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The pathophysiologic mechanism of sickle cell disease (SCD) involves polymerization of deoxygenated haemoglobin S (HbS), leading to red blood cell (RBC) sickling, decreased RBC deformability, microvascular obstruction, haemolysis, anaemia and downstream clinical complications. Pharmacological increase in the concentration of oxygenated HbS in RBCs has been shown to be a novel approach to inhibit HbS polymerization and reduce RBC sickling and haemolysis. We report that GBT021601, a small molecule that increases HbS-oxygen affinity, inhibits HbS polymerization and prevents RBC sickling in blood from patients with SCD. Moreover, in a murine model of SCD (SS mice), GBT021601 reduces RBC sickling, improves RBC deformability, prolongs RBC half-life and restores haemoglobin levels to the normal range, while improving oxygen delivery and increasing tolerance to severe hypoxia. Notably, oral dosing of GBT021601 in animals results in higher levels of Hb occupancy than voxelotor and suggests the feasibility of once-daily dosing in humans. In summary, GBT021601 improves RBC health and normalizes haemoglobin in SS mice, suggesting that it may be useful for the treatment of SCD. These data are being used as a foundation for clinical research and development of GBT021601.

Infection with COVID-19 has resulted in over 276,000 deaths in the United States and over 1.5 million deaths globally, with upwards of 15% of patients requiring hospitalization. Severe COVID-19 infection is, in essence, a microvascular disease. This contention has been emphasized throughout the course of the pandemic, particularly due to the clinical manifestation of severe infection. In fact, it has been hypothesized and shown in particular instances that microvascular function is a significant prognosticator for morbidity and mortality. Initially thought to be isolated to the pulmonary system and resulting in ARDS, patients with COVID-19 have been observed to have acute cardiac, renal, and thrombolytic complications. Therefore, severe COVID-19 is a vascular disease that has systemic implications. The objective of this review is to provide a mechanistic background for the microvascular nature of severe COVID-19 infection, with a particular emphasis on dysfunction of the endothelial glycocalyx and nitric oxide mediated pathogenesis.

For the past thirty years, hemoglobin-based oxygen carriers (HBOCs) have been under development as a red blood cell substitute. Side-effects such as vasoconstriction, oxidative injury, and cardiac toxicity have prevented clinical approval of HBOCs. Recently, high molecular weight (MW) polymerized human hemoglobin (PolyhHb) has shown positive results in rats. Studies have demonstrated that high MW PolyhHb increased O2 delivery, with minimal effects on blood pressure, without vasoconstriction, and devoid of toxicity. In this study, we used guinea pigs to evaluate the efficacy and safety of high MW PolyhHb, since like humans guinea pigs cannot produce endogenous ascorbic acid, which limits the capacity of both species to deal with oxidative stress. Hence, this study evaluated the efficacy and safety of resuscitation from severe hemorrhagic shock with high MW PolyhHb, fresh blood, and blood stored for 2 weeks. Animals were randomly assigned to each experimental group, and hemorrhage was induced by the withdrawal of 40% of the blood volume (BV, estimated as 7.5% of body weight) from the carotid artery catheter. Hypovolemic shock was maintained for 50 min. Resuscitation was implemented by infusing 25% of the animal's BV with the different treatments. Hemodynamics, blood gases, total hemoglobin, and lactate were not different before hemorrhage and during shock between groups. The hematocrit was lower for the PolyhHb group compared to the fresh and stored blood groups after resuscitation. Resuscitation with stored blood had lower blood pressure compared to fresh blood at 2 h. There was no difference in mean arterial pressure between groups at 24 h. Resuscitation with PolyhHb was not different from fresh blood for most parameters. Resuscitation with PolyhHb did not show any remarkable change in liver injury, inflammation, or cardiac damage. Resuscitation with stored blood showed changes in liver function and inflammation, but no kidney injury or systemic inflammation. Resuscitation with stored blood after 24 h displayed sympathetic hyper-activation and signs of cardiac injury. These results suggest that PolyhHb is an effective resuscitation alternative to blood. The decreased toxicities in terms of cardiac injury markers, vital organ function, and inflammation following PolyhHb resuscitation in guinea pigs indicate a favorable safety profile. These results are promising and support future studies with this new generation of PolyhHb as alternative to blood when blood is unavailable.

