Activation of calcineurin in human failing heart ventricle by endothelin-1, angiotensin II and urotensin II

Investigation of the effects of urotensin II receptors in LPS-induced inflammatory response in HUVEC cell line through calcineurin/NFATc/IL-2 pathway

PURPOSE

The effect of urotensin II (U-II), a powerful endogenous vasoconstrictor substance, on the immune system and its mediators is very important. It was herein aimed to demonstrate the possible relationship between the calcineurin/nuclear factor of activated T-cells cytoplasmic 1/interleukin-2 (CaN/NFATc/IL-2) pathway and urotensin receptors (UTRs) in inflammatory response due to lipopolysaccharide (LPS).

METHODS

An LPS-induced inflammation model was used on the human umbilical vein endothelial cells (HUVEC) cell line and drugs were applied accordingly, forming the following groups: Control Group, LPS Group, Agonist Group (10-8 ​M U-II), Antagonist Group (10-6 ​M palosuran), Tacrolimus (TAC) Group (10 ​ng/mL FK-506), Agonist ​+ ​TAC Group, and Antagonist ​+ ​TAC Group. Gene expression analyses were performed using real-time polymerase chain reaction (RT-PCR).

RESULTS

In the analysis of the cell viability at 48 and 72 ​h, there was a decrease in the Agonist Group, while in the Agonist ​+ ​TAC Group, the cell viability increased. In the Antagonist Group, cell viability was maintained when compared to the LPS Group, while in the TAC Group, this effect was reduced. The mRNA expression levels of UTR, CaN, NFATc, IL-2 receptor (IL-2R), IL-6 and nuclear factor kappa B (NF-κB) were higher in the LPS Group than in the Control Group, and even the UTR, CaN, NFATc, IL-2R were higher with agonist administration. This effect of the agonist was shown to be completely mitigated in the presence of the CaN inhibitor.

CONCLUSION

U-II and its receptors can perform key functions regarding the endothelial cell damage via the CaN/NFATc/IL-2 pathway.

The Microenvironment of the Pathogenesis of Cardiac Hypertrophy

Pathological cardiac hypertrophy is a key risk factor for the development of heart failure and predisposes individuals to cardiac arrhythmia and sudden death. While physiological cardiac hypertrophy is adaptive, hypertrophy resulting from conditions comprising hypertension, aortic stenosis, or genetic mutations, such as hypertrophic cardiomyopathy, is maladaptive. Here, we highlight the essential role and reciprocal interactions involving both cardiomyocytes and non-myocardial cells in response to pathological conditions. Prolonged cardiovascular stress causes cardiomyocytes and non-myocardial cells to enter an activated state releasing numerous pro-hypertrophic, pro-fibrotic, and pro-inflammatory mediators such as vasoactive hormones, growth factors, and cytokines, i.e., commencing signaling events that collectively cause cardiac hypertrophy. Fibrotic remodeling is mediated by cardiac fibroblasts as the central players, but also endothelial cells and resident and infiltrating immune cells enhance these processes. Many of these hypertrophic mediators are now being integrated into computational models that provide system-level insights and will help to translate our knowledge into new pharmacological targets. This perspective article summarizes the last decades' advances in cardiac hypertrophy research and discusses the herein-involved complex myocardial microenvironment and signaling components.

The endocrinological component and signaling pathways associated to cardiac hypertrophy

Although myocardial growth corresponds to an adaptive response to maintain cardiac contractile function, the cardiac hypertrophy is a condition that occurs in many cardiovascular diseases and typically precedes the onset of heart failure. Different endocrine factors such as thyroid hormones, insulin, insulin-like growth factor 1 (IGF-1), angiotensin II (Ang II), endothelin (ET-1), catecholamines, estrogen, among others represent important stimuli to cardiomyocyte hypertrophy. Thus, numerous endocrine disorders manifested as changes in the local environment or multiple organ systems are especially important in the context of progression from cardiac hypertrophy to heart failure. Based on that information, this review summarizes experimental findings regarding the influence of such hormones upon signalling pathways associated with cardiac hypertrophy. Understanding mechanisms through which hormones differentially regulate cardiac hypertrophy could open ways to obtain therapeutic approaches that contribute to prevent or delay the onset of heart failure related to endocrine diseases.

