Presentations

Abstract

Introduction: Idiopathic pulmonary fibrosis (IPF) represents the predominant form of idiopathic interstitial pneumonia, characterized by progressive lung fibrosis. The pathogenesis of IPF involves repeated injury to alveolar epithelial cells (AECs), which accelerates epithelial cell loss and fibrosis. Our previous research has demonstrated that the Tripartite motif containing 72 (TRIM72) is expressed in AECs and plays a crucial role in repairing damaged membranes of AECs, thereby mitigating lung injury and facilitating AEC repair. Preliminary findings from our laboratory indicate an increased expression of Zinc-Finger E-Box Binding Homeobox 1 (ZEB1), a key regulator of epithelial-mesenchymal transition (EMT), in AECs from TRIM72 knockout mice compared to wild-type (WT) epithelial cells following fibrosis. This study aims to elucidate the regulatory role of TRIM72 in controlling ZEB1 expression within models of lung injury and fibrosis and to explore the consequences of TRIM72-mediated suppression of ZEB1.

Methods: Rat lung epithelial cells (RLE-6TN) with or without lentivirus-mediated TRIM72 overexpression were cultured and exposed to 25 M bleomycin to induce injury and fibrosis. Western blotting was performed to examine ZEB1 and epithelial marker cadherin (E-cadherin) expression. Pulmonary fibrosis was induced by intratracheal administration of bleomycin (1.5 U/kg) in WT and AEC-specific TRIM72KO (SPC-TRIM72KO) mice. Immunostaining was used to analyze ZEB1 and mesenchymal marker -smooth muscle actin (-SMA) expression in lung tissue from WT Vs SPC-TRIM72KO mice post-fibrosis. Lung injury and fibrosis were evaluated by hematoxylin and eosin staining and Masson's trichrome staining respectively. ZEB1 and TRIM72 expression was further assessed in human lung tissues from normal and IPF lungs using immunostaining.

Results: ZEB1 expression was upregulated while E-cadherin expression was downregulated in RLE cells in response to bleomycin. However, TRIM72 overexpression reversed these changes. SPC-TRIM72KO mice had elevated expression of ZEB1 and -SMA levels in the lung as compared to WT counterpart post-fibrosis. We did observe significantly higher lung injury and fibrosis in SPC-TRIM72KO mice as compared to WT mice as revealed by immunostaining. Immunostaining further confirmed that ZEB1 expression was elevated in human fibrotic lung tissue, as compared to normal lung.

Conclusion: Our findings indicate that TRIM72 mitigates epithelial-mesenchymal transition mediated by ZEB1, leading to a reduction in lung fibrosis. This underscores the potential of targeting alveolar epithelial cell membrane repair via TRIM72 as a promising approach for developing therapies against idiopathic pulmonary fibrosis (IPF).