Variability in SARS-CoV-2 susceptibility and COVID-19 disease severity between individuals is partly due to genetic factors. Here, we identify 4 genomic loci with suggestive associations for SARS-CoV-2 susceptibility and 19 for COVID-19 disease severity. Four of these 23 loci likely have an ethnicity-specific component. Genome-wide association study (GWAS) signals in 11 loci colocalize with expression quantitative trait loci (eQTLs) associated with the expression of 20 genes in 62 tissues/cell types (range: 1:43 tissues/gene), including lung, brain, heart, muscle, and skin as well as the digestive system and immune system. We perform genetic fine mapping to compute 99% credible SNP sets, which identify 10 GWAS loci that have eight or fewer SNPs in the credible set, including three loci with one single likely causal SNP. Our study suggests that the diverse symptoms and disease severity of COVID-19 observed between individuals is associated with variants across the genome, affecting gene expression levels in a wide variety of tissue types.

Fluid resuscitation following severe inflammation-induced hypoperfusion is critical for the restoration of hemodynamics and the prevention of multiorgan dysfunction syndrome during septic shock. Fluid resuscitation with commercially available crystalloid and colloid solutions only provides transient benefits, followed by fluid extravasation and tissue edema through the inflamed endothelium. The increased molecular weight (M.W.) of polymerized human serum albumin (PolyHSA) can limit fluid extravasation, leading to restoration of hemodynamics. In this prospective study, we evaluated how fluid resuscitation with PolyHSA impacts the hemodynamic and immune response in a lipopolysaccharide (LPS) induced endotoxemia mouse model. Additionally, we evaluated fluid resuscitation with PolyHSA in a model of polymicrobial sepsis induced by cecal ligation and puncture (CLP). Resuscitation with PolyHSA attenuated the immune response and improved the maintenance of systemic hemodynamics and restoration of microcirculatory hemodynamics. This decrease in inflammatory immune response and maintenance of vascular wall shear stress likely contributes to the maintenance of vascular integrity following fluid resuscitation with PolyHSA. The sustained restoration of perfusion, decrease in pro-inflammatory immune response, and improved vascular integrity that results from the high M.W. of PolyHSA indicates that a PolyHSA based solution is a potential resuscitation fluid for endotoxic and septic shock.

Hemorrhagic shock (HS) is a severe life-threatening condition characterized by loss of blood volume and a lack of oxygen (O2) delivery to tissues. The objective of this study was to examine the impact of manipulating Starling forces in the microcirculation during HS to increase microvascular perfusion without restoring blood volume or increasing O2 carrying capacity. To decrease interstitial tissue pressure, we developed a non-contact system to locally apply negative pressure and manipulate the pressure balance in capillaries, while allowing for visualization of the microcirculation. Golden Syrian hamsters were instrumented with dorsal window chambers and subjected to a controlled hemorrhaged of 50% of the animal's blood volume without any fluid resuscitation. A negative pressure chamber was attached to the dorsal window chamber and a constant negative pressure was applied. Hemodynamic parameters (including microvascular diameter, blood flow, and functional capillary density [FCD]) were measured before and during the four hours following the hemorrhage, with and without applied negative pressure. Blood flow significantly increased in arterioles during negative pressure. The increase in flow through arterioles also improved microvascular perfusion as reflected by increased FCD. These results indicate that negative pressure increases flow in the microcirculation when fluid resuscitation is not available, thus restoring blood flow, oxygen delivery, and preventing the accumulation of metabolic waste. Applying negative pressure might allow for control of microvascular blood flow and oxygen delivery to specific tissue areas.

