Release and degradation of angiotensin I and angiotensin II from angiotensinogen by neutrophil serine proteinases

Differential effects of angiotensin II and aldosterone on human neutrophil adhesion and concomitant secretion of proteins, free amino acids and reactive oxygen and nitrogen species

Invasion and adhesion of neutrophils into tissues and their concomitant secretion play an important role in the development of vascular pathologies, including abdominal aortic aneurysm (AAA). Chronic administration of angiotensin II is used to initiate AAA formation in mice. The role of aldosterone in this process is being studied. We conducted for the first time a complex comparative study of the effects of angiotensin II and aldosterone on the adhesion of human neutrophils to fibronectin and the concomitant secretion of proteins, free amino acids as well as reactive oxygen (ROS) and nitrogen (NO) species. Neither angiotensin II nor aldosterone affected the attachment of neutrophils to fibronectin and the concomitant production of ROS. We showed for the first time that aldosterone stimulated the release of amino acid hydroxylysine, a product of lysyl hydroxylase, the activity of which is positively correlated with cell invasiveness. Aldosterone also initiates the secretion of matrix metalloproteinase 9 (MMP-9) and cathepsin G, which may reorganize the extracellular matrix and stimulate the recruitment and adhesion of neutrophils to the aortic walls. Angiotensin II did not affect protein secretion. It may contribute to neutrophil-induced vascular injury by inhibiting the production of NO or by increasing the secretion of isoleucine. Our results suggest that it is aldosterone-induced neutrophil secretion that may play a significant role in neutrophil-induced vascular wall destruction in angiotensin II-induced AAA or other vascular complications.

Inflammation-Associated Cytotoxic Agents in Tumorigenesis

Chronic inflammatory processes are related to all stages of tumorigenesis. As inflammation is closely associated with the activation and release of different cytotoxic agents, the interplay between cytotoxic agents and antagonizing principles is highlighted in this review to address the question of how tumor cells overcome the enhanced values of cytotoxic agents in tumors. In tumor cells, the enhanced formation of mitochondrial-derived reactive species and elevated values of iron ions and free heme are antagonized by an overexpression of enzymes and proteins, contributing to the antioxidative defense and maintenance of redox homeostasis. Through these mechanisms, tumor cells can even survive additional stress caused by radio- and chemotherapy. Through the secretion of active agents from tumor cells, immune cells are suppressed in the tumor microenvironment and an enhanced formation of extracellular matrix components is induced. Different oxidant- and protease-based cytotoxic agents are involved in tumor-mediated immunosuppression, tumor growth, tumor cell invasion, and metastasis. Considering the special metabolic conditions in tumors, the main focus here was directed on the disturbed balance between the cytotoxic agents and protective mechanisms in late-stage tumors. This knowledge is mandatory for the implementation of novel anti-cancerous therapeutic approaches.

Host-Derived Cytotoxic Agents in Chronic Inflammation and Disease Progression

At inflammatory sites, cytotoxic agents are released and generated from invading immune cells and damaged tissue cells. The further fate of the inflammation highly depends on the presence of antagonizing principles that are able to inactivate these host-derived cytotoxic agents. As long as the affected tissues are well equipped with ready-to-use protective mechanisms, no damage by cytotoxic agents occurs and resolution of inflammation is initiated. However, long-lasting and severe immune responses can be associated with the decline, exhaustion, or inactivation of selected antagonizing principles. Hence, cytotoxic agents are only partially inactivated and contribute to damage of yet-unperturbed cells. Consequently, a chronic inflammatory process results. In this vicious circle of permanent cell destruction, not only novel cytotoxic elements but also novel alarmins and antigens are liberated from affected cells. In severe cases, very low protection leads to organ failure, sepsis, and septic shock. In this review, the major classes of host-derived cytotoxic agents (reactive species, oxidized heme proteins and free heme, transition metal ions, serine proteases, matrix metalloproteases, and pro-inflammatory peptides), their corresponding protective principles, and resulting implications on the pathogenesis of diseases are highlighted.

Ivermectin Affects Neutrophil-Induced Inflammation through Inhibition of Hydroxylysine but Stimulation of Cathepsin G and Phenylalanine Secretion

The invasion and integrin-dependent adhesion of neutrophils to lung tissues and their secretion lead to the development of pneumonia in various pulmonary pathologies, including acute respiratory distress syndrome in coronavirus disease. We studied the effect of ivermectin, a possible therapeutic agent for inflammation and cancer, on integrin-dependent neutrophil adhesion to fibronectin and the concomitant secretion. Ivermectin did not affect the attachment of neutrophils to the substrate and the reactive oxygen species production but sharply inhibited the adhesion-induced release of hydroxylysine and stimulated the release of phenylalanine and cathepsin G. Hydroxylysine is a product of lysyl hydroxylase, which is overexpressed in tumor cells with an increased ability to invade and metastasize. The inhibition of hydroxylysine release by ivermectin, by analogy, may indicate the suppression of neutrophil invasion into tissue. The increase in the release of phenylalanine in our experiments coincided with the secretion of cathepsin G, which indicates the possible role of this enzyme in the cleavage of phenylalanine. What is the substrate in such a reaction is unknown. We demonstrated that exogenously added angiotensin II (1-8) can serve as a substrate for phenylalanine cleavage. Mass spectrometry revealed the formation of angiotensin II (1-7) in the secretion of neutrophils, which attached to fibronectin in the presence of ivermectin and exogenous angiotensin II (1-8), indicating a possible involvement of ivermectin in the inactivation of angiotensin II.

