Glucocorticoid (GC)-induced
hypertension is a common clinical problem still poorly understood. The presence of GC receptor (GR) in vascular smooth muscle and endothelial cells suggests a direct role for GC in vasculature. In response to hemodynamic shear stress, endothelium tonically releases
nitric oxide (NO), endothelial-derived hyperpolarizing factor (
EDHF) and
prostacyclin contributing to vascular homeostasis. Recently,
hydrogen sulfide (H2S) has been proposed as a candidate for
EDHF. H2S is endogenously mainly formed from
L-cysteine by the action of
cystathionine-β-synthase (CBS) and
cystathionine-γ-
lyase (CSE). It plays many physiological roles and contributes to cardiovascular function. Here we have evaluated the role played by H2S in mesenteric arterial bed and in carotid artery harvested from rats treated with vehicle or
dexamethasone (DEX; 1.5 mg/kg/day) for 8 days. During treatments systolic blood pressure was significantly increased in conscious rats.
EDHF contribution was evaluated in ex-vivo by performing a concentration-response curve induced by
acetylcholine (Ach) in presence of a combination of
indomethacin and L-
NG-Nitroarginine methyl ester in both vascular districts.
EDHF-mediated relaxation was significantly reduced in DEX-treated group in both mesenteric bed and carotid artery.
EDHF-mediated relaxation was abolished by pre-treatment with both
apamin and
charybdotoxin, inhibitors of small and big
calcium-dependent potassium channels respectively, or with
propargylglycine, inhibitor of CSE. Western blot analysis revealed a marked reduction in CBS and CSE expression as well as H2S production in homogenates of mesenteric arterial bed and carotid artery from DEX-treated rats. In parallel, H2S plasma levels were significantly reduced in DEX group compared with vehicle. In conclusion, an impairment in
EDHF/H2S signaling occurs in earlier state of GC-induced
hypertension in rats suggesting that counteracting this dysfunction may be beneficial to manage DEX-associated increase in blood pressure.