- Title
- Mechanisms and therapeutic targeting of immunometabolism in lung disease
- Creator
- Balachandran, Lohis
- Relation
- University of Newcastle Research Higher Degree Thesis
- Resource Type
- thesis
- Date
- 2021
- Description
- Research Doctorate - Doctor of Philosophy (PhD)
- Description
- Chronic obstructive pulmonary disease (COPD) is a heterogenous progressive chronic respiratory disease. It is characterised by persistent lung inflammation, airway remodelling, and emphysema, leading to impaired lung function and gas exchange. COPD is the third leading cause of death globally with cigarette smoke (CS) inhalation a major cause, but bushfire smoke and air pollution other important factors. Current treatments only alleviate the symptoms and do not prevent progression or reverse disease features, and there are no cures. The underlying pathogenic mechanisms remain poorly understood, and there is a substantial need to develop effective treatments. Inflammatory cells, especially macrophages and neutrophils, are increased in COPD patient lungs. Macrophages are responsible for removing the invading pathogens and can switch between anti- and pro-inflammatory responses. They can have alterations in metabolism linked to driving inflammation or being anti-inflammatory in processes termed immunometabolism. The study investigated the mechanisms involved in immune cells' ability to shift their phenotypes by reprogramming their metabolic pathways. We hypothesised that CS induces aberrant immunometabolic changes in COPD that causes phenotypic skewing of macrophages to pro-inflammatory phenotype and metabolic modulators could be novel treatments to block these immunometabolic changes to reduce COPD severity. Mice were exposed to nose-only inhalation of CS for 8-weeks to induce experimental COPD with the hallmark features of the human disease. We observed increased inflammation and oxidative stress in experimental COPD. Lung macrophages isolated from mice with experimental COPD showed increased basal glycolysis and oxygen consumption rate (OCR) rate measured using a Seahorse Bioscience Metabolic Flux Analyser indicating metabolic alterations response to CS exposure. Experimental COPD mice were treated with various metabolic modulators that targeted glycolysis, Krebs cycle and electron transport metabolic (ETC) pathways, and the impact on the key disease features was assessed. We first studied inhibiting glycolysis with 2-deoxy-D-glucose (2DG), which reduced the influx of inflammatory cells in bronchoalveolar lavage (BAL) and significantly reduced lactate dehydrogenase (LDHA) mRNA expression, a marker of cell death, and ATP production in vitro. TEPP-46, which activates pyruvate kinase M2 (PKM2) by tetramerisation, also reduced LDHA mRNA expression and rescued lung function impairment by reducing airway resistance. Dichloroacetate, an inhibitor of pyruvate dehydrogenase kinase, reduced CS-induced airway inflammation and ameliorated lung function impairment in experimental mice. We then assessed the impact of intervening in the Krebs cycle. Two succinate dehydrogenase (SDH) inhibitors were tested. Dimethyl malonate (DMM) reduced airway inflammation, whereas itaconate improved lung function in experimental COPD. We then assessed the impact of intervening in the electron transport chain. Metformin, an inhibitor of complex I, reduced inflammatory cell influx and MARCO mRNA expression. Modulating two metabolic pathways simultaneously using DMM with metformin (inhibiting SDH of Krebs cycle and complex I of ETC) and 2DG with metformin (inhibiting glycolysis and complex I of ETC) reduced the infiltration of inflammatory cells into the airways and partially rescue of lung function impairment. These results demonstrate for the first time that a) altering lung macrophage metabolic phenotype by CS exposure is associated with inflammatory activation, and b) modulation of metabolic pathways can reduce inflammation, pathology, and lung function impairment in experimental COPD. Further investigations will delineate the mechanisms of immunometabolism driving COPD pathology and will develop effective therapeutic strategies for COPD.
- Subject
- immunometabolism; COPD; metabolic modulator; therapeutic targeting
- Identifier
- http://hdl.handle.net/1959.13/1432950
- Identifier
- uon:39137
- Rights
- Copyright 2021 Lohis Balachandran
- Language
- eng
- Full Text
- Hits: 520
- Visitors: 821
- Downloads: 372
| Thumbnail | File | Description | Size | Format | |||
|---|---|---|---|---|---|---|---|
| View Details Download | ATTACHMENT01 | Thesis | 10 MB | Adobe Acrobat PDF | View Details Download | ||
| View Details Download | ATTACHMENT02 | Abstract | 514 KB | Adobe Acrobat PDF | View Details Download |