[Activation of human neutrophils by hemin]

Activation of neutrophils by free heme is considered as one of the mechanisms for cellular dysfunction under the conditions of hemorrhage or tissue damage. We studied about the effects of hemin, ferriprotoporphyrin IX, on human neutrophil activation by measurements of adhesion molecule expression and reactive oxygen species (ROS) production. Human neutrophils purified from heparinized blood of healthy volunteers were stimulated with hemin. Surface expression of CD11b and L-selectin were evaluated by flow cytometry, and superoxide production was detected by chemiluminescence. Hemin increased the expression of CD11b and produced superoxide accompanying by increase in intracellular free calcium concentration. Thus, free heme-molecule is suggested to possess the activity to initiate or aggravate tissue injuries. Since neutrophils do not express CD163, scavenger receptor for hemoglobin-haptoglobin complex, the mechanisms by which hemin exerts these effects are still to be studied.