NLRP12-PANoptosome activates PANoptosis and pathology in response to heme and PAMPs.

Cytosolic innate immune sensors are critical for host defense and form complexes, such as inflammasomes and PANoptosomes, that induce inflammatory cell death. The sensor NLRP12 is associated with infectious and inflammatory diseases, but its activating triggers and roles in cell death and inflammation remain unclear. Here, we discovered that NLRP12 drives inflammasome and PANoptosome activation, cell death, and inflammation in response to heme plus PAMPs or TNF. TLR2/4-mediated signaling through IRF1 induced Nlrp12 expression, which led to inflammasome formation to induce maturation of IL-1ß and IL-18. The inflammasome also served as an integral component of a larger NLRP12-PANoptosome that drove inflammatory cell death through caspase-8/RIPK3. Deletion of Nlrp12 protected mice from acute kidney injury and lethality in a hemolytic model. Overall, we identified NLRP12 as an essential cytosolic sensor for heme plus PAMPs-mediated PANoptosis, inflammation, and pathology, suggesting that NLRP12 and molecules in this pathway are potential drug targets for hemolytic and inflammatory diseases.

Iron scavenging and myeloid cell polarization.

Myeloid cells that populate all human organs and blood are a versatile class of innate immune cells. They are crucial for sensing and regulating processes as diverse as tissue homeostasis and inflammation and are frequently characterized by their roles in either regulating or promoting inflammation. Recent studies in cultured cells and mouse models highlight the role of iron in skewing the functional properties of myeloid cells in tissue damage and repair. Here, we review certain emerging concepts on how iron influences and determines myeloid cell polarization in the context of its uptake, storage, and metabolism, including in conditions such as multiple sclerosis (MS), sickle cell disease, and tumors.

A cholesterol-binding bacterial toxin provides a strategy for identifying a specific Scap inhibitor that blocks lipid synthesis in animal cells.

Lipid synthesis is regulated by the actions of Scap, a polytopic membrane protein that binds cholesterol in membranes of the endoplasmic reticulum (ER). When ER cholesterol levels are low, Scap activates SREBPs, transcription factors that upregulate genes for synthesis of cholesterol, fatty acids, and triglycerides. When ER cholesterol levels rise, the sterol binds to Scap, triggering conformational changes that prevent activation of SREBPs and halting synthesis of lipids. To achieve a molecular understanding of how cholesterol regulates the Scap/SREBP machine and to identify therapeutics for dysregulated lipid metabolism, cholesterol-mimetic compounds that specifically bind and inhibit Scap are needed. To accomplish this goal, we focused on Anthrolysin O (ALO), a pore-forming bacterial toxin that binds cholesterol with a specificity and sensitivity that is uncannily similar to Scap. We reasoned that a small molecule that would bind and inhibit ALO might also inhibit Scap. High-throughput screening of a ~300,000-compound library for ALO-binding unearthed one molecule, termed UT-59, which binds to Scap's cholesterol-binding site. Upon binding, UT-59 triggers the same conformation changes in Scap as those induced by cholesterol and blocks activation of SREBPs and lipogenesis in cultured cells. UT-59 also inhibits SREBP activation in the mouse liver. Unlike five previously reported inhibitors of SREBP activation, UT-59 is the only one that acts specifically by binding to Scap's cholesterol-binding site. Our approach to identify specific Scap inhibitors such as UT-59 holds great promise in developing therapeutic leads for human diseases stemming from elevated SREBP activation, such as fatty liver and certain cancers.

The complement alternative pathway in paroxysmal nocturnal hemoglobinuria: From a pathogenic mechanism to a therapeutic target.

