Roles of fibroblast Na^+/Ca^<2+> exchangers in fibrosis

我们研究了缺氧对大鼠心脏成纤维细胞Na^+/Ca^<2+>交换体和瞬时受体电位melastatin（TRPM 2）通道表达水平的影响。使用Aneropac在缺氧条件下培养心脏成纤维细胞24小时。当缺氧暴露的细胞被全细胞钳夹时，观察到膜电流显著增加。该电流为非选择性阳离子电流，并被克霉唑抑制，表明电流可能是TRPM 2电流。mRNA分析表明缺氧暴露的成纤维细胞中TRPM 2表达增加。当在细胞中引入siRNA时，缺氧不增加非选择性阳离子电流，也不增加TRPM 2 mRNA。H_2O_2是TRPM 2的激活剂。当缺氧暴露的细胞负载Fura-2时，H_2O_2（300μM）显著增加缺氧暴露的成纤维细胞内Ca^<2+>浓度，而在常氧暴露的对照细胞中则没有。低氧暴露降低了Na^+/Ca^<2+>交换体的表达。我们的结论是，缺氧增加心脏成纤维细胞TRPM 2的表达，但降低Na^+/Ca^<2+>交换蛋白的表达。这些现象可能有助于心脏缺氧后成纤维细胞的活化和纤维化的加速。

We studies the effect of hypoxia on the expression levels of Na^+/Ca^<2+> exchangers and transient receptor potential melastatin(TRPM2) channels in cardiac fibroblasts obtained primarily from rat hearts. Cardiac fibroblasts were cultured under hypoxic condition for 24 hours using Aneropac. When the hypoxia-exposed cells were whole-cell clamped, significant increase in membrane current was observed. The current was a non-selective cation current and was inhibited by clotrimazole, indicating that curren is likely TRPM2 current. mRNA analysis indicated increase in TRPM2 expression in hypoxia exposed fibroblasts. When siRNA was introduced in the cells, hypoxia did not increase the nonselective cation current nor TRPM2 mRNA. H_2O_2 is an activator of TRPM2. When hypoxia-exposed cells were fura-2 loaded, H_2O_2(300μM) increased intracellular Ca^<2+> concentration significantly in hypoxia-exposed fibroblasts but not in normoxia-exposed control cells. Na^+/Ca^<2+> exchanger expression was decreased by hypoxia exposure. We concluded that hypoxia increase TRPM2 expression but decrease Na^+/Ca^<2+> exchanger expression in cardiac fibroblasts. These phenomena may contribute to activation of fibroblasts and acceleration of fibrosis after hypoxia in the heart.