Translational research of hemoglobin vesicles as a transfusion alternative

Absence of Anaphylactic Reactions to Injection of Hemoglobin Vesicles (Artificial Red Cells) to Rodents

The safety and efficacy of hemoglobin vesicles (HbVs) as artificial oxygen carriers encapsulating a purified and concentrated Hb solution in liposomes have been studied extensively. The HbV surface, modified with PEG by incorporating a PEG-conjugated phospholipid, is beneficial for storage and biocompatibility. However, it might be possible that interaction of PEG and the pre-existing anti-PEG antibody in the bloodstream causes acute adverse reaction. This study used two sets of experiments with rats and guinea pigs to ascertain whether the anti-PEG antibody generated by the PEG-modified HbV injection can induce anaphylactic reactions. SD rats received repeated intravenous injection of HbV at a dose rate of 16 or 32 mL/kg three times. Not anti-PEG IgG but anti-PEG IgM was detected. Nevertheless, no anaphylactic reaction occurred. Guinea pigs were used to study the presence of active systemic anaphylaxis further after injections of the PEG-modified liposomes used for HbV. The animals were sensitized by three repeated subcutaneous injections of PEG-modified liposomes (PEG-liposome) along with adjuvant at 1 week intervals. For comparison, unmodified liposomes (liposome) and 10 times excessively PEG-modified liposomes with ionizable lipid (10PEG-DODAP-liposome) were used. Inclusion of PEG modification induced not only anti-PEG IgM but also anti-PEG IgG. Three weeks after the final injection, intravenous injection of both PEG-liposome and liposome (1 mL/kg) induced no anaphylactic reaction. However, the injection of 10PEG-DODAP-liposome showed one lethal anaphylaxis case and one mild anaphylaxis case. Antisera obtained from the animal sensitized as described above were inoculated (0.05 mL) intradermally into fresh guinea pigs. The presence of passive cutaneous anaphylaxis was evaluated after intravenous injections (1 mL/kg) of three liposomes with Evans blue. No dye leakage was detected at any inoculated skin point for PEG-liposome or liposome, but a slight leakage was detected in one inoculated skin point for 10PEG-DODAP-liposome. These results indicate the absence of acute allergic reactions at repeated injections of HbVs despite the anti-PEG antibody induction. Not all the PEG-modified liposomes show anaphylaxis, and it may depend on the amount of PEGylated phospholipid and lipid composition of PEG-modified liposomes.

Protective Effect of Modified Hemoglobin on Rabbits and Goats in High-Altitude Sickness

The prevalence and severity of high-altitude sickness increases with increasing altitude. Prevention of hypoxia caused by high-altitude sickness is an urgent problem. As a novel oxygen-carrying fluid, modified hemoglobin can carry oxygen in a full oxygen partial pressure environment and release oxygen in a low oxygen partial pressure environment. It is unclear whether modified hemoglobin can improve hypoxic injury on a plateau. Using hypobaric chamber rabbit (5000 m) and plateau goat (3600 m) models, general behavioral scores and vital signs, hemodynamic, vital organ functions, and blood gas are measured. The results show that the general behavioral scores and vital signs decrease significantly in the hypobaric chamber or plateau, and the modified hemoglobin can effectively improve the general behavioral scores and vital signs in rabbits and goats, and reduce the degree of damage to vital organs. Further studies reveal that arterial partial pressure of oxygen (PaO2 ) and arterial oxygen saturation (SaO2 ) on the plateau decrease rapidly, and the modified hemoglobin could increase PaO2 and SaO2 ; thus, increasing the oxygen-carrying capacity. Moreover, modified hemoglobin has few side effects on hemodynamics and kidney injury. These results indicate that modified hemoglobin has a protective effect against high-altitude sickness.

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.

Oxidation reactions of cellular and acellular hemoglobins: Implications for human health

Oxygen reversibly binds to the redox active iron, a transition metal in human Hemoglobin (Hb), which subsequently undergoes oxidation in air. This process is akin to iron rusting in non-biological systems. This results in the formation of non-oxygen carrying methemoglobin (ferric) (Fe3+) and reactive oxygen species (ROS). In circulating red blood cells (RBCs), Hb remains largely in the ferrous functional form (HbF2+) throughout the RBC's lifespan due to the presence of effective enzymatic and non-enzymatic proteins that keep the levels of metHb to a minimum (1%–3%). In biological systems Hb is viewed as a Fenton reagent where oxidative toxicity is attributed to the formation of a highly reactive hydroxyl radical (OH•) generated by the reaction between Hb's iron (Fe2+) and hydrogen peroxide (H2O2). However, recent research on both cellular and acellular Hbs revealed that the protein engages in enzymatic-like activity when challenged with H2O2, resulting in the formation of a highly reactive ferryl heme (Fe4+) that can target other biological molecules before it self-destructs. Accumulating evidence from several in vitro and in vivo studies are summarized in this review to show that Hb's pseudoperoxidase activity is physiologically more dominant than the Fenton reaction and it plays a pivotal role in the pathophysiology of several blood disorders, storage lesions associated with old blood, and in the toxicity associated with the infusion of Hb-derived oxygen therapeutics.

