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Nonalcoholic fatty liver disease (NAFLD) is a progressive liver disease with ever-growing incidence in the industrialized world. It starts with the simple accumulation of lipids in the hepatocyte and can progress to the more severe nonalcoholic steatohepatitis (NASH), which is associated with inflammation, fibrosis, and cirrhosis. There is increasing awareness that reactive oxygen species and electrophiles are implicated in the pathogenesis of NASH. Transcription factor nuclear factor erythroid 2-related factor 2 (Nrf2) is a positive regulator of the expression of a battery of genes involved in the protection against oxidative/electrophilic stress. In rodents, Nrf2 is also known to participate in hepatic fatty acid metabolism, as a negative regulator of genes that promote hepatosteatosis. We review relevant evidence in the literature that these two mechanisms may contribute to the protective role of Nrf2 in the development of hepatic steatosis and in the progression to steatohepatitis, particularly in young animals. We propose that age may be a key to explain contradictory findings in the literature. In summary, Nrf2 mediates the crosstalk between lipid metabolism and antioxidant defense mechanisms in experimental models of NAFLD, and the nutritional or pharmacological induction of Nrf2 represents a promising potential new strategy for its prevention and treatment.

Malaria and iron deficiency are major global health problems with extensive epidemiological overlap. Iron deficiency-induced anaemia can protect the host from malaria by limiting parasite growth. On the other hand, iron deficiency can significantly disrupt immune cell function. However, the impact of host cell iron scarcity beyond anaemia remains elusive in malaria. To address this, we employed a transgenic mouse model carrying a mutation in the transferrin receptor ( Tfrc Y20H/Y20H ), which limits the ability of cells to internalise iron from plasma. At homeostasis Tfrc Y20H/Y20H mice appear healthy and are not anaemic. However, Tfrc Y20H/Y20H mice infected with Plasmodium chabaudi chabaudi AS showed significantly higher peak parasitaemia and body weight loss. We found that Tfrc Y20H/Y20H mice displayed a similar trajectory of malaria-induced anaemia as wild-type mice, and elevated circulating iron did not increase peak parasitaemia. Instead, P . chabaudi infected Tfrc Y20H/Y20H mice had an impaired innate and adaptive immune response, marked by decreased cell proliferation and cytokine production. Moreover, we demonstrated that these immune cell impairments were cell-intrinsic, as ex vivo iron supplementation fully recovered CD4 + T cell and B cell function. Despite the inhibited immune response and increased parasitaemia, Tfrc Y20H/Y20H mice displayed mitigated liver damage, characterised by decreased parasite sequestration in the liver and an attenuated hepatic immune response. Together, these results show that host cell iron scarcity inhibits the immune response but prevents excessive hepatic tissue damage during malaria infection. These divergent effects shed light on the role of iron in the complex balance between protection and pathology in malaria.

Iron is critical for life but toxic in excess because of iron-catalysed formation of pro-oxidants that cause tissue damage in a range of disorders. The transcription factor nuclear factor erythroid 2-related factor 2 (Nrf2) orchestrates cell-intrinsic protective antioxidant responses, while the peptide hormone hepcidin maintains systemic iron homoeostasis, but is pathophysiologically decreased in haemochromatosis and β-thalassaemia. Here, we show that Nrf2 is activated by iron-induced, mitochondria-derived pro-oxidants and drives bone morphogenetic protein 6 (Bmp6) expression in liver sinusoidal endothelial cells, which in turn increases hepcidin synthesis by neighbouring hepatocytes. In Nrf2 knockout mice, the Bmp6–hepcidin response to oral and parenteral iron is impaired, and iron accumulation and hepatic damage are increased. Pharmacological activation of Nrf2 stimulates the Bmp6–hepcidin axis, improving iron homoeostasis in haemochromatosis and counteracting the inhibition of Bmp6 by erythroferrone in β-thalassaemia. We propose that Nrf2 links cellular sensing of excess toxic iron to the control of systemic iron homoeostasis and antioxidant responses, and may be a therapeutic target for iron-associated disorders. Iron homoeostasis is tightly orchestrated to avoid toxic iron overload. Here Lim and colleagues show that iron excess activates Nrf2 via mitochondrial reactive oxygen species, enhancing the expression of Bmp6 in liver sinusoidal endothelial cells, which in turn promotes hepcidin expression by hepatocytes, decreasing systemic iron levels.