Paroxysmal nocturnal hemoglobinuria (PNH) is a rare clonal, not malignant, hematological disease characterized by intravascular hemolysis, thrombophilia and bone marrow failure. While this latter presentation is due to a T-cell mediated auto-immune disorder resembling acquired aplastic anemia, the first two clinical presentations are largely driven by the complement pathway. Indeed, PNH is characterized by a broad impairment of complement regulation on affected cells, which is due to the lack of the complement regulators CD55 and CD59. The deficiency of these two proteins from PNH blood cells is due to the somatic mutation in the phosphatidylinositol N-acetylglucosaminyltransferase subunit A gene causing the disease, which impairs the surface expression of all proteins linked via the glycosylphosphatidylinositol anchor. The lack of the complement regulators CD55 and CD59 on PNH erythrocytes accounts for the hallmark of PNH, which is the chronic, complement-mediated intravascular hemolysis. This hemolysis results from the impaired regulation of the alternative pathway upstream in the complement cascade, as well as of the downstream terminal pathway. PNH represented the first indication for the development of anti-complement agents, and the therapeutic interception of the complement cascade at the level of C5 led to remarkable changes in the natural history of the disease. Nevertheless, the clinical use of an inhibitor of the terminal pathway highlighted the broader derangement of complement regulation in PNH, shedding light on the pivotal role of the complement alternative pathway. Here we review the current understanding of the role of the alternative pathway in PNH, including the emergence of C3-mediated extravascular hemolysis in PNH patients on anti-C5 therapies. These observations provide the rationale for the development of novel complement inhibitors for the treatment of PNH. Recent preclinical and clinical data on proximal complement inhibitors intercepting the alternative pathway with the aim of improving the treatment of PNH are discussed, together with their clinical implications which are animating a lively debate in the scientific community.

Neutrophils as drivers of vascular injury in sickle cell disease.

While neutrophils are the main effectors of protective innate immune responses, they are also key players in inflammatory pathologies. Sickle cell disease (SCD) is a genetic blood disorder in which red blood cells (RBCs) are constantly destroyed in the circulation which generates a highly inflammatory environment that culminates in vascular occlusions. Vaso-occlusion is the hallmark of SCD and a predictor of disease severity. Neutrophils initiate and propagate SCD-related vaso-occlusion through adhesive interactions with the activated and dysfunctional endothelium, sickle RBCs, and platelets, leading to acute and chronic complications that progress to irreversible organ damage and ultimately death. The use of SCD humanized mouse models, in combination with in vivo imaging techniques, has emerged as a fundamental tool to understand the dynamics of neutrophils under complex inflammatory contexts and their contribution to vascular injury in SCD. In this review, we discuss the various mechanisms by which circulating neutrophils sense and respond to the wide range of stimuli present in the blood of SCD patients and mice. We argue that the central role of neutrophils in SCD can be rationalized to develop targets for the management of clinical complications in SCD patients.

Discovering C3 targeting therapies for paroxysmal nocturnal hemoglobinuria: Achievements and pitfalls.

The treatment of paroxysmal nocturnal hemoglobinuria (PNH) was revolutionized by the introduction of the anti-C5 agent eculizumab, which resulted in sustained control of intravascular hemolysis, leading to transfusion avoidance and hemoglobin stabilization in at least half of all patients. Nevertheless, extravascular hemolysis mediated by C3 has emerged as inescapable phenomenon in PNH patients on anti-C5 treatment, frequently limiting its hematological benefit. More than 10 years ago we postulated that therapeutic interception of the complement cascade at the level of C3 should improve the clinical response in PNH. Compstatin is a 13-residue disulfide-bridged peptide binding to both human C3 and C3b, eventually disabling the formation of C3 convertases and thereby preventing complement activation via all three of its activating pathways. Several generations of compstatin analogs have been tested in vitro, and their clinical evaluation has begun in PNH and other complement-mediated diseases. Pegcetacoplan, a pegylated form of the compstatin analog POT-4, has been investigated in two phase I/II and one phase III study in PNH patients. In the phase III study, PNH patients with residual anemia already on eculizumab were randomized to receive either pegcetacoplan or eculizumab in a head-to-head comparison. At week 16, pegcetacoplan was superior to eculizumab in terms of hemoglobin change from baseline (the primary endpoint), as well as in other secondary endpoints tracking intravascular and extravascular hemolysis. Pegcetacoplan showed a good safety profile, even though breakthrough hemolysis emerged as a possible risk requiring additional attention. Here we review all the available data regarding this innovative treatment that has recently been approved for the treatment of PNH.

The serine protease inhibitor HAMpin-1 produced by the ectoparasite Hyalomma anatolicum salivary gland modulates the host complement system.

