Gene inactivation of proprotein convertase subtilisin/kexin type 9 reduces atherosclerosis in mice

Silencing hepatic PCSK9 via novel chimeric AAV8 mitigates the progression of atherosclerosis by inhibiting inflammation in ApoE-/- mice

Adeno-associated virus (AAV) is the most widely utilized vector for gene therapy. Proprotein convertase subtilisin/kexin type 9 (PCSK9), predominantly expressed in the liver, plays a crucial role in lipid regulation and atherosclerosis progression. Here, we developed a novel chimeric AAV8.P-PCSK9 short hairpin RNA (shRNA) vector that incorporates a cross-species specific shRNA targeting PCSK9 to assess its effects on lipid levels and atherosclerosis in mice. AAV8.P demonstrated superior transduction efficiency and safety, achieving about 90% liver transduction and maintaining transgene expression for up to a year. The AAV8.P-PCSK9 shRNA exhibited typical liver-tropism and effectively silenced hepatic PCSK9. Moreover, it significantly lowered serum cholesterol and triglyceride levels while increasing LDL-R level without causing hepatotoxicity in wild-type mice. Additionally, it decreased PCSK9 expression and elevated low-density lipoprotein receptor expression in Apolipoprotein E-deficient mice, leading to early changes in lipid profiles but lacking a sustained impact on circulating lipids. Importantly, silencing PCSK9 resulted in reduced plaque areas with enhanced stability, decreased inflammatory macrophage infiltration, and lower levels of vascular and systemic inflammatory markers. These findings indicate that targeted silencing of hepatic PCSK9 significantly reduces lipid levels and effectively mitigates atherosclerosis progression by inhibiting inflammatory responses via the AAV8.P-PCSK9 shRNA vector, thereby providing critical support for its clinical translation.

PCSK9 with a gain of function D374Y mutation aggravates atherosclerosis by inhibiting PPARα expression

The preprotein convertase, Bacillus subtilis protease/kexin type 9 serine protease (PCSK9), has garnered significant attention as a potential lipid lowering and therapeutic drug target for atherosclerosis (AS). Peroxisome proliferator-activated receptor alpha (PPARα) is expressed in various tissues and has crucial roles in lipid metabolism and the inflammatory response; however, the precise impact of PCSK9 on AS progression through its regulation of PPARα remains uncertain. The present study aimed to examine the impact of introducing stable liver transduction of human derived PCSK9 with a gain of function D374Y mutation (PCSK9DY) into systemic PPARα knockout mice (PPARα-/-) on plasma lipid levels and AS. Enzymatic assays were employed to evaluate plasma lipid concentrations at various time points, and aortic plaque formation and the degree of inflammatory infiltration quantified. Subsequently, we validated our in vivo results using mouse primary peritoneal macrophages (MPMs). Furthermore, AAV8.2-PPARα virus vector was transduced into transgenic mice of human PCSK9(hPCSK9DY-Tg) by tail vein, and the changes of plasma lipid level and AS were detected. PCSK9DY expression exacerbated symptoms of hypercholesterolemia in PPARα-/- mice. En face analysis and quantification of aortic root sections demonstrated a significant increase in aortic plaque area and inflammatory infiltration in PCSK9DY transduced PPARα-/- mice. Secretion of inflammatory cytokines was elevated in PCSK9DY transduced PPARα-/- mice. In vitro, recombinant hPCSK9 protein promotes the foam cell formation and inflammatory cytokines secretion of PPARα-/- MPMs by increasing the expression of SR-A and TLR4/NF-κB pathway proteins. AAV8.2-PPARα virus vector can reduce the plasma lipid level and AS formation in hPCSK9DY-Tg mice. These finding demonstrate that PCSK9DY expression notably facilitated AS progression in PPARα-/- mice by increasing plasma lipid concentrations and inflammation. However, overexpression of PPARα can reduce AS formation in hPCSK9DY-Tg mice.

Engineered extracellular vesicles as nanosponges for lysosomal degradation of PCSK9

Proprotein convertase subtilisin/kexin type 9 (PCSK9) plays a crucial role in the degradation of the low-density lipoprotein receptor (LDLR), and PCSK9 inhibition emerges as an attractive strategy for atherosclerosis management. In this study, extracellular vesicles (EVs) were engineered to nanosponges, which could efficiently adsorb and deliver PCSK9 into lysosomes for degradation. Briefly, nanosponges were engineered by modifying EVs with EGF-A/PTGFRN fusion protein (PCSK9 binding domain EGF-A from the mutant LDLR with higher affinity was fused to the C terminus of prostaglandin F2 receptor negative regulator). The modification endowed the EVs with hundreds of EGF-As displayed on the surface, and thus the capacity to adsorb PCSK9 efficiently. The adsorbed PCSK9 would thus be delivered into lysosomes for degradation when the nanosponges were endocytosed by liver cells, thus releasing endogenous LDLR from degradation. In the ApoE-/- mouse model, tail vein-injected nanosponges were able to degrade PCSK9, increase LDLR expression, lower the LDL-C level, and thus alleviate atherosclerosis. In summary, here we not only develop a novel strategy for PCSK9 inhibition but we also propose a universal method for adsorption and degradation of circulating proteins for disease management.

PCSK9 in metabolism and diseases

PCSK9 is a serine protease that regulates plasma levels of low-density lipoprotein (LDL) and cholesterol by mediating the endolysosomal degradation of LDL receptor (LDLR) in the liver. When PCSK9 functions unchecked, it leads to increased degradation of LDLR, resulting in elevated circulatory levels of LDL and cholesterol. This dysregulation contributes to lipid and cholesterol metabolism abnormalities, foam cell formation, and the development of various diseases, including cardiovascular disease (CVD), viral infections, cancer, and sepsis. Emerging clinical and experimental evidence highlights an imperative role for PCSK9 in metabolic anomalies such as hypercholesterolemia and hyperlipidemia, as well as inflammation, and disturbances in mitochondrial homeostasis. Moreover, metabolic hormones - including insulin, glucagon, adipokines, natriuretic peptides, and sex steroids - regulate the expression and circulatory levels of PCSK9, thus influencing cardiovascular and metabolic functions. In this comprehensive review, we aim to elucidate the regulatory role of PCSK9 in lipid and cholesterol metabolism, pathophysiology of diseases such as CVD, infections, cancer, and sepsis, as well as its pharmaceutical and non-pharmaceutical targeting for therapeutic management of these conditions.

PCSK9 Expression in Vascular Smooth Muscle Cells: Role of Insulin Resistance and High Glucose

Beyond the regulation of cholesterol metabolism, a number of extrahepatic functions of proprotein convertase subtilisin/kexin type 9 (PCSK9) have been increasingly identified. The main purpose of this study was to verify whether PCSK9 expression in vascular smooth muscle cells (VSMC) is influenced by insulin resistance and high glucose (HG). In cultured rat aortic VSMC from lean insulin-sensitive Zucker rats (LZRs) and obese insulin-resistant Zucker rats (OZRs), a classical animal model of insulin resistance, we evaluated PCSK9 expression with or without the monoclonal antibodies against PCSK9 Alirocumab and Evolocumab or the synthetic PCSK9-binding peptide PEP 2-8. Effects and molecular mechanisms underlying altered PCSK9 expression were evaluated by proliferation and migration assay, reactive oxygen species (ROS) production, and involvement of PKC, NADPH-oxidase, MAPK/ERK-1/2 pathway activation. As a result, we found that, in comparison with LZR, VSMC from OZR showed basal PCSK9 overexpression mitigated by Alirocumab, Evolocumab, PEP 2-8, and the inhibitors of PKC, NADPH-oxidase, and MAPK. The finding of PCSK9 upregulation in VSMC from OZR paralleled with increased ROS production, proliferation, and migration. HG increased PCSK9 expression in VSMC from LZR, but not in OZR, via oxidative stress and with effects reduced by PCSK9 inhibitors. These findings suggest that a dysregulation of PCSK9 in VSMC could be involved in vascular damage in metabolic disorders, such as obesity and diabetes.

Disruption of PCSK9 Suppresses Inflammation and Attenuates Abdominal Aortic Aneurysm Formation

BACKGROUND

Abdominal aortic aneurysm (AAA) is a chronic vascular inflammatory disease without effective medications. PCSK9 (proprotein convertase subtilisin/kexin 9), a serine protease from the proprotein convertase family, has recently been associated with AAA in human genome-wide association studies. However, its role in AAA is unknown.

METHODS

Transcriptional and histological expression of PCSK9 was examined in AAA tissues and healthy controls. The impact of PCSK9 deletion and inhibition on AAA formation was assessed in mice with hyperlipidemia and Ang II (angiotensin II) overproduction. AAA lesion morphology was assessed by tissue staining. MMP (matrix metalloproteinase) activity was evaluated by gelatin zymography, and leukocyte-vessel wall interaction was monitored by intravital microscopy. RNA sequencing was used to characterize the downstream signaling of PCSK9.

