Reactive oxygen species released from astrocytes treated with amyloid beta oligomers elicit neuronal calcium signals...

Area of Science:

• Neuroscience
• Cell Biology
• Molecular Biology

Background:

• Signal transducer and activator of transcription 3 (STAT3) is vital for nervous system development and function.
• Amyloid beta oligomers (AβOs) are implicated in synaptotoxicity and neurodegenerative diseases.
• STAT3 phosphorylation, particularly at serine-727 (pSerSTAT3), influences its nuclear localization and transcriptional activity.

Purpose of the Study:

• To investigate the role of astrocyte-released mediators in regulating neuronal pSerSTAT3 nuclear localization following AβO exposure.
• To elucidate the signaling pathways, including reactive oxygen species (ROS) and calcium, involved in AβO-induced changes in neuronal STAT3.

Main Methods:

• Treatment of mixed neuron-astrocyte and astrocyte-poor neuronal cultures with AβOs.
• Analysis of nuclear pSerSTAT3 levels via Western blotting or immunofluorescence.
• Utilizing astrocyte-conditioned medium to isolate astrocyte-derived factors.
• Employing extracellular catalase to assess the role of ROS.
• Investigating intracellular calcium signaling using ryanodine-sensitive channels.
• Assessing the transcriptional regulation of STAT3 target genes (BCL2, Survivin, BAX).

Main Results:

• AβO treatment of mixed cultures decreased nuclear pSerSTAT3 in neurons, an effect dependent on astrocytes.
• Conditioned medium from AβO-treated astrocytes mimicked this effect, indicating astrocyte-released mediators.
• Extracellular catalase and blockage of ryanodine-sensitive calcium channels prevented pSerSTAT3 nuclear depletion.
• AβO-induced astrocyte mediators increased neuronal oxidative tone and triggered calcium signals.
• Downstream effects included decreased BCL2 and Survivin transcription and an increased BAX/BCL2 ratio.

Conclusions:

• Astrocytes release ROS in response to AβOs, contributing to neuronal pSerSTAT3 nuclear depletion.
• Neuronal oxidative stress and calcium signaling are critical mediators of this process.
• The AβO-induced pathway leads to reduced STAT3 protective transcriptional activity, potentially impacting neuronal survival.