Hana Manceau

Background & Aims: Hyperferritinemia frequently remains unexplained despite comprehensive evaluation. We conducted a sequencing‐based exome association study to identify genetic variants associated with plasma ferritin levels in patients with unexplained hyperferritinemia. Methods: Gene‐based association testing using the combined multivariate and collapsing method with Bayesian inference was performed in patients referred for clinical exome sequencing ( n = 392) after excluding known causes of hyperferritinemia. Findings were validated in an independent replication cohort ( n = 263). Functional studies included Muc13 knockout mice, intestinal cell models, proteomic analysis, and site‐directed mutagenesis. Results: The MUC13 p.Arg503Ser variant showed extreme Bayesian evidence for association with increased plasma ferritin, iron, and transferrin saturation in the homozygous state. In the replication cohort, the homozygous 503Ser genotype was the strongest independent predictor of elevated transferrin saturation (odds ratio, 4.52; 95% CI, 1.55–13.19; p = 0.006). Conversely, Muc13 knockout mice exhibited lower plasma iron and transferrin saturation, consistent with a role for MUC13 in intestinal iron absorption. In human intestinal cells, MUC13 knockdown reduced ferric iron uptake, whereas MUC13 overexpression increased it. Proteomic analysis identified integrin alpha 6 and integrin beta 4 as MUC13‐associated candidates. Cells expressing the homozygous 503Ser variant showed higher cell surface MUC13 expression and increased ferritin heavy chain 1, calreticulin, and nuclear factor erythroid 2‐related factor 2 levels after iron exposure. Conclusions: These findings support a role for MUC13 in intestinal ferric iron absorption and a causal link between the MUC13 homozygous 503Ser genotype and enhanced cellular iron uptake, which could contribute to a better understanding of unexplained hyperferritinemia.

Cerebral malaria (CM), the most lethal complication of Plasmodium falciparum severe malaria (SM), remains fatal for 15–25% of affected children despite the availability of treatment. P. falciparum infects and multiplies in erythrocytes, contributing to anemia, parasite sequestration, and inflammation. An unbiased proteomic assessment of infected erythrocytes and plasma samples from 24 Beninese children was performed to study the complex mechanisms underlying CM. A significant down-regulation of proteins from the ubiquitin–proteasome pathway and an up-regulation of the erythroid precursor marker transferrin receptor protein 1 ( TFRC ) were associated with infected erythrocytes from CM patients. At the plasma level, the samples clustered according to clinical presentation. Significantly, increased levels of the 20S proteasome components were associated with SM. Targeted quantification assays confirmed these findings on a larger cohort ( n = 340). These findings suggest that parasites causing CM preferentially infect reticulocytes or erythroblasts and alter their maturation. Importantly, the host plasma proteome serves as a specific signature of SM and presents a remarkable opportunity for developing innovative diagnostic and prognostic biomarkers.

Reversible atransferrinemia in a patient with chronic enteropathy: is transferrin mandatory for iron transport?

Iron deficiency is a significant comorbidity of heart failure (HF), defined as the inability of the myocardium to provide sufficient blood flow. However, iron deficiency remains insufficiently detected. Iron-deficiency anemia, defined as a decrease in hemoglobin caused by iron deficiency, is a late consequence of iron deficiency, and the symptoms of iron deficiency, which are not specific, are often confused with those of HF or comorbidities. HF patients with iron deficiency are often rehospitalized and present reduced survival. The correction of iron deficiency in HF patients is associated with improved functional capacity, quality of life, and rehospitalization rates. Because of the inflammation associated with chronic HF, which complicates the picture of nutritional deficiency, only the parenteral route can bypass the tissue sequestration of iron and the inhibition of intestinal iron absorption. Given the negative impact of iron deficiency on HF progression, the frequency and financial implications of rehospitalizations due to decompensation episodes, and the efficacy of this supplementation, screening for this frequent comorbidity should be part of routine testing in all HF patients. Indeed, recent European guidelines recommend screening for iron deficiency (serum ferritin and transferrin saturation coefficient) in all patients with suspected HF, regular iron parameters assessment in all patients with HF, and intravenous iron supplementation in symptomatic patients with proven deficiency. We thus aim to summarize all currently available data regarding this common and easily improvable comorbidity.

