MO596HYPERPHOSPHATEMIA INDUCES ENDOTHELIN-1 SYNTHESIS AND INFLAMMATION IN LUNG FIBROBLASTS

Abstract

Abstract Background and Aims Hyperphosphatemia is an aging-related condition associated to chronic diseases such as chronic kidney disease (CKD). In both cases, aging and CKD, it has been described a decline lung function, however, relationship between high serum levels of phosphate and lung damage has not been described yet. The aim of this work was to evaluate if phosphate could induce inflammation in lung, studying the mechanisms implied. Method In vitro studies were performed on a cell line from human lung fibroblasts (Wi-38) which were treated with a phosphate donor termed β-glycerophosphate (BGP, 10 mM) and also with endothelin 1 (ET-1, 10 nM) at different times. To assess inflammation, the expression of several cytokines such as TNF-α,IL-1β, IL-6 and MCP-1 were measured by real time PCR. mRNA expressions of prepro-ET-1 and endothelin-converting enzyme-1 (ECE-1) were also analyzed by real time PCR. Reactive oxygen species (ROS) production was evaluated by confocal microscopy in live cells using the fluorogenic probe CellROX as oxidative stress reagent. Results Treatment with BGP induced a significant rise of the pro-inflammatory cytokines expression, TNF-α, IL-1β, IL-6 and MCP-1, on lung fibroblasts. Moreover, BGP was able to regulate ET-1 system, as we found a significant increase of mRNA expressions not only of prepro-ET-1 but also of ECE-1, reaching a peak around 2 and 6 hours, respectively. Later, it was checked whether ET-1 could induce inflammation itself in lung fibroblasts. Cells incubated with ET-1 show similar results as BGP, increasing expressions of all cytokines, TNF-α, IL-1β, IL-6 and MCP-1.ET-1 response was earlier than BGP, around at 2 hours with ET-1 instead of at 8 hours with BGP. In order to elucidate a possible mechanism, ROS production was assessed after BGP treatment. BGP induced ROS production at 15 min in lung fibroblasts. Conclusion BGP induces the synthesis of pro-inflammatory cytokines as well as the system of synthesis of ET-1, besides to rise ROS production.ET-1 itself also increases pro-inflammatory cytokines expression. ET-1 could contribute to the inflammation observed in lung fibroblast after BGP treatment. We propose oxidative stress as a potential mechanism implied, as it is well known that ROS can mediate in inflammation and in the ET system. However, more studies are necessary to confirm this role. All in all, these results relate hyperphosphatemia with a higher inflammation in lung fibroblasts which could decline lung function in chronic diseases associated to aging as CKD.