Proprotein Convertase Subtilisin/kexin Type 9 Overexpression Research Articles

PCSK9 promotes tumor cell proliferation and migration by facilitating CCL25 secretion in esophageal squamous cell carcinoma.

Proprotein convertase subtilisin/kexin type 9 (PCSK9) serves an important role in maintaining plasma cholesterol levels, and fatty acid metabolism is involved in the progression of various types of cancer. In the present study, the role of PCSK9 in the development of esophageal squamous cell carcinoma (ESCC) was investigated. PCSK9 expression was compared between ESCC and normal esophageal epithelial tissues using reverse transcription-quantitative PCR. In addition, the association between PCSK9 expression and clinical staging and prognosis was assessed by immunohistochemistry. The effects of PCSK9 overexpression or knockdown on cell proliferation was evaluated using Cell Counting Kit-8 and colony formation assays. The invasion and migration of cancer cells was assessed using wound healing and Transwell assays. Western blotting was performed to evaluate changes in the expression levels of epithelial-mesenchymal transition (EMT)-related proteins. ELISA was performed to detect the effects of PCSK9 on chemokine (C-C motif) ligand 25 (CCL25) secretion. The results revealed that PCSK9 was highly expressed in ESCC tissues compared with that in normal esophageal tissues, and the high expression of PCSK9 was associated with a poor prognosis. Furthermore, PCSK9 could promote the proliferation, migration and invasion of ESCC cells in vitro. Mechanistically, PCSK9 could promote EMT by secreting CCL25. In conclusion, patients with ESCC may benefit from a novel therapeutic strategy based on these findings.

RETRACTED ARTICLE: circABCA3 knockdown relieves hypoxia-induced human cardiac microvascular endothelial cell dysfunction by targeting the miR-671-5p/PCSK9 axis.

Endothelial cell dysfunction is one of the important stages in the development of acute myocardial infarction (AMI). However, whether circABCA3 (hsa_circ_0037516) mediates AMI development by regulating endothelial cell dysfunction remains unclear. The GEO database (GSE169594 and GSE160717) was used to screen the differentially expressed circRNAs. Hypoxia-induced human cardiac microvascular endothelial cells (HCMECs) were used to mimic AMI cell model. The expression of circABCA3, microRNA (miR)-671-5p, and proprotein convertase subtilisin/kexin type 9 (PCSK9) was detected by quantitative real-time PCR. Cell proliferation, migration, angiogenesis, and apoptosis were measured using cell counting kit 8 assay, EdU assay, transwell assay, wound healing assay, tube formation assay, and flow cytometry. RNA interaction was verified using dual-luciferase reporter assay and RIP assay. The protein expression of PCSK9 and apoptosis-related markers was analyzed by western blot. According to the screening of GEO database, circABCA3 was a highly expressed circRNA in blood samples of AMI patients. circABCA3 was overexpressed in AMI patients and hypoxia-induced HCMECs. Silencing of circABCA3 enhanced proliferation, migration, and angiogenesis and inhibited apoptosis in hypoxia-induced HCMECs. circABCA3 sponged miR-671-5p to positively regulate PCSK9 expression. miR-671-5p inhibitor or PCSK9 overexpression overturned the regulation of circABCA3 knockdown on hypoxia-induced HCMEC dysfunction. circABCA3 might be a potential target for alleviating AMI process, in which knockdown relieved hypoxia-induced HCMEC dysfunction by regulating the miR-671-5p/PCSK9 axis.

PCSK9 Promotes Hypoxia-Induced EC Pyroptosis by Regulating Smac Mitochondrion-Cytoplasm Translocation in Critical Limb Ischemia

Hypoxia-induced endothelial cell death and impaired angiogenesis are the main pathophysiological features of critical limb ischemia. Mechanistically, proprotein convertase subtilisin/kexin type 9 (PCSK9) promoted Smac translocation from mitochondria to the cytoplasm. Inhibition of Smac release into the cytoplasm attenuated PCSK9-mediated hypoxia-induced pyroptosis. Functionally, PCSK9 overexpression impaired angiogenesis invitro and reduced blood perfusion in mice with lower limb ischemia, but the effect was reversed by PCSK9 inhibition. This study demonstrates that PCSK9 aggravates pyroptosis by regulating Smac mitochondrion-cytoplasm translocation in the vascular endothelium, providing novel insights into PCSK9 as a potential therapeutic target in critical limb ischemia.

