Red Blood Cell Membrane Integrity Research Articles

#2505 PTEN ablation in osteocytes exacerbates anemia in mice with subtotal nephrectomy

Abstract Background and Aims The identification of novel roles for bone as a principal endocrine organ has grown in recent decades, being now recognized for its contribution to the regulation of numerous systemic functions. In previous studies, we observed that 5/6Nx mice with osteocytic deletion of phosphatase and tensin homolog (PTEN), exhibited higher bone volume in 5/6Nx mice, consistent with studies under normal renal conditions. However, we also noted a decrease in blood hemoglobin levels, prompting further exploration. This study aims to elucidate the causative actions by which specific PTEN deletion in osteocytes influences red blood cell (RBC) homeostasis and to identify its possible involvement in anemia development. Method To achieve this goal, we used mice with targeted PTEN deletion in osteocytes (PTEN Ocy-cKO) by crossing DMP1-Cre ± and PTENflox/flox mice, subjected to subtotal nephrectomy (5/6Nx) at 2 months of age. Two weeks post-surgery, bone and blood samples were collected for plasma biochemistry, blood count, RBC membrane integrity, and preliminary bone+bone marrow proteomic analysis. Cre-negative mice and animals with normal renal function were included as controls. Results Our findings revealed that PTEN Ocy-cKO mice, under both normal and reduced renal function conditions, showed higher bone volume than corresponding controls. In terms of blood homeostasis, PTEN Ocy-cKO mice with normal renal function showed splenomegaly and a lower number of circulating RBCs. Notably, PTEN Ocy-cKO mice undergoing 5/6Nx experienced a profound decrease in RBC number in only two weeks, independent of renal erythropoietin expression. Further exploration ruled out bone marrow failure as a cause, as the erythroid progenitor (CD45-CD71+Ter119+) population remained similar in both groups. Extramedullary hematopoiesis was observed in the spleen, in addition to increased circulating reticulocyte number in the PTEN Ocy-cKO mice. Finally, altered RBC membrane protein patterns in PTEN Ocy-cKO mice suggested reduced mechanical/osmotic resistance. Preliminary proteomic analysis identified downregulation of Slc4a1 (Band3) and Phosphofructokinase (Pfkm), whose deficiencies have been previously linked to anemia. Conclusion In conclusion, our results propose that osteocytes contribute to RBC homeostasis through a pathway downstream of PTEN, and open a new avenue for understanding anemia in chronic kidney disease and a potential target for future treatments.

Pyruvate kinase activators: targeting red cell metabolism in sickle cell disease.

Hemoglobin S (HbS) polymerization, red blood cell (RBC) sickling, chronic anemia, and vaso-occlusion are core to sickle cell disease (SCD) pathophysiology. Pyruvate kinase (PK) activators are a novel class of drugs that target RBC metabolism by reducing the buildup of the glycolytic intermediate 2,3-diphosphoglycerate (2,3-DPG) and increasing production of adenosine triphosphate (ATP). Lower 2,3-DPG level is associated with an increase in oxygen affinity and reduction in HbS polymerization, while increased RBC ATP may improve RBC membrane integrity and survival. There are currently 3 PK activators in clinical development for SCD: mitapivat (AG-348), etavopivat (FT-4202), and the second-generation molecule AG-946. Preclinical and clinical data from these 3 molecules demonstrate the ability of PK activators to lower 2,3-DPG levels and increase ATP levels in animal models and patients with SCD, as well as influence a number of potential pathways in SCD, including hemoglobin oxygen affinity, RBC sickling, RBC deformability, RBC hydration, inflammation, oxidative stress, hypercoagulability, and adhesion. Furthermore, early-phase clinical trials of mitapivat and etavopivat have demonstrated the safety and tolerability of PK activators in patients with SCD, and phase 2/3 trials for both drugs are ongoing. Additional considerations for this novel therapeutic approach include the balance between increasing hemoglobin oxygen affinity and tissue oxygen delivery, the cost and accessibility of these drugs, and the potential of multimodal therapy with existing and novel therapies targeting different disease mechanisms in SCD.

Intermittent scavenging of storage lesion from stored red blood cells by electrospun nanofibrous sheets enhances their quality and shelf-life

Transfusion of healthy red blood cells (RBCs) is a lifesaving process. However, upon storing RBCs, a wide range of damage-associate molecular patterns (DAMPs), such as cell-free DNA, nucleosomes, free-hemoglobin, and poly-unsaturated-fatty-acids are generated. DAMPs can further damage RBCs; thus, the quality of stored RBCs declines during the storage and limits their shelf-life. Since these DAMPs consist of either positive or negative charged species, we developed taurine and acridine containing electrospun-nanofibrous-sheets (Tau-AcrNFS), featuring anionic, cationic charges and an DNA intercalating group on their surfaces. We show that Tau-AcrNFS are efficient in scavenging DAMPs from stored human and mice RBCs ex vivo. We find that intermittent scavenging of DAMPs by Tau-AcrNFS during the storage reduces the loss of RBC membrane integrity and reduces discocytes-to-spheroechinocytes transformation in stored-old-RBCs. We perform RBC-transfusion studies in mice to reveal that intermittent removal of DAMPs enhances the quality of stored-old-RBCs equivalent to freshly collected RBCs, and increases their shelf-life by ~22%. Such prophylactic technology may lead to the development of novel blood bags or medical device, and may therefore impact healthcare by reducing transfusion-related adverse effects.

