Proprotein convertase subtilisin kexin 9 is associated with disease activity and is implicated in immune activation in systemic lupus erythematosus

Contrasting effects of intracellular and extracellular human PCSK9 on inflammation, lipid alteration and cell death

Proprotein convertase subtilisin/kexin type 9 (PCSK9) is one of the major regulators of low-density lipoprotein receptor (LDLR). Information on role and regulation of PCSK9 in lung is very limited. Our study focuses on understanding the role and regulation of PCSK9 in the lung. PCSK9 levels are higher in Bronchoalveolar lavage fluid (BALF) of smokers with or without chronic obstructive pulmonary diseases (COPD) compared to BALF of nonsmokers. PCSK9-stimulated cells induce proinflammatory cytokines and activation of MAPKp38. PCSK9 transcripts are highly expressed in healthy individuals compared to COPD, pulmonary fibrosis or pulmonary systemic sclerosis. Cigarette smoke extract reduce PCSK9 levels in undifferentiated pulmonary bronchial epithelial cells (PBEC) but induce in differentiated PBEC. PCSK9 inhibition affect biological pathways, induces lipid peroxidation, and higher level of apoptosis in response to staurosporine. Our results suggest that higher levels of PCSK9 in BALF acts as an inflammatory marker. Furthermore, extracellular and intracellular PCSK9 play different roles.

PCSK9 Inhibitors and the Risk of Vitiligo: A Mendelian Randomization Study

Lipid-lowering agents have been suggested as a therapeutic option for vitiligo on the basis of the potential pathogenic role of lipid metabolism abnormalities. We aimed to explore the impact of genetically proxied lipid-lowering agents on the risk of vitiligo and potentially associated mediators. GWAS summary statistics for European ancestry were extracted from the largest available meta-analysis for vitiligo: the Global Lipids Genetics Consortium for 7 lipid profiles and 2 large biobanks, UK Biobank and deCODE, for 4719 proteins. After identifying lipid-lowering agents with genetically proxied protective effects against vitiligo using lipid-lowering and protein-inhibition Mendelian randomization (MR) analyses, multivariable and 2-step MR analyses were conducted to identify potential mediators between lipid-lowering agents and vitiligo. Lipid-lowering MR indicated a potential role of PCSK9 in reducing the vitiligo risk (OR [95% confidence interval] = 0.71 [0.52-0.95]), which was replicated in PCSK9-inhibition MR analyses across 2 separate biobanks (UK Biobank: OR [95% confidence interval] = 0.82 [0.71-0.96]; deCODE: OR [95% confidence interval] = 0.78 [0.67-0.91]). Multivariable MR suggested that well-known lipid profiles do not mediate the relationship between PCSK9 and vitiligo, whereas 2-step MR analyses identified 5 potential protein mediators (CCN5, CXCL12, FCRL1, legumain, and FGF2). Hence, PCSK9 inhibitor may attenuate the vitiligo risk; PCSK9 and the potential protein mediators can serve as promising novel therapeutic targets for its effective treatment.

Association between genetically proxied PCSK9 inhibition and systemic lupus erythematosus risk: A mendelian randomization study

BACKGROUND

Preclinical and epidemiological studies suggest that proprotein convertase subtilisin/kexin type 9 (PCSK9) had a potential effect on the development of SLE, but it was unclear whether a causal relationship exists. We aimed to investigate the association between genetically proxied inhibition of PCSK9 and the risk of SLE using a two-sample Mendelian randomization (MR) approach.

METHODS

Single nucleotide polymorphisms (SNPs) associated with PCSK9 were extracted from pooled data obtained from the Global Lipid Genetics Consortium (GLGC) Genome-wide Association Study (GWAS) related to LDL-c levels, which was used as a proxy for PCSK9 inhibition. Pooled statistics for SLE were obtained from an independent GWAS dataset including 5201 SLE patients and 9066 controls. Inverse variance-weighted random-effects models were used to examine the association between genetically proxied inhibition of PCSK9 and the risk of SLE. MR-Egger, weighted median, weighted mode, Simple mode, and co-location analyses were used as sensitivity analyses to test the robustness of the analyses.

