Neutrophil Elastase Reprograms Macrophage Function in Chronic Obstructive Pulmonary Disease
Abstract
This proposal directly addresses a Fiscal Year 2018 (FY18) Peer Reviewed Medical Research Program (PRMRP) Topic Area/Area of Encouragement: Respiratory Health/The Causes of Chronic Obstructive Pulmonary Disease (COPD). COPD is a major chronic lung disease characterized by both chronic bronchitis and emphysema. Both processes cause recurrent episodes (acute exacerbations) of cough, sputum production, and shortness of breath, and ultimately lead to lung failure. COPD is the third leading cause of death in the United States, and Veterans are three times more likely to develop COPD than the general population. Although tobacco smoke is the major cause of disease, environmental exposures including smoke form burn pits, biomass fuel, molds, and pollens are other significant exposures. Currently treatment is symptomatic and there is no cure. The progression of COPD is due in part to the failure of the major immune cell in the lung, the macrophage, to clear bacteria and viruses, to clear air pollutant particles, and to resolve inflammation (the excessive number of immune cells attracted to the lung). There is evidence that a major pro-inflammation protein in the COPD airway, neutrophil elastase (NE), perpetuates the immune failure, but the mechanism is not known. In this application, we present compelling evidence that NE is taken up by macrophages, but instead of destroying NE, NE takes over the macrophage. NE degrades important protective proteins, histone deacetylases, resulting in increased expression and/or modifications of pro-inflammatory cytokines that are released by the macrophage. Furthermore, NE degrades or modifies histones, the major proteins regulating DNA structure (chromatin) resulting in abnormal chromatin structure and macrophage release of DNA into the airway space. Based on these observations, we propose the following hypothesis of how NE is a central factor promoting COPD: Aim 1: NE is taken up by macrophages and accumulates in the nucleus (where DNA and chromatin proteins are localized). NE degrades histone deacetylase 2 (HDAC2) and possibly other HDACs resulting in increased acetylation of transcription factors or chromatin binding proteins including Histone 3, NFkappaBp65, and High mobility group box 1 (HMGB1), and increased release of pro-inflammatory proteins called cytokines. Aim 2: NE also cleaves histone H3 and alters the H3 amino acid arginine to change it to citrulline. Both processes unwind DNA so that it is more susceptible to be packaged for secretion from the cell as a structure called a macrophage extracellular trap (MET). Both released cytokines and released METs increase airway inflammation. This process induces lung injury that is progressive. To test this hypothesis, we are collaborating with Dr. Leonard Moses, McGuire VA Medical Center, and Dr. Aamer Syed, Virginia Commonwealth University Medical Center, to recruit subjects with COPD to obtain blood for human blood monocyte isolation. We will culture these cells to generate macrophages (hBMDM). For Aim 1, human BMDM will be treated with NE or control solution and tested for (1) NE uptake into the cells; (2) NE protease activity in the cell; (3) HDAC2 protein levels and activity levels, and evaluation of the protein levels of the other 10 HDACs and 7 Sirtuins; (4) acetylation of specific proteins that regulate gene expression: Histone 3, p65, HMGB1; (5) suppression of HDAC or Sirtuin expression to determine whether loss of that enzyme is sufficient to cause acetylation of downstream targets; and (6) cytokine mRNA and protein levels in the culture media. For Aim 2, we will determine whether (1) NE causes degradation of histone H3; (2) NE increases H3 modified arginine to citrulline; (3) NE causes unwinding/decondensation of the chromatin DNA; (4) NE increases DNA released into the culture media; and (5) NE changes the proteins released into the media to include proteins that are associated with DNA and constitute
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Nov 19, 2019
- Source ID
- W81XWH1910375
Entities
People
- Judith A Voynow
Organizations
- United States Army
- Virginia Commonwealth University