The expression of TNF-alpha converting enzyme at the site of ruptured plaques in patients with acute myocardial infarction

Expression of HMGB1, TGF-β1, BIRC3, ADAM17, CDKN1A, and FTO in Relation to Left Ventricular Remodeling in Patients Six Months after the First Myocardial Infarction: A Prospective Study

Background: After myocardial infarction (MI), adverse left ventricular (LV) remodeling may occur. This is followed by LV hypertrophy and eventually heart failure. The remodeling process is complex and goes through multiple phases. The aim of this study was to investigate the expression of HMGB1, TGF-β1, BIRC3, ADAM17, CDKN1A, and FTO, each involved in a specific step of LV remodeling, in association with the change in the echocardiographic parameters of LV structure and function used to assess the LV remodeling process in the peripheral blood mononuclear cells (PBMCs) of patients six months after the first MI. The expression of selected genes was also determined in PBMCs of controls. Methods: The study group consisted of 99 MI patients, who were prospectively followed-up for 6 months, and 25 controls. Cardiac parameters, measured via conventional 2D echocardiography, were evaluated at two time points: 3-5 days and 6 months after MI. The mRNA expression six-months-post-MI was detected using TaqMan® technology (Applied Biosystems, Thermo Fisher Scientific, Waltham, MA, USA). Results:HMGB1 mRNA was significantly higher in patients with adverse LV remodeling six-months-post-MI than in patients without adverse LV remodeling (p = 0.04). HMGB1 mRNA was significantly upregulated in patients with dilated LV end-diastolic diameter (LVEDD) (p = 0.03); dilated LV end-diastolic volume index (LVEDVi) (p = 0.03); severely dilated LV end-systolic volume index (LVESVi) (p = 0.006); impaired LV ejection fraction (LVEF) (p = 0.01); and LV enlargement (p = 0.03). It was also significantly upregulated in PBMCs from patients compared to controls (p = 0.005). TGF-β1 and BIRC3 mRNA were significantly lower in patients compared to controls (p = 0.02 and p = 0.05, respectively). Conclusions: Our results suggest that HMGB1 is involved in adverse LV remodeling six-months-post-MI, even on the mRNA level. Further research and validation are needed.

EGFR stimulation enables IL-6 trans-signalling via iRhom2-dependent ADAM17 activation in mammary epithelial cells

The cytokine interleukin-6 (IL-6) has considerable pro-inflammatory properties and is a driver of many physiological and pathophysiological processes. Cellular responses to IL-6 are mediated by membrane-bound or soluble forms of the IL-6 receptor (IL-6R) complexed with the signal-transducing subunit gp130. While expression of the membrane-bound IL-6R is restricted to selected cell types, soluble IL-6R (sIL-6R) enables gp130 engagement on all cells, a process termed IL-6 trans-signalling and considered to be pro-inflammatory. sIL-6R is predominantly generated through proteolytic processing by the metalloproteinase ADAM17. ADAM17 also liberates ligands of the epidermal growth factor receptor (EGFR), which is a prerequisite for EGFR activation and results in stimulation of proliferative signals. Hyperactivation of EGFR mostly due to activating mutations drives cancer development. Here, we reveal an important link between overshooting EGFR signalling and the IL-6 trans-signalling pathway. In epithelial cells, EGFR activity induces not only IL-6 expression but also the proteolytic release of sIL-6R from the cell membrane by increasing ADAM17 surface activity. We find that this derives from the transcriptional upregulation of iRhom2, a crucial regulator of ADAM17 trafficking and activation, upon EGFR engagement, which results in increased surface localization of ADAM17. Also, phosphorylation of the EGFR-downstream mediator ERK mediates ADAM17 activity via interaction with iRhom2. In sum, our study reveals an unforeseen interplay between EGFR activation and IL-6 trans-signalling, which has been shown to be fundamental in inflammation and cancer.

TACE/ADAM17 substrates associate with ACS (Ep-CAM, HB-EGF) and follow-up MACE (TNFR1 and TNFR2)

Background and aims

TACE/ADAM17 is a membrane bound metalloprotease, which cleaves substrates involved in immune and inflammatory responses and plays a role in coronary artery disease (CAD). We measured TACE and its substrates in CAD patients to identify potential biomarkers within this molecular pathway with potential for acute coronary syndrome (ACS) and major adverse cardiovascular events (MACE) prediction.

Methods

Blood samples were obtained from consecutive patients (n = 229) with coronary angiographic evidence of CAD admitted with ACS or electively. MACE were recorded after a median 3-year follow-up. Controls (n = 115) had a <10% CAD risk as per the HeartSCORE. TACE and TIMP3 protein and mRNA levels were measured by ELISA and RT-qPCR respectively. TACE substrates were measured using a multiplex proximity extension assay.

Results

TACE mRNA and cell protein levels (p < 0.01) and TACE substrates LDLR (p = 0.006), TRANCE (p = 0.045), LAG-3 (p < 0.001) and ACE2 (p < 0.001) plasma levels were significantly higher in CAD patients versus controls. TACE inhibitor TIMP3 mRNA levels were significantly lower in CAD patients and tended to be lower in the ACS population (p < 0.05). TACE substrates TNFR1 (OR:3.237,CI:1.514-6.923,p = 0.002), HB-EGF (OR:0.484,CI:0.288-0.813,p = 0.006) and Ep-CAM (OR:0.555,CI:0.327-0.829,p = 0.004) accurately classified ACS patients with HB-EGF and Ep-CAM levels being lower compared to electively admitted patients. TNFR1 (OR:2.317,CI:1.377-3.898,p = 0.002) and TNFR2 (OR:1.902,CI:1.072-3.373,p = 0.028) were significantly higher on admission in those patients who developed MACE within 3 years.

Conclusions

We demonstrate a possible role of TACE substrates LAG-3, HB-EGF and Ep-CAM in atherosclerotic plaque development and stability. We also underline the importance of measuring TNFR1 and TNFR2 earlier than previously appreciated for MACE prediction. We report an important role of TIMP3 in regulating TACE levels.

