Proprotein Convertase Subtilisin/kexin 9 Expression Research Articles

Disruption of PCSK9 Suppresses Inflammation and Attenuates Abdominal Aortic Aneurysm Formation.

Abdominal aortic aneurysm (AAA) is a chronic vascular inflammatory disease without effective medications. PCSK9 (proprotein convertase subtilisin/kexin 9), a serine protease from the proprotein convertase family, has recently been associated with AAA in human genome-wide association studies. However, its role in AAA is unknown. Transcriptional and histological expression of PCSK9 was examined in AAA tissues and healthy controls. The impact of PCSK9 deletion and inhibition on AAA formation was assessed in mice with hyperlipidemia and Ang II (angiotensin II) overproduction. AAA lesion morphology was assessed by tissue staining. MMP (matrix metalloproteinase) activity was evaluated by gelatin zymography, and leukocyte-vessel wall interaction was monitored by intravital microscopy. RNA sequencing was used to characterize the downstream signaling of PCSK9. PCSK9 expression was upregulated and colocalized with macrophages in human and mouse AAAs. Pcsk9 deletion attenuated AAA formation, improved survival, and decreased systemic inflammation, without altering circulating cholesterol levels. Pcsk9 deficiency reduced aortic infiltration of macrophages and elastin degradation, without affecting vascular smooth muscle cell apoptosis and proliferation. Mechanistically, PCSK9 was essential in leukocyte-endothelium adhesion and expression of proinflammatory cytokines and MMP9 by macrophages. RNA sequencing of stimulated macrophages revealed that Pcsk9 deficiency upregulated histone deacetylase SIRT1 (sirtuin-1) and suppressed NF-κB (nuclear factor-κB) inflammatory signaling. SIRT1 inhibition attenuated the proinflammatory actions of PCSK9. Furthermore, administration of PCSK9 small interfering RNA or antibody constrained AAA formation/progression and inhibited vascular inflammation. PCSK9 critically mediates macrophage inflammation and elastin degradation, promoting AAA formation. PCSK9 inhibitors bear a promise to curtail AAA, beyond being used as cholesterol-lowering drugs.

High-Fat Diet Enhances Platelet Activation and Is Associated with Proprotein Convertase Subtilisin Kexin 9: An Animal Study.

Platelet activation and proprotein convertase subtilisin kexin 9 (PCSK9) play pivotal roles in the progression of atherosclerosis to cardiovascular events. It has been reported that hyperlipidemia, a well-documented risk factors for cardiovascular diseases, tends increase platelet activation and PCSK9 expression. However, little is known about this specific mechanism, particularly how nutrition affects platelet activation and PCSK9 levels in hyperlipidemia conditions. This study aimed to assess how a high-fat diet influences platelet activation, its association with PCSK9, and the effects on blood pressure in an animal model. Here, male Wistar rats were divided into four groups, subjected to different high-fat diets for ten weeks with varying nutrient components. The results showed that high-fat diet-induced hypercholesterolemia and hypertriglyceridemia significantly increased the plasma levels of β-thromboglobulin (β-TG), p-selectin, and platelet factor 4 (PF-4). The blood pressure readings were also elevated post high-fat diet induction. Interestingly, the group with the highest percentage of saturated fatty acid and trans-fat exhibited the highest PCSK9 levels, along with the highest increase in plasma cholesterol, triglycerides, and platelet activation parameters. These findings confirm that high-fat diet-induced hypercholesterolemia and hypertriglyceridemia stimulate platelet activity and PCSK9 levels. Moreover, our results suggest that PCSK9, implicated in hypercholesterolemia and hypertriglyceridemia, may synergistically mediate platelet hyperactivity, aligning with clinical studies. Notably, our results highlight the association between a high-fat diet and PCSK9, providing insights for drug discovery targeting platelet activation in atherosclerosis-induced cardiovascular diseases.

Identification and validation of PCSK9 as a prognostic and immune-related influencing factor in tumorigenesis: a pan-cancer analysis.

