Neurohumoral mechanisms in heart failure: a central role for the renin-angiotensin system

More than a key-the pathological roles of SARS-CoV-2 spike protein in COVID-19 related cardiac injury

Cardiac injury is common in hospitalized coronavirus disease 2019 (COVID-19) patients and cardiac abnormalities have been observed in a significant number of recovered COVID-19 patients, portending long-term health issues for millions of infected individuals. To better understand how Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2, CoV-2 for short) damages the heart, it is critical to fully comprehend the biology of CoV-2 encoded proteins, each of which may play multiple pathological roles. For example, CoV-2 spike glycoprotein (CoV-2-S) not only engages angiotensin converting enzyme II (ACE2) to mediate virus infection but also directly activates immune responses. In this work, the goal is to review the known pathological roles of CoV-2-S in the cardiovascular system, thereby shedding lights on the pathogenesis of COVID-19 related cardiac injury.

Cancer antigen-125 and outcomes in acute heart failure: a systematic review and meta-analysis

Background

Carbohydrate antigen-125 (CA125) is an ovarian cancer marker, but recent work has examined its role in risk stratification in heart failure. A recent meta-analysis examined its prognostic value in heart failure generally. However, there has been no systematic evaluation of its role specifically in acute heart failure (AHF).

Methods

PubMed and EMBASE databases were searched until 11 May 2018 for studies that evaluated the prognostic value of CA125 in AHF.

Results

A total of 129 and 179 entries were retrieved from PubMed and EMBASE. Sixteen studies (15 cohort studies, 1 randomised trial) including 8401 subjects with AHF (mean age 71 years old, 52% male, mean follow-up 13 months, range of patients 525.1±598.2) were included. High CA125 levels were associated with a 68% increase in all-cause mortality (8 studies, HRs: 1.68, 95% CI 1.36 to 2.07; p<0.0001; I²: 74%) and 77% increase in heart failure-related readmissions (5 studies, HRs: 1.77, 95% CI 1.22 to 2.59; p<0.01; I²: 73%). CA125 levels were higher in patients with fluid overload symptoms and signs compared with those without them, with a mean difference of 54.8 U/mL (5 studies, SE: 13.2 U/mL; p<0.0001; I²: 78%).

Conclusion

Our meta-analysis found that high CA125 levels are associated with AHF symptoms, heart failure-related hospital readmissions and all-cause mortality. Therefore, CA125 emerges as a useful risk stratification tool for identifying high-risk patients with more severe fluid overload, as well as for monitoring following an AHF episode.

Cardiac disease and arrhythmogenesis: Mechanistic insights from mouse models

The mouse is the second mammalian species, after the human, in which substantial amount of the genomic information has been analyzed. With advances in transgenic technology, mutagenesis is now much easier to carry out in mice. Consequently, an increasing number of transgenic mouse systems have been generated for the study of cardiac arrhythmias in ion channelopathies and cardiomyopathies. Mouse hearts are also amenable to physical manipulation such as coronary artery ligation and transverse aortic constriction to induce heart failure, radiofrequency ablation of the AV node to model complete AV block and even implantation of a miniature pacemaker to induce cardiac dyssynchrony. Last but not least, pharmacological models, despite being simplistic, have enabled us to understand the physiological mechanisms of arrhythmias and evaluate the anti-arrhythmic properties of experimental agents, such as gap junction modulators, that may be exert therapeutic effects in other cardiac diseases. In this article, we examine these in turn, demonstrating that primary inherited arrhythmic syndromes are now recognized to be more complex than abnormality in a particular ion channel, involving alterations in gene expression and structural remodelling. Conversely, in cardiomyopathies and heart failure, mutations in ion channels and proteins have been identified as underlying causes, and electrophysiological remodelling are recognized pathological features. Transgenic techniques causing mutagenesis in mice are extremely powerful in dissecting the relative contributions of different genes play in producing disease phenotypes. Mouse models can serve as useful systems in which to explore how protein defects contribute to arrhythmias and direct future therapy.

