Infiltration of neutrophils by intrapleural injection of tumour necrosis factor, interleukin-1, and interleukin-8 in rats, and its modification by actinomycin D.

1. To assess in vivo chemotactic activity of tumour necrosis factor (TNF), interleukin-1 (IL-1), IL-8, and cytokine-induced neutrophil chemoattractant (CINC), we injected these cytokines into the pleural cavity of rats. 2. CINC (0.1-1 microgram) and recombinant human IL-8 (rhIL-8, 0.2-5 micrograms) caused neutrophil infiltration into the rat pleural cavity in a dose-dependent fashion, peaking at 3 h. The number of leukocytes in the peripheral blood did not change significantly. 3. RhTNF alpha and rhIL-1 alpha also induced neutrophil accumulation. The dose response curves of rhTNF alpha (0.67 ng-6.7 micrograms) and rhIL-1 alpha (0.45 ng-4.5 micrograms) at 3 h were bell shaped. On the other hand, unlike CINC and rhIL-8, rhTNF alpha and rhIL-1 alpha caused transient marked leukopenia at 3 h in a simple dose-dependent fashion. 4. Concomitant injection of actinomycin D dose-dependently and completely at 10 micrograms inhibited neutrophil infiltration induced by rhTNF alpha (0.67 microgram) and rhIL-1 alpha (0.45 microgram) at 3 h. However, that induced by CINC or rhIL-8 was not affected by actinomycin D. 5. Peaking at 1 h, CINC production in the pleural cavity was found after intrapleural injection of rhTNF alpha (0.67 microgram) or rhIL-1 alpha (0.45 microgram), but not after that of rhIL-8 (5 micrograms). The CINC production induced by rhTNF alpha or rhIL-1 alpha and the neutrophil infiltration was suppressed by concomitant injection of actinomycin D (1 and 10 micrograms). 6. These results indicate that CINC and IL-8 themselves are direct chemoattractants for neutrophils, whereas TNF and IL-1 induce neutrophil infiltration indirectly via newly synthesized mRNA for chemotactic protein including CINC, which may be involved in neutrophil emigration at local inflammatory sites in rats.