Keap1 is associated with cytoprotective signaling. These roles of Keap1 typically focus on its role as a degrader of the antioxidant response (AR) transcription factor, Nrf2, and the inhibition of this process upon Keap1 labeling by electrophiles. However, work from several laboratories has reemphasized both the important role of Nrf2 binding in negatively regulating AR, and the fact that electrophile Keap1 modification dissociates Nrf2 from Keap1. This model appears to be applicable to other signaling modes regulated by Keap1. Here we use recent data we have derived using experiments in zebrafish and cultured cells to discuss different models of Keap1 regulation.

The nuclear factor-erythroid 2 p45-related factor 2 (Nrf2, also called Nfe2l2)/Kelchlike ECH-associated protein 1 (Keap1) signaling is the major regulator of redox homeostasis. The imbalance of redox homeostasis causes oxidative stress. Keap1 is the one that regulates Nrf2 by binding to Nrf2. Nrf2/Keap1 signaling is reported to be involved in cancer cell growth and survival. The high level of Nrf2 in cancers is associated with poor prognosis, resistance to therapeutics and rapid proliferation framing Nrf2 as an interesting target in cancer biology. Sirtuins (SIRT1-7) are class III histone deacetylases with NAD+-dependent deacetylase activity. High levels of SIRT6 are contributing to cancer progression in many types of human tumors, and its overexpression has been reported to involve positive modulation of the Nrf2/Keap1 pathway, suggesting SIRT6 is a key regulator of this Nrf2/Keap1 Signaling. The natural or synthetic compound that inhibits key regulators of Nrf2 signaling becomes an attractive target. In the present study, we investigated the pharmacological effect of Ethyl (5-(4-Chlorophenyl)-2-methyl-1H-imidazol-4-yl) - acetate an imidazole derivative on Nrf2/Keap1 in A549 and NIC-H460 cell lines. Imidazole derivative inhibited the SIRT6 expression at gene and protein levels. The gene and protein expression of Nrf2 and Keap1 were modulated during SIRT6 inhibition. The level of anti-oxidant enzymes such as GSH, GPx, Catalase, and % ROS scavenging activity were depleted upon SIRT6 inhibition. Further, morphological studies support ROS generation, mitochondrial damage, nuclear damage, and apoptosis. The molecular examination of apoptosis by gene and protein expression of apoptotic factors confirms apoptotic cell death. Our results suggest that the Imidazole derivative affects Nrf2/Keap1 signaling by targeting SIRT6 might be a new promising approach to cancer treatment opportunity for disrupting Nrf2/Keap1 signaling in lung cancer.

Cells that experience high levels of oxidative stress respond with the induction of antioxidant proteins through the activation of the transcription factor Nrf2. Nrf2 is negatively regulated by Keap1 which binds to Nrf2 to facilitate its ubiquitination and ensuing proteasomal degradation under basal conditions. Here, we study protein folding and misfolding in Nrf2 and Keap1 in yeast, mammalian cells, and purified proteins under oxidative stress conditions. Both Nrf2 and Keap1 are susceptible to protein misfolding and inclusion formation upon oxidative stress. We propose that the intrinsically disordered regions within Nrf2 and the high cysteine content of Keap1 contribute to their oxidation and the ensuing misfolding. Our work reveals previously unexplored aspects of Nrf2 and Keap1 regulation and dysregulation by oxidation-induced protein misfolding.

The gas molecules O2, NO, H2S, CO, CH4 , have been increasingly used for medical purposes. Beside these gas molecules, H2, the smallest diatomic molecule in nature, has become a rising star in gas medicine in the past few decades. As a non-toxic and easily accessible gas, H2 has shown preventive and therapeutic effects on various diseases of the respiratory, cardiovascular, central nervous and other systems, but the mechanisms are still unclear and even controversial, especially the mechanism of H2 as a selective radical scavenger. Mitochondria are the main organelles regulating energy metabolism in living organisms, as well as the main organelle of reactive oxygen species generation and target. We propose that the protective role of H2 may be mainly dependent on its unique penetrating ability to everywhere of the cells to regulate mitochondrial homeostasis by activating the Keap1-Nrf2 phase II antioxidant system, rather than its direct free radical scavenging activity. In this review, we summarize the protective effects and focus on the mechanism of H2 as a mitochondria-targeting nutrient by activating the Keap1-Nrf2 system in different disease models, and wish to provide a more rational theoretical support for the medical applications of hydrogen.

Reactive oxygen species (ROS) are a major risk factor for the development of oxidation and inflammation. Ryegrass (pasture), a natural dietary fiber source, acts as an antioxidant with well-known anti-inflammatory properties. The current study aimed to examine the alkaline phosphatase (ALP)-dependent Kelch-like-ECH-associated protein 1- Nuclear factor erythroid 2-related factor 2 (Keap1-Nrf2) signaling pathway that facilitates the anti-oxidative and anti-inflammatory properties of pasture and its protective effects on ileal permeability, systemic inflammation, nutrient absorption, liver dysfunction, growth performance, intestinal organ development, and metabolic syndrome in commercial diet-challenged geese. The lipopolysaccharides (LPS), ALP, ROS, and tight junction proteins were determined from the ileum tissues, and the antioxidant enzymes, immunoglobulins, and metabolic syndrome were determined from liver tissues via Enzyme-linked immunosorbent assay (ELISA) kits. While the Nrf2 and LPS/ROS/Keap1-induced inflammatory cytokines were determined by the quantitative reverse transcription polymerase chain reaction (RT-qPCR) method. The intestinal morphology was examined by Hematoxylin and Eosin (H&E) staining to determine nutrient absorption in ileal tissues. Pasture-dependent ALP activity significantly ameliorated commercial diet-induced LPS and ROS-facilitated ileal barrier dysfunction and systemic inflammation. The pasture supplementation induced nutrient absorption by influencing intestinal organ development. Our biochemical assays showed that the activation of Nrf2 significantly increased antioxidant enzymes and immunoglobulins, and decreased Keap1 and malondialdehyde (MDA) concentrations in the liver tissues after pasture supplementation. The correlation analysis of ALP, LPS, ROS, and Keap1-Nrf2 pathway-dependent antioxidant enzymes with other host markers showed that pasture supplementation induced intestinal barrier function via reducing LPS/ROS-induced intestinal permeability and systemic inflammation in the ileum and liver tissues. Pasture intake might attenuate LPS/ROS-induced gut permeability, systemic inflammation, and metabolic syndrome and augment gut barrier functions, nutrient absorption, immunity, and growth performance, possibly by its Keap1-Nrf2 pathway-dependent antioxidant properties.

Treatment of various diseases, in particular cancer, usually needs targeting biologically active molecules at a selected subcellular compartment. We modified our previously developed modular nanotransporters (MNTs) for targeting mitochondria. The new MNTs are capable of binding to the protein predominantly localized on the outer mitochondrial membrane, Keap1. These MNTs possessing antiKeap1 monobody co-localize with mitochondria upon addition to the cells. They efficiently interact with Keap1 both in solution and within living cells. A conjugate of the MNT with a photosensitizer, chlorin e6, demonstrates significantly higher photocytotoxicity than chlorine e6 alone. We assume that MNTs of this kind can improve efficiency of therapeutic photosensitizers and radionuclides emitting short-range particles.