Endogenous Thioredoxin Is Required for Redox Cycling of Anthracyclines and p53-dependent Apoptosis in Cancer Cells

Abstract

Apoptosis is a major mechanism of cancer cell destruction by chemotherapy and radiotherapy. The anthracycline class of antitumor drugs undergoes redox cycling in living cells producing increased amounts of reactive oxygen species and semiquinone radical, both of which can cause DNA damage, and consequently trigger apoptotic death of cancer cells. We show here that MCF-7 cells overexpressing thioredoxin (Trx) were more apoptotic in response to daunomycin. Thioredoxin (Trx) 2 is a low molecular mass protein (12 kDa) that is widely distributed; Trx is found within the cytoplasmic, membrane, extracellular, and mitochondrial cellular fractions (1, 2). The Trx system includes Trx, Trx reductase, and peroxiredoxins. Trx reductase is an efficient protein-disulfide reductase that uses NADPH as a source of reducing equivalents. Besides being an antioxidant itself (3, 4), Trx also plays an important role in regulating the expression of other antioxidant genes such as manganese superoxide dismutase (5). Trx overexpression also enhances the expression of peroxiredoxin that could reduce peroxides to molecular oxygen and H 2 O (6). Trx has been shown to regenerate oxidatively inactivated proteins (7,8). In addition to its role as an antioxidant protein, Trx has been shown to have growth promoting properties (9). In contrast, a recent study has demonstrated that overexpression of redox-active Trx could promote cell death via activation of caspase-8 (10). Additional studies have shown that Trx reductase is critical for cell death, and a Trx-dependent mechanism has been suggested (11). Recent studies also indicate that caspases, the executioner of cell death by apoptosis, could be activated by Trx due to its disulfide reducing properties (12). Caspases are rich in cysteine motifs that are required for their catalytic activity. Therefore, oxidation could inhibit caspase activity, which could be restored by the Trx system (12). Furthermore Trx also has been shown to promote p53-DNA binding due to its reducing actions on DNA-binding cysteine motifs on p53 (14). Taken together, accumulating evidence suggests that Trx is a multifunctional protein, which can participate in proliferation as well as cell death process. The antioxidative action of Trx could be due to its manganese superoxide dismutase inducing properties (5, 15) as well as direct scavenging of hydroxyl radicals or singlet oxygen.The anthracycline class of anticancer drugs such as doxorubicin or daunomycin has been shown to induce p53-dependent apoptosis in cancer cells (16,17). Additionally anthracyclines have also been shown to cause DNA damage, which increases p53 expression (18,19). p53 is a sequence-specific transcription factor, which can induce proapoptotic or suppress antiapoptotic genes in response to DNA damage or irreparable cell cycle arrest (20). Phosphorylation of p53 on the Ser 15 residue dissociates MDM2 and activates p53 as a transcription factor, which binds to various p53-dependent genes resulting in their activation or repression (20). While evaluating ...

Thioredoxin Uses a GSH-independent Route to Deglutathionylate Endothelial Nitric-oxide Synthase and Protect against Myocardial Infarction

“…Adenovirus Production-AdenoX system was obtained from Stratagene Corp. (La Jolla, CA), and LacZ or Trx cDNA was cloned into pAdenoX vector as described previously (49). Recombinant virus was allowed to infect HEK293 cells for generation of viral particles.…”

Redox Control Systems in the Nucleus: Mechanisms and Functions

“…The p53 forms a disulfide bond under mild oxidizing conditions by cis-diaminedichloroplatinum (II), and disulfide bond formation correlates with inhibition of the transcriptional activity of p53 (180). Trx1 enhances p53 DNA-binding activity directly or through Ref-1 mediation (186), whereas dominantnegative Trx1 inhibited p53 DNA-binding activity (156). It has been suggested that a protective role for the nuclear Trx1 in cisplatin-induced apoptosis is perhaps mediated by p53-dependent mechanism (17).…”

Reduction of endoplasmic reticulum Ca2+ levels favors plasma membrane surface exposure of calreticulin

“…Thus, the anthracyclin-stimulated CRT exposure is not mediated by a classical DNA damage response (which would involve the nucleus). Anthracyclins have been reported to exert a direct toxic effect on the PM, 13 to stimulate ceramide synthesis, 14 to induce the generation of reactive oxygen species, 15,16 and to affect intracellular Ca 2 þ homeostasis, mainly by reducing ER Ca 2 þ concentrations, 17,18 perhaps through a direct effect on ER proteins such as calsequestrin. 19 Based on the aforementioned information, we decided to investigate the impact of ER Ca 2 þ homeostasis on the regulation of CRT exposure on the surface of anthracyclintreated tumor cells.…”