The heart regulates the endocrine response to heart failure: cardiac contribution to circulating neprilysin

A comprehensive review of the literature on CD10: its function, clinical application, and prospects

CD10, a zinc-dependent metalloprotease found on the cell surface, plays a pivotal role in an array of physiological and pathological processes including cardiovascular regulation, immune function, fetal development, pain response, oncogenesis, and aging. Recognized as a biomarker for hematopoietic and tissue stem cells, CD10 has garnered attention for its prognostic potential in the progression of leukemia and various solid tumors. Recent studies underscore its regulatory significance and therapeutic promise in combating Alzheimer's disease (AD), and it is noted for its protective role in preventing heart failure (HF), obesity, and type-2 diabetes. Furthermore, CD10/substance P interaction has also been shown to contribute to the pain signaling regulation and immunomodulation in diseases such as complex regional pain syndrome (CRPS) and osteoarthritis (OA). The emergence of COVID-19 has sparked interest in CD10's involvement in the disease's pathogenesis. Given its association with multiple disease states, CD10 is a prime therapeutic target; inhibitors targeting CD10 are now being advanced as therapeutic agents. This review compiles recent and earlier literature on CD10, elucidating its physicochemical attributes, tissue-specific expression, and molecular functions. Furthermore, it details the association of CD10 with various diseases and the clinical advancements of its inhibitors, providing a comprehensive overview of its growing significance in medical research.

Impact of sacubitril/valsartan on cardiac and systemic hypoxia in chronic heart failure

In heart failure patients with reduced ejection fraction, Sacubitril/valsartan (S/V) increased proBNP T71 glycosylation, which is regulated negatively by hypoxia via miR-30a in vitro. Using a cohort of 73 HFrEF patients who were transitioned from standard HF medication to S/V, we found that the increase in proBNP T71 glycosylation after S/V was associated with a decrease in cardiac hypoxia. We further found that plasma levels of K709-acteylated HIF1α, HIF-regulated and HIF-independent biomarkers also evolved consistently with a decrease in hypoxia. We further confirmed that biomarker changes were related to hypoxia, in a rat model subjected to isobaric hypoxia. We measured them in rats subjected to isobaric hypoxia. Overall, these data strongly suggest that optimally treated HFrEF patients exhibited subclinical hypoxia that is improved by S/V. The data also posit proBNP T71 glycosylation as a biomarker of cardiac hypoxia.

Neprilysin Inhibition in the Prevention of Anthracycline-Induced Cardiotoxicity

Anthracycline-induced cardiotoxicity (AIC) poses a clinical challenge in the management of cancer patients. AIC is characterized by myocardial systolic dysfunction and remodeling, caused by cardiomyocyte DNA damage, oxidative stress, mitochondrial dysfunction, or renin-angiotensin-aldosterone system (RAAS) dysregulation. In the past decade, after positive results of a PARADIGM-HF trial, a new class of drugs, namely angiotensin receptor/neprilysin inhibitors (ARNi), was incorporated into the management of patients with heart failure with reduced ejection fraction. As demonstrated in a variety of preclinical studies of cardiovascular diseases, the cardioprotective effects of ARNi administration are associated with decreased oxidative stress levels, the inhibition of myocardial inflammatory response, protection against mitochondrial damage and endothelial dysfunction, and improvement in the RAAS imbalance. However, data on ARNi's effectiveness in the prevention of AIC remains limited. Several reports of ARNi administration in animal models of AIC have shown promising results, as ARNi prevented ventricular systolic dysfunction and electrocardiographic changes and ameliorated oxidative stress, mitochondrial dysfunction, endoplasmic reticulum stress, and the inflammatory response associated with anthracyclines. There is currently an ongoing PRADAII trial aimed to assess the efficacy of ARNi in patients receiving breast cancer treatment, which is expected to be completed by late 2025.

