MO581: Hyperphosphatemia Induces Lung Fibrosis in OLD Mice

Autor: Ana Asenjo-Bueno, Elena Alcalde-Estevez, Patricia Martínez Miguel, Gemma Olmos, Maria Piedad Ruiz-Torres, Susana López-Ongil
Rok vydání: 2022
Předmět:
Zdroj: Nephrology Dialysis Transplantation. 37
ISSN: 1460-2385
0931-0509
Popis: BACKGROUND AND AIM Hyperphosphatemia is a common condition associated with chronic kidney disease (CKD) and also with aging. Furthermore, lung dysfunction is described in both cases; however, the relationship between high phosphate levels and lung function is still unknown. The aim of this work is to analyze the effect of hyperphosphatemia in the development of lung fibrosis related to aging. METHODS For in vivo studies, C57BL6 male mice of 5 months old (Young) and 24 months old (Old) fed with a standard diet containing 0.6% phosphate were used. Additionally, some old mice were fed with a hypophosphatemic diet containing 0.2% phosphate (Old-Low P) for the last 3 months. Serum phosphate levels were measured with DIPI-500 assay. Lung fibrosis was evaluated by Sirius Red staining and by expression of extracellular matrix proteins such as fibronectin or collagen V assessed by western blot. In vitro studies were performed on a human cell line from lung fibroblasts (Wi-38), which were treated with a phosphate donor called β-glycerophosphate (BGP, 10 mM) at different times. Fibrosis was detected by expression of fibronectin by western blot as in lung tissues. Oxidative stress was measured by confocal microscopy using the fluorogenic probe CellROX. EMSA assays was used to check the activation of fibronectin promoter by NFκB transcription factor. RESULTS Old mice that showed higher serum phosphate levels had more lung fibrosis than young mice. Old mice fed with the low phosphate diet, which had less serum phosphate levels, reduced significantly the lung fibrosis respect to old mice fed with the standard diet. In order to elucidate a possible mechanism, in vitro studies were performed in lung fibroblasts treated with BGP. BGP induced a significant increased on fibronectin expression. BGP also rose oxidative stress at short times. As NF-kB transcription factor can be activated by oxidative stress, we checked whether BGP induced the binding of this factor to fibronectin promoter to upregulate this gene. The EMSA analysis showed that BGP promoted the binding of NF-κB to fibronectin promoter. Besides, in the presence of an antioxidant such as catalase, BGP did not induce the binding of NF-kB to fibronectin promoter, suggesting a role for oxidative stress. CONCLUSION Old mice showed hyperphosphatemia and lung fibrosis, which both were improved using a low phosphate diet. In vitro studies in lung fibroblasts confirmed that fibrosis induced by BGP seems to be mediated by activation on NF-kB via oxidative stress. These results show a relationship between hyperphosphatemia and lung fibrosis in aging; however, more studies are necessary in order to elucidate the relationship with other chronic diseases related to aging.
Databáze: OpenAIRE
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