Objective: To explore the efficacy of cortex mori extract in the treatment of rats with Mycoplasma pneumonia (MP) pneumonia and its effects on high mobility group protein (HMGB-1) / Toll-like receptor 4 (TLR4) signaling pathway. Methods: Wistar male rats were randomly divided into the control group

MP pneumonia model group

azithromycin group (positive control)

and low

medium and high dose cortex mori extract groups (2

4 and 8 g/ (kg·d))

with 12 rats in each group. Except for the control group

other rats were used to establish the MP pneumonia rat model and given the corresponding doses of drugs. The total number of inflammatory cells in the bronchoalveolar lavage fluid (BALF) was counted under the microscope

the levels of inflammatory cytokines in serum were detected by enzyme-linked immunosorbent assay (ELISA)

the pathological changes of lung tissue were observed by Hematoxylin-Eosin (HE) staining

the expression levels of HMGB-1

TLR4

and p-NF-κB p65 proteins in lung tissues were determined by Western blotting and immunohistochemistry. Results: The pulmonary tissue cells of rats in the control group were arranged normally without any lesions

the pulmonary tissue of rats in the MP pneumonia model group displayed abnormalities with a large number of inflammatory cells infiltration. After the administration of cortex mori extract

the pulmonary tissue damage of rats decreased significantly

and the inflammatory cell infiltration decreased markedly. Compared with the control group

the MP pneumonia model group exhibited a significant increases in the pulmonary coefficient

total number of inflammatory cells in BALF

serum levels of interleukin (IL)-6 and tumor necrosis factor (TNF)-α

as well as the protein levels of HMGB-1

TLR4 and p-NF-κB p65 in pulmonary tissue

along with a significant decrease in IL-10 levels (P<0. 05). Compared with the model group

the above mentioned indicators of rats in each dose group of cortex mori extract and azithromycin group showed reverse trends (P<0. 05). Conclusion: Cortex mori extract may reduce inflammation by inhibiting HMGB-1/ TLR4 signaling pathway

and play a protective role in rats with MP pneumonia.