rIFN-gamma-activated rat neutrophils induce tumor cell apoptosis by nitric oxide.
We have previously shown that 1) neutrophils activated with various cytokines, including rat recombinant interferon gamma (rIFN-gamma), inhibit tumor cell growth and that 2) nitric oxide (NO) is the effector molecule in tumor inhibition by rIFN-gamma-stimulated rat peritoneal exudate neutrophils. In this study, we examined the nature of tumor cell death induced by rat peritoneal neutrophils activated by rIFN-gamma in order to clarify the mechanism of apoptosis in neoplastic tumor cell death. DNA of 3 syngeneic rat tumor cell lines was significantly fragmented within 3 hr of incubation in the presence of rIFN-gamma-activated neutrophils, and this effect was dependent on both the concentration of rIFN-gamma and the number of neutrophils. This DNA fragmentation was inhibited by L-N-(I-iminoethyl)-ornithine (L-NIO), a NO synthase inhibitor, but not by superoxide dismutase (SOD). Tumor cells treated with the activated neutrophils were shown by electron microscopy to be apoptotic, exhibiting necrotic features with a longer incubation. On the other hand, cytolysis of tumor cells, as determined by a [3H]-uridine release assay, was first observed only at 24 hr of incubation with the rIFN- gamma-activated neutrophils. Taken together, our results suggest that tumor cell apoptosis by activated neutrophils is NO-dependent and that apoptotic tumor cells undergo necrosis as a secondary process. We suggest that tumor cell apoptosis induced by activated neutrophils plays an important role in regulation of neoplastic tumor cell growth and death in vivo.
Uchida
T
T
Department of Immunology and Parasitology, Yamagata University School of Medicine, Japan.
Yamashita
T
T
Araki
A
A
Watanabe
H
H
Sendo
F
F
D000818:Animals; D017209:Apoptosis; D053938:DNA Fragmentation / Q000187:drug effects; D004273:DNA, Neoplasm / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D005260:Female; D007371:Interferon-gamma / Q000494:pharmacology*; D008854:Microscopy, Electron; D018375:Neutrophil Activation / Q000187:drug effects*; D009504:Neutrophils / Q000187:drug effects / Q000502:physiology*; D009569:Nitric Oxide / Q000502:physiology*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D009952:Ornithine / Q000031:analogs & derivatives / Q000494:pharmacology; D051381:Rats; D011994:Recombinant Proteins; D013482:Superoxide Dismutase / Q000494:pharmacology; D014407:Tumor Cells, Cultured / Q000473:pathology*
D004273:DNA, Neoplasm; D011994:Recombinant Proteins; D009569:Nitric Oxide; C065027:N(G)-iminoethylornithine; D007371:Interferon-gamma; D009952:Ornithine; D019001:Nitric Oxide Synthase; D013482:Superoxide Dismutase