Pleiotropic Anti-atherosclerotic Effects of PCSK9 Inhibitors From Molecular Biology to Clinical Translation

Therapeutic PCSK9 targeting: Inside versus outside the hepatocyte?

As a major regulator of LDL receptor (LDLR) activity and thus of LDL-cholesterol (LDL-C) levels, proprotein convertase subtilisin/kexin type 9 (PCSK9) represents an obvious therapeutic target for lipid lowering. The PCSK9 inhibitors, alirocumab and evolocumab, are human monoclonal antibodies (mAbs) that act outside the cell by complexing circulating PCSK9 and thus preventing its binding to the LDLR. In contrast, inclisiran, a small interfering RNA (siRNA), inhibits hepatic synthesis of PCSK9, thereby resulting in reduced amounts of the protein inside and outside the cell. Both approaches result in decreased plasma LDL-C concentrations and improved cardiovascular outcomes. Marginally superior LDL-C reduction (≈ 60 %) is achieved with mAbs as compared to the siRNA (≈ 50 %); head-to-head comparisons are required to confirm between-class differences in efficacy. Both drug classes have shown variability in LDL-C lowering response between individuals in waterfall analyses. Whereas mAb-mediated inhibition leads to a compensatory increase in plasma PCSK9 levels, siRNA treatment reduces them. These agents differ in their pharmacokinetic and pharmacodynamic features, which may translate into distinct clinical opportunities under acute (e.g. acute coronary syndromes) as compared to chronic conditions. Both drug classes provide additional reduction in LDL-C levels (up to 50 %) beyond those achieved with statin therapy, facilitating attainment of guideline-recommended LDL-C goals in high and very high-risk patients. Additional PCSK9 inhibitors, including an oral macrocyclic peptide, a small PCSK9 binding protein and a novel small molecule, plus hepatic gene editing of PCSK9, are under development. This review critically appraises pharmacological strategies to target PCSK9 either inside or outside the cell.

Anti-inflammatory effects of proprotein convertase subtilisin/kexin 9 inhibitor therapy in the early phase of acute myocardial infarction

This study examined the anti-inflammatory and endothelial function-enhancing effects of proprotein convertase subtilisin/kexin 9 (PCSK9) inhibitor therapy in the early phase after acute myocardial infarction (AMI) by assessing changes in tumor necrosis factor-α (TNF-α) levels and the L-arginine/asymmetric-dimethylarginine (ADMA) ratio. This retrospective, single-center cohort study included patients who underwent successful timely primary percutaneous coronary intervention (PCI) for first-onset AMI between September 2017 and March 2018. The PCSK9 inhibitor group comprised patients who received 75 mg alirocumab up to 7 days after AMI, while the standard therapy group comprised patients who did not. We evaluated the change in TNF-α levels and the L-arginine/ADMA ratio at the time of hospital admission and prior to discharge. PCSK9 inhibitor therapy in the early phase after AMI suppressed TNF-α levels (standard therapy group, 1.64 ± 2.14 pg/mL vs. PCSK9 inhibitor group, 0.26 ± 0.33 pg/mL; p = 0.033) and increased the L-arginine/ADMA ratio (standard therapy group, - 13.0 ± 39.7 vs. PCSK9 inhibitor group, 23.2 ± 39.7; p = 0.042). Upon multiple regression analysis adjusted for sex, age, and peak creatine kinase levels, PCSK9 inhibitor therapy was associated with TNF-α suppression (p = 0.025; β = - 0.235, 95% confidence interval [CI], - 0.436 to - 0.033). The L-arginine/ADMA ratio was also analyzed using multiple regression, adjusted for sex, age, peak creatine kinase levels, and smoking, showing a significant improvement in the ratio (p = 0.018; β = 41.913, 95% CI, 10.337-73.491). Moreover, a weak negative correlation was suggested between the change in TNF-α levels and the change in L-arginine/ADMA ratio (r = - 0.393, p = 0.058). PCSK9 inhibitor therapy in the early phase after AMI suppresses TNF-α levels and improves the L-arginine/ADMA ratio, potentially indicating anti-inflammatory and endothelial function-enhancing effects.

Atherosclerosis and the Bidirectional Relationship Between Cancer and Cardiovascular Disease: From Bench to Bedside, Part 2 Management

The first part of this review highlighted the evolving landscape of atherosclerosis, noting emerging cardiometabolic risk factors, the growing impact of exposomes, and social determinants of health. The prominent role of atherosclerosis in the bidirectional relationship between cardiovascular disease and cancer was also discussed. In this second part, we examine the complex interplay between multimorbid cardio-oncologic patients, cardiometabolic risk factors, and the harmful environments that lend a "syndemic" nature to these chronic diseases. We summarize management strategies targeting disordered cardiometabolic factors to mitigate cardiovascular disease and explore molecular mechanisms enabling more tailored therapies. Importantly, we emphasize the early interception of atherosclerosis through multifactorial interventions that detect subclinical signs (via biomarkers and imaging) to treat modifiable risk factors and prevent clinical events. A concerted preventive effort-referred to by some as a "preventome"-is essential to reduce the burden of atherosclerosis-driven chronic diseases, shifting from mere chronic disease management to the proactive promotion of "chronic health".

Major adverse events associated with lipid reduction in inclisiran:a pharmacovigilance research of the FAERS database

OBJECTIVE

The effectiveness and safety of the short-interfering RNA drug inclisiran in lowering patients' lipoprotein cholesterol levels to lower their risk of cardiovascular disease are presently being investigated. Based on the real-world adverse event report record in the FDA Adverse Event Reporting System, this article explores the occurrence and risk of adverse events during inclisiran treatment.

RESEARCH DESIGN AND METHODS

We retrieved and screened all available data from the Food and Drug Administration website for the period from 2009 to the third quarter of 2023. In addition, we conducted a descriptive analysis of adverse event reports and calculated relevant pharmacovigilance measures, including reporting odds ratio, proportional reporting ratio, Bayesian confidence propagation neural network, and empirical Bayesian geometric mean.

RESULTS

4054 adverse reaction reports were filtered from 1151 patient reports of inclisiran. The top three incidence rates of adverse reaction signals for System Organ Class in adverse event reports are GENERAL DISORDERS AND ADMINITRATION SITE CONDITIONS (24.9% reported), MUSCOSKELETAL AND CONNECTIVE TISSUE DISORDERS (18.5% reported), and GASTROINTESTINAL DISORDERS (8.7% reported). The top five preferred terms screened for frequency of occurrence with the strongest risk signals for each of the top three system organ categories are INJECTION SITE PAIN，MYALGIA and DIARRHOEA.

CONCLUSIONS

Inclisiran has good long-term treatment outcomes and safety and can be used for a long time. However, attention should be paid to adverse events with high-risk signals, especially Injection Site Reactions.

The Emerging Role of PCSK9 in the Pathogenesis of Alzheimer's Disease: A Possible Target for the Disease Treatment

Alzheimer's disease (AD) is a multifactorial neurodegenerative disease mainly caused by β-amyloid (Aβ) accumulation in the brain. Among the several factors that may concur to AD development, elevated cholesterol levels and brain cholesterol dyshomeostasis have been recognized to play a relevant role. Proprotein convertase subtilisin/kexin type 9 (PCSK9) is a protein primarily known to regulate plasma low-density lipoproteins (LDLs) rich in cholesterol and to be one of the main causes of familial hypercholesterolemia. In addition to that, PCSK9 is also recognized to carry out diverse important activities in the brain, including control of neuronal differentiation, apoptosis, and, importantly, LDL receptors functionality. Moreover, PCSK9 appeared to be directly involved in some of the principal processes responsible for AD development, such as inflammation, oxidative stress, and Aβ deposition. On these bases, PCSK9 management might represent a promising approach for AD treatment. The purpose of this review is to elucidate the role of PCSK9, whether or not cholesterol-related, in AD pathogenesis and to give an updated overview of the most innovative therapeutic strategies developed so far to counteract the pleiotropic activities of both humoral and brain PCSK9, focusing in particular on their potentiality for AD management.

