TGF‐β and LPS modulate ADP‐induced migration of microglial cells through P2Y1 and P2Y12 receptor expression

Abstract

J. Neurochem. (2010) 115, 450–459. Abstract Nucleotides act as early signals for microglial recruitment to sites of CNS injury. As microglial motility and activation can be influenced by several local factors at the site of the lesion, we investigated the effects of interferon‐gamma, lipopolysaccharide (LPS) or transforming growth factor‐β (TGF‐β) addition to mixed glial cell cultures, on microglial migration in response to ADP, P2Y12 and P2Y1 mRNA expression as well as on the expression of an array of genes associated with the process of microglial activation. First, we demonstrated, by pharmacological inhibition and by using small interfering RNAs, that in addition to P2Y12, P2Y1 is involved in ADP‐stimulated microglial migration. The ability of specific agonists to induce Ca2+ mobilization further confirmed the expression of functional P2Y receptors in microglia. Then, we found that migratory capability and expression of both P2Y receptors were abrogated in microglial cells from LPS‐stimulated mixed glial cultures, while TGF‐β increased ADP‐induced migration and the expression of P2Y12 and P2Y1 receptors. Interferon‐gamma did not influence receptor expression or microglial migration. Finally, the patterns of gene expression induced in microglia by LPS or TGF‐β treatment of mixed glial cultures were clearly distinct. LPS induced a set of classical pro‐inflammatory genes, whereas TGF‐β increased the expression of genes associated with atypical microglial phenotype, namely arginase‐1 and TGF‐β genes. These results imply that both P2Y1 and P2Y12 may guide microglia toward the lesion. They also suggest that the modulation of microglial purinergic receptors expression by local factors, through direct and/or astrocyte‐mediated actions, may represent a novel mechanism affecting neuroinflammatory response.

Astrocytic P2Y1 receptor is involved in the regulation of cytokine/chemokine transcription and cerebral damage in a rat model of cerebral ischemia

“…In addition, in vitro studies have also confirmed P2Y 1 R expression in microglia (Ballerini et al, 2005;De Simone et al, 2010). However, in this report, we have shown that the P2Y 1 R is expressed on astrocytes before and after focal cerebral ischemia, using an in vivo model.…”

P2Y receptors on astrocytes and microglia mediate opposite effects in astroglial proliferation

“…2a). These results suggest that ADPβS activates microglia P2Y 1,12 and/or P2Y 13 receptors, which induce the release of diffusible messengers that attenuate its proliferative effect in astrocytes. They further suggest that the co-presence of astrocytes and microglia, and eventually their physical contact, facilitates the release of these inhibitory messengers since CCCM-S, but not MCM-S, attenuated ADPβS proliferative effect ( Table 2).…”

“…Therefore, besides the inhibitory influence provided by the presence of microglia, activation of microglia P2Y receptors sensitive to ADPβS seem to contribute to the release of messengers that interfere with the proliferative effects mediated by astroglial P2Y receptors. Microglia express P2Y 1 , P2Y 12 and P2Y 13 receptors [34,35], which are activated by ADPβS and may regulate the release of messengers, such as interleukin-10 [46]. These messengers may regulate astroglial proliferation mediated by P2Y receptors through a functional interaction occurring at the receptor level and/or at the intracellular signal transduction pathways.…”

“…In injury models, astroglial proliferation was found to be mediated by P2Y 1 receptors [9,10], and recently, we have shown that P2Y 12 receptors may also be involved in this response [11]. Additionally, nucleotides activate microglia P2 receptors which induce chemotaxis [12,13], phagocytosis [14], the release of trophic factors [15] and cytokines [16] that may have protective effects in cerebral injury [17,18]. Several cytokines and growth factors released by microglia, such as interleukin-1β, interleukin-6, interferon-γ, tumour necrosis factor-α and fibroblast growth factor-2 stimulate astrogliosis [19][20][21] whereas others, such as interleukin-10, attenuate astroglial reactivity through a decrease in microglia activation [22,23].…”

Supportive or detrimental roles of P2Y receptors in brain pathology?—The two faces of P2Y receptors in stroke and neurodegeneration detected in neural cell and in animal model studies

“…The activation of P2Y 12 and P2Y 1 receptors of resting microglia causes their migration along a concentration gradient of ATP/ADP towards the injury. Phagocytosis of injured cells is induced by P2Y 6 receptors activated by UTP/UDP [46][47][48]. Considering this model, P2Y receptors became a pharmacological target for neuroinflammation.…”