Severe Hypotension With Concomitant Sodium-Glucose Co-Transporter-2 Inhibitor and Angiotensin Receptor-Neprilysin Inhibitor Therapy in a Patient With Heart Failure Reduced Ejection Fraction: A Case Report

Background: Large cardiovascular outcomes trials in individuals with heart failure, with and without diabetes, have demonstrated a significant risk reduction in the composite outcome of cardiovascular death or hospitalizations for heart failure with SGLT2 inhibitor therapy. These positive outcomes have led to the recommendation that SGLT2 inhibitors serve as backbone therapy in patients with heart failure reduced ejection fraction (HFrEF). To date, there has not been enough participants in clinical trials on concomitant SGLT2 inhibitor and angiotensin receptor-neprilysin inhibitor therapy to evaluate the benefits and risks of combination therapy with these two agents outside of smaller subgroup analyses. Case Summary: This case describes a Black female with diabetes meeting her glycemic targets and concomitant stable NYHA FC II HFrEF on guideline-directed medical therapy (GDMT) with sacubitril/valsartan, spironolactone and metoprolol succinate who developed severe hypotension and dehydration requiring hospitalization after initiation of SGLT2 inhibitor therapy. Practice Implications: This case report raises the question of whether those with type 2 diabetes, and/or those on background angiotensin receptor-neprilysin inhibitor therapy, who are euvolemic or sensitive to diuretic therapy should be started on lower dose dapagliflozin and titrated to 10 mg daily based on response. It also raises awareness to the potential increased diuretic effect produced with concomitant use of sacubitril/valsartan and dapagliflozin. Caution and education to mitigate the risk for volume depletion should be provided to those patients who are euvolemic and initiated on a SGLT2 inhibitor, regardless of their background diuretic and GDMT. Conclusion: Future research should focus on the benefits and safety considerations and provide education on how to best initiate and adjust SGLT2 inhibitors in the setting of sacubitril/valsartan use in diverse heart failure patient populations.

Angiotensin-Neprilysin inhibition in heart failure with preserved ejection fraction: A meta-analysis of randomized controlled trials

BACKGROUND

The effect of sacubitril/valsartan on patients with heart failure (HF) with preserved ejection fraction (HFpEF) is a topic of ongoing debate.

METHODS

Medline was queried from inception through the last week of May 2023 for randomized studies assessing the effects of sacubitril/valsartan in patients with HFpEF. For continuous outcomes, we pooled either the geometric mean ratios (gMR) or weighted mean difference (WMD) with 95% confidence intervals (CI). For dichotomous outcomes, we pooled Risk ratios (RR) with 95% CI.

RESULTS

Four trials were included (N=8,129). Compared to the control, sacubitril/valsartan was associated with a reduction in NT-proBNP levels (gMR: 0.84, 95% CI 0.80, 0.88) and improvement in KCCQ score (WMD: 0.85, 95% CI: 0.02, 1.67). We observed no differences for HF hospitalization (RR: 0.90, 95% CI: 0.79, 1.01), cardiovascular mortality (RR: 0.83, 95% CI: 0.52, 1.32), all-cause mortality (RR: 0.99, 95% CI: 0.86-1.13) and improvement (RR: 1.15, 95% CI: 0.93, 1.42) or worsening (RR: 0.92, 95% CI: 0.78, 1.09) of NYHA class between the sacubitril/valsartan and comparator group. Sacubitril/valsartan was generally safe, and patients were less likely to have a ≥50% decline in eGFR compared to control (RR: 0.60, 95% CI: 0.39, 0.92).

CONCLUSION

Pooled analysis suggests that sacubitril/valsartan reduces natriuretic peptide levels and improves the quality of life in patients with HFpEF, which may translate into better clinical outcomes as observed by a numerical trend towards improvement in major HF outcomes with sacubitril/valsartan therapy.

Patient-Centered Heart Failure Therapy

Simultaneous initiation of quadruple therapy with angiotensin receptor-neprilysin inhibitor, beta-adrenergic receptor blocker, mineralocorticoid receptor antagonist, and sodium glucose cotransporter 2 inhibitor aims at prompt improvement and prevention of readmission in patients hospitalized for heart failure with reduced ejection fraction. However, titration of quadruple therapy is time consuming. Lengthy up-titration of quadruple therapy may negate the benefit of early initiation. Quadruple therapy should start with a sodium glucose cotransporter 2 inhibition and a mineralocorticoid antagonist, as both enable safe decongestion and require minimal or no titration. Depending on the level of decongestion and clinical characteristics, patients receive an angiotensin receptor-neprilysin inhibitor or a beta-adrenergic receptor blocker to be titrated after hospital discharge. Outpatient addition of an angiotensin receptor-neprilysin inhibitor to a beta-adrenergic receptor blocker or vice versa completes the quadruple therapy scheme. By focusing on decongestion and matching intervention to patients' profile, the present therapeutic sequence allows rapid implementation of quadruple therapy at fully recommended doses.

Comparison of the effects of angiotensin receptor-neprilysin inhibitors and thiazide diuretic/renin-angiotensin system inhibitor combination therapy in hypertensive patients: a retrospective cohort study

Angiotensin receptor-neprilysin inhibitors (ARNIs) have been approved as antihypertensive agents in Japan, and thiazide diuretics (TZDs) are widely used concomitantly with renin-angiotensin system inhibitors (RASIs) for hypertension. This retrospective study included patients with hypertension who switched from RASI to ARNI therapy (ARNI group) and those who were prescribed TZDs with RASIs (TZD/RASI group). Drug-related changes in the estimated glomerular filtration rate (eGFR), blood pressure (BP), body weight (BW), serum electrolytes, uric acid (UA), and triglyceride levels were compared between the two groups. Overall, 70 participants (31 and 39 in the ARNI and TZD/RASI groups, respectively) were enrolled and observed for a median of 2 months. According to linear mixed models, compared with the TZD/RASI group, the ARNI group exhibited a significant change in mean eGFR of 3.71 mL/min/1.73 m2 [95% confidence interval (CI), 0.57-6.84; P = 0.02] from the time of switching drug to the next outpatient visit. Further, compared with the TZD/RASI group, the ARNI group exhibited significant changes in mean serum UA (-1.27; 95% CI, -1.66 to -0.88), sodium (1.22; 95% CI, 0.12 to -2.32), chloride (2.14; 95% CI, 0.75-3.52), and triglyceride (-52.1; 95% CI, -100.9 to -3.29) levels. Conversely, serum potassium levels, BW, and systolic and diastolic BP did not differ significantly between the two groups (P = 0.69, 0.44, 0.49, and 0.66, respectively). Compared with the combination therapy of TZD and RASI, ARNI therapy causes less renal dysfunction, hyperuricemia, and hypertriglyceridemia with fewer electrolyte abnormalities and no significant difference in antihypertensive effects.

Frailty and uptake of angiotensin receptor neprilysin inhibitor for heart failure with reduced ejection fraction

BACKGROUND

Frail older adults may be less likely to receive guideline-directed medical therapy (GDMT)-renin-angiotensin blockers, beta-blockers, and mineralocorticoid receptor antagonists-for heart failure with reduced ejection fraction (HFrEF). We aimed to examine the uptake of angiotensin receptor neprilysin inhibitor (ARNI) and GDMT in frail older adults with HFrEF.

METHODS

Using 2015-2019 Medicare data, we estimated the proportion of beneficiaries with HFrEF receiving ARNI and GDMT each year by frailty status, defined by a claims-based frailty index. Logistic regression was used to identify clinical characteristics associated with ARNI initiation. Cox proportional hazards regression was used to examine the association of GDMT use in 2015 and death or heart failure hospitalization in 2016-2019.

RESULTS

Among 147,506-180,386 beneficiaries with HFrEF (mean age: 77 years; 27% women; 42.6-49.1% frail) in 2015-2019, the proportion of patients receiving ARNI increased in both non-frail (0.4%-16.4%) and frail (0.3%-13.7%) patients (p for yearly-trend-by-frailty = 0.970). Among those not receiving a renin-angiotensin system blocker, patients with age ≥ 85 years (odds ratio [95% CI], 0.89 [0.80-0.99]), dementia (0.88 [0.81-0.96]), and frailty (0.87 [0.81-0.94]) were less likely to initiate ARNI. The proportion of patients receiving all 3 GDMT classes increased in non-frail patients (22.0%-27.0%) but changed minimally in frail patients (19.6%-21.8%). Regardless of frailty status, treatment with at least 1 class of GDMT was associated with lower death or heart failure hospitalization than no GDMT medications (hazard ratio [95% CI], 0.94 [0.91-0.97], 0.92 [0.89-0.94], 0.94 [0.91-0.97] for 1, 2, and 3 classes, respectively).

CONCLUSIONS

Our results suggest an evidence-practice gap in the use of ARNI and GDMT in Medicare beneficiaries with HFrEF, particularly those with frailty. Efforts to narrow this gap are needed to reduce the burden of HFrEF in older adults.

