A small-molecule inhibitor of PCSK9 transcription ameliorates atherosclerosis through the modulation of FoxO1/3 and HNF1α

A novel small-molecule PCSK9 inhibitor E28362 ameliorates hyperlipidemia and atherosclerosis

Proprotein convertase subtilisin/kexin type 9 (PCSK9) binds to the epidermal growth factor precursor homologous domain A (EGF-A) of low-density lipoprotein receptor (LDLR) in the liver and triggers the degradation of LDLR via the lysosomal pathway, consequently leading to an elevation in plasma LDL-C levels. Inhibiting PCSK9 prolongs the lifespan of LDLR and maintains cholesterol homeostasis in the body. Thus, PCSK9 is an innovative pharmacological target for treating hypercholesterolemia and atherosclerosis. In this study, we discovered that E28362 was a novel small-molecule PCSK9 inhibitor by conducting a virtual screening of a library containing 40,000 compounds. E28362 (5, 10, 20 μM) dose-dependently increased the protein levels of LDLR in both total protein and the membrane fraction in both HepG2 and AML12 cells, and enhanced the uptake of DiI-LDL in AML12 cells. MTT assay showed that E28362 up to 80 μM had no obvious toxicity in HepG2, AML12, and HEK293a cells. The effects of E28362 on hyperlipidemia and atherosclerosis were evaluated in three different animal models. In high-fat diet-fed golden hamsters, administration of E28362 (6.7, 20, 60 mg·kg-1·d-1, i.g.) for 4 weeks significantly reduced plasma total cholesterol (TC), triglyceride (TG), low-density lipoprotein-cholesterol (LDL-C) and PCSK9 levels, and reduced liver TC and TG contents. In Western diet-fed ApoE-/- mice (20, 60 mg·kg-1·d-1, i.g.) and human PCSK9 D374Y overexpression mice (60 mg·kg-1·d-1, i.g.), administration of E28362 for 12 weeks significantly decreased plasma LDL-C levels and the area of atherosclerotic lesions in en face aortas and aortic roots. Moreover, E28362 significantly increased the protein expression level of LDLR in the liver. We revealed that E28362 selectively bound to PCSK9 in HepG2 and AML12 cells, blocked the interaction between LDLR and PCSK9, and induced the degradation of PCSK9 through the ubiquitin-proteasome pathway, which finally resulted in increased LDLR protein levels. In conclusion, E28362 can block the interaction between PCSK9 and LDLR, induce the degradation of PCSK9, increase LDLR protein levels, and alleviate hyperlipidemia and atherosclerosis in three distinct animal models, suggesting that E28362 is a promising lead compound for the treatment of hyperlipidemia and atherosclerosis.

Atherosclerotic three-layer nanomatrix vascular sheets for high-throughput therapeutic evaluation

In vitro atherosclerosis models are essential to evaluate therapeutics before in vivo and clinical studies, but significant limitations remain, such as the lack of three-layer vascular architecture and limited atherosclerotic features. Moreover, no scalable 3D atherosclerosis model is available for making high-throughput assays for therapeutic evaluation. Herein, we report an in vitro 3D three-layer nanomatrix vascular sheet with critical atherosclerosis multi-features (VSA), including endothelial dysfunction, monocyte recruitment, macrophages, extracellular matrix remodeling, smooth muscle cell phenotype transition, inflammatory cytokine secretion, foam cells, and calcification initiation. Notably, we present the creation of high-throughput functional assays with VSAs and the use of these assays for evaluating therapeutics for atherosclerosis treatment. The therapeutics include conventional drugs (statin and sirolimus), candidates for treating atherosclerosis (curcumin and colchicine), and potential gene therapy (miR-146a-loaded liposomes). The high efficiency and flexibility of the scalable VSA functional assays should facilitate drug discovery and development for atherosclerosis.

Targeting proprotein convertase subtilisin/kexin type 9 (PCSK9): from bench to bedside

Proprotein convertase subtilisin/kexin type 9 (PCSK9) has evolved as a pivotal enzyme in lipid metabolism and a revolutionary therapeutic target for hypercholesterolemia and its related cardiovascular diseases (CVD). This comprehensive review delineates the intricate roles and wide-ranging implications of PCSK9, extending beyond CVD to emphasize its significance in diverse physiological and pathological states, including liver diseases, infectious diseases, autoimmune disorders, and notably, cancer. Our exploration offers insights into the interaction between PCSK9 and low-density lipoprotein receptors (LDLRs), elucidating its substantial impact on cholesterol homeostasis and cardiovascular health. It also details the evolution of PCSK9-targeted therapies, translating foundational bench discoveries into bedside applications for optimized patient care. The advent and clinical approval of innovative PCSK9 inhibitory therapies (PCSK9-iTs), including three monoclonal antibodies (Evolocumab, Alirocumab, and Tafolecimab) and one small interfering RNA (siRNA, Inclisiran), have marked a significant breakthrough in cardiovascular medicine. These therapies have demonstrated unparalleled efficacy in mitigating hypercholesterolemia, reducing cardiovascular risks, and have showcased profound value in clinical applications, offering novel therapeutic avenues and a promising future in personalized medicine for cardiovascular disorders. Furthermore, emerging research, inclusive of our findings, unveils PCSK9's potential role as a pivotal indicator for cancer prognosis and its prospective application as a transformative target for cancer treatment. This review also highlights PCSK9's aberrant expression in various cancer forms, its association with cancer prognosis, and its crucial roles in carcinogenesis and cancer immunity. In conclusion, this synthesized review integrates existing knowledge and novel insights on PCSK9, providing a holistic perspective on its transformative impact in reshaping therapeutic paradigms across various disorders. It emphasizes the clinical value and effect of PCSK9-iT, underscoring its potential in advancing the landscape of biomedical research and its capabilities in heralding new eras in personalized medicine.

