Haem detoxification by an insect

Abstract

Haem is involved in many biological reactions, including oxygen transport, respiration and photosynthesis. In the free state, however, haem can generate reactive oxygen species that can damage biological molecules. It can also disrupt the phospholipid bilayer of cell membranes¹. In Plasmodium parasites, which are the aetiological agents of malaria disease, up to 80% of host-cell haemoglobin is digested², leaving the free haem group to be detoxified in the parasite's food vacuole by polymerizing it into a harmless dark-brown crystalline structure called malaria pigment or haemozoin³. Haem detoxification is also a challenge for blood-sucking insects, which digest several times their own weight of vertebrate blood during a blood meal. Here we show that haem polymerization into haemozoin is not exclusive to Plasmodium: it also occurs in the midgut of the blood-sucking insect Rhodnius prolixus(Hemiptera), an important vector of Trypanosoma cruzi, the causative agent of Chagas’ disease.