Common acute lymphocytic leukemia antigen is identical to neutral endopeptidase

Neprilysin Inhibitors in Heart Failure: The Science, Mechanism of Action, Clinical Studies, and Unanswered Questions

This article provides a contemporary review and a new perspective on the role of neprilysin inhibition in heart failure (HF) in the context of recent clinical trials and addresses potential mechanisms and unanswered questions in certain HF patient populations. Neprilysin is an endopeptidase that cleaves a variety of peptides such as natriuretic peptides, bradykinin, adrenomedullin, substance P, angiotensin I and II, and endothelin. It has a broad role in cardiovascular, renal, pulmonary, gastrointestinal, endocrine, and neurologic functions. The combined angiotensin receptor and neprilysin inhibitor (ARNi) has been developed with an intent to increase vasodilatory natriuretic peptides and prevent counterregulatory activation of the angiotensin system. ARNi therapy is very effective in reducing the risks of death and hospitalization for HF in patients with HF and New York Heart Association functional class II to III symptoms, but studies failed to show any benefits with ARNi when compared with angiotensin-converting enzyme inhibitors or angiotensin receptor blocker in patients with advanced HF with reduced ejection fraction or in patients following myocardial infarction with left ventricular dysfunction but without HF. These raise the questions about whether the enzymatic breakdown of natriuretic peptides may not be a very effective solution in advanced HF patients when there is downstream blunting of the response to natriuretic peptides or among post-myocardial infarction patients in the absence of HF when there may not be a need for increased natriuretic peptide availability. Furthermore, there is a need for additional studies to determine the long-term effects of ARNi on albuminuria, obesity, glycemic control and lipid profile, blood pressure, and cognitive function in patients with HF.

A Novel Mutation of the Membrane Metallo-Endopeptidase Gene Related to Late-Onset Hereditary Polyneuropathy: Case Report and Review of the Literature

The advent of next generation sequencing has revolutionized diagnostic approaches to hereditary polyneuropathies. Recently, mutations on the membrane metallo-endopeptidase (MME) gene, encoding neprilysin, have been related to the development of late-onset Charcot-Marie-Tooth disease type 2 (CMT2). Here, we report the first Greek patient presenting with a slowly progressive late-onset axonal polyneuropathy and a novel, likely pathogenic, heterozygous variant in the MME gene. In addition, we have performed a systematic review of all published case reports of patients with MME mutations. The results of the studies show that MME variants can be inherited as both fully penetrant autosomal-recessive and incompletely penetrant autosomal-dominant traits. A number of heterozygous variants characterized as incompletely penetrant impose an increased risk of developing a CMT2-like phenotype late in life, identical to the case study described here. Greater mutation numbers in different populations and mutation-specific functional studies will be essential to identify the pathogenicity and inheritance of more MME variants.

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.

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.

[CD10 expression in stromal cells of patients with breast cancer: a poor prognostic marker]

Introduction

markers in breast cancer stem cells, such as cluster of differentiation 10 (CD10), would be correlated with invasive and metastatic potential of several types of cancer, contributing to tumor growth and metastases. In patients with breast cancer, its prognostic value is still controversial, given the discrepancy of results. The purpose of the study was to study CD10 expression in stromal cells of patients with breast cancer as well as to evaluate the prognostic value of this expression.

Method

we conducted a retrospective, descriptive and prognostic study. It involved 57 patients with invasive cancer of no special type, whose data were collected in the Department of Pathological Anatomy at the Mongi Slim Hospital over a 38-month period. CD10 expression was studied immunohistochemically and interpreted by semi-quantitative scoring system based on three categories with thresholds of 10 and 30%.

Results

the average age of patients was 56.4 years. Twenty-eight patients (49%) had labeled CD10 stromal, half of patients had a score of 1 (low) and the other half had 2 (high). This labeling significantly reduced recurrence-free survival (p=0.001). However, it had no influence on overall survival (p=0.84). The correlation study showed that CD10 expression in stromal cells was significantly correlated with 12 poor prognostic factors in patients with breast cancer.

Conclusion

CD10 expression in stromal cells of invasive breast cancer is a poor prognostic factor, predictive of poor survival without recurrence and associated with a high invasive and metastatic potential.

Neutral Endopeptidase (Neprilysin) in Therapy and Diagnostics: Yin and Yang

Neprilysin (NEP) is a zinc-dependent metalloproteinase that exists in organisms in both transmembrane and soluble forms. NEP substrates are involved in regulating the cardiovascular and nervous systems. In this review, we discuss some of the biochemical characteristics and physiological functions of this enzyme with special emphasis on the use of NEP as a therapeutic target. The history and various physiological aspects of applying NEP inhibitors for treating heart failure and attempts to increase NEP activity when treating Alzheimer's disease using gene and cell therapies are described. Another important issue discussed is the role of NEP as a potential marker for predicting the risk of cardiovascular disease complications. The diagnostic and prognostic performance of soluble NEP in various types of heart failure is analyzed and presented. We also discuss the methods and approaches for measuring NEP activity for prognosis and diagnosis, as well as a possible new role of natriuretic peptides (NEP substrates) in cardiovascular diagnostics.

Expression of neprilysin in periodontitis-affected gingival tissues

OBJECTIVE

Although the pathogeneses of Alzheimer's disease (AD) and periodontal diseases have overlapping features, including ageing and chronic inflammation, the association between AD and periodontitis remains unclear. To explore the pathogenesis of periodontitis, a comprehensive gene expression/transcriptome analysis in periodontitis-affected gingival tissues found that the AD pathway was significantly up-regulated in periodontitis-affected gingival tissues. AD-related genes, amyloid beta precursor protein (APP), interleukin-1 beta and compliment 1QA, were significantly elevated in periodontitis. In the present study, balance between mRNA expression of APP and a potent amyloid degradation enzyme, neprilysin (NEP), as well as protein localisation of APP and NEP were analysed.

DESIGN

Eighteen periodontitis-affected and 18 clinically healthy control gingival tissues were taken from patients with severe chronic periodontitis or undergoing tooth extraction. Total RNA was purified and used for quantitative reverse transcription real-time polymerase chain reaction (qRT-PCR). The localisation of APP and NEP was analysed by immunohistochemistry (IHC).

RESULTS

Both APP and NEP genes were up-regulated in periodontitis-affected gingival tissues. APP-expressing macrophages and NEP-expressing neutrophils and fibroblasts, reflecting inflammatory stages, were detected in inflamed gingival tissues by IHC.

CONCLUSION

The up-regulation of APP and NEP mRNA levels in periodontitis-affected gingival tissues compared with healthy controls was confirmed by qRT-PCR analyses. Since NEP is one of the primary enzymes that degrades amyloid beta, increased NEP mRNA levels in periodontitis may act as an inhibitor of amyloid beta accumulation in gingival tissues, balancing increased APP mRNA expression. However, NEP has several effects including degradation of vasoactive substances; therefore, further sresearch is needed.

