Hemoglobin-based oxygen carriers for hemorrhagic shock

Therapeutic delivery of oxygen using artificial oxygen carriers demonstrates the possibility of treating a wide range of diseases

Artificial oxygen carriers have emerged as potential substitutes for red blood cells in situations of major blood loss, including accidents, surgical procedures, trauma, childbirth, stomach ulcers, hemorrhagic shock, and blood vessel ruptures which can lead to sudden reduction in blood volume. The therapeutic delivery of oxygen utilizing artificial oxygen carriers as red blood cell substitutes presents a promising avenue for treating a spectrum of disease models. Apart from that, the recent advancement of artificial oxygen carriers intended to supplant conventional blood transfusions draws significant attention due to the exigencies of warfare and the ongoing challenges posed by the COVID-19 pandemic. However, there is a pressing need to formulate stable, non-toxic, and immunologically inert oxygen carriers. Even though numerous challenges are encountered in the development of artificial oxygen carriers, their applicability extends to various medical treatments, encompassing elective and cardiovascular surgeries, hemorrhagic shock, decompression illness, acute stroke, myocardial infarction, sickle cell crisis, and proficient addressing conditions such as cerebral hypoxia. Therefore, this paper provides an overview of therapeutic oxygen delivery using assorted types of artificial oxygen carriers, including hemoglobin-based, perfluorocarbon-based, stem cell-derived, and oxygen micro/nanobubbles, in the treatment of diverse disease models. Additionally, it discusses the potential side effects and limitations associated with these interventions, while incorporating completed and ongoing research and recent clinical developments. Finally, the prospective solutions and general demands of the perfect artificial oxygen carriers were anticipated to be a reference for subsequent research endeavors.

LncRNA-TUG1: Implications in the Myocardial and Endothelial Cell Oxidative Stress Injury Caused by Hemorrhagic Shock and Fluid Resuscitation

BACKGROUND

LncRNA taurine-upregulated gene 1 (TUG1) can regulate vascular endothelial cell injury, a critical mechanism in treating hemorrhagic shock and fluid resuscitation (HS/R). Therefore, this study explored the influence of TUG1 in HS/R.

METHODS

An in vivo rat model of ischemia-reperfusion (I/R) injury post-HS/R and an in vitro model of oxidative stress injury in rat cardiomyocyte cell line (H9C2) were constructed. In vivo, we silenced TUG1 and quantified its expression along with inflammatory factors through quantitative reverse transcription polymerase chain reaction (qRT-PCR), mean arterial pressure (MAP) detection and blood gas analysis. Myocardial functional impairment was assessed via Triphenyl-2H-Tetrazolium Chloride (TTC), Hematoxylin and eosin, and Terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end labeling (TUNEL) stainings. Oxidative stress level in rat serum was measured. In vitro, we examined the changes of cell viability, apoptosis, oxidative stress levels, inflammatory factor secretion and nuclear factor-κB (NF-κB)/p65 expression by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), flow cytometry, Enzyme-linked immunosorbent assay (ELISA) and Western blot.

RESULTS

TUG1 level was elevated in rats of I/R model caused by HS/R. TUG1 silencing ameliorated the decline in MAP, acid-base imbalance and myocardial tissue damage, and suppressed oxidative stress and inflammatory factor levels in model rat. TUG1 silencing enhanced viability, impeded apoptosis, and reduced oxidative stress, inflammatory factor contents and NF-κB/p65 expression in H2O2 treated H9C2 cells.

CONCLUSION

TUG1 participates in regulating oxidative stress damage and inflammation induced by HS/R.