Angiotensin II type 1 receptor antagonists in animal models of vascular, cardiac, metabolic and renal disease

We have reviewed the effects of angiotensin II type 1 receptor antagonists (ARBs) in various animal models of hypertension, atherosclerosis, cardiac function, hypertrophy and fibrosis, glucose and lipid metabolism, and renal function and morphology. Those of azilsartan and telmisartan have been included comprehensively whereas those of other ARBs have been included systematically but without intention of completeness. ARBs as a class lower blood pressure in established hypertension and prevent hypertension development in all applicable animal models except those with a markedly suppressed renin-angiotensin system; blood pressure lowering even persists for a considerable time after discontinuation of treatment. This translates into a reduced mortality, particularly in models exhibiting marked hypertension. The retrieved data on vascular, cardiac and renal function and morphology as well as on glucose and lipid metabolism are discussed to address three main questions: 1. Can ARB effects on blood vessels, heart, kidney and metabolic function be explained by blood pressure lowering alone or are they additionally directly related to blockade of the renin-angiotensin system? 2. Are they shared by other inhibitors of the renin-angiotensin system, e.g. angiotensin converting enzyme inhibitors? 3. Are some effects specific for one or more compounds within the ARB class? Taken together these data profile ARBs as a drug class with unique properties that have beneficial effects far beyond those on blood pressure reduction and, in some cases distinct from those of angiotensin converting enzyme inhibitors. The clinical relevance of angiotensin receptor-independent effects of some ARBs remains to be determined.

Angiotensin II and the JNK pathway mediate urotensin II expression in response to hypoxia in rat cardiomyocytes

Cardiomyocyte hypoxia causes cardiac hypertrophy through cardiac-restricted gene expression. Urotensin II (UII) cooperates with activating protein 1 (AP1) to regulate cardiomyocyte growth in response to myocardial injuries. Angiotensin II (AngII) stimulates UII expression, reactive oxygen species (ROS) production, and cardiac hypertrophy. This study aimed to evaluate the expression of UII, ROS, and AngII as well as their genetic transcription after hypoxia treatment in neonatal cardiomyocytes. Cultured neonatal rat cardiomyocytes were subjected to hypoxia for different time periods. UII (Uts2) protein levels increased after 2.5% hypoxia for 4 h with earlier expression of AngII and ROS. Both hypoxia and exogenously added AngII or Dp44mT under normoxia stimulated UII expression, whereas AngII receptor blockers, JNK inhibitors (SP600125), JNK siRNA, or N-acetyl-l-cysteine (NAC) suppressed UII expression. The gel shift assay indicated that hypoxia induced an increase in DNA-protein binding between UII and AP1. The luciferase assay confirmed an increase in transcription activity of AP1 to the UII promoter under hypoxia. After hypoxia, an increase in (3)H-proline incorporation in the cardiomyocytes and expression of myosin heavy chain protein, indicative of cardiomyocyte hypertrophy, were observed. In addition, hypoxia increased collagen I expression, which was inhibited by SP600125, NAC, and UII siRNA. In summary, hypoxia in cardiomyocytes increases UII and collagen I expression through the induction of AngII, ROS, and the JNK pathway causing cardiomyocyte hypertrophy and fibrosis.

Molecular distinction between physiological and pathological cardiac hypertrophy: experimental findings and therapeutic strategies