Investigating the Relationship Between Lipid-Lowering Agents and the Complications of Diabetic Retinopathy

BACKGROUND AND OBJECTIVE

As the therapeutic efficacy of lipid-lowering agents (LLA) against diabetic retinopathy (DR) remains controversial, this study aimed to evaluate whether various LLA therapies are associated with a reduced risk of DR progression.

PATIENTS AND METHODS

This retrospective study of the medical records of adults with type 2 diabetes mellitus and DR compared the risk of adverse progression of DR between patients who received statins, fibrates, proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitors, and no LLA (control).

RESULTS

Patients in the statin cohort had a reduced rate of progression to proliferative DR compared to controls (HR = 0.30, CI = 0.11 to 0.83). The PCSK9 inhibitor cohort had a reduced risk of progressing to other secondary complications of DR compared to the control (RR = 0.52, CI = 0.43 to 0.64), statin (RR = 0.69, CI = 0.61 to 0.79), and fibrate (RR = 0.67, CI = 0.59 to 0.77) cohorts.

CONCLUSIONS

These findings suggest use of statins and PCSK9 inhibitors are associated with a reduced risk of adverse progression of DR. [Ophthalmic Surg Lasers Imaging Retina 2024;55:706-713.].

Targeting Inflammatory Pathways in Atherosclerosis: Exploring New Opportunities for Treatment

PURPOSE OF THE REVIEW

This review discusses the molecular mechanisms involved in the immuno-pathogenesis of atherosclerosis, the pleiotropic anti-inflammatory effects of approved cardiovascular therapies and the available evidence on immunomodulatory therapies for atherosclerotic cardiovascular disease (ACVD). We highlight the importance of clinical and translational research in identifying molecular mechanisms and discovering new therapeutic targets.

RECENT FINDINGS

The CANTOS (Canakinumab Anti-Inflammatory Thrombosis Outcomes Study) trial was the first to demonstrate a reduction in cardiovascular (CV) risk with anti-inflammatory therapy, irrespective of serum lipid levels. ACVD is the leading cause of death worldwide. Although targeting principal risk factors significantly reduces CV risk, residual risk remains unaddressed. The immunological mechanisms underlying atherosclerosis represent attractive therapeutic targets. Several commonly used and non-primarily anti-inflammatory drugs (i.e. SGLT2i, and PCSK9i) exhibit pleiotropic properties. Otherwise, recent trials have investigated the blockade of primarily inflammatory compounds, trying to lower the residual risk via low-dose IL-2, PTPN22 and CD31 pathway modulation. In the era of precision medicine, modern approaches may explore new pharmacological targets, identify new markers of vascular inflammation, and evaluate therapeutic responses.

Circulating Endothelial Progenitor Cells in Patients with Established Cardiovascular Disease Treated with PCSK9 Monoclonal Antibodies

Background

The role of circulating endothelial progenitor cells (cEPCs) in vascular repair and their association to cardiovascular protection is well established.

Objectives

We examined the effect of proprotein convertase subtilisin kexin type 9 monoclonal antibodies (PCSK9 mAb) on cEPCs in adults with hypercholesterolemia and cardiovascular disease, aiming to establish a pleotropic class effect.

Methods

Non-interventional prospective study in patients with cardiovascular disease treated with either evolocumab or alirocumab. Patients were sampled for cEPCs at baseline, 1- and 3-months following initiation of PCSK9 mAb. cEPCs were assessed using flow cytometry by expression of CD34/CD133 and vascular endothelial growth factor receptor (VEGFR)-2, and functionally by formation of colony forming units (CFUs) and by Mitochondrial Tetrazolium (MTT) assay, indicative of cEPCs viability.

Results

51 patients (median age 67 (IQR 63,74) years;63 % male, median low-density lipoprotein-cholesterol (LDL-C) 125 (102,165) mg/dL) were initiated on PCSK9 mAb therapy (evolocumab n = 22, alirocumab n = 29) for secondary prevention. Following 3-month treatment with PCSK9 mAb, there was an increase in CD34(+)VEGFR-2(+) and CD133(+)VEGFR-2(+) levels (0.50 % [IQR 0.30,1.04] to 1.36 % [0.89, 1.73], p < 0.001 and 0.57 % [0.25,0.88] to 1.18 % [0.74,1.66], p < 0.001, respectively). Functionally, increase in EPCs-CFUs was evident (0.5 [0.0,1.0] to 2.0 [1.5,2.5], p < 0.001) with concomitant increase in MTT (0.11 [0.09,0.15] to 0.17 [0.12,0.21], p < 0.001). Stratifying by PCSK9 mAb, both agents were associated with an increase in cEPCs level and function.

Conclusions

In hypercholesterolemic patients with cardiovascular disease treated with PCSK9 mAb, there is an increase in cEPCs levels and function from baseline levels. These findings, which persist in both evolocumab and alirocumab, might suggest a novel pleiotropic class effect.

miR-148a-3p mitigation of coronary artery disease through PCSK9/NF-κB inhibition of vascular endothelial cell injury

Coronary artery disease (CAD) causes myocardial ischemia, narrowing or occlusion of the lumen. Although great progress has been made in the treatment of CAD, the existing treatment methods do not meet the clinical needs, so it is urgent to find new treatment methods. The aim of this study was to investigate the mechanism of action of miR-148a-3p in alleviating CAD by inhibiting vascular endothelial cell injury and to provide new ideas for the treatment of CAD. A cell model was constructed by lipopolysaccharide (LPS) induction of vascular endothelial cells, and a CAD rat model was established by a high-fat diet and intraperitoneal injection of posterior pituitary hormone. Relevant indices were detected by RT-qPCR, ELISA, Western blot, MTT, and flow cytometry. The results indicate that in LPS-induced vascular endothelial cell assays, miR-148a-3p inhibited the upregulation of PCSK9, thereby suppressing the NF-κB signaling pathway and promoting vascular endothelial cell proliferation. Overexpression of PCSK9 and the addition of NF-κB signaling pathway activator increased vascular endothelial cell apoptosis. In animal experiments, miR-148a-3p alleviated the symptoms of CAD rats, whereas overexpression of PCSK9 promoted apoptosis and increased atheromatous plaque area in CAD rats. In conclusion, miR-148a-3p inhibits the NF-κB signaling pathway through downregulation of PCSK9, thereby protecting vascular endothelial cells and alleviating CAD.

Effect of adding PCSK9 inhibitors to lipid-lowering interventions on arterial stiffness: A systematic review and meta-analysis

BACKGROUND

Atherosclerosis, a leading cause of mortality, necessitates effective management of hypercholesterolemia, specifically elevated low-density lipoprotein cholesterol (LDL-C). The emergence of proprotein convertase subtilisin/kexin type 9 inhibitors (PCSK9i) has revolutionised lipid-lowering. PCSK9i demonstrates substantial LDL-C reduction and cardiovascular benefits, particularly in statin-intolerant or nonresponsive individuals. However, the potential pleiotropic effects of PCSK9i, especially on arterial stiffness, remain a subject of investigation. This systematic review and meta-analysis seek to provide a nuanced understanding of the potential pleiotropic effects of PCSK9i, specifically on arterial health. The primary objective was to analyse the influence of PCSK9i on arterial stiffness, extending beyond traditional lipid-lowering metrics and contributing to a more comprehensive approach to cardiovascular risk reduction.

