Vorapaxar: The Current Role and Future Directions of a Novel Protease-Activated Receptor Antagonist for Risk Reduction in Atherosclerotic Disease

Stroke prevention strategies for cardiac surgery: a systematic review and meta-analysis of randomized controlled trials

BACKGROUND

Stroke is a much-feared complication of cardiac surgery, but existing literature on preventive strategies is fragmented. Hence, a systematic review and meta-analysis of stroke prevention strategies for cardiac surgery was conducted.

METHODS

An electronic literature search was conducted to retrieve randomized controlled trials (RCTs) investigating perioperative interventions for cardiac surgery, with stroke as an outcome. Random-effects meta-analyses were conducted to generate risk ratios (RRs), 95% confidence intervals (95% CI), and forest plots. Descriptive analysis and synthesis of literature was conducted for interventions not amenable to meta-analysis, focusing on risks of stroke, myocardial infarction and study-defined major adverse cardiovascular events (MACE).

RESULTS

Fifty-six RCTs (61 894 patients) were retrieved. Many included trials were underpowered to detect differences in stroke risk. Among pharmacological therapies, only preoperative amiodarone was shown to reduce stroke risk in one trial. Concomitant left atrial appendage closure (LAAC) significantly reduced stroke risk (RR = 0.55, 95% CI = 0.36-0.84, P = 0.006) in patients with preoperative atrial fibrillation, and there was no difference in on-pump versus off-pump coronary artery bypass grafting (CABG) (RR = 0.94, 95% CI = 0.64-1.37, P = 0.735). Much controversy exists in literature on the timing of carotid endarterectomy relative to CABG in patients with severe carotid stenosis. The use of preoperative remote ischemic preconditioning was not found to reduce rates of stroke or MACE.

CONCLUSION

This review presents a comprehensive synthesis of existing interventions for stroke prevention in cardiac surgery, and identifies gaps in research which may benefit from future, large-scale RCTs. LAAC should be considered to reduce stroke incidence in patients with preoperative atrial fibrillation.

Regulation of mitochondrial function by hydroquinone derivatives as prevention of platelet activation

Platelet activation plays an essential role in the pathogenesis of thrombotic events in different diseases (e.g., cancer, type 2 diabetes, Alzheimer's, and cardiovascular diseases, and even in patients diagnosed with coronavirus disease 2019). Therefore, antiplatelet therapy is essential to reduce thrombus formation. However, the utility of current antiplatelet drugs is limited. Therefore, identifying novel antiplatelet compounds is very important in developing new drugs. In this context, the involvement of mitochondrial function as an efficient energy source required for platelet activation is currently accepted; however, its contribution as an antiplatelet target still has little been exploited. Regarding this, the intramolecular hydrogen bonding of hydroquinone derivatives has been described as a structural motif that allows the reach of small molecules at mitochondria, which can exert antiplatelet activity, among others. In this review, we describe the role of mitochondrial function in platelet activation and how hydroquinone derivatives exert antiplatelet activity through mitochondrial regulation.

Protease-Activated Receptor Antagonist for Reducing Cardiovascular Events - A Review on Vorapaxar

Acute Coronary Syndrome (ACS) is a term that describes pathologies related to myocardial ischemia, and is comprised of unstable angina, non-ST elevation myocardial infarction, and ST elevation myocardial infarction. Urgent management of ACS is typically necessary to prevent future morbidity and mortality. Current medical recommendations of ACS management involve use of dual antiplatelet therapy, typically with aspirin and clopidogrel. However, newer therapies are being designed and researched to improve outcomes for patients with ACS. Vorapaxar is a novel antiplatelet therapy that inhibits thrombin-mediated platelet aggregation to prevent recurrence of ischemic events. It has been Food and Drug Administration approved for reduction of thrombotic cardiovascular events in patients with a history of MI or peripheral arterial disease with concomitant use of clopidogrel and/or aspirin, based upon the findings of the TRA 2°P-TIMI 50 trial. However, Vorapaxar was also found to have a significantly increased risk of bleeding, which must be considered when administering this drug. Based upon further subgroup analysis of both the TRA 2°P-TIMI 50 trial and TRACER trial, Vorapaxar was found to be potentially beneficial in patients with peripheral artery disease, coronary artery bypass grafting, and ischemic stroke. There are current trials in progress that are further evaluating the use of Vorapaxar in those conditions, and future research and trials are necessary to fully determine the utility of this drug.

