ATP Released From Astrocytes During Swelling Activates Chloride Channels

Abstract

ATP release from astrocytes contributes to calcium ([Ca(2+)]) wave propagation and may modulate neuronal excitability. In epithelial cells and hepatocytes, cell swelling causes ATP release, which leads to the activation of a volume-sensitive Cl(-) current (I(Cl,swell)) through an autocrine pathway involving purinergic receptors. Astrocyte swelling is counterbalanced by a regulatory volume decrease, involving efflux of metabolites and activation of I(Cl,swell) and K(+) currents. We used whole cell patch-clamp recordings in cultured astrocytes to investigate the autocrine role of ATP in the activation of I(Cl,swell) by hypo-osmotic solution (HOS). Apyrase, an ATP/ADP nucleotidase, inhibited HOS-activated I(Cl,swell), whereas ATP and the P2Y agonists, ADPbetaS and ADP, induced Cl(-) currents similar to I(Cl,swell). Neither the P2U agonist, UTP nor the P2X agonist, alpha,beta-methylene ATP, were effective. BzATP was less effective than ATP, suggesting that P2X7 receptors were not involved. P2 purinergic antagonists, suramin, RB2, and pyridoxalphosphate-6-azophenyl-2',4'-disulfonic acid (PPADS) reversibly inhibited activation of I(Cl,swell), suggesting that ATP-activated P2Y1 receptors. Thus ATP release mediates I(Cl,swell) in astrocytes through the activation of P2Y1-like receptors. The multidrug resistance protein (MRP) transport inhibitors probenicid, indomethacin, and MK-571 all potently inhibited I(Cl.swell). ATP release from astrocytes in HOS was observed directly using luciferin-luciferase and MK-571 reversibly depressed this HOS-induced ATP efflux. We conclude that ATP release via MRP and subsequent autocrine activation of purinergic receptors contributes to the activation of I(Cl,swell) in astrocytes by HOS-induced swelling.

CR1-mediated ATP Release by Human Red Blood Cells Promotes CR1 Clustering and Modulates the Immune Transfer Process

“…When RBC were treated with MK-571 (either 10 or 100 M) a dose-dependent response in ATP release was noted (Fig. 7C) in accordance with a previous report (26). However, when MK-571 (10 and 100 M) was added to the ATP standard, a significant decrease of the ATP readout was detected (Fig.…”

Chemosensory Information Processing between Keratinocytes and Trigeminal Neurons

“…ATP appears to be a common transmitter of external stimuli. Numerous mechanisms for the release of ATP from keratinocytes have been discussed to date: ATP-binding cassettes, exocytosis, connexins, and pannexins (40,41,50,51). However, the successful inhibition of Javanol-induced communication using the selective inhibitor probenecid (42) implicates pannexin 1.…”

Probenecid, a gout remedy, inhibits pannexin 1 channels

“…Accordingly, block of cAMP or cGMP release from erythrocytes (18,25), ATP release from glia cells (1,17), and block of dye loss in various cell types (20,21,23) by probenecid have been presented as evidence for a role of transporters in these phenomena. However, alternative pathways for the transit of these molecules across the plasma membrane have to be considered.…”