Targeting Fibrosis: ALA-PDT Triggers PINK1/Parkin-Dependent Mitophagy and Apoptosis in Fibroblasts

Fibroblasts are key contributors to fibrosis due to their hyperproliferative and apoptosis-resistant phenotype. This study explores how 5-aminolevulinic acid-mediated photodynamic therapy (ALA-PDT) induces apoptosis in fibroblasts by modulating mitochondrial quality control. ALA-PDT significantly reduces cell viability and proliferation, increases LDH release, and triggers apoptotic signaling. Mechanistically, ALA-PDT promotes excessive accumulation of mitochondrial and cytosolic reactive oxygen species (ROS), leading to mitochondrial dysfunction and energy stress. These alterations activate the AMPK/mTOR signaling cascade, which in turn upregulates PINK1/Parkin-mediated mitophagy. Suppression of mitophagy through siRNA targeting PINK1 or Parkin, or with pharmacological autophagy inhibitors, markedly attenuates ALA-PDT-induced apoptosis, confirming the pivotal role of mitophagy in this process. Transmission electron microscopy shows abundant autophagosome formation, while Western blotting validates the amount of mitophagy-related and apoptotic proteins. These findings establish a mechanistic link between ALA-PDT-induced oxidative stress and mitophagy-dependent apoptosis, identifying a novel anti-fibrotic pathway involving ROS-AMPK/mTOR-PINK1/Parkin signaling. The results offer a compelling molecular basis for using ALA-PDT as a targeted therapeutic strategy against fibrotic diseases by promoting the selective elimination of activated fibroblasts.