RESULTS

Genetically proxied inhibition of PCSK9 was associated with a reduced risk of SLE (OR = 0.51, 95% CI = 0.34 to 0.77, p = .001). This finding was replicated in an earlier GLGC GWAS analysis (OR = 0.59, 95% CI = 0.40 to 0.87, p = .007). Sensitivity analysis ensured that the results were robust. Co-localization analysis did not find evidence of shared causal variation between PCSK9 and SLE.

CONCLUSIONS

This Mendelian randomization study showed that PCSK9 was associated with SLE pathogenesis, and its inhibition was associated with a reduced risk of SLE. This study has offered a prospective therapeutic avenue for intervening in the progression of SLE by inhibiting PCSK9 levels.

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.

Association of lipid lowering drugs and the risk of systemic lupus erythematosus: a drug target Mendelian randomization

Background and objective: An interaction between low-density lipoprotein level, lipid-lowering drugs, and systemic lupus erythematosus (SLE) was reported by previous studies. However, whether lipid-lowering drugs provided protective effect for reducing the risk of SLE was unclear. We aimed to clarify this causal relationship through a drug-target Mendelian randomization (MR) study. Methods: Genetic instruments-single nucleotide polymorphism (SNPs)-were utilized to proxy inhibition of the three genes-3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR), proprotein convertase subtilisin/kexin type 9 (PCSK9), and Niemann-Pick C1-Like 1(NPC1L1), which was corresponded to three lipid-lowering drugs-statins, evolocumab, and ezetimibe. Low-density lipoprotein (LDL) cholesterol was selected as the biomarker for the measurement of the inhibitors of HMGCR, PCSK9, and NPC1L1, and the genetic data were acquired from the Global Lipids Genetics Consortium, which consisted of 1.3 million participants of European ancestry and 146.5 thousand participants of East Asian ancestry. The genetic dataset of SLE was acquired from two large-scale GWAS studies; one recruited 23,210 participants (7,219 SLE cases and 15,991 controls) of European ancestry and the other one recruited 12,653 participants (4,222 SLE cases and 8,431 controls) of Chinese ancestry. The primary analysis used the inverse variance weighted (IVW) method. Four additional sensitivity analyses, colocalization analysis, and stratification analysis were performed. Results: The primary analysis showed that inhibition of PCSK9 (evolocumab) was associated with a significantly lower risk of SLE [odds ratio (OR) 0.51, 95%CI 0.34 to 0.76, p = 0.001] in the European population. The secondary analyses had similar findings. Stratification analysis demonstrated that the preventive effect of PCSK9 inhibition for SLE was similar in both males and females. However, the results were not replicated in the East Asian population. The inhibition of HMGCR (statins) and NPC1L1 (ezetimibe) did not cause a lower risk of SLE. Conclusion: Evolocumab might provide a protective effect on the risk of SLE in the European population, but statins and ezetimibe might not have the protective effect. Further research is necessary to elucidate the specific mechanisms and potential therapeutic applications of PCSK9 inhibitors (evolocumab) in the context of SLE protection.

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.

Exploring the Link between Plasma Levels of PCSK9, Immune Dysregulation and Atherosclerosis in Patients with Primary Sjögren's Syndrome

Proprotein convertase subtilisin/kexin type 9 (PCSK9) regulates lipid metabolism contributing to cardiovascular (CV) risk in the general population. The relationship between PCSK9 and CV risk in systemic autoimmune diseases has been poorly explored. We investigated the association between plasma PCSK9, measures of immune-inflammatory status and markers of atherosclerosis in 52 consecutive patients with primary Sjögren's syndrome (pSS) in comparison to healthy controls (HCs). Median plasma PCSK9 levels were significantly higher in pSS patients versus HCs (162 (79-255) vs. 53 (39-99) ng/mL). Significantly higher prevalence of subclinical atherosclerosis and lower of dyslipidaemia (61% vs. 85%, p = 0.042) characterized pSS patients versus HCs. In pSS, no significant correlation emerged between PCSK9 and disease activity, atherosclerosis and lipid levels. In HCs, PCSK9 significantly correlated with lipid levels and atherosclerosis. Interestingly, significantly higher PCSK9 levels were found in HCs with high-to-very-high as compared to low-to-moderate CV risk (p = 0.018) while a non-significant trend towards higher PCSK9 levels was detected in pSS patients with low-to-moderate as compared to high-to-very-high CV risk (p = 0.060). This is the first demonstration that pSS patients, despite lower prevalence of dyslipidaemia and higher CV risk profile, are characterized by a 3-fold increase in PCSK9 levels in comparison to HCs. As PCSK9 does not correlate with measures of CV risk, its role in CV morbidity in pSS needs further investigation.