METHODS

A systematic search was conducted across major databases, clinical trial registries and grey literature. Inclusion criteria comprised adults in prospective cohort studies undergoing PCSK9i augmentation in lipid-lowering therapy, with a focus on arterial stiffness measured by pulse wave velocity (PWv). Random-effects meta-analyses, sensitivity analyses and meta-regression models were employed to assess the pooled effect of adding PCSK9i to lipid-lowering interventions on arterial stiffness.

RESULTS

Five studies (158 participants) met the inclusion criteria, demonstrating a significant reduction in PWv (mean difference: -2.61 m/s [95% CI: -3.70, -1.52]; ES: -1.62 [95% CI: -2.53, -.71]) upon adding PCSK9i to lipid-lowering interventions. Subgroup analysis and meta-regression models suggested potential sex-based and baseline PWv-dependent variations, emphasising patient-specific characteristics.

CONCLUSION

The meta-analysis provides robust evidence that adding PCSK9i to lipid-lowering interventions significantly improves arterial stiffness, indicating broader vascular benefits beyond LDL-C reduction.

Novel Molecules in Diabetes Mellitus, Dyslipidemia and Cardiovascular Disease 2.0

Diabetes mellitus, dyslipidemia and cardiovascular disorders represent very prevalent chronic diseases in developed countries contributing to a high morbidity and loss of quality of life [...].

Early Management of Blood Lipid Levels with Non-Statin Lipid-Lowering Drugs in Acute Coronary Syndrome: A Mini Review

Acute coronary syndrome (ACS) remains a major cause of morbidity and mortality, despite many improvements in its prevention and management. Lipid management is an important aspect of secondary prevention after ACS. Previous studies indicate that the early use of intensive statin therapy in patients with ACS may alleviate the risk of recurrent cardiovascular events and mortality. However, many patients do not reach the target low-density lipoprotein cholesterol (LDL-C) level of < 55 mg/dL with statin monotherapy, and muscle-related adverse effects caused by statins hinder adherence to treatment. Novel non-statin agents are recommended for patients who cannot achieve the target LDL-C levels with high-intensity statin therapy and those with statin intolerance. The combination of statins and non-statins may synergistically affect intensively lowering LDL-C through different mechanisms, which could lead to better cardiovascular outcomes than statin monotherapy. However, it remains uncertain whether the early use of combination lipid-lowering therapy is more beneficial. The present review summarizes the benefits of intensive statin monotherapy and their early combination with non-statin medications including ezetimibe, PCSK9 inhibitors, inclisiran, and bempedoic acid (BDA) in the management of ACS.

The LEPIS-HuR-TMOD4 axis regulates hepatic cholesterol homeostasis and accelerates atherosclerosis

BACKGROUND AND AIMS

Long noncoding RNAs (lncRNAs) play important roles in the progression of atherosclerosis. In this study, we identified an uncharacterized lncRNA, Liver Expressions by PSRC1 Induced Specifically (LEPIS). This study aimed to clarify the mechanism though which LEPIS affects atherosclerosis (AS).

METHODS

The expression of LEPIS and its potential target, tropomodulin 4 (TMOD4), was increased in the livers of ApoE-/- mice fed a high-fat diet (HFD). An ApoE-/- mouse model in which LEPIS or TMOD4 was overexpressed in the liver was established. The plaque load in the aorta was assessed, plasma was collected to measure blood lipid levels, and the liver was collected to study cholesterol metabolism.

RESULTS

We found that both LEPIS and TMOD4 increased the AS burden and reduced hepatic cholesterol levels. A further study revealed that LEPIS and TMOD4 affected the expression of genes related to hepatic cholesterol homeostasis, including proprotein convertase subtilisin/kexin type 9 (PCSK9) and low-density lipoprotein receptor (LDLR), which are closely related to hypercholesterolemia. Mechanistically, human antigen R (HuR), an RNA-binding protein (RBP), was shown to be critical for the regulation of TMOD4 by LEPIS. Furthermore, we found that verexpression of LEPIS promoted the shuttling of HuR from the nucleus to the cytoplasm, enhanced the stability of TMOD4 mRNA, and in turn promoted the expression of TMOD4. In addition, TMOD4 was found to affect intracellular cholesterol levels through PCSK9.

CONCLUSIONS

These results suggest that the LEPIS-HuR-TMOD4 axis is a potential intervention target for dysregulated hepatic cholesterol homeostasis and AS and may provide the basis for further reductions in the circulating LDL-C concentration and arterial plaque burden.

PCSK9 inhibitor in acute ischemic stroke patient receiving mechanical thrombectomy: early outcomes and safety

Background

Lipid-lowering therapies are mainstays in reducing recurrence after acute ischemic stroke (AIS). Evolocumab, a Proprotein convertase subtilisin-kexin type 9 (PCSK9) inhibitor, is a promising lipid-lowering agent known to decrease LDL cholesterol and mitigate vascular events alongside statins. However, its effects on the early functional outcomes post-mechanical thrombectomy (MT) remain unclear. This study aimed to assess the short-term effects and incidence of bleeding events after the early, off-label use of PCSK9 inhibitors in AIS patients undergoing MT.

Methods

We retrospectively analyzed patients who had MT at a Regional Stroke Center from December 2018 to April 2023. Our primary outcome was discharge functional outcomes. Secondary outcomes included early neurologic deterioration (END), symptomatic intracerebral hemorrhage (sICH), 3-month functional outcomes, 3-month recurrence rate, and lipid profiles.

Results

Of 261 patients (mean age 69.2 ± 11.7, men 42.9%), 42 were administered evolocumab peri-procedurally. While baseline characteristics were similar between the two groups, evolocumab group demonstrated improved discharge outcomes, with a lower mean NIHSS (8.8 ± 6.8 vs. 12.4 ± 9.8, p = 0.02) and a higher percentage of patients with discharge mRS ≤ 3 (52.4% vs. 35.6%, p = 0.041). The 3-month follow-up show a non-significant trend toward an improved outcome in the evolocumab group. Multivariable analysis indicated that evolocumab had a potential impact on favorable discharge outcomes (aOR 1.98[0.94-4.22] for mRS ≤ 3 and 0.47[0.27-0.84] for lower ordinal mRS). Notably, evolocuamb users exhibited fewer instances of END and sICH, although they do not reach statistical significance. Additionally, the evolocumab group demonstrated potential benefits in LDL cholesterol reduction over time.

Conclusion

Early use of evolocumab in AIS patients undergoing MT appeared to be safe and associated with better early functional outcomes. The potential benefit of the PCSK9 inhibitor shown here warrants further prospective studies.

Efficacy and safety of PCSK9 inhibitors for stroke prevention: Systematic review and meta-analysis

OBJECTIVE

Investigate the efficacy and safety of proprotein convertase subtilisin/kexin type 9 inhibitors (PCSK9i) on stroke prevention.

BACKGROUND

PCSK9i reduce low-density lipoprotein cholesterol (LDL-C) and lipoprotein a (LpA) levels. Their efficacy in reducing the risk of major cardiovascular events has been shown in multiple randomized clinical trials (RCT). However, clinical equipoise remains on the magnitude and mechanisms by which PCSK9i decrease the risk of stroke.

METHODS

We performed a systematic search of biomedical databases from inception to January 15, 2024, to identify RCTs that investigated the efficacy of PCSK9i versus placebo for major cardiovascular event prevention. The primary outcome was total stroke. The safety outcome was the risk of adverse neurological events, as defined by each trial. Effect size was represented by risk ratio (RR), and analysis was done using random-effects meta-analysis. Heterogeneity was assessed by I2 and Cochrane Q statistics. Meta-regression analyses were performed to assess the association between LDL-C and LpA reduction and stroke risk.