Proprotein convertase subtilisin/kexin type 9 targets megalin in the kidney proximal tubule and aggravates proteinuria in nephrotic syndrome

Proteinuria is a prominent feature of chronic kidney disease. Interventions that reduce proteinuria slow the progression of chronic kidney disease and the associated risk of cardiovascular disease. Here, we propose a mechanistic coupling between proteinuria and proprotein convertase subtilisin/kexin type 9 (PCSK9), a regulator of cholesterol and a therapeutic target in cardiovascular disease. PCSK9 undergoes glomerular filtration and is captured by megalin, the receptor responsible for driving protein reabsorption in the proximal tubule. Accordingly, megalin-deficient mice and patients carrying megalin pathogenic variants (Donnai Barrow syndrome) were characterized by elevated urinary PCSK9 excretion. Interestingly, PCSK9 knockout mice displayed increased kidney megalin while PCSK9 overexpression resulted in its reduction. Furthermore, PCSK9 promoted trafficking of megalin to lysosomes in cultured proximal tubule cells, suggesting that PCSK9 is a negative regulator of megalin. This effect can be accelerated under disease conditions since either genetic destruction of the glomerular filtration barrier in podocin knockout mice or minimal change disease (a common cause of nephrotic syndrome) in patients resulted in enhanced tubular PCSK9 uptake and urinary PCSK9 excretion. Pharmacological PCSK9 inhibition increased kidney megalin while reducing urinary albumin excretion in nephrotic mice. Thus, glomerular damage increases filtration of PCSK9 and concomitantly megalin degradation, resulting in escalated proteinuria.

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

Our previous study reveals that proprotein convertase subtilisin/kexin type 9 (PCSK9) is positively related to inflammatory markers, T helper (Th)-17 cells, and treatment response in ankylosing spondylitis (AS) patients. Subsequently, this study aimed to explore the effect of PCSK9 on Th cell differentiation and its potential molecular mechanism in AS. Serum PCSK9 was determined by enzyme-linked immunosorbent assay in 20 AS patients and 20 healthy controls (HCs). Then naïve CD4+ T cells were isolated from AS patients and infected with PCSK9 overexpression or knockdown adenovirus followed by polarization assay. Afterward, PMA (an NF-κB activator) was administrated. PCSK9 was increased in AS patients compared to HCs (p < .001), and it was positively related to Th1 cells (p = .050) and Th17 cells (p = .039) in AS patients. PCSK9 overexpression increased the CD4+ IFN-γ+ cells (p < .05), CD4+ IL-17A+ cells (p < .01), IFN-γ (p < .01), and IL-17A (p < .01), while it exhibited no effect on CD4+ IL-4+ cells or IL-4 (both p > .05); its knockdown displayed the opposite function on them. Moreover, PCSK9 overexpression upregulated the p-NF-κB p65/NF-κB p65 (p < .01), while it had no effect on p-ERK/ERK or p-JNK/JNK (both p > .05); its knockdown decreased p-NF-κB p65/NF-κB p65 (p < .01) and p-JNK/JNK (p < .05). Then, PMA upregulates p-NF-κB p65/NF-κB p65 (p < .001) and increased CD4+ IFN-γ+ cells, CD4+ IL-17A+ cells, IFN-γ, and IL-17A (all p < .01), also it alleviated the effect of PCSK9 knockdown on NF-κB inhibition and Th cell differentiation (all p < .01). PCSK9 enhances Th1 and Th17 cell differentiation in an NF-κB-dependent manner in AS, while further validation is necessary.

Silencing YY1 Alleviates Ox-LDL-Induced Inflammation and Lipid Accumulation in Macrophages through Regulation of PCSK9/ LDLR Signaling.

