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Background Over the last few years, accumulating data have implicated a role for ferritin as a signaling molecule and direct mediator of the immune system. Hyperferritinemia is associated with a multitude of clinical conditions and with worse prognosis in critically ill patients. Discussion There are four uncommon medical conditions characterized by high levels of ferritin, namely the macrophage activation syndrome (MAS), adult onset Still’s disease (AOSD), catastrophic antiphospholipid syndrome (cAPS) and septic shock, that share a similar clinical and laboratory features, and also respond to similar treatments, suggesting a common pathogenic mechanism. Ferritin is known to be a pro-inflammatory mediator inducing expression of pro-inflammatory molecules, yet it has opposing actions as a pro-inflammatory and as an immunosuppressant. We propose that the exceptionally high ferritin levels observed in these uncommon clinical conditions are not just the product of the inflammation but rather may contribute to the development of a cytokine storm. Summary Here we review and compare four clinical conditions and the role of ferritin as an immunomodulator. We would like to propose including these four conditions under a common syndrome entity termed “Hyperferritinemic Syndrome”.

WDR45 plays an essential role in the early stage of autophagy. De novo heterozygous mutations in WDR45 have been known to cause β-propeller protein-associated neurodegeneration (BPAN), a subtype of neurodegeneration with brain iron accumulation (NBIA). Although BPAN patients display global developmental delay with intellectual disability, the neurodevelopmental pathophysiology of BPAN remains largely unknown. In the present study, we analyzed the physiological role of Wdr45 and pathophysiological significance of the gene abnormality during mouse brain development. Morphological and biochemical analyses revealed that Wdr45 is expressed in a developmental stage-dependent manner in mouse brain. Wdr45 was also found to be located in excitatory synapses by biochemical fractionation. Since WDR45 mutations are thought to cause protein degradation, we conducted acute knockdown experiments by in utero electroporation in mice to recapitulate the pathophysiological conditions of BPAN. Knockdown of Wdr45 caused abnormal dendritic development and synaptogenesis during corticogenesis, both of which were significantly rescued by co-expression with RNAi-resistant version of Wdr45. In addition, terminal arbors of callosal axons were less developed in Wdr45-deficient cortical neurons of adult mouse when compared to control cells. These results strongly suggest a pathophysiological significance of WDR45 gene abnormalities in neurodevelopmental aspects of BPAN.

Background Sirolimus, the therapy choice for lymphangioleiomyomatosis (LAM), displayed cytostatic but not cytocidal action, with disease recurrence after withdrawal. The aim of this study is to identify novel potential biomarkers and therapeutic strategies for LAM patients. Methods TMT-labeling proteomics was utilized for screening the differentially expressed proteins (DEPs) in the plasma of 10 LAM patients and 6 controls. Plasma levels of transferrin (TRF), ferritin (FRT) and beta2-microglobulin (B2M) were validated in a cohort of 30 LAM patients and 20 controls. The diagnostic efficacy of TRF with/without VEGF-D was assessed using ROC curve analysis. The therapeutic effects of a ferroptosis inducer artesunate (ART) were evaluated both in vitro Tsc2 − / − MEFs cells and in xenograft LAM models. Results Proteomics analysis revealed 132 DEPs between LAM patients and controls, which primarily enriched in the regulation of iron ion transport. LAM patients had decreased TRF, elevated FRT and B2M levels compared with controls in the confirmation cohort ( p  = 0.0386, p  = 0.0327 and p  = 0.0155, respectively) which independent with VEGF-D level or rapamycin therapy. TRF positively correlated with both FEV 1 % predicted ( r  = 0.4486, p  = 0.0251) and DLCO% predicted ( r  = 0.4018, p  = 0.0516) of LAM patients. The combination of TRF and VEGF-D showed superior diagnostic value compared to individual indicator. ART induced the ferroptosis and inhibited the growth in Tsc2 − / − MEFs cells. In LAM animal models, ART exerted anti-tumor effects without obvious adverse effect. Conclusions LAM patients exhibit abnormal iron metabolism independent of VEGF-D level. Ferroptosis inducer ART holds promise as a therapeutic novel approach for treating LAM.

