Online

Raina, Mehak

Pharmacology

2023

M.S.

Idiopathic pulmonary fibrosis (IPF) is characterized by massive deposition of extracellular matrix in the lung interstitium leading to impaired structure and function of the lung. Besides aging, several genetic and environmental risk factors contribute to the development of IPF. Out of the main profibrotic molecular mechanisms that contribute to IPF pathogenesis, endoplasmic reticulum (ER) stress and reprogramming of the epithelial cells characterized by presence of aberrant cells (particularly basal cells) and transitional states has gained a lot of prominence in recent times. Previous research studies have demonstrated an upregulation in the ER stress markers and an increased expression of basal cell markers and transitional markers in the settings of pulmonary fibrosis. IPF is also characterized by modulation of redox-dependent cell signaling by glutathione (GSH) through the process of protein S-glutathionylation (PSSG), the process of conjugation of GSH to reactive protein cysteines in a post-translational modification. Our lab has previously demonstrated an increased PSSG in IPF samples and decreased expression and activity of glutaredoxin (GLRX), an oxidoreductase enzyme, that reverses the process of PSSG. Additionally, one of the key regulators of GSH, system xc- (xCT) has been implicated in regulating the expression of pro-fibrotic and pro-senescence markers and indirectly linked to the modulation of ER stress. Also, our lab has previously demonstrated an interplay between xCT and GLRX in the lung epithelial cells. The role of xCT in governing redox homeostasis and the interplay between xCT and GLRX and its impact on airway remodeling in the settings of pulmonary fibrosis is incompletely understood and needs to be studied in greater detail. The goal of my thesis was to address whether the interplay between GLRX and xCT regulates ER stress, epithelial plasticity and fibrosis sensitivity, using Glrx-/- and Slc7a11-/- mice subjected to bleomycin (BLM) model of fibrosis. Intriguingly, the expression of GLRX was increased in the Slc7a11 -/- mice compared to controls. Using different immunoassays, I demonstrated increased expression of GLRX in the Slc7a11-/- mice as previously seen. Interestingly, the combined deletion of Slc7a11 and Glrx significantly altered the GSH and PSSG status and the markers for aberrant epithelial cells, Krt5 and Krt8, were found to be significantly upregulated in the BLM treated mice compared to controls and the expression was highest in the Slc7a11-/- Glrx-/- mice. Overall, these findings point to the importance of SLC7A11 and GLRX modulating the epithelial reprogramming and airway remodeling in the settings of pulmonary fibrosis.