ADAMTS7 in cardiovascular disease: from bedside to bench and back again?

Design, synthesis and biological evaluation of arylsulfonamides as ADAMTS7 inhibitors

The proteolytic activity of the enzyme ADAMTS7 was recently shown to enhance the progression of atherosclerosis, in line with human genetic findings suggesting that ADAMTS7 has a role in the pathophysiology of coronary heart disease. Targeting the active site of ADAMTS7 with a small molecule inhibitor, therefore, has therapeutic potential. Here, we report the design and synthesis of a novel hydroxamate-based arylsulfonamide that is a potent and selective ADAMTS7 inhibitor. In silico studies guided the hit optimization process aiming to improve selectivity of the previously reported (non-selective) inhibitor EDV33. Our lead compound is a p-trifluoromethyl biphenyl sulfonamide, which displayed a 12-fold selectivity for ADAMTS7 (K i = 9 nM) over ADAMTS5 (K i = 110 nM) and an 8-fold increase in inhibition of ADAMTS7 compared to EDV33 (K i = 70 nM). The substitutions switched selectivity and produced a new potent ADAMTS7 inhibitor that can be taken forward for further characterisation.

Novel indel variation of LTBP4 gene associates with risk of sudden cardiac death in Chinese populations with coronary artery disease

The objective of this study is to investigate whether common genetic variants of the LTBP4 gene are linked to the susceptibility of sudden cardiac death in individuals who have atherosclerotic coronary artery disease (SCD-CAD) in Chinese populations. A total of 208 SCD-CAD cases and 638 controls were included in the analysis, and logistic regression was employed to assess the association between a 4-bp insertion/deletion polymorphism (rs34005443) within LTBP4 and the susceptibility to SCD-CAD among Chinese individuals. Logistic regression analysis demonstrated a notable association between the insertion allele of rs34005443 and an escalated susceptibility to SCD-CAD [odds ratio (OR) = 1.434; 95 % confidence interval:1.14-1.80; P = 1.79 × 10-3]. Genotype-phenotype correlation analysis was performed using Genotype-Tissue expression (GTEx) database and further validated by human myocardium using qPCR. Correlation analysis revealed that LTBP4 expression level was lower in samples with the insertion allele. Furthermore, the dual-luciferase activity assays indicated that rs34005443 may play a regulatory role. Additionally, we predicted 30 transcription factors that are likely to bind to rs34005443 and its highly linked genetic variants via 3DSNP database. Subsequent GO and KEGG analysis indicated that these transcription factors have a significant function in regulating gene expression. Finally, PPI network analysis suggested a tight connection between LTBP4 proteins and TGFβs, highlighting these genes as potential hub genes in the context of SCD-CAD. In summary, our study revealed that rs34005443 might contribute to SCD-CAD susceptibility by regulating LTBP4 expression. These findings revealed that this indel could be a potentially functional marker for molecular diagnosis and risk stratification of SCD-CAD.

BAY-9835: Discovery of the First Orally Bioavailable ADAMTS7 Inhibitor

The matrix metalloprotease ADAMTS7 has been identified by multiple genome-wide association studies as being involved in the development of coronary artery disease. Subsequent research revealed the proteolytic function of the enzyme to be relevant for atherogenesis and restenosis after vessel injury. Based on a publicly known dual ADAMTS4/ADAMTS5 inhibitor, we have in silico designed an ADAMTS7 inhibitor of the catalytic domain, which served as a starting point for an optimization campaign. Initially our inhibitors suffered from low selectivity vs MMP12. An X-ray cocrystal structure inspired us to exploit amino acid differences in the binding site of MMP12 and ADAMTS7 to improve selectivity. Further optimization composed of employing 5-membered heteroaromatic groups as hydantoin substituents to become more potent on ADAMTS7. Finally, fine-tuning of DMPK properties yielded BAY-9835, the first orally bioavailable ADAMTS7 inhibitor. Further optimization to improve selectivity vs ADAMTS12 seems possible, and a respective starting point could be identified.

ADAMTS-7 Modulates Atherosclerotic Plaque Formation by Degradation of TIMP-1

BACKGROUND

The ADAMTS7 locus was genome-wide significantly associated with coronary artery disease. Lack of the ECM (extracellular matrix) protease ADAMTS-7 (A disintegrin and metalloproteinase-7) was shown to reduce atherosclerotic plaque formation. Here, we sought to identify molecular mechanisms and downstream targets of ADAMTS-7 mediating the risk of atherosclerosis.

METHODS

Targets of ADAMTS-7 were identified by high-resolution mass spectrometry of atherosclerotic plaques from Apoe-/- and Apoe-/-Adamts7-/- mice. ECM proteins were identified using solubility profiling. Putative targets were validated using immunofluorescence, in vitro degradation assays, coimmunoprecipitation, and Förster resonance energy transfer-based protein-protein interaction assays. ADAMTS7 expression was measured in fibrous caps of human carotid artery plaques.

