Image-Guided Monitoring of Mitochondria and Blood-Brain Barrier Dysfunction in Amyotrophic Lateral Sclerosis Mice

Early detection of amyotrophic lateral sclerosis (ALS) progression is critical for improving disease management and therapeutic outcomes. However, the clinical heterogeneity and variability in ALS symptoms often lead to delayed diagnosis and suboptimal therapeutic interventions. Since mitochondrial dysfunction is a hallmark of ALS, we hypothesized that monitoring mitochondrial function could serve as a reliable strategy for early diagnosis and therapeutic monitoring of ALS. To address this, we synthesized and characterized 2 novel near-infrared fluorophores, ALS04 and ALS05, designed to target mitochondria and lysosomes. Their physicochemical properties, serum protein binding, fluorescence characteristics, photostability, and pharmacokinetics were systematically evaluated. We found that benzothiazole-based fluorophores exhibit excellent mitochondrial targeting, optimal optical properties, biocompatibility, and favorable biodistribution in vivo. Interestingly, ALS04 showed superior mitochondrial accumulation compared to ALS05, despite their similar physicochemical properties. This enhanced accumulation can be attributed to the lower molecular weight and higher lipophilicity of ALS04. Real-time fluorescence imaging revealed a substantial reduction in ALS04 signals in mitochondrial-rich tissues such as brown fat, highlighting its potential for monitoring mitochondrial dysfunction in early-stage ALS. Furthermore, the detection of ALS04 in the mouse brain suggests its ability to monitor blood-brain barrier hyperpermeability, another key feature of ALS pathology. These findings establish ALS04 as a promising noninvasive imaging tool for monitoring biomarkers associated with ALS progression. Its ability to detect early-stage pathophysiological changes in an ALS mouse model highlights its potential for advancing our understanding of ALS mechanisms and facilitating the identification of novel therapeutic targets.