RESULTS

Overall, 20 studies with 93,093 patients were included. The quality of the evidence was moderate and heterogeneity for all comparisons was low (I2 < 25 %). The mean age was 60.1 years for the PCSK9i group and 59.6 years for the placebo group, with a mean follow-up time of 60.1 weeks. PCSK9i reduced the LDL-C levels by 11 % and LpA levels by 8 %. PCSK9i were associated with a significant reduction in stroke risk (RR 0.75, 95 % CI 0.66-0.86, I2 = 0 %), without an increase in mortality (RR 0.97, 95 % CI 0.87-1.08, I2 = 0 %). The risk of adverse neurological events was similar between groups (RR 0.99, 95 % CI 0.84-1.18, I2 = 11 %). In meta-regression analyses, the stroke risk was not associated with the magnitude of the effect of PCSK9i on LDL-C (LDL C β = -0.01, 95 % CI = -0.03-0.02) and LpA (β = -0.01, 95 % CI = -0.06-0.04) levels.

CONCLUSIONS

PCSK9i significantly reduced the stroke risk, without increasing mortality or the risk of adverse neurological events. Our findings also suggest that the beneficial effect of PCSK9i on stroke risk is mediated by LDL-C- and LpA-independent mechanisms.

Effectiveness and safety of injectable PCSK9 inhibitors in dyslipidaemias' treatment and cardiovascular disease prevention: An overview of 86 systematic reviews and a network metaanalysis

OBJECTIVE

Multiple systematic reviews (SR) have been performed on the effects of proprotein convertase subtilisin/kexin type 9 inhibitors (PCSK9i), often providing conflicting findings. This overview and network meta-analysis (NMA) aimed to summarize SR findings on the efficacy and safety of PCSK9i and provide an updated NMA.

MATERIALS AND METHODS

MEDLINE (Pubmed), Scopus, Cochrane, Epistemonikos and Google Scholar were searched from inception to September 21, 2023 for SRs of randomized controlled trials (RCTs) and from January 1, 2020 to September 21, 2023 for additional RCTs. Double-independent study selection, data extraction and quality assessment were performed. Qualitative analysis was performed for SRs and a frequentist random-effects model NMA was performed for RCTs.

RESULTS

Totally, 86 SRs and 76 RCTs were included. Alirocumab (77/86 [90%]) and evolocumab (73/86 [85%]) were mostly analyzed. Associations from SRs (35/42 [83%]) and the updated NMA indicated PCSK9i benefit on major adverse cardiovascular events (MACEs). Reductions were also noted for cerebrovascular events (47/66 [71%]), coronary revascularization (29/33 [88%]) and myocardial infarction (41/63 [65%]). Alirocumab was associated with reductions on all-cause mortality (RR=0.82, 95%CI [0.72,0.94]). Data on any CV event reduction were conflicting (7/16 [44%]). Inclisiran appeared effective only on MACEs (RR=0.76, 95%CI [0.61,0.94]). No reductions in heart failure were observed (0/16). No increases were identified between PCSK9i and any (0/35) or serious adverse events (0/52). However, PCSK9i were associated with injection-site reactions (20/28 [71%]).

CONCLUSION

PCSK9i appeared to be effective in CV outcomes and their clinical application was generally safe.

Proprotein convertase subtisilin/kexin 9 levels decline with hepatitis C virus therapy in people with HIV/hepatitis C virus and correlate with inflammation

BACKGROUND

Proprotein convertase subtisilin/kexin 9 (PCSK9) raises low-density lipoprotein cholesterol (LDL-C) levels and is associated with inflammation, which is elevated in HIV and hepatitis C virus (HCV) infection. We compared PCSK9 levels in people with co-occurring HIV and HCV (HIV/HCV) vs. HIV alone, and evaluated the impact of HCV direct-acting antiviral (DAA) therapy on PCSK9.

DESIGN

A prospective, observational cohort study.

METHODS

Thirty-five adults with HIV/HCV and 37 with HIV alone were evaluated, all with HIV virologic suppression and without documented cardiovascular disease. Circulating PCSK9 and inflammatory biomarkers were measured at baseline and following HCV treatment or at week 52 (for HIV alone) and compared using Wilcoxon tests and Spearman correlations.

RESULTS

At baseline, PCSK9 trended higher in HIV/HCV vs. HIV alone (307 vs. 284 ng/ml, P  = 0.06). Twenty-nine participants with HIV/HCV completed DAA therapy with sustained virologic response. PCSK9 declined from baseline to posttreatment 1 (median 7.3 weeks after end of therapy [EOT]) and posttreatment 2 (median 43.5 weeks after EOT), reaching levels similar to HIV alone; median within-person reduction was -60.5 ng/ml ( P  = 0.003) and -55.6 ng/ml ( P  = 0.02), respectively. Decline in PCSK9 correlated with decline in soluble (s)E-selectin and sCD163 ( r  = 0.64, P  = 0.002; r  = 0.58, P  = 0.008, respectively), but not with changes in LDL-C or other biomarkers. No significant change in PCSK9 occurred in the HIV alone group over 52 weeks.

CONCLUSION

PCSK9 declined with DAA therapy in participants with HIV/HCV, correlating with declines in several inflammatory biomarkers but not LDL-C. Elevated PCSK9 with HCV may be linked to particular HCV-associated inflammatory pathways more so than cholesterol homeostasis.

Geranylgeranyl isoprenoids and hepatic Rap1a regulate basal and statin-induced expression of PCSK9

LDL-C lowering is the main goal of atherosclerotic cardiovascular disease prevention, and proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibition is now a validated therapeutic strategy that lowers serum LDL-C and reduces coronary events. Ironically, the most widely used medicine to lower cholesterol, statins, has been shown to increase circulating PCSK9 levels, which limits their efficacy. Here, we show that geranylgeranyl isoprenoids and hepatic Rap1a regulate both basal and statin-induced expression of PCSK9 and contribute to LDL-C homeostasis. Rap1a prenylation and activity is inhibited upon statin treatment, and statin-mediated PCSK9 induction is dependent on geranylgeranyl synthesis and hepatic Rap1a. Accordingly, treatment of mice with a small-molecule activator of Rap1a lowered PCSK9 protein and plasma cholesterol and inhibited statin-mediated PCSK9 induction in hepatocytes. The mechanism involves inhibition of the downstream RhoA-ROCK pathway and regulation of PCSK9 at the post-transcriptional level. These data further identify Rap1a as a novel regulator of PCSK9 protein and show that blocking Rap1a prenylation through lowering geranylgeranyl levels contributes to statin-mediated induction of PCSK9.

Potential Benefits and Risks Associated with the Use of Statins

HMG-CoA reductase inhibitors, commonly known as statins, are the primary treatment choice for cardiovascular diseases, which stand as the leading global cause of mortality. Statins also offer various pleiotropic effects, including improved endothelial function, anti-inflammatory properties, reduced oxidative stress, anti-thrombotic effects, and the stabilization of atherosclerotic plaques. However, the usage of statins can be accompanied by a range of adverse effects, such as the development of type 2 diabetes mellitus, muscular symptoms, liver toxicity, kidney diseases, cataracts, hemorrhagic strokes, and psychiatric complications. These issues are referred to as statin-associated symptoms (SAS) and are relatively infrequent in clinical trials, making it challenging to attribute them to statin use definitively. Therefore, these symptoms can lead to significant problems, necessitating dose adjustments or discontinuation of statin therapy. This review aims to provide a comprehensive overview of the mechanism of action, potential advantages, and associated risks of statin utilization in clinical settings.

