Soluble guanylyl cyclase is a target of angiotensin II-induced nitrosative stress in a hypertensive rat model

Abstract

Soluble guanylyl cyclase is a target of angiotensin II-induced nitrosative stress in a hypertensive rat model. Am J Physiol Heart Circ Physiol 303: H597-H604, 2012. First published June 22, 2012; doi:10.1152/ajpheart.00138.2012 by activating soluble guanylyl cyclase (sGC) is involved in vascular homeostasis via induction of smooth muscle relaxation. In cardiovascular diseases (CVDs), endothelial dysfunction with altered vascular reactivity is mostly attributed to decreased NO bioavailability via oxidative stress. However, in several studies, relaxation to NO is only partially restored by exogenous NO donors, suggesting sGC impairment. Conflicting results have been reported regarding the nature of this impairment, ranging from decreased expression of one or both subunits of sGC to heme oxidation. We showed that sGC activity is impaired by thiol S-nitrosation. Recently, angiotensin II (ANG II) chronic treatment, which induces hypertension, was shown to generate nitrosative stress in addition to oxidative stress. We hypothesized that S-nitrosation of sGC occurs in ANG II-induced hypertension, thereby leading to desensitization of sGC to NO hence vascular dysfunction. As expected, ANG II infusion increases blood pressure, aorta remodeling, and protein S-nitrosation. Intravital microscopy indicated that cremaster arterioles are resistant to NO-induced vasodilation in vivo in anesthetized ANG II-treated rats. Concomitantly, NO-induced cGMP production decreases, which correlated with S-nitrosation of sGC in hypertensive rats. This study suggests that S-nitrosation of sGC by ANG II contributes to vascular dysfunction. This was confirmed in vitro by using A7r5 smooth muscle cells infected with adenoviruses expressing sGC or cysteine mutants: ANG II decreases NO-stimulated activity in the wild-type but not in one mutant, C516A. This result indicates that cysteine 516 of sGC mediates ANG II-induced desensitization to NO in cells. nitric oxide resistance; vascular dysfunction; oxidative stress; hypertension SOLUBLE GUANYLYL CYCLASE (sGC) is the main receptor for nitric oxide (NO) and the enzyme responsible for the conversion of GTP into cGMP. As such, the NO-receptor sGC is crucially involved in the physiology of the cardiovascular system by modulating vessel tone. Indeed, mice lacking this receptor are hypertensive (5). Oxidative stress is associated with cardiovascular diseases (CVDs) such as hypertension, atherosclerosis, and diabetes. Most oxidative CVDs are accompanied by endothelial dysfunction and impaired vascular reactivity with decreased NO bioavailability. Nonetheless, it should be pointed out that oxidative stress affects as well the smooth muscle cell (SMC) layers where sGC is expressed. It has been reported that reactive oxygen species (ROS) alter sGC expression and activity (19,25,29). We (21) have previously shown that in vitro and in vivo S-nitrosation of sGC impairs its ability to be activated by NO. In particular, we established that infusion of low therapeutic doses of nitroglycerin in rats for 3 days i...

Angiotensin II-Induced Hypertension Is Attenuated by Reduction of Sympathetic Output in NO-Sensitive Guanylyl Cyclase 1 Knockout Mice

“…The impairment of NOmediated relaxation demonstrates that the effects of Ang II on the NO/cGMP cascade are not limited to the endothelium but also occur in smooth muscle cells, most likely on the level of the cGMP-forming/degrading enzymes. Respective Ang IIinduced alterations like reduced expression of NO-GC (Mollnau et al, 2002), S-nitrosation of sGC (Crassous et al, 2012), or enhanced expression of PDEs (Giachini et al, 2011) have been reported.…”

Newly Identified NO‐Sensor Guanylyl Cyclase/Connexin 43 Association Is Involved in Cardiac Electrical Function

“…Thus, to further establish a correlation between GC1‐Cx43 association and GJ function, we assessed the localization of Cx43 in the GCα1‐KO model and under AngII‐induced stress conditions. We used a model of AngII‐induced cardiac hypertrophy because we previously showed that in this model, GC1 is desensitized to NO stimulation (eg, reduced NO‐stimulated activity) 15. We assessed localization of Cx43 by measuring the amount of Cx43 outside the ID in 4 groups: WT, WT treated with AngII, GCα1‐KO, and GCα1‐KO treated with AngII, as described in Methods.…”

“…In addition to the GCα1‐KO mice model, we used an AngII‐induced hypertrophy mouse model for 2 reasons. First, we previously showed that AngII treatment desensitizes GC1 activity to NO stimulation in the vasculature15 and in the heart (Figure S5), giving us another model of the impaired NO‐GC‐cGMP pathway. Second, we wanted to assess whether stress‐induced disruption of the GC1‐Cx43 association could have a pathological relevance.…”

“…Our initial observation that GC1 was located at the ID and the novel finding of its proximity to Cx43 prompted us to investigate the potential function of the NO‐cGMP pathway in relation to Cx43 function. In addition to the GCα1‐KO mouse model, we used an angiotensin II (AngII)–induced cardiac hypertrophy mouse model because AngII‐treated animals have decreased NO‐stimulated GC1 activity in the cardiovascular system 15. In our specific model, we observed cardiac hypertrophy, but the cardiac remodeling associated with arrhythmic sudden death and heart failure has not yet taken place, unlike other renin‐angiotensin mouse models 16, 17…”

Thiol-Based Redox Modulation of Soluble Guanylyl Cyclase, the Nitric Oxide Receptor

“…Several reports from the late 70s and early 80s, before sGC was cloned, described how thiol oxidants and reductants affect basal or NO-stimulated sGC activity, and the potential involvement of disulfide bond formation in the effects (7-9, 45, 52). More recently, it was documented that posttranslational modification (PTM) of cysteine (Cys) thiols, in particular S-nitrosation (SNO), modulates sGC activity, and candidate regulatory Cys were identified in sGC (18,34,71,73,91,95,96).…”