Cysteine protease cathepsins in cardiovascular disease: from basic research to clinical trials

Cathepsin K deficiency prevented stress-related thrombosis in a mouse FeCl3 model

BACKGROUND

Exposure to chronic psychological stress (CPS) is a risk factor for thrombotic cardiocerebrovascular diseases (CCVDs). The expression and activity of the cysteine cathepsin K (CTSK) are upregulated in stressed cardiovascular tissues, and we investigated whether CTSK is involved in chronic stress-related thrombosis, focusing on stress serum-induced endothelial apoptosis.

METHODS AND RESULTS

Eight-week-old wild-type male mice (CTSK+/+) randomly divided to non-stress and 3-week restraint stress groups received a left carotid artery iron chloride3 (FeCl3)-induced thrombosis injury for biological and morphological evaluations at specific timepoints. On day 21 post-stress/injury, the stress had enhanced the arterial thrombi weights and lengths, in addition to harmful alterations of plasma ADAMTS13, von Willebrand factor, and plasminogen activation inhibitor-1, plus injured-artery endothelial loss and CTSK protein/mRNA expression. The stressed CTSK+/+ mice had increased levels of injured arterial cleaved Notch1, Hes1, cleaved caspase8, matrix metalloproteinase-9/-2, angiotensin type 1 receptor, galactin3, p16IN4A, p22phox, gp91phox, intracellular adhesion molecule-1, TNF-α, MCP-1, and TLR-4 proteins and/or genes. Pharmacological and genetic inhibitions of CTSK ameliorated the stress-induced thrombus formation and the observed molecular and morphological changes. In cultured HUVECs, CTSK overexpression and silencing respectively increased and mitigated stressed-serum- and H2O2-induced apoptosis associated with apoptosis-related protein changes. Recombinant human CTSK degraded γ-secretase substrate in a dose-dependent manor and activated Notch1 and Hes1 expression upregulation.

CONCLUSIONS

CTSK appeared to contribute to stress-related thrombosis in mice subjected to FeCl3 stress, possibly via the modulation of vascular inflammation, oxidative production and apoptosis, suggesting that CTSK could be an effective therapeutic target for CPS-related thrombotic events in patients with CCVDs.

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.

Recent advances in therapeutic engineered extracellular vesicles

Extracellular vesicles (EVs) are natural particles secreted by living cells, which hold significant potential for various therapeutic applications. Native EVs have specific components and structures, allowing them to cross biological barriers, and circulate in vivo for a long time. Native EVs have also been bioengineered to enhance their therapeutic efficacy and targeting affinity. Recently, the therapeutic potential of surface-engineered EVs has been explored in the treatment of tumors, autoimmune diseases, infections and other diseases by ongoing research and clinical trials. In this review, we will introduce the modified methods of engineered EVs, summarize the application of engineered EVs in preclinical and clinical trials, and discuss the opportunities and challenges for the clinical translation of surface-engineered EVs.

Ursolic acid alleviates meiotic abnormalities induced by 3-nitropropionic acid in mouse oocytes

3-nitropropionic acid (3-NPA), a toxic metabolite produced by mold, is mainly found in moldy sugarcane. 3-NPA inhibits the activity of succinate dehydrogenase that can induce oxidative stress injury in cells, reduce ATP production and induce oxidative stress in mouse ovaries to cause reproductive disorders. Ursolic acid (UA) has a variety of biological activities and is a pentacyclic triterpene compound found in many plants. This experiment aimed to investigate the cytotoxicity of 3-NPA during mouse oocyte in vitro maturation and the protective effects of UA on oocytes challenged with 3-NPA. The results showed that UA could alleviate 3-NPA-induced oocyte meiotic maturation failure. Specifically, 3-NPA induced a decrease in the first polar body extrusion rate of oocytes, abnormal distribution of cortical granules, and an increase in the proportion of spindle abnormalities. In addition, 3-NPA caused mitochondrial dysfunction and induced oxidative stress, including decreases in the GSH, mitochondrial membrane potential and ATP levels, and increases in the ROS levels, and these effects led to apoptosis and autophagy. The addition of UA could significantly improve the adverse effects caused by 3-NPA. In general, our data show that 3-NPA affects the normal development of oocytes during the in vitro culture, and the addition of UA can effectively repair the damage caused by 3-NPA to oocytes.

The multifaceted role of proteases and modern analytical methods for investigation of their catalytic activity

We discuss the diverse functions of proteases in the context of their biotechnological and medical significance, as well as analytical approaches used to determine the functional activity of these enzymes. An insight into modern approaches to studying the kinetics and specificity of proteases, based on spectral (absorption, fluorescence), mass spectrometric, immunological, calorimetric, and electrochemical methods of analysis is given. We also examine in detail electrochemical systems for determining the activity and specificity of proteases. Particular attention is given to exploring innovative electrochemical systems based on the detection of the electrochemical oxidation signal of amino acid residues, thereby eliminating the need for extra redox labels in the process of peptide synthesis. In the review, we highlight the main prospects for the further development of electrochemical systems for the study of biotechnologically and medically significant proteases, which will enable the miniaturization of the analytical process for determining the catalytic activity of these enzymes.

Cholesterol trafficking, lysosomal function, and atherosclerosis

Despite years of study and major research advances over the past 50 years, atherosclerotic diseases continue to rank as the leading global cause of death. Accumulation of cholesterol within the vascular wall remains the main problem and represents one of the early steps in the development of atherosclerotic lesions. There is a complex relationship between vesicular cholesterol transport and atherosclerosis, and abnormalities in cholesterol trafficking can contribute to the development and progression of the lesions. The dysregulation of vesicular cholesterol transport and lysosomal function fosters the buildup of cholesterol within various intracytoplasmic compartments, including lysosomes and lipid droplets. This, in turn, promotes the hallmark formation of foam cells, a defining feature of early atherosclerosis. Multiple cellular processes, encompassing endocytosis, exocytosis, intracellular trafficking, and autophagy, play crucial roles in influencing foam cell formation and atherosclerotic plaque stability. In this review, we highlight recent advances in the understanding of the intricate mechanisms of vesicular cholesterol transport and its relationship with atherosclerosis and discuss the importance of understanding these mechanisms in developing strategies to prevent or treat this prevalent cardiovascular disease.

Prevention of Protease-Induced Degradation of Desmoplakin via Small Molecule Binding

Desmoplakin (DSP) is a large (~260 kDa) protein found in the desmosome, the subcellular structure that links the intermediate filament network of one cell to its neighbor. A mutation "hot-spot" within the NH2-terminal of the DSP protein (residues 299-515) is associated with arrhythmogenic cardiomyopathy. In a subset of DSP variants, disease is linked to calpain hypersensitivity. Previous studies show that calpain hypersensitivity can be corrected in vitro through the addition of a bulky residue neighboring the cleavage site, suggesting that physically blocking calpain accessibility is a viable strategy to restore DSP levels. Here, we aim to find drug-like molecules that also block calpain-dependent degradation of DSP. To do this, we screened ~2500 small molecules to identify compounds that specifically rescue DSP protein levels in the presence of proteases. We find that several molecules, including sodium dodecyl sulfate, palmitoylethanolamide, GW0742, salirasib, eprosarten mesylate, and GSK1838705A prevent wildtype and disease-variant-carrying DSP protein degradation in the presence of both trypsin and calpain without altering protease function. Computational screenings did not predict which molecules would protect DSP, likely due to a lack of specific DSP-drug interactions. Molecular dynamic simulations of DSP-drug complexes suggest that some long hydrophobic molecules can bind in a shallow hydrophobic groove that runs alongside the protease cleavage site. Identification of these compounds lays the groundwork for pharmacological treatment for individuals harboring these hypersensitive DSP variants.