Add-On Cyclic Angiotensin-(1-7) with Cyclophosphamide Arrests Progressive Kidney Disease in Rats with ANCA Associated Glomerulonephritis

Rapidly progressive crescentic glomerulonephritis associated with anti-neutrophil cytoplasmic antibodies (ANCA-GN) is a major cause of renal failure. Current immunosuppressive therapies are associated with severe side effects, intensifying the need for new therapeutic strategies. The activation of Mas receptor/Angiotensin-(1-7) axis exerted renoprotection in chronic kidney disease. Here, we investigated the effect of adding the lanthionine-stabilized cyclic form of angiotensin-1-7 [cAng-(1-7)] to cyclophosphamide in a rat model of ANCA-GN. At the onset of proteinuria, Wistar Kyoto rats with ANCA-GN received vehicle or a single bolus of cyclophosphamide, with or without daily cAng-(1-7). Treatment with cAng-(1-7) plus cyclophosphamide reduced proteinuria by 85% vs. vehicle, and by 60% vs. cyclophosphamide, and dramatically limited glomerular crescents to less than 10%. The addition of cAng-(1-7) to cyclophosphamide protected against glomerular inflammation and endothelial rarefaction and restored the normal distribution of parietal epithelial cells. Ultrastructural analysis revealed a preserved GBM, glomerular endothelium and podocyte structure, demonstrating that combination therapy provided an additional layer of renoprotection. This study demonstrates that adding cAng-(1-7) to a partially effective dose of cyclophosphamide arrests the progression of renal disease in rats with ANCA-GN, suggesting that cAng-(1-7) could be a novel clinical approach for sparing immunosuppressants.

Biomarkers for Cancer Cachexia: A Mini Review

Cancer cachexia is a common condition in many cancer patients, particularly those with advanced disease. Cancer cachexia patients are generally less tolerant to chemotherapies and radiotherapies, largely limiting their treatment options. While the search for treatments of this condition are ongoing, standards for the efficacy of treatments have yet to be developed. Current diagnostic criteria for cancer cachexia are primarily based on loss of body mass and muscle function. However, these criteria are rather limiting, and in time, when weight loss is noticeable, it may be too late for treatment. Consequently, biomarkers for cancer cachexia would be valuable adjuncts to current diagnostic criteria, and for assessing potential treatments. Using high throughput methods such as "omics approaches", a plethora of potential biomarkers have been identified. This article reviews and summarizes current studies of biomarkers for cancer cachexia.

The Controversy of Renin-Angiotensin-System Blocker Facilitation Versus Countering COVID-19 Infection

The ongoing COVID-19 pandemic has produced serious turmoil world-wide. Lung injury causing acute respiratory distress syndrome seems to be a most dreaded complication occurring in ∼30%. Older patients with cardiovascular comorbidities and acute respiratory distress syndrome have an increased mortality. Although the precise mechanisms involved in the development of lung injury have not been fully elucidated, the role of the extended renin-angiotensin system seems to be pivotal. In this context, angiotensin-converting enzyme 2 (ACE2), an angiotensin-converting enzyme homologue, has been recognized as a facilitator of viral entry into the host, albeit its involvement in other counter-regulatory effects, such as converting angiotensin (Ang) II into Ang 1-7 with its known protective actions. Thus, concern was raised that the use of renin-angiotensin system inhibitors by increasing ACE2 expression may enhance patient susceptibility to the COVID-19 virus. However, current data have appeased such concerns because there has been no clinical evidence of a harmful effect of these agents as based on observational studies. However, properly designed future studies will be needed to further confirm or refute current evidence. Furthermore, other pathways may also play important roles in COVID-19 transmission and pathogenesis; spike (S) protein proteases facilitate viral transmission by cleaving S protein that promotes viral entry into the host; neprilysin (NEP), a neutral endopeptidase known to cleave natriuretic peptides, degrades Ang I into Ang 1-7; NEP can also catabolize bradykinin and thus mitigate bradykinin's role in inflammation, whereas, in the same context, specific bradykinin inhibitors may also negate bradykinin's harmful effects. Based on these intricate mechanisms, various preventive and therapeutic strategies may be devised, such as upregulating ACE2 and/or using recombinant ACE2, and exploiting the NEP, bradykinin and serine protease pathways, in addition to anti-inflammatory and antiviral therapies. These issues are herein reviewed, available studies are tabulated and pathogenetic mechanisms are pictorially illustrated.

Targeting Neprilysin (NEP) pathways: A potential new hope to defeat COVID-19 ghost

COVID-19 is an ongoing viral pandemic disease that is caused by SARS-CoV2, inducing severe pneumonia in humans. However, several classes of repurposed drugs have been recommended, no specific vaccines or effective therapeutic interventions for COVID-19 are developed till now. Viral dependence on ACE-2, as entry receptors, drove the researchers into RAS impact on COVID-19 pathogenesis. Several evidences have pointed at Neprilysin (NEP) as one of pulmonary RAS components. Considering the protective effect of NEP against pulmonary inflammatory reactions and fibrosis, it is suggested to direct the future efforts towards its potential role in COVID-19 pathophysiology. Thus, the review aimed to shed light on the potential beneficial effects of NEP pathways as a novel target for COVID-19 therapy by summarizing its possible molecular mechanisms. Additional experimental and clinical studies explaining more the relationships between NEP and COVID-19 will greatly benefit in designing the future treatment approaches.