Key Points Iron is essential but toxic. Mammals regulate systemic iron through acquisition and storage. Iron is absorbed in the gut and transported into plasma by an apical divalent metal transporter, DMT1, and a basolateral transporter, ferroportin. Only 1–2 mg of iron is absorbed per day in the gut. Most of the iron in the body is found as haem in red blood cells. Old red blood cells are ingested by macrophages and degraded; iron is then recycled back into plasma by ferroportin. Iron in plasma is carried by the protein transferrin, which provides a chelating environment in plasma and a delivery system to cells that express transferrin receptors. Iron in cells can be used for cellular processes or stored in the cytosolic protein ferritin. Levels of iron transporters, carriers and storage proteins are regulated transcriptionally and post-transcriptionally according to iron status. Hepcidin, a peptide hormone secreted by the liver, is the key molecule that regulates systemic iron metabolism by regulating iron entry into plasma. The transcription of hepcidin is tightly regulated by signalling molecules, which sense iron levels, oxygen levels and inflammation. Hepcidin binds to ferroportin, leading to ferroportin degradation and a consequent decrease in cellular iron export. Iron-overload diseases result from inappropriate iron acquisition in response to iron need. Excess iron can damage tissue, cause fibrosis and give rise to organ failure. Iron-deficiency disorders result in anaemia, which in turn give rise to poor oxygenation of tissue. Insight into the regulation of iron metabolism and iron-related diseases has occurred through genetics and the use of model organisms. Mammalian iron homeostasis is achieved through iron acquisition and storage. Intestinal iron absorption and macrophage-mediated recycling of iron from red blood cells are highly regulated. The discovery of iron transporters and insight into their regulation has provided important information about iron-related disorders. Mammalian iron homeostasis must be meticulously regulated so that this essential element is available for use, but at the same time prevented from promoting the formation of toxic radicals. Controlling the entry of iron into blood plasma is the main mechanism by which iron stores in the body are physiologically manipulated and regulated. Defects in iron acquisition at the cellular and systemic levels lead to human disorders, which involve either iron overload or iron deficiency. Discoveries of iron transporters and insights into their regulation have provided important information about iron metabolism and genetic iron disorders.

The peptide hormone hepcidin plays a central role in regulating dietary iron absorption and body iron distribution. Many human diseases are associated with alterations in hepcidin concentrations. The measurement of hepcidin in biological fluids is therefore a promising tool in the diagnosis and management of medical conditions in which iron metabolism is affected. We describe hepcidin structure, kinetics, function, and regulation. We moreover explore the therapeutic potential for modulating hepcidin expression and the diagnostic potential for hepcidin measurements in clinical practice. Cell-culture, animal, and human studies have shown that hepcidin is predominantly synthesized by hepatocytes, where its expression is regulated by body iron status, erythropoietic activity, oxygen tension, and inflammatory cytokines. Hepcidin lowers serum iron concentrations by counteracting the function of ferroportin, a major cellular iron exporter present in the membrane of macrophages, hepatocytes, and the basolateral site of enterocytes. Hepcidin is detected in biologic fluids as a 25 amino acid isoform, hepcidin-25, and 2 smaller forms, i.e., hepcidin-22 and -20; however, only hepcidin-25 has been shown to participate in the regulation of iron metabolism. Reliable assays to measure hepcidin in blood and urine by use of immunochemical and mass spectrometry methods have been developed. Results of proof-of-principle studies have highlighted hepcidin as a promising diagnostic tool and therapeutic target for iron disorders. However, before hepcidin measurements can be used in routine clinical practice, efforts will be required to assess the relevance of hepcidin isoform measurements, to harmonize the different assays, to define clinical decision limits, and to increase assay availability for clinical laboratories.

The ‘neurodegeneration with brain iron accumulation’ (NBIA) disease family entails movement or cognitive impairment, often with psychiatric features. To understand how iron loading affects the brain, we studied mice with disruption of two iron regulatory genes, hemochromatosis ( Hfe ) and transferrin receptor 2 ( Tfr2 ). Inductively coupled plasma atomic emission spectroscopy demonstrated increased iron in the Hfe −/− × Tfr2 mut brain ( P =0.002, n ≥5/group), primarily localized by Perls’ staining to myelinated structures. Western immunoblotting showed increases of the iron storage protein ferritin light polypeptide and microarray and real-time reverse transcription-PCR revealed decreased transcript levels ( P <0.04, n ≥5/group) for five other NBIA genes, phospholipase A2 group VI , fatty acid 2-hydroxylase , ceruloplasmin , chromosome 19 open reading frame 12 and ATPase type 13A2 . Apart from the ferroxidase ceruloplasmin, all are involved in myelin homeostasis; 16 other myelin-related genes also showed reduced expression ( P <0.05), although gross myelin structure and integrity appear unaffected ( P >0.05). Overlap ( P <0.0001) of differentially expressed genes in Hfe −/− × Tfr2 mut brain with human gene co-expression networks suggests iron loading influences expression of NBIA-related and myelin-related genes co-expressed in normal human basal ganglia. There was overlap ( P <0.0001) of genes differentially expressed in Hfe −/− × Tfr2 mut brain and post-mortem NBIA basal ganglia. Hfe −/− × Tfr2 mut mice were hyperactive ( P <0.0112) without apparent cognitive impairment by IntelliCage testing ( P >0.05). These results implicate myelin-related systems involved in NBIA neuropathogenesis in early responses to iron loading. This may contribute to behavioral symptoms in NBIA and hemochromatosis and is relevant to patients with abnormal iron status and psychiatric disorders involving myelin abnormalities or resistant to conventional treatments.