Multiplexed MRM-based proteomics for identification of circulating proteins as biomarkers of cardiovascular damage progression associated with diabetes mellitus

BACKGROUND

Type 2 diabetes mellitus (T2DM) increases the risk of coronary heart disease (CHD) by 2-4 fold, and is associated with endothelial dysfunction, dyslipidaemia, insulin resistance, and chronic hyperglycaemia. The aim of this investigation was to assess, by a multimarker mass spectrometry approach, the predictive role of circulating proteins as biomarkers of cardiovascular damage progression associated with diabetes mellitus.

METHODS

The study considered 34 patients with both T2DM and CHD, 31 patients with T2DM and without CHD, and 30 patients without diabetes with a diagnosis of CHD. Plasma samples of subjects were analysed through a multiplexed targeted liquid chromatography mass spectrometry (LC-MS)-based assay, namely Multiple Reaction Monitoring (MRM), allowing the simultaneous detection of peptides derived from a protein of interest. Gene Ontology (GO) Analysis was employed to identify enriched GO terms in the biological process, molecular function, or cellular component categories. Non-parametric multivariate methods were used to classify samples from patients and evaluate the relevance of the analysed proteins' panel.

RESULTS

A total of 81 proteins were successfully quantified in the human plasma samples. Gene Ontology analysis assessed terms related to blood microparticles, extracellular exosomes and collagen-containing extracellular matrix. Preliminary evaluation using analysis of variance (ANOVA) of the differences in the proteomic profile among patient groups identified 13 out of the 81 proteins as significantly different. Multivariate analysis, including cluster analysis and principal component analysis, identified relevant grouping of the 13 proteins. The first main cluster comprises apolipoprotein C-III, apolipoprotein C-II, apolipoprotein A-IV, retinol-binding protein 4, lysozyme C and cystatin-C; the second one includes, albeit with sub-grouping, alpha 2 macroglobulin, afamin, kininogen 1, vitronectin, vitamin K-dependent protein S, complement factor B and mannan-binding lectin serine protease 2. Receiver operating characteristic (ROC) curves obtained with the 13 selected proteins using a nominal logistic regression indicated a significant overall distinction (p < 0.001) among the three groups of subjects, with area under the ROC curve (AUC) ranging 0.91-0.97, and sensitivity and specificity ranging from 85 to 100%.

CONCLUSIONS

Targeted mass spectrometry approach indicated 13 multiple circulating proteins as possible biomarkers of cardiovascular damage progression associated with T2DM, with excellent classification results in terms of sensitivity and specificity.

Protease detection in the biosensor era: A review

Proteases have been proposed as potential biomarkers for several pathological conditions including cancers, multiple sclerosis and cardiovascular diseases, due to their ability to break down the components of extracellular matrix and basement membrane. The development of protease biosensors opened up the possibility to investigate the proteolytic activity of dysregulated proteases with higher efficiency over the traditional detection assays due to their quick detection capability, high sensitivity and selectivity, simple instrumentation and cost-effective fabrication processes. In contrast to the recently published review papers that primarily focused on one specific class of proteases or one specific detection method, this review article presents different optical and electrochemical detection methods that can be used to design biosensors for all major protease families. The benefits and drawbacks of various transducer techniques integrated into protease biosensing platforms are analyzed and compared. The main focus is on activity-based biosensors that use peptides as biorecognition elements. The effects of nanomaterials on biosensor performance are also discussed. This review should help readers to select the biosensor that best fits their needs, and contribute to the further development of this research field. Protease biosensors may allow better comprehension of protease overexperession and potentially enable novel devices for point-of-care testing.

Multi-proteomic Biomarker Risk Scores for Predicting Risk and Guiding Therapy in Patients with Coronary Artery Disease

PURPOSE OF REVIEW

Patients with established coronary artery disease (CAD) are at high residual risk for adverse events, despite guideline-based treatments. Herein, we aimed to determine whether risk scores based on multiple circulating biomarkers that represent activation of various pathophysiologically important pathways involved in atherosclerosis and myocardial dysfunction help identify those at greatest residual risk.

RECENT FINDINGS

Numerous circulating proteins, representing dysregulation of the pathways involved in the development and stability of coronary and myocardial diseases, have been identified. When aggregated together, biomarker risk scores (BRS) more accurately stratify patients with established CAD that may help target interventions in those individuals who are at elevated risk. Moreover, intensification of guideline-based therapies has been associated with parallel improvements in both BRS and outcomes, indicating that these risk scores may be employed clinically to target therapy. Multi-protein BRS are predictive of risk, independent of, and in addition to traditional risk factor assessments in patients with CAD. Those with elevated risk may benefit from optimization of therapies, and improvements in the BRS will identify those with improved outcomes.

The Serum ACE2, CTSL, AngII, and TNFα Levels after COVID-19 and mRNA Vaccines: The Molecular Basis

BACKGROUND

The SARS-CoV-2 virus as well as the COVID-19 mRNA vaccines cause an increased production of proinflammatory cytokines.

AIM

We investigated the relationship between ACE2, CTSL, AngII, TNFα and the serum levels of IL-6, IL-10, IL-33, IL-28A, CD40L, total IgM, IgG, IgA and absolute count of T- and B-lymphocytes in COVID-19 patients, vaccinees and healthy individuals.

METHODS

We measured the serum levels ACE2, AngII, CTSL, TNFα and humoral biomarkers (CD40L, IL-28A, IL-10, IL-33) by the ELISA method. Immunophenotyping of lymphocyte subpopulations was performed by flow cytometry. Total serum immunoglobulins were analyzed by the turbidimetry method.

RESULTS

The results established an increase in the total serum levels for ACE2, CTSL, AngII and TNFα by severely ill patients and vaccinated persons. The correlation analysis described a positive relationship between ACE2 and proinflammatory cytokines IL-33 (r = 0.539) and CD40L (r = 0.520), a positive relationship between AngII and CD40L (r = 0.504), as well as between AngII and IL-33 (r = 0.416), and a positive relationship between CTSL, total IgA (r = 0.437) and IL-28A (r = 0.592). Correlation analysis confirmed only two of the positive relationships between TNFα and IL-28A (r = 0.491) and CD40L (r = 0.458).

CONCLUSIONS

In summary, the findings presented in this study unveil a complex web of interactions within the immune system in response to SARS-CoV-2 infection and vaccination.

The Role of Cysteine Protease Cathepsins B, H, C, and X/Z in Neurodegenerative Diseases and Cancer

Papain-like cysteine proteases are composed of 11 human cysteine cathepsins, originally located in the lysosomes. They exhibit broad specificity and act as endopeptidases and/or exopeptidases. Among them, only cathepsins B, H, C, and X/Z exhibit exopeptidase activity. Recently, cysteine cathepsins have been found to be present outside the lysosomes and often participate in various pathological processes. Hence, they have been considered key signalling molecules. Their potentially hazardous proteolytic activities are tightly regulated. This review aims to discuss recent advances in understanding the structural aspects of these four cathepsins, mechanisms of their zymogen activation, regulation of their activities, and functional aspects of these enzymes in neurodegeneration and cancer. Neurodegenerative effects have been evaluated, particularly in Alzheimer's disease, Parkinson's disease, Huntington's disease, amyotrophic lateral sclerosis, multiple sclerosis, and neuropsychiatric disorders. Cysteine cathepsins also participate in tumour progression and metastasis through the overexpression and secretion of proteases, which trigger extracellular matrix degradation. To our knowledge, this is the first review to provide an in-depth analysis regarding the roles of cysteine cathepsins B, H, C, and X in neurodegenerative diseases and cancer. Further advances in understanding the functions of cysteine cathepsins in these conditions will result in the development of novel, targeted therapeutic strategies.

