Pro-inflammatory cytokines participate in the amplification of the inflammatory response during periodontitis disease by the transcription of the inducible nitric oxide synthase (iNOS) that results in the production of high amounts of NO [30] In the present study, periodontitis-challenged rats displayed a significant increase in nitrite/nitrate levels and expressed a significant increase in the mRNA of iNOS in gingival tissue, which was reduced by the treatment with P. floribundum (10 mg/kg). The gene discussed is NOS2; the disease is periodontitis.