PCSK9 plays a novel immunological role in oxidized LDL-induced dendritic cell maturation and activation of T cells from human blood and atherosclerotic plaque

Dendritic cells immunotargeted therapy for atherosclerosis

Atherosclerosis, a chronic inflammatory disease, is markedly influenced by both immune and inflammatory reactions throughout its progression. Dendritic cells, as pivotal antigen-presenting entities, play a crucial role in the initiation of immune responses and the preservation of immunological homeostasis. Accumulating data indicates that dendritic cells are present in healthy arteries and accumulate significantly in atherosclerotic plaques. Novel immunotherapeutic approaches and vaccination protocols have yielded substantial clinical advancements in managing chronic inflammatory diseases, with dendritic cell-centric modalities emerging for atherosclerotic management. In this review, we delineate the essential functions and underlying mechanisms of dendritic cells and their subsets in the modulation of atherosclerotic inflammation and immune responses. We underscore the immense promise of dendritic cell-based immunotherapeutic strategies, including vaccines and innovative combinations with nanotechnological drug delivery platforms for atherosclerosis treatment. We also discuss the challenges associated with dendritic cell immunotherapy and provide perspectives on the future direction of this field.

T cells in cardiac health and disease

Cardiovascular disease (CVD) remains the leading cause of morbidity and mortality worldwide, with inflammation playing a pivotal role in its pathogenesis. T lymphocytes are crucial components of the adaptive immune system that have emerged as key mediators in both cardiac health and the development and progression of CVD. This Review explores the diverse roles of T cell subsets, including Th1, Th17, γδ T cells, and Tregs, in myocardial inflammatory processes such as autoimmune myocarditis and myocardial infarction. We discuss the contribution of T cells to myocardial injury and remodeling, with emphasis on specific immune receptors, e.g., CD69, that have a critical role in regulating immune tolerance and maintaining the balance between T cell subsets in the heart. Additionally, we offer a perspective on recent advances in T cell-targeted therapies and their potential to modulate immune responses and improve clinical outcomes in patients with CVD and in heart transplant recipients. Understanding the intricate interplay between T cells and cardiovascular pathology is essential for developing novel immunotherapeutic strategies against CVD.

Causal relationship between immune cells and heart failure: A Mendelian randomization study

This study aimed to evaluate the causal effects of different immune cells on heart failure (HF) using Mendelian randomization (MR). Datasets for immune cell phenotypes and HF were obtained from European Bioinformatics Institute and FinnGen. Then, single nucleotide polymorphisms were screened according to the basic assumptions of MR. Subsequently, inverse variance weighted was used as primary tool for MR analysis, and Cochran Q and leave-one-out analyses were used to assess heterogeneity and robustness, respectively. MR analysis showed that cluster of differentiation (CD) 66b++ myeloid cell absolute count (AC) (odds ratio [OR] 1.043, 95% confidence interval [CI] 1.001-1.088, P = .045), human leukocyte antigen D-related on CD14- CD16+ monocyte (OR 1.030, 95% CI 1.005-1.056, P = .019), IgD on unsw mem (OR 1.046, 95% CI 1.015-1.078, P = .003), CD4 on CD4+ (OR 1.039, 95% CI 1.009-1.070, P = .011), CD24 on IgD+ CD38- (OR 1.026, 95% CI 1.000-1.052, P = .046), CD20 on CD24 + CD27+ (OR 1.032, 95% CI 1.003-1.061, P = .029), CD19 on CD20- (OR 1.037, 95% CI 1.005-1.071, P = .023), CD62L- CD86 + myeloid dendritic cell %DC (OR 1.032, 95% CI 1.004-1.061, P = .027), human leukocyte antigen D-related + CD4 + AC (OR 1.037, 95% CI 1.003-1.072, P = .032), and effector memory CD8br AC (OR 1.048, 95% CI 1.021-1.076, P < .001) were associated with increased genetic susceptibility to HF. Cochran Q and sensitivity analyses showed that the results had no heterogeneity and were robust. This MR analysis revealed 10 immune cell phenotypes associated with increased genetic susceptibility to HF. These findings provide new directions for understanding the pathogenesis of HF and developing novel therapies.

PCSK9 in T-cell function and the immune response

Proprotein convertase subtilisin/kexin type 9 (PCSK9) was first reported in 2003 and confirmed to be strongly associated with familial hypercholesterolemia. Small-molecule inhibitors targeting PCSK9 provide an effective and safe method for managing hypercholesterolemia and reducing the cardiovascular risk. In recent years, increasing evidence has indicated other important roles for PCSK9 in inflammation, tumors, and even immune regulation. PCSK9 might be an attractive regulator of T-cell activation and expansion. It might mediate inflammation and regulate other types of immune cells. In this review, we summarize the current advances in the field of PCSK9 and provide a narrative of the biological processes associated with PCSK9. The relationships between PCSK9 and different T cells were investigated in depth. Finally, the signaling pathways associated with PCSK9 and the immune response are also summarized in this review.

PCSK9 inhibition protects mice from food allergy

The Proprotein Convertase Subtilisin Kexin of type 9 (PCSK9) has been identified in 2003 as the third gene involved in familial hypercholesterolemia. PCSK9 binds to the membrane low-density lipoprotein receptor (LDLR) and promotes its cellular internalization and lysosomal degradation. Beyond this canonical role, PCSK9 was recently described to be involved in several immune responses. However, to date, the contribution of PCSK9 in food allergy remains unknown. Here, we showed that Pcsk9 deficiency or pharmacological inhibition of circulating PCSK9 with a specific monoclonal antibody (m-Ab) protected mice against symptoms of gliadin-induced-food allergy, such as increased intestinal transit time and ear oedema. Furthermore, specific PCSK9 inhibition during the elicitation steps of allergic process was sufficient to ensure anti-allergic effects in mice. Interestingly, the protective effect of PCSK9 inhibition against food allergy symptoms was independent of the LDLR as PCSK9 inhibitors remained effective in Ldlr deficient mice. In vitro, we showed that recombinant gain of function PCSK9 (PCSK9 D374Y) increased the percentage of mature bone marrow derived dendritic cells (BMDCs), promoted naïve T cell proliferation and potentiated the gliadin induced basophils degranulation. Altogether, our data demonstrate that PCSK9 inhibition is protective against gliadin induced food allergy in a LDLR-independent manner.

The role of PCSK9 in heart failure and other cardiovascular diseases-mechanisms of action beyond its effect on LDL cholesterol

Proprotein convertase subtilisin/kexin type-9 (PCSK9) is a protein that regulates low-density lipoprotein (LDL) cholesterol metabolism by binding to the hepatic LDL receptor (LDLR), ultimately leading to its lysosomal degradation and an increase in LDL cholesterol (LDLc) levels. Treatment strategies have been developed based on blocking PCSK9 with specific antibodies (alirocumab, evolocumab) and on blocking its production with small regulatory RNA (siRNA) (inclisiran). Clinical trials evaluating these drugs have confirmed their high efficacy in reducing serum LDLc levels and improving the prognosis in patients with atherosclerotic cardiovascular diseases. Most studies have focused on the action of PCSK9 on LDLRs and the subsequent increase in LDLc concentrations. Increasing evidence suggests that the adverse cardiovascular effects of PCSK9, particularly its atherosclerotic effects on the vascular wall, may also result from mechanisms independent of its effects on lipid metabolism. PCSK9 induces the expression of pro-inflammatory cytokines contributing to inflammation within the vascular wall and promotes apoptosis, pyroptosis, and ferroptosis of cardiomyocytes and is thus involved in the development and progression of heart failure. The elimination of PCSK9 may, therefore, not only be a treatment for hypercholesterolaemia but also for atherosclerosis and other cardiovascular diseases. The mechanisms of action of PCSK9 in the cardiovascular system are not yet fully understood. This article reviews the current understanding of the mechanisms of PCSK9 action in the cardiovascular system and its contribution to cardiovascular diseases. Knowledge of these mechanisms may contribute to the wider use of PCSK9 inhibitors in the treatment of cardiovascular diseases.