Pklr Variants Associated with Acute Pain in Sickle Cell Disease Influence ATP Concentrations in Red Blood Cells

Background: We previously demonstrated association of PKLR intron 2 variants with hospitalization rate for acute pain in people with sickle cell disease (SCD) and utilized allele-specific expression analysis to show that these variants influence PKLR activity (Wang et al, 2022). Pyruvate kinase (gene PKLR, protein PKR) is a rate-limiting enzyme in glycolysis. Reduced PKR activity leads to an increase in intracellular 2,3-diphosphoglycerate (2,3-DPG), and a concomitant decrease of adenosine triphosphate (ATP), factors that promote sickle hemoglobin (HbS) polymerization and red blood cell (RBC) sickling. On this basis, we explored how the "high risk" PKLR intron 2 variants affect levels of PKR protein expression, 2,3-DPG, ATP, oxygen dissociation (p50) and sickling kinetics (t50). Methods: We studied a total of 416 subjects which included 125 HbSS, 89 HbAS, and 202 ethnic-matched healthy controls (HbAA) enrolled under protocol NCT03685721 approved by the NHLBI Institutional Review Board. DNA was genome scanned using Ilumina's Infinium "MEGA" chip (1.7m markers). The results were quality controlled followed by genotype imputation based on the 1000 Genomes Project phase 3 data using the Michigan Imputation Server. Whole blood levels of ATP and 2,3-DPG were measured using LC-MS/MS with LLOQ at 50.0 μg/mL and converted to intracellular concentrations by dividing by the hematocrit (as a fraction). PKR was detected by antibody-based capture and detection using an electrochemiluminescence immunoassay (Meso Scale Discovery, Rockville, MD, USA) and the signal normalized to a control sample. A Hemox Analyzer [TCS, Scientific Corp, New Hope, PA] was used to obtain p50 values (defined as the partial pressure of oxygen at which Hb is 50% saturated with oxygen). t50 is single parameter measure of sickling kinetics (Dunkelberger et al, 2018). Single variant analyses (under additive genetic model adjusted for age and sex) were conducted in each of the Hb sub-populations for associations between the 7 PKLR variants (intron 4 - rs2071053, and intron 2 -rs8177970, rs116244351, rs114455416, rs12741350, rs3020781, and rs8177964) and the 5 parameters (PKR, 2,3-DPG, ATP, p50 and t50). False-discovery rate (FDR) adjusted p-values were calculated to account for the multiple testing issue. Results: Table 1A shows levels of the 5 parameters (ATP/HCT, 2,3-DPG/HCT, PKR, p50 and t50) in the 3 Hb genotypic groups (HbAA, HbAS and HbSS). Because patients with SCD have variable anemia, ATP and 2,3-DPG were normalized against HCT. The observed trending higher ATP / HCT and significantly elevated 2,3-DPG /HCT in HbSS compared to HbAS and to HbAA are consistent with previous reports (Poillon et al, 1990). HbSS subjects also had higher PKR protein expression, as well as right-shifted p50 values, compared to HbAS and HbAA (Table 1A), which suggest HbSS RBCs have lower specific activity of PKR. A one-way ANOVA showed that the differences in these mean values were highly significant (Table 1A). All 7 PKLR variants were associated with ATP levels in the HbAS group, of which 4 (rs8177970, rs116244351, rs114455416 and rs8177964) in intron 2 remained statistically significant after multiple testing adjustment (Table 1B). We also identified association between 3 variants (intron 2 - rs12741350, rs3020781, intron 4 - rs071053) and 2,3-DPG levels in the HbSS, as well as t50 in the HbAS group. Conclusion: ATP is essential for maintaining RBC membrane integrity and shape; reduced ATP dehydrates RBCs and promotes sickling. In a previous report, a PKLR intron 2 'high-risk" haplotype was implicated in acute sickle pain by affecting PKLR expression (Wang et al, 2022). In this follow-up study, we show that the same intron 2 "high-risk" haplotype negatively affects ATP levels when accounting for PKR expression, thus providing a biological basis for PKLR as a genetic modifier of SCD pain presentation. 3 of the 7 variants are also associated with elevated 2,3-DPG levels in HbSS as well as t50 (a single parameter that depends primarily on sickling kinetics) in HbAS. The variant associations are observed more clearly in HbAS but not in HbSS, possibly because of the much more homogeneous cell population in HbAS. We conclude that PKLR intron variants may directly contribute to the severity and frequency of acute pain episodes in SCD, thus additional studies with larger sample sizes are warranted. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

The compound effect of irradiation and familial pseudohyperkalemia on potassium leak from red blood cells.