A Functional Coupling Between Carbon Monoxide and Nitric Oxide Contributes to Increased Vasopressin Neuronal Activity in Heart Failure rats

Despite the pathophysiological importance of neurohumoral activation in patients with heart failure (HF), the precise underlying mechanisms contributing to elevated vasopressin (VP) activation in HF remains unknown. Carbon monoxide (CO) is a gaseous neurotransmitter in the central nervous system that stimulates VP neuronal firing activity. Recently, we showed that the excitatory effect of CO on VP neurons in the hypothalamic paraventricular nucleus (PVN) was mediated by inhibition of nitric oxide (NO). Given that previous studies showed that VP neuronal activity is enhanced, whereas NO inhibitory signaling is blunted in HF rats, we tested whether an enhanced endogenous CO availability within the PVN contributes to elevated VP neuronal activity and blunted NO signaling in HF rats. We found that both haeme-oxygenase 1 (the CO-synthesizing enzyme) protein and mRNA expression levels were enhanced in the PVN of HF compared with sham rats (∼18% and ∼38%, respectively). We report that in sham rats, bath application of a CO donor (tricarbonyldichlororuthenium dimer) increased the firing activity of identified PVN VP neurons (P < .05), whereas inhibition of endogenous CO production (Tin-protoporphyrin IX [SnPP]) failed to affect neuronal activity. In HF rats, however, SnPP decreased VP activity (P < .05), an effect that was occluded by previous NO synathase blockade NG-nitro-larginine methyl ester. Finally, we found that SnPP increased the mean frequency of γ-aminobutyric acid inhibitory postsynaptic currents in VP neurons in HF (P < .05) but not sham rats. Our results support an enhanced endogenous CO excitatory signaling in VP neurons, which likely contributes to blunted NO and γ-aminobutyric acid inhibitory function in HF rats.

Splice variant-specific silencing of angiotensin II type 1a receptor messenger RNA by RNA interference in vascular smooth muscle cells

In the rat, two distinct angiotensin II type 1a (rAT(1a)) receptor mRNAs are synthesized from a single rAT(1a) receptor gene by alternative splicing. These two transcripts are comprised of exons 1, 2, and 3 (E1,2,3) or exons 1 and 3 (E1,3). Since exon 3 contains the entire coding region, both transcripts encode identical rAT(1a) receptors. Real-time PCR revealed that in rat aortic smooth muscle cells (RASMC), E1,2,3 mRNA accounted for 69.5+/-0.9% of total rAT(1a) receptor mRNA. The aim of this study was to use RNA interference (RNAi) to selectively silence the rAT(1a) receptor splice variants. Forty-eight hour treatment of RASMC with E1,3-targeting siRNA (10nM; S1(E1,3)) resulted in a 91.2+/-0.5% (n=3, P<0.001) reduction in E1,3 mRNA and a 19.0+/-3.0% (n=4, P<0.05) reduction in AT(1) receptor specific binding compared with cells treated with a non-silencing control siRNA; under these conditions, no effect was observed on levels of E1,2,3 mRNA. Conversely, treatment with E1,2,3-targeting siRNA (S2(E2)) had no effect on E1,3 mRNA while reducing E1,2,3 mRNA by 73.9+/-4.2% (n=3, P<0.001), and AT(1) receptor binding by 39.4+/-5.4% (n=4, P<0.001) compared with control. These data show that the majority of functional AT(1) receptor expression in RASMC derives from the E1,2,3 splice variant. These data also demonstrate that rAT(1a) receptor mRNA can be silenced in a splice-variant specific manner using siRNA in RASMC, thus providing an excellent model system for investigating the role of alternative splicing in the regulation of rAT(1a) receptor expression.

