Thymidine and 2′-deoxyuridine reduce microglial activation and improve oxidative stress damage by modulating glycolytic metabolism on the Aβ25-35-induced brain injury

Alzheimer's disease (AD) is a progressive disease with a long duration and complicated pathogenesis. Thymidine (Thy) and 2'-deoxyuridine (2'-De) are pyrimidines nucleotides that are associated with nervous system diseases. However, it remains unclear whether Thy and 2'-De exert neuroprotective effects in AD. Therefore, this study was conducted to explore the interventional effects and mechanisms of Thy and 2'-De on the Aβ_25-35-induced brain injury. Donepezil (Do, 10 mg/kg/d), Thy (20 mg/kg/d), and 2'-De (20 mg/kg/d) were administered for 4 weeks after the injection of Aβ_25-35 peptides (200 μM, i.c.v.) to mice. UPLC-MS/MS method was performed to quantify Thy and 2'-De in the hippocampus of mice brain. The cognition ability, neuronal and mitochondria damage, and levels of Aβ_1-42/Aβ_1-40, p-Tau, Na⁺ K⁺-ATPase, apoptosis, oxidative stress, immune cells, and Iba 1⁺ were measured in Aβ_25-35-induced mice. The oxygen consumption (OCR) and extracellular acidification rate (ECAR) were measured using a seahorse analyzer in Aβ_25-35-induced N9 cells. Moreover, 2-Deoxy-D-glucose (2-DG), a glycolysis inhibitor, was added to explore the mechanisms underlying the effects of Thy and 2'-De on Aβ_25-35-induced N9 cells. The expression of Iba 1⁺ and levels of CD11b⁺ and reactive oxygen species (ROS) were measured after treatment with Thy (5 μM) and 2'-De (10 μM) against 2-DG (5 mM) in Aβ_25-35-induced N9 cells. The results suggested that Do, Thy, and 2'-De improved the cognition ability, attenuated the damage to hippocampus and mitochondria, downregulated the levels of Aβ_1-42/Aβ_1-40, p-Tau, Na⁺ K⁺-ATPase, apoptosis, oxidative stress, and Iba 1⁺, and regulated the immune response induced by Aβ_25-35 against the brain injury. Furthermore, Do, Thy, and 2'-De increased ATP production and inhibited glycolysis in Aβ_25-35-induced N9 cells. Moreover, 2-DG enhanced the effects of drugs, reduced microglial activation, and attenuated oxidative stress to interfere with Aβ_25-35-induced N9 cells. In conclusion, Thy and 2'-De reduced microglial activation and improved oxidative stress damage by modulating glycolytic metabolism on the Aβ_25-35-induced brain injury.