[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.

[Effects of magnetic resonance imaging on neutrophil functions].

We evaluated the effects of magnetic resonance (MR) imaging on human neutrophil functions. In addition of the counting of leukocyte and neutrophil number, expression levels of adhesion molecules on neutrophil surface such as CD11b and L-selectin, and reactive oxygen species (ROS) production were determined by means of flowcytometry. Complete blood count did not show any difference between before and after MR imaging in five normal healthy volunteers. The levels of cell surface adhesion molecules were not altered in both in vivo MR imaging (n=5) and in vitro MR exposure experiments (n=13). Moreover, the levels of ROS production were also not affected by in vivo MR imaging. On the other hand, neutrophils exposed to MR in vitro exhibited significant increase in ROS production after stimulation with fMLP combined with lipopolysaccharide, although no increase was observed with PMA stimulation. Actually, there have been no reports describing the complication relating to hyper-neutrophil function as far as we could search, but it might be necessary to evaluate the biological effects of MR imaging especially under the pathologic circumstances that induce neutrophil activation.

Albumin attenuates neutrophil activation induced by stimulators including antibodies against neutrophil-specific antigens.

As neutrophil activation is related to several adverse transfusion reactions, we studied about the activation induced by anti-neutrophil antibodies and the stabilizing effects of albumin pretreatment by means of flow cytometry. Anti-neutrophil monoclonal antibody (anti-HNA-1a, 1b, 2a) alone induced CD11b expression and shedding of L-selectin, and anti-HNA-1a reinforced reactive oxygen species (ROS) production. Albumin pretreatment significantly reduced CD11b expression and L-selectin shedding induced by fMLP and ROS production induced by PMA, G-CSF combined with PMA or LPS-fMLP, or anti-HNA-1a combined with PMA. These findings suggest that anti-HNA-1a is related to adverse reactions and albumin has a regulating effect on neutrophil activation.