Polysaccharides, the active component of Dendrobiumofficinale flower, ameliorates chronic pharyngitis in rats via TLR4/NF-κb pathway regulation

This study was to evaluate beneficial effects of polysaccharides from D. officinale flower (DOFP) on CP and its potential mechanisms.

DOFP exerts significant ameliorating effects on CP and it likely acts by inhibiting LPS/TLR4-associated inflammatory mediator activation and reducing excessive secretion of mucus by repairing the intestinal barrier in CP rats.

Chemical characterization of DOFP, including polysaccharide content and monosaccharide composition, structural characterization using Fourier transform infrared spectroscopy were performed. A CP model was established in rats by administering a mixture of Chinese Baijiu and chili pepper liquid, combined with low-concentration ammonia spraying. The general states, amount of oral secretion, and apparent state of the pharynx of CP rats were observed during the period of DOFP administration. Furthermore, hemorheological parameters were measured using an automatic hematology analyzer. The levels of tumor necrosis factor-α (TNF-α), interleukin 1β (1L-1β), lipopolysaccharide (LPS), and D-lactate (D-LA) in the serum were measured by enzyme-linked immunosorbent assay. Morphological changes in the pharynx and colon were observed by hematoxylin-eosin staining. The expression of nuclear factor-κB p65 (NF-κB p65), p-NF-κB p65, cyclooxygenase-2 (COX-2), interleukin 1β（IL-1β）and mucin 5AC (MUC5AC) in the pharynx,Claudin-1, Occludin, and interleukin 6 (IL-6) in the colon was detected by immunohistochemistry and Western Blot. The mRNA expression of TLR4, COX-2, and IL-1β in the pharynx were determined using reverse transcription quantitative real-time PCR.

In this study, DOFP with a total polysaccharide content of 71.44% and a composition of D-mannose, galacturonic acid, glucose, galactose, and arabinose in a molar ratio of 3.95:2.19:1.00:0.74:1.30, was isolated from the flowers of D. officinale. DOFP improved the general state and exhibited significant effects on reducing oral secretion, alleviating pharyngeal injury, suppressing inflammatory cell infiltration in the pharynx, decreasing the serum levels of TNF-α and IL-1β, and reducing the number of white blood cells and lymphocytes in the model rats. Moreover, the expressions of TLR4, p-NF-κB p65, COX-2, IL-1β and MUC5AC in the pharynx of model rats were obviously inhibited. In addition, the levels of LPS, D-LA in the serum and the protein expression of IL-6 in the colon were downregulated when the protein expression of Occludin and Claudin-1 in the colon were upregulated. Conclusions: DOFP exerts significant ameliorating effects on CP and it likely acts by inhibiting LPS/TLR4-associated inflammatory mediator activation and reducing excessive secretion of mucus by repairing the intestinal barrier in CP rats.