Txnrd2 Attenuates Early Brain Injury by Inhibition of Oxidative Stress and Endoplasmic Reticulum Stress via Trx2/Prx3 Pathway after Intracerebral Hemorrhage in Rats.

Thioredoxin-reductase 2 (Txnrd2) belongs to the thioredoxin-reductase family of selenoproteins and is a key antioxidant enzyme in mammalian cells to regulate redox homeostasis. Here, we reported that Txnrd2 exerted a major influence in brain damage caused by Intracerebral hemorrhage (ICH) by suppressing endoplasmic reticulum (ER) stress oxidative stress and via Trx2/Prx3 pathway. Furthermore, we demonstrated that pharmacological selenium (Se) rescued the brain damage after ICH by enhancing Txnrd2 expression. Primarily, expression and localization of Txnrd2, Trx2 and Prx3 were determined in collagenase IV-induced ICH model. Txnrd2 was then knocked down using siRNA interference in rats which were found to develop more severe encephaledema and neurological deficits. Mechanistically, we observed that loss of Txnrd2 leads to increased lipid peroxidation levels and ER stress protein expression in neurons and astrocytes. Additionally, it was revealed that Se effectively restored the expression of Txnrd2 in brain and inhibited both the activity of ER stress protein activity and the generation of reactive oxygen species (ROS) by promoting Trx2/Prx3 kilter when administrating sodium selenite in lateral ventricle. This study shed light on the effect of Txnrd2 in regulating oxidative stress and ER stress via Trx2/Prx3 pathway upon ICH and its promising potential as an ICH therapeutic target.

Tremella fuciformis polysaccharides alleviates UV-provoked skin cell damage via regulation of thioredoxin interacting protein and thioredoxin reductase 2.

INTRODUCTION: Skin is exposed to a wide range of environmental risk factors including ultraviolet (UV) and all kinds of pollutants. Excessive UV exposure contributes to many disorders, such as photoaging, skin inflammation, and carcinogenesis. Previous studies have shown that Tremella fuciformis polysaccharides (TFPS) have protective effects on oxidative stress in cells, but the specific protective mechanism has not been clarified. METHODS: To determine the effects of TFPS on UV-irritated human skin, we conducted a variety of studies, including Cell Counting Kit-8 (CCK-8), trypan blue, Western blot, apoptosis assays, reactive oxygen species (ROS) detection in primary skin keratinocytes, and chronic UV-irradiated mouse model. RESULTS: We first determined that TFPS protects human skin keratinocytes against UV radiation-induced apoptosis and ROS production. Moreover, TFPS regulates thioredoxin interacting protein (TXNIP) and thioredoxin reductase 2 (TXNRD2) levels in primary skin keratinocytes for photoprotection. Last, we found that topical TFPS treatment could alleviate the UV-induced skin damage in chronic UV-irradiated mouse model. CONCLUSION: Collectively, our work indicates the beneficial role of TFPS in UV-induced skin cell damage and provides a novel therapeutic reagent to prevent or alleviate the progress of photoaging and other UV-provoked skin diseases.

Sulfasalazine and Chromotrope 2B reduce oxidative stress in murine bone marrow-derived mesenchymal stem cells.

BACKGROUND: With advancing age of stem cells, dysregulation of various processes at the cellular level occurs, thereby decreasing their regeneration potential. One of the changes that occurs during the aging process is the accumulation of reactive oxygen species (ROS), which accelerates the processes of cellular senescence and cell death. The aim of this study is to evaluate two antioxidant compounds; Chromotrope 2B and Sulfasalazine, for their antioxidant effects on young and old rat bone marrow mesenchymal stem cells (MSCs). METHODS AND RESULTS: Oxidative stress was induced in MSCs by 5 µM dexamethasone for 96 h and the cells were treated with Chromotrope 2B or Sulfasalazine, 50 µM each. The effects of antioxidant treatment following oxidative stress induction was evaluated by transcriptional profiling of genes involved in the oxidative stress and telomere maintenance. Expression levels of Cat, Gpx7, Sod1, Dhcr24, Idh1, and Txnrd2 were found to be increased in young MSCs (yMSCs) as a result of oxidative stress, while Duox2, Parp1, and Tert1 expression were found to be decreased as compared to the control. In old MSCs (oMSCs), the expressions of Dhcr24, Txnrd2, and Parp1 increased, while that of Duox2, Gpx7, Idh1, and Sod1 decreased following oxidative stress. In both MSC groups, Chromotrope 2B prompted decrease in the ROS generation before and after the induction of oxidative stress. In oMSCs, ROS content was significantly reduced in the Sulfasalazine treated group. CONCLUSION: Our findings suggest that both Chromotrope 2B and Sulfasalazine possess the potential to reduce the ROS content in both age groups, though the latter was found to be more potent. These compounds can be used to precondition MSCs to enhance their regenerative potential for future cell-based therapeutics.