A Retrospective Cohort Evaluation of a Pharmacist-Led Approach for Transitioning Patients to an Angiotensin Receptor-Neprilysin Inhibitor

Background: Heart failure guidelines recommend replacing an angiotensin-converting enzyme inhibitor (ACEI) or angiotensin receptor blocker (ARB) with an angiotensin receptor neprilysin inhibitor (ARNI) to reduce morbidity and mortality in NYHA Class II-III patients with reduced ejection fraction (HFrEF). Objective: This study aims to determine if a pharmacist-led outpatient ARNI replacement and titration program led to more patients achieving target doses of ARNI compared to usual care. Methods: A single health system, retrospective electronic medical record review identified 791 patients with active ARNI prescriptions and at least two outpatient cardiology visits with a pharmacist or usual care provider between January 2015 through September 2018. The primary outcome was the percentage of patients who achieved a target ARNI dose of 97/103 mg twice daily. The secondary outcomes were the median dose achieved, number of visits required to achieve target dose, hospitalizations, and all-cause death. Results: ARNI was initiated and continued by a pharmacist in 64 patients and 727 by usual care. More patients in the pharmacist group, 60.9% (n = 39), achieved target dose vs. 18.0% (n = 131) of patients managed by usual care (95% CI, 0.31-0.55, p < 0.0001). The pharmacist group also had higher median total daily dose of ARNI (200 mg (IQR = 300) vs 100 mg (IQR = 100), p < 0.0001) and more likely to achieve a higher total daily dose in fewer visits. Conclusions: An advanced practice provider pharmacist-led outpatient ARNI replacement and titration program was more effective in achieving target doses of ARNI in HFrEF patients as compared to usual care.

Dual angiotensin receptor and neprilysin inhibitor reduced portal pressure through peripheral vasodilatation and decreasing systemic arterial pressure in cirrhotic rats

BACKGROUND

Portal hypertension develops along with the progression of liver cirrhosis. Natriuretic peptides have been shown to reduce portal pressure but concomitantly activate the renin-angiotensin-aldosterone system (RAAS). Angiotensin receptor-neprilysin inhibitors (ARNIs) upregulate natriuretic peptides and avoid the adverse effects of RAAS activation. ARNIs have been shown to reduce portal pressure in rats with pre-hepatic portal hypertension, which involves relatively little liver injury. This study aimed to evaluate the relevant effects of an ARNI in rats with both liver cirrhosis and portal hypertension.

METHODS

Male Sprague-Dawley rats received common bile duct ligation to induce liver cirrhosis and portal hypertension. Sham-operated rats served as surgical controls. All rats were randomly allocated into three groups to receive distilled water (vehicle), LCZ696 (an ARNI), or valsartan for 4 weeks. Portal hypertension and relevant derangements were assessed after treatment.

RESULTS

Portal hypertension and hyperdynamic circulation developed in the cirrhotic rats. In the rats with cirrhosis and portal hypertension, both LCZ696 and valsartan reduced portal hypertension, mean arterial pressure, and systemic vascular resistance. The decrease in portal pressure was highly associated with the reduction in arterial pressure and systemic vascular resistance. Blood flow in hepatic, splanchnic, and portosystemic collateral systems was not altered. LCZ696 did not significantly influence liver injury or plasma cytokine levels. Liver fibrosis and splanchnic angiogenesis were not affected.

CONCLUSION

ARNI treatment exerted portal pressure lowering effects via peripheral vasodilatation and decreasing systemic arterial pressure in the rats with liver cirrhosis and portal hypertension. Caution should be taken when using ARNIs in liver cirrhosis.

Clinical Response and Safety of Angiotensin Receptor and Neprilysin Inhibitor Combination in Advanced Chronic Kidney Disease and Heart Failure with Reduced Ejection Fraction

BACKGROUND

Though the combination of an angiotensin receptor blocker (ARB) and a neprilysin inhibitor (ARNi) has been shown to be useful in heart failure with reduced ejection fraction (HFrEF), its use has mostly been restricted to chronic kidney disease (CKD) patients with an estimated glomerular filtration rate (eGFR) &gt;30 mL/minute/1.73 m2 . We studied the role of ARNi in advanced CKD.

MATERIALS AND METHODS

Patients with HFrEF and advanced CKD with an eGFR of &lt;30 mL/ minute/1.73 m2 were given ARNi (sacubitril with valsartan) and prospectively studied for changes in hospitalization rate for HF, clinical symptoms, levels of N-terminal prohormone of brain natriuretic peptide (NT-proBNP), eGFR, and potassium.

RESULTS

Of 34 patients who received ARNi, five were excluded due to hyperkalemia and three due to a decrease in eGFR &gt;30% occurring within 1 month. The remaining 26 patients included 17 with diabetes mellitus (DM) and 23 with underlying coronary artery disease. A total of eight patients had stage 4 and 18 stage 5 CKDs, amongst which eight required hemodialysis. Following ARNi, there was a significant decrease in the need for hospitalization for breathlessness (2.04 ± 1.03-0.23 ± 0.51; p &lt; 0,05), New York Heart Association (NYHA) and Kansas City Cardiomyopathy Questionnaire (KCCQ) scores (3.77 ± 0.43-2.19 ± 0.56 and 28.58 ± 9.04-64.81 ± 14.3, respectively, p &lt; 0.001) and NT-pro-BNP levels (24761 ± 12157.51-20149.92 ± 13555.269, p &lt; 0.05) without significant change in eGFR after 6 months. There were no significant differences in the need for hospitalization, changes in NT proBNP levels and eGFR between stages 4 and 5.

CONCLUSION

Neprilysin inhibitor (ARNi) is effective and can be used with care even in patients with CKD stages 4 and 5 having HFrEF with monitoring of eGFR and potassium.

Optimal Pharmacologic Treatment of Heart Failure With Preserved and Mildly Reduced Ejection Fraction: A Meta-analysis

IMPORTANCE

In recent years, significant progress has been made in the pharmacologic treatment of heart failure (HF) with reduced ejection fraction (HFrEF), but there is still insufficient evidence for drug therapy for HF with preserved ejection fraction (HFpEF) and mildly reduced ejection fraction (HFmrEF).

OBJECTIVE

To compare the outcomes associated with different drug combinations for the treatment of HFpEF and HFmrEF.

DATA SOURCES

A search of the PubMed, Embase, and Cochrane Central Register of Controlled Trials (CENTRAL) databases was conducted for studies published from inception to October 9, 2021.

STUDY SELECTION

Randomized clinical trials on the use of angiotensin-converting enzyme (ACE) inhibitors, angiotensin receptor blockers (ARBs), angiotensin receptor-neprilysin inhibitors (ARNIs), mineralocorticoid receptor antagonists (MRAs), β-blockers, and sodium-glucose cotransporter 2 (SGLT2) inhibitors for patients with HFpEF or HFmrEF.

DATA EXTRACTION AND SYNTHESIS

Data extraction and bias assessment were independently performed by 2 reviewers following the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guideline. All data for 3 outcomes were pooled with a fixed-effect model.

MAIN OUTCOMES AND MEASURES

The main outcomes were first hospitalization for HF, all-cause mortality, and cardiovascular mortality. Hazard ratios (HRs) and 95% credible intervals (CrIs) were evaluated using a bayesian network meta-analysis model.

RESULTS

In this analysis, 19 randomized clinical trials, including 20 633 patients with HF and an ejection fraction of 40% or more, without a remarkable risk of bias were included. Compared with placebo, no treatments were associated with a significant reduction in the risk of all-cause death or cardiovascular death. SGLT2 inhibitors, ARNIs, and MRAs were associated with a significant decrease in the risk of HF hospitalization compared with placebo (SGLT2 inhibitors: HR, 0.71 [95% CrI, 0.60-0.83]; ARNIs: HR, 0.76 [95% CrI, 0.61-0.95]; MRAs: HR, 0.83 [95% CrI, 0.69-0.99]), and SGLT2 inhibitors were the optimal drug class in terms of reducing the risk for HF admission. Sensitivity analysis results demonstrated a progressive decrease in the risk of HF admission and an advance in mean rank associated with the increasing use of drug classes.

CONCLUSIONS AND RELEVANCE

The findings of this study suggest that SGLT2 inhibitors were the optimal drug class for HFpEF and HFmrEF, consistent with the most recent guideline recommendation. The incremental use of combinations of SGLT2 inhibitors, ACE inhibitors or ARBs, and β-blockers may be associated with accumulative benefits in HF hospitalization rather than all-cause death among patients with HFpEF and HFmrEF.

Valsartan and sacubitril combination treatment enhances collagen production in older adult human skin cells

Collagen is a major component of the skin's support system, allowing for its firmness, elasticity, and mechanical strength. Skin collagen production decreases as we age and is associated with increased sagging, wrinkling, and thinning. The Renin-Angiotensin System (RAS) is a key hormonal system that changes with age and affects multiple organ systems. The primary health benefits of Angiotensin (Ang) receptor type1 (AT1R) blockers are believed to arise from systemic effects on blood pressure. However, there is also a skin-specific RAS, though this system has been less well characterized. There are eight FDA-approved angiotensin receptor blockers (ARBs) on the market, although the impact of topical ARBs on aging skin is unknown. Here, we evaluated the topical penetration of gel formulations of eight ARBs using human cadaver skin. Our results show that valsartan achieved the highest skin penetration compared to other ARBs. We then treated human skin fibroblasts from 2-year-old and 57-year-old individuals with valsartan alone or in combination with the neprilysin inhibitor sacubitril. Sacubitril works synergistically with valsartan by inhibiting the degradation of angiotensin II, thereby increasing its bioavailability. Treatment of young and older adult human skin cells with valsartan and sacubitril led to a five-fold increase in collagen type-1 production in the young cells and a four-fold increase in collagen type-1 in older adult cells. This study demonstrates a potential novel application for the widely prescribed drug combination sacubitril-valsartan as a topical agent in aged skin.

