Heart failure is often accompanied by titin-dependent myocardial stiffness. Phosphorylation of titin by cGMP-dependent protein kinase I (PKGI) increases cardiomyocyte distensibility. The upstream ...pathways stimulating PKGI-mediated titin phosphorylation are unclear. We studied whether C-type natriuretic peptide (CNP), via its guanylyl cyclase-B (GC-B) receptor and cGMP/PKGI signaling, modulates titin-based ventricular compliance. To dissect GC-B-mediated effects of endogenous CNP in cardiomyocytes, we generated mice with cardiomyocyte-restricted GC-B deletion (CM GC-B-KO mice). The impact on heart morphology and function, myocyte passive tension, and titin isoform expression and phosphorylation was studied at baseline and after increased afterload induced by transverse aortic constriction (TAC). Pressure overload increased left ventricular endothelial CNP expression, with an early peak after 3 days. Concomitantly, titin phosphorylation at Ser4080, the site phosphorylated by PKGI, was augmented. Notably, in CM GC-B-KO mice this titin response was abolished. TAC-induced hypertrophy and fibrosis were not different between genotypes. However, the KO mice presented mild systolic and diastolic dysfunction together with myocyte stiffness, which were not observed in control littermates. In vitro, recombinant PKGI rescued reduced titin-Ser4080 phosphorylation and reverted passive stiffness of GC-B-deficient cardiomyocytes. CNP-induced activation of GC-B/cGMP/PKGI signaling in cardiomyocytes provides a protecting regulatory circuit preventing titin-based myocyte stiffening during early phases of pressure overload.
Excessive activation of cardiac fibroblasts (CFs) in response to injury provokes cardiac fibrosis, stiffness, and failure. The local mediators counterregulating this response remain unclear. ...Exogenous C-type natriuretic peptide (CNP) exerts antifibrotic effects in preclinical models. To unravel the role of the endogenous hormone, we generated mice with fibroblast-restricted deletion (KO) of guanylyl cyclase-B (GC-B), the cGMP-synthesizing CNP receptor. CNP activated GC-B/cGMP signaling in human and murine CFs, preventing proliferative and promigratory effects of angiotensin II (Ang II) and TGF-β. Fibroblast-specific GC-B-KO mice showed enhanced fibrosis in response to Ang II infusions. Moreover, after 2 weeks of mild pressure overload induced by transverse aortic constriction (TAC), such KO mice had augmented cardiac fibrosis and hypertrophy, together with systolic and diastolic contractile dysfunction. This was associated with increased expression of the profibrotic genes encoding collagen I, III, and periostin. Notably, such responses to Ang II and TAC were greater in female as compared with male KO mice. Enhanced Ang II-induced CNP expression in female hearts and augmented GC-B expression and activity in female CFs may contribute to this sex disparity. The results show that paracrine CNP signaling in CFs has antifibrotic and antihypertrophic effects. The CNP/GC-B/cGMP pathway might be a target for therapies combating pathological cardiac remodeling.
Occlusion of cerebral arteries leads to ischemic stroke accompanied by subsequent brain edema. Bradykinin (BK) is involved in the formation of cerebral edema, and natriuretic peptides (NPs) ...potentially have beneficial effects on brain edema formation via a still unknown mechanism. The aim of this study was clarifying the mechanisms of action of NPs on BK signaling, and their interactive effects after ischemic brain injury. We used a mouse model for stroke, the middle cerebral artery (MCA) occlusion. Brain lesion and edema were measured by microcomputerized tomography volumetric measurements. To determine the effects of NPs on the BK signaling pathway in the MCAs we measured changes in vessel diameter and membrane potentials in endothelial cells. To determine the effects of NPs on BK signaling pathway in isolated astrocytes and neurons, membrane potentials and intercellular Ca2+ concentrations were measured. Urodilatin inhibited and when applied together with BK, reduced the formation of the ischemic lesion via activation of G-Protein–Signaling Protein Type 4 at the cellular (atrocities, neurons) and blood vessel (endothelial cells and isolated MCA) level as well as in in vivo experiments. The results of this study show the existence of a natural antagonist of BK in the brain, and the possible use of NPs in the treatment of stroke.
