Protein-tyrosine phosphatases (PTPs) counteract protein tyrosine phosphorylation and cooperate with receptor-tyrosine kinases in the regulation of cell signaling. PTPs need to undergo oxidative ...inhibition for activation of cellular cascades of protein-tyrosine kinase phosphorylation following growth factor stimulation. It has remained enigmatic how such oxidation can occur in the presence of potent cellular reducing systems. Here, using in vitro biochemical assays with purified, recombinant protein, along with experiments in the adenocarcinoma cell line A431, we discovered that bicarbonate, which reacts with H2O2 to form the more reactive peroxymonocarbonate, potently facilitates H2O2-mediated PTP1B inactivation in the presence of thioredoxin reductase 1 (TrxR1), thioredoxin 1 (Trx1), and peroxiredoxin 2 (Prx2) together with NADPH. The cellular experiments revealed that intracellular bicarbonate proportionally dictates total protein phosphotyrosine levels obtained after stimulation with epidermal growth factor (EGF) and that bicarbonate levels directly correlate with the extent of PTP1B oxidation. In fact, EGF-induced cellular oxidation of PTP1B was completely dependent on the presence of bicarbonate. These results provide a plausible mechanism for PTP inactivation during cell signaling and explain long-standing observations that growth factor responses and protein phosphorylation cascades are intimately linked to the cellular acid–base balance.
Aluminium (Al) is the third most abundant element in the earth's crust and its compounds are used in the form of house hold utensils, medicines and in antiperspirant etc. Increasing number of ...evidences suggest the involvement of Al+3 ions in a variety of neurodegenerative disorders including Alzheimer's disease. Here, we have attempted to investigate the role of Al in endoplasmic reticulum stress and the regulation of p53 during neuronal apoptosis using neuroblastoma cell line. We observed that Al caused oxidative stress by increasing ROS production and intracellular calcium levels together with depletion of intracellular GSH levels. We also studied modulation of key pro- and anti-apoptotic proteins and found significant alterations in the levels of Nrf2, NQO1, pAKT, p21, Bax, Bcl2, Aβ1-40 and Cyt c together with increase in endoplasmic reticulum (ER) stress related proteins like CHOP and caspase 12. However, with respect to the role of p53, we observed downregulation of its transcript as well as protein levels while analysis of its ubiquitination status revealed no significant changes. Not only did Al increase the activities of caspase 9, caspase 12 and caspase 3, but, by the use of peptide inhibitors of specific and pan-caspases, we observed significant protection against neuronal cell death upon inhibition of caspase 12, demonstrating the prominent role of endoplasmic reticulum stress generated responses in Al toxicity. Overall our findings suggest that Al induces ER stress and ROS generation which compromises the antioxidant defenses of neuronal cells thereby promoting neuronal apoptosis in p53 independent pathway.
Cardiovascular diseases are the leading cause of death worldwide, and as rates continue to increase, discovering mechanisms and therapeutic targets become increasingly important. An underlying cause ...of most cardiovascular diseases is believed to be excess reactive oxygen or nitrogen species. Glutathione, the most abundant cellular antioxidant, plays an important role in the body's reaction to oxidative stress by forming reversible disulfide bridges with a variety of proteins, termed glutathionylation (GSylation). GSylation can alter the activity, function, and structure of proteins, making it a major regulator of cellular processes. Glutathione-protein mixed disulfide bonds are regulated by glutaredoxins (Glrxs), thioltransferase members of the thioredoxin family. Glrxs reduce GSylated proteins and make them available for another redox signaling cycle. Glrxs and GSylation play an important role in cardiovascular diseases, such as myocardial ischemia and reperfusion, cardiac hypertrophy, peripheral arterial disease, and atherosclerosis. This review primarily concerns the role of GSylation and Glrxs, particularly glutaredoxin-1 (Glrx), in cardiovascular diseases and the potential of Glrx as therapeutic agents.
Endoplasmic reticulum (ER) is the site of protein synthesis, protein folding, maintainance of calcium homeostasis, synthesis of lipids and sterols. Genetic or environmental insults can alter its ...function generating ER stress. ER senses stress mainly by three stress sensor pathways, namely protein kinase R-like endoplasmic reticulum kinase-eukaryotic translation-initiation factor 2
α
, inositol-requiring enzyme 1
α
-X-box-binding protein 1 and activating transcription factor 6-CREBH, which induce unfolded protein responses (UPR) after the recognition of stress. Recent studies have demonstrated that ER stress and UPR signaling are involved in cancer, metabolic disorders, inflammatory diseases, osteoporosis and neurodegenerative diseases. However, the precise knowledge regarding involvement of ER stress in different disease processes is still debatable. Here we discuss the possible role of ER stress in various disorders on the basis of existing literature. An attempt has also been made to highlight the present knowledge of this field which may help to elucidate and conjure basic mechanisms and novel insights into disease processes which could assist in devising better future diagnostic and therapeutic strategies.
