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Identification of a novel macrophage phenotype that develops in response to atherogenic phospholipids via Nrf2.

ABSTRACT: Macrophages change their phenotype and biological functions depending on the microenvironment. In atherosclerosis, oxidative tissue damage accompanies chronic inflammation; however, macrophage phenotypic changes in response to oxidatively modified molecules are not known.To examine macrophage phenotypic changes in response to oxidized phospholipids that are present in atherosclerotic lesions.We show that oxidized phospholipid-treated murine macrophages develop into a novel phenotype (Mox) that is strikingly different from the conventional M1 and M2 macrophage phenotypes. Compared to M1 and M2, Mox macrophages show a different gene expression pattern, as well as decreased phagocytotic and chemotactic capacity. Treatment with oxidized phospholipids induces both M1 and M2 macrophages to switch to the Mox phenotype. Whole-genome expression array analysis and subsequent gene ontology clustering revealed that the Mox phenotype was characterized by abundant overrepresentation of Nrf2-mediated expression of redox-regulatory genes. In macrophages isolated from Nrf2(-/-) mice, oxidized phospholipid-induced gene expression and regulation of redox status were compromised. Moreover, we found that Mox macrophages comprise 30% of all macrophages in advanced atherosclerotic lesions of low-density lipoprotein receptor knockout (LDLR(-/-)) mice.Together, we identify Nrf2 as a key regulator in the formation of a novel macrophage phenotype (Mox) that develops in response to oxidative tissue damage. The unique biological properties of Mox macrophages suggest this phenotype may play an important role in atherosclerotic lesion development as well as in other settings of chronic inflammation.

SUBMITTER: Kadl A

PROVIDER: S-EPMC2941538 | biostudies-literature | 2010 Sep

REPOSITORIES: biostudies-literature

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Identification of a novel macrophage phenotype that develops in response to atherogenic phospholipids via Nrf2.

Kadl Alexandra A Meher Akshaya K AK Sharma Poonam R PR Lee Monica Y MY Doran Amanda C AC Johnstone Scott R SR Elliott Michael R MR Gruber Florian F Han Jenny J Chen Wenshu W Kensler Thomas T Ravichandran Kodi S KS Isakson Brant E BE Wamhoff Brian R BR Leitinger Norbert N

Circulation research 20100722 6

<h4>Rationale</h4>Macrophages change their phenotype and biological functions depending on the microenvironment. In atherosclerosis, oxidative tissue damage accompanies chronic inflammation; however, macrophage phenotypic changes in response to oxidatively modified molecules are not known.<h4>Objective</h4>To examine macrophage phenotypic changes in response to oxidized phospholipids that are present in atherosclerotic lesions.<h4>Methods and results</h4>We show that oxidized phospholipid-treate ...[more]

PMID: 20651288

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Project description:BackgroundMany neurological diseases involve neuroinflammation, during which overproduction of cytokines by immune cells, especially microglia, can aggregate neuronal death. Ferroptosis is a recently discovered cell metabolism-related form of cell death and RSL3 is a well-known inducer of cell ferroptosis. Here, we aimed to investigate the effects of RSL3 in neuroinflammation and sensitivity of different type of microglia and macrophage to ferroptosis.MethodsHere, we used quantitative RT-PCR analysis and ELISA analysis to analyze the production of proinflammatory cytokine production of microglia and macrophages after lipopolysaccharides (LPS) stimulation. We used CCK8, LDH, and flow cytometry analysis to evaluate the sensitivity of different microglia and macrophages to RSL3-induced ferroptosis. Western blot was used to test the activation of inflammatory signaling pathway and knockdown efficiency. SiRNA-mediated interference was conducted to knockdown GPX4 or Nrf2 in BV2 microglia. Intraperitoneal injection of LPS was performed to evaluate systemic inflammation and neuroinflammation severity in in vivo conditions.ResultsWe found that ferroptosis inducer RSL3 inhibited lipopolysaccharides (LPS)-induced inflammation of microglia and peritoneal macrophages (PMs) in a cell ferroptosis-independent manner, whereas cell ferroptosis-conditioned medium significantly triggered inflammation of microglia and PMs. Different type of microglia and macrophages showed varied sensitivity to RSL3-induced ferroptosis. Mechanistically, RSL3 induced Nrf2 protein expression to inhibit RNA Polymerase II recruitment to transcription start site of proinflammatory cytokine genes to repress cytokine transcription, and protect cells from ferroptosis. Furthermore, simultaneously injection of RSL3 and Fer-1 ameliorated LPS-induced neuroinflammation in in vivo conditions.ConclusionsThese data revealed the proinflammatory role of ferroptosis in microglia and macrophages, identified RSL3 as a novel inhibitor of LPS-induced inflammation, and uncovered the molecular regulation of microglia and macrophage sensitivity to ferroptosis. Thus, targeting ferroptosis in diseases by using RSL3 should consider both the pro-ferroptosis effect and the anti-inflammation effect to achieve optimal outcome.

Dataset Information

Identification of a novel macrophage phenotype that develops in response to atherogenic phospholipids via Nrf2.

Publications

Identification of a novel macrophage phenotype that develops in response to atherogenic phospholipids via Nrf2.

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