Molecular cloning and sequencing of the cDNA for rat mesenteric arterial bed elastase-2, an angiotensin II-forming enzyme

A 28.5-kD protein expressed in rat mesenteric arterial bed (MAB) perfusate with angiotensin II-forming ability was previously characterized. This protein, a member of the elastase-2 family of enzymes, seems to be the only representative of this family of proteases to be secreted outside the digestive tract and implicated in the generation of angiotensin II. The cloning and sequencing of the cDNA for the rat MAB elastase-2 by using reverse transcription polymerase chain reaction are reported. The sequence of this cDNA was found to be identical to the sequence of the rat pancreatic elastase-2; the cDNA is 909 nucleotides in length plus a poly (A) tail and encodes a preproenzyme of 271 amino acids. Analysis of the putative amino acids in the extended angiotensin I binding site of the rat MAB elastase-2 reveals features that could explain the dipeptidyl carboxypeptidase-like activity required for efficient conversion of angiotensin I to angiotensin II. Additionally, the sequence reveals structural features that could contribute to the lack of activity of this enzyme toward angiotensin II. Rat MAB elastase-2 was expressed in mesenteric arteries and lung but not in aorta. These results may also indicate that rat MAB elastase-2 is expressed in resistance vessels but not in conduit vessels.

Perindopril treatment for congestive heart failure

Congestive heart failure (CHF) is the most common and lethal consequence of atherosclerotic cardiovascular disease, with a prevalence estimated between 1% and 10%, and very high associated mortality. Preventing the continued progression of established heart failure and improving the prognosis for patients with this disease is difficult, but angiotensin-converting enzyme (ACE) inhibitors have been shown to be effective in reducing mortality in patients with CHF. In a review of the worldwide literature of the efficacy and safety of perindopril erbumine for the treatment of patients with CHF, once-daily treatment with this ACE inhibitor was shown to be effective in patients with CHF of all severities. Its use is associated with a low risk of first-dose hypotension and no unwanted effects on blood pressure in normotensive patients. Perindopril also improves arterial compliance and reverses left ventricular hypertrophy in patients with hypertension. It is well tolerated and has no significant effects on heart rate, indexes of renal function, or plasma lipid profile. It also has no clinically significant interactions with other drugs, including digoxin, likely to be taken by patients with CHF.

Candesartan in heart failure--assessment of reduction in mortality and morbidity (CHARM): rationale and design. Charm-Programme Investigators

BACKGROUND

Chronic heart failure (CHF) is an increasing burden to health care. Pharmacological treatment with angiotensin-converting enzyme (ACE) inhibitors and beta blockers improve survival and reduce hospitalizations in patients with low left ventricular ejection fraction (LVEF). Despite these therapies, morbidity and mortality remains problematic. Furthermore, 30% to 50% of patients with CHF have a preserved LVEF. It is not known if treatments are of benefit in this group.

DESIGN

Candesartan in Heart Failure-Assessment of Reduction in Mortality and Morbidity (CHARM) is a program designed to investigate the clinical usefulness of the long-acting angiotensin II type 1 receptor blocker, candesartan cilexetil, in a broad spectrum of patients with symptomatic heart failure. Patients with systolic dysfunction, tolerant or intolerant to an ACE-inhibitor, and patients with preserved systolic function are included. Specifically, the CHARM program consists of 3 independent, parallel, placebo-controlled studies in patients with (1) LVEF less than or equal to 40%, ACE-inhibitor treated (n = 2,300); (2) LVEF less than or equal to 40%, ACE-inhibitor intolerant (n = 1,700); (3) LVEF greater than 40%, not treated with ACE inhibitors (n = 2,500). The 3 studies will be combined to evaluate the effect of candesartan cilexetil on all-cause mortality in the broad spectrum of symptomatic heart failure. The primary objective in each trial is to evaluate the effects on the combined endpoint of cardiovascular mortality or CHF hospitalization. Other endpoints include the effects on myocardial infarction, all-cause hospitalization, and resource utilization. CHARM is intended to randomize 6,500 patients with symptomatic heart failure from 26 countries in Europe, the United States, Canada, South Africa, and Australia. The CHARM program started to enroll patients in March 1999. The follow-up period is a minimum of 2 years. The study is expected to end in the third quarter of 2002.