S-glutathionylation is a reversible oxidative modification of protein cysteines that plays a critical role in redox signaling. Glutaredoxin-1 (Glrx), a glutathione-specific thioltransferase, removes ...protein S-glutathionylation. Glrx, though a cytosolic protein, can activate a nuclear protein Sirtuin-1 (SirT1) by removing its S-glutathionylation. Glrx ablation causes metabolic abnormalities and promotes controlled cell death and fibrosis in mice. Glyceraldehyde 3-phosphate dehydrogenase (GAPDH), a key enzyme of glycolysis, is sensitive to oxidative modifications and involved in apoptotic signaling via the SirT1/p53 pathway in the nucleus. We aimed to elucidate the extent to which S-glutathionylation of GAPDH and glutaredoxin-1 contribute to GAPDH/SirT1/p53 apoptosis pathway.
Exposure of HEK 293T cells to hydrogen peroxide (H2O2) caused rapid S-glutathionylation and nuclear translocation of GAPDH. Nuclear GAPDH peaked 10–15 min after the addition of H2O2. Overexpression of Glrx or redox dead mutant GAPDH inhibited S-glutathionylation and nuclear translocation. Nuclear GAPDH formed a protein complex with SirT1 and exchanged S-glutathionylation to SirT1 and inhibited its deacetylase activity. Inactivated SirT1 remained stably bound to acetylated-p53 and initiated apoptotic signaling resulting in cleavage of caspase-3. We observed similar effects in human primary aortic endothelial cells suggesting the GAPDH/SirT1/p53 pathway as a common apoptotic mechanism.
Abundant GAPDH with its highly reactive-cysteine thiolate may function as a cytoplasmic rheostat to sense oxidative stress. S-glutathionylation of GAPDH may relay the signal to the nucleus where GAPDH trans-glutathionylates nuclear proteins such as SirT1 to initiate apoptosis. Glrx reverses GAPDH S-glutathionylation and prevents its nuclear translocation and cytoplasmic-nuclear redox signaling leading to apoptosis. Our data suggest that trans-glutathionylation is a critical step in apoptotic signaling and a potential mechanism that cytosolic Glrx controls nuclear transcription factors.
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-Cytosolic glutaredoxin-1 reverses S-glutathionylation of SirT1 in the nucleus.-S-glutathionylation at Cys247 is required for GAPDH nuclear translocation.-Nuclear GAPDH interacts SirT1 and causes apoptosis via trans-glutathionylation.-Cys-mutant GAPDH attenuates its nuclear translocation and binding to SirT1.-Glutaredoxin-1 inhibits GAPDH nuclear translocation and SirT1-mediated apoptosis.
Extensive uses of silica nanoparticles (SiNPs) in biomedical and industrial fields have increased the risk of exposure, resulting concerns about their safety. We focussed on some of the safety ...aspects by studying neurobehavioural impairment, oxidative stress (OS), neurochemical and ultrastructural changes in corpus striatum (CS) of male Wistar rats exposed to 80-nm SiNPs. Moreover, its role in inducing mitochondrial and endoplasmic reticulum (ER) stress-mediated neuronal apoptosis was also investigated. The results demonstrated impairment in neurobehavioural indices, and a significant increase in lipid peroxide levels (LPO), hydrogen peroxide (H
2
O
2
), superoxide (O
2
-
) and protein carbonyl content, whereas there was a significant decrease in the activities of the enzymes, manganese superoxide dismutase (Mn SOD), glutathione peroxidase (GPx), catalase (CAT) and reduced glutathione (GSH) content, suggesting impaired antioxidant defence system. Protein (cytochrome
c
, Bcl-2, Bax, p53, caspase-3, caspase 12 and CHOP/Gadd153) and mRNA (Bcl-2, Bax, p53 and CHOP/Gadd153, cytochrome
c
) expression studies of mitochondrial and ER stress-related apoptotic factors suggested that both the cell organelles were involved in OS-mediated apoptosis in treated rat brain CS. Moreover, electron microscopic studies clearly showed mitochondrial and ER dysfunction. In conclusion, the result of the study suggested that subchronic SiNPs’ exposure has the potential to alter the behavioural activity and also to bring about changes in biochemical, neurochemical and ultrastructural profiles in CS region of rat brain. Furthermore, we also report SiNPs-induced apoptosis in CS, through mitochondrial and ER stress-mediated signalling.
