functional role of sodium glucose transporter in high glucose-mediated angiotensin type 1 receptor downregulation in human proximal tubule cells.
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钠葡萄糖转运蛋白在人近曲小管细胞高葡萄糖介导的血管紧张素 1 型受体下调中的功能作用。
DOI：
10.1152/ajprenal.00651.2011
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发表时间：
2012
期刊：
影响因子：
--
通讯作者：
Thekkumkara,Thomas
中科院分区：
文献类型：
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作者：
Yesudas,Rekha;Snyder,Russell;Abbruscato,Thomas;Thekkumkara,Thomas
先前，我们已经证明了人血管紧张素1型受体（hAT 1 R）启动子结构对于人近端小管上皮细胞中高葡萄糖（25 mM）介导的转录抑制的作用（hPTEC;托马斯BE，Thekartkara TJ.Mol Biol Cell 15：4347-4355，2004）。在本研究中，我们研究了葡萄糖转运蛋白在高葡萄糖介导的hAT 1 R抑制原代hPTEC中的作用。将细胞暴露于正常葡萄糖（5.5 mM）和高葡萄糖（25 mM），然后测定高血糖介导的受体表达和葡萄糖转运蛋白活性的变化。高糖暴露48 h后，ANG Ⅱ结合率（4，034 ± 163.3）dpm/mg蛋白降至1，360 ± 154.3 dpm/mg蛋白，hAT 1 R mRNA表达下降（60.6 ± 4.643%）。在类似条件下，我们观察到暴露于高血糖的细胞中葡萄糖摄取（流入）显著增加。我们的数据表明，葡萄糖内流的大小是浓度和时间依赖性的。在血糖正常的细胞中，根皮苷抑制钠-葡萄糖协同转运蛋白（SGLTs）和根皮素促进葡萄糖转运蛋白（GLUTs）分别使葡萄糖内流减少28.57 ± 0.9123和54.33 ± 1.202%。然而，在高血糖条件下抑制细胞中的SGLT使葡萄糖内流减少53.67 ± 2.906%，而GLUT介导的葡萄糖摄取保持不变（57.67 ± 3.180%）。此外，用SGLT抑制剂预处理细胞逆转了高糖介导的hAT 1 R下调，表明SGLT参与了高糖介导的hAT 1 R抑制。我们的研究结果表明，在hPTEC中，高血糖诱导的hAT 1 R下调主要是通过SGLT依赖性葡萄糖内流介导的。由于ANG II是hPTEC跨细胞钠重吸收和功能的重要调节剂，葡萄糖介导的hAT 1 R基因表达的变化可能参与糖尿病肾病的发病机制。
Previously, we have demonstrated human angiotensin type 1 receptor (hAT1R) promoter architecture with regard to the effect of high glucose (25 mM)-mediated transcriptional repression in human proximal tubule epithelial cells (hPTEC; Thomas BE, Thekkumkara TJ.Mol Biol Cell15: 4347–4355, 2004). In the present study, we investigated the role of glucose transporters in high glucose-mediated hAT1R repression in primary hPTEC. Cells were exposed to normal glucose (5.5 mM) and high glucose (25 mM), followed by determination of hyperglycemia-mediated changes in receptor expression and glucose transporter activity. Exposure of cells to high glucose resulted in downregulation of ANG II binding (4,034 ± 163.3 to 1,360 ± 154.3 dpm/mg protein) and hAT1R mRNA expression (reduced 60.6 ± 4.643%) at 48 h. Under similar conditions, we observed a significant increase in glucose uptake (influx) in cells exposed to hyperglycemia. Our data indicated that the magnitude of glucose influx is concentration and time dependent. In euglycemic cells, inhibiting sodium-glucose cotransporters (SGLTs) with phlorizin and facilitative glucose transporters (GLUTs) with phloretin decreased glucose influx by 28.57 ± 0.9123 and 54.33 ± 1.202%, respectively. However, inhibiting SGLTs in cells under hyperglycemic conditions decreased glucose influx by 53.67 ± 2.906%, while GLUT-mediated glucose uptake remained unaltered (57.67 ± 3.180%). Furthermore, pretreating cells with an SGLT inhibitor reversed high glucose-mediated downregulation of the hAT1R, suggesting an involvement of SGLT in high glucose-mediated hAT1R repression. Our results suggest that in hPTEC, hyperglycemia-induced hAT1R downregulation is largely mediated through SGLT-dependent glucose influx. As ANG II is an important modulator of hPTEC transcellular sodium reabsorption and function, glucose-mediated changes in hAT1R gene expression may participate in the pathogenesis of diabetic renal disease.