Mechanisms of toxicity of hemoglobin solutions

Mitigating hemoglobin-induced nephropathy: ApoHb-hp protection of podocytes

This study investigates hemoglobin (Hb)-induced kidney injury and the protective role of the ApoHemoglobin-Haptoglobin (ApoHb-Hp) complex against heme and Hb damage. Hb facilitates oxygen (O2) delivery but poses challenges outside red blood cells (RBCs) due to toxic Hb and heme mechanisms. These are managed by binding to serum proteins like Haptoglobin (Hp) and Hemopexin (Hpx). During hemolysis, depletion of Hp and Hpx leaves tissues vulnerable to Hb and heme. To address this, we developed the ApoHb-Hp complex, based on Apohemoglobin, which is produced by removing heme from Hb, conjugated with Hp. This complex acts as a dual scavenger for Hb and heme, preventing tissue damage. Our findings demonstrate that ApoHb-Hp significantly protects MPC5 podocytes from Hb-induced damage. Fluorescent staining showed a higher percentage of nephrin-positive cells in the ApoHb-Hp group, and MTT assays revealed enhanced cell viability compared to Hb alone. Additionally, ApoHb-Hp reduced reactive oxygen species (ROS) production, with the Hb group exhibiting significantly elevated ROS levels. The ApoHb-Hp complex mitigated the depletion of protective mechanisms, as shown by significant increases in superoxide dismutase (SOD) and glutathione (GSH). Moreover, ApoHb-Hp treatment reduced the activation of the NLRP3 inflammasome signaling pathway and inflammatory cytokines IL-1β and IL-18. These findings underscore the therapeutic potential of ApoHb-Hp in mitigating Hb-induced renal damage by preserving podocyte viability and reducing oxidative stress. Overall, ApoHb-Hp maintained protective mechanisms depleted otherwise by Hb. These findings highlight ApoHb-Hp's potential as a therapeutic agent against Hb-induced renal damage, offering insights into its mechanisms and implications for treating conditions involving hemolysis.

Measurement of Peritoneal Fluid Handling in Children on Continuous Ambulatory Peritoneal Dialysis Using Autologous Hemoglobin

Objective

Previous measurements of peritoneal fluid handling in children treated by continuous ambulatory peritoneal dialysis (CAPD) were performed with human albumin as a fluid marker. A major disadvantage of this substance is that endogenous patient albumin enters the peritoneal cavity during the dwell period. For this reason perito neal fluid kinetics were measured in a group of children on CAPD, using autologous hemoglobin as a volume marker.

Design

Autologous hemoglobin was added to dialysate containing 1.36% glucose as a volume marker. Marker clearance (MC), which is presently the best available approximation of lymphatic absorption in the clinical setting, and transcapillary ultrafiltration (TCUF) were measured during a 4-hour dwell.

Setting

University hospital.

Patients

Children on CAPD (N=9), with a median age of 8.1 years (range 2.1–13.2 years).

Results

MC was 521±166 mL/4 hour/1.73 m2, which is high compared to the literature data on adult CAPD patients. TCUF was 519±92 mL/4 hour/1.73 m2, which is similar to data concerning adult patients. TCUF reached no maximum during the 4-hour dwell, and the deviation of the TCUF curve from linear was markedly less than usually seen in adult patients.

Conclusions

MC in children treated with CAPD is higher when compared to the literature data on adults. Difficulties to achieve sufficient ultrafiltration in children could be caused by relatively small differences between MC and TCUF from the beginning to the end of the dwell.

In Vivo Effects of Stroma-Free Hemoglobin and Polyhemoglobin on Coagulation Factors in Rats

We studied the effects of rat stroma-free hemoglobin (rSFH), human stroma-free hemoglobin (hSFH), rat polyhemoglobin (rPoly), and human polyhemoglobin (hPoly) on coagulation factors in rats. Albumin and saline infused rats were controls. The infusion volume was 10% of the rat's blood volume. The concentrations of hemoglobin in this study were 7 g/dl.

Measurements for prothrombin time (PT) and activated partial thromboplastin time (PTT) were at 5 minutes, 2, 6, 24 and 72 hours after infusion. Factor X, fibrinogen, plasminogen, antithrombin III, and antiplasmin were followed at 24 and 72 hours after infusion. Compared with saline infused rats PT and PTT did not change significantly in those rats infused with Hb preparations. There was a transient increase of PTT from 2 to 24 hours after infusion in albumin infused rats. Factor X, fibrinogen, antithrombin III and antiplasmin showed no significant differences between Hb infused groups and saline infused group. Twenty-four hours and 72 hours after infusion plasminogen decreased in all groups except the albumin infused rats at 24 hours after infusion when compared with normal rat plasma pool. However, there were no significant differences in plasminogen levels between the hemoglobin infused groups and the control saline group.

Stroma-free and polyHb solutions (rSFH, hSFH, rPoly and hPoly) did not cause significant changes in prothrombin time and activated partial thromboplastin time in rats. The rats infused with hemoglobin solutions (rSFH, hSFH, rPoly, and hPloy) did not show significant differences in Factor X, fibrinogen, antithrombin III and antiplasmin levels compared with the control group.

