NOS2 and meningitis: Nitrite/nitrate and nitric oxide metabolites are observed in the brains of meningitis patients and experimental animals [154], while nitric oxide synthases (NOS) such as NOS2 are specifically linked to BBB breakdown and augmented proinflammatory cytokine profiles in experimental PM [132,155], as well as regulating caspase-3-driven neuronal apoptosis in the hippocampus [156].