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.

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

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

Platelet-Derived PCSK9 Is Associated with LDL Metabolism and Modulates Atherothrombotic Mechanisms in Coronary Artery Disease.

Platelets play a significant role in atherothrombosis. Proprotein convertase subtilisin/kexin type 9 (PCSK9) is critically involved in the regulation of LDL metabolism and interacts with platelet function. The effect of PCSK9 in platelet function is poorly understood. The authors of this article sought to characterize platelets as a major source of PCSK9 and PCSK9's role in atherothrombosis. In a large cohort of patients with coronary artery disease (CAD), platelet count, platelet reactivity, and platelet-derived PCSK9 release were analyzed. The role of platelet PCSK9 on platelet and monocyte function was investigated in vitro. Platelet count and hyper-reactivity correlated with plasma LDL in CAD. The circulating platelets express on their surface and release substantial amounts of PCSK9. Release of PCSK9 augmented platelet-dependent thrombosis, monocyte migration, and differentiation into macrophages/foam cells. Platelets and PCSK9 accumulated in tissue derived from atherosclerotic carotid arteries in areas of macrophages. PCSK9 inhibition reduced platelet activation and platelet-dependent thrombo-inflammation. The authors identified platelets as a source of PCSK9 in CAD, which may have an impact on LDL metabolism. Furthermore, platelet-derived PCSK9 contributes to atherothrombosis, and inhibition of PCSK9 attenuates thrombo-inflammation, which may contribute to the reported beneficial clinical effects.

Proprotein Convertase Subtilisin/Kexin Type 9: A View beyond the Canonical Cholesterol-Lowering Impact.

Proprotein convertase subtilisin/kexin type 9 (PCSK9), mainly synthetized and released by the liver, represents one of the key regulators of low-density lipoprotein cholesterol. Although genetic and interventional studies have demonstrated that lowering PCSK9 levels corresponds to a cardiovascular benefit, identification of non-cholesterol-related processes has emerged since its discovery. Besides liver, PCSK9 is also expressed in many tissues (eg, intestine, endocrine pancreas, and brain). The aim of the present review is to describe and discuss PCSK9 pathophysiology and possible non-lipid-lowering effects whether already extensively characterized (eg, inflammatory burden of atherosclerosis, triglyceride-rich lipoprotein metabolism, and platelet activation), or to be unraveled (eg, in adipose tissue). The identification of novel transcriptional factors in the promoter region of human PCSK9 (eg, ChREBP) characterizes new mechanisms explaining how controlling intrahepatic glucose may be a therapeutic strategy to reduce cardiovascular risk in type 2 diabetes. Finally, the evidence describing PCSK9 as involved in cell proliferation and apoptosis raises the possibility of this protein being involved in cancer risk.

Characterization of PCSK9 in the Blood and Skin of Psoriasis.

Mechanisms explaining the link between psoriasis, a proinflammatory condition, and cardiovascular disease are not fully known. PCSK9 is predominantly expressed in hepatocytes as a critical regulator of lipid metabolism, and clinical trials targeting PCSK9 reduce cardiovascular disease. Independent of its role in lipid metabolism, PCSK9 levels associate with endothelial dysfunction and predict cardiovascular events. We used two separate human psoriasis cohorts and the K14-Rac1V12-/+ murine model of psoriasis to investigate PCSK9 and cardiovascular risk in psoriasis. In both psoriasis cohorts (n = 88 and n = 20), PCSK9 levels were 20% and 13% higher than in age-, sex-, and cholesterol-matched controls, respectively (P < 0.05 for each comparison) and correlated with PASI (r = 0.43, P < 0.05). Despite no difference in hepatocyte expression, K14-Rac1V12-/+ mice demonstrated skin-specific PCSK9 staining, which was confirmed in human psoriatic lesional skin. In patients with psoriasis, PCSK9 levels correlated with impaired endothelial vascular health (e.g., early atherosclerosis, ß = 4.5, P < 0.01) and log converted coronary artery calcium score (ß = 0.30, P = 0.01), which remained significant after adjustment for Framingham risk, body mass index, and active biologic use. Taken together, these findings suggest, independent of cholesterol, an association between circulating PCSK9 and early as well as advanced stages of atherosclerosis in psoriasis.