Molecular mechanisms of sacubitril/valsartan in cardiac remodeling

Cardiovascular diseases have become a major clinical burden globally. Heart failure is one of the diseases that commonly emanates from progressive uncontrolled hypertension. This gives rise to the need for a new treatment for the disease. Sacubitril/valsartan is a new drug combination that has been approved for patients with heart failure. This review aims to detail the mechanism of action for sacubitril/valsartan in cardiac remodeling, a cellular and molecular process that occurs during the development of heart failure. Accumulating evidence has unveiled the cardioprotective effects of sacubitril/valsartan on cellular and molecular modulation in cardiac remodeling, with recent large-scale randomized clinical trials confirming its supremacy over other traditional heart failure treatments. However, its molecular mechanism of action in cardiac remodeling remains obscure. Therefore, comprehending the molecular mechanism of action of sacubitril/valsartan could help future research to study the drug’s potential therapy to reduce the severity of heart failure.

Soluble neprilysin and survival in critically ill patients

Background

Critically ill patients admitted to an intensive care unit (ICU) exhibit a high mortality rate irrespective of the initial cause of hospitalization. Neprilysin, a neutral endopeptidase degrading an array of vasoactive peptides became a drug target within the treatment of heart failure with reduced ejection fraction. The aim of this study was to analyse whether circulating levels of neprilysin at ICU admission are associated with 30 day mortality.

Methods and results

In this single‐centre prospective observational study, 222 consecutive patients admitted to a tertiary ICU at a university hospital were included. Blood was drawn at admission and soluble neprilysin levels were measured using ELISA. In the total cohort, soluble neprilysin levels did not differ according to survival status after 30 days as well as type of admission. However, in patients after surgery or heart valve intervention, 30 day survivors exhibited significantly lower circulating neprilysin levels as compared to those who died within 30 days (660.2, IQR: 156.4–2512.5 pg/mL vs. 6532.6, IQR: 1840.1–10 000.0 pg/mL; P = 0.02). Soluble neprilysin predicted mortality independently from age, gender, and commonly used scores of risk‐prediction (EuroSCORE II, STS‐score, and SAPS II score). Additionally, soluble neprilysin was markedly elevated in patients with sepsis and septic shock (P < 0.05).

Conclusion

At the time of ICU admission, circulating levels of neprilysin independently predicted 30 day mortality in patients following cardiac surgery or heart valve intervention, but not in critically ill medical patients. Furthermore, patients suffering from sepsis and septic shock displayed significantly increased circulating neprilysin levels.

Novel O-[11C]-methylated derivatives of the neprilysin inhibitor sacubitril: Radiosynthesis, autoradiography and plasma stability evaluation

INTRODUCTION

The O-[11C]methylated derivatives of the clinically used neprilysin inhibitor (NEPi) sacubitril ([11C]SacOMe, (2R,4S)-ethyl 5-([biphenyl]-4-yl)-4-(4-[11C]methoxy-4-oxobutanamido)-2-methylpentanoate) and LBQ657 ([11C]MeOLBQ, (2R,4S)-5-(biphenyl-4-yl)-4-[(3-carboxypropionyl)amino]-2-methylpentanoic acid [11C]methyl ester and [11C]LBQOMe, (2R,4S)-5-(biphenyl-4-yl)-4-[(4-[11C]methoxy-4-oxobutanamido)]-2-methylpentanoic acid) were evaluated to determine their potential as PET imaging tracers and investigate the effect of such labeling esterification on neprilysin (NEP) binding.

METHODS

[11C]MeOLBQ, [11C]SacOMe and [11C]LBQOMe were synthesized by O-[11C]methylation using [11C]methyl triflate. Binding of these radiolabeled derivatives (5 nM) were assessed by autoradiography on rat neprilysin rich kidney slices with or without 10 μM NEPi (thiorphan or sacubitril) for 20 min at 37 °C. [11C]LBQOMe was further tested for binding selectivity in the presence of 10 μM of angiotensin-converting enzyme inhibitor (ACEi, captopril) or angiotensin II AT1 receptor blocker (AT1R, losartan). Radioligands were evaluated for their in vitro stability up to 20 min after incubation at 37 °C in rat and human plasma by reverse-phase column-switch HPLC. Non-radioactive SacOMe incubated in rat and human plasma was analyzed by HPLC-coupled with high resolution mass spectrometry (HRMS) to confirm the metabolites' identity. [11C]SacOMe main labeled metabolite was further analyzed by HPLC after incubation in rat kidney slices at 37 °C.