Rap1 in the Context of PCSK9, Atherosclerosis, and Diabetes

PURPOSE OF REVIEW

The focus of this article is to highlight the importance of the small GTPase, Ras-associated protein 1 (Rap1), in proprotein convertase subtilisin/kexin type 9 (PCSK9) regulation and atherosclerosis and type 2 diabetes etiology and discuss the potential therapeutic implications of targeting Rap1 in these disease areas.

REVIEW FINDINGS

Cardiometabolic disease characterized by obesity, glucose intolerance, dyslipidemia, and atherosclerotic cardiovascular disease remain an important cause of mortality. Evidence using mouse models of obesity and insulin resistance indicates that Rap1 deficiency increases proatherogenic PCSK9 and low-density lipoprotein cholesterol levels and predisposes these mice to develop obesity- and statin-induced hyperglycemia, which highlights Rap1's role in cardiometabolic dysfunction. Rap1 may also contribute to cardiovascular disease through its effects on vascular wall cells involved in the atherosclerosis progression. Rap1 activation, specifically in the liver, could be beneficial in the prevention of cardiometabolic perturbations, including type 2 diabetes, hypercholesterolemia, and atherosclerosis.

Antibody-mediated PCSK9 neutralization worsens outcome after bare-metal stent implantation in mice

AIMS

Despite advances in pharmacotherapy and device innovation, in-stent restenosis (ISR) and stent thrombosis (ST) remain serious complications following percutaneous coronary intervention (PCI) procedure with stent implantation. Proprotein convertase subtilisin/kexin type 9 (PCSK9) is an enzyme involved in plasma cholesterol homeostasis and recently emerged as a therapeutic target for hypercholesterolemia. Antibody-based PCSK9 inhibition is increasingly used in different subsets of patients, including those undergoing PCI. However, whether PCSK9 inhibition affects outcome after stent implantation remains unknown.

METHODS AND RESULTS

12 to 14 weeks old C57Bl/6 mice underwent carotid artery bare-metal stent implantation. Compared to sham intervention, stent implantation was associated with increased expression of several inflammatory mediators, including PCSK9. The increase in PCSK9 protein expression was confirmed in the stented vascular tissue, but not in plasma. To inhibit PCSK9, alirocumab was administered weekly to mice before stent implantation. After 6 weeks, histological examination revealed increased intimal hyperplasia in the stented segment of alirocumab-treated animals compared to controls. In vitro, alirocumab promoted migration and inhibited the onset of senescence in primary human vascular smooth muscle cells (VSMC). Conversely, it blunted the migration and increased the senescence of endothelial cells (EC).

CONCLUSION

Antibody-based PCSK9 inhibition promotes in-stent intimal hyperplasia and blunts vascular healing by increasing VSMC migration, while reducing that of EC. This effect is likely mediated, at least in part, by a differential effect on VSMC and EC senescence. The herein-reported data warrant additional investigations concerning the use of PCSK9 inhibitors in patients undergoing PCI with stent implantation.

Geranylgeranyl Isoprenoids and Hepatic Rap1a Regulate Basal and Statin-Induced Expression of PCSK9

Low-density lipoprotein cholesterol (LDL-C) lowering is the main goal of atherosclerotic cardiovascular disease prevention, and proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibition is now a validated therapeutic strategy that lowers serum LDL-C and reduces coronary events. Ironically, the most widely used medicine to lower cholesterol, statins, has been shown to increase circulating PCSK9 levels, which limits their efficacy. Here, we show that geranylgeranyl isoprenoids and hepatic Rap1a regulate both basal and statin induced expression of PCSK9 and contribute to LDL-C homeostasis. Rap1a prenylation and activity is inhibited upon statin treatment, and statin mediated PCSK9 induction is dependent on geranylgeranyl synthesis and hepatic Rap1a. Accordingly, treatment of mice with a small molecule activator of Rap1a lowered PCSK9 protein and plasma cholesterol and inhibited statin mediated PCSK9 induction in hepatocytes. The mechanism involves inhibition of the downstream RhoA-ROCK pathway and regulation of PCSK9 at the post transcriptional level. These data further identify Rap1a as a novel regulator of PCSK9 protein and show that blocking Rap1a prenylation through lowering geranylgeranyl levels contributes to statin-mediated induction of PCSK9.

Association of PCSK9 Inhibitor Initiation on Statin Adherence and Discontinuation

Background PCSK9is (proprotein convertase subtilisin/kexin type 9 inhibitors) are well tolerated, potently lower cholesterol, and decrease cardiovascular events when added to statins. However, statin adherence may decrease after PCSK9i initiation and alter clinical outcomes. We evaluate the association of PCSK9i initiation on statin discontinuation and adherence. Methods and Results In this retrospective pre-post difference-in-difference analysis, new PCSK9i claims were propensity matched with statin-alone users (April 2017-September 2019). The primary outcomes were statin adherence (proportion of days covered) and statin discontinuation (absence of statin coverage for at least 60 days) 12 months following PCSK9i initiation. Secondary outcomes included low-density lipoprotein cholesterol levels after 1 year. A total of 220 538 statin users and 700 PCSK9i users were identified, from which 178 on PCSK9i were included and matched to 712 on statins alone. At 12 months, mean statin proportion of days covered decreased from 67% to 48% in the PCSK9i group but increased from 68% to 86% in the statin-alone groups (P<0.0001). Statin discontinuation rates increased from 11% to 39% in the PCSK9i group and from 7% to 9% in the statin-alone group (P=0.0041). Patients with low-density lipoprotein cholesterol <70 mg/dL increased from 5% to 68% with PCSK9i but increased from 16% to 24% with statins alone (P<0.0001). Changes in hospitalization rates were similar between both groups during the follow-up period. Conclusions PCSK9i initiation was associated with decreased low-density lipoprotein cholesterol, higher statin discontinuation, and reduced statin adherence.

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.

Evidence of an anti-inflammatory effect of PCSK9 inhibitors within the human atherosclerotic plaque

BACKGROUND AND AIMS

Preclinical evidence suggests that proprotein convertase subtilisin-kexin type 9 (PCSK9) inhibitors hold anti-inflammatory properties independently of their ability to lower LDL-cholesterol (C). However, whether PCSK9 inhibitors exert anti-inflammatory effects within the atherosclerotic plaque in humans is unknown. We explored the impact of PCSK9 inhibitors, used as monotherapy, compared with other lipid-lowering drugs (oLLD) on the expression of inflammatory markers within the plaque, assessing also the subsequent incidence of cardiovascular events.

METHODS

In an observational study, we recruited 645 patients on stable therapy for at least six months and undergoing carotid endarterectomy, categorizing patients according to the use of PCSK9 inhibitors only (n = 159) or oLLD (n = 486). We evaluated the expression of NLRP3, caspase-1, IL-1β, TNFα, NF-kB, PCSK9, SIRT3, CD68, MMP-9, and collagen within the plaques in the two groups through immunohistochemistry, ELISA, or immunoblot. A composite outcome including non-fatal myocardial infarction, non-fatal stroke, and all-cause mortality was assessed during a 678 ± 120 days follow-up after the procedure.

RESULTS

Patients treated with PCSK9 inhibitors had a lower expression of pro-inflammatory proteins and a higher abundance of SIRT3 and collagen within the plaque, a result obtained despite comparable levels of circulating hs-CRP and observed also in LDL-C-matched subgroups with LDL-C levels <100 mg/dL. Patients treated with PCSK9 inhibitors showed a decreased risk of developing the outcome compared with patients on oLLD, also after adjustment for multiple variables including LDL-C (adjusted hazard ratio 0.262; 95% CI 0.131-0.524; p < 0.001). The expression of PCSK9 correlated positively with that of pro-inflammatory proteins, which burden was associated with a higher risk of developing the outcome, independently of the therapeutic regimen.

