Acute respiratory distress syndrome (ARDS) is a devastating lung disease in which excessive inflammation leads to lung dysfunction and often death. Attempts to use anti-inflammatory medications have been unsuccessful. Due to their high metabolic demands, neutrophils, macrophages, and lymphocytes rely upon glutamine metabolism for activation and function. Glutamine metabolism may thus represent a novel target to modulate the excessive, dysregulated inflammation seen in ARDS. In this proposal, the role of glutamine in established acute lung injury (ALI) will be explored via use of a glutamine analogue, DON (6-diazo-5-oxo-l-norleucine), which binds to and inhibits glutamine-utilizing enzymes and transporters. This inhibitor will be studied in two in vivo models of ARDS: intratracheal (IT) lipopolysaccharide (LPS) and IT bleomycin. These models allow evaluation of both the inflammatory phase, when neutrophils and inflammatory macrophages are the predominant cell types, and the resolution phase, when lymphocytes and macrophages mediate lung repair. Additionally, these models will allow us to study lung injury that resolves over time (LPS) and injury that progresses to fibrosis (bleomycin). Our initial studies suggest that DON ameliorates inflammation and promotes recovery in both models. Our hypothesis is that glutamine modulates immune responses, and by targeting glutamine metabolism the unremitting, dysregulated inflammation and wound healing in ALI can be mitigated.
Aim 1 tests the hypothesis that inhibition of glutamine metabolism reduces lung inflammation and promotes resolution of injury. Following induction of ALI with bleomycin, mice will receive DON either during established inflammation or later during the development of fibrosis. The effects of these inhibitors on inflammation and resolution of lung injury with be assessed.
Aim 2 tests the hypothesis that DON modulates neutrophil, macrophage, and lymphocyte activity and metabolism in vitro.
Aim 3 tests the hypothesis that DON modulates the lung metabolome and assesses changes in gene expression within lung inflammatory cells. Changes in metabolic pathways will be assessed by measurement of metabolites within the lungs. These experiments will provide greater understanding of the role of glutamine metabolism in ALI, both in individual immune cells and as an integrated process within the lungs, and will explore a novel mechanism by which to modulate pulmonary inflammation. Additionally, this proposal will facilitate development of essential skills and enhanced understanding of immunology and metabolism that will allow the candidate to become an academic physician-scientist. The candidate and her mentor have designed a training plan that combines this research proposal with coursework in immunology, metabolism, bioethics, statistics, and grantsmanship to build the foundation necessary for successful career development. They have also assembled an advisory committee consisting of experts in metabolism and immunology who will provide technical assistance and mentorship to prepare the candidate to achieve her goal of becoming an independent physician-scientist.
Acute respiratory distress syndrome (ARDS) is a devastating lung disease characterized by dysregulated, excessive inflammation. Glutamine is an amino acid that acts as a critical regulator of immune cell function. By exploring the role of glutamine in the function and activation of immune cells in ARDS, we can better understand the mechanisms that regulate immune responses in ARDS and identify novel targets for future therapies.