PCSK9 and atherosclerosis: Looking beyond LDL regulation.

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

Non-hematopoietic deficiency of proprotein convertase subtilisin/kexin type 9 deficiency leads to more severe anemia in a murine model of sickle cell disease.

Proprotein convertase subtilisin/kexin type 9 (PCSK9) deficiency leads to lower cholesterol and is associated with reduced vascular complications in the general population. Cholesterol lowering may also have beneficial effects in sickle cell disease (SCD). The objective of this study was to determine effects of PCSK9 deficiency in a mouse model of SCD. Bone marrow transplantation (BMT) was performed from donor SCD mice to wild-type, PCSK9-deficient, and LDLR-deficient recipients to generate SCD controls (Pcsk9+/+, SCDbmt) with preserved PCSK9 status, SCD mice with deficiency of PCSK9 (Pcsk9-/-, SCDbmt), and SCD mice with deficiency of LDLR (Ldlr-/-, SCDbmt). Although cholesterol levels were lower in Pcsk9-/-, SCDbmt mice compared to Pcsk9+/+, SCDbmt mice, anemia was more severe in Pcsk9-/-, SCDbmt mice. Increased reticulocytosis, enhanced ex vivo erythrocyte sickling, and increased erythrocyte phosphatidylserine exposure was also observed. Livers, spleens, and kidneys contained increased iron in Pcsk9-/-, SCDbmt mice compared to Pcsk9+/+, SCDbmt mice consistent with greater hemolysis. SCD mice with deficiency of LDLR (Ldlr-/-, SCDbmt mice) had similar anemia as Ldlr+/+, SCDbmt mice despite higher serum cholesterol. In conclusion, deficiency of PCSK9 is associated with worsened anemia in SCD mice due to increased hemolysis. These findings may have implications for lipid-lowering strategies in patients with SCD, as well as for potential novel modifiers of anemia severity.

Role of PCSK9 in the course of ejection fraction change after ST-segment elevation myocardial infarction: a pilot study.

AIMS: Proprotein convertase subtilisin/kexin type 9 (PCSK9) has emerged as a therapeutic target for reducing plasma low-density lipoprotein cholesterol. Beyond lipid control, recent findings suggest a deleterious effect of this protein in the pathogenesis of postmyocardial infarction left ventricle remodelling and heart failure-related complications. The aim of this study was to assess the relationship between circulating PCSK9 and 6 month cardiac magnetic resonance imaging-derived left ventricular ejection fraction (LVEF) after a first ST-segment elevation myocardial infarction (STEMI). METHODS AND RESULTS: We prospectively evaluated 40 patients with a first STEMI, LVEF < 50% and treated with primary percutaneous coronary intervention in which PCSK9 was measured 24 h postreperfusion. All patients underwent cardiac magnetic resonance imaging 1 week and 6 months after STEMI. Baseline characteristics were compared across median values of PCSK9. The association between PCSK9 levels and LVEF at 6 months was evaluated by analysis of covariance. The mean age of the sample was 60 ± 12 years and 33 (82.5%) were male patients. The infarct location was anterior in 27 patients (67.5%), and 9 patients (22.5%) were Killip class ≥ II. The mean 1 week and 6 month LVEF were 41 ± 7% and 48 ± 10%, respectively. The mean PCSK9 was 1.93 ± 0.38 U/mL. Testing the association between serum PCSK9 and 6 month LVEF with analysis of covariance revealed an inverse relationship (r = -0.35, P = 0.028). After multivariate adjustment, circulating PCSK9 remained significant and inversely associated with 6 month LVEF (P = 0.002). CONCLUSIONS: In patients with a first STEMI with reduced ejection fraction at index admission and treated with primary percutaneous coronary intervention, circulating PCSK9 was associated with lower LVEF at 6 months.

PCSK9-D374Y mediated LDL-R degradation can be functionally inhibited by EGF-A and truncated EGF-A peptides: An in vitro study.

