Leucocytes play an essential role in the pathogenesis of ischaemia and
reperfusion injury and inhibition of their adhesion and of mediator release can reduce vascular and tissue damage. Previous studies have shown that
cloricromene modifies several granulocyte as well as monocyte/macrophage functions and it has been shown that
cloricromene administration exerts a clear protective action in several experimental models of ischaemia. The present work describes new data on polymorphonuclear leukocyte (PMN) inhibition exerted by
cloricromene and compares these observations with earlier ones. Human washed PMN and human whole blood (HWB) were studied in vitro upon stimulation with f-MLP in the presence of
cytochalasin B, with opsonized
zymosan and with a
phorbol ester (PMA). Amongst
free radicals,
superoxide anions were chosen as index of oxidative burst. Phagocytosis and
beta-glucuronidase, as lysosomal release indicators, were measured to characterize PMN function:
cloricromene inhibited concentration-dependently all the parameters upon stimulation by each activator tested. Experiments performed in rabbit whole blood (RWB) showed that
cloricromene inhibited
free radical generation with IC50 values similar to those obtained in human whole blood. Comparing the action of
cloricromene on human cells in different tests, we found that some parameters were more sensitive than others, even when the same stimulus was used. In particular,
free radical generation was inhibited by
cloricromene with IC50 values below 36 microM, while other functions, like lysosomal release and phagocytosis were inhibited with IC50 values over 100 microM. These data confirm that
cloricromene exerts a notable inhibitory effect on PMN and may explain the activity of the compound, observed in vivo in several experimental models of ischaemia-reperfusion and
shock.