Format

Send to

Choose Destination
J Am Soc Nephrol. 2015 Sep;26(9):2152-62. doi: 10.1681/ASN.2014070642. Epub 2015 Mar 5.

Hyperphosphatemia, Phosphoprotein Phosphatases, and Microparticle Release in Vascular Endothelial Cells.

Author information

1
Departments of Infection, Immunity and Inflammation and.
2
Departments of Infection, Immunity and Inflammation and John Walls Renal Unit, University Hospitals of Leicester, Leicester, United Kingdom; and.
3
Cardiovascular Sciences, University of Leicester, Leicester, United Kingdom; Leicester National Institute for Health Research Cardiovascular Biomedical Research Unit Cardiovascular Sciences, University of Leicester, United Kingdom.
4
Departments of Infection, Immunity and Inflammation and ab74@leicester.ac.uk.

Abstract

Hyperphosphatemia in patients with advanced CKD is thought to be an important contributor to cardiovascular risk, in part because of endothelial cell (EC) dysfunction induced by inorganic phosphate (Pi). Such patients also have an elevated circulating concentration of procoagulant endothelial microparticles (MPs), leading to a prothrombotic state, which may contribute to acute occlusive events. We hypothesized that hyperphosphatemia leads to MP formation from ECs through an elevation of intracellular Pi concentration, which directly inhibits phosphoprotein phosphatases, triggering a global increase in phosphorylation and cytoskeletal changes. In cultured human ECs (EAhy926), incubation with elevated extracellular Pi (2.5 mM) led to a rise in intracellular Pi concentration within 90 minutes. This was mediated by PiT1/slc20a1 Pi transporters and led to global accumulation of tyrosine- and serine/threonine-phosphorylated proteins, a marked increase in cellular Tropomyosin-3, plasma membrane blebbing, and release of 0.1- to 1-μm-diameter MPs. The effect of Pi was independent of oxidative stress or apoptosis. Similarly, global inhibition of phosphoprotein phosphatases with orthovanadate or fluoride yielded a global protein phosphorylation response and rapid release of MPs. The Pi-induced MPs expressed VE-cadherin and superficial phosphatidylserine, and in a thrombin generation assay, they displayed significantly more procoagulant activity than particles derived from cells incubated in medium with a physiologic level of Pi (1 mM). These data show a mechanism of Pi-induced cellular stress and signaling, which may be widely applicable in mammalian cells, and in ECs, it provides a novel pathologic link between hyperphosphatemia, generation of MPs, and thrombotic risk.

KEYWORDS:

CKD; cardiovascular disease; cell signaling; endothelial cells; hyperphosphatemia; microparticle

PMID:
25745026
PMCID:
PMC4552113
DOI:
10.1681/ASN.2014070642
[Indexed for MEDLINE]
Free PMC Article

Supplemental Content

Full text links

Icon for HighWire Icon for PubMed Central
Loading ...
Support Center