Novel Insights Into the Effects of Interleukin 6 Antagonism in Non-ST-Segment-Elevation Myocardial Infarction Employing the SOMAscan Proteomics Platform

Background Interleukin 6 concentration is associated with myocardial injury, heart failure, and mortality after myocardial infarction. In the Norwegian tocilizumab non-ST-segment-elevation myocardial infarction trial, the first randomized trial of interleukin 6 blockade in myocardial infarction, concentration of both C-reactive protein and troponin T were reduced in the active treatment arm. In this follow-up study, an aptamer-based proteomic approach was employed to discover additional plasma proteins modulated by tocilizumab treatment to gain novel insights into the effects of this therapeutic approach. Methods and Results Plasma from percutaneous coronary intervention-treated patients, 24 in the active intervention and 24 in the placebo-control arm, drawn 48 hours postrandomization were randomly selected for analysis with the SOMAscan assay. Employing slow off-rate aptamers, the relative abundance of 1074 circulating proteins was measured. Proteins identified as being significantly different between groups were subsequently measured by enzyme immunoassay in the whole trial cohort (117 patients) at all time points (days 1-3 [7 time points] and 3 and 6 months). Five proteins identified by the SOMAscan assay, and subsequently confirmed by enzyme immunoassay, were significantly altered by tocilizumab administration. The acute-phase proteins lipopolysaccharide-binding protein, hepcidin, and insulin-like growth factor-binding protein 4 were all reduced during the hospitalization phase, as was the monocyte chemoattractant C-C motif chemokine ligand 23. Proteinase 3, released primarily from neutrophils, was significantly elevated. Conclusions Employing the SOMAscan aptamer-based proteomics platform, 5 proteins were newly identified that are modulated by interleukin 6 antagonism and may mediate the therapeutic effects of tocilizumab in non-ST-segment-elevation myocardial infarction.

Sodium tanshinone IIA sulfonate prevents the adverse left ventricular remodelling: Focus on polymorphonuclear neutrophil-derived granule components

AIMS

The aims of this study were to evaluate the effects of sodium tanshinone IIA sulfonate (STS) on left ventricular (LV) remodelling after for ST-elevated myocardial infarction (STEMI).

METHODS AND RESULTS

In this prospective, randomized clinical trial, 101 patients with the ST-elevated MI (STEMI) and a successful reperfusion were immediately randomized to receive STS (80 mg qd for 7 days) or saline control, along with standard therapy. The primary effectiveness endpoint is the % change in LV end diastolic volumes index (%∆ LVEDVi) as measured by echocardiography from baseline to 6 months. Secondary effectiveness endpoints include 6-month period for major adverse cardiac events (MACE), including the occurrence of recurrent myocardial infarction, death, hospitalization for heart failure and malignant arrhythmia. The 6-month changes in %∆ LVEDVi were significantly smaller in the STS group than in the control group [-5.05% vs 3.32%; P < 0.001]. With respect to MACE, there was a significant difference between those who received STS (8.16%) and those patients on control (26.00%) (P = 0.019). Meaningfully, results of parallel tests aimed at mechanistic explanation of the reported clinical effects, revealed a significantly reduced levels of neutrophils-derived granule components in the blood of STS treated patients.

CONCLUSION

We found that short-term treatment with STS reduced progressive left ventricular remodelling and subsequent better clinical outcome that could be mechanistically linked to the inhibition of the ultimate damage of infarcted myocardium by infiltrating neutrophils.

Proteinase 3; a potential target in chronic obstructive pulmonary disease and other chronic inflammatory diseases

Chronic Obstructive Pulmonary Disease (COPD) is a common, multifactorial lung disease which results in significant impairment of patients' health and a large impact on society and health care burden. It is believed to be the result of prolonged, destructive neutrophilic inflammation which results in progressive damage to lung structures. During this process, large quantities of neutrophil serine proteinases (NSPs) are released which initiate the damage and contribute towards driving a persistent inflammatory state.Neutrophil elastase has long been considered the key NSP involved in the pathophysiology of COPD. However, in recent years, a significant role for Proteinase 3 (PR3) in disease development has emerged, both in COPD and other chronic inflammatory conditions. Therefore, there is a need to investigate the importance of PR3 in disease development and hence its potential as a therapeutic target. Research into PR3 has largely been confined to its role as an autoantigen, but PR3 is involved in triggering inflammatory pathways, disrupting cellular signalling, degrading key structural proteins, and pathogen response.This review summarises what is presently known about PR3, explores its involvement particularly in the development of COPD, and indicates areas requiring further investigation.

Role of the Renin Angiotensin System in Blood Pressure Allostasis-induced by Severe Food Restriction in Female Fischer rats

Severe food restriction (FR) is associated with blood pressure (BP) and cardiovascular dysfunction. The renin-angiotensin system (RAS) regulates BP and its dysregulation contributes to impaired cardiovascular function. Female Fischer rats were maintained on a control (CT) or severe FR (40% of CT) diet for 14 days. In response to severe FR, BP allostasis was achieved by up-regulating circulating Ang-[1–8] by 1.3-fold through increased angiotensin converting enzyme (ACE) activity and by increasing the expression of AT₁Rs 1.7-fold in mesenteric vessels. Activation of the RAS countered the depressor effect of the severe plasma volume reduction (≥30%). The RAS, however, still underperformed as evidenced by reduced pressor responses to Ang-[1–8] even though AT₁Rs were still responsive to the depressor effects of an AT₁R antagonist. The aldosterone (ALDO) response was also inadequate as no changes in plasma ALDO were observed after the large fall in plasma volume. These findings have implications for individuals who have experienced a period(s) of severe FR (e.g., anorexia nervosa, dieters, natural disasters) and suggests increased activity of the RAS in order to achieve allostasis contributes to the cardiovascular dysfunction associated with inadequate food intake.

