Guanylyl cyclases are a family of enzymes that catalyze the conversion of GTP to cGMP. The family comprises both membrane-bound and soluble isoforms that are expressed in nearly all cell types. They are regulated by diverse extracellular agonists that include peptide hormones, bacterial toxins, and free radicals, as well as intracellular molecules, such as calcium and adenine nucleotides. Stimulation of guanylyl cyclases and the resultant accumulation of cGMP regulates complex signaling cascades through immediate downstream effectors, including cGMP-dependent protein kinases, cGMP-regulated phosphodiesterases, and cyclic nucleotide-gated ion channels. Guanylyl cyclases and cGMP-mediated signaling cascades play a central role in the regulation of diverse (patho)physiological processes, including vascular smooth muscle motility, intestinal fluid and electrolyte homeostasis, and retinal phototransduction. Topics addressed in this review include the structure and chromosomal localization of the genes for guanylyl cyclases, structure and function of the members of the guanylyl cyclase family, molecular mechanisms regulating enzymatic activity, and molecular sequences coupling ligand binding to catalytic activity. A brief overview is presented of the downstream events controlled by guanylyl cyclases, including the effectors that are regulated by cGMP and the role that guanylyl cyclases play in cell physiology and pathophysiology.
[Show abstract][Hide abstract] ABSTRACT: Ischemia-reperfusion injury can cause renal damage, and phosphodiesterase inhibitors are reported to regulate antioxidant activity. We investigated the prevention of renal damage using tadalafil after renal ischemia reperfusion (I/R) injury in rats. A total of 21 adult male Wistar albino rats were randomly divided into three groups of seven, including Group 1-control, Group 2-I/R, and Group 3-tadalafil + I/R group (I/R-T group) received tadalafil intraperitoneally at 30 minutes before ischemia. Inducible nitric oxide synthase, endothelial nitric oxide synthase, malondialdehyde, and total antioxidant capacity levels were evaluated, and histopathological changes and apoptosis in the groups were examined. Tadalafil decreased malondialdehyde levels in the I/R group and increased the total antioxidant capacity level. Histopathological and immunohistochemical findings revealed that tadalafil decreased renal injury scores and the ratios of injured cells, as measured through apoptotic protease activating factor 1, inducible nitric oxide synthase, and endothelial nitric oxide synthase levels. We suggest that tadalafil has protective effects against I/R-related renal tissue injury.
The Kaohsiung journal of medical sciences 09/2015; 31(9):454-62. DOI:10.1016/j.kjms.2015.06.005 · 0.80 Impact Factor
"Furthermore, while both sGC and pGC activation results in the accumulation of cGMP within cells, pGC activation (in contrast to sGC) also results in significant release of cGMP into the extracellular space and circulation.7–11 Therefore, while both sGC and pGC increase intracellular cGMP, the resulting biological actions are quite different.4,12–13 "
[Show abstract][Hide abstract] ABSTRACT: Systemic hypertension is a common characteristic in acute heart failure (HF). This increasingly recognized phenotype is commonly associated with renal dysfunction and there is an unmet need for renal enhancing therapies. In a canine model of HF and acute vasoconstrictive hypertension we characterized and compared the cardiorenal actions of M-atrial natriuretic peptide (M-ANP), a novel particulate guanylyl cyclase (pGC) activator, and nitroglycerin, a soluble guanylyl cyclase (sGC) activator.
HF was induced by rapid RV pacing (180 beats per minute) for 10 days. On day 11, hypertension was induced by continuous angiotensin II infusion. We characterized the cardiorenal and humoral actions prior to, during, and following intravenous M-ANP (n=7), nitroglycerin (n=7), and vehicle (n=7) infusion. Mean arterial pressure (MAP) was reduced by M-ANP (139±4 to 118±3 mm Hg, P<0.05) and nitroglycerin (137±3 to 116±4 mm Hg, P<0.05); similar findings were recorded for pulmonary wedge pressure (PCWP) with M-ANP (12±2 to 6±2 mm Hg, P<0.05) and nitroglycerin (12±1 to 6±1 mm Hg, P<0.05). M-ANP enhanced renal function with significant increases (P<0.05) in glomerular filtration rate (38±4 to 53±5 mL/min), renal blood flow (132±18 to 236±23 mL/min), and natriuresis (11±4 to 689±37 mEq/min) and also inhibited aldosterone activation (32±3 to 23±2 ng/dL, P<0.05), whereas nitroglycerin had no significant (P>0.05) effects on these renal parameters or aldosterone activation.
Our results advance the differential cardiorenal actions of pGC (M-ANP) and sGC (nitroglycerin) mediated cGMP activation. These distinct renal and aldosterone modulating actions make M-ANP an attractive therapeutic for HF with concomitant hypertension, where renal protection is a key therapeutic goal.
Journal of the American Heart Association 12/2014; 3(1):e000206. DOI:10.1161/JAHA.113.000206 · 4.31 Impact Factor
"In order to evaluate if the CPA effect on basal cGMP accumulation is still observed under increased concentrations of cGMP, accumulation of cGMP was stimulated using sodium nitroprusside (100 μM), a NO donor and activator of soluble guanylyl cyclase (see Lucas et al., 2000). The effect of CPA on cGMP accumulation, in the absence or in the presence of SNP, was evaluated in both males and females Wistar rats. "
[Show abstract][Hide abstract] ABSTRACT: Adenosine A1 receptor is highly expressed in hippocampus where it inhibits neurotransmitter release and has neuroprotective activity. Similar actions are obtained by increasing cGMP concentration, but a clear link between adenosine A1 receptor and cGMP levels remains to be established. The present work aims to investigate if cGMP formation is modulated by adenosine A1 receptors at the hippocampus and if this effect is gender dependent. cGMP accumulation, induced by phosphodiesterases inhibitors Zaprinast (100μM) and Bay 60-7550 (10μM), and cAMP accumulation, induced by Forskolin (20μM) and Rolipram (50μM), were quantified in rat hippocampal slices using specific enzymatic immunoassays. N6-cyclopentyladenosine (CPA, 100nM) alone failed to modify basal cGMP accumulation. However, the presence of adenosine deaminase (ADA, 2U/ml) unmasked a CPA (0.03-300nM) stimulatory effect on basal cGMP accumulation (EC50: 4.2±1.4nM; Emax: 17%±0.9%). ADA influence on CPA activity was specific for cGMP, since inhibition of cAMP accumulation by CPA wasn't affected by the presence of ADA, though ADA inhibited cAMP accumulation in the absence of CPA. Increasing cGMP accumulation, by about four-fold, with sodium nitroprusside (SNP, 100μM) abolished the CPA (100nM) effect on cGMP accumulation in males but didn't modify the effect of CPA in female rats. This effect was reversed by 8-Cyclopentyl-1,3-dipropylxanthine (DPCPX, 100nM), indicating an adenosine A1 receptor mediated effect on cGMP accumulation. In conclusion, adenosine A1 receptors increase intracellular cGMP formation at hippocampus both in males and females under basal conditions, but only in females when cGMP levels are increased by SNP.
European Journal of Pharmacology 10/2014; 744. DOI:10.1016/j.ejphar.2014.09.045 · 2.53 Impact Factor
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