Modulation of the AT(2) subtype receptor gene activation and expression bythe AT(1) receptor in endothelial cells

Objective To investigate whether angiotensin II type 2 (AT(2)) receptor (AT (2)-r) promoter activity and expression are modulated by angiotensin II (An g II), and whether the AT(1) receptor (AT(1)-r) is involved in this effect. Design and methods Primary endothelial cells obtained from neonatal rat aor ta, expressing both receptors, were transfected with the rat AT(2)-r promot er region cloned into a pCAT-reporter vector. The reporter-expression study was performed in a transient transfection assay system. Transfected cells were studied following angiotensin-converting enzyme inhibition to prevent endogenous formation of Ang II, Cells were subsequently stimulated for 6 h with Ang II, either alone or in combination with the AT(1)-r antagonist DuP 753. AT(2)-r mRNA was assessed by RNase protection assay during the same ph armacological stimuli. Results Stimulation with Ang II caused an increase in promoter activity (+5 0%, P < 0.05 versus baseline), whereas mRNA expression was reduced by 50% ( P < 0.05 versus baseline). Concomitant treatment with DuP753 and Ang II was associated with a 98% increase in promoter activity (P < 0.05 versus basel ine). DuP753 also prevented the reduction in mRNA; it actually produced a 1 00% increase in AT(2)-r mRNA accumulation (P < 0.01 versus baseline), Studi es with the AT(2)-r antagonist PD123319 indicate that the AT(2)-r is also i nvolved in the regulation of AT(2)-r gene promoter activity. Conclusions These data indicate that Ang II increases AT(2)-r promoter acti vity and decreases AT(2)-r mRNA accumulation in endothelial cells, The AT(1 ) subtype receptor is involved in the modulation of both effects of Ang II. These findings suggest that changes in the expression of AT(2) receptors m ay occur during treatment with AT(1)-r antagonists, and they indicate the e xistence of a cross-talk between AT(1) and AT(2) receptors. J Hypertens 199 9, 17:1873-1877 (C) Lippincott Williams & Wilkins.