Aluminum: Real Ghost in Aged Brains Mahdi, Abbas Ali; Rizvi, Syed Husain Mustafa; Parveen, Arshiya
Indian journal of clinical biochemistry,
05/2022, Letnik:
30, Številka:
S1
Journal Article
Recenzirano
Aluminum (Al) is the third most abundant element in the earth crust and it is not essential for living organisms. This metal has no biological function; however, its exposure is very common to human ...beings by ways like industrialization, utensils, medicines, antiperspirants etc. It has been reported that as one ages Al accumulate in brain and other organs resulting in their dysfunction and toxicity. There is an increasing amount of evidence suggesting the involvement of Al.sup.+3 ions in a variety of neurodegenerative disorders such as Alzheimer's disease and Parkinsonism etc. Al could enter the brain from systemic circulation: blood-brain barrier (BBB), nasal-olfactory pathway and cerebrospinal fluid. The important carriers for brain Al influx may be Transferrin-mediated transport and monocarboxylate transporter. Our in vivo and in vitro results suggest the role of Al in brain dysfunction and neurodegenerative mechanism. We found Al exposure to be associated with oxidative stress, cognitive decline and ultrastructural changes in experimental animal's brain and the same results were found in our in vitro model system. Moreover, we also demonstrated the role of Al in mitochondrial and endoplasmic reticulum stress mediated apoptotic pathway and found that Al induces ER stress and release of mitochondrial cytochrome c to promote apoptosis. Furthermore, in addition to its neurotoxicity, Al is a potent stimulator of the immune response. Our results also showed that Al activates inflammatory proteins and altered TNFalpha, IL1b, IL6 and IL10 mRNA levels. Overall, these results indicated that Al disturbed the redox state of the neuronal cells which results into the activation of various signaling including apoptosis and inflammatory pathways which promotes neuronal cell death.
Diabetes leads to dysregulated macrophage immunometabolism, contributing to accelerated atherosclerosis progression. Identifying critical factors to restore metabolic alterations and promote ...resolution of inflammation remains an unmet goal. MicroRNAs (miRs) orchestrate multiple signaling events in macrophages, yet their therapeutic potential in diabetes-associated atherosclerosis remains unclear.
MiRNA profiling revealed significantly lower miR-369-3p expression in aortic intimal lesions from Ldlr-/- mice on a high-fat sucrose containing (HFSC) diet for 12 weeks. miR-369-3p was also reduced in peripheral blood mononuclear cells (PBMCs) from diabetic patients with coronary artery disease (CAD). Cell-type expression profiling showed miR-369-3p enrichment in aortic macrophages. In vitro, oxLDL treatment reduced miR-369-3p expression in mouse bone marrow-derived macrophages (BMDMs). Metabolic profiling in BMDMs revealed that miR-369-3p overexpression blocked the oxLDL-mediated increase in the cellular metabolite succinate and reduced mitochondrial respiration (OXPHOS) and inflammation (lL-1β, TNF-a, IL-6). Mechanistically, miR-369-3p targeted the succinate receptor (GPR91) and alleviated the oxLDL-induced activation of inflammasome signaling pathways. Therapeutic administration of miR-369-3p mimics in HFSC-fed Ldlr-/- mice reduced GPR91 expression in lesional macrophages and diabetes-accelerated atherosclerosis, evident by a decrease in plaque size and pro-inflammatory Ly6Chi monocytes. RNA-seq analyses showed more pro-resolving pathways in plaque macrophages from miR-369-3p treated mice, consistent with an increase in macrophage efferocytosis in lesions. Finally, a GPR91 antagonist attenuated oxLDL-induced inflammation in primary monocytes from human subjects with diabetes.
These findings establish a therapeutic role for miR-369-3p in halting diabetes-associated atherosclerosis by regulating GPR91 and macrophage succinate metabolism.
Man made nanoparticles and materials are being rapidly produced in large quantities throughout the world. With the increased probability of exposure from large yield industry production, the issue of ...toxicity has led to new investigations of dosing and exposure to elemental metals. Although a wide and growing number of applications for nano materials exist, there is a serious lack of information concerning the human health and environmental implications of these manufactured nano materials. The results presented here demonstrate that MnNPs adversely affect SH-SY5Y human neuroblastoma cell and induce significant cytotoxicity and oxidative stress with a clear dose dependent manner. This findings is of special interest as the particular role of neurons in several neurodegenerative diseases has been intensely discussed, and it seems likely that this cell type is being initially during pathogens. The high vulnerability of SH-SY5Y human neuroblastoma cell toward MnNPs exposure, as demonstrated here.
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