Keap1在氧化应激方面的研究进展

外界环境的刺激会破坏生物体内的氧化还原平衡,产生氧化应激。为了应对氧化应激产生的毒性作用,体内细胞在进化过程中产生了复杂的机制来应对氧化应激,Keap1（Kelch-like Ech-associated protein-1）是抗氧化应答机制中最重要的分子之一。本文从Keap1的克隆和表达、定位及结构以及功能方面对Keap1在生物体内应对氧化应激所起的作用进行了综述。     

Epigallocatechin gallate potentially abrogates fluoride induced lung oxidative stress,inflammation via Nrf2/Keap1 signaling pathway in rats: An in-vivo and in-silico study

BackgroundSince this Nrf2-dependent cellular defense response is able to protect multi-organs, including cancer, neurodegenerative diseases, cardiovascular diseases, inflammation and chronic lung injury. The antioxidant and anti-inflammatory potential of Epigallocatechin gallate (EGCG) and Nrf2/Keap1 signaling mechanisms in pulmonary toxicity have not been clarified. In the present study, we demonstrated that protective efficacy of EGCG against fluoride (Fl) induced oxidative stress mediated lung injury in rats.MethodsThe animals were divided in to four groups. Group 1: Control rats received normal saline; Group 2 rats received EGCG (40 mg/kg/bw) alone for four weeks; Group 3 rats received Fl (25 mg/kg/bw) alone for four weeks, Group 4 rats received EGCG (90 min before administration) along with Fl for four weeks.ResultsOral administration of Fl (25 mg/kg/bw) significantly (p < 0.05) increased the ROS, inflammatory cytokines, lung edema, melonaldehyde (MDA) and myeloperoxidase (MPO) in rats. In addition, upon administration of Fl significantly (p < 0.05) decreased the antioxidant status, Nrf2, and HO-1 with increased Keap1 protein. Histological and immunohistochemical (iNOS) study also revealed the Fl induced significant (p < 0.05) changes in the lung tissue of rats. Pre-administration of EGCG significantly (p < 0.05) improved the antioxidant status, and inhibited the oxidative stress, inflammatory cytokines, and Keap1 protein via the activation of Nrf2 translocation in to the nucleus. Moreover, the molecular docking studies also support the antioxidant potential of EGCG and Nrf2 activation.ConclusionTaken together, our data indicate that EGCG potentially abrogates Fl induced oxidative lung injury by activation of the Nrf2/Keap1 pathway in rats.     

Sulforaphane protects kidneys against ischemia-reperfusion injury through induction of the Nrf2-dependent phase 2 enzyme

Reactive oxygen species are important mediators that exert a toxic effect during ischemia-reperfusion injury of various organs. Sulforaphane, which is a naturally occurring isothiocyanate that is present in cruciferous vegetables such as broccoli, is known to be an indirect antioxidant that acts by inducing Nrf2-dependent phase 2 enzymes. Phase 2 enzymes such as heme oxygenase-1, NAD(P)H: quinone oxidoreductase 1, glutathione reductase, and glutathione peroxidase participate in adaptive and protective responses to oxidative stress and various inflammatory stimuli. Therefore, we evaluated the preactivation of Nrf2 by sulforaphane to determine if it could inhibit ischemia-reperfusion-induced kidney damage. Treatment of HK2 renal tubular epithelial cells with sulforaphane effectively protected cells against cytotoxicity induced by hypoxia-reoxygenation, and sulforaphane dramatically induced phase 2 enzymes by decreasing the Keap1 protein levels and increasing Nrf2 nuclear translocation. Additionally, a second set of experiments using a renal ischemia-reperfusion model produced results that were essentially the same as those observed when HK2 cells were used; namely, that sulforaphane induced Nrf2-dependent phase 2 enzymes and thereby improved ischemia-reperfusion-induced changes in the lipid hydroperoxides, glutathione, creatinine clearance, kidney weight, and histologic abnormalities. Collectively, these results suggest that sulforaphane can be used as an effective adjunct for the prevention of renal oxidative insults during ischemia-reperfusion injury.     

Regulation of Nrf2-Mediated Phase II Detoxification and Anti-oxidant Genes

The molecular mechanisms by which a variety of naturally-occurring dietary compounds exert chemopreventive effects have been a subject of intense scientific investigations. Induction of phase II detoxification and anti-oxidant enzymes through activation of Nrf2/ARE-dependent gene is recognized as one of the major cellular defense mechanisms against oxidative or xenobiotic stresses and currently represents a critical chemopreventive mechanism of action. In the present review, the functional significance of Keap1/Nrf2 protein module in regulating ARE-dependent phase II detoxification and anti-oxidant gene expression is discussed. The biochemical mechanisms underlying the phosphorylation and expression of Keap1/Nrf2 proteins that are controlled by the intracellular signaling kinases and ubiquitin-mediated E3 ligase system as well as control of nucleocytoplasmic translocation of Nrf2 by its innate nuclear export signal (NES) are described.     

Role of Nrf2 in preventing ethanol-induced oxidative stress and lipid accumulation

Oxidative stress and lipid accumulation play important roles in alcohol-induced liver injury. Previous reports showed that, in livers of nuclear factor erythroid 2-related factor 2 (Nrf2)-activated mice, genes involved in antioxidant defense are induced, whereas genes involved in lipid biosynthesis are suppressed. To investigate the role of Nrf2 in ethanol-induced hepatic alterations, Nrf2-null mice, wild-type mice, kelch-like ECH-associated protein 1-knockdown (Keap1-KD) mice with enhanced Nrf2, and Keap1-hepatocyte knockout (Keap1-HKO) mice with maximum Nrf2 activation, were treated with ethanol (5 g/kg, po). Blood and liver samples were collected 6 h thereafter. Ethanol increased alanine aminotransferase and lactate dehydrogenase activities as well as thiobarbituric acid reactive substances in serum of Nrf2-null and wild-type mice, but not in Nrf2-enhanced mice. After ethanol administration, mitochondrial glutathione concentrations decreased markedly in Nrf2-null mice but not in Nrf2-enhanced mice. H₂DCFDA staining of primary hepatocytes isolated from the four genotypes of mice indicates that oxidative stress was higher in Nrf2-null cells, and lower in Nrf2-enhanced cells than in wild-type cells. Ethanol increased serum triglycerides and hepatic free fatty acids in Nrf2-null mice, and these increases were blunted in Nrf2-enhanced mice. In addition, the basal mRNA and nuclear protein levels of sterol regulatory element-binding protein 1(Srebp-1) were decreased with graded Nrf2 activation. Ethanol further induced Srebp-1 mRNA in Nrf2-null mice but not in Nrf2-enhanced mice. In conclusion, Nrf2 activation prevented alcohol-induced oxidative stress and accumulation of free fatty acids in liver by increasing genes involved in antioxidant defense and decreasing genes involved in lipogenesis.