Human STEAP3 mutations with no phenotypic red cell changes

Ferroptosis regulates hemolysis in stored murine and human red blood cells

Red blood cell (RBC) metabolism regulates hemolysis during aging in vivo and in the blood bank. Here, we leveraged a diversity outbred mouse population to map the genetic drivers of fresh/stored RBC metabolism and extravascular hemolysis upon storage and transfusion in 350 mice. We identify the ferrireductase Steap3 as a critical regulator of a ferroptosis-like process of lipid peroxidation. Steap3 polymorphisms were associated with RBC iron content, in vitro hemolysis, and in vivo extravascular hemolysis both in mice and 13,091 blood donors from the Recipient Epidemiology and Donor evaluation Study. Using metabolite Quantitative Trait Loci analyses, we identified a network of gene products (FADS1/2, EPHX2 and LPCAT3) - enriched in donors of African descent - associated with oxylipin metabolism in stored human RBCs and related to Steap3 or its transcriptional regulator, the tumor protein TP53. Genetic variants were associated with lower in vivo hemolysis in thousands of single-unit transfusion recipients.

Highlights

Steap3 regulates lipid peroxidation and extravascular hemolysis in 350 diversity outbred miceSteap3 SNPs are linked to RBC iron, hemolysis, vesiculation in 13,091 blood donorsmQTL analyses of oxylipins identified ferroptosis-related gene products FADS1/2, EPHX2, LPCAT3Ferroptosis markers are linked to hemoglobin increments in transfusion recipients.

Graphical abstract

Comprehensive Genomic Analysis Identifies a Diverse Landscape of Sideroblastic and Nonsideroblastic Iron-Related Anemias with Novel and Pathogenic Variants in an Iron-Deficient Endemic Setting

Inherited iron metabolism defects are possibly missed or underdiagnosed in iron-deficient endemic settings because of a lack of awareness or a methodical screening approach. Hence, we systematically evaluated anemia cases (2019 to 2021) based on clinical phenotype, normal screening tests (high-performance liquid chromatography, α gene sequencing, erythrocyte sedimentation rate, C-reactive protein, and tissue transglutaminase), and abnormal iron profile by targeted next-generation sequencing (26-gene panel) supplemented with whole-exome sequencing, multiplex ligation probe amplification/mitochondrial DNA sequencing, and chromosomal microarray. Novel variants in ALAS2, STEAP3, and HSPA9 genes were functionally validated. A total of 290 anemia cases were screened, and 41 (14%) enrolled for genomic testing as per inclusion criteria. Comprehensive genomic testing revealed pathogenic variants in 23 of 41 cases (56%). Congenital sideroblastic anemia was the most common diagnosis (14/23; 61%), with pathogenic variations in ALAS2 (n = 6), SLC25A38 (n = 3), HSPA9 (n = 2) and HSCB, SLC19A2, and mitochondrial DNA deletion (n = 1 each). Nonsideroblastic iron defects included STEAP3-related microcytic anemia (2/23; 8.7%) and hypotransferrenemia (1/23; 4.3%). A total of 6 of 22 cases (27%) revealed a non-iron metabolism gene defect on whole-exome sequencing. Eleven novel variants (including variants of uncertain significance) were noted in 13 cases. Genotype-phenotype correlation revealed a significant association of frameshift/nonsense/splice variants with lower presentation age (0.8 months versus 9 years; P < 0.01) compared with missense variants. The systematic evaluation helped uncover an inherited iron defect in 41% (17/41) of cases, suggesting the need for active screening and awareness for these rare diseases in an iron-deficient endemic population.

Erythrocyte metabolism

Our aim is to present an updated overview of the erythrocyte metabolism highlighting its richness and complexity. We have manually collected and connected the available biochemical pathways and integrated them into a functional metabolic map. The focus of this map is on the main biochemical pathways consisting of glycolysis, the pentose phosphate pathway, redox metabolism, oxygen metabolism, purine/nucleoside metabolism, and membrane transport. Other recently emerging pathways are also curated, like the methionine salvage pathway, the glyoxalase system, carnitine metabolism, and the lands cycle, as well as remnants of the carboxylic acid metabolism. An additional goal of this review is to present the dynamics of erythrocyte metabolism, providing key numbers used to perform basic quantitative analyses. By synthesizing experimental and computational data, we conclude that glycolysis, pentose phosphate pathway, and redox metabolism are the foundations of erythrocyte metabolism. Additionally, the erythrocyte can sense oxygen levels and oxidative stress adjusting its mechanics, metabolism, and function. In conclusion, fine-tuning of erythrocyte metabolism controls one of the most important biological processes, that is, oxygen loading, transport, and delivery.

