Neurotoxicity from glutathione depletion is mediated by Cu-dependent p53 activation

All roads lead to Rome - a review of the potential mechanisms by which exerkines exhibit neuroprotective effects in Alzheimer's disease

Age-related neurodegenerative disorders such as Alzheimer’s disease (AD) have become a critical public health issue due to the significantly extended human lifespan, leading to considerable economic and social burdens. Traditional therapies for AD such as medicine and surgery remain ineffective, impractical, and expensive. Many studies have shown that a variety of bioactive substances released by physical exercise (called “exerkines”) help to maintain and improve the normal functions of the brain in terms of cognition, emotion, and psychomotor coordination. Increasing evidence suggests that exerkines may exert beneficial effects in AD as well. This review summarizes the neuroprotective effects of exerkines in AD, focusing on the underlying molecular mechanism and the dynamic expression of exerkines after physical exercise. The findings described in this review will help direct research into novel targets for the treatment of AD and develop customized exercise therapy for individuals of different ages, genders, and health conditions.

Hydrogen sulfide increases copper-dependent neurotoxicity via intracellular copper accumulation

Copper (Cu) is an essential trace element and acts as a redox cofactor for many enzymes; however, excess Cu is toxic to cells. Hydrogen sulfide (H2S) is a well-known toxic gaseous molecule, but it has various biological effects such as neuromodulation and vasodilation. H2S was recently demonstrated to be involved in the detoxification of heavy metals, including zinc and cadmium, suggesting that H2S helps to maintain the homeostasis of heavy metals in cells. However, it is unclear how H2S impacts cellular Cu dynamics. In this study, we examined the effects of H2S on Cu cytotoxicity. Human neuroblastoma SH-SY5Y cells were exposed to CuSO4 in the presence of the H2S donor NaHS. CuSO4 alone slightly induced cell injury, whereas the combination of CuSO4 and NaHS (Cu/NaHS) increased Cu cytotoxicity. The Cu chelator bathocuproinedisulfonic acid mitigated Cu/NaHS-induced cytotoxicity. Compared with CuSO4 alone, Cu/NaHS markedly promoted ROS generation, mitochondrial dysfunction, and a decrease in ATP production. In addition, reporter assay using the metal responsive element (MRE)-driven reporter plasmid revealed that Cu/NaHS augmented Cu-dependent MRE activation. The amount of intracellular Cu was significantly higher in cells treated with Cu/NaHS than in those treated with CuSO4 alone. Moreover, Cu/NaHS markedly suppressed the level of the Cu exporter ATP7A, but not ATP7B, protein, whereas the combination did not affect that of the Cu importer CTR1 protein. Taken together, we conclude that the marked decrease in the ATP7A protein level by Cu/NaHS promotes intracellular Cu accumulation and leads to increased Cu cytotoxicity.

Tantalizing role of p53 molecular pathways and its coherent medications in neurodegenerative diseases

Neurodegenerative diseases are incongruous, commonly age-related disorders characterized by progressive neuronal loss, comprising the most prevalent being Alzheimer's disease, Parkinson's disease, and Huntington's disease. Perilous health states are anticipated following the neurodegeneration. Their etiology remains largely ambiguous, while various mechanisms are ascribed to their pathogenesis. A recommended conception is regarding the role of p53, as a transcription factor regulating numerous cellular pathways comprising apoptosis. Neuronal fates are a feasible occurrence that contributes to all neurodegenerative diseases. In this work, we review the research investigated the potential role of p53 in the pathogenesis of these diseases. We put special emphasis on intricate We not only describe aberrant changes in p53 level/activity observed in CNS regions affected by particular diseases but, most importantly, put special attention to the complicated reciprocal tuning connections prevailing between p53 and molecules considered in pathological hallmarks of these disorders. Natural and synthetic medications regulating p53 expression are regarded as well.