The formation of macrophage foam cells stimulated by oxidized low-density lipoprotein (ox-LDL) is deemed an important cause of atherosclerosis. Transcription factor Yin Yang 1 (YY1), which is a universally expressed multifunctional protein, is closely related to cell metabolism disorders such as lipid metabolism, sugar metabolism, and bile acid metabolism. However, whether YY1 is involved in macrophage inflammation and lipid accumulation still remains unknown. After mouse macrophage cell line RAW264.7 cells were induced by ox-LDL, YY1 and proprotein convertase subtilisin/kexin type 9 (PCSK9) expressions were found to be increased while low-density lipoprotein receptor (LDLR) expression was lowly expressed. Subsequently, through reverse transcription-quantitative polymerase chain reaction (RT-qPCR), Western blot analysis, Oil Red O staining and cholesterol quantification, it turned out that silencing of YY1 attenuated the inflammatory response and lipid accumulation in RAW264.7 cells caused by ox-LDL. Moreover, results from the JASPAR database, chromatin immunoprecipitation (ChIP) assay, luciferase reporter assay and Western blot analysis suggested that YY1 activated PCSK9 by binding to PCSK9 promoter and modulated the expression of LDLR in the downstream of PCSK9. In addition, the results of functional experiments demonstrated that the inhibitory effects of YY1 interference on ox-LDL-mediated macrophage inflammation and lipid accumulation were reversed by PCSK9 overexpression. To sum up, YY1 depletion inhibited its activation of PCSK9, thereby reducing cellular inflammatory response, cholesterol homeostasis imbalance, and lipid accumulation caused by ox-LDL.

The Nonproteolytic Intracellular Domain of Membrane-Type 1 Matrix Metalloproteinase Coordinately Modulates Abdominal Aortic Aneurysm and Atherosclerosis in Mice-Brief Report.

MT1-MMP (membrane-type 1 matrix metalloproteinase, MMP-14) is a transmembrane-anchored protein with an extracellular proteinase domain and a cytoplasmic tail devoid of proteolytic functions but capable of mediating intracellular signaling that regulates tissue homeostasis. MT1-MMP extracellular proteolytic activity has been shown to regulate pathological remodeling in aortic aneurysm and atherosclerosis. However, the role of the nonproteolytic intracellular domain of MT1-MMP in vascular remodeling in abdominal aortic aneurysms (AAA) is unknown. We generated a mutant mouse that harbors a point mutation (Y573D) in the MT1-MMP cytoplasmic domain that abrogates the MT1-MMP signaling function without affecting its proteolytic activity. These mice and their control wild-type littermates were subjected to experimental AAA modeled by angiotensin II infusion combined with PCSK9 (proprotein convertase subtilisin/kexin type 9) overexpression and high-cholesterol feeding. The mutant mice developed more severe AAA than the control mice, with concomitant generation of intraaneurysmal atherosclerotic lesions and dramatically increased macrophage infiltration and elastin degradation. Aortic lesion-associated and bone marrow-derived macrophages from the mutant mice exhibited an enhanced inflammatory state and expressed elevated levels of proinflammatory Netrin-1, a protein previously demonstrated to promote both atherosclerosis and AAA. Our findings show that the cytoplasmic domain of MT1-MMP safeguards from AAA and atherosclerotic plaque development through a proteolysis-independent signaling mechanism associated with Netrin-1 expression. This unexpected function of MT1-MMP unveils a novel mechanism of synchronous onset of AAA and atherogenesis and highlights its importance in the control of vascular wall homeostasis.

S-palmitoylation of PCSK9 induces sorafenib resistance in liver cancer by activating the PI3K/AKT pathway.

Sorafenib is currently the first-line treatment for advanced hepatocellular carcinoma (HCC). However, sorafenib resistance remains a significant challenge. Aberrant AKT signaling activation is a crucial mechanism driving sorafenib resistance in HCC. Proprotein convertase subtilisin/kexin type 9 (PCSK9) plays a vital role in antitumor immune responses. In this study, we demonstrate that aberrant PCSK9 upregulation promotes cell proliferation and sorafenib resistance in HCC by inducing AKT-S473 phosphorylation. After palmitoylation at cysteine 600, the binding affinity between PCSK9 and tensin homolog (PTEN) is dramatically increased, inducing lysosome-mediated PTEN degradation and subsequent AKT activation. We identify zinc finger DHHC-type palmitoyltransferase 16 (ZDHHC16) as a palmitoyltransferase that promotes PCSK9 palmitoylation at cysteine 600. We also develop a biologically active PCSK9-derived peptide that competitively inhibits PCSK9 palmitoylation, suppressing AKT phosphorylation and augmenting the antitumor effects of sorafenib in HCC.