Background Colorectal cancer (CRC) is the third most commonly diagnosed cancer and the second deadliest malignancy worldwide. Current dietary habits are associated with increased levels of iron and heme, both of which increase the risk of developing CRC. The harmful effects of iron overload are related to the induction of iron-mediated pro-tumorigenic pathways, including carcinogenesis and hyperproliferation. On the other hand, iron deficiency may also promote CRC development and progression by contributing to genome instability, therapy resistance, and diminished immune responses. In addition to the relevance of systemic iron levels, iron-regulatory mechanisms in the tumor microenvironment are also believed to play a significant role in CRC and to influence disease outcome. Furthermore, CRC cells are more prone to escape iron-dependent cell death (ferroptosis) than non-malignant cells due to the constitutive activation of antioxidant genes expression. There is wide evidence that inhibition of ferroptosis may contribute to the resistance of CRC to established chemotherapeutic regimens. As such, ferroptosis inducers represent promising therapeutic drugs for CRC. Conclusions and perspectives This review addresses the complex role of iron in CRC, particularly in what concerns the consequences of iron excess or deprivation in tumor development and progression. We also dissect the regulation of cellular iron metabolism in the CRC microenvironment and emphasize the role of hypoxia and of oxidative stress ( e.g. ferroptosis) in CRC. Finally, we underline some iron-related players as potential therapeutic targets against CRC malignancy.

Iron overload (IOL) is hypothesized to contribute to dysplastic erythropoiesis. Several conditions, including myelodysplastic syndrome, thalassemia and sickle cell anemia, are characterized by ineffective erythropoiesis and IOL. Iron is pro-oxidant and may participate in the pathophysiology of these conditions by increasing genomic instability and altering the microenvironment. There is, however, lack of in vivo evidence demonstrating a role of IOL and oxidative damage in dysplastic erythropoiesis. NRF2 transcription factor is the master regulator of antioxidant defenses, playing a crucial role in the cellular response to IOL in the liver. Here, we crossed Nrf2 −/− with hemochromatosis ( Hfe −/− ) or hepcidin-null ( Hamp1 −/− ) mice. Double-knockout mice developed features of ineffective erythropoiesis and myelodysplasia including macrocytic anemia, splenomegaly, and accumulation of immature dysplastic bone marrow (BM) cells. BM cells from Nrf2 / Hamp1 −/− mice showed increased in vitro clonogenic potential and, upon serial transplantation, recipients disclosed cytopenias, despite normal engraftment, suggesting defective differentiation. Unstimulated karyotype analysis showed increased chromosome instability and aneuploidy in Nrf2 / Hamp1 −/− BM cells. In HFE-related hemochromatosis patients, NRF2 promoter SNP rs35652124 genotype TT (predicted to decrease NRF2 expression) associated with increased MCV, consistent with erythroid dysplasia. Our results suggest that IOL induces ineffective erythropoiesis and dysplastic hematologic features through oxidative damage in Nrf2-deficient cells.

Iron is critical for life but toxic in excess because of iron-catalysed formation of pro-oxidants that cause tissue damage in a range of disorders. The Nrf2 transcription factor orchestrates cell-intrinsic protective antioxidant responses, and the peptide hormone hepcidin maintains systemic iron homeostasis, but is pathophysiologically decreased in haemochromatosis and beta-thalassaemia. Here, we show that Nrf2 is activated by iron-induced, mitochondria-derived pro-oxidants and drives Bmp6 expression in liver sinusoid endothelial cells, which in turn increases hepcidin synthesis by neighbouring hepatocytes. In Nrf2 knockout mice, the Bmp6-hepcidin response to oral and parenteral iron is impaired and iron accumulation and hepatic damage are increased. Pharmacological activation of Nrf2 stimulates the Bmp6-hepcidin axis, improving iron homeostasis in haemochromatosis and counteracting the inhibition of Bmp6 by erythroferrone in beta-thalassaemia. We propose that Nrf2 links cellular sensing of excess toxic iron to control of systemic iron homeostasis and antioxidant responses, and may be a therapeutic target for iron-associated disorders.

