This review summarizes current and prior observations regarding transfusion-related immunomodulation (TRIM) and puts these ideas into a modern immunological context, incorporating concepts from ...innate, adaptive, and nutritional immunity. We propose that TRIM research focus on determining whether there are specific, well-defined immunosuppressive effects from transfusing 'pure' red blood cells (RBCs) themselves, along with the by-products produced by the stored RBCs as a result of the 'storage lesion.' Macrophages are a key cell type involved in physiological and pathological RBC clearance and iron recycling. The plasticity and diversity of macrophages makes these cells potential mediators of immune suppression that could constitute TRIM.
Recent reports identified the capacity of macrophages and monocytes to exhibit 'memory.' Exposure to various stimuli, such as engulfment of apoptotic cells and interactions with ß-glucan and lipopolysaccharide, were found to induce epigenetic, metabolic, and functional changes in certain myeloid cells, particularly macrophages and monocytes.
Macrophages may mediate the immunosuppressive aspects of TRIM that arise as a result of transfused RBCs and their storage lesion induced by-products.
The SARS-CoV-2 beta coronavirus is the etiological driver of COVID-19 disease, which is primarily characterized by shortness of breath, persistent dry cough, and fever. Because they transport oxygen, ...red blood cells (RBCs) may play a role in the severity of hypoxemia in COVID-19 patients. The present study combines state-of-the-art metabolomics, proteomics, and lipidomics approaches to investigate the impact of COVID-19 on RBCs from 23 healthy subjects and 29 molecularly diagnosed COVID-19 patients. RBCs from COVID-19 patients had increased levels of glycolytic intermediates, accompanied by oxidation and fragmentation of ankyrin, spectrin beta, and the N-terminal cytosolic domain of band 3 (AE1). Significantly altered lipid metabolism was also observed, in particular, short- and medium-chain saturated fatty acids, acyl-carnitines, and sphingolipids. Nonetheless, there were no alterations of clinical hematological parameters, such as RBC count, hematocrit, or mean corpuscular hemoglobin concentration, with only minor increases in mean corpuscular volume. Taken together, these results suggest a significant impact of SARS-CoV-2 infection on RBC structural membrane homeostasis at the protein and lipid levels. Increases in RBC glycolytic metabolites are consistent with a theoretically improved capacity of hemoglobin to off-load oxygen as a function of allosteric modulation by high-energy phosphate compounds, perhaps to counteract COVID-19-induced hypoxia. Conversely, because the N-terminus of AE1 stabilizes deoxyhemoglobin and finely tunes oxygen off-loading and metabolic rewiring toward the hexose monophosphate shunt, RBCs from COVID-19 patients may be less capable of responding to environmental variations in hemoglobin oxygen saturation/oxidant stress when traveling from the lungs to peripheral capillaries and vice versa.
Macrophages play important roles in recycling iron derived from the clearance of red blood cells (RBCs). They are also a critically important component of host defense, protecting against invading ...pathogens. However, the effects on macrophage biology of acutely ingesting large numbers of RBCs are not completely understood. To investigate this issue, we used a mouse model of RBC transfusion and clearance, which mimics the clinical setting. In this model, transfusions of refrigerator storage-damaged (ie, “old”) RBCs led to increased erythrophagocytosis by splenic red pulp macrophages (RPMs). This robust erythrophagocytosis induced ferroptosis, an iron-dependent form of cell death, in RPMs. This was accompanied by increases in reactive oxygen species and lipid peroxidation in vivo, which were reduced by treatment in vitro with ferrostatin-1, a ferroptosis inhibitor. Old RBC transfusions also induced RPM-dependent chemokine expression by splenic Ly6Chi monocytes, which signaled Ly6Chi monocyte migration from bone marrow to spleen, where these cells subsequently differentiated into RPMs. The combination of cell division among remaining splenic RPMs, along with the influx of bone marrow–derived Ly6Chi monocytes, suggests that, following RPM depletion induced by robust erythrophagocytosis, there is a coordinated effort to restore homeostasis of the RPM population by local self-maintenance and contributions from circulating monocytes. In conclusion, these findings may be clinically relevant to pathological conditions that can arise as a result of increased erythrophagocytosis, such as transfusion-related immunomodulation and impaired host immunity.
•Transfusions of storage-damaged RBCs induce an RPM-dependent inflammatory response by splenic Ly6Chi monocytes.•Macrophages undergo ferroptosis following increased erythrophagocytosis and are replaced by circulating monocytes and local cell division.
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Emily Cooley was a highly regarded medical technologist and morphologist. The “Emily Cooley Lectureship and Award” was established to honor her, in particular, and medical technologists, in general. ...This article reviews some basic concepts about the “life of a red blood cell” (RBC) and uses these to discuss the actual and potential consequences that occur in patients after clearance of transfused refrigerator storage–damaged RBCs by extravascular hemolysis.