Microvascular fluid exchange is primarily dependent on Starling forces and both the active and passive myogenic response of arterioles and post-capillary venules. Arterioles are classically considered resistance vessels, while venules are considered capacitance vessels with high distensibility and low tonic sympathetic stimulation at rest. However, few studies have investigated the effects of modulating interstitial hydrostatic pressure, particularly in the context of hemorrhagic shock. The objective of this study was to investigate the mechanics of arterioles and functional capillary density (FCD) during application of negative tissue interstitial pressure after 40% total blood volume hemorrhagic shock. In this study, we characterized systemic and microcirculatory hemodynamic parameters, including FCD, in hamsters instrumented with a dorsal window chamber and a custom-designed negative pressure application device via intravital microscopy. In large arterioles, application of negative pressure after hemorrhagic shock resulted in a 13 ± 11% decrease in flow compared with only a 7 ± 9% decrease in flow after hemorrhagic shock alone after 90 minutes. In post-capillary venules, however, application of negative pressure after hemorrhagic shock resulted in a 31 ± 4% decrease in flow compared with only an 8 ± 5% decrease in flow after hemorrhagic shock alone after 90 minutes. Normalized FCD was observed to significantly improve after application of negative pressure after hemorrhagic shock (0.66 ± 0.02) compared to hemorrhagic shock without application of negative pressure (0.50 ± 0.04). Our study demonstrates that application of negative pressure acutely improves FCD during hemorrhagic shock, though it does not normalize FCD. These results suggest that by increasing the hydrostatic pressure gradient between the microvasculature and interstitium, microvascular perfusion can be transiently restored in the absence of volume resuscitation. This study has significant clinical implications, particularly in negative pressure wound therapy, and offers an alternative mechanism to improve microvascular perfusion during hypovolemic shock.

Traumatic brain injury (TBI) is often accompanied by hemorrhage, and treatment of hemorrhagic shock (HS) after TBI is particularly challenging because the two therapeutic treatment strategies for TBI and HS often conflict. Ischemia/reperfusion injury from HS resuscitation can be exaggerated by TBI-induced loss of autoregulation. In HS resuscitation, the goal is to restore lost blood volume, while in the treatment of TBI the priority is focused on maintenance of adequate cerebral perfusion pressure and avoidance of secondary bleeding. In this study, we investigate the responses to resuscitation from severe HS after TBI in rats, using fresh blood, polymerized human hemoglobin (PolyhHb), and lactated Ringer's (LR). Rats were subjected to TBI by pneumatic controlled cortical impact. Shortly after TBI, HS was induced by blood withdrawal to reduce mean arterial pressure (MAP) to 35-40 mmHg for 90 min before resuscitation. Resuscitation fluids were delivered to restore MAP to ~ 65 mmHg and animals were monitored for 120 min. Increased systolic blood pressure variability (SBPV) confirmed TBI-induced loss of autoregulation. MAP after resuscitation was significantly higher in the blood and PolyhHb groups compared to the LR group. Furthermore, blood and PolyhHb restored diastolic pressure, while this remained depressed for the LR group, indicating a loss of vascular tone. Lactate increased in all groups during HS, and only returned to baseline level in the blood reperfused group. The PolyhHb group possessed lower SBPV compared to LR and blood groups. Finally, sympathetic nervous system (SNS) modulation was higher for the LR group and lower for the PolyhHb group compared to the blood group after reperfusion. In conclusion, our results suggest that PolyhHb could be an alternative to blood for resuscitation from HS after TBI when blood is not available, assuming additional testing demonstrate similar favorable results. PolyhHb restored hemodynamics and oxygen delivery, without the logistical constraints of refrigerated blood.