Perindopril effects on angiotensin I elimination in lung after experimental myocardial injury induced by intracoronary microembolization in rats

The objective of the study was to determine whether angiotensin (Ang) I elimination in lung circulation depends on the degree of myocardial damage with and without early long-term perindopril treatment in a rat model of myocardial injury induced by intracoronary microembolization. Twenty-one days after surgery, steady-state arterial [125I]-Ang I and [125I]-Ang II blood concentrations were measured after high-performance liquid chromatography separation during i.v. infusion of [125I]-Ang I in three groups of male Wistar conscious rats: (a) sham-operated rats receiving saline (sham group, n = 6); (b) rats after coronary microembolization receiving saline (saline group, n = 7); and (c) rats after coronary microembolization receiving perindopril (2 mg/kg/day; from days 2-20 after embolization; perindopril group, n = 6). Ang I clearance and the Ang I-to-Ang II concentration ratio (R) were estimated. The embolization per se resulted in focal fibrosis, appearance of hypertrophic and dystrophic cardiac myocytes, and was accompanied by increased Ang I clearance (1,479 vs. 314 ml/min in sham group), 1.8-fold decreased [125I]-Ang II arterial level, and decreased R (0.5 vs. 1.2 in sham group; p < 0.05). Only Ang I concentrations and R were correlated with number of scars (r = -0.77; p < 0.05; and r = -0.82; p < 0.01, respectively). Captopril bolus (1 mg/kg, i.v.) caused similar reduction in [125I]-Ang II blood concentration in both sham and saline groups, but a significant increase of [125I]-Ang I blood concentration was detected in the sham group only. Thus in rats with coronary microembolization, a higher proportion of Ang I in lung circulation is eliminated by pathways independent of angiotensin-converting enzyme. In the perindopril group, a reduced number of scars (seven vs. 17 per slice in the saline group; p < 0.05), density of dystrophic and hypertrophic cardiac myocytes, and increased content of cell glycogen were observed. It was accompanied by normalized arterial [125I]-Ang I concentration, Ang I clearance, and R; [125I]-Ang II concentration tended to that in sham group. Only in the sham and perindopril groups was there significant correlation between Ang I and Ang II concentrations. The clear relation between number of scars per slice and R (r = -0.83; p < 0.01) was observed in all rats with embolized coronary vessels (saline and perindopril groups together). In conclusion, in this experimental, model Ang I elimination in the lung circulation was directly related to the degree of myocardial damage. Early perindopril treatment prevented maladaptive changes in Ang I processing and led to significant reduction of the undesirable aftereffects of myocardial tissue damage. Our data demonstrate the cardioprotective action of perindopril based on its beneficial influence on the renin-angiotensin system disturbances.

Time-related adaptations in plasma neurohormone levels and hemodynamics after myocardial infarction in the rat

BACKGROUND

Neurohormonal activation plays an important role in the progression of heart failure. In this study, we investigated the progression of neurohormonal activation in conjunction with the hemodynamic status of the rat after myocardial infarction (MI).

METHODS AND RESULTS

Male Wistar rats were subjected to sham or MI surgery. At 1, 3, 5, and 13 weeks after surgery, cardiac output (CO), mean arterial pressure (MAP), and total peripheral resistance (TPR), were measured. In separate groups of rats, blood was sampled at 1, 5, and 13 weeks after surgery and analyzed for various neurohormones. At 1 week after surgery, CO and TPR were not altered in MI rats, but plasma neurohormonal levels were elevated. At 3 and 5 weeks after surgery, reduced CO, increased TPR, and normal MAP were measured in MI rats compared to sham rats, but only endothelin levels were elevated. At 13 weeks after surgery, MAP was reduced in MI rats and CO and TPR were comparable between groups. Neurohormonal activation was again apparent in MI rats.

CONCLUSIONS

Myocardial infarction in the rat induces early neurohormonal activation, which normalizes hemodynamic parameters. A compensatory phase follows. At 13 weeks after MI, plasma concentrations of neurohormones are again elevated, perhaps as a sign of transition to decompensation.