Causal effects of lipid-lowering drugs on inflammatory skin diseases: Evidence from drug target Mendelian randomisation

Clinical research has revealed that inflammatory skin diseases are associated with dyslipidaemia. Modulating lipids is also a rising potential treatment option. However, there is heterogeneity in the existing evidence and a lack of large-scale clinical trials. Observational research is prone to bias, making it difficult to determine causality. This study aimed to evaluate the causal association between lipid-lowering drugs and inflammatory skin diseases. A drug target Mendelian randomisation (MR) analysis was conducted. Genetic targets of lipid-lowering drugs, including proprotein convertase subtilis kexin 9 (PCSK9) and 3-hydroxy-3-methylglutaryl-assisted enzyme A reductase (HMGCR) inhibitor, were screened. Common inflammatory skin diseases, including psoriasis, allergic urticaria, rosacea, atopic dermatitis, systemic sclerosis and seborrhoeic dermatitis, were considered as outcomes. Gene-predicted inhibition of PCSK9 was causally associated with a decreased risk of psoriasis (ORIVW [95%CI] = 0.600 [0.474-0.761], p = 2.48 × 10-5) and atopic dermatitis (ORIVW [95%CI] = 0.781 [0.633-0.964], p = 2.17 × 10-2). Gene-predicted inhibition of HMGCR decreased the risk of seborrhoeic dermatitis (ORIVW [95%CI] = 0.407 [0.168-0.984], p = 4.61 × 10-2) but increased the risk of allergic urticaria (ORIVW [95%CI] = 3.421 [1.374-8.520], p = 8.24 × 10-3) and rosacea (ORIVW [95%CI] = 3.132 [1.260-7.786], p = 1.40 × 10-2). Among all causal associations, only PCSK9 inhibition demonstrated a robust causal effect on psoriasis after a more rigorous Bonferroni test (p < 4.17 × 10-3, which is 0.05/12). Modulating lipids via PCSK9 inhibition may offer potential therapeutic targets for psoriasis and atopic dermatitis. Given the potential cutaneous side effects associated with HMGCR inhibitors, PCSK9 inhibitors could be considered viable alternatives in lipid-lowering medication.

Association between PCSK9 inhibitors and acute kidney injury: a pharmacovigilance study

Background

PCSK9 inhibitors are a novel class of lipid-lowering medications, and numerous clinical studies have confirmed their significant role in improving the progression of chronic kidney disease. However, recent case reports have indicated new evidence regarding their association with acute kidney injury (AKI), with some patients experiencing acute tubular injury after PCSK9 inhibitors use.

Objectives

To clarify the relationship between PCSK9 inhibitors and AKI, we conducted a pharmacovigilance study.

Methods

Using the Food and Drug Administration Adverse Event Reporting System (FAERS) database from the third quarter of 2015 to the fourth quarter of 2022, a disproportionality analysis was employed to identify adverse events suggestive of AKI after PCSK9 inhibitors use. The drugs of interest included evolocumab and alirocumab.

Results

A total of 144,341 adverse event reports related to PCSK9 inhibitors were analyzed, among which 444 cases were suspected of AKI for evolocumab, and 172 cases for alirocumab. Evolocumab had a greater impact on AKI in males (ROR 1.4, 95% CI 1.54-1.69). The ROR and 95% CI for evolocumab and Alirocumab were 0.13 (0.12-0.14) and 0.26 (0.23-0.30) respectively. Further analysis of AKI associated with the concomitant use of PCSK9 inhibitors with cephalosporins, furosemide, torsemide, pantoprazole, omeprazole, and esomeprazole revealed ROR and 95% CI of 0.38 (0.23-0.62), 0.38 (0.31-0.48), 0.18 (0.08-0.38), 0.23 (0.17-0.29), 0.20 (0.16-0.26), and 0.14 (0.10-0.20) respectively.

Conclusion

Through the FAERS database, we analyzed the clinical characteristics of AKI associated with PCSK9 inhibitors, exploring its risks. Our findings suggest that PCSK9 inhibitors might have a potential protective effect against AKI and exhibit similar effects when co-administered with other nephrotoxic drugs.

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.

The Link between miRNAs and PCKS9 in Atherosclerosis

Cardiovascular disease (CDV) represents the major cause of death globally. Atherosclerosis, as the primary cause of CVD, is a chronic immune-inflammatory disorder with complex multifactorial pathophysiology encompassing oxidative stress, enhanced immune-inflammatory cascade, endothelial dysfunction, and thrombosis. An initiating event in atherosclerosis is the subendothelial accumulation of low-density lipoprotein (LDL), followed by the localization of macrophages to fatty deposits on blood vessel walls, forming lipid-laden macrophages (foam cells) that secrete compounds involved in plaque formation. Given the fact that foam cells are one of the key culprits that underlie the pathophysiology of atherosclerosis, special attention has been paid to the investigation of the efficient therapeutic approach to overcome the dysregulation of metabolism of cholesterol in macrophages, decrease the foam cell formation and/or to force its degradation. Proprotein convertase subtilisin/kexin type 9 (PCSK9) is a secretory serine proteinase that has emerged as a significant regulator of the lipid metabolism pathway. PCSK9 activation leads to the degradation of LDL receptors (LDLRs), increasing LDL cholesterol (LDL-C) levels in the circulation. PCSK9 pathway dysregulation has been identified as one of the mechanisms involved in atherosclerosis. In addition, microRNAs (miRNAs) are investigated as important epigenetic factors in the pathophysiology of atherosclerosis and dysregulation of lipid metabolism. This review article summarizes the recent findings connecting the role of PCSK9 in atherosclerosis and the involvement of various miRNAs in regulating the expression of PCSK9-related genes. We also discuss PCSK9 pathway-targeting therapeutic interventions based on PCSK9 inhibition, and miRNA levels manipulation by therapeutic agents.

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

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

PCSK9 ablation attenuates Aβ pathology, neuroinflammation and cognitive dysfunctions in 5XFAD mice

BACKGROUND

Increasing evidence highlights the importance of novel players in Alzheimer's disease (AD) pathophysiology, including alterations of lipid metabolism and neuroinflammation. Indeed, a potential involvement of Proprotein convertase subtilisin/kexin type 9 (PCSK9) in AD has been recently postulated. Here, we first investigated the effects of PCSK9 on neuroinflammation in vitro. Then, we examined the impact of a genetic ablation of PCSK9 on cognitive performance in a severe mouse model of AD. Finally, in the same animals we evaluated the effect of PCSK9 loss on Aβ pathology, neuroinflammation, and brain lipids.

METHODS

For in vitro studies, U373 human astrocytoma cells were treated with Aβ fibrils and human recombinant PCSK9. mRNA expression of the proinflammatory cytokines and inflammasome-related genes were evaluated by q-PCR, while MCP-1 secretion was measured by ELISA. For in vivo studies, the cognitive performance of a newly generated mouse line - obtained by crossing 5XFADHet with PCSK9KO mice - was tested by the Morris water maze test. After sacrifice, immunohistochemical analyses were performed to evaluate Aβ plaque deposition, distribution and composition, BACE1 immunoreactivity, as well as microglia and astrocyte reactivity. Cholesterol and hydroxysterols levels in mouse brains were quantified by fluorometric and LC-MS/MS analyses, respectively. Statistical comparisons were performed according to one- or two-way ANOVA, two-way repeated measure ANOVA or Chi-square test.

RESULTS

In vitro, PCSK9 significantly increased IL6, IL1B and TNFΑ mRNA levels in Aβ fibrils-treated U373 cells, without influencing inflammasome gene expression, except for an increase in NLRC4 mRNA levels. In vivo, PCSK9 ablation in 5XFAD mice significantly improved the performance at the Morris water maze test; these changes were accompanied by a reduced corticohippocampal Aβ burden without affecting plaque spatial/regional distribution and composition or global BACE1 expression. Furthermore, PCSK9 loss in 5XFAD mice induced decreased microgliosis and astrocyte reactivity in several brain regions. Conversely, knocking out PCSK9 had minimal impact on brain cholesterol and hydroxysterol levels.

CONCLUSIONS

In vitro studies showed a pro-inflammatory effect of PCSK9. Consistently, in vivo data indicated a protective role of PCSK9 ablation against cognitive impairments, associated with improved Aβ pathology and attenuated neuroinflammation in a severe mouse model of AD. PCSK9 may thus be considered a novel pharmacological target for the treatment of AD.

MicroRNA-mediated Regulation of LDL Receptor: Biological and Pharmacological Implications

One of the main causes of atherosclerosis is a disruption in cellular cholesterol hemostasis. The low-density lipoprotein receptor (LDLR) is an important factor in maintaining cholesterol homeostasis by the receptor-mediated endocytosis of LDL particles. Defective hepatic LDLR activity and uptake of LDL particles lead to elevated blood levels of low-density lipoprotein cholesterol (LDL-C), which is associated with a higher risk of atherosclerotic cardiovascular disease. LDLR expression can be affected by microRNAs (miRNAs). Some miRNAs, like miR-148a, miR-185, miR-224, miR-520, miR-128-1, miR-27a/b, miR-130b, and miR-301 seem to be important post-transcriptional regulators of LDLR related genes. These findings indicate the critical role of miRNAs in regulating LDL metabolism. The aim of this review was to provide insight into the miRNAs involved in LDLR activity and their potential roles in the treatment of cardiovascular disease.