Amelioration of immune overactivity during sepsis is key to restoring hemodynamics, microvascular blood flow, and tissue oxygenation, and in preventing multi-organ dysfunction syndrome. The systemic inflammatory response syndrome that results from sepsis ultimately leads to degradation of the endothelial glycocalyx and subsequently increased vascular leakage. Current fluid resuscitation techniques only transiently improve outcomes in sepsis, and can cause edema. Nitric oxide (NO) treatment for sepsis has shown promise in the past, but implementation is difficult due to the challenges associated with delivery and the transient nature of NO. To address this, we tested the anti-inflammatory efficacy of sustained delivery of exogenous NO using i.v. infused NO releasing nanoparticles (NO-np). The impact of NO-np on microhemodynamics and immune response in a lipopolysaccharide (LPS) induced endotoxemia mouse model was evaluated. NO-np treatment significantly attenuated the pro-inflammatory response by promoting M2 macrophage repolarization, which reduced the presence of pro-inflammatory cytokines in the serum and slowed vascular extravasation. Combined, this resulted in significantly improved microvascular blood flow and 72-h survival of animals treated with NO-np. The results from this study suggest that sustained supplementation of endogenous NO ameliorates and may prevent the morbidities of acute systemic inflammatory conditions. Given that endothelial dysfunction is a common denominator in many acute inflammatory conditions, it is likely that NO enhancement strategies may be useful for the treatment of sepsis and other acute inflammatory insults that trigger severe systemic pro-inflammatory responses and often result in a cytokine storm, as seen in COVID-19.

Cisplatin is a promising therapeutic for the treatment of non-small cell lung cancer (NSCLC). Unfortunately, a significant portion of NSCLC patients relapse due to cisplatin chemoresistance. This chemoresistance is thought to be primarily associated with hypoxia in the tumor microenvironment. Administration of hemoglobin (Hb)-based oxygen (O2) carriers (HBOCs) is a promising strategy to alleviate hypoxia in the tumor, which may make cisplatin more effective. In this study, we administered a high O2 affinity, relaxed state (R-state) polymerized hemoglobin (PolyHb) to three different NSCLC cell lines cultured in vitro and implanted in vivo into healthy mice. The R-state PolyHb administered in this study is unable to deliver O2 unless under severe hypoxia which significantly limits its oxygenation potential. In vitro sensitivity studies indicate that the administration of PolyHb increases the effectiveness of cisplatin under hypoxic conditions. Additional animal studies revealed that co-administration of PolyHb with cisplatin attenuated tumor growth without alleviating hypoxia. Analysis of reactive O2 species production in the presence of hypoxic culture indicates that exogenous ROS production by oxidized PolyHb may the mechanism of chemosensitization. This ROS mechanism, coupled with oxygenation, may be a potential chemosensitizing strategy for use in NSCLC treatment.

BackgroundHemoglobin (Hb)-based oxygen carriers (HBOCs) have been proposed as alternatives to blood for decades. Previous studies demonstrated that large molecular diameter HBOCs based on polymerized bovine Hb (PolybHb) attenuate Hb side-effects and toxicity. The objective of this study was to test the safety and efficacy of tense state PolybHb after long-term storage.Methods and resultsPolybHb was subjected to diafiltration to remove low molecular weight (< 500 kDa) species and stored for 2 years. PolybHb was studied in parallel with blood, collected from rats and stored leukodepleted under blood bank conditions for 3 weeks. Rats were hemorrhaged and resuscitated to 90% of the blood pressure before the hemorrhage with fresh blood, stored blood, fresh PolybHb, or 2-year-stored PolybHb. Hemorrhagic shock impaired oxygen delivery and cardiac function. Resuscitation restored blood pressure and cardiac function, but stored blood required a significantly larger transfusion volume to recover from shock compared with fresh blood and PolybHb (fresh and stored). Stored blood transfusion elevated markers of organ damage compared with all other groups.ConclusionsThese studies indicate that large molecular diameter PolybHb is as efficacious as fresh blood in restoring cardiac function and confirm the lack of degradation of PolybHb's safety or efficacy during long-term storage.