A novel hemoglobin-adenosine-glutathione based blood substitute: evaluation of its effects on human blood ex vivo

Chemically modified hemoglobin (Hb) solutions are under current investigation as potential red cell substitutes. Researchers at Texas Tech University have developed a novel free Hb based blood substitute product. This blood substitute is composed of purified bovine Hb cross-linked intramolecularly with o-adenosine-5'-triphosphate and intermolecularly with o-adenosine, and conjugated with reduced glutathione (GSH). In this study, we compared the effects of our novel blood substitute and unmodified (U) Hb, by using allogenic plasma as the control, on human blood components: red blood cells (RBCs), platelets, monocytes (Mo), and low-density lipoproteins (LDLs). The pro-oxidant potential of both Hb solutions on RBCs was examined by the measurement of osmotic and mechanical fragility, conjugated dienes (CD), lipid hydroperoxides (LOOH), thiobarbituric acid reactants (TBAR-S), isoprostanes (8-iso PGF2alpha) and intracellular GSH. The oxidative modification of LDLs was assessed by CD, LOOH, and TBAR-S, and the degree of apolipoprotein (apo) B cross-linking. The effects of Hb on platelets have been studied by monitoring their responses to the aggregation agonists: collagen, ADP, epinephrine, and arachidonic acid. Monocytes were cultured with Hb solutions or plasma and tested for TNF-alpha and IL-1beta release, then examined by electron microscopy. Results indicate that native UHb initiates oxidative stress of many blood components and aggravates inflammatory responses of Mo. It also caused an increase in RBC osmotic and mechanical fragility (p < 0.001). While the level of GSH was slightly changed, the lipid peroxidation of RBC increased (p < 0.001). UHb was found to be a stimulator of 8-iso PGF2alpha synthesis, a potent modulator of LDLs, and an effective potentiator of agonist induced platelet aggregation. Contrarily, our novel blood substitute did not seem to induce oxidative stress nor to increase Mo inflammatory reactions. The osmotic and mechanical fragility of RBCs was similar to that of the control. Such modified Hb failed to alter LDLs, increase the production of 8-iso PGF2alpha, but markedly inhibited platelet aggregation. The effect of this novel blood substitute can be linked with the cytoprotective and anti-inflammatory properties of adenosine, which is used as a cross-linker and surface modifier, and a modification procedure that lowers the hemoglobin pro-oxidant potential.

Protective effects of plasma replacement fluids on erythrocytes exposed to mechanical stress

Haemoglobin release from 40 suspensions of packed red blood cells in modified fluid gelatin, 4% albumin solution, 6% hydroxyethyl starch and normal saline was investigated in vitro during circulation with a roller pump from a heart-lung machine for 120 min at a flow rate of 2.5 l.min-1 at room temperature. The lowest haemoglobin release was obtained with erythrocytes in modified fluid gelatin, whereas free haemoglobin concentrations became progressively higher with albumin, hydroxyethyl starch and normal saline [median free haemoglobin (interquartile range) after 120 min circulation: gelatin 493 (360-601) mg.l-1, albumin 692 (590-1111) mg.l-1, hydroxyethyl starch 1121 (692-1518) mg.l-1, normal saline 1178 (881-1757) mg.l-1, p < 0.001]. Modified fluid gelatin appears to have potent erythrocyte protective properties similar to those of albumin. This effect could decrease mechanical haemolysis during extracorporeal circulation or cell saver autotransfusion if modified fluid gelatin is used as part of a priming solution or as an additive in wash solutions.

Modified hemoglobin blood substitutes: present status and future perspectives

Biotechnological techniques of cross-linking and microencapsulation of hemoglobin result in blood substitutes that can replace red blood cells. Unlike red blood cells they can be sterilized by pasteurization, ultrafiltration and chemical means. This removes microorganisms responsible for AIDS, hepatitis, etc. Since they are free of red blood cell blood group antigens, there is no need for cross-matching or typing. This saves time and facilities and allows on-the-spot transfusion such as the infusion of salt solution. Furthermore, they can be stored for a long time. Hemoglobin for modification can be extracted from human red blood cells. Other sources of hemoglobin include bovine hemoglobin and recombinant human hemoglobin. Clinical trials are ongoing testing the possible uses of cross-linked hemoglobin in cardiac, orthopedic, trauma and other types of surgery. It is also being tested for the replacement of lost blood in severe bleeding due to trauma or other causes. Cross-linked hemoglobins are first generation blood substitutes that only fulfil some of the functions of red blood cells. New generations of more complete red blood cell substitutes are being developed. These include cross-linked hemoglobin-catalase-superoxide dismutase and microencapsulated hemoglobin-enzyme systems.

