Redox regulation of antioxidants, autophagy, and the response to stress: Implications for electrophile therapeutics

Redox networks in the cell integrate signaling pathways that control metabolism, energetics, cell survival, and death. The physiological second messengers that modulate these pathways include nitric oxide, hydrogen peroxide, and electrophiles. Electrophiles are produced in the cell via both enzymatic and nonenzymatic lipid peroxidation and are also relatively abundant constituents of the diet. These compounds bind covalently to families of cysteine-containing, redox-sensing proteins that constitute the electrophile-responsive proteome, the subproteomes of which are found in localized intracellular domains. These include those proteins controlling responses to oxidative stress in the cytosol-notably the Keap1-Nrf2 pathway, the autophagy-lysosomal pathway, and proteins in other compartments including mitochondria and endoplasmic reticulum. The signaling pathways through which electrophiles function have unique characteristics that could be exploited for novel therapeutic interventions; however, development of such therapeutic strategies has been challenging due to a lack of basic understanding of the mechanisms controlling this form of redox signaling. In this review, we discuss current knowledge of the basic mechanisms of thiol-electrophile signaling and its potential impact on the translation of this important field of redox biology to the clinic. Emerging understanding of thiol-electrophile interactions and redox signaling suggests replacement of the oxidative stress hypothesis with a new redox biology paradigm, which provides an exciting and influential framework for guiding translational research.