Dataset Information

Novel phosphate-activated macrophages prevent ectopic calcification by increasing extracellular ATP and pyrophosphate.

ABSTRACT:

Purpose

Phosphorus is an essential nutrient involved in many pathobiological processes. Less than 1% of phosphorus is found in extracellular fluids as inorganic phosphate ion (Pi) in solution. High serum Pi level promotes ectopic calcification in many tissues, including blood vessels. Here, we studied the effect of elevated Pi concentration on macrophage polarization and calcification. Macrophages, present in virtually all tissues, play key roles in health and disease and display remarkable plasticity, being able to change their physiology in response to environmental cues.

Methods and results

High-throughput transcriptomic analysis and functional studies demonstrated that Pi induces unpolarized macrophages to adopt a phenotype closely resembling that of alternatively-activated M2 macrophages, as revealed by arginine hydrolysis and energetic and antioxidant profiles. Pi-induced macrophages showed an anti-calcifying action mediated by increased availability of extracellular ATP and pyrophosphate.

Conclusion

We conclude that the ability of Pi-activated macrophages to prevent calcium-phosphate deposition is a compensatory mechanism protecting tissues from hyperphosphatemia-induced pathologic calcification.

SUBMITTER: Villa-Bellosta R

PROVIDER: S-EPMC5376322 | biostudies-literature | 2017

REPOSITORIES: biostudies-literature

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Publications

Novel phosphate-activated macrophages prevent ectopic calcification by increasing extracellular ATP and pyrophosphate.

Villa-Bellosta Ricardo R Hamczyk Magda R MR Andrés Vicente V

PloS one 20170331 3

<h4>Purpose</h4>Phosphorus is an essential nutrient involved in many pathobiological processes. Less than 1% of phosphorus is found in extracellular fluids as inorganic phosphate ion (Pi) in solution. High serum Pi level promotes ectopic calcification in many tissues, including blood vessels. Here, we studied the effect of elevated Pi concentration on macrophage polarization and calcification. Macrophages, present in virtually all tissues, play key roles in health and disease and display remarka ...[more]

PMID: 28362852

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Project description:Vascular calcification is a multifaceted process involving gain of calcification inducers and loss of calcification inhibitors. One such inhibitor is inorganic pyrophosphate (PP(i)), and regulated generation and homeostasis of extracellular PP(i) is a critical determinant of soft-tissue mineralization. We recently described an autocrine mechanism of extracellular PP(i) generation in cultured rat aortic vascular smooth muscle cells (VSMC) that involves both ATP release coupled to the ectophosphodiesterase/pyrophosphatase ENPP1 and efflux of intracellular PP(i) mediated or regulated by the plasma membrane protein ANK. We now report that increased cAMP signaling and elevated extracellular inorganic phosphate (P(i)) act synergistically to induce calcification of these VSMC that is correlated with progressive reduction in ability to accumulate extracellular PP(i). Attenuated PP(i) accumulation was mediated in part by cAMP-dependent decrease in ANK expression coordinated with cAMP-dependent increase in expression of TNAP, the tissue nonselective alkaline phosphatase that degrades PP(i). Stimulation of cAMP signaling did not alter ATP release or ENPP1 expression, and the cAMP-induced changes in ANK and TNAP expression were not sufficient to induce calcification. Elevated extracellular P(i) alone elicited only minor calcification and no significant changes in ANK, TNAP, or ENPP1. In contrast, combined with a cAMP stimulus, elevated P(i) induced decreases in the ATP release pathway(s) that supports ENPP1 activity; this resulted in markedly reduced rates of PP(i) accumulation that facilitated robust calcification. Calcified VSMC were characterized by maintained expression of multiple SMC differentiation marker proteins including smooth muscle (SM) alpha-actin, SM22alpha, and calponin. Notably, addition of exogenous ATP (or PP(i) per se) rescued cAMP + phosphate-treated VSMC cultures from progression to the calcified state. These observations support a model in which extracellular PP(i) generation mediated by both ANK- and ATP release-dependent mechanisms serves as a critical regulator of VSMC calcification.

Project description:Ectopic adenosine triphosphate synthase (eATP synthase) was found on the cell surface to generate extracellular ATP in various cancer cells. Recently using proteomics approach, several reports identified ATP synthase in extracellular vesicles (EVs) which are important in cell-cell communications. However, the functions of ATP synthase in EVs are still unclear. Here we increased the expression of eATP synthase on the plasma membrane of lung cancer A549 cells via 0.1% FBS starvation and collected EVs including microvesicles and exosomes from the culture medium using serial centrifugation. Both of them were assuredly isolated and confirmed by transmission electron microscopy, nano tracking analysis, and specific EV markers. We also used western blot to demonstrate the presence of ATP synthase in EVs. Besides, dot blot experiment revealed that the F1 portion faced towards extracellular space using anti-ATP beta subunit antibody. Under starvation, the expression of eATP synthase was enhanced on cell surface and exosomes as well as increased EV secretion. To further investigate the functions, we first elucidated whether eATP synthase on EV membrane produced ATP by ATP luciferase analysis. Our data showed that there was no significant ATP production. Moreover, we performed proteomic analysis using dimethyl labeling and LC-MS/MS to compare the difference between EVs released by A549 control and starvation. We identified a total of 1504 and 869 proteins in microvesicles and exosomes, respectively. Using 1.5- and 0.67-fold change as the thresholds, there were 171 and 46 differential expressed proteins in microvesicles and exosomes, respectively. Seven ATP synthase subunits in microvesicles and five in exosomes were identified. The proteomic data were further analyzed using gene set enrichment analysis (GSEA) within the C2 (curated gene sets) subclasses and setting 0.25 as FDR cutoff to find out biological functions related to eATP synthase. Among these up-regulated terms, metabolism, cell cycle and apoptosis were enriched, which indicating that starvation influences cell behavior. Additionally, the immune response is upregulated strikingly in exosomes within C2 gene set. One of these immune response pathways, MHC-1 antigen presentation, was previously proved to interact with eATP synthase which could be recognized by several immune cells.

Dataset Information

Novel phosphate-activated macrophages prevent ectopic calcification by increasing extracellular ATP and pyrophosphate.

Purpose

Methods and results

Conclusion

Publications

Novel phosphate-activated macrophages prevent ectopic calcification by increasing extracellular ATP and pyrophosphate.

Similar Datasets

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