The role of ADAM17 during liver damage

A disintegrin and metalloprotease (ADAM) 17 is a membrane bound protease, involved in the cleavage and thus regulation of various membrane proteins, which are critical during liver injury. Among ADAM17 substrates are tumor necrosis factor α (TNFα), tumor necrosis factor receptor 1 and 2 (TNFR1, TNFR2), the epidermal growth factor receptor (EGFR) ligands amphiregulin (AR) and heparin-binding-EGF-like growth factor (HB-EGF), the interleukin-6 receptor (IL-6R) and the receptor for a hepatocyte growth factor (HGF), c-Met. TNFα and its binding receptors can promote liver injury by inducing apoptosis and necroptosis in liver cells. Consistently, hepatocyte specific deletion of ADAM17 resulted in increased liver cell damage following CD95 stimulation. IL-6 trans-signaling is critical for liver regeneration and can alleviate liver damage. EGFR ligands can prevent liver damage and deletion of amphiregulin and HB-EGF can result in increased hepatocyte death and reduced proliferation. All of which indicates that ADAM17 has a central role in liver injury and recovery from it. Furthermore, inactive rhomboid proteins (iRhom) are involved in the trafficking and maturation of ADAM17 and have been linked to liver damage. Taken together, ADAM17 can contribute in a complex way to liver damage and injury.

Heparan sulfate promotes differentiation of white adipocytes to maintain insulin sensitivity and glucose homeostasis

Heparan sulfate (HS), a highly sulfated linear polysaccharide, is involved in diverse biological functions in various tissues. Although previous studies have suggested a possible contribution of HS to the differentiation of white adipocytes, there has been no direct evidence supporting this. Here, we inhibited the synthesis of HS chains in 3T3-L1 cells using CRISPR–Cas9 technology, resulting in impaired differentiation of adipocytes with attenuated bone morphogenetic protein 4 (BMP4)–fibroblast growth factor 1 (FGF1) signaling pathways. HS reduction resulted in reduced glucose uptake and decreased insulin-dependent intracellular signaling. We then made heterozygous mutant mice for the Ext1 gene, which encodes an enzyme essential for the HS biosynthesis, specifically in the visceral white adipose tissue (Fabp4-Cre⁺::Ext1^flox/WT mice, hereafter called Ext1^Δ/WT) to confirm the importance of HS in vivo. The expression levels of transcription factors that control adipocyte differentiation, such as peroxisome proliferator–activated receptor gamma, were reduced in Ext1^Δ/WT adipocytes, which contained smaller, unilocular lipid droplets, reduced levels of enzymes involved in lipid synthesis, and altered expression of BMP4–FGF1 signaling molecules. Furthermore, we examined the impact of HS reduction in visceral white adipose tissue on systemic glucose homeostasis. We observed that Ext1^Δ/WT mice showed glucose intolerance because of insulin resistance. Our results demonstrate that HS plays a crucial role in the differentiation of white adipocytes through BMP4–FGF1 signaling pathways, thereby contributing to insulin sensitivity and glucose homeostasis.

Contribution of ADAM17 and related ADAMs in cardiovascular diseases

A disintegrin and metalloproteases (ADAMs) are key mediators of cell signaling by ectodomain shedding of various growth factors, cytokines, receptors and adhesion molecules at the cellular membrane. ADAMs regulate cell proliferation, cell growth, inflammation, and other regular cellular processes. ADAM17, the most extensively studied ADAM family member, is also known as tumor necrosis factor (TNF)-α converting enzyme (TACE). ADAMs-mediated shedding of cytokines such as TNF-α orchestrates immune system or inflammatory cascades and ADAMs-mediated shedding of growth factors causes cell growth or proliferation by transactivation of the growth factor receptors including epidermal growth factor receptor. Therefore, increased ADAMs-mediated shedding can induce inflammation, tissue remodeling and dysfunction associated with various cardiovascular diseases such as hypertension and atherosclerosis, and ADAMs can be a potential therapeutic target in these diseases. In this review, we focus on the role of ADAMs in cardiovascular pathophysiology and cardiovascular diseases. The main aim of this review is to stimulate new interest in this area by highlighting remarkable evidence.

Endothelial Barrier Function and Leukocyte Transmigration in Atherosclerosis

The vascular endothelium is a highly specialized barrier that controls passage of fluids and migration of cells from the lumen into the vessel wall. Endothelial cells assist leukocytes to extravasate and despite the variety in the specific mechanisms utilized by different leukocytes to cross different vascular beds, there is a general principle of capture, rolling, slow rolling, arrest, crawling, and ultimately diapedesis via a paracellular or transcellular route. In atherosclerosis, the barrier function of the endothelium is impaired leading to uncontrolled leukocyte extravasation and vascular leakage. This is also observed in the neovessels that grow into the atherosclerotic plaque leading to intraplaque hemorrhage and plaque destabilization. This review focuses on the vascular endothelial barrier function and the interaction between endothelial cells and leukocytes during transmigration. We will discuss the role of endothelial dysfunction, transendothelial migration of leukocytes and plaque angiogenesis in atherosclerosis.

ACE2/ADAM17/TMPRSS2 Interplay May Be the Main Risk Factor for COVID-19

The Coronavirus Disease 2019 (COVID-19) has already caused hundreds of thousands of deaths worldwide in a few months. Cardiovascular disease, hypertension, diabetes and chronic lung disease have been identified as the main COVID-19 comorbidities. Moreover, despite similar infection rates between men and women, the most severe course of the disease is higher in elderly and co-morbid male patients. Therefore, the occurrence of specific comorbidities associated with renin-angiotensin system (RAS) imbalance mediated by the interaction between angiotensin-converting enzyme 2 (ACE2) and desintegrin and metalloproteinase domain 17 (ADAM17), along with specific genetic factors mainly associated with type II transmembrane serine protease (TMPRSS2) expression, could be decisive for the clinical outcome of COVID-19. Indeed, the exacerbated ADAM17-mediated ACE2, TNF-α, and IL-6R secretion emerges as a possible underlying mechanism for the acute inflammatory immune response and the activation of the coagulation cascade. Therefore, in this review, we focus on the main pathophysiological aspects of ACE2, ADAM17, and TMPRSS2 host proteins in COVID-19. Additionally, we discuss a possible mechanism to explain the deleterious effect of ADAM17 and TMPRSS2 over-activation in the COVID-19 outcome.

iRhom2: An Emerging Adaptor Regulating Immunity and Disease

The rhomboid family are evolutionary conserved intramembrane proteases. Their inactive members, iRhom in Drosophila melanogaster and iRhom1 and iRhom2 in mammals, lack the catalytic center and are hence labelled “inactive” rhomboid family members. In mammals, both iRhoms are involved in maturation and trafficking of the ubiquitous transmembrane protease a disintegrin and metalloprotease (ADAM) 17, which through cleaving many biologically active molecules has a critical role in tumor necrosis factor alpha (TNFα), epidermal growth factor receptor (EGFR), interleukin-6 (IL-6) and Notch signaling. Accordingly, with iRhom2 having a profound influence on ADAM17 activation and substrate specificity it regulates these signaling pathways. Moreover, iRhom2 has a role in the innate immune response to both RNA and DNA viruses and in regulation of keratin subtype expression in wound healing and cancer. Here we review the role of iRhom2 in immunity and disease, both dependent and independent of its regulation of ADAM17.

