PM₁₀ Disrupts Mitochondrial Homeostasis in Corneal Epithelial Cells: Protective Effects of SKQ1

Airborne particulate matter with a diameter of <10 μm (PM₁₀) can damage the corneal epithelium by inducing oxidative stress, disrupting the NRF2 antioxidant pathway, and triggering epithelial barrier dysfunction and inflammation. However, the role of mitochondria in mediating PM₁₀-induced damage remains unexplored. This study investigated the impact of PM₁₀ on mitochondrial homeostasis in both immortalized human corneal epithelial cells (HCE-2) and the mouse corneal epithelium, as well as the protective effects of SKQ1. For in vivo assessment, female C57BL/6 mice were exposed to either control air or PM₁₀ (±SKQ1) in a whole-body exposure chamber for 2 weeks (3 h/day, 5 days/week, with weekends off). In vitro, HCE-2 cells were exposed to 100 μg/mL PM₁₀ (±SKQ1) for 24 h, and mitochondrial function and morphology were evaluated. In vitro, PM₁₀ significantly impaired mitochondrial function by reducing basal, maximal, and ATP-linked respiration; reserve capacity; and coupling efficiency compared to the control and SKQ1 groups. PM₁₀ also downregulated mitofusin1 (MFN1) and optic atrophy1 (OPA1) and upregulated dynamin-related protein1 (DRP1) and mitochondrial fission protein1 (FIS1) in HCE-2 cells. In addition, PM₁₀ exposure significantly decreased the mitochondrial membrane potential; mitochondrial DNA copy number; and cytochrome c oxidase subunit 4 isoform 1 (COX4i1), mitochondrial transcription factor A (TFAM), and peroxisome proliferator-activated receptor gamma coactivator 1 alpha (PGC-1α) levels. SKQ1 pre-treatment significantly attenuated these effects. In vivo, PM₁₀ exposure significantly decreased the levels of MFN1, TFAM, COX4i1, and superoxide dismutase (SOD2), whereas SKQ1 treatment significantly reversed these effects. Overall, these findings demonstrate that PM₁₀ exposure induces mitochondrial fragmentation, disrupts mitochondrial biogenesis and quality control, and reduces mitochondrial respiration, resulting in mitochondrial dysfunction. SKQ1 effectively reversed these changes, suggesting its potential as a therapeutic strategy to protect corneal epithelial cells from PM₁₀-induced mitochondrial damage.