Palmitate Stimulates the Epithelial Sodium Channel by Elevating Intracellular Calcium, Reactive Oxygen Species, and Phosphoinositide 3-Kinase Activity.
Palmitate Stimulates the Epithelial Sodium Channel by Elevating Intracellular Calcium, Reactive Oxygen Species, and Phosphoinositide 3-Kinase Activity.
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棕榈酸酯通过提高细胞内钙、活性氧和磷酸肌醇 3-激酶活性来刺激上皮钠通道。
DOI：
10.1155/2018/7560610
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发表时间：
2018
期刊：
影响因子：
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通讯作者：
Ma He-Ping
中科院分区：
文献类型：
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作者：
Wang Qiu-Shi;Liang Chen;Niu Na;Yang Xu;Chen Xiao;Song Bin-Lin;Yu Chang-Jiang;Wu Ming-Ming;Zhang Zhi-Ren;Ma He-Ping
先前的研究表明，肾脏中的上皮钠通道（ENaC）在糖尿病中上调。在这里，我们发现远端肾单位细胞中的ENaC单通道活性被棕榈酸盐显著增加，棕榈酸盐是一种游离脂肪酸，在糖尿病中升高。我们还表明，棕榈酸酯增加细胞内Ca 2+，并且在用BAPTA-AM螯合细胞内Ca 2+后，棕榈酸酯未能影响ENaC活性。用2-氨基乙氧基二苯基硼酸酯（2-APB，一种IP 3受体的抑制剂）处理细胞，可消除细胞内Ca 2+和ENaC活性的升高。用夹竹桃素（一种NADPH氧化酶抑制剂）、二硫苏糖醇/NaHS（还原剂）或LY 294002（一种磷酸肌醇3激酶（PI 3 K）抑制剂）处理细胞可阻止棕榈酸诱导的ENaC活性，而硫柳汞（一种氧化剂）模拟棕榈酸对ENaC活性的影响。然而，这些处理并没有改变细胞内Ca 2+的水平，表明活性氧（ROS）的升高和PI 3 K的激活是信号级联的下游。由于我们已经表明ROS通过激活PI 3 K刺激ENaC，这些数据共同表明棕榈酸酯首先升高细胞内Ca 2+，然后激活NADPH氧化酶以升高细胞内ROS和PI 3 K活性，最后通过激活的PI 3 K增加ENaC活性。
Previous studies indicate that the epithelial sodium channel (ENaC) in the kidney is upregulated in diabetes mellitus. Here, we show that ENaC single‐channel activity in distal nephron cells was significantly increased by palmitate, a free fatty acid which is elevated in diabetes mellitus. We also show that palmitate increased intracellular Ca2+and that after chelating intracellular Ca2+with BAPTA‐AM, palmitate failed to affect ENaC activity. Treatment of the cells with 2‐aminoethoxydiphenyl borate (2‐APB, an inhibitor of IP3receptors) abolished the elevation of both intracellular Ca2+and ENaC activity. Treatment of the cells with apocynin (an NADPH oxidase inhibitor), dithiothreitol/NaHS (reducing agents), or LY294002 (a phosphoinositide 3‐kinase (PI3K) inhibitor) prevented palmitate‐induced ENaC activity, whereas thimerosal (an oxidizing agent) mimicked the effects of palmitate on ENaC activity. However, these treatments did not alter the levels of intracellular Ca2+, indicating that elevation of reactive oxygen species (ROS) and activation of PI3K are downstream of the signaling cascade. Since we have shown that ROS stimulate ENaC by activating PI3K, these data together suggest that palmitate first elevates intracellular Ca2+, then activates an NADPH oxidase to elevate intracellular ROS and PI3K activity, and finally increases ENaC activity via the activated PI3K.