Cathepsin L expression and regulation in human abdominal aortic aneurysm, atherosclerosis, and vascular cells

Integrative analysis of single-Cell RNA sequencing and experimental validation in the study of abdominal aortic aneurysm progression

BACKGROUND

Abdominal aortic aneurysm (AAA) is a complex vascular disorder characterized by the progressive dilation of the abdominal aorta, with a high risk of rupture and mortality. Understanding the cellular interactions and molecular mechanisms underlying AAA development is critical for identifying potential therapeutic targets.

METHODS

This study utilized datasets GSE197748, GSE164678 and GSE183464 from the GEO database, encompassing bulk and single-cell RNA sequencing data from AAA and control samples. We performed principal component analysis, differential expression analysis, and functional enrichment analysis to identify key pathways involved in AAA. Cell-cell interactions were investigated using CellPhoneDB, focusing on fibroblasts, vascular smooth muscle cells (VSMCs), and macrophages. We further validated our findings using a mouse model of AAA induced by porcine pancreatic enzyme infusion, followed by gene expression analysis and co-immunoprecipitation experiments.

RESULTS

Our analysis revealed significant alterations in gene expression profiles between AAA and control samples, with a pronounced immune response and cell adhesion pathways being implicated. Single-cell RNA sequencing data highlighted an increased proportion of pro-inflammatory macrophages, along with changes in the composition of fibroblasts and VSMCs in AAA. CellPhoneDB analysis identified critical ligand-receptor interactions, notably collagen type I alpha 1 chain (COL1A1)/COL1A2-CD18 and thrombospondin 1 (THBS1)-CD3, suggesting complex communication networks between fibroblasts and VSMCs. In vivo experiments confirmed the upregulation of these genes in AAA mice and demonstrated the functional interaction between COL1A1/COL1A2 and CD18.

CONCLUSION

The interaction between fibroblasts and VSMCs, mediated by specific ligand-receptor pairs such as COL1A1/COL1A2-CD18 and THBS1-CD3, plays a pivotal role in AAA pathogenesis.

Dysregulated Genes and Signaling Pathways in the Formation and Rupture of Intracranial Aneurysm

Intracranial aneurysm (IA) has the potential to rupture. Despite scientific advances, we are still not in a position to screen patients for IA and identify those at risk of rupture. It is critical to comprehend the molecular basis of disease to facilitate the development of novel diagnostic strategies. We used transcriptomics to identify the dysregulated genes and understand their role in the disease biology. In particular, RNA-Seq was performed in tissue samples of controls, unruptured IA, and ruptured IA. Dysregulated genes (DGs) were identified and analyzed to understand the functional aspects of molecules. Subsequently, candidate genes were validated at both transcript and protein level. There were 314 DGs in patients with unruptured IA when compared to control samples. Out of these, SPARC and OSM were validated as candidate molecules in unruptured IA. PI3K-AKT signaling pathway was found to be an important pathway for the formation of IA. Similarly, 301 DGs were identified in the samples of ruptured IA when compared with unruptured IAs. CTSL was found to be a key candidate molecule which along with Hippo signaling pathway may be involved in the rupture of IA. We conclude that activation of PI3K-AKT signaling pathway by OSM along with up-regulation of SPARC is important for the formation of IA. Further, regulation of Hippo pathway through PI3K-AKT signaling results in the down-regulation of YAP1 gene. This along with up-regulation of CTSL leads to further weakening of aneurysm wall and its subsequent rupture.

Legumain in cardiovascular diseases

Cardiovascular diseases (CVDs) are the leading cause of death worldwide, having become a global public health problem, so the pathophysiological mechanisms and therapeutic strategies of CVDs need further study. Legumain is a powerful enzyme that is widely distributed in mammals and plays an important role in a variety of biological processes. Recent research suggests that legumain is associated with the occurrence and progression of CVDs. In this review, we provide a comprehensive overview of legumain in the pathogenesis of CVDs. The role of legumain in CVDs, such as carotid atherosclerosis, pulmonary hypertension, coronary artery disease, peripheral arterial disease, aortic aneurysms and dissection, is discussed. The potential applications of legumain as a biomarker of these diseases are also explored. By understanding the role of legumain in the pathogenesis of CVDs, we aim to support new therapeutic strategies to prevent or treat these diseases.

Anticoagulant and antiplatelet treatment effects on the incidence of major cardiovascular events in patients with coronary artery ectasia: An updated systematic review

INTRODUCTION

Coronary artery ectasia (CAE), widenings in sections of the arteries, is a rare condition found in up to 3-5% of angiography cases. Sometimes recurrence of major adverse cardiac events (MACE) has been reported in the CAE subjects. The present systematic review aims to collect and summarize reports on whether the use of anticoagulants in addition to single antiplatelet/dual antiplatelet therapy (SAPT/DAPT) in CAE patients with significant occlusion/heavy thrombus is efficient and safe in decreasing the incidence/recurrence of MACE.

MATERIAL AND METHODS

A systematically comprehensive search was performed covering PubMed, Scopus, ISI Web of Science, and Google Scholar databases.

RESULTS

Twenty-five studies were found including 20 case reports, four case series, and one randomized clinical trial. Of 20 case reports 15 were male (75 %), and five were female (25 %). Of the four the case series, all showed positive outcomes after DAPT plus anticoagulant in more than 50 % of patients; two took only DAPT and 13 took anticoagulant ± DAPT, and five compared both. Cases received DAPT only experienced recurrences of MACE. The other cases were uneventful with less MACE and better outcomes after the use of anticoagulant ± DAPT. Results of these case-series included 457 CAE patients showed that more than 80 % of subjects were male, and in all studies tailored pharmacological interventions, including antiplatelet and anticoagulant (warfarin) therapies, resulted in less MACE and mortality.

CONCLUSION

It can be concluded that antiplatelet (SAPT/DAPT) must be applied in combination with anticoagulants to provide more efficient protection against MACE in CAE patients. However, further high-quality randomized clinical trials are needed to confirm the results.

Cathepsin L induces cellular senescence by upregulating CUX1 and p16INK4a

Cathepsin L (CTSL) has been implicated in aging and age-related diseases, such as cardiovascular diseases, specifically atherosclerosis. However, the underlying mechanism(s) is not well documented. Recently, we demonstrated a role of CUT-like homeobox 1 (CUX1) in regulating the p16INK4a-dependent cellular senescence in human endothelial cells (ECs) and vascular smooth muscle cells (VSMCs) via its binding to an atherosclerosis-associated functional SNP (fSNP) rs1537371 on the CDKN2A/B locus. In this study, to determine if CTSL, which was reported to proteolytically activate CUX1, regulates cellular senescence via CUX1, we measured the expression of CTSL, together with CUX1 and p16INK4a, in human ECs and VSMCs undergoing senescence. We discovered that CUX1 is not a substrate that is cleaved by CTSL. Instead, CTSL is an upstream regulator that activates CUX1 transcription indirectly in a process that requires the proteolytic activity of CTSL. Our findings suggest that there is a transcription factor in between CTSL and CUX1, and cleavage of this factor by CTSL can activate CUX1 transcription, inducing endothelial senescence. Thus, our findings provide new insights into the signal transduction pathway that leads to atherosclerosis-associated cellular senescence.

The Aging Lacrimal Gland of Female C57BL/6J Mice Exhibits Multinucleate Macrophage Infiltration Associated With Lipid Dysregulation

Purpose

Loss of function of the lacrimal gland (LG), which produces the aqueous tear film, is implicated in age-related dry eye. To better understand this deterioration, we evaluated changes in lipid metabolism and inflammation in LGs from an aging model.

Methods

LG sections from female C57BL/6J mice of different ages (young, 2-3 months; intermediate, 10-14 months; old,  ≥24 months) were stained with Oil Red-O or Toluidine blue to detect lipids. Quantitative real-time polymerase chain reaction (qRT-PCR) analysis and western blotting of LG lysates determined differences in the expression of genes and proteins related to lipid metabolism. A photobleaching protocol to quench age-related autofluorescence was used in LG sections to evaluate changes in immunofluorescence associated with NPC1, NPC2, CTSL, and macrophages (F4/80, CD11b) with age using confocal fluorescence microscopy.