CONCLUSIONS

The use of PCSK9 inhibitors is accompanied by a beneficial remodelling of the inflammatory burden within the human atheroma, an effect possibly or partly independent of their LDL-C lowering ability. This phenomenon might provide an additional cardiovascular benefit.

Understanding the molecular mechanisms of statin pleiotropic effects

Statins represent the cornerstone of pharmacotherapy for the prevention of atherosclerotic cardiovascular disease. These medications not only reduce low-density lipoprotein cholesterol (LDL-C) via inhibition of 3-hydroxy-3-methylglutarate attached to CoA reductase, the key rate-limiting step in the cholesterol biosynthetic pathway, but also upregulate expression of the low-density lipoprotein receptor, improving serum clearance. Given LDL-C is a causal risk factor for the development of atherosclerosis, these complementary mechanisms largely explain why statin therapy leads to reductions in major adverse cardiovascular events. However, decades of basic and clinical research have suggested that statins may exert other effects independent of LDL-C lowering, termed pleiotropic effects, which have become a topic of debate among the scientific community. While some literature suggests statins may improve plaque stability, reduce inflammation and thrombosis, decrease oxidative stress, and improve endothelial function and vascular tone, other studies have suggested potential harmful pleiotropic effects related to increased risk of muscle-related side effects, diabetes, hemorrhagic stroke, and cognitive decline. Furthermore, the introduction of newer, non-statin LDL-C lowering therapies, including ezetimibe, proprotein convertase subtilisin/Kexin Type 9, and bempedoic acid, have challenged the statin pleiotropy theory. This review aims to provide a historical background on the development of statins, explore the mechanistic underpinnings of statin pleiotropy, review the available literature, and provide up to date examples that suggest statins may exert effects outside of LDL-C lowering and the cardiovascular system.

Soluble PCSK9 Inhibition: Indications, Clinical Impact, New Molecular Insights and Practical Approach-Where Do We Stand?

Current research on cardiovascular prevention predominantly focuses on risk-stratification and management of patients with coronary artery disease (CAD) to optimize their prognosis. Several basic, translational and clinical research efforts aim to determine the etiological mechanisms underlying CAD pathogenesis and to identify lifestyle-dependent metabolic risk factors or genetic and epigenetic parameters responsible for CAD occurrence and/or progression. A log-linear association between the absolute exposure of LDL cholesterol (LDL-C) and the risk of atherosclerotic cardio-vascular disease (ASCVD) was well documented over the year. LDL-C was identified as the principal enemy to fight against, and soluble proprotein convertase subtilisin kexin type 9 (PCSK9) was attributed the role of a powerful regulator of blood LDL-C levels. The two currently available antibodies (alirocumab and evolocumab) against PCSK9 are fully human engineered IgG that bind to soluble PCSK9 and avoid its interaction with the LDLR. As documented by modern and dedicated "game-changer" trials, antibodies against soluble PCSK9 reduce LDL-C levels by at least 60 percent when used alone and up to 85 percent when used in combination with high-intensity statins and/or other hypolipidemic therapies, including ezetimibe. Their clinical indications are well established, but new areas of use are advocated. Several clues suggest that regulation of PCSK9 represents a cornerstone of cardiovascular prevention, partly because of some pleiotropic effects attributed to these newly developed drugs. New mechanisms of PCSK9 regulation are being explored, and further efforts need to be put in place to reach patients with these new therapies. The aim of this manuscript is to perform a narrative review of the literature on soluble PCSK9 inhibitor drugs, with a focus on their indications and clinical impact.

PCSK9 Inhibitors Reduce PCSK9 and Early Atherogenic Biomarkers in Stimulated Human Coronary Artery Endothelial Cells

Despite reports on the efficacy of proprotein convertase subtilisin-Kexin type 9 (PCSK9) inhibitors as a potent lipid-lowering agent in various large-scale clinical trials, the anti-atherogenic properties of PCSK9 inhibitors in reducing PCSK9 and atherogenesis biomarkers via the NF-ĸB and eNOS pathway has yet to be established. This study aimed to investigate the effects of PCSK9 inhibitors on PCSK9, targeted early atherogenesis biomarkers, and monocyte binding in stimulated human coronary artery endothelial cells (HCAEC). HCAEC were stimulated with lipopolysaccharides (LPS) and incubated with evolocumab and alirocumab. The protein and gene expression of PCSK9, interleukin-6 (IL-6), E-selectin, intercellular adhesion molecule 1 (ICAM-1), nuclear factor kappa B (NF-ĸB) p65, and endothelial nitric oxide synthase (eNOS) were measured using ELISA and QuantiGene plex, respectively. The binding of U937 monocytes to endothelial cell capacity was measured by the Rose Bengal method. The anti-atherogenic effects of evolocumab and alirocumab were contributed to by the downregulation of PCSK9, early atherogenesis biomarkers, and the significant inhibition of monocyte adhesion to the endothelial cells via the NF-ĸB and eNOS pathways. These suggest the beyond cholesterol-lowering beneficial effects of PCSK9 inhibitors in impeding atherogenesis during the initial phase of atherosclerotic plaque development, hence their potential role in preventing atherosclerosis-related complications.

PCSK9 as an Atherothrombotic Risk Factor

Disturbances in lipid metabolism are among the most important risk factors for atherosclerotic cardiovascular disease. Proprotein convertase subtilisin/kexin type 9 (PCSK9) is a key protein in lipid metabolism that is also involved in the production of inflammatory cytokines, endothelial dysfunction and aherosclerotic plaque development. Studies have shown a connection between PCSK9 and various indicators of inflammation. Signalling pathways that include PCSK9 play important role in the initiation and development of atherosclerotic lesions by inducing vascular inflammation. Studies so far have suggested that PCSK9 is associated with procoagulation, enhancing the development of atherosclerosis. Experimentally, it was also found that an increased concentration of PCSK9 significantly accelerated the apoptosis of endothelial cells and reduced endothelial function, which created conditions for the development of atherosclerosis. PCSK9 inhibitors can therefore improve clinical outcomes not only in a lipid-dependent manner, but also through lipid-independent pathways. The aim of our review was to shed light on the impact of PCSK9 on these factors, which are not directly related to low-density lipoprotein (LDL) cholesterol metabolism.

PCSK9 inhibitors for anti-inflammation in atherosclerosis: protocol for a systematic review and meta-analysis of randomised controlled trials

INTRODUCTION

Atherosclerosis is the leading cause of cardiovascular disease (CVD), which is one of the most common causes of morbidity and mortality worldwide. Lipid accumulation and inflammation play a crucial role in the pathogenesis of atherosclerosis. Proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitors are an emerging lipid-lowering agent reported as a potential anti-inflammation effect in the prevention of CVD. However, the anti-inflammatory effect is still elusive. Therefore, a systematic review and meta-analysis is needed to analyse the anti-inflammatory effect of PCSK9 inhibitors on atherosclerosis in practice.

METHODS AND ANALYSIS

This protocol was conducted following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses Protocols. We will include double-blind, randomised controlled trials that reported changes in the levels of inflammatory markers, with an intervention arm of PCSK9 inhibitors and a treatment duration of more than 2 weeks. The following databases will be mainly searched from 1 January 2003 to the formal search date: PubMed, Embase, Web of Science and the Cochrane Central Register of Controlled Trials. The primary aim is to assess the effect of PCSK9 inhibitors on inflammatory markers, including circulating inflammatory markers such as C-reactive protein, high-sensitivity C-reactive protein, white cell counts, IL-1β, IL-6 and TNF-α and local inflammatory markers such as the most diseased segment target-to-background ratio of the index vessel in adult patients with atherosclerosis. We will assess the quality of evidence, heterogeneity and report bias following the recommendations of the Cochrane Handbook for Systematic Reviews of Interventions.

