Liposome-Encapsulated Hemoglobin Transfusion Rescues Rats Undergoing Progressive Hemodilution From Lethal Organ Hypoxia Without Scavenging Nitric Oxide

Intraosseous infusion of liposome-encapsulated hemoglobin (HbV) acutely prevents hemorrhagic anemia-induced lethal arrhythmias and its efficacy persists with preventing proarrhythmic side effects in subacute phase of severe hemodilution model

BACKGROUND

Artificial oxygen carriers (HbV) can treat hemorrhagic shock with lethal arrhythmias (VT/VF). No reports exist on subacute HbV's effects.

METHODS

Acute and subacute resuscitation effects with anti-arrhythmogenesis of HbV were studied in 85% blood exchange rat model (85%-Model). Lethal 85%-Model was created by bone marrow transfusion and femoral artery bleeding in 80 SD rats in HbV-administered group (HbV-group), washed erythrocyte-administered group (wRBC-group), and 5% albumin-administered group (ALB-group). Survival rates, anti-arrhythmic efficacy by optical mapping analysis (OMP) with electrophysiological stimulation (EPS) in Langendorff heart, cardiac autonomic activity by heart rate variability (HRV) and ventricular arrhythmias by 24-hour electrocardiogram telemetry monitoring (24h-ECG) in awake, and left ventricular function by echocardiography (LVEF) were measured.

RESULTS

All rats in HbV- and wRBC-groups survived for 4 weeks whereas no rats in ALB-group. HbV and wRBC acutely suppressed VT/VF in Langendorff heart through ameliorating action potential duration dispersion (APDd) analyzed by OMP with EPS. For subacute analysis, 50% blood exchange by 5% albumin was utilized (ALB-group 50). Subacute salutary effect on APDd and VT/VF inducibility was confirmed in HbV- and wRBC-groups. 24h-ECG showed that HbV and wRBC suppressed none-sustained VT (NSVT) and sympathetic component of HRV (LF/HF) with preserved LVEF (HbV-group, wRBC-group vs. ALB-group 50;NSVT numbers/days, 0.5±0.3, 0.4±0.3 vs. 3.9±1.2*; LF/HF, 1.1±0.2, 0.8±0.2 vs. 3.5±1.0*;LVEF, 84±5, 83±4, vs. 77±4%*; *p<0.05).

CONCLUSIONS

Collectively, HbV has sustained antiarrhythmic effect in subacute 85%-Model by ameliorating electrical remodeling and improving arrhythmogenic modifying factors (HRV and LVEF). These findings are useful in now continuing clinical trials of HbV.

Liposome-encapsulated hemoglobin (HbV) transfusion rescues rats undergoing progressive lethal 85% hemorrhage as a result of an anti-arrhythmogenic effect on the myocardium

Liposome-encapsulated hemoglobin vesicles (HbV) can serve as a blood substitute with oxygen-carrying capacity comparable to that of human blood and lethal hemorrhage is associated with lethal arrhythmias. To investigate the resuscitation effect of HbV on lethal hemorrhage and anti-arrhythmogenesis, we performed optical mapping analysis (OMP) and electrophysiological study (EPS) in graded blood exchange (85% blood loss) in the rat model. We also measured cardiac autonomic activity, as assessed by heart rate variability (HRV), and changes in plasma norepinephrine and left ventricle ejection fraction (LVEF) by echocardiography. Pathological study on Connexin43 was performed. A 5% albumin (ALB group), washed rat erythrocytes (wRBC group), and HbV (HbV group) were used as a resuscitation fluid. The survival effects over 24 hours were examined. All rats died in the ALB group, whereas almost all survived for 24-hours period in wRBC and HbV groups. OMP showed impaired action potential duration dispersion (APDd) in the ALB group, whereas normal APDs in HbV and wRBC groups. Lethal arrhythmias were induced by EPS in the ALB group, but not in wRBC and HbV groups. HRV indices, LVEF, Connexin43 were preserved in HbV and wRBC groups. Lethal hemorrhage causes lethal arrhythmias in the presence of impaired APDd. HbV acutely rescues lethal hemorrhage by preventing lethal arrhythmias and preserving arrhythmogenic factors.