Copper in the suprachiasmatic circadian clock: A possible link between multiple circadian oscillators

The mammalian circadian clock in the suprachiasmatic nucleus (SCN) is very robust, able to coordinate our daily physiological and behavioral rhythms with exquisite accuracy. Simultaneously, the SCN clock is highly sensitive to environmental timing cues such as the solar cycle. This duality of resiliency and sensitivity may be sustained in part by a complex intertwining of three cellular oscillators: transcription/translation, metabolic/redox, and membrane excitability. We suggest here that one of the links connecting these oscillators may be forged from copper (Cu). Cellular Cu levels are highly regulated in the brain and peripherally, and Cu affects cellular metabolism, redox state, cell signaling, and transcription. We have shown that both Cu chelation and application induce nighttime phase shifts of the SCN clock in vitro and that these treatments affect glutamate, N-methyl-D-aspartate receptor, and associated signaling processes differently. More recently we found that Cu induces mitogen-activated protein kinase-dependent phase shifts, while the mechanisms by which Cu removal induces phase shifts remain unclear. Lastly, we have found that two Cu transporters are expressed in the SCN, and that one of these transporters (ATP7A) exhibits a day/night rhythm. Our results suggest that Cu homeostasis is tightly regulated in the SCN, and that changes in Cu levels may serve as a time cue for the circadian clock. We discuss these findings in light of the existing literature and current models of multiple coupled circadian oscillators in the SCN.

A Cystine-Rich Whey Supplement (Immunocal®) Provides Neuroprotection from Diverse Oxidative Stress-Inducing Agents In Vitro by Preserving Cellular Glutathione

Oxidative stress is a principal mechanism underlying the pathophysiology of neurodegeneration. Therefore, nutritional enhancement of endogenous antioxidant defenses may represent a viable treatment option. We investigated the neuroprotective properties of a unique whey protein supplement (Immunocal®) that provides an essential precursor (cystine) for synthesis of the endogenous antioxidant, glutathione (GSH). Primary cultures of rat cerebellar granule neurons (CGNs), NSC34 motor neuronal cells, or HT22 hippocampal cells were preincubated in medium containing Immunocal and then subsequently treated with agents known to induce oxidative stress. Immunocal protected CGNs against neurotoxicity induced by the Bcl-2 inhibitor, HA14-1, the nitric oxide donor, sodium nitroprusside, CuCl₂, and AlCl₃. Immunocal also significantly reduced NSC34 cell death due to either H₂O₂ or glutamate and mitigated toxicity in HT22 cells overexpressing β-amyloid_1-42. The neuroprotective effects of Immunocal were blocked by inhibition of γ-glutamyl-cysteine ligase, demonstrating dependence on de novo GSH synthesis. These findings indicate that sustaining GSH with Immunocal significantly protects neurons against diverse inducers of oxidative stress. Thus, Immunocal is a nutritional supplement worthy of testing in preclinical animal models of neurodegeneration and in future clinical trials of patients afflicted by these diseases.

Temozolomide-Mediated Apoptotic Death Is Improved by Thymoquinone in U87MG Cell Line

Apoptosis induction of cancer cells can be an appropriate strategy by which chemotherapeutic agents kill tumor cells. The aim of the present study was to investigate the effect of temozolomide and thymoquinone combination on apoptotic pathway of human glioblastoma multiforme cell line (U87MG). U87MG cells were cultured, treated with temozolomide and thymoquinone, and cell proliferation was measured. Apoptosis cell death and its possible mechanism were investigated by various methods. Combination of temozolomide and thymoquinone had a synergistic effect on cells viability. Thymoquinone intensified the temozolomide-induced apoptosis. Combination of temozolomide and thymoquinone can be a good strategy for treatment of glioblastoma.

Lipophilic adamantyl- or deferasirox-based conjugates of desferrioxamine B have enhanced neuroprotective capacity: implications for Parkinson disease

Parkinson disease (PD) is a neurodegenerative disease characterized by death of dopaminergic neurons in the substantia nigra region of the brain. Iron content is also elevated in this region in PD and is implicated in the pathobiology of the disease. Desferrioxamine B (DFOB) is a high-affinity iron chelator and has shown efficacy in animal models of Parkinson disease. The high water solubility of DFOB, however, attenuates its ability to enter the brain. In this study, we have conjugated DFOB to derivatives of adamantane or the clinical iron chelator deferasirox to produce lipophilic compounds designed to increase the bioavailability of DFOB to brain cells. We found that the novel compounds are highly effective in preventing iron-mediated paraquat and hydrogen peroxide toxicity in neuronal-like BE2-M17 dopaminergic cells, primary neurons, and iron-loaded or glutathione-depleted primary astrocytes. The compounds also alleviated paraquat toxicity in BE2-M17 cells that express the PD-causing A30P mutation of α-synuclein. This protection was ∼66-fold more potent than DFOB alone and also more effective than other cell-permeative metal chelators, clioquinol and phenanthroline. These results demonstrate that increasing the bioavailability of DFOB through the conjugation of lipophilic fragments greatly enhances its protective capacity. These novel compounds have potential as therapeutics for the treatment of PD and other conditions of Fe dyshomeostasis.

