Role of reactive oxygen species in the neural and hormonal regulation of the PNMT gene in PC12 cells

Abstract

In adrenergic cells norepinephrine is N‐methylated by the enzyme phenylethanolamine N‐methyltransferase (PNMT) to produce epinephrine. Prior studies have demonstrated that the PNMT gene in adrenal chromaffin cells may be regulated hormonally via the hypothalamic‐pituitary‐adrenal axis and neurally via stimulation of the splanchnic nerve. Further, 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 CoCl2 on the hormonal and neural stimulation of PNMT. RT‐PCR analyses show inductions of the PNMT intron‐retaining and intronless mRNA splice variants by CoCl2 (3.0‐ and 1.76‐fold respectively). Transient transfection assays of cells treated simultaneously with CoCl2 and 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 CoCl2‐induced ROS on the neural stimulation of PNMT. Our findings demonstrate that CoCl2‐induced ROS have synergistic effects on the hormonal and neural activation of the PNMT promoter and suggest post‐transcriptional regulation of PNMT following hormonal or neural activation during hypoxia. This study was funded by the Natural Sciences and Engineering Research Council of Canada.