Uremic toxins are considered a risk factor for cardiovascular disorders in kidney diseases, but it is not known whether, under inflammatory conditions, they affect adhesion molecule expression on endothelial cells, which may play a critical role in acute kidney injury (AKI). In the present study, in cardiovascular surgery-related AKI patients, who are known to have high plasma levels of the uremic toxin indoxyl sulfate (IS), plasma levels of IL-1β were found to be positively correlated with plasma levels of the adhesion molecule E-selectin. In addition, high E-selectin and IL-1β expression were seen in the kidney of ischemia/reperfusion mice in vivo. We also examined the effects of IS on E-selectin expression by IL-1β-treated human umbilical vein endothelial cells (HUVECs) and the underlying mechanism. IS pretreatment of HUVECs significantly increased IL-1β-induced E-selectin expression, monocyte adhesion, and the phosphorylation of mitogen-activated protein kinases (ERK, p38, and JNK) and transcription factors (NF-κB and AP-1), and phosphorylation was decreased by pretreatment with inhibitors of ERK1/2 (PD98059), p38 MAPK (SB202190), and JNK (SP600125). Furthermore, IS increased IL-1β-induced reactive oxygen species (ROS) production and this effect was inhibited by pretreatment with N-acetylcysteine (a ROS scavenger) or apocynin (a NADPH oxidase inhibitor). Gel shift assays and ChIP-PCR demonstrated that IS enhanced E-selectin expression in IL-1-treated HUVECs by increasing NF-κB and AP-1 DNA-binding activities. Moreover, IS-enhanced E-selectin expression in IL-1β-treated HUVECs was inhibited by Bay11-7082, a NF-κB inhibitor. Thus, IS may play an important role in the development of cardiovascular disorders in kidney diseases during inflammation by increasing endothelial expression of E-selectin.
Keywords: Acute kidney injury; E-selectin; Endothelial cells; Indoxyl sulfate; Reactive oxygen species.