Enhancing Nrf2 Pathway by Disruption of Keap1 in Myeloid Leukocytes Protects against Sepsis

Abstract

Rationale: Sepsis syndrome is characterized by inappropriate amplified systemic inflammatory response and bacteremia that promote multiorgan failure and mortality. Nuclear factor-erythroid 2 p45-related factor 2 (Nrf2) regulates a pleiotropic cytoprotective defense program including antioxidants and protects against several inflammatory disorders by inhibiting oxidative tissue injuries. However, the role of enhanced Nrf2 activity in modulating innate immune responses to microbial infection and pathogenesis of sepsis is unclear. Objectives: To determine whether Nrf2 in myeloid leukocytes alters inflammatory response and protects against sepsis. Methods: Mice with deletion of Nrf2 or kelch-like ECH-associated protein (Keap1) in myeloid leukocyte cells and respective floxed controls were subjected to cecal ligation and puncture-induced sepsis and were assessed for survival, organ injury, systemic inflammation, and bacteremia. Using LPS-stimulated peritoneal macrophages, Toll-like receptor (TLR) 4 surface trafficking and downstream signaling events were analyzed. Measurements and Main Results: Mortality, organ injury, circulating levels of inflammatory mediators, and bacteremia were markedly reduced in LysM-Keap1 2/2 compared with respective floxed controls (Keap1 f/f or Nrf2 f/f ) and significantly elevated in LysM-Nrf2 2/2 mice after cecal ligation and puncture. Peritoneal macrophages from septic LysM-Keap1 2/2 mice showed a greater bacterial phagocytic activity compared with LysM-Nrf2 2/2 and floxed controls. LPS stimulation resulted in greater reactive oxygen species-induced cell surface transport of TLR4 from trans-Golgi network and subsequent TLR4 downstream signaling (recruitment of MYD88 and TRIF, phosphorylation of IkB and IRF3, and cytokine expression) in macrophages of LysM-Nrf2 2/2 compared with LysM-Keap1 2/2 mice and floxed controls. Conclusions: Our study shows that Nrf2 acts as a critical immunomodulator in leukocytes, controls host inflammatory response to bacterial infection, and protects against sepsis.

Heme Oxygenase-1 and Carbon Monoxide Promote Burkholderia pseudomallei Infection

“…In several experimental models, including LPS-and CLP-induced septic shock (17)(18)(19) or hyperoxia-induced acute lung injury (51), Nrf2 deficiency was associated with increased inflammation and tissue injury. Absence of Nrf2 was shown to suppress the alveolar transcriptional network for mitochondrial biogenesis and antiinflammation, which worsens acute lung injury in an S. aureus pneumonia model (40).…”

“…There it binds specifically with transcription cofactors to the antioxidant response elements and thereby regulates the activation of most antioxidant and phase II enzyme genes (e.g., heme oxygenase-1 [HO-1], peroxiredoxins 1 and 6) to maintain cellular redox homeostasis. Disruption of Nrf2 increases mortality of mice in LPS-as well as cecal ligation and puncture (CLP)-induced sepsis (17)(18)(19). In Nrf2-deficient mice, LPS elicits stronger pulmonary inflammation associated with enhanced levels of inflammatory cytokines and ROS production (20).…”

T Lymphocyte–Specific Activation of Nrf2 Protects from AKI

“…The effect of Keap1 deletion on antioxidant gene expression in this study is corroborated by previous studies in non-T cell models. 18,19 Nrf2 Augmentation Affects Immune Cell Recruitment, Activation, and Intracellular Cytokine Production By T Cells We further compared phenotypic changes, activation status, and cytokine production in CD45 + TCR + cells isolated from Figure 1). We further examined the expression of CD69 to assess activation status of CD4, CD8, and doublenegative (DN) T cells isolated from kidneys of CD4-Keap1-KO and Keap1 F/F mice ( Figure 2D We then studied the effect of Nrf2 activation on proinflammatory cytokine production by renal T cells by assessing intracellular levels of TNF-a, IFN-g, and IL-17 in CD4, CD8, and DNT cells isolated from CD4-Keap1-KO and Keap1 F/F kidneys ( Figure 2E).…”

“…18,19 CD4-Cre mice were purchased from Taconics (Hudson, NY). In these CD4-Cre mice, the transgene is under the control of the CD4 promoter/ enhancer/silencer, which first allows expression of CD4-Cre in thymocytes at the double-positive (CD4 …”

Park7 interacts with p47phox to direct NADPH oxidase-dependent ROS production and protect against sepsis

“…Oxidative stress has been implicated in the pathogenesis of PD, because neuronal cells with either Park7 deletion or Park7 downregulation are sensitive to oxidative stress [14,15]. Given the antioxidant feature of Park7 and that oxidative stress is tightly related to inflammatory responses and survival in experimental sepsis [12,16], we hypothesized that Park7 protects against sepsis by modulating the cellular redox state.…”