Amiloride kills malignant glioma cells independent of its inhibition of the sodium-hydrogen exchanger
Amiloride kills malignant glioma cells independent of its inhibition of the sodium-hydrogen exchanger
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DOI：
10.1124/jpet.103.065029
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发表时间：
2004-07-01
影响因子：
3.5
通讯作者：
Gorin, F
中科院分区：
文献类型：
--
作者：
Hegde, M;Roscoe, J;Gorin, F
先前，我们证明了恶性胶质瘤细胞系由于i型钠/氢交换剂（NHE1）活性增加而增加细胞内pH（pH(i)）。7.2 - 7.4的生物碱pH(i)有利于糖酵解、DNA合成和细胞周期进展。相反，pH(i)的降低与转化细胞类型的增殖率降低有关。系统比较了直接降低pH(i)和抑制NHE1对人恶性胶质瘤细胞和大鼠原代星形胶质细胞的影响。cariporide和直接酸化至pH(i) 6.9都不能改变人类U87或U118恶性胶质瘤细胞系的增殖率或存活率。然而，当浓度（500 muM）超过其对胶质瘤细胞NHE1的抑制（IC50 = 17 muM）时，阿米洛利显著损害胶质瘤细胞的增殖和活力，而不影响星形胶质细胞。防止pH(i)的降低并没有改变药物对胶质瘤细胞的抗增殖和细胞毒性作用。这些发现表明，阿米洛利对胶质瘤细胞的细胞毒性作用独立于其抑制NHE1或降低细胞内pH的能力(i)。amiloride衍生物2,4二氯苯氨（DCB）抑制钠钙交换剂（NCX），在低剂量（20mum）下对胶质瘤细胞具有抗增殖和细胞毒性。相比之下，KB-R7943[（2-[2-[4-硝基苯氧基]苯基]乙基）-异硫脲甲基磺酸盐]优先阻断NCX（反向模式）钠依赖性钙内流，对胶质瘤细胞无毒。有人提出DCB （20mum）和amiloride （500mum）损害NCX的钙外流，导致细胞内钙升高，从而引发形态学坏死，主要是caspase不依赖型胶质瘤细胞死亡。
Previously, we demonstrated that malignant glioma cell lines have increased intracellular pH (pH(i)) as a result of increased activities of the type I sodium/hydrogen exchanger (NHE1). This alkalotic pH(i) of 7.2 to 7.4 is favorable for augmented glycolysis, DNA synthesis, and cell cycle progression. Conversely, reductions in pH(i) have been associated with reduced rates of proliferation in transformed cell types. The effects of reducing pH(i) directly and by NHE1 inhibition on human malignant glioma cells were systematically compared with those on primary rat astrocytes. Neither cariporide, nor direct acidification to pH(i) 6.9 altered the proliferative rates or viabilities of human U87 or U118 malignant glioma cell lines. However, amiloride significantly impaired glioma cell proliferation and viability while not affecting astrocytes at concentrations (500 muM) that exceeded its inhibition of NHE1 in glioma cells (IC50 = 17 muM). Preventing a reduction of pH(i) did not alter the drug's antiproliferative and cytotoxic effects on glioma cells. These findings indicated that amiloride's cytotoxic effects on glioma cells are independent of its ability to inhibit NHE1 or to reduce intracellular pH(i). The amiloride derivative 2,4 dichlorobenzamil (DCB) inhibits the sodium-calcium exchanger (NCX) and was both antiproliferative and cytotoxic to glioma cells at low doses (20 muM). By contrast, KB-R7943 [(2-[2-[4-nitrobenzyloxy]phenyl]ethyl)-isothioureamethanesulfonate] preferentially blocks sodium-dependent calcium influx by NCX ( reverse mode) and was nontoxic to glioma cells. It is proposed that DCB (20 muM) and amiloride (500 muM) impair calcium efflux by NCX, leading to elevations of intracellular calcium that initiate a morphologically necrotic, predominantly caspase-independent glioma cell death.