Anti-inflammatory effect of novel analogs of natural enkephalinase inhibitors in a mouse model of experimental colitis

Aim: The pharmacotherapy of inflammatory bowel disease is difficult and currently available treatments bring mostly poor and unsatisfactory results. Results: The purpose of this work was the synthesis of opiorphin, sialorphin, spinorphin and a series of their analogs and the in vitro characterization of their effect on degradation of enkephalin by neutral endopeptidase and aminopeptidase N. Consequently, we investigated in vivo the anti-inflammatory effect of the most active inhibitors selected in the in vitro studies (Pal-KKQRFSR & Pal-KKQHNPR). Putative inhibitor – enzyme (neutral endopeptidase or aminopeptidase N) complexes are also presented and their binding interfaces are identified. Conclusion: Our results suggest that Pal-KKQHNPR has the potential to become a valuable template for anti-inflammatory therapeutics for the treatment of GI tract inflammation.

The anti-inflammatory Annexin A1 induces the clearance and degradation of the amyloid-β peptide

Background

The toxicity of amyloid-β (Aβ) peptide present in the brain of Alzheimer’s disease (AD) patients is thought to be mediated via the increased secretion of pro-inflammatory mediators, which can lead to neuronal dysfunction and cell death. In addition, we have previously shown that inflammation can affect Aβ generation. More recently, we have reported that in vitro administration of the anti-inflammatory mediator Annexin A1 (ANXA1) following an inflammatory challenge suppressed microglial activation and this effect was mediated through formyl peptide receptor-like 1 (FPRL1/FPR2) signalling. The aim of this study was to determine the potential role of ANXA1 in the generation and clearance of Aβ.

Methods

We first compared ANXA1 protein expression in the brains of AD patients and healthy controls as well as in the 5XFAD model of AD. To determine the role of ANXA1 in the processing of amyloid precursor protein (APP) and the degradation of Aβ, N2a neuroblastoma cells were treated with human recombinant ANXA1 or transfected with ANXA1 siRNA. We also investigated the effect of ANXA1 on Aβ phagocytosis and microglial activation in BV2 cells treated with synthetic Aβ.

Results

Our data show that ANXA1 is increased in the brains of AD patients and animal models of AD at early stages. ANXA1 was able to reduce the levels of Aβ by increasing its enzymatic degradation by neprilysin in N2a cells and to stimulate Aβ phagocytosis by microglia. These effects were mediated through FPRL1 receptors. In addition, ANXA1 inhibited the Aβ-stimulated secretion of inflammatory mediators by microglia.

Conclusions

These data suggest that ANXA1 plays a pivotal role in Aβ clearance and supports the use of ANXA1 as potential pharmacological tool for AD therapeutics.

Electronic supplementary material

The online version of this article (doi:10.1186/s12974-016-0692-6) contains supplementary material, which is available to authorized users.

Epithelial-mesenchymal interaction mechanisms leading to the over-expression of neprilysin are involved in the UVB-induced formation of wrinkles in the skin

In clinical studies, the formation of facial wrinkles has been closely linked to the loss of elastic properties of the skin. Repetitive UVB irradiation of animal skin at suberythemal doses significantly reduces its elastic properties, resulting in the formation of wrinkles. That also elicits a marked alteration in the three-dimensional structure of elastic fibres, which is closely associated with a subsequent reduction in the elastic properties of the skin. While UVB irradiation stimulates the activity of skin fibroblast-derived elastase in the dermis, a synthetic inhibitor specific for skin fibroblast-derived elastase as well as an extract of Zingiber officinale (L.) Rose capable of inhibiting skin fibroblast-derived elastase, but not neutrophil elastase, prevented wrinkle formation in our studies of animal and human facial skin, respectively. The close interrelationship among wrinkle formation, elastic properties and elastic fibre linearity is revealed by the effects of different concentrations of the elastase inhibitor, which indicates that enhanced elastase activity by dermal fibroblasts plays a pivotal role in the UVB wrinkling mechanism. Fortunately, we were able to identify human skin fibroblast-derived elastase as the previously known enzyme neprilysin/neutral endopeptidase. Using both a UVB-conditioned medium assay and a co-culture system, we characterized the epithelial-mesenchymal interaction between keratinocytes and fibroblasts which leads to increased expression of neprilysin at the transcriptional, translational and enzymatic levels. Our results demonstrate that interleukin-1α and granulocyte-macrophage colony-stimulating factor are intrinsic cytokines secreted by UVB-exposed keratinocytes that stimulate the expression of neprilysin by skin fibroblasts.

Biological mechanisms underlying the ultraviolet radiation-induced formation of skin wrinkling and sagging II: over-expression of neprilysin plays an essential role

Our previous studies strongly indicated that the up-regulated activity of skin fibroblast-derived elastase plays a pivotal role in wrinkling and/or sagging of the skin via the impairment of elastic fiber configuration and the subsequent loss of skin elasticity. Fortunately, we succeeded in identifying human skin fibroblast-derived elastase as a previously known enzyme, neprilysin or neutral endopeptidase (NEP). We have also characterized epithelial-mesenchymal paracrine cytokine interactions between UVB-exposed-keratinocytes and dermal fibroblasts and found that interleukin-1α and granulocyte macrophage colony stimulatory factor (GM-CSF) are intrinsic cytokines secreted by UVB-exposed keratinocytes that stimulate the expression of neprilysin by fibroblasts. On the other hand, direct UVA exposure of human fibroblasts significantly stimulates the secretion of IL-6 and also elicits a significant increase in the gene expression of matrix metallo-protease(MMP)-1 as well as neprilysin (to a lesser extent), which is followed by distinct increases in their protein and enzymatic activity levels. Direct UVA exposure of human keratinocytes also stimulates the secretion of IL-6, IL-8 and GM-CSF but not of IL-1 and endothelin-1. These findings suggest that GM-CSF secreted by UVA-exposed keratinocytes as well as IL-6 secreted by UVA-exposed dermal fibroblasts play important and additional roles in UVA-induced sagging and wrinkling by up-regulation of neprilysin and MMP-1, respectively, in dermal fibroblasts.

Amyloid-clearing proteins and their epigenetic regulation as a therapeutic target in Alzheimer's disease

Abnormal elevation of amyloid β-peptide (Aβ) levels in the brain is the primary trigger for neuronal cell death specific to Alzheimer’s disease (AD). It is now evident that Aβ levels in the brain are manipulable due to a dynamic equilibrium between its production from the amyloid precursor protein (APP) and removal by amyloid clearance proteins. Clearance can be either enzymic or non-enzymic (binding/transport proteins). Intriguingly several of the main amyloid-degrading enzymes (ADEs) are members of the M13 peptidase family (neprilysin (NEP), NEP2 and the endothelin converting enzymes (ECE-1 and -2)). A distinct metallopeptidase, insulin-degrading enzyme (IDE), also contributes to Aβ degradation in the brain. The ADE family currently embraces more than 20 members, both membrane-bound and soluble, and of differing cellular locations. NEP plays an important role in brain function terminating neuropeptide signals. Its decrease in specific brain areas with age or after hypoxia, ischaemia or stroke contribute significantly to the development of AD pathology. The recently discovered mechanism of epigenetic regulation of NEP (and other genes) by the APP intracellular domain (AICD) and its dependence on the cell type and APP isoform expression suggest possibilities for selective manipulation of NEP gene expression in neuronal cells. We have also observed that another amyloid-clearing protein, namely transthyretin (TTR), is also regulated in the neuronal cell by a mechanism similar to NEP. Dependence of amyloid clearance proteins on histone deacetylases and the ability of HDAC inhibitors to up-regulate their expression in the brain opens new avenues for developing preventive strategies in AD.

