Macrophage Iron Metabolism Research Articles

Iron-laden macrophage-mediated paracrine profibrotic signaling induces lung fibroblast activation.

Idiopathic pulmonary fibrosis (IPF) is a devastating condition characterized by progressive lung scarring and uncontrolled fibroblast proliferation, inevitably leading to organ dysfunction and mortality. Although elevated iron levels have been observed in patients and animal models of lung fibrosis, the mechanisms linking iron dysregulation to lung fibrosis pathogenesis, particularly the role of macrophages in orchestrating this process, remain poorly elucidated. Here we evaluate iron metabolism in macrophages during pulmonary fibrosis using both in vivo and in vitro approaches. In murine bleomycin- and amiodarone-induced pulmonary fibrosis models, we observed significant iron deposition and lipid peroxidation in pulmonary macrophages. Intriguingly, the ferroptosis regulator glutathione peroxidase 4 (GPX4) was upregulated in pulmonary macrophages following bleomycin instillation, a finding corroborated by single-cell RNA sequencing analysis. Moreover, macrophages isolated from fibrotic mouse lungs exhibited increased transforming growth factor (TGF)-β1 expression that correlated with lipid peroxidation. In vitro, iron overload in bone marrow-derived macrophages triggered lipid peroxidation and TGF-β1 upregulation, which was effectively suppressed by ferroptosis inhibitors. When cocultured with iron-overloaded macrophages, lung fibroblasts exhibited heightened activation, evidenced by increased α-smooth muscle actin and fibronectin expression. Importantly, this profibrotic effect was attenuated by treating macrophages with a ferroptosis inhibitor or blocking TGF-β receptor signaling in fibroblasts. Collectively, our study elucidates a novel mechanistic paradigm in which the accumulation of iron within macrophages initiates lipid peroxidation, thereby amplifying TGF-β1 production, subsequently instigating fibroblast activation through paracrine signaling. Thus, inhibiting iron overload and lipid peroxidation warrants further exploration as a strategy to suppress fibrotic stimulation by disease-associated macrophages. NEW & NOTEWORTHY This study investigates the role of iron in pulmonary fibrosis, specifically focusing on macrophage-mediated mechanisms. Iron accumulation in fibrotic lung macrophages triggers lipid peroxidation and an upregulation of transforming growth factor (TGF)-β1 expression. Coculturing iron-laden macrophages activates lung fibroblasts in a TGF-β1-dependent manner, which can be mitigated by ferroptosis inhibitors. These findings underscore the potential of targeting iron overload and lipid peroxidation as a promising strategy to alleviate fibrotic stimulation provoked by disease-associated macrophages.

A Multifunctional Tissue-Engineering Hydrogel Aimed to Regulate Bacterial Ferroptosis-Like Death and Overcoming Infection Toward Bone Remodeling.

Infection is the most common complication after orthopedic surgery and can result in prolonged ailments such as chronic wounds, enlarged bone defects, and osteomyelitis. Iron, which is essential for bacterial metabolism and immune cell functions, is extremely important. Bacteria harness iron from nearby cells to promote biofilm formation, ensuring their survival. Iron deficiency within the infection microenvironment (IME) consequently hampers macrophage function, enabling further dissemination of the infection and hindering macrophage polarization to the M2 phenotype. Therefore, a novel approach is proposed to regulate macrophage polarization, aiming to restore the inflammatory immune environment. A composite hydrogel derived from natural polymers is developed to address infections and manage iron metabolism in macrophages. This IME-responsive hydrogel, named FCL-ECMH, is synthesized by encapsulating vermiculite functional core layers within a decellularized extracellular matrix hydrogel. It is noteworthy that FCL-ECMH can produce reactive oxygen species within the IME. Supplementary photothermal treatment enhances bacterial iron uptake, leading to ferroptosis-like death. This process also rejuvenates the iron-enriched macrophages around the IME, thereby enhancing their antibacterial and tissue repair functions. In vivo experiments confirmed the antibacterial and repair-promoting capabilities of FCL-ECMH, indicating its potential for clinical applications.