Eosinophils promote pulmonary matrix destruction and emphysema via Cathepsin L

Patients with chronic obstructive pulmonary disease (COPD) who exhibit elevated blood eosinophil levels often experience worsened lung function and more severe emphysema. This implies the potential involvement of eosinophils in the development of emphysema. However, the precise mechanisms underlying the development of eosinophil-mediated emphysema remain unclear. In this study, we employed single-cell RNA sequencing to identify eosinophil subgroups in mouse models of asthma and emphysema, followed by functional analyses of these subgroups. Assessment of accumulated eosinophils unveiled distinct transcriptomes in the lungs of mice with elastase-induced emphysema and ovalbumin-induced asthma. Depletion of eosinophils through the use of anti-interleukin-5 antibodies ameliorated elastase-induced emphysema. A particularly noteworthy discovery is that eosinophil-derived cathepsin L contributed to the degradation of the extracellular matrix, thereby leading to emphysema in pulmonary tissue. Inhibition of cathepsin L resulted in a reduction of elastase-induced emphysema in a mouse model. Importantly, eosinophil levels correlated positively with serum cathepsin L levels, which were higher in emphysema patients than those without emphysema. Expression of cathepsin L in eosinophils demonstrated a direct association with lung emphysema in COPD patients. Collectively, these findings underscore the significant role of eosinophil-derived cathepsin L in extracellular matrix degradation and remodeling, and its relevance to emphysema in COPD patients. Consequently, targeting eosinophil-derived cathepsin L could potentially offer a therapeutic avenue for emphysema patients. Further investigations are warranted to explore therapeutic strategies targeting cathepsin L in emphysema patients.

Positional proteomics: is the technology ready to study clinical cohorts?

INTRODUCTION

Positional proteomics provides proteome-wide information on protein termini and their modifications, uniquely enabling unambiguous identification of site-specific, limited proteolysis. Such proteolytic cleavage irreversibly modifies protein sequences resulting in new proteoforms with distinct protease-generated neo-N and C-termini and altered localization and activity. Misregulated proteolysis is implicated in a wide variety of human diseases. Protein termini, therefore, constitute a huge, largely unexplored source of specific analytes that provides a deep view into the functional proteome and a treasure trove for biomarkers.

AREAS COVERED

We briefly review principal approaches to define protein termini and discuss recent advances in method development. We further highlight the potential of positional proteomics to identify and trace specific proteoforms, with a focus on proteolytic processes altered in disease. Lastly, we discuss current challenges and potential for applying positional proteomics in biomarker and pre-clinical research.

EXPERT OPINION

Recent developments in positional proteomics have provided significant advances in sensitivity and throughput. In-depth analysis of proteolytic processes in clinical cohorts thus appears feasible in the near future. We argue that this will provide insights into the functional state of the proteome and offer new opportunities to utilize proteolytic processes altered or targeted in disease as specific diagnostic, prognostic and companion biomarkers.

Cathepsin B S-nitrosylation promotes ADAR1-mediated editing of its own mRNA transcript via an ADD1/MATR3 regulatory axis

Genetic information is generally transferred from RNA to protein according to the classic "Central Dogma". Here, we made a striking discovery that post-translational modification of a protein specifically regulates the editing of its own mRNA. We show that S-nitrosylation of cathepsin B (CTSB) exclusively alters the adenosine-to-inosine (A-to-I) editing of its own mRNA. Mechanistically, CTSB S-nitrosylation promotes the dephosphorylation and nuclear translocation of ADD1, leading to the recruitment of MATR3 and ADAR1 to CTSB mRNA. ADAR1-mediated A-to-I RNA editing enables the binding of HuR to CTSB mRNA, resulting in increased CTSB mRNA stability and subsequently higher steady-state levels of CTSB protein. Together, we uncovered a unique feedforward mechanism of protein expression regulation mediated by the ADD1/MATR3/ADAR1 regulatory axis. Our study demonstrates a novel reverse flow of information from the post-translational modification of a protein back to the post-transcriptional regulation of its own mRNA precursor. We coined this process as "Protein-directed EDiting of its Own mRNA by ADAR1 (PEDORA)" and suggest that this constitutes an additional layer of protein expression control. "PEDORA" could represent a currently hidden mechanism in eukaryotic gene expression regulation.

Structural Transitions of Papain-like Cysteine Proteases: Implications for Sensor Development

The significant role of papain-like cysteine proteases, including papain, cathepsin L and SARS-CoV-2 PLpro, in biomedicine and biotechnology makes them interesting model systems for sensor development. These enzymes have a free thiol group that is suitable for many sensor designs including strong binding to gold nanoparticles or low-molecular-weight inhibitors. Focusing on the importance of the preservation of native protein structure for inhibitor-binding and molecular-imprinting, which has been applied in some efficient examples of sensor development, the aim of this work was to examine the effects of the free-thiol-group's reversible blocking on papain denaturation that is the basis of its activity loss and aggregation. To utilize biophysical methods common in protein structural transitions characterization, such as fluorimetry and high-resolution infrared spectroscopy, low-molecular-weight electrophilic thiol blocking reagent S-Methyl methanethiosulfonate (MMTS) was used in solution. MMTS binding led to a two-fold increase in 8-Anilinonaphthalene-1-sulfonic acid fluorescence, indicating increased hydrophobic residue exposure. A more in-depth analysis showed significant transitions on the secondary structure level upon MMTS binding, mostly characterized by the lowered content of α-helices and unordered structures (either for approximately one third), and the increase in aggregation-specific β-sheets (from 25 to 52%) in a dose-dependant manner. The recovery of this inhibited protein showed that reversibility of inhibition is accompanied by reversibility of protein denaturation. Nevertheless, a 100-fold molar excess of the inhibitor led to the incomplete recovery of proteolytic activity, which can be explained by irreversible denaturation. The structural stability of the C-terminal β-sheet rich domain of the papain-like cysteine protease family opens up an interesting possibility to use its foldamers as a strategy for sensor development and other multiple potential applications that rely on the great commercial value of papain-like cysteine proteases.

Overcoming cohort heterogeneity for the prediction of subclinical cardiovascular disease risk

Cardiovascular disease remains a leading cause of mortality with an estimated half a billion people affected in 2019. However, detecting signals between specific pathophysiology and coronary plaque phenotypes using complex multi-omic discovery datasets remains challenging due to the diversity of individuals and their risk factors. Given the complex cohort heterogeneity present in those with coronary artery disease (CAD), we illustrate several different methods, both knowledge-guided and data-driven approaches, for identifying subcohorts of individuals with subclinical CAD and distinct metabolomic signatures. We then demonstrate that utilizing these subcohorts can improve the prediction of subclinical CAD and can facilitate the discovery of novel biomarkers of subclinical disease. Analyses acknowledging cohort heterogeneity through identifying and utilizing these subcohorts may be able to advance our understanding of CVD and provide more effective preventative treatments to reduce the burden of this disease in individuals and in society as a whole.

Surface-Functionalized Stem Cell-Derived Extracellular Vesicles for Vascular Elastic Matrix Regenerative Repair

Extracellular vesicles (EVs) are nanosized vesicles that carry cell-specific biomolecular information. Our previous studies showed that adult human bone marrow mesenchymal stem cell (BM-MSC)-derived EVs provide antiproteolytic and proregenerative effects in cultures of smooth muscle cells (SMCs) derived from an elastase-infused rat abdominal aortic aneurysm (AAA) model, and this is promising toward their use as a therapeutic platform for naturally irreversible elastic matrix aberrations in the aortic wall. Since systemically administered EVs poorly home into sites of tissue injury, disease strategies to improve their affinity toward target tissues are of great significance for EV-based treatment strategies. Toward this goal, in this work, we developed a postisolation surface modification strategy to target MSC-derived EVs to the AAA wall. The EVs were surface-conjugated with a short, synthetic, azide-modified peptide sequence for targeted binding to cathepsin K (CatK), a cysteine protease overexpressed in the AAA wall. Conjugation was performed using a copper-free click chemistry method. We determined that such conjugation improved EV uptake into cultured aneurysmal SMCs in culture and their binding to the wall of matrix injured vessels ex vivo. The proregenerative and antiproteolytic effects of MSC-EVs on cultured rat aneurysmal SMCs were also unaffected following peptide conjugation. From this study, it appears that modification with short synthetic peptide sequences seems to be an effective strategy for improving the cell-specific uptake of EVs and may be effective in facilitating AAA-targeted therapy.