PCSK9 Suppresses M2-Like Tumor-Associated Macrophage Polarization by Regulating the Secretion of OX40L from Hepatocellular Carcinoma Cells

ABSTRACT Background Proprotein convertase subtilisin/kexin type 9 (PCSK9) participates in the development of various cancers, including hepatocellular carcinoma (HCC). Here, we attempted to reveal the underlying mechanism of PCSK9 in HCC. Methods Tumor tissues and adjacent tissues were separated from HCC patients to detect PCSK9 expression. Then, PCSK9 was overexpressed or silenced in HCC cells (MHCC97H or Huh7), and then the cell supernatant was incubated with THP-1 macrophages. OX40L neutralizing antibody (nAb) was used to inhibit OX40L activity. The expression of macrophage markers was examined by immunohistochemical staining and flow cytometry. Finally, tumor-bearing mouse model was constructed by inoculation of LV-PCSK9 infected MHCC97H cells to verify the role of PCSK in HCC. Results PCSK9 expression was decreased in tumor tissues of HCC patient specimens. HCC patients displayed M2 macrophage infiltration in tumor tissues. Moreover, PCSK9-silenced Huh7 cell supernatant promoted cell migration, and enhanced the proportion of CD206-positive cells and the expression of M2 macrophage markers IL-10 and ARG-1 in THP-1 macrophages. PCSK9-overexpressing MHCC97H cell supernatant inhibited THP-1 macrophage migration and M2-like tumor-associated macrophage (TAM) polarization, which was abolished by OX40L nAb treatment. PCSK9 overexpression enhanced the expression of OX40L in MHCC97H cells. In tumor-bearing mouse models, PCSK9 overexpression inhibited tumor growth and M2 polarization of TAMs in HCC by promoting OX40L expression. Conclusion: This work demonstrated that PCSK9 suppressed M2-like TAM polarization by regulating the secretion of OX40L from hepatocellular carcinoma cells. This study suggests that PCSK9 may be a potential target for HCC treatment.

PCSK9 (Proprotein Convertase Subtilisin/Kexin Type 9) Triggers Vascular Smooth Muscle Cell Senescence and Apoptosis: Implication of Its Direct Role in Degenerative Vascular Disease.

PCSK9 (proprotein convertase subtilisin/kexin type 9) plays a critical role in cholesterol metabolism via the PCSK9-LDLR (low-density lipoprotein receptor) axis in the liver; however, evidence indicates that PCSK9 directly contributes to the pathogenesis of various diseases through mechanisms independent of its LDL-cholesterol regulation. The objective of this study was to determine how PCSK9 directly acts on vascular smooth muscle cells (SMCs), contributing to degenerative vascular disease. Approach and Results: We first examined the effects of PCSK9 on cultured human aortic SMCs. Overexpression of PCSK9 downregulated the expression of ApoER2 (apolipoprotein E receptor 2), a known target of PCSK9. Treatment with soluble recombinant human ApoER2 or the DNA synthesis inhibitor, hydroxyurea, inhibited PCSK9-induced polyploidization and other cellular responses of human SMCs. Treatment with antibodies against ApoER2 resulted in similar effects to those observed with PCSK9 overexpression. Inducible, SMC-specific knockout of Pcsk9 accelerated neointima formation in mouse carotid arteries and reduced age-related arterial stiffness. PCSK9 was expressed in SMCs of human atherosclerotic lesions and abundant in the "shoulder" regions of vulnerable atherosclerotic plaques. PCSK9 was also expressed in SMCs of abdominal aortic aneurysm, which was inversely related to the expression of smooth muscle α-actin. Our findings demonstrate that PCSK9 inhibits proliferation and induces polyploidization, senescence, and apoptosis, which may be relevant to various degenerative vascular diseases.

Silencing Myeloid Netrin-1 Induces Inflammation Resolution and Plaque Regression.