Hydroxyethyl Starch-Bovine Hemoglobin Conjugate as an Effective Oxygen Carrier with the Ability to Expand Plasma

Hemorrhagic shock leads to intravasal volume deficiency, tissue hypoxia, and cellular anaerobic metabolism. Hemoglobin (Hb) could deliver oxygen for hypoxic tissues but is unable to expand plasma. Hydroxyethyl starch (HES) could compensate for the intravasal volume deficiency but cannot deliver oxygen. Thus, bovine Hb (bHb) was conjugated with HES (130 kDa and 200 kDa) to develop an oxygen carrier with the ability to expand plasma. Conjugation with HES increased the hydrodynamic volume, colloidal osmotic pressure, and viscosity of bHb. It slightly perturbed the quaternary structure and heme environment of bHb. The partial oxygen pressures at 50% saturation (P 50) of the two conjugates (bHb-HES130 and bHb-HES200) were 15.1 and 13.9 mmHg, respectively. The two conjugates showed no apparent side effects on the morphology and rigidity, hemolysis, and platelet aggregation of red blood cells of Wistar rats. Thus, bHb-HES130 and bHb-HES200 were expected to function as an effective oxygen carrier with the ability to expand plasma.

Pilot scale production and characterization of next generation high molecular weight and tense quaternary state polymerized human hemoglobin

Polymerized human hemoglobin (PolyhHb) is being studied as a possible red blood cell (RBC) substitute for use in scenarios where blood is not available. While the oxygen (O2 ) carrying capacity of PolyhHb makes it appealing as an O2 therapeutic, the commercial PolyhHb PolyHeme® (Northfield Laboratories Inc.) was never approved for clinical use due to the presence of large quantities of low molecular weight (LMW) polymeric hemoglobin (Hb) species (<500 kDa), which have been shown to elicit vasoconstriction, systemic hypertension, and oxidative tissue injury in vivo. Previous bench-top scale studies in our lab demonstrated the ability to synthesize and purify PolyhHb using a two-stage tangential flow filtration purification process to remove almost all undesirable Hb species (>0.2 µm and <500 kDa) in the material, to create a product that should be safer for transfusion. Therefore, to enable future large animal studies and eventual human clinical trials, PolyhHb synthesis and purification processes need to be scaled up to the pilot scale. Hence in this study, we describe the pilot scale synthesis and purification of PolyhHb. Characterization of pilot scale PolyhHb showed that PolyhHb could be successfully produced to yield biophysical properties conducive for its use as an RBC substitute. Size exclusion high performance liquid chromatography showed that pilot scale PolyhHb yielded a high molecular weight Hb polymer containing a small percentage of LMW Hb species (<500 kDa). Additionally, the auto-oxidation rate of pilot scale PolyhHb was even lower than that of previous generations of PolyhHb. Taken together, these results demonstrate that PolyhHb has the ability to be seamlessly manufactured at the pilot scale to enable future large animal studies and clinical trials.

Protective effects of HBOC on pulmonary vascular leakage after haemorrhagic shock and the underlying mechanisms

Volume resuscitation is an important early treatment for haemorrhagic shock. Haemoglobin-based oxygen carrier (HBOC) can expand the volume and provide oxygen for tissues. Vascular leakage is common complication in the process of haemorrhagic shock and resuscitation. The aim of this study was to observe the effects of HBOC (a bovine-derived, cross-linked tetramer haemoglobin oxygen-carrying solution, 0.5 g/L) on vascular leakage in rats after haemorrhagic shock. A haemorrhagic shock rat model and hypoxic vascular endothelial cells (VECs) were used. The role of intercellular junctions and endothelial glycocalyx in the protective effects of HBOC and the relationship with mitochondrial function were analysed. After haemorrhagic shock, the pulmonary vascular permeability to FITC-BSA, Evans Blue was increased, endothelial glycocalyx was destroyed and the expression of intercellular junction proteins was decreased. After haemorrhagic shock, a small volume of HBOC solution (6 ml/kg) protected pulmonary vascular permeability, increased structural thickness of endothelial glycocalyx, the levels of its components and increased expression levels of the intercellular junction proteins ZO-1, VE-cadherin and occludin. Moreover, HBOC significantly increased oxygen delivery and consumption in rats, improved VEC mitochondrial function and structure. In conclusion, HBOC mitigates endothelial leakage by protecting endothelial glycocalyx and intercellular junctions through improving mitochondrial function and tissue oxygen delivery.