Proprotein convertase subtilisin/kexin-9 (PCSK9) has been primarily studied in the cardiovascular field however, its role in cancer pathophysiology remains incompletely defined. Recently, a pivotal role for PCSK9 in cancer immunotherapy was proposed based on the finding that PCSK9 inhibition was associated with enhancing the antigen presentation efficacy of target programmed cell death-1 (PD-1). Herein, we provide results of a comprehensive pan-cancer analysis of PCSK9 that assessed its prognostic and immunological functions in cancer. Using a variety of available online cancer-related databases including TIMER, cBioPortal, and GEPIA, we identified the abnormal expression of PCSK9 and its potential clinical associations in diverse cancer types including liver, brain and lung. We also validated its role in progression-free survival (PFS) and immune infiltration in neuroblastoma. Overall, the pan-cancer survival analysis revealed an association between dysregulated PCSK9 and poor clinical outcomes in various cancer types. Specifically, PCSK9 was extensively genetically altered across most cancer types and was consistently found in different tumor types and substages when compared with adjacent normal tissues. Thus, aberrant DNA methylation may be responsible for PCSK9 expression in many cancer types. Focusing on liver hepatocellular carcinoma (LIHC), we found that PCSK9 expression correlated with clinicopathological characteristics following stratified prognostic analyses. PCSK9 expression was significantly associated with immune infiltrate since specific markers of CD8+ T cells, macrophage polarization, and exhausted T cells exhibited different PCSK9-related immune infiltration patterns in LIHC and lung squamous cell carcinoma. In addition, PCSK9 was connected with resistance of drugs such as erlotinib and docetaxel. Finally, we validated PCSK9 expression in clinical neuroblastoma samples and concluded that PCSK9 appeared to correlate with a poor PFS and natural killer cell infiltration in neuroblastoma patients. PCSK9 could serve as a robust prognostic pan-cancer biomarker given its correlation with immune infiltrates in different cancer types, thus potentially highlighting a new direction for targeted clinical therapy of cancers.

Assessing the Impact of PCSK9 and HMGCR Inhibition on Liver Function: Drug-Target Mendelian Randomization Analyses in Four Ancestries

Observational studies have linked lipid-lowering drug targets pro-protein convertase subtilisin/kexin 9 (PCSK9) and HMG-CoA reductase (HMGCR) with adverse liver outcomes; however, liver disease incidence varies across diverse populations, and the long-term hepatic impact of these lipid-lowering drugs among non-white Europeans remains largely unknown. We use single nucleotide polymorphisms (SNPs) in PCSK9 and HMGCR loci from genome-wide association study data of low-density lipoprotein cholesterol in 4 populations (East Asian [EAS], South Asian [SAS], African [AFR], and European [EUR]) to perform drug-target Mendelian randomization investigating relationships between PCSK9 and HMGCR inhibition and alanine aminotransferase (ALT), aspartate aminotransferase (AST), gamma-glutamyl transferase (GGT), alkaline phosphatase (ALP), and bilirubin. Analyses of PCSK9 instruments, including functional variants R46L and E670G, failed to find evidence for relationships of low-density lipoprotein cholesterol lowering via PCSK9 variants and adverse effects on ALT, AST, GGT, or ALP among the cohorts. PCSK9 inhibition was associated with increased direct bilirubin levels in EUR (β= 0.089; P value= 5.69× 10-6) and, nominally, in AFR (β= 0.181; P value= .044). HMGCR inhibition was associated with reduced AST in SAS (β= -0.705; P value= .005) and, nominally, reduced AST in EAS (β= -0.096; P value= .03), reduced ALP in EUR (β= -2.078; P value= .014), and increased direct bilirubin in EUR (β= 0.071; P value= .032). Sensitivity analyses using genetic instruments derived from circulating PCSK9 protein levels, tissue-specific PCSK9 expression, and HMGCR expression were in alignment, strengthening causal inference. We did not find ALT, AST, GGT, or ALP associated with genetically proxied PCSK9 and HMGCR inhibition across ancestries. We identified possible relationships in several ancestries between PCSK9 and increased direct and total bilirubin and between HMGCR and reduced AST. These findings support long-term safety profiles and low hepatotoxic risk of PCSK9 and HMGCR inhibition in diverse populations.

Immune Regulation of the Liver Through the PCSK9/CD36 Pathway During Heart Transplant Rejection.

PCSK9 (proprotein convertase subtilisin/kexin 9), which is mainly secreted by the liver, is not only a therapeutic target for hyperlipidemia and cardiovascular disease, but also has been implicated in the immune regulation of infections and tumors. However, the role of PCSK9 and the liver in heart transplant rejection (HTR) and the underlying mechanisms remain unclear. We assessed serum PCSK9 expression in both murine and human recipients during HTR and investigated the effect of PCSK9 ablation on HTR by using global knockout mice and a neutralizing antibody. Moreover, we performed multiorgan histological and transcriptome analyses, and multiomics and single-cell RNA-sequencing studies of the liver during HTR, as well. We further used hepatocyte-specific Pcsk9 knockout mice to investigate whether the liver regulated HTR through PCSK9. Last, we explored the regulatory effect of the PCSK9/CD36 pathway on the phenotype and function of macrophages in vitro and in vivo. Here, we report that murine and human recipients have high serum PCSK9 levels during HTR. PCSK9 ablation prolonged cardiac allograft survival and attenuated the infiltration of inflammatory cells in the graft and the expansion of alloreactive T cells in the spleen. Next, we demonstrated that PCSK9 was mainly produced and significantly upregulated in the recipient liver, which also showed a series of signaling changes, including changes in the TNF-α (tumor necrosis factor α) and IFN-γ (interferon γ) signaling pathways and the bile acid and fatty acid metabolism pathways. We found mechanistically that TNF-α and IFN-γ synergistically promoted PCSK9 expression in hepatocytes through the transcription factor SREBP2 (sterol regulatory element binding protein 2). Moreover, in vitro and in vivo studies indicated that PCSK9 inhibited CD36 expression and fatty acid uptake by macrophages and strengthened the proinflammatory phenotype, which facilitated their ability to promote proliferation and IFN-γ production by donor-reactive T cells. Last, we found that the protective effect of PCSK9 ablation against HTR is dependent on the CD36 pathway in the recipient. This study reveals a novel mechanism for immune regulation by the liver through the PCSK9/CD36 pathway during HTR, which influences the phenotype and function of macrophages and suggests that the modulation of this pathway may be a potential therapeutic target to prevent HTR.