Methionine enkephalin (MENK) protected macrophages from ferroptosis by downregulating HMOX1 and ferritin

ObjectiveThe aim of this work was to investigate the immunological effect of MENK by analyzing the protein spectrum and bioinformatics of macrophage RAW264.7, and to explore the relationship between macrophage and ferroptosis.ResultWe employed proteomic analysis to identify differentially expressed proteins (DEPs) between macrophages and macrophages intervened by MENK. A total of 208 DEPs were identified. Among these, 96 proteins had upregulated expression and 112 proteins had downregulated expression. Proteomic analysis revealed a significant enrichment of DEPs associated with iron metabolism. The identification of hub genes was conducted using KEGG pathway diagrams and protein-protein interaction (PPI) analysis. The hub genes identified in this study include HMOX1 and Ferritin (FTH and FTL). A correlation was established between HMOX1, FTH, and FTL in the GO and KEGG databases. The results of PCR, WB and immunofluorescence showed that MENK downregulated the level of HMOX1 and FTH.ConclusionMENK had the potential to become an adjuvant chemotherapy drug by regulating iron metabolism in macrophages, reducing levels of HMOX1 and ferritin. We proposed an innovative research direction on the therapeutic potential of MENK, focusing on the relationship between ferroptosis and macrophage activity.

Heme oxygenase-1 increases intracellular iron storage and suppresses inflammatory response of macrophages by inhibiting M1 polarization.

Heme oxygenase-1 (HO-1) catalyzes the first and rate-limiting enzymatic step of heme degradation, producing carbon monoxide, biliverdin, and free iron. Most iron is derived from aged erythrocytes by the decomposition of heme, which happened mainly in macrophages. However, the role of HO-1 on iron metabolism and function of macrophage is unclear. The present study investigated the effect of HO-1 on iron metabolism in macrophages, and explored the role of HO-1 on inflammatory response, polarization, and migration of macrophages. HO-1 inducer Hemin or HO-1 inhibitor zinc protoporphyrin was intravenously injected to C57BL/6J mice every 4 d for 28 d. We found that HO-1 was mainly located in the cytoplasm of splenic macrophages of mice. Activation of HO-1 by Hemin significantly increased iron deposition in the spleen, up-regulated the gene expression of ferritin and ferroportin, and down-regulated gene expression of divalent metal transporter 1 and hepcidin. Induced HO-1 by Hemin treatment increased intracellular iron levels of macrophages, slowed down the absorption of extracellular iron, and accelerated the excretion of intracellular iron. In addition, activation of HO-1 significantly decreased the expression of pro-inflammatory cytokines including interleukin (IL)-6, IL-1β, and inducible nitric oxide synthase, but increased the expression of anti-inflammatory cytokines such as IL-10. Furthermore, activation of HO-1 inhibited macrophages to M1-type polarization, and increased the migration rate of macrophages. This study demonstrated that HO-1 was able to regulate iron metabolism, exert anti-inflammatory effects, and inhibit macrophages polarization to M1 type.

Cardiac iron metabolism during aging – Role of inflammation and proteolysis

Iron is the most abundant trace element in the human body. Since iron can switch between its 2-valent and 3-valent form it is essential in various physiological processes such as energy production, proliferation or DNA synthesis. Especially high metabolic organs such as the heart rely on iron-associated iron-sulfur and heme proteins. However, due to switches in iron oxidation state, iron overload exhibits high toxicity through formation of reactive oxygen species, underlining the importance of balanced iron levels. Growing evidence demonstrates disturbance of this balance during aging. While age-associated cardiovascular diseases are often related to iron deficiency, in physiological aging cardiac iron accumulates. To understand these changes, we focused on inflammation and proteolysis, two hallmarks of aging, and their role in iron metabolism. Via the IL-6-hepcidin axis, inflammation and iron status are strongly connected often resulting in anemia accompanied by infiltration of macrophages. This tight connection between anemia and inflammation highlights the importance of the macrophage iron metabolism during inflammation. Age-related decrease in proteolytic activity additionally affects iron balance due to impaired degradation of iron metabolism proteins. Therefore, this review accentuates alterations in iron metabolism during aging with regards to inflammation and proteolysis to draw attention to their implications and associations.