PCSK9 inhibition ameliorates experimental autoimmune myocarditis by reducing Th17 cell differentiation through LDLR/STAT-3/ROR-γt pathway

Proprotein convertase subtilisin kexin type 9 (PCSK9) was characterized as a protein regulating circulating cholesterol metabolism; however, recent studies demonstrated a role for PCSK9 in inflammatory and autoimmune diseases unrelated to cholesterol alterations. The implication of PCSK9 in myocarditis is unclear and we aim at investigating the roles and mechanisms of PCSK9 in myocarditis. Male BALB/c mice received subcutaneous immunization with MyHC-α peptide on days 0 and 7 to establish the experimental autoimmune myocarditis (EAM) model. PCSK9 inhibitor, evolocumab, was administered subcutaneously once a week starting on day 0 and all mice were euthanized on day 21. Our results showed that PCSK9 inhibition ameliorated the cardiac inflammation of EAM mice. PCSK9 inhibition reduced both the levels of cardiac and peripheral blood PCSK9. We found that CD4+ T cells, CD8+ T cells, macrophages, and cardiomyocytes in the heart of EAM mice could express PCSK9. PCSK9 inhibition decreased the differentiation of cardiac Th17 cells by lowering ROR-γt levels but had no effects on Th1, Th2, and Treg cell differentiation. In vitro experiments of CD4+ T cells, we found that PCSK9 directly promoted Th17 cell differentiation through LDLR/STAT3/ROR-γt pathway. Collectively, we demonstrated that PCSK9 inhibition ameliorated the severity of EAM mice by reducing Th17 cell differentiation. PCSK9 is a promising target for treating myocarditis.

Therapeutically targeting type I interferon directly to XCR1+ dendritic cells reveals the role of cDC1s in anti-drug antibodies

Conventional type 1 dendritic cells (cDC1s) are superior in antigen cross-presentation and priming CD8+ T cell anti-tumor immunity and thus, are a target of high interest for cancer immunotherapy. Type I interferon (IFN) is a potent inducer of antigen cross-presentation, but, unfortunately, shows only modest results in the clinic given the short half-life and high toxicity of current type I IFN therapies, which limit IFN exposure in the tumor. CD8+ T cell immunity is dependent on IFN signaling in cDC1s and preclinical studies suggest targeting IFN directly to cDC1s may be sufficient to drive anti-tumor immunity. Here, we engineered an anti-XCR1 antibody (Ab) and IFN mutein (IFNmut) fusion protein (XCR1Ab-IFNmut) to determine whether systemic delivery could drive selective and sustained type I IFN signaling in cDC1s leading to anti-tumor activity and, in parallel, reduced systemic toxicity. We found that the XCR1Ab-IFNmut fusion specifically enhanced cDC1 activation in the tumor and spleen compared to an untargeted control IFN. However, multiple treatments with the XCR1Ab-IFNmut fusion resulted in robust anti-drug antibodies (ADA) and loss of drug exposure. Using other cDC1-targeting Ab-IFNmut fusions, we found that localizing IFN directly to cDC1s activates their ability to promote ADA responses, regardless of the cDC1 targeting antigen. The development of ADA remains a major hurdle in immunotherapy drug development and the cellular and molecular mechanisms governing the development of ADA responses in humans is not well understood. Our results reveal a role of cDC1s in ADA generation and highlight the potential ADA challenges with targeting immunostimulatory agents to this cellular compartment.

Reactive oxygen species, toxicity, oxidative stress, and antioxidants: chronic diseases and aging

A physiological level of oxygen/nitrogen free radicals and non-radical reactive species (collectively known as ROS/RNS) is termed oxidative eustress or "good stress" and is characterized by low to mild levels of oxidants involved in the regulation of various biochemical transformations such as carboxylation, hydroxylation, peroxidation, or modulation of signal transduction pathways such as Nuclear factor-κB (NF-κB), Mitogen-activated protein kinase (MAPK) cascade, phosphoinositide-3-kinase, nuclear factor erythroid 2-related factor 2 (Nrf2) and other processes. Increased levels of ROS/RNS, generated from both endogenous (mitochondria, NADPH oxidases) and/or exogenous sources (radiation, certain drugs, foods, cigarette smoking, pollution) result in a harmful condition termed oxidative stress ("bad stress"). Although it is widely accepted, that many chronic diseases are multifactorial in origin, they share oxidative stress as a common denominator. Here we review the importance of oxidative stress and the mechanisms through which oxidative stress contributes to the pathological states of an organism. Attention is focused on the chemistry of ROS and RNS (e.g. superoxide radical, hydrogen peroxide, hydroxyl radicals, peroxyl radicals, nitric oxide, peroxynitrite), and their role in oxidative damage of DNA, proteins, and membrane lipids. Quantitative and qualitative assessment of oxidative stress biomarkers is also discussed. Oxidative stress contributes to the pathology of cancer, cardiovascular diseases, diabetes, neurological disorders (Alzheimer's and Parkinson's diseases, Down syndrome), psychiatric diseases (depression, schizophrenia, bipolar disorder), renal disease, lung disease (chronic pulmonary obstruction, lung cancer), and aging. The concerted action of antioxidants to ameliorate the harmful effect of oxidative stress is achieved by antioxidant enzymes (Superoxide dismutases-SODs, catalase, glutathione peroxidase-GPx), and small molecular weight antioxidants (vitamins C and E, flavonoids, carotenoids, melatonin, ergothioneine, and others). Perhaps one of the most effective low molecular weight antioxidants is vitamin E, the first line of defense against the peroxidation of lipids. A promising approach appears to be the use of certain antioxidants (e.g. flavonoids), showing weak prooxidant properties that may boost cellular antioxidant systems and thus act as preventive anticancer agents. Redox metal-based enzyme mimetic compounds as potential pharmaceutical interventions and sirtuins as promising therapeutic targets for age-related diseases and anti-aging strategies are discussed.

PCSK9, A Promising Novel Target for Age-Related Cardiovascular Dysfunction

Cardiovascular diseases (CVDs) are the leading cause of death among elderly people. Proprotein convertase subtilisin/kexin type 9 (PCSK9) is an important regulator of cholesterol metabolism. Herein, we investigated the role of PCSK9 in age-related CVD. Both in humans and rats, blood PCSK9 level correlated positively with increasing age and the development of cardiovascular dysfunction. Age-related fatty degeneration of liver tissue positively correlated with serum PCSK9 levels in the rat model, while development of age-related nonalcoholic fatty liver disease correlated with cardiovascular functional impairment. Network analysis identified PCSK9 as an important factor in age-associated lipid alterations and it correlated positively with intima-media thickness, a clinical parameter of CVD risk. PCSK9 inhibition with alirocumab effectively reduced the CVD progression in aging rats, suggesting that PCSK9 plays an important role in cardiovascular aging.

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.

What are the benefits and drawbacks of statins in carotid artery disease? A perspective review

INTRODUCTION

The prevalence of carotid artery stenosis in the general population is approximately 3%, but approximately 20% among people with acute ischemic stroke. Statins are recommended by multiple international guidelines as the drug of choice for lipid control in people with asymptomatic or symptomatic carotid artery stenosis due to their lipid-lowering and other pleiotropic effects.

AREAS COVERED

This review discusses the guidelines for statin usage as a cornerstone in the prevention and management of atherosclerotic carotid artery disease and the impact of statins on stroke incidence and mortality. Statin side effects, alternative therapy, and genetic polymorphisms are reviewed.

EXPERT OPINION

Statin therapy is associated with a decreased incidence of stroke and mortality as well as improved outcomes for patients treated with carotid revascularization. Statins are a safe and effective class of medications, but the initiation of therapy warrants close monitoring to avoid rare and potentially serious side effects. Lack of clinical efficacy or the presence of side effects suggests a need for treatment with an alternative therapy such as PCSK9 inhibitors. Understanding the interplay between the mechanisms of statins and PCSK9 inhibition therapies will allow optimal benefits while minimizing risks. Future research into genetic polymorphisms may improve patient selection for personalized therapy.

