Protective Role of C3aR (C3a Anaphylatoxin Receptor) Against Atherosclerosis in Atherosclerosis-Prone Mice

Arterioscler Thromb Vasc Biol. 2020 Sep;40(9):2070-2083. doi: 10.1161/ATVBAHA.120.314150. Epub 2020 Jul 30.

Abstract

Objective: Emerging evidence suggests that C3aR (C3a anaphylatoxin receptor) signaling has protective roles in various inflammatory-related diseases. However, its role in atherosclerosis has been unknown. The purpose of the study was to investigate the possible protective role of C3aR in aortic atherosclerosis and explore molecular and cellular mechanisms involved in the protection. Approach and Results: C3ar-/-/Apoe-/- mice were generated by cross-breeding of atherosclerosis-prone Apoe-/- mice and C3ar-/- mice. C3ar-/-/Apoe-/- mice and Apoe-/- mice (as a control) underwent high-fat diet for 16 weeks were assessed for (1) atherosclerotic plaque burden, (2) aortic tissue inflammation, (3) recruitment of CD11b+ leukocytes into atherosclerotic lesions, and (4) systemic inflammatory responses. Compared with Apoe-/- mice, C3ar-/-/Apoe-/- mice developed more severe atherosclerosis. In addition, C3ar-/-/Apoe-/- mice have increased local production of proinflammatory mediators (eg, CCL2 [chemokine (C-C motif) ligand 2], TNF [tumor necrosis factor]-α) and infiltration of monocyte/macrophage in aortic tissue, and their lesional macrophages displayed an M1-like phenotype. Local pathological changes were associated with enhanced systemic inflammatory responses (ie, elevated plasma levels of CCL2 and TNF-α, increased circulating inflammatory cells). In vitro analyses using peritoneal macrophages showed that C3a stimulation resulted in upregulation of M2-associated signaling and molecules, but suppression of M1-associated signaling and molecules, supporting the roles of C3a/C3aR axis in mediating anti-inflammatory response and promoting M2 macrophage polarization.

Conclusions: Our findings demonstrate a protective role for C3aR in the development of atherosclerosis and suggest that C3aR confers the protection through C3a/C3aR axis-mediated negative regulation of proinflammatory responses and modulation of macrophage toward the anti-inflammatory phenotype.

Keywords: atherosclerosis; complement C3a receptor; inflammation; macrophages.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Aorta / immunology
  • Aorta / metabolism*
  • Aorta / pathology
  • Aortic Diseases / immunology
  • Aortic Diseases / metabolism
  • Aortic Diseases / pathology
  • Aortic Diseases / prevention & control*
  • Atherosclerosis / immunology
  • Atherosclerosis / metabolism
  • Atherosclerosis / pathology
  • Atherosclerosis / prevention & control*
  • Cells, Cultured
  • Chemokine CCL2 / metabolism
  • Chemotaxis
  • Disease Models, Animal
  • Inflammation / immunology
  • Inflammation / metabolism
  • Inflammation / pathology
  • Inflammation / prevention & control*
  • Inflammation Mediators / metabolism
  • Macrophages, Peritoneal / immunology
  • Macrophages, Peritoneal / metabolism*
  • Macrophages, Peritoneal / pathology
  • Male
  • Mice, Inbred C57BL
  • Mice, Knockout, ApoE
  • NF-kappa B / metabolism
  • Phenotype
  • Plaque, Atherosclerotic
  • Proto-Oncogene Proteins c-akt / metabolism
  • Receptors, G-Protein-Coupled / deficiency
  • Receptors, G-Protein-Coupled / genetics
  • Receptors, G-Protein-Coupled / metabolism*
  • Signal Transduction
  • TOR Serine-Threonine Kinases / metabolism
  • Tumor Necrosis Factor-alpha / metabolism

Substances

  • C3a-derived anaphylatoxin receptor, mouse
  • Ccl2 protein, mouse
  • Chemokine CCL2
  • Inflammation Mediators
  • NF-kappa B
  • Receptors, G-Protein-Coupled
  • Tnf protein, mouse
  • Tumor Necrosis Factor-alpha
  • mTOR protein, mouse
  • Proto-Oncogene Proteins c-akt
  • TOR Serine-Threonine Kinases