RESULTS

PCSK9 expression was upregulated and colocalized with macrophages in human and mouse AAAs. Pcsk9 deletion attenuated AAA formation, improved survival, and decreased systemic inflammation, without altering circulating cholesterol levels. Pcsk9 deficiency reduced aortic infiltration of macrophages and elastin degradation, without affecting vascular smooth muscle cell apoptosis and proliferation. Mechanistically, PCSK9 was essential in leukocyte-endothelium adhesion and expression of proinflammatory cytokines and MMP9 by macrophages. RNA sequencing of stimulated macrophages revealed that Pcsk9 deficiency upregulated histone deacetylase SIRT1 (sirtuin-1) and suppressed NF-κB (nuclear factor-κB) inflammatory signaling. SIRT1 inhibition attenuated the proinflammatory actions of PCSK9. Furthermore, administration of PCSK9 small interfering RNA or antibody constrained AAA formation/progression and inhibited vascular inflammation.

CONCLUSIONS

PCSK9 critically mediates macrophage inflammation and elastin degradation, promoting AAA formation. PCSK9 inhibitors bear a promise to curtail AAA, beyond being used as cholesterol-lowering drugs.

Associations Between Gene Variants of Lipid-Lowering Drug Targets and Adverse Outcomes After Ischemic Stroke

BACKGROUND

The association of lipid-lowering drug targets and their gene variants with cardiovascular diseases has been previously clarified. However, the relationship between gene variants of lipid-lowering drug targets and the adverse prognosis of ischemic stroke patients remains unclear.

METHODS AND RESULTS

Multiple single-nucleotide polymorphisms associated with 6 lipid-lowering drug targets were genotyped for patients with ischemic stroke. The primary outcome was death or major disability within 2 years after ischemic stroke. Genetic risk score was constructed from significant single-nucleotide polymorphisms identified via additive models, which was calculated by multiplying the number of risk alleles at each locus by the corresponding beta coefficient and then summing the products. The rs2006760-C of the HMGCR, rs11206510-T of PCSK9, and rs1864163-G and rs9929488-G of CETP were associated with increased odds of adverse outcomes within 2 years after ischemic stroke. Each additional risk allele was associated with higher odds of adverse outcomes. Genetic risk score was positively associated with the odds of primary outcome (odds ratio [OR], 1.48 [95% CI, 1.15-1.90]; Ptrend = 0.001), major disability (OR, 1.56 [95% CI, 1.16-2.08]; Ptrend = 0.002), death (hazard ratio [HR], 1.58 [95% CI, 1.12-2.25]; Ptrend = 0.011), and the composite outcome of death or cardiovascular events (HR, 1.41 [95% CI, 1.08-1.85]; Ptrend = 0.010) when 2 extreme quartiles were compared.

CONCLUSIONS

rs2006760-C of HMGCR, rs11206510-T of PCSK9, and rs1864163-G and rs9929488-G of CETP were associated with increased odds of adverse outcomes within 2 years after ischemic stroke. Furthermore, higher GRS was positively related to the odds of poor outcomes in patients with ischemic stroke. Registration: URL: https://www.clinicaltrials.gov; Identifier: NCT01840072.

PCSK9 E670G polymorphism increases risk of coronary artery disease in a Chinese Han population

OBJECTIVE

Coronary artery disease (CAD) is the leading cause of morbidity and mortality in the world. The proprotein convertase subtilisin/kexin type 9 (PCSK9) E670G polymorphism has been reported to be associated with variability in levels of low density lipoprotein cholesterol, a risk factor for CAD. However, the relationship between PCSK9 E670G and CAD is still not fully elucidated.

METHODS

A total of 225 patients and 189 control subjects were recruited in this study. DNA was extracted from peripheral blood samples and was genotyped by mass array method. In addition, we also conducted a meta-analysis of case-control studies to elucidate the relationship of CAD and polymorphism.

RESULTS

The GG genotype of PCSK9 E670G was associated with a higher risk of CAD [odds ratio (OR) 2.994, 95% confidence interval (CI): 1.174-7.631], even adjusting for risk factors (OR 2.794, 95% CI: 1.215-7.460). Logistic regression analysis showed that the dominant genetic model increased the CAD risk (OR 2.313, 95% CI: 1.070-6.983) after adjusting the confounding factors. Meta-analysis results of 13 studies revealed that PCSK9 E670G polymorphism was correlated with CAD risk under different genetic models.

CONCLUSION

Our results demonstrated that PCSK9 E670G genotype was associated with a high risk of CAD.

PCSK9 and Coronary Artery Plaque-New Opportunity or Red Herring?

PURPOSE OF REVIEW

Although the clinical benefit of reducing low-density lipoprotein cholesterol (LDLc) in patients with coronary artery disease (CAD) is well-established, the impact on plaque composition and stability is less clear. Our narrative review aimed to assess the clinical effects of proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitors on coronary plaque characteristics specifically focusing from atheroma progression to regression and stabilization.

RECENT FINDINGS

The combination of statin therapy and PCSK9 inhibitors (evolocumab and alirocumab) promotes plaque stability in patients following an acute coronary syndrome. The GLAGOV study highlighted the relationship between achieved LDLc levels and changes in percentage atheroma volume. Similarly, the PACMAN-AMI study concluded that the qualitative and quantitative changes in coronary plaque were associated with the levels of LDLc. Assessing the severity of coronary artery stenosis and the extent of atherosclerotic burden by means of imaging techniques (e.g., IVUS, OCT and near-infrared spectroscopic) have significantly advanced our understanding of the benefits from promoting plaque regression and achieving to features of plaque stabilization through increasingly intensive lipid-lowering strategies.

The impact of histone lactylation on the tumor microenvironment and metabolic pathways and its potential in cancer therapy

BACKGROUND

The complexity of cancer is intricately linked to its multifaceted biological processes, including the roles of the tumor microenvironment (TME) as well as genetic and metabolic regulation. Histone lactylation has recently emerged as a novel epigenetic modification mechanism that plays a pivotal role in regulating cancer initiation, proliferation, invasion, and metastasis.

OBJECTIVE

This review aims to elucidate the role of histone lactylation in modulating various aspects of tumor biology, including DNA repair mechanisms, glycolytic metabolic abnormalities, functions of non-tumor cells in the TME, and the promotion of tumor inflammatory responses and immune escape. Additionally, the review explores potential therapeutic strategies targeting histone lactylation.

METHODS

A comprehensive literature review was performed, analyzing recent findings on histone lactylation and its impact on cancer biology. This involved a systematic examination of studies focusing on biochemical pathways, cellular interactions, and clinical implications related to histone lactylation.

RESULTS

Histone lactylation was identified as a critical regulator of tumor cell DNA repair mechanisms and glycolytic metabolic abnormalities. It also significantly influences the functions of non-tumor cells within the TME, promoting tumor inflammatory responses and immune escape. Moreover, histone lactylation acts as a multifunctional biological signaling molecule impacting immune responses within the TME. Various cell types within the TME, including T cells and macrophages, were found to regulate tumor growth and immune escape mechanisms through lactylation.

CONCLUSION

Histone lactylation offers a novel perspective on tumor metabolism and its role in cancer development. It presents promising opportunities for the development of innovative cancer therapies. This review underscores the potential of histone lactylation as a therapeutic target, paving the way for new strategies in cancer treatment.

Proprotein Convertase Subtilisin/Kexin Type 9 Inhibitors in Patients Following Acute Coronary Syndromes: From Lipid Lowering and Plaque Stabilization to Improved Outcomes

Lipid lowering, with the use of statins after an acute coronary syndrome (ACS), is a cornerstone, well-established strategy for the secondary prevention of ischemic events in this high-risk cohort. In addition to the positive effect on lipid levels, statins have also been linked to improved atherosclerotic plaque characteristics, such as plaque regression and inflammation reduction, associated with the extent of reduction in LDL-C. The recent emergence of PCSK9 inhibitors for the management of dyslipidemia and the more extensive lipid lowering provided by these agents may provide better prevention for ACS patients when initiated after the ACS event. Several trials have evaluated the immediate post-ACS initiation of PCSK9 inhibitors, which has shown, to date, beneficial results. Furthermore, PCSK9 inhibitors have been linked with positive plaque remodeling and associated mortality benefits, which makes their use in the initial management strategy of such patients appealing. Therefore, in this review, we will analyze the rationale behind immediate lipid lowering after an ACS, report the evidence of PCSK9 inhibition immediately after the ACS event and the available data on plaque stabilization, and discuss treatment algorithms and clinical perspectives for the use of these agents in this clinical setting.

The role of proprotein convertase subtilisin/kexin 9 (PCSK9) in macrophage activation: a focus on its LDL receptor-independent mechanisms

Recent clinical trials demonstrated that proprotein convertase subtilisin/kexin 9 (PCSK9) inhibitors reduce cardiovascular events without affecting systemic inflammation in the patients with coronary artery disease, as determined by high sensitivity C-reactive protein (CRP) levels. However, its pro-inflammatory effects in cardiovascular disease in humans and experimental animals beyond the traditional cholesterol receptor-dependent lipid metabolism have also called attention of the scientific community. PCSK9 may target receptors associated with inflammation other than the low-density lipoprotein receptor (LDLR) and members of the LDLR family. Accumulating evidence suggests that PCSK9 promotes macrophage activation not only via lipid-dependent mechanisms, but also lipid-independent and LDLR-dependent or -independent mechanisms. In addition to dyslipidemia, PCSK9 may thus be a potential therapeutic target for various pro-inflammatory diseases.