Results

Old LGs showed increased lipids prominent in basal aggregates in acinar cells and in extra-acinar sites. LG gene expression of Npc1, Npc2, Lipa, and Mcoln2, encoding proteins involved in lipid metabolism, was increased with age. NPC1 was also significantly increased in old LGs by western blotting. In photobleached LG sections, confocal fluorescence microscopy imaging of NPC1, NPC2, and CTSL immunofluorescence showed age-associated enrichment in macrophages labeled to detect F4/80. Although mononuclear macrophages were detectable in LG at all ages, this novel multinucleate macrophage population containing NPC1, NPC2, and CTSL and enriched in F4/80 and some CD11b was increased with age at extra-acinar sites.

Conclusions

Lipid-metabolizing proteins enriched in F4/80-positive multinucleated macrophages are increased in old LGs adjacent to sites of lipid deposition in acini.

Genetic insights into the role of cathepsins in cardiovascular diseases: a Mendelian randomization study

AIMS

This study aimed to explore the causal relationships between cathepsins and cardiovascular diseases (CVDs) by Mendelian randomization (MR) analysis.

METHODS AND RESULTS

Single nucleotide polymorphisms (SNPs) associated with nine cathepsin types (cathepsins B, E, F, G, H, O, S, L2, and Z) were obtained from the INTERVAL study (3301 individuals). CVDs data were acquired from the UK Biobank (coronary atherosclerosis: 14 334 cases, 346 860 controls) and a genome-wide association study (GWAS) (myocardial infarction: 20 917 cases, 440 906 controls; myocarditis: 633 cases, 427 278 controls; chronic heart failure: 14 262 cases, 471 898 controls; angina pectoris: 30 025 cases, 440 906 controls; stable angina pectoris: 17 894 cases, 325 132 controls; unstable angina pectoris: 9481 cases, 446 987 controls; pericarditis: 1795 cases, 453 370 controls). Inverse variance weighted (IVW), MR-Egger, weighted median methods were adopted to conduct univariable MR (UVMR), reverse MR, multivariable MR (MVMR) analyses to estimate causality. The UVMR analyses demonstrated significant causal relationships between higher cathepsin E levels and increased risk of coronary atherosclerosis [IVW: P = 0.0051, odds ratio (OR) = 1.0033, 95% confidence interval (CI) = 1.0010-1.0056] and myocardial infarction (IVW: P = 0.0097, OR = 1.0553, 95% CI = 1.0131-1.0993), while elevated cathepsin L2 levels were causally related to reduced risk of myocarditis (IVW: P = 0.0120, OR = 0.6895, 95% CI = 0.5158-0.9216) and chronic heart failure (IVW: P = 0.0134, OR = 0.9316, 95% CI = 0.8807-0.9854). Reverse MR analyses revealed that myocardial infarction increased cathepsin O levels (IVW: P = 0.0400, OR = 1.0708, 95% CI = 1.0031-1.1431). MVMR analyses treating nine cathepsins together revealed that the positive causality between cathepsin E levels and coronary atherosclerosis risk (IVW: P = 0.0390, OR = 1.0030, 95% CI = 1.0000-1.0060), and the protective effect of cathepsin L2 levels on myocarditis (IVW: P = 0.0030, OR = 0.6610, 95% CI = 0.5031-0.8676) and chronic heart failure (IVW: P = 0.0090, OR = 0.9259, 95% CI = 0.8737-0.9812) remained, as higher cathepsin O levels were found to be causally related to increased risks of myocarditis (IVW: P = 0.0030, OR = 1.6145, 95% CI = 1.1829-2.2034) and chronic heart failure (IVW: P = 0.0300, OR = 1.0779, 95% CI = 1.0070-1.1537).

CONCLUSIONS

The study highlights the causalities of cathepsin E, L2, and O on CVDs, offering insights into their roles in cardiovascular biomarkers and therapeutic targets development. Further research is required to apply these genetic findings clinically.

Unravelling the role of cathepsins in cardiovascular diseases

Lysosomal cathepsins as a regulatory medium have been assessed as potential therapeutic targets for the treatment of various cardiac diseases such as abdominal aortic aneurysm, hypertension, cardiomyopathy, coronary heart disease, atherosclerosis, etc. They are ubiquitous lysosomal proteases with papain-like folded protein structures that are involved in a variety of physiological processes, such as the digestion of proteins, activation of pro-inflammatory molecules, degradation of extracellular matrix components, and maturation of peptide hormones. Cathepsins are classified into three major groups: cysteine cathepsins, aspartic cathepsins, and serine-threonine cathepsins. Each of these groups is further divided into subgroups based on their substrate specificity, structural characteristics, and biochemical properties. Several studies suggest that cathepsins control the degradation of ECM components such as collagen and elastin fibres. These enzymes are highly expressed in macrophages and inflammatory cells, and their upregulation has been demonstrated to be critical in the progression of atherosclerotic lesions. Additionally, increased cathepsin activity has been linked to increased vascular inflammation and oxidative stress, both of which are associated with CVDs. Specifically, the inhibition of cathepsins may reduce the release of pro-apoptotic mediators such as caspase-3 and PARP-1, which are thought to contribute to plaque instability. The potential of cathepsins as biomarkers and therapeutic targets has also been supported by the identification of potential cathepsin inhibitors, which could be used to modulate the activities of cathepsins in a range of diseases. This review shall familiarise the readers with the role of cysteinyl cathepsins and their inhibitors in the pathogenesis of cardiovascular diseases.

Novel pharmacological approaches in abdominal aortic aneurysm

Abdominal aortic aneurysm (AAA) is a severe vascular disease and a major public health issue with an unmet medical need for therapy. This disease is featured by a progressive dilation of the abdominal aorta, boosted by atherosclerosis, ageing, and smoking as major risk factors. Aneurysm growth increases the risk of aortic rupture, a life-threatening emergency with high mortality rates. Despite the increasing progress in our knowledge about the etiopathology of AAA, an effective pharmacological treatment against this disorder remains elusive and surgical repair is still the unique available therapeutic approach for high-risk patients. Meanwhile, there is no medical alternative for patients with small aneurysms but close surveillance. Clinical trials assessing the efficacy of antihypertensive agents, statins, doxycycline, or anti-platelet drugs, among others, failed to demonstrate a clear benefit limiting AAA growth, while data from ongoing clinical trials addressing the benefit of metformin on aneurysm progression are eagerly awaited. Recent preclinical studies have postulated new therapeutic targets and pharmacological strategies paving the way for the implementation of future clinical studies exploring these novel therapeutic strategies. This review summarises some of the most relevant clinical and preclinical studies in search of new therapeutic approaches for AAA.

Cathepsin L was involved in vascular aging by mediating phenotypic transformation of vascular cells

Vascular media and adventitia-induced remodeling plays an important role in vascular aging. However, the mechanism remains unclear. This study aims to investigate the mechanisms underlying vascular aging. Transcriptome analysis revealed that the expression of cathepsin L (CTSL) significantly decreased in arteries of old mice (24 months old) compared with that in arteries of young mice (4 months old), which was confirmed by immunohistochemistry and Western blot. The expression of CTSL in adventitia fibroblasts (AFs) and vascular smooth muscle cells (VSMCs) of aged mice was lower than that of young mice. Compared with wild-type control mice, CTSL knockout (CTSL ^{- /-}) mice had increased collagen deposition (fibrosis) and decreased telomerase activity and LC3Ⅱ/ LC3Ⅰratio. The expression of mammalian target of rapamycin (mTOR) and osteopontin (OPN) increased in aortas of CTSL^-/-mice compared with that in aortas of wild-type control mice. In vitro, lentivirus-mediated CTSL knockdown induced VSMCs senescence and AFs transformed into myofibroblasts (MFs). Rapamycin, a mTOR inhibitor, inhibited CTSL deficiency induced VSMCs senescence, osteopontin (OPN) secretion and AFs migration. In conclusion, the decreased level of CTSL with age may participate in vascular aging by promoting the phenotypic transformation of vascular cells.