Malaria and iron deficiency are major global health problems with extensive epidemiological overlap. Iron deficiency-induced anaemia can protect the host from malaria by limiting parasite growth. On the other hand, iron deficiency can significantly disrupt immune cell function. However, the impact of host cell iron scarcity beyond anaemia remains elusive in malaria. To address this, we employed a transgenic mouse model carrying a mutation in the transferrin receptor (TfrcY20H/Y20H), which limits the ability of cells to internalise iron from plasma. At homeostasis TfrcY20H/Y20H mice appear healthy and are not anaemic. However, TfrcY20H/Y20H mice infected with Plasmodium chabaudi chabaudi AS showed significantly higher peak parasitaemia and body weight loss. We found that TfrcY20H/Y20H mice displayed a similar trajectory of malaria-induced anaemia as wild-type mice, and elevated circulating iron did not increase peak parasitaemia. Instead, P. chabaudi infected TfrcY20H/Y20H mice had an impaired innate and adaptive immune response, marked by decreased cell proliferation and cytokine production. Moreover, we demonstrated that these immune cell impairments were cell-intrinsic, as ex vivo iron supplementation fully recovered CD4 T cell and B cell function. Despite the inhibited immune response and increased parasitaemia, TfrcY20H/Y20H mice displayed mitigated liver damage, characterised by decreased parasite sequestration in the liver and an attenuated hepatic immune response. Together, these results show that host cell iron scarcity inhibits the immune response but prevents excessive hepatic tissue damage during malaria infection. These divergent effects shed light on the role of iron in the complex balance between protection and pathology in malaria.Competing Interest StatementThe authors have declared no competing interest.

Abstract Acute myeloid leukemia (AML) is a heterogeneous disease with poor prognosis and limited treatment strategies. Determining the role of cell-extrinsic regulators of leukemic cells is vital to gain clinical insights into the biology of AML. Iron is a key extrinsic regulator of cancer but its systemic regulation remains poorly explored in AML. To address this question, we studied iron metabolism in AML patients at diagnosis and mechanisms involved using the syngeneic MLL-AF9-induced AML mouse model. We found that AML is a disorder with a unique iron profile not associated with inflammation or transfusion and characterized by high ferritin, low transferrin, high transferrin saturation (TSAT), and high hepcidin. The increased TSAT in particular, contrasts with observations in other cancer types and in anemia of inflammation. Using the MLL-AF9 mouse model of AML, we demonstrated that leukemic blasts take up iron and that the AML-induced loss of erythroblasts is responsible for iron redistribution and an increase in TSAT. We also show that elevated TSAT at diagnosis is independently associated with increased overall survival in AML and suggest that TSAT may be a relevant prognostic marker in AML. Competing Interest Statement The authors have declared no competing interest.

Patient-derived xenografts (PDX) are valuable tools to model human disease and test new therapies. Here, we report, for the first time, a PDX model recapitulating the unique characteristics of a VEXAS patient (unique patient number UPN1).

Discrepancies between subjective and objective measures of total sleep time (TST) are frequent among insomnia patients, but this issue remains scarcely investigated in obstructive sleep apnea (OSA). We aimed to evaluate if sleep perception is affected by the severity of OSA. We performed a 3-month cross-sectional study of Brazilian adults undergoing overnight polysomnography (PSG). TST was objectively assessed from PSG and by a self-reported questionnaire (subjective measurement). Sleep perception index (SPI) was defined by the ratio of subjective and objective values. Diagnosis of OSA was based on an apnea/hypopnea index (AHI) [greater than or equal to] 5.0/h, being its severity classified according to AHI thresholds: 5.0-14.9/h (mild OSA), 15.0-29.9/h (moderate OSA), and [greater than or equal to] 30.0/h (severe OSA). Overall, 727 patients were included (58.0% males). A significant difference was found in SPI between non-OSA and OSA groups (p = 0.014). Mean SPI values significantly decreased as the OSA severity increased: without OSA (100.1 ± 40.9%), mild OSA (95.1 ± 24.6%), moderate OSA (93.5 ± 25.2%), and severe OSA (90.6 ± 28.2%), p = 0.036. Using logistic regression, increasing SPI was associated with a reduction in the likelihood of presenting any OSA (p = 0.018), moderate/severe OSA (p = 0.019), and severe OSA (p = 0.028). However, insomnia was not considered as an independent variable for the presence of any OSA, moderate/severe OSA, and severe OSA (all p-values > 0.05). In a clinical referral cohort, SPI significantly decreases with increasing OSA severity, but is not modified by the presence of insomnia symptoms.