Identification of benzothiazoles as novel PCSK9 inhibitors

Proprotein convertase subtilisin kexin type 9 (PCSK9) is a clinically validated target on the treatment of cardiovascular disease (CVD). PCSK9 can regulate the hepatocyte surface low density lipoprotein receptor (LDLR) level by binding to LDLR and leading to their degradation in the lysosome. The clinical use of two monoclonal antibodies (alirocumab and evolocumab, approved in 2015) and one small interfering RNA (inclisiran, approved in 2020) which can inhibit PCSK9 function proved that they are very effective in lowering low density lipoprotein cholesterol (LDL-C). However, the high treatment costs and parenteral administration of these drugs prohibited widespread use and reduced their long-term advantage. Comparatively, small molecule drugs have many incomparable advantages of macromolecules, such as lower treatment cost, more drug administration options, superior pharmacokinetic properties, less adverse immunogenic responses and better affordable production. In this paper, we identified a series of benzothiazoles small molecule PCSK9 inhibitors through extensive screening. The structure and activity relationship (SAR) was summarized to facilitate further optimization. Moreover, the primary mechanism of action of the most potent compound was also investigated.

Role of proprotein convertase subtilisin/kexin type 9 (PCSK9) in diabetic complications

Cardiovascular disease (CVD) complications have remained a major cause of death among patients with diabetes. Hence, there is a need for effective therapeutics against diabetes-induced CVD complications. Since its discovery, proprotein convertase subtilisin/kexin type 9 (PCSK9) has been reported to be involved in the pathology of various CVDs, with studies showing a positive association between plasma levels of PCSK9, hyperglycemia, and dyslipidemia. PCSK9 regulates lipid homeostasis by interacting with low-density lipoprotein receptors (LDLRs) present in hepatocytes and subsequently induces LDLR degradation via receptor-mediated endocytosis, thereby reducing LDL uptake from circulation. In addition, PCSK9 also induces pro-inflammatory cytokine expression and apoptotic cell death in diabetic-CVD. Furthermore, therapies designed to inhibit PCSK9 effectively reduces diabetic dyslipidemia with clinical studies reporting reduced cardiovascular events in patients with diabetes and no significant adverse effect on glycemic controls. In this review, we discuss the role of PCSK9 in the pathogenesis of diabetes-induced CVD and the potential mechanisms by which PCSK9 inhibition reduces cardiovascular events in diabetic patients.

Effect of PCSK9 on atherosclerotic cardiovascular diseases and its mechanisms: Focus on immune regulation

Atherosclerosis is a basic pathological characteristic of many cardiovascular diseases, and if not effectively treated, patients with such disease may progress to atherosclerotic cardiovascular diseases (ASCVDs) and even heart failure. The level of plasma proprotein convertase subtilisin/kexin type 9 (PCSK9) is significantly higher in patients with ASCVDs than in the healthy population, suggesting that it may be a promising new target for the treatment of ASCVDs. PCSK9 produced by the liver and released into circulation inhibits the clearance of plasma low-density lipoprotein-cholesterol (LDL-C), mainly by downregulating the level of LDL-C receptor (LDLR) on the surface of hepatocytes, leading to upregulated LDL-C in plasma. Numerous studies have revealed that PCSK9 may cause poor prognosis of ASCVDs by activating the inflammatory response and promoting the process of thrombosis and cell death independent of its lipid-regulatory function, yet the underlying mechanisms still need to be further clarified. In patients with ASCVDs who are intolerant to statins or whose plasma LDL-C levels fail to descend to the target value after treatment with high-dose statins, PCSK9 inhibitors often improve their clinical outcomes. Here, we summarize the biological characteristics and functional mechanisms of PCSK9, highlighting its immunoregulatory function. We also discuss the effects of PCSK9 on common ASCVDs.

Structure-activity relationship and biological evaluation of xanthine derivatives as PCSK9 inhibitors for the treatment of atherosclerosis

Developing non-statin small molecules for the treatment of hypercholesterolemia remains challenging. The proprotein convertase subtilisin/kexin type 9 (PCSK9)-targeted therapies have attracted considerable attentions. Forty-five 7030B-C5 derivatives were synthesized and evaluated for the PCSK9 repression activity, taking the PCSK9 transcriptional inhibitor 7030B-C5 as the lead. Structure-activity relationship (SAR) analysis at C8 and N7-position was carried out, and compound 3s and 5r exhibited comparable PCSK9 transcriptional inhibitory activity but much lower cytotoxicity with the therapeutic index (TI) values doubled of that of 7030B-C5. In the in vitro assay, both compounds significantly reduced the level of PCSK9 protein and increased LDL receptor (LDLR) protein level. What's more, both compounds promoted LDL cholesterol (LDL-C) clearance more efficiently than 7030B-C5 in HepG2 cells. Most importantly, compound 3s reduced the atherosclerotic plaque areas with promising lipid-lowing effects in ApoE KO mice with a higher in vivo activity and lower toxicity. The regulatory mechanism of 3s was explored that it might target the transcription factor HNF1α and/or HINFP upstream of PCSK9 transcription, similar to that of 7030B-C5. Thus, 3s was considered as a potential anti-atherosclerosis drug candidate as a novel PCSK9 down-regulatory agent, worthy of further investigations.

PCSK9 Inhibition: From Current Advances to Evolving Future

Proprotein convertase subtilisin/kexin type 9 (PCSK9) is a secretory serine protease synthesized primarily by the liver. It mainly promotes the degradation of low-density lipoprotein receptor (LDL-R) by binding LDL-R, reducing low-density lipoprotein cholesterol (LDL-C) clearance. In addition to regulating LDL-R, PCSK9 inhibitors can also bind Toll-like receptors (TLRs), scavenger receptor B (SR-B/CD36), low-density lipoprotein receptor-related protein 1 (LRP1), apolipoprotein E receptor-2 (ApoER2) and very-low-density lipoprotein receptor (VLDL-R) reducing the lipoprotein concentration and slowing thrombosis. In addition to cardiovascular diseases, PCSK9 is also used in pancreatic cancer, sepsis, and Parkinson’s disease. Currently marketed PCSK9 inhibitors include alirocumab, evolocumab, and inclisiran, as well as small molecules, nucleic acid drugs, and vaccines under development. This review systematically summarized the application, preclinical studies, safety, mechanism of action, and latest research progress of PCSK9 inhibitors, aiming to provide ideas for the drug research and development and the clinical application of PCSK9 in cardiovascular diseases and expand its application in other diseases.