Ticks are notable vectors of diseases affecting both humans and animals, with Hyalomma anatolicum being of particular significance due to its wide distribution and capability to transmit a variety of pathogens, including Theileria annulata, and Crimean-Congo haemorrhagic fever (CCHF) virus. This study aimed to investigate the inhibitory effects of Hyalomma anatolicum salivary gland extract (HaSGE) and the identification of its key component on the complement system of the host's innate immune defense. We demonstrated that HaSGE exerts a dose-dependent inhibition on the complement activation in a host-specific manner. Mechanistic studies revealed that HaSGE interferes with blocking the deposition and cleavage of complement proteins C3 and C5, thus preventing the formation of the membrane attack complex (MAC). Further, we identified a serine protease inhibitor, HAMpin-1, from the HaSGE through proteomic analysis and characterized its structure, function, and interaction with complement proteins. HAMpin-1 exhibited potent inhibitory activity against chymotrypsin and cathepsin-G, and notably, it is the first serpin from ticks shown to inhibit the classical and lectin pathways of the complement system. The expression of HAMpin-1 was highest in the salivary glands, suggesting its crucial role in blood feeding and immune evasion. Our findings revealed one of the potential mechanisms employed by H. anatolicum to modulate host immune responses at the interface, offering new insights into tick-host interactions.

SLUSH peptides of the PSMß family enable Staphylococcus lugdunensis to use erythrocytes as a sole source of nutrient iron.

During infection, the host employs nutritional immunity to restrict access to iron. Staphylococcus lugdunensis has been recognized for its ability to utilize host-derived heme to overcome iron restriction. However, the mechanism behind this process involves the release of hemoglobin from erythrocytes, and the hemolytic factors of S. lugdunensis remain poorly understood. S. lugdunensis encodes four phenol-soluble modulins (PSMs), short peptides with hemolytic activity. The peptides SLUSH A, SLUSH B, and SLUSH C are ß-type PSMs, and OrfX is an α-type PSM. Our study shows the SLUSH locus to be essential for the hemolytic phenotype of S. lugdunensis. All four peptides individually exhibited hemolytic activity against human and sheep erythrocytes, but synergism with sphingomyelinase was observed exclusively against sheep erythrocytes. Furthermore, our findings demonstrate that SLUSH is crucial for allowing the utilization of erythrocytes as the sole source of nutritional iron and confirm the transcriptional regulation of SLUSH by Agr. Additionally, our study reveals that SLUSH peptides stimulate the human immune system. Our analysis identifies SLUSH as a pivotal hemolytic factor of S. lugdunensis and demonstrates its concerted action with heme acquisition systems to overcome iron limitation in the presence of host erythrocytes.

Megalin-related mechanism of hemolysis-induced acute kidney injury and the therapeutic strategy.

Hemolysis-induced acute kidney injury (AKI) is attributed to heme-mediated proximal tubule epithelial cell (PTEC) injury and tubular cast formation due to intratubular protein condensation. Megalin is a multiligand endocytic receptor for proteins, peptides, and drugs in PTECs and mediates the uptake of free hemoglobin and the heme-scavenging protein α1-microglobulin. However, understanding of how megalin is involved in the development of hemolysis-induced AKI remains elusive. Here, we investigated the megalin-related pathogenesis of hemolysis-induced AKI and a therapeutic strategy using cilastatin, a megalin blocker. A phenylhydrazine-induced hemolysis model developed in kidney-specific mosaic megalin knockout (MegKO) mice confirmed megalin-dependent PTEC injury revealed by the co-expression of kidney injury molecule-1 (KIM-1). In the hemolysis model in kidney-specific conditional MegKO mice, the uptake of hemoglobin and α1-microglobulin as well as KIM-1 expression in PTECs was suppressed, but tubular cast formation was augmented, likely due to the nonselective inhibition of protein reabsorption in PTECs. Quartz crystal microbalance analysis revealed that cilastatin suppressed the binding of megalin with hemoglobin and α1-microglobulin. Cilastatin also inhibited the specific uptake of fluorescent hemoglobin by megalin-expressing rat yolk sac tumor-derived L2 cells. In a mouse model of hemolysis-induced AKI, repeated cilastatin administration suppressed PTEC injury by inhibiting the uptake of hemoglobin and α1-microglobulin and also prevented cast formation. Hemopexin, another heme-scavenging protein, was also found to be a novel ligand of megalin, and its binding to megalin and uptake by PTECs in the hemolysis model were suppressed by cilastatin. Mass spectrometry-based semiquantitative analysis of urinary proteins in cilastatin-treated C57BL/6J mice indicated that cilastatin suppressed the reabsorption of a limited number of megalin ligands in PTECs, including α1-microglobulin and hemopexin. Collectively, cilastatin-mediated selective megalin blockade is an effective therapeutic strategy to prevent both heme-mediated PTEC injury and cast formation in hemolysis-induced AKI. © 2024 The Pathological Society of Great Britain and Ireland.