Künstliche Sauerstofftransporter können mehr als Sauerstoff liefern

Zum gegenwärtigen Zeitpunkt ist in der EU und den USA kein artifizieller Sauerstofftransporter zugelassen. Hämoglobin-basierte Sauerstoff-Carrier (HBOC) sind bereits seit Jahrzehnten Gegenstand wissenschaftlicher Untersuchungen. Ein wesentliches Hindernis bei der Zulassung war bisher der Anspruch der Entwickler, einen universell einsetzbaren Blutersatz zu produzieren. Die Beschränkung auf eine Indikation scheint erfolgversprechender zu sein. Der Ansatz, nicht nur Sauerstoff von der Lunge zum Gewebe, sondern auch der Abtransport von Kohlendioxid vom Gewebe zur Lunge zu transportieren, der effektiver als mit Erythrozyten durchgeführt werden kann, erscheint besonders attraktiv. Aufgrund vielversprechender präklinischer sowie klinischer Untersuchungen besteht die Hoffnung, dass in absehbarer Zeit auch in der EU künstliche Sauerstofftransporter für therapeutische Zwecke zur Verfügung stehen werden.

Metal-Organic Framework Encapsulating Hemoglobin as a High-Stable and Long-Circulating Oxygen Carriers to Treat Hemorrhagic Shock

As an oxygen-transporting protein, free hemoglobin (Hb) often suffers from the disadvantage of undesirable stability and short blood circulation, which severely impairs the potential clinical applications as the blood substitute. In this work, Hb was facilely encapsulated into a kind of metal-organic frameworks (MOFs) (ZIF-8) inspired by the natural biomineralization process. The obtained ZIF-8 encapsulating Hb (ZIF-8@Hb) showed the small hydrodynamic size of 180.8 nm and neutral zeta potential of -2.1 mV by adjusting the ratio of Hb in ZIF-8 frameworks. Intriguingly, Hb encapsulated by ZIF-8 exhibited significantly enhanced stability in alkaline, oxidation, high temperature, or enzymatic environment compared with free Hb because of the excellent protective MOF coatings. More importantly, the negative charge of Hb neutralized the original positive charge of ZIF-8, which led to the better biocompatibility, lower protein adsorption, and macrophage uptake of ZIF-8@Hb than bare ZIF-8 nanoparticles. Furthermore, ZIF-8@Hb displayed extended blood circulation with the elimination half-life of 13.9 h as well as reduced nonspecific distribution in normal organs compared with free Hb or ZIF-8 nanoparticles. With the above advantages, ZIF-8@Hb showed significantly extended survival time of mice in a disease model of hemorrhagic shock compared with free Hb or bare ZIF-8 nanoparticles. Overall, this work offers a high-stable and long-circulating oxygen carrier platform, which may find wide applications as a blood substitute to treat various oxygen-relevant diseases.

Efficacy of Resuscitative Transfusion With Hemoglobin Vesicles in the Treatment of Massive Hemorrhage in Rabbits With Thrombocytopenic Coagulopathy and Its Effect on Hemostasis by Platelet Transfusion

INTRODUCTION

We have developed hemoglobin vesicles (HbVs) as a substitute for red blood cells (RBCs). We investigated the efficacy of HbV transfusion in the treatment of massive hemorrhage in rabbits in the setting of thrombocytopenic coagulopathy, focusing on the efficacy of hemostasis by subsequent platelet transfusion.

METHODS

Thrombocytopenic coagulopathy was induced in rabbits by repeated blood withdrawal and isovolemic retransfusion of autologous RBC (platelet counts <45,000/μL). A penetrating liver injury was then made. For 30 min, bleeding volume was measured every 10 min, after which subjects were transfused with an equivalent volume of stored RBC, HbV, or platelet poor plasma (PPP) to compensate for blood loss, simulating initial prehospital resuscitation. Thereafter, we transfused platelet rich plasma (PRP) to stop bleeding, which simulated inhospital resuscitation.