Resveratrol protects against postmenopausal atherosclerosis progression through reducing PCSK9 expression via the regulation of the ERα-mediated signaling pathway

Elevated circulating proprotein convertase subtilisin/kexin 9 (PCSK9) levels are an important contributor to postmenopausal atherosclerosis (AS). We have previously reported that resveratrol (RSV), as a phytoestrogen, reduces hepatocyte steatosis and PCSK9 expression in L02 cells. This study aimed to investigate how RSV reduces PCSK9 expression to inhibit postmenopausal AS progression. Here, we found that treatment of Ovx/ApoE −/− mice with RSV significantly reduced dyslipidemia, plasma PCSK9 concentration and aortic plaque area. In addition, RSV significantly inhibited liver fat accumulation and improved the hepatocyte ultrastructure. Further studies showed that RSV upregulated estrogen receptor α (ERα) expression, while reduced the liver X receptor α (LXRα) expression and sterol regulatory-element-binding protein-1c (SREBP-1c) transcriptional activity. In vitro, RSV inhibited insulin-induced elevated intracellular/extracellular PCSK9 levels, enhanced receptor-mediated uptake of low-density lipoproteins in HepG2 cells. Furthermore, RSV attenuated the activity of the SRE-dependent PCSK9 promoter. However, these effects can be partially reversed by the antiestrogen ICI 182,780. Attenuation of these changes with ERα inhibition suggest that RSV may prevent the progression of postmenopausal AS by reducing PCSK9 expression in hepatocytes through ERα-mediated signaling.

Abstract 350: Disruption Of Proprotein Convertase Subtilisin/Kexin 9 Suppresses Inflammation And Attenuates Abdominal Aortic Aneurysm Formation

Objective: Abdominal aortic aneurysm (AAA) is a degenerative inflammatory disease, with its rupture highly lethal. There have been no effective pharmacological medications. Proprotein convertase subtilisin/kexin 9 (PCSK9), which is known to modulate cholesterol metabolism, has recently been associated with AAA in human genome-wide association studies. However, its role in AAA pathogenesis is unknown. Approach and Results: Histology staining of mouse aortic aneurysmal tissue showed PCSK9 expression and its colocalization with macrophages. To investigate the role of PCSK9 in AAA formation, mice deficient in PCSK9 were crossed with ApoE SA/SA mice, which are hypercholesterolemic and inducible to develop angiotensin II-mediated hypertension upon doxycycline (Dox) administration. Deletion of PCSK9 reduced both incidence and severity of AAA and increased survival rate, without changing plasma cholesterol levels. This was associated with decreased aortic expression and activity of matrix metalloproteinase 9 (MMP9), less elastin breakdown, and reduced aortic expansion and aneurysm rupture. Additionally, PCSK9 deficiency suppressed systemic inflammatory response and macrophage infiltration into AAA lesions. In isolated macrophages stimulated with LPS, the upregulated expression of pro-inflammatory cytokines ( Tnfa, Il1b, Il6 ) was dramatically diminished in PCSK9-deficient macrophages. Furthermore, administration of PCSK9-specific siRNA in mice resulted in less macrophage accumulation in the aneurysmal aortic wall, decreased MMP9-mediated elastin degradation, and substantially constrained AAA formation. Conclusions: Endogenous PCSK9 promotes AAA formation, consistent with its novel action in mediating systemic and local inflammation, particularly, the macrophage-dependent MMP9 activity. Pharmacological inhibition of PCSK9 might be a promising strategy to curtail AAA. Key Words: aneurysm, PCSK9, elastin, inflammation, macrophages

Differential cholesterol uptake in liver cells: A role for PCSK9.