Klebsiella pneumoniae manipulates human macrophages to acquire iron.

Klebsiella pneumoniae (KP) is a major cause of hospital-acquired infections, such as pneumonia. Moreover, it is classified as a pathogen of concern due to sprawling anti-microbial resistance. During infection, the gram-negative pathogen is capable of establishing an intracellular niche in macrophages by altering cellular metabolism. One factor critically affecting the host-pathogen interaction is the availability of essential nutrients, like iron, which is required for KP to proliferate but which also modulates anti-microbial immune effector pathways. We hypothesized, that KP manipulates macrophage iron homeostasis to acquire this crucial nutrient for sustained proliferation. We applied an in-vitro infection model, in which human macrophage-like PMA-differentiated THP1 cells were infected with KP (strain ATCC 43816). During a 24-h course of infection, we quantified the number of intracellular bacteria via serial plating of cell lysates and evaluated the effects of different stimuli on intracellular bacterial numbers and iron acquisition. Furthermore, we analyzed host and pathogen specific gene and protein expression of key iron metabolism molecules. Viable bacteria are recovered from macrophage cell lysates during the course of infection, indicative of persistence of bacteria within host cells and inefficient pathogen clearing by macrophages. Strikingly, following KP infection macrophages strongly induce the expression of the main cellular iron importer transferrin-receptor-1 (TFR1). Accordingly, intracellular KP proliferation is further augmented by the addition of iron loaded transferrin. The induction of TFR1 is mediated via the STAT-6-IL-10 axis, and pharmacological inhibition of this pathway reduces macrophage iron uptake, elicits bacterial iron starvation, and decreases bacterial survival. Our results suggest, that KP manipulates macrophage iron metabolism to acquire iron once confined inside the host cell and enforces intracellular bacterial persistence. This is facilitated by microbial mediated induction of TFR1 via the STAT-6-IL-10 axis. Mechanistic insights into immune metabolism will provide opportunities for the development of novel antimicrobial therapies.

Melittin regulates iron homeostasis and mediates macrophage polarization in rats with lumbar spinal stenosis

Lumbar spinal stenosis (LSS) is defined as spinal canal narrowing, resulting in the compression of the nerves traversing the lower back into the leg. Inflammation is the most common cause of LSS. Elevated iron stores are often associated with chronic inflammation resulting in nerve damage-induced pain. Macrophage polarization to either the M1 (inflammatory) or M2 (anti-inflammatory) type is essential for regulating host defenses and promoting tissue repair. However, the precise role of macrophage polarization in iron release or retention in LSS pathophysiology remains elusive. Melittin, a component of bee venom, modulates iron metabolism-related macrophage polarization and is beneficial in LSS. We treated primary peritoneal macrophages with melittin and assessed macrophage polarization by immunofluorescence staining. Melittin (100 and 250 µg/kg) effects on iron deposition-induced macrophage polarization were also evaluated using immunochemistry, real-time PCR, and flow cytometry in an LSS rat model. Locomotor function was assessed using the Basso–Beattie–Bresnahan (BBB) locomotor rating scale, ladder scoring, and von Frey test for up to 3 weeks. Melittin induced M2 polarization of iron-insulted primary macrophages in vitro and increased the proportion of M2 macrophages in the damaged spinal cord in vivo. Moreover, melittin attenuated iron overload-induced M1 polarization by regulating iron metabolism-related genes in rats with LSS. In conclusion, melittin improves locomotor recovery and stimulates axonal growth following LSS. Additionally, it promotes functional recovery in LSS rat models by regulating macrophage iron metabolism, thereby activating M2 macrophages, suggesting its potential application in LSS treatment.