Expression of adhesion molecules and von Willebrand factor in human coronary artery endothelial cells incubated with differently modified hemoglobin solutions

Previous studies have established a linkage between free Hb molecules and the production of inflammatory mediators by the reticuloendothelial cells. An important aspect of the endothelial response to the inflammatory stimuli is the expression of adhesion molecules on the luminal surface. Therefore, the present study was designed to investigate the effects of various free-Hb based oxygen carrying solutions on the intracellular adhesion molecule-1 (ICAM-1), the vascular cell adhesion molecule-1 (VCAM-1) and also von Willebrand factor (vWF) expression by human endothelium. Human coronary artery endothelial cells (HCAEC) were cultured on glass coverslips until they reached confluence, then incubated for 18 hours with endothelial basal medium (EBM) supplemented with 5% FBS and a 0.1 mmol or 0.2 mmol of the bovine Hb solutions: 1) pure unmodified bovine Hb (UHb); 2) modified bovine Hb solution (Hb-PP-GSH) prepared according to our newly developed procedure (U.S. Patent No. 5,439,882); and 3) modified bovine Hb solution polymerized with glutaraldehyde (GLUT-Hb). The HCAECs were also incubated with EBM (negative control) and EBM containing bacterial endotoxins in a concentration of 50 EU/ml (positive control). After treatment, cells were exposed to primary antibodies; anti-human ICAM-1, anti-human VCAM-1 or anti-human vWF, and consequently to the secondary antibody (fluorescein isothiocyanate-conjugated F(ab)2). Immunofluorescence analysis revealed different expressions of ICAM-1 and VCAM-1 on the surface membranes of variously treated cells. Although negative control cells had an undetectable level of adhesion molecules, the positive control cells, activated by endotoxin, exhibited high immunoreactivity for ICAM-1 and VCAM-1. The Hb's treated cells demonstrated differing degrees of activation. An insignificant expression of ICAM-1 was observed in HCAEC, following treatment with a 0.1 or 0.2 mmol of Hb-PP-GSH and 0.1 mmol of UHb. Cell treated with 0.2 mmol of UHb and both concentrations of GLUT-Hb demonstrated a massive expression of this adhesion molecule. A similar effects was observed during induction of VCAM-1. While a lack of expression was noted with both concentrations of Hb-PP-GSH and 0.1 mmol of UHb, the GLUT-Hb stimulated significant VCAM-1 induction at all tested concentrations. Immunofluorescence analysis confirmed the expression of vWF uniformly in HCAEC from the different experimental groups. The data suggest, vWF expression was unaffected by all but the GLUT-Hb treatment. In conclusion, the Hb stimulatory activity toward ICAM-1 and VCAM-1 inductions were related with the type of Hb chemical modification method. Although modification of Hb with glutaraldehyde potentiates adhesion molecules expression, our novel Hb modification procedure, which comprises intramolecular cross-linking with o-adenosine triphosphate and intermolecular with o-adenosine, and combined with reduced glutathione, apparently prevents these inflammatory events.

Resuscitation with increasing doses of diaspirin crosslinked hemoglobin in swine

This study examined the effects of administering 0.5, 4, 10, and 30 mL/kg of Diaspirin Crosslinked Hemoglobin (DCLHb) in a swine model of non-lethal hemorrhagic shock. Thirty unanesthetized animals were bled (30 mL/kg, 1 mL/kg/min) and either recovered without treatment (Untreated Control, UC) or infused with 10 g/dL DCLHb (0.5, 4.0, 10 or 30 mL/kg at 1 mL/kg/min) or Lactated Ringer (LR, 90 mL/kg at 3 mL/kg/min). DCLHb caused dose-related increases in MAP. Both the 10 and 30 mL/kg doses of DCLHb increased MAP more than UC or LR. Lower doses of DCLHb and LR had effects on MAP similar to UC. After hemorrhage, CO increased in all groups. The effect of DCLHb on CO was dose-related. Only LR and 30 mL/kg of DCLHb transiently (through 90 min) increased CO more than UC. CO in animals given lower doses of DCLHb was comparable to UC. DCLHb (10 and 30 mL/kg) improved base excess and lactate concentrations, two indices of global perfusion, more rapidly and to a greater extent than either UC or LR. In this swine model of hemorrhage, even small doses of DCLHb exerted measurable beneficial effects on blood pressure and perfusion.

Role of endothelin in the cardiovascular effects of diaspirin crosslinked and stroma reduced hemoglobin

OBJECTIVES

Diaspirin crosslinked hemoglobin is a resuscitative solution with excellent oxygen-carrying capacity. Diaspirin crosslinked hemoglobin produces an immediate increase in blood pressure and marked regional circulatory changes in rats and pigs. Our objective was to determine the role of endothelin in the cardiovascular actions of diaspirin crosslinked hemoglobin (modified) and (unmodified) stroma reduced hemoglobin solutions.

DESIGN

Prospective, randomized comparison of cardiovascular effects of diaspirin crosslinked and stroma reduced hemoglobin in control rats and in rats pretreated with cyclo(D-Asp-Pro-D-Val-Leu-D-Trp) (BQ-123), an endothelin-A receptor antagonist.

SETTING

Research laboratory.

SUBJECTS

Male Sprague-Dawley rats.

INTERVENTIONS

Modified, highly purified, and heat pasteurized (diaspirin crosslinked) and unmodified (stroma reduced) hemoglobin in control (untreated) and BQ-123 (5 mg/kg/hr iv)-treated rats.