The clearance of low-density lipoprotein (LDL) particles from the circulation is regulated by the LDL receptor (LDLR) and proprotein convertase subtilisin/kexin 9 (PCSK9) interaction. Its disruption reduces blood cholesterol levels and delays atherosclerosis progression. Whether other members of the LDLR superfamily are in vivo targets of PCSK9has been poorly explored. The aim of this work was to study the interaction between PCSK9 and members of the LDLR superfamily in the regulation of liver cholesterol homeostasis in an in vivo low-density lipoprotein receptor related protein 5 (LRP5) deficient mice model challenged with high-fat diet. Our results show that Wt and Lrp5-/- mice fed a hypercholesterolemic diet (HC) have increased cholesterol ester accumulation and decreased liver LDLR and LRP5gene and protein expression. Very low-density lipoprotein receptor (VLDLR), LRP6, LRP2, and LRP1 expression levels were analyzed in liver samples and show that they do not participate in Lrp5-/- liver cholesterol uptake. Immunoprecipitation experiments show that LRP5 forms a complex with PCSK9 in liver-specific fat-storing stellate cells but not in structural HepG2 cells. Hepatic stellate cells silenced for LRP5 and/or PCSK9 expression and challenged with lipids show reduced cholesterol ester accumulation, indicating that both proteins are involved in lipid processing in the liver. Our results indicate that cholesterol esters accumulate in livers of Wt mice in a LDLR-family-members dependent manner as VLDLR, LRP2, and LRP6show increased expression in HC mice. However, this increase is lost in livers of Lrp5-/- mice, where scavenger receptors are involved in cholesterol uptake. PCSK9 expression is strongly downregulated in mice livers after HC feeding. However PCSK9 and LRP5 bind in the cytoplasm of fat storing liver cells, indicating that this PCSK9-LRP5 interaction is cell-type specific and that both proteins contribute to lipid uptake.

Liraglutide blocks the proliferation, migration and phenotypic switching of Homocysteine (Hcy)-induced vascular smooth muscle cells (VSMCs) by suppressing proprotein convertase subtilisin kexin9 (PCSK9)/ low-density lipoprotein receptor (LDLR)

ABSTRACT Liraglutide, a glucagon-like peptide 1 (GLP1) receptor agonist, is known to inhibit the atherosclerosis of apoE mice and suppress the cellular behaviors of VSMCs induced by AngII. This study aimed to explore whether liraglutide can reduce the proliferation, invasion and phenotypic transformation of VSMCs induced by Hcy and the underlying mechanism. Hcy was used to induce the proliferation of VSMCs, and liraglutide was then used to expose the cells for assessing cell proliferation. Afterward, the cell migration and phenotypic switch were evaluated to observe the effects of liraglutide. Meanwhile, the expression of PCSK9 and LDLR was detected. After overexpressing PCSK9, the changes in proliferation, cell migration and phenotypic switch were estimated again. Hcy promoted cell proliferation of VSMCs, whereas liraglutide blocked the proliferation, migration and phenotypic switch of Hcy-induced VSMCs. Furthermore, the expression of PCSK9 was downregulated and LDLR expression was upregulated after liraglutide administration in Hcy-induced VSMCs. After overexpressing PCSK9, the proliferation, migration and phenotypic switch of Hcy-induced VSMCs were enhanced. Liraglutide blocked the proliferation, migration and phenotypic switching of Hcy-induced VSMCs by suppressing PCSK9/LDLR. This finding provided the basis for the future application of liraglutide as an effective drug for therapeutic strategy in targeting AS.

Ascorbic acid enhances low-density lipoprotein receptor expression by suppressing proprotein convertase subtilisin/kexin 9 expression

Ascorbic acid, a water-soluble antioxidant, regulates various biological processes and is thought to influence cholesterol. However, little is known about the mechanisms underpinning ascorbic acid-mediated cholesterol metabolism. Here, we determined if ascorbic acid can regulate expression of proprotein convertase subtilisin/kexin 9 (PCSK9), which binds low-density lipoprotein receptor (LDLR) leading to its intracellular degradation, to influence low-density lipoprotein (LDL) metabolism. At cellular levels, ascorbic acid inhibited PCSK9 expression in HepG2 and Huh7 cell lines. Consequently, LDLR expression and cellular LDL uptake were enhanced. Similar effects of ascorbic acid on PCSK9 and LDLR expression were observed in mouse primary hepatocytes. Mechanistically, ascorbic acid suppressed PCSK9 expression in a forkhead box O3-dependent manner. In addition, ascorbic acid increased LDLR transcription by regulating sterol regulatory element-binding protein 2. In vivo, administration of ascorbic acid reduced serum PCSK9 levels and enhanced liver LDLR expression in C57BL/6J mice. Reciprocally, lack of ascorbic acid supplementation in L-gulono-γ-lactone oxidase deficient (Gulo-/-) mice increased circulating PCSK9 and LDL levels, and decreased liver LDLR expression, whereas ascorbic acid supplementation decreased PCSK9 and increased LDLR expression, ameliorating LDL levels in Gulo-/- mice fed a high fat diet. Moreover, ascorbic acid levels were negatively correlated to PCSK9, total and LDL levels in human serum samples. Taken together, these findings suggest that ascorbic acid reduces PCSK9 expression, leading to increased LDLR expression and cellular LDL uptake. Thus, supplementation of ascorbic acid may ameliorate lipid profiles in ascorbic acid-deficient species.

