Exercise Rehabilitation and/or Astragaloside Attenuate Amyloid-Beta Pathology by Reversing BDNF/TrkB Signaling De�cits and Mitochondrial Dysfunction

Background: Although there are numerous investigations regarding the bene�cial effects of exercise rehabilitation (ER) or astragaloside (AST) after amyloid-beta (Ab) pathology, the mechanisms are still not well understood. We aim to assess whether ER and/or AST counteract Ab pathology via diminishing brain-derived neurotrophic factor (BDNF) signaling de�cits and mitochondrial dysfunction. Methods: Ab 1-42 were microinjected into the bilateral ventricles to induce Ab neuropathology in rats. The Alzet osmotic pump containing full of AST was implanted subcutaneously during surgery. The ER group of rats started at seven days post-surgery and lasted for four weeks. The ANA12 was administrated once per day to the endpoint of the experiments to antagonize the BDNF action. Neurobehavioral functions were evaluated by Y-maze, radial maze, and rotarod tests one day before surgery and 14 to 35 days post-surgery. Cortical and hippocampal expressions of both BDNF/TrkB and cathepsin D were determined by Western blotting method. The rat primary cultured cortical neurons were incubated with BDNF and/or AST and ANA12 followed by exposure to aggregated Ab for 24 hours. The cell viability (by MTT assay), mitochondrial membrane permeability and electrochemical potential (by JC-1 stain), DNA fragmentation (sub-G1 and DNA ladder assay), synaptic plasticity (by immuno�uorescence stain), and pTrkB/pAkt/pGSK3b/b-catenin signaling (by Western blot) were determined. Results: ER and/or AST reversed neurobehavioral disorders, downregulation of cortical and hippocampal expression of both BDNF/TrkB and cathepsin D, neural pathology, Ab accumulation, and altered microglial polarization caused by Ab. In vitro studies also con�rmed that topical application of BDNF and/or AST reversed the Ab-induced cytotoxicity, apoptosis, mitochondrial distress, synaptotoxicity, and b-catenin in altered cortical In the bene�cial effects of combined ER (or BDNF) and AST therapy in vivo and in vitro were superior to ER (or BDNF) or AST alone. Furthermore, we observed that any gains from ER (or BDNF) and/or AST could be signi�cantly eliminated by ANA-12, a potent BDNF/TrkB antagonist. neurological injury via restoration of brain BDNF/TrkB signaling and mitochondrial function in Ab-treated rats Our results showed that ANA12 signi�cantly wiped out the bene�cial effects from ER and/or AST therapy in Ab-microinjected rats or in cultured rat cortical neurons. These results indicate that antagonism of cortical and hippocampal BDNF/TrkB signaling with ANA12 signi�cantly alleviates the bene�cial effects from ER and/or AST in AD pathology. Our present �ndings are consistent with a recent investigation showing that ANA12 alleviates the bene�cial effects from overexpression of hippocampal BDNF in post-stroke cognitive de�cits [45]. immediately. Rats were returned to the standard housing. The ANA-12 (1mg/kg/day, i.p.) was administrated once per day to the endpoint of the experiments. Starting seven days later, some received four weeks of exercise rehabilitation (ER). (B) In the in vitro study, the primary cultured cortical neurons were prepared from embryonic day (D17-18) of Sprague-Dawley rat fetuses. Neuronal cultures were maintained for eight days in vitro before the various chemical treatments. After the medium was refreshed, the cortical neuron cultures were incubated with BDNF (400 ng/ml) and/or AST (400 μg/ml) and/or ANA12 (35-60 μM) followed by exposure to 60 μM aggregated Aβ25-35 for 24 hours. The cell or cell lysate was harvested for cell viability (by MTT assay), mitochondrial membrane permeability and electrochemical potential (by JC-1 stain), DNA fragmentation (sub-G1 and DNA ladder assay), synaptic plasticity (by immuno�uorescence stain), and pTrkB/pAkt/pGSK3β/β-catenin signaling (by Western blot) measurement.