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

我们研究了低氧对大鼠心脏成纤维细胞Na~+/Ca~(2+)/Ca~(2+)和GT~(2+)交换器和瞬时受体电位褪黑素(TRPM2)通道表达水平的影响。心脏成纤维细胞在低氧条件下用Aneropac培养24小时。当低氧暴露的细胞被全细胞钳制时，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，提示该电流可能是TRPM2电流。MRNA分析表明，低氧暴露的成纤维细胞TRPM2表达增加。当细胞内引入siRNA时，低氧不增加非选择性阳离子电流，也不增加TRPM2基因的表达。H_2O_2是TRPM2的活化剂。当低氧暴露细胞负载Fura-2时，H_2O_2(300μM)可使低氧暴露成纤维细胞内钙离子浓度显著升高，而常氧对照组细胞内钙离子浓度无明显变化。低氧可降低Na~+/Ca~(2+)&gt；交换器的表达。结论：低氧使心脏成纤维细胞TRPM2表达增加，而Na~+/Ca~(2+)和GT~(2+)交换蛋白表达降低。这些现象可能与心脏缺氧后成纤维细胞的激活和纤维化的加速有关。

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.