•Urodilatin inhibits the effects of bradykinin.•Those inhibitions are shown in neurons and astrocytes, endothelial cells and intact middle cerebral artery.•Action of urodilatin leads to ameliorations of the development of stroke symptoms, brain lesions, and edema after MCAO.
In patients after acute myocardial infarction (AMI), the initial extent of necrosis and inflammation determine clinical outcome. One early event in AMI is the increased cardiac expression of atrial ...natriuretic peptide (NP) and B-type NP, with their plasma levels correlating with severity of ischemia. It was shown that NPs, via their cGMP-forming guanylyl cyclase-A (GC-A) receptor and cGMP-dependent kinase I (cGKI), strengthen systemic endothelial barrier properties in acute inflammation.
We studied whether endothelial actions of local NPs modulate myocardial injury and early inflammation after AMI.
Necrosis and inflammation after experimental AMI were compared between control mice and littermates with endothelial-restricted inactivation of GC-A (knockout mice with endothelial GC-A deletion) or cGKI (knockout mice with endothelial cGKI deletion). Unexpectedly, myocardial infarct size and neutrophil infiltration/activity 2 days after AMI were attenuated in knockout mice with endothelial GC-A deletion and unaltered in knockout mice with endothelial cGKI deletion. Molecular studies revealed that hypoxia and tumor necrosis factor-α, conditions accompanying AMI, reduce the endothelial expression of cGKI and enhance cGMP-stimulated phosphodiesterase 2A (PDE2A) levels. Real-time cAMP measurements in endothelial microdomains using a novel fluorescence resonance energy transfer biosensor revealed that PDE2 mediates NP/cGMP-driven decreases of submembrane cAMP levels. Finally, intravital microscopy studies of the mouse cremaster microcirculation showed that tumor necrosis factor-α-induced endothelial NP/GC-A/cGMP/PDE2 signaling impairs endothelial barrier functions.
Hypoxia and cytokines, such as tumor necrosis factor-α, modify the endothelial postreceptor signaling pathways of NPs, with downregulation of cGKI, induction of PDE2A, and altered cGMP/cAMP cross talk. Increased expression of PDE2 can mediate hyperpermeability effects of paracrine endothelial NP/GC-A/cGMP signaling and facilitate neutrophil extravasation during the early phase after MI.
Cardiac ANP (atrial natriuretic peptide) moderates arterial blood pressure. The mechanisms mediating its hypotensive effects are complex and involve inhibition of the renin-angiotensin-aldosterone ...system, increased natriuresis, endothelial permeability, and vasodilatation. The contribution of the direct vasodilating effects of ANP to blood pressure homeostasis is controversial because variable levels of the ANP receptor, GC-A (guanylyl cyclase-A), are expressed among vascular beds. Here, we show that ANP stimulates GC-A/cyclic GMP signaling in cultured microvascular pericytes and thereby the phosphorylation of the regulatory subunit of myosin phosphatase 1 by cGMP-dependent protein kinase I. Moreover, ANP prevents the calcium and contractile responses of pericytes to endothelin-1 as well as microvascular constrictions. In mice with conditional inactivation (knock-out) of GC-A in microcirculatory pericytes, such vasodilating effects of ANP on precapillary arterioles and capillaries were fully abolished. Concordantly, these mice have increased blood pressure despite preserved renal excretory function. Furthermore, acute intravascular volume expansion, which caused release of cardiac ANP, did not affect blood pressure of control mice but provoked hypertensive reactions in pericyte GC-A knock-out littermates. We conclude that GC-A/cGMP-dependent modulation of pericytes and microcirculatory tone contributes to the acute and chronic moderation of arterial blood pressure by ANP. Graphic Abstract A graphic abstract is available for this article.