Urine RAS components in mice and people with type 1 diabetes and chronic kidney disease

The pathways implicated in diabetic kidney disease (DKD) are largely derived from animal models. To examine if alterations in renin-angiotensin system (RAS) in humans are concordant with those in rodent models, we measured concentration of angiotensinogen (AOG), cathepsin D (CTSD), angiotensin-converting enzyme (ACE), and ACE2 and enzymatic activities of ACE, ACE2, and aminopeptidase-A in FVB mice 13-20 wk after treatment with streptozotocin (n = 9) or vehicle (n = 15) and people with long-standing type 1 diabetes, with (n = 37) or without (n = 81) DKD. In streptozotocin-treated mice, urine AOG and CTSD were 10.4- and 3.0-fold higher than in controls, respectively (P < 0.001). Enzymatic activities of ACE, ACE2, and APA were 6.2-, 3.2-, and 18.8-fold higher, respectively, in diabetic animals (P < 0.001). Angiotensin II was 2.4-fold higher in diabetic animals (P = 0.017). Compared with people without DKD, those with DKD had higher urine AOG (170 vs. 15 μg/g) and CTSD (147 vs. 31 μg/g). In people with DKD, urine ACE concentration was 1.8-fold higher (1.4 vs. 0.8 μg/g in those without DKD), while its enzymatic activity was 0.6-fold lower (1.0 vs. 1.6 × 10⁹ RFU/g in those without DKD). Lower ACE activity, but not ACE protein concentration, was associated with ACE inhibitor (ACEI) treatment. After adjustment for clinical covariates, AOG, CTSD, ACE concentration, and ACE activity remained associated with DKD. In conclusion, in mice with streptozotocin-induced diabetes and in humans with DKD, urine concentrations and enzymatic activities of several RAS components are concordantly increased, consistent with enhanced RAS activity and greater angiotensin II formation. ACEI use was associated with a specific reduction in urine ACE activity, not ACE protein concentration, suggesting that it may be a marker of exposure to this widely-used therapy.

Intracrine angiotensin II functions originate from noncanonical pathways in the human heart

Although it is well-known that excess renin angiotensin system (RAS) activity contributes to the pathophysiology of cardiac and vascular disease, tissue-based expression of RAS genes has given rise to the possibility that intracellularly produced angiotensin II (Ang II) may be a critical contributor to disease processes. An extended form of angiotensin I (Ang I), the dodecapeptide angiotensin-(1-12) [Ang-(1-12)], that generates Ang II directly from chymase, particularly in the human heart, reinforces the possibility that an alternative noncanonical renin independent pathway for Ang II formation may be important in explaining the mechanisms by which the hormone contributes to adverse cardiac and vascular remodeling. This review summarizes the work that has been done in evaluating the functional significance of Ang-(1-12) and how this substrate generated from angiotensinogen by a yet to be identified enzyme enhances knowledge about Ang II pathological actions.

Identification of neutrophil-derived proteases and angiotensin II as biomarkers of cancer cachexia

Background:

Cachexia is a metabolic disorder characterised by muscle wasting, diminished response to anti-cancer treatments and poor quality of life. Our objective was to identify blood-based biomarkers of cachexia in advanced cancer patients. Hence, we characterised the plasma cytokine and blood cell mRNA profiles of patients grouped in three cohorts: patients with cachexia, pre-cachexia (no cachexia but high CRP levels: ⩾5 mg l⁻¹) and no cachexia (no cachexia and CRP: <5 mg l⁻¹).

Methods:

A total of 122 newly diagnosed cancer patients with seven cancer types were studied prior to their initial therapy. Plasma levels of 22 cytokines were quantified using the bio-plex technology. mRNAs isolated from whole blood and expression profiles were determined by the chip array technology and Ingenuity Pathway Analysis (IPA) software.

Results:

In comparison with non-cachectic individuals, both pre-cachectic and cachectic patients showed an increase (⩾1.5-folds) in mRNA expression of neutrophil-derived proteases (NDPs) and significantly elevated angiotensin II (Ang II) (P=0.005 and P=0.02, respectively), TGFβ1 (P=0.042 and P<0.0001, respectively) and CRP (both P<0.0001) in the plasma. Moreover, cachectic patients displayed a significant increase in IL-6 (P=0.005), IL-8 (P=0.001) and absolute neutrophil counts (P=0.007).

Conclusions:

Ang II, TGFβ1, CRP and NDP are blood biomarkers for cancer cachexia. These findings contribute to early diagnosis and prevention of cachexia.

Update on the role of angiotensin in the pathophysiology of coronary atherothrombosis

BACKGROUND

Coronary atherothrombosis due to atherosclerotic plaque rupture or erosion is frequently associated with acute coronary syndromes (ACS). Significant efforts have been made to elucidate the pathophysiological mechanisms underlying acute coronary events.

MATERIALS AND METHODS

This narrative review is based on the material searched for and obtained via PubMed up to August 2014. The search terms we used were as follows: 'angiotensin, acute coronary syndromes, acute myocardial infarction' in combination with 'atherosclerosis, vulnerability, clinical trial, ACE inhibitors, inflammation'.

RESULTS

Among several regulatory components, the renin-angiotensin system (RAS) was shown as a key pathway modulating coronary atherosclerotic plaque vulnerability. Indeed, these molecules are involved in all stages of atherogenesis. Classically, the RAS is composed by a series of enzymatic reactions leading to the angiotensin (Ang) II generation and activity. However, the knowledge of RAS has expanded and become more complex. The discovery of novel components and their functions has revealed additional pathways that contribute to or counterbalance the actions of Ang II. In this review, we discussed on recent findings concerning the role of different angiotensin peptides in the pathophysiology of ACS and coronary atherothrombosis, exploring the link between these molecules and atherosclerotic plaque vulnerability.

