ABSTRACT
BACKGROUND: Alzheimer's disease (AD) has challenged single-target therapeutic strategies, raising the possibility that combined therapies may offer a more effective treatment strategy. OBJECTIVE: There is substantial evidence for the efficacy of leptin (L) (neuroprotective hormone) and pioglitazone (P) (anti-inflammatory agent) as monotherapies in AD. We have previously shown that combination treatment of L+P in APP/PS1 mice at the onset of pathology significantly improved memory and reduced brain Aß levels relative to control mice. In this new study, we sought to replicate our previous findings in a new cohort of APP/PS1 mice to further confirm whether the combined treatment of L+P is superior to each treatment individually. METHODS: We have re-evaluated the effects of L+P co-treatment in APP/PS1 mice using thioflavin-S staining, MOAß immunolabeling, and enzyme-linked immunosorbent assay (ELISA) to examine effects on Aß levels and pathology, relative to animals that received L or P individually. RESULTS: We demonstrated that a combination of L and P significantly enhances the anti-Aß effect of L or P in the hippocampus of APP/PS1 mice. CONCLUSION: Our findings suggest that combining L and P significantly enhances the anti-Aß effect of L or P in the hippocampus of APP/PS1 mice and maybe a potential new effective strategy for AD therapy.
Subject(s)
Amyloid beta-Peptides/metabolism , Hippocampus/metabolism , Hypoglycemic Agents/administration & dosage , Leptin/administration & dosage , Mice, Transgenic , Pioglitazone/administration & dosage , Alzheimer Disease/pathology , Animals , Disease Models, Animal , Humans , Male , Memory , MiceABSTRACT
Axon degeneration and axonal loss is a feature of neurodegenerative disease and injury and occurs via programmed pathways that are distinct from cell death pathways. While the pathways of axonal loss following axon severing are well described, less is known about axonal loss following other neurodegenerative insults. Here we use primary mouse cortical neuron cultures grown in compartmentalized chambers to investigate the role of calcium in the degeneration of axons that occurs following a somal insult by the excitotoxin kainic acid. Calcium influx has been implicated in both excitotoxicity and axon degeneration mechanisms, however the link between a somal insult and axonal calcium increase is unclear. Live imaging of axons demonstrated that pharmacologically preventing intracellular calcium increases through the endoplasmic reticulum or mitochondria significantly (p < 0.05) reduced axon degeneration. Live calcium-imaging with the Ca2+ indicator Fluo-4 demonstrated that kainic acid exposure to the soma resulted in a rapid, and transient, increase in calcium in the axon, which occured even at low kainic acid concentrations that do not cause axon degeneration within 24 h. However, this calcium transient was followed by a gradual increase in axonal calcium, which was associated with axonal loss. Furthermore, treatment with a range of doses of the microtubule stabilizing drug taxol, which protects against axon fragmentation in this model, prevented this gradual calcium increase, suggesting that the intra-axonal calcium changes are downstream of microtubule associated events. Biochemical analysis of taxol treated neurons demonstrated a shift in microtubule post-translational modifications, with a significant (p < 0.05) increase in acetylated tubulin and a significant (p < 0.05) decrease in tyrosinated tubulin, suggestive of a more stable microtubule pool. Together our results suggest that axonal degeneration following excitotoxicity is dependent on an increase in axonal calcium, which is downstream of a microtubule-dependent event.