Role of toll-like receptor 4 on tissue factor regulation in human monocytes

Abstract Background Inflammation and coagulation play a pivotal role in the pathogenesis of acute coronary events and an extensive cross-talk links the two systems, whereby inflammation activates coagulation and coagulation affects inflammatory activity. Infact, pro-inflammatory stimuli can induce tissue factor (TF) expression, the principal initiator of the clotting cascade, in circulating monocytes and activate pathways leading to thrombin generation.In turn, TF may bind cellular receptors which may affect the production and release of inflammatory mediators. According to our recent results, proprotein convertase subtilisin/kexin9 (PCSK9) and Gamma-Glutamyltransferase (GGT), two molecules involved in the pathogenesis of cardiovascular disease, are able to up-regulate TF expression in monocytes by activating NFkB pathway but the mechanism and the receptor involved in this biological response is unknown. One plausible possibility is that both molecules bind a Toll-like Receptor (TLR)4 located on membranes of human and cultured monocytes,activating the TLR4/MyD88-NFkB pathway and eventually leading to stimulation of TF expression. Aim To assess whether both molecules are able to bind to TLR4 located on the surface of human monocytes and whether this specific binding involves the TLR4/MyD88-NFkB pathway on TF modulation. Methods THP-1 cells, a human monocytic cell line derived from an acute monocytic leukemia patient, was used as in vitro model. The cells were stimulated with human (h) recombinant (r) PCSK9 (5 μg/ml) and hrGGT (1 μg/ml) or pre-incubated with BAY-117082 (BAY, 10–5M) a NFκB inhibitor, CLI-095 (3x10–6M), a highly Myd88/TLR4 signaling specific inhibitor and LPS-RS (1 μg/ml) a TLR4 antagonist. TF procoagulant activity (PCA), was assessed by 1-stage clotting assay and the results expressed by ρg/mL of active protein. Experimental series were carried out in endotoxin-free conditions, in order to exclude lipopolysaccharide (LPS)-dependent immune responses. Results hrPCSK9 and hrGGT stimulated TF expression (PCA: from 50±20 to 120±20, n=10, p<0.01) and (PCA: from 190±140 to 460±360, n=15, p<0.001) respectively, an effect down-regulated by BAY,a NFκB inhibitor (PCA by hrPCSK9: −71±23%, n=5, p<0.01; PCA by hrGGT: −90±21%, n=7, p<0.001). CLI-095, a TLR4 inhibitor (PCA by hrPCSK9: −86±26%, n=3, p<0.05; and PCA by GGT: −89±10%, n=5, p<0.001).LPS-RS, a TLR4 antagonist, (PCA by hrPCSK9: −74±25%, n=3, p<0.05; PCA by hrGGT: −70±17%, n=5, p<0.001) abolished both PCSK9 and GGT-induced TF expression. Conclusions These data are the first demonstration of a direct role of PCSK9 and GGT as active mediators of inflammatory-based thrombotic diseases. The possible mechanism of action involves recognition of two proteins by TLR4 on monocytes membrane surface, lead to activation of the transcription factor NFκB. Further studies will be needed to better understand the regulatory mechanisms underlying this complex set of biological responses that bind TLR4 modulation and TF expression. Funding Acknowledgement Type of funding source: None

