Discovery of direct inhibitors of Keap1–Nrf2 protein–protein interaction as potential therapeutic and preventive agents

Abstract

The Keap1–Nrf2–ARE pathway is an important antioxidant defense mechanism that protects cells from oxidative stress and the Keap1–Nrf2 protein–protein interaction (PPI) has become an important drug target to upregulate the expression of ARE-controlled cytoprotective oxidative stress response enzymes in the development of therapeutic and preventive agents for a number of diseases and conditions. However, most known Nrf2 activators/ARE inducers are indirect inhibitors of Keap1–Nrf2 PPI and they are electrophilic species that act by modifying the sulfhydryl groups of Keap1׳s cysteine residues. The electrophilicity of these indirect inhibitors may cause "off-target" side effects by reacting with cysteine residues of other important cellular proteins. Efforts have recently been focused on the development of direct inhibitors of Keap1–Nrf2 PPI. This article reviews these recent research efforts including the development of high throughput screening assays, the discovery of peptide and small molecule direct inhibitors, and the biophysical characterization of the binding of these inhibitors to the target Keap1 Kelch domain protein. These non-covalent direct inhibitors of Keap1–Nrf2 PPI could potentially be developed into effective therapeutic or preventive agents for a variety of diseases and conditions.

Expression of redox sensing factor Nrf2 in lung macrophages and type II pneumocytes as a prognostic factor in pneumothorax recurrence

“…Exposure to cigarette smoke causes more severe emphysema-like symptoms, and is associated with oxidative DNA adduct formation, apoptosis, and elevated Nrf2 expression (5,10). Nrf2 has an essential protective role in the lungs against oxidative airway diseases, by controlling the expression of antioxidant response element-regulated antioxidant and cytoprotective genes (7). However, the present study showed no significant correlation between smoking status and the expression level of Nrf2 in PSP patients ( Table 2).…”

“…Under normal conditions, Nrf2 is sequestered in the cytosol and bound to the actin cytoskeleton by Kelchassociated protein 1, a cytosolic regulatory protein. When oxidative stress occurs, Nrf2 translocates into the nucleus and binds to the promoter sequence of antioxidant genes (7). In some pulmonary diseases, Nrf2 plays a cytoprotective role by induction of a suite of various antioxidants and phase II enzymes to restore redox homeostasis (7).…”

“…When oxidative stress occurs, Nrf2 translocates into the nucleus and binds to the promoter sequence of antioxidant genes (7). In some pulmonary diseases, Nrf2 plays a cytoprotective role by induction of a suite of various antioxidants and phase II enzymes to restore redox homeostasis (7). Previous studies reported that PI3K/AKT, through Nrf2 and its target genes (heme oxygenase 1 and NADPH quinone oxidoreductase), suppressed hyperoxia-induced acute lung injury in lung epithelial cells and alveolar macrophages as well as in mice model (8,9).…”

Transcription Factor NRF2 as a Therapeutic Target for Chronic Diseases: A Systems Medicine Approach

“…The discovery of new peptides and small-molecule inhibitors of the KEAP1/NRF2 interaction has been reviewed recently (Abed et al, 2015;Jiang et al, 2016). Briefly, a series of truncated NRF2 peptides was initially evaluated as direct inhibitors of PPI using surface plasmon resonance and fluorescence polarization assays (Hu et al, 2013).…”

The role of modulation of antioxidant enzyme systems in the treatment of neurodegenerative diseases

“…The high electrophilicity of traditional Nrf2-activators poses the risk of ''off-target'' effects due to their ability to react with the cysteines of other proteins. Therefore, there has been an increased interest in the direct targeting of Nrf2/Keap1 protein-protein interaction (PPI) as an alternative strategy (recently reviewed by Wells 162 and Abed et al 163 ). High-throughput screening using fluorescence polarisation (FP) assay yielded several micromolar hits 164,165 .…”