Macrophage Trafficking, Inflammatory Resolution, and Genomics in Atherosclerosis: JACC Macrophage in CVD Series (Part 2)

Atherosclerosis is characterized by the retention of modified lipoproteins in the arterial wall. These modified lipoproteins activate resident macrophages and the recruitment of monocyte-derived cells, which differentiate into mononuclear phagocytes that ingest the deposited lipoproteins to become "foam cells": a hallmark of this disease. In this Part 2 of a 4-part review series covering the macrophage in cardiovascular disease, we critically review the contributions and relevant pathobiology of monocytes, macrophages, and foam cells as relevant to atherosclerosis. We also review evidence that via various pathways, a failure of the resolution of inflammation is an additional key aspect of this disease process. Finally, we consider the likely role played by genomics and biological networks in controlling the macrophage phenotype in atherosclerosis. Collectively, these data provide substantial insights on the atherosclerotic process, while concurrently offering numerous molecular and genomic candidates that appear to hold great promise for selective targeting as clinical therapies.

Status update on iRhom and ADAM17: It's still complicated

Several membrane-bound proteins with a single transmembrane domain are subjected to limited proteolysis at the cell surface. This cleavage leads to the release of their biologically active ectodomains, which can trigger different signalling pathways. In many cases, this ectodomain shedding is mediated by members of the family of a disintegrins and metalloproteinases (ADAMs). ADAM17 in particular is responsible for the cleavage of several proinflammatory mediators, growth factors, receptors and adhesion molecules. Due to its direct involvement in the release of these signalling molecules, ADAM17 can be positively and negatively involved in various physiological processes as well as in inflammatory, fibrotic and malignant pathologies. This central role of ADAM17 in a variety of processes requires strict multi-level regulation, including phosphorylation, various conformational changes and endogenous inhibitors. Recent research has shown that an early, crucial control mechanism is interaction with certain adapter proteins identified as iRhom1 and iRhom2, which are pseudoproteases of the rhomboid superfamily. Thus, iRhoms have also a decisive influence on physiological and pathophysiological signalling processes regulated by ADAM17. Their characteristic gene expression profiles, the specific consequences of gene knockouts and finally the occurrence of disease-associated mutations suggest that iRhom1 and iRhom2 undergo different gene regulation in order to fulfil their function in different cell types and are therefore only partially redundant. Therefore, there is not only interest in ADAM17, but also in iRhoms as therapeutic targets. However, to exploit the therapeutic potential, the regulation of ADAM17 activity and in particular its interaction with iRhoms must be well understood.

Elevated expression of the metalloproteinase ADAM8 associates with vascular diseases in mice and humans

BACKGROUND AND AIMS

Members of the family of a disintegrin and metalloproteinases (ADAMs) and their substrates have been previously shown to modulate the inflammatory response in cardiac diseases, but studies investigating the relevance of ADAM8 are still rare. Our aim is to provide evidence for the inflammatory dysregulation of ADAM8 in vascular diseases and its association with disease severity.

METHODS

Western-type diet fed Apoe^-/- and Ldlr^-/- mice and artery ligation served as murine model for atherosclerosis and myocardial infarction, respectively. Human bypass grafts were used to study the association with coronary artery disease (CAD), with the simplified acute physiology score II (SAPS II) as a measure of postoperative organ dysfunction. Human primary vascular and blood cells were analyzed under basal and inflammatory conditions. mRNA levels were determined by RT-qPCR, ADAM8 protein levels by ELISA, immunohistochemistry or flow cytometry.

RESULTS

ADAM8/ADAM8 expression is associated with atherosclerosis and CAD such as myocardial infarction in both mice and humans, especially in endothelial cells and leukocytes. We observed a strong in vivo and in vitro correlation of ADAM8 with the vascular disease markers VCAM-1, ICAM-1, TNF, IL-6, and CCL-2. Serum analysis revealed a significant elevation of soluble ADAM8 serum levels correlating with soluble CXCL16 levels and SAPS II.

CONCLUSIONS

We demonstrate a general association of ADAM8 with cardiovascular diseases in mice and humans predominantly acting in endothelial cells and leukocytes. The correlation with postoperative organ dysfunctions in CAD patients highlights the value of further studies investigating the specific function of ADAM8 in cardiovascular diseases.

Rapid and sensitive detection of the activity of ADAM17 using a graphene oxide-based fluorescence sensor

A disintegrin and metalloproteinase 17 (ADAM17) has become a novel biomarker and potential therapeutic target for the early detection and treatment of human cancers. In this work, by covalently attaching fluorescently labeled ADAM17 substrate peptide (Pep-FAM) molecules to carboxylated graphene oxide (cGO) and monitoring the cleavage of the peptide substrate by ADAM17, we developed a cGO-Pep-FAM fluorescence sensor for the rapid, sensitive and accurate detection of ADAM17. The sensor was highly sensitive with a detection limit of 17.5 picomolar. Furthermore, the sensor was selective: structure similar proteases such as ADAM9 and MMP-9 would not interfere with ADAM17 detection. In addition, simulated serum samples were successfully analyzed. Our developed cGO-Pep-FAM sensing strategy should find useful applications in disease diagnosis and drug screening.

Neutrophil and Macrophage Cell Surface Colony-Stimulating Factor 1 Shed by ADAM17 Drives Mouse Macrophage Proliferation in Acute and Chronic Inflammation

Macrophages are prominent cells in acute and chronic inflammatory diseases. Recent studies highlight a role for macrophage proliferation post-monocyte recruitment under inflammatory conditions. Using an acute peritonitis model, we identify a significant defect in macrophage proliferation in mice lacking the leukocyte transmembrane protease ADAM17. The defect is associated with decreased levels of macrophage colony-stimulating factor 1 (CSF-1) in the peritoneum and is rescued by intraperitoneal injection of CSF-1. Cell surface CSF-1 (csCSF-1) is one of the substrates of ADAM17. We demonstrate that both infiltrated neutrophils and macrophages are major sources of csCSF-1. Furthermore, acute shedding of csCSF-1 following neutrophil extravasation is associated with elevated expression of iRhom2, a member of the rhomboid-like superfamily, which promotes ADAM17 maturation and trafficking to the neutrophil surface. Accordingly, deletion of hematopoietic iRhom2 is sufficient to prevent csCSF-1 release from neutrophils and macrophages and to prevent macrophage proliferation. In acute inflammation, csCSF-1 release and macrophage proliferation are self-limiting due to transient leukocyte recruitment and temporally restricted csCSF-1 expression. In chronic inflammation, such as atherosclerosis, the ADAM17-mediated lesional macrophage proliferative response is prolonged. Our results demonstrate a novel mechanism whereby ADAM17 promotes macrophage proliferation in states of acute and chronic inflammation.