Investigation of the Compatibility between Warheads and Peptidomimetic Sequences of Protease Inhibitors-A Comprehensive Reactivity and Selectivity Study

Covalent peptidomimetic protease inhibitors have gained a lot of attention in drug development in recent years. They are designed to covalently bind the catalytically active amino acids through electrophilic groups called warheads. Covalent inhibition has an advantage in terms of pharmacodynamic properties but can also bear toxicity risks due to non-selective off-target protein binding. Therefore, the right combination of a reactive warhead with a well-suited peptidomimetic sequence is of great importance. Herein, the selectivities of well-known warheads combined with peptidomimetic sequences suited for five different proteases were investigated, highlighting the impact of both structure parts (warhead and peptidomimetic sequence) for affinity and selectivity. Molecular docking gave insights into the predicted binding modes of the inhibitors inside the binding pockets of the different enzymes. Moreover, the warheads were investigated by NMR and LC-MS reactivity assays against serine/threonine and cysteine nucleophile models, as well as by quantum mechanics simulations.

Cathepsins in the extracellular space: Focusing on non-lysosomal proteolytic functions with clinical implications

Cathepsins can be found in the extracellular space, cytoplasm, and nucleus. It was initially suspected that the primary physiological function of the cathepsins was to break down intracellular protein, and that they also had a role in pathological processes including inflammation and apoptosis. However, the many actions of cathepsins outside the cell and their complicated biological impacts have garnered much interest. Cathepsins play significant roles in a number of illnesses by regulating parenchymal cell proliferation, cell migration, viral invasion, inflammation, and immunological responses through extracellular matrix remodeling, signaling disruption, leukocyte recruitment, and cell adhesion. In this review, we outline the physiological roles of cathepsins in the extracellular space, the crucial pathological functions performed by cathepsins in illnesses, and the recent breakthroughs in the detection and therapy of specific inhibitors and fluorescent probes in associated dysfunction.

COVID-19 signalome: Potential therapeutic interventions

The COVID-19 pandemic has triggered intensive research and development of drugs and vaccines against SARS-CoV-2 during the last two years. The major success was especially observed with development of vaccines based on viral vectors, nucleic acids and whole viral particles, which have received emergent authorization leading to global mass vaccinations. Although the vaccine programs have made a big impact on COVID-19 spread and severity, emerging novel variants have raised serious concerns about vaccine efficacy. Due to the urgent demand, drug development had originally to rely on repurposing of antiviral drugs developed against other infectious diseases. For both drug and vaccine development the focus has been mainly on SARS-CoV-2 surface proteins and host cell receptors involved in viral attachment and entry. In this review, we expand the spectrum of SARS-CoV-2 targets by investigating the COVID-19 signalome. In addition to the SARS-CoV-2 Spike protein, the envelope, membrane, and nucleoprotein targets have been subjected to research. Moreover, viral proteases have presented the possibility to develop different strategies for the inhibition of SARS-CoV-2 replication and spread. Several signaling pathways involving the renin-angiotensin system, angiotensin-converting enzymes, immune pathways, hypoxia, and calcium signaling have provided attractive alternative targets for more efficient drug development.

Defining atherosclerotic plaque biology by mass spectrometry-based omics approaches

Atherosclerosis is the principal cause of vascular diseases and one of the leading causes of worldwide death. Even though several insights into its natural course, risk factors and interventions have been identified, it is still an ongoing global pandemic. Since the structure and biochemical composition of the plaques show high heterogeneity, a comprehensive understanding of the intraplaque composition, its microenvironment, and the mechanisms of the progression and instability across different vascular beds at their progression stages is crucial for better risk stratification and treatment modalities. Even though several cell-based studies, animal studies, and extensive multicentric population studies have been conducted concerning cardiovascular diseases for assessing the risk factors and plaque biology, the studies on human clinical samples are very limited. New novel approaches utilize samples from percutaneous coronary interventions, which could possibly gain more access to clinical samples at different stages of the diseases without complex invasive resections. As an emerging technological platform in disease discovery research, mass spectrometry-based omics technologies offer capabilities for a comprehensive understanding of the mechanisms linked to several vascular diseases. Here, we discuss the cellular and molecular processes of atherosclerosis, different mass spectrometry-based omics approaches, and the studies mostly done on clinical samples of atheroma plaque using mass spectrometry-based proteomics, metabolomics and lipidomics approaches.

RNA modifications in cardiovascular health and disease

RNA is not always a faithful copy of DNA. Advances in tools enabling the interrogation of the exact RNA sequence have permitted revision of how genetic information is transferred. We now know that RNA is a dynamic molecule, amenable to chemical modifications of its four canonical nucleotides by dedicated RNA-binding enzymes. The ever-expanding catalogue of identified RNA modifications in mammals has led to a burst of studies in the past 5 years that have explored the biological relevance of the RNA modifications, also known as epitranscriptome. These studies concluded that chemical modification of RNA nucleotides alters several properties of RNA molecules including sequence, secondary structure, RNA-protein interaction, localization and processing. Importantly, a plethora of cellular functions during development, homeostasis and disease are controlled by RNA modification enzymes. Understanding the regulatory interface between a single-nucleotide modification and cellular function will pave the way towards the development of novel diagnostic, prognostic and therapeutic tools for the management of diseases, including cardiovascular disease. In this Review, we use two well-studied and abundant RNA modifications - adenosine-to-inosine RNA editing and N⁶-methyladenosine RNA methylation - as examples on which to base the discussion about the current knowledge on installation or removal of RNA modifications, their effect on biological processes related to cardiovascular health and disease, and the potential for development and application of epitranscriptome-based prognostic, diagnostic and therapeutic tools for cardiovascular disease.

Cysteine cathepsins: A long and winding road towards clinics

Biomedical research often focuses on properties that differentiate between diseased and healthy tissue; one of the current focuses is elevated expression and altered localisation of proteases. Among these proteases, dysregulation of cysteine cathepsins can frequently be observed in inflammation-associated diseases, which tips the functional balance from normal physiological to pathological manifestations. Their overexpression and secretion regularly exhibit a strong correlation with the development and progression of such diseases, making them attractive pharmacological targets. But beyond their mostly detrimental role in inflammation-associated diseases, cysteine cathepsins are physiologically highly important enzymes involved in various biological processes crucial for maintaining homeostasis and responding to different stimuli. Consequently, several challenges have emerged during the efforts made to translate basic research data into clinical applications. In this review, we present both physiological and pathological roles of cysteine cathepsins and discuss the clinical potential of cysteine cathepsin-targeting strategies for disease management and diagnosis.

