Targeting Filamin A Reduces Macrophage Activity and Atherosclerosis

Circulation. 2019 Jul 2;140(1):67-79. doi: 10.1161/CIRCULATIONAHA.119.039697. Epub 2019 Apr 24.

Abstract

Background: The actin-binding protein FLNA (filamin A) regulates signal transduction important for cell locomotion, but the role of macrophage-specific FLNA during atherogenesis has not been explored.

Methods: We analyzed FLNA expression in human carotid atherosclerotic plaques by immunofluorescence. We also produced mice with Flna-deficient macrophages by breeding conditional Flna-knockout mice ( Flna o/fl) with mice expressing Cre from the macrophage-specific lysosome M promoter ( LC). Atherosclerosis in vivo was studied by transplanting bone marrow from male Flna o/fl/ LC mice to atherogenic low-density lipoprotein receptor-deficient ( Ldlr-/-) mice; and by infecting Flna o/fl and Flna o/fl/ LC mice with AdPCSK9 (adenoviral vector overexpressing proprotein convertase subtilisin/kexin type 9). Furthermore, C57BL/6 mice were infected with AdPCSK9 and then treated with the calpain inhibitor calpeptin to inhibit FLNA cleavage.

Results: We found that macrophage FLNA expression was higher in advanced than in intermediate human atherosclerotic plaques. Flna o/fl/ LC macrophages proliferated and migrated less than controls; expressed lower levels of phosphorylated AKT and ERK1/2; exhibited reduced foam cell formation and lipid uptake; and excreted more lipids. The deficiency of Flna in macrophages markedly reduced the size of aortic atherosclerotic plaques in both Ldlr-/-BMT: Flnao/fl/LC and AdPCSK9-infected Flna o/fl/ LC mice. Intima/media ratios and numbers of CD68-positive macrophages in atherosclerotic plaques were lower in Flna-deficient mice than in control mice. Moreover, we found that STAT3 interacts with a calpain-cleaved carboxyl-terminal fragment of FLNA. Inhibiting calpain-mediated FLNA cleavage with calpeptin in macrophages reduced nuclear levels of phosphorylated STAT3, interleukin 6 secretion, foam cell formation, and lipid uptake. Finally, calpeptin treatment reduced the size of atherosclerotic plaques in C57BL/6 mice infected with AdPCSK9.

Conclusions: Genetic inactivation of Flna and chemical inhibition of calpain-dependent cleavage of FLNA impaired macrophage signaling and function, and reduced atherosclerosis in mice, suggesting that drugs targeting FLNA may be useful in the treatment of atherosclerosis.

Keywords: cytoskeleton; endarterectomy; lipids; models, animal.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Atherosclerosis / genetics*
  • Atherosclerosis / metabolism*
  • Atherosclerosis / pathology
  • Cells, Cultured
  • Filamins / antagonists & inhibitors
  • Filamins / deficiency*
  • Filamins / genetics*
  • Gene Targeting / methods*
  • Humans
  • Macrophage Activation / physiology*
  • Macrophages / metabolism
  • Male
  • Mice
  • Mice, Inbred C57BL
  • Mice, Knockout

Substances

  • Filamins