Morroniside on anti-inflammation activities in rats following acute myocardial infarction

Our previous studies have confirmed that morroniside has neuroprotective effects. However, the effects of morroniside on cardiac myocardium remain unknown. Rats were anaesthetized with 10% chloral hydrate (0.35~0.4 mL/kg) and an acute myocardial infarction (AMI) was induced by ligating the anterior descending coronary artery (LAD). Following AMI, morroniside was administered intragastrically for 3 consecutive days at doses of 45, 90 and 180 mg/kg, respectively. Lactate dehydrogenase (LDH) and cardiac troponin T (cTnT) activities in AMI rats in the serum were detected with commercial kits. The expression of IL-6, IL-1β and TNF-α in myocardium was detected by Western blotting analysis. We observed a significant decline in the Q(q) wave amplitude in morroniside-treated rats after 72 h. Additionally, treatment of morroniside decreased the levels of LDH and cTnT in AMI rats. We also observed that morroniside reduced the expression of IL-6, IL-1β and TNF-α in myocardium. Taken together, our findings demonstrate that morroniside had effective anti-inflammatory properties in AMI rats.

miRNA-21 Expression in the Serum of Elderly Patients with Acute Myocardial Infarction

BACKGROUND The aims of this study were to examine the expression of miRNA-21 in the serum of elderly patients (>65 years) with acute myocardial infarction (AMI) and to investigate the potential role of serum miRNA-21 as a marker of early cardiac myocyte damage. MATERIAL AND METHODS Thirty-eight elderly patients with recent AMI, 27 elderly patients with unstable angina pectoris, and 25 healthy elderly individuals were included in the study. Serum miRNA-21 expression was determined following total RNA extraction and reverse-transcribed into cDNA, followed by reverse transcription-polymerase chain reaction (RT-PCR). Serum creatine kinase MB isoenzyme (CK-MB) and cardiac troponin I (cTnI) levels were analyzed by electrochemiluminescence. Apoptosis of human cardiac myocytes (HCM) was analyzed using fluorescence-activated cell sorting (FACS), and protein expression of caspase-3 was detected using Western blot. RESULTS Expression levels of miRNA-21 in the serum of elderly patients with AMI were positively correlated with serum levels of CK-MB (r=0.3683, P=0.0229) and cTnI (r=0.5128, P=0.009). Following tumor necrosis factor (TNF)-α induction, the apoptosis rates of HCM transfected with the miRNA-21 mimic short hairpin RNA (shRNA) were downregulated by 39.1% compared with control HCM cells, and protein expression of c-Jun N-terminal kinases (JNK) and p38 were unchanged (P>0.05); protein expression of p-JNK, p-p38 and caspase-3 were downregulated by 37.1%, 35.8%, and 36.0%, respectively. CONCLUSIONS Expression of miRNA-21 was upregulated in the serum of elderly patients with AMI, which inhibited TNF-a induced apoptosis in HCM by activating the JNK/p38/caspase-3 signaling pathway.

Systemic Inflammation and Arrhythmogenesis: A Review of Mechanistic and Clinical Perspectives

In the recent decades, systemic inflammation, as a clinical phenomenon, has been the focus of extensive research particularly with regard to its potential association with a variety of cardiovascular diseases including atherogenesis and acute coronary syndromes. Within this context, there also exists a potential link between systemic inflammation and cardiac arrhythmogenesis in various aspects. Accordingly, systemic inflammation response as measured with inflammation markers (cytokines, etc) has been investigated in the setting of well-known cardiac arrhythmias including atrial fibrillation and ventricular tachycardia. Based on current literature, clinical utility of these markers might potentially yield important prognostic implications in the setting of certain arrhythmogenic conditions. On the other hand, there exists limited data regarding therapeutic implications including clinical benefit of primary anti-inflammatory agents (corticosteroids, colchicine, etc) in the setting of arrhythmia management. The present review primarily aims to discuss potential triggers and fundamental mechanisms of inflammation-related arrhythmias along with a particular emphasis on clinical implications of systemic inflammation in the setting of cardiac arrhythmogenesis.

Adam17 Deficiency Promotes Atherosclerosis by Enhanced TNFR2 Signaling in Mice

OBJECTIVE

ADAM17 (a disintegrin and metalloproteinase 17) is a sheddase releasing different types of membrane-bound proteins, including adhesion molecules, cytokines, and their receptors as well as inflammatory mediators. Because these substrates modulate important mechanisms of atherosclerosis, we hypothesized that ADAM17 might be involved in the pathogenesis of this frequent disease.

APPROACH AND RESULTS

Because Adam17-knockout mice are not viable, we studied the effect of Adam17 deficiency on atherosclerosis in Adam17 hypomorphic mice (Adam17^ex/ex), which have low residual Adam17 expression. To induce atherosclerosis, mice were crossed onto the low-density lipoprotein receptor (Ldlr)-deficient background. We found that Adam17^ex/ex.Ldlr^-/- mice developed ≈1.5-fold larger atherosclerotic lesions, which contained more macrophages and vascular smooth muscle cells than wild-type littermate controls (Adam17^wt/wt.Ldlr^-/-). Reduced Adam17-mediated shedding led to significantly increased protein levels of membrane-resident TNFα (tumor necrosis factor) and TNFR2 (tumor necrosis factor receptor 2), resulting in a constitutive activation of TNFR2 signaling. At the same time, Adam17 deficiency promoted proatherosclerotic cellular functions, such as increased proliferation and reduced apoptosis in cultured macrophages and vascular smooth muscle cells and increased adhesion of macrophages to vascular endothelial cells. Because siRNA (small interfering RNA)-mediated knockdown of Tnfr2 rescued from aberrant proliferation and from misregulation of apoptosis in Adam17-depleted cells, our data indicate that TNFR2 is an important effector of ADAM17 in our mouse model.

CONCLUSIONS

Our results provide evidence for an atheroprotective role of ADAM17, which might be mediated by cleaving membrane-bound TNFα and TNFR2, thereby preventing overactivation of endogenous TNFR2 signaling in cells of the vasculature.

A Disintegrin and Metalloprotease 17 in the Cardiovascular and Central Nervous Systems

ADAM17 is a metalloprotease and disintegrin that lodges in the plasmatic membrane of several cell types and is able to cleave a wide variety of cell surface proteins. It is somatically expressed in mammalian organisms and its proteolytic action influences several physiological and pathological processes. This review focuses on the structure of ADAM17, its signaling in the cardiovascular system and its participation in certain disorders involving the heart, blood vessels, and neural regulation of autonomic and cardiovascular modulation.