BACKGROUND AND AIMS: Proprotein convertase subtilisin/kexin type 9 (PCSK9) binds to low density lipoprotein receptor (LDLR) through the LDLR epidermal growth factor-like repeat A (EGF-A) domain and induces receptor internalization and degradation. PCSK9 has emerged as a novel therapeutic target for hypercholesterolemia. Clinical studies with PCSK9 inhibiting antibodies have demonstrated strong LDL-c lowering effects, but other therapeutic approaches using small molecule inhibitors for targeting PCSK9 functions may offer supplementary therapeutic options. The aim of our study was to evaluate the effect of synthetic EGF-A analogs on mutated (D374Y) PCSK9-D374Y mediated LDLR degradation in vitro. METHODS: Huh7 human hepatoma cells were transiently transfected to overexpress the gain-of-function D374Y PCSK9 mutation, which has been associated with severe hypercholesterolemia in humans. RESULTS: Transient transfection of cells with PCSK9-D374Y expression vector very effectively enhanced degradation of mature LDLR in Huh7. Treatment with both EGF-A and EGF-A truncated peptides inhibited this effect and showed increased LDLR protein in Huh7 cells transfected with PCSK9-D374Y in a clear concentration dependent manner. Huh7 transfected cells treated with increasing concentration of EGF-A analogs also showed an increase internalization of labeled Dil-LDL. CONCLUSIONS: The result of our study shows that EGF-A analogs are able to effectively hamper the enhanced degradation of LDLR in liver cells expressing PCSK9-D374Y.

The impact of dyslipidemia and oxidative stress on vasoactive mediators in patients with renal dysfunction.

Hyperlipidemia and oxidative stress are indispensable features of chronic kidney disease (CKD) that favor the development of atherogenic plaques and cardiovascular disease (CVD). A number of vasoactive mediators including proprotein convertase subtilisin-kexin type 9 (PCSK9), endothelin-1, nitric oxide, and angiotensin II have fundamental roles in the pathophysiology of atherosclerotic events; moreover, their levels are affected by dyslipidemia and oxidative stress due to renal dysfunction. Therefore, therapeutic measures aimed at correcting dyslipidemia and alleviating oxidative stress could potentially protect against CVD in CKD patients. In this review, we discuss the relation between dyslipidemia, oxidative stress, and vasoactive mediators as well as the available treatment options against these disturbances in CKD patients.

Impact of LDLR and PCSK9 pathogenic variants in Japanese heterozygous familial hypercholesterolemia patients.

BACKGROUND AND AIMS: More than 4970 variants in the low-density lipoprotein receptor (LDLR) gene and 350 variants in the proprotein convertase subtilisin/kexin 9 (PCSK9) gene have been reported in familial hypercholesterolemia (FH) patients. However, the effects of these variants on FH pathophysiology have not been fully clarified. We aimed to update the LDLR and PCSK9 variants in Japanese heterozygous FH (HeFH) patients and annotate their clinical significance for the genetic diagnosis of HeFH. METHODS: A genetic analysis of the LDLR and PCSK9 genes was performed in 801 clinically diagnosed HeFH patients. The association of the pathogenic variants with the clinical FH phenotype was examined. RESULTS: Pathogenic variants in the LDLR and PCSK9 genes were found in 46% (n = 296) and 7.8% (n = 51) of unrelated FH patients (n = 650), respectively. The prevalence of Achilles tendon thickness was low (44%) in patients harbouring PCSK9 pathogenic variants. Furthermore, 17% of unrelated FH patients harboured one of five frequent LDLR pathogenic variants: c.1845+2T > C, c.1012T > A: p.(Cys338Ser), c.1297G > C: p.(Asp433His), c.1702C > G: p.(Leu568Val), and c.2431A > T: p.(Lys811*). Patients harbouring the c.1845+2T > C and c.1702C > G: p.(Leu568Val) variants had significantly lower serum LDL-cholesterol levels and higher serum HDL-cholesterol levels, respectively, compared with those harbouring the other LDLR pathogenic variants. The proportion of LDLR pathogenic variants was higher in patients with a younger age of coronary artery disease (CAD) onset and significantly decreased as the age of CAD onset increased. CONCLUSIONS: This study annotated the clinical significance and characteristics of LDLR and PCSK9 pathogenic variants in Japanese HeFH patients.

Atopic Dermatitis-Like Rash During Evolocumab Treatment of Familial Hypercholesterolemia.

