ABSTRACT
Dendrobium officinale can serve as Chinese medicinal material effective in nourishing yin, clearing heat, and producing fluid, and is used to treat throat diseases, but its active substances and mechanism are not clear. To clarify the active fraction and underlying mechanism of D. officinale against chronic pharyngitis(CP), the present study induced a CP model in rats by pepper water combined with low-concentration ammonia, and crude polysaccharides of D. officinale(DOP), non-polysaccharides of D. officinale(DON), and total extract of D. officinale(DOT)(0.33 g·kg~(-1), calculated according to the crude drug) were administered by gavage for six weeks. The changes in oral secretions and pharyngeal conditions of rats with CP were observed and rated. The hematological indicators were determined by an automatic hematology analyzer. The serum levels of pro-inflammatory factors, such as tumor necrosis factor-alpha(TNF-α), interleukin 1β(IL-1β), and interleukin 6(IL-6), and T-lymphocyte cytokines, including interferon γ(IFN-γ), interleukin 4(IL-4), interleukin 17(IL-17), and transforming growth factor β1(TGF-β1) were detected by the enzyme-linked immunosorbent assay(ELISA). The proportions of CD3~+, CD4~+, and CD8~+cells in peripheral blood T lymphocyte subsets were determined by the flow cytometry. The histomorphological changes of the pharynx were observed by hematoxylin-eosin(HE) staining. The protein expression of nuclear factor-κB P65(NF-κB P65), cyclooxygenase-2(COX-2), F4/80, and monocyte chemoattractant protein-1(MCP-1) in the pharynx were detected by immunohistochemistry and Western blot. The results showed that DOP and DON could significantly relieve pharyngeal lesions, reduce white blood cells(WBC) and lymphocytes(LYMP), decrease the levels of pro-inflammatory factors TNF-α, IL-6, and IL-1β, and inhibit the protein expression of NF-κB P65, COX-2, F4/80, and MCP-1 in the pharynx. DOP was superior in reducing oral secretions and serum IL-17 level and inferior in increasing CD4~+/CD8~+ratio to DON. It is suggested that both polysaccharides and non-polysaccharides of D. officinale have anti-PC effects and the anti-inflammatory mechanism may be related to the regulation of T lymphocyte distribution and inhibition of the inflammatory signaling pathways mediated by NF-κB P65. The anti-inflammatory effect of DOP may be related to the regulation of Th17/Treg balance, while that of DON may be related to the regulation of the Th/Tc ratio.