Contribution of Epithelial Hypoxia Signaling to Pulmonary Fibrosis: Role of FAK1 and Galectin-1 as Driver Molecules

Idiopathic Pulmonary Fibrosis (IPF) is a deadly disease of unknown origin, which causes 80,000 deaths every year in the US and Europe combined. Unknown etiology and late diagnosis, combined with limited treatment options, contribute to a dismal survival rate of 3-5 years post diagnosis. Although molecular mechanisms underlying IPF pathogenesis and progression have been studied for over two decades, lack of in vivo models that recapitulate chronic, progressive, and irreversible nature of IPF have contributed to limited therapeutic success in clinical trials. Currently, only two drugs, Pirfenidone and Nintedanib, are approved for IPF treatment in the US, with their efficacy yet to be completely determined. Patients with IPF often observe lung infections, alveolar collapse, and respiratory failure, which are associated with focal edema and local hypoxia and contribute to development of hypoxemia associated with acute exacerbation of IPF (AE-IPF). In my thesis, I posit that hypoxic injury to the lung epithelium can initiate profibrotic signaling that can contribute to pathogenesis and progression of pulmonary fibrosis in vitro and in vivo. In my in silico studies, I analyzed human protein kinases to identify structural peculiarities that diversify their functions and highlight central hub kinases governing cell signaling. Using this approach, I identified Focal Adhesion Kinase 1 (FAK1) as a central hub kinase contributing to cytoskeletal remodeling. My proteomics and transcriptional studies defined in vitro effect of hypoxia in activation of lung epithelial cells. Using systems biology approaches, I identified interplay between transforming growth factor – β (TGF–β) signaling, hypoxia signaling, and FAK1 signaling. Further, my studies identified Galectin-1 as a novel mediator of hypoxia-induced pulmonary fibrosis. To mimic exacerbation of PF in patients, I developed a novel mouse model of exacerbated pulmonary fibrosis using subclinical bleomycin injury with chronic hypoxia. Further, to fill the existing requirement of an in vivo model of chronic PF, I characterized a triple transgenic mouse model that conditionally activates hypoxia signaling in the lung epithelial cells and causes progressive PF over a span of 12 weeks. Lastly, I performed RNA-Seq experiments on primary AEC2s isolated from our transgenic mouse model to identify a hypoxia-mediated profibrotic role of microRNA-96 in down-regulation of PTEN, a tumor suppressor and anti-fibrotic protein. In conclusion, my studies established in vitro and in vivo roles of hypoxia in profibrotic activation of lung epithelium and identifies FAK1 and Gal-1 as key drivers of hypoxia-mediated fibrosis, which should be further evaluated in animal and human studies to determine their therapeutic potential