Background Eph-ephrin signalling plays important roles in various developmental processes, in the pathogenesis of cancer, stem cell differentiation and inflammation including regulation in T and B cell function. However, the role in acute inflammation associated with acute bacterial infection (i.e. bacterial peritonitis) is not yet defined. In the present study we have evaluated to the role of Eph-ephrin signalling in the course of acute bacterial peritonitis.
Methods Animals were divided in two groups: (1) control animals were administered EphA4-Fc-ΔLBD (ligand binding domain deleted) protein, which does not activate ephrin receptors, 18 hours prior to infection, and, (2) experimental animals received EphA4-Fc antibody (1mg/kg/ip) which blocks EphA-ephrinA signalling. Animals were subject to acute bacterial peritonitis by injecting enterobacteria (106 LogCFU) (isolated and cultured overnight) intraperitoneally. Mice were sacrificed at time 2 and 6 hours post-infection and neutrophil infiltration, bacterial load and various pro-inflammatory cytokines were measured in peritoneal lavage fluid (PLF) by using flow cytometer and ELISA respectively.
Results The bacterial count two hour post-infection were significantly (p≤0.05) lower in EphA4-Fc treated group compared to control antibody (EphA4-Fc-ΔLBD) treated animals. This observation was further supported by the finding that EphA4-Fc treated animals exhibited higher degree of neutrophil infiltration as compared to control group. The neutrophil infiltration is controlled by potent pro-inflammatory cytokines (i.e. IL-1β, IL-6 and IL-8) released at site of infection. Our ELISA results showed significantly ((p≤0.001) higher levels of IL-1β and IL-8 in EphA4-Fc treated group as compared to control group. However, IL-6 levels iwere lower in EphA4-Fc treated group.
Conclusion EphA4-Fc antibody pre-treatment in C57BL/6 mice provides protection against bacterial peritonitis by increased clearance of the pathogen through increased neutrophil infiltration at site of infection. Further studies using specific Eph receptor KO mice are required to know the exact mechanism of Eph-ephrin signalling in host pathogen interaction.