Inorganic polyphosphate elicits pro‐inflammatory responses through activation of the mammalian target of rapamycin complexes 1 and 2 in vascular endothelial cells

Publisher： John Wiley & Sons Inc

E-ISSN： 1538-7836|13|5|860-871

ISSN： 1538-7933

Source： JOURNAL OF THROMBOSIS AND HAEMOSTASIS, Vol.13, Iss.5, 2015-05, pp. : 860-871

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Abstract

SummaryBackgroundInorganic polyphosphate (polyP) elicits pro‐inflammatory signaling responses in endothelial cells through interaction with two receptors, RAGE and P2Y1. It is known that polyP activates mTOR signaling in breast cancer cells.ObjectivesThe objective of this study is to understand the mechanism of the polyP‐mediated signaling pathway in endothelial cells and to determine whether polyP exerts its pro‐inflammatory effect through activation of mTOR.MethodsmTOR activation by polyP or platelet releasates in cellular and animal models was monitored in the absence and presence of pharmacological inhibitors and/or siRNA knockdown of specific signaling molecules.ResultsPolyP effectively induced phosphorylation of mTOR complex 1 (mTORC1) substrate, p70S6K, in endothelial cells by an AKT‐dependent but ERK‐independent mechanism. The siRNA knockdown of both RAGE and P2Y1 or specific inhibitors of the PI3K/PLC/PKC/Ca2+ signaling axis inhibited polyP‐mediated p70S6K phosphorylation. Moreover, either rapamycin or siRNA knockdown of raptor (mTORC1‐specific component) abrogated polyP‐mediated phosphorylation of p70S6K. By contrast, the siRNA knockdown of rictor (mTOR complex 2‐specific component) but not raptor eliminated the barrier‐disruptive effect of polyP. Specific NF‐κB inhibitors abrogated polyP‐mediated phosphorylation of p70S6K and rapamycin suppressed polyP‐induced activation of NF‐κB. Finally, specific inhibitors of the mTOR signaling network eliminated polyP‐mediated vascular leakage and leukocyte recruitment in animal models.ConclusionsPolyP, through interaction with RAGE and P2Y1, activates both the mTORC1 and mTORC2 signaling network. Both the pro‐inflammatory and mTOR signaling functions of polyP are linked.