Functions of Monocytes and Macrophages and the Associated Effective Molecules and Mechanisms at the Early Stage of Atherosclerosis.

OBJECTIVE

This study aimed to explore the functions and possible underlying regulatory molecules and mechanisms of monocytes and macrophages under early atherosclerotic conditions.

METHODS

THP-1-derived monocytes or macrophages were induced by 50 μg/ml oxidized low density lipoprotein (ox-LDL) for 24 hours, and the degree of lipid metabolism and inflammation were determined. In addition, we identified differentially expressed genes, noncoding ribonucleic acids (RNAs), pathways and mechanisms by RNA sequencing, and performed further correlation analysis and molecular expression verification.

RESULTS

Monocytes could not form foam cells with oil red O staining directly and had low levels of lipids as determined by total cholesterol and triglycerides assays, cholesterol uptake molecules CD36, the class A macrophage scavenger receptor and lectin-like oxidized low-density lipoprotein receptor-1 and cholesterol efflux molecules ATP binding cassette transporter A1, ATP binding cassette transporter G1 and liver X receptor α, and inflammatory factors, which were markedly different from those in macrophages. Additionally, sequencing data showed obviously differentially expressed genes, microRNAs and long noncoding RNAs in the atherosclerotic group. We identified 15 upregulated and downregulated genes, and 10 biological processes and pathways involved in atherosclerosis. Specifically, fatty acid desaturase 2 and apolipoprotein A1 in the peroxisome proliferator-activated receptor signaling pathway were differentially expressed in stimulated macrophages, whereas no changes were observed in the monocyte groups. Furthermore, correlation analysis showed differential expressed lncRNAs targeting miRNAs and mRNAs, and 24 competing endogenous RNA (ceRNA) networks of long noncoding RNA-microRNA-messenger RNA in early oxidative macrophages.

CONCLUSIONS

Monocytes did not directly participate in lipid metabolism before differentiation into macrophages at the early stage in vitro. Furthermore, noncoding RNAs and ceRNA networks might play important roles in regulating the lipid metabolism of macrophages at the early stage of atherosclerosis.