Transcriptional control by HNF-1: Emerging evidence showing its role in lipid metabolism and lipid metabolism disorders

The present review focuses on the roles and underlying mechanisms of action of hepatic nuclear factor-1 (HNF-1) in lipid metabolism and the development of lipid metabolism disorders. HNF-1 is a transcriptional regulator that can form homodimers, and the HNF-1α and HNF-1β isomers can form heterodimers. Both homo- and heterodimers recognize and bind to specific cis-acting elements in gene promoters to transactivate transcription and to coordinate the expression of target lipid-related genes, thereby influencing the homeostasis of lipid metabolism. HNF-1 was shown to restrain lipid anabolism, including synthesis, absorption, and storage, by inhibiting the expression of lipogenesis-related genes, such as peroxisome proliferator-activated receptor γ (PPARγ) and sterol regulatory element-binding protein-1/2 (SREBP-1/2). Moreover, HNF-1 enhances the expression of various genes, such as proprotein convertase subtilisin/kexin type 9 (PCSK9), glutathione peroxidase 1 (GPx1), and suppressor of cytokine signaling-3 (SOCS-3) and negatively regulates signal transducer and activator of transcription (STAT) to facilitate lipid catabolism in hepatocytes. HNF-1 reduces hepatocellular lipid decomposition, which alleviates the progression of nonalcoholic fatty liver disease (NAFLD). HNF-1 impairs preadipocyte differentiation to reduce the number of adipocytes, stunting the development of obesity. Furthermore, HNF-1 reduces free cholesterol levels in the plasma to inhibit aortic lipid deposition and lipid plaque formation, relieving dyslipidemia and preventing the development of atherosclerotic cardiovascular disease (ASCVD). In summary, HNF-1 transcriptionally regulates lipid-related genes to manipulate intracorporeal balance of lipid metabolism and to suppress the development of lipid metabolism disorders.

Regulatory Non-Coding RNAs in Familial Hypercholesterolemia, Theranostic Applications

Familial hypercholesterolemia (FH) is a common monogenic disease which is associated with high serum levels of low-density lipoprotein cholesterol (LDL-C) and leads to atherosclerosis and cardiovascular disease (CVD). Early diagnosis and effective treatment strategy can significantly improve prognosis. Recently, non-coding RNAs (ncRNAs) have emerged as novel biomarkers for the diagnosis and innovative targets for therapeutics. Non-coding RNAs have essential roles in the regulation of LDL-C homeostasis, suggesting that manipulation and regulating ncRNAs could be a promising theranostic approach to ameliorate clinical complications of FH, particularly cardiovascular disease. In this review, we briefly discussed the mechanisms and pathophysiology of FH and novel therapeutic strategies for the treatment of FH. Moreover, the theranostic effects of different non-coding RNAs for the treatment and diagnosis of FH were highlighted. Finally, the advantages and disadvantages of ncRNA-based therapies vs. conventional therapies were discussed.

20(S)-Protopanaxadiol decreases atherosclerosis in ApoE KO mice by increasing the levels of LDLR and inhibiting its binding with PCSK9

Chinese medicinal and edible plants such as Panax notoginseng and ginseng are widely used for the treatment of atherosclerosis (AS). AS is the main pathological basis of cardiac-cerebral vascular disease, which seriously threatens human health and quality of life. Low-density lipoprotein (LDL) is the main pathogenic factor of AS. The LDL receptor (LDLR) is an important protein that functions to mediate the uptake and degradation of plasma LDL. Proprotein Convertase Subtilisin/Kexin Type 9 (PCSK9) can mediate the internalization and degradation of LDLR. So, increasing the LDLR level by inhibiting PCSK9 is an important means of prevention and treatment of AS. In this study, by combining interaction technology (surface plasmon resonance, SPR) of small molecule compounds with membrane receptor proteins, cell experiments, and in vivo experiments, it is proved for the first time that 20(S)-protopanaxadiol (PPD), as a hydrolytic product of Panax notoginseng saponins in the intestinal tract, can bind to the extracellular domain of LDLR and inhibit the role of Proprotein Convertase Subtilisin/Kexin Type 9 (PCSK9) in mediating LDLR degradation. The results showed that PPD significantly reduced aortic plaques and hepatic steatosis in HFD-fed ApoE KO mice. LDLR protein levels were elevated in the liver tissues isolated from PPD-treated HFD-fed ApoE KO mice and PPD-treated HepG2 cells. Our findings demonstrated that PPD significantly increased LDLR levels and reduced AS in the HFD-fed ApoE KO mice on account of LDLR degradation being inhibited by PPD inhibiting the interaction between PCSK9 and LDLR.

A mathematical model of in vitro hepatocellular cholesterol and lipoprotein metabolism for hyperlipidemia therapy

Cardiovascular diseases associated with high cholesterol (hypercholesterolemia) and low-density lipoproteins (LDL) levels are significant contributors to total mortality in developing and developed countries. Mathematical modeling of LDL metabolism is an important step in the development of drugs for hypercholesterolemia. The aim of this work was to develop and to analyze an integrated mathematical model of cholesterol metabolism in liver cells and its interaction with two types of drugs, statins and PCSK9 inhibitors. The model consisted of 21 ordinary differential equations (ODE) describing cholesterol biosynthesis and lipoprotein endocytosis in liver cells in vitro. The model was tested for its ability to mimic known biochemical effects of familial hypercholesterolemia, statin therapy, and PCSK9 inhibitors. The model qualitatively reproduced the well-known biology of cholesterol regulation, which confirms its potential for minimizing cellular research in initial testing of new drugs for cardiology.