Inhibition of myocardial cathepsin-L release during reperfusion following myocardial infarction improves cardiac function and reduces infarct size

AIMS

Identifying novel mediators of lethal myocardial reperfusion injury that can be targeted during primary percutaneous coronary intervention (PPCI) is key to limiting the progression of patients with ST-elevation myocardial infarction (STEMI) to heart failure. Here, we show through parallel clinical and integrative preclinical studies the significance of the protease cathepsin-L on cardiac function during reperfusion injury.

METHODS AND RESULTS

We found that direct cardiac release of cathepsin-L in STEMI patients (n = 76) immediately post-PPCI leads to elevated serum cathepsin-L levels and that serum levels of cathepsin-L in the first 24 h post-reperfusion are associated with reduced cardiac contractile function and increased infarct size. Preclinical studies demonstrate that inhibition of cathepsin-L release following reperfusion injury with CAA0225 reduces infarct size and improves cardiac contractile function by limiting abnormal cardiomyocyte calcium handling and apoptosis.

CONCLUSION

Our findings suggest that cathepsin-L is a novel therapeutic target that could be exploited clinically to counteract the deleterious effects of acute reperfusion injury after an acute STEMI.

The role of vascular smooth muscle cells in the development of aortic aneurysms and dissections

BACKGROUND

Aortic aneurysms (AA) are pathological dilations of the aorta, associated with an overall mortality rate up to 90% in case of rupture. In addition to dilation, the aortic layers can separate by a tear within the layers, defined as aortic dissections (AD). Vascular smooth muscle cells (vSMC) are the predominant cell type within the aortic wall and dysregulation of vSMC functions contributes to AA and AD development and progression. However, since the exact underlying mechanism is poorly understood, finding potential therapeutic targets for AA and AD is challenging and surgery remains the only treatment option.

METHODS

In this review, we summarize current knowledge about vSMC functions within the aortic wall and give an overview of how vSMC functions are altered in AA and AD pathogenesis, organized per anatomical location (abdominal or thoracic aorta).

RESULTS

Important functions of vSMC in healthy or diseased conditions are apoptosis, phenotypic switch, extracellular matrix regeneration and degradation, proliferation and contractility. Stressors within the aortic wall, including inflammatory cell infiltration and (epi)genetic changes, modulate vSMC functions and cause disturbance of processes within vSMC, such as changes in TGF-β signalling and regulatory RNA expression.

CONCLUSION

This review underscores a central role of vSMC dysfunction in abdominal and thoracic AA and AD development and progression. Further research focused on vSMC dysfunction in the aortic wall is necessary to find potential targets for noninvasive AA and AD treatment options.

Fungal Proteases as Emerging Biocatalysts to Meet the Current Challenges and Recent Developments in Biomedical Therapies: An Updated Review

With the increasing world population, demand for industrialization has also increased to fulfill humans' living standards. Fungi are considered a source of essential constituents to produce the biocatalytic enzymes, including amylases, proteases, lipases, and cellulases that contain broad-spectrum industrial and emerging applications. The present review discussed the origin, nature, mechanism of action, emerging aspects of genetic engineering for designing novel proteases, genome editing of fungal strains through CRISPR technology, present challenges and future recommendations of fungal proteases. The emerging evidence revealed that fungal proteases show a protective role to many environmental exposures and discovered that an imbalance of protease inhibitors and proteases in the epithelial barriers leads to the protection of chronic eosinophilic airway inflammation. Moreover, mitoproteases recently were found to execute intense proteolytic processes that are crucial for mitochondrial integrity and homeostasis function, including mitochondrial biogenesis, protein synthesis, and apoptosis. The emerging evidence revealed that CRISPR/Cas9 technology had been successfully developed in various filamentous fungi and higher fungi for editing of specific genes. In addition to medical importance, fungal proteases are extensively used in different industries such as foods to prepare butter, fruits, juices, and cheese, and to increase their shelf life. It is concluded that hydrolysis of proteins in industries is one of the most significant applications of fungal enzymes that led to massive usage of proteomics.

LIF, a mitogen for choroidal endothelial cells, protects the choriocapillaris: implications for prevention of geographic atrophy

In the course of our studies aiming to discover vascular bed-specific endothelial cell (EC) mitogens, we identified leukemia inhibitory factor (LIF) as a mitogen for bovine choroidal EC (BCE), although LIF has been mainly characterized as an EC growth inhibitor and an anti-angiogenic molecule. LIF stimulated growth of BCE while it inhibited, as previously reported, bovine aortic EC (BAE) growth. The JAK-STAT3 pathway mediated LIF actions in both BCE and BAE cells, but a caspase-independent proapoptotic signal mediated by cathepsins was triggered in BAE but not in BCE. LIF administration directly promoted activation of STAT3 and increased blood vessel density in mouse eyes. LIF also had protective effects on the choriocapillaris in a model of oxidative retinal injury. Analysis of available single-cell transcriptomic datasets shows strong expression of the specific LIF receptor in mouse and human choroidal EC. Our data suggest that LIF administration may be an innovative approach to prevent atrophy associated with AMD, through protection of the choriocapillaris.

Beyond Vessel Diameters: Non-invasive Monitoring of Flow Patterns and Immune Cell Recruitment in Murine Abdominal Aortic Disorders by Multiparametric MRI

The pathophysiology of the initiation and progression of abdominal aortic aneurysms (AAAs) and aortic dissections (AADs) is still unclear. However, there is strong evidence that monocytes and macrophages are of crucial importance in these processes. Here, we utilized a molecular imaging approach based on background-free ¹⁹F MRI and employed perfluorocarbon nanoemulsions (PFCs) for in situ ¹⁹F labeling of monocytes/macrophages to monitor vascular inflammation and AAA/AAD formation in angiotensin II (angII)-treated apolipoproteinE-deficient (apoE^-/-) mice. In parallel, we used conventional ¹H MRI for the characterization of aortic flow patterns and morphology. AngII (1 μg/kg/min) was infused into apoE^-/- mice via osmotic minipumps for 10 days and mice were monitored by multiparametric ¹H/¹⁹F MRI. PFCs were intravenously injected directly after pump implantation followed by additional applications on day 2 and 4 to allow an efficient ¹⁹F loading of circulating monocytes. The combination of angiographic, hemodynamic, and anatomical measurements allowed an unequivocal classification of mice in groups with developing AAAs, AADs or without any obvious aortic vessel alterations despite the exposure to angII. Maximal luminal and external diameters of the aorta were enlarged in AAAs, whereas AADs showed either a slight decrease of the luminal diameter or no alteration. ¹H/¹⁹F MRI after intravenous PFC application demonstrated significantly higher ¹⁹F signals in aortae of mice that developed AAAs or AADs as compared to mice in which no aortic disorders were detected. High resolution ¹H/¹⁹F MRI of excised aortae revealed a patchy pattern of the ¹⁹F signals predominantly in the adventitia of the aorta. Histological analysis confirmed the presence of macrophages in this area and flow cytometry revealed higher numbers of immune cells in aortae of mice that have developed AAA/AAD. Importantly, there was a linear correlation of the ¹⁹F signal with the total number of infiltrated macrophages. In conclusion, our approach enables a precise differentiation between AAA and AAD as well as visualization and quantitative assessment of inflammatory active vascular lesions, and therefore may help to unravel the complex interplay between macrophage accumulation, vascular inflammation, and the development and progression of AAAs and AADs.

Cathepsin C Is Involved in Macrophage M1 Polarization via p38/MAPK Pathway in Sudden Cardiac Death

This study was aimed at identifying molecular markers associated with the pathogenesis of sudden cardiac death (SCD). It provides a proteomic analysis of human left anterior descending coronary artery from subjects diagnosed with SCD through histological examination and cases of nondisease accidental deaths through autopsy. A total of 2784 proteins were obtained from label-free quantitative proteomic analysis. This included a total of 265 differential proteins which were involved in SCD-related processes, such as inflammation, muscle system process regulation, metal ion transport, and lysosomal pathway. Western blotting was carried out to measure the expressions of cathepsin C (CTSC), focal adhesion kinase (FAK), p-FAK, and proteins related to the p38/MAPK signaling pathway, whereas immunohistochemistry was performed to determine the localization and expression of CTSC, TNF-α, and CD206 in arterial tissues. It was found that CTSC were the most expressed proteins with a significant upward trend in SCD cases. Besides, CTSC regulated macrophage polarization to M1 through the FAK-induced p38/MAPK signaling pathway. This promoted the release of inflammatory factors and eventually increased the inflammatory response. In conclusion, this study implies that CTSC may be one of the key molecular targets for promoting macrophage M1 polarization in SCD, which may provide new therapeutic insights into the treatment of inflammatory diseases.

