Increased inorganic phosphate induces human endothelial cell apoptosis in vitro

Abstract

Chronic kidney disease with hyperphosphatemia is associated with accelerated atherosclerosis and endothelial dysfunction. However, the contribution of high serum phosphate levels to endothelial injury is incompletely understood. The aim of this work was to evaluate the responses of endothelial cells to elevated levels of extracellular phosphate in vitro. High phosphate in concentrations similar to those observed in uremia-associated hyperphosphatemia (>2.5 mM) induced apoptosis in two endothelial cell lines (EAhy926 cells and GM-7373 cells). This effect was enhanced when cells were incubated for 24 h in the presence of 2.8 mM calcium instead of 1.8 mM. By treating cells with 0.5 or 1.0 mM phosphonoformic acid, an inhibitor of the phosphate transporter, death was completely prevented. The process of phosphate-induced apoptosis was further characterized by increased oxidative stress, as detected by increased ROS generation and disruption of the mitochondrial membrane potential at approximately 2 h after treatment, followed by caspase activation. These findings show that hyperphosphatemia causes endothelial cell apoptosis, a process that impairs endothelial integrity. Endothelial cell injury induced by high phosphate concentrations may be an initial event leading to vascular complications in patients with chronic kidney disease.

Role of nutrient transporters in lifestyle-related diseases

“…Other studies, including our investigation, demonstrated that elevation of extracellular phosphate levels could induce endothelial dysfunction by an increase in oxidative stress and apoptosis, and a decrease in eNOS activity 48,49) . Inhibition of phosphate transport activity by phosphonoformic acid or siRNA can inhibit both calcification in vascular smooth muscle cells 44,50) and oxidative stress in endothelial cells 48,49) . Therefore, the phosphate transport activity of type III sodium-dependent phosphate transporters is important in the development of vascular complications leading to arteriosclerosis.…”

Reduction of Hyperphosphatemia is Related with the Reduction of C-Reactive Protein in Dialysis Patients. Study in Sevelamer-Resistant Dialysis Patients Treated with Chitosan Chewing Gum as Salivary Phosphate Binder

“…PO 4 and Ca × PO 4 were evaluated at the beginning of the study, after 1 and 2 weeks of chewing gum use and after 2 and 4 weeks from the chewing gum use withdrawal. 8 hsCRP was measured from the available blood samples corresponding to the beginning of the study, after 2 weeks of chewing gum use, and after 4 weeks from the chewing gum use withdrawal, and analyzed with corresponding PO 4 and Ca × PO 4 values.…”

“…Serum PO 4 and calcium levels were determined by a spectrophotometric assay using a flex reagent cartridge (Dade Behring, Newark, NJ, USA) and hsCRP by immunonephelometry (Dade Behring).…”

“…7 We have shown in sevelamer-resistant dialysis patients that treatment with a chewing gum loaded with chitosan, a salivary phosphate binder, as an add-on to sevelamer, markedly reduced salivary PO 4 level as well as serum PO 4 and Ca × PO 4 to normal. 8 To give support to a direct proinflammatory role of hyperphosphatemia "per se" in humans, we have considered in this study our previously studied dialysis patients with sevelamer hydrochloride-"resistant" hyperphosphatemia in whom serum PO 4 was normalized by the treatment with a chewing gum loaded with chitosan, a salivary phosphate binder, as an add-on to sevelamer, 8 to retrospectively evaluate their high sensitive (hs) CRP and the relationship with hyperphosphatemia and Ca × PO 4 .…”

Papel Do Fosfato Na Doença Cardiovascular: Marcador Ou Causador De Lesão?

“…41 Além disso, o Pi pode induzir a apoptose de células endoteliais através do aumento do estresse oxidativo. 42 Uma das maiores dificuldades em interpretar os efeitos deletérios do Pi in vivo é determinar se eles são resultado de sua ação direta ou de mecanismos indiretos, por exemplo, via aumento de FGF-23 e PTH. Através de estudos em modelo animal (ratos) de DRC, nos quais os animais foram submetidos a paratireoidectomia e, posteriormente, à infusão contínua controlada de PTH, Neves e cols.…”