FLUID RESUSCITATION WITH HEMOGLOBIN VESICLES IN A RABBIT MODEL OF ACUTE HEMORRHAGIC SHOCK

Research of storable and ready-to-use artificial red blood cells (hemoglobin vesicles) for emergency medicine and other clinical applications

Hemoglobin (Hb) is the most abundant protein in blood, with concentration of about 12-15 g/dl. The highly concentrated Hb solution (35 g/dl) is compartmentalized in red blood cells (RBCs). Once Hb is released from RBCs by hemolysis during blood circulation, it induces renal and cardiovascular toxicities. To date, hemoglobin-based oxygen carriers of various types have been developed as blood substitutes to mitigate the Hb toxicities. One method is Hb encapsulation in phospholipid vesicles (liposomes). Although the Hb toxicity can be shielded, it is equally important to ensure the biocompatibility of the liposomal membrane. We have developed Hb-vesicles (HbV). A new encapsulation method using a rotation-revolution mixer which enabled efficient production of HbV with a high yield has considerably facilitated R&D of HbV. Along with our academic consortium, we have studied the preclinical safety and efficacy of HbV extensively as a transfusion alternative, and finally conducted a phase I clinical trial. Moreover, carbonyl-HbV and met-HbV are developed respectively for an anti-inflammatory and anti-oxidative agent and an antidote for poisons. This review paper specifically presents past trials of liposome encapsulated Hb, biocompatible lipid bilayer membranes, and efficient HbV preparation methods, in addition to potential clinical applications of HbV based on results of our in vivo studies.

Kidney Microcirculation as a Target for Innovative Therapies in AKI

Acute kidney injury (AKI) is a serious multifactorial conditions accompanied by the loss of function and damage. The renal microcirculation plays a crucial role in maintaining the kidney’s functional and structural integrity for oxygen and nutrient supply and waste product removal. However, alterations in microcirculation and oxygenation due to renal perfusion defects, hypoxia, renal tubular, and endothelial damage can result in AKI and the loss of renal function regardless of systemic hemodynamic changes. The unique structural organization of the renal microvasculature and the presence of autoregulation make it difficult to understand the mechanisms and the occurrence of AKI following disorders such as septic, hemorrhagic, or cardiogenic shock; ischemia/reperfusion; chronic heart failure; cardiorenal syndrome; and hemodilution. In this review, we describe the organization of microcirculation, autoregulation, and pathophysiological alterations leading to AKI. We then suggest innovative therapies focused on the protection of the renal microcirculation and oxygenation to prevent AKI.

Translational research of hemoglobin vesicles as a transfusion alternative

Clinical situations arise in which blood for transfusion becomes scarce or unavailable. Considerable demand for a transfusion alternative persists because of various difficulties posed by blood donation and transfusion systems. Hemoglobin-vesicles (HbV) are artificial oxygen carriers being developed for use as a transfusion alternative. Just as biomembranes of red blood cells (RBCs) do, phospholipid vesicles (liposomes) for Hb encapsulation can protect the human body from toxic effects of molecular Hb. The main HbV component, Hb, is obtained from discarded human donated blood. Therefore, HbV can be categorized as a biologic agent targeting oxygen for peripheral tissues. The purification procedure strictly eliminates the possibility of viral contamination. It also removes all concomitant unstable enzymes present in RBC for utmost safety from infection. The deoxygenated HbVs, which are storable for over years at ambient temperature, can function as an alternative to blood transfusion for resuscitation from hemorrhagic shock and O₂ therapeutics. Moreover, a recent study clarified beneficial effects for anti-oxidation and anti-inflammation by carbon monoxide (CO)-bound HbVs. Autoxidation of HbV (HbO₂ → metHb + O₂-.) is unavoidable after intravenous administration. Co-injection of methylene blue can extract the intraerythrocytic glycolytic electron energy effectively and reduce metHb. Other phenothiazine dyes can also function as electron mediators to improve the functional life span of HbV. This review paper summarizes recent progress of the research and development of HbV, aimed at clinical applications.

