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Inhibition of proteasome‐mediated glucocorticoid receptor degradation restores nitric oxide bioavailability in myocardial endothelial cells in vitro
Author(s) -
Blecharz Kinga G.,
Burek Malgorzata,
Bauersachs Johann,
Thum Thomas,
Tsikas Dimitrios,
Widder Julian,
Roewer Norbert,
Förster Carola Y.
Publication year - 2014
Publication title -
biology of the cell
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.543
H-Index - 85
eISSN - 1768-322X
pISSN - 0248-4900
DOI - 10.1111/boc.201300083
Subject(s) - tetrahydrobiopterin , enos , biology , nitric oxide , glucocorticoid receptor , glucocorticoid , medicine , mg132 , proteasome , endocrinology , nitric oxide synthase type iii , nitric oxide synthase , biopterin , proteasome inhibitor , pharmacology , microbiology and biotechnology
Background Information Glucocorticoids (GCs), including the synthetic GC derivate dexamethasone, are widely used as immunomodulators. One of the numerous side effects of dexamethasone therapy is hypertension arising from reduced release of the endothelium‐derived vasodilator nitric oxide (NO). Results Herein, we described the role of dexamethasone and its glucocorticoid receptor (GR) in the regulation of NO synthesis in vitro using the mouse myocardial microvascular endothelial cell line, MyEND. GC treatment caused a firm decrease of extracellular NO levels, whereas the expression of endothelial NO synthase (eNOS) was not affected. However, GC application induced an impairment of tetrahydrobiopterin (BH 4 ) concentrations as well as GTP cyclohydrolase‐1 (GTPCH‐1) expression, both essential factors for NO production upstream of eNOS. Moreover, dexamethasone stimulation resulted in a substantially decreased GR gene and protein expression in MyEND cells. Importantly, inhibition of proteasome‐mediated proteolysis of the GR or overexpression of an ubiquitination‐defective GR construct improved the bioavailability of BH 4 and strengthened GTPCH‐1 expression and eNOS activity. Conclusions Summarising our results, we propose a new mechanism involved in the regulation of NO signalling by GCs in myocardial endothelial cells. We suggest that a sufficient GR protein expression plays a crucial role for the management of GC‐induced harmful adverse effects, including deregulations of vasorelaxation arising from disturbed NO biosynthesis.