The effect of stress on the inflammatory response to Porphyromonas gingivalis in a mouse subcutaneous chamber model

Background: The impact of emotional stress on the outcome of infectious dis eases was studied in animal models and humans, but data related to the effe ct of stress on periodontal infection are limited. Using the subcutaneous c hamber model in mice, the present study was carried out to investigate the effect of stress on the host response to Porphyromonas gingivalis. Methods: Mice with subcutaneous chambers (2 per animal) were divided into 4 treatment groups: cold-stress; isolation-stress; corticosterone (CS)-injec ted; and controls. On the third day of stress conditions, heat-killed P. gi ngivalis were injected into the chambers. The chambers were sampled 1 and 5 days later and analyzed for leukocyte number, tumor necrosis factor (TNF)- alpha levels, and interferon (IFN)-gamma levels. Results: Injection of P. gingivalis induced the migration of leukocytes int o the chambers and increased the intrachamber levels of IFN-gamma and TNF-a lpha. There were no significant differences in cell number and IFN-gamma le vels between the different treatment groups, but the levels of TNF-alpha we re significantly lower in the isolation-stress and cold-stress groups compa red to control animals. CS-injected animals were not different from control s. In addition, the levels of TNF-alpha in the stressed animals were lower on the fifth day post-injection than on the first day, but not in the CS an d control group. Conclusions: The results suggest that the levels of TNF-alpha induced by P. gingivalis in the infection site are downregulated in stressed animals, an d CS is not the sole mediator responsible. The stress-induced reduction in TNF-alpha levels might have an impact on the pathogenesis of periodontal di sease in humans experiencing emotional stress.