Cholesterol crystals enhance TLR2- and TLR4-mediated pro-inflammatory cytokine responses of monocytes to the proatherogenic oral bacterium Porphyromonas gingivalis

PLoS One. 2017 Feb 24;12(2):e0172773. doi: 10.1371/journal.pone.0172773. eCollection 2017.

Abstract

Cholesterol deposits and pro-inflammatory cytokines play an essential role in the pathogenesis of atherosclerosis, a predominant cause of cardiovascular disease (CVD). Epidemiological evidence has linked periodontal disease (PD) with atherosclerotic CVD. Accordingly, viable periodontal pathogens, including Porphyromonas gingivalis, have been found in atherosclerotic plaques in humans and mice. We aimed to determine whether cholesterol crystals (CHCs) and oral bacteria synergize in the stimulation of human monocytes. Incubation of human monocytes with CHCs induced secretion of interleukin (IL)-1β, tumor necrosis factor (TNF)-α, IL-6, and IL-8. Moreover, CHCs markedly enhanced secretion of IL-1β by monocytes stimulated with the toll-like receptor (TLR) 4 agonist Escherichia coli lipopolysaccharide (LPS), and the TLR2 agonist Staphylococcus aureus lipoteichoic acid. Notably, CHCs also enhanced IL-1β secretion induced by P. gingivalis LPS and IL-1β secretion induced by whole P. gingivalis bacteria. This enhancement was abrogated by the NLRP3 inflammasome inhibitors Z-YVAD-FMK and glibenclamide. CHCs had no effect on cytokine production induced by P. gingivalis gingipains. Taken together, our findings support that CHCs, via stimulation of NLRP3 inflammasomes, act in synergy with the periodontal pathogen P. gingivalis to promote monocyte secretion of pro-atherogenic cytokines.

MeSH terms

  • Animals
  • Atherosclerosis / complications
  • Atherosclerosis / metabolism*
  • Atherosclerosis / microbiology
  • Cholesterol / chemistry
  • Cholesterol / metabolism*
  • Humans
  • Inflammasomes / drug effects
  • Inflammasomes / metabolism
  • Interleukin-1beta / metabolism
  • Interleukin-6 / metabolism
  • Interleukin-8 / metabolism
  • Mice
  • Monocytes / metabolism
  • Monocytes / microbiology
  • NLR Family, Pyrin Domain-Containing 3 Protein / antagonists & inhibitors
  • NLR Family, Pyrin Domain-Containing 3 Protein / genetics*
  • Periodontal Diseases / complications
  • Periodontal Diseases / metabolism*
  • Periodontal Diseases / microbiology
  • Plaque, Atherosclerotic / metabolism
  • Plaque, Atherosclerotic / microbiology
  • Porphyromonas gingivalis / metabolism
  • Porphyromonas gingivalis / pathogenicity
  • Staphylococcus aureus / chemistry
  • Staphylococcus aureus / pathogenicity
  • Toll-Like Receptor 2 / administration & dosage
  • Toll-Like Receptor 2 / agonists
  • Toll-Like Receptor 2 / metabolism
  • Toll-Like Receptor 4 / administration & dosage
  • Toll-Like Receptor 4 / agonists
  • Toll-Like Receptor 4 / metabolism
  • Tumor Necrosis Factor-alpha / metabolism

Substances

  • Inflammasomes
  • Interleukin-1beta
  • Interleukin-6
  • Interleukin-8
  • NLR Family, Pyrin Domain-Containing 3 Protein
  • TLR2 protein, human
  • TLR4 protein, human
  • Toll-Like Receptor 2
  • Toll-Like Receptor 4
  • Tumor Necrosis Factor-alpha
  • Cholesterol

Grants and funding

This work was funded by Danish Council for Independent Research (grant number: 1333-00190A, grant recipient: Tania Køllgaard, TK), (URL: http://ufm.dk/forskning-og-innovation/rad-og-udvalg/det-frie-forskningsrad/radet/dff-sundhed-og-sygdom) and Aase og Ejnar Danielsens Fond (grant number: 10-001018 (grant recipient: TK), (URL: http://www.danielsensfond.dk/Default.aspx). The funders had no role in study design, data collection and analyses, decision to publish, or preparation of the manuscript.