Neprilysin, the kidney brush border neutral proteinase: a possible potential target for ischemic renal injury

Epithelial FETUB-mediated the inhibition of NEP activity aggravates asthma

BACKGROUND

Neuropeptide accumulation exacerbates asthma, with reduced neprilysin (NEP) activity implicated. However, this regulatory mechanism remains unexplored.

OBJECTIVE

To identify and characterize epithelial-derived modulators of NEP activity and their role in asthma pathogenesis.

METHODS

Bioinformatics and molecular docking identified fetuin B (FETUB) as a NEP inhibitor. FETUB expression in human lung tissue was assessed by immunohistochemistry, and its levels in exhaled breath condensate (EBC) and serum were quantified by ELISA. Functional assays and a lung-specific FETUB knockdown mouse model using Adeno-associated virus (AAV) vector confirmed its role in NEP inhibition and asthma pathogenesis.

RESULTS

Bioinformatic analysis, protein binding assays, and fluorescence substrate degradation experiments confirmed that FETUB is an inhibitor of NEP. Serum FETUB levels were elevated in asthmatics and positively correlated with serum IgE, eosinophil counts. Similarly, in asthmatic EBC, FETUB levels were significantly higher than in healthy controls and negatively correlated with asthma control test, FEV1 and FEV1%pred. The expression of FETUB was elevated in asthma lung tissue and primarily localized to airway epithelial cells. Combined bioinformatics and experimental data indicated that IL-13 as a key inducer of epithelial FETUB expression. Lung-specific FETUB knockdown restored NEP activity, reduced neuropeptides CGRP and SP, and improved airway inflammation and hyperresponsiveness in asthma.

CONCLUSION

The findings suggest that epithelial-derived FETUB exacerbates airway inflammation and hyperresponsiveness in asthma through the inhibition of NEP activity and the resultant accumulation of CGRP and SP.

Protective effect of valsartan alone and in combination with neprilysin inhibitor (valsartan + sacubitril) against hepatic ischemia-reperfusion injury: targeting angiotensin II receptor-neprilysin and modulating SMAD-4/NF-κβ/JNK pathways in rats

Ischemia-reperfusion injury (IRI) is a common pathogenic situation that arises throughout all liver surgeries, including liver transplants. We aimed to compare the preventive effects of valsartan (VST) against valsartan + sacubitril (LCZ696) on hepatic injury caused by IRI. A total of thirty-six male Westar albino rats were split into six groups randomly: sham, IRI, VST + IRI, LCZ696 + IRI, VST, and LCZ696. The medicines were given orally for 10 days in a row. Hepatic tissues and blood were examined through histopathological imaging and immunohistochemical detection of hepatic SMAD-4 protein expression plus serum aminotransferase (ALT, AST) and gamma-glutamyl transferase (GGT) levels. Angiotensin II, aldosterone, and plasma renin activity were evaluated in rat serum. Liver tissue homogenate was utilized to assess reduced glutathione (GSH), myeloperoxidase (MPO), malondialdehyde (MDA), and total nitric oxide (NOx) levels. Pro-inflammatory indicators, tumor necrosis factor-alpha (TNF-α), and interleukin-1β (IL-1β), moreover with apoptosis indicators, BCL2-associated X protein (Bax), B-cell lymphoma 2 (Bcl-2), and galactine-9 (GAL9) proteins plus caspase-3, were measured in hepatic tissue homogenate. Hepatic endothelin-1 and neprilysin activity were evaluated. Western blot was done for c-Jun N-terminal kinase (JNK-7) plus nuclear factor-kappa B (NF-κβ) expressions. The study revealed that VST and LCZ696 pretreatment showed significant restoration of liver injury, correction of oxidative profile, and inhibition in the angiotensin II receptor-neprilysin pathway. Inflammatory mediators and apoptosis were significantly inhibited. The expression of SMAD-4, JNK-7, and NF-κβ proteins was notably diminished. The improvement in hepatic architecture supports these histopathological results. In conclusion, LCZ696 possesses a potentially significant protective effect against liver IRI superior to VST alone.

Balancing renal Ang-II/Ang-(1-7) by xanthenone; an ACE2 activator; contributes to the attenuation of Ang-II/p38 MAPK/NF-κB p65 and Bax/caspase-3 pathways in amphotericin B-induced nephrotoxicity in rats

Despite the great importance of amphotericin B for the management of life-threatening systemic fungal infections, its nephrotoxic effect restricts its repeated administration. This study was designed to examine the prospective modulatory effects of xanthenone, an ACE2 activator, against amphotericin B nephrotoxicity. Male Wistar rats were allocated into four groups; control (1^st), Xanthenone (2^nd), Amphotericin B (3^rd), and Xanthenone + Amphotericin B (4^th). The second and fourth groups received xanthenone (2 mg/kg; s.c.) daily for 14 consecutive days. Amphotericin B (18.5 mg/kg; i.p.) was administered to the third and fourth groups daily starting from day 8. After 2 weeks, samples were withdrawn for analysis. The histopathological findings, molecular and biochemical markers showed that amphotericin B caused marked renal injury. Pretreatment with xanthenone ameliorated amphotericin B-induced deterioration in kidney function biomarkers (creatinine, urea, cystatin C, KIM-1) and guarded against the disturbance of serum electrolytes (Na⁺, K⁺, Mg²⁺) due to amphotericin B-induced tubular dysfunction. Besides, the ACE2 activator xanthenone-balanced renal Ang-II/Ang-(1-7), and so the inflammatory signaling p38 MAPK/NF-κB p65 and its downstream inflammatory cytokines (TNF-α, IL-6) were attenuated. Meanwhile, the anti-oxidant signaling Nrf2/HO-1 and glutathione content were preserved, but the lipid peroxidation marker MDA was declined. These regulatory effects of xanthenone eventually enhanced Bcl-2 (anti-apoptotic), but reduced Bax (pro-apoptotic) and cleaved caspase-3 (apoptotic executioner) protein expressions. Collectively, the regulatory effects of xanthenone on renal Ang-II/Ang-(1-7) could at least partially contribute to the mitigation of amphotericin B nephrotoxicity by attenuating inflammatory signaling, oxidative stress, and apoptosis, thus improving the tolerability to amphotericin B.