Global trends and research hotspots of PCSK9 and cardiovascular disease: a bibliometric and visual analysis

Background

Cardiovascular disease (CVD) is a prevalent non-communicable disease globally and holds the position of being the primary cause of mortality worldwide. Consequently, considerable focus has been directed towards the prevention and management of CVD. PCSK9, a frequently targeted element in the treatment and prevention of CVD, can reduce cardiovascular risk by effectively lowering lipid levels even in the context of statin therapy. It also exhibits substantial potential in the diagnosis and treatment of familial hypercholesterolemia from genetic aspects. This bibliometric study aims to analyze and visualize the global trends and emerging hotspots of PCSK9 and CVD researches and provide researchers with new perspectives in further studies.

Methods

The data was obtained from the Web of Science Core Collection database. A total of 2,474 publications related to PCSK9 and CVD published between January 2006 and July 2023 were included. The VOSviewer was used to analyze most-cited references, co-authorship, co-citation, co-occurrence and generate a collaborative network map of authors, countries, and institutions. CiteSpace was used to analyze author and institution centroids, keyword bursts, and timeline graphs.

Result

A total of 2,474 articles related to CVD and PCSK9 were included. The number of articles and citations show an increasing trend from year to year. Publications were mainly from the United States. The most active institution was Amgen Inc. Watts, Gerald F. was the most prolific author. Atherosclerosis was the most published journal. Literature co-citation and keyword co-occurrence revealed that early studies focused on the lipid-lowering effects of PCSK9 inhibitors in the context of statins therapy, long-term efficacy, adverse effects, LDLR, diagnosis and treatment of familial hypercholesterolemia. In recent years, myocardial ischemic protection, CRISPR-based editing, and new therapeutic strategies for arteriosclerotic cardiovascular disease have gotten wide attention. The protein convertase, inflammation, beta-polyacetate, and inclisiran may be the important future research directions.

Conclusion

This study analyses the current status and global trends in the CVD and PCSK9 studies comprehensively, which may provide researchers and policymakers with new and comprehensive perspectives on in this field of research.

Tailoring Treatment in Cardiovascular Diseases: The Role of Targeted Therapies

Cardiovascular diseases (CVDs) remain the leading cause of morbidity and mortality around the globe. To address this public health burden, innovative therapeutic agents are being developed to specifically target molecular and genetic markers. Various therapeutic modalities have been implemented, including vaccines, monoclonal or bispecific antibodies, and gene-based therapies. Such drugs precisely target the underlying disease pathophysiology, aiming at notable molecules such as lipid metabolism regulators, proinflammatory cytokines, and growth factors. This review focuses on the latest advancements in different targeted therapies. It provides an insightful overview of the current landscape of targeted cardiovascular therapies, highlighting promising strategies with potential to transform the treatment of CVDs into an era of precision medicine.

Atherosclerosis and Toll-Like Receptor4 (TLR4), Lectin-Like Oxidized Low-Density Lipoprotein-1 (LOX-1), and Proprotein Convertase Subtilisin/Kexin Type9 (PCSK9)

Atherosclerosis is a leading cause of death in the world. A significant body of evidence suggests that inflammation and various players are implicated and have pivotal roles in the formation of atherosclerotic plaques. Toll-like receptor 4 (TLR4) is linked with different stages of atherosclerosis. This receptor is highly expressed in the endothelial cells (ECs) and atherosclerotic plaques. TLR4 activation can lead to the production of inflammatory cytokines and related responses. Lectin-like oxidized low-density lipoprotein-1 (LOX-1), an integral membrane glycoprotein with widespread expression on the ECs, is involved in atherosclerosis and has some common pathways with TLR4 in atherosclerotic lesions. In addition, proprotein convertase subtilisin/kexin type9 (PCSK9), which is a regulatory enzyme with different roles in cholesterol uptake, is implicated in atherosclerosis. At present, TLR4, PCSK9, and LOX-1 are increasingly acknowledged as key players in the pathogenesis of atherosclerotic cardiovascular diseases. Herein, we presented the current evidence on the structure, functions, and roles of TLR4, PCSK9, and LOX-1 in atherosclerosis.

Incidence of microvascular dysfunction is increased in hyperlipidemic mice, reducing cerebral blood flow and impairing remote memory

Introduction

The development of cognitive dysfunction is not necessarily associated with diet-induced obesity. We hypothesized that cognitive dysfunction might require additional vascular damage, for example, in atherosclerotic mice.

Methods

We induced atherosclerosis in male C57BL/6N mice by injecting AAV-PCSK9DY (2x1011 VG) and feeding them a cholesterol-rich Western diet. After 3 months, mice were examined for cognition using Barnes maze procedure and for cerebral blood flow. Cerebral vascular morphology was examined by immunehistology.

Results

In AAV-PCSK9DY-treated mice, plaque burden, plasma cholesterol, and triglycerides are elevated. RNAseq analyses followed by KEGG annotation show increased expression of genes linked to inflammatory processes in the aortas of these mice. In AAV-PCSK9DY-treated mice learning was delayed and long-term memory impaired. Blood flow was reduced in the cingulate cortex (-17%), caudate putamen (-15%), and hippocampus (-10%). Immunohistological studies also show an increased incidence of string vessels and pericytes (CD31/Col IV staining) in the hippocampus accompanied by patchy blood-brain barrier leaks (IgG staining) and increased macrophage infiltrations (CD68 staining).

Discussion

We conclude that the hyperlipidemic PCSK9DY mouse model can serve as an appropriate approach to induce microvascular dysfunction that leads to reduced blood flow in the hippocampus, which could explain the cognitive dysfunction in these mice.

PCSK-9 inhibitors: a new direction for the future treatment of ischemic stroke

Ischemic stroke, the most prevalent and serious manifestation of cerebrovascular disease, is the main cause of neurological problems that require hospitalization, resulting in disability and death worldwide. Currently, clinical practice focuses on the effective management of blood lipids as a crucial approach to preventing and treating ischemic stroke. In recent years, a great breakthrough in ischemic stroke treatment has been witnessed with the emergence and use of a novel lipid-lowering medication, Proprotein convertase subtilisin kexin type 9 (PCSK9) inhibitor. And its remarkable potential for reducing the occurrence of ischemic stroke is being acknowledged. This article aims to provide a comprehensive review, encompassing the association between PCSK9 and the heightened risk of ischemic stroke, the mechanisms, and the extensive evidence supporting the proven efficacy of PCSK9 inhibitors in clinical practice. Through this present study, we can gain deeper insights into the utilization and impact of PCSK9 inhibitors in treating ischemic stroke.

The translational potential of miR-26 in atherosclerosis and development of agents for its target genes ACC1/2, COL1A1, CPT1A, FBP1, DGAT2, and SMAD7

Atherosclerosis is one of the leading causes of death worldwide. miR-26 is a potential biomarker of atherosclerosis. Standardized diagnostic tests for miR-26 (MIR26-DX) have been developed, but the fastest progress has been in predicting the efficacy of IFN-α therapy for hepatocellular carcinoma (HCC, phase 3). MiR-26 slows atherosclerosis development by suppressing ACC1/2, ACLY, ACSL3/4, ALDH3A2, ALPL, BMP2, CD36, COL1A1, CPT1A, CTGF, DGAT2, EHHADH, FAS, FBP1, GATA4, GSK3β, G6PC, Gys2, HMGA1, HMGB1, LDLR, LIPC, IL-1β, IL-6, JAG2, KCNJ2, MALT1, β-MHC, NF-κB, PCK1, PLCβ1, PYGL, RUNX2, SCD1, SMAD1/4/5/7, SREBF1, TAB3, TAK1, TCF7L2, and TNF-α expression. Many agents targeting these genes, such as the ACC1/2 inhibitors GS-0976, PF-05221304, and MK-4074; the DGAT2 inhibitors IONIS-DGAT2Rx, PF-06427878, PF-0685571, and PF-07202954; the COL1A1 inhibitor HT-100; the stimulants 68Ga-CBP8 and RCT-01; the CPT1A inhibitors etomoxir, perhexiline, and teglicar; the FBP1 inhibitors CS-917 and MB07803; and the SMAD7 inhibitor mongersen, have been investigated in clinical trials. Interestingly, miR-26 better reduced intima-media thickness (IMT) than PCSK9 or CT-1 knockout. Many PCSK9 inhibitors, including alirocumab, evolocumab, inclisiran, AZD8233, Civi-007, MK-0616, and LIB003, have been investigated in clinical trials. Recombinant CT-1 was also investigated in clinical trials. Therefore, miR-26 is a promising target for agent development. miR-26 promotes foam cell formation by reducing ABCA1 and ARL4C expression. Multiple materials can be used to deliver miR-26, but it is unclear which material is most suitable for mass production and clinical applications. This review focuses on the potential use of miR-26 in treating atherosclerosis to support the development of agents targeting it.

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.

