Biology subjects

Zimring, J. C.

Publications and source records attributed to Zimring, J. C..

5 recordsLinked to original sources

bioRxiv2023

Reticulocytes in donor RBC units enhance RBC alloimmunization

Although red blood cell (RBC) transfusions save lives, some patients develop clinically-significant alloantibodies against donor blood group antigens, which then have adverse effects in multiple clinical settings. Few effective measures exist to prevent RBC alloimmunization and/or eliminate alloantibodies in sensitized patients. Donor-related factors may influence alloimmunization; thus, there is an unmet clinical need to identify which RBC units are immunogenic. Repeat volunteer blood donors and donors on iron supplements have elevated reticulocyte counts compared to healthy non-donors. Early reticulocytes retain mitochondria and other components, which may act as danger signals in immune responses. Herein, we tested whether reticulocytes in donor RBC units could enhance RBC alloimmunization. Using a murine model, we demonstrate that transfusing donor RBC units with increased reticulocyte frequencies dose-dependently increase RBC alloimmunization rates and alloantibody levels. Transfusing reticulocyte-rich RBC units was associated with increased RBC clearance from the circulation and a robust proinflammatory cytokine response. As compared to previously reported post-transfusion RBC consumption patterns, erythrophagocytosis from reticulocyte-rich units was increasingly performed by splenic B cells. These data suggest that reticulocytes in a donated RBC unit impact the quality of blood transfused, are targeted to a distinct compartment, and may be an underappreciated risk factor for RBC alloimmunization.

immunology↗

bioRxiv2022

Genome-wide metabolite quantitative trait loci analysis (mQTL) in red blood cells from volunteer blood donors

The Red Blood Cell (RBC)-Omics study, part of the larger NHLBI-funded Recipient Epidemiology and Donor Evaluation Study (REDS-III), aims to understand the genetic contribution to blood donor RBC characteristics. Previous work identified donor demographic, behavioral, genetic and metabolic underpinnings to blood donation, storage, and - to a lesser extent - transfusion outcomes, but none have yet linked the genetic and metabolic bodies of work. We performed a Genome-Wide Association (GWA) analysis using RBC-Omics study participants with generated untargeted metabolomics data to identify metabolite quantitative trait loci (mQTL) in RBCs. We performed GWA analyses of 382 metabolites in 243 individuals imputed using the 1000 Genomes Project phase 3 all-ancestry reference panel. Analyses were conducted using ProbABEL and adjusted for sex, age, donation center, number of whole blood donations in the past two years, and first ten principal components of ancestry. Our results identified 423 independent genetic loci associated with 132 metabolites (p < 5x10-8). Potentially novel locus-metabolite associations were identified for FLVCR1 and choline, and for LPCAT3 and the lysophosphatidylserine 16.0, 18.0, 18.1, and 18.2; these associations are supported by published rare disease and mouse studies. We also confirmed previous metabolite GWA results for associations including N(6)-Methyl-L-lysine and PYROXD2, and various carnitines and SLC22A16. Association between pyruvate levels and G6PD polymorphisms was validated in an independent cohort and novel murine models of G6PD deficiency (African and Mediterranean variants). We demonstrate that it is possible to perform metabolomics-scale GWA analyses with a modest, trans-ancestry sample size. Key pointsO_LIMetabolite heterogeneity in fresh (<14 day old) RBCs donated by volunteer donors is linked to genetic polymorphisms; C_LIO_LIWe report 2,831 high-confidence SNP-metabolite linkages (p < 5.0 x 10-8). Pyruvate levels in fresh RBCs are associated with glucose-6-phosphate dehydrogenase (G6PD) status C_LI

biochemistry↗

bioRxiv2021

Innate and adaptive immunity to transfused allogenic red blood cells in mice requires MyD88