Targeted Strategy in Lipid-Lowering Therapy

Dyslipidemia is characterized by a diminished lipid profile, including increased level of total cholesterol and low-density lipoprotein cholesterol (LDL-c) and reduced level of high-density lipoprotein cholesterol (HDL-c). Lipid-lowering agents represent an efficient tool for the prevention or reduction of progression of atherosclerosis, coronary heart diseases and metabolic syndrome. Statins, ezetimibe, and recently proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitors are the most effective and used drugs in clinical lipid-lowering therapy. These drugs are mainly aimed to lower cholesterol levels by different mechanisms of actions. Statins, the agents of the first-line therapy—known as 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) reductase inhibitors—suppress the liver cholesterol synthesis. Ezetimibe as the second-line therapy can decrease cholesterol by inhibiting cholesterol absorption. Finally, the PCSK9 inhibitors act as an inducer of LDL excretion. In spite of their beneficial lipid-lowering properties, many patients suffer from their serious side effects, route of administration, or unsatisfactory physicochemical characteristics. Clinical demand for dose reduction and the improvement of bioavailability as well as pharmacodynamic and pharmacokinetic profile has resulted in the development of a new targeted therapy that includes nanoparticle carriers, emulsions or vaccination often associated with another more subtle form of administration. Targeted therapy aims to exert a more potent drug profile with lipid-lowering properties either alone or in mutual combination to potentiate their beneficial effects. This review describes the most effective lipid-lowering drugs, their favorable and adverse effects, as well as targeted therapy and alternative treatments to help reduce or prevent atherosclerotic processes and cardiovascular events.

Secreted frizzled-related protein 4 exerts anti-atherosclerotic effects by reducing inflammation and oxidative stress

Atherosclerosis and its sequelae, such as coronary artery disease (CAD), are the most common diseases worldwide and the leading causes of morbidity and mortality in most countries. Our previous studies have shown that circulating secreted frizzled-related protein 4 (SFRP4) levels are increased in patients with CAD. However, the role of SFRP4 in the development of atherosclerosis remains unclear; thus, the purpose of this study was to determine the effect of SFRP4 on high-fat diet (HFD)-induced atherosclerosis and explore the possible mechanisms. In this study, we found for the first time that administration of recombinant SFRP4 alleviates atherosclerosis in ApoE-/- mice by reducing inflammation and oxidative stress. In addition, the anti-atherosclerotic effect of SFRP4 was associated with inhibition of the Wnt/β-catenin signaling pathway, and Wnt1 overexpression abolished the anti-atherosclerotic effects of SFRP4. Taken together, our results highlight the potential beneficial effect of SFRP4 as a therapeutic agent for atherosclerosis and CAD.

Acanthaster planci Inhibits PCSK9 Gene Expression via Peroxisome Proliferator Response Element (PPRE) and Activation of MEK and PKC Signaling Pathways in Human Liver Cells

A constantly elevated level of low-density lipoprotein cholesterol (LDL-C) is mainly associated with the development of atherosclerosis. The use of statins as a treatment for reducing plasma LDL-C levels has led, in some cases, to adverse side effects, including a decrease in hepatic LDL receptor (LDLR), the receptor responsible for the uptake of circulating LDL-C. Proprotein convertase subtilisin/kexin type 9 (PCSK9) is an enzyme responsible for directing the LDLR–LDL-C complex to lysosomal degradation upon transport into cells, preventing the recycling of LDLR to the cell surface. Therefore, PCSK9 may offer a new target for reducing the levels of plasma LDL-C. In this study, we investigated the mechanisms of action of a selected fraction of A. planci on PCSK9 gene expression, as well as the effect of the fraction on the level of LDLR protein and the uptake of LDL-C. Using real-time PCR, it was shown that the selected A. planci fraction reduced the gene expression of PCSK9 in human liver HepG2 cells. Immunocytochemistry analysis demonstrated that the selected A. planci fraction increased the LDLR protein level and LDL-C uptake in HepG2 cells. Promoter mutational and gene expression analyses revealed that PPRE, a binding site for peroxisome proliferator–activated receptor (PPAR), was responsible for mediating the inhibitory effect of the selected fraction on PCSK9 mRNA. In addition, MAP kinase and PKC components of the signal transduction pathway were activated, inducing the action of the selected A. planci fraction in decreasing PCSK9 gene expression. These findings suggest that the selected fraction shows good potential for reducing circulating LDL-C and, thus, may be a good therapeutic intervention to prevent the progression of atherosclerosis.

Development of small-molecule PCSK9 inhibitors for the treatment of hypercholesterolemia

When secreted into the circulation, proprotein convertase subtilisin kexin type 9 (PCSK9) blocks the low-density lipoprotein receptors (LDL-R) and, as a consequence, low-density lipoprotein cholesterol (LDL-C) levels increase. Therefore, PCSK9 has emerged as a potential therapeutic target for lowering LDL-C levels and preventing atherosclerosis. The US Food and Drug Administration (FDA) has approved two monoclonal antibodies (mAbs) against PCSK9, but the expensive manufacturing process limits their use. Subsequently, there have been tremendous efforts to develop cost-effective small molecules specific to PCSK9 over the past few years. These small molecules are promising therapeutics that act by preventing the synthesis of PCSK9, its secretion from cells, or the PCSK9-LDRL interaction. In this review, we summarize recent developments in the discovery of small-molecule PCSK9 inhibitors, focusing on their design, therapeutic effects, specific targets, and mechanisms of action.

A Comprehensive Review of PCSK9 Inhibitors

Cardiovascular disease (CVD) is the leading cause of death in the United States and worldwide. A major risk factor for this condition is increased serum low-density lipoprotein cholesterol (LDL-C) levels for which statins have been successful in reducing serum LDL-C to healthy concentrations. However, patients who are statin intolerant or those who do not achieve their treatment goals while on high-intensity statin therapy, such as those with familial hypercholesterolemia, remain at risk. With the discovery of PCSK9 inhibitors, the ability to provide more aggressive treatment for patients with homozygous and heterozygous familial hypercholesterolemia has increased. Ezetimibe reduces LDL-C by 15%-20% when combined with statin.^2,3 Protein convertase subtilisin/kexin type 9 (PCSK9) inhibitors have been found to achieve profound reductions in LDL-C (54%-74%) when added to statins. They have shown dramatic effects at lowering major adverse cardiovascular events (MACE) in high-risk patients⁴ with LDL-C levels ≥70 mg/dL and can be used in populations that are statin intolerant or not at goal levels with maximally tolerated statin therapy. PCSK9 inhibitors also produce minimal side effects. Myopathy, a common side effect for patients on statins, has been rare in patients on PCSK9 inhibitors. Randomized trials have shown that reduction in LDL-C has translated to clinical benefits even in patients who have not achieved their LDL-C target.