RESULTS

The novel [11C]SacOMe and [11C]LBQOMe were produced in 32 ± 3% RCY and 15 ± 6% at EOS (decay-corrected from [11C]CO2, n = 3), high molar activity (407 ± 92 GBq/μmol and 260 ± 92 GBq/μmol), and high chemical (≥90%) and radiochemical (≥99%) purities in a total synthesis time of 31 and 34 min, respectively. High accumulation of [11C]SacOMe and [11C]LBQOMe in kidneys was completely blocked (>99.9%) by pre-incubation with NEPi, whereas [11C]MeOLBQ displayed negligible uptake in autoradiography studies. [11C]LBQOMe binding was not affected by saturating doses of losartan or captopril indicating binding selectivity for NEP. While [11C]SacOMe and [11C]LBQOMe were stable in human plasma (>92%) even after 20 min incubation at 37 °C, rat plasma analyses exhibited >95% biotransformation of [11C]SacOMe, 40% of [11C]LBQOMe and >80% loss of the 11C-methyl group of [11C]MeOLBQ after 5 min of incubation. Comparable results using the non-radioactive SacOMe were obtained by HPLC-HRMS. Radio-HPLC analysis of the extracted activity of rat kidney slices incubated with [11C]SacOMe demonstrated that >95% of the radioactive signal corresponded to [11C]LBQOMe as the main metabolite.

CONCLUSION

The desethyl active metabolite of [11C]SacOMe, [11C]LBQOMe, displayed stability in human plasma, binding selectivity for neprilysin over ACE or AT1R in rat kidney slices. Rapid plasmatic dealkylation at the 2-methylbutanoic acid position is in line with the necessity of incorporating the labeling group on oxobutanoic acid side in the strategy to develop a stable O-alkylated labeled derivative of sacubitril.

Low- vs high-dose ARNI effects on clinical status, exercise performance and cardiac function in real-life HFrEF patients

Purpose

Only a few studies are available on dose-related effects of sacubitril/valsartan (angiotensin receptor neprilysin inhibition (ARNI)) in real-life patients with heart failure and reduced ejection fraction (HFrEF). We sought to investigate clinical and functional effects in real-life HFrEF patients receiving ARNI at a different cumulative dose.

Methods

This was an observational study in consecutive outpatients admitted for HFrEF from October 2017 to June 2019. The PARADIGM criteria were needed for enrolment. ARNI was uptitrated according to blood pressure, drug tolerability, renal function and kaliemia. At least 10-month follow-up was required in each patient. Clinical assessment, Kansas City Cardiomyopathy Questionnaire (KCCQ) score, 6-min walk test and strain echocardiography were performed in each patient on a regular basis during the observational period. At the end of the study, patients were divided into two groups based on the median yearly dose of the ARNI medication.

Results

A total of 90 patients, 64 ± 11 years, 82% males, were enrolled. The cut-off dose was established in 75 mg BID, and the study population was divided into group A (≤ 75 mg), 52 patients (58%), and group B (> 75 mg), 38 patients (42%). The follow-up duration was 12 months (range 11–13). NYHA class, KCCQ score and 6MWT performance ameliorated in both groups, with a quicker time to benefit in group B. The proportion of patients walking > 350 m increased from 21 to 58% in group A (p < 0.001), and from 29 to 82% in group B (p < 0.001). A positive effect was also disclosed in the left ventricular remodelling, strain deformation and diastolic function.

Conclusion

One-year ARNI treatment was effective in our real-life HFrEF patient population, leading to clinical and functional improvement in both study groups, slightly greater and with a shorter time to benefit in group B.

Supplementary information

The online version contains supplementary material available at 10.1007/s00228-021-03210-0.

Circulating heart failure biomarkers beyond natriuretic peptides: review from the Biomarker Study Group of the Heart Failure Association (HFA), European Society of Cardiology (ESC)

New biomarkers are being evaluated for their ability to advance the management of patients with heart failure. Despite a large pool of interesting candidate biomarkers, besides natriuretic peptides virtually none have succeeded in being applied into the clinical setting. In this review, we examine the most promising emerging candidates for clinical assessment and management of patients with heart failure. We discuss high-sensitivity cardiac troponins (Tn), procalcitonin, novel kidney markers, soluble suppression of tumorigenicity 2 (sST2), galectin-3, growth differentiation factor-15 (GDF-15), cluster of differentiation 146 (CD146), neprilysin, adrenomedullin (ADM), and also discuss proteomics and genetic-based risk scores. We focused on guidance and assistance with daily clinical care decision-making. For each biomarker, analytical considerations are discussed, as well as performance regarding diagnosis and prognosis. Furthermore, we discuss potential implementation in clinical algorithms and in ongoing clinical trials.

