Noninvasive Detection of Oxidative Stress in a Mouse Model of 4R Tauopathy via Positron Emission Tomography with...

Oxidative stress, defined as the excessive production of reactive oxygen species (ROS), is a crucial factor in the pathogenesis of various neurodegenerative diseases, including the 4-repeat (4R) tauopathies. Collectively, the 4R tauopathies are characterized by the progressive aggregation of tau protein isoforms with four microtubule-binding domains in and around brain cells. The cyclical relationship between oxidative stress and 4R tau aggregation suggests that a means of imaging ROS noninvasively could be a valuable tool for the study and treatment of 4R tauopathy in both humans and animal models. To demonstrate the potential of the ROS-sensitive positron emission tomography (PET) radiotracer [¹⁸F]ROStrace as a means of filling this methodological gap, we performed [¹⁸F]ROStrace PET imaging on PS19 mice, which exhibit 4R tau aggregation similar to that seen in human 4R tauopathy. Significant increases in [¹⁸F]ROStrace signal became detectable in the hippocampus of 6-11-month-old (mo) PS19 animals and spread to the brainstem, midbrain, and thalamus of 11+ mo animals. Additionally, older PS19 mice displayed higher whole-brain average [¹⁸F]ROStrace signal compared to age-matched controls (p = 0.042), and tau pathology consistently colocalized with multiple fluorescent indicators of oxidative stress in PS19 brain samples. These results provide novel evidence that 4R tau aggregation is associated with increased oxidative stress in PS19 mouse brain and advance [¹⁸F]ROStrace as a noninvasive technology for the detection of oxidative stress in neurodegenerative diseases involving tau pathology.