Background/Aim: Klotho, an anti-aging gene, is expressed in the kidneys, and its renal expression is decreased in chronic kidney disease (CKD). The present study aimed to examine whether renal expression of Klotho is regulated by indoxyl sulfate, a uremic toxin, using rat kidneys and human proximal tubular cells (HK-2). Methods: The effect of indoxyl sulfate on renal expression of Klotho was examined using (1) Dahl salt-resistant normotensive rats (DN), (2) Dahl salt-resistant normotensive indoxyl sulfate-administered rats (DN+IS), (3) Dahl salt-sensitive hypertensive rats (DH), and (4) Dahl salt-sensitive hypertensive indoxyl sulfate-administered rats (DH+IS). The effects of indoxyl sulfate, inhibitors of nuclear factor-ĸB (NF-ĸB) and an antioxidant on the expression of Klotho in HK-2 cells were examined. Results: DH+IS and DN+IS rats showed decreased expression of Klotho mRNA in the kidneys as compared with DH and DN rats, respectively. Indoxyl sulfate suppressed the expression of Klotho mRNA and protein in HK-2 cells, whereas an antioxidant, N-acetylcysteine, and NF-ĸB inhibitors, pyrrolidine dithiocarbamate and isohelenin, alleviated these effects. Conclusions: Indoxyl sulfate downregulates Klotho expression in kidneys through production of reactive oxygen species and activation of NF-ĸB in proximal tubular cells. Indoxyl sulfate may be involved in reduced renal expression of Klotho in CKD.

Keywords:
Reactive oxygen species, Nuclear factor-ŠB, Proximal tubular cells, Chronic kidney disease, Indoxyl sulfate, Uremic toxin
1.
Kuro-o M, Matsumura Y, Aizawa H, Kawaguchi H, Suga T, Utsugi T, Ohyama Y, Kurabayashi M, Kaname T, Kume E, Iwasaki H, Iida A, Shiraki-Iida T, Nishikawa S, Nagai R, Nabeshima Y: Mutation of the mouse Klotho gene leads to a syndrome resembling aging. Nature 1997;390:45–51.
2.
Kuro-o M: Klotho and aging. Biochim Biophys Acta 2009;1790:1049–1058.
3.
Wang Y, Sun Z: Current understanding of Klotho. Ageing Res Rev 2009;8:43–51.
4.
Aizawa H, Saito Y, Nakamura T, Inoue M, Imanari T, Ohyama Y, Matsumura Y, Masuda H, Oba S, Mise N, Kimura K, Hasegawa A, Kurabayashi M, Kuro-o M, Nabeshima Y, Nagai R: Downregulation of the Klotho gene in the kidney under sustained circulatory stress in rats. Biochem Biophys Res Commun 1998:249:865–871.
5.
Koh N, Fujimori T, Nishiguchi S, Tamori A, Shiomi S, Nakatani T, Sugimura K, Kishimoto T, Kinoshita S, Kuroki T, Nabeshima Y: Severely reduced production of Klotho in human chronic renal failure kidney. Biochem Biophys Res Commun 2001;280:1015–1020.
6.
Miyazaki T, Ise M, Seo H, Niwa T: Indoxyl sulfate increases the gene expression of TGF-β1, TIMP-1 and pro-α(I) collagen in uremic rat kidneys. Kidney Int Suppl 1997;63:S15–S22.
7.
Niwa T, Ise M: Indoxyl sulfate, a circulating uremic toxin, stimulates the progression of glomerular sclerosis. J Lab Clin Med 1994;124:96–104.
8.
Niwa T, Ise M, Miyazaki T: Progression of glomerular sclerosis in experimental uremic rats by administration of indole, a precursor of indoxyl sulfate. Am J Nephrol 1994;14:207–212.
9.
Enomoto A, Takeda M, Tojo A, Sekine T, Cha SH, Khamdang S, Takayama F, Aoyama I, Nakamura S, Endou H, Niwa T: Role of organic anion transporters in the tubular transport of indoxyl sulfate and the induction of its nephrotoxicity. J Am Soc Nephrol 2002;13:1711–1720.