Cathepsin S Inhibition Suppresses Experimental Systemic Lupus Erythematosus-Associated Pulmonary Arterial Remodeling

Patients with systemic lupus erythematosus (SLE) associated with pulmonary arterial hypnertension (PAH) receive targeted therapy for PAH to decrease pulmonary arterial systolic pressure and significantly prolong their survival. Cysteine cathepsin proteases play critical roles in the progression of cardiovascular disease. Inhibition of cathepsin S (Cat S) has been shown to improve SLE and lupus nephritis. However, the effect of Cat S inhibitors on SLE-associated PAH (SLE-PAH) remains unclear, and there is no animal model for translational research on SLE-PAH. We hypothesized that the inhibition of Cat S may affect PAH development and arterial remodeling associated with SLE. A female animal model of SLE-PAH, female MRL/lpr (Lupus), was used to evaluate the role of pulmonary arterial remodeling in SLE. The key finding of the research work is the establishment of an animal model of SLE associated with PAH in female MRL/lpr mice that is able to evaluate pulmonary arterial remodeling starting from the age of 11 weeks to 15 weeks. Cat S protein level was identified as a marker of experimental SLE. Pulmonary hypertension in female MRL/lpr (Lupus) mice was treated by administering the selective Cat S inhibitor Millipore-219393, which stimulated peroxisome proliferator-activated receptor-gamma (PPARγ) in the lungs to inhibit Cat S expression and pulmonary arterial remodeling. Studies provide an animal model of female MRL/lpr (Lupus) associated with PAH and a deeper understanding of the pathogenesis of SLE-PAH. The results may define the role of cathepsin S in preventing progressive and fatal SLE-PAH and provide approaches for therapeutic interventions in SLE-PAH.

Cathepsin B/HSP70 complex induced by Ilexsaponin I suppresses NLRP3 inflammasome activation in myocardial ischemia/reperfusion injury

BACKGROUND

Myocardial ischemia/reperfusion injury (MI/RI) is a clinical issue in MI therapy that requires effective intervention. Cathepsin B (CTSB) plays an essential role in regulating cell death, inflammatory response and angiogenesis. Ilexsaponin I (ISI), a triterpenoid saponin obtained from Ilex pubescens Hook. et Arn, has anti-inflammatory and cardioprotective effects. However, the effect of ISI on MI/RI is unclear.

PURPOSE

The study aims to disclose the mechanism of ISI as a potent therapeutic agent for MI/RI.

METHODS

Left anterior descending (LAD) coronary artery ligation and oxygen-glucose deprivation and reperfusion (OGD/R) were used to establish MI/RI model in vivo and in vitro. ELISA, western blot and immunofluorescence were carried out to detect CTSB activity and NLRP3 inflammasome activation. Coimmunoprecipitation (Co-IP), molecular docking and surface plasmon resonance (SPR) analysis were used to detect the interaction of CTSB/HSP70 complex. Infarct area determination, echocardiography and hematoxylin and eosin (HE) staining were performed to assess the cardioprotection of ISI in vivo.

RESULTS

Plasma CTSB was elevated in patients after percutaneous coronary intervention (PCI), and was positively correlated with the level of cTnI in plasma, which was also found in MI/RI rat model. ISI significantly suppressed the overexpression and activity of CTSB after MI/RI or OGD/R. ISI remarkably suppressed CTSB triggered-NLRP3 inflammasome activation and reduced the maturation of IL-1β and IL-18. Importantly, we firstly found that ISI promoted CTSB/HSP70 complex formation to disrupt CTSB/NLRP3 complex, leading to NLRP3 inflammasome inactivation. ISI could also limit infarct size, improve cardiac function and reduce inflammatory infiltrates in vivo and protected H9c2 cells against OGD/R insult in vitro. Interrupting the HSP70 and CTSB interaction with HSP70 siRNA blocked the effect of ISI on CTSB, NLRP3 inflammasome activation and the cardioprotective effect.

CONCLUSION

ISI probably exerts cardioprotective effect against MI/RI by modulating HSP70 competitively bind to CTSB to suppress the activation of the NLRP3 inflammasome.

Cathepsin S Levels and Survival Among Patients With Non-ST-Segment Elevation Acute Coronary Syndromes

BACKGROUND

Patients with non-ST-segment elevation acute coronary syndromes (NSTE-ACS) are at high residual risk for long-term cardiovascular (CV) mortality. Cathepsin S (CTSS) is a lysosomal cysteine protease with elastolytic and collagenolytic activity that has been involved in atherosclerotic plaque rupture.

OBJECTIVES

The purpose of this study was to determine the following: 1) the prognostic value of circulating CTSS measured at patient admission for long-term mortality in NSTE-ACS; and 2) its additive value over the GRACE (Global Registry of Acute Coronary Events) risk score.

METHODS

This was a single-center cohort study, consecutively recruiting patients with adjudicated NSTE-ACS (n = 1,112) from the emergency department of an academic hospital. CTSS was measured in serum using enzyme-linked immunosorbent assay. All-cause mortality at 8 years was the primary endpoint. CV death was the secondary endpoint.

RESULTS

In total, 367 (33.0%) deaths were recorded. CTSS was associated with increased risk of all-cause mortality (HR for highest vs lowest quarter of CTSS: 1.89; 95% CI: 1.34-2.66; P < 0.001) and CV death (HR: 2.58; 95% CI: 1.15-5.77; P = 0.021) after adjusting for traditional CV risk factors, high-sensitivity C-reactive protein, left ventricular ejection fraction, high-sensitivity troponin-T, revascularization and index diagnosis (unstable angina/ non-ST-segment elevation myocardial infarction). When CTSS was added to the GRACE score, it conferred significant discrimination and reclassification value for all-cause mortality (Delta Harrell's C: 0.03; 95% CI: 0.012-0.047; P = 0.001; and net reclassification improvement = 0.202; P = 0.003) and CV death (AUC: 0.056; 95% CI: 0.017-0.095; P = 0.005; and net reclassification improvement = 0.390; P = 0.001) even after additionally considering high-sensitivity troponin-T and left ventricular ejection fraction.

CONCLUSIONS

Circulating CTSS is a predictor of long-term mortality and improves risk stratification of patients with NSTE-ACS over the GRACE score.

Hydrolysis improves the inhibition efficacy of bovine lactoferrin against infection by SARS-CoV-2 pseudovirus

The entry of SARS-CoV-2 into host cells may involve the spike protein cleavage by cathepsin L (CTSL). Certain food proteins such as lactoferrin (Lf) inhibit CTSL. The current study investigated the impact of hydrolysis (0–180 min) by proteinase K on electrophoretic pattern, secondary structure, cathepsin inhibitory and SARS-CoV-2 pseudovirus infectivity inhibitory of bovine Lf. Gel electrophoresis indicated that hydrolysis cut Lf molecules to half lobes (∼40 kDa) and produced peptides ≤18 kDa. Approximation of the secondary structural features through analysis of the second-derivative amide I band collected by infra-red spectroscopy suggested a correlative–causative relationship between cathepsin inhibition and the content of helix-unordered structures in Lf hydrolysate. The half maximal inhibitory concentration (IC₅₀) of Lf hydrolysed for 90 min (H90) against CTSL was about 100 times smaller than that of the Lf hydrolysed for 0 min (H0). H90 had also double activity against SARS-CoV-2 pseudo-types infectivity compared with H0.

New insights into macrophage subsets in atherosclerosis

Macrophages in atherosclerotic patients are notably plastic and heterogeneous. Single-cell RNA sequencing (Sc RNA-seq) can provide information about all the RNAs in individual cells, and it is used to identify cell subpopulations in atherosclerosis (AS) and reveal the heterogeneity of these cells. Recently, some findings from Sc RNA-seq experiments have suggested the existence of multiple macrophage subsets in atherosclerotic plaque lesions, and these subsets exhibit significant differences in their gene expression levels and functions. These cells affect various aspects of plaque lesion development, stabilization, and regression, as well as plaque rupture. This article aims to review the content and results of current studies that used RNA-seq to explore the different types of macrophages in AS and the related molecular mechanisms as well as to identify the potential roles of these macrophage types in the pathogenesis of atherosclerotic plaques. Also, this review listed some new therapeutic targets for delaying atherosclerotic lesion progression and treatment based on the experimental results.

Cathepsin K Deficiency Prevented Kidney Damage and Dysfunction in Response to 5/6 Nephrectomy Injury in Mice With or Without Chronic Stress

Background:

Chronic psychological stress is a risk factor for kidney disease, including kidney dysfunction and hypertension. Lysosomal CatK (cathepsin K) participates in various human pathobiologies. We investigated the role of CatK in kidney remodeling and hypertension in response to 5/6 nephrectomy injury in mice with or without chronic stress.