Cardiac hypertrophy can be defined as an increase in heart mass. Pathological cardiac hypertrophy (heart growth that occurs in settings of disease, e.g. hypertension) is a key risk factor for heart failure. Pathological hypertrophy is associated with increased interstitial fibrosis, cell death and cardiac dysfunction. In contrast, physiological cardiac hypertrophy (heart growth that occurs in response to chronic exercise training, i.e. the 'athlete's heart') is reversible and is characterized by normal cardiac morphology (i.e. no fibrosis or apoptosis) and normal or enhanced cardiac function. Given that there are clear functional, structural, metabolic and molecular differences between pathological and physiological hypertrophy, a key question in cardiovascular medicine is whether mechanisms responsible for enhancing function of the athlete's heart can be exploited to benefit patients with pathological hypertrophy and heart failure. This review summarizes key experimental findings that have contributed to our understanding of pathological and physiological heart growth. In particular, we focus on signaling pathways that play a causal role in the development of pathological and physiological hypertrophy. We discuss molecular mechanisms associated with features of cardiac hypertrophy, including protein synthesis, sarcomeric organization, fibrosis, cell death and energy metabolism and provide a summary of profiling studies that have examined genes, microRNAs and proteins that are differentially expressed in models of pathological and physiological hypertrophy. How gender and sex hormones affect cardiac hypertrophy is also discussed. Finally, we explore how knowledge of molecular mechanisms underlying pathological and physiological hypertrophy may influence therapeutic strategies for the treatment of cardiovascular disease and heart failure.

Direct inotropic effects of exogenous and endogenous urotensin-II: divergent actions in failing and nonfailing human myocardium

BACKGROUND

Urotensin-II (U-II) is an endogenous peptide upregulated in failing hearts. To date, insights into the myocardial actions of U-II have been obscured by its potent vasoconstrictor effects and interspecies differences in physiological responses to U-II.

METHODS AND RESULTS

We examined the direct effects of exogenous U-II on in vitro contractility in nonfailing and failing human myocardial trabeculae (n=47). Rapid cooling contractures (RCC) were used to examine sarcoplasmic reticulum Ca(2+) load. In nonfailing myocardium, exogenous U-II increased developed force (DF), rates of force generation and decline and RCC amplitude suggesting increased sarcoplasmic reticulum Ca(2+) load. In isolated myocyte suspensions from nonfailing hearts, U-II increased phospholamban phosphorylation. In failing myocardium, exogenous U-II reduced DF and rates of force generation and decline without a significant change in RCC amplitude in trabeculae or a change in phospholamban phosphorylation in myocytes. To examine the effects of endogenous U-II, we administered the peptidic U-II receptor antagonist (UT-A) GSK248451A to isolated trabeculae. UT-A induced a decrease in DF in nonfailing myocardium and an increase in DF in failing myocardium. UT-A increased RCC amplitude slightly in both nonfailing and failing myocardium. During ongoing UT-A, exogenous U-II had little effect on DF and RCC amplitude, confirming effective receptor blockade.

CONCLUSIONS

U-II modulates contractility independent of vasoconstriction with opposite effects in failing and nonfailing hearts. Positive inotropic responses to UT-A alone suggests that increased endogenous U-II constrains contractility in failing hearts via an autocrine or paracrine mechanism. These findings support a potential therapeutic role for UT-A in heart failure.

