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Hemoglobin-based oxygen carriers (HBOCs): structural alterations that affect free radical generation
A I Alayash1, B A Ryan, J C Fratantoni
1Center for Biologics Evaluation and Research, Bethesda, MD.
Summary
Modified hemoglobins (HbA-FMDA, HbBv-FMDA, HbA-DBBF) show varied free radical generation when exposed to hydrogen peroxide. Bovine hemoglobin (HbBv-FMDA) demonstrated the lowest free radical activity, indicating altered oxidation-reduction reactions.
Area of Science:
- Biochemistry
- Chemical Biology
- Biophysical Chemistry
Background:
- Hemoglobin-based oxygen carriers (HBOCs) are investigated as blood substitutes.
- Chemical modifications alter hemoglobin's properties, including oxygen affinity and reactivity.
- Understanding HBOCs' interaction with reactive oxygen species is crucial for safety and efficacy.
Purpose of the Study:
- To investigate how chemical modifications affecting hemoglobin's oxygen affinity influence its oxidation-reduction reactions.
- To compare the free radical generation and reactivity of different chemically modified human and bovine hemoglobins.
Main Methods:
- Synthesis of three modified hemoglobins: HbA-FMDA, HbBv-FMDA, and HbA-DBBF.
- Assessing free radical generation by measuring formaldehyde (HCHO) formation from dimethylsulfoxide (Me2SO) upon exposure to hydrogen peroxide (H2O2).
- Monitoring spectral changes induced by H2O2 and evaluating free radical interaction via NADPH oxidation and aniline hydroxylation assays.
Main Results:
- Modified hemoglobins (HbA-DBBF, HbA-FMDA, HbBv-FMDA) exhibited reduced rates of HCHO formation compared to native hemoglobin (HbAo).
- HbBv-FMDA showed significantly lower rates of HCHO formation, spectral changes, NADPH oxidation, and aniline hydroxylation, indicating reduced free radical activity.
- Mannitol and thiourea, free radical scavengers, decreased both spectral changes and HCHO formation rates.
Conclusions:
- Chemical modification of hemoglobins alters their interaction with oxidative stress.
- HbBv-FMDA exhibits diminished capacity for free radical generation and interaction compared to other modified HBOCs.
- These findings highlight the importance of evaluating the oxidative properties of HBOCs for potential therapeutic applications.