Indoxyl sulfate enhances angiotensin II signaling through upregulation of epidermal growth factor receptor expression in vascular smooth muscle cells

Abstract

Aims: Indoxyl sulfate, a uremic toxin, is considered a risk factor for arteriosclerosis in patients with chronic kidney disease (CKD). We previously reported the actions of indoxyl sulfate including crosstalk with platelet-derived growth factor (PDGF) signaling in vascular smooth muscle cells (VSMCs). The present study examines whether indoxyl sulfate enhances angiotensin II (Ang II) signaling because serum levels of Ang II are elevated in patients with CKD.

Main methods: The effect of indoxyl sulfate and Ang II on phosphorylation of ERK and epidermal growth factor receptor (EGFR), and migration were determined using VSMCs. The expression of EGFR was determined using not only VSMCs but also artery of normal, uremic, and indoxyl sulfate-administrated uremic rats.

Key findings: Ang II-dependent phosphorylation of ERK and EGFR, and migration of VSMCs were augmented by a prior 24-h incubation with indoxyl sulfate even in the absence of indoxyl sulfate during Ang II stimulation. The expression of EGFR was increased in indoxyl sulfate-stimulated cultured VSMCs. In arterial VSMCs of rats, serum levels of indoxyl sulfate reflected the expression level of EGFR. The upregulated EGFR expression by indoxyl sulfate was suppressed by the antioxidant, N-acetylcysteine. An EGFR inhibitor, AG1478, repressed the enhancement of Ang II-induced cellular effects by indoxyl sulfate. Taken together, these findings indicate that indoxyl sulfate enhances Ang II signaling through reactive oxygen species-induced EGFR expression.

Significance: The actions of indoxyl sulfate including crosstalk with Ang II signaling may be closely involved in the pathogenesis of CKD associated with arteriosclerosis.