Exposing the High Heterogeneity of Circulating Pro B-Type Natriuretic Peptide Fragments in Healthy Individuals and Heart Failure Patients

BACKGROUND

The high molecular complexity of variably O-glycosylated and degraded pro B-type natriuretic peptide (proBNP) derived molecular forms challenges current immunoassays. Antibodies used show pronounced differences in cross-reactivities with these circulating fragments, which still need to be better characterized on a molecular level. To pave the way for advanced quantitative assays in the future, it is critical to fully understand these circulating forms.

METHODS

Plasma samples were collected from 8 heart failure (HF) patients and 2 healthy controls. NT-proBNP and proBNP were purified by immunoprecipitation and analyzed by nano-flow liquid chromatography coupled to high-resolution mass spectrometry. Fragments formed during proteolysis in solution digestion were distinguished from naturally occurring peptides by using an 18O stable isotope labeling strategy.

RESULTS

We detected 16 previously unknown circulating fragments of proBNP peptides (9 of which are located in the N-terminal and 7 in the C-terminal region), revealing a more advanced state of degradation than previously known. Two of these fragments are indicative of either unidentified processing modes or a far-reaching C-terminal degradation (or a combination thereof) of the precursor proBNP.

CONCLUSIONS

Our results further restrict ideal target epitopes for immunoassay antibodies and expand the current thinking of diversity, degradation, and processing of proBNP, as well as the distribution of circulating forms.

Neprilysin expression and functions in development, ageing and disease

Neprilysin (NEP) is an integral membrane-bound metallopeptidase with a wide spectrum of substrates and physiological functions. It plays an important role in proteolytic processes in the kidney, cardiovascular regulation, immune response, cell proliferation, foetal development etc. It is an important neuropeptidase and amyloid-degrading enzyme which makes NEP a therapeutic target in Alzheimer's disease (AD). Moreover, it plays a preventive role in development of cancer, obesity and type-2 diabetes. Recently a role of NEP in COVID-19 pathogenesis has also been suggested. Despite intensive research into NEP structure and functions in different organisms, changes in its expression and regulation during brain development and ageing, especially in age-related pathologies, is still not fully understood. This prevents development of pharmacological treatments from various diseases in which NEP is implicated although recently a dual-acting drug sacubitril-valsartan (LCZ696) combining a NEP inhibitor and angiotensin receptor blocker has been approved for treatment of heart failure. Also, various natural compounds capable of upregulating NEP expression, including green tea (EGCG), have been proposed as a preventive medicine in prostate cancer and AD. This review summarizes the existing literature and our own research on the expression and activity of NEP in normal brain development, ageing and under pathological conditions.

Neprilysin as a Biomarker: Challenges and Opportunities

Neprilysin (NEP) inhibition is a successful novel therapeutic approach in heart failure with reduced ejection fraction. Assessing individual NEP status might be important for gathering insights into mechanisms of disease and optimising individualised patient care. NEP is a zinc-dependent multisubstrate-metabolising oligoendopeptidase localised in the plasma membrane with the catalytic site facing the extracellular space. Although NEP activity in vivo is predominantly tissue-based, NEP can be released into the circulation via ectodomain shedding and exosomes. Attempts to determine circulating NEP concentrations and activity have not yet resulted in convincingly coherent results relating NEP biomarkers to heart failure disease severity or outcomes. NEP is naturally expressed on neutrophils, opening up the possibility of measuring a membrane-associated form with integrity. Small studies have linked NEP expression on neutrophils with inflammatory state and initial data might indicate its role in heart failure with reduced ejection fraction. Future studies need to assess the regulation of systemic NEP activity, which is assumed to be tissue-based, and the relationship of NEP activation with disease state. The relationship between tissue NEP activity and easily accessible circulating NEP biomarkers and the impact of the latter remains to be established.

Heart Failure With Reduced Ejection Fraction Is Characterized by Systemic NEP Downregulation

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The kidneys might play a crucial role in regulating systemic NEP actions based on 20 to 100 higher NEP content and activity of the kidneys compared with any other organ.