Thromboprophylaxis with argatroban in critically ill patients with sepsis: a review

During sepsis, an initial prothrombotic shift takes place, in which coagulatory acute-phase proteins are increased, while anticoagulatory factors and platelet count decrease. Further on, the fibrinolytic system becomes impaired, which contributes to disease severity. At a later stage in sepsis, coagulation factors may become depleted, and sepsis patients may shift into a hypo-coagulable state with an increased bleeding risk. During the pro-coagulatory shift, critically ill patients have an increased thrombosis risk that ranges from developing micro-thromboses that impair organ function to life-threatening thromboembolic events. Here, thrombin plays a key role in coagulation as well as in inflammation. For thromboprophylaxis, low molecular weight heparins (LMWH) and unfractionated heparins (UFHs) are recommended. Nevertheless, there are conditions such as heparin resistance or heparin-induced thrombocytopenia (HIT), wherein heparin becomes ineffective or even puts the patient at an increased prothrombotic risk. In these cases, argatroban, a direct thrombin inhibitor (DTI), might be a potential alternative anticoagulatory strategy. Yet, caution is advised with regard to dosing of argatroban especially in sepsis. Therefore, the starting dose of argatroban is recommended to be low and should be titrated to the targeted anticoagulation level and be closely monitored in the further course of treatment. The authors of this review recommend using DTIs such as argatroban as an alternative anticoagulant in critically ill patients suffering from sepsis or COVID-19 with suspected or confirmed HIT, HIT-like conditions, impaired fibrinolysis, in patients on extracorporeal circuits and patients with heparin resistance, when closely monitored.

[The role of thrombin in the pathogenesis of atherosclerosis and its complications]

Thrombin is a key regulator of the homeostasis system. Also, it actively participates in progression of various systemic diseases, including atherosclerosis. There is a large amount of experimental and clinical data on the involvement of thrombin in the pathogenesis of ischemic heart disease (IHD). Thus, studying thrombin activity regulation is promising. Also, the question whether it is possible to use biomarkers of thrombin activity as predictors of cardiovascular complications in IHD patients is relevant. The present review focuses on major mechanisms of thrombin functioning, its role in development and progression of atherosclerosis, and available tests for evaluation of thrombin functional activity. Major clinical studies are discussed that evaluated the efficacy of thrombin inhibitors and protease-activated receptor antagonists.

A High-Throughput Phenotypic Screen of the 'Pandemic Response Box' Identifies a Quinoline Derivative with Significant Anthelmintic Activity

Parasitic nematodes cause diseases in livestock animals and major economic losses to the agricultural industry worldwide. Nematodes of the order Strongylida, including Haemonchus contortus, are particularly important. The excessive use of anthelmintic compounds to treat infections and disease has led to widespread resistance to these compounds in nematodes, such that there is a need for new anthelmintics with distinctive mechanisms of action. With a focus on discovering new anthelmintic entities, we screened 400 chemically diverse compounds within the 'Pandemic Response Box' (from Medicines for Malaria Venture, MMV) for activity against H. contortus and its free-living relative, Caenorhabditis elegans-a model organism. Using established phenotypic assays, test compounds were evaluated in vitro for their ability to inhibit the motility and/or development of H. contortus and C. elegans. Dose-response evaluations identified a compound, MMV1581032, that significantly the motility of H. contortus larvae (IC₅₀ = 3.4 ± 1.1 μM) and young adults of C. elegans (IC₅₀ = 7.1 ± 4.6 μM), and the development of H. contortus larvae (IC₅₀ = 2.2 ± 0.7 μM). The favourable characteristics of MMV1581032, such as suitable physicochemical properties and an efficient, cost-effective pathway to analogue synthesis, indicates a promising candidate for further evaluation as a nematocide. Future work will focus on a structure-activity relationship investigation of this chemical scaffold, a toxicity assessment of potent analogues and a mechanism/mode of action investigation.