The Concentration of PCSK9-Lp(a) Complexes and the Level of Blood Monocytes in Males with Coronary Atherosclerosis

In this study we analyzed the concentration of lipoprotein(a) (Lp(a)), PCSK9-Lp(a) complexes and the circulating monocyte subsets in coronary atherosclerosis. For this study, 257 patients with coronary atherosclerosis and 68 patients without stenotic atherosclerosis in the coronary, carotid and lower extremity arteries (control group) were enrolled. The monocyte subpopulations (classical CD14++CD16-, intermediate CD14++CD16+ and non-classical CD14+CD16++) were analyzed by direct immunofluorescence and flow cytometry. The Lp(a) and PCSK9-Lp(a) complexes in the serum were detected by ELISA. The concentration of Lp(a) was higher in the coronary atherosclerosis group compared with the controls (23.0 (9.1; 73.3) mg/dL versus 10.7 (4.7; 25.0) mg/dL, p < 0.05). No correlations between the level of Lp(a) and the concentration of the PCSK9-Lp(a) complexes, nor between the level of Lp(a) or PCSK9 and the total number of monocytes, were observed in either group. A slight positive correlation between the concentration of PCSK9-Lp(a) complexes and the absolute level of monocytes was obtained (r = 0.20, p = 0.002) in the patients with atherosclerosis due to the intermediate monocyte subsets (r = 0.33, p = 0.04). According to regression analysis, both the PCSK9-Lp(a) complexes concentration and BMI were related to the absolute number of blood monocytes in patients with atherosclerosis. Further studies are required to determine the pathogenetic contribution of PCSK9-Lp(a) complexes to the development of atherosclerosis.

The evolving landscape of PCSK9 inhibition in cancer

Cancer is a disease with a significant global burden in terms of premature mortality, loss of productivity, healthcare expenditures, and impact on mental health. Recent decades have seen numerous advances in cancer research and treatment options. Recently, a new role of cholesterol-lowering PCSK9 inhibitor therapy has come to light in the context of cancer. PCSK9 is an enzyme that induces the degradation of low-density lipoprotein receptors (LDLRs), which are responsible for clearing cholesterol from the serum. Thus, PCSK9 inhibition is currently used to treat hypercholesterolemia, as it can upregulate LDLRs and enable cholesterol reduction through these receptors. The cholesterol-lowering effects of PCSK9 inhibitors have been suggested as a potential mechanism to combat cancer, as cancer cells have been found to increasingly rely on cholesterol for their growth needs. Additionally, PCSK9 inhibition has demonstrated the potential to induce cancer cell apoptosis through several pathways, increase the efficacy of a class of existing anticancer therapies, and boost the host immune response to cancer. A role in managing cancer- or cancer treatment-related development of dyslipidemia and life-threatening sepsis has also been suggested. This review examines the current evidence regarding the effects of PCSK9 inhibition in the context of different cancers and cancer-associated complications.

PCSK9 promotes T helper 1 and T helper 17 cell differentiation by activating the nuclear factor-κB pathway in ankylosing spondylitis

OBJECTIVE

Our previous study reveals that proprotein convertase subtilisin/kexin type 9 (PCSK9) is positively related to inflammatory markers, T helper (Th)-17 cells, and treatment response in ankylosing spondylitis (AS) patients. Subsequently, this study aimed to explore the effect of PCSK9 on Th cell differentiation and its potential molecular mechanism in AS.

METHODS

Serum PCSK9 was determined by enzyme-linked immunosorbent assay in 20 AS patients and 20 healthy controls (HCs). Then naïve CD4+ T cells were isolated from AS patients and infected with PCSK9 overexpression or knockdown adenovirus followed by polarization assay. Afterward, PMA (an NF-κB activator) was administrated.

RESULTS

PCSK9 was increased in AS patients compared to HCs (p < .001), and it was positively related to Th1 cells (p = .050) and Th17 cells (p = .039) in AS patients. PCSK9 overexpression increased the CD4+ IFN-γ+ cells (p < .05), CD4+ IL-17A+ cells (p < .01), IFN-γ (p < .01), and IL-17A (p < .01), while it exhibited no effect on CD4+ IL-4+ cells or IL-4 (both p > .05); its knockdown displayed the opposite function on them. Moreover, PCSK9 overexpression upregulated the p-NF-κB p65/NF-κB p65 (p < .01), while it had no effect on p-ERK/ERK or p-JNK/JNK (both p > .05); its knockdown decreased p-NF-κB p65/NF-κB p65 (p < .01) and p-JNK/JNK (p < .05). Then, PMA upregulates p-NF-κB p65/NF-κB p65 (p < .001) and increased CD4+ IFN-γ+ cells, CD4+ IL-17A+ cells, IFN-γ, and IL-17A (all p < .01), also it alleviated the effect of PCSK9 knockdown on NF-κB inhibition and Th cell differentiation (all p < .01).

CONCLUSION

PCSK9 enhances Th1 and Th17 cell differentiation in an NF-κB-dependent manner in AS, while further validation is necessary.

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

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

Serum cholesterol loading capacity of macrophages is regulated by seropositivity and C-reactive protein in rheumatoid arthritis patients

OBJECTIVE

Excessive cholesterol accumulation in macrophages is the pivotal step underlying atherosclerotic plaque formation. We here explore factors in the serum of patients with RA, and mechanisms through which they interact with and influence cholesterol loading capacity (CLC) of macrophages.

METHODS

In a cross-sectional observational cohort of 104 patients with RA, CLC was measured as intracellular cholesterol content in human THP-1-derived macrophages after incubation with patient serum. Low-density lipoprotein (LDL) oxidation was measured in terms of oxidized phospholipids on apoB100-containing particles (oxPL-apoB100). Antibodies against oxidized LDL (anti-oxLDL), proprotein convertase subtilisin/Kexin type-9 (PCSK9) and high-sensitivity CRP were also quantified. All analyses adjusted for atherosclerotic cardiovascular disease (ASCVD) risk score, obesity, total LDL, statin use, age at diagnosis, and anti-oxLDL IgM.

RESULTS

OxPL-apoB100, anti-oxLDL IgG and PCSK9 were positively associated with CLC (all P < 0.020). OxPL-apoB100 directly influenced CLC only in dual RF- and ACPA-positive patients [unstandardized b (95% bootstrap CI)=2.08 (0.38, 3.79)]. An indirect effect of oxPL-apoB100 on CLC through anti-oxLDL IgG increased, along with level of CRP [index of moderated mediation = 0.55 (0.05-1.17)]. CRP also moderated yet another indirect effect of oxPL-apoB100 on CLC through upregulation of PCSK9, but only among dual-seropositive patients [conditional indirect effect = 0.64 (0.13-1.30)].

CONCLUSION

Oxidized LDL can directly influence CLC in dual-seropositive RA patients. Two additional and independent pathways-via anti-oxLDL IgG and PCSK9-may mediate the effects of oxPL-apoB100 on CLC, depending on CRP and seropositivity status. If externally validated, these findings may have clinical implications for cardiovascular risk prevention.

Systemic lupus erythematosus and cardiovascular disease

The prognosis in systemic lupus erythematosus (SLE) has improved due to better treatment and care, but cardiovascular disease (CVD) still remains an important clinical problem, since the risk of CVD in SLE is much higher than among controls. Atherosclerosis is the main cause of CVD in the general population, and in SLE, increased atherosclerosis, especially the prevalence of atherosclerotic plaques, has been demonstrated. Atherosclerosis is an inflammatory condition, where immunity plays an important role. Interestingly, oxidized low-density lipoprotein, defective clearance of dead cells, and inflammation, with a pro-inflammatory T-cell profile are characteristics of both atherosclerosis and SLE. In addition to atherosclerosis as an underlying cause of CVD in SLE, there are also other non-mutually exclusive mechanisms, and the most important of these are antiphospholipid antibodies (aPL) leading to the antiphospholipid antibody syndrome with both arterial and venous thrombosis. aPL can cause direct pro-inflammatory and prothrombotic effects on endothelial and other cells and also interfere with the coagulation, for example, by inhibiting annexin A5 from its antithrombotic and protective effects. Antibodies against phosphorylcholine (anti-PC) and other small lipid-related epitopes, sometimes called natural antibodies, are negatively associated with CVD and atherosclerosis in SLE. Taken together, a combination of traditional risk factors such as hypertension and dyslipidemia, and nontraditional ones, especially aPL, inflammation, and low anti-PC are implicated in the increased risk of CVD in SLE. Close monitoring of both traditional risk factors and nontraditional ones, including treatment of disease manifestations, not lest renal disease in SLE, is warranted.