10.
Motojima M, Hosokawa A, Yamato H, Muraki T, Yoshioka T: Uremic toxins of organic anions up-regulate PAI-1 expression by induction of NF-ĸB and free radical in proximal tubular cells. Kidney Int 2003;63:1671–1680.
11.
Shimizu H, Bolati D, Adijiang A, Enomoto A, Nishijima F, Dateki M, Niwa T: Senescence and dysfunction of proximal tubular cells are associated with activated p53 expression by indoxyl sulfate. Am J Physiol Cell Physiol 2010;299:C1110–C1117.
12.
Lekawanvijit S, Adrahtas A, Kelly DJ, Kompa AR, Wang BH, Krum H: Does indoxyl sulfate, a uraemic toxin, have direct effects on cardiac fibroblasts and myocytes? Eur Heart J 2010;31:1771–1779.
13.
Tumur Z, Shimizu H, Enomoto A, Miyazaki H, Niwa T: Indoxyl sulfate upregulates expression of ICAM-1 and MCP-1 by oxidative stress-induced NF-kappaB activation. Am J Nephrol 2010;31:435–441.
14.
Muteliefu G, Enomoto A, Niwa T: Indoxyl sulfate promotes proliferation of human aortic smooth muscle cells by inducing oxidative stress. J Ren Nutr 2009;19:29–32.
15.
Shimizu H, Hirose Y, Nishijima F, Tsubakihara Y, Miyazaki H: ROS and PDGF-β receptors are critically involved in indoxyl sulfate actions that promote vascular smooth muscle cell proliferation and migration. Am J Physiol Cell Physiol 2009;297:C389–C396.
16.
Adijiang A, Goto S, Uramoto S, Nishijima F, Niwa T: Indoxyl sulphate promotes aortic calcification with expression of osteoblast-specific proteins in hypertensive rats. Nephrol Dial Transplant 2008;23:1892–1901.
17.
Muteliefu G, Enomoto A, Jiang P, Takahashi M, Niwa T: Indoxyl sulphate induces oxidative stress and the expression of osteoblast-specific proteins in vascular smooth muscle cells. Nephrol Dial Transplant 2009;24:2051–2058.
18.
Taki K, Tsuruta Y, Niwa T: Indoxyl sulfate and atherosclerotic risk factors in hemodialysis patients. Am J Nephrol 2007;27:30–35.
19.
Miyazaki T, Aoyama I, Ise M, Seo H, Niwa T: An oral sorbent reduces overload of indoxyl sulfate and gene expression of TGF-β1 in uremic rat kidneys. Nephrol Dial Transplant 2000;15:1773–1781.
20.
Adijiang A, Niwa T: An oral sorbent, AST-120, increases Klotho expression and inhibits cell senescence in the kidney of uremic rats. Am J Nephrol 2010;31:160–164.
21.
Adijiang A, Shimizu H, Higuchi Y, Nishijima F, Niwa T: Indoxyl sulfate reduces Klotho expression and promotes senescence in the kidneys of hypertensive rats. J Ren Nutr 2011;21:105–109.
22.
Adijiang A, Higuchi Y, Nishijima F, Shimizu H, Niwa T: Indoxyl sulfate, a uremic toxin, promotes cell senescence in aorta of hypertensive rats. Biochem Biophys Res Commun 2010;399:637–641.
23.
Hwang I, Choi YS, Jeon MY, Jeong S: NF-ĸB p65 represses β-catenin-activated transcription of cyclin D1. Biochem Biophys Res Commun 2010;403:79–84.
24.
Zhang H, Li Y, Fan Y, Wu J, Zhao B, Guan Y, Chien S, Wang N: Klotho is a target gene of PPAR-gamma. Kidney Int 2008;74:732–739.
25.
Ruan H, Pownall HJ, Lodish HF: Troglitazone antagonizes tumor necrosis factor-alpha-induced reprogramming of adipocyte gene expression by inhibiting the transcriptional regulatory functions of NF-ĸB. J Biol Chem 2003;278:28181–28192.
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2011
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