RAPID KILLING OF HUMAN NEUTROPHILS BY THE POTENT ACTIVATOR PHORBOL 12-MYRISTATE 13-ACETATE (PMA) ACCOMPANIED BY CHANGES DIFFERENT FROM TYPICAL APOPTOSIS OR NECROSIS

To elucidate the relationship between activation of neutrophils and th eir subsequent death, the effect of phorbol 12-myristate 13-acetate (P MA), a potent activator of neutrophils, was examined. PMA-treated neut rophils showed morphological changes quite different from those of typ ical apoptosis or necrosis, After fusion of the lobate nucleus, nuclea r contents of chromatin uniformly decreased in compactness and soon af ter the nuclear envelope was broken. Even at this stage, cytoplasmic o rganelles did not undergo degeneration. Membrane permeability began in creasing at 3 h of incubation with PMA, subsequent to nuclear change, Conventional agarose gel electrophoresis and pulsed field gel electrop horesis of DNA from PMA-treated neutrophils revealed no DNA degradatio n products smaller than 300 kbp. PKC inhibitors, staurosporine and H-7 , prevented cytotoxicity by PMA. Furthermore, antioxidants, thiourea, dimethylthiourea, pyrrolidimethiocarbamate, and N-acetyl-L-cysteine, b ut not superoxide dismutase, were also active ill preventing PMA cytot oxicity, suggesting that cell suicide resulting from PMA treatment is due to oxygen radicals, especially the hydroxyl radical, A certain pop ulation of neutrophils phagocytosing opsonized zymosan also showed cha nges similar to those observed in PMA-treated cells.