Legumain suppresses OxLDL-induced macrophage apoptosis through enhancement of the autophagy pathway

Gene. 2018 Apr 30;652:16-24. doi: 10.1016/j.gene.2018.02.012. Epub 2018 Feb 4.

Abstract

Objective: Autophagy plays a prominent role in the pathogenesis of plaques formation and progression of atherosclerosis (AS). The cysteine protease legumain is known to participate in atherogenesis, but its function and underlying mechanism in AS macrophages remain unclear.

Methods: The expressions of legumain in plaques isolated from AS patients and in macrophages stimulated with oxLDL were examined. Moreover, we effectively altered legumain expression in macrophages to characterize the effect of legumain on oxLDL-induced macrophage apoptosis. The expression of apoptotic and autophagic factors was analysed.

Results: Legumain was present in plaques, and its expression was upregulated in macrophages treated with oxLDL. Suppressing legumain significantly increased oxLDL-induced macrophage apoptosis and the expression of caspase 3, caspase 9 and Bax. However, legumain overexpression decreased macrophage apoptosis upon oxLDL exposure and the levels of caspase 3, caspase 9 and Bax. In addition, recombinant legumain protein suppressed macrophage apoptosis. Biochemical experiments revealed that legumain deficiency decreased the levels of Beclin1 and LC3, whereas increased legumain expression increased the levels of Beclin1 and LC3 significantly.

Conclusion: Legumain regulates oxLDL-induced macrophage apoptosis by enhancing the autophagy pathway, which may also influence the vulnerability of atherosclerotic plaques.

Keywords: Apoptosis; Atherosclerosis; Autophagy; Legumain; Macrophage.

MeSH terms

  • Aged
  • Animals
  • Apoptosis / drug effects
  • Autophagy / drug effects*
  • Beclin-1 / genetics
  • Beclin-1 / metabolism
  • Carotid Arteries / drug effects
  • Carotid Arteries / metabolism
  • Carotid Arteries / pathology
  • Carotid Stenosis / genetics*
  • Carotid Stenosis / metabolism
  • Carotid Stenosis / pathology
  • Caspase 3 / genetics
  • Caspase 3 / metabolism
  • Caspase 9 / genetics
  • Caspase 9 / metabolism
  • Cysteine Endopeptidases / genetics
  • Cysteine Endopeptidases / metabolism
  • Cysteine Endopeptidases / pharmacology*
  • Female
  • Gene Expression Regulation
  • Humans
  • Lipoproteins, LDL / antagonists & inhibitors*
  • Lipoproteins, LDL / pharmacology
  • Male
  • Mice
  • Microtubule-Associated Proteins / genetics
  • Microtubule-Associated Proteins / metabolism
  • Plaque, Atherosclerotic / genetics*
  • Plaque, Atherosclerotic / metabolism
  • Plaque, Atherosclerotic / pathology
  • RAW 264.7 Cells
  • RNA, Small Interfering / genetics
  • RNA, Small Interfering / metabolism
  • Signal Transduction
  • THP-1 Cells
  • bcl-2-Associated X Protein / genetics
  • bcl-2-Associated X Protein / metabolism

Substances

  • BAX protein, human
  • BECN1 protein, human
  • Beclin-1
  • Lipoproteins, LDL
  • MAP1LC3A protein, human
  • Microtubule-Associated Proteins
  • RNA, Small Interfering
  • bcl-2-Associated X Protein
  • oxidized low density lipoprotein
  • CASP3 protein, human
  • CASP9 protein, human
  • Caspase 3
  • Caspase 9
  • Cysteine Endopeptidases
  • asparaginylendopeptidase