University of Ottawa Heart Institute, 40 Ruskin Street, Ottawa, ON, K1Y 4W7, Canada.
Department of Cellular and Molecular Medicine, University of Ottawa, 451 Smyth Rd, Ottawa, ON, K1H 8M5, Canada.
Pflugers Arch. 2019 Dec;471(11-12):1551-1564. doi: 10.1007/s00424-019-02325-9. Epub 2019 Nov 12.
Hydrogen sulfide (HS) is endogenously produced in pancreatic ß cells and its level is elevated in diabetes. Here, we report that HS affects insulin secretion via two mechanisms that converge on cytosolic free Ca ([Ca]), a key mediator of insulin exocytosis. Cellular calcium imaging, using Fura-2 or Fluo-4, showed that exposure of INS-1E cells to HS (30-100 μM) reduced both [Ca] levels (by 21.7 ± 2.3%) and oscillation frequency (p < 0.01, n = 4). Consistent with a role of plasma membrane K channels (plasma-K), the effects of HS on [Ca] were blocked by gliclazide (a blocker of plasma-K channels), but were mimicked by diazoxide (an activator of plasma-K channels). Surprisingly, when Ca entry via plasma membrane was inhibited using Ca-free external solutions, HS increased [Ca] by 39.7 ± 3.6% suggesting Ca release from intracellular stores. HS-induced [Ca] increases were abolished by either FCCP (which depletes Ca stored in mitochondria) or cyclosporine A (an inhibitor of mitochondrial permeability transition pore, mPTP) suggesting that HS induces Ca release from mitochondria. Measurement of mitochondrial membrane potential (MMP) suggested that HS causes MMP depolarization, which was blocked by cyclosporine A. Finally, insulin measurements by ELISA indicated that HS decreased insulin release from INS-1E cells, but after plasma membrane Ca entry was blocked by nifedipine, HS-induced mitochondrial Ca release is able to increase insulin release. Together, our results indicate that HS has dual effects on insulin release suggesting that, with different metabolic conditions, HS may differentially modulate the insulin release from pancreatic ß cells and play a role in ß cell dysfunction.
硫化氢 (HS) 在胰岛 β 细胞内源性产生，其水平在糖尿病中升高。在这里，我们报告 HS 通过两种机制影响胰岛素分泌，这两种机制都集中在细胞质游离 Ca([Ca]) 上，Ca 是胰岛素胞吐的关键介质。使用 Fura-2 或 Fluo-4 的细胞钙成像显示，暴露于 HS（30-100 μM）的 INS-1E 细胞降低了[Ca]水平（降低 21.7±2.3%，p<0.01，n=4）和振荡频率。与质膜 K 通道（plasma-K）的作用一致，HS 对[Ca]的作用被格列齐特（plasma-K 通道阻滞剂）阻断，但被二氮嗪（plasma-K 通道激活剂）模拟。令人惊讶的是，当使用无钙外部溶液抑制质膜 Ca 内流时，HS 使[Ca]增加 39.7±3.6%，表明 Ca 从细胞内储存库中释放。HS 诱导的[Ca]增加被 FCCP（耗尽储存在线粒体中的 Ca）或环孢素 A（线粒体通透性转换孔，mPTP 的抑制剂）完全阻断，表明 HS 诱导 Ca 从线粒体中释放。线粒体膜电位 (MMP) 的测量表明 HS 导致 MMP 去极化，环孢素 A 可阻断该去极化。最后，通过 ELISA 测量胰岛素表明，HS 减少 INS-1E 细胞的胰岛素释放，但在硝苯地平阻断质膜 Ca 内流后，HS 诱导的线粒体 Ca 释放能够增加胰岛素释放。总之，我们的结果表明 HS 对胰岛素释放有双重影响，表明在不同的代谢条件下，HS 可能以不同的方式调节胰岛 β 细胞的胰岛素释放并在 β 细胞功能障碍中发挥作用。
