Macrophages in sensing and executing ferroptosis

点击翻译按钮获取中文摘要

Ferroptosis is characterized by lipid peroxidation and its iron dependency. Whereas several tumor cell lines are highly vulnerable to ferroptosis inducers, primary human macrophages are basically inert to this form of regulated cell death. Pilot data show that hypoxia as well as RSL3 increase the expression of iron storage proteins in macrophages such as ferritin heavy (FTH), iron export proteins, i.e. ferroportin (FPN) and ceruloplasmin (CP), which causes iron oxidation and export. We hypothesize that the increased ability to store or export iron protects macrophages from ferroptosis. Experimentally, we alter the ability of macrophages to store and/or export iron by knocking down FTH, FPN, and/or CP to increase their ferroptosis vulnerability. The relationship between iron storage and the ability to enter ferroptotic cell death pathways will be analyzed under hypoxia vs. normoxia as well as for classically vs. alternatively polarized macrophages, because these conditions are known to alter cellular iron metabolism. In the tumor microenvironment, macrophages may deliver iron to tumor cells and support their growth. We hypothesize that this ability sensitizes tumor cells to ferroptosis. We will test our hypothesis in 3D tumor models using wild-type macrophages compared to cells with an attenuated ability to deliver iron to tumor cells. Referring to the ability of macrophages to increase iron storage and thus, to gain ferroptosis resistance under hypoxia, which naturally occurs in 3D tumor models, macrophages with a knockdown of FTH, FPN, or CP will be used in 3D culture with the intention to kill not only tumor cells but also macrophages by ferrroptosis. The professional phagocytotic capacity of macrophages makes them the primary cell to move to, to recognize, and to ingest dying cells, respectively to respond to signals generated by dying cells. This is of particular importance in the tumor microenvironment, where dying tumor cells shape the phenotype of macrophages. At present it is largely unknown how ferroptotic cells interact with macrophages. Thus, we analyze how ferroptotic cells signal towards macrophages and study “find-me”, “eat-me”, and “don’t eat-me” signals of ferroptotic cells by using lipidomics, metabolomics, and proteomics. By these methods, we intend to unravel alterations in redox signaling cascades, in the secretome of ferroptotic cells, and finally their implications on macrophages. This will be followed in 2D and 3D culture using spheroids and organoids with monocytes/macrophage infiltration to mimic a preclinical relevant tumor model. We aim at investigating how macrophages regulate their sensitivity to ferroptosis by adjusting iron metabolism and how ferroptotic tumor cells polarize macrophages. Understanding these basic mechanisms will be critical to propose ferroptosis as a tool for tumor therapy.