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Negative feedback regulation of reactive oxygen species on AT1 receptor gene expression
Author(s) -
Nickenig Georg,
Strehlow Kerstin,
Bäumer Anselm T,
Baudler Stefanie,
Waßmann Sven,
Sauer Heinrich,
Böhm Michael
Publication year - 2000
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1038/sj.bjp.0703623
Subject(s) - angiotensin ii receptor type 1 , angiotensin ii , receptor , angiotensin receptor , chemistry , protease activated receptor 2 , medicine , receptor expression , endocrinology , microbiology and biotechnology , biology , enzyme linked receptor , biochemistry
Free radicals as well as the AT1 receptor are involved in the pathogenesis of cardiovascular disease. Both the intracellular mechanisms of AT1 receptor regulation and the effect of free radicals on AT1 receptor expression are currently unknown. This study investigates the role of free radicals in the modulation of AT1 receptor expression and in the angiotensin II‐induced AT1 receptor regulation. AT1 receptor mRNA was assessed by Northern blotting and AT1 receptor density by radioligand binding assays, respectively, in vascular smooth muscle cells (VSMC). Free radical release was measured by confocal laser scanning microscopy. AT1 receptor mRNA transcription rate was determined by nuclear run‐on assays and AT1 receptor mRNA half‐life was measured under transcriptional blockade. Angiotensin II caused a time‐dependent decrease of AT1 receptor mRNA expression in rat VSMC in culture (30±6% at 4 h with 100 n M angiotensin II). This was followed by a consistent decrease in AT1 receptor density. Angiotensin II caused release of reactive oxygen species in VSMC which was abolished by preincubation with 100 μ M diphenylene iodonium (DPI). DPI inhibited partially the down‐regulating effect of angiotensin II on the AT1 receptor. Incubation of VSMC with either hydrogen peroxide or xanthine/xanthine oxidase caused a dose‐dependent decrease in AT1 receptor mRNA expression which was not mediated by a decreased rate of transcription but rather through destabilization of AT1 receptor mRNA. Experiments which included preincubation of VSMC with various intracellular inhibitors suggested that free radicals caused AT1 receptor downregulation through activation of p38‐MAP kinase and intracellular release of calcium. However, angiotensin II‐induced AT1 receptor expression was not inhibited by blockade of p38‐MAP kinase activation or intracellular calcium release. Free radicals may at least in part mediate angiotensin II‐induced AT1 receptor regulation through direct post‐transcriptional effects on AT1 receptor mRNA expression which involves intracellular release of calcium and activation of p38‐MAP kinase. These findings may help to clarify the intracellular mechanisms involved in AT1 receptor regulation and reveal a novel biological feature for reactive oxygen species.British Journal of Pharmacology (2000) 131 , 795–803; doi: 10.1038/sj.bjp.0703623