Extracellular methemoglobin primes red blood cell aggregation in malaria: an in vitro mechanistic study

Toxic byproducts from infected RBC cause rheological alteration and RBC aggregation. Malaria culture supernatant has the ability to exhibit RBC aggregation. Ammonium sulfate fractionation and immunodepletion of methemoglobin from culture supernatant confirms methemoglobin as a major aggregant. In vitro treatment of RBC with methemoglobin induces irreversible high order RBC aggregates, resistant to shear stress and physical forces. Methemoglobin-mediated ROS generation in the external micro-environment to develop oxidative stress close to RBC membrane seems to be responsible for initiating and forming high order RBC aggregates through phosphatidyl-serine externalization. Removal of oxidative stress through antioxidant treatment abolishes high order RBC aggregate formation. In conclusion, we discovered a novel pathway of methemoglobin-mediated RBC aggregation and its potential role in patho-physiological effects during malaria.