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Interferon-gamma-induced apoptosis and activation of THP-1 macrophages
Yosuke Inagaki1, Sho-ichi Yamagishi, Shinjiro Amano
1Department of Medicine, Division of Endocrinology and Metabolism, Kurume University School of Medicine, Japan.
Abstract:
Apoptotic macrophages are frequently observed in human atherosclerotic lesions, and are considered to be involved in plaque instability in atherosclerosis. However, the molecular mechanism that promotes programmed cell death of macrophages in atherosclerosis remains to be elucidated. In this study, we investigated the effects of interferon-gamma (IFN-gamma), a cytokine secreted by activated T helper 1 (Th1) lymphocytes, on apoptotic cell death of THP-1 macrophages. Further we studied whether these apoptotic macrophages could be simultaneously activated in vitro and subsequently overgenerate monocyte chemoattractant protein-1 (MCP-1). When THP-1 macrophages were cultured with various concentrations of IFN-gamma, DNA synthesis was significantly decreased. IFN-gamma was found significantly to induce apoptotic cell death in THP-1 macrophages. RNase protection assay revealed that IFN-gamma up-regulated the mRNA levels of two pro-apoptotic molecules, tumor necrosis factor-alpha receptor 1 (TNFR1) and caspase-8, in THP-1 cells. Furthermore, TNF-alpha antibodies were found completely to neutralize the IFN-gamma-induced inhibition in DNA synthesis as well as apoptotic cell death in macrophages. IFN-gamma was found to activate these macrophages to stimulate MCP-1 production. The results suggest that IFN-gamma not only exerted apoptotic effects on macrophages, but also activated them and subsequently overgenerated MCP-1, and was thus involved in the development and progression of atherosclerosis.
Insights
Interferon-gamma (IFN-gamma) induces macrophage apoptosis and activates them to overproduce monocyte chemoattractant protein-1 (MCP-1), contributing to atherosclerosis development.
Area of Science:
- Immunology
- Cardiovascular Biology
Background:
- Macrophage apoptosis is implicated in atherosclerotic plaque instability.
- The precise molecular mechanisms driving macrophage cell death in atherosclerosis require further investigation.
Purpose of the Study:
- To investigate the effects of interferon-gamma (IFN-gamma) on macrophage apoptosis.
- To determine if IFN-gamma-induced apoptotic macrophages can be activated to overproduce monocyte chemoattractant protein-1 (MCP-1).
Main Methods:
- THP-1 macrophages were cultured with varying concentrations of IFN-gamma.
- Apoptotic cell death and DNA synthesis were assessed.
- Messenger RNA (mRNA) levels of pro-apoptotic molecules were analyzed using RNase protection assay.
- The role of tumor necrosis factor-alpha (TNF-alpha) was evaluated using TNF-alpha antibodies.
Main Results:
- IFN-gamma significantly decreased DNA synthesis and induced apoptotic cell death in THP-1 macrophages.
- IFN-gamma upregulated mRNA levels of tumor necrosis factor-alpha receptor 1 (TNFR1) and caspase-8.
- TNF-alpha antibodies neutralized IFN-gamma's effects on DNA synthesis and apoptosis.
- IFN-gamma activated macrophages, leading to increased MCP-1 production.
Conclusions:
- IFN-gamma induces apoptosis in macrophages via TNFR1 and caspase-8.
- IFN-gamma simultaneously activates macrophages, promoting MCP-1 overproduction.
- These dual effects suggest IFN-gamma plays a role in atherosclerosis development and progression.