Related Experiment Video
Updated: May 22, 2026
Investigation of Macrophage Polarization Using Bone Marrow Derived Macrophages
Published on: June 23, 2013
The activation state of macrophages alters their ability to suppress preadipocyte apoptosis
André S D Molgat1, AnneMarie Gagnon, Charlie Foster
1Chronic Disease Program, Ottawa Hospital Research Institute, Canada K1H 8L6.
Abstract:
Adipose tissue contains macrophages whose state of activation is regulated as obesity develops. Macrophage-secreted factors influence critical processes involved in adipose tissue homeostasis, including preadipocyte proliferation and differentiation into adipocytes. Macrophage-conditioned medium (MacCM) from J774A.1 macrophages protects 3T3-L1 preadipocytes from apoptosis through platelet-derived growth factor (PDGF) signaling. Here, we investigated the effect of macrophage activation on MacCM-dependent preadipocyte survival. MacCM was prepared following activation of either J774A.1 macrophages with lipopolysaccharide (LPS) or human primary monocyte-derived macrophages (MD-macrophages) with LPS or interleukin 4 (IL4). 3T3-L1 and human primary preadipocytes were induced to undergo apoptosis in MacCM, and apoptosis was quantified by cell enumeration or Hoechst nuclear staining. Preadipocyte PDGF signaling was assessed by immunoblot analysis of phosphorylated PDGF receptor, Akt, and ERK1/2. Pro-inflammatory activation of J774A.1 macrophages with LPS inhibited the pro-survival activity of MacCM on 3T3-L1 preadipocytes, despite intact PDGF signaling. Upregulation of macrophage tumor necrosis factor a (TNFα) expression occurred in response to LPS, and TNFα was demonstrated to be responsible for the inability of LPS-J774A.1-MacCM to inhibit preadipocyte apoptosis. Furthermore, MacCM from human MD-macrophages (MD-MacCM) inhibited apoptosis of primary human preadipocytes. MD-MacCM from LPS-treated macrophages, but not IL4-treated anti-inflammatory macrophages, was unable to protect human preadipocytes from cell death. In both murine cell lines and human primary cells, pro-inflammatory activation of macrophages inhibits their pro-survival activity, favoring preadipocyte death. These findings may be relevant to preadipocyte fate and adipose tissue remodeling in obesity.
Insights
Pro-inflammatory macrophage activation impairs their ability to protect preadipocytes from cell death, impacting adipose tissue homeostasis. This suggests a role in obesity-related adipose tissue remodeling.
Area of Science:
- Cell Biology
- Immunology
- Metabolism
Background:
- Adipose tissue macrophages (ATMs) regulate adipose tissue homeostasis.
- Macrophage-secreted factors influence preadipocyte proliferation, differentiation, and survival.
- Macrophage-conditioned medium (MacCM) can protect preadipocytes from apoptosis via platelet-derived growth factor (PDGF) signaling.
Purpose of the Study:
- To investigate how macrophage activation state affects MacCM's ability to promote preadipocyte survival.
- To determine the role of pro-inflammatory versus anti-inflammatory activation in macrophage-mediated preadipocyte fate.
- To explore the implications for adipose tissue remodeling in obesity.
Main Methods:
- Prepared MacCM from J774A.1 macrophages and human primary monocyte-derived macrophages activated with lipopolysaccharide (LPS) or interleukin-4 (IL4).
- Exposed 3T3-L1 and primary human preadipocytes to MacCM and induced apoptosis.
- Quantified apoptosis using cell enumeration and Hoechst staining; assessed PDGF signaling via immunoblot analysis.
Main Results:
- Pro-inflammatory activation of J774A.1 macrophages with LPS inhibited MacCM's pro-survival effect on 3T3-L1 preadipocytes, despite intact PDGF signaling.
- Tumor necrosis factor alpha (TNFα) produced by LPS-activated macrophages was responsible for this loss of pro-survival activity.
- MacCM from LPS-activated human macrophages, but not IL4-activated macrophages, failed to protect primary human preadipocytes from apoptosis.
- Pro-inflammatory macrophage activation inhibited pro-survival activity, promoting preadipocyte death in both murine and human systems.
Conclusions:
- Pro-inflammatory activation of macrophages diminishes their capacity to support preadipocyte survival.
- This shift in macrophage function may contribute to adipose tissue dysfunction and remodeling observed in obesity.
- Understanding these macrophage-mediated effects is crucial for addressing metabolic disorders.
Related Concept Videos
01:17Phagocytosis of Apoptotic Cells
Normal cells contain receptors that prevent them from being recognized by phagocytes.
01:38Inflammation