The Use of Hemoglobin Vesicles for Delivering Medicinal Gas for the Treatment of Intractable Disorders

Bioactive gaseous molecules, such as oxygen (O₂) and carbon monoxide (CO), are essential elements for most living organisms to maintain their homeostasis and biological activities. An accumulating body of evidence suggests that such molecules can be used in clinics as a medical gas in the treatment of various intractable disorders. Recent developments in hemoglobin-encapsulated liposomes, namely hemoglobin vesicles (HbV), possess great potential for retaining O₂ and CO and could lead to strategies for the development of novel pharmacological agents as medical gas donors. HbV with either O₂ or CO bound to it has been demonstrated to have therapeutic potential for treating certain intractable disorders and has the possibility to serve as diagnostic and augmenting product by virtue of unique physicochemical characteristics of HbV. The present review provides an overview of the present status of the use of O₂- or CO-binding HbV in experimental animal models of intractable disorders and discusses prospective clinical applications of HbV as a medical gas donor.

Overview of Potential Clinical Applications of Hemoglobin Vesicles (HbV) as Artificial Red Cells, Evidenced by Preclinical Studies of the Academic Research Consortium

Hemoglobin (Hb) is the most abundant protein in whole blood. This fact implies that the oxygen binding and releasing function of Hb is the most vital for sustaining life. All Hb is compartmentalized in red blood cells (RBCs) with corpuscular Hb concentration of about 35 g/dL, covered with a thin biomembrane. In spite of its abundance, Hb sometimes shows toxicity once it is leaked from RBCs. The shielding effect of the RBC membrane is physiologically important. Based on this structural importance, we have studied artificial red cells (Hb vesicles, HbV) as artificial oxygen carriers, which encapsulate a purified and concentrated Hb solution in phospholipid vesicles, mimicking the cellular structure of RBCs. Our academic research consortium has clarified the safety and efficacy of this HbV, aiming at clinical applications. Because of some superior characteristics to those of RBCs, HbV has the potential for use not only as a transfusion alternative but also for oxygen and carbon monoxide therapeutics, perfusate for transplant organs, and photosensitizer. In this review paper, such potential applications are summarized.

Beneficial effects of novel cross-linked hemoglobin YQ23 on hemorrhagic shock in rats and pigs

BACKGROUND

To overcome the problems of previously reported hemoglobin-based oxygen carriers, we developed a stabilized nonpolymeric cross-linked tetrameric hemoglobin solution (YQ23). The aims of this study were to investigate the oxygen carrying and releasing properties of this novel hemoglobin-based oxygen carrier and to determine whether it has beneficial effects for hemorrhagic shock.

METHODS

Using a hemorrhagic shock model in Sprague-Dawley rats and mini-pigs, we tested the effects of infusing 0.1, 0.3, and 0.5 g/kg YQ23 on animal survival, tissue oxygen delivery (DO₂) and consumption (VO₂), hemodynamics parameters, and liver, renal, and cardiac function.

RESULTS

YQ23 infusion increased the survival rate of rats and pigs with severe hemorrhagic shock in a dose-dependent manner. Moreover, it improved the hemodynamic parameters, cardiac output, DO₂ and VO₂, and the mitochondrial respiratory function of vital organs. Among the three doses of YQ23, 0.5 gHb/kg YQ23 achieved a similar beneficial effect as whole blood.

CONCLUSIONS

This study indicated that the novel cross-linked tetrameric hemoglobin YQ23 has good oxygen carrying and releasing properties and exhibits beneficial effects on hemorrhagic shock in rats and pigs by improving the oxygen carrying and delivery function of blood, which maintains organ function.

