Objective        To determine whether Toll-like receptor 4 (TLR4) promoting VSMCs-deriv

ed foam cells formation is related with the abnormal expression of ATP-binding cassette transporter 1 (ABCA1).       Methods        Vascular smooth muscle cells (VSMCs) were isolated from male C57BL/6J (TLR4

-/-

) and C57BL/10ScNj (TLR4

-/-

) mice respectively

and primary cultured and identified. The obtained VSMCs were divided into wild type blank control cells

oxLDL-treated wild type cells (50 μg/mL oxLDL)

TLR4

-/-

blank control cells and oxLDL-treated TLR4

-/-

cells. Neutral lipid inclusions in the VSMCs induced by oxLDL were assessed by Oil Red O staining. Lipid accumulation was quantitated by isopropanol extraction of Oil Red O from stained cells and optical density determinations at 518 nm. The mRNA and/or protein levels of TLR4

ABCA1

IL-1β and TNF-α were determined by Western blotting and RT-qPCR. The NF-κB translocation was identified by immunofluorescence assay.       Results        Oil red O staining indicated that a large amount of lipid was accumulated in oxLDL-treated wild type VSMCs

with the OD value increased by 2.3 folds compared with that of blank control (

P

0.01). Only few lipids were found in oxLDL-treated TLR4

-/-

VSMCs

with no significant difference with the untreated cells (

P

0.05). The ABCA1 expression at mRNA and protein levels was reduced by 61% (P0.05) and 44% (

P

0.01)

respectively

in oxLDL-treated wild type VSMCs than in untreated cells. However

in the TLR4

-/-

VSMCs stimulated by oxLDL

the ABCA1 mRNA and protein expression were 2.3-fold (

P

0.05) and 1.7-fold higher (

P

0.05) than the TLR4

-/-

blank control

respectively. The translocation of NF-κB was activated by TLR4 in oxLDL-treated wild type VSMCs

and the IL-1β and TNF-α mRNA expression were 3.9 folds (

P

0.05) and 1.7 folds (

P

0.05) respectively of wild type blank controls. However

in oxLDL-treated TLR4 knockout VSMCs

NF-κB translocation and the expression of TNF-α had no significant change

but the expression

of IL-1β was enhanced by 1.2 times (

P

0.05) when compared with untreated TLR4

-/-

VSMCs.       Conclusion       TLR4 and its mediating inflammation are involved in the abnormal expression of ABCA1 during VSMCs-derived foam cells formation.