Effect of salidroside on the immune function of BCG-infected macrophages

Objective·To Investigate the effects of salidroside (SAL) on the immune response of macrophages infected with BCG.Methods·RAW264.7 mouse macrophages were infected with BCG, and the experiments were divided into blank control (BCG), salidroside (SAL+BCG), isoniazid (INH+BCG), and salidroside+isoniazid (SAL+INH+BCG) groups. The effects of SAL and INH on the proliferation of RAW264.7 cells were detected by MTT colorimetric assay, and the experimental concentrations of SAL and INH were screened. After the establishment of the BCG-infected macrophage model, intracellular bacterial survival was detected by bacterial plate count and flow cytometry following salidroside pretreatment. The levels of tumor necrosis factor-α (TNF-α), interferon-γ (IFN-γ), interleukin-6 (IL-6) , and interleukin-10 (IL-10) in the culture supernatants were measured by enzyme-linked immunosorbent assay, and apoptosis levels were assessed by flow cytometry.Results·SAL at a concentration of 800 μmol/L and INH at 10 μmol/L were selected for subsequent experiments. Compared with the BCG group, SAL pretreatment for 36 h had the best effect, and the growth of BCG in macrophages in the administered group was inhibited. The inhibitory effect of the combined application of SAL and INH was obvious and statistically significant. Compared with the BCG group, SAL alone led to decreased secretion of TNF-α, IFN-γ, IL-6, and IL-10, although the differences were not statistically significant. However, the combination of SAL and INH caused a significant decrease in the levels of TNF-α, IL-6 and IL-10 in the supernatants of the cells (all P<0.05). Compared with the BCG group, in the early stage of the infection, SAL and INH were able to significantly reduce the apoptotic levels of BCG-infected RAW264.7 cells (P=0.008, P=0.032), and the combined application of SAL and INH significantly enhanced the apoptosis levels of BCG-infected RAW264.7 cells in the late stage of infection (P=0.001).Conclusion·In BCG-infected macrophages, SAL can exhibit antimycobacterial effects on the host by enhancing macrophage immune function, suppressing intracellular bacterial survival, and concurrently mitigating the inflammatory response elicited by BCG infection.