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New role of PCSK9 in atherosclerotic inflammation promotion involving the TLR4/NF-κB pathway

  • Author Footnotes
    1 These authors contributed equally to this work.
    Zhi-Han Tang
    Footnotes
    1 These authors contributed equally to this work.
    Affiliations
    Institute of Cardiovascular Disease, Key Lab for Arteriosclerology of Hunan Province, University of South China, Hengyang, Hunan 421001, China

    Laboratory of Experimental Surgery, University of South China, Hengyang, Hunan 421001, China
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  • Author Footnotes
    1 These authors contributed equally to this work.
    Juan Peng
    Footnotes
    1 These authors contributed equally to this work.
    Affiliations
    Institute of Cardiovascular Disease, Key Lab for Arteriosclerology of Hunan Province, University of South China, Hengyang, Hunan 421001, China
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  • Zhong Ren
    Affiliations
    Institute of Cardiovascular Disease, Key Lab for Arteriosclerology of Hunan Province, University of South China, Hengyang, Hunan 421001, China
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  • Jing Yang
    Affiliations
    Laboratory of Clinical Research, University of South China, Hengyang, 421001, China
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  • Ting-Ting Li
    Affiliations
    Institute of Cardiovascular Disease, Key Lab for Arteriosclerology of Hunan Province, University of South China, Hengyang, Hunan 421001, China
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  • Tao-Hua Li
    Affiliations
    Institute of Cardiovascular Disease, Key Lab for Arteriosclerology of Hunan Province, University of South China, Hengyang, Hunan 421001, China
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  • Zuo Wang
    Affiliations
    Institute of Cardiovascular Disease, Key Lab for Arteriosclerology of Hunan Province, University of South China, Hengyang, Hunan 421001, China
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  • Dang-Heng Wei
    Affiliations
    Institute of Cardiovascular Disease, Key Lab for Arteriosclerology of Hunan Province, University of South China, Hengyang, Hunan 421001, China
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  • Lu-Shan Liu
    Affiliations
    Institute of Cardiovascular Disease, Key Lab for Arteriosclerology of Hunan Province, University of South China, Hengyang, Hunan 421001, China
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  • Xi-Long Zheng
    Affiliations
    Department of Biochemistry and Molecular Biology, The Libin Cardiovascular Institute of Alberta, The University of Calgary, Health Sciences Center, 3330 Hospital Drive NW, Calgary, Alberta T2N 4N1, Canada
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  • Zhi-Sheng Jiang
    Correspondence
    Corresponding author.
    Affiliations
    Institute of Cardiovascular Disease, Key Lab for Arteriosclerology of Hunan Province, University of South China, Hengyang, Hunan 421001, China
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  • Author Footnotes
    1 These authors contributed equally to this work.

      Highlights

      • PCSK9 silencing directly decreases vascular inflammation in apoE KO mice.
      • PCSK9 silencing reduces the expression of TLR4 and NF-κB in the atherosclerotic aortas of apoE KO mice.
      • PCSK9 promotes inflammatory cytokine secretion in RAW264.7 macrophage.
      • PCSK9 activates the TLR4/NF-κB pathway in RAW264.7 macrophage.

      Abstract

      Background and aims

      Proprotein convertase subtilisin/kexin 9 (PCSK9) has emerged as a popular target in the development of new cholesterol-lowering drugs and therapeutic interventions for atherosclerosis. PCSK9 could accelerate atherosclerosis through mechanisms beyond the degradation of the hepatic low-density lipoprotein receptor. Several clinical studies suggested that PCSK9 is involved in atherosclerotic inflammation. Accordingly, this study aimed to explore the role of PCSK9 in vascular inflammation that promotes atherosclerotic progression.

      Methods

      We examined whether PCSK9 silencing via transduction with the lentivirus-mediated PCSK9 shRNA (LV-PCSK9 shRNA) vector affects the formation of vascular lesions in hyperlipidemia-induced atherosclerosis in apolipoprotein E knockout (apoE KO) mice. In vitro, the effects of PCSK9 on oxLDL-induced macrophages inflammation were investigate using LV-PCSK9 and LV-PCSK9 shRNA for PCSK9 overexpression and PCSK9 silencing.

      Results

      Immunohistochemical analysis showed that PCSK9 expression increased within atherosclerotic plaques in apoE KO mice. These in vivo results showed that the LV-PCSK9 shRNA group of mice developed less aortic atherosclerotic plaques compared with the control group. These lesions also had the reduced number of macrophages and decreased expression of vascular inflammation regulators, such as tumor necrosis factor-α, interleukin 1 beta, monocyte chemoattractant protein-1, toll-like receptor 4 and nuclear factor kappa B (NF-κB). We further showed that PCSK9 overexpression in macrophages in vitro increased the secretion of oxLDL-induced proinflammatory cytokines. PCSK9 overexpression upregulated TLR4 expression and increased p-IκBα levels, IkBα degradation, and NF-κB nuclear translocation in macrophages, but PCSK9 knockdown had the opposite effects in oxLDL-treated macrophages.

      Conclusions

      PCSK9 gene interference could suppress atherosclerosis directly through decreasing vascular inflammation and inhibiting the TLR4/NF-κB signaling pathway without affecting plasma cholesterol level in high-fat diet-fed apoE KO mice. PCSK9 may be an inflammatory mediator in the pathogenesis of atherosclerosis.

      Keywords

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      Linked Article

      • PCSK9 antagonists and inflammation
        AtherosclerosisVol. 268
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          In their recent contribution to Atherosclerosis, Tang et al. [1] have hypothesized that a PCSK9 gene interference could directly suppress atheroma development by decreasing vascular inflammation, suggesting that this might be the protective mechanism of PCSK9 inhibitors (PCSK9i) in coronary patients. The major end-point trials do not clearly indicate that an anti-inflammatory activity of both bococizumab [2] and evolocumab [3] may be responsible for the observed coronary prevention, while in a combined analysis of these trials, the impressive LDL-cholesterol reductions appeared to be definitely responsible for the lower cardiovascular outcomes, with a nearly identical effect on risk as that of statins [4].
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      • Reply to: “PCSK9 antagonists and inflammation”
        AtherosclerosisVol. 268
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          We would like to thank Ruscica et al. for their interest in our work published in Atherosclerosis [1]. Our study suggests that PCSK9 silencing attenuates atherosclerotic plaque inflammation without affecting plasma lipids levels in apoE KO mice [1]. This conclusion was well supported by other published studies. For example, both PCSK9 monoclonal antibody alirocumab and AT04A anti-PCSK9 vaccine have also been reported to reduce vascular inflammation and atherosclerotic lesions in APOE*3Leiden.CETP mice [2,3].
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