MEASUREMENTS AND MAIN RESULTS

Infusion of stroma reduced hemoglobin (400 mg/kg iv) in control rats produced an increase in blood pressure (43%) and total peripheral resistance (65%) without any change in heart rate, cardiac output, and stroke volume. Stroma reduced hemoglobin decreased blood flow to the kidneys and liver, increased blood flow to the heart, and had no effect on blood flow to the brain, gastrointestinal tract, spleen, musculoskeletal system, skin, and mesentery and pancreas. Infusion of stroma reduced hemoglobin in rats treated with BQ-123 (5 mg/kg/hr iv) increased the blood pressure to a similar degree when compared with control rats, but the increase in total peripheral resistance was significantly attenuated. The stroma reduced hemoglobin-induced decrease in blood flow to the kidneys and liver was significantly attenuated in BQ-123-treated rats as compared with control rats. However, the stroma reduced hemoglobin-induced increase in blood flow to the heart of BQ-123-treated rats was similar to the increase in control rats. Infusion of diaspirin crosslinked hemoglobin (400 mg/kg iv) produced increases in blood pressure (81%), cardiac output (36%), stroke volume (30%), and total peripheral vascular resistance (45%), along with increases in blood flow to the heart, spleen, gastrointestinal tract, and skin of control rats. The blood flows to the brain, kidneys, liver, musculoskeletal system, and mesentery and pancreas were not altered by diaspirin crosslinked hemoglobin in control rats. The increases in blood pressure, cardiac output, stroke volume, and total peripheral vascular resistance by diaspirin crosslinked hemoglobin were significantly blocked in BQ-123-treated rats as compared with control rats. The increases in blood flow to the heart, spleen, and skin by diaspirin crosslinked hemoglobin were significantly blocked in BQ-123-treated rats as compared with control rats. Diaspirin crosslinked hemoglobin produced an increase in the blood flow to the brain and a decrease in blood flow to the kidney and musculoskeletal system of BQ-123-treated rats as compared with control rats. Blood plasma endothelin-1-like immunoreactivity was found to be significantly increased after treatment with diaspirin crosslinked hemoglobin or stroma reduced hemoglobin.

CONCLUSIONS

The endothelin-A receptor antagonist, BQ-123, could attenuate the systemic hemodynamic and regional circulatory effects of diaspirin crosslinked hemoglobin and stroma reduced hemoglobin. However, the increase in blood flow to the heart induced by stroma reduced hemoglobin could not be attenuated by BQ-123.

Effects of bacterial endotoxin on human cross-linked and native hemoglobins

Previous investigations have demonstrated that hemoglobin (Hb) is a binding protein for bacterial endotoxin (lipopolysaccharide, LPS) and that the structure and biological activity of LPS are altered in the presence of Hb. In the present study, the influence of LPS on the structure of native human HbA0 and covalently cross-linked Hb (alpha alpha Hb) was studied by analyzing the absorption and circular dichroic spectra of Hb in the wavelength region of 200-650 nm. Incubation of oxyHb with each of several LPSs resulted in a decrease in the intensity of the major Soret band at 414 nm with a shift in the maximum peak to 410 nm, decreases in the intensities of the major visible region peaks at 541 and 577 nm, and the appearance of increased absorbance in the visible region in the range of 630 nm. The resultant spectra are characteristic of methemoglobin formation. These spectral changes were time-dependent and LPS-concentration-dependent. Production of methemoglobin was prominent with chemically modified, partially deacetylated rough LPS, and was observed to a lesser extent both with native, complete rough and with native smooth LPSs. The influence of LPS on the absorption spectrum of methemoglobin also was directly tested. The conversion of methemoglobin to hemichrome in the presence of LPS was demonstrated and was shown to be reversible. Analysis of circular dichroic spectra of Hb demonstrated LPS-induced spectral changes in the visible and Soret regions consistent with the production of a substantial quantity of metHb, but did not demonstrate any alteration in the far-UV region (210-240 nm). Moreover, Hb oxygen affinity was only slightly altered after incubation with any of several LPSs. In conclusion, analyses of absorption and circular dichroic spectra reveal the potential of LPS to produce a facilitated oxidation of both alpha alpha-cross-linked human Hb and native human HbA0, without substantial changes in the secondary structure of the globin.

Oxygen transport and cardiovascular effects of resuscitation from severe hemorrhagic shock using hemoglobin solutions

OBJECTIVE

To test the short-term efficacy of three hemoglobin solutions in restoring cardiac output, intravascular pressures, oxygen transport (DO2), and oxygen consumption (VO2) after resuscitation from severe hemorrhagic shock.

DESIGN

Prospective study.

SETTING

Research laboratory.

SUBJECTS

Beagle dogs.

INTERVENTIONS

After anesthesia and instrumentation, hemorrhagic shock was induced for 2 hrs by blood withdrawal to maintain systolic blood pressure at 50 mm Hg. Resuscitation then occurred with one of four different resuscitation fluids. One group of dogs was not resuscitated. Survival rate was monitored for 8 days.