Pathway-based analysis of the hidden genetic heterogeneities in cancers

Many cancers apparently showing similar phenotypes are actually distinct at the molecular level, leading to very different responses to the same treatment. It has been recently demonstrated that pathway-based approaches are robust and reliable for genetic analysis of cancers. Nevertheless, it remains unclear whether such function-based approaches are useful in deciphering molecular heterogeneities in cancers. Therefore, we aimed to test this possibility in the present study. First, we used a NCI60 dataset to validate the ability of pathways to correctly partition samples. Next, we applied the proposed method to identify the hidden subtypes in diffuse large B-cell lymphoma (DLBCL). Finally, the clinical significance of the identified subtypes was verified using survival analysis. For the NCI60 dataset, we achieved highly accurate partitions that best fit the clinical cancer phenotypes. Subsequently, for a DLBCL dataset, we identified three hidden subtypes that showed very different 10-year overall survival rates (90%, 46% and 20%) and were highly significantly (P=0.008) correlated with the clinical survival rate. This study demonstrated that the pathway-based approach is promising for unveiling genetic heterogeneities in complex human diseases.

Neprilysin and Aβ Clearance: Impact of the APP Intracellular Domain in NEP Regulation and Implications in Alzheimer's Disease

One of the characteristic hallmarks of Alzheimer's disease (AD) is an accumulation of amyloid β (Aβ) leading to plaque formation and toxic oligomeric Aβ complexes. Besides the de novo synthesis of Aβ caused by amyloidogenic processing of the amyloid precursor protein (APP), Aβ levels are also highly dependent on Aβ degradation. Several enzymes are described to cleave Aβ. In this review we focus on one of the most prominent Aβ degrading enzymes, the zinc-metalloprotease Neprilysin (NEP). In the first part of the review we discuss beside the general role of NEP in Aβ degradation the alterations of the enzyme observed during normal aging and the progression of AD. In vivo and cell culture experiments reveal that a decreased NEP level results in an increased Aβ level and vice versa. In a pathological situation like AD, it has been reported that NEP levels and activity are decreased and it has been suggested that certain polymorphisms in the NEP gene result in an increased risk for AD. Conversely, increasing NEP activity in AD mouse models revealed an improvement in some behavioral tests. Therefore it has been suggested that increasing NEP might be an interesting potential target to treat or to be protective for AD making it indispensable to understand the regulation of NEP. Interestingly, it is discussed that the APP intracellular domain (AICD), one of the cleavage products of APP processing, which has high similarities to Notch receptor processing, might be involved in the transcriptional regulation of NEP. However, the mechanisms of NEP regulation by AICD, which might be helpful to develop new therapeutic strategies, are up to now controversially discussed and summarized in the second part of this review. In addition, we review the impact of AICD not only in the transcriptional regulation of NEP but also of further genes.

Prognostic impact of CD10 expression in clinical outcome of invasive breast carcinoma

BACKGROUND

Early diagnosis and treatment for breast cancers has greatly improved in recent years, however, subset of this disease with early recurrence have remained to be unpredictable. Several studies has addressed that strong CD10 expression in tumor stroma is associated with poor survival rate of breast cancers, but no correlation between CD10 expression and disease-free survival has been elucidated yet. For these reasons, this study with modified immunohistochemical (IHC) staining evaluated the expression of CD10 in invasive breast carcinomas (IBCs) and analyzed correlations between CD10 expression on tumor cells, stromal cells and myeloid-like cells with clinicopathological parameters and recurrence status.

METHOD

IHC staining method was performed on formalin-fixed paraffin-embedded sections of 73 cases of primary IBCs, with record of pathological characteristics of subjects followed up from 1998 to 2007.

RESULTS

Stromal CD10 expression was observed in 39/73 cases (53.4 %) with strong expression in 41.0 %. Three cases stained positive for myeloid-like cells and five for carcinomatous cells, of which 6 cases had recurrence and/or regional LN status. Stromal CD10 expression was significantly higher in the unfavorable group (69.6 %; 16/23 cases) compared with the favorable group (32.1 %; 9/28 cases) (p = 0.048). The levels of CD10 expression showed significant difference among clinical outcomes (recurrence or non-recurrence), independent of regional LN status (p = 0.034), histology type (p = 0.044), ER status (p = 0.042), PgR status (p = 0.039), Her2 status (p = 0.038) and Ki67 index (p = 0.036) (partial Pearson correlations). Cox proportional-hazards regression showed that risk factors for disease-free survival were stromal CD10 expression [CD10±, CD10+ versus CD10++; p = 0.003; HR 2.824 (1.427-5.591)]; regional LN status [N0, N1, N2, versus N3; p = 0.004; HR 2.107 (1.262-3.517)] and PgR status [negative versus positive, p = 0.006, HR 0.172 (0.049-0.596)].

CONCLUSION

CD10 expression on stroma with or without other positive tumor cells and/or myeloid-like cells may function as a powerful prognostic factor for IBC disease-free survival rates, predicting of potential recurrence. It can be determined by a simple modified IHC staining method, which is independent of other prognostic morphologic markers and biomarkers in IBC.

The concept of the onychodermis (specialized nail mesenchyme): an embryological assessment and a comparative analysis with the hair follicle

BACKGROUND

Recently, an intriguing concept was introduced into the literature that defines the area underlying the nail bed as a specific mesenchymal substructure unique to the nail organ. It has been termed onychodermis. The onychodermis expresses CD10 with remarkable specificity. Herein, we compare adult and fetal human hair follicles with fetal nail organs in an attempt to draw analogies for the mesenchyme associated with both adnexal structures.

METHODS

We examined immunohistochemically samples from adult and fetal hair follicles for the expression of CD10, CD34 and the mesenchymal stem cell marker nestin and compared the antigen profile with that of the fetal nail organ.

RESULTS

The CD10-positive/CD34-negative onychodermis is prominently visible at the end of the second trimester. A corresponding follicular structure was not identified, either in the adult or in the developing hair follicle. Nestin staining does not define the onychodermis.