Fatigue of red blood cells under periodic squeezes in ECMO.

Hemolysis usually happens instantly when red blood cells (RBCs) rupture under a high shear stress. However, it is also found to happen gradually in the extracorporeal membrane oxygenation (ECMO) under low but periodic squeezes. In particular, the gradual hemolysis is accompanied by a progressive change in morphology of RBCs. In this work, the gradual hemolysis is studied in a microfluidic device with arrays of narrow gaps the same as the constructions in ECMO. RBCs are seen to deform periodically when they flow through the narrow gaps, which causes the release of adenosine-triphosphate (ATP) from RBCs. The reduced ATP level in the cells leads to the fatigue of RBCs with the progressive changes in morphology and the gradual loss of deformability. An empirical model for the fatigue of RBCs is established under the periodic squeezes with controlled deformation, and it reveals a different way of the hemolysis that is dominated by the squeeze frequency. This finding brings a new insight into the mechanism of hemolysis, and it helps to improve the design of circulatory support devices.

Hemoglobin scavenger receptor CD163 as a potential biomarker of hemolysis-induced hepatobiliary injury in sickle cell disease.

Sickle cell disease (SCD)-associated chronic hemolysis promotes oxidative stress, inflammation, and thrombosis leading to organ damage, including liver damage. Hemoglobin scavenger receptor CD163 plays a protective role in SCD by scavenging both hemoglobin-haptoglobin complexes and cell-free hemoglobin. A limited number of studies in the past have shown a positive correlation of CD163 expression with poor disease outcomes in patients with SCD. However, the role and regulation of CD163 in SCD-related hepatobiliary injury have not been fully elucidated yet. Here we show that chronic liver injury in SCD patients is associated with elevated levels of hepatic membrane-bound CD163. Hemolysis and increase in hepatic heme, hemoglobin, and iron levels elevate CD163 expression in the SCD mouse liver. Mechanistically we show that heme oxygenase-1 (HO-1) positively regulates membrane-bound CD163 expression independent of nuclear factor erythroid 2-related factor 2 (NRF2) signaling in SCD liver. We further demonstrate that the interaction between CD163 and HO-1 is not dependent on CD163-hemoglobin binding. These findings indicate that CD163 is a potential biomarker of SCD-associated hepatobiliary injury. Understanding the role of HO-1 in membrane-bound CD163 regulation may help identify novel therapeutic targets for hemolysis-induced chronic liver injury.

A rationally engineered small antimicrobial peptide with potent antibacterial activity.

Antimicrobial resistance (AMR) is a silent pandemic declared by the WHO that requires urgent attention in the post-COVID world. AMR is a critical public health concern worldwide, potentially affecting people at different stages of life, including the veterinary and agriculture industries. Notably, very few new-age antimicrobial agents are in the current developmental pipeline. Thus, the design, discovery, and development of new antimicrobial agents are required to address the menace of AMR. Antimicrobial peptides (AMPs) are an important class of antimicrobial agents for combating AMR due to their broad-spectrum activity and ability to evade AMR through a multimodal mechanism of action. However, molecular size, aggregability, proteolytic degradation, cytotoxicity, and hemolysis activity significantly limit the clinical application of natural AMPs. The de novo design and engineering of a short synthetic amphipathic AMP (≤16 aa, Mol. Wt. ≤ 2 kDa) with an unusual architecture comprised of coded and noncoded amino acids (NCAAs) is presented here, which demonstrates potent antibacterial activity against a few selected bacterial strains mentioned in the WHO priority list. The designer AMP is conformationally ordered in solution and effectively permeabilizes the outer and inner membranes, leading to bacterial growth inhibition and death. Additionally, the peptide is resistant to proteolysis and has negligible cytotoxicity and hemolysis activity up to 150 µM toward cultured human cell lines and erythrocytes. The designer AMP is unique and appears to be a potent therapeutic candidate, which can be subsequently subjected to preclinical studies to explicitly understand and address the menace of AMR.

Adaptive Effects of Intermittent Hypoxia Training on Oxygen-Dependent Processes as a Potential Therapeutic Strategy Tool.