Rationale: Therapeutic efforts to decrease atherosclerotic cardiovascular disease risk have focused largely on reducing atherogenic lipoproteins, yet lipid-lowering therapies alone are insufficient to fully regress plaque burden. We postulate that arterial repair requires resolution of a maladaptive immune response and that targeting factors that hinder inflammation resolution will facilitate plaque regression. Objective: The guidance molecule Ntn1 (netrin-1) is secreted by macrophages in atherosclerotic plaques, where it sustains inflammation by enhancing macrophage survival and blocking macrophage emigration. We tested whether silencing Ntn1 in advanced atherosclerosis could resolve arterial inflammation and regress plaques. Methods and Results: To temporally silence Ntn1 in myeloid cells, we generated genetically modified mice in which Ntn1 could be selectively deleted in monocytes and macrophages using a tamoxifen-induced CX3CR1-driven cre recombinase (Ntn1fl/flCx3cr1creERT2+) and littermate control mice (Ntn1fl/flCx3cr1WT). Mice were fed Western diet in the setting of hepatic PCSK9 (proprotein convertase subtilisin/kexin type 9) overexpression to render them atherosclerotic and then treated with tamoxifen to initiate deletion of myeloid Ntn1 (MøΔNtn1) or not in controls (MøWT). Morphometric analyses performed 4 weeks later showed that myeloid Ntn1 silencing reduced plaque burden in the aorta (−50%) and plaque complexity in the aortic root. Monocyte-macrophage tracing experiments revealed lower monocyte recruitment, macrophage retention, and proliferation in MøΔNtn1 compared with MøWT plaques, indicating a restructuring of monocyte-macrophage dynamics in the artery wall upon Ntn1 silencing. Single-cell RNA sequencing of aortic immune cells before and after Ntn1 silencing revealed upregulation of gene pathways involved in macrophage phagocytosis and migration, including the Ccr7 chemokine receptor signaling pathway required for macrophage emigration from plaques and atherosclerosis regression. Additionally, plaques from MøΔNtn1 mice showed hallmarks of inflammation resolution, including higher levels of proresolving macrophages, IL (interleukin)-10, and efferocytosis, as compared to plaques from MøWT mice. Conclusion: Our data show that targeting Ntn1 in advanced atherosclerosis ameliorates atherosclerotic inflammation and promotes plaque regression.

PCSK9 Induces Rat Smooth Muscle Cell Proliferation and Counteracts the Pleiotropic Effects of Simvastatin.

Human atherosclerotic plaque contains smooth muscle cells (SMCs) negative for the contractile phenotype (α-smooth muscle actin) but positive for proprotein convertase subtilisin/kexin type 9 (PCSK9). Thus, we generated rat SMCs which overexpressed human PCSK9 (SMCsPCSK9) with the aim of investigating the role of PCSK9 in the phenotype of SMCs. PCSK9 overexpression in SMCsPCSK9 led to a significant downregulation of the low-density lipoprotein receptor (Ldlr) as well as transgelin (Sm22α), a marker of the contractile phenotype. The cell proliferation rate of SMCsPCSK9 was significantly faster than that of the control SMCs (SMCspuro). Interestingly, overexpression of PCSK9 did not impact the migratory capacity of SMCs in response to 10% FCS, as determined by Boyden’s chamber assay. Expression and activity of 3-hydroxy-3-methylglutaryl-coenzyme A reductase (Hmgcr) was significantly increased in the presence of PCSK9, both in SMCPCSK9 and after treatment with recombinant PCSK9. The transcriptional activity of sterol regulatory element-binding protein (SREBP) was also increased in the presence of PSCK9, suggesting a direct role of PCSK9 in the control of SRE-responsive genes, like HMGCR. We also observed that cholesterol biosynthesis is elevated in SMCPCSK9, potentially explaining the increased proliferation observed in these cells. Finally, concentration-dependent experiments with simvastatin demonstrated that SMCsPCSK9 were partially resistant to the antiproliferative and antimigratory effect of this drug. Taken together, these data further support a direct role of PCSK9 in proliferation, migration, and phenotypic changes in SMCs—pivotal features of atherosclerotic plaque development. We also provide new evidence on the role of PCSK9 in the pharmacological response to statins—gold standard lipid-lowering drugs with pleiotropic action.

PCSK9 mediates the oxidative low‑density lipoprotein‑induced pyroptosis of vascularendothelialcells via the UQCRC1/ROS pathway.

The present study aimed to explore the role and mechanisms of proprotein convertase subtilisin/kexin type 9 (PCSK9) in the oxidized low-density lipoprotein (oxLDL)-induced pyroptosis of vascular endothelial cells. For this purpose, human umbilical vein endothelial cells (HUVECs) were incubated with oxLDL (100 µg/ml) for 24 h to induce pyroptosis, which was detected using PI/hoechst33342 double staining. The expression of pyroptosis-associated molecules was measured by western blot analysis and RT-qPCR. Reactive oxygen species (ROS) and membrane potential were examined through ROS probe and JC-1 staining, respectively. PCSK9 and mitochondrial ubiquinol-cytochrome c reductase core protein 1 (UQCRC1) protein were knocked down by small interfering RNA (siRNA). PCSK9 was overexpressed by lentivirus. The results revealed that oxLDL induced HUVEC injury, pyroptosis and inflammatory factor release, and upregulated the expression of PCSK9 protein in the HUVECs in a concentration-dependent manner. The silencing of PCSK9 expression with siRNA suppressed the oxLDL-induced damage to HUVECs, the release of inflammatory substances and the occurrence of pyroptosis. In addition, oxLDL inhibited UQCRC1 expression, promoted mitochondrial membrane potential collapse and damaged mitochondrial function; however, these processes were reversed by the silencing of PCSK9. PCSK9 overexpression induced the pyroptosis of HUVECs, the generation of ROS and the disorder of mitochondrial function by inhibiting UQCRC1. Therefore, PCSK9 mediates the oxLDL-induced pyroptosis of vascular endothelial cells via the UQCRC1/ROS pathway.

