Detection of hemin release during hemoglobin S denaturation

Area of Science:

• Hematology
• Biochemistry
• Molecular Biology

Background:

• Sickle hemoglobin (HbS) is prone to instability, leading to red blood cell damage through mechanisms like micro-Heinz body formation.
• The role of hemin, a potent hemolytic agent, in sickle hemoglobin denaturation and its contribution to red cell pathology remains unclear.

Purpose of the Study:

• To investigate the generation of hemin during sickle hemoglobin denaturation.
• To quantify hemin levels in sickle cell disease patients' red blood cells.

Main Methods:

• Separation and quantitation of hemin using Dowex AG 1-X8 anion-exchange resin under high-ionic strength conditions.
• Mechanical shaking of oxyhemoglobin S and oxyhemoglobin A to assess denaturation rates and hemin release.
• Measurement of hemin content in hemolysates from sickle cell disease patients and normal individuals.

Main Results:

• Oxyhemoglobin S denatures significantly faster than oxyhemoglobin A upon mechanical shaking, with higher hemin levels detected.
• Sickle cell disease patients exhibit a three- to fivefold increase in red blood cell hemin content compared to normal individuals.
• Elevated hemin levels in sickle cell disease patients range from 0.4 to 0.75 mumol/L, versus 0.1 to 0.15 mumol/L in controls.

Conclusions:

• The inherent instability of sickle oxyhemoglobin contributes to increased intracellular hemoglobin precipitation and hemin release.
• Released hemin may play a significant role in the membrane damage observed in sickle red blood cells.
• This study provides evidence for hemin generation as a key factor in sickle cell pathophysiology.