Salidroside regulates inflammatory pathway of alveolar macrophages by influencing the secretion of miRNA-146a exosomes by lung epithelial cells

The purpose of this study was to explore the investigative mechanism of salidroside (SAL) on LPS-induced acute lung injury (ALI)/acute respiratory distress syndrome (ARDS). The exosomes from RLE-6TN are extracted and identified by transmission electron microscopy, particle size analysis and protein marker detection, and co-cultured with NR8383 cells. The ALI/ARDS model of SD rats was established by LPS (10 mg/kg) intratracheal instillation. Following a four-hour intratracheal instillation of LPS, 50 mu l of RLE-6TN exosomes were injected through the tail vein. After that, SAL and miR-146a antagomir were injected into the tail vein for 72 h, respectively. As the changes of HE stain, body weight and ALI score are observed. The expression of miR-146a, TLR4, NF-kB, IRAK1, TRAF6 and their related proteins were detected by RT-PCR and Western blot, respectively. TNF-alpha, IL-6, IL-8 and IL-1 beta inflammatory factors were detected by ELISA. The expression of miR-146a, NF-kB, IRAK, TRAF6 and related inflammatory factors in LPS-induced NR8383 was significantly higher than that in the control group, while SAL has greatly reduced the expression of TLR4 mediated NF-kB inflammatory pathway and related inflammatory factors. SAL can significantly improve the LPS-induced lung morphological abnormalities, slowed down the rate of weight loss in rats, and reducing the ALI score. The expression trend of NF-kB, IRAK, TRAF6 and related inflammatory factors in rats' lung tissues was consistent with that in NR8383 cells. SAL has a protective effect on ALI/ARDS caused by sepsis, which is likely to be developed to a potential treatment for the disease. To sum up, this study provides a new theoretical basis for the treatment of ALI/ARDS with SAL.