Compatibility in vitro of albumin-heme (O(2) carrier) with blood cell components

Linking Labile Heme with Thrombosis

Thrombosis is one of the leading causes of death worldwide. As such, it also occurs as one of the major complications in hemolytic diseases, like hemolytic uremic syndrome, hemorrhage and sickle cell disease. Under these conditions, red blood cell lysis finally leads to the release of large amounts of labile heme into the vascular compartment. This, in turn, can trigger oxidative stress and proinflammatory reactions. Moreover, the heme-induced activation of the blood coagulation system was suggested as a mechanism for the initiation of thrombotic events under hemolytic conditions. Studies of heme infusion and subsequent thrombotic reactions support this assumption. Furthermore, several direct effects of heme on different cellular and protein components of the blood coagulation system were reported. However, these effects are controversially discussed or not yet fully understood. This review summarizes the existing reports on heme and its interference in coagulation processes, emphasizing the relevance of considering heme in the context of the treatment of thrombosis in patients with hemolytic disorders.

Pharmaceutical aspects of the recombinant human serum albumin dimer: structural characteristics, biological properties, and medical applications

Human serum albumin is the most abundant protein in the blood. It is clinically used in the treatment of severe hypoalbuminemia and as a plasma expander. The use of albumins as a carrier for drugs is currently being developed, and some are now in the preclinical and clinical trial stages. The main technologies for utilizing an albumin as a drug carrier are protein fusion, polymerization and surface modification, and so on. Among these technologies, albumin dimerization has wide clinical applications as a plasma expander as well as a drug carrier. Despite the fact that many reports have appeared on drugs using an albumin dimer as a carrier, our knowledge of the characteristics of the albumin dimer itself is incomplete. In this review, we summarize the structural characteristics of recombinant albumin dimers produced by two methods, namely, chemical linkage with 1,6-bis(maleimido)hexane and genetically linked with an amino acid linker, and the physicochemical characteristics and biological properties of these preparations. Finally, the potential for pharmaceutical applications of albumin dimers in clinical situations is discussed.

Polymer/hemoglobin assemblies: biodegradable oxygen carriers for artificial red blood cells

In routine clinical procedures, blood transfusion is now suffering from the defects of the blood products, like cross-matching, short storage time and virus infection. Various blood substitutes have been designed by researchers through continual efforts. With recent progress in nanotechnology, new types of artificial red blood cells with cellular structure are available. This article aims to describe some artificial red blood cells which encapsulate or conjugate hemoglobin molecules through various approaches, especially the nanoscale self-assembly technique, to mitigate the adverse effects of free hemoglobin molecules. These types of artificial red blood cell systems, which make use of biodegradable polymers as matrix materials, show advantages over the traditional types.

Influence of O2-carrying plasma hemoprotein “albumin-heme” on complement system and platelet activationin vitro and physiological responses to exchange transfusion

Recombinant human serum albumin (HSA) including the synthetic iron(II)-porphyrin (FeP), albumin-heme (HSA-FeP), is a unique O(2)-carrying plasma hemoprotein as a red blood cell substitute. We have investigated the possible influence of HSA-FeP on the complement system and platelet activation in vitro. The amounts of the serum complement titer CH(50) and terminal complement complex SC5b-9 of human blood serum, incubated with HSA-FeP (10, 20, and 40 vol %), were almost the same as those of the corresponding samples with HSA. The effect of HSA-FeP on the platelet reactivity has been demonstrated by conformational changes in the membrane glycoprotein IIb/IIIa and surface expression of an alpha-granule membrane protein P-selectin. Platelet activation in response to the ADP-stimulation was not influenced by the presence of HSA-FeP. It can be concluded that the albumin-heme solution does not facilitate the immunological reaction and platelet activation. Moreover, a 20% exchange transfusion with HSA-FeP into anesthetized rats has been performed to evaluate the circulation and blood parameters for 6 h. Time course changes in all parameters showed features identical to the control group (without infusion) and HSA group.