Emodin alleviates aortic valvular calcification by inhibiting the AKT/FOXO1 pathway

BACKGROUND

Valvular calcification commonly occurs in elderly individuals, and is increasingly considered an important economic and health burden. However, no efficient drugs against valvular calcification are available. The present work aimed to examine emodin's suppressive effect on high-calcium-dependent valve calcification and explore the underpinning mechanisms.

METHODS

Experiments were carried out in mice receiving vitamin D (Vit D) to induce valvular calcification.

RESULTS

Cell viability and apoptosis assays demonstrated celastrol suppressed proliferation and increased apoptosis in porcine aortic valve interstitial cells (PAVICs) at concentrations higher than 10 μM. Emodin (5 μM) attenuated the upregulation of osteogenic genes as well as calcium accumulation in PAVICs under high-calcium conditions. The elevations of calcium content in serum and valve, and calcium accumulation in valve and artery were suppressed by emodin in mice with valvular calcification after joint treatment with adenine and Vit D. In addition, p-AKT and p-FOXO1 were upregulated in PAVICs under high-calcium conditions, and this effect was reversed by emodin treatment. SC79, an AKT activator, reversed emodin's suppressive effects on increased calcium content, calcium deposition and osteogenic gene expression in PAVICs induced by calcific medium.

CONCLUSIONS

These data demonstrated emodin alleviates high-calcium-associated valvular calcification via AKT/FOXO1 signaling suppression, providing new insights into therapeutic strategies for clinical valvular calcification.

Acaudina molpadioides mediates lipid uptake by suppressing PCSK9 transcription and increasing LDL receptor in human liver cells

Acaudina molpadioides has been long used as traditional medicinal resources and reported to demonstrate various important bioactivities such as anticoagulation, antithrombosis, anti-hyperglycemia and anticancer. However, its lipid lowering activity is yet to be fully explored. Proprotein convertase subtilisin/kexin type 9 (PCSK9) is an enzyme that enhances the lysosomal degradation of hepatic low density lipoprotein receptor (LDLR) resulting in excessive accumulation of the plasma levels of LDL-cholesterols (LDL-C) which subsequently accelerate atherosclerosis. In the present study, A. molpadioides fractions were subjected to promoter-reporter luciferase assay to determine its role as PCSK9 inhibitors. It was found both fractions (EFA and EFB) reduced the transcriptional activity of PCSK9 promoter. Among the seven 5′end deletion constructs of PCSK9 promoter, fragments D1 (−1,711/−94), D3 (−709/−94) and D4 (−440/−94), were suppressed in the presence of both fractions whereas D2 (−1,214/−94), and, D6 (−351/−94) as well as D7 (−335/−94) were inhibited only by EFA and EFB, respectively. Further transcription factor binding sites prediction using MatInspector software discovered various potential cis-regulatory elements namely, PPAR, KLFs, RBPJ-kappa and SREBP that may potentially be involved in ameliorating the transcriptional activity of PCSK9. Immunofluorescence staining was used to evaluate the effects of both fractions on LDL-C and LDLR. Results showed that levels of LDL-C uptake in EFA-treated cells were 69.1% followed by EFB at 32.6%, as compared to untreated control after 24 h treatment. The LDLR protein distribution was induced by 62.41% and 32.2%, which corresponded to an increase in LDL-C uptake in both EFA and EFB treatment, respectively. Hence, the inhibition of PCSK9 by bioactive compounds in EFA and EFB could be another promising therapeutic agent in reducing the cholesterol levels and atherosclerosis by targeting PCSK9.

Nutrigenetics and nutrigenomics-A personalized approach to nutrition

The prevalence of non-communicable diseases has been on an upward trajectory for some time and this puts an enormous burden on the healthcare expenditure. Lifestyle modifications including dietary interventions hold an immense promise to manage and prevent these diseases. Recent advances in genomic research provide evidence that focussing these efforts on individual variations in abilities to metabolize nutrients (nutrigenetics) and exploring the role of dietary compounds on gene expression (nutrigenomics and nutri-epigenomics) can lead to more meaningful personalized dietary strategies to promote optimal health. This chapter aims to provide examples on these gene-diet interactions at multiple levels to support the need of embedding targeted dietary interventions as a way forward to prevent, avoid and manage diseases.

Regulation of PCSK9 Expression and Function: Mechanisms and Therapeutic Implications

Proprotein convertase subtilisin/kexin type 9 (PCSK9) promotes degradation of low-density lipoprotein receptor (LDLR) and plays a central role in regulating plasma levels of LDL cholesterol levels, lipoprotein(a) and triglyceride-rich lipoproteins, increasing the risk of cardiovascular disease. Additionally, PCSK9 promotes degradation of major histocompatibility protein class I and reduces intratumoral infiltration of cytotoxic T cells. Inhibition of PCSK9 increases expression of LDLR, thereby reducing plasma levels of lipoproteins and the risk of cardiovascular disease. PCSK9 inhibition also increases cell surface levels of major histocompatibility protein class I in cancer cells and suppresses tumor growth. Therefore, PCSK9 plays a vital role in the pathogenesis of cardiovascular disease and cancer, the top two causes of morbidity and mortality worldwide. Monoclonal anti-PCSK9 antibody-based therapy is currently the only available treatment that can effectively reduce plasma LDL-C levels and suppress tumor growth. However, high expenses limit their widespread use. PCSK9 promotes lysosomal degradation of its substrates, but the detailed molecular mechanism by which PCSK9 promotes degradation of its substrates is not completely understood, impeding the development of more cost-effective alternative strategies to inhibit PCSK9. Here, we review our current understanding of PCSK9 and focus on the regulation of its expression and functions.

