Expression of Proinflammatory Cytokine Genes in Mouse Peritoneal Tissue Infected with Bacteroides fragilis

ABSTRACT

OBJECTIVE: Bacteroides fragilis, normal colonic inhabitant, is the most frequently isolated anaerobes in infected tissues, particularly in intraabdominal abscesses. In the acute infection model with abscesses, the response to B. fragilis infection is characterized by infiltration of neutrophils and macrophages. This study was designed to determine whether proinflammatory cytokines could be upregulated in peritoneal tissue of B. fragilis-infected mouse model. METHODS: After C57BL/6 mice were infected with abscess-inducing encapsulated B. fragilis, RNA was extracted from the intraperitoneal tissues. Cellular RNA was also extracted from mouse peritoneal macrophages (MPM) and human peripheral blood mononuclear cells (PBMC) after infection with B. fragilis. Expression of various cytokine mRNA was assessed using RT-PCR and standard RNA. Each cytokine protein was also measured by ELISA. RESULTS: B. fragilis-infected intraperitoneal tissues showed upregulated expression of IL-1u, IL-6 and TNFu mRNA. Expression of IL-1u and TNFu mRNA and protein was significantly higher in MPM or PBMC infected with B. fragilis than in those without infection. However, expression of IL-6 mRNA and protein was not increased in MPM or PBMC infected with B. fragilis compared with those without infection. CONCLUSION: These results suggest that the cytokines can be involved in immunopathologic reactions of the peritoneal tissue infected with B. jragilis.