Thioredoxin Reductase 2 Synergizes with Cytochrome c, Somatic to Alleviate Doxorubicin-Induced Oxidative Stress in Cardiomyocytes and Mouse Myocardium.

Doxorubicin (DOX) may cause multiple side effects, which include cardiotoxicity. Hence, to ascertain the impact of thioredoxin reductase 2 (TXNRD2) and cytochrome c, somatic (CYCS) on DOX-induced oxidative stress (OS) in cardiomyocytes and mouse myocardium, this study was implemented. DOX was utilized to treat cardiomyocytes and mice, and TXNRD2 and CYCS expression in cell supernatant and mouse myocardial tissues was detected. TXNRD2 and/or CYCS were overexpressed in DOX-induced cardiomyocytes and mice. In cardiomyocytes, cell viability and the levels of reactive oxygen species (ROS), superoxide dismutase (SOD), catalase (CAT), malondialdehyde (MDA), and glutathione (GSH) were measured. In mice, pathologic changes of the heart, ejection fraction (EF), fractional shortening (FS), and heart weight (HW) /tibial length (TL) ratio, and the contents of lactic dehydrogenase (LDH), creatine kinase-MB (CK-MB), and cardiac troponin I (cTnI) were analyzed. To assess the binding between TXNRD2 and CYCS, coimmunoprecipitation and glutathione S-transferase pull-down assays were performed. TXNRD2 and CYCS were downregulated in DOX-treated cardiomyocytes and mice. Mechanistically, TXNRD2 interacted with CYCS. Overexpression of TXNRD2 or CYCS augmented viability and SOD, CAT, and GSH levels but reduced ROS and MDA contents in DOX-induced cardiomyocytes, which was further facilitated by simultaneous overexpression of TXNRD2 or CYCS. Moreover, TXNRD2 or CYCS upregulation improved the pathologic changes in myocardial tissues, along with increases in EF, FS, and HW/TL ratio of the heart and SOD, CAT, and GSH levels and decreases in LDH, CK-MB, cTnI, ROS, and MDA levels. TXNRD2 coordinated with CYCS to alleviate DOX-induced OS in cardiomyocytes and mouse myocardium.

Selenoprotein Gene mRNA Expression Evaluation During Renal Ischemia-Reperfusion Injury in Rats and Ebselen Intervention Effects.

Effects of selenoproteins on many renal diseases have been reported. However, their role in renal ischemia-reperfusion (I/R) injury is unclear. The present study was performed to investigate the impact of ebselen and renal I/R injury on the expression of selenoproteins. Sprague-Dawley rats were pretreated with or without ebselen (10 mg/kg) through a daily single oral administration from 3 days before renal I/R surgery. RT-qPCR (real-time quantitative PCR) was performed to determine the mRNA expression of 25 selenoprotein genes in the renal tissues. The expression levels of two selenoproteins, including GPX3 (glutathione peroxidase 3) and DIO1 (iodothyronine deiodinase 1), were evaluated by Western blot or/and IHF (immunohistofluorescence) assays. Furthermore, renal function, renal damage, oxidative stress, and apoptosis were assessed. The results showed that in renal I/R injury, the mRNA levels of 15 selenoprotein genes (GPX1, GPX3, GPX4, DIO1, DIO2, TXNRD2, TXNRD3, SEPHS2, MSRB1, SELENOF, SELENOK, SELENOO, SELENOP, SELENOS, and SELENOT) were decreased, whereas those of eight selenoprotein genes (GPX2, GPX6, DIO3, TXNRD1, SELENOH, SELENOM, SELENOV, and SELENOW) were increased. I/R also induced a reduction in the expression levels of GPX3 and DIO1 proteins. In addition, our results indicated that ebselen reversed the changes in those selenoprotein genes, excluding SELENOH, SELENOM, SELENOP, and SELENOT, in renal I/R injury and alleviated I/R-induced renal dysfunction, tissue damage, oxidative stress, and apoptosis. To our knowledge, this is the first study to investigate the changes of 25 mammalian selenoprotein genes in renal I/R injury kidneys. The present study also provided more evidence for the roles of ebselen against renal I/R injury.

