P2 receptor‐mediated stimulation of the PI3‐K/Akt‐pathway in vivo

Abstract

ATP acts as a growth factor as well as a toxic agent by stimulating P2 receptors. The P2 receptor-activated signaling cascades mediating cellular growth and cell survival after injury are only incompletely understood. Therefore, the aim of the present study was to identify the role of the phosphoinositide 3 kinase (PI3-K/Akt) and the mitogen-activated protein kinase/extracellular signal regulated protein kinase (MAPK/ERK) pathways in P2Y receptor-mediated astrogliosis after traumatic injury and after microinfusion of ADP beta S (P2Y(1,12,13) receptor agonist) into the rat nucleus accumbens (NAc). Mechanical damage and even more the concomitant treatment with ADP beta S, enhanced P2Y(1) receptor-expression in the NAc, which could be reduced by pretreatment with the P2X/Y receptor antagonist PPADS. Quantitative Western blot analysis indicated a significant increase in phosphorylated (p)Akt and pERK1/2 2 h after ADP beta S-microinjection. Pretreatment with PPADS or wortmannin abolished the up-regulation of pAkt by injury alone or ADP beta S-treatment. The ADP beta S-enhanced expression of the early apoptosis marker active caspase 3 was reduced by PPADS and PD98059, but not by wortmannin. Multiple immunofluorescence labeling indicated a time-dependent expression of pAkt and pMAPK on astrocytes and neurons and additionally the colocalization of pAkt, pMAPK, and active caspase 3 with the P2Y(1) receptor especially at astrocytes. In conclusion, the data show for the first time the involvement of PI3-K/Akt-pathway in processes of injury-induced astroglial proliferation and anti-apoptosis via activation of P2Y(1) receptors in vivo, suggesting specific roles of P2 receptors in glial cell pathophysiology in neurodegenerative diseases.

Akt1 mediates purinergic-dependent NOS3 activation in thick ascending limbs

“…Additionally, ATP and P2 receptors were shown to increase endothelial cell migration and adhesion in a PI3 kinase-dependent manner (17). Similarly, in vivo microinjections of ATP into the nucleus accumbens activated the PI3 kinase/Akt signaling pathway, leading to neuron proliferation, and this was blocked by the P2 receptor antagonist PPADS (8).…”

Injured astrocytes are repaired by Synaptotagmin XI-regulated lysosome exocytosis

“…20,57 ATP released by astrocytes activates AKT and ERK signaling, resulting in gliosis following traumatic brain injury. 58,59 Injury-triggered extracellular ATP also affects microglial response following brain injury. 60,61 We have identified that injury-triggered lysosome exocytosis causes secretion of acid sphingomyelinase (ASM), which is needed for cell membrane repair.…”

Purinergic control of AMPK activation by ATP released through connexin 43 hemichannels: pivotal roles in hemichannel-mediated cell injury

“…Here, it is most probable that signaling is mediated by the P2Y receptor signal transduction pathway. As G-protein-coupled receptors, P2Y family members activate phospholipase C (PLC) to hydrolyze phosphatidylinositol 4,5-bisphosphate to 1,2-diacylglycerol and inositol triphosphate, subsequently causing the release of intracellular Ca 2+ and the activation of protein kinase C (PKC), as well as downstream signaling cascades such as those mediated by mitogen-activated protein kinase and PI3K (Franke et al, 2009;Thelen and Didichenko, 1997). In support of an involvement of this pathway, we observed that the PLC inhibitor U73122 potentiated, whereas PLC activator m-3M3FBS suppressed AMPK activation (supplementary material Fig.…”