Familial pseudohyperkalemia (FP) is a rare asymptomatic condition characterized by an increased rate of potassium leak from red blood cells (RBC) on refrigeration. Gamma irradiation compromises RBC membrane integrity and accelerates potassium leakage. Here, we compared the effect of irradiation, applied early or late in storage, on FP versus non-FP RBC. Five FP and 10 non-FP individuals from the National Institute for Health Research Cambridge BioResource, UK, and three FP and six non-FP individuals identified by Australian Red Cross Lifeblood consented to the study. Blood was collected according to standard practice in each center, held overnight at 18-24°C, leucocyte-depleted, and processed into red cell concentrates (RCC) in Saline Adenine Glucose Mannitol. On Day 1, RCC were split equally into six Red Cell Splits (RCS). Two RCS remained non-irradiated, two were irradiated on Day 1 and two were irradiated on Day 14. RBCs were tested over cold storage for quality parameters. As expected, non-irradiated FP RCS had significantly higher supernatant potassium levels than controls throughout 28 days of storage (p < .001). When irradiated early, FP RCS released potassium at similar rates to control. When irradiated late, FP RCS supernatants had higher initial post-irradiation potassium concentration than controls but were similar to controls by the end of storage (14 days post-irradiation). No other parameters studied showed a significant difference between FP and control. FP does not increase the rate of potassium leak from irradiated RBCs. Irradiation may cause a membrane defect similar to that in FP RBCs.

Innate immune Galectin-7 specifically targets microbes that decorate themselves in blood group-like antigens

SummaryAdaptive immunity can target a nearly infinite range of antigens, yet it is tempered by tolerogenic mechanisms that limit autoimmunity. Such immunological tolerance, however, creates a gap in adaptive immunity against microbes decorated with self-like antigens as a form of molecular mimicry. Our results demonstrate that the innate immune lectin galectin-7 (Gal-7) binds a variety of distinct microbes, all of which share features of blood group-like antigens. Gal-7 binding to each blood group expressing microbe, including strains of Escherichia coli, Klebsiella pneumoniae, Providencia alcalifaciens, and Streptococcus pneumoniae, results in loss of microbial viability. Although Gal-7 also binds red blood cells (RBCs), this interaction does not alter RBC membrane integrity. These results demonstrate that Gal-7 recognizes a diverse range of microbes, each of which use molecular mimicry while failing to induce host cell injury, and thus may provide an innate form of immunity against molecular mimicry.

Iron chelation therapy with deferiprone improves oxidative status and red blood cell quality and reduces redox-active iron in β-thalassemia/hemoglobin E patients.

The oxidative status of twenty-three β-thalassemia/hemoglobin E patients was evaluated after administration of 75mg/kg deferiprone (GPO-L-ONE®) divided into 3 doses daily for 12 months. Serum ferritin was significantly decreased; the median value at the initial and final assessments was 2842 and 1719ng/mL, respectively. Progressive improvement with significant changes in antioxidant enzyme activity, including plasma paraoxonase (PON) and platelet-activating factor acetylhydrolase (PAF-AH), and in antioxidant enzymes in red blood cells (glutathione peroxidase (GPx), catalase and superoxide dismutase (SOD)) were observed at 3-6months of treatment. The levels of total GSH in red blood cells were significantly increased at the end of the study. Improved red blood cell membrane integrity was also demonstrated using the EPR spin labeling technique. Membrane fluidity at the surface and hydrophobic regions of the red blood cell membrane was significantly changed after 12 months of treatment. In addition, a significant increase in hemoglobin content was observed (6.6±0.7 and 7.5±1.3g/dL at the initial assessment and at 6 months, respectively). Correlations were observed between hemoglobin content, membrane fluidity and antioxidant enzymes in red blood cells. The antioxidant activity of deferiprone may partly be explained by progressive reduction of redox active iron that catalyzes free radical reactions, as demonstrated by the EPR spin trapping technique. In conclusion, iron chelation therapy with deferiprone notably improved the oxidative status in thalassemia, consequently reducing the risk of oxidative-related complications. Furthermore, the improvement in red blood cell quality may improve the anemia situation in patients.