CONCLUSIONS

Treatments selectively targeting angiotensins (including Mas and AT2 agonists, ACE2 recombinant, or Ang-(1-7) and almandine in oral formulations) have been tested in animal studies or in small human subgroups, expanding the perspective in the ACS prevention. These novel strategies, especially in the counter-regulatory axis ACE2/Ang-(1-7)/Mas, might be promising to reduce plaque vulnerability and inflammation.

Role of renin-angiotensin system in activation of macrophages by modified lipoproteins

Angiotensin II favors the development of atherosclerosis. Our goal was to determine if foam cell formation increases angiotensin II generation by the endogenous renin-angiotensin system (RAS) and if endogenously produced angiotensin II promotes lipid accumulation in macrophages. Differentiated THP-1 cells were treated with acetylated low-density lipoproteins (ac-LDL), native LDL (n-LDL), or no LDL. Expression of RAS genes was assessed and angiotensin I/II levels were quantified in media and cell lysate. Ac-LDL increased angiotensin I/II levels and the angiotensin II/I ratio in cells and media after foam cell formation. Renin mRNA or activity did not change, but renin blockade completely inhibited the increase in angiotensin II. Angiotensinogen mRNA but not protein level was increased. Angiotensin-converting enzyme (ACE) and cathepsin G mRNA and activities were enhanced by ac-LDL. Inhibition of renin, ACE, or the angiotensin II receptor 1 (AT1-receptor) largely abolished cholesteryl ester formation in cells exposed to ac-LDL and decreased scavenger receptor A (SR-A) and acyl-coenzyme A:cholesterol acyltransferase 1 (ACAT-1) protein levels. Inhibition of renin or the AT1-receptor in cells treated with oxidized LDL also decreased SR-A and ACAT-1 protein and foam cell formation. ac-LDL also increased angiotensin II by human peripheral blood monocyte-derived macrophages, whereas blockade of renin decreased cholesterol ester formation in these macrophages. These findings indicate that, during foam cell formation, angiotensin II generation by the endogenous RAS is stimulated and that endogenously generated angiotensin II is crucial for cholesterol ester accumulation in macrophages exposed to modified LDL.

Neutrophil roles in left ventricular remodeling following myocardial infarction

Polymorphonuclear granulocytes (PMNs; neutrophils) serve as key effector cells in the innate immune system and provide the first line of defense against invading microorganisms. In addition to producing inflammatory cytokines and chemokines and undergoing a respiratory burst that stimulates the release of reactive oxygen species, PMNs also degranulate to release components that kill pathogens. Recently, neutrophil extracellular traps have been shown to be an alternative way to trap microorganisms and contain infection. PMN-derived granule components are also involved in multiple non-infectious inflammatory processes, including the response to myocardial infarction (MI). In this review, we will discuss the biological characteristics, recruitment, activation, and removal of PMNs, as well as the roles of PMN-derived granule proteins in inflammation and innate immunity, focusing on the MI setting when applicable. We also discuss future perspectives that will direct research in PMN biology.

Regulation of the renin-angiotensin system (RAS) in BeWo and HTR-8/SVneo trophoblast cell lines

OBJECTIVES

The renin-angiotensin system (RAS) is implicated in placentation. We determined which RAS pathways are present in two trophoblast cell lines (HTR-8/SVneo and BeWo cells) and the effects of cAMP, which stimulates renal renin.

STUDY DESIGN

The effect of cAMP on RAS gene expression and on prorenin and angiotensin peptides in HTR-8/SVneo and BeWo cells were investigated.

RESULTS

In HTR-8/SVneo cells, prorenin mRNA (REN) and protein, (pro)renin receptor (ATP6AP2) and angiotensin II type 1 receptor (AGTR1) were stimulated by cAMP (P < 0.05, P < 0.05, P < 0.001 and P < 0.05, respectively). HTR-8/SVneo cells also expressed angiotensinogen (AGT) and angiotensin converting enzyme 1 (ACE1), but did not express AGTR2 or ACE2 nor the Ang 1-7 receptor (MAS1). BeWo cells did not express REN, and REN was not inducible by cAMP, but cAMP increased ACE2 and MAS1 (both P < 0.05) and decreased AGT (P < 0.05). BeWo cells expressed AGT, ACE1, ACE2 and MAS1 but not ATP6AP2, AGTR1 nor AGTR2. There was net destruction of Ang II in media from HTR-8/SVneo and BeWo incubations and net production of Ang 1-7 by BeWo and untreated HTR-8/SVneo cells.

CONCLUSION

HTR-8/SVneo cells express REN and produce prorenin as well as expressing other RAS genes likely to regulate Ang II/AT(1)R interactions and respond to cAMP, like renal renin-secreting cells. They are more similar to early gestation placentae and are therefore useful for studying effects of renin/ACE/Ang II/AT₁R on cell function. BeWo cells express the ACE2/Ang 1-7/Mas pathway, which is sensitive to cAMP and therefore are useful for studying the effects of ACE2/Ang 1-7/Mas on trophoblast function.

