The Importance of Systemic Cytokines in the Pathogenesis of Polymicrobial Sepsis and Dehydroepiandrosterone Treatment in a Rodent Model

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Abstract
The pathogenesis of sepsis is still undetermined to a large extent. It is an established fact that female gender is associated with a lower mortality and that sex steroid hormones influence the immunologic response. Dehydroepiandrosterone (DHEA) seems to have a protective immunologic effect in sepsis. It is still unknown in which way DHEA influences the pathogenesis of sepsis. Therefore, the effect of DHEA application on cytokine concentrations in tumor necrosis factor (TNF) receptor (TNF-RI−/−) and interleukin-6 (IL-6−/−) knockout mice was determined. In a model of polymicrobial sepsis induced by coecal ligation and puncture (CLP), the effect of DHEA on survival and cytokine concentrations was examined. For clarification of the role of TNF-RI, CLP was performed in TNF-RI knockout mice (TNF-RI−/−). In addition, IL-6 knockout mice (IL-6−/−) were used to clarify the role of IL-6. Furthermore, experiments were performed in mice that were not genetically modified (wild type, WT). The protective effect of DHEA could be confirmed in this CLP model. DHEA application was associated with a reduction in mortality in WT animals. Moreover, DHEA-treated animals demonstrated a reduction in systemic inflammatory effects, as determined by proinflammatory cytokines TNF-α, IL-1β, IL-6, and the antiinflammatory cytokine IL-10. In this work, it was shown that the TNF-RI is essential for survival after CLP. DHEA application was associated with a reduction of mortality of 100% in TNF-RI−/− mice after CLP to 50%. This result engages, that the effect of DHEA is TNF-RI independent. However, the application of DHEA had no influence on the mortality in IL-6−/− mice. It can be concluded that the protective effect of DHEA in polymicrobial sepsis is mediated IL-6 dependently. DHEA reduces the systemic inflammation, measurable via the proinflammatory cytokines TNF-α, IL-1β, IL-6, and the antiinflammatory cytokine IL-10. IL-6 might be involved in the DHEA-mediated reduction of postseptic complications. In contrast, DHEA seems to be TNF-RI independent. Consequently, DHEA might be useful as an adjunct therapy for the immune modulation in sepsis.