Lipoxin A4 attenuates MSU-crystal-induced NLRP3 inflammasome activation through suppressing Nrf2 thereby increasing TXNRD2.

Gout is a common inflammatory disease. The activation of NLRP3 inflammasome induced by monosodium urate (MSU) crystals has a critical role in gout, and its prevention is beneficial for patients. Lipoxin A4 (LXA4) is an endogenous lipoxygenase-derived eicosanoid mediator with powerful anti-inflammatory properties. However, whether LXA4 can suppress NLRP3 inflammasome activation induced by MSU crystals remains unclear. This study aimed to investigate the protective effect of LXA4 on MSU-crystal-induced NLRP3 inflammasome activation and its underlying molecular mechanisms. We found that LXA4 inhibited MSU-crystal-induced NLRP3 inflammasome activation, interleukin (IL)-1ß maturation, and pyroptosis. More specifically, LXA4 suppressed the assembly of the NLRP3 inflammasome, including oligomerization and speck formation of ASC, and ASC-NLRP3 interaction. Furthermore, LXA4 suppressed oxidative stress, the upstream events for NLRP3 inflammasome activation, as evidenced by the fact that LXA4 eliminated total reactive oxygen species (ROS) generation and alleviated nicotinamide adenine dinucleotide phosphate (NADPH) oxidase activation and mitochondrial dysfunction. However, LXA4 also depressed the Nrf2 activation, a critical molecule in the antioxidant pathway, and then exerted an inhibitory impact on Klf9 expression and promotional impact on TXNRD2 expression, two molecules located downstream of Nrf2 in sequence. Knockdown of TXNRD2 reversed the LXA4-induced depression of ROS and NLRP3 inflammasome. Moreover, LXA4 alleviated joint inflammation and decreased the production of cleaved caspase-1 and matured IL-1ß in gouty arthritis rats. Taken together, our findings demonstrate that LXA4 can attenuate MSU-crystal-induced NLRP3 inflammasome activation, probably through suppressing Nrf2 activation to increase TXNRD2 expression. The present study highlights the potential of LXA4 as an attractive new gout treatment candidate.

Regulation of the molecular repertoires of oxidative stress response in the gills and olfactory organ of Atlantic salmon following infection and treatment of the parasite Neoparameoba perurans.