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Tissue NEP expression seems to be downregulated and translates into reduced tissue protein concentrations and activity in HF.

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Neither plasma or liquor NEP concentrations and activities reflect tissue NEP regulation; therefore, using NEP as a circulating biomarker seems to be questionable.

Based on the investigation of neprilysin (NEP) regulation in a translational porcine model of chronic heart failure (HF), this study concluded: 1) that kidneys might play a crucial part in systemic NEP regulation based on 20 to 100 higher NEP content and/or activity compared with any other organ; 2) NEP seems to be downregulated under HF conditions; and 3) that the value of plasma NEP concentrations and activity as biomarkers is questionable. For the first time, these data provide basic knowledge on HF-related pathophysiological alterations of the NEP system and contribute to understanding the mechanism of action of angiotensin-receptor neprilysin-inhibitors, which remains elusive despite broad clinical applications.

Autoregulation of Pulsatile Bioprosthetic Total Artificial Heart is Involved in Endothelial Homeostasis Preservation

Pulsatile Carmat bioprosthetic total artificial heart (C-TAH) is designed to be implanted in patients with biventricular end-stage heart failure. Since flow variation might contribute to endothelial dysfunction, we explored circulating endothelial biomarkers after C-TAH implantation in seven patients and compared the manual and autoregulated mode. Markers of endothelial dysfunction and regeneration were compared before and during a 6- to 9-month follow-up after implantation. The follow-up was divided into three periods (< 3, 3-6, and > 6 months) and used to estimate the temporal trends during the study period. A linear mixed model was used to analyze repeated measures and association between tested parameters according to the mode of C-TAH and the time. Relevance of soluble endoglin (sEndoglin) level increase has been tested on differentiation and migration potential of human vasculogenic progenitor cells (endothelial colony forming cells [ECFCs]). Normal sEndoglin and soluble endothelial protein C receptor (sEPCR) levels were found in patients after implantation with autoregulated C-TAH, whereas they significantly increased in the manual mode, as compared with pretransplant values (p = 0.005 and 0.001, respectively). In the autoregulated mode, a significant increase in the mobilization of cytokine stromal cell-derived factor 1 was found (p = 0.03). After adjustment on the mode of C-TAH, creatinine or C-reactive protein level, sEndoglin, and sEPCR, were found significantly associated with plasma total protein levels. Moreover, a significant decrease in pseudotubes formation and migration ability was observed in vitro in ECFCs receiving sEndoglin activation. Our combined analysis of endothelial biomarkers confirms the favorable impact of blood flow variation achieved with autoregulation in patients implanted with the bioprosthetic total artificial heart.

Cardiorenal Interactions Revisited: How to Improve Heart Failure Outcomes in Patients With Chronic Kidney Disease

PURPOSE OF THE REVIEW

To summarize current advances in the understanding and management of heart failure (HF) in patients with advanced chronic kidney disease (CKD).

RECENT FINDINGS

Diagnosis of HF and treatment of congestion are crucial in the management of patients with advanced CKD to reduce symptoms, preserve organ function, and improve outcomes. Echocardiography and cardiovascular biomarkers may help to differentiate cardiac from non-cardiac components of overhydration. Renal replacement therapy or ultrafiltration may be required to treat congestion. Furthermore, patients with advanced CKD are frequently undertreated with disease-modifying HF therapies, but the use of beta-blockers and ACEi should be considered under close monitoring of kidney function and serum potassium. The use of the new oral potassium binders may translate into improved outcomes. The treatment of HF in patients with advanced CKD requires a multi-disciplinary approach. New diagnostic and therapeutic strategies are under evaluation and may contribute to improved outcomes.

