Activation of Nrf2 by MIND4-17 protects osteoblasts from hydrogen peroxide-induced oxidative stress

MIND4-17 is a recently developed NF-E2-related factor 2 (Nrf2) activator, which uniquely causes Nrf2 disassociation from Keap1. Here, we showed that pretreatment with MIND4-17 significantly inhibited hydrogen peroxide (H2O2-)induced viability reduction of primary osteoblasts and OB-6 osteoblastic cells. Meanwhile, MIND4-17 inhibited both apoptotic and non-apoptotic osteoblast cell death by H2O2. MIND4-17 treatment induced Keap1-Nrf2 disassociation, causing Nrf2 stabilization, accumulation and nuclear translocation in osteoblasts, leading to transcription of several Nrf2-dependent genes, including heme oxygenase 1 (HO-1), NAD(P) H quinone oxidoreductase 1 (NQO1), gamma-glutamylcysteine synthetase modifier subunit (GCLM) and catalytic subunit (GCLC). Additionally, MIND4-17 largely attenuated H2O2-reactive oxygen species (ROS) production, lipid peroxidation and DNA damages. Nrf2 knockdown by targeted short hairpin RNA (shRNA) exacerbated H2O2-induced cytotoxicity in OB-6 osteoblastic cells, and nullified MIND4-17-mediated cytoprotection against H2O2. Meanwhile, Keap1 shRNA took over MIND4-17's actions and protected OB-6 cells from H2O2. Together, MIND4-17 activates Nrf2 signaling and protects osteoblasts from H2O2.