In proliferative retinopathies, complications derived from neovascularization cause blindness. During early disease, pericyte's apoptosis contributes to endothelial dysfunction and leakage. Hypoxia ...then drives VEGF (vascular endothelial growth factor) secretion and pathological neoangiogenesis. Cardiac ANP (atrial natriuretic peptide) contributes to systemic microcirculatory homeostasis. ANP is also formed in the retina, with unclear functions. Here, we characterized whether endogenously formed ANP regulates retinal (neo)angiogenesis. Approach and Results: Retinal vascular development and ischemia-driven neovascularization were studied in mice with global deletion of GC-A (guanylyl cyclase-A), the cGMP (cyclic guanosine monophosphate)-forming ANP receptor. Mice with a floxed GC-A gene were interbred with
lines to dissect the endothelial, astrocyte versus pericyte-mediated actions of ANP in vivo. In neonates with global GC-A deletion (KO), vascular development was mildly delayed. Moreover, such KO mice showed augmented vascular regression and exacerbated ischemia-driven neovascularization in the model of oxygen-induced retinopathy. Notably, absence of GC-A in endothelial cells did not impact retinal vascular development or pathological neovascularization. In vitro ANP/GC-A/cGMP signaling, via activation of cGMP-dependent protein kinase I, inhibited hypoxia-driven astrocyte's VEGF secretion and TGF-β (transforming growth factor beta)-induced pericyte apoptosis. In neonates lacking ANP/GC-A signaling in astrocytes, vascular development and hyperoxia-driven vascular regression were unaltered; ischemia-induced neovascularization was modestly increased. Remarkably, inactivation of GC-A in pericytes retarded physiological retinal vascularization and markedly enhanced cell apoptosis, vascular regression, and subsequent neovascularization in oxygen-induced retinopathy.
Protective pericyte effects of the ANP/GC-A/cGMP pathway counterregulate the initiation and progression of experimental proliferative retinopathy. Our observations indicate augmentation of endogenous pericyte ANP signaling as target for treatment of retinopathies associated with neovascularization.
Stroke is the third leading cause of death in the Western world. Ischemic stroke is characterized by a rapid loss of brain function due to disturbance in the blood supply to a part of the brain. Due ...to fixed intracranial space, any increase in intracranial fluid volume, or progressive brain edema formation, contributes to further deterioration of the already impaired brain function. Bradykinin increases blood–brain barrier permeability and raises intracranial capillary blood pressure by arterial dilatation and venous constriction leading to brain edema formation. The aim of this paper is to summarize the recent research in the field of bradykinin function (structure, synthesis, signaling pathways, mechanism of action) followed by characterization of different types of brain edema development related to ischemic brain injury, together with the involvement of bradykinin in edema formation. Since there is currently no causal treatment addressing brain edema after ischemic stroke, specific bradykinin receptor antagonists are proposed as a possible new therapeutic approach.
The objective of this study was to verify the presence of oxidative enzymes in the quadriceps femoris muscle of Lika Pramenka sheep and to evaluate the effect of supplement from button mushrooms, ...Agaricus bisporus (A. bisporus), on the histochemical and morphological characteristics of the muscles. Fourteen oneyear-old Lika Pramenka sheep were randomly divided into two groups (control and experimental groups) comprising 7 animals each. The experiment was conducted over a period of 6 weeks of the winter feeding period. The control group of sheep was fed with a standard feed without antimicrobials or growth promoters. The experimental group was given the same feed but with an additional 1.5% of dry A. bisporus. During the experiment access to water and feed was ad libitum. Samples were tested for the size and type of muscle fibers, as well as for the presence of oxidative enzymes. The diameter of muscle fibers and histochemical reactions profiles were significantly greater in animals fed with the A. bisporus supplement. On the basis of the increased activity of oxidative enzymes, which resulted in pronounced cell metabolism