Examination of central nervous system by functional observation battery after massive intravenous infusion of carbon monoxide-bound and oxygen-bound hemoglobin vesicles in rats

Carbon monoxide (CO) is known as a toxic gas inducing "CO poisoning", which acutely affects the central nervous system (CNS) and which persistently affects brain functions depending on the exposure time and CO concentration. By contrast, in pathological rodent models, intravenous infusion of CO-bound hemoglobin vesicles (CO-HbV) has shown various beneficial effects such as anti-oxidative and anti-inflammatory reactions. This study assessed effects of CO-HbV infusion on CNS using a functional observation battery, sensory reflexes, grip strength, and landing foot splay measurements. The test fluids were CO-HbV and O₂-bound HbV (O₂-HbV) suspended in saline ([Hb] ​= ​10 ​g/dL), and saline alone for comparison. The rats received either 16 or 32 ​mL/kg of fluid intravenously at 1.5 ​mL/min/kg. Observations were made before infusion, and at 5 ​min, 4, 8, 24, 48 and 72 ​h after infusion. Massive doses of 16 and 32 ​mL/kg respectively corresponded to about 29 and 57% of the whole circulating blood volume (56 ​mL/kg). No toxicological effect was observed in any measurement item for any group in comparison to the control saline infusion group. Histopathological examination of hippocampal tissue at 14 days after infusion showed the number of necrotic cells to be minimal. Results obtained from rats in this experiment suggest that the massive intravenous infusion of CO-HbV yields beneficial anti-oxidative and anti-inflammatory effects without showing CO-poisoning-related symptoms of CNS damage.

Liposomal methemoglobin as a potent antidote for hydrogen sulfide poisoning

Hydrogen sulfide (H₂S) induces acute and lethal toxicity at high concentrations. However, no specific antidotes for H₂S poisoning have been approved. Liposomal methemoglobin (metHb@Lipo) was developed as an antidote for cyanide poisoning. As the toxic mechanism of H₂S poisoning is the same as that of cyanide poisoning, metHb@Lipo could potentially be used as an antidote for H₂S poisoning. In this study, we evaluated the antidotal efficacy of metHb@Lipo against H₂S poisoning. Stopped-flow rapid-scan spectrophotometry clearly showed that metHb@Lipo scavenged H₂S rapidly. Additionally, metHb@Lipo showed cytoprotective effects against H₂S exposure in H9c2 cells by maintaining mitochondrial function. MetHb@Lipo treatment also improved the survival rate after H₂S exposure in vivo, with the maintenance of cytochrome c oxidase activity and suppression of metabolic acidosis. Moreover, metHb@Lipo therapy maintained significant antidotal efficacy even after 1-year-storage at 4-37 °C. In conclusion, metHb@Lipo is a candidate antidote for H₂S poisoning.

Liposomal Artificial Red Blood Cell-Based Carbon Monoxide Donor Is a Potent Renoprotectant against Cisplatin-Induced Acute Kidney Injury

Cisplatin (CDDP) is an essential anti-tumor agent for chemotherapeutic regimens against various types of cancer. However, the progression of nephrotoxicity, which is the main adverse effect of CDDP, leads to discontinuation of CDDP chemotherapy. Therefore, development of a renoprotectant against CDDP-induced nephrotoxicity is crucial. Here, the potential of a carbon monoxide (CO)-loaded hemoglobin-vesicle (CO-HbV) as a renoprotectant for CDDP-induced nephrotoxicity was evaluated for its renoprotective effects against CDDP-induced nephrotoxicity, inhibitory effects on the anti-tumor activity of CDDP, and anti-tumor activity. In healthy mice, after pretreatment with either saline, HbV, or CO-HbV prior to CDDP administration, only the CO-HbV pretreatment group ameliorated the progression of CDDP-induced nephrotoxicity by suppressing apoptosis via caspase-3. In experiments using B16-F10 melanoma cells, the half-maximal inhibitory concentration of CDDP decreased with co-incubation with CO-HbV, owing to the anti-tumor activity of CO. CO-HbV pretreatment had no impact on the anti-tumor activity of CDDP in B16-F10 melanoma cell-bearing mice, which was consistent with the results of the cell experiment. Furthermore, CO-HbV pretreatment improved body growth and survival rates. In conclusion, CO-HbV pretreatment is a potent renoprotectant for CDDP-induced nephrotoxicity, allowing treatment with CDDP to be conducted without failure of cancer treatment.

Industrially Compatible Transfusable iPSC-Derived RBCs: Progress, Challenges and Prospective Solutions

Amidst the global shortfalls in blood supply, storage limitations of donor blood and the availability of potential blood substitutes for transfusion applications, society has pivoted towards in vitro generation of red blood cells (RBCs) as a means to solve these issues. Many conventional research studies over the past few decades have found success in differentiating hematopoietic stem and progenitor cells (HSPCs) from cord blood, adult bone marrow and peripheral blood sources. More recently, techniques that involve immortalization of erythroblast sources have also gained traction in tackling this problem. However, the RBCs generated from human induced pluripotent stem cells (hiPSCs) still remain as the most favorable solution due to many of its added advantages. In this review, we focus on the breakthroughs for high-density cultures of hiPSC-derived RBCs, and highlight the major challenges and prospective solutions throughout the whole process of erythropoiesis for hiPSC-derived RBCs. Furthermore, we elaborate on the recent advances and techniques used to achieve cost-effective, high-density cultures of GMP-compliant RBCs, and on their relevant novel applications after downstream processing and purification.