Candesartan inhibits LPS-induced expression increase of toll-like receptor 4 and downstream inflammatory factors likely via angiotensin II type 1 receptor independent pathway in human renal tubular epithelial cells

The present study was to determine whether candesartan, an angiotensin II type 1 receptor blocker (ARB), exerts anti-inflammatory effects through inhibiting the toll-like receptor 4 (TLR4) pathway in human renal tubular epithelial cells (HKCs). The experiments were carried on cultured HKCs. By means of flow cytometry, Western blot, RT-PCR and ELISA techniques, the TLR4 protein, angiotensin II type 1 receptor (AT1R) and phosphorylated nuclear factor-kappa B (NF-κB) p65 protein level, mRNA levels of macrophage chemoattractant protein-1 (MCP-1) and regulated upon expression normal T cell expressed and secreted (RANTES), as well as MCP-1 and RANTES protein concentrations in conditioned media were measured. The results showed that lipopolysaccharide (LPS) upregulated the TLR4 protein level in cultured HKCs. Application of LPS increased NF-κB activation and induced release of its downstream inflammatory factors including MCP-1 and RANTES. Candesartan reversed LPS-induced upregulation of TLR4 expression, inhibited NF-κB activation, and reduced MCP-1 and RANTES release. However, knockdown on AT1R by siRNA did not change those previous effects of candesartan. These results suggest that candesartan-induced anti-inflammatory effect may be through a novel pathway, independent of AT1R.