Suppression of lipopolysaccharide-induced upregulation of toll-like receptor 4 by emodin in mouse proximal tubular epithelial cells

Abstract

The aim of this study was to investigate the effects of emodin, the major component of Rheum palmatum, on lipopolysaccharide (LPS)-induced toll-like receptor 4 (TLR4) expression in cultured mouse tubular epithelial cells (TECs). The TECs were obtained from mice and incubated with LPS and/or indicated concentrations of emodin for 24 h. Cytokeratin, α-SMA and vimentin were detected using immunohistochemistry. The TLR4 protein level was detected by flow cytometry. TNFα and IL-6 protein levels were measured using an enzyme-linked immunosorbent assay (ELISA). mRNA expression of TLR4, TNFα and IL-6 was detected using a reverse-transcription polymerase chain reaction (RT-PCR). Results showed that a concentration of 102 ng/ml LPS significantly upregulated TLR4 mRNA and protein levels. TNFα and IL-6 mRNA and protein levels were also increased. Emodin (at doses of 40, 20 and 10 µM) was able to inhibit LPS-induced TLR4 protein synthesis in cultured TECs. However, TNFα and IL-6 protein expression was decreased in cells treated with emodin at concentrations of 40 and 20 µM. These results demonstrate that an elevated expression of inflammatory cytokines and TLR4 in cells stimulated with LPS, were simultaneously inhibited by emodin. Emodin is therefore able to inhibit the LPS-induced expression of TLR4 in order to downregulate TNFα and IL-6 synthesis in TECs, which may contribute to the protective effects of emodin in renal disease.

LPS Induces Hyper‐Permeability of Intestinal Epithelial Cells

“…The effect of LPS on TLR4 expression has been the object of conflicting results (Bosisio et al, ). While in some cases it was found to up‐regulate TLR4 (Muzio et al, ; Visintin et al, ; Zhu et al, ) other studies showed that LPS decreased or did not change TLR4 levels (Medvedev et al, ; Nomura et al, ). This alternating effect of LPS on TLR4 expression can be attributed to its' differential effect in different organs (Matsumura et al, ) and a result of different concentrations and time exposures protocols (Muzio et al, ; Nomura et al, ; Visintin et al, ).…”

Gene alterations in monocytes are pathogenic factors for immunoglobulin a nephropathy by bioinformatics analysis of microarray data

“…Increased TLRs, such as TLR-4, has been detected in circulating monocytes of patients with IgAN [ 31 ]. Expression of IL6 protein is also increased in mouse proximal tubular epithelial cells, accompanying by the upregulation of TLR4 mRNA [ 32 ]. IL1B, encoded by IL1B gene, is a member of interleukin 1 cytokine family and crucial for the regulation of inflammatory response [ 33 ].…”

Efficacy and Safety of Niaoduqing Particles for Delaying Moderate-to-severe Renal Dysfunction

“…[ 21 ] As the main active ingredient of rhubarb, emodin regulates lipopolysaccharide-induced toll-like receptor 4 and reduces the expression of tumor necrosis factor alpha and interleukin 6, all three being synthesized by renal tubular epithelial cells. [ 22 ] Emodin also acts as an anti-inflammatory agent by inhibiting the differentiation and maturation of dendritic cells and increasing the number of regulatory T-cells. [ 23 ] Astragaloside is a main active ingredient in traditional Chinese medicine and acts both as an anti-inflammatory and antifibrotic agent,[ 24 25 ] while salvianolic acid A has been shown to have cardiovascular protective effects.…”