CONCLUSIONS

The concept of the onychodermis is equally valid in the developing nail organ where it is also defined by its expression for CD10. Its function may be related to the anchorage of the overlying nail bed but may also involve a more dynamic role in the induction of hard keratins in the latter, contributing to the formation of the nail plate.

The Alzheimer's amyloid-degrading peptidase, neprilysin: can we control it?

The amyloid cascade hypothesis of Alzheimer's disease (AD) postulates that accumulation in the brain of amyloid β-peptide (Aβ) is the primary trigger for neuronal loss specific to this pathology. In healthy brain, Aβ levels are regulated by a dynamic equilibrium between Aβ release from the amyloid precursor protein (APP) and its removal by perivascular drainage or by amyloid-degrading enzymes (ADEs). During the last decade, the ADE family was fast growing, and currently it embraces more than 20 members. There are solid data supporting involvement of each of them in Aβ clearance but a zinc metallopeptidase neprilysin (NEP) is considered as a major ADE. NEP plays an important role in brain function due to its role in terminating neuropeptide signalling and its decrease during ageing or after such pathologies as hypoxia or ischemia contribute significantly to the development of AD pathology. The recently discovered mechanism of epigenetic regulation of NEP by the APP intracellular domain (AICD) opens new avenues for its therapeutic manipulation and raises hope for developing preventive strategies in AD. However, consideration needs to be given to the diverse physiological roles of NEP. This paper critically evaluates general biochemical and physiological functions of NEP and their therapeutic relevance.

Metalloproteases and Proteolytic Processing

Proteolytic enzymes constitute around 2% of the human genome and are involved in all stages of cell and organism development from fertilization through to cell death. In the human genome the major classes of peptidases are represented by cysteine-, serine- and metalloenzymes, which possess a wide spectrum of substrate specificity and physiological functions. The identification of many novel peptidases from genome sequencing programmes has suggested potential new therapeutic targets. In addition, several well characterised peptidases were recently shown to possess new and unexpected biological roles in neuroinflammation, cancer and angiogenesis, cardiovascular diseases and neurodegeneration. This chapter will briefly characterize the main classes of metallopeptidases and their roles in health and disease. Particular attention will be paid to the angiotensin-converting enzyme (ACE), neprilysin (NEP) and adamalysin (ADAM) families of proteases and their pathophysiological roles with a particular emphasis on cancer and neurodegeneration. The roles and mechanisms of protein shedding which primarily involve the ADAMs family of metallopeptidases will be explained using amyloid protein precursor (APP) processing cascades as a well characterized example. The therapeutic significance of modulating (activating or inhibiting) metallopeptidase activity will be a particular focus of this chapter.

Neprilysin is identical to skin fibroblast elastase: its role in skin aging and UV responses

Although human skin fibroblast (HSF) elastase has been characterized as a membrane-bound metalloproteinase, little is known about its structure, amino acid sequence, and encoding gene. As there are similarities in the molecular weights and inhibitory profiles of HSF elastase and neprilysin (neutral endopeptidase 24.11 (NEP)), in this study we tested the hypothesis that they are identical using immunoprecipitation and transfection methods. An immunoprecipitation study demonstrated that HSF elastase activity co-immunoprecipitated with anti-NEP in lysates of cultured HSF. Transfection of an NEP cDNA expression vector into COS-1 cells elicited the expression of HSF elastase and NEP activities in the transfected cells. These findings strongly suggest that HSF elastase is identical to NEP, which functions mainly in neuron-associated cells to degrade neuropeptides. Analysis of the expression pattern of NEP revealed that its expression was remarkably up-regulated at the gene, protein, and enzymatic activity levels during the replicative senescence of cultured HSF. Further, the activity of NEP was markedly enhanced in a pattern similar to elastase activity during the intrinsic aging of mouse skin, in UVA-exposed HSF as well as in HSF treated with conditioned medium from UVB-exposed human keratinocytes. Analysis of the cytokine profile for the stimulation of NEP and HSF elastase activities in HSF demonstrated that among the 11 cytokines tested, IL-1α, IL-1β, IL-6, IL-8, and GM-CSF had the potential to significantly stimulate both activities similarly, again supporting the identity of HSF elastase and NEP.

beta-Amyloid degradation and Alzheimer's disease

Extensive β-amyloid (Aβ) deposits in brain parenchyma in the form of senile plaques and in blood vessels in the form of amyloid angiopathy are pathological hallmarks of Alzheimer's disease (AD). The mechanisms underlying Aβ deposition remain unclear. Major efforts have focused on Aβ production, but there is little to suggest that increased production of Aβ plays a role in Aβ deposition, except for rare familial forms of AD. Thus, other mechanisms must be involved in the accumulation of Aβ in AD. Recent data shows that impaired clearance may play an important role in Aβ accumulation in the pathogenesis of AD. This review focuses on our current knowledge of Aβ-degrading enzymes, including neprilysin (NEP), endothelin-converting enzyme (ECE), insulin-degrading enzyme (IDE), angiotensin-converting enzyme (ACE), and the plasmin/uPA/tPA system as they relate to amyloid deposition in AD.

The use of Fluorescence Resonance Energy Transfer (FRET) peptidesfor measurement of clinically important proteolytic enzymes

Proteolytic enzymes have a fundamental role in many biological processes and are associated with multiple pathological conditions. Therefore, targeting these enzymes may be important for a better understanding of their function and development of therapeutic inhibitors. Fluorescence Resonance Energy Transfer (FRET) peptides are convenient tools for the study of peptidases specificity as they allow monitoring of the reaction on a continuous basis, providing a rapid method for the determination of enzymatic activity. Hydrolysis of a peptide bond between the donor/acceptor pair generates fluorescence that permits the measurement of the activity of nanomolar concentrations of the enzyme. The assays can be performed directly in a cuvette of the fluorimeter or adapted for determinations in a 96-well fluorescence plate reader. The synthesis of FRET peptides containing ortho-aminobenzoic acid (Abz) as fluorescent group and 2, 4-dinitrophenyl (Dnp) or N-(2, 4-dinitrophenyl)ethylenediamine (EDDnp) as quencher was optimized by our group and became an important line of research at the Department of Biophysics of the Federal University of São Paulo. Recently, Abz/Dnp FRET peptide libraries were developed allowing high-throughput screening of peptidases substrate specificity. This review presents the consolidation of our research activities undertaken between 1993 and 2008 on the synthesis of peptides and study of peptidases specificities.

CD10 AND CD34 expression in childhood acute lymphoblastic leukemia in Morocco: clinical relevance and outcome

CD10 and CD34 expression in 86 Moroccan children with acute lymphoblastic leukemias (ALL) and the relevance to prognosis, diagnosis, and outcome during a 5-year follow-up were examined. At diagnosis, 57% of patients had CD10(+) blasts, while 35% had CD34(+) blasts. The CD10(+) blast frequency was much higher (80%) in B-ALL than in T-ALL (20%). The frequency of CD34(+) blasts was higher in B-ALL (48%) compared to T-ALL (16%). The 5-year survival curves showed that children with CD10(+) B-ALL had a significantly longer survival rate than those with CD10(-), as observed for T-ALL. The survival rate of B-ALL expressing CD34 was higher than that of CD34(-). Thus, CD34 and CD10 expression may have prognostic value and is associated with a better clinical outcome.

