Defining the role of epithelial LKB1 in idiopathic pulmonary fibrosis

Abstract

Lung fibrosis, prevalent mainly among those over 50, is witnessing an increase in global cases, partly due to an ageing population and exacerbated by the COVID-19 pandemic’s aftermath. Idiopathic pulmonary fibrosis (IPF), a form of this chronic disease, is characterized by a progressive buildup of extracellular matrix and lung parenchyma growth, with its root cause still unidentified. Despite its gradual onset, it eventually leads to symptoms like dry cough and breathing difficulties, thereby reducing survival rates. The ongoing challenge is to develop effective treatments, highlighting the need for innovative therapeutic strategies. The mechanisms underlying fibrosis progression remain largely elusive. Previous studies have shown that inhibiting autophagy in alveolar epithelial cells can amplify myofibroblast differentiation in pulmonary fibrosis through paracrine signalling, thus fostering epithelial-mesenchymal transition (EMT). Autophagy, a cellular recycling process, is a potential treatment strategy in several medical fields. In the context of IPF, diminished autophagic activity, linked with ageing, accelerates bronchial epithelial cell ageing and promotes lung fibroblast differentiation, facilitating EMT. This reversible process, regulated by transcription factors like Snail and ZEB, has implications in various biological phenomena including cancer metastasis and organ fibrosis. Our research reveals significant alterations in the global transcriptomics of ATII cells following LKB1 or STK11 depletion, highlighting the activation of critical pathways like ”TNFα signalling via NFκB” and ”EMT”. The data, confirmed through various analyses, underscore LKB1’s pivotal role in initiating the EMT process in these cells. Further, we identified the primary pathway amplified by LKB1 depletion as ”Hallmark TNFα signalling via NFκB”, confirmed by reporter assays. Our study further elucidated LKB1’s influence on autophagy in ATII cells, indicating that its depletion disrupts autophagy, as revealed by western blot and immunofluorescence analyses. The study also explored the activation of the p62-NFκB pathway in ATII cells due to LKB1 depletion, indicating a potential regulatory mechanism involving Schematic representation showing depletion of LKB1 leads to altered global transcriptomics, emphasizing the activation of ”TNFα signalling via NFκB” and ”EMT”. This inactivation disrupts autophagy and suggests a potential mechanism underlying direct initiation to epithelial-mesenchymal transition (EMT) (shown as yellow module) and indirect induction of epithelial-fibroblasts crosstalk via paracrine signalling (purple module). These molecular changes induced by LKB1 inhibition contribute to the progression of pulmonary fibrosis, highlighting the intricate interplay between ATII cells and fibroblasts. p62 and p65 in controlling Snail2 expression. This suggests that LKB1 inactivation in ATII cells might foster EMT through the p62-NFκB pathway. In IPF-affected lungs, this is triggered by the downregulation of CAB39L, a vital component of the LKB1 complex. Our research, including 3D co-cultures and RNA-seq analyses, affirmed that the interaction between LKB1-depleted ATII cells and fibroblasts enhances myofibroblast differentiation. Preliminary studies in mice further corroborated the role of Lkb1 deletion in impairing lung functionality (Figure. 1). In conclusion, our findings indicate that LKB1 inhibition-induced reduced autophagy can stimulate EMT in ATII cells, fostering fibrosis through abnormal epithelial-fibroblast interactions.

More information

Identifiers

ORCID for Yihua Wang: orcid.org/0000-0001-5561-0648

ORCID for Paul Skipp: orcid.org/0000-0002-2995-2959

ORCID for Rob Ewing: orcid.org/0000-0001-6510-4001

Catalogue record

Export record