MEASUREMENTS AND MAIN RESULTS

In 33 beagle dogs, cardiovascular variables (DO2 and VO2) were compared after resuscitation with 8% stroma-free hemoglobin, 4% or 8% pyridoxalated-hemoglobin-polyoxyethylene conjugate (PHP44 and PHP88, respectively), or autologous whole blood. The dogs were anesthetized, paralyzed, mechanically ventilated (FIO2 of 0.21), and instrumented with arterial and pulmonary artery catheters. An average of 63% of estimated blood volume was removed to maintain systolic blood pressure at 50 mm Hg for 2 hrs. The dogs then were either not resuscitated (n = 4) or resuscitated with 8% stroma-free hemoglobin (n = 7), PHP44 (n = 6), PHP88 (n = 8), or whole blood (n = 8), with a volume equivalent to the withdrawn blood. Cardiovascular variables, DO2, VO2, oxygen extraction ratios, and blood concentrations of lactic acid and catecholamines were determined before, and for < or = 6 hrs after, resuscitation from hemorrhagic shock. Blood smears were microscopically examined. In addition, the survival rate was monitored for 8 days after resuscitation. By 2 hrs of hemorrhagic shock, there was a large decrease in DO2 (p < .05) and an increase in oxygen extraction ratio from 0.27 to 0.70 (p < .05). There was a 3.5-fold increase in lactate concentrations and a 25-fold increase in catecholamine concentrations as compared with preshock values. All dogs not resuscitated died within 1.75 hrs after 2 hrs of shock. After resuscitation with whole blood, all cardiovascular and oxygen transport variables returned to approximately prehemorrhage values and remained so throughout the measurement period. After resuscitation with any hemoglobin solution, DO2 returned transiently to control values. However, recovery of DO2 was short-lived in all hemoglobin solution groups, and, by 4 hrs postresuscitation in all groups, DO2 was less than the DO2 of the dogs receiving whole blood (p < .05). These changes were associated with decreases in total hemoglobin concentrations compared with the values immediately before resuscitation (p < .05). In addition, with resuscitation using the PHP solutions, blood smears demonstrated aggregation of red blood cells and platelets. On day 8 after hemorrhagic shock, the survival rate was 100% for whole blood and PHP44, 86% for 8% stroma-free hemoglobin, and 33% for PHP88.

CONCLUSIONS

Resuscitation from severe hemorrhagic shock with 8% stroma-free hemoglobin, PHP44, or PHP88 is equally effective in restoring cardiac index and vascular pressures as using whole blood. However, resuscitation with the three hemoglobin solutions only transiently restored DO2 after hemorrhagic shock. The subsequent reduction of DO2 compared with the DO2 value using whole blood was due mostly to hemodilution. With the two PHP solutions, formation of red blood cell aggregates probably resulted in sequestration of red cell mass and additional loss of oxygen carrying capacity.

Diaspirin crosslinked hemoglobin (DCLHb): absence of increased free radical generation following administration in a rabbit model of renal ischemia and reperfusion

In control rabbits, a renal ischemia of 60 min followed by 10 min of reperfusion resulted in an enhanced free radical production in cortical tissue, as assessed by a significant decrease of free glutathione (42%), protein-bound GSH (17%), and vitamin E (49%). In contrast, catalase or glutathione peroxidase activities were not affected by these experimental conditions. Free radical production in this model was also measured directly using electron spin resonance (ESR) spectroscopy associated with a PBN (alpha-phenyl N-tert-butyl-nitrone) spin trap agent in the venous blood arising from the ischemic kidney. The signal consisted of a triplet of doublets. In contrast, no signal could be detected in control blood samples taken prior to inducing ischemia. The burst of free radical production occurred in the early phase after restoration of flow in the kidneys rendered ischemic, as evidenced by a signal of weak intensity which generally appeared within the third minute after reperfusion and progressively increased to form a well-defined asymmetric signal following 10 min of reperfusion. The precise nature of free radicals trapped by the PBN agent remains, however, to be elucidated, but analysis of the coupling constants (aN = 14.5-15 G; a beta H = 2.5-3 G) and asymmetry of the central doublets suggests that the ESR signal may arise from a nitorxy-radical adduct resulting from the spin trapping by PBN of both oxygen- or carbon-centered radicals of lipid origin. As evidenced by both direct and indirect measurements, exchange of rabbit blood immediately after inducing renal ischemia with 30 ml/kg of Diaspirin Crosslinked Hemoglobin (7.5 g/dl in lactated electrolyte) or human serum albumin (7.5 g/dl in lactated electrolyte) did not exacerbate free radical production mediated by an ischemia reperfusion phenomenon, a typical situation found in a resuscitation setting.

Histopathologic study following administration of liposome-encapsulated hemoglobin in the normovolemic rat

Liposome encapsulated hemoglobin is being developed as an artificial resuscitative fluid for in vivo oxygen delivery. In the present report, we examine the effect of accumulation of liposome encapsulated hemoglobin on the structure of reticuloendothelial organs following administration of liposome encapsulated bovine hemoglobin in the normovolemic rat. We have also examined the administration of the liposome vehicle, tetrameric bovine hemoglobin, and liposome encapsulated bovine hemoglobin that had been lyophilized with 300 mM trehalose and rehydrated just before injection. Following injection into the tail vein, rats were sacrificed and liver, spleen, kidney, and lung harvested at 2 h, 24 h, 1 week, and 2 weeks for analysis. Gross pathologic findings of animals injected with liposome encapsulated hemoglobin showed statistically significant splenomegaly with a waxy parenchymal pallor at early time points. Microscopic findings indicate that the liver and spleen are principally involved with liposome encapsulated hemoglobin removal over the course of 24 h with transient cytoplasmic vacuolization in tissue resident phagocytes as evidenced by both light and electron microscopic examination. Presence of liposome encapsulated hemoglobin in these vacuoles was confirmed by oil red O and prussian blue stains. Splenic weight was observed to decline after 24 h but still remained significant above sham-treated controls at 2 weeks and could be correlated with increased hematopoietic activity.(ABSTRACT TRUNCATED AT 250 WORDS)

