Following ulcer onset, decreased levels of NO, iNOS, PGE2, and MTL, alongside increased levels of TNF-α, IL-6, and MDA, directly induce a reduction in the abundance of bacteria, including Rothia, Streptococcus, Corynebacterium, Globicatella, Romboutsia, and Lactobacillus, with this effect being more pronounced in the oral cavity. Here, NOS2 is linked to ulcer disease.