Triglyceride-Rich Lipoproteins Modulate the Distribution and Extravasation of Ly6C/Gr1low Monocytes

• Hypertriglyceridemia promotes the extravasation of Gr1low monocytes
• CD68+ tissue macrophages accumulate in the absence of overt inflammation
• Hypertriglyceridemia is associated with increased CCL4 levels
• CCL4 is involved in the migration of Gr1low monocytes

SummaryMonocytes are heterogeneous effector cells involved in the maintenance and restoration of tissue integrity. However, their response to hyperlipidemia remains poorly understood. Here, we report that in the presence of elevated levels of triglyceride-rich lipoproteins, induced by administration of poloxamer 407, the blood numbers of non-classical Ly6C/Gr1low monocytes drop, while the number of bone marrow progenitors remains similar. We observed an increased crawling and retention of the Gr1low monocytes at the endothelial interface and a marked accumulation of CD68+ macrophages in several organs. Hypertriglyceridemia was accompanied by an increased expression of tissue, and plasma CCL4 and blood Gr1low monocyte depletion involved a pertussis-toxin-sensitive receptor axis. Collectively, these findings demonstrate that a triglyceride-rich environment can alter blood monocyte distribution, promoting the extravasation of Gr1low cells. The behavior of these cells in response to dyslipidemia highlights the significant impact that high levels of triglyceride-rich lipoproteins may have on innate immune cells.

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