Neuroprotective effects of combination therapy of regional cold perfusion and hemoglobin-based oxygen carrier administration on rat transient cerebral ischemia.

Regional cold perfusion and hemoglobin-based oxygen carrier administration both exert neuroprotective effects against cerebral ischemia reperfusion injury. We herein investigated whether the combination of these two therapies leads to stronger neuroprotective effects. Combination therapy was performed with the regional perfusion of cold HemoAct, a core-shell structured hemoglobin-albumin cluster, in a rat transient middle cerebral artery occlusion model. The effects of combination therapy, the intra-arterial administration of 10 °C HemoAct (10H) initiated at the onset of reperfusion, were compared with those of monotherapies, the intra-arterial administration of 10 °C saline (10S) and 37 °C HemoAct (37H), and an untreated control under the condition of 2-hour ischemia/24-hour reperfusion. The durability of therapeutic effects and the therapeutic time window of combination therapy were assessed based on comparisons with the 10H and control groups. Significantly better neurological findings and smaller infarct volumes were observed in the three treated (10S, 37H, and 10H) groups than in the control group. Among the 3 treated groups, only the 10H group showed significant improvements over the control group in the other items examined, including cerebral blood flow reduction, brain edema, and protein extravasation. The significant therapeutic effects of combination therapy on neurological disabilities and infarct volumes were confirmed at least until 7 days after reperfusion. Furthermore, combination therapy ameliorated neurological disabilities and hemorrhagic transformation in rats subjected to 4- and 5-hour ischemia/24-hour reperfusion. Since therapeutic effects may be expected until at least 5 h of complete ischemia and reperfusion, this combination therapy is a promising neuroprotective strategy against severe ischemic stroke.

Genetically engineered haemoglobin wrapped covalently with human serum albumins as an artificial O2 carrier.

We describe the synthesis and O2 affinity of genetically engineered human adult haemoglobin (rHbA) wrapped covalently with recombinant human serum albumins (rHSAs) as an artificial O2 carrier used for a completely synthetic red blood cell (RBC) substitute. Wild-type rHbA [rHbA(wt)] expressed in yeast species Pichia pastoris shows an identical amino acid sequence and three-dimensional structure to those of native HbA. It is particularly interesting that two orientations of the prosthetic haem group in rHbA(wt) were aligned by gentle heating in the natural form. Covalent wrapping of rHbA(wt) with three rHSAs conferred a core-shell structured haemoglobin-albumin cluster: rHbA(wt)-rHSA3. Three variant clusters containing an rHbA mutant core were also created: Leu-ß28 → Phe, Leu-ß28 → Trp, and Leu-ß28 → Tyr/His-ß63 → Gln. Replacement of Leu-ß28 with Trp decreased the distal space in the haem pocket, thereby yielding a cluster with moderately low O2 affinity which is nearly the same as that of human RBC.

Hemoglobin(ßC93A)-Albumin Cluster: Mutation of Cysteine-ß93 to Alanine Allows Moderate Reduction of O2 Affinity by Inositol Hexaphosphate.

Covalent wrapping of recombinant human hemoglobin (Cys-ß93→Ala) variant rHb(ßC93A) by human serum albumin (HSA) yielded the rHb(ßC93A)-HSA3 cluster as an artificial O2 carrier as a red blood cell substitute. Complexation of inositol hexaphosphate to the central rHb(ßC93A) core reduced the O2 affinity moderately, in much the same way as that of naked hemoglobin. This reduction might be attributable to the inert, small Ala-ß93 residue, which cannot be reacted with the bulky maleimide crosslinker.

Hemoglobin-albumin cluster: physiological responses after exchange transfusion into rats and blood circulation persistence in dogs.

A core-shell protein cluster comprising hemoglobin and human serum albumins, hemoglobin-albumin cluster (Hb-HSA3), was designed and synthesized for use as an artificial O2 carrier and red blood cell (RBC) substitute. For initial preclinical safety evaluation of the Hb-HSA3 solution, we observed blood compatibility in vitro, physiological responses after exchange transfusion into rats and blood circulation lifetime in dogs. Dilution of human whole blood with Hb-HSA3 showed an appropriate decrease in blood cell number, proportional to the mixing volume ratio. Time courses in the circulation parameters and blood gas parameters after 20% exchange transfusion with Hb-HSA3 in anesthetized rats were almost identical to those observed in a sham group (without infusion) and an HSA group (with HSA administration) for 6 h. Serum biochemical tests of the withdrawn blood indicated safety of the protein cluster. Furthermore, fluorescent Hb-HSA3 was infused into beagle dogs to assess blood retention. Fluorescence measurements of the blood samples enabled us to ascertain the cluster half-life within the intravascular space. Histopathologic inspections of the vital organs imply no abnormality in tissues. All these results indicate sufficient initial preclinical safety of Hb-HSA3 as an alternative material for use in RBC transfusion.

Novel Hemoglobin-Based Oxygen Carrier Bound With Albumin Shows Neuroprotection With Possible Antioxidant Effects.

Background and Purpose- A hemoglobin-albumin cluster, 1 core of hemoglobin covalently bound with 3 shell albumins, designated as HemoAct was developed as a hemoglobin-based oxygen carrier. We aim to investigate neuroprotection by HemoAct in transient cerebral ischemia and elucidate its underlying mechanisms. Methods- Male rats were subjected to 2-hour transient middle cerebral artery occlusion and were then administered HemoAct transarterially at the onset of reperfusion. Neurological and pathological findings were examined after 24 hours of reperfusion to identify neuroprotection by HemoAct. Intermittent measurements of cortical blood flow and oxygen content were performed, and a histopathologic analysis was conducted on rats during the early phase of reperfusion to assess the therapeutic mechanism of HemoAct. In addition, the antioxidant effects of HemoAct were examined in hypoxia/reoxygenation-treated rat brain microvascular endothelial cells. Results- Neurological deterioration, infarct and edema development, and the activation of MMP-9 (matrix metalloprotease-9) and lipid peroxidation after 24 hours of reperfusion were significantly ameliorated by the HemoAct treatment. Reductions in blood flow and tissue partial oxygen pressure in the cortical penumbra after 6 hours of reperfusion were significantly ameliorated by the HemoAct treatment. The histopathologic analysis of the cortical penumbra revealed that HemoAct in HemoAct-treated rats showed superior microvascular perfusion with the mitigation of microvascular narrowing changes than autologous erythrocytes in nontreated rats. Although HemoAct extravasated into the ischemic core with serum protein, it did not induce an increase in serum extravasation or reactive oxygen species production in the ischemic core. In vitro experiments with rat brain microvascular endothelial cells revealed that HemoAct significantly suppressed cellular reactive oxygen species production in hypoxia/reoxygenation-treated cells, similar to albumin. Conclusions- HemoAct exerted robust neuroprotection in transient cerebral ischemia. Superior microvascular perfusion with an oxygen delivery capability and possible antioxidant effects appear to be the underlying neuroprotective mechanisms.