Yippee like 4 (Ypel4) is essential for normal mouse red blood cell membrane integrity

The YPEL family genes are highly conserved across a diverse range of eukaryotic organisms and thus potentially involved in essential cellular processes. Ypel4, one of five YPEL family gene orthologs in mouse and human, is highly and specifically expressed in late terminal erythroid differentiation (TED). In this study, we investigated the role of Ypel4 in murine erythropoiesis, providing for the first time an in-depth description of a Ypel4-null phenotype in vivo. We demonstrated that the Ypel4-null mice displayed a secondary polycythemia with macro- and reticulocytosis. While lack of Ypel4 did not affect steady-state TED in the bone marrow or spleen, the anemia-recovering capacity of Ypel4-null cells was diminished. Furthermore, Ypel4-null red blood cells (RBC) were cleared from the circulation at an increased rate, demonstrating an intrinsic defect of RBCs. Scanning electron micrographs revealed an ovalocytic morphology of Ypel4-null RBCs and functional testing confirmed reduced deformability. Even though Band 3 protein levels were shown to be reduced in Ypel4-null RBC membranes, we could not find support for a physical interaction between YPEL4 and the Band 3 protein. In conclusion, our findings provide crucial insights into the role of Ypel4 in preserving normal red cell membrane integrity.

Fluorescent Heme Degradation Products Are Biomarkers of Oxidative Stress and Linked to Impaired Membrane Integrity in Avian Red Blood Cells.

Oxidative stress is generally understood to be an important mediator of life-history traits, yet the specific relationships between oxidative stress and life-history traits have been difficult to describe because there is often a lack of covariation among biomarkers of oxidative stress. For instance, although oxidative damage to red blood cell (RBC) membranes can lead to pathological conditions (i.e., anemia), in some cases there is not a clear relationship between lipid oxidation and RBC membrane resistance to pro-oxidants. Alternatively, oxidative damage to hemoglobin may be an indirect mechanism contributing to RBC membrane damage. To better understand the mechanisms contributing to oxidative damage and probe new approaches to measuring oxidative stress, we used a series of in vitro and in vivo procedures in zebra finches (Taeniopygia guttata) to explore (1) whether avian RBCs exposed to a pro-oxidant generate fluorescent heme degradation products (HDPs), (2) whether HDPs interact with RBC membranes, and (3) whether HDPs are linked to impaired RBC integrity. We found that finch RBCs exposed in vitro to hydrogen peroxide produced fluorescent HDPs and HDPs associated with RBC membranes. Exposure to hydrogen peroxide also caused a reduction in hemoglobin and an increase in percent methemoglobin (a hemoglobin oxidation product), further indicating hemoglobin degradation. Moreover, HDP fluorescence correlated with impaired membrane integrity and erythrocyte osmotic fragility in vivo. This study suggests that reactive oxygen species may indirectly impair RBC membrane integrity via hemoglobin degradation products that associate with RBC membranes and that HDPs may be an inexpensive and logistically simple tool for measuring oxidative stress.

RGD-Modified Nano-Liposomes Encapsulated Eptifibatide with Proper Hemocompatibility and Cytotoxicity Effect.

BackgroundEptifibatide (Integrilin®) is a hepta-peptide drug which specifically prevents the aggregation of activated platelets. The peptide drugs are encapsulated into nanolipisomes in order to decreasing their side effects and improving their half-life and bioavailability.ObjectivesIn this study, the in vitro cytotoxicity and hemocompatibility of RGD-modified nano-liposomes (RGD-MNL) encapsulated a highly potent antiplatelet drug (eptifibatide) was investigated.Material and MethodsRGD-MNL encapsulated eptifibatide was prepared using lipid film hydration and freeze/thawing method. The morphology and size distribution (about 90 nm) of RGD-MNL were characterized using transmission electron microscopy (TEM). The in-vitro cytotoxicity of nano-liposomes was examined using the MTT, LDH release and reactive oxygen species (ROS) generation assays. The effect of RGD-MNL on red blood cells (RBC) was investigated using hemolysis and LDH release assays.ResultsThe results revealed that RGD-MNL had no significant cytotoxic effect on HeLa and HUVEC cell lines, and also no ROS generation increase in the cells. In addition, the adverse effect of RGD-MNL on LDH release and membrane integrity of RBC was not observed.ConclusionsIn conclusion, the recommended RGD-MNL formulations have not any significant cytotoxicity on normal cells or RBC and have potential for protecting and enhancing the activity of antiplatelet drugs.

