Abstract: Objective To investigate the effects of emodin on oxidative stress injury and microRNA-34a/silent information regulator factor 2 related enzyme 1 (miR-34a/SIRT1) axis in streptococcus pneumoniae pneumonia rat model. Methods According to random number table, sixty rats were divided into sham operation group, model group, low-dose (20 mg/kg) emodin group, middle-dose (40 mg/kg) emodin group and high-dose (80 mg/kg) emodin group, with 12 rats in each group. The model of pneumonia was established by intratracheal instillation of streptococcus pneumoniae. At 24 h after successful modeling, the emodin intervention group was intraperitoneally injected with emodin solution once a day for 7 days. HE staining was used to detect the pathological changes of lung tissue. Enzyme-linked immunosorbent assay (ELISA) was used to detect the levels of tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6) and glutathione peroxidase (GSH-Px). UV-VIS spectrophotometer was used to detect the levels of superoxide dismutase (SOD) and malondialdehyde (MDA). The levels of miR-34a and SIRT1 mRNA in lung tissue were detected by qPCR. The expression of SIRT1 protein was detected by Western blot assay. Results In the sham operation group, the lung tissue was normal without obvious pathological changes. In the model group, it was found that the alveoli collapsed and a large number of inflammatory cells infiltrated. In the low, middle and high dose emodin groups, the inflammatory lesions of lung tissue were alleviated. Compared with those in the sham operation group, the levels of TNF-α, IL-6, MDA and miR-34a were significantly higher in the model group (P <0.05), and the levels of SOD, GSH-Px and SIRT1 mRNA and protein in lung tissue were significantly lower (P < 0.05). Compared with those in the model group, the levels of TNF- α, IL-6, MDA and miR-34a were significantly lower in the middle and high-dose emodin groups (P < 0.05), and the levels of SOD, GSH-Px and SIRT1 mRNA and protein in lung tissue were significantly higher (P < 0.05), in which the high-dose emodin group showed the most obvious changes. Conclusion Emodin can reduce inflammatory reaction and oxidative stress injury in rat model of streptococcus pneumoniae pneumonia, which may be related to the regulation of miR-34a/SIRT1 axis.

Key words: emodin, pneumonia, pneumococcal, rats, Sprague-Dawley, oxidative stress, microRNA-34a/silent information regulator factor 2 related enzyme 1 axis