Enhanced ADAM17 expression is associated with cardiac remodeling in rats with acute myocardial infarction

AIM

This study aimed to investigate the dynamic expression of A-disintegrin-and-metalloproteinase-17 (ADAM17) during cardiac remodeling after acute myocardial infarction (AMI).

MAIN METHODS

Forty male Wistar rats with a permanent ligation of the left anterior descending artery were equally divided into four groups based on predefined sacrifice time: MI1d, MI1w, MI4w and MI12w. As controls, 36 rats only with left thoracotomy were equally divided into four groups. Cardiac remodeling was assessed by echocardiography and hematoxylin and eosin (H&E) staining. ADAM17 mRNA was detected by real-time reverse transcription polymerase chain reaction, and protein expression of ADAM17, tissue inhibitor of metalloproteinases-3 (TIMP-3) and TNF-α was analyzed by western blotting.

KEY FINDINGS

The systolic function was sharply worsened in the MI1w group (versus the Con1w group, P<0.05), but left ventricular weight index was significantly increased after 4weeks post-MI (P<0.05). H&E staining revealed that one week after AMI, myocardial tissue in the epicardial border zone of the infarcted heart was mixed with broken mitochondrial cristae and decreased matrix density. ADAM17 mRNA and protein expression was significantly increased, accompanied by decreased TIMP-3 and upregulated TNF-α expression in the MI1w group (versus the MI1d group, all P<0.05). Moreover, dynamic ADAM17 mRNA expression was positively correlated with enlarged LVEDd and LVESd (P=0.001, P=0.003) and negatively with LVEF (P=0.039) in AMI rats.

SIGNIFICANCE

Enhanced ADAM17 expression, along with decreased TIMP-3 and increased TNF-α expression, especially within one week after AMI, is associated with cardiac remodeling.

Cardiomyocyte A Disintegrin And Metalloproteinase 17 (ADAM17) Is Essential in Post-Myocardial Infarction Repair by Regulating Angiogenesis

BACKGROUND

A disintegrin and metalloproteinase 17 (ADAM17) is a membrane-bound enzyme that mediates shedding of many membrane-bound molecules, thereby regulating multiple cellular responses. We investigated the role of cardiomyocyte ADAM17 in myocardial infarction (MI).

METHODS AND RESULTS

Cardiomyocyte-specific ADAM17 knockdown mice (ADAM17(flox/flox)/α-MHC-Cre; f/f/Cre) and parallel controls (ADAM17(flox/flox); f/f) were subjected to MI by ligation of the left anterior descending artery. Post MI, f/f/Cre mice showed compromised survival, higher rates of cardiac rupture, more severe left ventricular dilation, and suppressed ejection fraction compared with parallel f/f-MI mice. Ex vivo ischemic injury (isolated hearts) resulted in comparable recovery in both genotypes. Myocardial vascular density (fluorescent-labeled lectin perfusion and CD31 immunofluorescence staining) was significantly lower in the infarct areas of f/f/Cre-MI compared with f/f-MI mice. Activation of vascular endothelial growth factor receptor 2 (VEGFR2), its mRNA, and total protein levels were reduced in infarcted myocardium in ADAM17 knockdown mice. Transcriptional regulation of VEGFR2 by ADAM17 was confirmed in cocultured cardiomyocyte-fibroblast as ischemia-induced VEGFR2 expression was blocked by ADAM17-siRNA. Meanwhile, ADAM17-siRNA did not alter VEGFA bioavailability in the conditioned media. ADAM17 knockdown mice (f/f/Cre-MI) exhibited reduced nuclear factor-κB activation (DNA binding) in the infarcted myocardium, which could underlie the suppressed VEGFR2 expression in these hearts. Post MI, inflammatory response was not altered by ADAM17 downregulation.

CONCLUSIONS

This study highlights the key role of cardiomyocyte ADAM17 in post-MI recovery by regulating VEGFR2 transcription and angiogenesis, thereby limiting left ventricular dilation and dysfunction. Therefore, ADAM17 upregulation, within the physiological range, could provide protective effects in ischemic cardiomyopathy.

Systems analysis of gene ontology and biological pathways involved in post-myocardial infarction responses

Background

Pathway analysis has been widely used to gain insight into essential mechanisms of the response to myocardial infarction (MI). Currently, there exist multiple pathway databases that organize molecular datasets and manually curate pathway maps for biological interpretation at varying forms of organization. However, inconsistencies among different databases in pathway descriptions, frequently due to conflicting results in the literature, can generate incorrect interpretations. Furthermore, although pathway analysis software provides detailed images of interactions among molecules, it does not exhibit how pathways interact with one another or with other biological processes under specific conditions.

Methods

We propose a novel method to standardize descriptions of enriched pathways for a set of genes/proteins using Gene Ontology terms. We used this method to examine the relationships among pathways and biological processes for a set of condition-specific genes/proteins, represented as a functional biological pathway-process network. We applied this algorithm to a set of 613 MI-specific proteins we previously identified.

Results

A total of 96 pathways from Biocarta, KEGG, and Reactome, and 448 Gene Ontology Biological Processes were enriched with these 613 proteins. The pathways were represented as Boolean functions of biological processes, delivering an interactive scheme to organize enriched information with an emphasis on involvement of biological processes in pathways. We extracted a network focusing on MI to demonstrate that tyrosine phosphorylation of Signal Transducer and Activator of Transcription (STAT) protein, positive regulation of collagen metabolic process, coagulation, and positive/negative regulation of blood coagulation have immediate impacts on the MI response.

Conclusions

Our method organized biological processes and pathways in an unbiased approach to provide an intuitive way to identify biological properties of pathways under specific conditions. Pathways from different databases have similar descriptions yet diverse biological processes, indicating variation in their ability to share similar functional characteristics. The coverages of pathways can be expanded with the incorporation of more biological processes, predicting involvement of protein members in pathways. Further, detailed analyses of the functional biological pathway-process network will allow researchers and scientists to explore critical routes in biological systems in the progression of disease.

Elevated serum levels of soluble Axl in acute coronary syndrome

BACKGROUND

Morbidities related to atherosclerosis, such as acute coronary syndrome (ACS), remain the leading cause of mortality. Axl is a receptor tyrosine kinase that is expressed in mammalian vascular and immune cells. Axl signaling is involved in the regulation of the inflammatory response. A considerable amount of evidence indicates that inflammation is responsible for the development of atherosclerosis in patients with ACS.

