Abstract
Indoxyl sulphate (IS) is a protein-bound uremic toxin that results from the metabolism of dietary tryptophan normally excreted by kidney through the proximal tubules. Thus the toxin accumulates in the blood of patients with impaired renal function such as in chronic kidney disease (CKD). High IS serum levels in patients with CKD suggest its involvement in CKD progression and in the onset of complications. Its presence in plasma is also a powerful predictor of overall and cardiovascular morbidity/mortality. IS is a well known nephrovascular toxin but very little is known regarding its effects on the immune system and in particular during inflammation. In this study we examined the effect of IS on macrophage activation in response to lipopolysaccharide from E. coli (LPS), a gram negative bacterial endotoxin associated with inflammation and septic shock. To simulate the uremic condition, J774A.1 macrophages were incubated with IS at concentrations observed in uremic patients (1000–62.5 µM) both alone and during LPS challenge. IS alone induced release of reactive oxygen species (ROS), through a mechanism involving pro- and anti-oxidant systems, and alteration in intracellular calcium homeostasis. When added to J774A.1 macrophages in presence of LPS, IS significantly increased the nitric oxide (NO) release, inducible nitric oxide synthase (iNOS) and cycloxygenase-2 (COX-2) expression. IS pre-treatment was also associated with an increase in tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) production by macrophages stimulated with LPS. Mechanistic studies revealed that IS increased LPS-induced NF-kB nuclear translocation, ROS release and altered calcium concentrations, mainly because of mitochondrial calcium overloading. Moreover also in primary mouse peritoneal macrophages IS enhances the inflammatory response to LPS increasing ROS, NO, iNOS, COX-2, TNF-α, IL-6 and NF-kB levels.This study provides evidences that IS stimulates macrophage function and enhances inflammatory reasponse associated with LPS, thus contributing to altered immune response dysfunctions observed in CKD.
Highlights
Chronic kidney disease (CKD) progression leads to the dysfunction of multiple organs with clinical features constituting the uremic syndrome that, despite pharmacological and dialytic treatment remains associated with multiple complications [1,2,3]
indoxyl sulphate (IS) doesn’t affect macrophage viability To elucidate the influence of IS on viability of J774A.1 and mouse peritoneal macrophages under our experimental conditions, cells were treated with IS (1000–62.5 mM) for 24 h
IS enhances reactive oxygen species (ROS) release from macrophages: effect of diphenyleneiodonium chlorhyde (DPI) and NAC To investigate whether IS mediates oxidative stress in J774A.1 macrophages, we evaluated its effect on intracellular ROS by flow cytometry
Summary
Chronic kidney disease (CKD) progression leads to the dysfunction of multiple organs with clinical features constituting the uremic syndrome that, despite pharmacological and dialytic treatment remains associated with multiple complications [1,2,3]. This syndrome is attributed to the progressive retention of a large number of compounds which, under normal conditions, are excreted by healthy kidneys. These compounds are called uremic toxins because of their harmful effects in various physiological functions in CKD patients [1,2]. A diminished immune defence contributes to the high prevalence of infections, whereas preactivation and priming of immune cells leads to inflammation and to cardiovascular disease
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