The present study investigated the involvement of key molecular regulators of oxidative stress in amoebic gill disease (AGD), a parasitic infestation in Atlantic salmon. In addition, the study evaluated how these molecular biomarkers responded when AGD-affected fish were exposed to a candidate chemotherapeutic peracetic acid (PAA). Atlantic salmon were experimentally infected with the parasite Neoparameoba perurans, the causative agent of AGD, by bath exposure and after 2 weeks, the fish were treated with three commercial PAA products (i.e., Perfectoxid, AquaDes and ADDIAqua) at a dose of 5 ppm. Two exposure durations were evaluated - 30 min and 60 min. Sampling was performed 24 h and 2 weeks after PAA treatment (equivalent to 2- and 4-weeks post infection). At each sampling point, the following parameters were evaluated: gross gill pathology, gill parasitic load, plasma reactive oxygen species (ROS) and total antioxidant capacity (TAC), histopathology and gene expression profiling of genes with key involvement in oxidative stress in the gills and olfactory organ. AGD did not result in systemic oxidative stress as ROS and TAC levels remained unchanged. There were no clear patterns of AGD-mediated regulation of the oxidative stress biomarkers in both the gills and olfactory organ; significant changes in the expression were mostly related to time rather than infection status. However, the expression profiles of the oxidative stress biomarkers in AGD-affected salmon, following treatment with PAA, revealed that gills and olfactory organ responded differently - upregulation was prominent in the gills while downregulation was more frequent in the olfactory organ. The expression of catalase, glutathione S-transferase and thioredoxin reductase 2 was significantly affected by the treatments, both in the gills and olfactory organ, and these alterations were influenced by the duration of exposure and PAA product type. Parasitic load in the gills did significantly increase after treatment regardless of the product and exposure duration; the parasite was undetectable in some fish treated with AquaDes for 30 mins. However, PAA treated groups for 30 min showed lower macroscopic gill scores than the infected-untreated fish. Histology disclosed the classic pathological findings such as multifocal hyperplasia and increased number of mucous cells in AGD-affected fish. Microscopic scoring of gill injuries showed that AGD-infected-PAA-treated fish had lower scores, however, an overall trend could not be established. The morphology and structural integrity of the olfactory organ were not significantly altered by parasitism or PAA treatment. Collectively, the results indicate that AGD did not affect the systemic and mucosal oxidative status of Atlantic salmon. However, such a striking profile was changed when AGD-affected fish were exposed to oxidative chemotherapeutics. Moreover, the gills and olfactory organ demonstrated distinct patterns of gene expression of oxidative stress biomarkers in AGD-infected-PAA-treated fish. Lastly, PAA treatment did not fully resolve the infection, but appeared not to worsen the mucosal health either.

Mitochondrial TrxR2 regulates metabolism and protects from metabolic disease through enhanced TCA and ETC function.

Mitochondrial dysfunction is a key driver of diabetes and other metabolic diseases. Mitochondrial redox state is highly impactful to metabolic function but the mechanism driving this is unclear. We generated a transgenic mouse which overexpressed the redox enzyme Thioredoxin Reductase 2 (TrxR2), the rate limiting enzyme in the mitochondrial thioredoxin system. We found augmentation of TrxR2 to enhance metabolism in mice under a normal diet and to increase resistance to high-fat diet induced metabolic dysfunction by both increasing glucose tolerance and decreasing fat deposition. We show this to be caused by increased mitochondrial function which is driven at least in part by enhancements to the tricarboxylic acid cycle and electron transport chain function. Our findings demonstrate a role for TrxR2 and mitochondrial thioredoxin as metabolic regulators and show a critical role for redox enzymes in controlling functionality of key mitochondrial metabolic systems.

Synthesis of mitochondria-targeted menadione cation derivatives: Inhibiting mitochondrial thioredoxin reductase (TrxR2) and inducing apoptosis in MGC-803 cells.

Menadione (VK3) is used as a powerful inducer of cellular reactive oxygen species (ROS) for many years and displays the high anti-cancer activities in vivo. Recently, the development of mitochondria-targeted drugs has been more and more appreciated. Here, the thirteen derivatives of VK3 were synthesized, which could localize in mitochondria by the triphenylphosphonium (TPP) cation or the nitrogen-based cation. The results of cytotoxicity from six human cancer cell lines showed that the targeted compounds T1-T13 displayed higher activity than VK3 with the average IC50 value around 1 µM. The results of cytotoxicity indicated that the substitutes on C-2, the linear alkyl chains on C-3 and cation moiety all could affect the cytotoxicity. The mechanistic studies showed that five representative compounds (T2, T3, T5, T8 and T13) could localize in cellular mitochondria, elicit ROS burst and collapse mitochondrial membrane potential (ΔΨm), leading to cytochrome C release and apoptosis in MGC-803 cells. Particularly, they could obviously inhibit mitochondrial thioredoxin reductase TrxR2 expression, thus leading to aggravate cellular oxidative stress.

Genetic models of latent tuberculosis in mice reveal differential influence of adaptive immunity.