Molecular probes for selective detection of cysteine cathepsins

Cysteine cathepsins are proteases critical in physiopathological processes and show potential as targets or biomarkers for diseases and medical conditions. The 11 members of the cathepsin family are redundant in some cases but remarkably independent of others, demanding the development of both pan-cathepsin targeting tools as well as probes that are selective for specific cathepsins with little off-target activity. This review addresses the diverse design strategies that have been employed to accomplish this tailored selectivity among cysteine cathepsin targets and the imaging modalities incorporated. The power of these diverse tools is contextualized by briefly highlighting the nature of a few prominent cysteine cathepsins, their involvement in select diseases, and the application of cathepsin imaging probes in research spanning basic biochemical studies to clinical applications.

Cystatin C predicts the risk of incident cerebrovascular disease in the elderly: A meta-analysis on survival date studies

BACKGROUND

Stroke is the third leading cause of global year of life lost in all-age and second-ranked cause of disability adjusted life years in middle-aged and elder population. Therefore, it is critical to study the relationship between vascular-related risk factors and cerebrovascular diseases. Several cross-sectional studies have shown that Cystatin C (Cys C) is an independent risk factor for cerebrovascular diseases and levels of Cys C are significantly higher in stroke patients than in healthy individuals. In this meta-analysis, we introduce a Cox proportional hazards model to evaluate the causality between Cys C and the risk of cerebrovascular accident in the elderly.

METHODS

We searched PubMed, EMBASE, the Web of Science, and the Cochrane Library from 1985 to 2019 for studies on the relationship between serum Cys C and incidence stroke with Cox proportional hazards models. We conducted a subgroup analysis of the selected studies to determine a connection between atherosclerosis and stroke. Finally, 7 research studies, including 26,768 patients without a history of cerebrovascular, were studied.

RESULTS

After comparing the maximum and minimum Cys C levels, the hazard ratio for all types of stroke, including ischemic and hemorrhagic stroke, was 1.18 (95% confidence interval 1.04-1.31) with moderate heterogeneity (I2 = 43.0%; P = .119) in a fixed-effect model after pooled adjustment for other potential risk factors. In the subgroup analysis, the hazard ratio and 95% confidence interval for Cys C stratified by atherosclerosis was 1.85 (0.97-2.72). As shown in Egger linear regression test, there was no distinct publication bias (P = .153).

CONCLUSION

Increased serum Cys C is significantly associated with future stroke events in the elderly, especially in patients with carotid atherosclerosis. Thus, serum levels of Cys C could serve as a predicted biomarker for stroke attack.

Dual-Mechanism Quenched Fluorogenic Probe Provides Selective and Rapid Detection of Cathepsin L Activity*

Cathepsin L (CTL) is a cysteine protease demonstrating upregulated activity in many disease states. Overlapping substrate specificity makes selective detection of CTL activity difficult to parse from that of its close homologue CTV and the ubiquitous CTB. Current probes of CTL activity have limited applications due to either poor contrast or extra assay steps required to achieve selectivity. We have developed a fluorogenic probe, CTLAP, that displays good selectivity for CTL over CTB and CTV while exhibiting low background fluorescence attributed to dual quenching mechanisms. CTLAP achieves optimum CTL selectivity in the first 10 min of incubation, thus suggesting that it is amenable for rapid detection of CTL, even in the presence of competing cathepsins.

Lysosome (Dys)function in Atherosclerosis-A Big Weight on the Shoulders of a Small Organelle

Atherosclerosis is a progressive insidious chronic disease that underlies most of the cardiovascular pathologies, including myocardial infarction and ischemic stroke. The malfunctioning of the lysosomal compartment has a central role in the etiology and pathogenesis of atherosclerosis. Lysosomes are the degradative organelles of mammalian cells and process endogenous and exogenous substrates in a very efficient manner. Dysfunction of these organelles and consequent inefficient degradation of modified low-density lipoproteins (LDL) and apoptotic cells in atherosclerotic lesions have, therefore, numerous deleterious consequences for cellular homeostasis and disease progression. Lysosome dysfunction has been mostly studied in the context of the inherited lysosomal storage disorders (LSDs). However, over the last years it has become increasingly evident that the consequences of this phenomenon are more far-reaching, also influencing the progression of multiple acquired human pathologies, such as neurodegenerative diseases, cancer, and cardiovascular diseases (CVDs). During the formation of atherosclerotic plaques, the lysosomal compartment of the various cells constituting the arterial wall is under severe stress, due to the tremendous amounts of lipoproteins being processed by these cells. The uncontrolled uptake of modified lipoproteins by arterial phagocytic cells, namely macrophages and vascular smooth muscle cells (VSMCs), is the initial step that triggers the pathogenic cascade culminating in the formation of atheroma. These cells become pathogenic "foam cells," which are characterized by dysfunctional lipid-laden lysosomes. Here, we summarize the current knowledge regarding the origin and impact of the malfunctioning of the lysosomal compartment in plaque cells. We further analyze how the field of LSD research may contribute with some insights to the study of CVDs, particularly how therapeutic approaches that target the lysosomes in LSDs could be applied to hamper atherosclerosis progression and associated mortality.

Cathepsin L plays a key role in SARS-CoV-2 infection in humans and humanized mice and is a promising target for new drug development

To discover new drugs to combat COVID-19, an understanding of the molecular basis of SARS-CoV-2 infection is urgently needed. Here, for the first time, we report the crucial role of cathepsin L (CTSL) in patients with COVID-19. The circulating level of CTSL was elevated after SARS-CoV-2 infection and was positively correlated with disease course and severity. Correspondingly, SARS-CoV-2 pseudovirus infection increased CTSL expression in human cells in vitro and human ACE2 transgenic mice in vivo, while CTSL overexpression, in turn, enhanced pseudovirus infection in human cells. CTSL functionally cleaved the SARS-CoV-2 spike protein and enhanced virus entry, as evidenced by CTSL overexpression and knockdown in vitro and application of CTSL inhibitor drugs in vivo. Furthermore, amantadine, a licensed anti-influenza drug, significantly inhibited CTSL activity after SARS-CoV-2 pseudovirus infection and prevented infection both in vitro and in vivo. Therefore, CTSL is a promising target for new anti-COVID-19 drug development.

Yellow Tea Stimulates Thermogenesis in Mice through Heterogeneous Browning of Adipose Tissues

SCOPE

Large-leaf yellow tea (YT) exhibits interesting beneficial metabolic effects in previous studies. Here, the authors elucidated the actions of YT on thermogenesis, energy metabolism, and adipocyte metabolic conversion.

METHODS AND RESULTS

Five-week-old male C57BL/6 mice are fed low-fat diet, high-fat diet (HFD), and HFD supplemented with 0.5% or 2.5% YT. After treatment for 10 or 14 weeks, YT enhances energy expenditure, O2 consumption and CO2 production. YT strongly boosts thermogenic program in brown adipose tissue (BAT) and subcutaneous adipose tissue (SAT), while only weakly in epididymal adipose tissue (EAT). These are accompanied by higher body temperature, increased mitochondrial copy numbers, and upregulation of thermogenic genes (Ucp1, Pgc1α, etc.) and proteins. The classic brown adipocyte markers (Eva1, Zic1) are induced only in BAT, while beige adipocyte markers (Tbx1, Tmem26) are boosted only in SAT. Furthermore, subcutaneous-originated preadipocytes are induced by YT in vitro to differentiate to brown-like adipocytes - a browning effect.

CONCLUSION

Dietary YT induces adaptive thermogenesis through increasing mitochondrial biogenesis in EAT, inducing beigeing in SAT and enhancing browning in the BAT.