ETHICS AND DISSEMINATION

Due to the systematic review being based on published studies, no ethics approval is required. The study results will be presented at international conferences and published in a peer-reviewed journal.

PROSPERO REGISTRATION NUMBER

CRD42022297710.

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.

Functional Crosstalk between PCSK9 Internalization and Pro-Inflammatory Activation in Human Macrophages: Role of Reactive Oxygen Species Release

Atherosclerosis is a cardiovascular disease caused mainly by dyslipidemia and is characterized by the formation of an atheroma plaque and chronic inflammation. Proprotein convertase subtilisin/kexin type 9 (PCSK9) is a protease that induces the degradation of the LDL receptor (LDLR), which contributes to increased levels of LDL cholesterol and the progress of atherosclerosis. Given that macrophages are relevant components of the lipidic and inflammatory environment of atherosclerosis, we studied the effects of PCSK9 treatment on human macrophages. Our data show that human macrophages do not express PCSK9 but rapidly incorporate the circulating protein through the LDLR and also activate the pro-inflammatory TLR4 pathway. Both LDLR and TLR4 are internalized after incubation of macrophages with exogenous PCSK9. PCSK9 uptake increases the production of reactive oxygen species and reduces the expression of genes involved in lipid metabolism and cholesterol efflux, while enhancing the production of pro-inflammatory cytokines through a TLR4-dependent mechanism. Under these conditions, the viability of macrophages is compromised, leading to increased cell death. These results provide novel insights into the role of PCSK9 in the crosstalk of lipids and cholesterol metabolism through the LDLR and on the pro-inflammatory activation of macrophages through TLR4 signaling. These pathways are relevant in the outcome of atherosclerosis and highlight the relevance of PCSK9 as a therapeutic target for the treatment of cardiovascular diseases.

[Inclisiran - a new era in lipid-lowering therapy]

Inclisiran is a novel hypolipidemic drug that inhibits synthesis of the PCSK9 protein through the process called RNA interference. Inclisiran is a double-stranded, modified RNA bound to the N-acetylgalactosamine (GalNAc) carbohydrate molecule, a ligand of the acialoglycoprotein receptor, that is expressed by hepatocytes. After entering hepatocytes, inclisiran cleaves matrix RNA and, thereby, reduces the PCSK9 protein synthesis. This, in turn, enhances the uptake of circulating low-density lipoproteins (LDL) by specific receptors on hepatocytes, thereby lowering LDL levels in circulation. Efficacy and safety of inclisiran for lowering LDL cholesterol (C) in blood and its effect on the risk of clinical complications of atherosclerosis have been studied in the ORION program that includes multiple clinical trials. According to results of this program, inclisiran effectively reduces both LDL-C levels and the incidence of cardiovascular complications in the absence of clinically significant adverse reactions. An important advantage of inclisiran compared with other lipid-lowering drugs is the administration schedule (twice a year), which allows a considerable improvement of patients' compliance with the treatment and also of the effectiveness of the hypolipidemic treatment.

Impact of PCSK9 Inhibition on Proinflammatory Cytokines and Matrix Metalloproteinases Release in Patients with Mixed Hyperlipidemia and Vulnerable Atherosclerotic Plaque

Atherosclerosis is a disorder in which, in addition to high cholesterol levels, several plasma factors play a significant role in its development. Among these cytokines and molecules are interleukin 6 (IL-6), interleukin 18 (IL-18), tumor necrosis factor α (TNF-α), metalloproteinase 2 (MMP-2), and metalloproteinase 9 (MMP-9), all of which may contribute to the stabilization of atherosclerotic plaque. The purpose of this study was to determine the effect of advanced lipid-lowering therapy on the levels of these determinants by utilizing proprotein convertase subtilisin/kexin type 9 (PCSK-9) inhibitors in patients with verified high-risk atherosclerotic plaque. Methods: The study involved patients with dyslipidemia who had the presence of unstable atherosclerotic plaque verified by ultrasonography and who were eligible to begin alirocumab treatment. The levels of IL-6, IL, 18, TNF-α, and MMPs were determined in this group before and after three months of therapy. After treatment, a statistically significant decrease in concentrations of Il-18, Il-6, TNF-α (p < 0.001) and MMP-2 (p < 0.05) was observed. Additionally, we observed that the concentrations of these markers were significantly higher in the group of patients prior to initiating therapy than in the control group. Our study’s results suggest that PCSK-9 inhibitor therapy significantly reduces the concentration of factors influencing the stability of atherosclerotic plaque, which may explain their essential importance in reducing cardiovascular risk in patients receiving this treatment.

Non-Lipid Effects of PCSK9 Monoclonal Antibodies on Vessel Wall

Elevated low density lipoprotein (LDL) cholesterol and lipoprotein(a) (Lp(a)) levels have an important role in the development and progression of atherosclerosis, followed by cardiovascular events. Besides statins and other lipid-modifying drugs, PCSK9 monoclonal antibodies are known to reduce hyperlipidemia. PCSK9 monoclonal antibodies decrease LDL cholesterol levels through inducing the upregulation of the LDL receptors and moderately decrease Lp(a) levels. In addition, PCSK9 monoclonal antibodies have shown non-lipid effects. PCSK9 monoclonal antibodies reduce platelet aggregation and activation, and increase platelet responsiveness to acetylsalicylic acid. Evolocumab as well as alirocumab decrease an incidence of venous thromboembolism, which is associated with the decrease of Lp(a) values. Besides interweaving in haemostasis, PCSK9 monoclonal antibodies play an important role in reducing the inflammation and improving the endothelial function. The aim of this review is to present the mechanisms of PCSK9 monoclonal antibodies on the aforementioned risk factors.

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.

Use of Proprotein Converse Subtilisin/Kexin Type 9 Inhibitor to Treat Cholesterol Crystal Embolisms after Catheterization: A Report of Three Cases

Cholesterol crystal embolism (CCE) is a serious complication that occurs after cardiac and vascular procedures. CCE involves multiple organs, and the prognosis and renal function of patients is poor. Although the efficacy of steroid, statin, and low-density lipoprotein apheresis has been reported, no definitive treatment has been established. We herein report three consecutive cases treated with conventional steroid therapy with proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitor after catheterization. The renal function was preserved, steroid therapy was stopped, and wound healing of blue toes was achieved. PCSK9 inhibitor therapy was safe in the present patient and may be a potential treatment option for CCE.

Inclisiran: a small interfering RNA strategy targeting PCSK9 to treat hypercholesterolemia

INTRODUCTION

Inclisiran is a novel posttranscriptional gene silencing therapy that inhibits proprotein convertase subtilisin/kexin type 9 (PCSK9) synthesis by RNA interference and has a potent, dose-dependent, durable effect in lowering LDL-C, and therefore is an effective drug to treat dyslipidemia, reducing the risk for acute cardiovascular (CV) events. It is safe and well-tolerated.

AREAS COVERED

This paper aims to review the mechanism of action of inclisiran while evaluating its efficacy and safety in the treatment of dyslipidemia from data of the clinical trials in the ORION program.

