Generation of Free Oxygen Radicals and the Toxicity of Hemoglobin Solutions

Abstract

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.

A role for iron and oxygen chemistry in preserving soft tissues, cells and molecules from deep time

“…Control tissues were prepared identically, then incubated in either sterile distilled water or phosphate buffered saline (PBS). Haemoglobin was chosen to test its preservation properties for four reasons: (i) HB is in known to be bacteriostatic [63,64]; (ii) in the presence of dioxygen, HB produces free radicals [65]; (iii) blood vessels fill with large amounts of HB after death as red cells begin to die and lyse, thus it is naturally present in large vertebrates [45]; and (iv) haeme released from HB, when degraded, will release iron, possibly accounting for the iron particles associated with preserved soft tissues [42,66] (figure 1).…”

“…Without HB treatment, blood vessels were more stable in the absence of oxygen, whereas the most rapid degradation occurred with oxygen present and HB absent. Two possible explanations for the HB/O 2 effect on stabilizing blood vessel tissues are based on earlier observations in different environments: (i) enhanced tissue fixation by free radicals, initiated by haeme-oxygen interactions [65]; or (ii) inhibition of microbial growth by free radicals [63,64]. Ironically, haeme, a molecule thought to have contributed to the formation of life [41,74], may contribute to preservation after death.…”

Cell-Free Hemoglobin Preserves Renal Function during Normothermic Ischemia

“…In the past, there has been concern that hemoglobin solutions might potentiate the oxidant stress of ischemia-reperfusion [9]. Use of early hemoglobin solutions resulted in nephrotoxicity thought to be due to contaminating stromal phospholipids [10]. As hemoglobin solutions were spiked with greater concentrations of phospholipids, the level of H 2 O 2 and lipid peroxides rose dramatically resulting in cellular injury and enzyme release.…”

Artificial Oxygen Carriers: Exactly How Close Are We to an Ultimate Product?

“…Taking into consideration the fact that these products were designed before Hb's redox reactivity became manageable , it became obvious that they were not ready for treating critically ill patients, especially those with compromised antioxidant status.…”

“…The main advantage is that these Hbs are perfect oxygen carriers, are an easy target for any chemical modification, and are readily available. The disadvantages are that these Hbs are potent oxidizers and activators of redox (NF‐kappa B) and oxygen (HIF‐1) regulated transcription factors . There is an established link between Hb‐mediated oxidative reactions and inflammatory responses .…”