Vitamin E Analogue Protects Red Blood Cells against Storage-Induced Oxidative Damage

Background: To investigate i) the effects of Trolox® or mannitol, which represent two different classes of antioxidants, on oxidative changes generated in manually isolated red blood cells (RBCs) from citrate-phosphate-dextrose (CPD) preserved whole blood, followed by up to 20 days refrigerated storage, and ii) whether Trolox supplemented to the blood bank-manufactured saline-adenine-glucose-mannitol (SAGM) preserved RBC units would offer better storage conditions compared with SAGM alone. Methods: The percentage of hemolysis and extracellular activity of lactate dehydrogenase (LDH) was measured to assess RBC membrane integrity. Lipid peroxidation, reduced glutathione (GSH) levels and total antioxidant capacity (TAC) were quantified by thiobarbituric acid-reactive substances (TBARS), Ellman's reagent and 2, 2'-azinobis-(3-ethylbenzothiazoline-6-sulfonate) (ABTS^.+) based assay, respectively. Results: Trolox was little more effective than mannitol in protecting against progressive RBC hemolysis. Trolox (0.125-3.125 mmol/l) inhibited storage-induced leakage of LDH, lipid peroxidation, and to a lesser extent GSH depletion. Mannitol at these concentrations neither inhibited TBARS formation nor prevented GSH depletion. RBC units stored in SAGM-Trolox had significantly lower hemolysis, LDH leakage, and lipid peroxidation level compared to RBCs stored in SAGM. Conclusion: There is evidence of the beneficial effects of supplementing RBC-additive solutions with membrane-interacting antioxidants such as vitamin E analogues.

Metabolomic Analysis and Antioxidant Effect of Amla (Emblica officinalis) Extract in Preventing Oxidative Stress-Induced Red Cell Damage and Plasma Protein Alterations: An In Vitro Study.

Amla (Emblica officinalis) has antidiabetic, hypolipidemic, anti-inflammatory, and antioxidant properties, but its effect on free radical induced red cell damage and membrane and plasma protein alterations has not been adequately addressed. The aim of the present study was to evaluate the antioxidant property of amla against oxidative stress-induced red cell damage and plasma protein alterations. Red blood cells (RBCs) were preincubated with different concentrations of amla extract (50, 100, 150, and 200 μg/mL) and then treated with physiological (5 mM) and pathological (50 mM) concentrations of glucose for 24 h. In another in vitro study the plasma was pretreated with different concentrations of amla extract and then incubated with 2, 2'-Azo-Bis (2-methylpropionamidine) dihydrochloride (AAPH) for 2 h. After the incubation RBC-malondialdehyde (MDA), RBC-reduced glutathione (GSH), RBC indices, RBC morphometric study, plasma MDA, protein carbonylation, total protein, and albumin were estimated. The antioxidant property of amla was assessed by DPPH assay. RBC-MDA levels were significantly decreased and RBC-GSH levels were significantly increased with higher concentration of amla extract (150 and 200 μg/mL). Red cell count and its indices were improved with the increasing concentration of amla. In addition, at higher concentration, amla restored the RBC membrane integrity. The plasma in vitro study also showed that amla improved the plasma MDA, protein carbonylation, total protein, and albumin levels. Amla extract effectively protected the RBCs and plasma proteins from the reactive oxygen species induced oxidative damage. Liquid chromatography-mass spectrometry (LC-MS) analysis of the extract revealed the presence of gallic acid, quinic acid, and quercetin as the major constituents in addition to the other flavonoids.

Attenuation of Red Blood Cell Storage Lesions with Vitamin C.

Stored red blood cells (RBCs) undergo oxidative stress that induces deleterious metabolic, structural, biochemical, and molecular changes collectively referred to as “storage lesions”. We hypothesized that vitamin C (VitC, reduced or oxidized) would reduce red cell storage lesions, thus prolonging their storage duration. Whole-blood-derived, leuko-reduced, SAGM (saline-adenine-glucose-mannitol)-preserved RBC concentrates were equally divided into four pediatric storage bags and the following additions made: (1) saline (saline); (2) 0.3 mmol/L reduced VitC (Lo VitC); (3) 3 mmol/L reduced VitC (Hi VitC); or (4) 0.3 mmol/L oxidized VitC (dehydroascorbic acid, DHA) as final concentrations. Biochemical and rheological parameters were serially assessed at baseline (prior to supplementation) and Days 7, 21, 42, and 56 for RBC VitC concentration, pH, osmotic fragility by mechanical fragility index, and percent hemolysis, LDH release, glutathione depletion, RBC membrane integrity by scanning electron microscopy, and Western blot for β-spectrin. VitC exposure (reduced and oxidized) significantly increased RBC antioxidant status with varying dynamics and produced trends in reduction in osmotic fragility and increases in membrane integrity. Conclusion: VitC partially protects RBC from oxidative changes during storage. Combining VitC with other antioxidants has the potential to improve long-term storage of RBC.