RESULTS

In humans, ADAMTS7 expression was higher in caps of unstable as compared to stable carotid plaques. Compared to Apoe-/- mice, atherosclerotic aortas of Apoe-/- mice lacking Adamts-7 (Apoe-/-Adamts7-/-) contained higher protein levels of Timp-1 (tissue inhibitor of metalloprotease-1). In coimmunoprecipitation experiments, the catalytic domain of ADAMTS-7 bound to TIMP-1, which was degraded in the presence of ADAMTS-7 in vitro. ADAMTS-7 reduced the inhibitory capacity of TIMP-1 at its canonical target MMP-9 (matrix metalloprotease-9). As a downstream mechanism, we investigated collagen content in plaques of Apoe-/- and Apoe-/-Adamts7-/- mice after a Western diet. Picrosirius red staining of the aortic root revealed less collagen as a readout of higher MMP-9 activity in Apoe-/- as compared to Apoe-/- Adamts7-/- mice. To facilitate high-throughput screening for ADAMTS-7 inhibitors with the aim of decreasing TIMP-1 degradation, we designed a Förster resonance energy transfer-based assay targeting the ADAMTS-7 catalytic site.

CONCLUSIONS

ADAMTS-7, which is induced in unstable atherosclerotic plaques, decreases TIMP-1 stability reducing its inhibitory effect on MMP-9, which is known to promote collagen degradation and is likewise associated with coronary artery disease. Disrupting the interaction of ADAMTS-7 and TIMP-1 might be a strategy to increase collagen content and plaque stability for the reduction of atherosclerosis-related events.

LTBP4 in Health and Disease

Latent transforming growth factor β (TGFβ)-binding protein (LTBP) 4, a member of the LTBP family, shows structural homology with fibrillins. Both these protein types are characterized by calcium-binding epidermal growth factor-like repeats interspersed with 8-cysteine domains. Based on its domain composition and distribution, LTBP4 is thought to adopt an extended structure, facilitating the linear deposition of tropoelastin onto microfibrils. In humans, mutations in LTBP4 result in autosomal recessive cutis laxa type 1C, characterized by redundant skin, pulmonary emphysema, and valvular heart disease. LTBP4 is an essential regulator of TGFβ signaling and is related to development, immunity, injury repair, and diseases, playing a central role in regulating inflammation, fibrosis, and cancer progression. In this review, we focus on medical disorders or diseases that may be manipulated by LTBP4 in order to enhance the understanding of this protein.

Proteomic discovery of substrates of the cardiovascular protease ADAMTS7

The protease ADAMTS7 functions in the extracellular matrix (ECM) of the cardiovascular system. However, its physiological substrate specificity and mechanism of regulation remain to be explored. To address this, we conducted an unbiased substrate analysis using terminal amine isotopic labeling of substrates (TAILS). The analysis identified candidate substrates of ADAMTS7 in the human fibroblast secretome, including proteins with a wide range of functions, such as collagenous and noncollagenous extracellular matrix proteins, growth factors, proteases, and cell-surface receptors. It also suggested that autolysis occurs at Glu-729-Val-730 and Glu-732-Ala-733 in the ADAMTS7 Spacer domain, which was corroborated by N-terminal sequencing and Western blotting. Importantly, TAILS also identified proteolysis of the latent TGF-β-binding proteins 3 and 4 (LTBP3/4) at a Glu-Val and Glu-Ala site, respectively. Using purified enzyme and substrate, we confirmed ADAMTS7-catalyzed proteolysis of recombinant LTBP4. Moreover, we identified multiple additional scissile bonds in an N-terminal linker region of LTBP4 that connects fibulin-5/tropoelastin and fibrillin-1-binding regions, which have an important role in elastogenesis. ADAMTS7-mediated cleavage of LTBP4 was efficiently inhibited by the metalloprotease inhibitor TIMP-4, but not by TIMP-1 and less efficiently by TIMP-2 and TIMP-3. As TIMP-4 expression is prevalent in cardiovascular tissues, we propose that TIMP-4 represents the primary endogenous ADAMTS7 inhibitor. In summary, our findings reveal LTBP4 as an ADAMTS7 substrate, whose cleavage may potentially impact elastogenesis in the cardiovascular system. We also identify TIMP-4 as a likely physiological ADAMTS7 inhibitor.

