NOS2 and infection: It was also noted that the mean mRNA levels of proinflammatory-related molecules, including interleukin-6 (Il6), tumor necrosis factor-α (Tnf) and inducible nitric oxide synthase (Nos2), in MG6 microglial cells were significantly increased after infection with P. gingivalis without change in the cell viability (Supplementary Fig. S1a–e).