Proprotein Convertase Subtilisin/Kexin Type 9 Promotes Gastric Cancer Metastasis and Suppresses Apoptosis by Facilitating MAPK Signaling Pathway Through HSP70 Up-Regulation.

ObjectiveTo examine the effect of proprotein convertase subtilisin/kexin type 9 (PCSK9) on gastric cancer (GC) progression and prognosis, and to explore the underlying mechanism.MethodsPCSK9 expression levels in human GC tissues were determined by quantitative real-time PCR, western blotting, and immunohistochemical assay. PCSK9 serum levels were detected by enzyme-linked immunosorbent assay. The relationships of PCSK9 and GC progression and survival were analyzed using the Chi-square test, Kaplan-Meier analysis, and Cox proportional hazards model. The effect of PCSK9 on cell invasion, migration, and apoptosis were determined in human GC cell lines and mouse xenograft model separately using PCSK9 knockdown and overexpression strategies. The PCSK9 interacting molecules, screened by co-immunoprecipitation combined with LC-MS/MS, were identified by immunofluorescence localization and western blotting. Additionally, the mitogen-activated protein kinase (MAPK) pathway was assessed by western blotting.ResultsPCSK9 mRNA and protein levels were significantly elevated in GC tissues compared with the paired normal tissues at our medical center (P < 0.001). Notably, the up-regulation of PCSK9 expression in GC tissues was related to tumor progression and poor survival. GC patients had higher serum levels of PCSK9 than the age-matched healthy controls (P < 0.001); PCSK9 promoted invasive and migratory ability and inhibited apoptosis in GC cells with no apparent affection in cell proliferation. The silencing of PCSK9 reversed these effects, suppressing tumor metastasis in vitro and in vivo. Furthermore, PCSK9 maintained these functions through up-regulating heat shock protein 70 (HSP70), ultimately facilitating the mitogen-activated protein kinase (MAPK) pathway.ConclusionCollectively, our data revealed that high PCSK9 expression levels in GC tissue were correlated with GC progression and poor prognosis and that PCSK9 could promote GC metastasis and suppress apoptosis by facilitating MAPK signaling pathway through HSP70 up-regulation. PCSK9 may represent a novel potential therapeutic target in GC.

Pro-protein convertase subtilisin/kexin type 9 promotes intestinal tumor development by activating Janus kinase 2/signal transducer and activator of transcription 3/SOCS3 signaling in ApcMin/+ mice.

IntroductionPro-protein convertase subtilisin/kexin type 9 (PCSK9) regulates lipoprotein homeostasis in humans. Evolocumab is a selective PCSK9 inhibitor that can reduce low-density lipoprotein cholesterol (LDLC) level and decrease hypercholesterolemia. The current study aimed to explore whether PCSK9 increases the risk of colorectal cancer.MethodsFirst, we utilized the classic intestinal tumor ApcMin/+ mouse model and PCSK9 knock-in (KI) mice to establish ApcMin/+PCSK9(KI) mice. Then, we investigated the effect of PCSK9 overexpression in ApcMin/+PCSK9(KI) mice and PCSK9 inhibition using evolocumab on the progression of intestinal tumors in vivo by hematoxylin and eosin (HE) staining, Western blot, and immunohistochemistry (IHC) assay.ResultsApcMin/+PCSK9(KI) mice had higher numbers and larger sizes of adenomas, with 83.3% of these mice developing adenocarcinoma (vs. 16.7% of ApcMin/+ mice). However, treatment with evolocumab reduced the number and size of adenomas and prevented the development of adenocarcinomas in ApcMin/+ mice. PCSK9 overexpression reduced tumor cell apoptosis, the Bax/bcl-2 ratio, and the levels of cytokine signaling 3 protein (SOCS3) suppressors, but activated Janus kinase 2 (JAK2)/signal transducer and activator of transcription 3 (STAT3) signaling in intestinal tumors. In contrast, evolocumab treatment had the opposite effect on ApcMin/+mice.ConclusionPCSK9 might act as an oncogene or have an oncogenic role in the development and progression of colorectal cancer in vivo via activation of JAK2/STAT3/SOCS3 signaling.

