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Published on: January 22, 2022
Targeting CDK5 in Astrocytes Promotes Calcium Homeostasis Under Excitotoxic Conditions
Luisa Fernanda Toro-Fernández1,2, Juan Camilo Zuluaga-Monares1,2, Ana María Saldarriaga-Cartagena1,2
1Instituto de Biología, Facultad de Ciencias Exactas y Naturales, Universidad de Antioquia, Medellín, Colombia.
Abstract:
Glutamate excitotoxicity triggers overactivation of CDK5 and increases calcium influx in neural cells, which promotes dendritic retraction, spine loss, increased mitochondrial calcium from the endoplasmic reticulum, and neuronal death. Our previous studies showed that CDK5 knockdown (KD) in astrocytes improves neurovascular integrity and cognitive functions and exerts neuroprotective effects. However, how CDK5-targeted astrocytes affect calcium regulation and whether this phenomenon is associated with changes in neuronal plasticity have not yet been analyzed. In this study, CDK5 KD astrocytes transplanted in CA3 remained at the injection site without proliferation, regulated calcium in the CA1 hippocampal region after excitotoxicity by glutamate in ex vivo hippocampal slices, improving synapsin and PSD95 clustering. These CDK5 KD astrocytes induced astrocyte stellation and neuroprotection after excitotoxicity induced by glutamate in vitro. Also, these effects were supported by CDK5 inhibition (CDK5i) in vitro through intracellular stabilization of calcium levels in astrocytes. Additionally, these cells in cocultures restored calcium homeostasis in neurons, redistributing calcium from somas to dendrites, accompanied by dendrite branching, higher dendritic spines and synapsin-PSD95 clustering. In summary, induction of calcium homeostasis at the CA1 hippocampal area by CDK5 KD astrocytes transplanted in the CA3 area highlights the role of astrocytes as a cell therapy target due to CDK5-KD astrocyte-mediated synaptic clustering, calcium spreading regulation between both areas, and recovery of the intracellular astrocyte-neuron calcium imbalance and plasticity impairment generated by glutamate excitotoxicity.
Insights
Targeting CDK5 in astrocytes restores calcium balance and neuronal plasticity after glutamate excitotoxicity. This cell therapy approach in the hippocampus promotes neuroprotection and synaptic recovery.
Area of Science:
- Neuroscience
- Cell Biology
- Neuropharmacology
Background:
- Glutamate excitotoxicity activates CDK5, disrupting calcium homeostasis and leading to neuronal death.
- Previous research indicated CDK5 knockdown (KD) in astrocytes offers neuroprotection and improves cognitive function.
- The specific impact of CDK5-targeted astrocytes on neuronal calcium regulation and plasticity remains unclear.
Purpose of the Study:
- To investigate how CDK5 KD astrocytes influence calcium regulation in hippocampal neurons following glutamate excitotoxicity.
- To determine if CDK5 KD astrocytes can restore neuronal plasticity and synaptic integrity.
- To evaluate the therapeutic potential of CDK5 KD astrocytes for excitotoxicity-induced neuronal damage.
Main Methods:
- Transplantation of CDK5 KD astrocytes into the CA3 region of hippocampal slices.
- Induction of excitotoxicity using glutamate in vitro and ex vivo.
- Assessment of calcium levels, astrocyte morphology, synaptic markers (synapsin, PSD95), dendritic branching, and spine density in co-cultures.
Main Results:
- Transplanted CDK5 KD astrocytes regulated calcium in the CA1 region and improved synapsin and PSD95 clustering after glutamate excitotoxicity.
- CDK5 KD astrocytes induced astrocyte stellation and neuroprotection in vitro, effects mimicked by CDK5 inhibition (CDK5i).
- Co-cultures with CDK5 KD astrocytes restored neuronal calcium homeostasis, promoting dendrite branching, spine density, and synaptic clustering.
Conclusions:
- CDK5 KD astrocytes effectively restore calcium homeostasis in the hippocampus after glutamate excitotoxicity.
- Astrocytes engineered to target CDK5 show promise as a cell therapy for neurodegenerative conditions involving excitotoxicity.
- This approach highlights the role of astrocytes in regulating inter-regional calcium signaling and synaptic plasticity.