Background: Severe acute respiratory syndrome caused by the novel coronavirus (SARS-CoV-2) is frequently associated with gastrointestinal manifestations. Herein we evaluated the interest in measuring the intestinal fatty acid-binding protein (I-FABP), a biomarker of intestinal injury, in COVID-19 patients. Methods: Serum I-FABP was analyzed in 28 consecutive patients hospitalized for a PCR-confirmed COVID-19, in 24 hospitalized patients with non-COVID-19 pulmonary diseases, and 79 patients admitted to the emergency room for abdominal pain. Results: I-FABP serum concentrations were significantly lower in patients with COVID-19, as compared to patients with non-COVID-19 pulmonary diseases [70.3 pg/mL (47–167.9) vs. 161.1 pg/mL (88.98–305.2), respectively, p = 0.008]. I-FABP concentrations in these two populations were significantly lower than in patients with abdominal pain without COVID-19 [344.8 pg/mL (268.9–579.6)]. I-FABP was neither associated with severity nor the duration of symptoms. I-FABP was correlated with polymorphonuclear cell counts. Conclusions: In this pilot study, we observed a low I-FABP concentration in COVID-19 patients either with or without gastrointestinal symptoms, of which the pathophysiological mechanisms and clinical impact remain to be established. Further explorations on a larger cohort of patients will be needed to unravel the molecular mechanism of such observation, including the effects of malabsorption and/or abnormal lipid metabolism.

Ferroptosis is an iron-dependent form of cell death characterized by intracellular lipid peroxide accumulation and redox imbalance. Ferroptosis shows specific biological and morphological features when compared to the other cell death patterns. The loss of lipid peroxide repair activity by glutathione peroxidase 4 (GPX4), the presence of redox-active iron and the oxidation of polyunsaturated fatty acid (PUFA)-containing phospholipids are considered as distinct fingerprints of ferroptosis. Several pathways, including amino acid and iron metabolism, ferritinophagy, cell adhesion, p53, Keap1/Nrf2 and phospholipid biosynthesis, can modify susceptibility to ferroptosis. Through the decades, various diseases, including acute kidney injury; cancer; ischemia–reperfusion injury; and cardiovascular, neurodegenerative and hepatic disorders, have been associated with ferroptosis. In this review, we provide a comprehensive analysis of the main biological and biochemical mechanisms of ferroptosis and an overview of chemicals used as inducers and inhibitors. Then, we report the contribution of ferroptosis to the spectrum of liver diseases, acute or chronic. Finally, we discuss the use of ferroptosis as a therapeutic approach against hepatocellular carcinoma, the most common form of primary liver cancer.

Background: 5‐Aminolevulinic acid (ALA) is the first precursor of heme biosynthesis pathway. The exogenous addition of ALA to cells leads to protoporphyrin IX (PPIX) accumulation that has been exploited in photodynamic diagnostic and photodynamic therapy. Several types of ALA transporters have been described depending on the cell type, but there was no clear entry pathway for erythroid cells. The 18 kDa translocator protein (TSPO) has been proposed to be involved in the transport of porphyrins and heme analogs.Results: ALA‐induced PPIX accumulation in erythroleukemia cells (UT‐7 and K562) was impaired by PK 11195, a competitive inhibitor of both transmembrane proteins TSPO (1 and 2). PK 11195 did not modify the activity of the enzymes of heme biosynthesis, suggesting that ALA entry at the plasma membrane was the limiting factor. In contrast, porphobilinogen (PBG)‐induced PPIX accumulation was not affected by PK 11195, suggesting that plasma membrane TSPO2 is a selective transporter of ALA. Overexpression of TSPO2 at the plasma membrane of erythroleukemia cells increased ALA‐induced PPIX accumulation, confirming the role of TSPO2 in the import of ALA into the cells.Conclusions: ALA‐induced PPIX accumulation in erythroid cells involves TSPO2 as a selective translocator through the plasma membrane.Significance: This is the first characterisation of molecular mechanisms involving a new actor in ALA transport in ALA‐induced PPIX accumulation in erythroleukemia cells, which could be inhibited by specific drug ligands.