Complement activation by liposome-encapsulated hemoglobin in vitro: the role of endotoxin contamination

Incubation of liposome-encapsulated Hb (LEH) with rat serum at 37 degrees C led to accelerated decay of serum hemolytic complement (C) activity (CH50/ml). Empty liposomes (L) caused less decrease of CH50/ml, whereas free Hb had no effect on C activity. The LEH- and L-induced increases in C consumption were unlikely a consequence of endotoxin (LPS) contamination, as spiking of rat serum with LPS caused reduction in C only at levels significantly higher than those detectable in LEH or L. LPS-induced C consumption was not potentiated by free hemoglobin.

Effect of a bovine hemoglobin preparation on the response of the FSaIIC fibrosarcoma to chemotherapeutic alkylating agents

Polymerized bovine hemoglobin solutions (PBHS) are being actively investigated as blood substitutes. In studies analogous to those we conducted with perfluorochemical emulsions/carbogen, we have examined the effect of PBHS +/- carbogen (95% O2, 5% CO2) breathing on the antitumor efficacy of melphalan, cyclophosphamide, N,N'-bis(2-chloroethyl)-N-nitrosourea (BCNU) and cis-diamminedichloroplatinum(II) (cis-platin). The tumor growth delay of the FSaIIC fibrosarcoma treated with melphalan (10 mg/kg), cyclophosphamide (150 mg/kg), cisplatin (10 mg/kg) and BCNU (15 mg/kg) was increased about 2.2-fold, about 2.1-fold, about 1.2-fold and about 1.5-fold, respectively, when PBHS (12 mg/kg) was administered i.v. before each drug was injected i.p. The tumor growth delay produced by each drug was further increased when carbogen breathing for 6 h was allowed after administration of the drug and PBHS. In tumor cell survival experiments 24 h following drug treatment, the addition of PBHS increased the tumor cell killing of both melphalan and cyclophosphamide by about a factor of 10 at the lowest doses of each drug tested (10 mg/kg for melphalan and 100 mg/kg for cyclophosphamide) compared to the drug alone. However, at higher drug doses this effect was lost. The toxicity of each antitumor agent toward bone marrow (granulocyte/macrophage-colony-forming units) was increased 2- to 3-fold by the combined treatment. These results suggest that use of PBHS +/- carbogen breathing may add significantly to the efficacy of antitumor alkylating agents, however, the in vivo/in vitro data suggest that there will be increased bone marrow toxicity with this approach. This needs to be taken into account in the design of clinical trials.

PEG-bovine hemoglobin: safety in a canine dehydrated hypovolemic-hemorrhagic shock model

An initial evaluation of PEG-bHb was performed using a modified hypovolemic shock model. PEG-bHb had a substantially longer intravascular half-life than native Hb and no measurable hemoglobinuria was observed in the canine. PEG-bHb allowed successful resuscitation with an oxygen carrying capacity of 14-22% over that of lactated Ringer's solution.

Effects of X-linked hemoglobin on in-vitro platelet function

The in-vitro function of platelets in 1:1 mixtures of fresh whole blood and 10% DBBF alpha-alpha cross-linked hemoglobin in Ringer's acetate buffer was assessed by quantitative aggregation after challenge with common agonists and compared to the function of platelets in similar dilutions of whole blood in saline. Whole blood aggregometry was performed after addition of ADP, collagen, and ristocetin. Aggregation was quantified by measuring the change in impedance as drawn on the chart recording. No difference in mean impedance change was noted between the groups of blood samples which were incubated and tested in the hemoglobin solution and those incubated and tested in saline. In addition, incubation and stirring of the above mixtures over a period of six minutes without the addition of agonists did not result in spontaneous platelet aggregation. We conclude that alpha-alpha cross-linked hemoglobin, in the concentration studied, does not affect in-vitro platelet function, as measured by whole blood aggregometry.

A preclinical screening test for modified hemoglobin to bridge the gap between animal safety studies and use in human

The infusion of large amount of modified hemoglobin as blood substitute can potentially result in hypersensitivity and anaphylactic reactions, antibody-antigen reactions and others. Animal safety studies are important. However, response in animals may not be the same as in human. Before injecting into human, we may need to use an in-vitro screening procedure. One approach is based on testing the effects of modified Hb on complement activation (C3a) of human plasma. This paper describes this screening test. It also discusses how this may potentially be used. For instance using this to test for contamination from trace membrane fragments with blood group antigen or lipids, antibody-antigen complexes, endotoxin, trace fragments of microorganisms, residual amounts of some polymers, emulsifying agents, and organic solvents. There is also the possibility of obtaining plasma from a very large human population and analyse each of these to study the epidemiology of adverse reactions in different groups and types of patients.