Increased Circulating Cathepsin L in Patients with Coronary Artery Disease

Cathepsin L (CatL) is a potent collagenase involved in atherosclerotic vascular remodeling and dysfunction in animals and humans. This study investigated the hypothesis that plasma CatL is associated with the prevalence of coronary artery disease (CAD). Between February May 2011 and January 2013, 206 consecutive subjects were enrolled from among patients who underwent coronary angiography and percutaneous coronary intervention treatment. Age-matched subjects (n = 215) served as controls. Plasma CatL and high-sensitive C-reactive protein (hs-CRP) and high-density lipoprotein cholesterol were measured. The patients with CAD had significantly higher plasma CatL levels compared to the controls (1.4 ± 0.4 versus 0.4 ± 0.2 ng/mL, P < 0.001), and the patients with acute coronary syndrome had significantly higher plasma CatL levels compared to those with stable angina pectoris (1.7 ± 0.7 versus 0.8 ± 0.4 ng/mL, P < 0.01). Linear regression analysis showed that overall, the plasma CatL levels were inversely correlated with the high-density lipoprotein levels (r = -0.32, P < 0.01) and positively with hs-CRP levels (r = 0.35, P < 0.01). Multiple logistic regression analyses shows that cathepsin L levels were independent predictors of CAD (add ratio, 1.8; 95% CI, 1.2 to 2.1; P < 0.01). These data demonstrated that increased levels of plasma CatL are closely associated with the presence of CAD and that circulating CatL serves as a useful biomarker for CAD.

Nicotine Modulates CTSS (Cathepsin S) Synthesis and Secretion Through Regulating the Autophagy-Lysosomal Machinery in Atherosclerosis

OBJECTIVE

Increased CTSS (cathepsin S) has been reported to play a critical role in atherosclerosis progression. Both CTSS synthesis and secretion are essential for exerting its functions. However, the underlying mechanisms contributing to CTSS synthesis and secretion in atherosclerosis remain unclear. Approach and Results: In this study, we showed that nicotine activated autophagy and upregulated CTSS expression in vascular smooth muscle cells and in atherosclerotic plaques. Western blotting and immunofluorescent staining showed that nicotine inhibited the mTORC1 (mammalian target of rapamycin complex 1) activity, promoted the nuclear translocation of TFEB (transcription factor EB), and upregulated the expression of CTSS. Chromatin immunoprecipitation-qualificative polymerase chain reaction, electrophoretic mobility shift assay, and luciferase reporter assay further demonstrated that TFEB directly bound to the CTSS promoter. mTORC1 inhibition by nicotine or rapamycin promoted lysosomal exocytosis and CTSS secretion. Live cell assays and IP-MS (immunoprecipitation-mass spectrometry) identified that the interactions involving Rab10 (Rab10, member RAS oncogene family) and mTORC1 control CTSS secretion. Nicotine promoted vascular smooth muscle cell migration by upregulating CTSS, and CTSS inhibition suppressed nicotine-induced atherosclerosis in vivo.

CONCLUSIONS

We concluded that nicotine mediates CTSS synthesis and secretion through regulating the autophagy-lysosomal machinery, which offers a potential therapeutic target for atherosclerosis treatment.

Cathepsins in the Pathophysiology of Mucopolysaccharidoses: New Perspectives for Therapy

Cathepsins (CTSs) are ubiquitously expressed proteases normally found in the endolysosomal compartment where they mediate protein degradation and turnover. However, CTSs are also found in the cytoplasm, nucleus, and extracellular matrix where they actively participate in cell signaling, protein processing, and trafficking through the plasma and nuclear membranes and between intracellular organelles. Dysregulation in CTS expression and/or activity disrupts cellular homeostasis, thus contributing to many human diseases, including inflammatory and cardiovascular diseases, neurodegenerative disorders, diabetes, obesity, cancer, kidney dysfunction, and others. This review aimed to highlight the involvement of CTSs in inherited lysosomal storage disorders, with a primary focus to the emerging evidence on the role of CTSs in the pathophysiology of Mucopolysaccharidoses (MPSs). These latter diseases are characterized by severe neurological, skeletal and cardiovascular phenotypes, and no effective cure exists to date. The advance in the knowledge of the molecular mechanisms underlying the activity of CTSs in MPSs may open a new challenge for the development of novel therapeutic approaches for the cure of such intractable diseases.

Cysteinyl cathepsins in cardiovascular diseases

Cysteinyl cathepsins are lysosomal/endosomal proteases that mediate bulk protein degradation in these intracellular acidic compartments. Yet, studies indicate that these proteases also appear in the nucleus, nuclear membrane, cytosol, plasma membrane, and extracellular space. Patients with cardiovascular diseases (CVD) show increased levels of cathepsins in the heart, aorta, and plasma. Plasma cathepsins often serve as biomarkers or risk factors of CVD. In aortic diseases, such as atherosclerosis and abdominal aneurysms, cathepsins play pathogenic roles, but many of the same cathepsins are cardioprotective in hypertensive, hypertrophic, and infarcted hearts. During the development of CVD, cathepsins are regulated by inflammatory cytokines, growth factors, hypertensive stimuli, oxidative stress, and many others. Cathepsin activities in inflammatory molecule activation, immunity, cell migration, cholesterol metabolism, neovascularization, cell death, cell signaling, and tissue fibrosis all contribute to CVD and are reviewed in this article in memory of Dr. Nobuhiko Katunuma for his contribution to the field.

Is Anticoagulant Necessary in Patients with Coronary Artery Ectasia Presenting with Acute Coronary Syndrome? A Systematic Review of Case Reports

Coronary artery ectasia is found in 3 to 8% of patient's undergoing angiography and may sometimes induce acute myocardial infarction. Some articles reported a recurrence of acute coronary syndrome (ACS) in the presence of coronary artery ectasia (CAE). Our study aims to summarize the latest evidence on whether the use of anticoagulant in addition to SAPT/DAPT (single antiplatelet/dual antiplatelet) treating ACS with CAE patients is necessary. Since the trials concerning our objectives were scarce, we pooled case reports/series. We performed a comprehensive search on case reports/series on coronary artery ectasia that presented with acute coronary syndrome published until March 2019. We collected 13 cases from 11 reports. Out of 13 patients, 5 (38.5%) took DAPT only without anticoagulant and 8 (61.5%) took anticoagulant ± DAPT. Three out of five (60%) who took DAPT only, experienced recurrences at 1st and 2nd months' follow-up. The other two (40%) was uneventful at a mean of two months' follow-up. Eight patients who took anticoagulant were uneventful for a mean of 8.4 months. Those who took anticoagulant were at lower risk of experiencing ACS recurrence ( p  = 0.035). Two of the patients who experienced recurrence became 6 and 12 months free after optimal anticoagulation. The author of this study proposed that anticoagulant must be considered should SAPT/DAPT failed to provide adequate protection to the recurrence of ACS, especially in CAE patients who did not have other obvious stenotic lesions. However, the evidence is weak since this study only pooled case reports/series.

The role of cathepsin D in the pathophysiology of heart failure and its potentially beneficial properties: a translational approach

Aims

Cathepsin D is a ubiquitous lysosomal protease that is primarily secreted due to oxidative stress. The role of circulating cathepsin D in heart failure (HF) is unknown. The aim of this study is to determine the association between circulating cathepsin D levels and clinical outcomes in patients with HF and to investigate the biological settings that induce the release of cathepsin D in HF.

Methods and results

Cathepsin D levels were studied in 2174 patients with HF from the BIOSTAT‐CHF index study. Results were validated in 1700 HF patients from the BIOSTAT‐CHF validation cohort. The primary combined outcome was all‐cause mortality and/or HF hospitalizations. Human pluripotent stem cell‐derived cardiomyocytes were subjected to hypoxic, pro‐inflammatory signalling and stretch conditions. Additionally, cathepsin D expression was inhibited by targeted short hairpin RNAs (shRNA). Higher levels of cathepsin D were independently associated with diabetes mellitus, renal failure and higher levels of interleukin‐6 and N‐terminal pro‐B‐type natriuretic peptide (P < 0.001 for all). Cathepsin D levels were independently associated with the primary combined outcome [hazard ratio (HR) per standard deviation (SD): 1.12; 95% confidence interval (CI) 1.02–1.23], which was validated in an independent cohort (HR per SD: 1.23, 95% CI 1.09–1.40). In vitro experiments demonstrated that human stem cell‐derived cardiomyocytes released cathepsin D and troponin T in response to mechanical stretch. ShRNA‐mediated silencing of cathepsin D resulted in increased necrosis, abrogated autophagy, increased stress‐induced metabolism, and increased release of troponin T from human stem cell‐derived cardiomyocytes under stress.