Causal relationship between PCSK9 inhibitor and autoimmune diseases: a drug target Mendelian randomization study

BACKGROUND

In addition to decreasing the level of cholesterol, proprotein convertase subtilis kexin 9 (PCSK9) inhibitor has pleiotropic effects, including immune regulation. However, the impact of PCSK9 on autoimmune diseases is controversial. Therefore, we used drug target Mendelian randomization (MR) analysis to investigate the effect of PCSK9 inhibitor on different autoimmune diseases.

METHODS

We collected single nucleotide polymorphisms (SNPs) of PCSK9 from published genome-wide association studies statistics and conducted drug target MR analysis to detect the causal relationship between PCSK9 inhibitor and the risk of autoimmune diseases. 3-Hydroxy-3-methylglutaryl-assisted enzyme A reductase (HMGCR) inhibitor, the drug target of statin, was used to compare the effect with that of PCSK9 inhibitor. With the risk of coronary heart disease as a positive control, primary outcomes included the risk of systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), myasthenia gravis (MG), multiple sclerosis (MS), asthma, Crohn's disease (CD), ulcerative colitis (UC), and type 1 diabetes (T1D).

RESULTS

PCSK9 inhibitor significantly reduced the risk of SLE (OR [95%CI] = 0.47 [0.30 to 0.76], p = 1.74 × 10-3) but increased the risk of asthma (OR [95%CI] = 1.15 [1.03 to 1.29], p = 1.68 × 10-2) and CD (OR [95%CI] = 1.38 [1.05 to 1.83], p = 2.28 × 10-2). In contrast, HMGCR inhibitor increased the risk of RA (OR [95%CI] = 1.58 [1.19 to 2.11], p = 1.67 × 10-3), asthma (OR [95%CI] = 1.21 [1.04 to 1.40], p = 1.17 × 10-2), and CD (OR [95%CI] = 1.60 [1.08 to 2.39], p = 2.04 × 10-2).

CONCLUSIONS

PCSK9 inhibitor significantly reduced the risk of SLE but increased the risk of asthma and CD. In contrast, HMGCR inhibitor may be a risk factor for RA, asthma, and CD.

Circulating Proprotein Convertase Subtilisin/Kexin Type 9 (PCSK9) is Associated with Disease Activity and Risk of Incident Cardiovascular Disease in Patients with Systemic Lupus Erythematosus

To study the relationship of serum PCSK9 and disease activity and major adverse cardiovascular events (MACEs) in systemic lupus erythematosus (SLE). Consecutive patients who fulfilled ≥ 4 ACR criteria for SLE and consented for a biomarker study in 2009-2013 were included. Stored serum samples were assayed for PCSK9. PCSK9 levels were correlated with SLE disease activity scores. Patients were divided into two groups according to the median PCSK9 level and new MACEs over time were evaluated. The effect of PCSK9 level on MACEs and mortality was studied by Cox regression, adjusted for confounders. A total of 539 SLE patients were studied (93% women, age 41.9 ± 14.0 years). The median PCSK9 level at baseline was 220 ng/ml. Patients with higher PCSK9 (≥ 220 ng/ml; n = 269) had significantly higher SLE disease activity index (SLEDAI) than those with lower PCSK9 (< 220 ng/ml; n = 270). PCSK9 levels were significantly higher in patients with active renal than active non-renal SLE, which in turn were significantly higher than those with inactive SLE or healthy controls. PCSK9 level correlated with SLEDAI in the overall population (ρ = 0.30; p < 0.001). Over 91.3 ± 18.6 months, 29 patients developed 31 MACEs and 40 patients succumbed (25% for vascular events). The cumulative incidence of MACEs at 5 years was 4.8% in the higher PCSK9 and 1.1% in the lower PCSK9 group (HR2.51[1.11-5.70]; p = 0.03). Cox regression revealed higher PCSK9 was significantly associated with MACEs (HR1.003[1.000-1.005] per ng/ml; p = 0.02) independent of age, sex, renal function, baseline disease activity score, traditional atherosclerotic risk factors, antiphospholipid antibody and the use of aspirin/warfarin, statins and immunosuppressive drugs. PCSK9 level was also independently associated with all-cause (HR1.002[1.000-1.004] per ng/ml; p = 0.03) and vascular mortality (HR1.004[1.000-1.007]; p = 0.04). We concluded that serum PCSK9 level correlates with SLE disease activity. Higher serum PCSK9 levels are associated with increased risk of cardiovascular events and mortality in SLE.

