ROS in gastrointestinal inflammation: Rescue or Sabotage?

The intestine is comprised of many distinct cell types that respond to commensal microbiota or pathogens with immune tolerance and proinflammatory signals respectively. Reactive oxygen species (ROS) produced by mucosa-resident cells or by newly recruited innate immune cells are essential for antimicrobial responses and regulation of signalling pathways including processes involved in wound healing. Impaired ROS production due to inactivating patient variants in genes encoding NADPH oxidases as ROS source have been associated with Crohn's disease and pancolitis, whereas overproduction of ROS due to up-regulation of oxidases or altered mitochondrial function was linked to ileitis and ulcerative colitis. Here, we discuss recent advances in our understanding of how maintaining a redox balance is crucial to preserve gut homeostasis.