Stabilization of Nrf2 by tBHQ Confers Protection against Oxidative Stress-Induced Cell Death in Human Neural Stem Cells

Abstract

Recent studies indicate that NF-E2 related factor 2 (Nrf2) is a substrate for the ubiquitin-proteasome pathway. The present study is aimed to determine whether increased protein stability is a mechanism by which quinone compounds, like tert-butylhydroquinone (tBHQ), may enhance Nrf2-mediated transcriptional activation and subsequent antioxidant protection. H2O2-induced necrotic cell death, evidenced by transmission electronic microscope (TEM) imaging with no caspase 3 activation and PARP cleavage, was significantly attenuated by pretreatment with tBHQ or overexpression of Nrf2 through advenovirus-mediated infection in human neural stem cells (hNSCs). Microarray analysis showed that those identified antioxidant genes, responsible for antiapoptotic action in IMR-32 cells (J. Li et al., 2002, J. Biol. Chem. 277, 388-394), were also coordinately upregulated through Nrf2-dependent antioxidant responsive element (ARE) activation in hNSC. The stabilization of Nrf2 by tBHQ in IMR-32 cells was evidenced by a pulse-chase assay showing no significant increase in Nrf2 protein synthesis after tBHQ treatment, and by ubiquitin immunoprecipitation showing that tBHQ stabilized ubiquitinated Nrf2. An in vitro proteasomal activity assay showed that tBHQ did not act as a 20S/26S proteasome inhibitor. Nrf2 stabilization by tBHQ also was observed in hNSCs. Taken together, this study suggests that identified antioxidant genes, which were upregulated through tBHQ induced Nrf2 stabilization, confer protection on target cells against H2O2-induced apoptotic cell death in neuroblastoma cells as well as the necrotic cell death in the hNSC. Nrf2 stabilization by pharmacological modulation or adenovirus-mediated Nrf2 overexpression, therefore, might be viable strategies to prevent a wide-spectrum of oxidative stress-related neuronal cell injuries.

Nrf2 activation in the treatment of neurodegenerative diseases: a focus on its role in mitochondrial bioenergetics and function

“…Its oral formulation BG-12 has been recently approved for the treatment of multiple sclerosis (Linker et al, 2011). Other molecules able to stabilize Nrf2 are the quinone compound tert-butylhydroquinone (tBHQ) (Li et al, 2005) and the triterpenoids bardoxolone methyl (Dinkova-Kostova et al, 2005) and RTA 408 (Probst et al, 2015), both of which are currently in clinical trials.…”

Oxidative stress in spinal cord injury and antioxidant-based intervention

“…Activation of Nrf2 and Nrf2-mediated antioxidant enzyme gene expression by pro-oxidants, including H 2 O 2 at moderate non-lethal doses suggests that Nrf2 signaling may control the adaptive response of neuronal cells to oxidative insults. 29 This potential Nrf2-mediated adaptive response to oxidative stress is particularly relevant to SCI where the increased level of ROS is constantly generated for a prolonged period of time leading to progressive oxidative stress in secondary injury of SCI. 18 Systematic increases in Nrf2 and ARE-driven heme oxygenase-1 in the spinal cord of SOD G93A rats, an experimental model of ALS, have been reported, 30,31 which may represent an adaptive response to oxidative stress.…”

“…Studies have suggested that the protective role of these compounds against oxidative stress damage is mediated, at least partially, by effects on signaling molecules including extracellular signal-regulated kinase, nuclear factor kB and Nrf2. 18,[27][28][29][30][31] Nrf2 signaling appears to has a central role in regulating the induction of antioxidants by phenolic compounds. 18,[27][28][29][30][31] …”

BG00012 - A Novel Oral Therapy in Development for the Treatment of Multiple Sclerosis

“…31,33,34 Recent studies have demonstrated that BG00012 and monomethyl fumarate can activate Nrf2 in vitro. 35 The Nrf2 pathway has been implicated as a mediator of a range of neuroprotective effects in the CNS, including inhibition of oxidative and excitotoxic neuronal damage, [36][37][38][39][40] protection of the BBB 41 and regulation of myelin maintenance. 42 Hence, the current body of experimental evidence suggests that BG00012 may provide a dual neuroprotective and anti-inflammatory a report by therapeutic effect not targeted by contemporary MS therapies (see Figure 2).…”