Anti-Inflammatory Effects of Lipid-Lowering Drugs and Supplements-A Narrative Review

Cardiovascular diseases (CVD) are the leading cause of death worldwide. Since the establishment of the "lipid hypothesis", according to which, cholesterol level is directly correlated to the risk of CVD, many different lipid-lowering agents have been introduced in clinical practice. A majority of these drugs, in addition to their lipid-lowering properties, may also exhibit some anti-inflammatory and immunomodulatory activities. This hypothesis was based on the observation that a decrease in lipid levels occurs along with a decrease in inflammation. Insufficient reduction in the inflammation during treatment with lipid-lowering drugs could be one of the explanations for treatment failure and recurrent CVD events. Thus, the aim of this narrative review was to evaluate the anti-inflammatory properties of currently available lipid-lowering medications including statins, ezetimibe, bile acid sequestrants (BAS), proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitors, fibrates, omega-3 fatty acids, and niacin, as well as dietary supplements and novel drugs used in modern times.

Atherosclerotic Cardiovascular Risk Stratification in the Rheumatic Diseases:: An Integrative, Multiparametric Approach

Cardiovascular disease (CVD) risk is increased in most inflammatory rheumatic diseases (IRDs), reiterating the role of inflammation in the initiation and progression of atherosclerosis. An inverse association of CVD risk with body weight and lipid levels has been described in IRDs. Coronary artery calcium scores, plaque burden and characteristics, and carotid plaques on ultrasound optimize CVD risk estimate in IRDs. Biomarkers of cardiac injury, autoantibodies, lipid biomarkers, and cytokines also improve risk assessment in IRDs. Machine learning and deep learning algorithms for phenotype and image analysis hold promise to improve CVD risk stratification in IRDs.

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.

Mendelian randomization and pathway analysis demonstrate shared genetic associations between lupus and coronary artery disease

Coronary artery disease (CAD) is a leading cause of death in patients with systemic lupus erythematosus (SLE). Despite clinical evidence supporting an association between SLE and CAD, pleiotropy-adjusted genetic association studies are limited and focus on only a few common risk loci. Here, we identify a net positive causal estimate of SLE-associated non-HLA SNPs on CAD by traditional Mendelian randomization (MR) approaches. Pathway analysis using SNP-to-gene mapping followed by unsupervised clustering based on protein-protein interactions (PPIs) identifies biological networks composed of positive and negative causal sets of genes. In addition, we confirm the casual effects of specific SNP-to-gene modules on CAD using only SNP mapping to each PPI-defined functional gene set as instrumental variables. This PPI-based MR approach elucidates various molecular pathways with causal implications between SLE and CAD and identifies biological pathways likely causative of both pathologies, revealing known and novel therapeutic interventions for managing CAD in SLE.

The role of proprotein convertase subtilisin/kexin type 9 (PCSK9) in the pathophysiology of psoriasis and systemic lupus erythematosus

Inflammation and atherogenic dyslipidaemia are often observed in skin diseases and represent an increased risk of cardiovascular disorders. Proprotein convertase subtilisin/kexin type 9 plays an important role in the regulation of serum low-density lipoprotein cholesterol levels. Its biological role, however, seems to go much beyond the regulation of cholesterol metabolism. The article presents potential pathophysiological links between inflammatory process and lipid disorders based on the example of psoriasis and systemic lupus erythematosus.