New opportunities in the management and treatment of refractory hypercholesterolemia using in vivo CRISPR-mediated genome/base editing

AIMS

Refractory hypercholesterolemia (RH), caused primarily by the loss-of-function mutation of LDL receptor (LDLR) gene seen in HoFH and HeFH patients, remains a major risk factor for atherosclerotic cardiovascular disease (ASCVD). Statin and ezetimibe combination therapy lower circulating LDL by 30% in HoFH patients. PCSK9 mAB, being an LDLR-dependent therapy, is not effective in HoFH, but lowers LDL by 25% in HeFH patients. A maximum reduction of 50% was noted in HoFH patients treated with ANGPTL3 mAB, which was not enough to achieve therapeutic goal of LDL. Therefore, new approaches are warranted to offer hopes to individuals intolerant to higher dose statins and not able to achieve recommended LDL level.

DATA SYNTHESIS

New approaches to lower LDL include gene therapy and gene editing. AAV-based gene therapy has shown encouraging results in animal models. Using CRISPR/Cas9-mediated genome/base editing, gain of function and loss of function have been successfully done in animal models. Recent progress in the refinement of genome/base editing has overcome the issues of off-target mutagenesis with ∼1% mutagenesis in case of PCSK9 and almost no off-target mutagenesis in inactivating ANGPTL3 in animal models showing 50% reduction in cholesterol. Current approaches using CRISPR-Cas9 genome/base editing targeting LDLR-dependent and LDLR-independent pathways are underway.

CONCLUSIONS

The new information on gain of LDLR function and inactivation of ANGPTL3 together with developments in genome/base editing technology to overcome off-target insertion and deletion mutagenesis offer hope to refractory hypercholesterolemic individuals who are at a higher risk of developing ASCVD.

A bibliometric analysis of PCSK9 inhibitors from 2007 to 2022

Background

Since the approval of the proprotein convertase subtilisin/kexin type 9 (PCSK9) monoclonal antibodies for marketing in 2015, PCSK9 inhibitors have attracted significant interest in the field of cardiovascular endocrinology. A large number of clinical trials have confirmed the efficacy and safety of PCSK9 inhibitors in reducing cholesterol and the risk of cardiovascular events. No bibliometric analysis of PCSK9 inhibitors has been performed as of yet. This study aims to analyze the research trends and hotspots of PCSK9 inhibitors through bibliometric analysis.

Methods

We searched the Web of Science Core Collection (WoSCC) database for PCSK9 inhibitor-related publications from 2007 to 2022. Data visualization analysis was performed using CiteSpace software. Microsoft Excel and Graphpad software were used for the drawing of some tables and figures.

Results

A total of 1072 pieces of literature were retrieved between 2007 and 2022. The number of publications concerning PCSK9 inhibitors is growing annually. The top five countries with the most articles published were the United States, England, Canada, Italy, and France. Harvard University, Amgen, Brigham & Women's Hospital, Harvard Medical School, and Imperial College London are the five institutions with the highest output. The Journal of Clinical Lipidology is the most popular journal in this field. The most frequently cited journal is the New England Journal of Medicine. As for authors, Sabatine MS and Giugliano RP from Brigham & Women's Hospital have the highest number of published articles. Amgen is the funding agency for most of the research. According to keyword analysis, "low density lipoprotein", "familial hypercholesterolemia", "PCSK9 inhibitor", "PCSK9", and "efficacy" are the five keywords with the highest frequency of co-occurrence.

Conclusion

The past 15 years have witnessed a rapid and fruitful development of PCSK9 inhibitors. The research trend and focus for PCSK9 inhibitors are from the mechanism of reducing low-density lipoprotein cholesterol to related clinical trials. Developed countries such as the United States have contributed prominently in this area. Coronary artery and inflammation are currently at the forefront of research in the field and are in an explosion period.

Brazilin from Caesalpinia sappan L. as a Proprotein Convertase Subtilisin/Kexin Type 9 (PCSK9) Inhibitor: Pharmacophore-Based Virtual Screening, In Silico Molecular Docking, and In Vitro Studies

Background

Proprotein convertase subtilisin/kexin type 9 (PCSK9) is a crucial regulator of low-density lipoprotein cholesterol (LDL-c) levels, as it binds to and degrades the LDL receptor (LDLR) in the lysosome of hepatocytes. Elevated levels of PCSK9 have been linked to an increased LDL-c plasma levels, thereby increasing the risk of cardiovascular disease (CVD), making it an attractive target for therapeutic interventions. As a way to inhibit PCSK9 action, we searched for naturally derived small molecules which can block the binding of PCSK9 to the LDLR.

Methods

In this study, we carried out in silico studies which consist of virtual screening using an optimized pharmacophore model and molecular docking studies using Pyrx 0.98. Effects of the candidate compounds were evaluated using in vitro PCSK9-LDLR binding assays kit.

Results

Eleven natural compounds that bind to PCSK9 were virtually screened form HerbalDB database, including brazilin. Next, molecular docking studies using Pyrx 0.98 showed that brazilin had the highest binding affinity with PCSK9 at -9.0 (Kcal/mol), which was higher than that of the other ten compounds. Subsequent in vitro PCSK9-LDLR binding assays established that brazilin decreased the binding of PCSK9 to the EGF-A fragment of the LDLR in a dose-dependent manner, with an IC50 value of 2.19 μM.

Conclusion

We have identified brazilin, which is derived from the Caesalpinia sappan herb, which can act as a small molecule inhibitor of PCSK9. Our findings suggest that screening for small molecules that can block the interaction between PCSK9 and the LDLR in silico and in vitro may be a promising approach for developing novel lipid-lowering therapy.

Recent Advances in Anti-Atherosclerosis and Potential Therapeutic Targets for Nanomaterial-Derived Drug Formulations

Atherosclerosis, the leading cause of death worldwide, is responsible for ≈17.6 million deaths globally each year. Most therapeutic drugs for atherosclerosis have low delivery efficiencies and significant side effects, and this has hampered the development of effective treatment strategies. Diversified nanomaterials can improve drug properties and are considered to be key for the development of improved treatment strategies for atherosclerosis. The pathological mechanisms underlying atherosclerosis is summarized, rationally designed nanoparticle-mediated therapeutic strategies, and potential future therapeutic targets for nanodelivery. The content of this study reveals the potential and challenges of nanoparticle use for the treatment of atherosclerosis and highlights new effective design ideas.

Circulating PCSK9 as a prognostic biomarker of cardiovascular events in individuals with type 2 diabetes: evidence from a 16.8-year follow-up study

BACKGROUND

Atherosclerotic cardiovascular disease (ASCVD) is the leading cause of morbidity and mortality, being twofold to fourfold more common in patients with type 2 diabetes mellitus (T2DM) than in individuals without diabetes. However, despite this decade-old knowledge, the identification of a specific prognostic risk biomarker remains particularly challenging.

METHODS

Taking advantage of a large sample of Caucasian patients (n = 529) with a diagnosis of T2DM followed for a median of 16.8 years, the present study was aimed at testing the hypothesis that fasting serum proprotein convertase subtilisin/kexin type 9 (PCSK9) levels could be prognostic for major adverse cardiovascular events (MACE) and all-cause mortality.

RESULTS

Median levels of PCSK9 were 259.8 ng/mL, being higher in women compared to men and increasing even more in the presence of a complication (e.g., diabetic kidney disease). PCSK9 positively correlated with markers of blood glucose homeostasis (e.g., HbA1c, fasting insulin and HOMA-IR) and the atherogenic lipid profile (e.g., non-HDL-C, apoB and remnant cholesterol). Serum PCSK9 predicted new-onset of MACE, either fatal or non-fatal, only in women (Odds Ratio: 2.26, 95% CI 1.12-4.58) and all-cause mortality only in men (Hazard Ratio: 1.79, 95% CI 1.13-2.82).

CONCLUSIONS

Considering that up to two-thirds of individuals with T2DM develop ASCVD in their lifetime, the assessment of circulating PCSK9 levels can be envisioned within the context of a biomarker-based strategy of risk stratification. However, the sex difference found highlights an urgent need to develop sex-specific risk assessment strategies.

TRIAL REGISTRATION

It is a retrospective study.

The Anti-Thrombotic Effects of PCSK9 Inhibitors

Atherosclerosis is the primary process that underlies cardiovascular disease. The connection between LDL cholesterol and the formation of atherosclerotic plaques is established by solid evidence. PCSK9 inhibitors have proven to be a valuable and practical resource for lowering the LDL cholesterol of many patients in recent years. Their inhibitory effect on atherosclerosis progression seems to be driven not just by lipid metabolism modification but also by LDL-independent mechanisms. We review the effect of PCSK9 inhibitors on various mechanisms involving platelet activation, inflammation, endothelial dysfunction, and the resultant clot formation. The main effectors of PCSK9 activation of platelets are CD36 receptors, lipoprotein(a), oxidised LDL particles, tissue factor, and factor VIII. Many more molecules are under investigation, and this area of research is growing rapidly.

