Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2017 Nov;79(4):477-486.
doi: 10.18999/nagjms.79.4.477.

Indole-3-propionic acid suppresses indoxyl sulfate-induced expression of fibrotic and inflammatory genes in proximal tubular cells

Maimaiti Yisireyili  1 , Kyosuke Takeshita  1 , Shinichi Saito  2 , Toyoaki Murohara  1 , Toshimitsu Niwa  3
Affiliations

Indole-3-propionic acid suppresses indoxyl sulfate-induced expression of fibrotic and inflammatory genes in proximal tubular cells

Maimaiti Yisireyili et al. Nagoya J Med Sci. 2017 Nov.

Abstract

Indoxyl sulfate (IS) induces fibrosis and inflammation in kidneys via oxidative stress through the induction of transforming growth factor-β1 (TGF-β1) and monocyte chemotactic protein-1 (MCP-1). Furthermore, IS is a potent endogenous agonist for aryl hydrocarbon receptor (AHR), which regulates the transcription of genes such as cytochrome P450 (CYP) 1A1. Indole-3-propionic acid (IPA) is an antioxidant and has been reported to be neuroprotective. We determined whether IPA suppresses IS-induced expression of AHR, CYP1A1, TGF-β1, and MCP-1 in proximal tubular cells. The effects of IS on the expression of AHR, CYP1A1, TGF-β1, and MCP-1 were studied using normotensive rats and hypertensive rats. The effects of IPA on IS-induced expression of AHR, CYP1A1, TGF-β1, and MCP-1 were studied using proximal tubular cells (HK-2). Furthermore, the effects of IPA on IS-induced expression and phosphorylation of signal transducer and activator of transcription 3 (Stat3) were studied in HK-2 cells. Administration of IS induced the expression of AHR, CYP1A1, TGF-β1, and MCP-1 in the tubular cells of rat kidneys. IPA significantly suppressed IS-induced mRNA and protein expression of AHR, CYP1A1, TGF-β1, and MCP-1 in HK-2 cells. IPA suppressed the IS-induced expression and phosphorylation of Stat3 in HK-2 cells. Furthermore, knockdown of Stat3 inhibited the IS-induced mRNA and protein expression of AHR, CYP1A1, TGF-β1, and MCP-1 in HK-2 cells. In conclusion, IPA suppressed the IS-induced expression of AHR, CYP1A1, TGF-β1, and MCP-1 through suppression of Stat3 in proximal tubular cells. Thus, IPA suppresses IS-induced expression of fibrotic and inflammatory genes in proximal tubular cells.

Keywords: TGF-β1; aryl hydrocarbon receptor; indole-3-propionic acid; indoxyl sulfate; proximal tubular cells.

PubMed Disclaimer

Figures

Fig. 1
Fig. 1
Immunostaining of AHR, CYP1A1, TGF-β1, and MCP-1 in rat kidney Immunostaining of AHR (a), CYP1A1 (b), TGF-β1 (c), and MCP-1 (d) (× 200), and quantitative data of AHR (e), CYP1A1 (f), TGF-β1 (g), and MCP-1 (h)-positive areas in the kidneys of DN, DN+IS, DH, and DH+IS rats (mean ± SE, n=8). *P<0.01 vs DN, **P<0.001 vs DN, ***P<0.0001 vs DN, #P<0.001 vs DH.
Fig. 2
Fig. 2
IPA suppresses the IS-induced expression of AHR, CYP1A1, TGF-β1, and MCP-1 in HK-2 cells. Serum starved HK-2 cells were pretreated with 1000 μmol/L of IPA for 30 min before incubation with IS (250 μmol/L) for 24 h. The mRNA and protein expressions of AHR (a, e), CYP1A1 (b, f) , TGF-β1 (c, g), and MCP-1 (d, h) in cultured HK-2 cells (mean ± SE, n=4). The size of TGF-β1 was 20 kDa, an active (mature) form. *P<0.01, **P<0.001 vs control, #P<0.01 vs IS-treated cells.
Fig. 3
Fig. 3
IPA suppresses the IS-induced expression of Stat3 in HK-2 cells. Immunostaining of phospho-Stat3 (Tyr705) and Stat3 in the kidneys of DN, DN+IS, DH, and DH+IS rats (× 200) (a, b). Serum-starved HK-2 cells were incubated with or without 1000 μmol/L of IPA for 30 min, followed by incubation with IS (250 μmol/L) for the indicated times (min). (c) Phosphorylated Stat3 (Tyr705) and total Stat3 protein expression in IS-treated HK-2 cells (mean ± SE, n=4). *P<0.01 vs 0 min. (d) phosphorylated Stat3 (Tyr705) and total Stat3 protein expressions in (IPA+IS) -treated HK-2 cells (mean ± SE, n=4). *P<0.01 vs 0 min. (e) Comparison of the ratio of phosphorylated Stat3 (Tyr705) and total Stat3 protein expressions at 3 and 5 min between IS-treated HK-2 cells and (IPA+IS)-treated HK-2 cells (mean ± SE, n=4). †P<0.001 vs IS at 3 min, ‡P<0.001 vs IS at 5 min. (f) Protein expression of Stat3 in cultured HK-2 cells. Serum starved HK-2 cells were pretreated with 1000 μmol/L IPA for 30 min before incubation with IS for 24 h (mean ± SE, n=4). *P<0.01, **P<0.001 vs control, #P<0.01 vs IS-treated cells.
Fig. 4
Fig. 4
Stat3 siRNA suppresses the IS-induced expression of AHR, CYP1A1, TGF-β1, and MCP-1 in HK-2 cells. HK-2 cells were transfected with or without Stat3 siRNA (10 nmol/L) and then serum starved for 24 h, followed by incubation with IS (250 μmol/L) for 24 h. The mRNA and protein expressions of AHR (a, e), CYP1A1 (b, f) , TGF-β1 (c, g), and MCP-1 (d, h) in cultured HK-2 cells (mean ± SE, n=4). *P<0.01, **P<0.001 vs control, #P<0.01, ##P<0.001 vs IS-treated cells. Ctrl: control.
See this image and copyright information in PMC

Similar articles

See all similar articles

Cited by

See all "Cited by" articles

References

    1. Niwa T, Ise M. Indoxyl sulfate, a circulating uremic toxin, stimulates the progression of glomerular sclerosis. J Lab Clin Med, 1994; 124: 96-104. - PubMed
    1. 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. - PubMed
    1. Miyazaki T, Ise M, Seo H, Niwa T. Indoxyl sulfate increases the gene expressions of TGF-beta1, TIMP-1 and pro-alpha 1(I) collagen in uremic rat kidneys. Kidney Int, 1997; S62: S15-22. - PubMed
    1. Niwa T, Indoxyl sulfate is a nephro-vascular toxin. J Ren Nutr, 2010; 20(Suppl 1): S2-S6. - PubMed
    1. Shimizu H, Bolati D, Adijiang A, Enomoto A, Nishijima F, Dateki M, et al. 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. - PubMed

Publication types

LinkOut - more resources