The immunosuppression pathway of tumor-associated macrophages is controlled by heme oxygenase-1 in glioblastoma patients.

The immunosuppressive tumor microenvironment (TME) in glioblastoma (GBM) is mainly driven by tumor-associated macrophages (TAMs). We explored whether their sustained iron metabolism and immunosuppressive activity were correlated, and whether blocking the central enzyme of the heme catabolism pathway, heme oxygenase-1 (HO-1), could reverse their tolerogenic activity. To this end, we investigated iron metabolism in bone marrow-derived macrophages (BMDMs) isolated from GBM specimens and in in vitro-derived macrophages (Mφ) from healthy donor (HD) blood monocytes. We found that HO-1 inhibition abrogated the immunosuppressive activity of both BMDMs and Mφ, and that immunosuppression requires both cell-to-cell contact and soluble factors, as HO-1 inhibition abolished IL-10 release, and significantly reduced STAT3 activation as well as PD-L1 expression. Interestingly, not only did HO-1 inhibition downregulate IDO1 and ARG-2 gene expression, but also reduced IDO1 enzymatic activity. Moreover, T cell activation status affected PD-L1 expression and IDO1 activity, which were upregulated in the presence of activated, but not resting, T cells. Our results highlight the crucial role of HO-1 in the immunosuppressive activity of macrophages in the GBM TME and demonstrate the feasibility of reprogramming them as an alternative therapeutic strategy for restoring immune surveillance.

Crosstalk between Heme Oxygenase-1 and Iron Metabolism in Macrophages: Implications for the Modulation of Inflammation and Immunity.

Heme oxygenase-1 (HO-1) is an enzyme that catalyzes the degradation of heme, releasing equimolar amounts of carbon monoxide (CO), biliverdin (BV), and iron. The anti-inflammatory and antioxidant properties of HO-1 activity are conferred in part by the release of CO and BV and are extensively characterized. However, iron constitutes an important product of HO-1 activity involved in the regulation of several cellular biological processes. The macrophage-mediated recycling of heme molecules, in particular those contained in hemoglobin, constitutes the major mechanism through which living organisms acquire iron. This process is finely regulated by the activities of HO-1 and of the iron exporter protein ferroportin. The expression of both proteins can be induced or suppressed in response to pro- and anti-inflammatory stimuli in macrophages from different tissues, which alters the intracellular iron concentrations of these cells. As we discuss in this review article, changes in intracellular iron levels play important roles in the regulation of cellular oxidation reactions as well as in the transcriptional and translational regulation of the expression of proteins related to inflammation and immune responses, and therefore, iron metabolism represents a potential target for the development of novel therapeutic strategies focused on the modulation of immunity and inflammation.

Targeted autophagy disruption reveals the central role of macrophage iron metabolism in systemic iron homeostasis

AbstractIron homeostasis depends on both intracellular control through iron-responsive proteins and the systemic level of iron through hepcidin-ferroportin axis. Indeed, the hormone hepcidin downregulates the ferroportin iron exporter to control iron recycling from macrophages and iron uptake from enterocytes. Here, we focused on the role of autophagy in macrophage iron metabolism and systemic iron homeostasis. Mice deficient for autophagy in macrophages (LysM-Atg5−/−) mimicked a primary iron overload phenotype, resulting in high ferroportin expression in both macrophages and enterocytes that correlated with marked parenchymal iron overload. Furthermore, LysM-Atg5−/− mice exhibited increased hematopoietic activity with no sign of anemia but correlating with rather high plasma iron level. Compared with wild-type cells, bone marrow–derived macrophages from LysM-Atg5−/− mice had significantly increased ferroportin expression and decreased iron content, confirming high iron export. In erythrophagocytic macrophages, autophagy regulates hemosiderin storage mechanisms as well as degradation of ferroportin and subsequently its plasma membrane localization and iron export; furthermore, ferroportin colocalization with hepcidin indicates hepcidin autocrine activity. Relatively high hepatic hepcidin expression and decreased hepcidin level in the spleen of LysM-Atg5−/− mice, correlating with low hemosiderin iron storage, as well as in erythrophagocytic Atg5−/− macrophages were evidenced. Therefore, our results highlight the critical role of autophagy in macrophages for iron trafficking and systemic iron homeostasis. We propose that in macrophages, autophagy restricts ferroportin level and iron export, resulting in hepcidin expression with an autocrine-paracrine effect that plays a role in the regulation of ferroportin expression in duodenal enterocytes.

