Proanthocyanidins Activate Nrf2/ARE Signaling Pathway in Intestinal Epithelial Cells by Inhibiting the Ubiquitinated Degradation of Nrf2.

Nrf2 plays a key role in the antioxidant system, and many antioxidants can activate the Nrf2/ARE signaling pathway and alleviate oxidative stress. However, the underlying mechanisms of antioxidants, such as proanthocyanidin- (PC-) induced Nrf2 activation, remain poorly understood. In this study, PC was used on MODE-K cells at different concentrations (0, 1, 2.5, and 5 µg/mL) and different times (0, 3, 6, 12, and 24 h); then, immunoprecipitation, immunofluorescence, and Western blotting were performed to test Nrf2, Bach1, Keap1, HO-1, and NQO1 protein expressions in MODE-K cells. Results showed that PC increased Nrf2, HO-1, and NQO1 protein expressions, decreased Keap1 and Bach1 protein expressions, and enhanced ARE gene activity. PC also decreased the ubiquitinated degradation of the Nrf2 protein, increased Nrf2 protein stability, and increased Nrf2 protein expression by inhibiting Keap1-dependent Nrf2 protein degradation, promoted Nrf2 entry into the nucleus, competed with Bach1, and activated ARE elements, which in turn initiated the Nrf2/ARE signaling pathway. Thus, we conclude that PC activates the Nrf2/ARE signaling pathway in intestinal epithelial cells by inhibiting the ubiquitinated degradation of Nrf2, increasing Nrf2 protein stability and expression, and then regulating key antioxidant enzymes such as HO-1 and NQO1 to initiate cytoprotective effects.

MicroRNA-21 is involved in osteosarcoma cell invasion and migration.

MicroRNAs are involved in different cancer-related processes. MicroRNA-21 (miR-21), as an oncomiR, is overexpressed in all kinds of tumors and the role of miR-21 in carcinogenesis is elucidated in many cancers gradually. However, the function of miR-21 in osteosarcoma is still unclear. In our study, we found that miR-21 was significantly overexpressed in osteosarcoma tissues. More importantly, we confirmed that knockdown of miR-21 greatly decreased cell invasion and migration of MG-63. Furthermore, we identified that RECK (reversion-inducing-cysteine-rich protein with kazal motifs), a tumor suppressor gene, was a direct target of miR-21. Finally, the expression of RECK protein negatively correlated with the expression of miR-21 in human osteosarcoma tissues, indicating the potential regulation of RECK by miR-21. Our results suggest that miR-21 expression has a key role in regulating cellular processes in osteosarcoma, likely through regulating RECK and may serve as a therapeutic target.