Novel Oral Nano-hepatic targeted anti-PCSK9 in hypercholesterolemia

Proprotein convertase subtilisin/kexin type 9 is a protease enzyme secreted by liver that downregulates hepatic low-density lipoprotein receptor (LDLR) by binding and chaperoning LDLR to lysosomes for degradation, causing hypercholesteremia. The development of anti-PCSK9therapeutics attracted considerable attention for the management of cardiovascular disease risk. However, only subcutaneous injectable PCSK9 monoclonal antibodies have been FDA approved. Oral administration of small-molecule PCSK9 inhibitors has the potential to become a practical therapeutic option if achievable. In the present work, we used nanotechnological approaches to develop the first small oral molecule nano-hepatic targeted anti-PCSK9. Using high-throughput optimization and a series of evaluations, a stable water-dispersible 150-200nm nano-encapsulated drug (named P-4) conjugated with hepatic targeting moiety was synthesized and characterized (named P-21). Pharmacodynamic (PD), pharmacokinetic (PK) and bioavailability studies were conducted using a high fat diet nutritionally induced hypercholesterolemia mouse model to evaluate the efficacy of P-21 as an anti-PCSK9 LDL-cholesterol lowering hepatic targeted nanodrug. The PD results demonstrate that P-21 in a dose-dependent manner is highly effective in lowering LDL-C by 50-90%. PK results show the maximum plasma concentration (C_max) of P-4 was observed after 30min of administration with 31% oral bioavailability and had a sustained longer half-life up to 24h. In vivo safety studies in rats showed no apparent adverse effects, normal chemical biomarkers and normal histopathological findings in all P-21 treated groups at different escalating doses. Compared to the FDA-approved monoclonal antibodies, P-21 offers a more efficient, and practical treatment protocol for targeting uncontrolled hypercholesterolemia in reducing the risk of cardiovascular diseases. The present study introduced a nano-targeted drug delivery approaches for PCSK9/LDLR antagonist.

PCSK9 inhibition-based therapeutic approaches: an immunotherapy perspective

Proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitors (PCSK9-I) are novel therapeutic tools to decrease cardiovascular risk. These agents work by lowering the low-density lipoprotein cholesterol (LDL-C) in hypercholesterolemic patients who are statin resistant/intolerant. Current clinically approved and investigational PCSK9-I act generally by blocking PCSK9 activity in the plasma or suppressing its expression or secretion by hepatocytes. The most widely investigated method is the disruption of PCSK9/LDL receptor (LDLR) interaction by fully-humanized monoclonal antibodies (mAbs), evolocumab and alirocumab, which have been approved for the therapy of hypercholesterolemia and atherosclerotic cardiovascular disease (CVD). Besides, a small interfering RNA called inclisiran, which specifically suppresses PCSK9 expression in hepatocytes, is as effective as mAbs but with administration twice a year. Because of the high costs of such therapeutic approaches, several other PCSK9-I have been surveyed, including peptide-based anti-PCSK9 vaccines and small oral anti-PCSK9 molecules, which are under investigation in preclinical and phase I clinical studies. Interestingly, anti-PCSK9 vaccination has been found to serve as a more widely feasible and more cost-effective therapeutic tool over mAb PCSK9-I for managing hypercholesterolemia. The present review will discuss LDL-lowering and cardioprotective effects of PCSK9-I, mainly immunotherapy-based inhibitors including mAbs and vaccines, in preclinical and clinical studies.

Pterostilbene Increases LDL Metabolism in HL-1 Cardiomyocytes by Modulating the PCSK9/HNF1α/SREBP2/LDLR Signaling Cascade, Upregulating Epigenetic hsa-miR-335 and hsa-miR-6825, and LDL Receptor Expression

Proprotein convertase subtilisin/kexin type 9 (PCSK9) can promote the degradation of low-density lipoprotein (LDL) receptor (LDLR), leading to hypercholesterolemia and myocardial dysfunction. The intracellular regulatory mechanism by which the natural polyphenol pterostilbene modulates the PCSK9/LDLR signaling pathway in cardiomyocytes has not been evaluated. We conducted Western blotting, flow cytometry, immunofluorescence staining, and mean fluorescence intensity analyses of pterostilbene-treated mouse HL-1 cardiomyocytes. Pterostilbene did not alter cardiomyocyte viability. Compared to the control group, treatment with both 2.5 and 5 μM pterostilbene significantly increased the LDLR protein expression accompanied by increased uptake of LDL. The expression of the mature PCSK9 was significantly suppressed at the protein and mRNA level by the treatment with both 2.5 and 5 μM pterostilbene, respectively, compared to the control. Furthermore, 2.5 and 5 μM pterostilbene treatment resulted in a significant reduction in the protein hepatic nuclear factor 1α (HNF1α)/histone deacetylase 2 (HDAC2) ratio and sterol regulatory element-binding protein-2 (SREBP2)/HDAC2 ratio. The expression of both hypoxia-inducible factor-1 α (HIF1α) and nuclear factor erythroid 2-related factor 2 (Nrf2) at the protein level was also suppressed. Pterostilbene as compared to short hairpin RNA against SREBP2 induced a higher protein expression of LDLR and lower nuclear accumulation of HNF1α and SREBP2. In addition, pterostilbene reduced PCSK9/SREBP2 interaction and mRNA expression by increasing the expression of hsa-miR-335 and hsa-miR-6825, which, in turn, increased LDLR mRNA expression. In cardiomyocytes, pterostilbene dose-dependently decreases and increases the protein and mRNA expression of PCSK9 and LDLR, respectively, by suppressing four transcription factors, HNF1α, SREBP2, HIF1α, and Nrf2, and enhancing the expression of hsa-miR-335 and hsa-miR-6825, which suppress PCSK9/SREBP2 interaction.

