Keap1-Nrf2 Protein-Protein Interaction inhibitors(Japan Tobacco)

Inhibiting the protein-protein interaction (PPI) between Keap1 and Nrf2 is theoretically an effective and safe strategy for activation of Nrf2 pathway to treat major depressive disorder (MDD). In this study, through bioinformatic analysis of the brain tissues and peripheral blood of MDD patients and depressive mice, we confirmed the involvement of oxidative stress, inflammation, and the Keap1-Nrf2 pathway in depression. Subsequently, we developed a series of phosphodiester amino acidic diaminonaphthalene compounds as Keap1-Nrf2 PPI inhibitors for the first time. Screening using the LPS-stimulated SH-SY5Y and BV2 cell models identified compound 4-95 showing the best anti-oxidative stress and anti-inflammatory efficacy. The ability of 4-95 to penetrate the blood-brain-barrier was significantly enhanced. In a chronic unpredictable mild stress mouse model, treatment with 4-95 effectively ameliorated anxiety and depression behavior and restored serum neurotransmitter levels by promoting the Nrf2 nuclear translocation. Consequently, oxidative stress was reduced, and the expression of synaptic plasticity biomarkers, such as postsynaptic density protein 95 (PSD95) and synapsin 1 (SYN1) were significantly increased, suggesting the recovery of neuronal function. Collectively, our findings demonstrate that the Keap1-Nrf2 PPI inhibitor holds great promise as a preclinical candidate for the treatment of depression.

The Keap1-Nrf2 pathway is an essential system that maintains redox homeostasis and modulates key metabolic processes, including metabolism of amino acids to promote the synthesis of antioxidant enzymes. Inhibitors of the protein-protein interaction (PPI) between Keap1 and Nrf2 have emerged as a promising strategy for developing novel classes of antioxidant agents that selectively activate this pathway without off-target effects. Carotenoids, a large family of lipophilic isoprenoids synthesized by all photosynthetic organisms, are well-known for their antioxidant activities. However, the ability of carotenoids to inhibit the Keap1-Nrf2 PPI through the involvement of specific amino acid residues has not yet been revealed. We utilized molecular docking, molecular dynamic simulations, and pharmacokinetic prediction techniques to investigate the potential of eight oxygenated carotenoids, known as xanthophylls, to inhibit Keap1. Among the compounds investigated, fucoxanthin and astaxanthin established multiple hydrogen-bonding and hydrophobic interactions within the Kelch domain of Keap1, showing remarkable binding affinities. Furthermore, fucoxanthin and astaxanthin displayed the ability to form a stable complex with Keap1 and fit into the binding pocket of its Kelch domain. These analyses led to the identification of critical amino acid residues in the binding pocket of Keap1 which are involved in the interaction with carotenoid xanthophylls. Our analyses further revealed that fucoxanthin and astaxanthin demonstrate a favorable safety profile and possess pharmacokinetic properties consistent with acceptable drug-like characteristics. These findings lay the preliminary foundation for developing a novel class of Keap1-Nrf2 PPI inhibitors with potential applications against oxidative stress-related diseases.