A Review of Progress on Targeting LDL Receptor-Dependent and -Independent Pathways for the Treatment of Hypercholesterolemia, a Major Risk Factor of ASCVD

Since the discovery of the LDL receptor in 1973 by Brown and Goldstein as a causative protein in hypercholesterolemia, tremendous amounts of effort have gone into finding ways to manage high LDL cholesterol in familial hypercholesterolemic (HoFH and HeFH) individuals with loss-of-function mutations in the LDL receptor (LDLR) gene. Statins proved to be the first blockbuster drug, helping both HoFH and HeFH individuals by inhibiting the cholesterol synthesis pathway rate-limiting enzyme HMG-CoA reductase and inducing the LDL receptor. However, statins could not achieve the therapeutic goal of LDL. Other therapies targeting LDLR include PCSK9, which lowers LDLR by promoting LDLR degradation. Inducible degrader of LDLR (IDOL) also controls the LDLR protein, but an IDOL-based therapy is yet to be developed. Among the LDLR-independent pathways, such as angiopoietin-like 3 (ANGPTL3), apolipoprotein (apo) B, apoC-III and CETP, only ANGPTL3 offers the advantage of treating both HoFH and HeFH patients and showing relatively better preclinical and clinical efficacy in animal models and hypercholesterolemic individuals, respectively. While loss-of-LDLR-function mutations have been known for decades, gain-of-LDLR-function mutations have recently been identified in some individuals. The new information on gain of LDLR function, together with CRISPR-Cas9 genome/base editing technology to target LDLR and ANGPTL3, offers promise to HoFH and HeFH individuals who are at a higher risk of developing atherosclerotic cardiovascular disease (ASCVD).

Proprotein convertase subtilisin/kexin type 9 genetic screening using the vervet (Chlorocebus aethiops) model

BACKGROUND

The proprotein convertase subtilisin/kexin type 9 (PCSK9) gene has come to prominence due to its reported function in the clearance of low-density lipoprotein cholesterol. The vervet monkey (Chlorocebus aethiops) was utilized to study the genetics of PCSK9 gene.

METHOD

Sixteen vervet monkeys were selected to screen for possible PCSK9 polymorphisms and to determine gene expression.

RESULTS

Four PCSK9 sequence variants (T112T, R148S, H177N and G635G) were identified and three of these variants (H177N, R148S, and G635G) were categorized as loss of function mutations. A decline in gene expression levels was also observed in animals harboring these three variants. Although the selected variants might have affected the level of gene expression in the selected animals, individual variation was also noticed in some of these individuals with the G635G variant.

CONCLUSION

Based on the findings obtained from this study, it is suggestive that the activity of PCSK9 was hindered.

Interleukin-8 (IL-8) as a Potential Mediator of an Association between Trimethylamine N-Oxide (TMAO) and Proprotein Convertase Subtilisin/Kexin Type 9 (PCSK9) among African Americans at Risk of Cardiovascular Disease

Trimethylamine N-oxide (TMAO)-a microbial metabolite derived from the hepatic-gut axis-is linked to inflammation, hyperlipidemia, and cardiovascular disease (CVD). Proprotein convertase subtilisin/kexin type 9 (PCSK9), which is largely hepatically expressed, blocks low-density lipoprotein (LDL) receptor recycling, also leading to hyperlipidemia. The primary objective of this study was to investigate a previously hypothesized potential relationship between TMAO and PCSK9 in order to explore novel mechanisms linking TMAO and CVD risk. African American adults at risk of CVD living in the Washington DC area were recruited to participate in a cross-sectional community-based study (n = 60, 93% female, BMI = 33). Fasting levels of inflammatory cytokines (i.e., interleukin (IL)-1 beta, tumor necrosis factor-alpha, and interleukin-8), TMAO, and PCSK9 were measured using Luminex and ELISA, respectively. Univariate and multivariate linear regression analyses and structural equation mediation analyses were conducted using STATA. All models were adjusted for body mass index (BMI) and atherosclerotic CVD risk score (ASCVD). A significant association between TMAO and PCSK9 was identified (β = 0.31, p = 0.02). Both TMAO and PCSK9 were significantly associated with IL-8 (TMAO: β = 0.45, p = 0.00; PCSK9: β = 0.23, p = 0.05) in adjusted models. Mediation analysis indicated that 34.77% of the relationship between TMAO and PCSK9 was explained by IL-8. Our findings indicate a potential PCSK9-involved pathway for TMAO and CVD risk, with potential mediation by IL-8.

Jha P, Lupieri A, Nakano T, Passos LS, Rogers MA, Becker-Greene D, Le TD, Decano JL, Ho Lee L, Guimaraes GC, Abdelhamid I, Halu A, Muscoloni A, V. Cannistraci C, Higashi H, Zhang H, Vromman A, Libby P, Keith Ozaki C, Sharma A, Singh SA, Aikawa E, Aikawa M. Proprotein Convertase Subtilisin/Kexin 9 (PCSK9) Promotes Macrophage Activation via LDL Receptor-Independent Mechanisms

BACKGROUND

Activated macrophages contribute to the pathogenesis of vascular disease. Vein graft failure is a major clinical problem with limited therapeutic options. PCSK9 (proprotein convertase subtilisin/kexin 9) increases low-density lipoprotein (LDL)-cholesterol levels via LDL receptor (LDLR) degradation. The role of PCSK9 in macrophage activation and vein graft failure is largely unknown, especially through LDLR-independent mechanisms. This study aimed to explore a novel mechanism of macrophage activation and vein graft disease induced by circulating PCSK9 in an LDLR-independent fashion.

METHODS

We used Ldlr^-/- mice to examine the LDLR-independent roles of circulating PCSK9 in experimental vein grafts. Adeno-associated virus (AAV) vector encoding a gain-of-function mutant of PCSK9 (rAAV8/D377Y-mPCSK9) induced hepatic PCSK9 overproduction. To explore novel inflammatory targets of PCSK9, we used systems biology in Ldlr^-/- mouse macrophages.

RESULTS

In Ldlr^-/- mice, AAV-PCSK9 increased circulating PCSK9, but did not change serum cholesterol and triglyceride levels. AAV-PCSK9 promoted vein graft lesion development when compared with control AAV. In vivo molecular imaging revealed that AAV-PCSK9 increased macrophage accumulation and matrix metalloproteinase activity associated with decreased fibrillar collagen, a molecular determinant of atherosclerotic plaque stability. AAV-PCSK9 induced mRNA expression of the pro-inflammatory mediators IL-1β (interleukin-1 beta), TNFα (tumor necrosis factor alpha), and MCP-1 (monocyte chemoattractant protein-1) in peritoneal macrophages underpinned by an in vitro analysis of Ldlr^-/- mouse macrophages stimulated with endotoxin-free recombinant PCSK9. A combination of unbiased global transcriptomics and new network-based hyperedge entanglement prediction analysis identified the NF-κB (nuclear factor-kappa B) signaling molecules, lectin-like oxidized LOX-1 (LDL receptor-1), and SDC4 (syndecan-4) as potential PCSK9 targets mediating pro-inflammatory responses in macrophages.

CONCLUSIONS

Circulating PCSK9 induces macrophage activation and vein graft lesion development via LDLR-independent mechanisms. PCSK9 may be a potential target for pharmacologic treatment for this unmet medical need.

The circulating furin-cleaved/mature PCSK9 ratio has a potential prognostic significance in statin-naïve patients with acute ST elevation myocardial infarction

Background and aims

Proprotein convertase subtilisin/kexin type 9 (PCSK9) circulates as mature and furin-cleaved forms, but their biological functions are uncertain. We investigated whether their levels associate with prognosis in patients with acute ST elevation myocardial infarction (STEMI).

Methods

We enrolled 160 statin-naïve patients with acute STEMI and followed for 3 years. PCSK9 subtype levels were determined by an enzyme-linked immunosorbent assay before and at five timepoints up to 48 h after emergent coronary intervention. The occurrence of coronary and cardiac events was compared between subjects stratified by the PCSK9 level.

Results

One hundred and twenty-six patients completed 3 years of follow-up. In the acute phase, both PCSK9 subtype levels decreased, and thereafter increased from 6 to 48 h (mature: from 198 ± 67 to 334 ± 116 ng/mL, furin-cleaved: from 20 ± 7 to 39 ± 16 ng/mL, both p < 0.01). Major cardiac events occurred in 46 patients. The furin-cleaved/mature PCSK9 ratio at 48 h after coronary intervention predicted the likelihood of experiencing of events; patients in the third tertile had lower event-free survival than those in the first and second tetiles in Kaplan-Meier analysis (p = 0.004). Multivariate Cox regression analysis revealed that this ratio had a greater impact (HR: 1.92; 95% CI: 1.06-3.45, p = 0.03) on events than other known atherosclerosis risk factors.

Conclusions

The furin-cleaved/mature PCSK9 ratio was associated with 3-year cardiovascular events in statin-naïve patients with acute STEMI, suggesting a potential link between furin cleavage process of PCSK9 and its effect on prognosis. (249 words).

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.

