Weitsman Gregory E, Ravid Amiram, Liberman Uri A, Koren Ruth
Department of Physiology and Pharmacology, Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel.
Int J Cancer. 2003 Aug 20;106(2):178-86. doi: 10.1002/ijc.11202.
Calcitriol, the hormonal form of vitamin D, potentiates the activity of some common anticancer drugs and agents of the anticancer immune system, including tumor necrosis factor alpha (TNFalpha). TNFalpha-induced cytotoxicity is due to both caspase-dependent and -independent pathways. Cotreatment with calcitriol enhanced both modes of TNFalpha-induced death in MCF-7 breast cancer cells. It increased caspase-3-like activity as assayed by the cleavage of poly-(ADP-ribose)polymerase and of the fluorogenic substrate ac-DEVD-AMC. It also enhanced TNFalpha-induced caspase-independent cytotoxicity in the presence of the pan-caspase inhibitor zD-2,6-dichlorobenzoyloxymethylketone. The antioxidants N-acetylcysteine, reduced glutathione, lipoic acid and ascorbic acid markedly reduced the enhancing effect of the hormone on TNFalpha-induced caspase activation. N-acetylcysteine and reduced glutathione also decreased caspase-independent cytotoxicity in the presence or absence of calcitriol, indicating that reactive oxygen species (ROS) have a key role in the cross talk between TNFalpha and calcitriol. Mitochondrial damage is common to both TNFalpha-induced caspase-dependent and -independent pathways and may underlie excessive production of ROS. Mitochondrial membrane potential (DeltaPsi) was assessed by the specific potential-sensitive fluorescent probe JC-1. The hormone augmented the drop in DeltaPsi and release of cytochrome c from mitochondria, induced by TNFalpha. The effect of calcitriol on DeltaPsi was mimicked by rotenone, which increased both the drop in DeltaPsi and caspase activation induced by TNFalpha. It is possible that the interaction of TNFalpha and calcitriol on the level of the mitochondria is the underlying mechanism responsible for the enhancement of TNFalpha-induced, ROS-mediated caspase-dependent and -independent cell death.
骨化三醇，即维生素D的激素形式，可增强一些常见抗癌药物及抗癌免疫系统因子的活性，包括肿瘤坏死因子α（TNFα）。TNFα诱导的细胞毒性是由半胱天冬酶依赖性和非依赖性途径介导的。与骨化三醇联合处理增强了TNFα诱导的MCF - 7乳腺癌细胞死亡的两种模式。通过聚（ADP - 核糖）聚合酶和荧光底物ac - DEVD - AMC的裂解检测发现，它增加了类半胱天冬酶 - 3的活性。在泛半胱天冬酶抑制剂zD - 2,6 - 二氯苯甲酰氧基甲基酮存在的情况下，它还增强了TNFα诱导的非半胱天冬酶依赖性细胞毒性。抗氧化剂N - 乙酰半胱氨酸、还原型谷胱甘肽、硫辛酸和抗坏血酸显著降低了该激素对TNFα诱导的半胱天冬酶激活的增强作用。无论有无骨化三醇，N - 乙酰半胱氨酸和还原型谷胱甘肽也都降低了非半胱天冬酶依赖性细胞毒性，这表明活性氧（ROS）在TNFα与骨化三醇的相互作用中起关键作用。线粒体损伤在TNFα诱导的半胱天冬酶依赖性和非依赖性途径中都很常见，可能是ROS过量产生的基础。通过特异性电位敏感荧光探针JC - 1评估线粒体膜电位（ΔΨ）。该激素增强了TNFα诱导的ΔΨ下降和细胞色素c从线粒体的释放。鱼藤酮模拟了骨化三醇对ΔΨ的影响，它增加了TNFα诱导的ΔΨ下降和半胱天冬酶激活。TNFα与骨化三醇在线粒体水平上的相互作用可能是增强TNFα诱导的、ROS介导的半胱天冬酶依赖性和非依赖性细胞死亡的潜在机制。