Studying latent Mycobacterium tuberculosis (Mtb) infection has been limited by the lack of a suitable mouse model. We discovered that transient depletion of biotin protein ligase (BPL) and thioredoxin reductase (TrxB2) results in latent infections during which Mtb cannot be detected but that relapse in a subset of mice. The immune requirements for Mtb control during latency, and the frequency of relapse, were strikingly different depending on how latency was established. TrxB2 depletion resulted in a latent infection that required adaptive immunity for control and reactivated with high frequency, whereas latent infection after BPL depletion was independent of adaptive immunity and rarely reactivated. We identified immune signatures of T cells indicative of relapse and demonstrated that BCG vaccination failed to protect mice from TB relapse. These reproducible genetic latency models allow investigation of the host immunological determinants that control the latent state and offer opportunities to evaluate therapeutic strategies in settings that mimic aspects of latency and TB relapse in humans.

Long-term administration of low-dose selenium nanoparticles with different sizes aggravated atherosclerotic lesions and exhibited toxicity in apolipoprotein E-deficient mice.

Exploration of long-term in vivo effects of nanomaterials, particularly those with potential biomedical applications, is quite important for better understanding and evaluating their biosafety. Selenium nanoparticles (SeNPs) has been considered as a good candidate in biomedical applications due to its high bioavailability, considerable biological activity, and low toxicity. However, its long-term biological effects and biosafety remain unknown. Our previous study demonstrated that 8-week supplementation with SeNPs (50 µg Se/kg/day) was safe and had an anti-atherosclerotic activity in apolipoprotein E-deficient (ApoE-/-) mice, a well-known animal model of atherosclerosis. As a chronic disease, atherosclerosis needs long-term drug therapy. The aim of this study is to investigate the long-term effects of SeNPs with different sizes on atherosclerotic lesions and their biosafety in ApoE-/- mice fed with a high fat diet. Unexpectedly, the results showed that 24-week administration of SeNPs even at a low dose (50 µg Se/kg/day) aggravated atherosclerotic lesions. Furthermore, SeNPs exacerbated oxidative stress by inhibiting the activities of antioxidant enzymes and the expression of antioxidant selenoenzymes. SeNPs also exacerbated hyperlipidaemia by inducing hepatic lipid metabolic disorder. In the meanwhile, SeNPs aggravated organ injury, especially liver and kidney injury. The above adverse effects of SeNPs were size dependent: SeNPs with the size of 40.4 nm showed the highest adverse effects among the SeNPs with three sizes (23.1 nm, 40.4 nm, and 86.8 nm). In conclusion, the present work shows that long-term administration of low-dose SeNPs aggravated atherosclerotic lesions by enhancing oxidative stress and hyperlipidaemia in ApoE-/- mice, indicative of cardiovascular toxicity. Moreover, long-term administration of SeNPs led to injury to liver and kidney. These results offer novel insights for better understanding the biosafety of SeNPs and other biomedical nanomaterials.

A redox-active crosslinker reveals an essential and inhibitable oxidative folding network in the endoplasmic reticulum of malaria parasites.

Malaria remains a major global health problem, creating a constant need for research to identify druggable weaknesses in P. falciparum biology. As important components of cellular redox biology, members of the Thioredoxin (Trx) superfamily of proteins have received interest as potential drug targets in Apicomplexans. However, the function and essentiality of endoplasmic reticulum (ER)-localized Trx-domain proteins within P. falciparum has not been investigated. We generated conditional mutants of the protein PfJ2-an ER chaperone and member of the Trx superfamily-and show that it is essential for asexual parasite survival. Using a crosslinker specific for redox-active cysteines, we identified PfJ2 substrates as PfPDI8 and PfPDI11, both members of the Trx superfamily as well, which suggests a redox-regulatory role for PfJ2. Knockdown of these PDIs in PfJ2 conditional mutants show that PfPDI11 may not be essential. However, PfPDI8 is required for asexual growth and our data suggest it may work in a complex with PfJ2 and other ER chaperones. Finally, we show that the redox interactions between these Trx-domain proteins in the parasite ER and their substrates are sensitive to small molecule inhibition. Together these data build a model for how Trx-domain proteins in the P. falciparum ER work together to assist protein folding and demonstrate the suitability of ER-localized Trx-domain proteins for antimalarial drug development.

The mitochondrial thioredoxin reductase system (TrxR2) in vascular endothelium controls peroxynitrite levels and tissue integrity.