TAMI-43. IMPACT OF SEX AND RADIATION ON IRON TRAFFICKING IN BONE MARROW DERIVED MACROPHAGES

Abstract The tumor microenvironment in glioblastoma provides cancer cells with favorable conditions to proliferate and invade surrounding tissues. Macrophages comprise a large portion of the glioblastoma tumor microenvironment (TME) both in terms of volume and function. These cells have been reported to influence tumor progression by modulating immune responses, remodeling extracellular matrix, and providing nutrients to cancer cells among numerous other functions. Radiation therapy forms one of the pillars of glioblastoma management along with surgical resection and chemotherapy. Here we investigated the effects of radiation on macrophage iron metabolism. Using mouse bone-marrow-derived macrophages (BMDMs) we performed in-vitro 59Fe radiotracer assays to study how radiation exposure modified iron trafficking in these cells. We found that low dose radiation at 0.25, 0.5, or 2 Gy from a 60Co source stimulated iron release from the BMDMs with maximal release occurring at 0.5 Gy. Moreover, we observed that iron release was dependent on the amount of serum present in culture media with cells cultured in 20% fetal bovine serum (FBS) showing reduced iron release profiles compared to those cultured in 10% or 1% FBS. Since glioblastoma patients exhibit sexually dimorphic survival outcomes, we investigated whether these radiation-induced responses occurred in a sexually dimorphic pattern. At radiation doses of 0.25 Gy we observed that male macrophages tended to release more iron than female macrophages despite no differences in iron uptake between the sexes – raising the question as to whether differential iron trafficking in response to treatment contributes to the poorer survival outcomes observed in males. Our data suggest that delineating how supporting cells such as macrophages respond to glioblastoma treatment regimens may provide insights into addressing mechanisms of treatment resistance and further our understanding of the sexual dimorphism observed in patient outcomes.

Altered iron metabolism in cystic fibrosis macrophages: the impact of CFTR modulators and implications for Pseudomonas aeruginosa survival

Cystic fibrosis (CF) is a genetic disease caused by mutations in the CF transmembrane conductance regulator (CFTR) gene, resulting in chronic bacterial lung infections and tissue damage. CF macrophages exhibit reduced bacterial killing and increased inflammatory signaling. Iron is elevated in the CF lung and is a critical nutrient for bacteria, including the common CF pathogen Pseudomonas aeruginosa (Pa). While macrophages are a key regulatory component of extracellular iron, iron metabolism has yet to be characterized in human CF macrophages. Secreted and total protein levels were analyzed in non-CF and F508del/F508del CF monocyte derived macrophages (MDMs) with and without clinically approved CFTR modulators ivacaftor/lumacaftor. CF macrophage transferrin receptor 1 (TfR1) was reduced with ivacaftor/lumacaftor treatment. When activated with LPS, CF macrophage expressed reduced ferroportin (Fpn). After the addition of exogenous iron, total iron was elevated in conditioned media from CF MDMs and reduced in conditioned media from ivacaftor/lumacaftor treated CF MDMs. Pa biofilm formation and viability were elevated in conditioned media from CF MDMs and biofilm formation was reduced in the presence of conditioned media from ivacaftor/lumacaftor treated CF MDMs. Defects in iron metabolism observed in this study may inform host–pathogen interactions between CF macrophages and Pa.

