The Nox2 NADPH oxidase regulates neutrophilic inflammation in the oral cavity

The leukocyte NADPH oxidase 2 (NOX2) is an important regulator of inflammatory responses, independent of its antimicrobial activity. Inactivating mutations in NOX2 cause chronic granulomatous disease (CGD), a severe immunodeficiency associated with recurrent infections and dysregulated neutrophilic inflammation. Recurrent oral ulcers, stomatitis, gingivitis, and other inflammatory issues affecting the oral mucosa have been observed in patients with CGD; however, the underlying mechanisms are not known. Here, we present evidence that the extensive inflammatory destruction of oral mucosal tissues observed in Nox2-deficient or Cybb ^KO mice was not caused by impaired antimicrobial surveillance against oral pathobionts but instead resulted from a cell-intrinsic dysregulation of neutrophil inflammatory responses. Transcriptional and cellular profiling of oral tissues isolated from wild-type and Cybb ^KO mice showed a dominant neutrophil signature, which was accompanied by a significant upregulation of several bone-resorbing, tissue-degrading inflammatory cytokines and a reduced expression of nuclear factor erythroid 2-related factor 2 (Nrf2) regulated genes. Mechanistically, hyperinflammatory responses were mitigated by restoring Nrf2 transcriptional activity using a synthetic agonist. Thus, our studies show that Nox2 oxidase and its derived reactive oxygen species are crucial for balanced recruitment and cell-intrinsic regulation of neutrophil inflammatory responses within oral tissues in an Nrf2-dependent manner.