Effect of halloysite nanotubes on the structure and function of important multiple blood components

Many researchers have investigated the application of halloysite nanotubes (HNTs) in biomedicine, because of their special nanoscale hollow tubular structure. Although the cytocompatibility of HNTs has been studied, their blood compatibility has not been systematically investigated. In this work, the effect of HNTs on the structure and function of different blood components has been studied, including the morphology and hemolysis of red blood cells (RBCs). Based on scanning electron microscopy (SEM) observations, optical density test and flow cytometry analysis, we found that HNTs can affect the morphology and membrane integrity of RBCs in phosphate buffered saline (PBS) in a content-dependent way. In particular, based on UV–vis absorption spectra, fluorescence spectra and circular dichroism (CD) spectra, HNTs can alter the secondary structure and conformation of human fibrinogen and γ-globulins. In addition, the detection of biomarker molecules C3a and C5a in plasma suggests that HNTs can trigger complement activation. In the blood clotting assay, HNTs were found to significantly prolong the activated partial thromboplastin time (APTT), shorten the prothrombin time (PT) of platelet-poor plasma (PPP), and change the thromboelastography (TEG) parameters of whole blood coagulation. Furthermore, confocal laser scanning microscopy and flow cytometry analysis were used to test intracellular uptake by macrophages, and the cellular uptake of HNTs in the RAW 264.7 was found to be content-dependent, but not time-dependent. These findings provide insight for the potential use of HNTs as biofriendly nanocontainers for biomaterials in vivo.

Vitamin C and Trolox decrease oxidative stress and hemolysis in cold-stored human red blood cells

ABSTRACTObjectives: To investigate the effects of sodium ascorbate (SA) (5–3125 μM) and a combination of SA and Trolox (25 and 125 μM) on oxidative changes generated in red blood cells (RBCs) followed by up to 20 days refrigerated storage.Methods: RBCs were isolated from CPD-preserved human blood. Percentage of hemolysis and extracellular activity of lactate dehydrogenase (LDH) were measured to assess the RBC membrane integrity. Lipid peroxidation (LPO), glutathione (GSH) and total antioxidant capacity (TAC) were quantified by thiobarbituric acid-reactive substances, Ellman’s reagent and 2,2′-azinobis-(3-ethylbenzothiazoline-6-sulfonate) -based assay, respectively.Results: SA failed to reduce the storage-induced hemolysis and RBC membrane permeability. Addition of SA resulted in a concentration-independent LPO inhibition and increased TAC. A combination of SA/Trolox supplemented to the RBC medium significantly inhibited hemolysis, LDH leakage, LPO, GSH depletion and enhanced TAC.Discussion: The effects of vitamin C action are closely concentration-dependent and may be modulated by a variety of compounds (e.g. Hb degradation products) released from RBCs during the prolonged storage, changing its properties from anti- to pro-oxidative. The two different class antioxidants (SA/Trolox) could possibly cooperate to be good potential RBC storage additives ensuring both antiradical and membrane stabilizing protection.

Identification of potential protein quality markers in pathogen inactivated and gamma-irradiated red cell concentrates.

Post-collection manipulations (PCMs) aim to increase blood product safety. However, PCMs improve safety at a cost to quality, causing elevated hemolysis. As hemolysis is linked to red blood cell membrane integrity, a quantitative proteomics approach was employed to assess membrane proteome alterations induced by PCMs. Three ABO-matched whole blood (WB) units were pooled-and-split into three identical units. One WB unit was treated with riboflavin/ultraviolet illumination prior to red cell concentrate (RCC) production (RCCWB* ). Two WB units were produced into RCC; one was gamma-irradiated (RCCγ ) and the other was left untreated as control (RCCØ ). In vitro quality parameters were measured during storage. Membrane protein profiles of RCCØ , RCCγ , and RCCWB* were assessed on selected hemoglobin-depleted membrane fractions using a quantitative proteomics approach based on iTRAQ. Quantitative proteomic analysis identified 100 proteins at the membrane, with seven unique proteins exhibiting significant changes in RCCWB* at day 28 of storage. Membrane peroxiredoxin-2, catalase, and proteasome levels demonstrated robust negative correlation with percentage hemolysis. Overall, the in vitro parameters and alterations of membrane protein profiles indicated that pathogen inactivation treatment impacts RCC quality more severely than gamma-irradiation and that it may induce damage through a predominately oxidative mechanism.