Polymerized hemoglobin (PolyHb) is a promising hemoglobin (Hb)-based oxygen carrier currently undergoing development as a red blood cell substitute. Unfortunately, commercially developed products are composed of low-molecular-weight (LMW) PolyHb molecules, which extravasate, scavenge nitric oxide, and result in vasoconstriction and hypertension. The naturally occurring Hb-scavenging species haptoglobin (Hp), combined with the purified heme-scavenging species apohemoglobin (apoHb), is a potential candidate to alleviate the pressor effect of PolyHb. This study evaluated the protective activity of administering the apoHb-Hp complex to mitigate the vasoactive response induced by the transfusion of LMW PolyHb. Hp binding to PolyHb was characterized in vitro. The effectiveness of apoHb-Hp administration on reducing the vasoconstriction and pressor effects of PolyHb was assessed by measuring systemic and microcirculatory hemodynamics. Transfusion of LMW PolyHb to vehicle control pretreated animals increased mean arterial pressure while decreasing arteriole diameter and functional capillary density. However, transfusion of LMW PolyHb to apoHb-Hp pretreated animals prevented changes in mean arterial pressure, heart rate, arteriole diameter, blood flow, and functional capillary density relative to before transfusion. These results indicate that the increased size of PolyHb after binding to the apoHb-Hp complex may help compartmentalize PolyHb in the vascular space and thus reduce extravasation, nitric oxide scavenging, and toxicity responsible for vasoconstriction and systemic hypertension.

The microcirculation is a complex network of vessels ranging from as large as 100 μm to as small as 5 μm. This complex network is responsible for the regulation of oxygen to the surrounding tissues and ensures metabolite washout. With a more complete understanding of the microcirculation's physiologic and pathologic tendencies, engineers can create new solutions to combat blood pathologies and shock-related diseases. Over the last number of decades a grown interest in the microcirculation has resulted in the development of fundamental techniques to quantify the microvasculature flow and the release of oxygen to tissues.

BackgroundResuscitation from hemorrhagic shock (HS) by blood transfusion restores oxygen (O2) delivery and provides hemodynamic stability. Current regulations allow red blood cells (RBCs) to be stored and used for up to 42 days. During storage, RBCs undergo many structural and functional changes. These storage lesions have been associated with adverse events and increased mortality after transfusion, increasing the need for improved RBC storage protocols. This study evaluates the efficacy of anaerobically stored RBCs to resuscitate rats from severe HS compared with conventionally stored RBCs.Methods and resultsRat RBCs were stored under anaerobic, anaerobic/hypercapnic, or conventional conditions for a period of 3 weeks. Hemorrhage was induced by controlled bleeding, shock was maintained for 30 min, and RBCs were transfused to restore and maintain blood pressure near the prhemorrhage level. All storage conditions met current regulatory 24-h posttransfusion recovery requirements. Transfusion of anaerobically stored RBCs required significantly less RBC volume to restore and maintain hemodynamics. Anaerobic or anaerobic/hypercapnic RBCs restored hemodynamics better than conventionally stored RBCs. Resuscitation with conventionally stored RBCs impaired indices of left ventricular cardiac function, increased hypoxic tissue staining and inflammatory markers, and affected organ function compared with anaerobically stored RBCs.ConclusionsResuscitation from HS via transfusion of anaerobically stored RBCs recovered cardiac function, restored hemodynamic stability, and improved outcomes.

The mechanical properties and deformability of Red Blood Cells (RBCs) are important determinants of blood rheology and microvascular hemodynamics. The objective of this study is to quantify the mechanical properties and wall shear stress experienced by the RBC membrane during capillary plug flow in vivo utilizing high speed video recording from intravital microscopy, biomechanical modeling, and computational methods. Capillaries were imaged in the rat cremaster muscle pre- and post-RBC transfusion of stored RBCs for 2-weeks. RBC membrane contours were extracted utilizing image processing and parametrized. RBC parameterizations were used to determine updated deformation gradient and Lagrangian Green strain tensors for each point along the parametrization and for each frame during plug flow. The updated Lagrangian Green strain and Displacement Gradient tensors were numerically fit to the Navier-Lame equations along the parameterized boundary to determined Lame's constants. Mechanical properties and wall shear stress were determined before and transfusion, were grouped in three populations of erythrocytes: native cells (NC) or circulating cells before transfusion, and two distinct population of cells after transfusion with stored cells (SC1 and SC2). The distinction, between the heterogeneous populations of cells present after the transfusion, SC1 and SC2, was obtained through principle component analysis (PCA) of the mechanical properties along the membrane. Cells with the first two principle components within 3 standard deviations of the mean, were labeled as SC1, and those with the first two principle components greater than 3 standard deviations from the mean were labeled as SC2. The calculated shear modulus average was 1.1±0.2, 0.90±0.15, and 12 ± 8 MPa for NC, SC1, and SC2, respectively. The calculated young's modulus average was 3.3±0.6, 2.6±0.4, and 32±20 MPa for NC, SC1, and SC2, respectively. o our knowledge, the methods presented here are the first estimation of the erythrocyte mechanical properties and shear stress in vivo during capillary plug flow. In summary, the methods introduced in this study may provide a new avenue of investigation of erythrocyte mechanics in the context of hematologic conditions that adversely affect erythrocyte mechanical properties.

