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P2Z/P2X7 receptor-dependent apoptosis of dendritic cells
R Coutinho-Silva1, P M Persechini, R D Bisaggio
1Unité de Biologie des Interactions Cellulaires, Centre National de la Recherche Scientifique 1960, Paris, France.
Abstract:
Macrophages and thymocytes express P2Z/P2X7 nucleotide receptors that bind extracellular ATP. These receptors play a role in immune development and control of microbial infections, but their presence on dendritic cells has not been reported. We investigated whether extracellular ATP could trigger P2Z/P2X7 receptor-dependent apoptosis of dendritic cells. Apoptosis could be selectively triggered by tetrabasic ATP, since other purine/pyrimidine nucleotides were ineffective, and it was mimicked by the P2Z receptor agonist, benzoylbenzoyl ATP, and blocked by magnesium and the irreversible antagonist, oxidized ATP. RT-PCR analysis confirmed the mRNA expression of the P2Z/P2X7 receptor and the absence of P2X1. Caspase inhibitors and cycloheximide had only a partial effect on the apoptosis, suggesting that a caspase-independent mechanism may also be operative. Brief treatment with ATP led to an increase in the intracellular calcium concentration and permeabilization of the plasma membrane to Lucifer yellow, which diffused throughout the dendritic cell cytosol. Other small extracellular molecules may thus attain a similar intracellular distribution, perhaps activating endogenous proteases that contribute to initiation of apoptosis.
Insights
Extracellular ATP triggers apoptosis in dendritic cells via P2Z/P2X7 receptors. This finding reveals a new mechanism for immune cell regulation and potential therapeutic targets in immune responses.
Area of Science:
- Immunology
- Cell Biology
Background:
- Macrophages and thymocytes express P2Z/P2X7 nucleotide receptors, crucial for immune development and infection control.
- The presence and function of these receptors on dendritic cells remained uninvestigated.
Purpose of the Study:
- To determine if extracellular ATP induces P2Z/P2X7 receptor-dependent apoptosis in dendritic cells.
- To elucidate the signaling pathways involved in ATP-induced dendritic cell apoptosis.
Main Methods:
- Dendritic cells were treated with various nucleotides and receptor agonists/antagonists.
- RT-PCR was used to confirm P2Z/P2X7 receptor mRNA expression.
- Caspase inhibitors and cycloheximide were employed to assess apoptotic pathways.
- Intracellular calcium levels and plasma membrane integrity were measured.
Main Results:
- Tetrabasic ATP selectively induced apoptosis in dendritic cells, mimicked by benzoylbenzoyl ATP and blocked by magnesium and oxidized ATP.
- RT-PCR confirmed P2Z/P2X7 receptor mRNA expression, with no P2X1 detected.
- Apoptosis was only partially inhibited by caspase inhibitors and cycloheximide, suggesting a caspase-independent pathway.
- ATP treatment increased intracellular calcium and plasma membrane permeability.
Conclusions:
- Dendritic cells express functional P2Z/P2X7 receptors that mediate ATP-induced apoptosis.
- A caspase-independent mechanism contributes to this apoptotic process.
- Extracellular ATP may influence dendritic cell function and survival through P2Z/P2X7 receptor activation.