Effects of β2/aβ2 on oxLDL-induced CD36 activation in THP-1 macrophages

Aims:β2-glycoprotein I/anti-β2-glycoprotein I antibody complex (β2/aβ2) could promote oxLDL-induced endothelial inflammation through Toll-like receptor 4 (TLR4), therefore accelerates atherosclerosis in patients with anti-phospholipid syndrome (APS). However, effects of β2/aβ2 and TLR4 on oxLDL-induced CD36 activation in macrophages remain to be elucidated and are currently under investigation.

Materials and methods:THP-1 macrophages with or without the pre-treatment of TAK-242, a TLR4 inhibitor, were treated with RPMI 1640, oxLDL, oxLDL+β2/aβ2 or oxLDL + LPS.CD36 expression and subsequent intracellular lipid accumulation, cholesterol-transportation-related proteins (ACAT1, ABCG1 and ABCA1) expression, inflammatory cytokines (IL-1β, TNF-α and IL-6) secretion, focal adhesion kinases (FAK) activation and matrix metalloproteinases (MMP-2 and MMP-9) expression by these THP-1 macrophages were evaluated. Moreover, effects of TLR4 on oxLDL+β2/aβ2-induced peroxisome proliferators-activated receptor-γ (PPAR-γ) expression and CD36 translocation have also been observed.

Key findings:Compared with oxLDL-treated ones, CD36 expression, intracellular lipid accumulation and FAK activation were inhibited, whereas the levels of inflammatory cytokines and MMPs were upregulated in THP-1 macrophages treated with oxLDL+β2/aβ2 (p < 0.05). Moreover, observed differences between oxLDL-treated and oxLDL+β2/aβ2-treated THP-1 macrophages could be reversed by TAK-242 pre-treatment (p < 0.05). Furthermore, oxLDL+β2/aβ2 promoted PPAR-γ expression and CD36 cytoplasmic translocation in THP-1 macrophages, these effects could also be attenuated by TAK-242 (p < 0.05).

Significance:Through a TLR4 dependent manner, β2/aβ2 inhibited oxLDL-induced CD36 expression, lipid accumulation and FAK activation, while promoted inflammatory cytokines and MMPs expression in THP-1 macrophages, indicating the novel dual roles played by β2/aβ2 in APS-related atherosclerosis.

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