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Leukocyte Bim deficiency does not impact atherogenesis in ldlr ^-/- mice, despite a pronounced induction of autoimmune inflammation.

ABSTRACT: Proapoptotic Bcl-2 family member Bim is particularly relevant for deletion of autoreactive and activated T and B cells, implicating Bim in autoimmunity. As atherosclerosis is a chronic inflammatory process with features of autoimmune disease, we investigated the impact of hematopoietic Bim deficiency on plaque formation and parameters of plaque stability. Bim ^-/- or wild type bone marrow transplanted ldlr ^-/- mice were fed a Western type diet (WTD) for 5 or 10 weeks, after which they were immunophenotyped and atherosclerotic lesions were analyzed. Bim ^-/- transplanted mice displayed splenomegaly and overt lymphocytosis. CD4⁺ and CD8⁺ T cells were more activated (increased CD69 and CD71 expression, increased interferon gamma production). B cells were elevated by 147%, with a shift towards the pro-atherogenic IgG-producing B2 cell phenotype, resulting in a doubling of anti-oxLDL IgG1 antibody titers in serum of bim ^-/- mice. Bim ^-/- mice displayed massive intraplaque accumulation of Ig complexes and of lesional T cells, although this did not translate in changes in plaque size or stability features (apoptotic cell and macrophage content). The surprising lack in plaque phenotype despite the profound pro-atherogenic immune effects may be attributable to the sharp reduction of serum cholesterol levels in WTD fed bim ^-/- mice.

SUBMITTER: Temmerman L

PROVIDER: S-EPMC5465223 | biostudies-literature | 2017 Jun

REPOSITORIES: biostudies-literature

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Leukocyte Bim deficiency does not impact atherogenesis in ldlr -/- mice, despite a pronounced induction of autoimmune inflammation.

Temmerman Lieve L Westra Marijke M MM Bot Ilze I van Vlijmen Bart J M BJM van Bree Niek N Bot Martine M Habets Kim L L KLL Keulers Tom G H TGH van der Vlag Johan J Cotter Thomas G TG van Berkel Theo J C TJC Biessen Erik A L EAL

Scientific reports 20170608 1

Proapoptotic Bcl-2 family member Bim is particularly relevant for deletion of autoreactive and activated T and B cells, implicating Bim in autoimmunity. As atherosclerosis is a chronic inflammatory process with features of autoimmune disease, we investigated the impact of hematopoietic Bim deficiency on plaque formation and parameters of plaque stability. Bim -/- or wild type bone marrow transplanted ldlr -/- mice were fed a Western type diet (WTD) for 5 or 10 weeks, after ...[more]

PMID: 28596542

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Project description:IntroductionThe interleukin-1 (IL-1) family and the NLR family pyrin domain-containing 3 (NLRP3) inflammasome contribute to atherogenesis but the underlying mechanisms are incompletely understood. Unlike IL-1β, IL-1α is not dependent on the NLRP3 inflammasome to exert its pro-inflammatory effects. Here, a non-genetic model was applied to characterize the role of IL-1α, IL-1β, and NLRP3 for the pathogenesis of atherosclerosis.MethodsAtherogenesis was induced by gain-of-function PCSK9-AAV8 mutant viruses and feeding of a high-fat western diet (WTD) for 12 weeks in C57Bl6/J wildtype mice (WT) and in Il1a-/-, Nlrp3-/-, and Il1b-/- mice.ResultsPCSK9-Il1a-/- mice showed reduced atherosclerotic plaque area in the aortic root with lower lipid accumulation, while no difference was observed between PCSK9-WT, PCSK9-Nlrp3-/- and PCSK9-Il1b-/- mice. Serum proteomic analysis showed a reduction of pro-inflammatory cytokines (e.g., IL-1β, IL-6) in PCSK9-Il1a-/- as well as in PCSK9-Nlrp3-/- and PCSK9-Il1b-/- mice. Bone marrow dendritic cells (BMDC) of PCSK9-WT, PCSK9-Nlrp3-/-, and PCSK9-Il1b-/- mice and primary human monocytes showed translocation of IL-1α to the plasma membrane (csIL-1α) upon stimulation with LPS. The translocation of IL-1α to the cell surface was regulated by myristoylation and increased in mice with hypercholesterolemia. CsIL-1α and IL1R1 protein-protein interaction on endothelial cells induced VCAM1 expression and monocyte adhesion, which was abrogated by the administration of neutralizing antibodies against IL-1α and IL1R1.ConclusionThe results highlight the importance of IL-1α on the cell surface of circulating leucocytes for the development of atherosclerosis. PCSK9-Il1a-/- mice, but not PCSK9-Nlrp3-/- or PCSK9-Il1b-/- mice, are protected from atherosclerosis after induction of hypercholesterolemia independent of circulating cytokines. Myristoylation and translocation of IL-1α to the cell surface in myeloid cells facilitates leukocyte adhesion and contributes to the development of atherosclerosis.

Dataset Information

Leukocyte Bim deficiency does not impact atherogenesis in ldlr ^-/- mice, despite a pronounced induction of autoimmune inflammation.

Publications

Leukocyte Bim deficiency does not impact atherogenesis in ldlr <sup>-/-</sup> mice, despite a pronounced induction of autoimmune inflammation.

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