METHODS

To assess the relation of Axl and ACS, we recruited 64 patients with coronary heart disease: 34 with ACS, 30 with stable coronary heart disease, and 24 apparently healthy controls. Serum concentrations of soluble Axl (sAxl) were quantified by enzyme-linked immunosorbent assay. High-sensitivity C-reactive protein, tumor necrosis factor alpha, troponin I, and other routine biochemical markers were also measured.

RESULTS

The levels of sAxl were significantly higher in patients with ACS than in the controls (P=0.005). Furthermore, correlation analysis indicated that sAxl was significantly associated with serum levels of high-sensitivity C-reactive protein (r=0.283, P=0.008), tumor necrosis factor alpha (r=0.565, P<0.001), and troponin I (r=0.264, P=0.013). Logistic regression analysis (odds ratio=1.038, 95% confidence interval, 1.008-1.069, P=0.012) indicated a significant association between sAxl and ACS.

CONCLUSIONS

Serum levels of sAxl correlate to inflammatory biochemical markers. These findings demonstrate for the first time that sAxl does have a role in ACS, presumably connected to the inflammation.

Oxidative stress: dual pathway induction in cardiorenal syndrome type 1 pathogenesis

Cardiorenal Syndrome Type 1 (Type 1) is a specific condition which is characterized by a rapid worsening of cardiac function leading to acute kidney injury (AKI). Even though its pathophysiology is complex and not still completely understood, oxidative stress seems to play a pivotal role. In this study, we examined the putative role of oxidative stress in the pathogenesis of CRS Type 1. Twenty-three patients with acute heart failure (AHF) were included in the study. Subsequently, 11 patients who developed AKI due to AHF were classified as CRS Type 1. Quantitative determinations for IL-6, myeloperoxidase (MPO), nitric oxide (NO), copper/zinc superoxide dismutase (Cu/ZnSOD), and endogenous peroxidase activity (EPA) were performed. CRS Type 1 patients displayed significant augmentation in circulating ROS and RNS, as well as expression of IL-6. Quantitative analysis of all oxidative stress markers showed significantly lower oxidative stress levels in controls and AHF compared to CRS Type 1 patients (P < 0.05). This pilot study demonstrates the significantly heightened presence of dual oxidative stress pathway induction in CRS Type 1 compared to AHF patients. Our findings indicate that oxidative stress is a potential therapeutic target, as it promotes inflammation by ROS/RNS-linked pathogenesis.

A score including ADAM17 substrates correlates to recurring cardiovascular event in subjects with atherosclerosis

OBJECTIVE

Atherosclerosis disease is a leading cause for mortality and morbidity. The narrowing/rupture of a vulnerable atherosclerotic plaque is accountable for acute cardiovascular events. However, despite of an intensive research, a reliable clinical method which may disclose a vulnerable patient is still unavailable.

APPROACH AND RESULTS

We tested the association of ADAM17 (A Disintegrin and Metallo Protease Domain 17) circulating substrates (sICAM-1, sVCAM-1, sIL6R and sTNFR1) with a second major cardiovascular events [MACEs] (cardiovascular death, peripheral artery surgeries, non-fatal myocardial infarction and non-fatal stroke) in 298 patients belonging to the Vascular Diabetes (AVD) study. To evaluate ADAM17 activity we create ADAM17 score through a RECPAM model. Finally we tested the discrimination ability and the reclassification of clinical models. At follow-up (mean 47 months, range 1-118 months), 55 MACEs occurred (14 nonfatal MI, 14 nonfatal strokes, 17 peripheral artery procedures and 10 cardiovascular deaths) (incidence = 7.8% person-years). An increased risk for incident events was observed among the high ADAM17 score individuals both in univariable (HR 19.20, 95% CI 15.82-63.36, p < 0.001) and multivariable analysis (HR 3.42, 95% CI 1.55-7.54, p < 0.001). Finally we found that ADAM17 score significantly increases the prediction accuracy of the Framingham Recurring-Coronary-Heart-Disease-Score, with a significant improvement in discrimination (integrated discrimination improvement = 9%, p = 0.012) and correctly reclassifying 10% of events and 41% of non-events resulting in a cNRI = 0.51 (p = 0.005).

CONCLUSION

We demonstrated a positive role of ADAM17 activity to predicting CV events. We think that an approach that targets strategies beyond classic cardiovascular risk factors control is necessary in individuals with an established vascular atherosclerosis.

Association between ADAM17 promoter polymorphisms and ischemic stroke in a Chinese population

AIM

Stroke is a leading cause of death and disability worldwide. Most ischemic strokes (IS) are caused by atherosclerosis. Recently, the pivotal role of ADAM17 in atherosclerosis has been thoroughly addressed. However, the association between ADAM17 and IS has not yet been thoroughly explored. The present study therefore aimed to investigate the association between disintegrin and metalloproteinase 17 (ADAM17) gene polymorphisms and the risk of ischemic stroke (IS).

METHODS

The associations between five ADAM17 promoter polymorphisms and the risk of IS were assessed in 342 patients with IS and 296 age-matched healthy individuals in a case-control study.

RESULTS

The allele and genotype frequencies of the ADAM17 polymorphisms (rs11684747, rs11689958, rs12692386, rs55790676 and rs1524668) did not differ significantly between the IS patients and healthy control group subjects. In addition, no significant associations were detected between the ADAM17 haplotypes and IS. The mean intima-media thickness in the IS patients was not associated with the ADAM17 polymorphisms. When the IS patients were stratified according to their OCSP classification, the genotype frequencies of the ADAM17-rs1524668 polymorphism exhibited a significant association with the PACI subtype of IS. Moreover, the ADAM17-rs12692386 A＞G polymorphism was found to be associated with a higher ADAM17 mRNA expression.

CONCLUSIONS

The SNPs in the ADAM17 promoter region do not appear to be major contributors to the pathogenesis of IS. However, the rs12692386 G ADAM17 allele is correlated with a higher expression of ADAM17 mRNA, which may play a role in increasing inflammation in IS patients. Furthermore, the ADAM17-rs1524668 polymorphism is linked to a higher risk of PACI-type stroke, confirming the role of ADAM17 in the pathophysiology of PACI, with potentially important therapeutic implications.