Methods:

Male 7-week-old WT (wild type; CatK^+/+) and CatK-deficient (CatK^−/−) mice that were or were not subjected to chronic stress underwent 5/6 nephrectomy. At 8 weeks post-stress/surgery, the stress was observed to have accelerated injury-induced glomerulosclerosis, proteinuria, and blood pressure elevation.

Results:

Compared with the nonstressed mice, the stressed mice showed increased levels of TLR (Toll-like receptor)-2/4, p22^phox, gp91^phox, CatK, MMP (matrix metalloproteinase)-2/9, collagen type I and III genes, PPAR-γ (peroxisome proliferator-activated receptor-gamma), NLRP-3 (NOD-like receptor thermal protein domain associated protein 3), p21, p16, and cleaved caspase-8 proteins, podocyte foot process effacement, macrophage accumulation, apoptosis, and decreased levels of Bcl-2 (B cell lymphoma 2) and Sirt1, as well as decreased glomerular desmin expression in the kidneys. These harmful changes were retarded by the genetic or pharmacological inhibition of CatK. Consistently, CatK inhibition ameliorated 5/6 nephrectomy–related kidney injury and dysfunction. In mesangial cells, CatK silencing or overexpression, respectively, reduced or increased the PPAR-γ and cleaved caspase-8 protein levels, providing evidence and a mechanistic explanation of CatK’s involvement in PPAR-γ/caspase-8–mediated cell apoptosis in response to superoxide and stressed serum.

Conclusions:

These results demonstrate that CatK plays an essential role in kidney remodeling and hypertension in response to 5/6 nephrectomy or stress, possibly via a reduction of glomerular inflammation, apoptosis, and fibrosis, suggesting a novel therapeutic strategy for controlling kidney injury in mice under chronic psychological stress conditions.

Radiotracers to Address Unmet Clinical Needs in Cardiovascular Imaging, Part 2: Inflammation, Fibrosis, Thrombosis, Calcification, and Amyloidosis Imaging

Cardiovascular imaging is evolving in response to systemwide trends toward molecular characterization and personalized therapies. The development of new radiotracers for PET and SPECT imaging is central to addressing the numerous unmet diagnostic needs that relate to these changes. In this 2-part review, we discuss select radiotracers that may help address key unmet clinical diagnostic needs in cardiovascular medicine. Part 1 examined key technical considerations pertaining to cardiovascular radiotracer development and reviewed emerging radiotracers for perfusion and neuronal imaging. Part 2 covers radiotracers for imaging cardiovascular inflammation, thrombosis, fibrosis, calcification, and amyloidosis. These radiotracers have the potential to address several unmet needs related to the risk stratification of atheroma, detection of thrombi, and the diagnosis, characterization, and risk stratification of cardiomyopathies. In the first section, we discuss radiotracers targeting various aspects of inflammatory responses in pathologies such as myocardial infarction, myocarditis, sarcoidosis, atherosclerosis, and vasculitis. In a subsequent section, we discuss radiotracers for the detection of systemic and device-related thrombi, such as those targeting fibrin (e.g., ⁶⁴Cu-labeled fibrin-binding probe 8). We also cover emerging radiotracers for the imaging of cardiovascular fibrosis, such as those targeting fibroblast activation protein (e.g., ⁶⁸Ga-fibroblast activation protein inhibitor). Lastly, we briefly review radiotracers for imaging of cardiovascular calcification (¹⁸F-NaF) and amyloidosis (e.g., ^99mTc-pyrophosphate and ¹⁸F-florbetapir).

Mucopolysaccharidosis Type IVA: Extracellular Matrix Biomarkers in Cardiovascular Disease

Cardiovascular disease (CVD) in Mucopolysaccharidosis Type IVA (Morquio A), signified by valvular disease and cardiac hypertrophy, is the second leading cause of death and remains untouched by current therapies. Enzyme replacement therapy (ERT) is the gold-standard treatment for MPS disorders including Morquio A. Early administration of ERT improves outcomes of patients from childhood to adulthood while posing new challenges including prognosis of CVD and ERT's negligible effect on cardiovascular health. Thus, having accurate biomarkers for CVD could be critical. Here we show that cathepsin S (CTSS) and elastin (ELN) can be used as biomarkers of extracellular matrix remodeling in Morquio A disease. We found in a cohort of 54 treatment naïve Morquio A patients and 74 normal controls that CTSS shows promising attributes as a biomarker in young Morquio A children. On the other hand, ELN shows promising attributes as a biomarker in adolescent and adult Morquio A. Plasma/urine keratan sulfate (KS), and urinary glycosaminoglycan (GAG) levels were significantly higher in Morquio A patients (p < 0.001) which decreased with age of patients. CTSS levels did not correlate with patients' phenotypic severity but differed significantly between patients (median range 5.45-8.52 ng/mL) and normal controls (median range 9.61-15.9 ng/mL; p < 0.001). We also studied α -2-macroglobulin (A2M), C-reactive protein (CRP), and circulating vascular cell adhesion molecule-1 (sVCAM-1) in a subset of samples to understand the relation between ECM biomarkers and the severity of CVD in Morquio A patients. Our experiments revealed that CRP and sVCAM-1 levels were lower in Morquio A patients compared to normal controls. We also observed a strong inverse correlation between urine/plasma KS and CRP (p = 0.013 and p = 0.022, respectively) in Morquio A patients as well as a moderate correlation between sVCAM-1 and CTSS in Morquio A patients at all ages (p = 0.03). As the first study to date investigating CTSS and ELN levels in Morquio A patients and in the normal population, our results establish a starting point for more elaborate studies in larger populations to understand how CTSS and ELN levels correlate with Morquio A severity.

The pathological role of damaged organelles in renal tubular epithelial cells in the progression of acute kidney injury

Acute kidney injury (AKI) is a common clinical condition associated with high morbidity and mortality. The pathogenesis of AKI has not been fully elucidated, with a lack of effective treatment. Renal tubular epithelial cells (TECs) play an important role in AKI, and their damage and repair largely determine the progression and prognosis of AKI. In recent decades, it has been found that the mitochondria, endoplasmic reticulum (ER), lysosomes, and other organelles in TECs are damaged to varying degrees in AKI, and that they can influence each other through various signaling mechanisms that affect the recovery of TECs. However, the association between these multifaceted signaling platforms, particularly between mitochondria and lysosomes during AKI remains unclear. This review summarizes the specific pathophysiological mechanisms of the main TECs organelles in the context of AKI, particularly the potential interactions among them, in order to provide insights into possible novel treatment strategies.

Major Vault Protein Prevents Atherosclerotic Plaque Destabilization by Suppressing Macrophage ASK1-JNK Signaling

BACKGROUND

Macrophages are implicated in atherosclerotic plaque instability by inflammation and degradation of extracellular matrix. However, the regulatory mechanisms driving these macrophage-associated processes are not well understood. Here, we aimed to identify the plaque destabilization-associated cytokines and signaling pathways in macrophages.

METHODS

The atherosclerotic models of myeloid-specific MVP (major vault protein) knockout mice and control mice were generated. Atherosclerotic instability, macrophage inflammatory signaling, and active cytokines released by macrophages were examined in vivo and in vitro by using cellular and molecular biological approaches.

RESULTS

MVP deficiency in myeloid cells exacerbated murine plaque instability by increasing production of both MMP (matrix metallopeptidase)-9 and proinflammatory cytokines in artery wall. Mechanistically, expression of MMP-9 was mediated via ASK1 (apoptosis signal-regulating kinase 1)-MKK-4 (mitogen-activated protein kinase kinase 4)-JNK (c-Jun N-terminal kinase) signaling in macrophages. MVP and its α-helical domain could bind with ASK1 and inhibit its dimerization and phosphorylation. A 62 amino acid peptide (MVP-[686-747]) in the α-helical domain of MVP showed a crucial role in preventing macrophage MMP-9 production and plaque instability.