Population Pharmacokinetics and Pharmacodynamics of AG-519, a Pyruvate Kinase Activator for the Treatment of Pyruvate Kinase Deficiency, in Human Healthy Volunteers

INTRODUCTIONPyruvate kinase (PK) deficiency is a life-long chronic hemolytic anemia with a variable clinical presentation, ranging from mild to life-threatening, and is associated with severe, debilitating co-morbidities. PK deficiency is caused by mutations in the PKLR gene, which in the red blood cell (RBC) results in defective pyruvate kinase isoform R (PK-R). PK-R catalyzes the final and irreversible step in glycolysis, the process on which mature RBCs rely almost exclusively to generate the energy carrier molecule, adenosine triphosphate (ATP). PK-R is thus a key enzyme for maintaining RBC energy levels, and it has been proposed that ATP levels are critical for optimally maintaining RBC membrane integrity. PK-deficient RBCs and their progenitors are characterized by changes in metabolism associated with defective glycolysis, including a build-up of phosphoenolpyruvate (PEP) and 2,3-diphosphoglycerate (2,3-DPG), and lowered ATP levels.AG-519 is a potent, highly selective and orally bioavailable PK-R activator shown preclinically to have none of the aromatase inhibitory effects that were observed with AG-348, the first small molecule PK-R activator to enter clinical trials. It is hypothesized that intervention with AG-519 restores glycolytic pathway activity and normalizes RBC metabolism. Treatment of PK-deficient patient RBCs ex vivo with AG-519 results in increased ATP levels, and reductions in 2,3-DPG, consistent with pharmacological activation of PK-R enzyme activity. This analysis integrates the pharmacokinetic and pharmacodynamic (PK/PD) properties of AG-519 in healthy volunteers using population PK/PD modeling and simulation.METHODSPK/PD modeling using a non-linear mixed effects approach was performed to understand the pharmacokinetics of AG-519 and PK/PD relationship of AG-519 to 2,3-DPG, ATP and PK-R enzyme activity in humans. The PK/PD model integrated data from a phase 1, single-center, randomized, double-blind, placebo-controlled study. Data in single and multiple ascending dose escalation arms were included in the analysis, which comprises a total of 88 human volunteers. AG-519 dose levels ranged from 10-1250 mg. Blood was collected from all patients to assess AG-519 pharmacokinetics and levels of ATP and 2,3-DPG in blood, as well as PK-R activity. Population simulations using the final model were performed to examine the dose-exposure-biomarkers relationship.RESULTSAG-519 showed rapid absorption kinetics following oral administration. Area under the concentration-time curve of plasma AG-519 increased in a dose-proportional manner following single and multiple dosing. A three-compartment model with non-linear absorption compartment and linear elimination best described the pharmacokinetics of AG-519. Systemic clearance appeared to be time-invariant and no auto-induction was observed with multiple dosing. The PK/PD relationship between plasma AG-519 and ATP or 2,3-DPG in human volunteers was best fitted by a turnover model where the drug effect was described by an Emax model. A direct Emax model best described the relationship between plasma AG-519 and PK-R enzyme activity. Evaluation of ATP and 2,3-DPG levels and PK-R activity confirmed the potent effect of AG-519 on PK-R. A direct comparison of AG-519 target engagement and biomarker response to AG-348 will also be presented. Population PK/PD model simulations suggested that the doses selected in the phase 1 study covered a large exposure-response range of the three biomarkers, and provided a systematic and integrated framework for the understanding of AG-519 pharmacokinetics and pharmacodynamics, as well as a rationale for dose selection in future trials.CONCLUSIONSThis study represents a comprehensive longitudinal PK/PD analysis of AG-519 in humans. This integrated PK/PD model formed the basis for understanding the exposure-response relationship of the ongoing phase 1 study and provided guidance on dose selection to inform the future development of AG-519. DisclosuresLe:Agios Pharmaceuticals, Inc.: Employment, Equity Ownership. Cohen:Agios Pharmaceuticals, Inc.: Consultancy. Barbier:Agios Pharmaceuticals, Inc.: Employment, Equity Ownership. Merica:Agios Pharmaceuticals, Inc.: Employment, Equity Ownership. Kung:Agios Pharmaceuticals, Inc.: Employment, Equity Ownership. Kosinski:Agios Pharmaceuticals, Inc.: Employment, Equity Ownership. Biller:Agios Pharmaceuticals, Inc.: Employment, Equity Ownership. Yang:Agios Pharmaceuticals, Inc.: Employment, Equity Ownership.

A Two-Site Interaction Underpins TRIM25 Activation of the RIG-I Anti-Viral Response