The mitochondrial thioredoxin/peroxiredoxin system encompasses NADPH, thioredoxin reductase 2 (TrxR2), thioredoxin 2, and peroxiredoxins 3 and 5 (Prx3 and Prx5) and is crucial to regulate cell redox homeostasis via the efficient catabolism of peroxides (TrxR2 and Trxrd2 refer to the mitochondrial thioredoxin reductase protein and gene, respectively). Here, we report that endothelial TrxR2 controls both the steady-state concentration of peroxynitrite, the product of the reaction of superoxide radical and nitric oxide, and the integrity of the vascular system. Mice with endothelial deletion of the Trxrd2 gene develop increased vascular stiffness and hypertrophy of the vascular wall. Furthermore, they suffer from renal abnormalities, including thickening of the Bowman's capsule, glomerulosclerosis, and functional alterations. Mechanistically, we show that loss of Trxrd2 results in enhanced peroxynitrite steady-state levels in both vascular endothelial cells and vessels by using a highly sensitive redox probe, fluorescein-boronate. High steady-state peroxynitrite levels were further found to coincide with elevated protein tyrosine nitration in renal tissue and a substantial change of the redox state of Prx3 toward the oxidized protein, even though glutaredoxin 2 (Grx2) expression increased in parallel. Additional studies using a mitochondria-specific fluorescence probe (MitoPY1) in vessels revealed that enhanced peroxynitrite levels are indeed generated in mitochondria. Treatment with Mn(III)tetrakis(1-methyl-4-pyridyl)porphyrin [Mn(III)TMPyP], a peroxynitrite-decomposition catalyst, blunted intravascular formation of peroxynitrite. Our data provide compelling evidence for a yet-unrecognized role of TrxR2 in balancing the nitric oxide/peroxynitrite ratio in endothelial cells in vivo and thus establish a link between enhanced mitochondrial peroxynitrite and disruption of vascular integrity.

miR-195-5p exerts tumor-suppressive functions in human lung cancer cells through targeting TrxR2.

miR-195-5p has been widely explored in various cancers and is considered as a tumor-suppressive microRNA. However, its roles in human lung cancer pathogenesis are not fully elucidated. In this study, we aimed to explore how miR-195-5p is involved in malignant behaviors of lung adenocarcinoma (LUAD) cells. miR-195-5p expression was examined in the tumor tissues of patients with LUAD and human LUAD cell lines including A549 and PC-9. Thioredoxin reductase 2 (TrxR2) was predicted to be an mRNA target of miR-195-5p using online tools and validated by the Dual-Luciferase Reporter Assay. Lentivirus infection was used for gene overexpression, while gene knockdown was achieved by RNA interference. Cell proliferation was determined by Cell Counting Kit-8 and 5-ethynyl-2'-deoxyuridine methods, and cell migration and invasion were assayed with transwell experiments. Cell apoptosis was determined by annexin V staining-based flow cytometry. The antitumor effects of miR-195-5p were also evaluated in nude mice xenografted with A549 cells. We found that miR-195-5p was lowly expressed in human LUAD cells, and its overexpression markedly suppressed cell proliferation, migration, and invasion and increased the apoptosis of LUAD cells in vitro. TrxR2 knockdown phenocopied the tumor-suppressive effects of miR-195-5p overexpression, while simultaneous TrxR2 overexpression remarkably reversed the effects of miR-195-5p overexpression on malignant behaviors of A549 and PC-9 cells. Additionally, miR-195-5p overexpression inhibited the growth of xenografted A549 tumor in nude mice. Our work verified that miR-195-5p exerts tumor-suppressive functions in LUAD cells through targeting TrxR2 and suggested that the miR-195-5p/TrxR2 axis is a potential biomarker for LUAD therapy.

Synthesis of mitochondria-targeted coumarin-3-carboxamide fluorescent derivatives: Inhibiting mitochondrial TrxR2 and cell proliferation on breast cancer cells.

