Macrophage polarisation by fatty acids is PPARgamma-dependent

Area of Science:

• Cardiovascular Disease Research
• Immunology
• Metabolic Pathways

Background:

• Elevated plasma free fatty acids (FAs) are linked to cardiovascular disease risk.
• Monocyte phenotype and function are crucial in atherogenesis.

Purpose of the Study:

• To investigate the differential effects of saturated palmitate and unsaturated oleate on monocyte phenotype and function.
• To elucidate the molecular mechanisms underlying palmitate-induced monocyte activation and adhesion.

Main Methods:

• Monocytes were incubated with palmitate or oleate.
• Cell surface marker expression (CD11b, CD36), oxidized LDL uptake, endothelial adhesion, ceramide levels, glutathione, ROS, and cytokine production were assessed.
• Inhibitors of ceramide synthesis and ROS were used.

Main Results:

• Palmitate, not oleate, increased monocyte CD11b and CD36 expression, associated with increased C16 ceramide, sphingomyelin, reduced glutathione, and ROS.
• Palmitate-induced monocytes showed increased oxidized LDL uptake and adhesion to endothelium.
• Ceramide synthesis inhibition blocked CD11b/CD36 increase, while ROS inhibition affected mitochondrial ROS and metabolism.
• Palmitate-primed monocytes exhibited increased TNF-α and IL-6 production upon differentiation, involving ceramide-dependent mechanisms.

Conclusions:

• Palmitate, a saturated FA, promotes pro-atherogenic monocyte changes, including increased CD11b/CD36 expression, LDL uptake, and endothelial adhesion, mediated by de novo ceramide synthesis.
• Dietary fatty acids differentially impact monocyte polarization and inflammatory responses, with palmitate driving pro-inflammatory cytokine production via ceramide pathways.