Using ROS as a Second Messenger, NADPH Oxidase 2 Mediates Macrophage Senescence via Interaction with NF-κB during Pseudomonas aeruginosa Infection

Pseudomonas aeruginosa (PA) is one of the most prevalent pathogens that cause nosocomial infection in critical patients. However, the mechanisms underlying macrophage growth status and functional changes during PA infection are yet unknown. In the present study, NADPH oxidase, gp91(phox) (NOX2) mediated macrophage to senescence in a PAO1 colony-dependent manner. gp91(phox) might regulate the senescence process through mutual interaction with the NF-κB pathway. During infection, the overexpression or downregulation of gp91(phox) in macrophage could affect the nuclear activity of NF-κB p65, while the downregulation of NF-κB p65 led to a suppressed expression of gp91(phox). Reactive oxygen species (ROS) served as the second messenger between both molecules as the ROS inhibitor, N-acetylcysteine (NAC), could partially restore these changes. Consequently, the level of ROS and inflammatory cytokines, including IL-6 and TNFα, elevated during PAO1 infection, and their production altered as a result of the genetic manipulation of gp91(phox) and NF-κB p65, as well as NAC treatment. Also, the senescent phenotypes, SA-β-gal staining and p16(ink4a), changed after genetic manipulation with gp91(phox) and NF-κB p65 and NAC treatment. The capacity of phagocytosis in macrophages was decreased during senescence. In conclusion, PA directs the macrophage towards senescence, and senescent macrophages exhibit a decreased ability of phagocytosis. This process of senescence was regulated by the interactions between NADPH oxidase gp91(phox) and NF-κB p65 via ROS as a second messenger.