Inhibitors of protease activated receptor 4 (PAR4): a review of recent patents (2013-2021)

INTRODUCTION

Protease-activated receptor 4 (PAR4), belonging to a subfamily of G-protein-coupled receptors (GPCR), is expressed on the surface of Human platelets, and the activation of it can lead to platelets aggregation. Studies demonstrated that PAR4 inhibition protect mice from arterial/arteriolar thrombosis, pulmonary embolism and cerebral infarct, while do not affect the haemostatic responses integrity. Therefore, PAR4 has been a promising target for the development of anti-thrombotic agents.

AREAS COVERED

This review covers recent patents and literature on PAR4 and their application published between 2013 and 2021.

EXPERT OPINION

PAR4 is a promising anti-thrombotic target and PAR4 inhibitors are important biologically active compounds for the treatment of thrombosis. Most the recent patents and literature focus on PAR4 selective inhibitors, and BMS-986120 and BMS-986141, which were developed by BMS, have entered clinical trials. With the deep understanding of the crystal structures and biological functions of PAR4, we believe that many other novel types of molecules targeting PAR4 would enter the clinical studies or the market.

Antiplasmodial activity of the natural product compounds alstonine and himbeline

Malaria, caused by Plasmodium parasites, continues to be a devastating global health issue. Despite a decline in malaria related deaths over the last decade, overall progress has plateaued. Key challenges to malaria prevention and control include the lack of a broadly effective vaccine and parasite drug resistance, including to the current gold standard artemisinin combination therapies (ACTs). New drugs with unique modes of action are therefore a priority for both the treatment and prevention of malaria. Unlike treatment drugs which need to kill parasites quickly to reduce or prevent clinical symptoms, compounds that kill parasites more slowly may be an option for malaria prevention. Natural products and natural product derived compounds have historically been an excellent source of antimalarial drugs, including the artemisinin component of ACTs. In this study, 424 natural product derived compounds were screened for in vitro activity against P. falciparum in assays designed to detect slow action activity, with 46 hit compounds identified as having >50% inhibition at 10 μM. Dose response assays revealed nine compounds with submicromolar activity, with slow action activity confirmed for two compounds, alstonine and himbeline (50% inhibitory concentration (IC₅₀) 0.17 and 0.58 μM, respectively). Both compounds displayed >140-fold better activity against P. falciparum versus two human cell lines (Selectivity Index (SI) >1,111 and > 144, respectively). Importantly, P. falciparum multi-drug resistant lines showed no cross-resistance to alstonine or himbeline, with some resistant lines being more sensitive to these two compounds compared to the drug sensitive line. In addition, alstonine displayed cross-species activity against the zoonotic species, P. knowelsi (IC₅₀ ~1 μM). Outcomes of this study provide a starting point for further investigations into these compounds as antiplasmodial drug candidates and the investigation of their molecular targets.

