Primaquine-induced
hemolytic anemia is a toxic side effect that is due to premature splenic sequestration of intact erythrocytes. Previous studies have suggested that a phenolic metabolite,
5-hydroxyprimaquine (5-HPQ), mediates
primaquine hemotoxicity by generating
reactive oxygen species (ROS) within erythrocytes that overwhelm
antioxidant defenses. However, the nature of the oxidative stress is not understood, and the molecular targets, whether
protein and/or
lipid, are unknown. To investigate the mechanism underlying the hemolytic activity of
5-HPQ, we have examined the effect of hemolytic concentrations of
5-HPQ on ROS formation within rat erythrocytes using the cellular ROS probe, 2',7'-dichlorodihydrofluoresein diacetate. In addition, we examined the effect of
5-HPQ on
membrane lipids and
cytoskeletal proteins. The data indicate that
5-HPQ causes a prolonged, concentration-dependent generation of ROS within erythrocytes. Interestingly, 5-HPQ-generated ROS was not associated with the onset of lipid peroxidation or an alteration in
phosphatidylserine asymmetry. Instead,
5-HPQ induced oxidative injury to the erythrocyte cytoskeleton, as evidenced by changes in the normal electrophoretic pattern of membrane ghost
proteins. Immunoblotting with an anti-
hemoglobin antibody revealed that these changes were due primarily to the formation of
disulfide-linked
hemoglobin-skeletal
protein adducts. The data suggest that cytoskeletal
protein damage, rather than
membrane lipid peroxidation or loss of
phosphatidylserine asymmetry, underlies the process of removal of erythrocytes exposed to
5-HPQ.