Expression of P2X receptors on rat microglial cells during early development

Abstract

We have used single- and double-labeling immunfluorescence and reverse transcription-polymerase chain reaction (RT-PCR) methods to examine expression of P2X receptor subtypes on microglial cells of brain in late embryonic and postnatal rat, in the N9 microglial cell line and primary cultured microglial cells. P2X1, P2X4, and P2X7 receptors were shown on microglial cells from late embryonic day 16. Almost all the microglial cells that were positive for the marker ED1, expressed P2X1 and P2X4 receptors, whereas only about 30% of the cells with ED1-immunoreactivity were found to express the P2X7 receptor. Positive cells were localized mainly in the white matter and around ventricles. From postnatal day 7, many microglial cells with P2X4 receptor-immunoreactivity were seen around the blood vessels. At postnatal day 30, microglial cells with P2X1 receptor-immunoreactivity disappeared and the cells with P2X4 receptor-immunoreactivity were mainly localized around blood vessels and lining the subarachnoid space. From postnatal day 30, the microglial cells with P2X7 receptor-immunoreactivity were found to be distributed widely in the forebrain. Cells with P2X7 receptor-immunoreactivity from P30 were not labeled by ED1, but some were labeled by isolectin B4. The expression of P2X1, P2X4, and P2X7 receptor mRNA and protein on primary cultures of rat microglial cells and on the N9 microglial cell line was demonstrated with immunocytochemistry and RT-PCR. This is the first report that the P2X1 receptor is expressed on microglial cells, at least in early development, before postnatal day 30.

Reversed Na+/Ca2+Exchange Contributes to Ca2+Influx and Respiratory Burst in Microglia

“…Especially under pathological conditions, several pathways can potentially cause a rise in cytoplasmic Na + . For instance, microglia have Na + -permeable ion channels, including non-selective cation channels, 42 and ionotropic purinergic receptors [50][51][52] (reviewed in refs. 15 and 53) that can be activated by ATP release from damaged cells.…”

Microglia Proliferation Is Controlled by P2X7 Receptors in a Pannexin-1-Independent Manner during Early Embryonic Spinal Cord Invasion

“…Microglia are known to express ionotropic P2X1R, P2X4R, and P2X7R in the adult (Kettenmann et al, 2011) and during substantia nigra pars compacta development (Xiang and Burnstock, 2005). We first determined the expression of these P2XRs using qPCR in FACS-sorted microglia of E13.5 CX3CR1eGFP mouse embryonic SCs.…”

“…Their expression in prenatal microglia (Xiang and Burnstock, 2005), let alone their function, was, however, unknown. Although we found low P2X1R mRNA expression in embryonic microglia, we cannot exclude the possibility that functional P2X1Rs are expressed on the cell membrane.…”

“…In the adult, in vitro studies have shown that a number of factors, among which purinergic receptors, such as P2X7R (Monif et al, 2009), evoke both microglia activation and proliferation (Kettenmann et al, 2011). While P2X7R, in addition to P2X4R and P2X1R, is also expressed by embryonic microglia (Xiang and Burnstock, 2005), its functions remain unknown at these developmental stages. In the adult, P2X7R is involved, in addition to microglia activation and proliferation, in a variety of important effector functions of microglia (Kettenmann et al, 2011), including the release of interleukin (IL)-1␤, IL-1␣, and TNF-␣ (Ferrari et al, 1997;Hide et al, 2000;Brough et al, 2002;Mingam et al, 2008).…”

Immunocytochemical localization of NTPDases1 and 2 in the neural retina of mouse and zebrafish

“…In our study, NTPDase1 is also expressed by axons of GCs in the nerve fiber layer. In this layer, NTPDase1 might also be expressed by microglia or astrocytes, which have been shown to harbor P2X receptors (Bianco et al, 2005;Xiang and Burnstock, 2005) and to release ATP (Newman, 2006). The regionalized presence of NTPDase1 would suggest a rapid hydrolysis of both ATP and ADP released in the vicinity of the enzyme, limiting the activation of P2 receptors and quickly rising extracellular AMP concentration.…”