Fatty acid species differentially regulate macrophage polarization and oxidative stress with secondary effects on...

Metabolic dysfunction-associated steatohepatitis (MASH) is characterized by lipid accumulation, inflammation, and fibrosis. Macrophage-hepatic stellate cell (HSC) communication plays a key role in fibrogenesis; however, how fatty acid species influence macrophage polarization remains unclear. Bone marrow-derived macrophages (BMDMs) were polarized toward M1 or M2 phenotypes in the presence of palmitic acid (PA), oleic acid (OA), or palmitoleic acid (PO). Polarization markers, reactive oxygen species (ROS), and peroxisome proliferator-activated receptor gamma (PPARγ) expression were analyzed by RT-qPCR, Western blotting, and chemiluminescence. Primary HSCs were exposed to fatty acids or conditioned media from treated macrophages. PA enhanced selected inflammatory macrophage responses and increased ROS production under M1-polarizing conditions. OA enhanced ROS production in M1 macrophages and suppressed several M2-associated markers, whereas PO reduced inflammatory responses and ROS under M1-polarizing conditions. Direct fatty acid exposure did not significantly alter HSC activation markers. Conditioned media from polarized macrophages, particularly M1 macrophages, reduced α-SMA and cytoglobin protein expression in HSCs, while fatty acid-specific effects were modest and marker-dependent. Fatty acid species differentially modulate macrophage polarization and redox activity, partly in association with PPARγ signaling. These macrophage changes may secondarily affect macrophage-HSC communication and stellate cell redox-related responses, providing insight into lipid regulation of immune-stromal interactions in the liver.