Protease-activated receptor 1 as a potential therapeutic target for COVID-19

Acute respiratory disease caused by a novel coronavirus (SARS-CoV-2) has spread all over the world, since its discovery in 2019, Wuhan, China. This disease is called COVID-19 and already killed over 1 million people worldwide. The clinical symptoms include fever, dry cough, dyspnea, headache, dizziness, generalized weakness, vomiting, and diarrhea. Unfortunately, so far, there is no validated vaccine, and its management consists mainly of supportive care. Venous thrombosis and pulmonary embolism are highly prevalent in patients suffering from severe COVID-19. In fact, a prothrombotic state seems to be present in most fatal cases of the disease. SARS-CoV-2 leads to the production of proinflammatory cytokines, causing immune-mediated tissue damage, disruption of the endothelial barrier, and uncontrolled thrombogenesis. Thrombin is the key regulator of coagulation and fibrin formation. In severe COVID-19, a dysfunctional of physiological anticoagulant mechanisms leads to a progressive increase of thrombin activity, which is associated with acute respiratory distress syndrome development and a poor prognosis. Protease-activated receptor type 1 (PAR1) is the main thrombin receptor and may represent an essential link between coagulation and inflammation in the pathophysiology of COVID-19. In this review, we discuss the potential role of PAR1 inhibition and regulation in COVID-19 treatment.

Influence of pentoxifylline on gene expression of PAG1/ miR-1206/ SNHG14 in ischemic heart disease

The regulation by immune checkpoint is able to prevent excessive tissue damage caused by ischemia reperfusion (I/R); therefore, the study aims to investigate the behavior of phosphoprotein associated with glycosphingolipid-enriched microdomains 1 (PAG1) mRNA, miR-1206 and small nucleolar RNA host gene 14 (SNHG14) during I/R and intake of pentoxifylline (PTX) as a protective drug. The relative expression level of PAG1/miR-1206/SNHG14 was determined by qRT-PCR. Cardiac tissue levels of cytotoxic T-lymphocyte associated antigen 4 (CTLA4) and PAG1 protein expression were determined by ELISA technique. The regulatory T cells achieved by the flow cytometry. The results found that the relative expression of SNHG14 was significantly upregulated in I/R, but suppressed in PTX treated groups with enhancement of the relative expression level of miR-1206. The gene and protein expression of PAG1 were downregulated with effective doses of PTX. The results showed that (30 and 40 mg/kg bwt) PTX dose suppressed the CTLA4 development significantly. The mean of the regulatory T cell in PTX protective groups is significantly reduced at (p < 0.001) in a comparison with I/R group. Spearman's correlation analysis revealed a significant negative correlation between SNHG14 and miR-1206, but a significant positive correlation between SNHG14 and PAG1 in I/R heart tissue. The results indicated that miR-1206 and SNHG14 can be used as biomarkers with perfect sensitivity and specificity. Using PTX reduced cardiac tissue damage. SNHG14 and miR-1206 can be used as a diagnostic tool in I/R.

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Positive correlation between SNHG14 and PAG1 relative expression in I/R heart tissues.

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SNHG14 and miR-1206 can be used as a diagnostic tool in ischemia reperfusion.

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Negative correlation between SNHG14 and miR-1206.

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Using pentoxifylline as a protective drug renders cardiac tissues more resistance to ischemia.

Protease-activated receptors: An illustrated review

Proteases are important regulators of cell behavior, survival, and apoptosis. They communicate to cells directly through a special class of G‐protein–coupled receptors known as protease‐activated receptors (PARs). N‐terminal PAR proteolysis unmasks a neo‐N‐terminus, which serves as a tethered ligand to activate PARs. Using this unique irreversible activation mechanism, PARs relay information across cell membranes. The year 2020 is the 30th year since discovery of the first member of this family, PAR1. In this illustrated review, we highlight achievements in the PAR field over the past 3 decades. Additionally, the known expression profiles of PARs in human tissues and across species are portrayed. We also illustrate the tethered ligand activation mechanism, which is unique to PARs, and PAR regulatory mechanisms. PAR1 was originally named “thrombin receptor” because thrombin was the first protease identified to activate PAR1. However, over the past 30 years, a growing number of proteases have been found to cleave PARs and trigger differential downstream signaling depending on cleavage site, cell type, and species. We exemplify the diversity of PAR1‐mediated signaling outcomes in platelets and endothelial cells as pertinent examples to the hemostasis, thrombosis, and vascular biology fields. Further, the termination and regulation of PAR signaling via endocytosis and currently available pharmacologic approaches are depicted. We conclude with portrayal of clinically translational aspects of PAR biology including pharmacologic manipulation and single‐nucleotide polymorphisms.

