NADPH oxidase-dependent reactive oxygen species mediate amplified TLR4 signaling and sepsis-induced mortality in Nrf2-deficient mice.
Sepsis syndrome is characterized by a dysregulated inflammatory response to infection. NADPH oxidase-dependent reactive oxygen species (ROS) play significant roles in the pathophysiology of sepsis. We previously showed that disruption of Nrf2, a master regulator of antioxidant defenses, caused a dysregulation of innate immune response that resulted in greater mortality in a polymicrobial sepsis and LPS shock model; however, the underlying mechanisms are unclear. In the current study, compared with wild-type (Nrf2(+/+)) macrophages, we observed greater protein kinase C-induced NADPH oxidase-dependent ROS generation in Nrf2-disrupted (Nrf2(-/-)) macrophages that was modulated by glutathione levels. To address the NADPH oxidase-mediated hyperinflammatory response and sepsis-induced lung injury and mortality in Nrf2(-/-) mice, we used double knockout mice lacking Nrf2 and NADPH oxidase subunit, gp91(phox) (Nrf2(-/-)//gp91(phox-/-)). Compared with Nrf2(+/+) macrophages, LPS induced greater activation of TLR4 as evident by TLR4 surface trafficking and downstream recruitment of MyD88 and Toll/IL-1R domain-containing adaptor in Nrf2(-/-) macrophages that was diminished by ablation of gp91(phox). Similarly, phosphorylation of IkappaB and IFN regulatory factor 3 as well as cytokine expression was markedly higher in Nrf2(-/-) macrophages; whereas, it was similar in Nrf2(+/+) and Nrf2(-/-)//gp91(phox-/-). In vivo studies showed greater LPS-induced pulmonary inflammation in Nrf2(-/-) mice that was significantly reduced by ablation of gp91(phox). Furthermore, LPS shock and polymicrobial sepsis induced early and greater mortality in Nrf2(-/-) mice; whereas, Nrf2(-/-)//gp91(phox-/-) showed prolonged survival. Together, these results demonstrate that Nrf2 is essential for the regulation of NADPH oxidase-dependent ROS-mediated TLR4 activation and lethal innate immune response in sepsis.
Kong
Xiaoni
X
Department of Environmental Health Sciences, Bloomberg School of Public Health, The Johns Hopkins University, Baltimore, MD 21205, USA.
Thimmulappa
Rajesh
R
Kombairaju
Ponvijay
P
Biswal
Shyam
S
D000818:Animals; D018836:Inflammation Mediators / Q000502:physiology; D008070:Lipopolysaccharides / Q000037:antagonists & inhibitors / Q000633:toxicity; D008168:Lung / Q000276:immunology / Q000473:pathology; D016676:Macrophages, Alveolar / Q000276:immunology / Q000378:metabolism / Q000473:pathology; D017737:Macrophages, Peritoneal / Q000276:immunology / Q000378:metabolism / Q000473:pathology; D008562:Membrane Glycoproteins / Q000172:deficiency / Q000235:genetics; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D000074662:NADPH Oxidase 2; D019255:NADPH Oxidases / Q000037:antagonists & inhibitors / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D051267:NF-E2-Related Factor 2 / Q000172:deficiency* / Q000235:genetics* / Q000502:physiology; D017382:Reactive Oxygen Species / Q000037:antagonists & inhibitors / Q000378:metabolism*; D018805:Sepsis / Q000276:immunology* / Q000378:metabolism* / Q000401:mortality; D015398:Signal Transduction / Q000276:immunology*; D051197:Toll-Like Receptor 4 / Q000378:metabolism / Q000502:physiology*
D018836:Inflammation Mediators; D008070:Lipopolysaccharides; D008562:Membrane Glycoproteins; D051267:NF-E2-Related Factor 2; C495636:Nfe2l2 protein, mouse; D017382:Reactive Oxygen Species; C493487:Tlr4 protein, mouse; D051197:Toll-Like Receptor 4; C488842:Cybb protein, mouse; D000074662:NADPH Oxidase 2; D019255:NADPH Oxidases