Blood substitutes based on modified hemoglobin prepared by encapsulation or crosslinking: an overview

Modified hemoglobin consists of (1) encapsulated hemoglobin and (2) crosslinked hemoglobin (polyhemoglobin, intramolecularly cross-linked hemoglobin and conjugated hemoglobin). There have been new advances in all types of modified hemoglobins. Modified hemoglobins are effective in hemorrhagic shock. However, it is important to define hemorrhagic shock models and experimental designs. Important progress has been made in research on vasoactivities, organ perfusion, organ preservation, biodistribution, hematology, complement activation immunology and other areas. A preclinical screening test may bridge the gap between animal safety studies and injection into human. Potential new sources of hemoglobin included bovine hemoglobin, recombinant human hemoglobin and synthetic heme.

Effect of oxygen level on the enhancement of tumor response to radiation by perfluorochemical emulsions or a bovine hemoglobin preparation

Attempts to correct tumor hypoxia with oxygen-carrying solutions have used high concentrations of inspired oxygen (FiO2 100% or 95%). In the clinic, however, obtaining such high levels of FiO2 using mask ventilation in older patients or in children may be difficult. Since lower levels of FiO2 had not been previously tested, we examined the antitumor efficacy of FiO2 levels of 65, 85, and 95% breathed for 1 hr prior to and during irradiation used with the concentrated perfluorochemical emulsion F44E, the less concentrated emulsion, Fluosol-DA, or a new preparation consisting of purified bovine hemoglobin solution, PBHS. When tested in mice bearing the Lewis lung carcinoma with 2, 3, or 4 Gy daily for 5 days, daily Fluosol-DA produced only a small increase in the slope of the tumor growth delay versus irradiation alone, when used with 85% FiO2 (dose modifying factor [DMF] 1.3), but produced a DMF of 2.1 with 95% FiO2. Various concentrations of F44E (2, 4, or 8 g PFC/kg) each required a 95% FiO2 for full effect but the 8 g/kg dose had a discernable effect with an FiO2 of 65% and 85% (DMF 1.25 and 1.30, respectively). For PBHS, in contrast, a DMF of 1.6 was observed at 20% FiO2, but surprisingly this increased further to 2.1 with 95% FiO2. Further investigations of PBHS with irradiation demonstrated that daily administration of PBHS (12 ml/kg) 1 hr before single Xray fractions of 5, 10, 15, or 20 Gy with 20% FiO2 resulted in a DMF of 1.6-1.7 in the FSaIIC fibrosarcoma compared with irradiation alone when ascertained by tumor cell excision assay. These results indicate that to achieve maximum antitumor benefit with these oxygen-carrying solutions with radiation therapy, care must be taken to insure that FiO2 levels near 100% are achieved.

The effects of alpha-alpha cross-linked hemoglobin on the feeding and locomotor activity of rats

The feeding and locomotor activities of rats were used as an assay for the potentially toxic effects of an oxygen-carrying blood substitute. Rats lived in individual cages where they could feed ad lib by pressing a lever once for each small food pellet, drink water, or run in a wheel; a 12-h light/dark cycle was continuously in effect. After being anesthetized and hemorrhaged one-third of their total blood volume, individual rats were resuscitated with one of the following fluids: their own shed blood (OB), bis(3,5-dibromosalicylfumarate) alpha-alpha cross-linked hemoglobin (HbXL), human serum albumin (HSA), or Ringer's lactate (RL). Rats in a fifth group were not resuscitated (NR). During the dark period on the day of hemorrhage, the food intake and running activity of rats in all groups decreased. Food intake and locomotor activity of rats in the HbXL, NR and OB groups were more suppressed than the HSA or RL groups. The food intake of rats in the HbXL and NR groups remained significantly more suppressed during the dark period of the first recovery day; running continued to be suppressed in the HbXL group on the first recovery day, but not the second recovery day. In an effort to determine the extent to which the rats in the HbXL group were impaired, an increasing number of lever presses was required for each food pellet beginning with recovery day number 3 for all treatment groups. As the ratio of presses per pellet was increased, food intake decreased and running increased for all groups; no differences between groups were significant.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of homologous and heterologous stroma-free hemoglobin and polyhemoglobin on complement activation, leucocytes and platelets

This is a study of the effects of stroma-free hemoglobin(Hb) and polyhemoglobin on C3 and C3a levels and on blood cell counts. The effects of membrane stroma from red cells and endotoxins on complement activation were also investigated. Plasma samples from rats were incubated with hemoglobin solutions or control solutions. C3 was measured using anti-rat C3 by nephelometric method. C3a was measured using radioimmunoassay. C3 and C3a were also determined in rats receiving hemoglobin solutions, red cell stroma solutions, or a solution containing complement activators (membrane stroma and bacterial endotoxins). There were no significant differences in C3 or C3a levels between the plasma incubated with hemoglobin solutions and the control plasma incubated with saline (P greater than 0.05). Compared with the saline incubated plasma, C3 was significantly lower and C3a significantly higher in the zymosan treated plasma (P less than 0.01). In hemoglobin infused rats, there was no significant difference between pre-versus post-infusion values in C3 and C3a. There was a significant increase in C3a in the rats receiving stroma suspension (P less than 0.05) or stroma and endotoxins (P less than 0.02). Polyhemoglobin and stroma-free hemoglobin did not cause significant changes in total leucocyte, differential, or platelet counts. Our study suggests that purified stroma-free Hb and polyHb do not activate complement, and that C3a is a more sensitive parameter for monitoring complement activation than C3. On the other hand, contaminates in hemoglobin preparations, such as membrane stroma or endotoxins, activate the complement system.