Cholesterol-Rich Microdomains Contribute to PAR1 Signaling in Platelets Despite a Weak Localization of the Receptor in These Microdomains

Platelet protease-activated receptor 1 (PAR1) is a cell surface G-protein-coupled receptor (GPCR) that acts as a thrombin receptor promoting platelet aggregation. Targeting the PAR1 pathway by vorapaxar, a PAR1 antagonist, leads to a reduction in ischemic events in cardiovascular patients with a history of myocardial infarction or with peripheral arterial disease. In platelets, specialized microdomains highly enriched in cholesterol act as modulators of the activity of several GPCRs and play a pivotal role in the signaling pathway. However, their involvement in platelet PAR1 function remains incompletely characterized. In this context, we aimed to investigate whether activation of PAR1 in human platelets requires its localization in the membrane cholesterol-rich microdomains. Using confocal microscopy, biochemical isolation, and proteomics approaches, we found that PAR1 was not localized in cholesterol-rich microdomains in resting platelets, and only a small fraction of the receptor relocated to the microdomains following its activation. Vorapaxar treatment increased the level of PAR1 at the platelet surface, possibly by reducing its endocytosis, while its colocalization with cholesterol-rich microdomains remained weak. Consistent with a cholesterol-dependent activation of Akt and p38 MAP kinase in thrombin receptor-activating peptide (TRAP)-activated platelets, the proteomic data of cholesterol-rich microdomains isolated from TRAP-activated platelets showed the recruitment of proteins contributing to these signaling pathways. In conclusion, contrary to endothelial cells, we found that PAR1 was only weakly present in cholesterol-rich microdomains in human platelets but used these microdomains for efficient activation of downstream signaling pathways following TRAP activation.

Factors Affecting the Formation and Treatment of Thrombosis by Natural and Synthetic Compounds

Venous thromboembolism (VTE) refers to deep vein thrombosis (DVT), whose consequence may be a pulmonary embolism (PE). Thrombosis is associated with significant morbidity and mortality and is the third most common cardiovascular disease after myocardial infarction and stroke. DVT is associated with the formation of a blood clot in a deep vein in the body. Thrombosis promotes slowed blood flow, hypoxia, cell activation, and the associated release of many active substances involved in blood clot formation. All thrombi which adhere to endothelium consist of fibrin, platelets, and trapped red and white blood cells. In this review, we summarise the impact of various factors affecting haemostatic disorders leading to blood clot formation. The paper discusses the causes of thrombosis, the mechanism of blood clot formation, and factors such as hypoxia, the involvement of endothelial cells (ECs), and the activation of platelets and neutrophils along with the effects of bacteria and reactive oxygen species (ROS). Mechanisms related to the action of anticoagulants affecting coagulation factors including antiplatelet drugs have also been discussed. However, many aspects related to the pathogenesis of thrombosis still need to be clarified. A review of the drugs used to treat and prevent thrombosis and natural anticoagulants that occur in the plant world and are traditionally used in Far Eastern medicine has also been carried out.