Renin-angiotensin-aldosterone system inhibition in patients affected by heart failure: efficacy, mechanistic effects and practical use of sacubitril/valsartan. Position Paper of the Italian Society of Cardiology

Renin-angiotensin-aldosterone system (RAAS) inhibition is a mainstay of the pharmacological treatment of heart failure with reduced ejection fraction (HFrEF). In the last years RAAS blockade has been improved by the introduction of the Angiotensin Receptor-Neprilysin Inhibitor (ARNI) sacubitril/valsartan, that combines RAAS inhibition with the block of neprilysin, boosting the positive effects of natriuretic peptides. The PARADIGM-HF trial demonstrated a significant advantage of sacubitril/valsartan over enalapril on the reduction of cardiovascular (CV) mortality and heart failure hospitalizations rates. Then, several randomized clinical trials and observational studies investigated its role in different clinical settings and its efficacy has been fully recognized in the most recent HFrEF European and USA guidelines. The effects of sacubitril/valsartan on major CV outcomes are associated with reduction of NT-proBNP levels and reverse cardiac remodeling and mitral regurgitation, recognized as one of the mechanistic effects of the drug explaining the favorable prognostic effects. A careful evaluation of patients' clinical profile is relevant to implement the use of ARNI in the clinical practice and to obtain the maximal treatment efficacy. The present Position Paper reports the opinion of the Italian Society of Cardiology on the optimal blockade of the RAAS system in HF patients with the aim of fostering widespread implementation of scientific evidence and practice guidelines in the medical community.

Pharmacological Anti-Remodelling Effects of Disease-Modifying Drugs in Heart Failure with Reduced Ejection Fraction

Cardiac remodelling is an adverse phenomenon linked to heart failure progression and an important contributor to heart failure severity. Cardiac remodelling could represent the real therapeutic goal in the treatment of patients with heart failure with reduced ejection fraction, being potentially reversed through different pharmacotherapies. Currently, there are well-established drugs such as angiotensin-converting enzyme inhibitors/angiotensin II receptor blockers and β-blockers with anti-remodelling effects; recently, angiotensin receptor neprilysin inhibitor effects on inhibiting cardiac remodelling (improving N-terminal pro-B-type natriuretic peptide levels, echocardiographic parameters of reverse cardiac remodelling and right ventricular function in patients with heart failure with reduced ejection fraction) were demonstrated. More recently, hemodynamic consequences of gliflozins, reduced cardiac hydrostatic pressure as a possible cause of ventricular remodelling and hypertrophy were proposed to explain potential anti-remodelling effects of gliflozins. Gliflozins exert their cardioprotective effects by attenuating myofibroblast activity and collagen-mediated remodelling. Another postulated mechanism is represented by the reduction in sympathetic activity, through the reduction in renal afferent nervous activity and the suppression of central reflex mechanisms. Benefits of gliflozins on left ventricular hypertrophy, dilation, and systolic and diastolic function were also described. In this review, we aimed to provide a wide overview on cardiac remodelling with a particular focus on possible anti-remodelling effects of angiotensin receptor neprilysin inhibitors and gliflozins.

New Borane-Protected Derivatives of α-Aminophosphonous Acid as Anti-Osteosarcoma Agents: ADME Analysis and Molecular Modeling, In Vitro Studies on Anti-Cancer Activities, and NEP Inhibition as a Possible Mechanism of Anti-Proliferative Activity

Many organophosphorus compounds (OPs), especially various α-aminophosphonates, exhibit anti-cancer activities. They act, among others, as inhibitors of the proteases implicated in cancerogenesis. Thesetypes of inhibitors weredescribed, e.g., for neutral endopeptidase (NEP) expressed in different cancer cells, including osteosarcoma (OS). The aim of the present study isto evaluate new borane-protected derivatives of phosphonous acid (compounds 1–7) in terms of their drug-likeness properties, anti-osteosarcoma activities in vitro (against HOS and Saos-2 cells), and use as potential NEP inhibitors. The results revealed that all tested compounds exhibited the physicochemical and ADME properties typical for small-molecule drugs. However, compound 4 did not show capability of blood–brain barrier penetration (Lipiński and Veber rules;SwissAdme tool). Moreover, the α-aminophosphonite-boranes (compounds 4–7) exhibited stronger anti-proliferative activity against OS cells than the other phosphonous acid-borane derivatives (compounds 1–3),especially regarding HOS cells (MTT assay). The most promising compounds 4 and 6 induced apoptosis through the activation of caspase 3 and/or cell cycle arrest at the G₂ phase (flow cytometry). Compound 4 inhibited the migration and invasiveness of highly aggressive HOS cells (wound/transwell and BME-coated transwell assays, respectively). Additionally, compound 4 and, to a lesser extent, compound 6 inhibited NEP activity (fluorometric assay). This activity of compound 4 was involved in its anti-proliferative potential (BrdU assay). The present study shows that compound 4 can be considered a potential anti-osteosarcoma agent and a scaffold for the development of new NEP inhibitors.

Insulinotropic Effects of Neprilysin and/or Angiotensin Receptor Inhibition in Mice

Treatment of heart failure with the angiotensin receptor-neprilysin inhibitor sacubitril/valsartan improved glycemic control in individuals with type 2 diabetes. The relative contribution of neprilysin inhibition versus angiotensin II receptor antagonism to this glycemic benefit remains unknown. Thus, we sought to determine the relative effects of the neprilysin inhibitor sacubitril versus the angiotensin II receptor blocker valsartan on beta-cell function and glucose homeostasis in a mouse model of reduced first-phase insulin secretion, and whether any beneficial effects are additive/synergistic when combined in sacubitril/valsartan. High fat-fed C57BL/6J mice treated with low-dose streptozotocin (or vehicle) were followed for eight weeks on high fat diet alone or supplemented with sacubitril, valsartan or sacubitril/valsartan. Body weight and fed glucose levels were assessed weekly. At the end of the treatment period, insulin release in response to intravenous glucose, insulin sensitivity, and beta-cell mass were determined. Sacubitril and valsartan, but not sacubitril/valsartan, lowered fasting and fed glucose levels and increased insulin release in diabetic mice. None of the drugs altered insulin sensitivity or beta-cell mass, but all reduced body weight gain. Effects of the drugs on insulin release were reproduced in angiotensin II-treated islets from lean C57BL/6J mice, suggesting the insulin response to each of the drugs is due to a direct effect on islets and mechanisms therein. In summary, sacubitril and valsartan each exert beneficial insulinotropic, glycemic and weight-reducing effects in obese and/or diabetic mice when administered alone; however, when combined, mechanisms within the islet contribute to their inability to enhance insulin release.

[Angiotensine Receptor-Neprilysin Inhibitor combination is not the preferred medication for patients after acute myocardial infarction]

The PARADISE-MI study compared standard treatment with an ACE inhibitor (ramipril) after an acute myocardial infarction with the newer sacubitril/ valsartan combination (so-called ARNI) medication in 5661 patients. Most patients had a reduced cardiac function (40% ejection fraction or less) and in about 50% of patients it was accompanied by complaints of congestion. The expected 15% reduction in primary endpoint cardiovascular death or rehospitalization or extra visits for heart failure was not met after 22 months. The study is characterized by an increased incidence of symptomatic hypotension of 28,3% in the group treated with the ARNI, compared to an incidence of 21,9% in the group treated with the ACE inhibitor. The interpretation of the trial is hampered by the mixed design of prevention and treatment trial for heart failure. A continuing careful approach is advised with ACE inhibitors as first choice in the first week(s) after myocardial infarction.

Acute Tubular Necrosis Associated with Angiotensin Receptor-neprilysin Inhibitor

Sacubitril/valsartan, an angiotensin receptor-neprilysin inhibitor (ARNI), significantly reduces mortality and morbidity in patients with chronic heart failure with a reduced ejection fraction (HFrEF). However, a considerable number of patients treated with sacubitril/valsartan experience hypotension, oliguria, progressive azotemia, and renal failure as adverse events. These issues have been linked to significant gaps in the usage and dosing of guideline-directed medical therapy with ARNI in patients with HFrEF. We herein report a relevant case of pathologically proven acute tubular necrosis after the first dose of sacubitril/valsartan, highlighting the importance of optimizing the medical therapy in an outpatient with HFrEF.

Angiotensin Receptor-Neprilysin Inhibitor in Acute Myocardial Infarction

In patient with symptomatic heart failure sacubitril valsartan has been found to reduces the risk of hospitalization and death from cardiovascular causes more effectively then angiotensin converting enzymes inhibitor trail comparing the effect of these drugs in acute myocardial infarction is lacking.

MATERIAL

We randomly assigned patient with acute myocardial infarction complicated with reduced LVEF, or pulmonary congestion to recieve sacubitril 97mg-valsartan 103mg and ramipril 5mg twice daily the primary outcome was death from cardiovascular causes or incident heart failure, outpatient symptomatic heart failure or heart failure leading to hospitalization whichever occure first.

