Electrophilic and oxidative stress contribute to major diseases such as cancer and diabetes. Small-molecule activators of the Nrf2 cytoprotective pathway show significant promise for prevention and amelioration of chronic diseases by combating these stressors through upregulation of detoxification and antioxidant enzymes. An understudied area is whether distinct small molecular Nrf2 activators can protect cells from all electrophilic and oxidative stressors, or whether certain molecules are better suited to protect against a particular type of stress.
In this study, human keratinocyte HaCaT cells were preincubated for 24 h with one of four Nrf2 activators before different stressors were added for an additional 24 h and cell death was assessed. Three electrophiles were tested: sulforaphane (SFN), the subject of over 70 clinical trials, the multiple sclerosis drug Tecfidera (dimethyl fumarate, DMF), and bardoxolone methyl (BARD), in clinical trials for treatment of chronic kidney diseases and other conditions including COVID-19. SFN, DMF, and BARD target C151 of the Keap1 protein, a negative regulator of Nrf2. Also tested was KI696, an inhibitor of the Keap1-Nrf2 interaction. Three chemically distinct stressors—hydrogen peroxide, menadione (a quinone that rapidly generates ROS through one-electron redox cycling), or chlorambucil (an alkylating chemotherapy agent)—were tested. Stressors were added to the cells at their LC50 concentration after pretreatment with a range of cytoprotective compound concentrations. Unexpectedly, SFN pretreatment showed little to no rescue for all stressors. However, DMF rescued the viability of cells stressed with hydrogen peroxide, menadione, and chlorambucil. BARD showed no rescue for hydrogen peroxide-treated cells. KI696 improved the cell’s ability to survive chlorambucil. The ability of a given Nrf2 activator (or lack thereof) to protect against a given stressor points to a need to better understand the cytoprotective environment (specific enzymes upregulated, glutathione levels, etc.) that best protect against specific stressors.
Support or Funding Information
Villanova Chemistry Department Summer Undergraduate Research Fellowship
Villanova Chemistry Department Summer Undergraduate Research Fellowshipamp;nbsp;