The domino effect triggered by the tethered ligand of the protease activated receptors

Protease activated receptors (PARs) are G-protein coupled receptors (GPCRs) that have a unique activation mechanism. Unlike other GPCRs that can be activated by free ligands, under physiological conditions, PARs are activated by the tethered ligand, which is a part of their N-terminus that is unmasked by proteolysis. It has been 30 years since the first member of the family, PAR1, was identified. In this review, we will discuss this unique tethered ligand mediate receptor activation of PARs in detail: how they interact with the proteases, the complex structural rearrangement of the receptors upon activation, and the termination of the signaling. We also summarize the structural studies of the PARs and how single nucleotide polymorphisms impact the receptor reactivity. Finally, we review the current strategies for inhibiting PAR function with therapeutic targets for anti-thrombosis. The focus of this review is PAR1 and PAR4 as they are the thrombin signal mediators on human platelets and therapeutics targets. We also include the structural studies of PAR2 as it informs the mechanism of action for PARs in general.

Granzyme A in Chikungunya and Other Arboviral Infections

Granzyme A (GzmA) is secreted by cytotoxic lymphocytes and has traditionally been viewed as a mediator of cell death. However, a growing body of data suggests the physiological role of GzmA is promotion of inflammation. Here, we show that GzmA is significantly elevated in the sera of chikungunya virus (CHIKV) patients and that GzmA levels correlated with viral loads and disease scores in these patients. Serum GzmA levels were also elevated in CHIKV mouse models, with NK cells the likely source. Infection of mice deficient in type I interferon responses with CHIKV, Zika virus, or dengue virus resulted in high levels of circulating GzmA. We also show that subcutaneous injection of enzymically active recombinant mouse GzmA was able to mediate inflammation, both locally at the injection site as well as at a distant site. Protease activated receptors (PARs) may represent targets for GzmA, and we show that treatment with PAR antagonist ameliorated GzmA- and CHIKV-mediated inflammation.

Using PAR4 Inhibition as an Anti-Thrombotic Approach: Why, How, and When?

Protease-activated receptors (PARs) are a family of four GPCRs with a variety of cellular functions, yet the only advanced clinical endeavours to target these receptors for therapeutic gain to date relates to the impairment of platelet function for anti-thrombotic therapy. The only approved PAR antagonist is the PAR1 inhibitor, vorapaxar—the sole anti-platelet drug against a new target approved in the past 20 years. However, there are two PARs on human platelets, PAR1 and PAR4, and more recent efforts have focused on the development of the first PAR4 antagonists, with first-in-class agents recently beginning clinical trial. Here, we review the rationale for this approach, outline the various modes of PAR4 inhibition, and speculate on the specific therapeutic potential of targeting PAR4 for the prevention of thrombotic conditions.

Role of NF-κB in Platelet Function

Platelets are megakaryocyte-derived fragments lacking nuclei and prepped to maintain primary hemostasis by initiating blood clots on injured vascular endothelia. Pathologically, platelets undergo the same physiological processes of activation, secretion, and aggregation yet with such pronouncedness that they orchestrate and make headway the progression of atherothrombotic diseases not only through clot formation but also via forcing a pro-inflammatory state. Indeed, nuclear factor-κB (NF-κB) is largely implicated in atherosclerosis and its pathological complication in atherothrombotic diseases due to its transcriptional role in maintaining pro-survival and pro-inflammatory states in vascular and blood cells. On the other hand, we know little on the functions of platelet NF-κB, which seems to function in other non-genomic ways to modulate atherothrombosis. Therein, this review will resemble a rich portfolio for NF-κB in platelets, specifically showing its implications at the levels of platelet survival and function. We will also share the knowledge thus far on the effects of active ingredients on NF-κB in general, as an extrapolative method to highlight the potential therapeutic targeting of NF-κB in coronary diseases. Finally, we will unzip a new horizon on a possible extra-platelet role of platelet NF-κB, which will better expand our knowledge on the etiology and pathophysiology of atherothrombosis.

