NOS2 and periodontitis: The bacterial pathogen is known to play a critical role in the initiation of inflammatory processes in periodontal tissues and host immune response by releasing several inflammatory mediators such as proinflammatory cytokines, prostaglandin E2 (PGE2), and reactive oxygen species (ROS), as well as upregulating periodontitis-related gene expression including inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), and matrix metalloproteinases (MMPs) [6–9].