Proprotein convertase subtilisin/kexin type 9 (PCSK9) is a serine protease that targets the low-density lipoprotein (LDL) receptor for lysosomal degradation. PCSK9 impedes the receptor-mediated clearance of LDL-cholesterol, thereby increasing serum LDL-cholesterol levels. Evolocumab, a human monoclonal antibody against PCSK9, effectively reduces serum LDL-cholesterol levels. We report the first known case of a patient who developed an atopic dermatitis (AD)-like rash during evolocumab therapy. A 43-year-old Japanese man with heterozygous familial hypercholesterolemia was treated with subcutaneous injection of 140 mg evolocumab biweekly, for 16 months. The therapy was then changed to subcutaneous injection of 420 mg evolocumab monthly. A few days after the first dose, the patient experienced pruritus and rash on his extremities. The rash worsened, while the pruritus subsided, then relapsed after the second and third doses. He had erythema and excoriation on his legs, lichenification over his popliteal fossa, xerosis on his forearms, an increased serum IgE level, and a family history of AD in his siblings. We made a provisional diagnosis of AD characterized by enhanced type 2 helper T (Th2) activity and treated him with topical corticosteroids and oral anti-histamines. His rash improved and did not relapse after the fifth dose; however, his LDL-cholesterol level increased. PCSK9 or oxidized LDL activates macrophages or dendritic cells, respectively, and enhances their activity to induce Th1 cells antagonizing Th2 cells. We hypothesized that high-dose evolocumab may suppress Th1 activity to antagonize Th2, and unmask Th2 disposition based on the patient's atopic diathesis, triggering the rash mimicking AD. Clinicians should be aware of rash development during evolocumab therapy.

PCSK9: A new participant in lipophagy in regulating atherosclerosis?

Proprotein convertase subtilisin kexin 9 (PCSK9) regulates lipid metabolism by degrading low-density lipoprotein receptor on the surface of hepatocytes. PCSK9-mediated lipid degradation is associated with lipophagy. Lipophagy is a process by which autophagosomes selectively sequester lipid-droplet-stored lipids and are delivered to lysosomes for degradation. Lipophagy was first discovered in hepatocytes, and its occurrence provides important fundamental insights into how lipid metabolism regulates cellular physiology and pathophysiology. Furthermore, PCSK9 may regulate lipid levels by affecting lipophagy. This review will discuss recent advances by which PCSK9 mediates lipid degradation via the lipophagy pathway and present lipophagy as a potential therapeutic target for atherosclerosis.

[Effect and mechanism of PCSK9 on lectin-like oxidized low-density lipoprotein receptor-1 mediated oxidized low-density lipoprotein uptake by THP-1 derived macrophages].

