1,720,991 research outputs found
CRITICAL ROLE OF THE THIOREDOXIN AND THE GLUTATHIONE SYSTEMS IN MITOCHONDRIAL PATHOPHYSIOLOGY
Full text linkThe thioredoxin and the glutathione systems are important thiol redox regulating networks. The mitochondrial thioredoxin system is composed by NADPH, thioredoxin reductase 2 (TrxR2) and thioredoxin 2 (Trx2) that, in turn, can reduce peroxiredoxin 3 (Prx3) which has a hydroperoxide scavenging activity.
Cyclophilin D (CypD) is a small protein of the mitochondrial matrix having a crucial role in the control of the mitochondrial membrane permeability transition. CypD activity and redox state were found to be subjected to thioredoxin system-mediated reduction in both isolated rat heart mitochondria and in human cell lines. Furthermore, CypD interaction with Trx2 and Prx3 was observed with both the co-immunoprecipitation technique and with a molecular docking prediction. Thus, CypD can be redox modulated by the mitochondrial thioredoxin system.
The thiol redox regulating systems, especially TrxR2, are often overexpressed in cancer cells to counteract the increased ROS level due to cancer progression. Therefore, the search for specific TrxR2 inhibitors is a possible new anticancer strategy. Several novel compounds, obtained in the frame of different international collaborations, were studied. In particular, a new Au(III) complex bearing a bidentate N-donor ligand, various cyclometalated 2,6-diphenylpyridine Au(III) complexes and a series of mono and bis N-heterocyclic carbene Au(I) complexes were synthesized and were found to inhibit selectively thioredoxin reductase, disrupting the overall cellular redox homeostasis in human ovarian cancer cell lines.
Afterwards, a class of non-gold based metallodrugs, derived from tamoxifen and called tamoxifen-like metallocifens (TLMs), were studied. Interestingly, TLMs act as pro-drugs. In fact, upon enzymatic oxidation, they can be transformed into new oxidized derivatives endowed with remarkable TrxR2 inhibitory properties. In the lymphoblastoid cell line Jurkat, TLMs-mediated TrxR2 inhibition stimulated Trx2 oxidation, ROS production and intrinsic apoptotic pathway activation.
The effects of TrxR2 genetic depletion was also investigated in different cancer cell lines utilizing the Crispr/Cas9 method. Notably, an inverse correlation between TrxR2 protein level and cellular ROS production was observed, indicating the strong pro-oxidizing condition derived from TrxR2 depletion.
Then, the research was focused on glutaredoxin 2 (Grx2). Grx2 was reported to link the thioredoxin and the glutathione systems, but its specific role in redox signaling events is unclear. Grx2 catalyzes protein de-glutathionylations and can also coordinate an iron-sulfur cluster, forming dimers. Grx2 monomeric and dimeric state was analyzed upon HeLa cells treatment with different oxidizing conditions. Grx2 stayed principally as an inactive dimer, while it dissociated, and its activity was stimulated specifically in the mitochondrial compartment, only upon the combined hindering of both the glutathione and the thioredoxin systems. A large increase of free iron ions in the mitochondrial matrix, induction of lipid peroxidation and decrease of the mitochondrial membrane potential were also observed, indicating that Grx2 monomerization implied the release of the iron-sulfur cluster.
In collaboration with Prof. A. Holmgren’s group at the Karolinska Institutet, the role of Grx2 in mitochondria has been further studied in a murine model knockout for Grx2 in mitochondria (mGrx2 KO). The overall redox state of mitochondria isolated from different organs of WT or mGrx2 KO mice at three months of age was assessed and interestingly it was not affected from Grx2 deletion. However, a significant increase of mitochondrial ROS production was noted in the liver associated to a decrease of the mitochondrial respiratory capacity, to a reduction of the mitochondrial membrane potential and to an increased sensitivity to calcium ions. Altogether, these results suggest that Grx2 deletion in mouse mitochondria affects mainly the mitochondrial functioning in the liver
Significance of the mitochondrial thioredoxin reductase in cancer cells: An update on role, targets and inhibitors
No full textDimers of Glutaredoxin 2 as Mitochondrial Redox Sensors in Selenite-induced Oxidative Stress