Proteinase 3 and prognosis of patients with acute myocardial infarction

A multimarker approach may be useful for risk stratification in AMI (acute myocardial infarction) patients, particularly utilizing pathways that are pathophysiologically distinct. Our aim was to assess the prognostic value of PR3 (proteinase 3) in patients post-AMI. We compared the prognostic value of PR3, an inflammatory marker, with an established marker NT-proBNP (N-terminal pro-B-type natriuretic peptide) post-AMI. We recruited 900 consecutive post-AMI patients (700 men; age, 64.6±12.4 years) in a prospective study with follow-up over 347 (0-764) days. Plasma PR3 was significantly higher in patients who died [666.2 (226.8-4035.5) ng/ml; P<0.001] or were readmitted with heart failure [598 (231.6-1803.9) ng/ml, P<0.004] compared with event-free survivors [486.9 (29.3-3118.2) ng/ml]. Using Cox modelling, log10 PR3 [HR (hazard ratio), 3.80] and log10 NT-proBNP (HR, 2.51) were significant independent predictors of death or heart failure. When patients were stratified by plasma NT-proBNP (median, 1023 pmol/l), PR3 gave additional predictive value for death or heart failure, in both the patients in whom NT-proBNP level was above the median (log rank for trend, 12.54; P<0.0004) and those with NT-proBNP level below the median (log rank for trend, 3.83; P<0.05). Neither marker predicted recurrent AMI. In conclusion, this is the first report showing a potential role for the serine protease PR3 in determining mortality and incidence of heart failure following AMI, independent of established conventional risk factors. PR3 may represent a clinically useful marker of prognosis after an AMI as part of a multimarker strategy.

Complementary effects of angiotensin-converting enzyme inhibitors and angiotensin receptor blockers in slowing the progression of chronic kidney disease

Chronic kidney disease (CKD) and end-stage renal disease continue to pose major healthcare challenges. Early initiation of therapy aimed at slowing the progression of CKD is essential. Increased renin-angiotensin-aldosterone-system activity and, in particular, elevated levels of angiotensin II (AII) play important roles in the development and progression of CKD. Therefore, pharmacologic therapies that block the effects of AII and reduce its pathogenic effects are cornerstones of clinical management. Angiotensin-converting enzyme inhibitors (ACEIs) and angiotensin receptor blockers (ARBs) have been shown to have renoprotective effects in addition to their ability to control blood pressure. There is accumulating clinical evidence that the combination of an ACEI and an ARB provides greater renal protection, particularly in decreasing proteinuria, than does either agent alone.

Effect of acetaldehyde upon cathepsin G and chymase. NRAS implications

Hypertension is commonly observed in alcoholics. Both the renin-angiotensin system (RAS) and the non-renin-angiotensin system (NRAS) have been implicated in the dynamics of blood pressure maintenance. In bilaterally nephrectomized rats, acetaldehyde has been reported to enhance the generation of the rate-limiting angiotensin I (ANG I) in the plasma, and in humans it inhibits the activity of several angiotensinases (A, B, and M) in the serum, thereby promoting a hypertensive set of reactions. We report here the results of a study on the effect of acetaldehyde upon cathepsin G and mast cell chymase. Acetaldehyde enhanced cathepsin G activity at all of the concentrations tested between 11.2 and 223.5 mM in a statistically significant manner. Since cathepsin G is one of several enzymes transforming ANG I into ANG II and is also capable of cleaving ANG II directly from angiotensinogen, we suggest that alcoholism, which will generate exogenous acetaldehyde from ingested alcohol, may be a contributory factor for an elevated cathepsin G activity and, consequently, hypertension via the NRAS. Chymase activity also is elevated in the presence of 440 mM acetaldehyde and diminished in the presence of 27 mM acetaldehyde. Since both enzymes also degrade ANG II, the degradative effects of each enzyme on ANG II may neutralize one another.

Mechanism of high glucose induced angiotensin II production in rat vascular smooth muscle cells

Angiotensin II (Ang II), a circulating hormone that can be synthesized locally in the vasculature, has been implicated in diabetes-associated vascular complications. This study was conducted to determine whether high glucose (HG) (approximately 23.1 mmol/L), a diabetic-like condition, stimulates Ang II generation and the underlying mechanism of its production in rat vascular smooth muscle cells. The contribution of various enzymes involved in Ang II generation was investigated by silencing their expression with small interfering RNA in cells exposed to normal glucose (approximately 4.1 mmol/L) and HG. Angiotensin I (Ang I) was generated from angiotensinogen by cathepsin D in the presence of normal glucose or HG. Although HG did not affect the rate of angiotensinogen conversion, it decreased expression of angiotensin-converting enzyme (ACE), downregulated ACE-dependent Ang II generation, and upregulated rat vascular chymase-dependent Ang II generation. The ACE inhibitor captopril reduced Ang II levels in the media by 90% in the presence of normal glucose and 19% in HG, whereas rat vascular chymase silencing reduced Ang II production in cells exposed to HG but not normal glucose. The glucose transporter inhibitor cytochalasin B, the aldose reductase inhibitor alrestatin, and the advanced glycation end product formation inhibitor aminoguanidine attenuated HG-induced Ang II generation. HG caused a transient increase in extracellular signal-regulated kinase (ERK)1/2 phosphorylation, and ERK1/2 inhibitors reduced Ang II accumulation by HG. These data suggest that polyol pathway metabolites and AGE can stimulate rat vascular chymase activity via ERK1/2 activation and increase Ang II production. In addition, decreased Ang II degradation, which, in part, could be attributable to a decrease in angiotensin-converting enzyme 2 expression observed in HG, contributes to increased accumulation of Ang II in vascular smooth muscle cells by HG.