and increased muscle mass, we conclude that A. bisporus displays growth promoter effects. Keywords: Agaricus bisporus, oxidative enzymes, Lika Pramenka sheep breed Cilj ovog istrazivanja bio je provjeriti prisutnost oksidativnih enzima u cetveroglavom bedrenom misicu (m. quadriceps femoris) ovaca pasmine Licka pramenka te procijeniti ucinak u hranu dodanog pripravka plemenite pecurke Agaricus bisporus (A. bisporus) na histokemijske i morfoloske karakteristike misica. Cetrnaest jednogodisnjih ovaca bilo je nasumicno odabrano i podijeljeno u dvije skupine (kontrolna i pokusna skupina) s po sedam zivotinja. Pokus je bio proveden tijekom 6 tjedana hranjenja. Kontrolna skupina bila je hranjena standardnom hranom, dok je pokusnoj skupini u standardnu hranu umjesano 1,5% suhog pripravka A. bisporus. Tijekom cijelog pokusnog razdoblja hrana i voda bile su zivotinjama dostupne ad libitum. Uzorci m. quadriceps femoris ovaca u pokusu bili su analizirani s obzirom na velicinu i tip misicnog vlakna, te na prisutnost oksidativnih enzima. Misicna vlakna vecih promjera i snaznije histokemijske reakcije zabiljezena su u ovaca hranjenih s dodatkom A. bisporus. Temeljem povecane aktivnosti oksidativnih enzima, sto je rezultiralo pojacanim stanicnim metabolizmom i povecanom misicnom masom ovaca hranjenih uz dodatak pripravka plemenite pecurke, mozemo zakljuciti da A. bisporus ima ucinak promotora rasta. Kljucne rijeci: Agaricus bisporus, oksidativni enzimi, ovce, Licka pramenka
The aim of the present study was to investigate and compare the morphometric characteristics of 'the flippers in male and female bottlenose dolphins (Tursiops truncatus) of various ages. We ...investigated the right flippers of 64 bottlenose dolphinc specimens -36 males and 28 females, in an age span of from 6 months to 28 years. Two numeric indices were suggested in order to establish the numerical relationship between the external measures of the flipper and the total body length of each animal. The index of the flipper measurements (IxF) directly showed the differences in flipper sizes in the investigated dolphins, whereas the index of the flipper measurements and the total body length (IxBL) displayed the differences in the flipper size in relation to the body length of the studied dolphins. By comparing these indices in dolphins of different ages, noticeable variations in flipper dimensions during total body growth were observed. In bottlenose dolphins, both flipper indices were highly correlated with the animal's body length. The mean value of the index of the flipper measurements and the total body length (IxBL) was somewhat higher in female bottlenose dolphins. Both the flipper indices were highly correlated with the animal's age, and our results suggest that the flipper grows until the tenth year of age, after which it does not change substantially until the 25th year of age. After that age the flipper size starts to decrease. Key words: bottlenose dolphin, flipper morphology, flipper mobility Cilj ovog istrazivanja bio je usporedba morfometrijskih obiljezja prsne peraje u muzjaka i zenki dobrih dupina razlicite dobi. Istrazene su desne prsne peraje od 64 dobra dupina (Tursiops truncatus)--36 muzjaka i 28 zenki u dobnom rasponu od 6 mjeseci do 28 godina. Predlozena su dva numericka indeksa kojima bi se utvrdila numericka povezanost izmedu vanjskih mjera prsne peraje i ukupne duzine tijela svake zivotinje. Indeks mjera prsne peraje (IxF) izravno pokazuje razlike u velicini prsne peraje istrazenih dupina, dok indeks mjera prsne peraje i ukupne duzine tijela (IxBL) pokazuje razlike u velicini prsne peraje u odnosu na ukupnu duzinu tijela istrazenih dupina. Usporedbom tih indeksa u dupina razlicite dobi utvrdene su varijacije u dimenzijama prsne peraje tijekom ukupnog rasta tijela zivotinje. U dobrih dupina, oba indeksa bila su u visokoj korelaciji s ukupnom duzinom tijela. Srednja vrijednost indeksa mjera prsne peraje i ukupne duzine tijela bila je nesto veca u skupini zenki istrazenih dupina. Oba indeksa bila su u visokoj korelaciji s dobi zivotinje te nase istrazivanje pokazuje da prsna peraja u dupina raste do dobi od 10 godina, nakon cega se znacajno ne mijenja do dobi od 25 godina. Nakon te dobi, velicina prsne peraje pocinje se smanjivati. Kljucne rijeci: dobri dupin, morfologijaprsne peraje, pokretljivost prsne peraje
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