Tert-butylhydroquinone induces mitochondrial oxidative stress causing Nrf2 activation

Abstract

Tert-butylhydroquinone (tBHQ), the major metabolite of butylated hydroxyanisole, induces an antioxidant response through the redox-sensitive transcription factor, nuclear factor-E2-related factor-2 (Nrf2). However, the mechanism by which tBHQ induces Nrf2 activity is not entirely understood. Here, we show that tBHQ preferentially alters the redox status in the mitochondrial compartment in HeLa cells. HeLa cells treated with tBHQ showed a preferential oxidation of mitochondrial thioredoxin-2 (Trx2), while cellular glutathione and cytosolic thioredoxin-1 were not affected. Preferential mitochondrial oxidation by tBHQ was supported by detection of reactive oxygen species (ROS) specific to this compartment. To determine the role of Trx2 in regulating downstream effects of tBHQ, HeLa cells were transiently transfected with an empty, Trx2, or C93S (Cys93Ser) Trx2 dominant-negative mutant expression vector. Overexpression of Trx2 decreased basal mitochondrial ROS production, whereas expression of C93S Trx2 enhanced it. In addition, under untreated conditions, expression of C93S Trx2 led to an increase in the basal activities of Nrf2. With tBHQ treatments, Trx2 overexpression suppressed Nrf2 accumulation and activity, whereas expression of C93S Trx2 had no effect on the degree of inducibility or Nrf2 accumulation but did increase the overall activity of Nrf2. Quantitative polymerase chain reaction analysis of Nrf2-regulated gene expression corroborate Trx2 control of tBHQ-mediated Nrf2 activation. These data show a compartment-specific effect where tBHQ-induced Nrf2 signaling is mediated by Trx2 and suggest that antioxidant status in various compartments would provide different levels of control of redox signaling.

Protective effect of nuclear factor E2-related factor 2 on inflammatory cytokine response to brominated diphenyl ether-47 in the HTR-8/SVneo human first trimester extravillous trophoblast cell line

“…tBHQ-stimulates ROS formation as a consequence of redox cycling, which subsequently stimulates nuclear translocation of Nrf2 and activates ARE-dependent gene expression (Gharavi et al , 2007; Itoh et al , 1999; Sian et al , 1994). Sulforaphane is an electrophile that can react with protein thiols to form thionoacyl adducts and is believed to modify cysteine residues in Keap 1 protein to a sulfenic acid (−SOH), resulting in a conformational change of Keap1, translocation of Nrf2, and upregulation of antioxidant genes (Imhoff and Hansen, 2010; Keum, 2011). The augmented GSH concentrations and increased antioxidant gene expression observed in the present study agree with prior reports that Nrf2 inducers increase cellular antioxidative capacity (Alfieri et al , 2011; Hara et al , 2003).…”

Visualization of the Drosophila dKeap1-CncC interaction on chromatin illumines cooperative, xenobiotic-specific gene activation

“…Paraquat can cause oxidative stress and is thought to activate Nrf2 through the oxidation of cysteine residues on Keap1 (Suntres, 2002). tBHQ can activate Nrf2 by increasing mitochondrial reactive oxygen species and the tBHQ metabolite tert-butylbenzoquinone can directly modify Keap1 (Imhoff and Hansen, 2010;Abiko et al, 2011). The mechanisms by which phenobarbital regulates Keap1-Nrf2 as well as dKeap1-CncC were not known.…”

Preventive effect of tert-butylhydroquinone on scrotal heat-induced damage in mouse testes

“…In the average male, mitochondrial oxidative damage from steroidogenesis may be more of a chronic than an acute factor, and might be important in reducing testosterone production (Chen and Zirkin, 1999;Luo et al, 2006). A recent study reported that tBHQ could induce mitochondrial oxidative stress in HeLa cells (Imhoff and Hansen, 2010). In the present study, the reduced testosterone level and low expression of CYP 17 may have resulted from the pre-treatment of tBHQ, which could have induced chronic and mitochondrial oxidative stress, and thus decreased testosterone synthesis in testes.…”