PCSK9 is Expressed in Human Visceral Adipose Tissue and Regulated by Insulin and Cardiac Natriuretic Peptides.

Proprotein convertase subtilisin/kexin type 9 (PCSK9) binds to and degrades the low-density lipoprotein receptor (LDLR), contributing to hypercholesterolemia. Adipose tissue plays a role in lipoprotein metabolism, but there are almost no data about PCSK9 and LDLR regulation in human adipocytes. We studied PCSK9 and LDLR regulation by insulin, atrial natriuretic peptide (ANP, a potent lipolytic agonist that antagonizes insulin), and LDL in visceral adipose tissue (VAT) and in human cultured adipocytes. PCSK9 was expressed in VAT and its expression was positively correlated with body mass index (BMI). Both intracellular mature and secreted PCSK9 were abundant in cultured human adipocytes. Insulin induced PCSK9, LDLR, and sterol-regulatory element-binding protein-1c (SREBP-1c) and -2 expression (SREBP-2). ANP reduced insulin-induced PCSK9, especially in the context of a medium simulating hyperglycemia. Human LDL induced both mature and secreted PCSK9 and reduced LDLR. ANP indirectly blocked the LDLR degradation, reducing the positive effect of LDL on PCSK9. In conclusion, PCSK9 is expressed in human adipocytes. When the expression of PCSK9 is induced, LDLR is reduced through the PCSK9-mediated degradation. On the contrary, when the induction of PCSK9 by insulin and LDL is partially blocked by ANP, the LDLR degradation is reduced. This suggests that NPs could be able to control LDLR levels, preventing PCSK9 overexpression.

Role of PCSK9 in the Development of Mouse Periodontitis Before and After Treatment: A Double-Edged Sword.

Periodontitis is a highly prevalent infectious disease associated genetically with coronary heart disease (CHD). The effects of proprotein convertase subtilisin/kexin type 9 (PCSK9), a critical regulator of CHD, on periodontitis have not been studied to date. Here, we found that PCSK9 expression was increased in periodontitis patients and Porphyromonas gingivalis (Pg)-infected mice. Loss of PCSK9 attenuated Pg-induced periodontal bone loss in mice. First, PCSK9 deficiency reduced the release of inflammation-associated cytokines, such as tumor necrosis factor alpha (TNF-α) and interleukin 1β, in vitro and in vivo. Second, its deficiency enhanced Pg and endotoxin clearance during Pg invasion in part by upregulating CD36 and low-density lipoprotein receptor (LDLR), respectively. However, after berberine treatment, periodontal bone regeneration in the PCSK9 knockout group was significantly lower than that in wild-type. This was because PCSK9 overexpression promoted osteogenic differentiation of periodontal ligament stem cells (PDLCs) prechallenged by TNF-α. Furthermore, PCSK9 could rescue PDLC osteogenesis by repressing the NF-κB signaling pathway by interacting with TRAF2. These results suggest that PCSK9 may be a potent drug target for treating periodontitis.

Ectopic Expression of PCSK9 by Smooth Muscle Cells Contributes to Aortic Dissection

Acute aortic dissection (AAD) is a common disease among the elderly. Although several risk factors of AAD have been reported, the molecular mechanism underlying AAD development remains to be elucidated. Proprotein convertase subtilisin/kexin type 9 (PCSK9) increases low-density lipoprotein cholesterol levels in blood by preventing its clearance. Therefore, PCSK9 inhibition is a promising therapeutic approach to treat cardiovascular diseases (CVDs). The objective of this study was to elucidate the role of PCSK9 in the pathogenesis of AAD. We used fluorescence immunohistochemistry to assess PCSK9 expression in aortic tissues resected from 10 AAD patients and in the normal aorta from 5 autopsy samples as well as in spontaneously hyperlipidemic apolipoprotein E-deficient mice used as an experimental AD model. We revealed a characteristic distribution pattern of PCSK9 in atherosclerotic plaques and the degenerated tunica media in AAD tissues, which was rarely observed in normal aortic tissues. Furthermore, PCSK9 was notably expressed around calcification areas formed by vascular smooth muscle cells, especially those of the synthetic phenotype. The results obtained in the animal model were consistent with PCSK9 expression in AAD tissues. Our findings suggest that PCSK9 overexpression in the aorta may promote AAD. This study adds to the growing body of evidence supporting the use of PCSK9 inhibitors for the management of CVDs.