CONCLUSIONS

MVP may act as an inhibitor for ASK1-JNK signaling-mediated MMP-9 production in macrophages and, thereby, attenuate unstable plaque formation. Our findings suggest that suppression of macrophage ASK1-JNK signaling may be a useful strategy antagonizing atherosclerotic diseases.

Therapeutic Targets for Heart Failure Identified Using Proteomics and Mendelian Randomization

BACKGROUND

Heart failure (HF) is a highly prevalent disorder for which disease mechanisms are incompletely understood. The discovery of disease-associated proteins with causal genetic evidence provides an opportunity to identify new therapeutic targets.

METHODS

We investigated the observational and causal associations of 90 cardiovascular proteins, which were measured using affinity-based proteomic assays. First, we estimated the associations of 90 cardiovascular proteins with incident heart failure by means of a fixed-effect meta-analysis of 4 population-based studies, composed of a total of 3019 participants with 732 HF events. The causal effects of HF-associated proteins were then investigated by Mendelian randomization, using cis-protein quantitative loci genetic instruments identified from genomewide association studies in more than 30 000 individuals. To improve the precision of causal estimates, we implemented an Mendelian randomization model that accounted for linkage disequilibrium between instruments and tested the robustness of causal estimates through a multiverse sensitivity analysis that included up to 120 combinations of instrument selection parameters and Mendelian randomization models per protein. The druggability of candidate proteins was surveyed, and mechanism of action and potential on-target side effects were explored with cross-trait Mendelian randomization analysis.

RESULTS

Forty-four of ninety proteins were positively associated with risk of incident HF (P<6.0×10-4). Among these, 8 proteins had evidence of a causal association with HF that was robust to multiverse sensitivity analysis: higher CSF-1 (macrophage colony-stimulating factor 1), Gal-3 (galectin-3) and KIM-1 (kidney injury molecule 1) were positively associated with risk of HF, whereas higher ADM (adrenomedullin), CHI3L1 (chitinase-3-like protein 1), CTSL1 (cathepsin L1), FGF-23 (fibroblast growth factor 23), and MMP-12 (matrix metalloproteinase-12) were protective. Therapeutics targeting ADM and Gal-3 are currently under evaluation in clinical trials, and all the remaining proteins were considered druggable, except KIM-1.

CONCLUSIONS

We identified 44 circulating proteins that were associated with incident HF, of which 8 showed evidence of a causal relationship and 7 were druggable, including adrenomedullin, which represents a particularly promising drug target. Our approach demonstrates a tractable roadmap for the triangulation of population genomic and proteomic data for the prioritization of therapeutic targets for complex human diseases.

Serum Metal Ion-Induced Cross-Linking of Photoelectrochemical Peptides and Circulating Proteins for Evaluating Cardiac Ischemia/Reperfusion

Patients having experienced the ischemia-reperfusion process are particularly vulnerable to subsequent heart attacks because this process can induce myocardial fibrosis, hallmarked by the release of reactive oxygen species and some proteases, such as cathepsin G, into the circulating blood. If these risk indicators can be monitored from the peripheral serum, early diagnosis and intervention may become a reality. For this purpose, we have designed an assay of free copper ions and cathepsin G in serum using only synthetic small molecules as the biosensing elements. No antibodies are needed to recognize the target protein, and no enzymes are needed to generate and amplify the biosensing signal. In this design, a short peptide can target-specifically recognize protease, while the copper ion in the serum can stimulate the photoelectrochemical activity of the probe, resulting in cross-linking of the serum proteins in a target protein-specific manner. Using this method, serum cathepsin G and free copper ion are found to be significantly elevated in the blood samples collected from patients with acute myocardial infarction and successful percutaneous coronary intervention in comparison with healthy controls, indicating a higher risk of subsequent myocardial injury and cardiovascular events. These results may point to the possible application of the proposed assay to evaluate the severity and prognosis of cardiac ischemia/reperfusion in the near future.

Circulating Cystatin C Is an Independent Risk Marker for Cardiovascular Outcomes, Development of Renal Impairment, and Long-Term Mortality in Patients With Stable Coronary Heart Disease: The LIPID Study

Background

Elevated plasma cystatin C levels reflect reduced renal function and increased cardiovascular risk. Less is known about whether the increased risk persists long‐term or is independent of renal function and other important biomarkers.

Methods and Results

Cystatin C and other biomarkers were measured at baseline (in 7863 patients) and 1 year later (in 6106 patients) in participants in the LIPID (Long‐Term Intervention with Pravastatin in Ischemic Disease) study, who had a previous acute coronary syndrome. Outcomes were ascertained during the study (median follow‐up, 6 years) and long‐term (median follow‐up, 16 years). Glomerular filtration rate (GFR) was estimated using Chronic Kidney Disease Epidemiology Collaboration equations (first GFR‐creatinine, then GFR‐creatinine‐cystatin C). Over 6 years, in fully adjusted multivariable time‐to‐event models, with respect to the primary end point of coronary heart disease mortality or nonfatal myocardial infarction, for comparison of Quartile 4 versus 1 of baseline cystatin C, the hazard ratio was 1.37 (95% CI, 1.07–1.74; P=0.01), and for major cardiovascular events was 1.47 (95% CI, 1.19–1.82; P<0.001). Over 16 years, the association of baseline cystatin C with coronary heart disease, cardiovascular, and all‐cause mortality persisted (each P<0.001) and remained significant after adjustment for estimated GFR‐creatinine‐cystatin C. Cystatin C also predicted the development of chronic kidney disease for 6 years (odds ratio, 6.61; 95% CI, 4.28–10.20) independently of estimated GFR‐creatinine and other risk factors. However, this association was no longer significant after adjustment for estimated GFR‐creatinine‐cystatin C.

Conclusions

Cystatin C independently predicted major cardiovascular events, development of chronic kidney disease, and cardiovascular and all‐cause mortality. Prediction of long‐term mortality was independent of improved estimation of GFR.

Registration

URL: https://anzctr.org.au; Unique identifier: ACTRN12616000535471.

Cathepsin S are involved in human carotid atherosclerotic disease progression, mainly by mediating phagosomes: bioinformatics and in vivo and vitro experiments

BACKGROUND

Atherosclerosis emerges as a result of multiple dynamic cell processes including endothelial damage, inflammatory and immune cell infiltration, foam cell formation, plaque rupture, and thrombosis. Animal experiments have indicated that cathepsins (CTSs) mediate the antigen transmission and inflammatory response involved in the atherosclerosis process, but the specific signal pathways and target cells of the CTSs involved in atherosclerosis are unknown.

METHODS

We used the GEO query package to download the dataset GSE28829 from the Gene Expression Omnibus (GEO) and filtered the data to check the standardization of the samples through the box chart. We then used the 'limma' package to analyze between-group differences and selected the corresponding differentially expressed genes of CTSs from the protein-protein interaction (PPI) network constructed with the STRING database, and then visualized the CTS-target genes. The best matching pathway and target cells were verified by a male mouse ligation experiment, single-sample GSEA (ssGSEA) analysis, and vitro experiment.

RESULTS

There were 275 differentially expressed genes (DEGs) selected from the GSE28829 dataset, and the DEGs were identified mainly in the PPI network; 58 core genes (APOE, CD74, CP, AIF1, etc.) target three selected CTS family members (CTSS, CTSB, and CTSC). After the enriched analysis, 15 CTS-target genes were markedly enriched in the phagosome signaling pathway. The mouse experiment results revealed that the percentages and numbers of monocytes and neutrophils and the number of CD68⁺ cells in CTSS deficiency (CatS^-/-) group were lower than those in the wildtype (CatS^+/+) group. CTSS mediating phagosome via macrophage were further verified by ssGSEA analysis and vitro experiment.