Expanding Biology of PCSK9: Roles in Atherosclerosis and Beyond

PURPOSE OF REVIEW

Since the discovery of PCSK9 in 2003, this proprotein convertase was shown to target specific receptors for degradation in endosomes/lysosomes, including LDLR and other family members and hence to enhance the levels of circulating LDL-cholesterol (LDLc). Accordingly, inhibitors of PCSK9, including monoclonal antibodies blocking its circulating activity and siRNA silencers of its hepatic expression, are now used in clinics worldwide to treat hypercholesterolemia patients effectively and safely in combination with statins and/or ezetimibe. These powerful treatments reduce the incidence of atherosclerosis by at least 20%. Since 2008, novel targets of PCSK9 began to be defined, thereby expanding its roles beyond LDLc regulation into the realm of inflammation, pathogen infections and cellular proliferation in various cancers and associated metastases.

RECENT FINDINGS

Some pathogens such as dengue virus exploit the ability of PCSK9 to target the LDLR for degradation to enhance their ability to infect cells. Aside from increasing the degradation of the LDLR and its family members VLDLR, ApoER2 and LRP1, circulating PCSK9 also reduces the levels of other receptors such as CD36 (implicated in fatty acid uptake), oxidized LDLR receptor (that clears oxidized LDLc) as well as major histocompatibility class-I (MHC-I) receptors (implicated in the immune response to antigens). Thus, these novel targets provided links between PCSK9 and inflammation/atherosclerosis, viral infections and cancer/metastasis. The functional activities of PCSK9, accelerated the development of novel therapies to inhibit PCSK9 functions, including small molecular inhibitors, long-term vaccines, and possibly CRISPR-based silencing of hepatic expression of PCSK9. The future of inhibitors/silencers of PCSK9 function or expression looks bright, as these are expected to provide a modern armamentarium to treat various pathologies beyond hypercholesterolemia and its effects on atherosclerosis.

Impact of early PCSK9 inhibitor treatment on heart after percutaneous coronary intervention in patients with STEMI: Design and rationale of the PERFECT II trial

Background and aims

Primary percutaneous coronary intervention (PPCI) is the most effective treatment strategy for ST-segment elevation myocardial infarction (STEMI). Nevertheless, dysregulated inflammation induced by myocardial reperfusion injury may increase the final infarct size and induce maladaptive myocardial remodeling. Proprotein convertase subtilisin/kexin 9 (PCSK9) inhibitor, as a novel and potent lipid-lowering drug, plays an important role in inflammation. The aim of this study is to investigate whether the early application of PCSK9 inhibitor can increase the myocardial salvage index (MSI) and improve ventricular remodeling in patients with STEMI.

Design

The PERFECT II trial is a prospective, open-label, multicenter, randomized controlled study involving 160 patients with STEMI who are scheduled to undergo PPCI. The eligible patients will be divided into PCSK9 inhibitor group and control group via the interactive web response system, at a 1:1 ratio. In the PCSK9 inhibitor group, the PCSK9 inhibitor alirocumab at a dose of 75 mg will be subcutaneously injected immediately after PPCI and administered every 2 weeks thereafter for 3 months based on conventional treatment. In the control group, conventional treatment will be administered. The primary endpoint is MSI, as measured by cardiac magnetic resonance imaging (CMR) at 1 week after PPCI. The secondary endpoints are the peak time of creatine kinase (CK)-MB and troponin I (TnI)/TnT after PPCI; the postoperative fall time of the ST segment on electrocardiography (ECG); the rate of plasma low-density lipoprotein cholesterol (LDL-C) compliance (&lt; 1.4 mmol/L and a reduction of &gt;50% from baseline) at 1, 3, and 6 months after PPCI; infarct size and ejection fraction (EF) measured by CMR at 6 months after PPCI; the occurrence of major adverse cardiovascular event (MACE: a composite of cardiovascular death, non-fatal myocardial infarction, stent thrombosis, repeat revascularization, stroke, and heart failure needed to be hospitalized).

Conclusions

This is the first multicenter study to investigate the effect of early application of the PCSK9 inhibitor alirocumab on MSI in patients with STEMI undergoing PPCI. The findings will provide an opportunity to explore novel ideas and methods for the treatment of acute myocardial infarction.

Trial registration

ClinicalTrials.gov, identifier: NCT05292404.

Sex difference in circulating PCSK9 and its clinical implications

Proprotein convertase subtilisin kexin type 9 (PCSK9) is a proprotein convertase that increases plasma low-density lipoprotein cholesterol (LDL-C) levels by triggering the degradation of LDL receptors (LDLRs). Beyond the regulation of circulating LDL-C, PCSK9 also has direct atherosclerotic effects on the vascular wall and is associated with coronary plaque inflammation. Interestingly, emerging data show that women have higher circulating PCSK9 concentrations than men, suggesting that the potential roles of PCSK9 may have different impacts according to sex. In this review, we summarize the studies concerning sex difference in circulating levels of PCSK9. In addition, we report on the sex differences in the relations of elevated circulating PCSK9 levels to the severity and prognosis of coronary artery disease, the incidence of type 2 diabetes mellitus, and neurological damage after cardiac arrest and liver injury, as well as inflammatory biomarkers and high-density lipoprotein cholesterol (HDL-C). Moreover, sex difference in the clinical efficacy of PCSK9 inhibitors application are reviewed. Finally, the underlying mechanisms of sex difference in circulating PCSK9 concentrations and the clinical implications are also discussed.

Mechanistic insight into premature atherosclerosis and cardiovascular complications in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is associated with a significant risk of cardiovascular disease (CVD), which substantially increases disease mortality and morbidity. The overall mechanisms associated with the development of premature atherosclerosis and CVD in SLE remain unclear, but has been considered as a result of an intricate interplay between the profound immune dysregulation and traditional CVD risk factors. Aberrant systemic inflammation in SLE may lead to an abnormal lipid profile and dysfunction, which can further fuel the pro-atherosclerotic environment. The existence of a strong imbalance between endothelial damage and vascular repair/angiogenesis promotes vascular injury, which is the early step in the progression of atherosclerotic CVD. Profound innate and adaptive immune dysregulation, characterized by excessive type I interferon burden, aberrant macrophage, platelet and complements activation, neutrophil dysregulation and neutrophil extracellular traps formation, uncontrolled T cell activation, and excessive autoantibody production and immune complex formation, have been proposed to promote accelerated CVD in SLE. While designing targeted therapies to correct the dysregulated immune activation may be beneficial in the treatment of SLE-related CVD, much additional work is needed to determine how to translate these findings into clinical practice. Additionally, a number of biomarkers display diagnostic potentials in improving CVD risk stratification in SLE, further prospective studies will help understand which biomarker(s) will be the most impactful one(s) in assessing SLE-linked CVD. Continued efforts to identify novel mechanisms and to establish criteria for assessing CVD risk as well as predicting CVD progression are in great need to improve CVD outcomes in SLE.

TREM-1 Modulates Dendritic Cells Maturation and Dendritic Cell-Mediated T-Cell Activation Induced by ox-LDL

Atherosclerosis is a chronic inflammatory disease. The triggering receptor expressed on myeloid cells-1 (TREM-1) plays a crucial role in inflammatory diseases; recently, it was identified as a major upstream proatherogenic receptor, but its mechanism is still unclear. In this study, we explore the role of TREM-1 on dendritic cells maturation and inflammatory responses induced by ox-LDL and its possible mechanism. Human dendritic cells were differentiated from blood monocytes and treated with ox-LDL. Naive autologous T cells were cocultured with pretreated DCs or treated directly. The expression of TREM-1 and inflammatory factors were evaluated by real-time PCR, western blot, and ELISA methods. And the expression of immune factors to evaluate the DCs maturation and T-cell activation were determined by the FACS. Our study showed that ox-LDL induced TREM-1 expression, DC maturation, and T-cell activation. T cells exposed to ox-LDL-treated DCs produced interferon-γ and interleukin-17 (IL-17). Blocking TREM-1 suppressed the DC maturation, showing lower expression of CD1a, CD40, CD86, CD83, and HLA-DR, and limited their production of tumor necrosis factor-alpha (TNF-α), IL-1β, IL-6, and monocyte chemoattractant protein-1 (MCP-1), meanwhile increased transforming growth factor-β(TGF-β) and IL-10 production. Ox-LDL induced miR-155, miR-27, Let-7c, and miR-185 expression; however, TREM-1 inhibiting decreased miRNA-155 expression. Furthermore, silencing miRNA-155 restores SOCS1 repression induced by ox-LDL. Experiments with T cells derived from carotid atherosclerotic plaques or healthy individuals showed similar results. Our results uncover a new link between ox-LDL and TREM-1 and may provide insight into this interaction in the context of atherosclerosis.

