Ishii Masakazu, Shimizu Shunichi, Hara Yuji, Hagiwara Tamio, Miyazaki Akira, Mori Yasuo, Kiuchi Yuji
Department of Pathophysiology, School of Pharmaceutical Sciences, Showa University, 1-5-8 Hatanodai, Shinagawa-ku, Tokyo 142-8555, Japan.
Cell Calcium. 2006 Jun;39(6):487-94. doi: 10.1016/j.ceca.2006.01.013. Epub 2006 Mar 20.
The melastatin-related transient receptor potential channel TRPM2 is a Ca(2+)-permeable channel that is activated by H(2)O(2), and the Ca(2+) influx through TRPM2 mediates cell death. However, the responsible oxidants for TRPM2 activation remain to be identified. In the present study, we investigated the involvement of hydroxyl radical on TRPM2 activation in TRPM2-expressing HEK293 cells and the rat beta-cell line RIN-5F. In both cell types, H(2)O(2) induced Ca(2+) influx in a concentration-dependent manner. However, the addition of hydroxyl radical, which was produced by mixing FeSO(4) and H(2)O(2), to the cells, did not increase intracellular Ca(2+) concentration. Interestingly, when H(2)O(2) was added to the cells under intracellular Fe(2+)-accumulated conditions, Ca(2+) influx was markedly enhanced compared to H(2)O(2) alone. In addition, the H(2)O(2)-induced Ca(2+) influx was reduced by hydroxyl radical scavengers and an iron chelator. Under intracellular Fe(2+)-accumulated conditions, H(2)O(2)-induced RIN-5F cell death through TRPM2 activation was also markedly enhanced. Hydroxyl radical scavengers and an iron chelator suppressed the RIN-5F cell death by H(2)O(2). These results strongly suggest that the intracellular hydroxyl radical plays a key role in the activation of TRPM2 during H(2)O(2) treatment, and TRPM2 activation mediated by hydroxyl radical is implicated in H(2)O(2)-induced cell death in the beta-cell line RIN-5F.
与褪黑素相关的瞬时受体电位通道TRPM2是一种Ca(2+)可渗透通道，可被H(2)O(2)激活，通过TRPM2的Ca(2+)内流介导细胞死亡。然而，负责激活TRPM2的氧化剂仍有待确定。在本研究中，我们研究了羟基自由基在表达TRPM2的HEK293细胞和大鼠β细胞系RIN-5F中对TRPM2激活的作用。在这两种细胞类型中，H(2)O(2)均以浓度依赖的方式诱导Ca(2+)内流。然而，将通过混合FeSO(4)和H(2)O(2)产生的羟基自由基添加到细胞中，并未增加细胞内Ca(2+)浓度。有趣的是，当在细胞内Fe(2+)积累的条件下向细胞中添加H(2)O(2)时，与单独使用H(2)O(2)相比，Ca(2+)内流明显增强。此外，羟基自由基清除剂和铁螯合剂可减少H(2)O(2)诱导的Ca(2+)内流。在细胞内Fe(2+)积累的条件下，H(2)O(2)通过TRPM2激活诱导的RIN-5F细胞死亡也明显增强。羟基自由基清除剂和铁螯合剂可抑制H(2)O(2)诱导的RIN-5F细胞死亡。这些结果强烈表明，细胞内羟基自由基在H(2)O(2)处理期间对TRPM2的激活起关键作用，并且由羟基自由基介导的TRPM2激活与β细胞系RIN-5F中H(2)O(2)诱导的细胞死亡有关。