Lack of hepatocellular CD10 along bile canaliculi is physiologic in early childhood and persistent in Alagille syndrome

Many tissues, including hepatobiliary cells, express neutral endopeptidase (CD10), encoded by MME. Serum neutral endopeptidase activity (NEA) has been recommended as a marker of cholestasis in adults but not in children with Alagille syndrome (AGS). We investigated ontogenic and disease-related differences in the expression of CD10. CD10 was found on canalicular surfaces of hepatocytes throughout the lobule in 16 adults and in 31 children aged > or =24 months, with and without cholestasis, but not in 39 children aged <24 months, with and without cholestasis. Ten AGS children aged 2 months to 6 years lacked any canalicular CD10 expression. Cholangiocyte apices and/or intrasinusoidal granulocytes marked for CD10 in all subjects. Liver membrane fractions from a child with cholestasis aged <24 months and from 2 AGS patients aged >24 months contained reduced levels of CD10. In contrast, AGS children and all controls expressed CD10 similarly on granulocytes. MME mRNA was found in the liver of children aged <24 months and of adults, all with cholestasis, and of AGS patients. Granulocyte MME mRNA levels were similar among all study subjects; however, liver MME mRNA levels were 6- to 140-fold less than in normal adults in all cholestatic subjects, including AGS children. Methylation of the MME promoter was not detected in the liver of AGS children. In conclusion, hepatocytes in early childhood physiologically lack immunohistochemically detectable CD10. Reduced MME mRNA in AGS is not due to MME promoter methylation. Liver CD10 in childhood appears to undergo reduced synthesis or rapid degradation, which persists in AGS. Absence of CD10 expression thus may limit NEA as a marker of cholestasis in young patients and in AGS.

Neprilysin carboxydipeptidase specificity studies and improvement in its detection with fluorescence energy transfer peptides

We examined the substrate specificity of the carboxydipeptidase activity of neprilysin (NEP) using fluorescence resonance energy transfer (FRET) peptides containing ortho-aminobenzoyl (Abz) and 2,4-dinitrophenyl (Dnp) as a donor/acceptor pair. Two peptide series with general sequences Abz-RXFK(Dnp)-OH and Abz-XRFK(Dnp)-OH (X denotes the position of the altered amino acid) were synthesized to study P1 (cleavage at the X-F bond) and P2 (cleavage at R-F bond) specificity, respectively. In these peptides a Phe residue was fixed in P1' to fulfill the well-known NEP S1' site requirement for a hydrophobic amino acid. In addition, we explored NEP capability to hydrolyze bradykinin (RPPGFSPFR) and its fluorescent derivative Abz-RPPGFSPFRQ-EDDnp (EDDnp=2,4-dinitrophenyl ethylenediamine). The enzyme acts upon bradykinin mainly as a carboxydipeptidase, preferentially cleaving Pro-Phe over the Gly-Phe bond in a 9:1 ratio, whereas Abz-RPPGFSPFRQ-EDDnp was hydrolyzed at the same bonds but at an inverted proportion of 1:9. The results show very efficient interaction of the substrates' C-terminal free carboxyl group with site S2' of NEP, confirming the enzyme's preference to act as carboxydipeptidase at substrates with a free carboxyl-terminus. Using data gathered from our study, we developed sensitive and selective NEP substrates that permit continuous measurement of the enzyme activity, even in crude tissue extracts.

New insights into the roles of metalloproteinases in neurodegeneration and neuroprotection

Proteolytic enzymes constitute around 2% of the human genome and are involved in many stages of cell development from fertilization to death (apoptosis). The identification of many novel proteases from genome-sequencing programs has suggested them as potential new therapeutic targets. In addition, several well-characterized metallopeptidases were recently shown to possess new biological roles in neuroinflammation and neurodegeneration. As a result of these studies, metabolism of the neurotoxic and inflammatory amyloid peptide (Abeta) is considered as a physiologically relevant process with several metallopeptidases being suggested for the role of amyloid-degrading enzymes. These include the neprilysin (NEP) family of metalloproteinases (including its homologue endothelin-converting enzyme), insulin-degrading enzyme, angiotensin-converting enzyme, plasmin, and, possibly, some other enzymes. NEP also has a role in metabolism of sensory and inflammatory neuropeptides such as tachykinins and neurokinins. The existence of natural enzymatic mechanisms for removal of amyloid peptides has extended the therapeutic avenues in Alzheimer's disease (AD) and neurodegeneration. The proteolytic events underlying AD are highly compartmentalized in the cell and formation of amyloid peptide from its precursor molecule APP (amyloid precursor protein) takes place both within intracellular compartments and in the plasma membrane, especially in lipid raft domains. Degradation of amyloid peptide by metallopeptidases can also be both intra- and extracellular depending on the activity of membrane-bound enzymes and their soluble partners. Soluble forms of proteases can be secreted or released from the cell surface through the activity of "sheddases"-another group of proteolytic enzymes involved in key cellular regulatory functions. The activity of proteases involved in amyloid metabolism depends on numerous factors (e.g., genetic, environmental, age), and some conditions (e.g., hypoxia and ischemia) shift the balance of amyloid metabolism toward accumulation of higher concentrations of Abeta. In this regard, regulation of the activity of amyloid-degrading enzymes should be considered as a viable strategy in neuroprotection.

Neonatal disease in neutral endopeptidase alloimmunization: lessons for immunological monitoring

Neutral endopeptidase (NEP) alloimmunization has recently been determined to cause severe forms of neonatal disease as a result of the transplacental passage of anti-NEP antibodies. However there is a wide spectrum of neonatal disease variability. We present the medical histories of a large family, specifically of two alloimmunized sisters in their second pregnancy in whom we established the basis of immunological surveillance and therapeutic intervention during pregnancy and after delivery. One mother developed dramatically high titers of IgG1 and IgG4, and was treated with IvIg and one plasma exchange, both of which substantially reduced the anti-NEP Ab titer. However, the neonatal syndrome observed in her infant was severe, partly due to treatment delay. Anti-NEP Ab were also found in the mother's milk and the infant's urine. In contrast, the other mother had a normal second pregnancy and delivered a healthy neonate, which was related to the fact that she only produced the non-complement activating IgG4 subclass of anti-NEP antibodies. Thus, anti-NEP Ab (titer and subclass) seem to be highly sensitive biomarkers of neonatal risk. Interventional strategy aimed at reducing anti-NEP titer, should be started early during pregnancy and, possibly, even before pregnancy in those mothers producing anti-NEP IgG1. Careful monitoring of anti-NEP Ab titer and subclass is mandatory in NEP-deficient mothers during their pregnancies.