Counter Regulation of Spic by NF-κB and STAT Signaling Controls Inflammation and Iron Metabolism in Macrophages

SUMMARYActivated macrophages must carefully calibrate their inflammatory responses to balance efficient pathogen control with inflammation-mediated tissue damage, but the molecular underpinnings of this “balancing act” remain unclear. Using genetically engineered mouse models and primary macrophage cultures, we show that Toll-like receptor (TLR) signaling induces the expression of the transcription factor Spic selectively in patrolling monocytes and tissue macrophages by a nuclear factor κB (NF-κB)-dependent mechanism. Functionally, Spic downregulates pro-inflammatory cytokines and promotes iron efflux by regulating ferroportin expression in activated macrophages. Notably, interferon-gamma blocks Spic expression in a STAT1-dependent manner. High levels of interferon-gamma are indicative of ongoing infection, and in its absence, activated macrophages appear to engage a “default” Spic-dependent anti-inflammatory pathway. We also provide evidence for the engagement of this pathway in sterile inflammation. Taken together, our findings uncover a pathway wherein counter-regulation of Spic by NF-κB and STATs attune inflammatory responses and iron metabolism in macrophages.

Salmonella effector SpvB interferes with intracellular iron homeostasis via regulation of transcription factor NRF2.

Iron is a necessary nutrient for humans and nearly all bacterial species. During Salmonella infection, macrophages limit the availability of iron to intracellular pathogens in one of the central components of nutritional immunity. However, Salmonella also have mechanisms to interfere with the antimicrobial effect of host iron withdrawal and meet their own nutrient requirements by scavenging iron from the host. Here, we provide what is, to our knowledge, the first report that SpvB, a pSLT-encoded cytotoxic protein whose function is associated with the intracellular stage of salmonellosis, perturbs macrophage iron metabolism, thereby facilitating Salmonella survival and intracellular replication. In investigating the underlying mechanism, we observed that the Salmonella effector SpvB down-regulated nuclear factor erythroid-derived 2-related factor 2 (NRF2), and its C-terminal domain was necessary and sufficient for NRF2 degradation via the proteasome pathway. Decreased NRF2 expression in the nucleus resulted in a decrease in its transcriptional target ferroportin, encoding the sole macrophage iron exporter, thus ultimately decreasing iron efflux and increasing the intracellular iron content. Additionally, SpvB contributes to the pathogenesis of Salmonella including severe serum hypoferremia, increased splenic and hepatic bacterial burden, and inflammatory injury in vivo. Together, our observations uncovered a novel contribution of SpvB to Salmonella pathology via interference with host intracellular iron metabolism.-Yang, S., Deng, Q., Sun, L., Dong, K., Li, Y., Wu, S., Huang, R. Salmonella effector SpvB interferes with intracellular iron homeostasis via regulation of transcription factor NRF2.

Glia maturation factor-γ regulates murine macrophage iron metabolism and M2 polarization through mitochondrial ROS

AbstractIn macrophages, cellular iron metabolism status is tightly integrated with macrophage phenotype and associated with mitochondrial function. However, how molecular events regulate mitochondrial activity to integrate regulation of iron metabolism and macrophage phenotype remains unclear. Here, we explored the important role of the actin-regulatory protein glia maturation factor-γ (GMFG) in the regulation of cellular iron metabolism and macrophage phenotype. We found that GMFG was downregulated in murine macrophages by exposure to iron and hydrogen peroxide. GMFG knockdown altered the expression of iron metabolism proteins and increased iron levels in murine macrophages and concomitantly promoted their polarization toward an anti-inflammatory M2 phenotype. GMFG-knockdown macrophages exhibited moderately increased levels of mitochondrial reactive oxygen species (mtROS), which were accompanied by decreased expression of some mitochondrial respiration chain components, including the iron-sulfur cluster assembly scaffold protein ISCU as well as the antioxidant enzymes SOD1 and SOD2. Importantly, treatment of GMFG-knockdown macrophages with the antioxidant N-acetylcysteine reversed the altered expression of iron metabolism proteins and significantly inhibited the enhanced gene expression of M2 macrophage markers, suggesting that mtROS is mechanistically linked to cellular iron metabolism and macrophage phenotype. Finally, GMFG interacted with the mitochondrial membrane ATPase ATAD3A, suggesting that GMFG knockdown–induced mtROS production might be attributed to alteration of mitochondrial function in macrophages. Our findings suggest that GMFG is an important regulator in cellular iron metabolism and macrophage phenotype and could be a novel therapeutic target for modulating macrophage function in immune and metabolic disorders.

