Respiratory chain remodeling is associated with impaired bioenergetic flexibility, oxidative stress, and metabolic alterations in PSP-RS organoids

Progressive supranuclear palsy-Richardson’s syndrome (PSP-RS) is a primary 4-repeat tauopathy characterized by selective neuronal vulnerability, yet the mechanisms linking tau pathology to mitochondrial dysfunction remain poorly understood. Here, we combined patient-derived midbrain organoids with functional bioenergetic analyses, quantitative proteomics, targeted metabolomics, and redox imaging to define the mitochondrial alterations associated with PSP-RS. PSP-RS organoids exhibited a marked reduction in maximal respiration and spare respiratory capacity, whereas basal respiration, mitochondrial content, and mitochondrial DNA copy number remained largely preserved, indicating a selective loss of respiratory reserve rather than overt energetic failure. Quantitative proteomic profiling revealed coordinated downregulation of electron transport chain (ETC) subunits, predominantly affecting complexes I, III, and V, providing a molecular correlate of the observed bioenergetic phenotype. These alterations were accompanied by increased mitochondrial superoxide production, mitochondrial membrane depolarization, reduced glutathione immunoreactivity, attenuated NRF2 signaling, and induction of stress-responsive antioxidant pathways, consistent with persistent mitochondrial oxidative stress. Targeted metabolomics further identified alterations in long-chain acylcarnitines together with metabolites involved in mitochondrial carbon and amino acid metabolism, indicating broader metabolic remodeling. Our findings support an association between respiratory chain remodeling, impaired bioenergetic flexibility, redox imbalance, and metabolic remodeling in PSP-RS organoids. This study establishes mitochondrial dysfunction as an integrated feature of PSP-RS and provides a framework for understanding the interplay between respiratory chain remodeling, oxidative stress, and metabolic reprogramming in a human disease-relevant model. Patient-derived progressive supranuclear palsy-Richardson’s syndrome (PSP-RS) midbrain organoids showing phospho-tau accumulation develop a coordinated mitochondrial phenotype characterized by electron transport chain (ETC) dysfunction, increased mitochondrial reactive oxygen species (ROS) production, and reduced mitochondrial membrane potential (ΔΨm). These alterations are associated with impaired antioxidant defenses, including reduced NRF2 signaling and glutathione (GSH) depletion, ultimately resulting in metabolic inflexibility. Together, these findings identify mitochondrial dysfunction as a central feature of PSP pathology linking bioenergetic impairment, redox imbalance, and metabolic remodeling.