Cholesterol crystals activate the NLRP3 inflammasome in human macrophages: a novel link between cholesterol metabolism and inflammation

PLoS One. 2010 Jul 23;5(7):e11765. doi: 10.1371/journal.pone.0011765.


Background: Chronic inflammation of the arterial wall is a key element in the pathogenesis of atherosclerosis, yet the factors that trigger and sustain the inflammation remain elusive. Inflammasomes are cytoplasmic caspase-1-activating protein complexes that promote maturation and secretion of the proinflammatory cytokines interleukin(IL)-1beta and IL-18. The most intensively studied inflammasome, NLRP3 inflammasome, is activated by diverse substances, including crystalline and particulate materials. As cholesterol crystals are abundant in atherosclerotic lesions, and IL-1beta has been linked to atherogenesis, we explored the possibility that cholesterol crystals promote inflammation by activating the inflammasome pathway.

Principal findings: Here we show that human macrophages avidly phagocytose cholesterol crystals and store the ingested cholesterol as cholesteryl esters. Importantly, cholesterol crystals induced dose-dependent secretion of mature IL-1beta from human monocytes and macrophages. The cholesterol crystal-induced secretion of IL-1beta was caspase-1-dependent, suggesting the involvement of an inflammasome-mediated pathway. Silencing of the NLRP3 receptor, the crucial component in NLRP3 inflammasome, completely abolished crystal-induced IL-1beta secretion, thus identifying NLRP3 inflammasome as the cholesterol crystal-responsive element in macrophages. The crystals were shown to induce leakage of the lysosomal protease cathepsin B into the cytoplasm and inhibition of this enzyme reduced cholesterol crystal-induced IL-1beta secretion, suggesting that NLRP3 inflammasome activation occurred via lysosomal destabilization.

Conclusions: The cholesterol crystal-induced inflammasome activation in macrophages may represent an important link between cholesterol metabolism and inflammation in atherosclerotic lesions.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Blotting, Western
  • Carrier Proteins / genetics
  • Carrier Proteins / physiology*
  • Caspase 1 / metabolism
  • Caspase Inhibitors
  • Cathepsin B / metabolism
  • Cells, Cultured
  • Cholesterol / chemistry
  • Cholesterol / metabolism
  • Cholesterol / pharmacology*
  • Chromatography, Thin Layer
  • Cytochalasin D / pharmacology
  • Cytoplasm / metabolism
  • Humans
  • Inflammation / genetics
  • Inflammation / immunology*
  • Interleukin-1beta / metabolism
  • Lipopolysaccharides / pharmacology
  • Lysosomes / drug effects
  • Lysosomes / metabolism
  • Macrophages / drug effects
  • Macrophages / metabolism*
  • Microscopy, Confocal
  • Monocytes / drug effects
  • Monocytes / metabolism
  • NLR Family, Pyrin Domain-Containing 3 Protein
  • Phagocytosis / drug effects
  • Phagocytosis / physiology
  • Potassium / metabolism
  • RNA, Small Interfering / genetics
  • RNA, Small Interfering / physiology
  • Reverse Transcriptase Polymerase Chain Reaction


  • Carrier Proteins
  • Caspase Inhibitors
  • Interleukin-1beta
  • Lipopolysaccharides
  • NLR Family, Pyrin Domain-Containing 3 Protein
  • NLRP3 protein, human
  • RNA, Small Interfering
  • Cytochalasin D
  • Cholesterol
  • Cathepsin B
  • Caspase 1
  • Potassium