Conclusions

Circulating cathepsin D levels are associated with HF severity and poorer outcome, and reduced levels of cathepsin D may have detrimental effects with therapeutic potential in HF.

High Plasma Levels of Legumain in Patients with Complex Coronary Lesions

Aim: The degradation of the vascular extracellular matrix is important for atherosclerosis. The cysteine protease legumain was shown to be upregulated in atherosclerotic plaques, especially unstable plaques. However, no study has reported blood legumain levels in patients with coronary artery disease (CAD).

Methods: We investigated plasma legumain and C-reactive protein (CRP) levels in 372 patients undergoing elective coronary angiography.

Results: CAD was found in 225 patients. Compared with patients without CAD, those with CAD had higher CRP levels (median 0.60 [0.32, 1.53] vs. 0.46 [0.22, 0.89] mg/L, P < 0.001), but no difference was found in legumain levels between patients with and without CAD (median 5.08 [3.87, 6.82] vs. 4.99 [3.84, 6.88] ng/mL). A stepwise increase in CRP was found depending on the number of > 50% stenotic vessels: 0.55 mg/L in 1-vessel, 0.71 mg/L in 2-vessel, and 0.86 mg/L in 3-vessel diseases (P < 0.001). However, legumain did not differ among 1-, 2-, and 3-vessel diseases (5.20, 4.93, and 5.01 ng/mL, respectively). Of 225 patients with CAD, 40 (18%) had complex lesions. No difference was found in CRP levels between patients with CAD with and without complex lesions (0.60 [0.34, 1.53] vs. 0.60 [0.32, 1.51] mg/L). Notably, legumain levels were higher in patients with CAD with complex lesions than without such lesions (6.05 [4.64, 8.64] vs. 4.93 [3.76, 6.52] ng/mL, P < 0.01). In multivariate analysis, legumain levels were not a factor for CAD, but were a factor for complex lesions. The odds ratio for complex lesions was 2.45 (95% CI = 1.26–4.79) for legumain > 5.5 ng/mL.

Conclusion: Plasma legumain levels were associated with the presence of complex coronary lesions.

Discovery of crucial cytokines associated with abdominal aortic aneurysm formation by protein array analysis

As a common disease, abdominal aortic aneurysm (AAA) features permanently progressively dilated abdominal aorta. Various cytokines are implicated in AAA pathogenesis. Clarification of involved cytokines combined with functional analysis may provide new insights into AAA pathogenesis. Using a mouse model, this study analyzed the cytokine profiles in AAA. Cytokines were measured in AAA tissues of saline control or angiotensin II-treated ApoE−/− mice using an antibody array of 200 cytokines, cytokine receptors, and related proteins. Statistical analysis revealed that 21 of 200 proteins were differentially expressed in AAA. These differentially expressed proteins were subjected to function and pathway enrichment analysis, which revealed that leukocyte migration and positive regulation of cell adhesion were the most significant biological processes. Specific signaling pathways, including Janus kinase/signal transducers and activators of transcription and cytokine–cytokine receptor interaction, were prominent in Kyoto encyclopedia of genes and genomes pathway enrichment analysis. Importantly, our data identified cytokines which had not previously been illustrated in AAA pathogenic pathways. Bivariate correlation analysis between these cytokines and protease activity showed that granulocyte colony-stimulating factor (G-CSF), macrophage inflammatory protein 1 g, cardiotrophin 1, milk fat globule-EGF factor 8 protein, interleukin 33, and periostin were positively correlated with matrix metalloprotease 1 (MMP-1), MMP-9, cathepsin B, and cathepsin L. G-CSF was positively correlated with cathepsin L. In conclusion, these results demonstrate that cytokine profile is significantly altered in AAA, and that the newly identified crucial cytokines may function potentially in AAA pathogenesis.

Impact statement

Various cytokines are known contributors to abdominal aortic aneurysm (AAA) pathologic processes, but the mechanisms underlying the pathogenesis remains unclear. We illustrated the altered cytokine profiles in AAA by high throughput antibody array of 200 cytokines, cytokine receptors and related proteins, as well as bioinformatics analysis of differentially expressed proteins in lesion tissues from AAA mice infused with angiotensin II. Functional analyses of differentially expressed cytokines showed clustering on cell migration and adhesion processes. More importantly, crucial cytokines whose association with AAA formation had not been established were identified. Significant correlations were found between these cytokines and protease activity. This study identifies several crucial markers for further researches on the molecular basis of AAA.

Identification of novel diagnostic and prognostic biomarkers for abdominal aortic aneurysm

Aims

Abdominal aortic aneurysm is a life-threatening condition due to the risk of aneurysm growth and rupture. There are no approved diagnostic or prognostic biomarkers for abdominal aortic aneurysm. We aimed to identify diagnostic and prognostic biomarkers for abdominal aortic aneurysm and to investigate their relationship with abdominal aortic aneurysm diameter and growth.

Methods

In this case-control study, patients were included from an abdominal aortic aneurysm screening study on men aged ≥65 years. Of 24,589 examined men, 415 had abdominal aortic aneurysm, out of whom 134 consented to participate in the present study. One hundred and thirty-six screened men with aortic diameter <30 mm, matched for comorbidities and time of sampling were included as non-abdominal aortic aneurysm patients. Ninety-one cardiovascular specific proteins in plasma samples were measured by the Proseek Multiplex CVD III96x96panel.

Results

After Bonferroni correction, plasma levels of 21 proteins associated with proteolysis, oxidative-stress, lipid metabolism, and inflammation were significantly increased, whereas levels of paraoxonase 3, associated with high-density lipoprotein metabolism, were decreased in abdominal aortic aneurysm patients. Combination of growth/differentiation factor 15 and cystatin B had the best ability to discriminate abdominal aortic aneurysm from non-abdominal aortic aneurysm (area under the curve, 0.76; sensitivity, 80% and specificity, 52%). Myeloperoxidase showed the best prognostic value (area under the curve, 0.71; sensitivity, 80% and specificity, 59%) and higher baseline levels of myeloperoxidase were significantly associated with faster abdominal aortic aneurysm growth compared with lower levels, independent of baseline diameter.

Conclusions

We have identified multiple proteins associated with abdominal aortic aneurysm diameter and growth with a potential to become novel diagnostic and prognostic biomarkers for abdominal aortic aneurysm.

Modulation of Cathepsin L Expression in the Coronary Arteries of Atherosclerotic Swine

INTRODUCTION

Neointimal hyperplasia (NIH) and restenosis after percutaneous transluminal coronary angioplasty (PTCA) and intravascular stenting remain a problem on a long-term basis by causing endothelial denudation and damage to the intima and media. Vascular sterile inflammation has been attributed to the formation of NIH. Cathepsin L (CTSL), a lysosome protease, is associated with diet-induced atherogenesis. Vitamin D regulates the actions and regulatory effects of proteases and protease inhibitors in different cell types. Objectives of this study are to evaluate the modulatory effect of vitamin D on CTSL activity in post-PTCA coronary arteries of atherosclerotic swine.

METHODS

Yucatan microswine were fed with high-cholesterol atherosclerotic diets. The swine were stratified to receive three diets: (1) vitamin D-deficient diet, (2) vitamin D-sufficient diet, and (3) vitamin D-supplement diet. After 6 mo, PTCA was performed in the left circumflex coronary artery (LCx). After 1 y, angiography and optical coherence tomography imaging were performed, and swine was euthanized. Coronary arteries were embedded in paraffin. Tissue sections were stained with hematoxylin and eosin. Expression of Ki67 and CTSL were evaluated by immunofluorescence.

RESULTS

Increased number of Ki67 + cells were observed in the postangioplasty LCx in vitamin D-deficient compared with vitamin D-sufficient or vitamin D-supplemented swine. Notably, the expression of CTSL was significantly increased in postangioplasty LCx of vitamin D-deficient swine compared with the vitamin D-sufficient or vitamin D-supplemented animal groups.