Objective: To investigate the effect and mechanism of proprotein convertase subtilisin type 9 (PCSK9) on lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1) mediated oxidized low-density lipoprotein (ox-LDL) uptake by mononuclear macrophage (THP-1) derived macrophages. Methods: THP-1 monocyte was incubated with PMA for 48 hours to induce the differentiation into macrophages. Macrophages were pretreated with human recombinant PCSK9 protein for 1 hour and incubated with ox-LDL for 24 hours to induce foam cells. Oil red O staining was used to observe the accumulation of lipid in the control group (foam cells) and groups treated with different concentrations of recombinant PCSK9 protein, and the intracellular cholesterol content was measured by enzyme method, and mRNA and protein expressions of LOX-1 were detected by real-time PCR and Western blot. The uptake of Dil-labeled oxidized low density lipoprotein (Dil-ox-LDL) was observed by fluorescence microscopy in control group (macrophage), PCSK9 protein treated group and PCSK9 protein plus anti-LOX-1 antibody and IgG antibody treated group. mRNA and protein expression of toll-like receptor 4 (TLR4), nuclear factor-kappa B (NF-κB), cyclooxygenase-2 (COX-2) were detected in control and PCSK9 protein treated group in the absence and presence of TLR4 inhibitor (TAK-242), NF-κB inhibitor (PDTC). In addition, reactive oxygen species (ROS) production was evaluated in the absence or presence of COX-2 inhibitor (NS-398) or reduced nicotinamide adenine dinucleotide phosphate (NADPH) oxidase inhibitor (DPI). The mRNA and protein expression of LOX-1 in the control group (PCSK9 protein pretreated foam cells) and PCSK9 protein group in the absence or presence of TAK-242, PDTC, NS-398 and DPI respectively. Results: (1) The total optical density of intracellular lipid droplets, total cholesterol level, cholesterol ester level and cholesterol ester/total cholesterol ratio as well as expression of LOX-1 were significantly higher in PCSK9 group than those in control group (all P<0.05). (2) The fluorescence intensity of Dil-ox-LDL was significantly higher in PCSK9 group and PCSK9+IgG antibody group than in the control group (all P<0.05). The fluorescence intensity was significantly lower in PCSK9+anti-LOX-1 antibody group than in PCSK9 group and PCSK9+IgG antibody group (all P<0.05). (3) The expressions of TLR4, NF-κB and COX-2 were significantly higher in PCSK9 group than in control group (all P<0.05). The expressions of TLR4, NF-κB and COX-2 were significantly lower in PCSK9+TAK-242 group and PCSK9+PDTC group than in PCSK9 group (all P<0.05). The ROS level was significantly higher in PCSK9 group than in the control group (P<0.05). The ROS levels were significantly lower in PCSK9+NS-398 and PCSK9+DPI groups than in PCSK9 group (all P<0.05). (4) The expressions of LOX-1 mRNA and protein were lower in respective PCSK9 protein plus TAK-242, PDTC, NS-398 or DPI group than in PCSK9 protein alone (all P<0.05). Conclusion: PCSK9 may regulate LOX-1 mediated ox-LDL uptake by the THP-1 derived macrophage via TLR4/NF-κB/COX-2/ROS pathway.

Emerging role of proprotein convertase subtilisin/kexin type-9 (PCSK-9) in inflammation and diseases.

Proprotein convertase subtilisin/kexin type-9 (PCSK9) is most recognized serine protease for its role in cardiovascular diseases (CVD). PCSK9 regulates plasma low-density lipoprotein cholesterol (LDL-C) levels by selectively targeting hepatic LDL receptors (LDLR) for degradation, thereby serving as a potential therapeutic target for CVD. New pharmacological agents under development aim to lower the risk of CVD by inhibiting PCSK9 extracellularly, although secondary effects of this approach are not yet studied. Here we review the history of PCSK9 and rationale behind developing inhibitors for CVD. Importantly, we summarized the studies investigating the role and impact of modulated PCSK9 levels in inflammation, specifically in sepsis, rheumatoid arthritis and other chronic inflammatory conditions. Furthermore, we summarized studies that investigated the interactions of PCSK9 with pro-inflammatory pathways, such as scavenger receptor CD36 and thrombospondin 1 (TSP-1) in inflammatory diseases. This review highlights the conflicting role that PCSK9 plays in different inflammatory disease states and postulates that any unwanted effects of PCSK9 inhibition in early clinical testing should critically be examined.

Cholesterol-Lowering Agents.

Loss-of-function variants in PCSK9 (proprotein convertase subtilisin-kexin type 9) are associated with lower lifetime risk of atherosclerotic cardiovascular disease) events. Confirmation of these genetic observations in large, prospective clinical trials in participants with atherosclerotic cardiovascular disease has provided guidance on risk stratification and enhanced our knowledge on hitherto unresolved and contentious issues concerning the efficacy and safety of markedly lowering LDL-C (low-density lipoprotein cholesterol). PCSK9 has a broad repertoire of molecular effects. Furthermore, clinical trials with PCSK9 inhibitors demonstrate that reductions in atherosclerotic cardiovascular disease events are more effective in patients with recent myocardial infarction, multiple myocardial infarctions, multivessel coronary artery disease, and lower extremity arterial disease. The potent LDL-C lowering efficacy of PCSK9 inhibitors provides the opportunity for more aggressive LDL-lowering strategies in high-risk patients with atherosclerotic cardiovascular disease and supports the notion that there is no lower limit for LDL-C. Aggressive LDL-C lowering with fully human PCSK9 monoclonal antibodies has been associated by a safety profile superior to that of other classes of LDL-lowering agents. These clinical trials provide evidence that LDL lowering with PCSK9 inhibitors is an effective therapy for lowering cardiovascular events in high-risk patients with LDL-C levels ≥70 mg/dL on maximally tolerated oral therapies, including statins and ezetimibe.

