| Summary: | Numerous clinical and experimental studies have implicated tumour necrosis factor (TNF) as a central mediator of acute lung injury (ALI). TNF signals through two cell surface receptors, TNFR1 and TNFR2, which initiate distinct signalling pathways and cellular responses. Using a novel, highly selective TNFR1 domain antibody GSK1995057 allied with TNF-receptor (TNFR) specific muteins, the work in this thesis investigated the roles of differential TNFR signalling in a range of human in vitro models of ALI using human lung microvascular endothelial cells (HMVEC-L), human alveolar type 2 cells (hAT2) and human neutrophils. In particular we focused on the cascade of events, which lead to neutrophil migration into the alveolar space during ALI. The TNFR1 signalling pathway mediated HMVEC-L activation (neutrophil adhesion molecule expression and chemokine/cytokine release) and injury (trans-endothelial resistance). These effects were associated with an amelioration of neutrophil migration through HMVEC-L monolayers. TNFR1 signalling also played key roles in neutrophil priming, activation, and cell fate. TNFR1 signalling mediated TNF-induced alterations in neutrophil cell surface molecule expression and reactive oxygen species production. TNFR1 antagonism also reversed TNF induced late survival (20 hours) of human neutrophils. In an attempt to generate translational data investigating the effects of differential TNFR1 signalling, we established a human ex vivo model of ALI. Using an LPS method of injury we demonstrated release of the pro-inflammatory cytokines TNF, interleukin (IL-)-8, IL-6 and IL-1β in the alveolar space. This was associated with a significant influx of healthy donor neutrophils and pulmonary oedema in LPS injured lung compared to control treated contralateral lung. These data suggest a central role for TNFR1 signalling in ALI. Translation of these in vitro data in our human ex vivo lung model may provide the basis for future clinical trials of selective TNFR1 antagonism in ALI.
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