LDL accelerates monocyte to macrophage differentiation: Effects on adhesion and anoikis

High LDL triggers dyslipidemia and atherosclerosis, a chronic inflammatory disease with participation of the innate immunity system. Monocytes are recruited to areas of LDL-induced endothelial damage and initiate differentiation. This study was aimed to investigate the effects of LDL on the early transitional stages of monocyte differentiation into macrophages.

Blood monocytes, isolated from healthy donors by their adhesion properties, were exposed to native-LDL (1.80 mg/mL) for 48-h. Monocyte phenotype was assessed at transcript and miRNA levels by real-time PCR. Protein-expression was determined by western-blot and flow-cytometry.

CD14 time-dependently decreased in adhered monocytes, reaching a >4 fold decrease at transcript- and protein-levels after 7-days in culture when cells were already differentiated into macrophages. At 4-days differentiation, monocytes exposed to LDL reduced CD14-transcrition >1.5 fold in mRNA (p = 0.002) and 34% CD14-protein (p = 0.039), whereas increased in CD16-expression (p = 0.019). Besides, LDL induced a significant increase in integrin CD49c (α3-subunit) at mRNA (>2 fold, p = 0.008) and protein (>3 fold, p = 0.045) level and a decrease in the apoptosis-effectors CASP8 and CASP3 (p = 0.002 and p = 0.035, respectively) as well as in the precursor form of the death-receptor DR5 (p = 0.045) without affecting its mRNA-expression level, suggesting a LDL-dependent post-transcriptional regulation of DR5. In silico prediction analysis indicated miR-126-3p as a candidate to regulate DR5-expression and miR-126-3p was shown affected by LDL reaching a significant increase (p = 0.033).

In differentiating human monocytes, LDL stimulates expression of cell-adhesion molecules and downregulates apoptosis-effectors, regulating anoikis and survival programs in the early stage macrophages.