Department of Pharmacology, Fukushima Medical University, School of Medicine, Japan.
J Pharmacol Sci. 2012;118(2):186-97. doi: 10.1254/jphs.11128fp. Epub 2012 Feb 1.
When cardiac tissue is exposed to hypoxia, myocytes are damaged, while fibroblasts are activated. However, it is unknown what changes are induced by hypoxia in cardiac fibroblasts. In this study, using the whole cell patch-clamp technique, we investigated the effect of hypoxia on membrane currents in fibroblasts primarily cultured from adult rat hearts. Cardiac fibroblasts were incubated for 24 h under normoxic or hypoxic conditions using Anaeropack. Hypoxia increased a current which reversed at around -20 mV in the cardiac fibroblasts. This current was inhibited by clotrimazole, which is an inhibitor of transient receptor potential melastatin 2 (TRPM2) channel and intermediate-conductance Ca(2+)-activated K(+) channel (KCa3.1). ADP ribose in the pipette solution enhanced this current. Quantitative RT-PCR revealed that mRNA of TRPM2, but not that of KCa3.1, was increased by hypoxia. RNA interference of TRPM2 prevented the development of the hypoxia-induced current. H(2)O(2), an activator of TRPM2 channel, induced a higher Ca(2+) elevation in hypoxia-exposed cardiac fibroblasts than that in normoxia-exposed cells. We conclude that hypoxia induces TRPM2 channel expression in adult rat cardiac fibroblasts.
当心肌组织暴露于缺氧环境时，心肌细胞会受损，而成纤维细胞则被激活。然而，目前尚不清楚缺氧对心肌成纤维细胞会产生什么影响。在这项研究中，我们使用全细胞膜片钳技术，研究了缺氧对成年大鼠心脏原代培养的成纤维细胞膜电流的影响。使用 Anaeropack 将心肌成纤维细胞在常氧或缺氧条件下孵育 24 小时。缺氧可增加一种在心肌成纤维细胞中反转电位约为-20 mV 的电流。这种电流被氯硝柳胺（一种瞬时受体电位 melastatin 2（TRPM2）通道和中间电导钙激活钾（KCa3.1）通道的抑制剂）抑制。在玻璃微电极内液中加入 ADP 核糖可增强该电流。定量 RT-PCR 显示，TRPM2 的 mRNA 而非 KCa3.1 的 mRNA 被缺氧上调。TRPM2 的 RNA 干扰可阻止缺氧诱导电流的产生。TRPM2 通道的激活剂 H2O2 可诱导缺氧暴露的心肌成纤维细胞中 [Ca2+]i 的升高幅度高于常氧暴露的细胞。我们的结论是，缺氧可诱导成年大鼠心肌成纤维细胞中 TRPM2 通道的表达。