CONCLUSIONS

CTSS are the main target molecules in the CTS family that are involved in atherosclerosis. The molecule participate in the progression of atherosclerosis by mediating the phagosome via macrophage.

Helicobacter pylori and gastric cancer: a lysosomal protease perspective

The intimate involvement of pathogens with the heightened risk for developing certain cancers is an area of research that has captured a great deal of attention over the last 10 years. One firmly established paradigm that highlights this aspect of disease progression is in the instance of Helicobacter pylori infection and the contribution it makes in elevating the risk for developing gastric cancer. Whilst the molecular mechanisms that pinpoint the contribution that this microorganism inflicts towards host cells during gastric cancer initiation have come into greater focus, another picture that has also emerged is one that implicates the host's immune system, and the chronic inflammation that can arise therefrom, as being a central contributory factor in disease progression. Consequently, when taken with the underlying role that the extracellular matrix plays in the development of most cancers, and how this dynamic can be modulated by proteases expressed from the tumor or inflammatory cells, a complex and detailed relationship shared between the individual cellular components and their surroundings is coming into focus. In this review article, we draw attention to the emerging role played by the cathepsin proteases in modulating the stage-specific progression of Helicobacter pylori-initiated gastric cancer and the underlying immune response, while highlighting the therapeutic significance of this dynamic and how it may be amenable for novel intervention strategies within a basic research or clinical setting.

Adenosine-to-inosine RNA editing contributes to type I interferon responses in systemic sclerosis

OBJECTIVE

Adenosine deaminase acting on RNA-1 (ADAR1) enzyme is a type I interferon (IFN)-stimulated gene (ISG) catalyzing the deamination of adenosine-to-inosine, a process called A-to-I RNA editing. A-to-I RNA editing takes place mainly in Alu elements comprising a primate-specific level of post-transcriptional gene regulation. Whether RNA editing is involved in type I IFN responses in systemic sclerosis (SSc) patients remains unknown.

METHODS

ISG expression was quantified in skin biopsies and peripheral blood mononuclear cells derived from SSc patients and healthy subjects. A-to-I RNA editing was examined in the ADAR1-target cathepsin S (CTSS) by an RNA editing assay. The effect of ADAR1 on interferon-α/β-induced CTSS expression was assessed in human endothelial cells in vitro.

RESULTS

Increased expression levels of the RNA editor ADAR1, and specifically the long ADAR1p150 isoform, and its target CTSS are strongly associated with type I IFN signature in skin biopsies and peripheral blood derived from SSc patients. Notably, IFN-α/β-treated human endothelial cells show 8-10-fold increased ADAR1p150 and 23-35-fold increased CTSS expression, while silencing of ADAR1 reduces CTSS expression by 60-70%. In SSc patients, increased RNA editing rate of individual adenosines located in CTSS 3' UTR Alu elements is associated with higher CTSS expression (r = 0.36-0.6, P < 0.05 for all). Similar findings were obtained in subjects with activated type I IFN responses including SLE patients or healthy subjects after influenza vaccination.

CONCLUSION

ADAR1p150-mediated A-to-I RNA editing is critically involved in type I IFN responses highlighting the importance of post-transcriptional regulation of proinflammatory gene expression in systemic autoimmunity, including SSc.

Novel Cysteine Protease Inhibitor Derived from the Haementeria vizottoi Leech: Recombinant Expression, Purification, and Characterization

Cathepsin L (CatL) is a lysosomal cysteine protease primarily involved in the terminal degradation of intracellular and endocytosed proteins. More specifically, in humans, CatL has been implicated in cancer progression and metastasis, as well as coronary artery diseases and others. Given this, the search for potent CatL inhibitors is of great importance. In the search for new molecules to perform proteolytic activity regulation, salivary secretions from hematophagous animals have been an important source, as they present protease inhibitors that evolved to disable host proteases. Based on the transcriptome of the Haementeria vizzotoi leech, the cDNA of Cystatin-Hv was selected for this study. Cystatin-Hv was expressed in Pichia pastoris and purified by two chromatographic steps. The kinetic results using human CatL indicated that Cystatin-Hv, in its recombinant form, is a potent inhibitor of this protease, with a K_i value of 7.9 nM. Consequently, the present study describes, for the first time, the attainment and the biochemical characterization of a recombinant cystatin from leeches as a potent CatL inhibitor. While searching out for new molecules of therapeutic interest, this leech cystatin opens up possibilities for the future use of this molecule in studies involving cellular and in vivo models.

Inflammation during the life cycle of the atherosclerotic plaque

Inflammation orchestrates each stage of the life cycle of atherosclerotic plaques. Indeed, inflammatory mediators likely link many traditional and emerging risk factors with atherogenesis. Atheroma initiation involves endothelial activation with recruitment of leucocytes to the arterial intima, where they interact with lipoproteins or their derivatives that have accumulated in this layer. The prolonged and usually clinically silent progression of atherosclerosis involves periods of smouldering inflammation, punctuated by episodes of acute activation that may arise from inflammatory mediators released from sites of extravascular injury or infection or from subclinical disruptions of the plaque. Smooth muscle cells and infiltrating leucocytes can proliferate but also undergo various forms of cell death that typically lead to formation of a lipid-rich 'necrotic' core within the evolving intimal lesion. Extracellular matrix synthesized by smooth muscle cells can form a fibrous cap that overlies the lesion's core. Thus, during progression of atheroma, cells not only procreate but perish. Inflammatory mediators participate in both processes. The ultimate clinical complication of atherosclerotic plaques involves disruption that provokes thrombosis, either by fracture of the plaque's fibrous cap or superficial erosion. The consequent clots can cause acute ischaemic syndromes if they embarrass perfusion. Incorporation of the thrombi can promote plaque healing and progressive intimal thickening that can aggravate stenosis and further limit downstream blood flow. Inflammatory mediators regulate many aspects of both plaque disruption and healing process. Thus, inflammatory processes contribute to all phases of the life cycle of atherosclerotic plaques, and represent ripe targets for mitigating the disease.

Therapeutic potential of targeting cathepsin S in pulmonary fibrosis

Cathepsin S (CTSS), a lysosomal protease, belongs to a family of cysteine cathepsin proteases that promote degradation of damaged proteins in the endolysosomal pathway. Aberrant CTSS expression and regulation are associated with the pathogenesis of several diseases, including lung diseases. CTSS overexpression causes a variety of pathological processes, including pulmonary fibrosis, with increased CTSS secretion and accelerated extracellular matrix remodeling. Compared to many other cysteine cathepsin family members, CTSS has unique features that it presents limited tissue expression and retains its enzymatic activity at a neutral pH, suggesting its decisive involvement in disease microenvironments. In this review, we investigated the role of CTSS in lung disease, exploring recent studies that have indicated that CTSS mediates fibrosis in unique ways, along with its structure, substrates, and distinct regulation. We also outlined examples of CTSS inhibitors in clinical and preclinical development and proposed CTSS as a potential therapeutic target for pulmonary fibrosis.

Clickable, selective, and cell-permeable activity-based probe of human cathepsin B - Minimalistic approach for enhanced selectivity

Human cathepsin B is a cysteine-dependent protease whose roles in both normal and diseased cellular states remain yet to be fully delineated. This is primarily due to overlapping substrate specificities and lack of unambiguously annotated physiological functions. In this work, a selective, cell-permeable, clickable and tagless small molecule cathepsin B probe, KDA-1, is developed and kinetically characterized. KDA-1 selectively targets active site Cys25 residue of cathepsin B for labeling and can detect active cellular cathepsin B in proteomes derived from live human MDA-MB-231 breast cancer cells and HEK293 cells. It is anticipated that KDA-1 probe will find suitable applications in functional proteomics involving human cathepsin B enzyme.