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.

Proprotein convertase subtilisin/kexin type 9 is associated with atherosclerosis in patients with Behcet's disease

OBJECTIVES

The incidence of cardiovascular disease is increased in patients with Behcet's disease (BD). Proprotein convertase subtilisin/kexin type 9 (PCSK9) causes the acceleration of atherosclerosis. We aimed to investigate whether there is a relationship between PCSK9 with carotid artery intima-media thickness (cIMT), a marker of subclinical atherosclerosis, and BD disease activity.

METHODS

Fifty-eight patients with BD and 58 age-, gender-, and body mass index (BMI)-matched healthy control subjects were included in the study. The disease activity of the patients was estimated. Individuals' cIMT values were measured, and PCSK9 levels were studied.

RESULTS

Patients with BD' cIMT (0.51 ± 0.1 vs 0.41 ± 0.1 mm, p < .001) and PCSK9 (623.2 ± 101.7 ± 10.1 vs 528.3 ± 242.7 ng/ml, p = .007), values were significantly higher than the control group. In stepwise regression analysis, there was an independent relationship between cIMT with PCSK9 (β = 0.179, p < .050). There was no independent relationship between disease activities with PCSK9. Based on the ROC curve analysis, the PCSK9 optimal cutoff value for cIMT was 595.1 ng/ml, sensitivity 66.7%, specificity 64.7% (AUC = 0.672; 95% CI: 0.530-0.815, p = .040).

CONCLUSION

There is a strong independent association between subclinical atherosclerosis and PCSK9 in patients with BD. There may be no independent association between PCSK9 and disease activity.

Proteomic Profiling of Cryoglobulinemia

Objective

We aimed to explore and identify candidate protein biomarkers of cryoglobulinemia (CGE) in disease control patients with negative cryoglobulin (DC) or healthy controls (HCs).

Methods

The tandem mass tag (TMT)-labeled serum quantitative proteomics approach was used to identify differentially expressed proteins between the CGE and DC groups. Ingenuity pathway analysis was used for functional annotation of differentially expressed proteins. Biomarker candidates were validated in another cohort using the parallel reaction monitoring (PRM) method. Apolipoprotein A1 (APOA1), apolipoprotein CIII (APOC3), adiponectin, and proprotein convertase subtilisin/kexin type-9 (PCSK9), which represent key proteins involved in the cholesterol metabolism pathway, were further verified in an increased number of samples by enzyme-linked immunosorbent assay (ELISA).

Results

A total of 1004 proteins were identified, of which 109 proteins were differentially expressed between the CGE and DC groups. These differentially expressed proteins were primarily involved in hepatic fibrosis/hepatic stellate cell activation and immune/inflammation-related pathways. In the disease and biofunction analysis, these proteins were mainly associated with the adhesion of blood cells, leukocyte migration, cholesterol transport, and transport of lipids. Twelve candidate biomarkers were validated by PRM-based proteomics, and proteins involved in the cholesterol metabolism pathway were further verified. APOA1, APOC3, adiponectin and PCSK9 concentrations were increased in CGE patients compared with healthy controls (P=0.0123, 0.1136, 0.5760, and 0.0019, respectively).

Conclusion

This report describes the first application of a TMT-PRM-ELISA workflow to identify and validate CGE-specific biomarkers in serum. APOA1 and PCSK9 have been confirmed to be increased in CGE patients, demonstrating that proteins involved in cholesterol metabolism are also implicated in the development of CGE. These findings contribute to pathogenesis research and biomarker discovery in CGE.

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.

