Abstract 4956: Intravital Microscopic Analysis Revealed Indoxyl Sulfate-induced Leukocyte Recruitment via E-selectin in Mice After Subtotal Renal Ablation
[Background] Despite positive correlation between chronic kidney disease (CKD) and atherosclerosis, a causative role of uremic toxins in vascular inflammation has not been well characterized. Indoxyl sulfate (IS) is one of the uremic toxins increased in CKD patients. However, the effect of IS on inflammation had not been tested. We thus examined an effect of IS on leukocyte-endothelial interaction in vivo and in vitro.
[Methods and Results] Pretreatment of HUVEC with IS (0.2 mM to 2.0 mM for 20 h) significantly enhanced THP-1 cell adhesion to TNF-α-activated HUVEC under flow condition (p<0.01). IS enhanced expression level of E-selectin, but not ICAM-1 or VCAM-1 in TNF-α-activated HUVEC. IS treatment induced phosphorylation of JNK and p65 component of NF-κB in TNF-α-activated HUVEC. IS-induced activation of NF-κB was further confirmed by luciferase assay using HUVEC transfected with an NF-κB firefly-luciferase cDNA construct. SP600125, a JNK inhibitor, and BAY11–7082, an NF-κB inhibitor, attenuated IS-induced E-selectin expression and subsequent THP-1 cells adhesion under flow. IS increased dihydroethidium-associated oxidative stress in HUVEC, which is stabilized by apocynin, an NAD(P)H oxidase inhibitor. Next, a pathophysiolocgical role of IS in CKD was examined in nephrectomized mice with (Nx+IS) or without IS (Nx). An intravital microscopic analysis revealed a significant induction of leukocyte adhesion to the femoral artery in the Nx+IS group when compared to Nx group (p<0.05). Expression levels of E-selectin and the NAD(P)H oxidase subunits (p47phox and p22phox) were increased in Nx+IS mice. When we monitored inflammatory markers of monocytes, expression of CD11b and production of ROS was significantly increased in Nx mice, which was blunted by an oral absorbent of IS.
[Conclusion] These results suggest that IS enhances leukocyte-endothelial cell interaction through up-regulation of E-selectin. The underlying mechanisms seem to involve oxidative stress-mediated JNK and NF-κB dependent pathways. These observations provide a novel role for IS in CKD-related vascular inflammation.