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

ABSTRACT

Indoxyl sulfate (IS) induces fibrosis and inflammation in kidneys via oxidative stress through the induction of transforming growth factor-ß1 (TGF-ß1) 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-ß1, and MCP-1 in proximal tubular cells. The effects of IS on the expression of AHR, CYP1A1, TGF-ß1, and MCP-1 were studied using normotensive rats and hypertensive rats. The effects of IPA on IS-induced expression of AHR, CYP1A1, TGF-ß1, 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-ß1, and MCP-1 in the tubular cells of rat kidneys. IPA significantly suppressed IS-induced mRNA and protein expression of AHR, CYP1A1, TGF-ß1, 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-ß1, and MCP-1 in HK-2 cells. In conclusion, IPA suppressed the IS-induced expression of AHR, CYP1A1, TGF-ß1, 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.