RT Journal Article
SR Electronic
T1 ATP-Induced Non-Neuronal Cell Permeabilization in the Rat Inner Retina
JF The Journal of Neuroscience
JO J. Neurosci.
FD Society for Neuroscience
SP 8577
OP 8583
DO 10.1523/JNEUROSCI.2812-04.2004
VO 24
IS 39
A1 Barbara Innocenti
A1 Sylke Pfeiffer
A1 Eberhart Zrenner
A1 Konrad Kohler
A1 Elke Guenther
YR 2004
UL http://www.jneurosci.org/content/24/39/8577.abstract
AB The P2X7 subtype holds a special position among P2X receptors because of its ability to act both as a classical, ligand-gated ion channel, and as a permeabilization pore that can induce cell death under prolonged activation by ATP. We have shown previously that, in rat retina, P2X7 receptors are located in the inner nuclear layer and ganglion cell layer (GCL). The present study was aimed at finding whether retinal P2X7 receptors can act as a mediator of cell permeabilization and, if so, at identifying the cellular target(s) of this effect. As an indicator of cell permeabilization, we used the fluorescent dye YO-PRO-1 (molecular weight, 375 Da), which enters cells only through large pores like those opened by prolonged or sustained stimulation of P2X7 receptors and binds to DNA, providing a stable labeling of the activated cells. Different agonists for P2 receptors were tested for their ability to cause cell permeabilization in flat-mounted rat retinas. Among them, only high concentrations of ATP (500 μM) and BzATP (2′,3′-O-(4-benzoyl-benzoyl)-ATP triethylammonium) (100 μM) were able to induce accumulation of YO-PRO-1 in the GCL and in the nerve fiber layer, suggesting that different cell types were responding to P2X7 stimulation. This effect was blocked by the P2 antagonists suramin and PPADS (pyridoxal-phosphate-6-azophenyl-2′,4′-disulfonic acid) and by the P2X7-selective inhibitor Brilliant Blue G. To identify the retinal cell types affected by ATP-induced permeabilization, we used in vivo labeling techniques. Our data clearly reveal that prolonged stimulation of P2X7 receptors elicits permeabilization exclusively in microglial cells but not in neurons of the inner retina.