A PCSK9 inhibitor induces a transient decrease in the neutrophil-lymphocyte ratio and monocyte-lymphocyte ratio in homozygous familial hypercholesterolemia patients

Background and aims

Extremely elevated levels of low-density lipoprotein-cholesterol (LDL-C) contribute to long-term chronic systemic inflammation in homozygous familial hypercholesterolemia (HoFH) patients. The aims of this study is to describe the inflammatory profile of HoFH patients and explore the effect of a PCSK9 inhibitor (PCSK9i) on a series of inflammatory biomarkers, including the neutrophil-lymphocyte ratio (NLR), platelet-lymphocyte ratio (PLR), monocyte-HDL ratio (MHR), monocyte-lymphocyte ratio (MLR) and mean platelet volume-lymphocyte ratio (MPVLR).

Methods

In this prospective cohort study, 25 definitive HoFH patients on high-intensity statins plus ezetimibe were administered subcutaneous injections of 420 mg PCSK9i every 4 weeks (Q4W). The biochemical parameters and inflammatory profile were analyzed on the day before PCSK9i therapy and 3 months and 6 months after PCSK9i therapy.

Results

HoFH on the maximum tolerated statin dose plus ezetimibe displayed elevated lipid and disturbed blood biomarker profiles. After 3 months of add-on PCSK9i therapy, a significant reduction in LDL-C was observed. Moreover, the percentage and count of neutrophils, monocyte counts, MPV, and two inflammatory biomarkers, the NLR and MLR, were reduced. However, at 6 months of PCSK9i treatment, the NLR and MLR returned to pre-PCSK9i treatment levels.

Conclusions

PCSK9i induces a transient decrease in the NLR and MLR in HoFH patients in a lipid-lowering independent manner.

Increased Circulating Levels of PCSK9 and Pro-Atherogenic Lipoprotein Profile in Pregnant Women with Maternal Supraphysiological Hypercholesterolemia

Maternal physiological hypercholesterolemia (MPH) occurs during pregnancy to assure fetal development. Some pregnant women develop maternal supraphysiological hypercholesterolemia (MSPH) characterized by increased levels of low-density lipoprotein (LDL). We aim to determine if proprotein convertase subtilisin/kexin type 9 (PCSK9) levels (a protein that regulate the availability of LDL receptor in the cells surface), as well as the composition and function of LDL, are modulated in MSPH women. This study included 122 pregnant women. Maternal total cholesterol (TC), LDL, triglycerides and PCSK9 increased from first (T1) to third trimester (T3) in MPH women. At T3, maternal TC, LDL, PCSK9 and placental abundances of PCSK9 were significantly higher in MPSH compared to MPH. Circulating PCSK9 levels were correlated with LDL at T3. In MSPH women, the levels of lipid peroxidation and oxidized LDL were significantly higher compared to MPH. LDL isolated from MSPH women presented significantly higher triglycerides and ApoB but lower levels of ApoAI compared to MPH. The formation of conjugated dienes was earlier in LDL from MSPH and in endothelial cells incubated with these LDLs; the levels of reactive oxygen species were significantly higher compared to LDL from MPH. We conclude that increased maternal PCSK9 would contribute to the maternal elevated levels of pro-atherogenic LDL in MSPH, which could eventually be related to maternal vascular dysfunction.

Associations Among PCSK9 Levels, Atherosclerosis-Derived Extracellular Vesicles, and Their miRNA Content in Adults With Obesity

Background: Extracellular vesicles (EV) concentration is generally increased in patients with cardiovascular diseases, although the protective role of EVs in atherosclerosis has been reported. Among the specific cargo of EVs, miRNAs contribute to different stages of atherosclerosis. Aim of the present report has been to investigate, in individuals with obesity, the interplay among EVs derived from cells relevant for the atherosclerotic process (i.e., platelets, endothelium, monocytes/macrophages, and neutrophils), their miRNA content and proprotein convertase subtilisin/kexin type 9 (PCSK9), one of the main regulators of low-density lipoprotein receptor (LDLR).

Methods and Results: EVs have been isolated from 936 individuals with obesity (body mass index = 33.6 ± 5.6 Kg/m²) and a raised cardiovascular risk (e.g., LDL-C = 131.6 ± 36.4 mg/dL, HOMA-IR = 3.1, and roughly 50% on anti-hypertensive medications). PCSK9 levels were negatively associated with EV count in the range 150–400 nm and with those derived from macrophages (CD14⁺), endothelium (CD105⁺), and neutrophils (CD66⁺). The association between PCSK9 and platelet-derived EVs (CD61⁺) was modified by platelet counts. PCSK9 was significantly associated with five EV-derived miRNAs (hsa-miRNA−362−5p,−150,−1244,−520b-3p,−638). Toll-like receptor 4 and estrogen receptor 1 were targeted by all five miRNAs and LDLR by four. The effect on LDLR expression is mainly driven by hsa-miR-150. Considering the implication of EV in atherosclerosis onset and progression, our findings show a potential role of PCSK9 to regulate EV-derived miRNAs, especially those involved in inflammation and expression of low-density lipoprotein receptor (LDLR) receptor.

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.

Leptin and PCSK9 concentrations are associated with vascular endothelial cytokines in patients with stable coronary heart disease

Leptin and proprotein convertase subtilisin kexin 9 (PCSK9) play an important role in regulating blood lipid concentration. Recently, they have been found to show the ability to independently regulate the immune response. Vascular immune response has an important pathological function in the development of coronary heart disease (CHD) and thrombosis. The aim of this study was to explore the relationship between leptin, PCSK9, and vascular endothelial cell related inflammatory factors. First, detailed clinical information were collected and analyzed for 27 patients with stable CHD and corresponding 27 healthy controls. Second, using liquid-phase protein chip technology, leptin, PCSK9, and vascular-related inflammatory factors, such as E-selectin, vascular cell adhesion protein 1 (VCAM-1), intercellular cell adhesion molecule-1 (ICAM-1), interferon-gamma (IFN-γ), and interleukin-17 (IL-17), were detected on the same platform. Finally, the correlation between leptin, PCSK9, and the inflammatory factors was analyzed. Through collecting clinical information of patients, it was suggested that there was a significant positive correlation between leptin and blood lipid level in CHD. Compared with healthy people, the levels of leptin, PCSK9, E-selectin, and ICAM-1 were significantly high in patients with CHD. There was a high positive correlation between leptin and E-selectin, ICAM-1, IFN-γ, and IL-17. Also, a high positive correlation between PCSK9 and E-selectin, IFN-γ, and IL-17 concentrations was observed. In general, leptin and PCSK9 may not only be able to regulate lipid metabolism, but may also be able to regulate inflammation in CHD.

The role of PCSK9 in inflammation, immunity, and autoimmune diseases

INTRODUCTION

Statins have pleiotropic effects, being both anti-inflammatory and immunomodulatory. Proprotein convertase subtilisin kexin 9 (PCSK9) targets the low-density lipoprotein receptor (LDLR), which increases LDL levels due to the lower expression of LDLR.

AREAS COVERED

Inhibition of PCSK9 by the use of antibodies represents a novel principle to lower LDL levels. LDL may have other properties than being a cholesterol carrier but is well established as a risk factor for cardiovascular disease and atherosclerosis. In atherosclerosis, the plaques are characterized by activated T cells and dendritic cells (DCs), dead cells, and OxLDL. The latter may be an important cause of the inflammation typical of atherosclerosis, by promoting a proinflammatory immune activation. This is inhibited by PCSK9 inhibition, and an anti-inflammatory type of immune activation is induced. OxLDL is raised in systemic lupus erythematosus (SLE), where both CVD and atherosclerosis are much increased compared to the general population. PCSK9 is reported to be associated with disease activity and complications in SLE. Also in other rheumatoid arthritis, PCSK9 may play a role.

EXPERT OPINION

PCSK9 has pleiotropic effects, being implicated in inflammation and immunity. Inhibition of PCSK9 is therefore interesting to study further as a potential therapy against inflammation and autoimmunity.