Transcriptional control by HNF-1: Emerging evidence showing its role in lipid metabolism and lipid metabolism disorders

The present review focuses on the roles and underlying mechanisms of action of hepatic nuclear factor-1 (HNF-1) in lipid metabolism and the development of lipid metabolism disorders. HNF-1 is a transcriptional regulator that can form homodimers, and the HNF-1α and HNF-1β isomers can form heterodimers. Both homo- and heterodimers recognize and bind to specific cis-acting elements in gene promoters to transactivate transcription and to coordinate the expression of target lipid-related genes, thereby influencing the homeostasis of lipid metabolism. HNF-1 was shown to restrain lipid anabolism, including synthesis, absorption, and storage, by inhibiting the expression of lipogenesis-related genes, such as peroxisome proliferator-activated receptor γ (PPARγ) and sterol regulatory element-binding protein-1/2 (SREBP-1/2). Moreover, HNF-1 enhances the expression of various genes, such as proprotein convertase subtilisin/kexin type 9 (PCSK9), glutathione peroxidase 1 (GPx1), and suppressor of cytokine signaling-3 (SOCS-3) and negatively regulates signal transducer and activator of transcription (STAT) to facilitate lipid catabolism in hepatocytes. HNF-1 reduces hepatocellular lipid decomposition, which alleviates the progression of nonalcoholic fatty liver disease (NAFLD). HNF-1 impairs preadipocyte differentiation to reduce the number of adipocytes, stunting the development of obesity. Furthermore, HNF-1 reduces free cholesterol levels in the plasma to inhibit aortic lipid deposition and lipid plaque formation, relieving dyslipidemia and preventing the development of atherosclerotic cardiovascular disease (ASCVD). In summary, HNF-1 transcriptionally regulates lipid-related genes to manipulate intracorporeal balance of lipid metabolism and to suppress the development of lipid metabolism disorders.

The emerging landscape of peptide-based inhibitors of PCSK9

Proprotein convertase subtilisin/kexin type 9 (PCSK9) is a clinically validated target for treating cardiovascular disease (CVD) due to its involvement in cholesterol metabolism. Although approved monoclonal antibodies (alirocumab and evolocumab) that inhibit PCSK9 function are very effective in lowering cholesterol, their limitations, including high treatment costs, have so far prohibited widespread use. Accordingly, there is great interest in alternative drug modalities to antibodies. Like antibodies, peptides are valuable therapeutics due to their high target potency and specificity. Furthermore, being smaller than antibodies means they have access to more drug administration options, are less likely to induce adverse immunogenic responses, and are better suited to affordable production. This review surveys the current peptide-based landscape aimed towards PCSK9 inhibition, covering pre-clinical to patented drug candidates and comparing them to current cholesterol lowering therapeutics. Classes of peptides reported to be inhibitors include nature-inspired disulfide-rich peptides, combinatorially derived cyclic peptides, and peptidomimetics. Their functional activities have been validated in biophysical and cellular assays, and in some cases pre-clinical mouse models. Recent efforts report peptides with potent sub-nanomolar binding affinities to PCSK9, which highlights their potential to achieve antibody-like potency. Studies are beginning to address pharmacokinetic properties of PCSK9-targeting peptides in more detail. We conclude by highlighting opportunities to investigate their biological effects in pre-clinical models of cardiovascular disease. The anticipation concerning the PCSK9-targeting peptide landscape is accelerating and it seems likely that a peptide-based therapeutic for treating PCSK9-mediated hypercholesterolemia may be clinically available in the near future.

Endothelial Dysfunction in Atherosclerotic Cardiovascular Diseases and Beyond: From Mechanism to Pharmacotherapies

The endothelium, a cellular monolayer lining the blood vessel wall, plays a critical role in maintaining multiorgan health and homeostasis. Endothelial functions in health include dynamic maintenance of vascular tone, angiogenesis, hemostasis, and the provision of an antioxidant, anti-inflammatory, and antithrombotic interface. Dysfunction of the vascular endothelium presents with impaired endothelium-dependent vasodilation, heightened oxidative stress, chronic inflammation, leukocyte adhesion and hyperpermeability, and endothelial cell senescence. Recent studies have implicated altered endothelial cell metabolism and endothelial-to-mesenchymal transition as new features of endothelial dysfunction. Endothelial dysfunction is regarded as a hallmark of many diverse human panvascular diseases, including atherosclerosis, hypertension, and diabetes. Endothelial dysfunction has also been implicated in severe coronavirus disease 2019. Many clinically used pharmacotherapies, ranging from traditional lipid-lowering drugs, antihypertensive drugs, and antidiabetic drugs to proprotein convertase subtilisin/kexin type 9 inhibitors and interleukin 1β monoclonal antibodies, counter endothelial dysfunction as part of their clinical benefits. The regulation of endothelial dysfunction by noncoding RNAs has provided novel insights into these newly described regulators of endothelial dysfunction, thus yielding potential new therapeutic approaches. Altogether, a better understanding of the versatile (dys)functions of endothelial cells will not only deepen our comprehension of human diseases but also accelerate effective therapeutic drug discovery. In this review, we provide a timely overview of the multiple layers of endothelial function, describe the consequences and mechanisms of endothelial dysfunction, and identify pathways to effective targeted therapies. SIGNIFICANCE STATEMENT: The endothelium was initially considered to be a semipermeable biomechanical barrier and gatekeeper of vascular health. In recent decades, a deepened understanding of the biological functions of the endothelium has led to its recognition as a ubiquitous tissue regulating vascular tone, cell behavior, innate immunity, cell-cell interactions, and cell metabolism in the vessel wall. Endothelial dysfunction is the hallmark of cardiovascular, metabolic, and emerging infectious diseases. Pharmacotherapies targeting endothelial dysfunction have potential for treatment of cardiovascular and many other diseases.

