Extracellular ATP and the P2X7 receptor in astrocyte-mediated motor neuron death: implications for amyotrophic lateral sclerosis.
BACKGROUND
During pathology of the nervous system, increased extracellular ATP acts both as a cytotoxic factor and pro-inflammatory mediator through P2X(7) receptors. In animal models of amyotrophic lateral sclerosis (ALS), astrocytes expressing superoxide dismutase 1 (SOD1G93A) mutations display a neuroinflammatory phenotype and contribute to disease progression and motor neuron death. Here we studied the role of extracellular ATP acting through P2X(7) receptors as an initiator of a neurotoxic phenotype that leads to astrocyte-mediated motor neuron death in non-transgenic and SOD1G93A astrocytes.


METHODS
We evaluated motor neuron survival after co-culture with SOD1G93A or non-transgenic astrocytes pretreated with agents known to modulate ATP release or P2X(7) receptor. We also characterized astrocyte proliferation and extracellular ATP degradation.


RESULTS
Repeated stimulation by ATP or the P2X(7)-selective agonist BzATP caused astrocytes to become neurotoxic, inducing death of motor neurons. Involvement of P2X(7) receptor was further confirmed by Brilliant blue G inhibition of ATP and BzATP effects. In SOD1G93A astrocyte cultures, pharmacological inhibition of P2X(7) receptor or increased extracellular ATP degradation with the enzyme apyrase was sufficient to completely abolish their toxicity towards motor neurons. SOD1G93A astrocytes also displayed increased ATP-dependent proliferation and a basal increase in extracellular ATP degradation.


CONCLUSIONS
Here we found that P2X(7) receptor activation in spinal cord astrocytes initiated a neurotoxic phenotype that leads to motor neuron death. Remarkably, the neurotoxic phenotype of SOD1G93A astrocytes depended upon basal activation the P2X(7) receptor. Thus, pharmacological inhibition of P2X(7) receptor might reduce neuroinflammation in ALS through astrocytes.
Institut Pasteur, Montevideo, Uruguay.
Mandi
M
Gandelman
Hugo
H
Peluffo
Joseph S
JS
Beckman
Patricia
P
Cassina
Luis
L
Barbeito
D000255:Adenosine Triphosphate / Q000378:metabolism*; D000690:Amyotrophic Lateral Sclerosis / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology; D000818:Animals; D001253:Astrocytes / Q000166:cytology / Q000378:metabolism*; D016923:Cell Death / Q000502:physiology*; D049109:Cell Proliferation; D002470:Cell Survival; D002478:Cells, Cultured; D018920:Coculture Techniques; D006801:Humans; D051379:Mice; D008822:Mice, Transgenic; D009046:Motor Neurons / Q000166:cytology / Q000502:physiology*; D009154:Mutation; D051381:Rats; D018048:Receptors, Purinergic P2 / Q000235:genetics / Q000378:metabolism*; D058486:Receptors, Purinergic P2X7; D015398:Signal Transduction / Q000502:physiology; D013482:Superoxide Dismutase / Q000235:genetics / Q000378:metabolism; D000072105:Superoxide Dismutase-1
C546468:P2RX7 protein, human; C546469:P2rx7 protein, mouse; D018048:Receptors, Purinergic P2; D058486:Receptors, Purinergic P2X7; C000606290:SOD1 protein, human; D000255:Adenosine Triphosphate; C000606291:Sod1 protein, mouse; C000606292:Sod1 protein, rat; D013482:Superoxide Dismutase; D000072105:Superoxide Dismutase-1