OBSERVATION

Total 566 patient was taken in randomization 283 receive sacubitril-valsartan and 283 receive ramipril over a median of 22 months total outcome occure in 138 patient in sacubitril-valsartan group and in137 patient with ramipril group(hazard ratio 0.90: 95%confidence interval death from cardiovascular causes or hospitalization for heart failure occure i 10.9% patient reciveing sacubitril-valsartan and in 11.8%patient with ramipril group death from cardiovascular causes is 5.9 and 6.7% respectively death from anyother causes is 7.5 and 8.5 % respectively in both sacubitril-valsartan and ramipril group.

CONCLUSION

Sacubitril-valsartan was not associated with significantly lower incidence of death from cardiovascular causes or incidents heart failure then ramipril in patients with acute myocardial infarction.

Treatment with angiotensin receptor neprilysin inhibitor for Taiwan heart failure patients: Rationale and baseline characteristics of the TAROT-HF study

BACKGROUND

This study used a real-world database to investigate the prescription patterns of sacubitril/valsartan (Sac/Val) among Taiwanese patients with heart failure with reduced ejection fraction (HFrEF).

METHODS

The Treatment with Angiotensin Receptor neprilysin inhibitor fOr Taiwan Heart Failure patients (TAROT-HF) study is a principal investigator-initiated, multicenter, observational, retrospective study on Taiwanese HFrEF patients. A total of 1772 patients with HFrEF (mean age 62.5 years, 75.3% male, mean left ventricular ejection fraction [LVEF] 29.3%) who received Sac/Val at 10 hospitals between 2017 and 2018 were enrolled at the date of Sac/Val initiation. Among these patients, 585 (33%) initially received Sac/Val during acute decompensated heart failure (HF) hospitalization (TAROT-AHF arm), whereas 1187 (67%) initially received the same at the outpatient clinic (TAROT-CHF arm).

RESULTS

A total of 1343 (75.8%) patients received an initial dose of 50 mg twice daily or fewer, whereas 422 (23.8%) received the standard initiation dose (100 mg twice daily). During outpatient Sac/Val initiation, the mean dosages were significantly higher than that following hospitalization (117 ± 55 mg vs 109 ± 57 mg; p = 0.014). Multivariate analysis identified younger age, higher systolic blood pressure, higher LVEF, prior use of renin-angiotensin system inhibitors, use of ivabradine, and a history of diabetes mellitus as independent factors for initiating a standard Sac/Val dose. Over a follow-up period of 18 months, incidences of cardiovascular death or first unplanned HF hospitalization were 18.69 and 33.11 per 100-person years for the TAROT-CHF and TAROT-AHF arms, respectively.

CONCLUSION

The TAROT-HF study provided an opportunity to describe the clinical features of patients with HFrEF who received Sac/Val, assess the real-world utilization and efficacy of Sac/Val, and compare these patients with those included in prior registries.

In-silico simulated prototype-patients using TPMS technology to study a potential adverse effect of sacubitril and valsartan

Unveiling the mechanism of action of a drug is key to understand the benefits and adverse reactions of a medication in an organism. However, in complex diseases such as heart diseases there is not a unique mechanism of action but a wide range of different responses depending on the patient. Exploring this collection of mechanisms is one of the clues for a future personalized medicine. The Therapeutic Performance Mapping System (TPMS) is a Systems Biology approach that generates multiple models of the mechanism of action of a drug. Each molecular mechanism generated could be associated to particular individuals, here defined as prototype-patients, hence the generation of models using TPMS technology may be used for detecting adverse effects to specific patients. TPMS operates by (1) modelling the responses in humans with an accurate description of a protein network and (2) applying a Multilayer Perceptron-like and sampling strategy to find all plausible solutions. In the present study, TPMS is applied to explore the diversity of mechanisms of action of the drug combination sacubitril/valsartan. We use TPMS to generate a wide range of models explaining the relationship between sacubitril/valsartan and heart failure (the indication), as well as evaluating their association with macular degeneration (a potential adverse effect). Among the models generated, we identify a set of mechanisms of action associated to a better response in terms of heart failure treatment, which could also be associated to macular degeneration development. Finally, a set of 30 potential biomarkers are proposed to identify mechanisms (or prototype-patients) more prone of suffering macular degeneration when presenting good heart failure response. All prototype-patients models generated are completely theoretical and therefore they do not necessarily involve clinical effects in real patients. Data and accession to software are available at http://sbi.upf.edu/data/tpms/

Enhanced functional connectivity and volume between cognitive and reward centers of naïve rodent brain produced by pro-dopaminergic agent KB220Z

Dopaminergic reward dysfunction in addictive behaviors is well supported in the literature. There is evidence that alterations in synchronous neural activity between brain regions subserving reward and various cognitive functions may significantly contribute to substance-related disorders. This study presents the first evidence showing that a pro-dopaminergic nutraceutical (KB220Z) significantly enhances, above placebo, functional connectivity between reward and cognitive brain areas in the rat. These include the nucleus accumbens, anterior cingulate gyrus, anterior thalamic nuclei, hippocampus, prelimbic and infralimbic loci. Significant functional connectivity, increased brain connectivity volume recruitment (potentially neuroplasticity), and dopaminergic functionality were found across the brain reward circuitry. Increases in functional connectivity were specific to these regions and were not broadly distributed across the brain. While these initial findings have been observed in drug naïve rodents, this robust, yet selective response implies clinical relevance for addicted individuals at risk for relapse, who show reductions in functional connectivity after protracted withdrawal. Future studies will evaluate KB220Z in animal models of addiction.

Enhanced proteolytic clearance of plasma Aβ by peripherally administered neprilysin does not result in reduced levels of brain Aβ in mice

Accumulation of β-amyloid (Aβ) in the brain is believed to contribute to the pathology of Alzheimer's Disease (AD). Aβ levels are controlled by the production of Aβ from amyloid precursor protein, degradation by proteases, and peripheral clearance. In this study we sought to determine whether enhancing clearance of plasma Aβ with a peripherally administered Aβ-degrading protease would reduce brain Aβ levels through a peripheral sink. Neprilysin (NEP) is a zinc-dependent metalloprotease that is one of the key Aβ-degrading enzymes in the brain. We developed a NEP fusion protein with in vitro degradation of Aβ and a 10 day plasma half-life in mouse. Intravenous administration of NEP to wild-type and APP23 transgenic mice resulted in dose-dependent clearance of plasma Aβ. However, this did not correspond to reduced levels of soluble brain Aβ with treatment up to 5 weeks in WT mice or formic acid-extractable brain Aβ with 3 month treatment in aged APP23. In contrast, intracranial injection of NEP resulted in an acute decrease in soluble brain Aβ. We found no change in amyloid precursor protein gene expression in mice treated with intravenous NEP, suggesting that the lack of effects in the brain following this route of administration was not caused by compensatory upregulation of Aβ production. Taken together, these results suggest a lack of a robust peripheral Aβ efflux sink through which brain amyloid burdens can be therapeutically reduced.

Degradation of islet amyloid polypeptide by neprilysin

AIMS/HYPOTHESIS

A progressive loss of pancreatic beta cell function, a decrease in beta cell mass and accumulation of islet amyloid is characteristic of type 2 diabetes mellitus. The main constituent of islet amyloid is islet amyloid polypeptide (IAPP). In this study, we examined the ability of the peptidase neprilysin to cleave IAPP and prevent human IAPP-induced pancreatic beta cell toxicity.

METHODS

Neprilysin and a catalytically compromised neprilysin mutant were tested for their ability to inhibit human IAPP fibrillisation and human IAPP-induced pancreatic beta cell cytotoxicity. Degradation of human IAPP by neprilysin was followed by HPLC, and the degradation products were identified by MS.

RESULTS

Neprilysin prevented IAPP fibrillisation by cleaving IAPP at Arg(11)-Leu(12), Leu(12)-Ala(13), Asn(14)-Phe(15), Phe(15)-Leu(16), Asn(22)-Phe(23) and Ala(25)-Ile(26). It also appears to prevent human IAPP fibrillisation through a non-catalytic interaction. Neprilysin protected against beta cell cytotoxicity induced by exogenously added or endogenously produced human IAPP.

CONCLUSIONS/INTERPRETATION

The data presented support a potential therapeutic role for neprilysin in preventing type 2 diabetes mellitus. This study supports the hypothesis that extracellular human IAPP contributes to human IAPP-induced beta cell cytotoxicity. Whether human IAPP exerts its cytotoxic effect through a totally extracellular mechanism or through a cellular reuptake mechanism is unclear at this time.

