CAT and Parkinson disease: It is well documented that accumulation of reactive oxygen species underlies PD-associated neuroinflammation and neurotoxicity.138 Exosomes loaded with either antioxidant enzyme catalase or a plasmid DNA-encoding catalase have been used to reduce neuroinflammatory responses and exert neuroprotective effects.139, 140 Similarly, neurotropic factors that improve neuronal functioning can also be developed as potential therapeutic cargos for exosomal delivery.