Angiotensin receptor blocker neprilysin inhibitors

Heart failure (HF) is a clinical syndrome that results from a structural or functional cardiac disorder that reduces the ability of the ventricle of the heart to fill with, or eject, blood. It is a multifaceted clinical condition that affects up to 2% of the population in the developed world, and is linked to significant morbidity and mortality; it is therefore considered a major concern for public health. Regarding the mechanism of HF, three neurohumoral factors - the renin-angiotensin-aldosterone system, the sympathetic nervous system, and natriuretic peptides - are related to the pathology of chronic HF (CHF), and the targets of treatment. Angiotensin receptor blocker and neprilysin inhibitor (angiotensin-receptor neprilysin inhibitor), namely sacubitril/valsartan (SAC/VAL), has been introduced as a treatment for CHF. SAC/VAL is an efficacious, safe, and cost-effective therapy that improves quality of life and longevity in patients with HF with reduced ejection fraction (HFrEF), and reduces hospital admissions. An in-hospital initiation strategy offers a potential new avenue to improve the clinical uptake of SAC/VAL. In the last five years, SAC/VAL has been established as a cornerstone component of comprehensive disease-modifying medical therapy in the management of chronic HFrEF. On the other hand, further work, with carefully designed and controlled preclinical studies, is necessary for understanding the molecular mechanisms, effects, and confirmation of issues such as long-term safety in both human and animal models.

Broadening COVID-19 Interventions to Drug Innovation: Neprilysin Pathway as a Friend, Foe, or Promising Molecular Target?

The coronavirus disease 2019 (COVID-19) pandemic caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus is anticipated to transition to an endemic state as vaccines are providing relief in some, but not all, countries. Drug discovery for COVID-19 can offer another tool in the fight against the pandemic. Additionally, COVID-19 impacts multiple organs that call for a systems medicine approach to planetary health and therapeutics innovation. In this context, innovation for drugs that prevent and treat COVID-19 is timely and much needed. As the virus variants emerge under different ecological conditions and contexts in the long haul, a broad array of vaccine and drug options will be necessary. This expert review article argues for a need to expand the COVID-19 interventions, including and beyond vaccines, to stimulate discovery and development of novel medicines against SARS-CoV-2 infection. The Renin-Angiotensin-Aldosterone System (RAAS) is known to play a major role in SARS-CoV-2 infection. Neprilysin (NEP) and angiotensin-converting enzyme (ACE) have emerged as the pharmaceutical targets of interest in the search for therapeutic interventions against COVID-19. While the NEP/ACE inhibitors offer promise for repurposing against COVID-19, they may display a multitude of effects in different organ systems, some beneficial, and others adverse, in modulating the inflammation responses in the course of COVID-19. This expert review offers an analysis and discussion to deepen our present understanding of the pathophysiological function of neprilysin in multiple organs, and the possible effects of NEP inhibitor-induced inflammatory responses in COVID-19-infected patients.

Repurposing of existing FDA approved drugs for Neprilysin inhibition: An in-silico study

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Drug repurposing of FDA approved drugs from ZINC 12 database was done using the crystal structure of extracellular domain of human NEP (PDB ID: 5JMY)

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The interactions with catalytic triad of HIS583, HIS587 and GLU646 are important for NEP inhibition.

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Based on XP molecular docking, binding energy, IFD-SP and MD simulation top 4 NEP inhibitors were identified.

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ZINC000000601283 and ZINC000003831594 were found to be stable during MD simulation and may act as NEP inhibitors.

Neprilysin (NEP) is a neutral endopeptidase with diverse physiological roles in the body. NEP's role in degradation of diverse classes of peptides such as amyloid beta, natriuretic peptide, substance P, angiotensin, endothelins, etc., is associated with pathologies of alzheimer's, kidney and heart diseases, obesity, diabetes and certain malignancies. Hence, the functional inhibition of NEP in the above systems can be a good therapeutic target. In the present study, in-silico drug repurposing approach was used to identify NEP inhibitors. Molecular docking was carried out using GLIDE tool. 2934 drugs from the ZINC12 database were screened using high throughput virtual screening (HTVS) followed by standard precision (SP) and extra precision (XP) docking. Based on the XP docking score and ligand interaction, the top 8 hits were subjected to free ligand binding energy calculation, to filter out 4 hits (ZINC000000001427, ZINC000001533877, ZINC000000601283, and ZINC000003831594). Further, induced fit docking-standard precision (IFD-SP) and molecular dynamics (MD) studies were performed. The results obtained from MD studies suggest that ZINC000000601283-NEP and ZINC000003831594-NEP complexes were most stable for 20ns simulation period as compared to ZINC000001533877-NEP and ZINC000000001427-NEP complexes. Interestingly, ZINC000000601283 and ZINC000003831594 showed similarity in binding with the reported NEP inhibitor sacubitrilat. Findings from this study suggest that ZINC000000601283 and ZINC000003831594 may act as NEP inhibitors. In future studies, the role of ZINC000000601283 and ZINC000003831594 in NEP inhibition should be tested in biological systems to evaluate therapeutic effect in NEP associated pathological conditions.