D-limonene modulates AMPK signaling to inhibit ox-LDL-induced foam cell formation

One of the primary mechanisms of atherosclerosis involves foam cell formation induced by oxidized low-density lipoprotein (ox-LDL). This study aims to explore the potential of D-limonene to inhibit ox-LDL-induced foam cell formation by activating the AMPK signaling pathway. THP-1 cells were differentiated into macrophages using PMA and subsequently divided into five groups: Control, ox-LDL, ox-LDL + LIM 25 µM, ox-LDL + LIM 50 µM, and ox-LDL + LIM 100 µM. Cell viability was assessed using the CCK-8 assay, foam cell formation was evaluated by Oil Red O staining, and inflammatory factor levels (IL-1β, IL-18, TNF-α) were measured using ELISA. Autophagosome formation was detected via immunofluorescence, and protein expressions related to foam cell formation and autophagy were analyzed by Western blotting. ox-LDL treatment markedly increased lipid accumulation, cholesterol levels, and inflammatory cytokine expression in macrophages while reducing autophagosome formation. D-limonene treatment significantly decreased the expression of SR-A and CD36, enhanced ABCA1 and ABCG1 levels, and reduced inflammatory cytokine levels. Additionally, autophagy-related proteins LC3-II/LC3-I, Atg5, and Beclin-1 were restored. D-limonene activated AMPK/p-AMPK and inhibited mTOR/p-mTOR signaling. By modulating the AMPK/mTOR signaling pathway, D-limonene effectively inhibits ox-LDL-induced foam cell formation and inflammation, suggesting a potential protective effect of D-limonene in ox-LDL-induced foam cell formation, which may provide experimental evidence for future in vivo studies on atherosclerosis.