Association of Circulating miR-145-5p and miR-let7c and Atherosclerotic Plaques in Hypertensive Patients

Aim: Hypertension is a strong risk factor for atherosclerosis. Increased carotid intima-media thickness (cIMT) and carotid plaques are considered subclinical markers of atherosclerosis. This study aimed at evaluating the serum expression of miRNAs previously related to adverse vascular remodeling and correlating them with carotid plaques and cIMT in hypertensive patients. Methods: We cross-sectionally evaluated the clinical and carotid characteristics as well as serum expression of miR-145-5p, miR-let7c, miR-92a, miR-30a and miR-451 in 177 hypertensive patients. Carotid plaques and cIMT were evaluated by ultrasound, and the expression of selected miRNAs was evaluated by a quantitative polymerase chain reaction. Results: Among all participants (age = 60.6 ± 10.7 years, 43% males), there were 59% with carotid plaques. We observed an increased expression of miR-145-5p (Fold Change = 2.0, p = 0.035) and miR-let7c (Fold Change = 3.8, p = 0.045) in participants with atherosclerotic plaque when compared to those without plaque. In the logistic regression analysis adjusted for relevant covariates, these miRNAs showed a stronger association with carotid plaques (miR-145-5p: Beta ± SE = 0.050 ± 0.020, p = 0.016 and miR-let7c: Beta ± SE = 0.056 ± 0.019, p = 0.003). Conclusions: Hypertensive patients with carotid plaques have an increased expression of miR-145-5p and miR-let7c, suggesting a potential role of these miRNAs as a biomarker for subclinical atherosclerosis in hypertensive individuals.

Beneficial effects of PCSK9 inhibition with alirocumab in familial hypercholesterolemia involve modulation of new immune players

Familial hypercholesterolemia (FH) is associated with low-grade systemic inflammation, a key driver of premature atherosclerosis. We investigated the effects of inhibiting proprotein convertase subtilisin/kexin type 9 (PCSK9) function on inflammatory state, endothelial dysfunction and cardiovascular outcomes in patients with FH. Fourteen patients with FH were evaluated before and 8 weeks after administration of a PCSK9 blocking monoclonal antibody (alirocumab, 150 mg/subcutaneous/14 days). In vivo and ex vivo analysis revealed that alirocumab blunted the attachment of leukocytes to TNFα-stimulated human umbilical arterial endothelial cells (HUAEC) and suppressed the activation of platelets and most leukocyte subsets, which was accompanied by the diminished expression of CX₃CR1, CXCR6 and CCR2 on several leukocyte subpopulations. By contrast, T-regulatory cell activation was enhanced by alirocumab treatment, which also elevated anti-inflammatory IL-10 plasma levels and lowered circulating pro-inflammatory cytokines. Plasma levels of IFNγ positively correlated with levels of total and LDL-cholesterol, whereas circulating IL-10 levels negatively correlated with these key lipid parameters. In vitro analysis revealed that TNFα stimulation of HUAEC increased the expression of PCSK9, whereas endothelial PCSK9 silencing reduced TNFα-induced mononuclear cell adhesion mediated by Nox5 up-regulation and p38-MAPK/NFκB activation, concomitant with reduced SREBP2 expression. PCSK9 silencing also decreased endothelial CX₃CL1 and CXCL16 expression and chemokine generation. In conclusion, PCSK9 inhibition impairs systemic inflammation and endothelial dysfunction by constraining leukocyte-endothelium interactions. PCSK9 blockade may constitute a new therapeutic approach to control the inflammatory state associated with FH, preventing further cardiovascular events in this cardiometabolic disorder.

Primary hypercholesterolemia and development of cardiovascular disorders: Cellular and molecular mechanisms involved in low-grade systemic inflammation and endothelial dysfunction

Primary hypercholesterolemia, a metabolic disorder characterized by elevated circulating levels of cholesterol products, mainly low-density lipoproteins, is associated with arteriosclerosis development. Cardiovascular disease, predominantly myocardial infarction and stroke, remains the main cause of death worldwide, with atherosclerosis considered to be the most common underlying pathology. In addition to elevated plasma levels of low-density lipoproteins, low-grade systemic inflammation and endothelial dysfunction seem to be the main drivers of premature atherosclerosis. Here we review current knowledge related to cellular and molecular mechanisms involved in low-grade systemic inflammation and endothelial dysfunction associated with primary hypercholesterolemia. We also discuss the contribution of different inflammatory mediators, immune players and signaling pathways implicated in leukocyte adhesion to the dysfunctional endothelium, a key feature of atherogenesis development. A better understanding of these processes linked to primary hypercholesterolemia should shed new light on cardiovascular disease development and might guide novel and effective therapeutic strategies to impair its progression.

Blood flow patterns regulate PCSK9 secretion via MyD88-mediated pro-inflammatory cytokines

AIMS

Blood flow patterns play an important role in the localization of atherosclerosis in the sense that low-flow state is pro-atherogenic, and helical flow is protective against atherosclerosis. Proprotein convertase subtilisin/kexin type 9 (PCSK9) regulates cholesterol metabolism via low-density lipoprotein receptor (LDLr) degradation and is highly expressed in the atherosclerotic tissues. This study was designed to investigate the role of different blood flow patterns in the regulation of PCSK9 expression.

METHODS AND RESULTS

We designed an experimental model guider to generate stable helical flow. Our data showed that compared with normal flow, low-flow state induces whereas helical flow inhibits PCSK9 expression in the rabbit thoracic aorta in an inflammatory state. Our data also identified that TLR4-MyD88-NF-κB signalling plays an important role in PCSK9 expression. On the other hand, TRIF pathway had almost no effect. Further studies showed that the signals downstream of NF-κB, such as pro-inflammatory cytokines (IL-1β, IL-18, MCP-1, IL-6, TNF-α, IL-12, IFNγ, and GM-CSF) directly influence PCSK9 expression. Interestingly, high fat diet further enhanced PCSK9 expression in an inflammatory milieu.

CONCLUSIONS

These observations suggest a link between abnormal flow patterns and PCSK9 expression in inflammatory states, which may qualify helical flow and pro-inflammatory cytokines as potential targets to treat PCSK9-related cardiovascular diseases.

Effects of Atorvastatin on T-Cell Activation and Apoptosis in Systemic Lupus Erythematosus and Novel Simulated Interactions With C-Reactive Protein and Interleukin 6

Objective

We study activation of T helper 17 (Th17) and regulatory T (Treg) cells and induction of apoptosis in cells from patients with systemic lupus erythematosus (SLE) compared with controls and effects of atorvastatin and its simulated interactions with other compounds.

Methods

Mononuclear cells from 10 patients with SLE and 10 controls were cultured in conditions that induce Th17 and/or Treg cell polarization and/or apoptosis and were studied by FACScan. Gene expression was determined by quantitative real‐time reverse transcription–polymerase chain reaction. Cytokines in plasma were determined by enzyme‐linked immunosorbent assay. The Search Tool for Interactions of Chemicals (STITCH) was used to retrieve information regarding the binding properties of atorvastatin.

Results

Among patients with SLE, the proportion of Th17 (CD4⁺IL17⁺) cells was higher compared with controls after activation, with Th17 or Treg polarizing cytokines, phorbol myristate acetate, and ionomycin. In contrast, Treg cells (CD4⁺CD25⁺CD127^dim/−) frequencies were lower. CD95 stimulation induced relatively more apoptosis in Treg cells and less in Th17 cells, as compared with controls. Addition of atorvastatin normalized Th17/Treg cell balance and apoptosis induction. Accordingly, the ratio of RORC/FoxP3 decreased in patients with SLE. Interleukin 17 and interleukin 6 (IL‐6) levels were increased in patients with SLE. Atorvastatin interacted strongly with C‐reactive protein (CRP) and also significantly with IL‐6.

Conclusion

There is a higher proportion of Th17 cells and a lower proportion of Treg cells in patients with SLE after activation. Th17 cells were more resistant than Treg cells to CD95‐induced apoptosis in SLE. Atorvastatin normalized these effects. Our findings reveal a novel mechanism behind the imbalance of Th17/Treg cells with implications for treatment in SLE. We determine for the first time simulated interaction between atorvastatin, CRP, and IL‐6, implying a novel role of atorvastatin.

