Abstract: SA-PO244
Systemic Phosphate Elevations Are Associated with Alveolar Calcification in Mice
Session Information
- CKD-MBD: Basic and Translational
October 26, 2024 | Location: Exhibit Hall, Convention Center
Abstract Time: 10:00 AM - 12:00 PM
Category: Bone and Mineral Metabolism
- 501 Bone and Mineral Metabolism: Basic
Authors
- Fajol, Abul, The University of Alabama at Birmingham Division of Nephrology, Birmingham, Alabama, United States
- Bollenbecker, Seth, Division of Pulmonary, Allergy and Critical Care Medicine, The University of Alabama at Birmingham, Birmingham, Alabama, United States
- Kumar, Parveen, Department of Urology, The University of Alabama at Birmingham, Birmingham, Alabama, United States
- Heitman, Kylie, The University of Alabama at Birmingham Division of Nephrology, Birmingham, Alabama, United States
- Thomas, Madison, The University of Alabama at Birmingham Division of Nephrology, Birmingham, Alabama, United States
- Li, Qing, The University of Alabama at Birmingham Division of Nephrology, Birmingham, Alabama, United States
- Komarova, Svetlana, The University of Alabama at Birmingham Division of Nephrology, Birmingham, Alabama, United States
- Mitchell, Tanecia, Department of Urology, The University of Alabama at Birmingham, Birmingham, Alabama, United States
- Krick, Stefanie, Division of Pulmonary, Allergy and Critical Care Medicine, The University of Alabama at Birmingham, Birmingham, Alabama, United States
- Faul, Christian, The University of Alabama at Birmingham Division of Nephrology, Birmingham, Alabama, United States
Background
Increases in serum phosphate levels (hyperphosphatemia) are associated with vascular calcification (VC) and mortality in patients with chronic kidney disease (CKD). Elevated phosphate can target vascular smooth muscle cells and induce inflammatory and osteogenic gene programs and VC. It is unknown whether high phosphate levels can also directly affect the lung.
Methods
We analyzed the lung phenotype of klotho-deficient (kl/kl) mice, which is a model for hyperphosphatemia and VC. Tissue calcifications were determined by µCT analysis, Alizarin red and von Kossa stainings,and tissue phosphate content by a colorimetric assay and ICP-MS. Nanoparticles in the bronchoalveolar lavage (BAL) fluid were quantified by NanoSight Technology and visualized by TEM. Cells in the BAL were analyzed by flow cytometry. Human alveolar epithelial cells (A549) and human lung fibroblasts (IMR-90) were cultured in the presence of high phosphate and analyzed by Alizarin red staining. Calcification events in lung tissue and cultured cells were also determined by qPCR analysis of osteogenic and inflammatory markers.
Results
We observed calcifications in the lung of kl/kl mice, especially in the alveolar region, as well as increased expression of osteogenic and inflammatory markers and elevated phosphate content. In the BAL of kl/kl mice, we detected increased numbers of macrophages and calcium-containing nanoparticles, which had a crystal-like morphology. No such alterations were observed in wildtype mice. A high magnesium diet reduced lung phosphate content and calcification. Exposure of A549 cells and IMR-90 to high phosphate induced osteogenic and inflammatory markers as well as calcium-phosphate deposition, which was abolished in cells co-treated with magnesium.
Conclusion
Our findings suggest that mice with hyperphosphatemia develop lung calcifications, which are accompanied by inflammation and by the appearance of calcium-phosphate crystals. Whether pulmonary calcification also occurs in CKD, needs to be determined. Our in vitro studies suggest that high phosphate can directly target lung cells and induce calcification. Therefore, lowering phosphate or preventing the formation of calcium-phosphate particles systemically or locally might have protective effects on the lung in diseases with hyperphosphatemia.
Funding
- NIDDK Support