CONCLUSIONS

Increased expression of CTSL correlates with the formation of NIH in the PTCA-injured coronary arteries. However, in the presence of sufficient or supplemented levels of vitamin D in the blood, CTSL expression was significantly reduced.

Expression levels of cathepsin L and cystatin C in a hyperglycemic environment were associated with aortic aneurysm development in a mouse model

Objectives

Diabetes mellitus (DM) attenuates the development of aortic aneurysms (AA). This study investigated the expression of cathepsin L and cystatin C in a hyperglycemic environment, and the influence of these proteins on AA development.

Methods

Mice were divided into AA and DM+AA groups (n=30 per group). DM was induced by injection of streptozotocin; AA was induced by injection of angiotensin II. Doppler examination was used to measure aortic diameter, and Weigert’s elastic stain was used to detect elastin degradation. Cathepsin L and cystatin C in aortic tissue were examined by western blotting, immunohistochemistry, and polymerase chain reaction.

Results

Aortic diameter in the DM+AA group was less than that in the AA group, and elastin fragmentation grade of the aortic wall was reduced in the DM+AA group. More cathepsin L-positive cells were observed in the AA group than in the DM+AA group; conversely, more cystatin C-positive cells were observed in the DM+AA group than in the AA group. Both protein and mRNA levels of cathepsin L and cystatin C showed similar trends to those observed in immunohistochemistry.

Conclusions

Expression levels of cathepsin L and cystatin C in a hyperglycemic environment were associated with AA development in a mouse model.

Human cathepsins K, L, and S: Related proteases, but unique fibrinolytic activity

BACKGROUND

Fibrin formation and dissolution are attributed to cascades of protease activation concluding with thrombin activation, and plasmin proteolysis for fibrin breakdown. Cysteine cathepsins are powerful proteases secreted by endothelial cells and others during cardiovascular disease and diabetes. Their fibrinolytic activity and putative role in hemostasis has not been well described.

METHODS

Fibrin gels were polymerized and incubated with recombinant human cathepsins (cat) K, L, or S, or plasmin, for dose-dependent and time-dependent studies. Dissolution of fibrin gels was imaged. SDS-PAGE was used to resolve cleaved fragments released from fibrin gels and remnant insoluble fibrin gel that was solubilized prior to electrophoresis to assess fibrin α, β, and γ polypeptide hydrolysis by cathepsins. Multiplex cathepsin zymography determined active amounts of cathepsins remaining.

RESULTS

There was significant loss of α and β fibrin polypeptides after incubation with cathepsins, with catS completely dissolving fibrin gel by 24 h. Binding to fibrin stabilized catL active time; it associated with cleaved fibrin fragments of multiple sizes. This was not observed for catK or S. CatS also remained active for longer times during fibrin incubation, but its association/binding did not withstand SDS-PAGE preparation.

CONCLUSIONS

Human cathepsins K, L, and S are fibrinolytic, and specifically can degrade the α and β fibrin polypeptide chains, generating fragments unique from plasmin.

GENERAL SIGNIFICANCE

Demonstration of cathepsins K, L, and S fibrinolytic activity leads to further investigation of contributory roles in disrupting vascular hemostasis, or breakdown of fibrin-based engineered vascular constructs where non-plasmin mediated fibrinolysis must be considered.

Circulating Vascular Basement Membrane Fragments are Associated with the Diameter of the Abdominal Aorta and Their Expression Pattern is Altered in AAA Tissue

OBJECTIVE

Abdominal aortic aneurysm (AAA) is characterised by enhanced proteolytic activity, and extracellular matrix (ECM) remodelling in the vascular wall. Type IV and XVIII collagen/endostatin are structural proteins in vascular basement membrane (VBM), a specialised ECM structure. Here the association between plasma levels of these collagens with the aortic diameter and expansion rate is studied, and their expression in aortic tissue characterised.

METHODS

This was a retrospective population based cohort study. Type IV and XVIII collagen/endostatin were analysed in plasma by ELISA assay in 615 men, divided into three groups based on the aortic diameter: 1) normal aorta ≤ 25 mm, 2) sub-aneurysmal aorta (SAA) 26-29 mm, and 3) AAA ≥ 30 mm. Follow up data were available for 159 men. The association between collagen levels and aortic diameter at baseline, and with the expansion rate at follow up were analysed in ordinal logistic regression and linear regression models, controlling for common confounding factors. Tissue expression of the collagens was analysed in normal aorta (n = 6) and AAA (n = 6) by immunofluorescence.

RESULTS

Plasma levels of type XVIII collagen/endostatin (136 ng/mL [SD 29] in individuals with a normal aorta diameter, 154 ng/ml [SD 45] in SAA, and 162 ng/ml [SD 46] in AAA; p = .001) and type IV collagen (105 ng/mL [SD 42] normal aorta, 124 ng/ml [SD 46] SAA, and 127 ng/ml [SD 47] AAA; p = .037) were associated with a larger aortic diameter. A significant association was found between the baseline levels of type XVIII/endostatin and the aortic expansion rate (p = .035), but in the multivariable model, only the initial aortic diameter remained significantly associated with expansion (p = .005). Altered expression patterns of both collagens were observed in AAA tissue.

CONCLUSION

Plasma levels of circulating type IV and XVIII collagen/endostatin increase with AAA diameter. The expression pattern of VBM proteins is altered in the aneurysm wall.

Endothelium as a Potential Target for Treatment of Abdominal Aortic Aneurysm

Abdominal aortic aneurysm (AAA) was previously ascribed to weaken defective medial arterial/adventitial layers, for example, smooth muscle/fibroblast cells. Therefore, besides surgical repair, medications targeting the medial layer to strengthen the aortic wall are the most feasible treatment strategy for AAA. However, so far, it is unclear whether such drugs have any beneficial effect on AAA prognosis, rate of aneurysm growth, rupture, or survival. Notably, clinical studies have shown that AAA is highly associated with endothelial dysfunction in the aged population. Additionally, animal models of endothelial dysfunction and endothelial nitric oxide synthase (eNOS) uncoupling had a very high rate of AAA formation, indicating there is crucial involvement of the endothelium and a possible pharmacological solution targeting the endothelium in AAA treatment. Endothelial cells have been found to trigger vascular wall remodeling by releasing proteases, or recruiting macrophages along with other neutrophils, into the medial layer. Moreover, inflammation and oxidative stress of the arterial wall were induced by endothelial dysfunction. Interestingly, there is a paradoxical differential correlation between diabetes and aneurysm formation in retinal capillaries and the aorta. Deciphering the significance of such a difference may explain current unsuccessful AAA medications and offer a solution to this treatment challenge. It is now believed that AAA and atherosclerosis are two separate but related diseases, based on their different clinical patterns which have further complicated the puzzle. Therefore, a thorough investigation of the interaction between endothelium and medial/adventitial layer may provide us a better understanding and new perspective on AAA formation, especially after taking into account the importance of endothelium in the development of AAA. Moreover, a novel medication strategy replacing the currently used, but suboptimal treatments for AAA, could be informed with this analysis.

Behead and live long or the tale of cathepsin L

In recent decades Saccharomyces cerevisiae has proven to be one of the most valuable model organisms of aging research. Pathways such as autophagy or the effect of substances like resveratrol and spermidine that prolong the replicative as well as chronological lifespan of cells were described for the first time in S. cerevisiae. In this study we describe the establishment of an aging reporter that allows a reliable and relative quick screening of substances and genes that have an impact on the replicative lifespan. A cDNA library of the flatworm Dugesia tigrina that can be immortalized by beheading was screened using this aging reporter. Of all the flatworm genes, only one could be identified that significantly increased the replicative lifespan of S.cerevisiae. This gene is the cysteine protease cathepsin L that was sequenced for the first time in this study. We were able to show that this protease has the capability to degrade such proteins as the yeast Sup35 protein or the human α‐synuclein protein in yeast cells that are both capable of forming cytosolic toxic aggregates. The degradation of these proteins by cathepsin L prevents the formation of these unfolded protein aggregates and this seems to be responsible for the increase in replicative lifespan.

Cystatin B, cathepsin L and D related to surrogate markers for cardiovascular disease in children

OBJECTIVE

This study investigated potential associations between novel biomarkers for cardiovascular disease and other surrogate markers for health.