This paper implements logistic regression models (LRMs) and feature selection for creating a predictive model for recovery form hemorrhagic shock (HS) with resuscitation using blood in the multiple experimental rat animal protocols. A total of 61 animals were studied across multiple HS experiments, which encompassed two different HS protocols and two resuscitation protocols using blood stored for short periods using five different techniques. Twenty-seven different systemic hemodynamics, cardiac function, and blood gas parameters were measured in each experiment, of which feature selection deemed only 25% of the them as relevant. The reduced feature set was used to train a final logistic regression model. A final test set accuracy is 84% compared to 74% for a baseline classifier using only MAP and HR measurements. Receiver operating characteristics (ROC) curve analysis and Cohens kappa statistics were also used as measures of performance, with the final reduced model outperforming the model, including all parameters. Our results suggest that LRMs trained with a combination of systemic hemodynamics, cardiac function, and blood gas parameters measured at multiple timepoints during HS can successfully classify HS recovery groups. Our results show the predictive ability of traditional and novel hemodynamic and cardiac function features and their combinations, many of which had not previously been taken into consideration, for monitoring HS. Furthermore, we have devised an effective methodology for feature selection and shown ways in which the performance of such predictive models should be assessed in future studies.

Acclimatization to hypoxia or high altitude involves physiological adaptation processes, to influence oxygen (O2) transport and utilization. Several natural products, including aromatic aldehydes and isothiocyanates stabilize the R-state of hemoglobin (Hb), increasing Hb-O2 affinity and Hb-O2 saturation. These products are a counter intuitive therapeutic strategy to increase O2 delivery during hypoxia. 5-Hydroxymethylfurfural (5-HMF) is well known Amadori compound formed during the Maillard reaction (the non-enzymatic browning and caramelization of carbohydrate-containing foods after thermal treatment), with well documented effects in Hb-O2 affinity. This study explores the therapeutic potential of 5-HMF on left ventricular (LV) cardiac function (LVCF) during hypoxia. Anesthetized Golden Syrian hamsters received 5-HMF i.v., at 100 mg/kg and were subjected to stepwise increased hypoxia (15, 10, and 5%) every 30 min. LVCF was assessed using a closed chest method with a miniaturized conductance catheter via continuous LV pressure-volume (PV) measurements. Heart hypoxic areas were studied using pimonidazole staining. 5-HMF improved cardiac indices, including stroke volume (SV), cardiac output (CO), ejection fraction (EF), and stroke work (SW) compared to the vehicle group. At 5% O2, SV, CO, EF, and SW were increased by 53, 42, 33, and 51% with 5-HMF relative to vehicle. Heart chronotropic activity was not statistically changed, suggesting that differences in LV-CF during hypoxia by 5-HMF were driven by volume dependent effects. Analysis of coronary blood flow and cardiac muscle metabolism suggest no direct pharmacological effects from 5-HMF, therefore these results can be attributed to 5-HMF-dependent increase in Hb-O2 affinity. These studies establish that naturally occurring aromatic aldehydes, such as 5-HMF, produce modification of hemoglobin oxygen affinity with promising therapeutic potential to increase O2 delivery during hypoxic hypoxia.