Deferoxamine preconditioning ameliorates mechanical ventilation-induced lung injury in rat model via ROS in alveolar macrophages: a randomized controlled study

BackgroundMechanical ventilation (MV) can provide effective breathing support; however, ventilatior-induced lung injury (VILI) has also been widely recognized in clinical practice, including in the healthy lung. Unfortunately, the morbidity and mortality of VILI remain unacceptably high, and no satisfactory therapeutic effect can be achieved. The current study aimed to examine the effects of iron chelator preconditioning on the mitochondrial reactive oxygen species (ROS) in alveolar macrophages and pathological lung injury in VILI.MethodsTwenty four healthy male Sprague–Dawley (SD) rats (250–300 g in weight) were randomly divided into 3 groups, including the control group (NC group, n = 8), the high-volume mechanical ventilation group (HV group, n = 8), and the deferoxamine treatment group (HV + DFO group, n = 8). Rats in the HV and HV + DFO groups were subjected to high-volume MV at a dose of 40 ml/kg. DFO was administered at a dose of 200 mg/kg 15 min prior to over-ventilation. Spontaneously breathing anesthetized rats were used as the controls. The animals were sacrificed after 4 h of high-volume ventilation or under control conditions, the animals were sacrificed. Purified alveolar macrophages from bronchoalveolar lavage fluid (BALF) and lung tissue were collected for further analysis through light microscopy and flow cytometry.ResultsCompared with the controls, the high-volume-ventilated rats had exhibited typical lung edema and histological lung injury, and ROS were markedly increased in alveolar macrophages and mitochondria. Moreover, all indices of VILI were remarkably different in rats treated with DFO preconditioning. DFO could ameliorate lung injury in the mechanically ventilated SD rat model.ConclusionsDFO preconditioning contributes to mitigating the histological lung damage while reducing ROS levels in alveolar macrophages and mitochondria, suggesting that iron metabolism in alveolar macrophages may participate in VILI.

Time-course assessment of the aggregation and metabolization of magnetic nanoparticles.

Magnetic iron oxide nanoparticles have great potential for biomedical applications. It is however imperative that these nanoreagents preserve their magnetic properties once inoculated, and that their degradation products can be eliminated. When placed in a biological milieu nanoparticles can aggregate and this can affect their magnetic properties and their degradation. In this work, we showed that iron oxide nanoparticles trigger the iron metabolism in macrophages, the main cell type involved in iron homeostasis in the organism. We also show that aggregation can affect nanoparticle magnetic properties when inoculated in animal models. This work confirms iron oxide nanoparticle biocompatibility and highlights the necessity to assess in vivo nanoparticle aggregation to successfully develop biomedical applications.

Iron Reduces M1 Macrophage Polarization in RAW264.7 Macrophages Associated with Inhibition of STAT1.