Monoclonal antibodies against metzincin targets

The metzincin clan of metalloproteinases includes the MMP, disintegrin and metalloproteinase (ADAM) and ADAM with thrombospondin motifs families, which cleave extracellular targets in a wide range of (patho)physiological processes. Antibodies constitute a powerful tool to modulate the activity of these enzymes for both therapeutic and research purposes. In this review, we give an overview of monoclonal antibodies (mAbs) that have been tested in preclinical disease models, human trials and important studies of metzincin structure and function. Initial attempts to develop therapeutic small molecule inhibitors against MMPs were hampered by structural similarities between metzincin active sites and, consequently, off-target effects. Therefore, more recently, mAbs have been developed that do not bind to the active site but bind to surface-exposed loops that are poorly conserved in closely related family members. Inhibition of protease activity by these mAbs occurs through a variety of mechanisms, including (i) barring access to the active site, (ii) disruption of exosite binding, and (iii) prevention of protease activation. These different modes of inhibition are discussed in the context of the antibodies' potency, selectivity and, importantly, the effects in models of disease and clinical trials. In addition, various innovative strategies that were used to generate anti-metzincin mAbs are discussed. LINKED ARTICLES: This article is part of a themed section on Translating the Matrix. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.1/issuetoc.

Evolving targets for the treatment of atherosclerosis

Atherosclerosis is a progressive disease of large arteries and a leading cause of cardiovascular diseases and stroke. Chronic inflammation, aberrant immune response, and disturbances to key enzymes involved with lipid metabolism are characteristic features of atherosclerosis. Apart from targeting the derangements in lipid metabolism, therapeutic modulation to regulate chronic inflammation and the immune system response may prove to be very promising strategies in the management of atherosclerosis. In recent years, various targets have been studied for the treatment of atherosclerosis. PCSK9, a serine protease, actively targets the LDL-R and causes lysosomal degradation, which leads to excessive accumulation of LDL-C. Regulatory T cells (Tregs) and Triggering Receptor Expressed on Myeloid cells-1 (TREM-1) affects the adaptive and innate immune response, respectively, and thus, therapeutic intervention of either of these targets would directly modulate disease progression. Advanced atherosclerotic lesions are characterized by an accumulation of apoptotic cells. Cluster of differentiation-47 (CD47), an anti-phagocytic known as the "don't eat me" signaling molecule, inhibits efferocytosis, which causes accumulation of cell debris in plaque. ADAMTS and Notch signaling potentially affect the formation of neointima by modulation of extracellular matrix components such as macrophages and vascular smooth muscle cells. This review provides insights on the molecular targets for therapeutic intervention of atherosclerosis, their effect at various stages of atherosclerosis development, and the therapies that have been designed and currently being evaluated in clinical trials.

Association of ADAMTS7 gene polymorphism with cardiovascular survival in coronary artery disease

Recent genetic studies have revealed an association between polymorphisms at the ADAMTS7 gene locus and coronary artery disease (CAD) risk. Functional studies have shown that a CAD-associated polymorphism (rs3825807) affects ADAMTS7 maturation and vascular smooth muscular cell (VSMC) migration. Here, we tested whether ADAMTS7 (A/G) SNP is associated with cardiovascular (CV) survival in patients with established CAD. A cohort of 1,128 patients with angiographic proven CAD, who were followed up prospectively for a mean follow-up period of 63 (range 6–182) mo, were genotyped for rs3825807 A/G. Survival statistics (Cox regression) compared heterozygous (AG) and wild-type (AA) with the reference homozygous GG. Kaplan-Meier (K-M) survival curves were performed according to ADAMTS7 genotypes for CV mortality. Results showed that 47.3% of patients were heterozygous (AG), 36.5% were homozygous for the wild-type allele (AA) and only 16.2% were homozygous for the GG genotype. During the follow-up period, 109 (9.7%) patients died, 77 (6.8%) of CV causes. Survival analysis showed that AA genotype was an independent risk factor for CV mortality compared with reference genotype GG (HR = 2.7, P = 0.025). At the end of follow-up, the estimated survival probability (K-M) was 89.8% for GG genotype, 82.2% for AG and 72.3% for AA genotype ( P = 0.039). Carriage of the mutant G allele of the ADAMTS7 gene was associated with improved CV survival in patients with documented CAD. The native overfunctional ADAMTS7 allele (A) may accelerate VSMC migration and lead to neointimal thickening, atherosclerosis progression and acute plaque events. ADAMTS7 gene should be further explored in CAD for risk prediction, mechanistic and therapeutic goals.

The Function and Roles of ADAMTS-7 in Inflammatory Diseases

The ADAMTS proteinases are a group of multidomain and secreted metalloproteinases containing the thrombospondin motifs. ADAMTS-7 is a member of ADAMTS family and plays a crucial role in the pathogenesis of arthritis. Overexpression of ADAMTS-7 gene promotes the breakdown of cartilage oligomeric matrix protein (COMP) matrix and accelerates the progression of both surgically induced osteoarthritis and collagen-induced arthritis. Moreover, ADAMTS-7 and tumor necrosis factor-α (TNF-α) form a positive feedback loop in osteoarthritis. More significantly, granulin-epithelin precursor, a growth factor has important roles in bone development and bone-associated diseases, disturbs the interaction between ADAMTS-7 and COMP, and prevents COMP degradation. This review is based on our results and provides an overview of current knowledge of ADAMTS-7, including its structure, function, gene regulation, and inflammatory diseases involvement.