Cell-free hemoglobin limits nitric oxide bioavailability in sickle-cell disease

Area of Science:

• Cardiovascular Science
• Hematology
• Physiology

Background:

• Cell-free hemoglobin causes vasoconstriction.
• Nitric oxide (NO) is crucial for vascular homeostasis.
• NO reacts much faster with cell-free hemoglobin than with red blood cells.

Purpose of the Study:

• To investigate the systemic effects of chronic hemolysis on nitric oxide bioavailability.
• To quantify the impact of decompartmentalized hemoglobin on nitric oxide consumption.
• To explore therapeutic strategies for restoring nitric oxide bioavailability in hemolytic disorders.

Main Methods:

• Analysis of plasma from sickle-cell disease patients.
• Measurement of nitric oxide consumption by cell-free hemoglobin.
• Assessment of forearm blood flow responses to nitric oxide donors.
• Evaluation of therapies inactivating plasma hemoglobin.

Main Results:

• Plasma from sickle-cell disease patients contains cell-free ferrous hemoglobin.
• Cell-free hemoglobin stoichiometrically consumes nitric oxide.
• Nitric oxide consumption abrogated forearm blood flow responses.
• Hemoglobin inactivation therapies restored nitric oxide bioavailability.

Conclusions:

• Decompartmentalization of hemoglobin significantly reduces nitric oxide bioavailability.
• This mechanism may explain vascular complications in acute and chronic hemolytic disorders.
• Therapeutic strategies targeting plasma hemoglobin hold promise for treating hemolytic disorders.