Red blood cell (RBC) transfusion therapy is essential for the survival of patients with hematological disorders such as sickle cell anemia. A potentially fatal complication of transfusion is development of non-ABO alloantibodies to polymorphic RBC antigens, yet mechanisms of alloantibody formation remain unclear. Human and mouse RBCs acquire a "storage lesion" prior to transfusion, which in mice contributes to immunogenicity. We previously reported that mouse splenic dendritic cells (DCs) are required for RBC alloimmunization and are activated by sterile and leukoreduced mouse RBCs after storage. Yet how syngeneic RBCs activate innate immune pathways to induce DC activation is unknown. We now show that DC activation to transfused RBCs occurs regardless of alloantigen presence, suggesting that RBC damage induced during storage triggers innate immune receptors. We discovered an unexpected dependence of RBC alloimmunization on the Toll-like receptor (TLR) signaling adaptor molecule MyD88. TLRs are a class of pattern recognition receptors (PRRs) that regulate DC activation and signal through two adaptor molecules, MyD88 and TRIF. We show that the inflammatory cytokine response, DC activation, and the subsequent alloantibody response to transfused syngeneic RBCs require MyD88 but not TRIF, suggesting a restricted set of PRRs are responsible for sensing RBCs and triggering alloimmunization.

immunology↗

bioRxiv2021

Hematologic and systemic metabolic alterations due to Mediterranean type II G6PD deficiency in a novel murine model

Deficiency of Glucose 6 phosphate dehydrogenase (G6PD) is the single most common enzymopathy, present in approximately 400 million humans (e.g. 5% of humans). Its prevalence is hypothesized to be due to conferring resistance to malaria. However, G6PD deficiency also results in hemolytic sequelae from oxidant stress. Moreover, G6PD deficiency is associated with kidney disease, diabetes, pulmonary hypertension, immunological defects, and neurodegenerative diseases. To date, the only available mouse models have decreased levels of G6PD due to promoter mutations, but with stable G6PD. However, human G6PD mutations are missense mutations that result in decreased enzymatic stability. As such, this results in very low activity in red blood cells and platelets that cannot synthesize new protein. To generate a more accurate model, the human sequence for a severe form of G6PD deficiency (Med -) was knocked into the murine G6PD locus. As predicted, G6PD levels were extremely low in RBCs and deficient mice have increased hemolytic sequalae to oxidant stress. G6PD levels were mildly decreased in non-erythroid organs, consistent with what has been observed in humans. Juxtaposition of G6PD deficient and wild-type mice revealed altered lipid metabolism in multiple organ systems. Together, these findings both establish a new mouse model of G6PD deficiency that more accurately reflects human G6PD deficiency and also advance our basic understanding of altered metabolism in this setting.

biochemistry↗

bioRxiv2020

The interactome of the N-terminus of band 3 regulates red blood cell metabolism and storage quality

Band 3 (anion exchanger 1 - AE1) is the most abundant membrane protein in red blood cells (RBCs), the most abundant cell in the human body. A compelling model, based on indirect evidence, posits that - at high oxygen saturation - the N-term cytosolic domain of AE1 binds to and inhibits glycolytic enzymes, thus diverting metabolic fluxes to the pentose phosphate pathway to generate reducing equivalents. Dysfunction of this mechanism occurs during RBC aging or storage under blood bank conditions, suggesting a role for AE1 in the regulation of blood storage quality and efficacy of transfusion - a life-saving intervention for millions of recipients worldwide. Here we leverage two murine models carrying genetic ablations of AE1 to provide the first direct mechanistic evidence of its role in metabolic regulation and blood storage quality. Observations in mice phenocopied those in a human subject lacking expression of AE11-11 (band 3 Neapolis), while common polymorphisms in the region coding for AE11-56 increased susceptibility to osmotic hemolysis in healthy blood donors. Through thermal proteome profiling and cross-linking proteomics, we provide the first comprehensive analysis of the RBC interactome, with a focus on AE11-56 and validate recombinant AE1 interactions with glyceraldehyde 3-phosphate dehydrogenase (GAPDH). Finally, we show that incubation with a cell-penetrating AE11-56 peptide can rescue the metabolic defect in glutathione recycling and boost post-transfusion recoveries of stored RBCs from healthy human donors and genetically ablated mice, paving the way for the in vivo metabolic manipulation of RBCs facing oxidant stress - a landmark of many diseases. Key pointsO_LIGenetic ablation of N-term of band 3 results in significant metabolic aberrations and poor post-transfusion recoveries in mice and humans; C_LIO_LIStructural studies on the N-term of band 3 reveal a complex interactome with several enzymes, including GAPDH; C_LI

biochemistry↗