Myocardial Electrical Remodeling and the Arrhythmogenic Substrate in Hemorrhagic Shock-Induced Heart: Anti-Arrhythmogenic Effect of Liposome-Encapsulated Hemoglobin (HbV) on the Myocardium

INTRODUCTION

Prolonged low blood pressure <40 mmHg in hemorrhagic shock (HS) causes irreversible heart dysfunction, 'Shock Heart Syndrome' (SHS), which is associated with lethal arrhythmias (ventricular tachycardia or ventricular fibrillation [VT/VF]) leading to a poor prognosis.

METHODS

To investigate whether the liposome-encapsulated human hemoglobin oxygen carrier (HbV) is comparable in effectiveness to autologous washed red blood cells (wRBCs) for improving arrhythmogenic properties in SHS, optical mapping analysis (OMP), electrophysiological study (EPS), and pathological examinations were performed in Sprague-Dawley rat hearts obtained from rats subjected to acute HS by withdrawing 30% of total blood volume. After acute HS, the rats were immediately resuscitated by transfusing exactly the same amount of saline (SAL), 5% albumin (5% ALB), HbV, or wRBCs. After excising the heart, OMP and EPS were performed in Langendorff-perfused hearts.

RESULTS

OMP showed a tendency for abnormal conduction and significantly impaired action potential duration dispersion (APDd) in both ventricles with SAL and 5% ALB. In contrast, myocardial conduction and APDd were substantially preserved with HbV and wRBCs. Sustained VT/VF was easily provoked by a burst pacing stimulus to the left ventricle with SAL and 5% ALB. No VT/VF was induced with HbV and wRBCs. Pathology showed myocardial structural damage characterized by worse myocardial cell damage and Connexin43 with SAL and 5% ALB, whereas it was attenuated with HbV and wRBCs.

CONCLUSIONS

Ventricular structural remodeling after HS causes VT/VF in the presence of APDd. Transfusion of HbV prevents VT/VF, similarly to transfusion of wRBCs, by preventing electrical remodeling and preserving myocardial structures in HS-induced SHS.

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.

Acute 40% exchange-transfusion with hemoglobin-vesicles in a mouse pneumonectomy model

OBJECTIVES

Hemoglobin vesicles (HbVs) function as a red blood cell (RBC) substitute and are composed of purified hemoglobin encapsulated in a phospholipid bilayer membrane. The performance of HbVs as a substitute for RBC transfusions was examined in a mouse model of pneumonectomy following acute 40% exchange-transfusion with HbVs.

METHODS

Before performing left pneumonectomies, 40% of the blood volume of mice was replaced with a) lactated Ringer's solution (control), b) 5% recombinant human serum albumin (rHSA), c) mouse RBCs shed in rHSA (mRBCs/rHSA), or d) HbV suspended in rHSA (HbV/rHSA). We compared postoperative a) survival, b) functional recovery, and c) histopathological, immunohistochemical, and inflammatory responses among the study groups.

RESULTS

In the HbV/rHSA and mRBC/rHSA groups, all mice survived ≥7 days after pneumonectomy, whereas 100% of the control mice died within a few h and 50% of mice in the rHSA group died within 24 h after pneumonectomy. Immunohistochemical staining for hypoxia-inducible factor-1α showed that hepatic and renal hypoxic injuries were prominently mitigated by HbV and mRBCs.

CONCLUSIONS

The oxygen-carrying performance of HbV was similar to that of mRBCs, even with impaired lung functions following pneumonectomy. HbV infusion did not interfere with the recovery from surgical injury. In the near future, HbVs could be used clinically as a substitute for the perioperative transfusion of RBCs, when or where donated RBCs are not immediately available.

