Nrf2 activation supports cell survival during hypoxia and hypoxia/reoxygenation in cardiomyoblasts; the roles of reactive oxygen and nitrogen species

Abstract

Adaptive mechanisms involving upregulation of cytoprotective genes under the control of transcription factors such as Nrf2 exist to protect cells from permanent damage and dysfunction under stress conditions. Here we explore of the hypothesis that Nrf2 activation by reactive oxygen and nitrogen species modulates cytotoxicity during hypoxia (H) with and without reoxygenation (H/R) in H9C2 cardiomyoblasts. Using MnTBap as a cell permeable superoxide dismutase (SOD) mimetic and peroxynitrite scavenger and L-NAME as an inhibitor of nitric oxide synthase (NOS), we have shown that MnTBap inhibited the cytotoxic effects of hypoxic stress with and without reoxygenation. However, L-NAME only afforded protection during H. Under reoxygenation, conditions, cytotoxicity was increased by the presence of L-NAME. Nrf2 activation was inhibited independently by MnTBap and L-NAME under H and H/R. The increased cytotoxicity and inhibition of Nrf2 activation by the presence of L-NAME during reoxygenation suggests that NOS activity plays an important role in cell survival at least in part via Nrf2-independent pathways. In contrast, O2−• scavenging by MnTBap prevented both toxicity and Nrf2 activation during H and H/R implying that toxicity is largely dependent on O2−•.To confirm the importance of Nrf2 for myoblast metabolism, Nrf2 knockdown with siRNA reduced cell survival by 50% during 4 h hypoxia with and without 2 h of reoxygenation and although cellular glutathione (GSH) was depleted during H and H/R, GSH loss was not exacerbated by Nrf2 knockdown. These data support distinctive roles for ROS and RNS during H and H/R for Nrf2 induction which are important for survival independently of GSH salvage.

Aspirin induces Nrf2‐mediated transcriptional activation of haem oxygenase‐1 in protection of human melanocytes from H2O2‐induced oxidative stress

“…Activation of the Nrf2‐ARE signaling pathway is known to protect against oxidative stress‐induced cell death . Given the association of ASA with Nrf2‐ARE pathway, we explored the ASA dependent role of Nrf2‐ARE antioxidation in this study.…”

Naringin protects against anoxia/reoxygenation-induced apoptosis in H9c2 cells via the Nrf2 signaling pathway

“…# Significant differences from the treatment with A/R alone (P < 0.05). 21,39 Under normal conditions, Nrf2 is located in the cytoplasm and binds with Keap1. 36 This important enzyme has been shown to reduce I/R-induced myocardial damage.…”

Calcitonin Gene-Related Peptide Improves Hypoxia-Induced Inflammation and Apoptosis via Nitric Oxide in H9c2 Cardiomyoblast Cells

“…The increased expression of a variety of endogenous inflammatory cytokines and proinflammatory proteins, including NO, leukotrienes, iNOS and TNF-α, result in myocardial dysfunction [40]. Kolamunne et al [41] showed that L -NAME has a cell-protective role only in the hypoxic state. Furthermore, a high concentration of exogenous NO opens mPTPs, resulting in apoptosis [42].…”