Differential Expression of PCSK9 Modulates Infection, Inflammation, and Coagulation in a Murine Model of Sepsis.

Proprotein convertase subtilisin/kexin type 9 (PCSK9) targets lipoprotein receptors for degradation, thereby reducing hepatic lipid clearance. PCSK9 inhibition reduces mortality in septic mice, presumably through increased hepatic clearance of pathogen lipids due to increased lipoprotein receptor concentrations. However, PCSK9 overexpression in vivo has not been studied in sepsis. Therefore, this study aimed to evaluate the effects of differential PCSK9 expression on systemic infection, inflammation, and coagulation in sepsis. Wild-type, PCSK9 knockout (KO), and transgenic (Tg) mice that overexpress PCSK9 were subjected to sham surgery or cecal ligation and puncture (CLP). Bacterial loads were measured in lungs, peritoneal cavity fluid, and blood. Organ pathology was assessed in lungs, liver, and kidneys. Lung myeloperoxidase activity, and plasma concentrations of alanine aminotransferase (ALT), creatinine, cell-free DNA (cfDNA), protein C, thrombin-antithrombin (TAT) complexes, interleukin (IL)-6, and IL-10 were also measured 6 h postoperatively. Morbidity was assessed for 16 h following CLP. Overexpression of PCSK9 in mice increased liver and kidney pathology, plasma IL-6, ALT, and TAT concentrations during sepsis, whereas PCSK9 KO mice exhibited reduced bacterial loads, lung and liver pathology, myeloperoxidase activity, plasma IL-10, and cfDNA during CLP-induced sepsis. All septic mice had reduced plasma levels of protein C, but the protein C ratio relative to normal was significantly decreased in PCSK9 Tg mice. Dyspnea, cyanosis, and overall grimace scores were greatest in septic mice overexpressing PCSK9, whereas PCSK9 KO mice retained core body temperature during sepsis. These findings demonstrate that PCSK9 deficiency confers protection against systemic bacterial dissemination, organ pathology, and tissue inflammation, particularly in the lungs and liver, while PCSK9 overexpression exacerbates multi-organ pathology as well as the hypercoagulable and pro-inflammatory states in early sepsis.

Tanshinone IIA Modulates Low Density Lipoprotein Uptake via Down-Regulation of PCSK9 Gene Expression in HepG2 Cells.

Tanshinone IIA, one of the most pharmacologically bioactive phytochemicals isolated from Salvia miltiorrhiza Bunge, possesses several biological activities such as anti-inflammation, anti-cancer, neuroprotection and hypolipidemic activities. In this study, we aim to investigate the hypocholesterolemic effect of tanshinone IIA in hepatic cells. We demonstrated that tanshinone IIA significantly increased the amount of low-density lipoprotein receptor (LDLR) and LDL uptake activity in HepG2 cells at the post-transcriptional regulation. We further demonstrated that tanshinone IIA inhibited the expression of proprotein convertase subtilisin/kexin type 9 (PCSK9) mRNA and mature protein, which may lead to an increase the cell-surface LDLR in hepatic cells. We further identified a regulatory DNA element involved in the tanshinone IIA-mediated PCSK9 down-regulation, which is located between the -411 and -336 positions of the PCSK9 promoter. Moreover, we found that tanshinone IIA markedly increased the nuclear forkhead box O3a (FoxO3a) level, enhanced FoxO3a/PCSK9 promoter complexes formation and decreased the PCSK9 promoter binding capacity of hepatocyte nuclear factor 1α (HNF-1α), resulting in suppression of PCSK9 gene expression. Finally, we found that the statin-induced PCSK9 overexpression was attenuated and the LDLR activity was elevated in a synergic manner by combination of tanshinone IIA treatment in HepG2 cells. Overall, our results reveal that the tanshinone IIA modulates LDLR level and activity via down-regulation of PCSK9 expression in hepatic cells. Our current findings provide a molecular basis of tanshinone IIA to develop PCSK9 inhibitors for cholesterol management.