HUMAN HEART ?-ADRENOCEPTORS: ?1-ADRENOCEPTOR DIVERSIFICATION THROUGH ?AFFINITY STATES? AND POLYMORPHISM

1. In atrium and ventricle from failing and non-failing human hearts, activation of beta(1)- or beta(2)-adrenoceptors causes increases in contractile force, hastening of relaxation, protein kinase A-catalysed phosphorylation of proteins implicated in the hastening of relaxation, phospholamban, troponin I and C-protein, consistent with coupling of both beta(1)- and beta(2)-adrenoceptors to stimulatory G(salpha)-protein but not inhibitory G(ialpha)-protein. 2. Two 'affinity states', namely beta(1H) and beta(1L), of the beta(1)-adrenoceptor exist. In human heart, noradrenaline elicits powerful increases in contractile force and hastening of relaxation. These effects are blocked with high affinity by beta-adenoceptor antagonists, including propranolol, (-)-pindolol, (-)-CGP 12177 and carvedilol. Some beta-blockers, typified by (-)-pindolol and (-)-CGP 12177, not only block the receptor, but also activate it, albeit at much higher concentrations (approximately 2 log units) than those required to antagonize the effects of catecholamines. In human heart, both (-)-CGP 12177 and (-)-pindolol increase contractile force and hasten relaxation. However, the involvement of the beta(1)-adrenoceptor was not immediately obvious because (-)-pindolol- and (-)-CGP 12177-evoked responses were relatively resistant to blockade by (-)-propranolol. Abrogation of cardiostimulant effects of (-)-CGP 12177 in beta(1)-/beta(2)-adrenoceptor double-knockout mice, but not beta(2)-adrenoceptor-knockout mice, revealed an obligatory role of the beta(1)-adrenoceptor. On the basis of these results, two 'affinity states' have been designated, the beta(1H)- and beta(1L)-adrenoceptor, where the beta(1H)-adrenoceptor is activated by noradrenaline and blocked with high affinity by beta-blockers and the beta(1L)-adrenoceptor is activated by drugs such as (-)-CGP 12177 and (-)-pindolol and blocked with low affinity by beta-blockers such as (-)-propranolol. The beta(1H)- and beta(1L)-adrenoceptor states are consistent with high- and low-affinity binding sites for (-)-[(3)H]-CGP 12177 radioligand binding found in cardiac muscle and recombinant beta(1)-adrenoceptors. 3. There are two common polymorphic locations of the beta(1)-adrenoceptor, at amino acids 49 (Ser/Gly) and 389 (Arg/Gly). Their existence has raised several questions, including their role in determining the effectiveness of heart failure treatment with beta-blockers. We have investigated the effect of long-term maximally tolerated carvedilol administration (> 1 year) on left ventricular ejection fraction (LVEF) in patients with non-ischaemic cardiomyopathy (mean left ventricular ejection fraction 23 +/- 7%; n = 135 patients). The administration of carvedilol improved LVEF to 37 +/- 13% (P < 0.005); however, the improvement was variable, with 32% of patients showing pound 5% improvement. Upon segregation of patients into Arg389Gly-beta(1)-adrenoceptors, it was found that carvedilol caused a greater increase in left ventricular ejection faction in patients carrying the Arg389 allele with Arg389Arg > Arg389Gly > Gly389Gly.

Urotensin II acutely increases myocardial length and distensibility: potential implications for diastolic function and ventricular remodeling

Urotensin II (U-II) is a cyclic peptide that may be involved in cardiovascular dysfunction. In the present study, the acute effects of U-II on diastolic properties of the myocardium were investigated. Increasing concentrations of U-II (10(-8) to 10(-6) M) were added to rabbit papillary muscles in the absence (n = 15) or presence of: (1) damaged endocardial endothelium (EE; n = 9); (2) U-II receptor antagonist, urantide (10(-5) M; n = 7); (3) nitric oxide (NO) synthase inhibitor, N(G)-Nitro-L-Arginine (10(-5) M; n = 9); (4) cyclooxygenase inhibitor, indomethacin (10(-5) M; n = 8); (5) NO synthase and cyclooxygenase inhibitors, N(G)-Nitro-L-Arginine (10(-5) M) and indomethacin (10(-5) M), respectively, (n = 8); or (6) protein kinase C (PKC) inhibitor, chelerythrine (10(-5) M; n = 9). Passive length-tension relations were constructed before and after a single concentration of U-II (10(-6) M; n = 3). U-II concentration dependently decreased inotropy and increased resting muscle length (RL). At 10(-6) M, active tension decreased 13.8 +/- 5.4%, and RL increased to 1.007 +/- 0.001 L/L (max). Correcting RL to its initial value resulted in an 18.1 +/- 3.0% decrease in resting tension, indicating decreased muscle stiffness, which was also suggested by the down and rightward shift of the passive length-tension relation. This effect remained unaffected by EE damage and PKC inhibition. In contrast, the presence of urantide and NO inhibition abolished the effects of U-II on myocardial stiffness, while cyclooxygenase inhibition significantly attenuated them. U-II decreases myocardial stiffness, an effect that is mediated by the urotensin-II receptor, NO, and prostaglandins. This represents a novel mechanism of acute neurohumoral modulation of diastolic function, suggesting that U-II is an important regulator of cardiac filling.