Curcumin nicotinate decreases serum LDL cholesterol through LDL receptor-mediated mechanism

Curcumin nicotinate (Curtn) is a synthesized ester derivative of curcumin and niacin. Our previous study has shown that Curtn lowers serum low-density lipoprotein cholesterol (LDL-C) levels in apoE^-/- mice and promotes LDL-C uptake into HepG2 cells in vitro. The present study was to test the hypothesis that Curtn decreases serum LDL-C levels through decreased expression of pro-protein convertase subtilisin/kexin type 9 (PCSK9) and subsequent increase in LDL receptor expression. Male Wistar rats on high-fat diet (HFD) were treated with Curtn or rosuvastatin. Curtn or rosuvastatin treatment significantly decreased serum levels of total cholesterol (TC) and LDL-C in rats on HFD with increased liver LDL receptor expression. LDL-C-lowering effect of Curtn was not observed in LDL receptor deficient (LDLR^-/-) mice on HFD, while rosuvastatin still decreased serum lipid levels in LDLR^-/- mice, indicating that the reduction of serum LDL-C levels by Curtn treatment was LDL receptor-dependent. Curtn treatment also significantly decreased the protein expression of PCSK9 in Wistar rats and LDLR^-/- mice. In HepG2 cells with overexpression of human PCSK9, Curtn treatment significantly increased LDL-C uptakes into hepatocytes, and increased LDL receptor distribution on cell surface in association with decreased PCSK9 protein expression. RNAi-LDLR significantly attenuated the effect of Curtn on LDLR distribution on cell surface. These data indicates that Curtn would decrease serum LDL-C level at least partially through inhibition of PCSK9 expression, and subsequent increase in LDL receptor expression and distribution in hepatocytes, serving as a potential novel compound to treat hyperlipidemia.

Recent Update on PCSK9 and Platelet Activation Experimental Research Methods: In Vitro and In Vivo Studies

Proprotein convertase subtilisin/kexin type 9 (PCSK9) is a crucial factor in the development and progression of cardiovascular diseases. PCSK9 has been demonstrated to modify LDL plasma levels and increase platelet activation, which promotes atherosclerosis, a defining feature of nearly all cardiovascular diseases. Platelet activation has been shown to promote and maintain the response to atherosclerosis development, from beginning to progression and exacerbation, which can lead to advanced cardiovascular events including myocardial infarction (MI) or death. Research on PCSK9 and platelet activation is currently underway with the main goal of reducing the risk of advanced cardiovascular events by preventing or slowing down atherosclerosis progression. Both in vitro and in vivo studies have been used to explore PCSK9 functions to develop new drugs targeting PCSK9. Finding the most suitable study models that represent the pathological and physiological systems found in humans is very important to achieving the goal. This review aimed to present a current and comprehensive overview of the experimental models that have been used to investigate the role of PCSK9 in platelet activation-induced atherosclerotic cardiovascular diseases.

Antitumor activity and molecular mechanism of proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibition

Proprotein convertase subtilisin/kexin type 9 (PCSK9) is a member of the proprotein convertase family of proteins that activate other proteins in cells. Functionally, PCSK9 binds to the receptor of low-density lipoprotein particles (LDL) to regulate cholesterol metabolism and lipoprotein homeostasis in human body. PCSK9 inhibition is a novel pharmacological strategy to control hypercholesterolemia and cardiovascular diseases. Recently accumulating evidence realizes that PCSK9 possesses other roles in cells, such as regulation of tissue inflammatory response, intratumoral immune cell infiltration, and tumor progression. This review discussed the advancement of PCSK9 research on its role and underlying mechanisms in tumor development and progression. For example, PCSK9 inhibition could attenuate progression of breast cancer, glioma, colon tumor, hepatocellular cancer, prostate cancer, and lung adenocarcinoma and promote apoptosis of glioma, prostate cancer, and hepatocellular cancer cells. PCSK9 deficiency could reduce liver metastasis of B16F1 melanoma cells by lowering the circulating cholesterol levels. PCSK9 gene knockdown substantially attenuated mouse tumor growth in vivo by activation of cytotoxic T cells, although PCSK9 knockdown had no effect on morphology and growth rate of different mouse cancer cell lines in vitro. PCSK9 inhibition thus can be used to control human cancers. Future preclinical and clinical studies are warranted to define anti-tumor activity of PCSK9 inhibition.

The Multifaceted Biology of PCSK9

This article reviews the discovery of PCSK9, its structure-function characteristics, and its presently known and proposed novel biological functions. The major critical function of PCSK9 deduced from human and mouse studies, as well as cellular and structural analyses, is its role in increasing the levels of circulating low-density lipoprotein (LDL)-cholesterol (LDLc), via its ability to enhance the sorting and escort of the cell surface LDL receptor (LDLR) to lysosomes. This implicates the binding of the catalytic domain of PCSK9 to the EGF-A domain of the LDLR. This also requires the presence of the C-terminal Cys/His-rich domain, its binding to the secreted cytosolic cyclase associated protein 1, and possibly another membrane-bound "protein X". Curiously, in PCSK9-deficient mice, an alternative to the downregulation of the surface levels of the LDLR by PCSK9 is taking place in the liver of female mice in a 17β-estradiol-dependent manner by still an unknown mechanism. Recent studies have extended our understanding of the biological functions of PCSK9, namely its implication in septic shock, vascular inflammation, viral infections (Dengue; SARS-CoV-2) or immune checkpoint modulation in cancer via the regulation of the cell surface levels of the T-cell receptor and MHC-I, which govern the antitumoral activity of CD8+ T cells. Because PCSK9 inhibition may be advantageous in these processes, the availability of injectable safe PCSK9 inhibitors that reduces by 50% to 60% LDLc above the effect of statins is highly valuable. Indeed, injectable PCSK9 monoclonal antibody or small interfering RNA could be added to current immunotherapies in cancer/metastasis.

The Relationship of Circulating Proprotein Convertase Subtilisin/Kexin Type 9 With TSH and Lipid Profile in Newly Diagnosed Patients With Subclinical and Overt Hypothyroidism

Introduction:

Overt and subclinical hypothyroidism are mostly associated with dyslipidemia, an essential cardiovascular risk factor. Recently, thyroid stimulating hormone (TSH) was identified to have a direct role on lipid metabolism via increased expression of hepatic proprotein convertase subtilisin/kexin type 9 (PCSK9). PCSK9 plays a crucial role in lipid metabolism via regulating LDL-C levels. Thus, we aimed to evaluate circulating PCSK9 levels and to assess its relationship with serum TSH and lipids in newly diagnosed patients had overt and subclinical hypothyroidism.

Methods:

In our study, we enrolled 60 newly diagnosed untreated patients with overt and subclinical hypothyroidism and 30 euthyroid subjects served as the control group. Serum TSH, FT4, FT3, lipid profile and circulating PCSK9 levels using ELISA kits were measured in all subjects. Our data were summarized using mean ± SD or median and interquartile range. Correlations between PCSK9 expression levels and different variables were done using Spearman correlation coefficient.

Results:

Circulating PCSK9 median levels were significantly increased in patients had overt and subclinical hypothyroidism (12.45 ng/ml, 7.50 ng/ml respectively) compared to the control group (3.30 ng/ml) (P < .001). Circulating PCSK9 levels significantly correlated positively with TSH, total cholesterol, triglycerides, and BMI, and negatively correlated with FT4 and FT3 among all studied subjects. Using multivariate regression analysis TSH was the only significant independent predictor of circulating PCSK9 (P < .001).

Conclusion:

Our results supports the new implication of TSH in lipid metabolism via the significant association with PCSK9. Whether this relationship between TSH and PCSK9 is a cause or just an association needs further evaluation.

Recent advance in treatment of atherosclerosis: Key targets and plaque-positioned delivery strategies

Atherosclerosis, a chronic inflammatory disease of vascular wall, is a progressive pathophysiological process with lipids oxidation/depositing initiation and innate/adaptive immune responses. The coordination of multi systems covering oxidative stress, dysfunctional endothelium, diseased lipid uptake, cell apoptosis, thrombotic and pro-inflammatory responding as well as switched SMCs contributes to plaque growth. In this circumstance, inevitably, targeting these processes is considered to be effective for treating atherosclerosis. Arriving, retention and working of payload candidates mediated by targets in lesion direct ultimate therapeutic outcomes. Accumulating a series of scientific studies and clinical practice in the past decades, lesion homing delivery strategies including stent/balloon/nanoparticle-based transportation worked as the potent promotor to ensure a therapeutic effect. The objective of this review is to achieve a very brief summary about the effective therapeutic methods cooperating specifical targets and positioning-delivery strategies in atherosclerosis for better outcomes.

Insight into the Evolving Role of PCSK9

Proprotein convertase subtilisin/kexin type 9 (PCSK9) is the last discovered member of the family of proprotein convertases (PCs), mainly synthetized in hepatic cells. This serine protease plays a pivotal role in the reduction of the number of low-density lipoprotein receptors (LDLRs) on the surface of hepatocytes, which leads to an increase in the level of cholesterol in the blood. This mechanism and the fact that gain of function (GOF) mutations in PCSK9 are responsible for causing familial hypercholesterolemia whereas loss-of-function (LOF) mutations are associated with hypocholesterolemia, prompted the invention of drugs that block PCSK9 action. The high efficiency of PCSK9 inhibitors (e.g., alirocumab, evolocumab) in decreasing cardiovascular risk, pleiotropic effects of other lipid-lowering drugs (e.g., statins) and the multifunctional character of other proprotein convertases, were the cause for proceeding studies on functions of PCSK9 beyond cholesterol metabolism. In this article, we summarize the current knowledge on the roles that PCSK9 plays in different tissues and perspectives for its clinical use.