SPRY/B30.2 domain-containing proteins are found in 103 human proteins that regulate numerous cellular processes including RNA processing, histone methylation, red blood cell membrane integrity, terminal erythroid cell differentiation and innate immune responses. Despite an increased understanding of SPRY/B30.2 domain function, some confusion remains as to the precise domain boundaries, the number and location of binding sites, and importantly how activation of these domains contribute to signal transduction. The B30.2 domain of tripartite motif 25 (TRIM25) interacts with the viral RNA sensor retinoic acid-inducible gene I (RIG-I), facilitating the formation of a RIG-I tetramer, which is required for activation of the innate immune response against RNA viruses such as influenza A, measles, HIV and hepatitis C. Here we have investigated the biochemical and structural changes associated with the activation of TRIM25 in the context of RIG-I binding. We solved a 1.8 Å crystal structure of the TRIM25 B30.2 domain and identified a putative RIG-I-binding site, which was confirmed by mutagenesis and functional analyses. Further mutagenesis identified a second site on the opposing face of the B30.2 domain that also specifically interacts with RIG-I. While the CARD1 domain of RIG-I is known to interact with the B30.2 domain of TRIM25, our data suggest that a conformational change within the CARD2 domain of RIG-I enables it to also interact with the B30.2 domain of TRIM25. We propose that both RIG-I CARDs interact with sites on opposing sides of the TRIM25 B30.2 domain to form a TRIM25/RIG-I complex that facilitates RIG-I tetramerisation and activation. The characterization of a dual binding mode for the TRIM25 B30.2 domain is a first for the SPRY/B30.2 domain family. Disease-associated polymorphisms of Pyrin, involved in Familial Mediterranean Fever, and mutational analyses of TRIM5a, required for HIV restriction, suggest that a second binding site may be a characteristic feature of other B30.2-containing TRIM proteins, and may facilitate the formation of large oligomeric complexes that are important for inflammasome function and HIV capsid destruction. DisclosuresNo relevant conflicts of interest to declare.

Thrombospondin-1 Stimulates Calcium Influx and Echinocytosis in Sickle Cell-Derived Red Blood Cells

Thrombospondin-1 (TSP1) is a secreted matricellular protein found preformed in platelet α-granules and upregulated in the plasma of patients with sickle cell disease (SCD). In preclinical models TSP1 enhances sickle red blood cell (RBC) binding to endothelial cells, while in murine sickle mice TSP1 promotes RBC echinocytosis and vaso-occlusion. Recently we reported elevated plasma TSP1 was associated with vaso-occlusive complications in SCD patients. Herein we tested the hypothesis that TSP1 compromises RBC membrane integrity via enhanced calcium influx leading to morphological changes, such as echinocytosis. RBC were collected via centrifugation of heparinized blood from human HbAA donors (n=3), SCD patients with homozygous HbSS SCD (n=4), and wild type C57BL/6J mice (n=2). Cells were then re-suspended in glucose and calcium-supplemented PBS, and treated with several concentrations of exogenous TSP1 (2.75 nM, 11 nM, 22 nM and 44 nM) for 2 hours at 37°C. RBC morphology was assessed by both light and electron microscopy. TSP1 modulation of RBC calcium influx was studied using the calcium fluorophore Fluo-3, AM. TSP1 treatment, in a dose-dependent manner, stimulated echinocytosis in human SCD and non-SCD RBC and in murine cells. In some instances electron microscopy showed echinocyte membrane projections with a string-of-beads appearance, suggestive of imminent microparticle shedding. TSP1 treatment, again in a dose-dependent manner, also significantly increased calcium influx in SCD (Figure, right panel) and non SCD RBC (Figure, left panel) and murine RBC (not shown). Interestingly, SCD RBC displayed more sensitivity to TSP1-mediated increases in cellular calcium as compared to normal cells. Our results show for the first time that TSP1, at doses found in patient plasma, stimulates significant echinocytosis and calcium influx in both normal and SCD RBC. These data identify a novel role for plasma TSP1 in promoting RBC pathology. Future studies are underway to elucidate this mechanism and its pathogenicity in humans with and without SCD. [Display omitted] DisclosuresIsenberg:Vasculox: Membership on an entity’s Board of Directors or advisory committees; Radiation Control Technologies: Membership on an entity’s Board of Directors or advisory committees.

Impact of graphene oxide on the structure and function of important multiple blood components by a dose‐dependent pattern

Graphene and its derivatives have become great concern in biomedical fields. Though many investigations about their toxicity have been reported, systematic investigation on the interaction with multiple blood components is lacking. In this work, we studied the effects of the graphene oxide (GO) on the structure and function of the blood components, especially, on morphology and hemolysis of red blood cells (RBCs), bovine serum albumin (BSA) and fibrinogen conformation, complement activation, and blood coagulation function. Scanning electron microscopy observation and hemolysis test results showed that the GO can affect RBC morphology and membrane integrity in a concentration-dependent way. Fluorescence and circular dichroism spectra showed that GO could alter the secondary structures and conformation of BSA and fibrinogen. In addition, the presence of GO could also trigger complement activation by detecting their key biomarker molecules in plasma. In the blood clotting process, the GO showed significant adverse effect on the activated partial thromboplastin time but not on prothrombin time of the platelet-poor plasma. Meanwhile, the GO also caused abnormal thromboelastography parameters of the whole blood coagulation. The results obtained in this study provides good insight into understanding the biomedical application of GO in vivo.