RESULTS

During the initial resuscitation, the HbV group was similar to the RBC group (but not the PPP group) in their hemodynamics and tissue circulation/oxygenation as assessed by plasma lactate levels. All rabbits showed similar bleeding volumes (20-30 mL) in this period. HbV-transfused rabbits sustained hemoglobin levels, but showed lower hematocrit levels compared with RBC-transfused rabbits. Subsequent PRP transfusion effectively stopped bleeding in all RBC-transfused rabbits (6/6) and most HbV-transfused rabbits (7/8) but not PPP-transfused rabbits (2/8). In addition, 83% of RBC-transfused rabbits and 75% of HbV-transfused rabbits survived for 24 h, although no PPP-transfused rabbits survived. HbV transfusion did not scavenge nitric oxide in rabbits.

CONCLUSIONS

HbV transfusion effectively rescued rabbits from severe hemorrhage with coagulopathy, without disturbing hemostasis after the platelet transfusion. HbV transfusion may be practical and useful in prehospital resuscitation.

Artificial Oxygen Carriers-Past, Present, and Future-a Review of the Most Innovative and Clinically Relevant Concepts

Blood transfusions are a daily practice in hospitals. Since these products are limited in availability and have various, harmful side effects, researchers have pursued the goal to develop artificial blood components for about 40 years. Development of oxygen therapeutics and stem cells are more recent goals. Medline (https://www.ncbi.nlm.nih.gov/pubmed/?holding=ideudelib), ClinicalTrials.gov (https://clinicaltrials.gov), EU Clinical Trials Register (https://www.clinicaltrialsregister.eu), and Australian New Zealand Clinical Trials Registry (http://www.anzctr.org.au) were searched up to July 2018 using search terms related to artificial blood products in order to identify new and ongoing research over the last 5 years. However, for products that are already well known and important to or relevant in gaining a better understanding of this field of research, the reader is punctually referred to some important articles published over 5 years ago. This review includes not only clinically relevant substances such as heme-oxygenating carriers, perfluorocarbon-based oxygen carriers, stem cells, and organ conservation, but also includes interesting preclinically advanced compounds depicting the pipeline of potential new products. In- depth insights into specific benefits and limitations of each substance, including the biochemical and physiologic background are included. "Fancy" ideas such as iron-based substances, O2 microbubbles, cyclodextranes, or lugworms are also elucidated. To conclude, this systematic up-to-date review includes all actual achievements and ongoing clinical trials in the field of artificial blood products to pursue the dream of artificial oxygen carrier supply. Research is on the right track, but the task is demanding and challenging.

Recent and prominent examples of nano- and microarchitectures as hemoglobin-based oxygen carriers

Blood transfusions, which usually consist in the administration of isolated red blood cells (RBCs), are crucial in traumatic injuries, pre-surgical conditions and anemias. Although RBCs transfusion from donors is a safe procedure, donor RBCs can only be stored for a maximum of 42 days under refrigerated conditions and, therefore, stockpiles of RBCs for use in acute disasters do not exist. With a worldwide shortage of donor blood that is expected to increase over time, the creation of oxygen-carriers with long storage life and compatibility without typing and cross-matching, persists as one of the foremost important challenges in biomedicine. However, research has so far failed to produce FDA approved RBCs substitutes (RBCSs) for human usage. As such, due to unacceptable toxicities, the first generation of oxygen-carriers has been withdrawn from the market. Being hemoglobin (Hb) the main component of RBCs, a lot of effort is being devoted in assembling semi-synthetic RBCS utilizing Hb as the oxygen-carrier component, the so-called Hb-based oxygen carriers (HBOCs). However, a native RBC also contains a multi-enzyme system to prevent the conversion of Hb into non-functional methemoglobin (metHb). Thus, the challenge for the fabrication of next-generation HBOCs relies in creating a system that takes advantage of the excellent oxygen-carrying capabilities of Hb, while preserving the redox environment of native RBCs that prevents or reverts the conversion of Hb into metHb. In this review, we feature the most recent advances in the assembly of the new generation of HBOCs with emphasis in two main approaches: the chemical modification of Hb either by cross-linking strategies or by conjugation to other polymers, and the Hb encapsulation strategies, usually in the form of lipidic or polymeric capsules. The applications of the aforementioned HBOCs as blood substitutes or for oxygen-delivery in tissue engineering are highlighted, followed by a discussion of successes, challenges and future trends in this field.

