FMO5 and infection: In the present study, the ROS-specific fluorescent staining assay confirmed that infection with L. interrogans caused a rapid increase in ROS in J774A.1 and THP-1 cells, which confirmed the results reported by Hu W, et al [12] and Marangoni A [19], with more significant up-regulation of ROS in J774A.1 cells, and the increase could be significantly inhibited by the NADPH oxidase inhibitor apocynin.