Targeting specific mitochondrial alterations to kill cancer cells without affecting their normal counterparts emerges as a feasible strategy. Coumarin derivatives have demonstrated the potential anti-breast cancer activities. By coupling coumarin-3-carboxamide derivatives with mitochondria carrier triphenylphosphonium, mitocoumarins 15a-c were produced and tested as the anti-breast cancer fluorescence agents. Among them, 15b as the amide-based drug potently suppressed the cell growth in MCF-7, MDA-231, SK-BR-3 breast cancer cells with the IC50 values from 3.0 to 4.1 µM, including the lower cytotoxicity to normal MCF-10A cells with the IC50 value around 45.30 ± 2.45 µM. In mechanistic study for 15b in MDA-MB-231 cells, it could localize in mitochondria to elicit ROS burst and collapse Δψm. Besides, it could deplete GSH by an irreversible alkylation process and moderately inhibit mitochondrial thioredoxin reductase TrxR2, thus leading to aggravate cellular oxidative stress. This study reported 15b might be useful for the further development into a mitochondria-targeted anti-triple negative breast cancer drug.

Role of 904 nm superpulsed laser-mediated photobiomodulation on nitroxidative stress and redox homeostasis in burn wound healing.

BACKGROUND: Burn wound healing is delayed due to several critical factors such as sustained inflammation, vascular disorder, neuropathy, enhanced proteolysis, infection, and oxidative stress. Burn wounds have limited oxygen supply owing to compromised blood circulation. Hypoxic burn milieu leads to free radicals overproduction incurring oxidative injury, which impedes repair process causing damage to cell membranes, proteins, lipids, and DNA. Photobiomodulation (PBM) with 904 nm superpulsed laser had shown potent healing efficacy via attenuating inflammation while enhancing proliferation, angiogenesis, collagen accumulation, and bioenergetic activation in burn wounds. METHODS: This study investigated the effects of 904 nm superpulsed laser at 0.4 mW/cm2 average power density, 0.2 J/cm2 total energy density, 100 Hz frequency, and 200 ns pulse width for 10 min daily for seven days postburn injury on nitroxidative stress, endogenous antioxidants status, and redox homeostasis. RESULTS: Photobiomodulation treatment significantly decreased reactive oxygen species, nitric oxide, and lipid peroxidation levels as compared to non-irradiated control. Further, protective action of PBM against protein oxidative damage was evidenced by reduced protein carbonylation and advanced oxidation protein product levels along with significantly enhanced endogenous antioxidants levels of SOD, catalase, GPx, GST, reduced glutathione, and thiol (T-SH, Np-SH, P-SH). Biochemical changes aid in reduction of oxidative stress and maintenance of redox homeostasis, which further well corroborated by significantly up-regulated protein expression of Nrf 2, hemeoxygenase (HO-1), and thioredoxin reductase 2 (Txnrd2). CONCLUSION: Photobiomodulation with 904 nm superpulsed laser led to reduction of nitroxidative stress, induction of endogenous antioxidants, and maintenance of redox homeostasis that could play a vital role in augmentation of burn wound healing.

KLF9 aggravates ischemic injury in cardiomyocytes through augmenting oxidative stress.

Cardiomyocyte injury caused by excessive oxidative stress underlies the pathogenesis of myocardial infarction (MI), a devastating disease leading to heart failure and death. The Krüppel-like factor 9 (KLF9) is a transcriptional factor that has recently been reported to regulate oxidative stress, however, whether it is associated with cardiomyocyte injury and MI is unknown. We found that KLF9 was upregulated in the heart from a rat MI model. In addition, KLF9 was also upregulated in cardiomyocytes exposed to ischemia in vitro, suggesting that KLF9 responds to MI-relevant stimuli. Moreover, KLF9 knockdown protected cardiomyocytes against ischemic injury. Mechanistically, KLF9 knockdown reduced reactive oxygen species (ROS) generation in ischemic cardiomyocytes through upregulating the antioxidant thioredoxin reductase 2 (Txnrd2), and more important, Txnrd2 silencing abrogated KLF9 knockdown-mediated cardioprotection in ischemic cardiomyocytes. Altogether, these results suggest that KLF9 aggravates ischemic injury in cardiomyocytes through undermining Txnrd2-mediated ROS clearance, which might offer KLF9 as a possible target in alleviating MI.

Repurposing of auranofin: Thioredoxin reductase remains a primary target of the drug.

