Neuroprotective Actions of Different Exogenous Nucleotides in H₂O₂-Induced Cell Death in PC-12 Cells

Exogenous nucleotides (NTs) are considered conditionally essential nutrients, and the brain cannot synthesize NTs de novo. Therefore, the external supplementation of exogenous NTs is of great significance for maintaining normal neuronal metabolism and function under certain conditions, such as brain aging. This study, therefore, sets out to assess the neuroprotective effect of four kinds of single exogenous NTs and a mixture of the NTs, and to elucidate the potential mechanism. A rat pheochromocytoma cell line PC-12 was treated with different concentrations of exogenous NTs after 4 h of exposure to 200 µM H₂O₂. We found that the exogenous NTs exerted significant neuroprotection through decreasing neuron apoptosis and DNA damage, ameliorating inflammation and mitochondrial dysfunction, promoting cell viability, and augmenting antioxidant activity, and that they tended to up-regulate the NAD⁺/SIRTI/PGC-1α pathway involved in mitochondrial biogenesis. Among the different NTs, the neuroprotective effect of AMP seemed to be more prominent, followed by the NT mixture, NMN, and CMP. AMP also exhibited the strongest antioxidant activity in H₂O₂-treated PC-12 cells. UMP was excellent at inhibiting neuronal inflammation and improving mitochondrial function, while GMP offered major advantages in stabilizing mitochondrial membrane potential. The mixture of NTs had a slightly better performance than NMN, especially in up-modulating the NAD⁺/SIRTI/PGC-1α pathway, which regulates mitochondrial biogenesis. These results suggest that antioxidant activity, anti-inflammatory activity, and protection of mitochondrial function are possible mechanisms of the neuroprotective actions of exogenous NTs, and that the optimization of the mixture ratio and the concentration of NTs may achieve a better outcome.