Activation of ET B receptors regulates the abundance of ET‐1 mRNA in vascular endothelial cells

Background and purpose: The factors that influence the cellular levels of endothelin‐1 (ET‐1) include transcription, mRNA localization, stability and translation, post‐translational maturation of preproET‐1 and degradation of ET‐1. We investigated the regulation of ET‐1 mRNA abundance by extracellular ET‐1 in porcine aortic endothelial cells (PAECs). Experimental approach: Passsage one cultures of PAECs were incubated in starving medium in the presence or absence of ET‐1 and antagonists or pharmacological inhibitors. PreproET‐1 mRNA, endothelin‐1 promoter activity, Erk and p38 MAPK activation were determined. Key results: Exogenous ET‐1 reduced cellular ET‐1 mRNA content: a reduction of 10 000‐fold was observed after 4 h. ET‐1 simultaneously reduced the stability of ET‐1 mRNA and increased the loading of RNA Polymerase II at the endothelin‐1 promoter. In the absence of exogenous ET‐1, the ET B ‐selective antagonist, BQ788, increased ET‐1 mRNA. An ET A ‐selective antagonist had no effect. ET‐1 mRNA returned to control levels within 24 h. Whereas activation of p38 MAPK induced by ET‐1 peaked at 30 min and returned to control levels within 90 min, Erk1/2 remained active after 4 h of stimulation. Inhibition of p38 MAPK prevented the ET‐1‐induced decrease in ET‐1 mRNA. In contrast, Erk1/2 inhibition increased ET‐1 mRNA. Similarly, inhibition of receptor internalization increased ET‐1 mRNA in the presence or absence of exogenous ET‐1. Conclusions and implications: These results suggest that extracellular ET‐1 regulates the abundance of ET‐1 mRNA in PAECs, in an ET B receptor‐dependent manner, by modulating both mRNA stability and transcription via mechanisms involving receptor endocytosis and both ERK and p38 MAPK pathways. British Journal of Pharmacology (2008) 153 , 1420–1431; doi: 10.1038/bjp.2008.25 ; published online 18 February 2008