Nitroglycerine-induced nitrate tolerance compromises propofol protection of the endothelial cells against TNF-α: the role of PKC-β2 and NADPH oxidase

Continuous treatment with organic nitrates causes nitrate tolerance and endothelial dysfunction, which is involved with protein kinase C (PKC) signal pathway and NADPH oxidase activation. We determined whether chronic administration with nitroglycerine compromises the protective effects of propofol against tumor necrosis factor (TNF-) induced toxicity in endothelial cells by PKC-β₂ dependent NADPH oxidase activation. Primary cultured human umbilical vein endothelial cells were either treated or untreated with TNF-α (40 ng/mL) alone or in the presence of the specific PKC-β₂ inhibitor CGP53353 (1 μM)), nitroglycerine (10 μM), propofol (100 μM), propofol plus nitroglycerin, or CGP53353 plus nitroglycerine, respectively, for 24 hours. TNF-α increased the levels of superoxide, Nox (nitrate and nitrite), malondialdehyde, and nitrotyrosine production, accompanied by increased protein expression of p-PKC-β₂, gP91phox, and endothelial cell apoptosis, whereas all these changes were further enhanced by nitroglycerine. CGP53353 and propofol, respectively, reduced TNF-α induced oxidative stress and cell toxicity. CGP53353 completely prevented TNF-α induced oxidative stress and cell toxicity in the presence or absence of nitroglycerine, while the protective effects of propofol were neutralized by nitroglycerine. It is concluded that nitroglycerine comprises the protective effects of propofol against TNF-α stimulation in endothelial cells, primarily through PKC-β₂ dependent NADPH oxidase activation.

Cardiovascular effects of tumour necrosis factor α antagonism in patients with acute myocardial infarction: a first in human study

OBJECTIVE

The inflammatory cytokine, tumour necrosis factor α (TNF-α), exerts deleterious cardiovascular effects. We wished to determine the effects of TNF-α antagonism on endothelial function and platelet activation in patients with acute myocardial infarction.

DESIGN AND SETTING AND PATIENTS

A double-blind, parallel group, randomised controlled trial performed in a tertiary referral cardiac centre. 26 patients presenting with acute myocardial infarction randomised to receive an intravenous infusion of etanercept (10 mg) or saline placebo.

MAIN OUTCOME MEASURES

Leucocyte count, plasma cytokine concentrations, flow cytometric measures of platelet activation and peripheral vasomotor and fibrinolytic function were determined before and 24 h after study intervention.

RESULTS

Consistent with effective conjugation of circulating TNF-α, plasma TNF-α concentrations increased in all patients following etanercept (254 ± 15 vs 0.12 ± 0.02 pg/ml; p < 0.0001), but not saline infusion. Etanercept treatment reduced neutrophil (7.4 ± 0.6 vs 8.8 ± 0.6 × 10(9) cells/l; p = 0.03) and plasma interleukin-6 concentrations (5.8 ± 2.0 vs 10.6 ± 4.0 pg/ml; p = 0.012) at 24 h but increased platelet-monocyte aggregation (30 ± 5 vs 20 ± 3%; p = 0.02). Vasodilatation in response to substance P, acetylcholine and sodium nitroprusside, and acute tissue plasminogen activator release were unaffected by either treatment (p > 0.1 for all).

CONCLUSIONS

Following acute myocardial infarction, etanercept reduces systemic inflammation but increases platelet activation without affecting peripheral vasomotor or fibrinolytic function. We conclude that TNF-α antagonism is unlikely to be a beneficial therapeutic strategy in patients with acute myocardial infarction.

The role of ADAM-mediated shedding in vascular biology

Within the vasculature the disintegrins and metalloproteinases (ADAMs) 8, 9, 10, 12, 15, 17, 19, 28 and 33 are expressed on endothelial cells, smooth muscle cells and on leukocytes. As surface-expressed proteases they mediate cleavage of vascular surface molecules at an extracellular site close to the membrane. This process is termed shedding and leads to the release of a soluble substrate ectodomain thereby critically modulating the biological function of the substrate. In the vasculature several surface molecules undergo ADAM-mediated shedding including tumour necrosis factor (TNF) α, interleukin (IL) 6 receptor α, L-selectin, vascular endothelial (VE)-cadherin, the transmembrane CX3C-chemokine ligand (CX3CL) 1, Notch, transforming growth factor (TGF) and heparin-binding epidermal growth factor (HB-EGF). These substrates play distinct roles in vascular biology by promoting inflammation, permeability changes, leukocyte recruitment, resolution of inflammation, regeneration and/or neovascularisation. Especially ADAM17 and ADAM10 are capable of cleaving many substrates with diverse function within the vasculature, whereas other ADAMs have a more restricted substrate range. Therefore, targeting ADAM17 or ADAM10 by pharmacologic inhibition or gene knockout not only attenuates the inflammatory response in animal models but also affects tissue regeneration and neovascularisation. Recent discoveries indicate that other ADAMs (e.g. ADAM8 and 9) also play important roles in vascular biology but appear to have more selective effects on vascular responses (e.g. on neovascularisation only). Although, targeting of ADAM17 and ADAM10 in inflammatory diseases is still a promising approach, temporal and spatial as well as substrate-specific inhibition approaches are required to minimise undesired side effects on vascular cells.

A disintegrin and metalloprotease 17 mediates neointimal hyperplasia in vasculature

The requirement of a metalloprotease, a disintegrin and metalloprotease 17 (ADAM17) for the growth of cultured vascular smooth muscle cells has been demonstrated in vitro. However, whether this metalloprotease is responsible for vascular remodeling in vivo remains unanswered. Rat carotid arteries were analyzed 2 weeks after a balloon angioplasty. The neointimal cells were strongly positive for ADAM17 immunostaining. Marked inhibition of intimal hyperplasia was observed in a dominant-negative ADAM17 adenovirus-treated carotid artery. Proliferating cell nuclear antigen-positive cells and phospho-epidermal growth factor receptor-positive cells in the neointima were reduced by dominant-negative ADAM17 as well. In contrast, the neointima formation, proliferating cell nuclear antigen-positive cells, and phospho-epidermal growth factor receptor-positive cells were markedly enhanced by wild-type ADAM17 adenovirus. In conclusion, ADAM17 activation is involved in epidermal growth factor receptor activation and subsequent neointimal hyperplasia after vascular injury. ADAM17 could be a novel therapeutic target for pathophysiological vascular remodeling.

Hypertonicity-enhanced TNF-α release from activated human monocytic THP-1 cells requires ERK activation

BACKGROUND

Hypertonic stress enhances tumor necrosis factor (TNF)-α expression in activated monocytes. However, the underlying mechanism is unknown. The produced TNF-α is primarily cleaved and released by TNF-α-converting enzyme (TACE), and the surface expression of TACE is down-regulated by endocytosis. As hypertonicity inhibits endocytosis, we evaluated the mechanism of hypertonicity-induced TNF-α release from activated human monocytic THP-1 cells.