1441LRP5 and PCSK9 in inflammatory cells immunomodulation

Abstract Background Atherosclerosis, the leading cause of cardiovascular diseases, is driven by high blood cholesterol levels and chronic inflammation. The disruption of the hepatic interaction between Proprotein Convertase Subtilisin/Kexin 9 (PCSK9) and Low-Density Lipoprotein Receptor (LDLR) downregulates blood cholesterol levels and reduces cardiovascular events. Recent data suggest that other members of the LDLR superfamily may be targets of PCSK9. Purpose The aim of this work is to determine if LDLR-related protein 5 (LRP5) is a PCSK9 target, and to study the role of PCSK9 and LRP5 in foam cell formation and hence, in the mechanism of lipid accumulation and atherosclerotic plaque formation. Methods Intracellular protein and lipid localization, cholesteryl esters (CE) accumulation; quantification of structural and inflammatory proteins expression and immunoprecipitation analyses were performed in primary cultures of human inflammatory cells (monocytes and macrophages) silenced for LRP5 or PCSK9 and challenged with modified LDLs. Results We first show that LRP5 is needed for macrophage lipid uptake since LRP5-silenced macrophages have less intracellular CE accumulation. In LDL treated macrophages internalization of LRP5-bound LDL starts after 30 minutes of incubation and lasts up to 24hours. The SREBP-2 promoter is not involved in LRP5 regulation but it does regulate macrophage PCSK9 expression. Immunoprecipitation experiments show that LRP5 forms a complex with PCSK9 in lipid-loaded macrophages. Finally we studied the role of PCSK9 and LRP5 in the inflammatory response by TLR4/NFkB signaling pathway. We show decreased TLR4 protein expression levels and decreased nuclear translocation of NFκB in PCSK9 silenced-inflammatory cells after lipid loading indicating a downregulation of the proinflammatory pathway TLR4/NFκB. Increased gene expression is observed in TNF-α and IL1β after lipid-loading that is abolished in PCSK9-silenced macrophages. Furthermore release of the proinflammatory cytokines TNF-α and IL1β is decreased in PCSK9-silenced macrophages. LRP5 protein expression is increased in lipid-loaded macrophages independent of the presence or absence of PCSK9. Conclusions These results demonstrate that, in human macrophages, LRP5 is internalized with lipids. Furthermore, PCSK9 and LRP5 can form a complex in the cytoplasm of lipid-loaded macrophages opening the possibility that PCSK9 induces lysosomal LRP5 degradation in a similar manner than it does with LDLR. Finally we also show that PCSK9 gene interference decreases inflammation and supports a role for PCSK9 as an inflammatory mediator in atherosclerosis. Acknowledgement/Funding CN16/11/00411-LB; TERCEL RD16/0011/018-LB; FIS2016-02014 -MBP; SEC2015 to MBP

Ginkgolide B Mediated Alleviation of Inflammatory Cascades and Altered Lipid Metabolism in HUVECs via Targeting PCSK-9 Expression and Functionality.

The potential of oxidized-LDL (Ox-LDL) to elicit inflammatory responses in macrophages leading to the atherosclerosis (AS) progression is well known. Since proprotein convertase subtilisin/Kexin-9 (PCSK-9), the posttranslational regulator of LDL-receptor, is associated with elevated LDL in the circulation, the present report was aimed to uncover the ameliorative effects of Ginkgolide B, a terpenic lactone from Ginkgo biloba, against Ox-LDL-induced alterations in cholesterol metabolism in HUVECs. Consequently, our results demonstrated that incubation with Ox-LDL significantly upregulated the PCSK-9 expression in HUVECs, which was significantly downregulated, both at mRNA and protein level, after Ginkgolide B treatment via subsequent suppression of sterol element binding protein (SREBP-2) expression. Moreover, Ginkgolide B-mediated inhibition of PCSK-9 activity was also validated by in silico methods which revealed that it interferes the PSCK-9 interaction with LDL-receptor (LDL-R). Interestingly, Ox-LDL-induced LDL-R expression was further enhanced by Ginkgolide B treatment in HUVECs. Moreover, Ginkgolide B treatment lead to downregulation of lectin-like Ox-LDL receptor (LOX-1) and NADPH oxidase (NOX-4) expression which was upregulated in Ox-LDL-treated HUVECs, along with the attenuation of mitochondrial ROS generation. Furthermore, Ginkgolide B significantly inhibited the augmented expression of intercellular adhesion molecule-1 (ICAM-1) and vascular adhesion molecule-1 (VCAM-1) in Ox-LDL-activated HUVECs. Ginkgolide B also significantly ameliorated the inflammatory response in Ox-LDL-activated HUVECs by suppressing the expression of IL-1α, IL-1β, IL-6, CXCL-1, CXCL-2, and monocyte chemotactic protein (MCP-1), at mRNA and protein level. Our in vitro and in silico study established that Ginkgolide B alleviated the Ox-LDL-induced inflammatory cascades and altered lipid metabolism in HUVECs by suppressing the PCSK-9 and, thus, could be established as a treasured alternative therapeutic candidate in the atherosclerosis management.

PCSK9 is Increased in Cerebrospinal Fluid of Individuals With Alcohol Use Disorder.

Recent studies have shown that alcohol use affects the regulation and expression of proprotein convertase subtilisin/kexin 9 (PCSK9). While a major role of PCSK9 in hepatic function and lipid regulation has been clearly established, other pleiotropic effects remain poorly understood. Existing research suggests a positive association between PCSK9 expression in the brain and psychopathology, with increased levels of PCSK9 in the cerebrospinal fluid (CSF) of individuals with dementia and epigenetic modifications of PCSK9 associated with alcohol use disorder (AUD). In this study, we hypothesized that chronic alcohol use would increase PCSK9 expression in CSF. PCSK9 levels in CSF were measured in individuals with AUD (n=42) admitted to an inpatient rehabilitation program and controls (n=25). CSF samples in AUD were assessed at 2 time points, at day 5 and day 21 after admission. Furthermore, plasma samples were collected and measured from the individuals with AUD. PCSK9 in CSF was significantly increased in the AUD group at day 5 and day 21 compared to the controls (p<0.0001). Plasma PCSK9 levels were correlated positively with CSF PCSK9 levels in AUD (p=0.0493). Our data suggest that PCSK9 is elevated in the CSF of individuals with AUD, which may indicate a potential role of PCSK9 in AUD. Additional studies are necessary to further elucidate the functions of PCSK9 in the brain.