The impact on renal function of fluid resuscitation with hemoglobin vesicle solution in moderate hemorrhagic shock

In this study, hemoglobin vesicle (HbV), a type of artificial oxygen carrier, was infused in a hemorrhagic shock model, and the findings were compared with those of red blood cell (RBC) transfusion to evaluate the effects on blood pressure and renal function. In rats maintained in hemorrhagic shock for 30 min under general anesthesia, either irradiated stored RBCs from the same strain or HbVs were used for resuscitation. Blood pressure, serum creatinine concentration, and creatinine clearance 24 h after shock were measured. At 2 and 24 h after shock, the kidneys were removed, and the heme oxygenase-1 (HO-1) mRNA level was measured. A histopathology study was performed 24 h after shock. In both the RBC and HbV group, blood pressure recovered significantly immediately after fluid resuscitation, and blood pressure 24 h after shock did not differ significantly between the two groups. Serum creatinine concentration and creatinine clearance 24 h after shock did not differ significantly between the two groups. After 24 h, there was no significant difference in HO-1 mRNA between the groups. In the renal histopathology samples taken at 24 h after shock, there were no obvious differences between the two groups. In conclusion, HbV transfusion improved blood pressure in a manner equivalent to RBC transfusion when administered during hemorrhagic shock, and no renal dysfunction was apparent after 24 h.

A transient inflammatory reaction in the lung after experimental hemorrhagic shock and resuscitation with a hemoglobin-vesicles solution compared with rat RBC transfusion

Transfusion for hemorrhagic shock can improve oxygenation, but immunoreactions may induce inflammation. Artificial oxygen carriers have been developed to address clinical concerns of infection and stability, but whether an artificial oxygen carrier might induce inflammation is not well known. To address this question, we compared inflammatory reactions after resuscitation with hemoglobin vesicles (HbVs) or red blood cells (RBCs) in a hemorrhagic shock rat model. Both HbVs and the stored and irradiated rat RBCs deprived of buffy coat were suspended in recombinant human serum albumin [(Hb) = 8.6 g/dL]. Under anesthesia, hemorrhagic shock was induced for 30 min, followed by resuscitation by 20 min transfusion of HbVs or rat RBCs in a volume equivalent to the volume of withdrawn blood. Lungs were excised 2 or 24 h after resuscitation, and mRNA levels of tumor necrosis factor alpha (TNF-alpha), intercellular adhesion molecule-1 (ICAM-1), nitric oxide synthase 2 (iNOS), nitric oxide synthase 3, hypoxia-inducible factor 1 alpha, and heme oxygenase 1 (HO-1) were measured. In rats resuscitated with HbVs, mRNA levels of TNF-alpha and HO-1 2 h after resuscitation were significantly higher than those in the rat RBC group, but the levels at 24 h were similar in both groups. The expression of iNOS and ICAM-1, second messengers of inflammation, was not affected, and inflammatory levels after 24 h with HbVs are similar to rat RBC transfusion. The rat RBC group did not show an expected inflammatory reaction related to a transfusion-induced lung injury, and a clinical relevance concerning this level of transient inflammatory reaction induced by HbVs is not known; however, attention to the early stage of resuscitation in ongoing studies of HbV is required.

Fluid resuscitation with artificial oxygen carriers in hemorrhaged rats: profiles of hemoglobin-vesicle degradation and hematopoiesis for 14 days

Polyethylene glycol (PEG)-modified hemoglobin (Hb) vesicles (HbVs) are artificial oxygen carriers encapsulating a concentrated Hb solution in phospholipid vesicles. In our previous studies, HbV showed a sufficient resuscitative effect comparable to that of red blood cells in hemorrhagic shock animal models during several hours' observation. However, the profiles of the recovery, including hematopoiesis and elimination of HbV, remain unknown. This study conducted 14-day observations of Wistar rats after hemorrhagic shock and fluid resuscitation with HbV suspended in recombinant human serum albumin. Shock was induced by 50% blood withdrawal from a femoral artery. The rats showed hypotension, metabolic acidosis, and hyperventilation. After 15 min, they received HbV or shed autologous blood through a femoral vein. Both groups showed rapid recovery of hemodynamic and blood gas parameters. No meaningful difference was found between groups. After decannulation and awakening, the rats were housed in cages. The reduced hematocrit of the HbV group returned to the original level in 7 days. Plasma enzyme levels were slightly higher in both groups at 1 day because of systemic reperfusion injury. Splenomegaly was considerable in the HbV group because of the HbV accumulation and extramedullar hematopoiesis, but it subsided within 14 days. Along with the HbV elimination in the spleen and liver, immunohistochemistry with anti-PEG antibody revealed that PEG-conjugated lipid had disappeared within 14 days. In conclusion, HbV showed a sufficient resuscitative effect comparable to that of red blood cell transfusion. Phagocytized HbV disappeared within 14 days. Elevated hematopoiesis contributed to complete hematocrit recovery within 7 days.

