Nucleotides released from Aβ_1–42‐treated microglial cells increase cell migration and Aβ_1–42 uptake through P2Y₂ receptor activation

Abstract

Amyloid β-protein (Aβ) deposits in brains of Alzheimer’s disease (AD) patients generate proinflammatory cytokines and chemokines that recruit microglial cells to phagocytose Aβ. Nucleotides released from apoptotic cells activate P2Y2 receptors (P2Y2Rs) in macrophages to promote clearance of dead cells. In this study, we investigated the role of P2Y2Rs in the phagocytosis and clearance of Aβ. Treatment of mouse primary microglial cells with fibrillar (fAβ1–42) and oligomeric (oAβ1–42)Aβ1–42 aggregation solutions caused a rapid release of ATP (maximum after 10 min). Furthermore, fAβ1–42 and oAβ1–42 treatment for 24 h caused an increase in P2Y2R gene expression. Treatment with fAβ1–42 and oAβ1–42 aggregation solutions increased the motility of neighboring microglial cells, a response inhibited by pre-treatment with apyrase, an enzyme that hydrolyzes nucleotides. The P2Y2R agonists ATP and UTP caused significant uptake of Aβ1–42 by microglial cells within 30 min, which reached a maximum within 1 h, but did not increase Aβ1–42 uptake by primary microglial cells isolated from P2Y2R−/− mice. Inhibitors of αv integrins, Src and Rac decreased UTP-induced Aβ1–42 uptake, suggesting that these previously identified components of the P2Y2R signaling pathway play a role in Aβ phagocytosis by microglial cells. Finally, we found that UTP treatment enhances Aβ1–42 degradation by microglial cells, but not in cells isolated from P2Y2R−/− mice. Taken together, our findings suggest that P2Y2Rs can activate microglial cells to enhance Aβ clearance and highlight the P2Y2R as a therapeutic target in AD.

Neuroprotective roles of the P2Y2 receptor

“…It has been reported that following injury or neuroinflammation, P2Y 6 Rs are functionally upregulated in microglial cells and their activation by UDP triggers phagocytosis [144]. Our data with mouse primary microglial cells indicate that P2Y 2 R activation enhances microglial cell migration (Table 1) and their uptake and degradation of neurotoxic oligomeric Aβ 1-42 ( Table 2), responses that were markedly decreased in microglia from P2Y 2 R −/− cells [145].…”

“…Although the endogenous expression of P2Y 2 Rs has been reported in mouse microglia [67,214], it seems likely that increased levels of proinflammatory cytokines should further increase P2Y 2 R expression in glial cells in vivo. Our recent in vitro data show that treatment of mouse primary oligomeric/oligomeric Aβ 1-42 upregulates P2Y 2 R expression [145] via a pathway likely involving P2X7R-mediated IL-1β release [16,75,105,[154][155][156]. It also has been determined that P2X7R activation increases P2Y 2 R expression in rat astrocytes [215].…”

P2Y2 nucleotide receptor activation enhances the aggregation and self-organization of dispersed salivary epithelial cells

“…4). Our group has previously shown that the P2Y 2 R contains an RGD motif in its first extracellular loop that enables receptor interaction with RGDbinding ␣ V ␤ 3/5 integrins to stimulate cell migration (6,26,64,117). However, P2Y 2 R interactions with other RGD-binding integrins have not been previously reported.…”

The P2Y2 receptor promotes Wnt3a- and EGF-induced epithelial tubular formation by IEC6 cells by binding to integrins

“…These nucleotides also promote the processing of the amyloid precursor protein. In addition, β-amyloid upregulates P2Y 2 R in microglial cells, which enhances phagocytosis and degradation of β-amyloid (Kim et al, 2012). Thus, P2Y 2 R expression in neurons and microglial cells under pro-inflammatory and pro-apoptotic conditions might prevent neurodegeneration.…”