DEXAMETHASONE INHIBITS THE PRODUCTION OF MACROPHAGE INFLAMMATORY PROTEIN-2 IN THE LEUKOCYTES IN RAT ALLERGIC INFLAMMATION

In the air pouch-type allergic inflammation model in rats, when the in filtrated leukocytes in the pouch fluid collected 4 h after antigen ch allenge were incubated, neutrophil chemotactic activity in the conditi oned medium increased time-dependently. They produced neutrophil chemo tactic factors, viz. leukocyte-derived neutrophil chemotactic factor ( LDNCF)-2, a major component, and LDNCF-1, a minor component. When the infiltrated leukocytes were incubated in the presence of dexamethasone , neutrophil chemotactic activity in the conditioned medium decreased in a concentration-dependent manner, and production of LDNCF-2 and LDN CF-1 was inhibited. Because purified LDNCF-2 had been found to be iden tical with rat macrophage inflammatory protein 2 (MIP-2), effects of d examethasone on the level of MIP-2 mRNA in the leukocytes were investi gated. Using the reverse transcription-polymerase chain reaction techn ique, it was demonstrated that dexamethasone suppressed the level of M IP-2 mRNA in the leukocytes. These results indicate that dexamethasone inhibits MIP-2 production at the transcription level.