PCSK9 and inflammation. Maybe a role in autoimmune diseases? Focus on rheumatoid arthritis and systemic lupus erythematosus

Despite a clear epidemiological link between autoimmune disease and cardiovascular (CV) risk exists, pathophysiological explanations are extremely complex and far from being elucidated. Dysregulation of metabolic pathways and chronic low-grade inflammation represent common pathways, but CV risk still remains underestimated in patients with autoimmune diseas. Among different candidate mediators, pro-protein convertase subtilisin/kexin type 9 (PCSK9) is attracting a growing attention, due to a combined effect on lipid metabolism and inflammatory response. Study on PCSK9 inhibitors have established a clear benefit on CV outcome without an established effect on inflammation. Conversely, evidence from sepsis and HIV infection strongly support a pro-inflammatory role of PCSK9. Still uncertain is instead the role of PCSK9 in autoimmune disease. So far reported clinical findings are controversial and likely reflect the poor knowledge of PCSK9 activity on monocyte/macrophage migration and activation. The complex signaling network around PCSK9 synthesis and metabolism may also have a role, especially concerning the involvement of scavenger receptors such as CD36. Such complexity in PCSK9 signaling seems particularly evident in autoimmune disease model. This would also potentially explain the observed independency between lipid profile and PCSK9 levels, the so-called "lipid paradox". In this narrative review we will summarize the current knowledge about the complex network of PCSK9 signaling. We will focus of upstream and downstream pathways with potential implication in autoimmune disease and potential effects of PCSK9 inhibiting strategies.

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.

Relationship between Circulating PCSK9 and Markers of Subclinical Atherosclerosis-The IMPROVE Study

(1) Background and purpose: circulating proprotein convertase subtilisin/kexin type 9 (PCSK9) is one of the key regulators of cholesterol metabolism. Despite this, its role as a player in atherosclerosis development is still matter of debate. Here, we investigated the relationships between this protein and several markers of subclinical atherosclerosis. (2) Methods: the IMPROVE study enrolled 3703 European subjects (54–79 years; 48% men; with ≥3 vascular risk factors), asymptomatic for cardiovascular diseases. PCSK9 levels were measured by ELISA. B-mode ultrasound was used to measure markers of carotid subclinical atherosclerosis. (3) Results: in the crude analysis, PCSK9 levels were associated with several baseline measures of carotid intima-media thickness (cIMT) (all p < 0.0001); with cIMT change over time (Fastest-IMTmax-progr) (p = 0.01); with inter-adventitia common carotid artery diameter (ICCAD) (p < 0.0001); and with the echolucency (Grey Scale Median; GSM) of both carotid plaque and plaque-free common carotid IMT (both p < 0.0001). However, after adjustment for age, sex, latitude, and pharmacological treatment, all the afore-mentioned correlations were no longer statistically significant. The lack of correlation was also observed after stratification for sex, latitude, and pharmacological treatments. (4) Conclusions: in subjects who are asymptomatic for cardiovascular diseases, PCSK9 plasma levels do not correlate with vascular damage and/or subclinical atherosclerosis of extracranial carotid arteries.

Variants of PCSK9 Gene Are Associated with Subclinical Atherosclerosis and Cardiometabolic Parameters in Mexicans. The GEA Project

Background: Coronary artery disease (CAD) is a chronic, inflammatory, and complex disease associated with vascular risk factors. Nowadays, the coronary artery calcium (CAC) is a specific marker of the presence and extent of atherosclerosis. Additionally, CAC is a predictor of future coronary events in asymptomatic individuals diagnosed with subclinical atherosclerosis (CAC > 0). In this study, our aim is to evaluate the participation of two polymorphisms of the PCSK9 gene as genetic markers for developing subclinical atherosclerosis and cardiometabolic risk factors in asymptomatic individuals. Methods: We analyzed two PCSK9 polymorphisms (rs2479409 and rs615563) in 394 individuals with subclinical atherosclerosis and 1102 healthy controls using real time- polymerase chain reaction (PCR). Results: Under various inheritance models adjusted for different confounding factors, the rs2479409 polymorphism was associated with an increased risk of developing subclinical atherosclerosis (OR = 1.53, P recessive = 0.041). Both polymorphisms were significantly associated with several cardiometabolic parameters. Conclusions: Our data suggest that rs2479409 polymorphism could be envisaged as a risk marker for subclinical atherosclerosis.

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.