Inorganic polyphosphate: a key modulator of inflammation

Inorganic polyphosphate (PolyP) is a molecule with prothrombotic and proinflammatory properties in blood. PolyP activates the NF-κB signaling pathway, increases the expression of cell surface adhesion molecules and disrupts the vascular barrier integrity of endothelial cells. PolyP-induced NF-κB activation and vascular hyperpermeability are regulated by the mammalian target of rapamycin complex-1 (mTORC1) and mTORC2 pathways, respectively. Through interaction with receptor for advanced glycation end products (RAGE) and P2Y₁ receptors, PolyP dramatically amplifies the proinflammatory responses of nuclear proteins. Moreover, PolyP-mediated activation of the contact pathway results in activation of the kallikrein-kinin system, which either directly or in cross-talk with the complement system induces inflammation in both cellular and animal systems. Thus, polyP is a novel therapeutic target for the treatment of metabolic and acute/chronic proinflammatory diseases, including severe sepsis, diabetes, cardiovascular disease and cancer. In this review, we discuss recent findings on the inflammatory properties of polyP and propose a model to explain the molecular mechanism of proinflammatory effects of this molecule in different systems.