Effects of indoxyl sulfate on adherens junctions of endothelial cells and the underlying signaling mechanism

Abstract

Uremic patients have a much higher risk of cardiovascular diseases and death. Uremic toxins are probably involved in the development of vascular endothelial dysfunction. Indoxyl sulfate (IS) is a uremic toxin that accumulates with deterioration of renal function. This study explored the effects of IS on the adherens junctions of vascular endothelial cells and revealed the underlying mechanism. Bovine pulmonary artery endothelial cells (BPAECs) were treated with IS, and the distribution of vascular endothelial cadherin (VE-cadherin), p120-catenin, β-catenin, and stress fibers was examined by immunofluorescence. IS treatment resulted in disruption of intercellular contacts between BPAECs with prominent parallel-oriented intracellular stress fiber formation. Intracellular free radical levels which measured by flow cytometry increased after IS treatment. The antioxidant, MnTMPyP, and an ERK pathway inhibitor, U0126, both significantly prevented IS-induced disruption of intercellular contacts. Western blotting analyses demonstrated that IS-induced phosphorylation of myosin light chain kinase (MLCK) and myosin light chains (MLC) as well as activation of extracellular-signal-regulated protein kinase (ERK1/ERK2). Pretreatment with MnTMPyP prevented ERK1/2 phosphorylation. U0126 prevented the IS-induced MLCK and MLC phosphorylation. MEK-ERK acted as the upstream regulator of the MLCK-MLC pathway. These findings suggest that the superoxide anion-MEK-ERK-MLCK-MLC signaling mediates IS-induced junctional dispersal of BPAECs.

Uremic Toxins and Their Effects on Multiple Organ Systems

“…Impaired function of the intestinal mucosal barrier may explain the persistence of systemic inflammation in the course of CKD [16,17,21,30,31,32,33]. …”

Neurocritical Care for Patients with Kidney Dysfunction

“…Potential BBB injury via the soluble receptor for advanced glycation end products (sRAGE) pathway is discussed in the BCerebral Microbleeds^section below. Both p-cresyl sulfate and indoxyl sulfate inhibit endothelial cell proliferation and induce the release of endothelial microparticles, a marker of endothelial cell damage [106,107]; indoxyl sulfate also induces junctional breakdown via MEK-ERK-mediated phosphorylation of the myosin light chain kinase and myosin light chain [108].…”

Role of Uremic Compounds in Organ Injury

“…Impaired function of the intestinal mucosal barrier and fluid overload in the early stages of kidney disease are thought to be directly responsible for the translocation of both intact bacteria and their fragments or bacterial bioproducts across the intestinal mucosal barrier into the circulation. The bacteria and their products affect the activation of the innate immune system which explains the persistence of systemic inflammation in the course of CKD [13,14,17,[27][28][29][30][31].…”