Dual oxidases and hydrogen peroxide in a complex dialogue between host mucosae and bacteria

Among the host defense mechanisms against bacteria, leukocyte phagocytosis leads to their hydrogen peroxide (H2O2)-mediated destruction. The recent discovery of dual oxidase (DUOX)-dependent H2O2 generation associated with peroxidase and thiocyanate secretion at the apex of mucosal cells has been similarly interpreted as a killing mechanism. However, the rapid degradation of H2O2 would be expected to reduce the efficiency of this system. It has been demonstrated that H2O2 acts as a chemorepellent for bacteria, and such an effect might be sufficient to block cellular infection. Therefore, H2O2 generation might represent one of the mechanisms that allows the coexistence of mucosae with potentially harmful bacteria. Here, we discuss the possible role of DUOXes and H2O2 in interactions between host mucosae and bacteria to maintain mucosal homeostasis.