IN-VIVO INDUCTION AND REGULATION OF INTERLEUKIN-8-LIKE CHEMOKINE GRO CINC-1 IN RAT MIDDLE-EAR/

Interleukin-8 possesses chemotactic-activating properties toward neutr ophils, and may contribute to the pathogenesis of middle ear inflammat ion. GRO/CINC-1 is a rat chemokine with structural and functional homo logy to human interleukin-8, the induction and regulation of which in the middle ear cavity in vivo remains to be established. The productio n of GRO/CINC-1 in middle ear lavage and gene expression in the middle mucosa was investigated using topical inoculation with lipopolysaccha ride (LPS) in the rat in vivo model. GRO/CINC-1 in middle ear lavage s howed time-and dose-dependent production under LPS stimulation. The pe ak of the GRO/CINC-1 production was reached by 4 h after LPS 1 h expos ure, whereas the level of production subsequently returned to the leve l without LPS stimulation at 8 h after LPS stimulation. The topical co rticosteroid perfusion in the middle ear after LPS stimulation signifi cantly reduced the production of GRO/CINC-1 in the middle ear cavity c ompared with that without corticosteroid. At the time of peak producti on, the expression of GRO/CINC-1 mRNA, evaluated using the polymerase chain reaction, was considerable in the middle ear mucosa. This invest igation of the characteristics of interleukin-8-like cytokine in the m iddle ear cavity using a rat in vivo model has extended the functional concept of chemokines at the initial stage in otitis media.