Generation of free oxygen radicals and the toxicity of hemoglobin solutions

The observed toxicity of hemoglobin solutions (HbS) might depend, at least in part, on the tendency of Hb to autoxidation with generation of oxygen free-radicals. Aims of this study were: (1) to quantitate plasma elevations of H2O2 and lipid peroxides after replacement of 1/3 of calculated blood volume in various groups of rabbits with different Hb solutions; (2) to correlate these elevations with parameters of brain, heart, lung, liver and kidney injury or dysfunction; and (3) investigate the protective effect of mannitol as a radical scavenger. One Hb solution contaminated with stromal phospholipids raised H2O2 from 31.2 +/- 1.9 to 166 +/- 20 mumol/ml, lipid peroxides from 1.62 +/- 0.5 to 7.29 +/- 0.3 nmol/ml, CK-BB (brain isoenzyme) from 250 +/- 25 to 470 +/- 50 IU/L, CK-MB (myocardial isoenzyme) from 2.98 +/- 0.03 to 10.73 +/- 1.3 IU/L and SGPT from 38.1 +/- 5 to 167 +/- 45 IU/L, and reduced PaO2 from 87 +/- 10 to 57.5 +/- 2.5 mm Hg and creatinine clearance from 1.5 +/- 0.3 to 0.13 +/- 0.03 mg/min/Kg. These changes were progressively less severe with pure unmodified Hb, pure Hb crosslinked with "o-ATP", and pure crosslinked Hb + mannitol (4 mg/ml). These observations indicate a significant role for oxygen-derived radicals in the toxicity of Hb solutions.

Whole complement hemolytic activity (CH50) following infusion of stroma-free and polyhemoglobin solutions in rats

We developed a method to determine whole complement hemolytic activity (CH50) in rat plasma using a modification of the method of Mayer(1). Plasma CH50 level in 30 male Sprague Dawley rats was 1000 +/- 200 units. Following infusions with human and rat stroma-free hemoglobin or polyhemoglobin solutions, CH50 did not change significantly in rats when compared to albumin infused rats. On the other hand, CH50 significantly decreased in the group receiving membrane stroma and bacterial endotoxins.

A screening test for modified hemoglobin blood substitutes before clinical use: based on C3a complement activation in human plasma

Modified hemoglobin preparations may potentially cause hypersensitivity and anaphylactic reactions, antibody-antigen reactions and other problems. Unfortunately response in animal safety studies may not reflect the same response in human. The next best test before clinical trial in human may the use of human plasma in-vitro. This paper present an in-vitro procedure based on complement activation (C3a) of human plasma. The procedure involves collecting heparinised blood and separating the plasma and freezing the heparinised plasma at -70 degrees C until use. Each 100 lambda of control or test samples is added to 400 lambda of this plasma. This is incubated at 37 degrees C, 60 rpm for 1 hour, then added to EDTA saline to stop the reaction and stored at -70 degrees C until analysed by standard radioimmunoassay for C3a. (C3 measurement is not sensitivity enough). Using the screening test procedure described above, C3a levels (ng/ml) in plasma were: control, 1,980 +/- 280; Zymosan, 20,000; Hemoglobin preparation A, 2,227 +/- 617; Hemoglobin preparation B, 4,967 +/- 153; A 75% + B 25%, 3,967 +/- 270; A 50% + B 50%, 4,553 +/- 517; A 25% + B 75%, 4,920 +/- 430. Hemoglobin preparation A did not cause significant increases in C3a complement activation. Hemoglobin preparation B caused significant increase in C3a complement activation. Serial dilution of Hemoglobin preparation B in Hemoglobin preparation A continued to cause the same degree of C3a complement activation. This is not due to C3 exhaustion because Zymosan resulted in C3a of greater than 20,000ng/ml. This appears to show that this screening test can detect complement activation even at low concentrations of the hemoglobin preparation.(ABSTRACT TRUNCATED AT 250 WORDS)

Development of selective adsorbent for free-hemoglobin

It is well-known that acute renal failure is often caused by hemolysis. Its possible causes may be free-hemoglobin (F-Hb), stroma freed from destroyed red blood cell, and their combined action. Especially, a great amount of F-Hb is liable to flow out during extracorporeal circulation. The plasma fractionation using a membrane has so far been applied to remove F-Hb (1). The molecular weight of F-Hb of 68,000 which is nearly equal to that of albumin has made it still difficult to separate F-Hb effectively. Recently, we have developed an adsorbent that is capable of selectively removing F-Hb and succeeded in obtaining its high adsorption performance.