Indoxyl sulfate suppresses endothelial progenitor cell-mediated neovascularization

Patients with chronic kidney disease have an increased prevalence of peripheral arterial disease. Endothelial progenitor cells (EPC) are pivotal in neovascularization, but their role in mediating peripheral arterial disease in chronic kidney disease is not fully known. Here we studied the impact of indoxyl sulfate, a protein-bound uremic toxin, on EPC function in response to tissue ischemia or cell hypoxia in mice that underwent subtotal nephrectomy or sham operation. At 16 weeks, unilateral hindlimb ischemia was induced in all. Four weeks later, subtotal nephrectomy mice had significantly increased plasma levels of indoxyl sulfate, reduced reperfusion, decreased EPC mobilization, and impaired neovascularization in ischemic hindlimbs compared with control mice. Treatment with AST-120, an oral adsorbent of uremic toxins, reversed these changes. Ischemia-induced protein expression including phospho-eNOS, phospho-STAT3, interleukin-10, and VEGF were significantly decreased in ischemic hindlimbs of subtotal nephrectomy mice versus control mice; all effects were reversed by AST-120. Subtotal nephrectomy mice fed a diet with indole for 12 weeks resulted in impaired neovascularization in ischemic hindlimbs; also reversed by AST-120. In cultured human EPCs, VEGF expression was increased in hypoxia through HIF-1 alpha and interleukin-10/STAT3 signaling; effects suppressed by pretreatment with indoxyl sulfate. Moreover, indoxyl sulfate markedly attenuated hypoxia-induced EPC migration and tube formation. Thus, indoxyl sulfate may be a therapeutic target for EPC-rescue of impaired neovascularization in patients with chronic kidney disease and peripheral arterial disease.