Backgrounds/Aims: Apoptotic macrophages are removed by neighboring phagocytes (efferocytosis), which is an important event in advanced atherosclerosis. We reported the long pentraxin 3 (PTX3) located at the membrane of late apoptotic macrophages, mediates efferocytosis in a cell model of advanced atherosclerosis. However, the mechanism underlying PTX3-mediated apoptotic cell clearance in atherogenesis is unclear.
Methods: We modeled macrophage apoptosis in advanced plaques by incubating macrophages (peritoneal macrophages isolated from C57 mice) with free cholesterol (free cholesterol-induced apoptotic macrophages, FC-AMs). FC-AMs were added to a monolayer of fresh phagocytes（macrophages） to study the engulfment response. The percentage of phagocytes that ingested FC-AMs was quantified by using confocal microscopy. C1q and C3b were detected by using fluorescence-activated cell sorter (FACS) and the confocal microscopy.
Results: We found that PTX3 significantly enhances complement C1q binding on FC-AMs and was correlated with improved activating of classic complement pathway. C3b was the characteristic component of activating of classic complement pathway, displayed the increased deposition on FC-AMs and mediated the phagocytosis of FC-AMs. This study replicated the role of PTX3-mediated efferocytosis, explored the mechanism of PTX3 involving efferocytosis in detail and provided theoretical evidences for PTX3-mediated cardio-protective functions in atherosclerosis.
Conclusion: PTX3 activated classic complement pathway and mediated phagocytosis of cholesterol-induced apoptotic macrophages in atherosclerosis.