Bench-to-bedside review: latest results in hemorrhagic shock

Hemorrhagic shock is a leading cause of death in trauma patients worldwide. Bleeding control, maintenance of tissue oxygenation with fluid resuscitation, coagulation support, and maintenance of normothermia remain mainstays of therapy for patients with hemorrhagic shock. Although now widely practised as standard in the USA and Europe, shock resuscitation strategies involving blood replacement and fluid volume loading to regain tissue perfusion and oxygenation vary between trauma centers; the primary cause of this is the scarcity of published evidence and lack of randomized controlled clinical trials. Despite enormous efforts to improve outcomes after severe hemorrhage, novel strategies based on experimental data have not resulted in profound changes in treatment philosophy. Recent clinical and experimental studies indicated the important influences of sex and genetics on pathophysiological mechanisms after hemorrhage. Those findings might provide one explanation why several promising experimental approaches have failed in the clinical arena. In this respect, more clinically relevant animal models should be used to investigate pathophysiology and novel treatment approaches. This review points out new therapeutic strategies, namely immunomodulation, cardiovascular maintenance, small volume resuscitation, and so on, that have been introduced in clinics or are in the process of being transferred from bench to bedside. Control of hemorrhage in the earliest phases of care, recognition and monitoring of individual risk factors, and therapeutic modulation of the inflammatory immune response will probably constitute the next generation of therapy in hemorrhagic shock. Further randomized controlled multicenter clinical trials are needed that utilize standardized criteria for enrolling patients, but existing ethical requirements must be maintained.

Haemoglobin-vesicles as artificial oxygen carriers: present situation and future visions

During the long history of development of haemoglobin (Hb)-based O2 carriers (HBOCs), many side effects of Hb molecules have become apparent. They imply the physiological importance of the cellular structure of red blood cells. Hb-vesicles (HbV) are artificial O2 carriers that encapsulate concentrated Hb solution with a thin lipid membrane. We have overcome the intrinsic issues of the suspension of HbV as a molecular assembly, such as stability for storage and in blood circulation, blood compatibility and prompt degradation in the reticuloendothelial system. Animal tests clarified the efficacy of HbV as a transfusion alternative and the possibility for other clinical applications. The results of ongoing HbV research make us confident in advancing further development of HbV, with the expectation of its eventual realization.

Fluid resuscitation with hemoglobin-vesicle solution does not increase hypoxia or inflammatory responses in moderate hemorrhagic shock

The aim of the present study was to compare the hypoxic and inflammatory effects of transfusing hemoglobin-vesicles (HbV) or lactated Ringer's (LR) solution on several organs in a hemorrhagic shock model. Hemorrhagic shock was induced in 48 anesthetized rats by withdrawing 28 mL/kg blood. The animals were resuscitated by replacing the blood with an equal volume of HbV solution or three times the volume of LR solution. The heart, lung, liver, kidney and spleen were extracted at different time points following resuscitation, and mRNA expression levels of hypoxia-induced factor 1-alpha (HIF-1alpha) and tumor necrosis factor-alpha (TNF-alpha) were determined. Blood lactate concentrations in the HbV group rapidly returned to baseline levels, whereas elevated lactate concentrations in the LR group were prolonged. There were no significant differences between the two resuscitation groups in terms of HIF-1alpha and TNF-alpha expression in the organs examined. HIF-1alpha and TNF-alpha expression in the lungs was significantly greater than in other organs. Our results suggest that resuscitation from hemorrhagic shock with HbV did not increase hypoxic or inflammatory effects in major organs, compared with resuscitation using LR solution, despite prolonged elevation of blood lactate.