OBJECTIVE: Iron deficiency has been reported to elevate A1C levels apart from glycemia. We examined the influence of iron deficiency on A1C distribution among adults without diabetes. RESEARCH DESIGN AND METHODS: Participants included adults without self-reported diabetes or chronic kidney disease in the National Health and Nutrition Examination Survey 1999-2006 who were aged ≥18 years of age and had complete blood counts, iron studies, and A1C levels. Iron deficiency was defined as at least two abnormalities including free erythrocyte protoporphyrin >70 μg/dl erythrocytes, transferrin saturation <16%, or serum ferritin [less-than or equal to]15 μg/l. Anemia was defined as hemoglobin <13.5 g/dl in men and <12.0 g/dl in women. RESULTS: Among women (n = 6,666), 13.7% had iron deficiency and 4.0% had iron deficiency anemia. Whereas 316 women with iron deficiency had A1C ≥5.5%, only 32 women with iron deficiency had A1C ≥6.5%. Among men (n = 3,869), only 13 had iron deficiency and A1C ≥5.5%, and only 1 had iron deficiency and A1C ≥6.5%. Among women, iron deficiency was associated with a greater odds of A1C ≥5.5% (odds ratio 1.39 [95% CI 1.11-1.73]) after adjustment for age, race/ethnicity, and waist circumference but not with a greater odds of A1C ≥6.5% (0.79 [0.33-1.85]). CONCLUSIONS: Iron deficiency is common among women and is associated with shifts in A1C distribution from <5.5 to ≥5.5%. Further research is needed to examine whether iron deficiency is associated with shifts at higher A1C levels.

Aceruloplasminemia is a monogenic disease caused by mutations in the ceruloplasmin gene that result in loss of protein ferroxidase activity. Ceruloplasmin plays a role in iron homeostasis, and its activity impairment leads to iron accumulation in liver, pancreas, and brain. Iron deposition promotes diabetes, retinal degeneration, and progressive neurodegeneration. Current therapies mainly based on iron chelation, partially control systemic iron deposition but are ineffective on neurodegeneration. We investigated the potential of ceruloplasmin replacement therapy in reducing the neurological pathology in the ceruloplasmin‐knockout (CpKO) mouse model of aceruloplasminemia. CpKO mice were intraperitoneal administered for 2 months with human ceruloplasmin that was able to enter the brain inducing replacement of the protein levels and rescue of ferroxidase activity. Ceruloplasmin‐treated mice showed amelioration of motor incoordination that was associated with diminished loss of Purkinje neurons and reduced brain iron deposition, in particular in the choroid plexus. Computational analysis showed that ceruloplasmin‐treated CpKO mice share a similar pattern with wild‐type animals, highlighting the efficacy of the therapy. These data suggest that enzyme replacement therapy may be a promising strategy for the treatment of aceruloplasminemia. Synopsis Aceruloplasminemia (Acp) is a rare genetic disease caused by absence of ceruloplasmin (Cp) ferroxidase activity, which leads to iron accumulation in viscera and brain, inducing inter alia neurodegeneration. Cp replacement therapy is shown as a promising therapeutic avenue in the treatment of Acp. Two months treatment with human Cp allowed the protein to accumulate in the brain, where it exerted ferroxidase activity. Cp administration reduced the total iron content in the whole brain, and the iron accumulation found in choroid plexus epithelium. The treatment with Cp prevented the loss of Purkinje cells in the cerebellum. An improvement in motor coordination was observed at the end of Cp treatment. Cp replacement therapy was able to ameliorate the neurological symptoms and could be a promising treatment also in human aceruloplasminemia. Graphical Abstract Aceruloplasminemia (Acp) is a rare genetic disease caused by absence of ceruloplasmin (Cp) ferroxidase activity, which leads to iron accumulation in viscera and brain, inducing inter alia neurodegeneration. Cp replacement therapy is shown as a promising therapeutic avenue in the treatment of Acp.

This article is one of ten reviews selected from the Annual Update in Intensive Care and Emergency Medicine 2019. Other selected articles can be found online at https://www.biomedcentral.com/collections/annualupdate2019 . Further information about the Annual Update in Intensive Care and Emergency Medicine is available from http://www.springer.com/series/8901 .

Aceruloplasminemia is a rare autosomal recessive genetic disease characterized by mild microcytic anemia, diabetes, retinopathy, liver disease, and progressive neurological symptoms due to iron accumulation in pancreas, retina, liver, and brain. The disease is caused by mutations in the Ceruloplasmin (CP) gene that produce a strong reduction or absence of ceruloplasmin ferroxidase activity, leading to an impairment of iron metabolism. Most patients described so far are from Japan. Prompt diagnosis and therapy are crucial to prevent neurological complications since, once established, they are usually irreversible. Here, we describe the largest series of non-Japanese patients with aceruloplasminemia published so far, including 13 individuals from 11 families carrying 13 mutations in the CP gene (7 missense, 3 frameshifts, and 3 splicing mutations), 10 of which are novel. All missense mutations were studied by computational modeling. Clinical manifestations were heterogeneous, but anemia, often but not necessarily microcytic, was frequently the earliest one. This study confirms the clinical and genetic heterogeneity of aceruloplasminemia, a disease expected to be increasingly diagnosed in the Next-Generation Sequencing (NGS) era. Unexplained anemia with low transferrin saturation and high ferritin levels without inflammation should prompt the suspicion of aceruloplasminemia, which can be easily confirmed by low serum ceruloplasmin levels. Collaborative joint efforts are needed to better understand the pathophysiology of this potentially disabling disease.