Periodontal diseases are chronic inflammatory infections associated with Gram-negative bacteria, including Porphyromonas gingivalis, Prevotella intermedia, and Actinobacillus actinomycetemcomitans, which stimulate nitric oxide (NO) production.[14] Moreover, NO is increased in inflamed gingival tissue;[15] expression of various cytokines and inducible nitric oxide (iNOS) may be involved in the inflammatory process in periodontitis. The gene discussed is NOS2; the disease is periodontitis.