Formononetin, a bioactive isoflavonoid constituent from Astragalus membranaceus (Fisch.) Bunge, ameliorates type 1 diabetes mellitus via activation of Keap1/Nrf2 signaling pathway: An integrated study supported by network pharmacology and experimental validation.

ETHNOPHARMACOLOGICAL RELEVANCE: Type 1 diabetes mellitus (T1DM) results from insulin deficiency due to the destruction of pancreatic ß-cells. Previously, our studies showed that inhibition of Keap1/Nrf2 signaling pathway promoted the onset of T1DM, which suggests that finding drugs that can activate the Keap1/Nrf2 signaling may be a promising therapeutic strategy for the T1DM treatment. Astragalus membranaceus (Fisch.) Bunge is a common traditional Chinese medicine that has been frequently applied in Chinese clinics for the treatment of diabetes and other diseases. Formononetin (FMNT), one of the major isoflavonoid constituents isolated from this herbal medicine, possesses diverse pharmacological benefits and T1DM therapeutic potential. However, the exact molecular mechanisms underlying the action of FMNT in ameliorating T1DM have yet to be fully elucidated. AIMS OF THE STUDY: This study is to investigate the regulation of FMNT on the Keap1/Nrf2 signaling pathway to ameliorate T1DM based on network pharmacology approach combined with experimental validation. MATERIALS AND METHODS: A mouse-derived pancreatic islet ß-cell line (MIN6) was used for the in vitro studies. An alloxan (ALX)-induced T1DM model in wild-type and Nrf2 knockout (Nrf2-/-) C57BL/6J mice were established for the in vivo experiments. The protective effects of FMNT against ALX-stimulated MIN6 cell injury were evaluated using MTT, EdU, apoptosis and comet assays. The levels of blood glucose in mice were measured by using a blood monitor and test strips. The protein expression was detected by Western blot analysis. Furthermore, the binding affinity of FMNT to Keap1 was evaluated using cellular thermal shift assay (CETSA), drug affinity responsive target stability (DARTS) assay, and solvent-induced protein precipitation (SIP) assay. The interaction pattern between FMNT and Keap1 was assessed by molecular docking and molecular dynamics simulation techniques. RESULTS: Network pharmacology analysis revealed that FMNT exerted its therapeutic effect against T1DM by mainly regulating oxidative stress response-associated signaling molecules and pathways, such as Nrf2 regulating anti-oxidant/detoxification enzymes and Keap1-Nrf2 signaling pathway. The in vivo results showed that FMNT significantly deceased the ALX-induced high blood glucose levels and conversely increased the ALX-induced low insulin contents. In vitro, FMNT markedly protected MIN6 cells from ALX-induced cytotoxicity, proliferation inhibition and DNA damage and reduced the ALX-stimulated cell apoptosis. FMNT also inhibited ALX-induced overproduction of intracellular ROS to alleviate oxidative stress. In addition, FMNT could bind to Keap1 to notably activate the Keap1/Nrf2 signaling to upregulate Nrf2 expression and promote the Nrf2 translocation from the cytoplasm to the nucleus, resulting in enhancing the expression of antioxidant proteins HO-1 and NQO1. Inhibition of Keap1/Nrf2 signaling by ALX was also markedly abolished in the cells and mice exposed to FMNT. Moreover, these effects of FMNT in ameliorating T1DM were not observed in Nrf2-/- mice. CONCLUSIONS: This study demonstrates that FMNT could bind to Keap1 to activate the Keap1/Nrf2 signaling to prevent intracellular ROS overproduction, thereby attenuating ALX-induced MIN6 cell injury and ameliorating ALX-stimulated T1DM. Results from this study might provide evidence and new insight into the therapeutic effect of FMNT and indicate that FMNT is a promising candidate agent for the treatment of T1DM in clinics.

Luteolin exhibits synergistic therapeutic efficacy with erastin to induce ferroptosis in colon cancer cells through the HIC1-mediated inhibition of GPX4 expression.

Colon cancer continues to be a prevalent gastrointestinal malignancy with a bleak prognosis. The induction of ferroptosis, a new form of regulated cell death, has emerged as a potentially effective strategy for the treatment of colon cancer. However, numerous colon cancer cells display resistance to ferroptosis induced by erastin, a well-established ferroptosis inducer. Finding drugs that can enhance the susceptibility of colon cancer cells to erastin is of utmost importance. This study aimed to examine the synergistic therapeutic impact of combining erastin with a bioactive flavonoid compound luteolin on the ferroptosis-mediated suppression of colon cancer. Human colon cancer HCT116 and SW480 cells were used for the in vitro studies and a xenograft of colon cancer model in BALB/c nude mice was established for the in vivo experiments. The results showed that combinative treatment of luteolin and erastin effectively inhibited the viability and proliferation of colon cancer cells. Luteolin and erastin cotreatment synergistically induced ferroptosis, concomitant with a reduction in glutathione and an elevation in lipid peroxides. In vivo, combinative treatment of luteolin and erastin exhibited a pronounced therapeutic effect on xenografts of colon cancer, characterized by a significant induction of ferroptosis. Mechanistically, luteolin in combination with erastin synergistically reduced the expression of glutathione peroxidase 4 (GPX4), an antioxidase overexpressed in colon cancer cells. Furthermore, luteolin and erastin cotreatment significantly upregulated the expression of hypermethylated in cancer 1 gene (HIC1), a transcriptional repressor also recognized as a tumor suppressor. HIC1 overexpression notably augmented the suppression of GPX4 expression and facilitated ferroptotic cell death. In contrast, HIC1 silencing attenuated the inhibition of GPX4 expression and eliminated the ferroptosis. Conclusively, these results clearly demonstrated that luteolin acts synergistically with erastin and renders colon cancer cells vulnerable to ferroptosis through the HIC1-mediated inhibition of GPX4 expression, which may act as a promising therapeutic strategy.