BACKGROUND/AIMS: Important benefits of intermittent hypoxic training (IHT) have emerged as an effective tool for enhancing adaptive potential in different pathological states, among which acute hypoxia dominates. Therefore, the aim of our study was to evaluate the mechanisms related to the effects of the nitric oxide system (nitrites, nitrates, carbamide, and total polyamine content) on ADP-stimulated oxygen consumption and oxidative phosphorylation in heart and liver mitochondria and biomarkers of oxidative stress in the blood, heart, and liver of rats exposed to the IHT method and acute hypoxia and treated with the amino acid L-arginine (600 mg/kg, 30 min) or the NO synthase inhibitor L-NNA (35 mg/kg, 30 min) prior to each IHT session. METHODS: We analysed the modulation of the system of oxygen-dependent processes (mitochondrial respiration with the oxygraphic method, microsomal oxidation, and lipoperoxidation processes using biochemical methods) in tissues during IHT in the formation of short-term and long-term effects (30, 60, and 180 days after the last IHT session) with simultaneous administration of L-arginine. In particular, we investigated how mitochondrial functions are modulated during intermittent hypoxia with the use of oxidation substrates (succinate or α-ketoglutarate) in bioenergetic mechanisms of cellular stability and adaptation. RESULTS: The IHT method is associated with a significant increase in the production of endogenous nitric oxide measured by the levels of its stable metabolite, nitrite anion, in both plasma (almost 7-fold) and erythrocytes (more than 7-fold) of rats. The intensification of nitric oxide-dependent pathways of metabolic transformations in the energy supply processes in the heart and liver, accompanied by oscillatory mechanisms of adaptation in the interval mode, causes a probable decrease in the production of urea and polyamines in plasma and liver, but not in erythrocytes. The administration of L-arginine prior to the IHT sessions increased the level of the nitrite-reducing component of the nitric oxide cycle, which persisted for up to 180 days of the experiment. CONCLUSION: Thus, the efficacy of IHT and its nitrite-dependent component shown in this study is associated with the formation of long-term adaptive responses by preventing the intensification of lipoperoxidation processes in tissues due to pronounced changes in the main enzymes of antioxidant defence and stabilisation of erythrocyte membranes, which has a pronounced protective effect on the system of regulation of oxygen-dependent processes as a whole.

Characterization and biological prospects of various calcined temperature-V2O5 nanoparticles synthesized by Citrus hystrix fruit extract.

In this study, a simple green synthesis of vanadium pentoxide nanoparticles (VNPs) was prepared by the extract of Kaffir lime fruit (Citrus hystrix) as a green reducing and stabilizing agent, along with the investigation of calcination temperature was carried out at 450 and 550 °C. It was affirmed that, at higher temperature (550 °C), the VNPs possessed a high degree crystalline following the construction of (001) lattice diffraction within an increase in crystalline size from 47.12 to 53.51 nm, although the band gap of the materials at 450 °C was lower than that of the VNPs-550 (2.53 versus 2.66 eV, respectively). Besides, the materials were assessed for the potential bioactivities toward antibacterial, antifungal, DNA cleavage, anti-inflammatory, and hemolytic performances. As a result, the antibacterial activity, with minimal inhalation concentration (MIC) < 6.25 µg/mL for both strains, and fungicidal one of the materials depicted the dose-dependent effects. Once, both VNPs exhibited the noticeable efficacy of the DNA microbial damage, meanwhile, the outstanding anti-inflammatory agent was involved with the IC50 of 123.636 and 227.706 µg/mL, accounting for VNPs-450 and VNPs-550, respectively. Furthermore, this study also demonstrated the hemolytic potential of the VNPs materials. These consequences declare the prospects of the VNPs as the smart and alternative material from the green procedure in biomedicine.

Engineering Therapeutics to Detoxify Hemoglobin, Heme, and Iron.

Hemolysis (i.e., red blood cell lysis) can increase circulatory levels of cell-free hemoglobin (Hb) and its degradation by-products, namely heme (h) and iron (Fe). Under homeostasis, minor increases in these three hemolytic by-products (Hb/h/Fe) are rapidly scavenged and cleared by natural plasma proteins. Under certain pathophysiological conditions, scavenging systems become overwhelmed, leading to the accumulation of Hb/h/Fe in the circulation. Unfortunately, these species cause various side effects such as vasoconstriction, hypertension, and oxidative organ damage. Therefore, various therapeutics strategies are in development, ranging from supplementation with depleted plasma scavenger proteins to engineered biomimetic protein constructs capable of scavenging multiple hemolytic species. In this review, we briefly describe hemolysis and the characteristics of the major plasma-derived protein scavengers of Hb/h/Fe. Finally, we present novel engineering approaches designed to address the toxicity of these hemolytic by-products.

