Glutaredoxin Protects Cerebellar Granule Neurons from Dopamine-induced Apoptosis by Dual Activation of the Ras-Phosphoinositide 3-Kinase and Jun N-terminal Kinase Pathways

Abstract

Excessive production of reactive oxygen species in living cells may damage their biological components. This condition, referred to as oxidative stress, is a common denominator of pathological conditions. Cells have evolved a wide array of antioxidant mechanisms including small reducing molecules (e.g. glutathione, ascorbic acid), antioxidative enzymes (e.g. catalase, superoxide dismutase, glutathione peroxidase; for review, see Refs. 1-4), and oxidoreductase enzymes such as thioredoxin and glutaredoxin (Grx) 1 (5).Grx are antioxidant enzymes by virtue of the reducing power of their active site (CXXC), which catalyzes the transfer of electrons from reduced glutathione to disulfides (5). This thiol disulfide interchange reaction is crucial for the maintenance of intracellular redox homeostasis, especially under oxidative stress (6). Mammalian Grx is widely expressed in different cell types, including neurons (7-11). The enzyme can restore the activity of glutathionylated proteins containing mixed disulfides between a protein thiol and GSH (inactive form) by reducing the disulfide bridge to give reduced GSH and the active protein form containing a free thiol. Examples of such GSHthiol regulation of activity can be found in tyrosine phosphatase 1B (13), phosphofructokinase (14, 15), nuclear factor-I (16), and polyomavirus enhancer-binding protein 2 (17). Thanks to the antioxidant properties of Grx activity, human Grx and Escherichia coli Grx2 can rescue cerebellar granule neurons from dopamine (DA)-induced oxidative stress (18).DA, the endogenous neurotransmitter of the nigrostriatal pathway, is a powerful oxidant that exerts its toxic effects through its oxidative metabolites. DA-induced oxidations are generally implicated in neurodegenerative processes (19,20) especially in Parkinson's disease (21,22). Administration of DA to rat striatum caused pre-and postsynaptic damage (23). Intraventricular injection of DA in rats resulted in dose-dependent death of the animals (24). In vitro studies have shown that DA can cause cell death in mesencephalic, striatal, and cortical primary neuron cultures (25-29). DA-induced cell death in sympathetic, cerebellar granule neurons, PC-12 cells, and thymocytes has all the features of apoptotic cell death (30 -32). Apart from the administration of Grx, the toxic effects of DA can be prevented by the application of small molecular weight antioxidants such as N-acetylcysteine, catalase, ascorbic acid, and dithiothreitol (30,31,33,34).Little is known about the molecules and signaling pathways involved in DA-induced apoptosis. Enhancement of the DNA binding activity of NF-B protects neurons from DA-induced apoptosis (18). A survival signal pathway that might activate NF-B is the Ras/PI3K/Akt/NF-B cascade (35,36).Ras is a family of proteins involved in the regulation of cell proliferation, cytoskeletal rearrangements, and differentiation and survival of different cell types (37,38). Ras activation is localized on the inner surface of the cell membrane where it * This research was suppor...

Oxidation and S-Nitrosylation of Cysteines in Human Cytosolic and Mitochondrial Glutaredoxins

“…Cytosolic Grx1 is implicated in several cellular processes that require strict redox control, for instance the regulation of transcription factors (18,53) and apoptosis (16,54,55). In this study, we have found that Grx1 itself is inhibited by oxidation and nitrosylation of structural Cys residues.…”

Targeted disruption of the glutaredoxin 1 gene does not sensitize adult mice to tissue injury induced by ischemia/reperfusion and hyperoxia

“…Thirdly, the use of cell death as an end point may not be appropriate for correlating the extent of cell injury to the level of protein S-glutathionylation. Nevertheless, overexpression of Grx1 has been shown to prevent cells from oxidant-mediated damage in response to dopamine, H 2 O 2 , and high concentrations of glucose [26][27][28][29][30][31]. These results support the hypothesis that oxidant-induced cell injury is partly mediated through S-glutathionylation of proteins.…”

“…As expected, cells overexpressing Grx1 are more resistant to doxorubicin-induced toxicity compared to control cells [26]. In addition, treatment of cultured cerebellar granule neurons with recombinant Grx protein of E. coli prevents cell death induced by dopamine, and the protection appears to be mediated through activation of the Ras/PI3K/ Ref-1/Akt/NF-κB pathway [27,28]. This protective mechanism was further elaborated in another study in which Grx1 overexpression was shown to protect H9c2 cells against toxicity of hydrogen peroxide (H 2 O 2 ) [29].…”

Short interfering RNA-mediated silencing of glutaredoxin 2 increases the sensitivity of HeLa cells toward doxorubicin and phenylarsine oxide

“…Grx1 also protects cells from apotosis induced by hydrogen peroxide by regulating the redox state of Akt (46). Escherichia coli Grx2 and human Grx1 have been shown to protect cerebellular granulae neurons from dopamine-induced apoptosis, involving the Ras-phosphoinositide 3-kinase and Jun N-terminal kinase pathways (47,48). On the other hand, apoptosis signal-regulating kinase 1 is inactive when bound to reduced Grx1 (49), and oxidation of Grx1 causes release of apoptosis signal-regulating kinase 1 and hence initiation of apoptosis.…”