Enzymatic pathways of the brain renin-angiotensin system: unsolved problems and continuing challenges

The brain renin-angiotensin system continues to be enigmatic more than 40 years after the brain was first recognized to be a site of action of angiotensin II. This review focuses on the enzymatic pathways for the formation and degradation of the growing number of active angiotensins in the brain. A brief description and nomenclature of the peptidases involved in the processing of angiotensin peptides in the brain is given. Of primary interest is the array of enzymes that degrade radiolabeled angiotensins in receptor binding assays. This poses major challenges to studies of brain angiotensin receptors and it is debatable whether an accurate determination of brain angiotensin receptor binding kinetics has yet been made. The quandary facing the investigator of brain angiotensin receptors is the need to protect the radioligand from metabolic alteration while maintaining the characteristics of the receptors in situ. It is the tenet of this review that we have yet to fully understand the binding characteristics of brain angiotensin receptors and the extent of their distribution in the brain because of our inability to fully protect the angiotensins from metabolic alteration until equilibrium binding conditions can be attained.

Angiotensin II type 1 receptor as a novel therapeutic target in rheumatoid arthritis: in vivo analyses in rodent models of arthritis and ex vivo analyses in human inflammatory synovitis

OBJECTIVE

Angiotensin II (Ang II) is known to have proinflammatory actions, and Ang II type 1 (AT(1)) receptors are up-regulated in the rheumatoid synovium, suggesting that this receptor could be a therapeutic target. The purpose of this study was to investigate the antiinflammatory potential of the selective AT(1) receptor antagonist losartan, which is currently used for the treatment of cardiovascular disease.

METHODS

Dose-ranging studies of losartan (1-50 mg/kg) were initially conducted in a rat model of acute (carrageenan/kaolin) arthritis, with subsequent evaluation in a rat model of adjuvant-induced arthritis (Freund's complete adjuvant). Losartan (10(-10) to 10(-6)M) was further tested ex vivo in human inflammatory synovitis, using collagenase-digested synovium.

RESULTS

Western blot and immunohistochemical analyses both revealed a substantial increase in AT(1) receptor protein content in synovium from acutely and chronically inflamed rat knee joints. Similarly, synovial Ang I/II protein content was elevated during inflammation. Losartan inhibited acute joint inflammation in a dose-dependent manner, with 15 mg/kg being the optimal dose (and used in subsequent studies). Both prophylactic and therapeutic administration of 15 mg/kg of losartan substantially reduced knee joint swelling in rats with adjuvant monarthritis (> or =50%; P < 0.0001). Losartan also suppressed tumor necrosis factor alpha generation from inflamed human synovium in a dose-dependent manner (P < 0.05).

CONCLUSION

Targeting the angiotensin pathway, particularly AT(1) receptors, could have significant therapeutic potential. Randomized placebo-controlled trials are now warranted to establish the extent to which angiotensin receptor blockers may provide antiinflammatory benefits.

Renal cathepsin G and angiotensin II generation

BACKGROUND

Alternative pathways of angiotensin II biosynthesis play a significant role in the renin-angiotensin system. In this study porcine renal tissue was investigated for angiotensin II-generating enzymes.

METHODS AND RESULTS

Protein extracts from porcine renal tissue were fractionated by liquid chromatography and tested for their angiotensin II-generating activity by the mass-spectrometry-assisted enzyme screening system (MES) and the active fractions were purified to near homogeneity. In one of these active fractions, inhibitable by an angiotensin-converting enzyme specific inhibitor, purified by anion-exchange chromatography, followed by hydroxyapatite chromatography, lectin affinity chromatography, size-exclusion chromatography and two-dimensional electrophoresis, angiotensin-converting enzyme was identified by a tryptic peptide matrix-assisted-laser-desorption/ionization (MALDI) mass fingerprint analysis. In a second active fraction, which was inhibited by chymostatin and antipain, yielded by anion-exchange chromatography, followed by hydroxyapatite chromatography, lectin affinity chromatography, chymostatin-antipain chromatography and one-dimensional electrophoresis, cathepsin G was identified by electro-spray ionization (ESI)-ion-trap mass spectrometry. The angiotensin-generating activities of the fraction containing angiotensin-converting enzyme and the fraction containing cathepsin G were in the same order of magnitude, thus showing that the contribution of cathepsin G towards the production of angiotensin II is significant.

CONCLUSION

This is the first time that cathepsin G has been identified in mammalian renal tissue.

Polymerization of human angiotensinogen: insights into its structural mechanism and functional significance

In the present study, we have investigated the in vitro polymerization of human plasma AGT (angiotensinogen), a non-inhibitory member of the serpin (SERine Protease INhibitor) family. Polymerization of AGT is thought to contribute to a high molecular mass form of the protein in plasma that is increased in pregnancy and pregnancy-associated hypertension. The results of the present study demonstrate that the polymerization of AGT occurs through a novel mechanism which is primarily dependent on non-covalent linkages, while additional disulfide linkages formed after prolonged incubation are not essential for either formation or stability of polymers. We present the first analyses of AGT polymers by electron microscopy, CD spectroscopy, stability assays and sensitivity to proteinases and we conclude that their structure differs from the 'loop-sheet' polymers typical of inhibitory serpins. Histidine residues within the unique N-terminal extension of AGT appear to influence polymer formation, although polymer formation can still take place after their removal by renin. At a functional level, we show that AGT polymers are not substrates for renin, so polymerization of AGT in plasma would predictably lead to decreased formation of AngI (angiotensin I) with blood pressure lowering. Polymerization may therefore be an appropriate response to hypertension. The ability of AGT to protect its renin cleavage site through polymerization may explain why the AngI decapeptide has remained linked to the large and apparently inactive serpin body throughout evolution.