SU58 - EPIGENOME-WIDE ASSOCIATION ANALYSIS AND REPLICATION IMPLICATES DEREGULATION OF PCSK9 IN ALCOHOL USE DISORDER

Alcohol Use Disorder (AUD) is a common and chronic disorder with substantial effects on personal and public health. The underlying pathophysiology is poorly understood but strong evidence suggests significant roles of both genetic and epigenetic components. Given that alcohol affects many organ systems, we performed a cross-tissue and cross-phenotypic analysis of genome-wide methylomic variation using Illumina HM450 and EPIC chip arrays in AUD samples from 3 discovery, 4 replication, and 2 translational cohorts. The discovery samples consisted of postmortem brain tissues (n=46), bloods form a resting-state functional connectivity imaging endophenotypes (n=68) and postmortem brain tissues sorted into neuronal and non-neuronal cells (n=58). Overrepresentation analyses identified 68 significant CpG probes of which the most significantly associated probe cg01444643 was in in the promoter of the proprotein convertase subtilisin/kexin 9 (PCSK9) gene (p=0.002). Biological validation showed that PCSK9 promoter methylation is conserved across tissues (brain-blood-liver) and positively correlated with expression. Replication in AUD datasets confirmed PCSK9 hypomethylation (n=392, p<0.05) and a translational mouse model of AUD showed that alcohol exposure leads to PCSK9 mRNA and protein downregulation (p<0.0001). Postmortem human liver tissue analyses in control (n=47) and liver transplant cases due to alcohol cirrhosis (n=50) showed marked increase of methylation at cg01444643 (P<0.0001) and significantly decreased PCSK9 expression (p<0.01). PCSK9 is primarily expressed in the liver and regulates low density lipoprotein cholesterol (LDL-C). Our finding of alcohol-induced epigenetic regulation of PCSK9 represents one of the underlying mechanisms between the well-known effects of alcohol on lipid metabolism and cardiovascular risk, with light alcohol use generally being protective while chronic heavy use has detrimental health outcomes.

Post-transcriptional Regulation of PCSK9 by miR-191, miR-222, and miR-224.

Since proprotein convertase subtilisin kexin 9 (PCSK9) discovery, a gene involved in LDL metabolism regulation and cardiovascular diseases (CVD), many therapeutic strategies have been introduced for direct targeting of PCSK9. The main goal of these strategies has been to reduce PCSK9 protein level either by application of antibodies or inhibition of its production. In this study, we have tried to discover microRNAs (miRNAs) which can target, and hence regulate, PCSK9 expression. Using bioinformatics tools, we selected three microRNAs with binding sites on 3′-UTR of PCSK9. The expression level of these miRNAs was examined in three different cell lines using real-time RT-PCR. We observed a reciprocal expression pattern between expression level of miR-191, miR-222, and miR-224 with that of PCSK9. Accordingly, the expression levels were highest in Huh7 cells which expressed the lowest level of PCSK9, compared to HepG2 and A549 cell lines. PCSK9 mRNA level also showed a significant decline in HepG2 cells transfected with the vectors overexpressing the aforementioned miRNAs. Furthermore, the miRNAs target sites were cloned in psiCHECK-2 vector, and a direct interaction of the miRNAs and the PCSK9 3′-UTR putative target sites was investigated by means of luciferase assay. Our findings revealed that miR-191, miR-222, and miR-224 can directly interact with PCSK9 3′-UTR and regulate its expression. In conclusion, our data introduces a role for miRNAs to regulate PCSK9 expression.

