Kaempferol suppresses lipid accumulation in macrophages through the downregulation of cluster of differentiation 36 and the upregulation of scavenger receptor class B type I and ATP-binding cassette transporters A1 and G1

Int J Mol Med. 2013 Feb;31(2):331-8. doi: 10.3892/ijmm.2012.1204. Epub 2012 Dec 5.

Abstract

The accumulation of foam cells in atherosclerotic lesions is a hallmark of early-stage atherosclerosis. Kaempferol has been shown to inhibit oxidized low-density lipoprotein (oxLDL) uptake by macrophages; however, the underlying molecular mechanisms are not yet fully investigated. In this study, we shown that treatment with kaempferol markedly suppresses oxLDL-induced macrophage foam cell formation, which occurs due to a decrease in lipid accumulation and an increase in cholesterol efflux from THP-1-derived macrophages. Additionally, the kaempferol treatment of macrophages led to the downregulation of cluster of differentiation 36 (CD36) protein levels, the upregulation of ATP-binding cassette (ABC) transporter A1 (ABCA1), scavenger receptor class B type I (SR-BI) and ABCG1 protein levels, while no effects on scavenger receptor A (SR-A) expression were observed. Kaempferol had similar effects on the mRNA and protein expression of ABCA1, SR-BI, SR-A, CD36 and ABCG1. The reduced CD36 expression following kaempferol treatment involved the inhibition of c-Jun-activator protein-1 (AP-1) nuclear translocation. The inhibition of AP-1 using the inhibitor, SP600125, confirmed this involvement, as the AP-1 inhibition significantly augmented the kaempferol-induced reduction in CD36 expression. Accordingly, the kaempferol-mediated suppression of lipid accumulation in macrophages was also augmented by SP600125. The increased expression of ABCA1, SR-BI and ABCG1 following kaempferol treatment was accompanied by the enhanced protein expression of heme oxygenase-1 (HO-1). This increase was reversed following the knockdown of the HO-1 gene using small hairpin RNA (shRNA). Moreover, the kaempferol-mediated attenuation of lipid accumulation and the promotion of cholesterol efflux was also inhibited by HO-1 shRNA. In conclusion, the c-Jun-AP‑1-dependent downregulation of CD36 and the HO-1-dependent upregulation of ABCG1, SR-BI and ABCA1 may mediate the beneficial effects of kaempferol on foam cell formation.

MeSH terms

  • ATP Binding Cassette Transporter 1
  • ATP Binding Cassette Transporter, Subfamily G, Member 1
  • ATP-Binding Cassette Transporters / genetics*
  • ATP-Binding Cassette Transporters / metabolism
  • CD36 Antigens / genetics*
  • CD36 Antigens / metabolism
  • Cell Line
  • Cell Survival / drug effects
  • Cholesterol / metabolism
  • Down-Regulation / drug effects
  • Heme Oxygenase-1 / genetics
  • Heme Oxygenase-1 / metabolism
  • Humans
  • Kaempferols / pharmacology*
  • Lipid Metabolism / drug effects*
  • Lipoproteins, LDL / metabolism
  • Macrophages / cytology
  • Macrophages / drug effects*
  • Macrophages / metabolism
  • Proto-Oncogene Proteins c-jun / metabolism
  • RNA Interference
  • RNA, Small Interfering / genetics
  • Signal Transduction / drug effects
  • Transcription Factor AP-1 / metabolism
  • Up-Regulation / drug effects

Substances

  • ABCA1 protein, human
  • ABCG1 protein, human
  • ATP Binding Cassette Transporter 1
  • ATP Binding Cassette Transporter, Subfamily G, Member 1
  • ATP-Binding Cassette Transporters
  • CD36 Antigens
  • Kaempferols
  • Lipoproteins, LDL
  • Proto-Oncogene Proteins c-jun
  • RNA, Small Interfering
  • Transcription Factor AP-1
  • oxidized low density lipoprotein
  • kaempferol
  • Cholesterol
  • HMOX1 protein, human
  • Heme Oxygenase-1