In this study, cell lines including SH-SY5Y cells from the Korean Cell Line Bank (KCLB), HT-22 cells, and Neuro2a cells from the American Type Culture Collection (ATCC) were cultured in 10% fetal bovine serum, penicillin, and streptomycin-supplemented Dulbecco’s modified Eagle’s medium. Additionally, human induced pluripotent stem cells (IPSCs) were provided by the National Stem Cell Bank of Korea and cultured using an mTeSR 1 Complete Kit. Knockdown SH-SY5Y cells were established via infection of control shRNA lentivirus particle-A, hAPP shRNA lentivirus particles, and hIFITM3 shRNA lentivirus particles. M. fermentans strain PG-18 was used for the preparation and infection process. To confirm the mechanism of cell death, an annexin V/PI apoptosis assay was performed. Furthermore, to induce differentiated SH-SY5Y cells, they were treated with PMA for 7 days. The conditioned medium was prepared and treated with fresh differentiated SH-SY5Y cells. Quantification of intracellular or secreted M. fermentans DNA levels and gene expression levels were performed using various kits. Western blotting and immunocytochemistry and immunohistochemistry analysis were also performed.