METHODS

Community sample of 170 (92 boys and 78 girls) children aged 8-11 years. Total fat mass (TBF) and abdominal fat (AFM) were measured by Dual-energy x-ray absorptiometry (DXA). Total body fat was also expressed as percentage of total body mass (BF%), and body fat distribution was calculated as AFM/TBF. Maximal oxygen uptake (VO2PEAK), systolic and diastolic blood pressure (SBP and DBP) and pulse pressure (PP) were measured. Echocardiography was performed. Left atrial size (LA) and left ventricular mass (LVM) were measured. A follow-up DXA scan was available in 152 children (84 boys and 68 girls). Frozen serum samples were analyzed for cystatin B, cathepsin L and cathepsin D.

RESULTS

Partial correlations between cystatin B versus lnTBF, lnBF%, lnAFM, AFM/TBF, VO2PEAK and PP were; r = 0.38, 0.36, 0.38, 0.29, -0.25 and 0.25, P = 0.001 or less for all. Weaker predominantly non-significant correlations were found for cathepsin L, whereas cathepsin D was not related to any surrogate markers for health. No significant correlations were found between biomarkers and change in body fat over 2 years.

CONCLUSION

Findings from this community-based cohort of young children show that surrogate markers for cardiovascular disease such as total fat mass, percent body fat, abdominal fat, body fat distribution, maximal oxygen uptake and pulse pressure were all associated with cystatin B. This was not found for cathepsin L or cathepsin D.

Cathepsin L deficiency results in reactive oxygen species (ROS) accumulation and vascular cells activation

Recent evidence suggests a link between cathepsin L (CTSL) and vascular diseases. However, its contribution to reactive oxygen species (ROS) homeostasis in the vasculature remains unknown. p66shc is a redox enzyme implicated in mitochondrial ROS generation and translation of oxidative signals. In this study, we explored the relationship between CTSL and oxidative damage in vasculature and whether the oxidative damage is mediated by p66shc.Carotid arteries from aged mice (24 months old) showed a reduction in CTSL expression compared with young wild-type mice (4 months old). Local knockdown of CTSL in carotid arteries of young mice by adenoviral vector encoding the short hairpin RNA targeting CTSL leading to premature vascular aging, as shown by mitochondrial disruption, increased β-galactosidase-positive cells, reduced telomerase activity, and up-regulation of p66shc. Knockdown of CTSL decreased the expression of mitochondrial oxidative phosphorylation (OXPHOS) complexes I, III, and IV, leading to increased mitochondrial ROS and hyperpolarization of the mitochondrial membrane in vitro. Furthermore, knockdown of CTSL also stimulated ROS production and senescence in vascular cells, accompanied by the up-regulation of p66shc.However, p66shc knockdown blunted the alteration in ROS production, and senescence in CTSL knockdown vascular cells. This study suggests that CTSL knockdown partially induces vascular cells damage via increased ROS production and up-regulation of p66shc.

Cysteine Protease Cathepsins in Atherosclerotic Cardiovascular Diseases

Atherosclerotic cardiovascular disease (ASCVD) is an inflammatory disease characterized by extensive arterial wall matrix protein degradation. Cysteine protease cathepsins play a pivotal role in extracellular matrix (ECM) remodeling and have been implicated in the development and progression of atherosclerosis-based cardiovascular diseases. An imbalance in expression between cathepsins (such as cathepsins S, K, L, C) and their inhibitor cystatin C may favor proteolysis of ECM in the pathogenesis of cardiovascular disease such as atherosclerosis, aneurysm formation, restenosis, and neovascularization. New insights into cathepsin functions have been made possible by the generation of knock-out mice and by the application of specific inhibitors. Inflammatory cytokines regulate the expression and activities of cathepsins in cultured vascular cells and macrophages. In addition, evaluations of the possibility of cathepsins as a diagnostic tool revealed that the circulating levels of cathepsin S, K, and L, and their endogenous inhibitor cystatin C could be promising biomarkers in the diagnosis of coronary artery disease, aneurysm, adiposity, peripheral arterial disease, and coronary artery calcification. In this review, we summarize the available information regarding the mechanistic contributions of cathepsins to ASCVD.

AT1-receptor blockade attenuates outward aortic remodeling associated with diet-induced obesity in mice

The renin-angiotensin system (RAS) and obesity have been implicated in vascular outward remodeling, including aneurysms, but the precise mechanisms are not yet understood. We investigated the effect of the angiotensin receptor type 1 (AT1-receptor) antagonist telmisartan on aortic outward remodeling in a diet-induced obesity model in mice. C57/Black6J mice were fed either a low-fat diet (LFD) or a high-fat diet (HFD) for 14 weeks. One group of HFD mice was additionally exposed to telmisartan (3 mg/kg per day) for the last 4 weeks. HFD led to aortic outward remodeling, characterized by increased proteolysis, along with structural changes, such as fragmentation of elastic fibers and decreased elastin content. Vascular damage was associated with up-regulation of matrix metalloproteinase (MMP)-2 (MMP-2), MMP-3, MMP-12, cathepsin D, and cathepsin B. HFD aortae exhibited an enhanced inflammatory status, characterized by tumor necrosis factor α (TNF-α) and interleukin-1β (IL-1β) colocalized with adipocytes in the adventitia. HFD resulted in a significant increase in aortic dimensions, evident by ultrasound measurements. Telmisartan abolished aortic dilatation and preserved elastin content. HFD induced enhanced expression of aortic MMP-2, MMP-9, and TNF-α was abrogated by telmisartan. Adventitial proteolytic and inflammatory factors were also examined in samples from human abdominal aneurysms. The expression of TNF-α, IL-1β, and MMP-9 was higher in the adventitial fat of diseased vessels compared with healthy tissues. Finally, adipocytes treated with TNF-α showed enhanced MMP-2, MMP-3, and cathepsin D, which was prevented by telmisartan. Taken together, HFD in mice induced aortic dilatation with up-regulation of matrix degrading and inflammatory pathways similar to those seen in human aortic aneurysmatic tissue. The HFD-induced vascular pathology was reduced by AT1-receptor antagonist telmisartan.

Protease Inhibitors in Tick Saliva: The Role of Serpins and Cystatins in Tick-host-Pathogen Interaction

The publication of the first tick sialome (salivary gland transcriptome) heralded a new era of research of tick protease inhibitors, which represent important constituents of the proteins secreted via tick saliva into the host. Three major groups of protease inhibitors are secreted into saliva: Kunitz inhibitors, serpins, and cystatins. Kunitz inhibitors are anti-hemostatic agents and tens of proteins with one or more Kunitz domains are known to block host coagulation and/or platelet aggregation. Serpins and cystatins are also anti-hemostatic effectors, but intriguingly, from the translational perspective, also act as pluripotent modulators of the host immune system. Here we focus especially on this latter aspect of protease inhibition by ticks and describe the current knowledge and data on secreted salivary serpins and cystatins and their role in tick-host-pathogen interaction triad. We also discuss the potential therapeutic use of tick protease inhibitors.

Monocytes and macrophages in abdominal aortic aneurysm

Abdominal aortic aneurysm (AAA) is a life-threatening disease associated with high morbidity, and high mortality in the event of aortic rupture. Major advances in open surgical and endovascular repair of AAA have been achieved during the past 2 decades. However, drug-based therapies are still lacking, highlighting a real need for better understanding of the molecular and cellular mechanisms involved in AAA formation and progression. The main pathological features of AAA include extracellular matrix remodelling associated with degeneration and loss of vascular smooth muscle cells and accumulation and activation of inflammatory cells. The inflammatory process has a crucial role in AAA and substantially influences many determinants of aortic wall remodelling. In this Review, we focus specifically on the involvement of monocytes and macrophages, summarizing current knowledge on the roles, origin, and functions of these cells in AAA development and its complications. Furthermore, we show and propose that distinct monocyte and macrophage subsets have critical and differential roles in initiation, progression, and healing of the aneurysmal process. On the basis of experimental and clinical studies, we review potential translational applications to detect, assess, and image macrophage subsets in AAA, and discuss the relevance of these applications for clinical practice.