title: Nuclear factor erythroid 2-related factor 2 regulates toll-like receptor 4 innate responses in mouse liver ischemia-reperfusion injury through Akt-forkhead box protein O1 signaling network.
abstract: BACKGROUND
  Nuclear factor erythroid 2-related factor 2 (Nrf2), a master regulator of the antioxidant host defense, maintains the cellular redox homeostasis.
  
  
  METHODS
  This study was designed to investigate the role and molecular mechanisms by which Nrf2 regulates toll-like receptor (TLR)4-driven inflammation response in a mouse model of hepatic warm ischemia (90 min) and reperfusion (6 hr) injury (IRI).
  
  
  RESULTS
  Activation of Nrf2 after preconditioning of wild-type mouse recipients with cobalt protoporphyrin ameliorated liver IRI, evidenced by improved hepatocellular function (serum alanine aminotransferase levels), and preserved tissue architecture (histology Suzuki's score). In marked contrast, ablation of Nrf2 signaling exacerbated IR-induced liver inflammation and damage in Nrf2 knockout hosts irrespective of adjunctive cobalt protoporphyrin treatment. The Nrf2 activation reduced macrophage and neutrophil trafficking, proinflammatory cytokine programs, and hepatocellular necrosis or apoptosis while increasing antiapoptotic functions in IR-stressed livers. At the molecular level, Nrf2 activation augmented heme oxygenase-1 expression and Stat3 phosphorylation and promoted PI3K-Akt while suppressing forkhead box O (Foxo)1 signaling. In contrast, Nrf2 deficiency diminished PI3K-Akt and enhanced Foxo1 expression in the ischemic livers. In parallel in vitro studies, Nrf2 knockdown in lipopolysaccharide-stimulated bone marrow-stimulated bone marrow-derived macrophages (BMMs) decreased heme oxygenase-1 and PI3K-Akt yet increased Foxo1 transcription, leading to enhanced expression of TLR4 proinflammatory mediators. Moreover, pretreatment of bone marrow-derived macrophages with PI3K inhibitor (LY294002) activated Foxo1 signaling, which in turn enhanced TLR4-driven innate responses in vitro.
  
  
  CONCLUSIONS
  Activation of Nrf2 promoted PI3K-Akt, and inhibited Foxo1 activity in IR-triggered local inflammation response. By identifying a novel integrated Nrf2-Akt-Foxo1 signaling network in PI3K-dependent regulation of TLR4-driven innate immune activation, this study provides the rationale for refined therapeutic approaches to manage liver inflammation and IRI in transplant recipients.
authors.affiliation: 1 Currently, Department of Hepatobiliary-Pancreatic Surgery, Lihuili Hospital, Ningbo University School of Medicine, Ningbo, China; formerly, Division of Liver and Pancreas Transplantation, Department of Surgery, Dumont-UCLA Transplant Center, Los Angeles, CA. 2 Department of Hepatobiliary-Pancreatic Surgery, Lihuili Hospital, Ningbo University School of Medicine, Ningbo, China. 3 Division of Liver and Pancreas Transplantation, Department of Surgery, Dumont-UCLA Transplant Center, Los Angeles, CA. 4 Department of Medical Biochemistry, Tohoku University Graduate School of Medicine, Aoba-ku, Sendai, Japan. 5 Department of Pathology and Laboratory Medicine, David Geffen School of Medicine at UCLA, Los Angeles, CA. 6 Address correspondence to: Jerzy W. Kupiec-Weglinski, M.D., Ph.D., Dumont-UCLA Transplant Center 77-120 CHS, 10833 Le Conte Ave, Los Angeles, CA.
authors.forename: Jing
authors.initials: J
authors.lastname: Huang
authors.forename: Shi
authors.initials: S
authors.lastname: Yue
authors.forename: Bibo
authors.initials: B
authors.lastname: Ke
authors.forename: Jianjun
authors.initials: J
authors.lastname: Zhu
authors.forename: Xiu-da
authors.initials: XD
authors.lastname: Shen
authors.forename: Yuan
authors.initials: Y
authors.lastname: Zhai
authors.forename: Masayuki
authors.initials: M
authors.lastname: Yamamoto
authors.forename: Ronald W
authors.initials: RW
authors.lastname: Busuttil
authors.forename: Jerzy W
authors.initials: JW
authors.lastname: Kupiec-Weglinski
mesh_terms: D000818:Animals; D017209:Apoptosis; D002867:Chromones / Q000737:chemistry; D000071161:Forkhead Box Protein O1; D051858:Forkhead Transcription Factors / Q000378:metabolism*; D006706:Homeostasis; D007249:Inflammation; D008070:Lipopolysaccharides / Q000737:chemistry; D008099:Liver / Q000473:pathology; D008264:Macrophages / Q000378:metabolism; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009025:Morpholines / Q000737:chemistry; D051267:NF-E2-Related Factor 2 / Q000378:metabolism*; D009336:Necrosis; D009504:Neutrophils / Q000378:metabolism; D010084:Oxidation-Reduction; D010766:Phosphorylation; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D011524:Protoporphyrins / Q000737:chemistry; D015427:Reperfusion Injury / Q000378:metabolism*; D050796:STAT3 Transcription Factor / Q000378:metabolism; D015398:Signal Transduction; D051197:Toll-Like Receptor 4 / Q000378:metabolism*; D052096:Warm Ischemia
chemical_list: D002867:Chromones; D000071161:Forkhead Box Protein O1; D051858:Forkhead Transcription Factors; C467200:Foxo1 protein, mouse; D008070:Lipopolysaccharides; D009025:Morpholines; D051267:NF-E2-Related Factor 2; C495636:Nfe2l2 protein, mouse; D011524:Protoporphyrins; D050796:STAT3 Transcription Factor; C494087:Stat3 protein, mouse; C493487:Tlr4 protein, mouse; D051197:Toll-Like Receptor 4; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; C007095:cobaltiprotoporphyrin; D051057:Proto-Oncogene Proteins c-akt