The Effects of the oxLDL/β2GPI/anti-β2GPI Complex on Macrophage Autophagy and its Mechanism

Background

Previous research has established that the oxidized low-density lipoprotein/β2-glycoprotein I/anti-β2-glycoprotein I antibody (oxLDL/β2GPI/anti-β2GPI) complex can stimulate macrophages to secrete molecules associated with atherosclerosis (AS), such as monocyte chemotactic protein 1 (MCP-1), tissue factor (TF), and tumor necrosis factor-α (TNF-α). This complex also enhances the uptake of oxLDL, thereby accelerating foam cell formation through the Toll-like receptor-4/nuclear factor kappa B (TLR4/NF-κB) pathway. Given the critical role of macrophage autophagy in the instability of vulnerable atherosclerotic plaques, it is imperative to investigate whether the oxLDL/β2GPI/anti-β2GPI complex influences macrophage autophagy in AS. This study aims to elucidate the effects and underlying mechanisms of the oxLDL/β2GPI/anti-β2GPI complex on macrophage autophagy in AS.

Methods

Experiments were conducted using murine macrophage RAW264.7 cells and the human monocytic cell line THP-1. Western blot analysis was employed to determine the expressions of autophagy-associated markers and signaling pathway proteins. Autophagosomes were detected through mRFP-GFP-LC3 adenoviral transfection and transmission electron microscopy (TEM).

Results

Treatment of macrophages with the oxLDL/β2GPI/anti-β2GPI complex resulted in decreased expressions of Beclin1 and LC3 proteins, alongside an upregulation of SQSTM1/P62 protein expression. Additionally, there was a reduction in the number of autophagosomes and autolysosomes. An increase in the phosphorylation levels of phosphoinositide-3-kinase (PI3K), protein kinase B (AKT), and mammalian target of rapamycin (mTOR) was also observed. Notably, the expressions of autophagy-associated markers were partially restored when the TLR4/NF-κB and PI3K/AKT/mTOR pathways were inhibited by their respective inhibitors.

Conclusions

Our findings indicate that the oxLDL/β2GPI/anti-β2GPI complex inhibits macrophage autophagy in AS via the TLR4/NF-κB and PI3K/AKT/mTOR signaling pathways.