Ablation of Plasma Prekallikrein Decreases LDL Cholesterol by Stabilizing LDL Receptor and Protects against Atherosclerosis

Background: High blood cholesterol accelerates the progression of atherosclerosis that is an asymptomatic process lasting for decades. Rupture of atherosclerotic plaques induces thrombosis that results in myocardial infarction or stroke. Lowering cholesterol levels is beneficial for preventing atherosclerotic cardiovascular disease (ASCVD). Methods: Low-density lipoprotein (LDL) receptor (LDLR) was used as the bait to identify its binding proteins in the plasma, and the coagulation factor prekallikrein (PK, encoded by the KLKB1 gene) was revealed. The correlation between serum PK protein content and lipid levels in young Chinese Han was then analyzed. To investigate the effects of PK ablation on LDLR and lipid levels in vivo, we genetically deleted Klkb1 in hamsters and heterozygous Ldlr knockout mice, as well as knocked Klkb1 down using adeno-associated virus-mediated shRNA in rats. The additive effect of PK and PCSK9 inhibition was evaluated as well. We also applied the anti-PK neutralizing antibody that blocked PK and LDLR interaction to mice. Mice lacking both PK and Apolipoprotein e (Klkb1^-/-Apoe^-/-) were generated to assess the role of PK in atherosclerosis. Results: PK directly bound LDLR and induced its lysosomal degradation. The serum PK concentrations positively correlated with LDL cholesterol levels in 198 young Chinese Han adults. Genetic depletion of Klkb1 increased hepatic LDLR and decreased circulating cholesterol in multiple rodent models. Inhibition of PCSK9 with Evolocumab further decreased plasma LDL cholesterol levels in Klkb1-deficient hamsters. The anti-PK neutralizing antibody could similarly lower plasma lipids through upregulating hepatic LDLR. Ablation of Klkb1 slowed down the progression of atherosclerosis in mice on Apoe-deficient background. Conclusions: PK regulates circulating cholesterol levels through binding to LDLR and inducing its lysosomal degradation. Ablation of PK stabilizes LDLR, decreases LDL cholesterol and prevents atherosclerotic plaque development. This study suggests that PK is a promising therapeutic target to treat ASCVD.

Proprotein Convertase Subtilisin/Kexin Type 9 and Inflammation: An Updated Review

The function of Proprotein Convertase Subtilisin/Kexin Type 9 (PCSK9), a novel plasma protein, has mainly been involved in cholesterol metabolism in the liver, while, more interestingly, recent data have shown that PCSK9 also took part in the modulation of inflammation, which appeared to be another explanation for the reduction of cardiovascular risk by PCSK9 inhibition besides its significant effect on lowering lower-density lipoprotein cholesterol (LDL-C) concentration. Overall, a series of previous studies suggested an association of PCSK9 with inflammation. Firstly, PCSK9 is able to induce the secretion of proinflammatory cytokines in macrophages and in other various tissues and elevated serum PCSK9 levels could be observed in pro-inflammatory conditions, such as sepsis, acute coronary syndrome (ACS). Secondly, detailed signaling pathway studies indicated that PCSK9 positively regulated toll-like receptor 4 expression and inflammatory cytokines expression followed by nuclear factor-kappa B (NF-kB) activation, together with apoptosis and autophagy progression. Besides, PCSK9 enhanced and interacted with scavenger receptors (SRs) of inflammatory mediators like lectin-like oxidized-LDL receptor-1 (LOX-1) to promote inflammatory response. Additionally, several studies also suggested that the role of PCSK9 in atherogenesis was intertwined with inflammation and the interacting effect shown between PCSK9 and LOX-1 was involved in the inflammatory response of atherosclerosis. Finally, emerging clinical trials indicated that PCSK9 inhibitors could reduce more events in patients with ACS accompanied by increased inflammatory status, which might be involved in its attenuating impact on arterial plaque. Hence, further understanding of the relationship between PCSK9 and inflammation would be necessary to help prevent and manage the atherosclerotic cardiovascular disease (ASCVD) clinically. This review article will update the recent advances in the link of PCSK9 with inflammation.

PCSK9 Promotes Cardiovascular Diseases: Recent Evidence about Its Association with Platelet Activation-Induced Myocardial Infarction

Cardiovascular diseases are the leading cause of death worldwide, with the majority of the cases being heart failure due to myocardial infarction. Research on cardiovascular diseases is currently underway, particularly on atherosclerosis prevention, to reduce the risk of myocardial infarction. Proprotein convertase subtilisin/kexin type 9 (PCSK9) has been reported to play a role in lipid metabolism, by enhancing low-density lipoprotein (LDL) receptor degradation. Therefore, PCSK9 inhibitors have been developed and found to successfully decrease LDL plasma levels. Recent experimental studies have also implicated PCSK9 in platelet activation, having a key role during atherosclerosis progression. Although numerous studies have addressed the role of PCSK9 role in controlling hypercholesterolemia, studies and discussions exploring its involvement in platelet activation are still limited. Hence, here, we address our current understanding of the pathophysiological process involved in atherosclerosis-induced myocardial infarction (MI) through platelet activation and highlight the molecular mechanisms used by PCSK9 in regulating platelet activation. Undoubtedly, a deeper understanding of the relationship between platelet activation and the underlying molecular mechanisms of PCSK9 in the context of MI progression will provide a new strategy for developing drugs that selectively inhibit the most relevant pathways in cardiovascular disease progression.

Effects of PCSK9 Targeting: Alleviating Oxidation, Inflammation, and Atherosclerosis

Characterized as a chronic inflammatory disease of the large arteries, atherosclerosis is the primary cause of cardiovascular disease, the leading contributor of morbidity and mortality worldwide. Elevated plasma cholesterol levels and chronic inflammation within the arterial plaque are major mediators of plaque initiation, progression, and instability. In 2003, the protein PCSK9 (proprotein convertase subtilisin/kexin 9) was discovered to play a critical role in cholesterol regulation, thus becoming a key player in the mechanisms behind atherosclerotic plaque development. Emerging evidence suggests that PCSK9 could potentially have effects on atherosclerosis that are independent of cholesterol levels. The objective of this review was to discuss the role on PCSK9 in oxidation, inflammation, and atherosclerosis. This function activates proinflammatory cytokine production and affects oxidative modifications within atherosclerotic lesions, revealing its more significant role in atherosclerosis. Although a variety of evidence demonstrates that PCSK9 plays a role in atherosclerotic inflammation, the direct mechanism of involvement is still unknown, driving a gap in knowledge to such a predominant player in cardiovascular disease. Investigation of proteins structurally related to PCSK9 may interestingly be the link in unveiling the mechanistic role of this protein’s involvement in oxidation and inflammation. Importantly, the unique structure of PCSK9 bears structural homology to a one‐of‐a‐kind domain found in the metabolic protein resistin, which is responsible for many of the same inflammatory outcomes as PCSK9. Closing this gap in knowledge of PCSK9`s role in atherosclerotic oxidation and inflammation will provide fundamental information for understanding, preventing, and treating cardiovascular disease.

PCSK9 as a Target for Development of a New Generation of Hypolipidemic Drugs

PCSK9 has now become an important target to create new classes of lipid-lowering drugs. The prevention of its interaction with LDL receptors allows an increase in the number of these receptors on the surface of the cell membrane of hepatocytes, which leads to an increase in the uptake of cholesterol-rich atherogenic LDL from the bloodstream. The PCSK9 antagonists described in this review belong to different classes of compounds, may have a low molecular weight or belong to macromolecular structures, and also demonstrate different mechanisms of action. The mechanisms of action include preventing the effective binding of PCSK9 to LDLR, stimulating the degradation of PCSK9, and even blocking its transcription or transport to the plasma membrane/cell surface. Although several types of antihyperlipidemic drugs have been introduced on the market and are actively used in clinical practice, they are not without disadvantages, such as well-known side effects (statins) or high costs (monoclonal antibodies). Thus, there is still a need for effective cholesterol-lowering drugs with minimal side effects, preferably orally bioavailable. Low-molecular-weight PCSK9 inhibitors could be a worthy alternative for this purpose.

The PCSK9 discovery, an inactive protease with varied functions in hypercholesterolemia, viral infections, and cancer

In 2003, the sequences of mammalian proprotein convertase subtilisin/kexin type 9 (PCSK9) were reported. Radiolabeling pulse-chase analyses demonstrated that PCSK9 was synthesized as a precursor (proPCSK9) that undergoes autocatalytic cleavage in the endoplasmic reticulum into PCSK9, which is then secreted as an inactive enzyme in complex with its inhibitory prodomain. Its high mRNA expression in liver hepatocytes and its gene localization on chromosome 1p32, a third locus associated with familial hypercholesterolemia, other than LDLR or APOB, led us to identify three patient families expressing the PCSK9 variants S127R or F216L. Although Pcsk9 and Ldlr were downregulated in mice that were fed a cholesterol-rich diet, PCSK9 overexpression led to the degradation of the LDLR. This led to the demonstration that gain-of-function and loss-of-function variations in PCSK9 modulate its bioactivity, whereby PCSK9 binds the LDLR in a nonenzymatic fashion to induce its degradation in endosomes/lysosomes. PCSK9 was also shown to play major roles in targeting other receptors for degradation, thereby regulating various processes, including hypercholesterolemia and associated atherosclerosis, vascular inflammation, viral infections, and immune checkpoint regulation in cancer. Injectable PCSK9 monoclonal antibody or siRNA is currently used in clinics worldwide to treat hypercholesterolemia and could be combined with current therapies in cancer/metastasis. In this review, we present the critical information that led to the discovery of PCSK9 and its implication in LDL-C metabolism. We further analyze the underlying functional mechanism(s) in the regulation of LDL-C, as well as the evolving novel roles of PCSK9 in both health and disease states.

