Functional analysis of low molecular weight stress protein in the central nerves

本研究旨在阐明血红素氧合酶-1（HO-1）和27 kD热休克蛋白（HSP 27）等低分子量应激蛋白在中枢神经系统中的作用。使用大鼠嗜铬细胞瘤PC 12细胞研究这些低分子量应激蛋白的细胞保护功能，该细胞条件性表达HO-1和HSP 27以响应多西环素。HSP 27可抑制血清去除诱导的细胞凋亡，而HO-1则无此作用。此外，这些低分子量应激蛋白的表达在用诱导氧化应激和遗传毒性的化合物处理的细胞中没有显示出保护功能。另一方面，由神经生长因子（NGF）诱导的分化细胞表现出对过氧化氢的敏感性增加，最能证明的是细胞谷胱甘肽含量减少。HO-1在这些细胞中的强制表达诱导细胞死亡，这是进一步增加了低浓度的HO-1底物氯化血红素。氯化血红素的这种作用被铁螯合剂去铁胺所抵消。这些结果表明，分子伴侣HSP 27抵消生长因子饥饿诱导的PC 12细胞凋亡。另一方面，认为氧化应激诱导的HO-1不仅在未分化细胞中不显示保护功能，而且通过酶反应产生铁促进分化细胞的细胞死亡。

The aim of this research was to clarify the function of the low molecular weight stress protein, such as heme oxygenase-1 (HO-1) and 27 kD heat shocking protein (HSP27), in the central nervous. The cell protection function of these low molecular weight stress proteins was investigated using rat pheochromocytoma PC12 cells, which conditionally express HO-1 and HSP27 in response to doxycycline. The apoptotic cell death induced by serum removal was suppressed by HSP27, whereas HO-1 showed no effect. Moreover, expression of these low molecular weight stress proteins showed no protective function in cells treated with compounds that induce oxidative stress and genotoxicity. Differentiated cells induced by nerve growth factor (NGF), on the other hand, showed increased susceptibility to hydrogen peroxide, most provably by reduced contents of cellular glutathione. Forced expression of HO-1 in these cells induced cell death, which was further increased by the low concentration of an HO-1 substrate hemin. This effect of hemin was canceled by deferoxamine, an iron-chelating agent. These results indicate that a molecular chaperon HSP27 counteracts apoptosis induced by growth factor starvation in PC12 cells. On the other hand, it is suggested that HO-1 induced by oxidative stress not only shows no a protection function in undifferentiated cells but also promotes cell death in differentiated cells through iron production by the enzyme reaction.