Noninvasive PET imaging of LPS-induced oxidative stress in skeletal muscle using a ROS-targeting radiotracer.

Skeletal muscle atrophy is characterized by the progressive loss of muscle mass and function, driven by multifactorial processes such as inflammation, mitochondrial dysfunction, and oxidative stress. Among these mechanisms, excessive generation of reactive oxygen species (ROS) represents a central pathogenic event that disrupts redox homeostasis and contributes to muscle degeneration. In this study, we primarily aimed to the feasibility of using the ROS-targeted PET radiotracer, [¹⁸F]ROStrace, as a non-invasive imaging tool for visualizing ROS accumulation in skeletal muscle. The association between [18F]ROStrace uptake and molecular or histological changes related to oxidative stress and atrophy was analyzed to biologically validate the imaging signal. Cellular uptake of [¹⁸F]ROStrace increased in a time-dependent manner in LPS-treated myotubes, reaching 18.0 ± 3.4%ID at 120 min. Uptake was significantly higher in LPS-treated myotubes (9.7 ± 0.4%ID) compared to antioxidant-pretreated cells (7.2 ± 0.4%ID, N-acetylcysteine), while oxidative stress-enhanced cells (piperlongumine-pretreated cells, 10.1 ± 1.3%ID) showed similar uptake to the LPS group. In vivo, LPS-treated mice exhibited markedly increased [¹⁸F]ROStrace uptake in hindlimb muscles compared to controls (2.2 ± 0.3 vs. 0.9 ± 0.2%ID/g, p < 0.001), reflecting elevated oxidative burden. The PET signal was associated with molecular and histological markers of redox imbalance, including upregulation of MuRF-1 and Atrogin-1 mRNA (~ 13-fold and ~ 10-fold, respectively), reduced muscle fiber cross-sectional area, and a two-fold increase in dihydroethidium (DHE) fluorescence. Collectively, these findings demonstrate that [¹⁸F]ROStrace PET imaging enables sensitive, in vivo assessment of oxidative stress in skeletal muscle, providing a foundation for early diagnosis and therapeutic monitoring of redox-associated muscle disorders.