NOS2 and periodontitis: Periodontitis-challenged group expressed a significant increase in the mRNA levels of TNF-α (P<0.001), IL-1β (P<0.0000001), COX-2 (P<0.000004), iNOS (p< 0.007), RANK (P<0.036), and RANK-L (P<0.05), when compared to naive group (Fig 6A–6F).