Divergent pathways for the angiotensin-(1-12) metabolism in the rat circulation and kidney

Evidence of endogenous angiotensin-(1-12) [Ang-(1-12)] may necessitate revision of the accepted view that Ang I is the immediate peptide product derived from the precursor protein angiotensinogen. As the processing of this peptide has not been fully elucidated, we characterized Ang-(1-12) metabolism in the serum and kidney of the mRen2.Lewis rat, a model of high circulating renin and ACE expression. A sensitive HPLC-based method to detect the metabolism ex vivo of low concentrations of (125)I-labeled Ang-(1-12) was utilized. Ang-(1-12) processing to serum did not reveal the participation of renin; however, serum ACE readily converted Ang-(1-12) to Ang I with subsequent metabolism to Ang II. Ang I and Ang II forming activities for serum ACE were 102±4 and 104±3 fmol/ml/min serum (n=3), respectively, and both products were abolished by the potent ACE inhibitor lisinopril. The metabolism of Ang-(1-12) in renal cortical membranes also revealed the formation of Ang I; however, the main products were Ang-(1-7) and Ang-(1-4) at 129±9 and 310±12 fmol/mg/min protein (n=4), respectively. Neprilysin inhibition abolished these products and substantially reduced the overall metabolism of Ang-(1-12). Incubation of Ang-(1-12) with either human or mouse neprilysin revealed identical products. We conclude that endogenous Ang-(1-12) may contribute to the expression of biologically active angiotensins through a renin-independent pathway. The preferred route for Ang-(1-12) metabolism likely reflects the relative tissue content of ACE and neprilysin.

Altered cardiac bradykinin metabolism in experimental diabetes caused by the variations of angiotensin-converting enzyme and other peptidases

The peptidases angiotensin-converting enzyme (ACE) and neutral endopeptidase 24.11 (NEP) mediate most of the kinin catabolism in normal cardiac tissue and are the molecular targets of inhibitory drugs that favorably influence diabetic complications. We studied the variations of those kininases in the myocardium of rats in experimental diabetes. ACE and NEP activities were significantly decreased in heart membranes 4-8weeks post-streptozotocin (STZ) injection. However, insulin-dependent diabetes did not modify significantly bradykinin (BK) half-life (t(1/2)) while the effect of both ACE (enalaprilat) and ACE and NEP (omapatrilat) inhibitors on BK degradation progressively decreased, which may be explained by the upregulation of other unidentified metallopeptidase(s). In vivo insulin treatment restored the activities of both ACE and NEP. ACE and NEP activities were significantly higher in hearts of young Zucker rats than in those of Sprague-Dawley rats. BK t(1/2) and the effects of peptidase inhibitors on t(1/2) varied accordingly. It is concluded that kininase activities are subjected to large and opposite variations in rat cardiac tissue in type I and II diabetes models. A number of tissue or molecular factors may determine these variations, such as remodeling of cardiac tissue, ectoenzyme shedding to the extracellular fluid and the pathologic regulation of peptidase gene expression.

Characterization of renin-angiotensin system enzyme activities in cultured mouse podocytes

Intraglomerular ANG II has been linked to glomerular injury. However, little is known about the contribution of podocytes (POD) to intraglomerular ANG II homeostasis. The aim of the present study was to examine the processing of angiotensin substrates by cultured POD. Our approach was to use matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry for peptide determination from conditioned cell media and customized AQUA peptides for quantification. Immortalized mouse POD were incubated with 1-2 microM ANG I, ANG II, or the renin substrate ANG-(1-14) for different time intervals and coincubated in parallel with various inhibitors. Human mesangial cells (MES) were used as controls. POD incubated with 1 microM ANG I primarily formed ANG-(1-9) and ANG-(1-7). In contrast, MES incubated with ANG I primarily generated ANG II. In POD, ANG-(1-7) was the predominant product, and its formation was inhibited by a neprilysin inhibitor. Modest angiotensin-converting enzyme (ACE) activity was also detected in POD, although only after cells were incubated with 2 microM ANG I. In addition, we observed that POD degraded ANG II into ANG III and ANG-(1-7). An aminopeptidase A inhibitor inhibited ANG III formation, and an ACE2 inhibitor led to ANG II accumulation. Furthermore, we found that POD converted ANG-(1-14) to ANG I and ANG-(1-7). This conversion was inhibited by a renin inhibitor. These findings demonstrate that POD express a functional intrinsic renin-angiotensin system characterized by neprilysin, aminopeptidase A, ACE2, and renin activities, which predominantly lead to ANG-(1-7) and ANG-(1-9) formation, as well as ANG II degradation. These findings may reflect a specific role of POD in maintenance of intraglomerular renin-angiotensin system balance.

Neprilysin protects human neuronal progenitor cells against impaired development caused by amyloid-β peptide

Transplantation of human neuronal progenitor cells (HNPC) is being considered for neuroreplacement therapy in beta-amyloidosis associated with neuronal loss in Down's syndrome and Alzheimer's disease. However, the influence of amyloid-beta-containing brain environment on the development of HNPCs is unknown. Recently, we demonstrated that amyloid-beta peptide (Abeta) impaired differentiation of HNPCs in culture through oxidative stress. Now we studied the effect of neprilysin, an Abeta-degrading enzyme, on development of neuronal colonies from neurospheres of HNPCs in the presence of Abeta1-40. Neprilysin increased the number of neurospheres that formed colonies of neuron-like cells. This effect of neprilysin was associated with reduced amounts of the monomeric and dimeric Abeta that remained in culture supernatants as well as the Abeta uptaken by differentiating HNPCs. Phosphoramidon, a neprilysin inhibitor, attenuated these effects of neprilysin. In control cultures of HNPCs that grew without exogenous Abeta1-40, the treatment with neprilysin reduced the number of developing colonies. This effect might result from degradation by neprilysin of endogenous Abeta produced and secreted by HNPCs or other peptides that are involved in neuronal development. The results demonstrate that even a partial reduction of extracellular Abeta levels by neprilysin may facilitate development of HNPCs into neurons in an environment overloaded with Abeta. This finding suggests that neprilysin could facilitate neuroreplacement therapy with HNPCs in treatment of neurodegenerative diseases.

Triple VPI CGS 35601 reduces high blood pressure in low-renin, high-salt Dahl salt-sensitive rats

We previously reported that CGS 35601, a potent triple inhibitor of angiotensin-converting enzyme, neutral endopeptidase, and endothelin-converting enzyme 1, completely normalized mean arterial blood pressure (MABP) in 36-week-old spontaneously hypertensive rats, a normal renin model. The aim of the present study was to determine the effects of this triple vasopeptidase inhibitor (VPI) on the hemodynamic profile of instrumented, conscious, and unrestrained Dahl salt-sensitive (DSS) rats, a gene-prone, high-salt diet-induced low-renin hypertension model. Male DSS rats (mean weight [+/-SEM], 385 +/- 10 g) were fed a normal diet (Group 1) or a high-salt diet (Groups 2 and 3; 8% NaCl in food) for 6 weeks and then instrumented with a carotid catheter and placed individually in metabolic cages for 30 days. The hemodynamic, hematological, and biochemical profiles were assessed daily. Dose-dependent treatment started after a 7-day stabilization period in Groups 1 and 2 (vehicle dosage, 250 microl/hr) and Group 3 (CGS 35601 dosages of 0.1, 1, and 5 mg/kg/day for 6 days per dose by means of constant intra-arterial infusion), followed by a 5-day washout period. Two additional groups included normotensive Wistar rats (Group 4) and DSS rats that received a double high-salt solid (8% NaCl) and liquid (1% NaCl) diet (Group 5). The MABP in rats receiving CGS 35601 decreased in a dose-dependent fashion toward the baseline level observed in DSS rats receiving a normal diet. The heart rate was unaffected. The hemodynamic profile returned to normal during the washout period. This novel triple VPI is a potent and effective antihypertensive agent with a safe short-term profile that may be of interest for treating hypertension and other cardiovascular diseases. Other hypertensive rat models are being tested.

The hemodynamic and metabolic profiles of Zucker diabetic fatty rats treated with a single molecule triple vasopeptidase inhibitor, CGS 35601

CGS 35601 is a triple vasopeptidase inhibitor (VPI) of angiotensin converting enzyme (ACE), neutral endopeptidase (NEP), and endothelin (ET) converting enzyme-1 (ECE-1), with respective IC(50) values of 22, 2, and 55 nM. The aim of the present study was to establish the hemodynamic profile of Zucker diabetic fatty (Zdf)-Fatty rats, a high-fat diet gene-prone model developing spontaneous Type 2 diabetes (T2D) and the effects of CGS 35601. Male Zdf-Fatty (14 weeks, n = 17-23), Zdf-Lean (14 weeks, n = 8-10), and Wistar (14 weeks, n = 9-10) rats on distinct diets were implanted with a catheter in the left carotid and placed individually in a metabolic cage for 30 days. The hemodynamic profile and some metabolic biomarkers were assessed daily. After a 7-day stabilization period, the Zdf-Fatty rats were divided into two groups: Group 1, controls (n = 7-10) receiving vehicle-saline (250 microl/hr) and Group 2, (n = 10-13) receiving increasing doses of CGS 35601 (0.1, 1, and 5 mg/kg/day x 6 days each, intra-arterially) followed by a 5-day washout period. Mean arterial blood pressure (MABP) of young Zdf-Fatty rats was compared with age-matched Zdf-Lean and Wistar rats, which were found similar. MABP decreased by 5.9% (from baseline at 102 +/- 5 to 96 +/- 4 mmHg), 12.7% (to 89 +/- 6 mmHg) and 21.6% (to 80 +/- 4 mmHg), at 0.1, 1, and 5 mg/kg/day, respectively, in CGS 35601-treated Zdf-Fatty rats. Systolic and diastolic blood pressures were similarly reduced. The heart rate was not affected. Hyperglycemic status and insulin-resistance were not modulated by short-term treatment. CGS 35601 presented an excellent short-term safety profile. This novel molecule and class of VPI may be of interest for lowering vascular tone. Further long-term studies, once cardiovascular and renal complications have developed in this T2D rat model are warranted to define the efficacy of this class of VPI.