The circulating form of neprilysin is not a general biomarker for overall survival in treatment-naïve cancer patients

The transmembrane zink-metalloendopeptidase neprilysin (NEP) is implicated in cardiovascular disease but also tumor biology. The aim of the study was to investigate the relationship of circulating NEP (cNEP) levels with established cardiovascular biomarkers and its effect on overall survival in an unselected cohort of treatment-naïve cancer patients. 555 consecutive cancer patients prior anticancer therapy were enrolled prospectively. NEP levels were determined alongside routine laboratory parameters, established cardiac biomarkers, i.e. NT-proBNP, hsTnT, MR-proANP, MR-proADM, CT-proET-1 and Copeptin, and inflammatory parameters, i.e. CRP, IL-6 and SAA, in venous plasma samples. All-cause mortality was the primary endpoint. cNEP levels of 276 pg/ml (IQR: 0–5981) displayed a weak inverse correlation with age [r = −0.12, p = 0.023] and inflammatory status [r = −0.14, p = 0.007 CRP; r = −0.20, p < 0.001 IL-6 and r = −0.18, p < 0.001 SAA]. cNEP was comparable between different tumor entities and stages and not related to functional parameters of other organ systems as kidney, liver or especially the heart. Moreover, cNEP was not associated with overall survival in the total cohort [adj.HR for ln (cNEP) 1.00, 95% CI: 0.94–1.06, p = 0.887] but in myelodysplatic malignancies [adj.HR for ln (cNEP) 1.27, 95% CI: 1.01–1.61, p = 0.044]. In conclusion, cNEP lacks association with outcome but for myelodysplastic disease. cNEP shows no correlation with established cardiovascular biomarkers related to prognosis, thereby holding a limited potential as a biomarker in cardio-oncology.

Neprilysin Inhibitors: Filling a Gap in Heart Failure Management, Albeit Amidst Controversy and at a Significant Cost

Dual angiotensin and neprilysin inhibition using the combination drug sacubitril-valsartan has ushered in a new era in the treatment of heart failure (HF). The randomized controlled PARADIGM-HF trial, which randomized 8399 patients with HF to enalapril or sacubitril-valsartan, showed a 20% reduction in mortality and HF hospitalization with the new drug. This has been heralded as a step toward filling a crucial gap in HF management by providing strong evidence that combined inhibition of the angiotensin receptor and neprilysin is superior to inhibition of the renin-angiotensin system alone in stable patients with chronic HF as it negates the deleterious effects of angiotensin while concomitantly augmenting the beneficial effects of the endogenous natriuretic peptide system. This new therapy is costly, and other confirmatory studies have been lacking for over 2 years since its approval by major regulatory authorities. As such, controversy and heated discussions have amassed, as has detailed information from a plethora of secondary analyses of this pivotal trial about the pros and cons of this promising new therapeutic strategy in HF management. The aim of this review was to provide a critical assessment of all these aspects.

Effects of sacubitril/valsartan on neprilysin targets and the metabolism of natriuretic peptides in chronic heart failure: a mechanistic clinical study

AIM

This study aimed at evaluating the effects of sacubitril/valsartan on neprilysin (NEP), and the metabolism of natriuretic peptides in heart failure (HF) and providing additional mechanistic information on the mode of action of the drug.

METHODS AND RESULTS

We enrolled 73 chronic HF patients who were switched from angiotensin-converting enzyme inhibitor or angiotensin receptor blocker to sacubitril/valsartan. In addition to clinical and echocardiographic assessment, plasma biomarkers were measured at baseline, day 30 and day 90 after initiation of treatment. Sacubitril/valsartan led to decrease in New York Heart Association class and improvement of echocardiographic parameters, as well as a dose-dependent decrease in soluble NEP (sNEP) activity, while sNEP concentration remained unchanged. Neprilysin inhibition translated into an increase in its substrates such as atrial natriuretic peptide (ANP), substance P, and glucagon-like peptide 1, the latter translating into a decrease in fructosamine. Cardiac troponin and soluble ST2 levels, biomarkers of HF severity unrelated to NEP metabolism also decreased. While there was a ∼4-fold increase in ANP, we observed no change in plasma brain natriuretic peptide (BNP) and plasma BNP activity, and a mild decrease in N-terminal proBNP (NT-proBNP) concentrations. Finally, we found a progressive increase in the relationship between BNP and NT-proBNP, which strongly correlated with an increase in T71 proBNP glycosylation (R² = 0.94).

CONCLUSION

Sacubitril/valsartan rapidly and strongly reduced sNEP activity, leading to an increase in levels of NEP substrates. These data suggest a pleiotropic favourable impact of sacubitril/valsartan on the metabolism of HF patients with ANP rather than BNP as major effectors amongst natriuretic peptides.