Auranofin is a gold (I)-containing compound used for the treatment of rheumatic arthritis. Auranofin has anticancer activity in animal models and is approved for clinical trials for lung and ovarian carcinomas. Both the cytosolic and mitochondrial forms of the selenoprotein thioredoxin reductase (TrxR) are well documented targets of auranofin. Auranofin was recently reported to also inhibit proteasome activity at the level of the proteasome-associated deubiquitinases (DUBs) UCHL5 and USP14. We here set out to re-examine the molecular mechanism underlying auranofin cytotoxicity towards cultured cancer cells. The effects of auranofin on the proteasome were examined in cells and in vitro, effects on DUB activity were assessed using different substrates. The cellular response to auranofin was compared to that of the 20S proteasome inhibitor bortezomib and the 19S DUB inhibitor b-AP15 using proteomics. Auranofin was found to inhibit mitochondrial activity and to an induce oxidative stress response at IC50 doses. At 2-3-fold higher doses, auranofin inhibits proteasome processing in cells. At such supra-pharmacological concentrations USP14 activity was inhibited. Analysis of protein expression profiles in drug-exposed tumor cells showed that auranofin induces a response distinct from that of the 20S proteasome inhibitor bortezomib and the DUB inhibitor b-AP15, both of which induced similar responses. Our results support the notion that the primary mechanism of action of auranofin is TrxR inhibition and suggest that proteasome DUB inhibition is an off-target effect. Whether proteasome inhibition will contribute to the antineoplastic effect of auranofin in treated patients is unclear but remains a possibility.

Significance of the mitochondrial thioredoxin reductase in cancer cells: An update on role, targets and inhibitors.

Thioredoxin reductase 2 (TrxR2) is a key component of the mitochondrial thioredoxin system able to transfer electrons to peroxiredoxin 3 (Prx3) in a reaction mediated by thioredoxin 2 (Trx2). In this way, both the level of hydrogen peroxide and thiol redox state are modulated. TrxR2 is often overexpressed in cancer cells conferring apoptosis resistance. Due to their exposed flexible arm containing selenocysteine, both cytosolic and mitochondrial TrxRs are inhibited by a large number of molecules. The various classes of inhibitors are listed and the molecules acting specifically on TrxR2 are extensively described. Particular emphasis is given to gold(I/III) complexes with phosphine, carbene or other ligands and to tamoxifen-like metallocifens. Also chemically unrelated organic molecules, including natural compounds and their derivatives, are taken into account. An important feature of many TrxR2 inhibitors is provided by their nature of delocalized lipophilic cations that allows their accumulation in mitochondria exploiting the organelle membrane potential. The consequences of TrxR2 inhibition are presented focusing especially on the impact on mitochondrial pathophysiology. Inhibition of TrxR2, by hindering the activity of Trx2 and Prx3, increases the mitochondrial concentration of reactive oxygen species and shifts the thiol redox state toward a more oxidized condition. This is reflected by alterations of specific targets involved in the release of pro-apoptotic factors such as cyclophilin D which acts as a regulator of the mitochondrial permeability transition pore. Therefore, the selective inhibition of TrxR2 could be utilized to induce cancer cell apoptosis.

Targeting a Sirt5-Positive Subpopulation Overcomes Multidrug Resistance in Wild-Type Kras Colorectal Carcinomas.

A major obstacle for successful management of patients with colorectal carcinoma (CRC) is resistance to anti-cancer cytotoxic treatments. Here, we identified a mechanism of multidrug resistance in wild-type Kras CRCs based on the survival of a cell subpopulation characterized by Sirt5 expression. Sirt5+ cells in wild-type Kras CRCs are resistant to either chemotherapeutic agents or cetuximab and serve as a reservoir for recurrence. Sirt5 demalonylates and inactivates succinate dehydrogenase complex subunit A (SDHA), leading to an accumulation of the oncometabolite succinate. Succinate binds to and activates a reactive oxygen species-scavenging enzyme, thioredoxin reductase 2 (TrxR2), to confer chemotherapy resistance. In contrast, Sirt5+ cells exhibit an elevated succinate-to-aKG ratio that inhibits aKG-dependent dioxygenases to maintain cetuximab resistance. Our findings suggest that Sirt5 inhibitors in combination with chemotherapeutic agents and/or cetuximab may represent a therapeutic strategy for CRC patients harboring wild-type Kras.