The mechanical properties and deformability of Red Blood Cells (RBCs) are important determinants of blood rheology and microvascular hemodynamics. The objective of this study is to quantify the mechanical properties and wall shear stress experienced by the RBC membrane during capillary plug flow in vivo utilizing high speed video recording from intravital microscopy, biomechanical modeling, and computational methods. Capillaries were imaged in the rat cremaster muscle pre- and post-RBC transfusion of stored RBCs for 2-weeks. RBC membrane contours were extracted utilizing image processing and parametrized. RBC parameterizations were used to determine updated deformation gradient and Lagrangian Green strain tensors for each point along the parametrization and for each frame during plug flow. The updated Lagrangian Green strain and Displacement Gradient tensors were numerically fit to the Navier-Lame equations along the parameterized boundary to determined Lame's constants. Mechanical properties and wall shear stress were determined before and transfusion, were grouped in three populations of erythrocytes: native cells (NC) or circulating cells before transfusion, and two distinct population of cells after transfusion with stored cells (SC1 and SC2). The distinction, between the heterogeneous populations of cells present after the transfusion, SC1 and SC2, was obtained through principle component analysis (PCA) of the mechanical properties along the membrane. Cells with the first two principle components within 3 standard deviations of the mean, were labeled as SC1, and those with the first two principle components greater than 3 standard deviations from the mean were labeled as SC2. The calculated shear modulus average was 1.1±0.2, 0.90±0.15, and 12 ± 8 MPa for NC, SC1, and SC2, respectively. The calculated young's modulus average was 3.3±0.6, 2.6±0.4, and 32±20 MPa for NC, SC1, and SC2, respectively. o our knowledge, the methods presented here are the first estimation of the erythrocyte mechanical properties and shear stress in vivo during capillary plug flow. In summary, the methods introduced in this study may provide a new avenue of investigation of erythrocyte mechanics in the context of hematologic conditions that adversely affect erythrocyte mechanical properties.

Oxygen plays a central role in cardiac energy metabolism. At high altitude where the ambient oxygen level is low, we found EDNRB is associated with human hypoxia adaptation. Our subsequent study in global heterozygous knockout mice (Ednrb-/+) revealed that cardiac function was conserved in these mice when exposed to extreme hypoxia. The major goal of this study was (i) to determine the functional role of cardiomyocyte EdnrB in maintaining cardiac function under hypoxic stress and (ii) to validate the phenotypes we detected in Ednrb-/+ mice using EDNRB blockers. Unlike the global knockouts, cardiac-specific heterozygote (EdnrBflox/+) and homozygote (EdnrBflox/flox) EdnrB knockout mice were phenotypically normal. When treated with graded low levels of oxygen (10% and 5% O2), both EdnrBflox/+ and EdnrBflox/flox were hypoxia tolerant. The cardiac indexes at 10% and 5% O2 for EdnrBflox/+ were significantly higher and lactate levels were significantly lower when compared to the cre-negative controls (P

BackgroundSmall rodent models are routinely used to evaluate the safety and efficacy of blood transfusions. Limited comprehensive literature exists about effect of different storage solutions in rat red blood cells (RBCs) characteristics. RBCs undergo time dependent biochemical and biophysical changes during storage known as hypothermic storage lesions (HSLs).ObjectiveThis study evaluates the effects of RBC additive solutions (AS) during storage of rat RBCs.MethodsBlood was leukoreduced and stored as per manufacturer instructions at 4°C up to 42-days. Three solutions, CPDA-1; AS-1; and AS-7 (SOLX), were evaluated. Biochemical parameters measured included extracellular K+, pH, hemolysis, 2,3-diphosphoglycerate (2,3-DPG), oxygen affinity, ATP, and lactate. Mechanical properties measured included RBC deformability, elongation index (EI), RBC membrane shear elastic modulus (SEM), mean corpuscular volume (MCV), viscosity, and aggregability.ResultsThere were no differences in biochemical or mechanical parameters at baseline or after one week of storage. However, after two weeks, AS-7 preserved biochemical and mechanical properties as compared to CPDA-1 and AS-1. Changes were observed to be significant after 14-days of storage. AS-7 prevented extracellular K+ increase, reduced acidosis, showed lower hemolysis, preserved ATP and 2,3-DPG levels (consequently oxygen affinity), and reduced lactate. AS-7, when compared to CPDA-1 and AS-1, prevented the reduction in RBC deformability and was found to preserve the EI at multiple shear stresses, the membrane SEM, the aggregability and viscosity.DiscussionRat RBCs stored with AS-7 presented reduced changes in biochemical and mechanical parameters, when compared with rat RBCs stored in CPDA-1 and AS-1, after as early as two weeks of storage.

