Park Sook-Eun, Park Jong-Wan, Cho Young-Suk, Ryu Ji-Hye, Paick Jae-Seung, Chun Yang-Sook
Cancer Research Institute, Seoul National University College of Medicine, 28 Yongon-dong, Chongno-gu, Seoul, Korea.
Prostate. 2007 Oct 1;67(14):1514-23. doi: 10.1002/pros.20641.
The prostate contains extremely high concentrations of zinc, which may be required for male reproduction. Although zinc is essential for many cellular functions, excessive zinc induces cellular toxicity in general. However, despite exposure to high zinc environment, prostate cells survive and proliferate. Thus, the aim of this study was to identify the intrinsic molecular species that endow prostate cells with the ability to overcome zinc toxicity.
Immunohistochemistry, histofluorescent zinc staining, Western blot, in vitro binding assay, immunoprecipitation, caspase activity assay, and proteasome activity assay.
In rat and human prostates, HIF-1alpha was found to be robustly expressed in epithelial layers containing high zinc levels. Moreover, in cultured prostate cells, HIF-1alpha expression was zinc-dependently induced even under normoxic conditions. Mechanistically, zinc ions inhibited HIF-1-prolyl hydroxylase (PHD) activity, and therefore blocked von Hippel-Lindau tumor suppressor protein (pVHL) binding to HIF-1alpha in vivo and in vitro. The HIF-1alpha stabilization was mediated by oxidative stress induced by zinc ion. Even when prostate cells were treated with high concentrations of zinc ion for extended times, only 10% of cells showed apoptotic death. However, this population of apoptotic cells was increased threefold after HIF-1alpha was knocked-down by siRNA.
These results suggest that HIF-1alpha functions as an intrinsic defense molecule that enables prostate cells to survive in a zinc-rich environment.
前列腺中锌的浓度极高，这可能是男性生殖所必需的。尽管锌对许多细胞功能至关重要，但一般来说，过量的锌会诱导细胞毒性。然而，尽管暴露于高锌环境中，前列腺细胞仍能存活和增殖。因此，本研究的目的是确定赋予前列腺细胞克服锌毒性能力的内在分子种类。
免疫组织化学、组织荧光锌染色、蛋白质印迹法、体外结合试验、免疫沉淀、半胱天冬酶活性测定和蛋白酶体活性测定。
在大鼠和人类前列腺中，发现缺氧诱导因子-1α（HIF-1α）在含锌量高的上皮层中大量表达。此外，在培养的前列腺细胞中，即使在常氧条件下，HIF-1α的表达也呈锌依赖性诱导。从机制上讲，锌离子抑制HIF-1脯氨酰羟化酶（PHD）的活性，从而在体内和体外阻断冯·希佩尔-林道肿瘤抑制蛋白（pVHL）与HIF-1α的结合。HIF-1α的稳定是由锌离子诱导的氧化应激介导的。即使前列腺细胞长时间用高浓度锌离子处理，也只有10%的细胞出现凋亡死亡。然而，在用小干扰RNA敲低HIF-1α后，这群凋亡细胞增加了三倍。
这些结果表明，HIF-1α作为一种内在防御分子，使前列腺细胞能够在富含锌的环境中存活。
