Purpose: Neurological diseases are increasing in prevalence as a growing number of people live past the age of 65 and beyond. Previous research has indicated that a common theme of many neurological disorders is increased oxidative stress in the mitochondria. In these studies, we aim to characterize methylene blue (MB) and a group of selected compounds as potential mitochondria selective regenerable antioxidants.

Methods: To achieve our aims, we plan to employ a multitude of cell toxicity assays to discern the effect of MB related compounds on cell viability, reactive oxygen species, and mitochondria membrane potential. Furthermore, we will measure the compound's effects on oxidative phosphorylation, anaerobic glycolysis, and mitochondria electron transport chain. These data will be correlated with the MB related compounds' redox potential.

Results: Compounds with a phenothiazine nucleus and a free 10 nitrogen have nanomolar cytoprotection in the toxicity assays compared to compounds with side chain attached to their 10-nitrogens, which have a decreased potency in our assays. Substitution of the 5 sulfur for a nitrogen also decreases the potency, but does not affect oxygen consumption. MB and toluidine blue uniquely transfer electrons directly from NADH to cytochrome c in the mitochondria electron transport chain.

Conclusions: MB and toluidine blue are highly potent regenerable antioxidants capable of enhancing oxidative phosphorylation. These properties are a combination of the compounds' low redox potential combined with a phenothiazine nucleus and amine side chains. As an FDA approved drug, MB has great potential as a treatment for neurological disorders.