Medical Sciences Division, Northern Ontario School of Medicine, Sudbury, ON, Canada.
Oxid Med Cell Longev. 2011;2011:756938. doi: 10.1155/2011/756938. Epub 2011 Oct 9.
The stress hormone, epinephrine, is produced predominantly by adrenal chromaffin cells and its biosynthesis is regulated by the enzyme phenylethanolamine N-methyltransferase (PNMT). Studies have demonstrated that PNMT may be regulated hormonally via the hypothalamic-pituitary-adrenal axis and neurally via the stimulation of the splanchnic nerve. Additionally, hypoxia has been shown to play a key role in the regulation of PNMT. The purpose of this study was to examine the impact of reactive oxygen species (ROS) produced by the hypoxia mimetic agent CoCl(2), on the hormonal and neural stimulation of PNMT in an in vitro cell culture model, utilizing the rat pheochromocytoma (PC12) cell line. RT-PCR analyses show inductions of the PNMT intron-retaining and intronless mRNA splice variants by CoCl(2) (3.0- and 1.76-fold, respectively). Transient transfection assays of cells treated simultaneously with CoCl(2) and the synthetic glucocorticoid, dexamethasone, show increased promoter activity (18.5-fold), while mRNA levels of both splice variants do not demonstrate synergistic effects. Similar results were observed when investigating the effects of CoCl(2)-induced ROS on the neural stimulation of PNMT via forskolin. Our findings demonstrate that CoCl(2)-induced ROS have synergistic effects on hormonal and neural activation of the PNMT promoter.
应激激素肾上腺素主要由肾上腺嗜铬细胞产生，其生物合成受苯乙醇胺 N-甲基转移酶（PNMT）的调节。研究表明，PNMT 可能通过下丘脑-垂体-肾上腺轴激素调节，通过内脏神经刺激神经调节。此外，缺氧已被证明在 PNMT 的调节中起关键作用。本研究旨在探讨缺氧模拟剂 CoCl₂产生的活性氧（ROS）对体外细胞培养模型中 PNMT 的激素和神经刺激的影响，利用大鼠嗜铬细胞瘤（PC12）细胞系。RT-PCR 分析显示 CoCl₂诱导 PNMT 内含子保留和无内含子 mRNA 剪接变体分别上调 3.0 倍和 1.76 倍。同时用 CoCl₂和合成糖皮质激素地塞米松处理细胞的瞬时转染试验显示启动子活性增加（18.5 倍），而两种剪接变体的 mRNA 水平均未显示协同作用。当研究 CoCl₂诱导的 ROS 对 forskolin 诱导的 PNMT 神经刺激的影响时，观察到类似的结果。我们的研究结果表明，CoCl₂诱导的 ROS 对 PNMT 激素和神经激活具有协同作用。