Bioinspired green synthesis of ZnO nanoparticles by marine-derived Streptomyces plicatus and its multifaceted biomedicinal properties.

The present study explores the bioinspired green synthesis of zinc oxide nanoparticles (ZnONPs) using marine Streptomyces plicatus and its potent antibacterial, antibiofilm activity against dental caries forming Streptococcus mutans MTCC and S. mutans clinical isolate (CI), cytotoxicity against oral KB cancer cells, hemolysis against blood erythrocytes and artemia toxicity. The bioinspired ZnONPs showed a distinctive absorption peak at 375 nm in UV-Vis spectra, the FT-IR spectra divulged the active functional groups, and XRD confirmed the crystalline nature of the nanoparticles with an average grain size of 41.76 nm. SEM analysis evidenced hexagonal morphology, and EDX spectra affirmed the presence of zinc. The ZnONPs exerted higher antagonistic activity against S. mutans MTCC (Inhibitory zone: 19 mm; MIC: 75 µg/ml) than S. mutans CI (Inhibitory zone: 17 mm; MIC: 100 µg/ml). Results of biofilm inhibitory activity showed a concentration-dependent reduction with S. mutans MTCC (15 %-95 %) more sensitive than S. mutans CI (13 %-89 %). The 50 % biofilm inhibitory concentration (BIC50) of ZnONPs against S. mutans MTCC was considerably lower (71.76 µg/ml) than S. mutans CI (78.13 µg/ml). Confocal Laser Scanning Microscopic visuals clearly implied that ZnONPs effectively distorted the biofilm architecture of both S. mutans MTCC and S. mutans CI. This was further bolstered by a remarkable rise in protein leakage (19 %-85 %; 15 %-77 %) and a fall in exopolysaccharide production (34 mg-7 mg; 49 mg-12 mg). MTT cytotoxicity of ZnONPs recorded an IC50 value of 22.06 µg/ml against KB cells. Acridine orange/ethidium bromide staining showed an increasing incidence of apoptosis in KB cells. Brine shrimp cytotoxicity using Artemia salina larvae recorded an LC50 value of 78.41 µg/ml. Hemolysis assay substantiated the biocompatibility of the ZnONPs. This study underscores the multifaceted application of bioinspired ZnONPs in dentistry.

Functional effects of an African glucose-6-phosphate dehydrogenase (G6PD) polymorphism (Val68Met) on red blood cell hemolytic propensity and post-transfusion recovery.

BACKGROUND: Donor genetic variation is associated with red blood cell (RBC) storage integrity and post-transfusion recovery. Our previous large-scale genome-wide association study demonstrated that the African G6PD deficient A- variant (rs1050828, Val68Met) is associated with higher oxidative hemolysis after cold storage. Despite a high prevalence of X-linked G6PD mutation in African American population (>10%), blood donors are not routinely screened for G6PD status and its importance in transfusion medicine is relatively understudied. STUDY DESIGN AND METHODS: To further evaluate the functional effects of the G6PD A- mutation, we created a novel mouse model carrying this genetic variant using CRISPR-Cas9. We hypothesize that this humanized G6PD A- variant is associated with reduced G6PD activity with a consequent effect on RBC hemolytic propensity and post-transfusion recovery. RESULTS: G6PD A- RBCs had reduced G6PD protein with ~5% residual enzymatic activity. Significantly increased in vitro hemolysis induced by oxidative stressors was observed in fresh and stored G6PD A- RBCs, along with a lower GSH:GSSG ratio. However, no differences were observed in storage hemolysis, osmotic fragility, mechanical fragility, reticulocytes, and post-transfusion recovery. Interestingly, a 14% reduction of 24-h survival following irradiation was observed in G6PD A- RBCs compared to WT RBCs. Metabolomic assessment of stored G6PD A- RBCs revealed an impaired pentose phosphate pathway (PPP) with increased glycolytic flux, decreasing cellular antioxidant capacity. DISCUSSION: This novel mouse model of the common G6PD A- variant has impaired antioxidant capacity like humans and low G6PD activity may reduce survival of transfused RBCs when irradiation is performed.