(-)-Adrenaline elicits positive inotropic, lusitropic, and biochemical effects through beta2 -adrenoceptors in human atrial myocardium from nonfailing and failing hearts, consistent with Gs coupling but not with Gi coupling

Activation of either coexisting beta1- or beta2 -adrenoceptors with noradrenaline or adrenaline, respectively, causes maximum increases of contractility of human atrial myocardium. Previous biochemical work with the beta2 -selective agonist zinterol is consistent with activation of the cascade beta2 -adrenoceptors-->Gsalpha-protein-->adenylyl cyclase-->cAMP-->protein kinase (PKA)-->phosphorylation of phospholamban, troponin I, and C-protein-->hastened relaxation of human atria from nonfailing hearts. However, in feline and rodent myocardium, catecholamines and zinterol usually do not hasten relaxation through activation of beta2 -adrenoceptors, presumably because of coupling of the receptors to Gi protein. It is unknown whether the endogenously occurring beta2 -adrenoceptor agonist adrenaline acts through the above cascade in human atrium and whether its mode of action could be changed in heart failure. We assessed the effects of (-)-adrenaline, mediated through beta2 -adrenoceptors (in the presence of CGP 20712A 300 nM to block beta1 -adrenoceptors), on contractility and relaxation of right atrial trabecula obtained from nonfailing and failing human hearts. Cyclic AMP levels were measured as well as phosphorylation of phospholamban, troponin I, and protein C with Western blots and the back-phosphorylation procedure. For comparison, beta1 -adrenoceptor-mediated effects of (-)-noradrenaline were investigated in the presence of ICI 118,551 (50 nM to block beta2 -adrenoceptors). The positive inotropic effects of both (-)-noradrenaline and (-)-adrenaline were accompanied by reductions in time to peak force and time to reach 50% relaxation. (-)-Adrenaline caused similar positive inotropic and lusitropic effects in atrial trabeculae from failing hearts. However, the inotropic potency, but not the lusitropic potency, of (-)-noradrenaline was reduced fourfold in atrial trabeculae from heart failure patients. Both (-)-adrenaline and (-)-noradrenaline enhanced cyclic AMP levels and produced phosphorylation of phospholamban, troponin I, and C-protein to a similar extent in atrial trabeculae from nonfailing hearts. The hastening of relaxation caused by (-)-adrenaline together with the PKA-catalyzed phosphorylation of the three proteins involved in relaxation, indicate coupling of beta2 -adrenoceptors to Gs protein. The phosphorylation of phospholamban at serine16 and threonine17 evoked by (-)-adrenaline through beta2 -adrenoceptors and by (-)-noradrenaline through beta1 -adrenoceptors was not different in atria from nonfailing and failing hearts. Activation of beta2 -adrenoceptors caused an increase in phosphorylase a activity in atrium from failing hearts further emphasizing the presence of the beta2 -adrenoceptor-Gsalpha-protein pathway in human heart. The positive inotropic and lusitropic potencies of (-)-adrenaline were conserved across Arg16Gly- and Gln27Glu-beta2 -adrenoceptor polymorphisms in the right atrium from patients undergoing coronary artery bypass surgery, chronically treated with beta1 -selective blockers. The persistent relaxant and biochemical effects of (-)-adrenaline through beta2 -adrenoceptors and of (-)-noradrenaline through beta1 -adrenoceptors in heart failure are inconsistent with an important role of coupling of beta2 -adrenoceptors with Gialpha-protein in human atrial myocardium.

Sex dimorphism in cardiac pathophysiology: experimental findings, hormonal mechanisms, and molecular mechanisms

The higher cardiovascular risk in men and post-menopausal women implies a protective action of estrogen. A large number of experimental studies have provided strong support to this concept. However, the recent clinical trials with negative outcomes regarding hormone replacement therapy call for "post hoc" reassessment of existing information, models, and research strategies as well as a summary of recent findings. Sex steroid hormones, in particular estrogen, regulate numerous processes that are related to the development and progression of cardiovascular disease through a variety of signaling pathways. Use of genetically modified models has resulted in interesting information on diverse actions mediated by steroid receptors. By focusing on experimental findings, we have reviewed hormonal, cellular, and signaling mechanisms responsible for sex dimorphism and actions of hormone replacement therapy and addressed current limitations and future directions of experimental research.