Testosterone replacement therapy in blood donors modulates erythrocyte metabolism and susceptibility to hemolysis in cold storage

BACKGROUND

Red blood cells (RBCs) derived from patients who receive testosterone replacement therapy (TRT) may be considered eligible for component production and transfusion. The aim of this study was to identify testosterone-dependent changes in RBC metabolism and to evaluate its impact on susceptibility to hemolysis during cold storage.

STUDY DESIGN AND METHODS

We characterized stored RBCs from two cohorts of TRT patients who were matched with control donors (no TRT) based upon sex, age, and ethnicity. We further evaluated the impact of testosterone deficiency (orchiectomy) on RBC metabolism in FVB/NJ mice. RBC metabolites were quantified by ultra-high-pressure liquid chromatography-mass spectrometry. RBC storage stability was determined in RBC units from TRT and controls by quantifying storage, osmotic, and oxidative hemolysis.

RESULTS

Orchiectomy in mice was associated with significant (P < 0.05) changes in RBC metabolism as compared with intact males including increased levels of acyl-carnitines, long-chain fatty acids (eg, docosapentaenoic acids), arginine, and dopamine. Stored RBCs from TRT patients exhibited higher levels of pentose phosphate pathway metabolites, glutathione, and oxidized purines (eg, hypoxanthine), suggestive of increased activation of antioxidant pathways in this group. Further analyses indicated significant changes in free fatty acids and acyl-carnitines in response to testosterone therapies. With regard to hemolysis, TRT was associated with enhanced susceptibility to osmotic hemolysis. Correlation analyses identified acyl-carnitines as significant modifiers of RBC predisposition to osmotic and oxidative hemolysis.

CONCLUSIONS

These observations provide new insights into testosterone-mediated changes in RBC metabolome and biology that may impact the storage capacity and posttransfusion efficacy of RBCs from TRT donors.

Iron-dependent histone 3 lysine 9 demethylation controls B cell proliferation and humoral immune responses

Trace elements play important roles in human health, but little is known about their functions in humoral immunity. Here, we show an important role for iron in inducing cyclin E and B cell proliferation. We find that iron-deficient individuals exhibit a significantly reduced antibody response to the measles vaccine when compared to iron-normal controls. Mice with iron deficiency also exhibit attenuated T-dependent or T-independent antigen-specific antibody responses. We show that iron is essential for B cell proliferation; both iron deficiency and α-ketoglutarate inhibition could suppress cyclin E1 induction and S phase entry of B cells upon activation. Finally, we demonstrate that three demethylases, KDM2B, KDM3B and KDM4C, are responsible for histone 3 lysine 9 (H3K9) demethylation at the cyclin E1 promoter, cyclin E1 induction and B cell proliferation. Thus, our data reveal a crucial role of H3K9 demethylation in B cell proliferation, and the importance of iron in humoral immunity.

Protect, repair, destroy or sacrifice: a role of oxidative stress biology in inter-donor variability of blood storage?

Red blood cells (RBCs) have been historically regarded as a critical model to investigate cellular and oxidant stress biology. First of all, they are constantly exposed to oxidant stress, as their main function is to transport and deliver oxygen to tissues. Second, they are devoid of de novo protein synthesis capacity, which prevents RBCs from replacing irreversibly oxidised proteins with newly synthesised ones. As such, RBCs have evolved to (i) protect themselves from oxidant stress, in order to prevent oxidant damage from reactive species; (ii) repair oxidatively damaged proteins, through mechanisms that involve glutathione and one-carbon metabolism; (iii) destroy irreversibly oxidised proteins through proteasomal or protease-dependent degradation; and (iv) sacrifice membrane portions through mechanism of vesiculation. In this brief review we will summarize these processes and their relevance to RBC redox biology (within the context of blood storage), with a focus on how polymorphisms in RBC antioxidant responses could contribute to explaining the heterogeneity in the progression and severity of the RBC storage lesion that can be observed across the healthy donor population.

Targeting iron metabolism in drug discovery and delivery

Iron fulfils a central role in many essential biochemical processes in human physiology; thus, proper processing of iron is crucial. Although iron metabolism is subject to relatively strict physiological control, numerous disorders, such as cancer and neurodegenerative diseases, have recently been linked to deregulated iron homeostasis. Consequently, iron metabolism constitutes a promising and largely unexploited therapeutic target for the development of new pharmacological treatments for these diseases. Several iron metabolism-targeted therapies are already under clinical evaluation for haematological disorders, and these and newly developed therapeutic agents are likely to have substantial benefit in the clinical management of iron metabolism-associated diseases, for which few efficacious treatments are currently available.