Effects of liposome-encapsulated hemoglobin on gastric wound healing in the rat

Liposome-encapsulated hemoglobin (LEH) may improve microcirculation and oxygen (O2 ) metabolism at a surgical wound to accelerate its healing. Ten mL/kg of LEH with high (h-LEH) or low O2 -affinity (l-LEH), homologous red blood cells (RBC), empty liposome or saline as a control was infused before a 10-mm incision and interrupted suture closure of the gastric wall in a total of 110 rats. Two and 4 days later, the stomach was excised for bursting pressure determination and histological sampling. The dose-response relationship was examined in 70 additional rats receiving progressively reduced doses of h-LEH. Hypoxia-inducible factor-1α (HIF-1α) was stained immunohistochemically in 54 other rats to examine its accumulation at the anastomotic sites. Bursting pressure of the surgical wound was significantly higher 2 days after surgery only in the h-LEH-treated rats (P < 0.05), but not at 4 days after surgery, when other rats showed increased bursting pressure to a nonsignificant level. Histological examination revealed less granulocyte infiltration, better granulation, and more macrophage infiltration in h-LEH-treated rats at 2 days, but no longer at 4 days postsurgery. Dose-response study revealed that 0.4 mL/kg of h-LEH (hemoglobin 24 mg/kg) was effective for elevating bursting pressure at 2 days. h-LEH-treated rats had significantly suppressed HIF-1α accumulation in the wound 6, 24, and 48 h after surgery as compared with control animals treated with homologous RBC or saline. In conclusion, the results suggest that h-LEH, but not l-LEH or homologous transfusion, may accelerate wound healing early after gastric incision and anastomosis in the rat. The mechanism(s) appears to be related to improved O2 supply, aerobic metabolism, and suppressed inflammation in the wound.

Myeloid knockout of HIF-1 α does not markedly affect hemorrhage/resuscitation-induced inflammation and hepatic injury

BACKGROUND

Hypoxia-inducible factor-1 α (HIF-1 α ) and NF- κ B play important roles in the inflammatory response after hemorrhagic shock and resuscitation (H/R). Here, the role of myeloid HIF-1 α in liver hypoxia, injury, and inflammation after H/R with special regard to NF- κ B activation was studied.

METHODS

Mice with a conditional HIF-1 α knockout (KO) in myeloid cell-line and wild-type (WT) controls were hemorrhaged for 90 min (30 ± 2 mm Hg) and resuscitated. Controls underwent only surgical procedures.

RESULTS

After six hours, H/R enhanced the expression of HIF-1 α -induced genes vascular endothelial growth factor (VEGF) and adrenomedullin (ADM). In KO mice, this was not observed. H/R-induced liver injury in HIF-1 α KO was comparable to WT. Elevated plasma interleukin-6 (IL-6) levels after H/R were not reduced by HIF-1 α KO. Local hepatic hypoxia was not significantly reduced in HIF-1 α KO compared to controls after H/R. H/R-induced NF- κB phosphorylation in liver did not significantly differ between WT and KO.

CONCLUSIONS

Here, deleting HIF-1 α in myeloid cells and thereby in Kupffer cells was not protective after H/R. This data indicates that other factors, such as NF- κB, due to its upregulated phosphorylation in WT and KO mice, contrary to HIF-1 α, are rather key modulators of inflammation after H/R in our model.

Fibrinogen γ-chain peptide-coated, ADP-encapsulated liposomes rescue thrombocytopenic rabbits from non-compressible liver hemorrhage

BACKGROUND

We developed a fibrinogen γ-chain (dodecapeptide HHLGGAKQAGDV [H12])-coated, ADP-encapsulated liposome (H12-[ADP]-liposome) that accumulates at bleeding sites via interaction with activated platelets via glycoprotein IIb-IIIa and augments platelet aggregation by releasing ADP.

OBJECTIVE

To evaluate the efficacy of H12-(ADP)-liposomes for treating liver hemorrhage in rabbits with acute thrombocytopenia.

METHODS

Thrombocytopenia (platelets < 50 000 μL(-1)) was induced in rabbits by repeated blood withdrawal (100 mL kg(-1) in total) and isovolemic transfusion of autologous washed red blood cells. H12-(ADP)-liposomes with platelet-poor plasma (PPP), platelet-rich plasma (PRP), PPP, ADP liposomes with PPP or H12-(PBS)-liposomes/PPP, were administered to the thrombocytopenic rabbits, and liver hemorrhage was induced by penetrating liver injury.

RESULTS

Administration of H12-(ADP)-liposomes and of PRP rescued all thrombocytopenic rabbits from liver hemorrhage as a result of potent hemostasis at the liver bleeding site, although rabbits receiving PPP or ADP liposomes showed 20% survival in the first 24 h. Administration of H12-(ADP)-liposomes and of PRP suppressed both bleeding volume and time from the site of liver injury. H12-(phosphate-buffered saline)-liposomes lacking ADP also improved rabbit survival after liver hemorrhage, although their hemostatic effect was weaker. In rabbits with severe thrombocytopenia (25 000 platelets μL(-1)), the hemostatic effects of H12-(ADP)-liposomes tended to be attenuated as compared with those of PRP treatment. Histologic examination revealed that H12-(ADP)-liposomes accumulated at the bleeding site in the liver. Notably, neither macrothombi nor microthrombi were detected in the lung, kidney or liver in rabbits treated with H12-(ADP)-liposomes.