Testosterone supplementation increases red blood cell susceptibility to oxidative stress, decreases membrane deformability, and decreases survival after cold storage and transfusion.

BACKGROUND: Blood collection from donors on testosterone therapy (TT) is restricted to red blood cell (RBC) concentrates to avoid patient exposure to supraphysiological testosterone (T). The objective of this study was to identify TT-related changes in RBC characteristics relevant to transfusion effectiveness in patients. STUDY DESIGN: This was a two-part study with cohorts of patients and blood donors on TT. In part 1, we conducted longitudinal evaluation of RBCs collected before and at three time points after initiation of T. RBC assays included storage and oxidative hemolysis, membrane deformability (elongation index), and oximetry. In part 2, we evaluated the fate of transfused RBCs from TT donors in immunodeficient mice and by retrospective analyses of NIH's vein-to-vein databases. RESULTS: TT increased oxidative hemolysis (1.45-fold change) and decreased RBC membrane deformability. Plasma free testosterone was positively correlated with oxidative hemolysis (r = .552) and negatively correlated with the elongation index (r = -.472). Stored and gamma-irradiated RBCs from TT donors had lower posttransfusion recovery in mice compared to controls (41.6 ± 12 vs. 55.3 ± 20.5%). Recipients of RBCs from male donors taking T had 25% lower hemoglobin increments compared to recipients of RBCs from non-TT male donors, and had increased incidence (OR, 1.80) of requiring additional RBC transfusions within 48 h of the index transfusion event. CONCLUSIONS: TT is associated with altered RBC characteristics and transfusion effectiveness. These results suggest that clinical utilization of TT RBCs may be less effective in recipients who benefit from longer RBC survival, such as chronically transfused patients.

The safety of ABO minor incompatible platelets transfusions using a rapid infuser.

BACKGROUND: Administering platelets through a rapid infuser is proven to be safe. However, the clinical significance of infusing ABO-incompatible platelets with red blood cells (RBCs) in a rapid infuser remains unclear. There is a theoretical risk that isoagglutinin in the plasma of a platelet unit can interact with RBCs and induce hemolysis. MATERIALS AND METHODS: Seven in vitro studies were performed including five cases (type A RBCs and type O platelets) and two controls (type A RBCs and platelets). Anti-A titers were measured in platelet units. An RBC unit and a platelet unit were mixed in the rapid infuser reservoir and incubated for 30 min. The primary outcome was the presence of hemolysis based on the following parameters: free hemoglobin concentration, hemolysis check, direct antiglobulin test (DAT), and direct agglutination. RESULTS: The post-mix DAT was positive for IgG in all test samples (5/5), and weakly positive for complement in 3/5. The changes in free Hb in test cases between measured and calculated post-mix spanned -2.2 to +3.4 mg/dL. Post-mix hemolysis check was negative in 3/5 and slightly positive in 2/5 cases, with no significant differences compared to the control case. Anti-A titers ranged from 16 to 512 and were not associated with hemolysis. All samples were negative for direct agglutination. CONCLUSION: Our study suggested that mixing ABO-incompatible platelets with RBCs in a rapid infuser does not induce in vitro hemolysis. These findings support the use of rapid infusers regardless of platelet compatibility in support of hemostatic resuscitation.

Nitric oxide: A potential etiological agent for vaso-occlusive crises in sickle cell disease.

Nitric oxide (NO), a vasodilator contributes to the vaso-occlusive crisis associated with the sickle cell disease (SCD). Vascular nitric oxide helps in vasodilation, controlled platelet aggregation, and preventing adhesion of sickled red blood cells to the endothelium. It decreases the expression of pro-inflammatory genes responsible for atherogenesis associated with SCD. Haemolysis and activated endothelium in SCD patients reduce the bioavailability of NO which promotes the severity of sickle cell disease mainly causes vaso-occlusive crises. Additionally, NO depletion can also contribute to the formation of thrombus, which can cause serious complications such as stroke, pulmonary embolism etc. Understanding the multifaceted role of NO provides valuable insights into its therapeutic potential for managing SCD and preventing associated complications. Various clinical trials and studies suggested the importance of artificially induced nitric oxide and its supplements in the reduction of severity. Further research on the mechanisms of NO depletion in SCD is needed to develop more effective treatment strategies and improve the management of this debilitating disease.