Structure-activity relationship and biological evaluation of berberine derivatives as PCSK9 down-regulating agents

Proprotein convertase subtilisin/kexin type 9 (PCSK9) is a secreted protein and its deficiency markedly enhanced the survival rate of patient with cardiovascular diseases (CVDs). Forty berberine (BBR) derivatives were synthesized and evaluated for their activities on down-regulating the transcription of PCSK9 in HepG2 cells, taking BBR as the lead. Structure-activity relationship (SAR) analysis revealed that 2,3-dimethoxy moiety might be beneficial for activity. Among them, 9k displayed the most potent activity with IC₅₀ value of 9.5 ± 0.5 μM, better than that of BBR. Also, it significantly decreased PCSK9 protein level at cellular level, as well as in the liver and serum of mice in vivo. Furthermore, 9k markedly increased LDLR expression and LDL-C clearance via down-regulating PCSK9 protein. The mechanism of action of 9k is targeting HNF1α and/or Sp1 cluster modulation upstream of PCSK9, a different one from BBR. Therefore, 9k might have the potential to be a novel PCSK9 transcriptional inhibitor for the treatment of atherosclerosis, worthy for further investigation.

General Perspectives for the Treatment of Atherosclerosis

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Atherosclerosis, a cardiovascular disease, is at the top of the list among the diseases leading to death. Although the biochemical and pathophysiological cascades involved within the development of atherosclerosis have been identified clearly, its nature is quite complex to be treated with a single agent targeting a pathway. Therefore, many natural and synthetic compounds have been suggested for the treatment of the disease. The majority of the drugs employed target one of the single components of the pathological outcomes, resulting in many times less effective and longterm treatments. In most cases, treatment options prevent further worsening of the symptoms rather than a radical treatment. Consequently, the current review has been prepared to focus on the validated and non-validated targets of atherosclerosis as well as the alternative treatment options such as hydroxymethyl glutaryl coenzyme A (HMG-CoA) reductase inhibitors, acyl-CoA cholesterol acyl transferase (ACAT) inhibitors, lipoprotein lipase stimulants, bile acid sequestrants, and some antioxidants. Related to the topic, both synthetic compounds designed employing medicinal chemistry skills and natural molecules becoming more popular in drug development are scrutinized in this mini review.

From methylene bridged diindole to carbonyl linked benzimidazoleindole: Development of potent and metabolically stable PCSK9 modulators

Proprotein convertase subtilisin/kexin type 9 (PCSK9) is a recently validated therapeutic target for lowering low-density lipoprotein cholesterol (LDL-C). Through phenotypic screening, we previously discovered a class of small-molecules with a 2,3'-diindolymethane (DIM) skeleton that can decrease the expression of PCSK9. But these compounds have low potency and low metabolically stability. After performing structure-activity relationship (SAR) optimization by nitrogen scan, deuterium substitution and fluorine scan, we identified a series of much more potent and metabolically stable PCSK9 modulators. A preliminary in vivo pharmacokinetic study was performed for representative analogues difluorodiindolyketone (DFDIK) 12 and difluorobenzoimidazolylindolylketone (DFBIIK-1) 13. The in vitro metabolic stability correlate well with the in vivo data. The most potent compound 21 has the EC₅₀ of 0.15 nM. Our SAR studies also indicated that the NH on the indole ring of 21 can tolerate more function groups, which may facilitate the mechanism of action studies and also allow further improvement of the pharmacological properties.

PCSK9 inhibitor and atorvastatin reduce cardiac impairment in ovariectomized prediabetic rats via improved mitochondrial function and Ca2+ regulation

Post‐menopausal women have a higher risk of developing cardiometabolic dysfunction. Atorvastatin attenuates dyslipidaemia and cardiac dysfunction but it can have undesirable effects including increased risk of diabetes and myalgia. Currently, the proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitor efficiently reduces low‐density lipoprotein cholesterol (LDL‐C) levels more effectively than atorvastatin. We have been suggested that PCSK9 inhibitor attenuated cardiometabolic impairment more effectively than atorvastatin in ovariectomized prediabetic rats. Female Wistar rats (n = 48) were fed a normal diet (ND) or high‐fat diet (HFD) for 12 weeks. Then, HFD rats were assigned to a sham‐operated (Sham) or ovariectomized (OVX) group. Six weeks after surgery, the OVX group was subdivided into 4 treatment groups: vehicle (HFOV), atorvastatin (HFOA) (40 mg/kg/day; s.c.), PCSK9 inhibitor (HFOP) (4 mg/kg/day; s.c.) and oestrogen (HFOE₂) (50 µg/kg/day; s.c.) for an additional 3 weeks. Metabolic parameters, cardiac and mitochondrial function, and [Ca²⁺]_i transients were evaluated. All HFD rats became obese‐insulin resistant. HFS rats had significantly impaired left ventricular (LV) function, cardiac mitochondrial function and [Ca²⁺]_i transient dysregulation. Oestrogen deprivation (HFOV) aggravated all of these impairments. Our findings indicated that the atorvastatin, PCSK9 inhibitor and oestrogen shared similar efficacy in the attenuation in cardiometabolic impairment in ovariectomized prediabetic rats.

Small rodent models of atherosclerosis

The ease of breeding, low cost of maintenance, and relatively short period for developing atherosclerosis make rodents ideal for atherosclerosis research. However, none of the current models accurately model human lipoprotein profile or atherosclerosis progression since each has its advantages and disadvantages. The advent of transgenic technologies much supports animal models' establishment. Notably, two classic transgenic mouse models, apoE-/- and Ldlr-/-, constitute the primary platforms for studying underlying mechanisms and development of pharmaceutical approaches. However, there exist crucial differences between mice and humans, such as the unhumanized lipoprotein profile, and the different plaque progression and characteristics. Among rodents, hamsters and guinea pigs might be the more realistic models in atherosclerosis research based on the similarities in lipoprotein metabolism to humans. Studies involving rat models, a rodent with natural resistance to atherosclerosis, have revealed evidence of atherosclerotic plaques under dietary induction and genetic manipulation by novel technologies, notably CRISPR-Cas9. Ldlr-/- hamster models were established in recent years with severe hyperlipidemia and atherosclerotic lesion formation, which could offer an alternative to classic transgenic mouse models. In this review, we provide an overview of classic and innovative small rodent models in atherosclerosis researches, including mice, rats, hamsters, and guinea pigs, focusing on their lipoprotein metabolism and histopathological changes.