An aqueous extract of Welsh onion green leaves increase ABCA1 and SR-BI expression in macrophage RAW 264.7 cells

The effects of the aqueous extracts of Welsh onion green leaves (WOE) on the expression of scavenger receptor class BI (SR-BI) and ATP-binding cassette A1 (ABCA1), the two high-density lipoprotein (HDL) receptors, presented in macrophage RAW 264.7 cells were investigated. WOE in the range of 0-0.5 mg/ml increased the protein expression of ABCA1 and SR-BI by a dose- and time-dependent manner in macrophages. On the other hand, lipopolysaccharide (LPS) at 200 ng/ml decreased ABCA1 and SR-BI protein expression, and WOE in the range of 0-1.0 mg/ml blocked LPS-decreased ABCA1 and SR-BI protein expression. Quercetin and kaempferol, the two major flavonoids presented in WOE, in the range of 0-3.4 mu g/ml also showed an inductive effect on the ABCA1 and SR-BI protein and a protective effect under LPS stimulation. Furthermore, determined by reverse transcription-polymerase chain reaction (RT-PCR), WOE in the range of 0-1.0 mg/ml increased the ABCA1 and SR-BI mRNA levels after 12 h treatment. LPS also obviously decreased ABCA1 and SR-BI mRNA in RAW 264.7 cells. These LPS resulted mRNA inhibitions were also markedly prevented by the addition of WOE, quercetin and kaempferol, respectively. These results suggest that WOE and its two major flavonoids, quercetin and kaempferol; have potential effect on increasing HDL receptor expression in macrophages. (c) 2007 Elsevier Ltd. All rights reserved.