METHODS

THP-1 cells were stimulated with lipopolysaccharide (LPS) or phorbol 12-myristate 13-acetate (PMA) in the presence or absence of hypertonic agents (150 mM sucrose or 150-300 mM NaCl). The amount of TNF-α mRNA and protein, surface expression of TACE and activation of signaling pathways (mitogen-activated protein kinase, Akt and NF-κB) were assayed.

RESULTS

Hypertonic sucrose and NaCl significantly enhanced TNF-α release from THP-1 cells upon LPS or PMA stimulation. Hypertonic sucrose and other endocytosis inhibitors increased surface expression of TACE, but their effects on TNF-α release were inconsistent. This enhancement effect by hypertonicity was not attenuated by inhibition of TACE or IκB kinase, but it was blocked by cycloheximide and a MAP/ERK kinase inhibitor. The LPS- or PMA-induced TNF-α mRNA expression was not increased; rather, it was inhibited by hypertonicity. ERK1/2 was re-activated after sucrose treatment in LPS-stimulated THP-1 cells.

CONCLUSIONS

Hypertonicity-enhanced TNF-α protein synthesis from LPS- or PMA-activated THP-1 cells requires ERK activation and may proceed without TACE.

GENERAL SIGNIFICANCE

A vast amount of TNF-α production was regulated by a crucial post-transcriptional manner in activated human monocytic leukemia cells, and it may possibly be contributed to the cachexia condition.

The "A Disintegrin And Metalloproteases" ADAM10 and ADAM17: novel drug targets with therapeutic potential?

Proteolytic ectodomain release, a process known as "shedding", has been recognised as a key mechanism for regulating the function of a diversity of cell surface proteins. A Disintegrin And Metalloproteinases (ADAMs) have emerged as the major proteinase family that mediates ectodomain shedding. Dysregulation of ectodomain shedding is associated with autoimmune and cardiovascular diseases, neurodegeneration, infection, inflammation and cancer. Therefore, ADAMs are increasingly regarded as attractive targets for novel therapies. ADAM10 and its close relative ADAM17 (TNF-alpha converting enzyme (TACE)) have been studied in particular in the context of ectodomain shedding and have been demonstrated as key molecules in most of the shedding events characterised to date. Whereas the level of expression of ADAM10 may be of importance in cancer and neurodegenerative disorders, ADAM17 mainly coordinates pro- and anti-inflammatory activities during immune response. Despite the high therapeutical potential of ADAM inhibition, all clinical trials using broad-spectrum metalloprotease inhibitors have failed so far. This review will cover the emerging roles of both ADAM10 and ADAM17 in the regulation of major physiological and developmental pathways and will discuss the suitability of specifically modulating the activities of both proteases as a feasible way to inhibit inflammatory states, cancer and neurodegeneration.

L-arginine enhances nitrative stress and exacerbates tumor necrosis factor-alpha toxicity to human endothelial cells in culture: prevention by propofol

Supplementation of L-arginine, a nitric oxide precursor, during the late phase of myocardial ischemia/reperfusion increases myocyte apoptosis and exacerbates myocardial injury, but the underlying mechanism is unclear. During myocardial ischemia/reperfusion, apoptosis of endothelial cells precedes that of cardiomyocyte. Tumor necrosis factor-alpha (TNF) production is increased during myocardial ischemia/reperfusion, which may exacerbate myocardial injury by inducing endothelial cell apoptosis. We postulated that L-arginine may exacerbate TNF-induced endothelial cell apoptosis by enhancing peroxynitrite-mediated nitrative stress. Cultured human umbilical vein endothelial cells were either not treated (control) or treated with TNF alone or with TNF in the presence of L-arginine, the nonselective nitric oxide synthase inhibitor N (omega)-nitro-L-arginine (L-NNA), propofol (an anesthetic that scavenges peroxynitrite), or L-arginine plus propofol, respectively, for 24 hours. TNF increased intracellular superoxide and hydrogen peroxide production accompanied by increases of inducible nitric oxide synthase (iNOS) protein expression and nitric oxide production. This was accompanied by increased protein expression of nitrotyrosine, a fingerprint of peroxynitrite and an index of nitrative stress, and increased endothelial cell apoptosis. L-arginine did not enhance TNF-induced increases of superoxide and peroxynitrite production but further increased TNF-induced increase of nitrotyrosine production and exacerbated TNF-mediated cell apoptosis. L-NNA and propofol, respectively, reduced TNF-induced nitrative stress and attenuated TNF cellular toxicity. The L-arginine-mediated enhancement of nitrative stress and TNF toxicity was attenuated by propofol. Thus, under pathological conditions associated with increased TNF production, L-arginine supplementation may further exacerbate TNF cellular toxicity by enhancing nitrative stress.

ADAM-17: the enzyme that does it all

This review focuses on the role of ADAM-17 in disease. Since its debut as the tumor necrosis factor converting enzyme (TACE), ADAM-17 has been reported to be an indispensible regulator of almost every cellular event from proliferation to migration. The central role of ADAM-17 in cell regulation is rooted in its diverse array of substrates: cytokines, growth factors, and their receptors as well as adhesion molecules are activated or inactivated by their cleavage with ADAM-17. It is therefore not surprising that ADAM-17 is implicated in numerous human diseases including cancer, heart disease, diabetes, rheumatoid arthritis, kidney fibrosis, Alzheimer's disease, and is a promising target for future treatments. The specific role of ADAM-17 in the pathophysiology of these diseases is very complex and depends on the cellular context. To exploit the therapeutic potential of ADAM-17, it is important to understand how its activity is regulated and how specific organs and cells can be targeted to inactivate or activate the enzyme.

Immune modulation: role of the inflammatory cytokine cascade in the failing human heart

Recent studies have determined that expression of inflammatory mediators, such as cytokines and chemokines, is an important factor in the development and progression of heart failure (HF). These inflammatory mediators are expressed in response to various myocardial insults, including myocardial ischemia, viral infection, and toxins, and appear to have a detrimental effect on cardiac function and prognosis in HF patients. Our previous reports have shown activation of inflammatory cytokines, particularly tumor necrosis factor-alpha (TNF-alpha), in the myocardium and peripheral monocytes in patients with HF. Indeed, sustained increases in cytokines, including TNF-alpha and its receptor, lead to monocyte phenotype transition, myocytic apoptosis, and activation of matrix metalloproteinase. This in turn modifies the interstitial matrix, augmenting further ventricular remodeling. Thus, in view of the emerging importance of TNF-alpha in the pathogenesis of HF, we review the effects of TNF-alpha on the physiology of the heart and the development of clinical strategies to target the inflammatory cytokine cascade.