Ascorbic acid decreases neutral endopeptidase activity in cultured osteoblastic cells

Neprilysin (NEP) is a plasma membrane-bound peptidase with wide expression in kidney, lung, brain and bone. Decreased NEP activity has been linked to increased growth of some cancer cells, but it is unknown whether its activity is related to growth of cells belonging to the osteoblast lineage. We assessed NEP activity in an osteoblastic cell line, PyMS, by cleavage of N-Dansyl-d-Ala-Gly-p-nitro-Phe-Gly to Dansyl-d-Ala-Gly. NEP activity was completely blocked by 1 muM thiorphan. Most agents affecting growth of these cells (e.g. calcium, insulin-like growth factor I and dexamethasone) did not regulate NEP activity. Ascorbic acid (ASA) increased thymidine incorporation into DNA and potentiated the stimulatory effect of IGF I on DNA synthesis, an effect which was attenuated by echistatin. ASA decreased NEP activity in a dose-dependent manner, and decreased Western-detectable NEP protein in plasma membranes. ASA affects both integrin receptor-mediated signalling and the processing of regulatory peptides.

Mechanism of Vasopeptidase Inhibitor-Induced Plasma Extravasation: Comparison of Omapatrilat and the Novel Neutral Endopeptidase 24.11/Angiotensin-Converting Enzyme Inhibitor GW796406

We describe N-[(2S)-2-(mercaptomethyl)-3-methylbutanoyl]-4-(1H-pyrazol-1-yl)-L-phenylalanine (GW796406), a vasopeptidase inhibitor (VPI) that possessed approximately 3-fold selectivity for neutral endopeptidase 24.11 (NEP) versus angiotensin-converting enzyme (ACE) in in vitro assays using rat and human enzymes. In the same assays, omapatrilat, the most extensively studied VPI, displayed approximately 3-fold selectivity for ACE. The in vivo ACE and NEP inhibition profile and the liability of the compounds to increase plasma extravasation were compared at two (low and high) therapeutically equivalent intravenous doses in the rat. At the low dose, both agents inhibited ACE activity by approximately 85%. Consistent with their in vitro ACE/NEP selectivity, omapatrilat produced 49% inhibition, whereas GW796406 produced >95% inhibition of NEP. Neither compound increased plasma extravasation. When the low dose was administered to rats pretreated with the NEP inhibitor ecadotril to normalize NEP background to <5% of control, only omapatrilat significantly increased plasma extravasation. At the high dose, omapatrilat and GW796406 produced profound, nonselective inhibition of ACE (>90%) and NEP (>95%), and they significantly increased plasma extravasation. The activity of the agents as inhibitors of dipeptidylpeptidase IV (DPP IV) and aminopeptidase P (APP) was also investigated. Neither compound inhibited DPP IV. Interestingly, omapatrilat, but not GW796406, was a relatively potent inhibitor of APP (IC50 = 260 nM). We investigated whether APP inhibition increased the plasma extravasation liability of GW796406. The low dose of GW796406 administered with apstatin, an APP inhibitor, did not increase plasma extravasation. This finding inferred that APP inhibition is not involved in plasma extravasation in the rat and that APP inhibition does not explain the increased plasma extravasation produced by omapatrilat in NEP-inhibited rats.

Anti-Progressive Effect of Neutral Endopeptidase 24.11 (NEP/CD10) on Cervical Carcinoma in vitro and in vivo

OBJECTIVES

Neutral endopeptidase 24.11 (NEP) is known to play important roles in the maintenance of homeostasis or in neoplastic transformation and tumor progression in certain human malignancies through the enzymatic inactivation of bioactive peptides such as endothelin-1 (ET-1), angiotensin-II, and bombesin.

METHODS

In this study, we first investigated NEP expression in cervical carcinoma by immunohistochemical staining and Western blot analysis. Next, we examined NEP functions in vitro and in vivo by generating NEP-overexpressing cervical carcinoma cells.

RESULTS

We found a significant decrease in cellular proliferative and invasive abilities with a reduced ET-1 concentration in the conditioned medium by NEP overexpression in cervical carcinoma CaSki cells, which have an ET-1 autocrine loop. In addition, these potentials were cancelled by blockade of NEP activity with a specific inhibitor. Although vector-transfected CaSki cells could grow even in serum-free media, NEP-overexpressing cells failed to proliferate in these media. Furthermore, we demonstrated that NEP suppressed tumor formation of subcutaneous xenografts using nude mice.

CONCLUSIONS

Our results indicated that NEP functions as a tumor-suppressor gene in cervical carcinoma cells, and its expression may have prognostic significance. Further elucidation of the mechanism underlying the observed effect of NEP will contribute to a better understanding of its role in the pathophysiology of cervical carcinoma.

Matrix metalloproteinase-activated doxorubicin prodrugs inhibit HT1080 xenograft growth better than doxorubicin with less toxicity

Matrix metalloproteinase (MMP)-activated prodrugs were formed by coupling MMP-cleavable peptides to doxorubicin. The resulting conjugates were excellent in vitro substrates for MMP-2, -9, and -14. HT1080, a fibrosarcoma cell line, was used as a model system to test these prodrugs because these cells, like tumor stromal fibroblasts, expressed several MMPs. In cultured HT1080 cells, simple MMP-cleavable peptides were primarily metabolized by neprilysin, a membrane-bound metalloproteinase. MMP-selective metabolism in cultured HT1080 cells was obtained by designing conjugates that were good MMP substrates but poor neprilysin substrates. To determine how conjugates were metabolized in animals, MMP-selective conjugates were given to mice with HT1080 xenografts and the distribution of doxorubicin was determined. These studies showed that MMP-selective conjugates were preferentially metabolized in HT1080 xenografts, relative to heart and plasma, leading to 10-fold increases in the tumor/heart ratio of doxorubicin. The doxorubicin deposited by a MMP-selective prodrug, compound 6, was more effective than doxorubicin at reducing HT1080 xenograft growth. In particular, compound 6 cured 8 of 10 mice with HT1080 xenografts at doses below the maximum tolerated dose, whereas doxorubicin cured 2 of 20 mice at its maximum tolerated dose. Compound 6 was less toxic than doxorubicin at this efficacious dose because mice treated with compound 6 had no detectable changes in body weight or reticulocytes, a marker for marrow toxicity. Hence, MMP-activated doxorubicin prodrugs have a much higher therapeutic index than doxorubicin using HT1080 xenografts as a preclinical model.

Vasopeptidase inhibition improves insulin sensitivity and endothelial function in the JCR:LA-cp rat

The insulin-resistant, hyperinsulinemic, normoglycemic, and obese JCR:LA-cp rat was used to study the effects of ramipril (an ACE inhibitor) and AVE7688 (a dual inhibitor of ACE and neutral endopeptidases) on insulin sensitivity and vascular function. Both compounds reduced the surge of plasma insulin in a meal tolerance test by approximately 50%. Ramipril had no effect on acetylcholine-induced relaxation but increased the sensitivity to sodium nitroprus-side at low concentrations. AVE7688 significantly reduced the EC50 for acetylcholine to relax phenylephrine-contracted aortic rings. None of the compounds affected the baseline coronary flow and reactive hyperemia. Coronary flow response to bradykinin in AVE7688- and ramipril-treated rat hearts showed a significantly lower EC50 than in control rats. Maximum flow rate was not different between groups. In summary, both ramipril and AVE7688 had significant hypoinsulinemic and insulin-sensitizing effects. Whereas ramipril had limited vascular effects, AVE7688 had more marked beneficial vascular effects, probably of endothelial origin and possibly related to lowered insulin levels.

Neutral Endopeptidase 24.11/CD10 Suppresses Progressive Potential in Ovarian Carcinoma In vitro and In vivo

Recently, numerous studies have shown that endothelin-1 (ET-1) is expressed in ovarian carcinoma and that ET-1 selectively acts as an autocrine or paracrine growth factor through the endothelin A receptor (ET(A)R), and is involved in cell proliferation, invasiveness, neovascularization, and prevention of apoptosis. Neutral endopeptidase 24.11 (NEP) is a cell surface aminopeptidase with a ubiquitous expression and is capable of degrading a number of bioactive peptides including ET-1. Our previous report showed that stromal NEP expression in ovarian carcinoma was down-regulated as the histologic grade advanced. Here, we confirmed that NEP was expressed in tumor cells as well as stromal tissues in ovarian carcinoma, and investigated the functions of NEP in this carcinoma. We showed that there was a significant decrease in cell proliferation and invasiveness with a reduction in the concentration of ET-1 in the conditioned medium on the NEP overexpression of NEP in ovarian carcinoma cells. In addition, the overexpression of NEP enhanced susceptibility to paclitaxel, resulting in an increased occurrence of apoptotic morphologic change. Furthermore, tumorigenesis was reduced in vivo with the overexpression of NEP, down-regulation of both matrix metalloproteinase-2, and vascular endothelial growth factor expression. This evidence suggests that NEP functionally suppresses the progression of ovarian carcinoma and further study of this enzyme may reveal an effective way to target ET-1 for the treatment of this carcinoma.