CONCLUSIONS

H12-(ADP)-liposomes appear to be a safe and effective therapeutic tool for acute thrombocytopenic trauma patients with massive bleeding.

Large scale production of vesicles by hollow fiber extrusion: a novel method for generating polymersome encapsulated hemoglobin dispersions

Vesicles, which include both liposomes and polymersomes (polymer vesicles), are being developed as therapeutic drug carriers. In this study, we present a fully scalable low pressure extrusion methodology for preparing vesicles. Vesicles were generated by continuous extrusion through a 200 nm pore diameter hollow fiber (HF) membrane. The first half of this study describes a method for generating empty polymersomes composed of different molecular weight amphiphilic poly(butadiene-b-ethylene oxide) (PBD-b-PEO) diblock copolymers on a large scale (50-100 mL) using a HF membrane. Monodisperse empty polymersomes were formed with particle diameters slightly less than 200 nm, which were close to the rated 200 nm pore size of the HF membrane. The second half of this study describes the successful encapsulation of hemoglobin (Hb) inside the aqueous core of polymersomes using the HF extrusion methodology. We demonstrate that polymersome encapsulated hemoglobin (PEH) particles formed by this technique had similar oxygen affinity, cooperativity coefficient, and methemoglobin (metHb) level compared to PEH particles formed by the 1 mL volume small scale manual extrusion method. Most notably, Hb encapsulation inside the polymer vesicles formed by the HF extrusion method increased 2-fold compared to the manual extrusion method. This work is important, since it will enable facile scale-up of homogeneous vesicle dispersions that are typically required for preclinical and clinical studies as well as industrial use.

Trauma-hemorrhage and hypoxia differentially influence kupffer cell phagocytic capacity: role of hypoxia-inducible-factor-1alpha and phosphoinositide 3-kinase/Akt activation

OBJECTIVE

We investigated whether Kupffer cell phagocytosis is differentially regulated following hypoxia (by breathing hypoxic gas) and trauma-hemorrhage. We hypothesized that the differences might result from a differential activation of hypoxia-inducible factor (HIF)-1alpha and phosphoinositide 3-kinase (PI3K)/Akt pathway under those conditions.

BACKGROUND

HIF-1alpha is a biologic O2 sensor enabling adaptation to hypoxia. Studies have shown that under hypoxic conditions, HIF-1alpha enhances macrophage phagocytosis. Trauma-hemorrhage also produces a hypoxic insult with HIF-1alpha activation; however, macrophage phagocytosis is suppressed under those conditions. Thus, signaling molecules other than HIF-1alpha should be taken into consideration in the regulation of macrophage phagocytosis following cellular hypoxia or trauma-hemorrhage.

METHODS

Male C3H/HeN mice were subjected to sham operation, trauma-hemorrhage (laparotomy, 90 minutes hemorrhagic shock, MAP 35 +/- 5 mm Hg followed by resuscitation) or hypoxia (5% O2 for 120 minutes). The trauma-hemorrhage and hypoxia groups received Wortmannin (PI3K inhibitor), YC-1 (HIF-1alpha inhibitor) or vehicle at the time of maximum bleedout in the trauma-hemorrhage group or at a PaO2 of 30 mm Hg during hypoxic air inhalation. Mice were killed 2 hours later and samples/cells collected.

RESULTS

While the systemic and Kupffer cell hypoxic states were similar in the trauma-hemorrhage and hypoxia groups, phagocytic capacity was suppressed following trauma-hemorrhage but enhanced in the hypoxia group. Kupffer cells from both groups showed increased HIF-1alpha activation, which was prevented by Wortmannin or YC-1 treatment. The increase in Kupffer cell phagocytosis following hypoxemia was also prevented by Wortmannin or YC-1 treatment. Akt activation was suppressed in the trauma-hemorrhage group, but enhanced in the hypoxia group. Wortmannin and YC-1 treatment prevented the increase in Akt activation.

CONCLUSIONS

These findings indicate that the suppression of Kupffer cell phagocytosis following trauma-hemorrhage is independent of cellular hypoxia and activation of HIF-1alpha, but it is possibly related to suppression of the Akt activation.