Full text linkGlutaredoxin 2 (Grx2) has been previously shown to link thioredoxin and glutathione systems by receiving reducing equivalents by both thioredoxin reductase and glutathione. Grx2 catalyzes protein glutathionylation/deglutathionylation and can coordinate an iron-sulfur cluster, forming inactive dimers stabilized by two molecules of glutathione. This protein is mainly located in the mitochondrial matrix, though other isoforms have been found in the cytosolic and nuclear cell compartments. In the present study, we have analyzed the monomeric and dimeric states of Grx2 under different redox conditions in HeLa cells, and sodium selenite was utilized as the principal oxidizing agent. After selenite treatment, an increased glutathione oxidation was associated to Grx2 monomerization and activation, specifically in the mitochondrial compartment. Interestingly, in mitochondria, a large decline of thioredoxin reductase activity was also observed concomitantly to Grx2 activity stimulation. In addition, Grx2 monomerization led to an increase free iron ions concentration in the mitochondrial matrix, induction of lipid peroxidation and decrease of the mitochondrial membrane potential, indicating that the disassembly of Grx2 dimer involved the release of the iron-sulfur cluster in the mitochondrial matrix. Moreover, sodium selenite-triggered lipid and protein oxidation was partially prevented by deferiprone, an iron chelator with mitochondriotropic properties, suggesting a role of the iron-sulfur cluster release in the observed impairment of mitochondrial functions. Thus, by sensing the overall cellular redox conditions, mitochondrial Grx2 dimers become active monomers upon oxidative stress induced by sodium selenite with the consequent release of the iron-sulfur cluster, leading to activation of the intrinsic apoptotic pathway
Insights into the Redox Activity of Platinum(II) Complexes Bearing a Mitochondriotropic Ligand in Cisplatin-resistant Ovarian Cancer Cell Lines
Full text link
Thiamine disulfide derivatives in thiol redox regulation: Role of thioredoxin and glutathione systems
Full text linkThiamine (vitamin B1), under the proper conditions, is able to reversibly open the thiazole ring, forming a thiol-bearing molecule that can be further oxidized to the corresponding disulfide. To improve the bioavailability of the vitamin, several derivatives of thiamine in the thioester or disulfide form were developed and extensively studied over time, as apparent from the literature. We have examined three thiamine-derived disulfides: thiamine disulfide, sulbutiamine, and fursultiamine with reference to their intervention in modulating the thiol redox state. First, we observed that both glutathione and thioredoxin (Trx) systems were able to reduce the three disulfides. In particular, thioredoxin reductase (TrxR) reduced these disulfides either directly or in the presence of Trx. In Caco-2 cells, the thiamine disulfide derivatives did not modify the total thiol content, which, however, was significantly decreased by the concomitant inhibition of TrxR. When oxidative stress was induced by tert-butyl hydroperoxide, the thiamine disulfides exerted a protective effect, indicating that the thiol form deriving from the reduction of the disulfides might be the active species. Further, the thiamine disulfides examined were shown to increase the nuclear levels of the transcription factor nuclear factor erythroid 2 related factor 2 and to stimulate both expression and activity of NAD(P)H quinone dehydrogenase 1 and TrxR. However, other enzymes of the glutathione and Trx systems were scarcely affected. As the thiol redox balance plays a critical role in oxidative stress and inflammation, the information presented can be of interest for further research, considering the potential favorable effect exerted in the cell by many sulfur compounds, including the thiamine-derived disulfides.Modulation of thiol redox signaling by thiamine disulfide derivatives depends on the relative efficiency of glutathione and thioredoxin systems. imag
Comparative analysis of the antioxidant capacity and lipid and protein oxidation of soy and oats beverages
Full text linkNrf2-Activating Bioactive Peptides Exert Anti-Inflammatory Activity through Inhibition of the NF-κB Pathway
Full text linkRedox status and inflammation are related to the pathogenesis of the majority of diseases.
Therefore, understanding the role of specific food-derived molecules in the regulation of their
specific pathways is a relevant issue. Our previous studies indicated that K-8-K and S-10-S, milk
and soy-derived bioactive peptides, respectively, exert antioxidant effects through activation of
the Keap1/Nrf2 pathway. A crosstalk between Nrf2 and NF-κB, mediated by the action of heme
oxygenase (HO-1), is well known. On this basis, we studied if these peptides, in addition to their
antioxidant activity, could exert anti-inflammatory effects in human cells. First, we observed an
increase of HO-1 expression in Caco-2 cells treated with K-8-K and S-10-S, following the activation
of the Keap1/Nrf2 pathway. Moreover, when cells are treated with the two peptides and stimulated
by TNF-α, the levels of NF-κB in the nucleus decreased in comparison with TNF-α alone. In the same
conditions, we observed the downregulation of the gene expression of proinflammatory cytokines
(IL1B, IL6, and TNF), while the anti-inflammatory cytokine gene, IL1RN, was upregulated in Caco-2
cells processed as reported above. Then, when the cells were pretreated with the two peptides
and stimulated with LPS, a different proinflammatory factor, (TNF-α) was estimated to have a
lower secretion in the supernatant of cells. In conclusion, these observations confirmed that Nrf2-
activating bioactive peptides, K-8-K and S-10-S, exerted anti-inflammatory effects by inhibiting the
NF-κB pathway
- …