Iron metabolism in inflammation has been mostly characterized in macrophages exposed to pathogens or inflammatory conditions. The aim of this study is to investigate the cross-regulatory interactions between M1 macrophage polarization and iron metabolism. Firstly, we characterized the transcription of genes related to iron homeostasis in M1 RAW264.7 macrophages stimulated by IFN-γ. The molecular signature of M1 macrophages showed high levels of iron storage (ferritin), a low level of iron export (ferroportin), and changes of iron regulators (hepcidin and transferrin receptors), which favour iron sequestration in the reticuloendothelial system and are benefit for inflammatory disorders. Then, we evaluated the effect of iron on M1 macrophage polarization. Iron significantly reduced mRNA levels of IL-6, IL-1β, TNF-α, and iNOS produced by IFN-γ-polarized M1 macrophages. Immunofluorescence analysis showed that iron also reduced iNOS production. However, iron did not compromise but enhanced the ability of M1-polarized macrophages to phagocytose FITC-dextran. Moreover, we demonstrated that STAT1 inhibition was required for reduction of iNOS and M1-related cytokines production by the present of iron. Together, these findings indicated that iron decreased polarization of M1 macrophages and inhibited the production of the proinflammatory cytokines. The results expanded our knowledge about the role of iron in macrophage polarization.

Iron gene expression profile in atherogenic Mox macrophages

RationaleThe role of macrophage iron in the physiopathology of atherosclerosis is an open question that needs to be clarified. In atherosclerotic lesions, recruited macrophages are submitted to cytokines and oxidized lipids which influence their phenotype. An important phenotypic population driven by oxidized phospholipids is the Mox macrophages which present unique biological properties but their iron phenotype is not well described. ObjectiveTo investigate the effect of Mox polarization by oxidized LDL (oxLDL) on macrophage iron metabolism in the absence or presence of proinflammatory stimuli. MethodsBone marrow-derived macrophages were treated with different sources of LDL and/or LPS/IFNγ (M1 activator). Expression of ferroportin (Slc40a1, alias Fpn), heme oxygenase-1 (Hmox1), H- and L-ferritin (Fth1 and Ftl1), hepcidin (Hamp), ceruloplasmin (Cp) and interleukine-6 (Il6) was followed by quantitative PCR. FPN and HMOX1 protein expression was analyzed by immunofluorescence and in-cell-Western blotting. ResultsMox macrophages expressed increased Hmox1 and Fth1 levels with basal FPN protein levels despite the significant increase of Fpn mRNA. Upregulation of Hmox1 and Fpn mRNA was specific to LDL oxidative modification and mediated by NRF2. The downregulation of both Cp isoforms and the upregulation of Hamp expression observed in Mox macrophages suggest that FPN mediated iron export could be compromised. Simultaneous exposure to oxLDL and LPS/IFNγ leads to a mixed Mox/M1 phenotype that is closer to M1. ConclusionA microenvironment rich in oxLDL and proinflammatory cytokines could promote macrophage iron retention and lipid accumulation profiles, a specific cell phenotype that likely contributes to lesion development and plaque instability in atherosclerosis.

Superparamagnetic iron oxide nanoparticle uptake alters M2 macrophage phenotype, iron metabolism, migration and invasion

Superparamagnetic iron oxide nanoparticles (SPIONs) have shown promise as contrast agents and nanocarriers for drug delivery. Their impact on M2-polarised macrophages has nonetheless not been well studied. Here we explored the effects of SPIONs coated with dimercaptosuccinic acid, aminopropyl silane or aminodextran in two M2 macrophage models (murine primary IL-4-activated bone marrow-derived macrophages and human M2-like differentiated THP-1 cells). All SPIONs were internalised and no cell toxicity was observed. SPION treatment produced reactive oxygen species and activated the extracellular signal-regulated kinase and AKT pathways. After 24-h SPION incubation, M2 macrophages switched their iron metabolism towards an iron-replete state. SPION treatment in both M2 macrophage models altered their M2 activation profiles, promoted IL-10 production, and stimulated protease-dependent invasion. These results highlight the need to evaluate the interactions between SPIONs and cells to take full advantage of the intrinsic properties of these nanoparticles in biological systems. From the Clinical EditorSuperparamagnetic iron oxide nanoparticles (SPIONs) have been used as an MRI contrast agent in many experimental studies. The authors here investigated the effects of these nanoparticles on M2 macrophages after cellular uptake. The findings of cell activation further enhanced our current knowledge on the interaction of SPIONS with macrophages.