Mitochondria‐Targeting SIRT3 Activator Effectively Controls Bleomycin‐Induced Pulmonary Fibrosis

Pulmonary fibrosis is a debilitating condition characterized by excessive collagen deposition and scar formation. Divergent factors often contribute to mitochondrial dysfunction. Oxidative stress is one of the major triggers for the development of pulmonary fibrosis through downregulation of SIRT3. This study aims to enhance the SIRT3 activity at the organelle level by a targeted drug delivery approach. C12 is a known molecule as a SIRT3 activator and is protective in pulmonary fibrosis in our previous studies. We have designed a mitochondrial-targeted delivery approach by introducing a triphenylphosphonium cation (TPP⁺) into the C12 molecule to enhance its mitochondrial specificity and efficacy. The newly designed MitoC12 attenuated the BLM-induced acute lung injury and pulmonary fibrosis more effectively than C12 primarily through activation of SIRT3. The cellular uptake studies revealed that MitoC12 concentrated more in mitochondria than the cytosolic fraction. MitoC12 reduced BLM-induced oxidative stress in BEAS-2B cells and inhibited TGF-β-induced pulmonary fibrosis in MRC-5 cells. MitoC12 inhibited the EMT by decreasing the expression of vimentin and N-cadherin and increasing the expression of E-cadherin. Further, the in vivo studies of MitoC12 exhibited a protective effect in BLM-induced pulmonary fibrosis by improving lung function, decreasing inflammation, and restoring lung architecture. MitoC12 reduced the collagen deposition and expression of fibrotic markers such as TGF-β, collagen 1A and 3A, α-SMA, fibronectin, and vimentin. Mechanistically, MitoC12 showed an anti-fibrotic effect through activation of SIRT3 thereby preventing mitochondrial dyshomeostasis through regulating MnSOD and OGG1 functioning. Overall, this study suggests that MitoC12 could be a potential therapeutic option for pulmonary fibrosis emphasizing TPP⁺-conjugated molecules in treating mitochondrial dysfunction-related diseases.