Adenoviral-Mediated SIRT1 Expression Restores Lung Architecture and Reduces Fibrotic Progression in Experimental Models

Background: Pulmonary fibrosis (PF) involves remodeling of lung architecture and limited therapeutic options are available. Sirtuin 1 (SIRT1), an epigenetic regulator, has emerged as a promising antifibrotic target due to its role in apoptosis, inflammation, and chromatin remodeling. Methods: We evaluated the effects of a recombinant adenovirus expressing human SIRT1 (Ad-SIRT1) both in vitro and in vivo. Human alveolar epithelial cells (A549) were transduced with Ad-SIRT1 or AdGFP and subjected to bleomycin-induced injury. Transduction efficiency, cell viability (MTT assay), SIRT1 localization (immunofluorescence), and expression of acetylated p53 and histone H3K9 (Western blot) were assessed. Pharmacological modulation of SIRT1 was also tested using the activator SRT1720 and the inhibitor EX527. For the in vivo experiments, mice with bleomycin-induced PF received intratracheal Ad-SIRT1 on day 15 after injury. Histological, immunohistochemical and molecular analyses were performed on day 21. Results: Ad-SIRT1-transduced A549 cells showed increased nuclear SIRT1 overexpression which restored viability of bleomycin-injured cells and reduced p53 and H3K9 acetylation, consistent with a protective deacetylating effect. These changes mirrored those obtained with SRT1720 and were reversed by EX527 treatment. In vivo, Ad-SIRT1 attenuated collagen deposition, reduced α-smooth muscle actin (α-SMA) expression, and decreased p53 and H3K9 acetylation. The histological scores were significantly improved compared to those of the fibrotic control group. Conclusion: Adenoviral SIRT1 gene delivery exerts protective effects on the alveolar epithelium in vitro and reverses established PF in vivo through epigenetic regulation of key profibrotic pathways. This dual approach highlights the translational potential of SIRT1 as a therapeutic target for PF.