The NRF2/KEAP1 Oxidative Stress Pathway: Mechanisms, Targets, and Therapeutic Interventions

The Nuclear factor erythroid 2-related factor 2 (NRF2)/Kelch-like ECH-associated protein 1 (KEAP1) pathway represents one of the most critical cellular defense mechanisms against oxidative stress and has emerged as a focal point in understanding redox homeostasis across numerous pathological conditions. This master regulatory pathway orchestrates the cellular response to reactive oxygen species (ROS) and other oxidative stressors, playing pivotal roles in both health and disease. As oxidative stress underlies numerous pathological conditions, from cardiovascular diseases to neurodegeneration and cancer, understanding this pathway offers substantial opportunities for therapeutic intervention.

Fundamental Mechanisms of the NRF2/KEAP1 Pathway

The NRF2/KEAP1 signaling pathway functions as a sophisticated cellular sensor and response system for oxidative and electrophilic stress. Under normal physiological conditions, KEAP1 serves as a negative regulator of NRF2, binding to it in the cytoplasm and facilitating its rapid degradation through the ubiquitin-proteasome system912. This tight regulation ensures that NRF2 activity remains at appropriate baseline levels in the absence of cellular stress.

When cells experience oxidative stress, the dynamics of this interaction change dramatically. Reactive oxygen species (ROS) or electrophilic molecules oxidize or modify critical cysteine residues within the KEAP1 protein structure9. This conformational change disrupts the KEAP1-NRF2 complex, preventing the ubiquitination and subsequent degradation of NRF213. Consequently, newly synthesized NRF2 accumulates and translocates from the cytoplasm to the nucleus, where it forms heterodimers with small Maf proteins. These complexes then bind to specific DNA sequences known as antioxidant response elements (AREs) located in the promoter regions of numerous cytoprotective genes510.

The molecular events following NRF2 nuclear translocation represent a coordinated cellular defense program. NRF2 activates the transcription of genes involved in various aspects of cellular protection, including direct antioxidant functions, detoxification processes, and metabolic reprogramming. This activation creates a comprehensive cellular response aimed at neutralizing oxidative threats and restoring redox balance1113.

Key Downstream Targets and Cellular Responses

The NRF2/KEAP1 pathway influences cellular physiology through multiple downstream effectors, creating a multi-layered defense against oxidative damage. Primary antioxidant enzymes upregulated through this pathway include heme oxygenase-1 (HO-1) and NAD(P)H quinone oxidoreductase 1 (NQO1), which directly combat oxidative stress by neutralizing free radicals110. Additionally, NRF2 activation enhances the expression of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx), critical enzymes that convert harmful ROS into less reactive molecules4616.

Beyond direct antioxidant functions, NRF2 regulates phase II detoxification enzymes that facilitate the elimination of potentially harmful compounds. This process involves conjugation reactions that transform lipophilic toxins into more water-soluble substances that can be excreted from the body1112. Through these mechanisms, the NRF2/KEAP1 pathway provides comprehensive protection against both endogenous and exogenous sources of oxidative stress.

Recent research has also uncovered a significant role for NRF2 in modulating mitochondrial homeostasis. Following nuclear translocation, NRF2 activates genes involved in various aspects of mitochondrial function, including biogenesis, dynamics, mitophagy, aerobic respiration, and energy metabolism9. This interconnection between NRF2 and mitochondrial function creates a regulatory circuit critical for maintaining cellular homeostasis, particularly in metabolically demanding tissues.

Pathophysiological Roles Across Multiple Conditions

The NRF2/KEAP1 pathway demonstrates remarkable versatility in its protective functions across diverse pathological states. In cardiovascular diseases, particularly myocardial ischemia/reperfusion injury, NRF2 activation mitigates oxidative damage and reduces cardiomyocyte apoptosis16. Research has shown that costunolide significantly decreases reactive oxygen species levels and ameliorates apoptosis of ischemia/reperfusion-injured cardiomyocytes through NRF2/KEAP1 pathway activation1.

In neurological conditions such as subarachnoid hemorrhage, the NRF2/KEAP1 pathway offers neuroprotection by reducing oxidative stress-induced damage3. Similarly, in metabolic disorders like Type II diabetes mellitus, this pathway counteracts oxidative stress that contributes to pathogenesis and disease progression11. The pathway also shows protective effects in inflammatory conditions affecting periodontal tissues, intestinal epithelium, and the renal system271016.