Oxidized low-density lipoprotein (oxLDL) affects load-free cell shortening of cardiomyocytes in a proprotein convertase subtilisin/kexin 9 (PCSK9)-dependent way

Recent studies have documented that oxidized low-density lipoprotein cholesterol (oxLDL) levels directly impact myocardial structure and function. However, the molecular mechanisms by which oxLDL affects cardiac myocytes are not well established. We addressed the question whether oxLDL modifies load-free cell shortening, a standardized readout of cardiac cellular function, and investigated whether proprotein convertase subtilisin/kexin-9 (PCSK9) is involved on oxLDL-dependent processes. Adult rat ventricular cardiomyocytes were isolated and incubated for 24 h with oxLDL. PCSK9 was silenced by administration of siRNA. Load-free cell shortening was analyzed via a line camera at a beating frequency of 2 Hz. RT-PCR and immunoblots were used to identify molecular pathways. We observed a concentration-dependent reduction of load-free cell shortening that was independent of cell damage (apoptosis, necrosis). The effect of oxLDL was attenuated by silencing of oxLDL receptors (LOX-1), blockade of p38 MAP kinase activation, and silencing of PCSK9. oxLDL increased the expression of PCSK9 and caused oxidative modification of tropomyosin. In conclusion, we found that oxLDL significantly impaired contractile function via induction of PCSK9. This is the first report about the expression of PCSK9 in adult terminal differentiated ventricular cardiomyocytes. The data are important in the light of recent development of PCSK9 inhibitory strategies.

Atorvastatin and lovastatin, but not pravastatin, increased cellular complex formation between PCSK9 and the LDL receptor in human hepatocyte-like C3A cells

Statins are the first-line treatment for hypercholesterolemic patients. Herein, the effects of three statins on complex formation between proprotein convertase subtilisin-kexin 9 (PCSK9) and the low density lipoprotein receptor (LDLR), a critical step for the PCSK9-dependent degradation of LDLR in the lysosome, were examined. Human hepatocyte-like C3A cells grown in control (containing 10% fetal bovine serum) or MITO+ (supplemented with BD™ MITO + serum extender) medium were also treated with atorvastatin (Atorv), lovastatin (Lov), or pravastatin (Prav) for 24 h. RNA and protein expression studies and determinations of PCSK9/LDLR complex formation were performed. As expected, the statins increased the expression of PCSK9 and LDLR independently of the medium employed. Interestingly, Atov and Lov caused increases in PCSK9/LDLR complex formation, whereas Prav decreased complex formation when compared to cells treated without drugs. These results may explain why Prav works better for statin intolerant patients than other statins such as Atorv and Lov.

Pro-inflammation NF-\u03baB signaling triggers a positive feedback via enhancing cholesterol accumulation in liver cancer cells

BackgroundHepatocellular carcinoma (HCC) develops in a complex microenvironment characterized by chronic inflammation. In recent years, cholesterol metabolic abnormalities have been implicated the importance in cancer cell physiology. This study was designed to investigate the relationship between inflammation and cholesterol accumulation in HCC cells.MethodsHuman HCC cells HepG2 and Huh7 were cultured and stimulated with lipopolysaccharide (LPS) for 24 h. The changes of HCC cells related to cholesterol metabolism including intracellular cholesterol concentrations, cholesterol uptake, and the expression of cholesterol-related genes 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR), LDL receptor (LDLR), sterol regulatory element-binding transcription factor 2 (SREBF2), and proprotein convertase subtilisin/kexin 9 (PCSK9) were comparatively analyzed. Simultaneously, the effects of nuclear factor-kappa B (NF-κB) signaling pathway on cholesterol metabolism were clarified by knocking-down of nuclear factor kappa-B kinase subunit alpha (IKKα) and TGF-beta-activated kinase 1 and MAP3K7-binding protein 3 (TAB3) via RNAi and microRNA (miR)-195. Subsequently, the roles of cholesterol accumulation in LPS induced pro-inflammatory effects were further investigated.ResultsPro-inflammatory factor LPS significantly increased intracellular cholesterol accumulation by upregulating the expression of HMGCR, LDLR, and SREBF2, while downregulating the expression of PCSK9. These effects were revealed to depend on NF-κB signaling pathway by knocking-down and overexpression of IKKα and TAB3. Additionally, miR-195, a regulator directly targeting IKKα and TAB3, blocked the effects of cholesterol accumulation, further supporting the critical role of pro-inflammation NF-κB signaling in regulating cholesterol accumulation. Intriguingly, the accumulation of cholesterol conversely exerted an augmented pro-inflammation effects by further activating NF-κB signaling pathway.ConclusionsThese results indicated that pro-inflammation effects of NF-κB signaling could be augmented by a positive feedback via enhancing the cholesterol accumulation in liver cancer cells.

Pro-inflammatory cytokines and adipokines regulate PCSK9 expression in HepG2 cells

Background and aim: Clinical, genetic and experimental evidence indicates that proprotein convertase subtilisin/kexin 9 (PCSK9) may be either a cause or an effect of metabolic syndrome (MetS). We have recently demonstrated that PCSK9 is regulated by pro-inflammatory cytokine TNF-α in a SOCS3-dependent manner (Ruscica et al., JBC, 2016). Thus, the present work aimed to further extend this observation and studied the possible molecular mechanisms linking the effects of cytokines (TNF-α) and adipokines (leptin and resistin) on de novo lipogenesis and PCSK9 expression.