Stromal-epithelial interactions influence prostate cancer cell invasion by altering the balance of metallopeptidase expression

Perturbations of stromal–epithelial interactions in the developing tumour can contribute to cancer invasion and metastasis. The structurally related metallopeptidases endothelin-converting enzyme (ECE) and neutral endopeptidase (NEP) contribute sequentially to the synthesis and inactivation of ET-1, a mitogenic peptide that has been shown to affect tumour behaviour. This study has investigated the interaction between metastatic tumour epithelial cells, which lack NEP, and stromal cells, which we have shown to express ECE-1 (stromal–epithelial interactions), using Matrigel invasion chambers. The epithelial cell lines utilised in this study include androgen-sensitive LNCaP, androgen-independent PC-3, Du145 and recently established PNT-1a, PNT2-C2 and P4E6 prostate cell lines. Specific inhibition of endogenous ECE-1 activity in stromal cells reduced PC-3 and Du145 invasion by 70 and 50%, respectively. Addition of recombinant NEP to inactivate endogenous mitogenic peptides resulted in 50 and 20% reductions in invasion in PC-3 and Du145 cells, respectively. Neutral endopeptidase effects were reversed in the presence of thiorphan, a specific NEP inhibitor. Supplementation of defined media with bradykinin and ET-1 significantly increased PC-3 invasion by 40 and 50%, respectively. Du145 cell invasion increased by approximately 100% on adding ET-1. These studies implicate the metallopeptidases NEP and ECE-1 as mediators of prostate cancer invasion via a stromal/epithelial interaction.

Dutch, Flemish, Italian, and Arctic mutations of APP and resistance of Abeta to physiologically relevant proteolytic degradation

The Dutch, Flemish, Italian, and Arctic mutations in the amyloid precursor protein (APP) gene encode changes within the sequence of the amyloid beta peptide (Abeta) and cause presenile cerebral amyloid angiopathy, cerebral parenchymal amyloidosis, or both. These disorders are caused by accumulation of Abeta, with no evidence of increased Abeta production. Our results showed that these mutations in Abeta make it resistant to proteolytic degradation by neprilysin, the peptidase with the most important role in catabolism of Abeta in the brain. These mutations in Abeta could thus be pathogenic not only by facilitating fibrillogenesis but also by extending the half-life of Abeta in the brain.

Tachykinins and tachykinin receptors in human uterus

(1) Studies were undertaken to determine the nature of the receptors mediating contractile effects of tachykinins in the uteri of nonpregnant women, and to analyse the expression of preprotachykinins (PPT), tachykinin receptors and the cell-surface peptidase, neprilysin (NEP), in the myometrium from pregnant and nonpregnant women. (2) The neurokinin B (NKB) precursor PPT-B was expressed in higher levels in the myometrium from nonpregnant than from pregnant women. Faint expression of PPT-A mRNA was detectable in the myometrium from nonpregnant but not pregnant women. PPT-C, the gene encoding the novel tachykinin peptide hemokinin-1 (HK-1), was present in trace amounts in the uteri from both pregnant and nonpregnant women. (3) Tachykinin NK(2) receptors were more strongly expressed in tissues from nonpregnant than from pregnant women. NK(1) receptor mRNA was present in low levels in tissues from both pregnant and nonpregnant women. A low abundance transcript corresponding to the NK(3) receptor was present only in tissues from nonpregnant women. (4) The mRNA expression of the tachykinin-degrading enzyme NEP was lower in tissues from nonpregnant than from pregnant women. (5) Substance P (SP), neurokinin A (NKA) and NKB, in the presence of the peptidase inhibitors thiorphan, captopril and bestatin, produced contractions of myometrium from nonpregnant women. The order of potency was NKA>>SP>/=NKB. The potency of NKA was unchanged in the absence of peptidase inhibitors. (6) The tachykinin NK(2) receptor-selective agonist [Lys(5)MeLeu(9)Nle(10)]NKA(4-l0) was approximately equipotent with NKA, but the tachykinin NK(1) and NK(3) receptor-selective agonists [Sar(9)Met(O(2))(11)]SP and [MePhe(7)]NKB were ineffective in the myometrium from nonpregnant women. (7) The uterotonic effects of [Lys(5)MeLeu(9)Nle(10)]NKA(4-10) were antagonized by the tachykinin NK(2) receptor-selective antagonist SR48968. Neither atropine, nor phentolamine nor tetrodotoxin affected responses to [Lys(5)MeLeu(9)Nle(10)]NKA(4-10). (8) These data are consistent with a role of tachykinins in the regulation of human uterine function, and reinforce the importance of NK(2) receptors in the regulation of myometrial contraction.

Neprilysin gene transfer reduces human amyloid pathology in transgenic mice

The degenerative process of Alzheimer's disease is linked to a shift in the balance between amyloid-beta (Abeta) production, clearance, and degradation. Neprilysin has recently been implicated as a major extracellular Abeta degrading enzyme in the brain. However, there has been no direct demonstration that neprilysin antagonizes the deposition of amyloid-beta in vivo. To address this issue, a lentiviral vector expressing human neprilysin (Lenti-Nep) was tested in transgenic mouse models of amyloidosis. We show that unilateral intracerebral injection of Lenti-Nep reduced amyloid-beta deposits by half relative to the untreated side. Furthermore, Lenti-Nep ameliorated neurodegenerative alterations in the frontal cortex and hippocampus of these transgenic mice. These data further support a role for neprilysin in regulating cerebral amyloid deposition and suggest that gene transfer approaches might have potential for the development of alternative therapies for Alzheimer's disease.

Emerging concepts of neurohumoral modulation in the treatment of congestive heart failure

The angiotensin converting enzyme (ACE), endothelin (ET) converting enzyme (ECE) and neutral endopeptidase (NEP) are all zinc-metallopeptidases expressed in almost all the organs, such as heart, vessels and kidneys. While ACE and ECE are respectively involved in the transformation of angiotensin I and Big-ET into angiotensin II and ET-1 respectively, which possess vasoconstrictor and mitogenic properties, NEP is involved in the degradation of atrial natriuric factor (ANF), which possesses vasorelaxant, diuretic/natriuretic and antihypertrophic properties. These three systems are activated in heart failure and modulate the progression of heart failure. This article will discuss preliminary date concerning simultaneous inhibition of ACE, ECE and/or NEP and their therapeutic potential interest in the treatment of heart failure.

Effects of the ECE/NEP inhibitor CGS 34225 on the big ET-1-induced pressor response and plasma atrial natriuretic peptide concentration in conscious rats

CGS 34226 is a thiol-containing, potent dual inhibitor of endothelin converting enzyme-1 (ECE-1) and neutral endopeptidase 24.11 (NEP) with IC(50) values of 11 and 5 nM respectively. The purpose of the present study was to characterize the inhibitory effects of CGS 34225, an orally active prodrug of CGS 34226, on ECE-1 and NEP in vivo. The effects on ECE-1 and NEP were assessed by determining the inhibition of big endothelin-1 (big ET-1)-induced increases in mean arterial pressure (MAP) and increases in plasma atrial natriuretic peptide (ANP) concentrations respectively, in conscious rats. Thirty and 120 min after the administration of vehicle, big ET-1 (0.3 nmol/kg, intravenously; i.v.) produced pressor responses of approximately 800 mmHg.min (area under the curve for change in MAPxtime). Treatment with CGS 34225 at 1 mgEq/kg, per os (p.o.), decreased the pressor effect of big ET-1 by 39 and 53% at 30 and 120 min respectively (P<0.05, both times). Increasing the dose of CGS 34255 to 30 mgEq/kg, p.o., resulted in greater inhibition, 84 and 92% (P<0.05) at 30 and 120 min respectively. Furthermore, at this higher dose, the inhibitory effect on ECE-1 was long-lasting, averaging 86, 75 and 30% (P<0.05, all times) at 4, 8 and 24 h respectively. In rats treated with vehicle, the infusion of ANP at 450 ng/kg per min i.v. resulted in plasma ANP concentrations of 3.9-4.8 ng/ml that remained relatively constant for 4 h. Treatment with CGS 34225 at 10 mgEq/kg, p.o., increased the ANP level to 7.7+/-1.0 and 10.6+/-1.8 ng/ml at 1 and 4 h after dosing (P<0.05, both times). These data demonstrate that CGS 34225 is a potent, orally active and long-acting inhibitor of ECE-1 and NEP in vivo. It is anticipated that compounds with this dual function may be useful in the treatment of cardiovascular diseases where the ET system plays a pathogenic role and the potentiation of ANP elicits therapeutic benefits.

Recombinant human neutral endopeptidase ameliorates pancreatic elastase-induced lung injury

BACKGROUND

Genetic deletion of neutral endopeptidase (NEP), a cell-surface metalloprotease that degrades proinflammatory peptides, exacerbates lung injury induced by pancreatic elastase in a model of pancreatitis-associated lung injury. We tested 3 hypotheses: (1) genetic deletion of NEP prolongs lung recovery after elastase injections; (2) elastase-mediated lung injury is associated with down-regulation of NEP; and (3) pretreatment of NEP (-/-) and (+/+) animals with recombinant human NEP (rhNEP) reduces pulmonary damage in this model.