The effect of pPolyHb on hemodynamic stability and mesenteric microcirculation in a rat model of hemorrhagic shock

The effects of polymerized porcine hemoglobin (pPolyHb) on hemodynamic stability and maintenance of mesenteric microvascular function were explored in a rat model of hemorrhagic shock (HS). Following controlled hemorrhage, rats were infused with equal volumes of either pPolyHb, hetastarch (HES), or red blood cell (RBC). The results showed that pPolyHb was superior to HES and RBC in restoring hemodynamic stability and reversing anaerobic metabolism. We observed a reduction in the diameter of mesenteric microvasculature after HS. Resuscitation with pPolyHb and RBC was able to restore the diameters of the venules and arterioles, whereas HES failed to restore the diameters during the observation period.

S100B protein in serum is elevated after global cerebral ischemic injury

BACKGROUND:

S100B protein in patients with cardiac arrest, hemorrhagic shock and other causes of global cerebral ischemic injury will be dramatically increased. Ischemic brain injury may elevate the level of serum S100B protein and the severity of brain damage.

METHODS:

This article is a critical and descriptive review on S100B protein in serum after ischemic brain injury. We searched Pubmed database with key words or terms such as “S100B protein”, “cardiac arrest”, “hemorrhagic shock” and “ischemia reperfusion injury” appeared in the last five years.

RESULTS:

S100B protein in patients with cardiac arrest, hemorrhagic shock and other causes of ischemic brain injury will be dramatically increased. Ischemic brain injury elevated the level of serum S100B protein, and the severity of brain damage.

CONCLUSION:

The level of S100B protein in serum is elevated after ischemic brain injury, but its mechanism is unclear.

Blood substitutes: why haven't we been more successful?

Persistent safety concerns have stalled the development of viable hemoglobin (Hb)-based oxygen carriers (HBOCs). HBOCs have several advantages over human blood, including availability, long-term storage, and lack of infectious risk. The basis of HBOC toxicity is poorly understood, however, several mechanisms have been suggested, including Hb extravasation across the blood vessel wall, scavenging of endothelial nitric oxide (NO), oversupply of oxygen, and heme-mediated oxidative side reactions. Although there are some in vitro and limited animal studies supporting these mechanisms, heme-mediated reactivity appears to provide an alternative path that can explain some of the observed pathophysiological changes. Moreover, recent mechanistic and animal studies support a role for globin and heme scavengers in controlling oxidative toxicity associated with Hb infusion.

Examining and mitigating acellular hemoglobin vasoactivity

SIGNIFICANCE

There has been a striking advancement in our understanding of red cell substitutes over the past decade. Although regulatory oversight has influenced many aspects of product development in this period, those who have approached the demonstration of efficacy of red cell substitutes have failed to understand their implication at the level of the microcirculation, where blood interacts closely with tissue.

RECENT ADVANCES

The understanding of the adverse effects of acellular hemoglobin (Hb)-based oxygen carriers (HBOCs) has fortunately expanded from Hb-induced renal toxicity to a more complete list of biochemical mechanism. In addition, various unexpected adverse reactions were seen in early clinical studies. The effects of the presence of acellular Hb in plasma are relatively unique because of the convergence of mechanical and biochemical natures.

CRITICAL ISSUES

Controlling the variables using genetic engineering and chemical modification to change specific characteristics of the Hb molecule may allow for solving the complex multivariate problems of acellular Hb vasoactivity. HBOCs may never be rendered free of negative effects; however, quantifying the nature and extent of microvascular complications establishes a platform for designing new ameliorative therapies.

FUTURE DIRECTIONS

It is time to leave behind the study of vasoactivity and toxicity based on bench-top measurements of biochemical changes and those based solely on systemic parameters in vivo, and move to a more holistic analysis of the mechanisms creating the problems, complemented with meaningful studies of efficacy.