OBJECTIVE To observe the anti-inflammatory effect of Houttuynia extract on rats with Mycoplasma pneumoniae infection and analyze the mechanisms of action.

METHODS The Wistar rats of SPF grade were divided into the blank group, the M.pneumoniae infection model group, the low-dose houttuynia extract group and the high-dose houttuynia extract group, with 9 rats in each group. The blank group and the model group were only treated with normal saline for gavage, the low-dose group and the high-dose group were respectively treated with 125 mg/kg and 500 mg/kg of houttuynia extract for gavage. The levels of peripheral blood transforming growth factor-β(TGF-β), Krebs Von den Lungen-6 (KL-6), surface active protein D (SP-D), inflammatory factors and the relative expression levels of Toll-like receptor 4 (TLR4), myeloid differentiation factor 88 (MyD88) and nuclear factor κB (NF-κB) mRNA were detected after the treatments for 7 consecutive days; the expression levels of TLR4, MyD88 and NF-κB proteins in lung tissues were detected by Western Blot.

RESULTS The levels of TGF-β, KL-6, SP-D, IL-13, TNF-α, the expression levels of TLR4, MyD88, NF-κB mRNA, and the expression levels of TLR4, MyD88 and NF-κB proteins were higher in the model group, the low-dose houttuynia extract group and the high-dose houttuynia extract group than in the blank group, while the IL-12 level was lower in the model group, the low-dose houttuynia extract group and the high-dose houttuynia extract group than in the blank group (P < 0.05). The levels of TGF-β, KL-6, SP-D, IL-13, TNF-α, the expression levels of TLR4, MyD88, NF-κB mRNA, and the expression levels of TLR4, MyD88 and NF-κB proteins were lower in the high-dose houttuynia extract group than in the model group and the low-dose houttuynia extract group; the IL-12 level of the high-dose houttuynia extract group was higher than that of the model group and the low-dose houttuynia extract group(P < 0.05).

CONCLUSION As a treatment intervention, Houttuynia extract may alleviate the local inflammatory response or even the inflammatory responses in bronchia and lung tissues so as to achieve favorable intervention effect.