METHODS

NEP (+/+) or (-/-) mice were injected with pancreatic elastase (0.085 U/g/dose intraperitoneally) or saline carrier at t = 0 hours and t = 1 hour. Some mice were pretreated with rhNEP (3 mg/kg intraperitoneally). Serum elastase, lung histologic score, myeloperoxidase, and NEP activities were measured at 4, 8, or 12 hours.

RESULTS

NEP (-/-) mice had worse pulmonary inflammation at 4 and 8 hours versus (+/+) mice. Lung NEP activity was similar in elastase-treated and control (+/+) animals. Pretreatment with rhNEP reduced myeloperoxidase and improved histology at 4 hours in NEP (-/-) and (+/+) mice.

CONCLUSIONS

Pancreatic elastase induces lung injury that is worse and prolonged in NEP (-/-) mice. Pretreatment with rhNEP ameliorates this injury. Thus, upregulation of NEP is a potential therapeutic approach for pancreatitis-associated lung injury.

Soluble recombinant neprilysin induces aggrecanase-mediated cleavage of aggrecan in cartilage explant cultures

Neprilysin (neutral endopeptidase, enkephalinase, CALLA, CD10, NEP) is a regulatory Zn metallopeptidase expressed in the brush border membranes of the kidney and has been found in porcine chondrocytes and rat articular cartilage as well as other cell types and tissues. Although its function in cartilage is not currently known, previous observations of high levels of NEP enzymatic activity in the synovial fluid of arthritic patients and on the chondrocyte membranes of human osteoarthritic cartilage have led to the hypothesis that NEP is involved in the inflammation or degradation pathways in articular cartilage. Our study localized endogenous NEP to the membranes of mature bovine articular chondrocytes in a tissue explant model and demonstrated that the addition of soluble recombinant NEP (sNEP) to the culture medium of bovine cartilage explants leads to the degradation of aggrecan through the action of aggrecanase. A 6-day exposure to sNEP was necessary to initiate the degradation, suggesting that the chondrocytes were responding in a delayed manner to an altered composition of regulatory peptides. This NEP-induced degradation was completely inhibited by the NEP inhibitors thiorphan and phosphoramidon. These results suggest that NEP is present as a transmembrane enzyme on articular chondrocytes where it can cleave regulatory peptides and lead to the induction of aggrecanase.

Negative feedback on the effects of stem cell factor on hematopoiesis is partly mediated through neutral endopeptidase activity on substance P: a combined functional and proteomic study

Hematopoietic regulation is a complex but dynamic process regulated by intercellular and intracellular interactions within the bone marrow (BM) microenvironment. Through neurokinin-1 (NK-1) and NK-2 receptors, peptides (eg, substance P [SP]) encoded by the preprotachykinin-I gene mediate distinct hematopoietic effects. Cytokines, associated with hematopoietic stimulation, and SP regulate the expression of each other in BM mesenchymal and immune cells. Neutral endopeptidase (NEP) uses SP as a substrate to produce SP(1-4), which inhibits the proliferation of matured myeloid progenitor. This study determines whether the degradation of SP to SP(1-4) by endogenous NEP in BM stroma could be a feedback on hematopoietic stimulation by stem cell factor (SCF). SP(1-4) induced the production of transforming growth factor (TGF)-beta and tumor necrosis factor-alpha in BM stroma. TGF-beta production accounted for part of the inhibitory effects by SP(1-4) on the proliferation of early (granulocyte-macrophage colony-forming units) and late (long-term culture-initiating cells) hematopoietic progenitors. Enzyme-linked immunosorbent assays and/or protein-chip arrays indicated a timeline change of SP to SP(1-4) in BM stroma stimulated with SCF, which correlated with increase in NEP messenger RNA. Since SP and its fragment, SP(1-4), interact with the same receptor to mediate opposing hematopoietic effects, 2 interactive studies were done to understand the dual responses of NK-1: (1) a 3-dimensional molecular model of NK-1 and SP and (2) screening of a random dodecapeptide library for SP(1-4) interacting sites. The effects of SP(1-4) on hematopoietic progenitors and the timeline change of SP to SP(1-4), together with the 3-dimensional model, provide a partial explanation for the feedback on the stimulatory effects of SCF and SP on hematopoiesis.

Deletion of neutral endopeptidase exacerbates intestinal inflammation induced by Clostridium difficile toxin A

Toxin A (TxA) of Clostridium difficile induces acute inflammation of the intestine initiated by release of substance P (SP) and activation of the neurokinin-1 receptor. However, the mechanisms that terminate this response are unknown. We determined whether the SP-degrading enzyme neutral endopeptidase (NEP, EC 3.4.24.11) terminates TxA-induced enteritis. We used both genetic deletion and pharmacological inhibition of NEP to test this hypothesis. In wild-type mice, instillation of TxA (0.5-5 microg) into ileal loops for 3 h dose dependently increased ileal fluid secretion, stimulated granulocyte transmigration determined by myeloperoxidase activity, and caused histological damage characterized by depletion of enterocytes, edema, and neutrophil accumulation. Deletion of NEP reduced the threshold secretory and inflammatory dose of TxA and exacerbated the inflammatory responses by more than twofold. This exacerbated inflammation was prevented by pretreatment with recombinant NEP. Conversely, pretreatment of wild-type mice with the NEP inhibitor phosphoramidon exacerbated enteritis. Thus NEP terminates enteritis induced by C. difficile TxA, underlying the importance of SP degradation in limiting neurogenic inflammation.

Delayed metabolism of human brain natriuretic peptide reflects resistance to neutral endopeptidase

Metabolism of natriuretic peptides is regulated by two degradative pathways: uptake by the clearance receptor (natriuretic peptide receptor C--NPR-C) and hydrolysis by neutral endopeptidase (NEP). Affinity studies favour a dominant role of NPR-C in hormone degradation in several species but do not account for the efficacy of NEP inhibitors in vivo, nor the uniquely prolonged half life (t((1/2))) of human brain natriuretic peptide (hBNP). Postulating that (1) delayed metabolism of hBNP reflects resistance to NEP and (2) interactions between NPR-C and NEP increase enzyme activity, we have used purified ovine and human NEP, plus ovine lung plasma membranes to study the relative importance of receptor and enzyme pathways. We have also related the findings to hormone metabolism in vivo. Binding affinities of atrial natriuretic peptide (ANP), hBNP and ovine BNP (oBNP) to oNPR-C were similar (K(d)=8-16 pM). In contrast, unlike ANP and oBNP, hBNP was not significantly degraded by purified oNEP or plasma membranes. Despite similar (and high) affinity of oNPR-C for oBNP and hBNP, the t((1/2)) of hBNP (12.7 min) was more than fourfold that of oBNP (2.6 min). Although we found no evidence for receptor-enzyme interaction, our results show that the delayed metabolism of hBNP reflects resistance to NEP. These findings have important implications for future treatment strategies in human disease.

Bombesin-like peptides and receptors in normal fetal baboon lung: roles in lung growth and maturation

Previously, we have shown that bombesin-like peptide (BLP) promotes fetal lung development in rodents and humans but mediates postnatal lung injury in hyperoxic baboons. The present study analyzed the normal ontogeny of BLP and BLP receptors as well as the effects of BLP on cultured normal fetal baboon lungs. Transcripts encoding gastrin-releasing peptide (GRP), a pulmonary BLP, were detectable on gestational day 60 (ED60), peaked on approximately ED90, and then declined before term (ED180). Numbers of BLP-immunopositive neuroendocrine cells peaked from ED80 to ED125 and declined by ED160, preceding GRP-receptor mRNAs detected from ED125 until birth. BLP (0.1-10 nM) stimulated type II cell differentiation in organ cultures as assessed by [(3)H]choline incorporation into surfactant phospholipids, electron microscopy, and increased surfactant protein (SP) A- and/or SP-C-immunopositive cells and SP-A mRNA. BLP also induced neuroendocrine differentiation on ED60. Cell proliferation was induced by GRP, peaking on ED90. Similarly, blocking BLP degradation stimulated lung growth and maturation, which was completely reversed by a BLP-specific antagonist. The dissociation between GRP and GRP-receptor gene expression during ontogeny suggests that novel BLP receptors and/or peptides might be implicated in these responses.

Effect of recombinant neutral endopeptidase (EC 3.4.24.11) on neuropeptide-mediated nasal fluid secretion and plasma exudation in the rat

The nasal mucosa harbors sensory nerves containing neuropeptides such as substance P (SP), which are released by capsaicin. The neuropeptides are degraded by peptidases, e.g., neutral endopeptidase (NEP) that is present in the nasal mucosa. We studied the effect of enzymatically active recombinant NEP (rNEP) on neuropeptide-evoked secretion of nasal fluid and plasma exudation in rats. rNEP administered intranasally (i.n.) reduced the capsaicin-evoked nasal fluid secretion but failed to reduce the secretion evoked by SP (exogenous) under the experimental conditions used. rNEP reduced the increase in nasal plasma exudation evoked by capsaicin (endogenous neuropeptides). Because rNEP reduced neuropeptide-mediated nasal fluid secretion and plasma exudation in the rat, we suggest that peptidase activity in the nasal mucosa will determine the magnitude of the response to locally released neuropeptides.