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Hyperphosphatemia Drives Procoagulant Microvesicle Generation in the Rat Partial Nephrectomy Model of CKD
Nima Abbasian1, Alison H Goodall1, James O Burton1,2
1Department of Cardiovascular Sciences, University of Leicester, and Leicester NIHR Cardiovascular Biomedical Research Unit, Leicester LE3 9QP, UK.
Insights
Hyperphosphatemia in chronic kidney disease (CKD) significantly increases blood clotting risk by elevating pro-coagulant microvesicles. Lowering phosphorus levels in CKD rats abolished these dangerous effects, highlighting phosphorus control as key for cardiovascular health.
Area of Science:
- Nephrology
- Cardiovascular Medicine
- Hematology
Background:
- Hyperphosphatemia is a known cardiovascular risk factor in Chronic Kidney Disease (CKD).
- In vitro studies suggest inorganic phosphate (Pi) acutely affects endothelial cells, promoting pro-coagulant microvesicles (MVs).
- Direct in vivo evidence linking hyperphosphatemia to pro-coagulant MVs in CKD was previously lacking.
Purpose of the Study:
- To investigate the in vivo effects of hyperphosphatemia on circulating pro-coagulant microvesicles in a rat model of CKD.
- To determine if elevated inorganic phosphate levels directly contribute to the generation of pro-coagulant MVs.
- To establish a link between hyperphosphatemia and thrombotic risk in the context of CKD.
Main Methods:
- A rat model of CKD was established using partial nephrectomy, with groups receiving either high (1.2%) or low (0.2%) dietary phosphorus, alongside sham-operated controls.
- Plasma microvesicles (MVs) were quantified using nanoparticle tracking analysis after 14 days.
- Pro-coagulant activity of isolated MVs was measured via calibrated automated thrombography, and endothelium-derived MVs were assessed using anti-CD144 immunoblotting.
Main Results:
- High phosphorus CKD rats exhibited significant hyperphosphatemia (4.11 mM vs 2.41 mM Pi) and elevated total plasma MVs (2.24 × 10^8/mL vs 1.31 × 10^8/mL) compared to controls.
- Increased CD144 expression (145% of control) and enhanced pro-coagulant activity (18.06 nM peak thrombin vs 4.99 nM) were observed in high phosphorus CKD rats.
- These adverse effects on MVs were completely abolished in CKD rats fed a low phosphorus diet.
Conclusions:
- Hyperphosphatemia, independent of CKD itself or a Pi-dependent hormonal response, is sufficient to induce a significant increase in circulating pro-coagulant MVs in vivo.
- This study demonstrates a direct mechanistic link between elevated inorganic phosphate levels and heightened thrombotic risk in CKD patients.
- Managing phosphorus levels is crucial for mitigating cardiovascular complications associated with hyperphosphatemia in CKD.
Abstract:
Hyperphosphatemia has been proposed as a cardiovascular risk factor, contributing to long-term vascular calcification in hyperphosphatemic Chronic Kidney Disease (CKD) patients. However, more recent studies have also demonstrated acute effects of inorganic phosphate (Pi) on endothelial cells in vitro, especially generation of pro-coagulant endothelial microvesicles (MV). Hitherto, such direct effects of hyperphosphatemia have not been reported in vivo. Thirty-six male Sprague-Dawley rats were randomly allocated to three experimental groups: (1) CKD induced by partial nephrectomy receiving high (1.2%) dietary phosphorus; (2) CKD receiving low (0.2%) dietary phosphorus; and (3) sham-operated controls receiving 1.2% phosphorus. After 14 days the animals were sacrificed and plasma MVs counted by nanoparticle tracking analysis. MVs isolated by centrifugation were assayed for pro-coagulant activity by calibrated automated thrombography, and relative content of endothelium-derived MVs was assessed by anti-CD144 immunoblotting. When compared with sham controls, high phosphorus CKD rats were shown to be hyperphosphatemic (4.11 ± 0.23 versus 2.41 ± 0.22 mM Pi, p < 0.0001) with elevated total plasma MVs (2.24 ± 0.37 versus 1.31 ± 0.24 × 108 per ml, p < 0.01), showing increased CD144 expression (145 ± 25% of control value, p < 0.0001), and enhanced procoagulant activity (18.06 ± 1.75 versus 4.99 ± 1.77 nM peak thrombin, p < 0.0001). These effects were abolished in the low phosphorus CKD group. In this rat model, hyperphosphatemia (or a Pi-dependent hormonal response derived from it) is sufficient to induce a marked increase in circulating pro-coagulant MVs, demonstrating an important link between hyperphosphatemia and thrombotic risk in CKD.