Association between PCSK9 Levels and Markers of Inflammation, Oxidative Stress, and Endothelial Dysfunction in a Population of Nondialysis Chronic Kidney Disease Patients

Proprotein convertase subtilisin/kexin 9 (PCSK9) plays an important role in lipid metabolism while available literature regarding its involvement in the pathogenesis of atherosclerosis and in the expression of genes associated with apoptosis and inflammation is constantly increasing. Patients with chronic kidney disease (CKD) experience disproportionately increased cardiovascular morbidity and mortality due to dyslipidemia, accelerated atherosclerosis, inflammation, oxidative stress, and other risk factors. In the present cross-sectional study, we investigated the possible association of serum PCSK9 levels with markers of inflammation, oxidative stress, and endothelial damage in patients with CKD. Patients and Methods. Ninety-two patients with CKD stages II-ΙV (eGFR CKD-EPI 47.3 ± 25.7 ml/min/1.73 m², mean age 66 years, 51 men) were included in the study. Plasma PCSK9 levels were correlated with comorbidities (arterial hypertension, diabetes mellitus, and history of cardiovascular disease), renal function indices (eGFR, proteinuria–UPR/24 h), lipid parameters (LDL-cholesterol, HDL-cholesterol, triglycerides, Lp(a), APO-A1, and APO-B), and soluble biomarkers of inflammation, oxidative stress, and endothelial damage (hs-CRP, fibrinogen, 8-epiPGF2a, ox-LDL, IL-6, TNF-α, sICAM-1, and sVCAM-1). Results. The mean plasma value of PCSK9 was 278.1 ng/ml. PCSK9 levels showed direct correlation with serum triglycerides (p = 0.03), Lp(a) (p = 0.01), and sICAM-1 levels (p = 0.03). There was no significant correlation between PCSK9 levels and indices of the renal function, other lipid profile parameters, inflammatory markers, or comorbidities. Multiple regression analysis showed a significant effect of Lp(a) on PCSK9 levels, and for each unit of higher Lp(a), an increase by 3.082 is expected (95% CI: 0.935-5.228, p = 0.006). At the same time, patients receiving statins are expected to have on average 63.8 ng/ml higher PCSK9 values compared to patients not receiving statins (95% CI: 14.6-113.5, p = 0.012). Conclusion. Plasma levels of PCSK9 in nondialysis CKD patients are correlated with endothelial dysfunction and lipid metabolism parameters. Statin intake increases PCSK9 levels significantly in this patient population. PCSK9 levels are not correlated with the severity of kidney disease. Major prospective studies are necessary to investigate the role of PCSK9 in the atherosclerotic cardiovascular outcome in CKD.

Immune metabolism: a bridge of dendritic cells function

An increasing number of researches have shown that cell metabolism regulates cell function. Dendritic cells (DCs), a professional antigen presenting cells, connect innate and adaptive immune responses. The preference of DCs for sugar or lipid affects its phenotypes and functions. In many diseases such as atherosclerosis (AS), diabetes mellitus and tumor, altered glucose or lipid level in microenvironment makes DCs exert ineffective or opposite immune roles, which accelerates the development of these diseases. In this article, we review the metabolism pathways of glucose and cholesterol in DCs, and the effects of metabolic changes on the phenotype and function of DCs. In addition, we discuss the effects of changes in glucose and lipid levels on DCs in the context of different diseases for better understanding the relationship between DCs and diseases. The immune metabolism of DCs may be a potential intervention link to treat metabolic-related immune diseases.

PCSK9 Functions in Atherosclerosis Are Not Limited to Plasmatic LDL-Cholesterol Regulation

The relevance of PCSK9 in atherosclerosis progression is demonstrated by the benefits observed in patients that have followed PCSK9-targeted therapies. The impact of these therapies is attributed to the plasma lipid-lowering effect induced when LDLR hepatic expression levels are recovered after the suppression of soluble PCSK9. Different studies show that PCSK9 is involved in other mechanisms that take place at different stages during atherosclerosis development. Indeed, PCSK9 regulates the expression of key receptors expressed in macrophages that contribute to lipid-loading, foam cell formation and atherosclerotic plaque formation. PCSK9 is also a regulator of vascular inflammation and its expression correlates with pro-inflammatory cytokines release, inflammatory cell recruitment and plaque destabilization. Furthermore, anti-PCSK9 approaches have demonstrated that by inhibiting PCSK9 activity, the progression of atherosclerotic disease is diminished. PCSK9 also modulates thrombosis by modifying platelets steady-state, leukocyte recruitment and clot formation. In this review we evaluate recent findings on PCSK9 functions in cardiovascular diseases beyond LDL-cholesterol plasma levels regulation.

Low levels of PCSK9 are associated with remission in patients with rheumatoid arthritis treated with anti-TNF-α: potential underlying mechanisms

Background

Proprotein convertase subtilisin kexin 9 (PCSK9) targets the LDL-receptor (LDLR) which raises LDL-levels. In addition, PCSK9 has proinflammatory immunological effects. Here, we investigate the role of PCSK9 in relation to the inflammatory activity in patients with rheumatoid arthritis (RA).

Methods

PCSK9-levels were determined at baseline by ELISA in 160 patients with RA not previously treated with biologics. The patients started anti-TNF-α (adalimumab, infliximab, or etanercept) treatment and were followed-up for 1 year. Disease activity was determined by DAS28.

Effects of PCSK9 on cytokine production from macrophages of healthy individuals and synoviocytes from RA patients and inhibition by anti-PCSK9 antibodies were studied in supernatants by ELISA.

Results

A significantly lower level of PCSK9 at baseline, p = 0.035, was observed in patients who reached remission within 1 year, defined as DAS28 < 2.6, compared to those not in remission. At 12 months of TNF-α antagonist treatment, the mean DAS28 was reduced but was significantly greater in patients with highest quartile PCSK9 (Q4) compared to those at lowest PCSK9 (Q1) in both crude (p = 0.01) and adjusted analysis (p = 0.004).

In vitro, PCSK9 induced TNF-alpha and IL-1beta in macrophages and monocyte chemoattractant protein-1 (MCP1) in synoviocytes. These effects were inhibited by anti-PCSK9 antibodies.

Conclusions

Low levels of PCSK9 at baseline are associated with being DAS28-responder to anti-TNF-α treatment in RA. An underlying cause could be that PCSK9 stimulates the production of proinflammatory cytokines from macrophages and synoviocytes, effects inhibited by anti-PCSK9 antibodies. PCSK9 could thus play an immunological role in RA.

Proprotein convertase subtilisin/kexin type 9 is related to disease activity and damage in patients with systemic erythematosus lupus

Background:

Proprotein convertase subtilisin/kexin type 9 (PCSK9) is a serine protease that regulates cholesterol metabolism through low-density lipoprotein receptor degradation and that has been linked to cardiovascular (CV) disease. The purpose of the present study was to examine whether PCSK9 levels are disrupted compared with controls in patients with systemic lupus erythematosus (SLE). We additionally sought to establish whether PCSK9 is related to both the abnormalities in the lipid profile and to the disease activity or damage of patients with SLE.

Methods:

We performed a cross-sectional study that encompassed 366 individuals: 195 SLE patients and 171 age-, sex-, and statin intake-matched controls. PCSK9, lipoproteins serum concentrations, and lipid profiles were assessed in patients and controls. A multivariable analysis, adjusted for standard CV risk factors, was performed to evaluate the role of PCSK9 in SLE-related dyslipidemia.

Results:

Most lipid related-molecules were decreased in patients with SLE compared with controls. This downregulation included PCSK9, with PCSK9 levels being lower in patients than controls in the full multivariable analysis, including the modifications in lipid profiles that the disease itself produces {beta coefficient –73 [95% confidence interval (CI) –91 to –54] ng/ml, p ⩽ 0.001}. Both SLICC and SLEDAI scores were independently and positively related to PCSK9. Patients currently on hydroxychloroquine exhibited decreased levels of PCSK9 compared with those that were not taking hydroxychloroquine [beta coefficient –30 (95% CI −54 to −6) ng/ml, p = 0.015].

Conclusion:

PCSK9 is downregulated in SLE compared with controls, but SLE patients with higher disease activity and damage exhibited higher PSCK9 serum levels.

Adaptive Immune Responses in Human Atherosclerosis

Atherosclerosis is a chronic inflammatory disease that is initiated by the deposition and accumulation of low-density lipoproteins in the artery wall. In this review, we will discuss the role of T- and B-cells in human plaques at different stages of atherosclerosis and the utility of profiling circulating immune cells to monitor atherosclerosis progression. Evidence supports a proatherogenic role for intraplaque T helper type 1 (Th1) cells, CD4⁺CD28^null T-cells, and natural killer T-cells, whereas Th2 cells and regulatory T-cells (Treg) have an atheroprotective role. Several studies indicate that intraplaque T-cells are activated upon recognition of endogenous antigens including heat shock protein 60 and oxidized low-density lipoprotein, but antigens derived from pathogens can also trigger T-cell proliferation and cytokine production. Future studies are needed to assess whether circulating cellular biomarkers can improve identification of vulnerable lesions so that effective intervention can be implemented before clinical manifestations are apparent.