PCSK9 Gene Participates in the Development of Primary Dyslipidemias

Dyslipidemias are a group of diseases, which are characterized by abnormal blood concentrations of cholesterol, triglycerides and/or low-density lipoprotein-cholesterol (LDL-c). Dyslipidemia is a determinant condition for the progress of an atherosclerotic plaque formation. The resulting atherogenicity is due to at least two mechanisms: first, to the accumulation in the plasma of lipid particles that have the capacity to alter the function of the endothelium and deposit at the atheromatous plaque, and second, at an insufficient concentration of multifactorial type of high density lipoprotein-cholesterol (HDL-c), whose function is to protect against the development of atherosclerosis. Its highest prevalence is encountered among individuals with diabetes, hypertension or overweight. Hyperlipidemia is one of the main predisposing factors for the development of cardiovascular disease. Hyperlipidemia can be the result of a genetic condition, the secondary expression of a primary process or the consequence of exogenous factors (food, cultural, socio-economic, etc.), all of which lead to the elevation of plasma lipid levels. The objective of this study was to carry out an analysis of the genes involved in the development of dyslipidemias that lead to cardiovascular disease with special emphasis on the proprotein convertase subtilin/kexin type 9 (PCSK9) gene. The PCSK9 gene participates in the development of primary dyslipidemias, mainly familial hypercholesterolemia, currently the pharmacological treatment of choice to reduce LDL-c are statins, however, it has been observed that these have been insufficient to eliminate cardiovascular risk, especially in subjects with primary forms of hypercholesterolemia related to genetic mutations, or statin intolerance.

Plasmatic PCSK9 Levels Are Associated with Very Fast Progression of Asymptomatic Degenerative Aortic Stenosis

The aim of this work was to study the association of potential biomarkers with fast aortic stenosis (AS) progression. Patients with moderate-to-severe AS were classified as very fast progressors (VFP) if exhibited an annualized change in peak velocity (aΔVmax) ≥0.45m/s/year and/or in aortic valve area (aΔAVA) ≥-0.2cm2/year. Respective cut-off values of ≥0.3m/s/year and ≥-0.1cm²/year defined fast progressors (FP), whereas the remaining patients were non-fast progressors (non-FP). Baseline markers of lipid metabolism, inflammation, and cardiac overload were determined. Two hundred and nine patients (97 non-FP, 38 FP, and 74 VFP) were included. PCSK9 levels were significantly associated with VFP (OR 1.014 [95%CI 1.005-1.024], for every 10 ng/mL), as were active smoking (OR 3.48) and body mass index (BMI, OR 1.09), with an AUC of 0.704 for the model. PCSK9 levels, active smoking, and BMI were associated with very fast AS progression in our series, suggesting that inflammation and calcification participate in disease progression.

The consequences of PCSK9 inhibition in selected tissues

Proprotein convertase subtilisin/kexin type 9 (PCSK9) is one of nine members of the proprotein convertase family. These serine proteases play a pivotal role in the post-translational modification of proteins and the activation of hormones, enzymes, transcription factors and growth factors. As a result, they participate in many physiological processes like embryogenesis, activity of central nervous system and lipid metabolism. Scientific studies show that the family of convertases is also involved in the pathogenesis of viral and bacterial infections, osteoporosis, hyperglycaemia, cardiovascular diseases, neurodegenerative disorders and cancer. The inhibition of PCSK9 by two currently approved for use monoclonal antibodies (alirocumab, evolocumab) slows down the degradation of low-density lipoprotein cholesterol receptors (LDLRs). This leads to increased density of LDLRs on the surface of hepatocytes, resulting in decreased level of low-density lipoprotein cholesterol (LDL-C) in the bloodstream, which is connected with the reduction of cardiovascular risk. PCSK9 inhibitors (PCSK9i) were created for the patients who could not achieve appropriate level of LDL-C using current statin and ezetimibe therapy. It seems that high therapeutic efficacy of PCSK9i will make them more common in the clinical use. The pleiotropic effects of previously mentioned lipid-lowering therapies were the reasons for literature review of possible positive and negative effects of PCSK9 inhibition beyond cholesterol metabolism.

PCSK9 Biology and Its Role in Atherothrombosis

It is now about 20 years since the first case of a gain-of-function mutation involving the as-yet-unknown actor in cholesterol homeostasis, proprotein convertase subtilisin/kexin type 9 (PCSK9), was described. It was soon clear that this protein would have been of huge scientific and clinical value as a therapeutic strategy for dyslipidemia and atherosclerosis-associated cardiovascular disease (CVD) management. Indeed, PCSK9 is a serine protease belonging to the proprotein convertase family, mainly produced by the liver, and essential for metabolism of LDL particles by inhibiting LDL receptor (LDLR) recirculation to the cell surface with the consequent upregulation of LDLR-dependent LDL-C levels. Beyond its effects on LDL metabolism, several studies revealed the existence of additional roles of PCSK9 in different stages of atherosclerosis, also for its ability to target other members of the LDLR family. PCSK9 from plasma and vascular cells can contribute to the development of atherosclerotic plaque and thrombosis by promoting platelet activation, leukocyte recruitment and clot formation, also through mechanisms not related to systemic lipid changes. These results further supported the value for the potential cardiovascular benefits of therapies based on PCSK9 inhibition. Actually, the passive immunization with anti-PCSK9 antibodies, evolocumab and alirocumab, is shown to be effective in dramatically reducing the LDL-C levels and attenuating CVD. While monoclonal antibodies sequester circulating PCSK9, inclisiran, a small interfering RNA, is a new drug that inhibits PCSK9 synthesis with the important advantage, compared with PCSK9 mAbs, to preserve its pharmacodynamic effects when administrated every 6 months. Here, we will focus on the major understandings related to PCSK9, from its discovery to its role in lipoprotein metabolism, involvement in atherothrombosis and a brief excursus on approved current therapies used to inhibit its action.

Pcsk9 is associated with severity of coronary artery lesions in male patients with premature myocardial infarction

BACKGROUND

Proprotein convertase subtilisin/kexin type 9 (Pcsk9) correlated with incidence and prognosis of coronary heart disease. However, it is unclear whether Pcsk9 contributed to coronary artery lesion severity in patients with premature myocardial infarction (PMI). The present study investigated associations between Pcsk9 and coronary artery lesion severity in PMI patients who underwent coronary angiography (CAG).

METHODS

This prospective cohort study included young men (age ≤ 45 years, n = 332) with acute MI who underwent CAG between January 2017 and July 2019. Serum Pcsk9 levels and clinical characteristics were evaluated. SYNTAX scores (SYNergy between percutaneous coronary intervention with [paclitaxel-eluting] TAXUS stent and cardiac surgery) were calculated to quantify coronary artery lesions.

RESULTS

Serum Pcsk9 levels were positively associated with SYNTAX scores (r = 0.173, P < 0.05). The diagnostic cutoff value of PSCK9 level was 122.9 ng/mL, yielding an area under the curve (AUC) of 0.63, sensitivity 81%, and specificity 40%. Serum Pcsk9, LDL-C, Apob, NT-proBnp, CK level, and diabetes history were independent predictors of high SYNTAX scores (P < 0.05). After stratifying by serum LDL-C level (cutoff = 2.6 mmol/L), medium-high Pcsk9 levels had increased risk of high SYNTAX scores in patients with high LDL-C (P < 0.05), and higher serum Pcsk9 levels had increased risk of major adverse cardiac events (MACE) after adjusting for confounding factors (P < 0.05).

CONCLUSION

Serum Pcsk9 levels correlates with severity of coronary artery lesion in PMI patients and may serve as a biomarker for severity of coronary artery stenosis in this patient population, which may contribute to risk stratification.

PCSK9 and atherosclerosis: Looking beyond LDL regulation

Proprotein Convertase Subtilisin/Kexin type 9 (PCSK9) is involved in cholesterol homeostasis. After binding to the complex low-density lipoprotein (LDL)-receptor, PCSK9 induces its intracellular degradation, thus reducing serum LDL clearance. In addition to the well-known activity on the hepatic LDL receptor-mediated pathway, PCSK9 has been, however, associated with vascular inflammation in atherogenesis. Indeed, PCSK9 is expressed by various cell types that are involved in atherosclerosis (e.g. endothelial cells, smooth muscle cells and macrophages) and is detected inside human atherosclerotic plaques. We here analyse the biology of PCSK9 and its possible involvement in molecular processes involved in atherosclerosis, beyond the regulation of circulating LDL cholesterol levels.