Physicochemical characterization of cross-linked human serum albumin dimer and its synthetic heme hybrid as an oxygen carrier

The recombinant human serum albumin (rHSA) dimer, which was cross-linked by a thiol group of Cys-34 with 1,6-bis(maleimido)hexane, has been physicochemically characterized. Reduction of the inert mixed-disulfide of Cys-34 beforehand improved the efficiency of the cross-linking reaction. The purified dimer showed a double mass and absorption coefficient, but unaltered molar ellipticity, isoelectric point (pI: 4.8) and denaturing temperature (65 degrees C). The concentration dependence of the colloid osmotic pressure (COP) demonstrated that the 8.5 g dL(-1) dimer solution has the same COP with the physiological 5 g dL(-1) rHSA. The antigenic epitopes of the albumin units are preserved after bridging the Cys-34, and the circulation lifetime of the 125I-labeled variant in rat was 18 h. A total of 16 molecules of the tetrakis[(1-methylcyclohexanamido)phenyl]porphinatoiron(II) derivative (FecycP) is incorporated into the hydrophobic cavities of the HSA dimer, giving an albumin-heme hybrid in dimeric form. It can reversibly bind and release O2 under physiological conditions (37 degrees C, pH 7.3) like hemoglobin or myoglobin. Magnetic circular dichroism (CD) revealed the formation of an O2-adduct complex and laser flash photolysis experiments showed the three-component kinetics of the O2-recombination reaction. The O2-binding affinity and the O2-association and -dissociation rate constants of this synthetic hemoprotein have also been evaluated.

Safety Evaluation of an Artificial O2 Carrier as a Red Blood Cell Substitute by Blood Biochemical Tests and Histopathology Observations

Recombinant human serum albumin (rHSA) incorporating synthetic heme with a covalently linked proximal base (albumin-heme [rHSA-hemel) is an artificial O2 carrier that can transport O2 like hemoglobin does in the blood stream. To evaluate the clinical safety of this compound, 20% and 40% exchange transfusions with rHSA-heme into anesthetized rats were followed by blood biochemical tests and histopathologic observations for 7 days. In the 20% rHSA-heme group, a total of 30 analytes by blood biochemical tests showed almost the same values as those observed in the reference 20% rHSA group. Although some abnormal values for liver parameters were found in the 40% rHSA-heme group, they returned to normal after 7 days. Histopathologic observations indicated that the administration of rHSA-heme in a volume of 20% total blood volume did not produce any negative side effects on the vital organs.

Exchange transfusion with synthetic oxygen-carrying plasma protein ?albumin-heme? into an acute anemia rat model after seventy-percent hemodilution

Recombinant human serum albumin (rHSA) incorporating the synthetic heme "albumin-heme" is an oxygen-carrying plasma protein that has the potential to be a red blood cell substitute. The physiological responses to a 30% exchange transfusion with two types of albumin-heme (rHSA-FecycP, rHSA-FepivP) solutions after 70% isovolemic hemodilution with 5 g/dL rHSA were investigated using anesthetized rats. The circulation parameters, blood parameters, renal cortical oxygen pressure (pO2), and muscle tissue pO2 were carefully monitored for 60 min after the injection. The declined mean arterial pressure and the mixed venous partial pO2 significantly recovered to 70.8 and 91.9% of the basal values by intravenous infusion of albumin-hemes, respectively. The lowered renal cortical pO2 also increased, indicating oxygen transport by this synthetic hemoprotein. The administration of albumin-heme into the acute anemia rat model after hemorrhage improved the circulatory volume and resuscitated the shock state. Both rHSA-FecycP and rHSA-FepivP transported oxygen through the body.

Exchange transfusion with entirely synthetic red-cell substitute albumin-heme into rats: Physiological responses and blood biochemical tests

Recombinant human serum albumin (rHSA) incorporating 2-[8-[N-(2-methylimidazolyl)]octanoyloxymethyl]-5,10,15,20-[tetrakis[alpha,alpha,alpha,alpha-o-(1-methylcyclohexanoyl)amino]phenyl]porphinatoiron(II) [albumin-heme (rHSA-heme)] is an artificial hemoprotein which has the capability to transport O(2) in vitro and in vivo. A 20% exchange transfusion with rHSA-heme into anesthetized rats has been performed to evaluate its clinical safety by monitoring the circulation parameters and blood parameters for 6 h after the infusion. Time course changes in all parameters essentially showed the same features as those of the control group (without infusion) and rHSA group (with administration of the same amount of rHSA). Blood biochemical tests of the withdrawn plasma at 6 h after the exchange transfusion have also been carried out. No significant difference was found between the rHSA-heme and rHSA groups, suggesting the initial clinical safety of this entirely synthetic O(2)-carrier as a red-cell substitute.