Intriguingly, the role of NRF2/KEAP1 signaling in cancer presents a paradox. In early stages of carcinogenesis, NRF2 activation appears protective, suppressing malignant transformation by neutralizing oxidative stress that can damage DNA and promote genetic instability813. However, in established tumors, constitutive NRF2 activation can become problematic, potentially conferring resistance to chemotherapy and radiation treatments1317. This dual nature of NRF2 function in cancer highlights the context-dependent effects of this pathway and underscores the complexity of targeting it therapeutically in oncology settings.

Evidence-Based Therapeutic Interventions

Numerous compounds have demonstrated efficacy in modulating the NRF2/KEAP1 pathway, with varying levels of evidence supporting their therapeutic potential. Among pharmacological agents with strong supporting evidence, costunolide has shown significant protection against myocardial ischemia/reperfusion injury by promoting the dissociation of the KEAP1/NRF2 complex1. Similarly, edaravone dexborneol effectively attenuates oxidative stress in subarachnoid hemorrhage models through NRF2 activation3.

Natural compounds represent another promising category of NRF2 modulators with substantial evidence. Antarctic krill oil has demonstrated clinical efficacy in attenuating oxidative stress via the KEAP1-NRF2 pathway in patients with coronary heart disease6. Administration of Antarctic krill oil significantly increased KEAP1 and NRF2 levels in peripheral blood leukocytes while reducing serum markers of oxidative stress, including reactive oxygen species and malondialdehyde6.

Vitamin C represents another well-studied intervention, showing protection against hypoxia-induced oxidative damage by enhancing the Nrf2/Keap1 signaling pathway4. In experimental models, vitamin C supplementation upregulated antioxidant enzyme activities and reduced inflammatory cytokines through this mechanism4. Similarly, mussel polysaccharide has demonstrated protective effects against cyclophosphamide-induced intestinal oxidative stress by activating the NRF2/KEAP1 pathway, increasing antioxidant enzyme expression, and improving intestinal morphology16.

Emerging Approaches with Developing Evidence

While several interventions targeting the NRF2/KEAP1 pathway have strong supporting evidence, others represent promising approaches still under investigation. Epigenetic regulation of the NRF2/KEAP1, for instance, has been identified as a potential strategy for cancer treatment, though specific interventions and clinical applications remain in developmental stages13. This approach recognizes that epigenetic mechanisms significantly influence NRF2/KEAP1 pathway activity and could provide more precise therapeutic targeting.

The role of phosphoglycerate mutase family member 5 (PGAM5) in heart failure represents another emerging area. Research suggests that PGAM5 protects against ROS-induced oxidative stress and ferroptosis through the Keap1/Nrf2 pathway15. While initial findings are promising, further validation of PGAM5-targeting approaches is needed before clinical applications can be considered.

Galectin-1 regulation of the Nrf2/Keap1 pathway, particularly in cancer drug resistance, represents another frontier with emerging evidence14. Recent studies suggest that galectin-1 may sustain activation of the NRF2 pathway, potentially promoting tumor cell proliferation and drug resistance. This relationship highlights potential targets for cancer therapy but requires additional research to fully elucidate mechanisms and develop effective interventions.

Various phytochemicals are being investigated for their effects on the NRF2/KEAP1 pathway, particularly in cancer contexts812. While many plant-derived compounds show promise in preliminary studies, more rigorous clinical evaluation is needed to establish definitive efficacy and optimal therapeutic applications.

Challenges and Future Directions

The complexity of the NRF2/KEAP1, pathway presents significant challenges for therapeutic targeting. The context-dependent nature of NRF2 activity—beneficial in many disorders but potentially detrimental in certain cancer scenarios—necessitates careful consideration of timing, dosage, and specificity of interventions1317. Future research must address these nuances to develop precision approaches that maximize therapeutic benefits while minimizing unintended consequences.

Interactions between the NRF2/KEAP1 pathway and other signaling systems represent another important frontier. Emerging research highlights connections between NRF2 activation and autophagy (particularly p62-dependent mechanisms), mitochondrial function, and inflammatory pathways like NF-κB1819. Understanding these intersections will likely yield more comprehensive therapeutic strategies that address multiple aspects of disease pathophysiology.

Conclusion

The NRF2/KEAP1 pathway stands as a central mediator of cellular responses to oxidative stress, with far-reaching implications across numerous pathological conditions. Through its regulation of antioxidant enzymes, detoxification processes, and mitochondrial function, this pathway provides critical protection against oxidative damage while influencing broader aspects of cellular homeostasis. While several compounds have demonstrated promising abilities to modulate this pathway therapeutically, continued research is essential to refine targeting strategies and develop more effective interventions. As our understanding of this complex signaling network continues to evolve, so too will our capacity to harness its protective potential in treating oxidative stress-related diseases.