Oyster metallothionein as an oxyradical scavenger: implications for hemocyte defense responses

In order to better understand the interplay between metallothionein (MT) an d reactive oxygen species (ROS) in oyster hemocytes, studies of the hydroge n peroxide (H2O2) scavenging properties of MT were carried out in a cell-fr ee system. Mammalian MT is involved in protection against oxidative stress by virtue of its ability to scavenge free radicals; therefore, the H2O2 sca venging potentials of Crassostrea virginica and rabbit MTS were compared. O yster and rabbit MTs showed similar dose-dependent suppression of H2O2-stim ulated, luminol-augmented chemiluminescence (CL); the EC50 for CL (25 mu M H2O2) was similar to 1.0 mu M MT for both species. The interaction of ROS w ith MT in hemocytes could play a role in protection of the cells and surrou nding tissues from oxidants associated with antimicrobial responses. Mobili zation of bound zinc from MT by hemocyte-derived ROS may produce aberrant r egulatory effects on various cellular processes. The data suggest that MT m ay be involved in immunoregulatory pathways in oyster hemocytes as a result of its ability to scavenge antimicrobial ROS. (C) 1999 Elsevier Science Lt d. All rights reserved.