Obesity-Derived Biomolecules Promote the Differentiation of THP1 Monocytes to Macrophages In Vitro.

Background: It is well known that the microenvironment in which an immune response develops, generally pro-inflammatory or immunosuppressive, along with other overproduced biomolecules recognized by pattern recognition receptors, may promote the stimulation and differentiation of monocytes into macrophages with effector functions. Low-density lipoprotein (LDL) plays a fundamental role in cholesterol transport. By contrast, its oxidized form (ox-LDL), which is overexpressed in conditions of obesity and chronic low-grade inflammation, has been associated with cardiovascular diseases. Depending on the microenvironmental context, prostaglandin E2 (PGE2) participates in various scenarios such as inflammation, anti-inflammation, and homeostasis. Therefore, obesity-derived biomolecules such as LDL, ox-LDL, and PGE2 could induce the differentiation of immune cells into effector populations with either pro-inflammatory or immunosuppressive profiles.

Methods: In the present work, we studied the effects of LDL, ox-LDL, and PGE2 on the differentiation of the human THP1 monocytic cell line into macrophages under two different protocols, analyzing several activation markers associated with either pro-inflammatory M1 or anti-inflammatory M2 profiles by flow cytometry and quantitative PCR (qPCR).

Results: Our data suggest that native LDL induces the differentiation of human THP1 monocytes into M1 macrophages even more efficiently than classic phorbol 12-myristate 13-acetate (PMA) stimulation, whereas ox-LDL and PGE2 induce the expression of activation markers similarly to interferon gamma or interleukin 4 during PMA preactivation of macrophages.

Conclusions: The results of this study add evidence to the role of obesity-derived biomolecules as non-canonical differentiation stimuli in macrophages, which could be relevant in contexts where these biomolecules are chronically overproduced, such as obesity, low-grade inflammation, type 2 diabetes, and cancer.