In the mid-20th century, Hemolytic Disease of the Fetus and Newborn, caused by maternal alloimmunization to the Rh(D) blood group antigen expressed by fetal red blood cells (i.e., "Rh disease"), was ...a major cause of fetal and neonatal morbidity and mortality. However, with the regulatory approval, in 1968, of IgG anti-Rh(D) immunoprophylaxis to prevent maternal sensitization, the prospect of eradicating Rh disease was at hand. Indeed, the combination of antenatal and post-partum immunoprophylaxis is ~99% effective at preventing maternal sensitization to Rh(D). To investigate global compliance with this therapeutic intervention, we used an epidemiological approach to estimate the current annual number of pregnancies worldwide involving an Rh(D)-negative mother and an Rh(D)-positive fetus. The annual number of doses of anti-Rh(D) IgG required for successful immunoprophylaxis for these cases was then calculated and compared with an estimate of the annual number of doses of anti-Rh(D) produced and provided worldwide. Our results suggest that ~50% of the women around the world who require this type of immunoprophylaxis do not receive it, presumably due to a lack of awareness, availability, and/or affordability, thereby putting hundreds of thousands of fetuses and neonates at risk for Rh disease each year. The global failure to provide this generally acknowledged standard-of-care to prevent Rh disease, even 50 years after its availability, contributes to an enormous, continuing burden of fetal and neonatal disease and provides a critically important challenge to the international health care system.
Hypoxanthine catabolism
is potentially dangerous as it fuels production of urate and, most importantly, hydrogen peroxide. However, it is unclear whether accumulation of intracellular and supernatant ...hypoxanthine in stored red blood cell units is clinically relevant for transfused recipients. Leukoreduced red blood cells from glucose-6-phosphate dehydrogenase-normal or -deficient human volunteers were stored in AS-3 under normoxic, hyperoxic, or hypoxic conditions (with oxygen saturation ranging from <3% to >95%). Red blood cells from healthy human volunteers were also collected at sea level or after 1-7 days at high altitude (>5000 m). Finally, C57BL/6J mouse red blood cells were incubated
with
C
-aspartate or
C
-adenosine under normoxic or hypoxic conditions, with or without deoxycoformycin, a purine deaminase inhibitor. Metabolomics analyses were performed on human and mouse red blood cells stored for up to 42 or 14 days, respectively, and correlated with 24 h post-transfusion red blood cell recovery. Hypoxanthine increased in stored red blood cell units as a function of oxygen levels. Stored red blood cells from human glucose-6-phosphate dehydrogenase-deficient donors had higher levels of deaminated purines. Hypoxia
and
decreased purine oxidation and enhanced purine salvage reactions in human and mouse red blood cells, which was partly explained by decreased adenosine monophosphate deaminase activity. In addition, hypoxanthine levels negatively correlated with post-transfusion red blood cell recovery in mice and - preliminarily albeit significantly - in humans. In conclusion, hypoxanthine is an
metabolic marker of the red blood cell storage lesion that negatively correlates with post-transfusion recovery
Storage-dependent hypoxanthine accumulation is ameliorated by hypoxia-induced decreases in purine deamination reaction rates.
BACKGROUNDReprogramming of host metabolism supports viral pathogenesis by fueling viral proliferation, by providing, for example, free amino acids and fatty acids as building blocks.METHODSTo ...investigate metabolic effects of SARS-CoV-2 infection, we evaluated serum metabolites of patients with COVID-19 (n = 33; diagnosed by nucleic acid testing), as compared with COVID-19-negative controls (n = 16).RESULTSTargeted and untargeted metabolomics analyses identified altered tryptophan metabolism into the kynurenine pathway, which regulates inflammation and immunity. Indeed, these changes in tryptophan metabolism correlated with interleukin-6 (IL-6) levels. Widespread dysregulation of nitrogen metabolism was also seen in infected patients, with altered levels of most amino acids, along with increased markers of oxidant stress (e.g., methionine sulfoxide, cystine), proteolysis, and renal dysfunction (e.g., creatine, creatinine, polyamines). Increased circulating levels of glucose and free fatty acids were also observed, consistent with altered carbon homeostasis. Interestingly, metabolite levels in these pathways correlated with clinical laboratory markers of inflammation (i.e., IL-6 and C-reactive protein) and renal function (i.e., blood urea nitrogen).CONCLUSIONIn conclusion, this initial observational study identified amino acid and fatty acid metabolism as correlates of COVID-19, providing mechanistic insights, potential markers of clinical severity, and potential therapeutic targets.FUNDINGBoettcher Foundation Webb-Waring Biomedical Research Award; National Institute of General and Medical Sciences, NIH; and National Heart, Lung, and Blood Institute, NIH.
Macaques are emerging as a critical animal model in transfusion medicine, because of their evolutionary similarity to humans and perceived utility in discovery and translational science. However, ...little is known about the metabolism of Rhesus macaque red blood cells (RBC) and how this compares to human RBC metabolism under standard blood banking conditions. Metabolomic and lipidomic analyses, and tracing experiments with 1,2,3-
C
glucose, were performed using fresh and stored RBC (sampled weekly until storage day 42) obtained from Rhesus macaques (n=20) and healthy human volunteers (n=21). These results were further validated with targeted quantification against stable isotope-labeled internal standards. Metabolomic analyses demonstrated inter-species differences in RBC metabolism independent of refrigerated storage. Although similar trends were observed throughout storage for several metabolic pathways, species- and sex-specific differences were also observed. The most notable differences were in glutathione and sulfur metabolites, purine and lipid oxidation metabolites, acylcarnitines, fatty acyl composition of several classes of lipids (including phosphatidylserines), glyoxylate pathway intermediates, and arginine and carboxylic acid metabolites. Species-specific dietary and environmental compounds were also detected. Overall, the results suggest an increased basal and refrigerator-storage-induced propensity for oxidant stress and lipid remodeling in Rhesus macaque RBC cells, as compared to human red cells. The overlap between Rhesus macaque and human RBC metabolic phenotypes suggests the potential utility of a translational model for simple RBC transfusions, although inter-species storage-dependent differences need to be considered when modeling complex disease states, such as transfusion in trauma/hemorrhagic shock models.
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