#302 Proteomic study reveals indoxyl sulfate induced changes in endothelial cells: role of extracellular vesicles in cardiovascular disease
Authors: Rubio Andrea Figuer , Santos Fátima Milhano , Ciordia Sergio , Valera Gemma , Martín-Jouve Beatriz , Hernández Juan Pablo , Bodega Guillermo , Chamond Manuel Ramírez , Carracedo Julia , Alique Matilde 
Published: May 2024

Abstract

Background and Aims
Chronic kidney disease (CKD) lead to the accumulation of uremic toxins in the bloodstream, among which indoxyl sulfate (IS) is the most prominent. IS causes damage to endothelial cells lining blood vessels, ultimately leading to cardiovascular diseases in patients with CKD. Under physiological conditions, extracellular vesicles (EVs) are released by cells as intercellular communicators; however, after damage, the cargo of the EVs can be modified. This makes EV potential markers of damage, possibly carrying proteins of interest. This study aimed to investigate the impact of IS on endothelial cells and the release of EVs to identify potential therapeutic targets for preventing endothelial injury.

Method
Human umbilical vein endothelial cells (HUVEC) were cultured under control conditions and with IS exposure (250 μM IS, 24 h, n = 5). The released EVs were isolated from the supernatants by differential centrifugation and characterized by TEM and flow cytometry to confirm their identity as EVs (following the MISEV2018 guidelines). Proteome profiles of both cells and EVs were analyzed using a mass spectrometer (Orbitrap Exploris™ 240), followed by a Gene Set Enrichment Analysis (GSEA) which revealed altered functions.

Results
A total of 5871 proteins were identified in the proteomic analysis of cells, and 3614 proteins in EVs (with a False Discovery Rate (FDR) &lt; 1%). In cells, 30 proteins were upregulated and 46 were found downregulated in response to IS, while in EVs, 51 proteins were found upregulated and 47 downregulated (IS vs C). GSEA revealed that IS potentiated adipogenesis (p-value &lt; 0.001), TNF-α signaling via NFкB (p-value = 0.006), and xenobiotic metabolism in cells (p-value = 0.012). In contrast, EVs from cells treated with IS exhibited downregulation of extracellular matrix components (p-value = 0.003), myogenesis (p-value 0.009), genes downregulated in response to ultraviolet radiation (p-value = 0.014) and TNF-α signaling via NFкB (p-value = 0.041).

Conclusion
IS induces a change in protein expression in cells and their EVs, potentiating inflammation and atherosclerotic plaque formation with extracellular matrix loss. All these modifications contribute to endothelial dysfunction, which is the first step in the development of cardiovascular disease in patients with CKD. This study shed light on novel targets for intervention strategies to mitigate cardiovascular complications in patients with CKD.

Funding
Grants from the Instituto de Salud Carlos III (ISCIII) and cofounded by Fondos Europeo de Desarrollo Regional (FEDER): “PI19/00240” and “PI20/01321” and “FI20/00018” contract by the Instituto de Salud Carlos III and Ayuda de la Línea de Actuación “Excelencia para el Profesorado Universitario de la UAH” (EPU-INV-UAH/2022/001) from Alcala University.