KFO 342 - P3: Myeloid differentiation in systemic inflammation

Basic data for this project

Description

Sepsis is a life-threatening condition and a leading cause of death worldwide. However, the pathophysiology of sepsis and its accompanying systemic inflammation is still poorly understood. The inflammatory response during SIRS consists of an acute phase of exacerbated inflammation and strong activation of the innate immune system and subsequently a prolonged hypo-inflammatory phase resulting in inadequate inflammatory reactivity, which represents a major risk factor for mortality during SIRS. Monocytes and macrophages belong to the first line of defence against infections or tissue damage. Depending on their differentiation and activation stage, they can exert either pro- and anti-inflammatory function. In the proposed project we will continue to investigate the role of two molecular targets involved in pro-inflammatory (S100A8/S100A9-proteins) and anti-inflammatory macrophage functions (CD163) in models of systemic inflammation as well as on their antagonistic regulation by the myeloid transcription factor interferon regulatory factor 8 (IRF8). To analyse the function of these molecules we have a unique number of functionally relevant knock-out mice strains including recently established conditional and inducible knock-out mice. These murine lines will allow the analysis of the regulation of systemic inflammation by CD163, IRF8 or S100A8/S100A9 proteins in a time and cell-specific manner. For more in-deep analysis of molecular mechanism regulated by these molecules at the cellular level, we will use both primary cells isolated from bone marrow, spleen, liver, peritoneum, blood and ER-Hoxb8-derived monocytes and macrophages. The biological relevance of CD163 (membrane-bound and soluble molecule), CD163+ macrophages and S100A8 and S100A9 and their regulation by IRF8 will be predominantly investigated in diverse models of systemic inflammation. We will also perform in vitro characterization of myeloid cells isolated from the newly established conditional and inducible knock-out mice. We will analyse the differentiation patterns of these cells and, using immunological, biochemical and molecular biology methods, we will investigate molecular events, signalling pathways and transcription factor activation induced by acute or prolonged triggering of TLR2 and TLR4 with both pathogen-derived, sterile endogenous ligands (S100A8 and S100A9) as well as induced during staphylococcal infections. In the translational part of the project, we want to link the pathways characterized in in vivo and in vitro studies in mice to the inflammatory response of monocytes in a clinically relevant human disease with systemic inflammation. With this approach, we will contribute to the better understanding of immune mechanisms governing systemic inflammation and define regulatory and pathological pathways in macrophages that may be relevant for development of innovative therapies for systemic inflammation.