Cryptoporus volvatus polysaccharides attenuate LPS-induced expression of pro-inflammatory factors via the TLR2 signaling pathway in human alveolar epithelial cells

Abstract

Context: Cryptoporus volvatus (Peck) Hubb grows wild in China, and its fruiting bodies have been used traditionally to treat asthma and bronchitis.Objectives: This study evaluates the anti-inflammatory effect of Cryptoporus polysaccharides (CP) extracted from fruiting bodies of C. volvatus on lipopolysaccharide (LPS)-induced pro-inflammatory factors and the signaling pathways involved in human alveolar epithelial cells.Materials and methods: To evaluate the effects of CP on LPS-induced pro-inflammatory factors, A549 cells were pre-incubated with CP 1, 10, and 100 μg/ml for 1 h and then stimulated with LPS 10 μg/ml for 24 h. The expression of pro-inflammatory factors monocyte chemoattractant protein-1 (MCP-1), tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), Toll-like receptor 2 (TLR2), and phosphorylation of ERK1/2, p38, and NF-κB p65 were measured by q-PCR, ELISA, and western blotting.Results: CP decreased LPS-induced mRNA expression of MCP-1, TNF-α, and IL-1β (IC50 = 83.3, 85.2, and 91.6 μg/ml, respectively) and their correspondent protein expression (IC50 = 88.6, 76.4, and 81.6 μg/ml, respectively). Investigation of potential mechanisms indicated that CP 100 μg/ml reduced LPS-induced expression of TLR2 mRNA (66.9%, p < 0.01) and protein (63.2%, p < 0.01) that was a result of the decreased pro-inflammatory factors. LPS induction increased the expression of TLR2 and the phosphorylation of p38 and ERK1/2, NF-kB p65 concomitantly. CP 100 μg/ml inhibited the LPS-induced phosphorylation of the signaling proteins (p < 0.05).Conclusions: This suggests that CP pretreatment down-regulates LPS-mediated inflammation in lung epithelial cells. This study further confirmed that CP is a potential anti-inflammatory drug for the treatment of airway inflammatory diseases.