Involvement of P2X7 receptors in the hypoxia-induced death of rat retinal neurons

Abstract

Purpose: To investigate the hypoxia-induced death of rat retinal neurons and to determine whether P2X(7) activation is involved in this type of neuronal death.

Methods: Cultured retinal neurons from fetal rats were used. The effects and time course of various degrees of hypoxia (1%-5% O(2)) in the death of retinal neurons, were examined. The effects of P2X(7) antagonists, oxidized adenosine triphosphate (oxidized ATP; 30-100 microM), and brilliant blue G (BBG; 100 nM-10 microM) on hypoxia-induced neuronal death, including apoptosis, were assessed by using trypan blue exclusion, TUNEL assays, and cleaved caspase-3 immunoreactivity. Immunocytochemical analysis was performed to determine whether these neurons express P2X(7) receptors. The effects of P2X(7) receptor stimulation, induced by the P2X(7) agonist benzoyl- benzoyl-ATP (BzATP), on neuronal viability and intracellular Ca(2+) levels ([Ca(2+)](i)) were examined.

Results: Retinal neuronal death increased according to the degree of hypoxia and became more severe after 12 hours. Both oxidized ATP and BBG significantly decreased hypoxia-induced neuronal death. Immunocytochemistry demonstrated that P2X(7) receptors were expressed by the cultured retinal neurons. ATP and BzATP caused P2X(7) receptor-dependent neuronal death in a dose-dependent manner and led to a sustained increase in [Ca(2+)](i), with BzATP being more effective than ATP. These effects were hypoxia-induced factor-1alpha- independent and were prevented by oxidized ATP.

Conclusions: The results suggest that the death of retinal neurons can be triggered by hypoxia and that P2X(7) activation is involved in the hypoxia-induced death of retinal neurons. P2X(7) antagonists can prevent hypoxia-induced damage in retinal neurons.