Decreased Expression and Activity of Neprilysin in Alzheimer Disease Are Associated With Cerebral Amyloid Angiopathy

Neprilysin (NEP) degrades amyloid-beta (Abeta) and is thought to contribute to its clearance from the brain. In Alzheimer disease (AD), downregulation of NEP has been suggested to contribute to the development of cerebral amyloid angiopathy (CAA). We examined the relationship among NEP, CAA, and APOE status in AD and elderly control cases. NEP was most abundant in the tunica media of cerebrocortical blood vessels and in pyramidal neurons. In homogenates of the frontal cortex, NEP protein levels were reduced in AD but not significantly; NEP enzymatic activity was significantly reduced in AD. Immunohistochemistry revealed a reduction of both vascular and parenchymal NEP. The loss of vessel-associated NEP in AD was inversely related to the severity of CAA, and analysis of cases with severe CAA showed that levels of vascular NEP were reduced to the same extent in Abeta-free and Abeta-laden vessels, strongly suggesting that the reduction in NEP is not simply secondary to CAA. Possession of APOE epsilon4 was associated with significantly lower levels of both parenchymal and vascular NEP. Colinearity of epsilon4 with the presence of moderate to severe CAA precluded assessment of the independence of this association from NEP levels. However, logistic regression analysis showed low NEP levels to be a significant independent predictor of moderate to severe CAA.

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.

Neutral endopeptidase (EC 3.4.24.11) in cirrhotic liver: a new target to treat portal hypertension?

BACKGROUND/AIMS

In liver cirrhosis atrial natriuretic peptide (ANP) decreases portal vascular resistance and tributary flow. The enzyme neutral endopeptidase (NEP) degrades ANP and bradykinin and generates endothelin-1 from big-endothelin. We determined the effects of NEP inhibition by candoxatrilat on hormonal status, liver function and arterial and portal pressures in rats with CCl4-induced cirrhosis.

METHODS

Two groups of seven control rats received 1 ml 5% glucose solution alone or containing 10 mg/kg candoxatrilat; three groups of 10 ascitic cirrhotic rats received placebo, 5 or 10 mg/kg candoxatrilat. NEP protein concentration and immunostaining were analyzed in normal and cirrhotic livers.

RESULTS

In cirrhotic rats 10 mg/kg candoxatrilat significantly increased steady-state indocyanine green clearance (a parameter reflecting liver plasma flow) (P<0.01), decreased portal pressure (P<0.01), had no effect on arterial pressure and plasma renin activity but increased ANP plasma levels (P<0.05) and urinary excretions (P<0.01) of ANP and cGMP. In the cytosol fraction of rat cirrhotic livers a 280% increase in NEP content was found (P<0.01), chiefly localized in desmin-positive myofibroblast-like cells of fibrous septa.

CONCLUSIONS

Candoxatrilat has few effects on systemic hemodynamics and hormonal status; its portal hypotensive action depends on effects exerted on intrahepatic vascular resistance.

Understanding molecular mechanisms of proteolysis in Alzheimer's disease: Progress toward therapeutic interventions

Amyloid beta peptide (Abeta) is not only a major constituent of extracellular fibrillary pathologies in Alzheimer's disease (AD) brains, but is also physiologically produced and metabolized in neurons. This fact led us to the notion that an age-related decrease in Abeta catabolism may contribute to the molecular pathogenesis of AD, providing a rationale for seeking proteolytic enzymes that degrade Abeta in the brain. Our recent studies have demonstrated that neprilysin is the most potent Abeta-degrading enzyme in vivo. Deficiency of endogenous neprilysin elevates the level of Abeta in brains of neprilysin-knockout mice in a gene dose-dependent manner, and an age-associated decline of neprilysin occurs in several regions of mouse brain. Neuropathological alterations in these same regions have been implicated in cognitive impairments of AD patients at an early stage of the disease. Furthermore, the level of neprilysin mRNA has been found to be significantly and selectively reduced in the hippocampus and temporal cortex of AD patients. A clarification of the role played by decreased neprilysin activity in the pathogenesis of AD has opened up the possibility of neprilysin up-regulation as a novel preventive and therapeutic approach to AD. Since the expression level and activity of neprilysin are likely to be regulated by neuropeptides and their receptors, non-peptidic agonists for these receptors might be effective agents to maintain a sufficient level of Abeta catabolism in brains of the elderly. In addition to Abeta deposits, intraneuronal fibrillary lesions, such as neurofibrillary tangles, are also a pathological hallmark of AD, and the extent of the resultant cytoskeletal disruptions may be dependent upon the activity levels of proteolytic enzymes. Among proteases for which major cytoskeletal components are good substrates, calpains were shown to participate in excitotoxic stress-induced neuritic degeneration in our recent analysis using genetically engineered mice. Moreover, we have found that this pathology can be reduced by controlling the activity of an endogenous calpain inhibitor known as calpastatin, providing a possible approach for the treatment of diverse neurodegenerative disorders, including AD.

Molecular pathomechanisms of membranous nephropathy: from Heymann nephritis to alloimmunization

Membranous nephropathy (MN), the most common cause of idiopathic nephrotic syndrome in white adults, is characterized by an accumulation of immune deposits on the outer aspect of the glomerular basement membrane. In Heymann nephritis, the rat experimental model for MN, megalin--the target antigen of the nephritogenic antibodies--is expressed on the surface of podocytes, where immune complexes are formed, leading to complement activation and nephrotic-range proteinuria. However, megalin cannot be held responsible for human MN because it has not been found in human podocytes or detected in subepithelial immune deposits in patients with MN. Several potential antigens have been identified in so-called secondary forms of MN, but there is no real proof that these antigens are pathogenic. In a subgroup of infants with antenatal MN, neutral endopeptidase (NEP) has been identified as the first protein target on human podocytes of nephritogenic antibodies. The infants' mothers became immunized during pregnancy against NEP expressed on syncytiotrophoblastic cells because they were NEP deficient as a result of truncating mutations in the MME gene. Severity of neonatal renal disease was determined by the mothers' IgG response that led to the formation of the membrane attack complex of complement in the subepithelial deposits. Alloimmunization against NEP is a novel pathomechanism of MN that might also account for some cases of MN after renal or bone marrow transplantation. Other types of alloimmunization should be investigated in MN but also in other renal and nonrenal diseases, particularly those that affect the pediatric age.