Pharmacological PAR-1 inhibition reduces blood glucose levels but does not improve kidney function in experimental type 2 diabetic nephropathy

Vorapaxar-dependent protease-activated receptor (PAR)-1 inhibition diminishes diabetic nephropathy in experimental type 1 diabetes. As most patients with diabetic nephropathy suffer from type 2 diabetes, the aim of this study was to investigate whether PAR-1 inhibition also limits diabetic nephropathy in experimental type 2 diabetes. Consequently, leptin-deficient black and tan brachyuric (BTBR^ob/ob) mice were randomly assigned to vorapaxar (1.75 mg/kg; twice weekly via oral gavage) or vehicle treatment, whereas matched wild-type (WT) BTBR (BTBR^WT) mice served as nondiabetic controls. Weight and (nonfasting) blood glucose levels were monitored for up to 18 wk, after which kidney function and histologic damage was evaluated postmortem. We show that blood glucose levels and body weight increased in diabetic BTBR^ob/ob mice compared with nondiabetic BTBR^WT controls. Vorapaxar-dependent PAR-1 inhibition reduced but did not normalize blood glucose levels in BTBR^ob/ob mice, whereas it potentiated the increase in body weight. Vorapaxar did not, however, preserve kidney function, whereas it only minimally reduced histopathological signs of kidney injury. Overall, we thus show that PAR-1 inhibition reduces blood glucose levels during the progression of diabetic nephropathy in experimental type 2 diabetes but does not improve renal function. This is in contrast to the therapeutic potential of vorapaxar in type 1 diabetes-induced nephropathy, highlighting the importance of disease-dependent treatment modalities.-Waasdorp, M., Florquin, S., Duitman, J., Spek, C. A. Pharmacological PAR-1 inhibition reduces blood glucose levels but does not improve kidney function in experimental type 2 diabetic nephropathy.

Activation of calcium signaling in human gingival fibroblasts by recombinant Porphyromonas gingivalis RgpB protein

Arginine-specific cysteine proteinases, such as Arg-gingipain B (RgpB), mediate inflammation by activating protease-activated receptors (PARs). Arg-gingipain B is produced by Porphyromonas gingivalis, and is implicated in the causation of periodontal disease. The purpose of the present study was to observe the influence of recombinant RgpB protein (rRgpB) on PAR activation by monitoring intracellular Ca2+ ion concentration ([Ca2+]i) and inositol-1,4,5-triphosphate (IP3) levels in human gingival fibroblasts (HGFs). Our findings showed that rRgpB could cause a transient increase in [Ca2+]i. This increase in [Ca2+]i was completely suppressed by vorapaxar, a PAR-1 antagonist. Recombinant Arg-gingipain B increased the concentration of IP3, reaching a maximum at 60 s after treatment; this was completely inhibited by vorapaxar. We therefore conclude that rRgpB-induced calcium signaling in HGFs is mainly caused by PAR-1 activation. This suggests that PAR-1 activation plays a significant role in chronic inflammatory periodontal disease induced by P. gingivalis RgpB.

Vorapaxar stabilizes permeability of the endothelial barrier under cholesterol stimulation via the AKT/JNK and NF‑κB signaling pathways

Atherosclerosis (AS) is an inflammatory disease that occurs in the arterial wall and is characterized by progressive lipid accumulation within the intima of large arteries, leading to the dysfunction of endothelial cells and further destruction of the endothelial barrier and vascular tone. Arterial intima injury accelerates the adhesion and activation of platelets at the injury site. The activation of platelets results in the secretion of growth factors, leading to the migration and proliferation of vascular smooth muscle cells (VSMCs), promoting the formation of plaque, resulting in the formation of thrombus. The present study found that vorapaxar could alleviate the inflammatory response induced by a high concentration of cholesterol stimulation and increase the release of nitric oxide (NO) via the protein kinase B (AKT) signaling pathway and regulation of the intracellular concentration of Ca2+ ([Ca2+]i). We also found that vorapaxar could reduce the damage of DNA caused by cholesterol stimulation and regulate the cell cycle via the AKT/JNK signaling pathway and its downstream molecules glycogen synthase kinase 3β (GSK‑3β) and connexin 43, maintaining the integrity of the endothelial barrier and proliferation of endothelial cells, serving a protective role in endothelial cells.

