Local expression of cytokine messenger RNA in rat model of Escherichia coli epididymitis.

PURPOSE: In order to investigate whether cytokines play an important role in the regulation of host defense against bacterial epididymitis, we examined the local expression of cytokine mRNA in a rat model of Escherichia coli epididymitis.
MATERIALS AND METHODS: Escherichia coli was inoculated into the spermatic cord of the rats and provoked epididymitis. At 6, 12, 24, 48, and 72 hours postinfection (p.i.) epididymides were harvested. We examined interleukin-6 (IL-6) and other inflammatory cytokine mRNAs in epididymides by Northern blotting and reverse transcriptase polymerase chain reaction (RT-PCR). Histopathological findings and immunohistochemistry for IL-6 were also examined.
RESULTS: Infected epididymides expressed IL-6 mRNA maximally at 6 hours p.i. and then the signal decreased by Northern blotting. mRNA for IL-1 beta and TNF-alpha also increased within 6 hours by RT-PCR. Histopathological examination showed that no inflammatory cells were observed at 6 hours p.i. and that inflammatory changes were most prominent at 72 hours p.i. Epididymal epithelium expressed IL-6 locally in response to local bacterial infection by immunohistochemistry.
CONCLUSIONS: mRNA for IL-1 beta, IL-6, and TNF-alpha is expressed locally in response to bacterial infection before inflammatory cell infiltration. This rapid expression in the epithelial cells may be important in host defense to local genital infection.