Heat shock protein and gliadin peptide promote development of peptidase antibodies in children with autism and patients with autoimmune disease

Searching for a mechanism underlying autoimmunity in autism, we postulated that gliadin peptides, heat shock protein 60 (HSP-60), and streptokinase (SK) bind to different peptidases resulting in autoantibody production against these components. We assessed this hypothesis in patients with autism and in those with mixed connective tissue diseases. Associated with antigliadin and anti-HSP antibodies, children with autism and patients with autoimmune disease developed anti-dipeptidylpeptidase I (DPP I), anti-dipeptidylpeptidase IV (DPP IV [or CD26]) and anti-aminopeptidase N (CD13) autoantibodies. A significant percentage of autoimmune and autistic sera were associated with elevated immunoglobulin G (IgG), IgM, or IgA antibodies against three peptidases, gliadin, and HSP-60. These antibodies are specific, since immune absorption demonstrated that only specific antigens (e.g., DPP IV absorption of anti-DPP IV), significantly reduced IgG, IgM, and IgA antibody levels. For direct demonstration of SK, HSP-60, and gliadin peptide binding to DPP IV, microtiter wells coated with DPP IV were reacted with SK, HSP-60, and gliadin. They were then reacted with anti-DPP IV or anti-SK, anti-HSP, and antigliadin antibodies. Adding SK, HSP-60, and gliadin peptides to DPP IV resulted in 27 to 43% inhibition of the DPP IV-anti-DPP IV reaction, but DPP IV-positive peptides caused 18 to 20% enhancement of antigen-antibody reactions. We propose that (i) superantigens (e.g., SK and HSP-60) and dietary proteins (e.g., gliadin peptides) in individuals with predisposing HLA molecules bind to aminopeptidases and (ii) they induce autoantibodies to peptides and tissue antigens. Dysfunctional membrane peptidases and autoantibody production may result in neuroimmune dysregulation and autoimmunity.

The wrickkened pathways of FGF23, MEPE and PHEX

The last 350 years since the publication of the first medical monograph on rickets (old English term wrickken) (Glisson et al., 1651) have seen spectacular advances in our understanding of mineral-homeostasis. Seminal and exciting discoveries have revealed the roles of PTH, vitamin D, and calcitonin in regulating calcium and phosphate, and maintaining healthy teeth and skeleton. However, it is clear that the PTH/Vitamin D axis does not account for the entire picture, and a new bone-renal metabolic milieu has emerged, implicating a novel set of matrix proteins, hormones, and Zn-metallopeptidases. The primary defects in X-linked hypophosphatemic rickets (HYP) and autosomal-dominant hypophosphatemic rickets (ADHR) are now identified as inactivating mutations in a Zn-metalloendopeptidase (PHEX) and activating mutations in fibroblast-growth-factor-23 (FGF23), respectively. In oncogenic hypophosphatemic osteomalacia (OHO), several tumor-expressed proteins (MEPE, FGF23, and FRP-4) have emerged as candidate mediators of the bone-renal pathophysiology. This has stimulated the proposal of a global model that takes into account the remarkable similarities between the inherited diseases (HYP and ADHR) and the tumor-acquired disease OHO. In HYP, loss of PHEX function is proposed to result in an increase in uncleaved full-length FGF23 and/or inappropriate processing of MEPE. In ADHR, a mutation in FGF23 results in resistance to proteolysis by PHEX or other proteases and an increase in half-life of full-length phosphaturic FGF23. In OHO, over-expression of FGF23 and/or MEPE is proposed to result in abnormal renal-phosphate handling and mineralization. Although this model is attractive, many questions remain unanswered, suggesting a more complex picture. The following review will present a global hypothesis that attempts to explain the experimental and clinical observations in HYP, ADHR, and OHO, plus diverse mouse models that include the MEPE null mutant, HYP-PHEX transgenic mouse, and MEPE-PHEX double-null-mutant.

Structure, evolutionary conservation, and functions of angiotensin- and endothelin-converting enzymes

Angiotensin-converting enzyme, a member of the M2 metalloprotease family, and endothelin-converting enzyme, a member of the M13 family, are key components in the regulation of blood pressure and electrolyte balance in mammals. From this point of view, they serve as important drug targets. Recently, the involvement of these enzymes in the development of Alzheimer's disease was discovered. The existence of homologs of these enzymes in invertebrates indicates that these enzyme systems are highly conserved during evolution. Most invertebrates lack a closed circulatory system, which excludes the need for blood pressure regulators. Therefore, these organisms represent excellent targets for gaining new insights and revealing additional physiological roles of these important enzymes. This chapter reviews the structural and functional aspects of ACE and ECE and will particularly focus on these enzyme homologues in invertebrates.

The type 1 CD10/neutral endopeptidase 24.11 promoter: functional characterization of the 5′-untranslated region

The cell surface zinc metalloproteinase CD10/neutral endopeptidase 24.11 (NEP) is expressed on normal and malignant lymphoid progenitors, granulocytes and a variety of epithelial cells. Because CD10/NEP functions as part of a regulatory loop that controls local concentrations of peptide substrates and associated peptide-mediated signal transduction, its role in each tissue is different depending on the availability of substrate. To characterize further how this widely distributed molecule is regulated differentially in each tissue, we analysed the major type 2 CD10/NEP promoter and found three functionally important transcription factor binding sites, one of which was identical to CCAAT-binding transcription factor/nuclear transcription factor Y. In this report, we analyse the type 1 CD10/NEP promoter and found a functionally important transcription factor binding site in the 5'-untranslated region. The results of the competition and supershift experiments demonstrated that the functionally important transcription factor was identical to Sp1. Our results suggest that ubiquitously expressed Sp1 may play an important role in differentiation stage-specific regulation of CD10/NEP expression in lymphoid lineage.

Methionine enkephalin suppresses metabolic activity of a leukemic cell line (NALM-1) and enhances CD10 expression

NALM-1 cells (a cell line derived from human pre-B leukemia) were exposed to the opioid pentapeptide methionine-enkephalin (Met-enkephalin) and/or to thiorphan, an inhibitor of the enzyme that degrades the enkephalins (membrane endopeptidase EC 3.4.24.11, CALLA, the CD10 marker). Metabolic and proliferative activity was assessed after 6, 24 and 48 h in microplates using a colorimetric assay with vital dye MTT. CD10 expression was determined by means of semi-quantitative RT-PCR. Exposure to the Met-enkephalin at concentrations of 10(-8)-10(-6) M for 6 h reduced the MTT-activity, and after 24 and 48 h the suppression waned. Thiorphan (5 x 10(-6) M) abrogated the suppressive effect of the enkephalin, and after 6 h converted suppression into stimulation. Met-enkephalin (10(-6) M) increased and thiorphan (2.5 x 10(-6)-10(-6) M) decreased expression of CD10 at the RNA level. Suppression of the MTT uptake was attributed to the products of Met-enkephalin degradation caused by the enzymatic activity of CD10.

Neutrophil infiltration of culprit lesions in acute coronary syndromes

BACKGROUND

Neutrophils in unstable atherosclerotic lesions have not received much consideration, despite accumulating evidence suggesting a link between systemic inflammation and acute coronary syndromes.

