Possible Roles of Protein Kinases in Neutrophil Chemotactic Factor Production by Leucocytes in Allergic Inflammation in Rats

1. In an air pouch-type allergic inflammation model in rats, leucocytes that had infiltrated into the pouch fluid collected 4 h after the antigen challenge produced proteinaceous chemotactic factors for neutrophils when they were incubated in the medium. 2. To clarify the mechanism of activation of the infiltrated leucocytes in producing these factors, the effects of protein kinase inhibitors on neutrophil chemotactic factor production were examined. 3. When the infiltrated leucocytes were incubated for 4 h in medium containing the non-selective protein kinase inhibitor K-252a (1-100 ng ml-1, 2.14-214 nM), the tyrosine kinase inhibitor genistein (1-50 micrograms ml-1, 3.7-185 microM), and the more selective protein kinase C inhibitor H-7 (5-100 micrograms ml-1, 13.7-274 microM); neutrophil chemotactic activity in the conditioned medium was decreased in a concentration-dependent manner, but the adenosine 3':5'-cyclic monophosphate (cAMP)-dependent protein kinase inhibitor H-89 (1-1000 ng ml-1, 2.24-2240 nM) showed no effect. 4. Isoelectric focusing of the conditioned medium revealed that the leucocytes produced two neutrophil chemotactic factors, leucocyte-derived neutrophil chemotactic factor (LDNCF) 1 and LDNCF-2. Treatment of the leucocytes with K-252a, genistein, and H-7, but not H-89, inhibited production of both LDNCF-1 and LDNCF-2. 5. These results suggest that activation of tyrosine kinase and protein kinase C, but not cAMP-dependent protein kinase, is responsible for the production of LDNCF-1 and LDNCF-2. 6. The steroidal anti-inflammatory drug dexamethasone and the protein synthesis inhibitor cycloheximide inhibited neutrophil chemotactic factor production in a concentration-dependent manner. Time-course experiments showed that the inhibitory effect by dexamethasone was apparent even 30 min after the incubation.7. Mechanism for inhibiting the production of LDNCF-1 and LDNCF-2 by dexamethasone is also discussed.