Ischemia-reperfusion injury increased vascular permeability, resulting in fluid extravasation from the intravascular compartment into the tissue space. Fluid and small protein extravasation lead to increased interstitial fluid pressure and capillary collapse, impairing capillary exchange. Polymerized human serum albumin (PolyHSA) has an increased molecular weight (MW) compared with unpolymerized human serum albumin (HSA) and can improve intravascular fluid retention and recovery from ischemia-reperfusion injury. To test the hypothesis that polymerization of HSA can improve recovery from ischemia-reperfusion injury, we studied how exchange transfusion of 20% of the blood volume with HSA or PolyHSA immediately before reperfusion can affect local ischemic tissue microhemodynamics, vascular integrity, and tissue viability in a hamster dorsal window chamber model. Microvascular flow and functional capillary density were maintained in animals exchanged with PolyHSA compared with HSA. Likewise, exchange transfusion with PolyHSA preserved vascular permeability measured with extravasation of fluorescently labeled dextran. The intravascular retention time of the exchanged PolyHSA was significantly longer compared with the intravascular retention time of HSA. Lastly, the viability of tissue subjected to ischemia-reperfusion injury increased in animals exchanged with PolyHSA compared with HSA. Therefore maintenance of microvascular perfusion, improvement in vascular integrity, and reduction in tissue damage resulting from reperfusion with PolyHSA suggest that PolyHSA is a promising fluid therapy to improve outcomes of ischemia-reperfusion injury. [ABSTRACT FROM AUTHOR]

Background : Globally, respiratory infections contribute to significant morbidity and mortality. However, genetic determinants of respiratory infections are understudied and remain poorly understood. Methods : We conducted a genome-wide association study in 19,459 hospitalised respiratory infection cases and 101,438 controls from UK Biobank (Stage 1). We followed-up well-imputed top signals from our Stage 1 analysis in 50,912 respiratory infection cases and 150,442 controls from 11 cohorts (Stage 2). We aggregated effect estimates across studies using inverse variance-weighted meta-analyses. Additionally, we investigated the function of the top signals in order to gain understanding of the underlying biological mechanisms. Results : From our Stage 1 analysis, we report 56 signals at P <5×10 -6 , one of which was genome-wide significant ( P <5×10 -8 ). The genome-wide significant signal was in an intron of PBX3 , a gene that encodes pre-B-cell leukaemia transcription factor 3, a homeodomain-containing transcription factor. Further, the genome-wide significant signal was found to colocalise with gene-specific expression quantitative trait loci (eQTLs) affecting expression of PBX3 in lung tissue, where the respiratory infection risk alleles were associated with decreased PBX3 expression in lung tissue, highlighting a possible biological mechanism. Of the 56 signals, 40 were well-imputed in UK Biobank and were investigated in Stage 2. None of the 40 signals replicated, with effect estimates attenuated. Conclusions : Our Stage 1 analysis implicated PBX3 as a candidate causal gene and suggests a possible role of transcription factor binding activity in respiratory infection susceptibility. However, the PBX3 signal, and the other well-imputed signals, did not replicate in the meta-analysis of Stages 1 and 2. Significant phenotypic heterogeneity and differences in study ascertainment may have contributed to this lack of statistical replication. Overall, our study highlighted putative associations and possible biological mechanisms that may provide insight into respiratory infection susceptibility., Competing Interests: Competing interests: IPH has funded research collaborations with GSK, Boehringer Ingelheim and Orion. LVW and MDT receive funding from GSK for a collaborative research project outside of the submitted work. JCB, AJY and HNG are employees of GSK and may own company stock. At the time of this study, DM, SHL, HM and EMH were employees of GSK and may own company stock. MHC has received grant support from GSK and Bayer, consulting or speaking fees from Genentech, AstraZeneca, and Illumina, outside of the submitted work., (Copyright: © 2023 Williams AT et al.)