METHODS AND RESULTS

Coronary artery segments were obtained at autopsy from 13 patients with acute myocardial infarction (AMI); 8 had a ruptured and 5 an eroded plaque. Patients (n=45) who had died of noncardiovascular diseases served as reference. Atherectomy specimens were obtained from 35 patients with stable angina pectoris (SAP) and from 32 patients with unstable angina pectoris (UAP). Antibodies against CD66b, elastase, myeloperoxidase, and CD11b identified neutrophils; CD10 identified neutral endopeptidase (NEP). CD66b-positive and NEP-positive neutrophils were counted and expressed as a number per square millimeter of tissue. All specimens with plaque rupture or erosion showed distinct neutrophil infiltration; the number did not differ between ruptured and eroded plaques. However, the number of NEP-positive neutrophils was significantly higher (P<0.0001) in ruptured plaques than in eroded plaques. UAP patients showed neutrophils in 14 of 32 culprit lesions; in SAP only 2 of 35 lesions contained neutrophils. The number of neutrophils and NEP-positive cells in patients with UAP was significantly higher (neutrophils, P<0.0005; NEP-positive cells, P<0.005) than in patients with SAP.

CONCLUSIONS

The observations suggest that neutrophil infiltration is actively associated with acute coronary events. The high number of NEP-positive neutrophils in ruptured plaques, compared with eroded plaques, may reflect differences in the underlying pathophysiological mechanisms.

Analysis of immunoglobulin VH genes in CD10-positive diffuse large B-cell lymphoma

CD10, a proteolytic enzyme seen in germinal center cells and in the majority of follicular lymphomas, is occasionally expressed in diffuse large B-cell lymphomas (DLBCL). To clarify the origin and cellular characteristics of CD10-positive DLBCL, we analyzed 36 de novo cases of DLBCL for somatic mutations of the immunoglobulin heavy chain variable region (VH) genes and for their immunophenotypes. Expression greater than that of grade 2 Bcl-6 was observed in 11 of the 30 CD10-negative cases (37%) and in all six CD10-positive cases (100%; P < 0.05) without expression of CD5, CD23, cyclin D1, CD30 or CD138. The average mutation frequencies of the six CD10-positive and 30 CD10-negative DLBCL were 12.9 and 9.8%, respectively. The range of SM frequencies in CD10-positive DLBCL (9.52-18.06) was distinctly narrower than that observed for CD10-negative DLBCL (0.69-26.89). These findings seem to indicate that CD10-positive DLBCL, originating from germinal center B cells, is a genetically and immunophenotypically more homogeneous group than CD10-negative DLBCL. Furthermore, three extranodal lymphomas, in five of the six CD10-positive DLBCL, showed ongoing mutation, indicating that antigen-driven, high-affinity somatic mutation may play an important role in clonal expansion in CD10-positive DLBCL. All four extranodal cases of the six CD10-positive DLBCL showed ongoing mutation and/or bcl-2/JH rearrangement. This result suggests that the cell origin of extranodal CD10-positive DLBCL may be the same as that of follicular lymphomas.

M13 endopeptidases: New conserved motifs correlated with structure, and simultaneous phylogenetic occurrence of PHEX and the bony fish

M13 endopeptidase alignments have focused mainly on mammalian sequences and on the active site region defining the catalytic sequence signatures. Aligning all available M13 from bacteria to human on a full-length basis, we have performed a sequence analysis. This enabled us to highlight the origin and function of the M13 PHEX subtype family endopeptidase (phosphate regulating gene with homologies to endopeptidases on the X chromosome). New evolutionary conserved regions in both prokaryotes and eukaryotes have been detected and eukaryotic-specific regions clearly delineated. Using the recently solved neprilysin structure, we have observed that all new motifs, except one, localize in the spatial vicinity of the previously reported catalytic signatures. Interestingly, a highly hydrophobic pocket containing three newly reported motifs is centered by the C-terminal tryptophan residue. Extensive M13 searches in complete and in progress higher eukaryotic genomes have lead to the identification of Danio rerio as the simplest organism having PHEX. Finally, the human PHEX substrate, the parathyroid hormone-related peptide, PTHrP(107-139), is absent in bony fish: this suggests the existence of further PHEX substrates common to both bony fishes and higher vertebrates.

In vitro cartilage formation by human adult stem cells from bone marrow stroma defines the sequence of cellular and molecular events during chondrogenesis

One approach to resolving the complexities of chondrogenesis is to examine simplified systems in vitro. We analyzed cartilage differentiation by human adult stem cells from bone marrow stroma. Marrow stromal cells were cultured as micromass pellets for 21 days in serum-free medium containing transforming growth factor (TGF)-beta3, dexamethasone, and bone morphogenetic protein (BMP)-6. Assays for pulse-labeled [3H]DNA and for total DNA indicated that there was little proliferation and a progressive loss of cells in the pellets. There were continuous increases in mRNAs for cartilage matrix (proteoglycans and COL2, -9, -10, and -11), receptors [fibroblast growth factor 2 (FGFR2) and parathyroid hormone-related peptide receptor (PTHrP-R)], and transcription factors (SOX5, -6, and -9) as demonstrated by histochemical and microarray assays. Reverse transcription-PCR assays for 11 mRNAs confirmed the microarray data. SOX4, vascular endothelial growth factor (VEGF), and matrix metalloproteinase 14 (MMP14) increased at day 1 and decreased thereafter, suggesting roles early in chondrogenesis. Also, forkhead, CD10, and MMP13 increased up to day 7 and decreased thereafter, suggesting roles in an intermediate stage of chondrogenesis. In addition, two collagens (COL3A1 and COL16A1), a signaling molecule (WNT11), a homeobox homolog (BAPX1), a receptor (IL-1R1), an IGFs modulator (IGFBP5), and a mettaloproteinase (MMP16) increased progressively up to about day 14, suggesting roles later in chondrogenesis. Our results indicate that the simplicity of the system makes it possible to define in detail the cellular and molecular events during chondrogenesis.

Beta-amyloid catabolism: roles for neprilysin (NEP) and other metallopeptidases?

The steady-state level of amyloid beta-peptide (Abeta) represents a balance between its biosynthesis from the amyloid precursor protein (APP) through the action of the beta- and gamma-secretases and its catabolism by a variety of proteolytic enzymes. Recent attention has focused on members of the neprilysin (NEP) family of zinc metalloproteinases in amyloid metabolism. NEP itself degrades both Abeta(1-40) and Abeta(1-42) in vitro and in vivo, and this metabolism is prevented by NEP inhibitors. Other NEP family members, for example endothelin-converting enzyme, may contribute to amyloid catabolism and may also play a role in neuroprotection. Another metalloproteinase, insulysin (insulin-degrading enzyme) has also been advocated as an amyloid-degrading enzyme and may contribute more generally to metabolism of amyloid-forming peptides. Other candidate enzymes proposed include angiotensin-converting enzyme, some matrix metalloproteinases, plasmin and, indirectly, thimet oligopeptidase (endopeptidase-24.15). This review critically evaluates the evidence relating to proteinases implicated in amyloid catabolism. Therapeutic strategies aimed at promoting A,beta degradation may provide a novel approach to the therapy of Alzheimer's disease.