Abstract 15214: Chlamydia Pneumoniae-Induced Foam Cell Formation Requires Nlrp3 Inflamasome Activation
Background and Objective: Foam cell formation (FCF) due to excessive accumulation of cholesterol by macrophages is a pathological hallmark of atherosclerosis. C. pneumoniae (Cp) promotes FCF in the presence of ox-LDL but the mechanism is unclear. Here we investigated the role of the NOD-like receptor family, pyrin domain containing 3 (NLRP3) inflammasome in Cp induced FCF and the regulation of cholesterol metabolism in macrophages.
Methods: Peritoneal macrophages from wild-type (WT), Nlrp3-/-, and Caspase1-/- mice were treated with live Cp. in the presence or absence of ox-LDL or IL-R antigonist, Anakinra. Intracellular lipids was assessed by Oil Red O staining to measure FCF. The expression of inflammatory cytokine IL-1α, IL-1β, TNF-α, cholesterol efflux transportor ABCA1, ABCG1, cholesterol uptake receptor CD36, Class B scavenger receptor (SR-B) and Cellular lipid synthesis and homeostasis transcription factor, Sterol regulatory element-binding protein- 2 (SREBP2) were examined in mRNA level by real-time RT-PCR and protein level by ELISA, FACS or Western blot analysis.
Results: peritoneal macrophages infected with Cp resulted in large accumulation of lipid droplets and FCF while co-cultured with LDL, and the secretion of IL-1 α and IL-1β cytokines were significant higher compared with the LDL treatment cells. Cp induced FCF increasing could be blocked by IL-1R antagonist, Anakinra treatment. FCF increasing was also attenuated in NLRP3 and Caspase1 KO macrophages compared to WT cells. Cp and ox-LDL induced IL-1β and IL-1 α secretion was blocked in Nlrp3-/- and Casasep1-/- cells. Additionally, the cholesterol efflux transporter ABCA1 and ABCG1 was expressed at much higher levels in Nlrp3-/- and Caspase1-/- macrophages compared to WT cells and Cp stimulation increased CD36 and SREBP2 in Wt cells and not in Nlrp3-/- and Casp1-/- macrophages.
Conclusion: These data suggest that Cp infection facilitates foam cell formation in the presence of oxLDL by producing IL-1 cytokines through the activation of the NLRP3 inflammasome, and that IL-1 signaling is involved in cholesterol metabolism.
- © 2013 by American Heart Association, Inc.