Acute lung injury is an event that occurs as a consequence of a variety of disease states which share a common pathobiological process, neutrophilic lung inflammation (NLI). NLI likely results from increased production of inflammatory cytokines and endothelial-leukocyte adhesion molecules, many of which are regulated by the ubiquitous transcription factor complex, NF-kappaB. Although NF-kappaB is necessary for directing high level transcription of many cytokines, adhesion molecules, and other pro-inflammatory genes in tissue culture, the extent to which NF-kappaB controls specific biological processes in vivo remains unanswered. Systemic inflammation induced by injection of bacterial lipopolysaccharide (LPS) results in a reproducible pattern of NF-kappaB activation in lung tissue, gene expression of several NF- kappaB-dependent cytokines, and NLI. At present, the proximate stimulus for NF-kappaB activation in the lung following LPS injection is unknown. NF-kappaB activation could occur as a result of direct stimulation of lung cells by LPS. Conversely, other mediators, such as TNFalpha or IL-1, could be primarily responsible for lung NF-kappaB activation in this setting. Another uncertainty is whether NF-kappaB is activated diffusely and simultaneously in all lung cells, or whether the timing and intensity of NF-kappaB activation differs among subpopulations of lung cells. The larger question concerns the extent to which NF-kappaB activation regulates production of cytokines and other pro-inflammatory molecules in vivo. It is uncertain whether NF-kappaB activation is merely a marker of significant acute inflammation. The following hypotheses are proposed to address these issues: 1) systemic LPS induces NF-kappaB activation in the lung through both direct stimulation of lung cells and action of the LPS-induced cytokines TNFalpha and IL-1,2) specific subsets of lung cells are differentially activated following LPS injection, and 3) targeting NF-kappaB in lung cells for molecular intervention will result in attenuation of LPS-induced neutrophilic lung inflammation. We have four specific aims to address these hypotheses using a murine model system of NLI following intraperitoneal injection of LPS. The first is to define the characteristic pattern of NF-kappaB activation in lung (compared to other organs) following intraperitoneal injection of LPS and relate NF-kappaB activation to expression of NF- kappaB dependent cytokine genes and NLI. The second specific aim is to investigate the specific cell types in the lung which respond to intraperitoneal LPS injection by activating NF-kappaB. The third specific aim is to modulate LPS-induced activation of NF-kappaB in the lungs by inhibiting the cytokine cascade or blocking IKappaB degradation. The last specific aim is to specifically target the NF- kappaB complex in the lung for molecular intervention using a trans- dominant inhibitor of the NF-kappaB complex. These studies should lead to a better understanding of the role of NF-kappaB in the molecular regulation of NLI, and may ultimately lead to better treatment strategies for the adult respiratory distress syndrome and other inflammatory lung diseases.
Showing the most recent 10 out of 47 publications