EXPERT OPINION

Data from the clinical trials in the ORION program demonstrated efficacy and safety of inclisiran in patients with dyslipidemia. Adverse events were similar in the inclisiran and placebo groups in the clinical trials, although injection-site reactions were more frequent with inclisiran than with placebo. Although the combination of efficacy and safety makes inclisiran a good option for the treatment of dyslipidemia compared to other PCSK9 targeting therapeutic strategies, however, further studies should exclude the possibility that inclisiran, through lower-affinity interactions, may influence other mRNAs in the physiological milieu.

PCSK9 inhibition could be effective for acute myocardial infarction

In this review, we will explore the role of PCSK9 and inhibition of PCSK9 in patients after acute myocardial infarction (MI). Despite the implementation of evidence-based therapies to improve outcomes, mortality at one-year remains at 12-15% and the need to further reduce complications related to MI persists. Mechanistic and epidemiologic studies suggest that the naturally occurring PCSK9 protein increases coronary plaque vulnerability through several pathways, including pro-inflammatory LDL-C oxidation and direct modification of plaque composition. PCSK9 inhibitors are a class of drugs with proven efficacy in patients with recent MI. The latest guidelines recommend the use of PCSK9 in patients with recent MI early in the process of care to reduce LDL-C values and associated morbidity. The use of PCSK9 inhibition could be beneficial for mortality reduction after an acute MI and should be tested in an appropriately powered randomized controlled trial.

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.

How low is safe? The frontier of very low (<30 mg/dL) LDL cholesterol

Low-density lipoprotein cholesterol (LDL-C) is a proven causative factor for developing atherosclerotic cardiovascular disease. Individuals with genetic conditions associated with lifelong very low LDL-C levels can be healthy. We now possess the pharmacological armamentarium (statins, ezetimibe, PCSK9 inhibitors) to reduce LDL-C to an unprecedented extent. Increasing numbers of patients are expected to achieve very low (<30 mg/dL) LDL-C. Cardiovascular event reduction increases log linearly in association with lowering LDL-C, without reaching any clear plateau even when very low LDL-C levels are achieved. It is still controversial whether lower LDL-C levels are associated with significant clinical adverse effects (e.g. new-onset diabetes mellitus or possibly haemorrhagic stroke) and long-term data are needed to address safety concerns. This review presents the familial conditions characterized by very low LDL-C, analyses trials with lipid-lowering agents where patients attained very low LDL-C, and summarizes the benefits and potential adverse effects associated with achieving very low LDL-C. Given the potential for cardiovascular benefit and short-term safe profile of very low LDL-C, it may be advantageous to attain such low levels in specific high-risk populations. Further studies are needed to compare the net clinical benefit of non-LDL-C-lowering interventions with very low LDL-C approaches, in addition to comparing the efficacy and safety of very low LDL-C levels vs. current recommended targets.

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.

Endogenous PCSK9 may influence circulating CD45neg/CD34bright and CD45neg/CD34bright/CD146neg cells in patients with type 2 diabetes mellitus

Protease proprotein convertase subtilisin/kexin type 9 (PCSK9) is a regulator of LDL cholesterol clearance and has been associated with cardiovascular risk. PCSK9 inhibitors increase in vivo circulating endothelial progenitor cells (EPCs), a subtype of immature cells involved in ongoing endothelial repair. We hypothesized that the effect of PCSK9 on vascular homeostasis may be mediated by EPCs in patients with or without type 2 diabetes mellitus (T2DM). Eighty-two patients (45 with, 37 without T2DM) at high cardiovascular risk were enrolled in this observational study. Statin treatment was associated with higher circulating levels of PCSK9 in patients with and without T2DM (p < 0.001 and p = 0.036) and with reduced CD45neg/CD34bright (total EPC compartment) (p = 0.016) and CD45neg/CD34bright/CD146neg (early EPC) (p = 0.040) only among patients with T2DM. In the whole group of patients, statin treatment was the only independent predictor of low number of CD45neg/CD34bright (β = - 0.230; p = 0.038, adjusted R2 = 0.041). Among T2DM patients, PCSK9 circulating levels were inversely related and predicted both the number of CD45neg/CD34bright (β = - 0.438; p = 0.003, adjusted R2 = 0.173), and CD45neg/CD34bright/CD146neg (β = - 0.458; p = 0.002, adjusted R2 = 0.191) independently of age, gender, BMI and statin treatment. In high-risk T2DM patients, high endogenous levels of PCSK9 may have a detrimental effect on EPCs by reducing the endothelial repair and worsening the progression of atherothrombosis.

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.

Cell adhesion molecule-mediated therapeutic strategies in atherosclerosis: From a biological basis and molecular mechanism to drug delivery nanosystems

Atherosclerosis (AS), characterized by pathological constriction of blood vessels due to chronic low-grade inflammation and lipid deposition, is a leading cause of human morbidity and mortality worldwide. Cell adhesion molecules (CAMs) have the ability to regulate the inflammatory response and endothelial function, as well as potentially driving plaque rupture, which all contribute to the progression of AS. Moreover, recent advances in the development of clinical agents in the cardiovascular field are based on CAMs, which show promising results in the fight against AS. Here, we review the current literature on mechanisms by which CAMs regulate atherosclerotic progression from the earliest induction of inflammation to plaques formation. In particular, we focused on therapeutic strategies based on CAMs inhibitors that prevent leukocyte from migrating to endothelium, including high-affinity antibodies and antagonists, nonspecific traditional medicinal formulas and lipid lowering drugs. The CAMs-based drug delivery nanosystem and the available data on the more reasonable and effective clinical application of CAMs inhibitors have been emphasized, raising hope for further progress in the field of AS therapy.

The Effect of Proprotein Convertase Subtilisin Kexin Type 9 Inhibitors on Circulating Endothelial Progenitor Cells in Patients with Cardiovascular Disease

PURPOSE

Circulating endothelial progenitor cells (cEPCs) are vital to vascular repair by re-endothelialization. We aimed to explore the effect of proprotein convertase subtilisin kexin type 9 inhibitors (PCSK9i) on cEPCs hypothesizing a possible pleiotropic effect.

METHODS

Patients with cardiovascular disease (CVD) were sampled for cEPCs at baseline and following the initiation of PCSK9i. cEPCs were assessed using flow cytometry by the expression of CD34⁽⁺⁾/CD133⁽⁺⁾ and vascular endothelial growth factor receptor (VEGFR)-2⁽⁺⁾, and by the formation of colony-forming units (CFUs) and production of VEGF.

RESULTS

Our cohort included 26 patients (median age 68 (IQR 63, 73) years; 69% male). Following 3 months of treatment with PCSK9i and a decline in low-density lipoprotein cholesterol levels (153 (IQR 116, 176) to 56 (IQR 28, 72) mg/dl), p < 0.001), there was an increase in CD34⁽⁺⁾/CD133⁽⁺⁾ and VEGFR-2⁽⁺⁾ cell levels (0.98% (IQR 0.37, 1.55) to 1.43% (IQR 0.90, 4.51), p = 0.002 and 0.66% (IQR 0.22, 0.99) to 1.53% (IQR 0.73, 2.70), p = 0.05, respectively). Functionally, increase in EPCs-CFUs was microscopically evident following treatment with PCSK9i (1 CFUs (IQR 0.0, 1.0) to 2.5 (IQR 1.5, 3), p < 0.001) with a concomitant increase in EPC's viability as demonstrated by an MTT assay (0.15 (IQR 0.11, 0.19) to 0.21 (IQR 0.18, 0.23), p < 0.001). VEGF levels increased following PCSK9i treatment (57 (IQR 18, 24) to 105 (IQR 43, 245), p = 0.006).

CONCLUSIONS

Patients with CVD treated with PCSK9i demonstrate higher levels of active cEPCs, reflecting the promotion of endothelial repair. These findings may represent a novel mechanism of action of PCSK9i.