Fixing the Unfixable: The Art of Optimizing Natural Products for Human Medicine

Molecules isolated from natural sources including bacteria, fungi, and plants are a long-standing source of therapeutics that continue to add to our medicinal arsenal today. Despite their potency and prominence in the clinic, complex natural products often exhibit a number of liabilities that hinder their development as therapeutics, which may be partially responsible for the current trend away from natural product discovery, research, and development. However, advances in synthetic biology and organic synthesis have inspired a new generation of natural product chemists to tackle powerful undeveloped scaffolds. In this Perspective, we will present case studies demonstrating the historical and current focus on making targeted, but significant, changes to natural product scaffolds via biosynthetic gene cluster manipulation, total synthesis, semisynthesis, or a combination of these methods, with a focus on increasing activity, decreasing toxicity, or improving chemical and pharmacological properties.

Protease-Activated Receptor 4 (PAR4): A Promising Target for Antiplatelet Therapy

Cardiovascular diseases (CVDs) are currently among the leading causes of death worldwide. Platelet aggregation is a key cellular component of arterial thrombi and major cause of CVDs. Protease-activated receptors (PARs), including PAR1, PAR2, PAR3 and PAR4, fall within a subfamily of seven-transmembrane G-protein-coupled receptors (GPCR). Human platelets express PAR1 and PAR4, which contribute to the signaling transduction processes. In association with CVDs, PAR4 not only contributes to platelet activation but also is a modulator of cellular responses that serve as hallmarks of inflammation. Although several antiplatelet drugs are available on the market, they have many side effects that limit their use. Emerging evidence shows that PAR4 targeting is a safer strategy for preventing thrombosis and consequently may improve the overall cardiac safety profile. Our present review summarizes the PAR4 structural characteristics, activation mechanism, role in the pathophysiology of diseases and understanding the association of PAR4 targeting for improved cardiac protection. Conclusively, this review highlights the importance of PAR4 antagonists and its potential utility in different CVDs.

Cyclic Nucleotide-Directed Protein Kinases in Cardiovascular Inflammation and Growth

Cardiovascular disease (CVD), including myocardial infarction (MI) and peripheral or coronary artery disease (PAD, CAD), remains the number one killer of individuals in the United States and worldwide, accounting for nearly 18 million (>30%) global deaths annually. Despite considerable basic science and clinical investigation aimed at identifying key etiologic components of and potential therapeutic targets for CVD, the number of individuals afflicted with these dreaded diseases continues to rise. Of the many biochemical, molecular, and cellular elements and processes characterized to date that have potential to control foundational facets of CVD, the multifaceted cyclic nucleotide pathways continue to be of primary basic science and clinical interest. Cyclic adenosine monophosphate (cyclic AMP) and cyclic guanosine monophosphate (cyclic GMP) and their plethora of downstream protein kinase effectors serve ubiquitous roles not only in cardiovascular homeostasis but also in the pathogenesis of CVD. Already a major target for clinical pharmacotherapy for CVD as well as other pathologies, novel and potentially clinically appealing actions of cyclic nucleotides and their downstream targets are still being discovered. With this in mind, this review article focuses on our current state of knowledge of the cyclic nucleotide-driven serine (Ser)/threonine (Thr) protein kinases in CVD with particular emphasis on cyclic AMP-dependent protein kinase (PKA) and cyclic GMP-dependent protein kinase (PKG). Attention is given to the regulatory interactions of these kinases with inflammatory components including interleukin 6 signals, with G protein-coupled receptor and growth factor signals, and with growth and synthetic transcriptional platforms underlying CVD pathogenesis. This article concludes with a brief discussion of potential future directions and highlights the importance for continued basic science and clinical study of cyclic nucleotide-directed protein kinases as emerging and crucial controllers of cardiac and vascular disease pathologies.