Apolipoproteins A and B and PCSK9: Nontraditional Cardiovascular Risk Factors in Chronic Kidney Disease and in End-Stage Renal Disease.

PURPOSE: Nontraditional cardiovascular risk factors as apolipoprotein A (ApoA), apolipoprotein B (ApoB), and the proprotein convertase subtilisin/kexin type 9 (PCSK9) increase the prevalence of cardiovascular mortality in chronic kidney disease (CKD) or in end-stage renal disease (ESRD) through quantitative alterations. This review is aimed at establishing the biomarker (ApoA, ApoB, and PCSK9) level variations in uremic patients, to identify the studies showing the association between these biomarkers and the development of cardiovascular events and to depict the therapeutic options to reduce cardiovascular risk in CKD and ESRD patients. METHODS: We searched the electronic database of PubMed, Scopus, EBSCO, and Cochrane CENTRAL for studies evaluating apolipoproteins and PCSK9 in CKD and ESRD. Randomized controlled trials, observational studies (including case-control, prospective or retrospective cohort), and reviews/meta-analysis were included if reference was made to those keys and cardiovascular outcomes in CKD/ESRD. RESULTS: 18 studies met inclusion criteria. Serum ApoA-I has been significantly associated with the development of new cardiovascular event and with cardiovascular mortality in ESRD patients. ApoA-IV level was independently associated with maximum carotid intima-media thickness (cIMT) and was a predictor for sudden cardiac death. The ApoB/ApoA-I ratio represents a strong predictor for coronary artery calcifications, cardiovascular mortality, and myocardial infarction in CKD/ESRD. Plasma levels of PCSK9 were not associated with cardiovascular events in CKD patients. CONCLUSIONS: Although the "dyslipidemic status" in CKD/ESRD is not clearly depicted, due to different research findings, ApoA-I, ApoA-IV, and ApoB/ApoA-I ratio could be predictors of cardiovascular risk. Serum PCSK9 levels were not associated with the cardiovascular events in patients with CKD/ESRD. Probably in the future, the treatment of dyslipidemia in CKD/ESRD will be aimed at discovering new effective therapies on the action of these biomarkers.

Proprotein Convertase Subtilisin/Kexin Type 9 Is Associated with Degenerating Adipocytes in Abdominal Aortic Aneurysm.

Abdominal aortic aneurysm (AAA) is a common disease among the elderly. Recently, proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitors have been indicated as useful therapeutic tools for the treatment of cardiovascular diseases. The aim of this study was to elucidate the role of PCSK9 in the pathogenesis of AAA. We used fluorescence immunohistochemistry to assess the expression of PCSK9 in aortic tissues resected from 24 patients with AAA. Histological examination showed that PCSK9 expression in the adventitia region of the aneurysms was decreased in AAA samples. In the same region, the expression of CD36 increased. We hypothesized that CD36 expression might upregulate the transport of fatty acids into cells such as the adipocytes, and subsequently cause degradation of the adventitia in the aortic wall, contributing to AAA development.

Proprotein convertase subtilisin/kexin type 9 inhibits interferon ß expression through interacting with ATF-2.

Proprotein convertase subtilisin/kexin type 9 (PCSK9) regulates lipid metabolism. A mutual interplay of lipid homeostasis and innate immune system has been increasingly recognized. We, therefore, studied the effect of PCSK9 on interferon (IFN) ß expression. We show that PCSK9 decreases IFNß promoter/enhancer activity, mRNA and protein levels, and its downstream 2',5'-oligoadenylate synthetase-1 mRNA level. ProPCSK9, but not the cleaved PCSK9, down-regulates IFNß promoter/enhancer activity. Moreover, PCSK9 decreases IFNß promoter/enhancer activity through the positive regulatory domain IV region where the activating transcription factor-2 (ATF-2)/c-Jun heterodimer binds. Mechanistically, we demonstrate an interaction between PCSK9 and ATF-2, which reduces ATF-2/c-Jun dimerization and ATF-2/c-Jun binding to the IFNß enhancer. This novel function of PCSK9 should have important implications in optimizing the clinical use of PCSK9 inhibitors.