P2Y receptor expression on astrocytes in the nucleus accumbens of rats

Abstract

The expression of purinoceptor (P2)Y-subtypes on astrocytes in vivo under physiological conditions and after stab wound injury was investigated. Reverse transcriptase-polymerase chain reaction with specific primers for the receptor-subtypes P2Y1,2,4,6,12 in tissue extracts of the nucleus accumbens of untreated rats revealed the presence of all P2Y receptor mRNAs investigated. Double immunofluorescence visualized with laser scanning microscopy indicated the expression of the P2Y1,4 receptors on glial fibrillary acidic protein (GFAP)-labeled astrocytes under physiological conditions. After stab wound injury the additional expression of the P2Y2 and P2Y6 receptors, and an up-regulation of the P2Y1,4 receptor-labeling on astrocytic cell bodies and/or processes was observed. Astrocytes of cortical, in contrast to accumbal areas exhibited P2Y1,2,4,6 receptor-immunoreactivity (IR) under control conditions, which was up-regulated after stab would injury. Labeling for the P2Y12 receptor was not observed on GFAP-positive cortical and accumbal astrocytes under any of the conditions used. For the first time, the co-localization of different P2 receptor-subtypes (e.g. P2Y1 and P2X3) on the same astrocyte was shown immunocytochemically. The up-regulation of P2Y1 receptor-IR on astrocytes and non-glial cells after mechanical injury could be facilitated by microinfusion of the P2Y1,12,13 receptor agonist adenosine 5'-O-(2-thiodiphosphate) (ADPbetaS). Proliferative changes after ADPbetaS-microinjection were characterized by means of double-staining with antibodies against GFAP and 5-bromo-2'-deoxyuridine. The non-selective P2 receptor antagonist pyridoxalphosphate-6-azophenyl-2',4'-disulphonic acid, the P2Y1 receptor antagonist N6-methyl-2'-deoxyadenosine 3',5'-bisphosphate and the P2Y1 receptor-antibody itself inhibited the agonist-induced effects. The data indicate the region-specific presence of P2Y receptors on astrocytes in vivo and their up-regulation after injury as well as the co-localization of P2X and P2Y receptor-subtypes on the same astrocyte. The dominant role of P2Y1 receptors in proliferation and the additional stimulation of non-P2Y1 receptors has been demonstrated in vivo suggesting the involvement of this receptor-type in the gliotic response under physiological and pathological conditions.

Purinergic mechanisms in neuroinflammation: An update from molecules to behavior

“…P2X4 is expressed at increased concentrations in response to tissue injury following spinal cord injury (Schwab et al, 2005), traumatic brain injury (Zhang et al, 2006) and in spinal cord microglia following peripheral nerve injury (Tsuda et al, 2003;Ulmann et al, 2008). After stab wound injury, P2X1 and P2X7 receptor immunoreactivity was observed on astrocytes that were previously absent (Franke et al, 2004). Cerebellar lesions produce up-regulation of P2X1 and P2X2 receptors in precerebellar nuclei (Florenzano et al, 2002).…”

“…P2Y 12 receptors, expressed on platelets, regulate various forms of inflammation and could either improve or worsen the scenario (Liverani et al, 2014a). In the CNS, P2Y 12 receptors are expressed on astrocytes, oligodendrocytes and the resting, ramified microglia executing surveillant functions (Amadio et al, 2014;Franke et al, 2004).…”

Neuroprotective roles of the P2Y2 receptor

“…Functional studies with astrocytes and oligodendrocytes have demonstrated a role for both P2Y 1 and P2Y 2 receptors in mediating ATP-evoked and IP 3 -dependent increases in [Ca 2+ ] i [20,80]. P2Y 2 Rs are upregulated in reactive astrocytes of the cortex and nucleus accumbens in rat due to mechanical injury, suggesting a role in modulating responses to trauma [126]. Furthermore, studies with astrocytic cells also suggest that P2Y 2 Rs play a role in astrocyte survival after injury [13,79].…”

“…In neural progenitor cells isolated from the subventricular zone of adult mouse brain, P2Y 2 R activation was shown to induce rapid and transient activation of the EGFR, ERK1/2, and CREB [160]. P2Y 2 R mRNA levels also were shown to increase during the acute and chronic stages of spinal cord injury [161] and with brain ischemia, mechanical injury to the nucleus accumbens, and brain trauma, an acute inflammatory response suggested to provide neuroprotection [126]. Other potential neuroprotective responses linked to P2Y 2 R function in primary cortical neurons include the activation of non-amyloidogenic APP processing [48].…”

“…Activated glia have been shown to produce neurotrophic factors [207,208] and stimulate neuronal outgrowth during development and repair of damaged brain cells in the adult [209]. P2Y 2 Rs regulate many of these responses associated with reactive gliosis [13,15,20,68,79,126]. Purinergic signaling has been shown to influence the initiation, progression, and downregulation of an inflammatory response [210], and the P2Y 2 R is an important mediator of neuroinflammation [15].…”