Pathophysiology of heart failure update: the role of neurohumoral activation in the progression of heart failure

Understanding the pathophysiologic mechanisms responsible for producing heart failure is necessary before effective treatments can be developed that increase survival and improve quality of life. Recent advances in the treatment of heart failure can be traced directly to improved appreciation of the role of neurohumoral activation in the pathophysiology of heart failure. Initially adaptive, neurohumoral activation ultimately results in a series of overadjustments that actively participate in the progression of heart failure. In this article, the role of neurohumoral activation, ventricular remodeling, and various peripheral vascular abnormalities in the pathophysiology of heart failure are explored.

Regulation of cytosolic proteins binding cis elements in the 5' leader sequence of the angiotensin AT1 receptor mRNA

RNA binding proteins (BPs) have been identified which bind within a -271 to -174 nt domain in the 5' leader sequence (5'LS) of the rat type 1 angiotensin (AT1) receptor mRNA and which encompass RNA cis elements upstream of -239. A 100 kDa RNA-protein complex is observed by UV-crosslinking in several tissues including brain, lung, and spleen. 5'LS RNA transcripts of the 1a and 1b AT receptor subtypes are strong competitors of 5'LS-protein complex formation. In contrast, antisense 5'LS AT1a transcripts, plasmid transcripts, poly U and poly A RNAs, or 5'LS AT1a cDNA are poor competitors. Deoxycorticosterone acetate (DOCA) decreased 5'LS-BP activities in the forebrain and hypothalamus under conditions known to significantly increase AT1 receptor expression. DOCA had no effect on 5'LS-BP activities in the pituitary which correlates with its lack of effect on pituitary AT1 receptor expression. These results indicate that DOCA differentially regulates 5'LS-BP activities in a tissue-specific manner and suggest that physiologically mediated changes in AT1 receptor expression are mediated by alterations in 5'LS-BP activities, which represents a previously unrecognized level of regulation for the renin angiotensin system.

Beneficial effects of 1-year captopril therapy in children with chronic aortic regurgitation who have no symptoms

OBJECTIVE

This prospective study was performed to assess the effects of 1 year of angiotensin-converting enzyme inhibition with captopril in 20 children (mean age 14.3+/-2.3 years) with asymptomatic chronic aortic regurgitation.

METHODS AND RESULTS

At 12 months patients receiving captopril had a significant reduction in left ventricular end-diastolic and end-systolic dimensions (57+/-9.3 vs 51+/-9.5 mm, p < 0.001; 35.4+/-6.1 vs 32+/-6.8 mm, p < 0.001), end-diastolic and end-systolic volume indexes (111+/-36 vs 94+/-29 ml/m2, p < 0.001; 35+/-13 vs 30+/-12 ml/m2, p < 0.001, respectively), and mass index (138+/-37 vs 109+/-32 gm/m2, p < 0.0001) determined by two-dimensional echocardiography. Meridian (p < 0.01) and circumferential (p < 0.0001) wall stresses also decreased significantly with therapy. Significant reduction (27.8%, p < 0.0001) was achieved in regurgitant fraction with captopril.

CONCLUSIONS

These data show that the long-term therapy with angiotensin-converting enzyme inhibitors is able to reverse left ventricular dilation and hypertrophy and suggest that such therapy has the potential to favorably influence the natural history of the disease in children.

Shared determinants of receptor binding for subtype selective, and dual endothelin-angiotensin antagonists on the AT1 angiotensin II receptor

Site-directed interspecies amino acid exchange was used to compare the binding determinants of a novel dual endothelial-angiotensin receptor ligand, L-746,072, with type-1 angiotensin receptor (AT1) selective antagonists on AT receptors expressed in COS cells. These studies suggest that residues on AT receptors which are non-conserved between amphibian and mammalian species play a greater role in subtype selective ligand recognition than for dual receptor ligands. These data also support the hypothesis that a common non-peptide binding site exists within transmembrane domains on peptidergic receptors.