Expression profiles of elastase1 (NvElastaseI) and secretory leukocyte protease inhibitor (NvSLPI) during forelimb regeneration in adult Notophthalmus viridescens suggest a role in epithelial remodeling and delamination

Extracellular proteases and their inhibitors may regulate a number of important processes involved in forelimb regeneration in the adult newt, including epithelial remodeling, breakdown of extracellular matrix, and dedifferentiation. We have identified a newt homologue of human ElastaseI (NvElastaseI) and its potential inhibitor, SLPI (NvSLPI), and evaluated their spatial and temporal expression during limb regeneration. NvElastaseI is upregulated early in regeneration and is associated with subdermal and wound epithelial cells, suggesting an involvement in wound healing and the generation of the wound epithelium. Up until 15 days post-amputation, NvElastaseI is also scattered throughout the developing blastema and may have a role in the dedifferentiation of stump tissues. NvSLPI is found at the interface between the intact skin and the wound epithelium, and may limit NvElastaseI activity. NvSLPI is also expressed in dermal glands, and is likely involved in anti-microbial activity or function. Quite apart from regeneration, complementary patterns of expression of NvElastaseI and NvSLPI are associated with newt epithelial sloughing.

Proteinase 3 is an IL-32 binding protein

IL-32, a recently discovered proinflammatory cytokine with four isoforms, induces IL-1beta, TNF-alpha, IL-6, and chemokines. Here, we used ligand (IL-32alpha) affinity chromatography in an attempt to isolate an IL-32alpha soluble receptor or binding protein. Recombinant IL-32alpha was covalently immobilized on agarose, and preparations of concentrated crude human urinary proteins were applied for chromatographic separation. A specific 30-kDa protein eluted from the column during acid washing and was identified by mass spectrometry as proteinase 3 (PR3) and confirmed by N-terminal microsequencing. PR3, a neutrophil granule serine protease, exists in a soluble or membrane form and is the major autoantigen for autoantibodies in the systemic vasculitic disease, Wegener's granulomatosis. The affinity of IL-32alpha to PR3 was determined by surface plasmon resonance. The dissociation constants were 2.65 +/- 0.4 nM for urinary PR3 and 1.2 +/- 0.05 nM for neutrophil-derived PR3. However, irreversible inactivation of PR3 enzymatic activity did not significantly change binding to the cytokine. Nevertheless, limited cleavage of IL-32 yielded products consistent with PR3 enzyme activity. Moreover, after limited cleavage by PR3, IL-32alpha was more active than intact IL-32alpha in inducing macrophage inflammatory protein-2 in mouse macrophages and IL-8 in human peripheral blood mononuclear cells. We suggest that PR3 is a specific IL-32alpha binding protein, independent of its enzymatic activity. However, limited cleavage of IL-32alpha by PR3 enhances activities of the cytokine. Therefore, specific inhibition of PR3 activity to process IL-32 or neutralization of IL-32 by inactive PR3 or its fragments may reduce the consequences of IL-32 in immune regulated diseases.

Identification of cDNAs associated with late dedifferentiation in adult newt forelimb regeneration

Epimorphic limb regeneration in the adult newt involves the dedifferentiation of differentiated cells to yield a pluripotent blastemal cell. These mesenchymal-like cells proliferate and subsequently respond to patterning and differentiation cues to form a new limb. Understanding the dedifferentiation process requires the selective identification of dedifferentiating cells within the heterogeneous population of cells in the regenerate. In this study, representational differences analysis was used to produce an enriched population of dedifferentiation-associated cDNA fragments. Fifty-nine unique cDNA fragments were identified, sequenced, and analyzed using bioinformatics tools and databases. Some of these clones demonstrate significant similarity to known genes in other species. Other clones can be linked by homology to pathways previously implicated in the dedifferentiation process. These data will form the basis for further analyses to elucidate the role of candidate genes in the dedifferentiation process during newt forelimb regeneration.

Proteinase 3 sidesteps caspases and cleaves p21(Waf1/Cip1/Sdi1) to induce endothelial cell apoptosis

BACKGROUND

Emerging data raise possibilities of a complex and specific biologic role for leukocyte-derived proteases in substrate processing and in signaling pathways. Neutrophil proteinase 3 (PR3) is a caspase-like protease that enters endothelial cells, cleaves nuclear factor-kappaB (NF-kappaB), and induces sustained JNK activation, implying that the major cell cycle inhibitor p21 may be inactivated. Cleavage of p21 by caspase-3 is reported to be required for endothelial cell apoptosis. We hypothesized that PR3 may target p21.

METHODS

Human umbilical vein endothelial cells (HUVEC) were treated with or without PR3 (5 microg/mL) from 0 hours or up to 8 hours, and analyzed for changes in cell cycle control proteins by immunoblotting, immunofluorescence and flow cytometry.

RESULTS

PR3 exposure resulted in cleavage of p21 between Thr80 and Gly81, loss of nuclear p21 by cytoplasmic sequestration and depletion of p21 from cyclin/cyclin-dependent kinase (CDK) complexes. Examination of cyclins D and E, p53, Rb, and p27 revealed a largely nonproliferative expression profile. Cells arrested in G1 were more susceptible to PR3 effects. We examined inflamed human colonic tissue and found a fragment similar in size to that generated by PR3 in HUVEC. Granzyme B, a T-cell homologue of PR3 that cleaves caspase substrates, also cleaves p21 between Asp62 and Phe63. A reported substrate of granzyme B and caspases, Bid, is cleaved by PR3 signifying commonality of substrates among these proteases.

CONCLUSION

A theme is developing that the granulocyte protease, PR3, is an exogenous caspase-like molecule that can sidestep intracellular caspase functions at sites of inflammation.