To determine whether methotrexate (MTX) can overcome the atherogenic effects of cyclooxygenase 2 (COX-2) inhibitors and interferon-γ (IFNγ), both of which suppress cholesterol efflux protein and promote foam cell transformation in human THP-1 monocyte/macrophages.
Message and protein levels of the reverse cholesterol transport proteins cholesterol 27-hydroxylase and ATP-binding cassette transporter A1 (ABCA1) in THP-1 cells were evaluated by real-time polymerase chain reaction and immunoblot, respectively. Expression was evaluated in cells incubated in the presence or absence of the COX-2 inhibitor NS398 or IFNγ, with and without MTX. Foam cell transformation of lipid-laden THP-1 macrophages was detected with oil red O staining and light microscopy.
MTX increased 27-hydroxylase message and completely blocked NS398-induced down-regulation of 27-hydroxylase (mean ± SEM 112.8 ± 13.1% for NS398 plus MTX versus 71.1 ± 4.3% for NS398 alone; P < 0.01). MTX also negated COX-2 inhibitor–mediated down-regulation of ABCA1. The ability of MTX to reverse inhibitory effects on 27-hydroxylase and ABCA1 was blocked by the adenosine A2A receptor–specific antagonist ZM241385. MTX also prevented NS398 and IFNγ from increasing transformation of lipid-laden THP-1 macrophages into foam cells.
This study provides evidence supporting the notion of an atheroprotective effect of MTX. Through adenosine A2A receptor activation, MTX promotes reverse cholesterol transport and limits foam cell formation in THP-1 macrophages. This is the first reported evidence that any commonly used medication can increase expression of antiatherogenic reverse cholesterol transport proteins and can counteract the effects of COX-2 inhibition. Our results suggest that one mechanism by which MTX protects against cardiovascular disease in rheumatoid arthritis patients is through facilitation of cholesterol outflow from cells of the artery wall.