GSTM1 and malaria: Based on the negative association we observed between plasma HO-1 and RBCs or Hb (both can be seen as markers of hemolysis in malaria), and considering that the release of free iron and heme-containing moieties that occurs during hemolysis leads to considerable damage of endothelial cells [48], [100], [101], we propose damaged endothelial cells as an important source of plasma HO-1.