Alantolactone induces apoptosis in glioblastoma cells via GSH depletion, ROS generation, and mitochondrial dysfunction

Glioblastoma multiforme (GBM) is the most malignant and aggressive primary brain tumor in adults. Despite concerted efforts to improve current therapies, the prognosis of glioblastoma remains very poor. Alantolactone, a sesquiterpene lactone compound, has been reported to exhibit antifungal, antibacteria, antihelminthic, and anticancer properties. In this study, we found that alantolactone effectively inhibits growth and triggers apoptosis in glioblastoma cells in a time- and dose-dependent manner. The alantolactone-induced apoptosis was found to be associated with glutathione (GSH) depletion, reactive oxygen species (ROS) generation, mitochondrial transmembrane potential dissipation, cardiolipin oxidation, upregulation of p53 and Bax, downregulation of Bcl-2, cytochrome c release, activation of caspases (caspase 9 and 3), and cleavage of poly (ADP-ribose) polymerase. This alantolactone-induced apoptosis and GSH depletion were effectively inhibited or abrogated by a thiol antioxidant, N-acetyl-L-cysteine, whereas other antioxidant (polyethylene glycol (PEG)-catalase and PEG-superoxide-dismutase) did not prevent apoptosis and GSH depletion. Alantolactone treatment inhibited the translocation of NF-κB into nucleus; however, NF-κB inhibitor, SN50 failed to potentiate alantolactone-induced apoptosis indicating that alantolactone induces NF-κB-independent apoptosis in glioma cells. These findings suggest that the sensitivity of tumor cells to alantolactone appears to results from GSH depletion and ROS production. Furthermore, our in vivo toxicity study demonstrated that alantolactone did not induce significant hepatotoxicity and nephrotoxicity in mice. Therefore, alantolactone may become a potential lead compound for future development of antiglioma therapy.

A potential copper-regulatory role for cytosolic expression of the DNA repair protein XRCC5

Copper (Cu) has a critical role in the generation of oxidative stress during neurodegeneration and cancer. Reactive oxygen species generated through abnormal elevation or deficiency of Cu can lead to lipid, protein, and DNA damage. Oxidation of DNA can induce strand breaks and is associated with altered cell fate including transformation or death. DNA repair is mediated through the action of the multimeric DNA-PK repair complex. The components of this complex are the Ku autoantigens, XRCC5 and XRCC6 (Ku80 and Ku70, respectively). How this repair complex responds to perturbed Cu homeostasis and Cu-mediated oxidative stress has not been investigated. We previously reported that XRCC5 expression is altered in response to cellular Cu levels, with low Cu inhibiting XRCC5 expression and high Cu levels enhancing expression. In this study we further investigated the interaction between XRCC5 and Cu. We report that cytosolic XRCC5 is increased in response to Cu, but not zinc, iron, or nickel, and the level of cytosolic XRCC5 correlates with protection against oxidative damage to DNA. These observations were made in both HeLa cells and fibroblasts. Cytosolic XRCC5 interacted with the Cu chaperone and detoxification protein human Atox1 homologue (HAH), and down regulation of XRCC5 expression using siRNA led to enhanced HAH expression when cells were exposed to Cu. XRCC5 could also be purified from cytosolic extracts using a Cu-loaded column. These findings provide further evidence that cytosolic XRCC5 has a key role in protection against DNA oxidation from Cu, through either direct sequestration or signaling through other Cu-detoxification molecules. Our findings have important implications for the development of therapeutic treatments targeting Cu in neurodegeneration and/or cancer.

Purification and biochemical characterization of glutathione S-transferase from Down syndrome and normal children erythrocytes: a comparative study

Down syndrome (DS) is the phenotypic manifestation of trisomy 21. Our study was concerned with the characterization and purification of glutathione S-transferase enzyme (GST) from normal and Down syndrome (DS) erythrocytes to illustrate the difference in the role of this enzyme in the cell. Glutathione S-transferase and glutathione (GSH) was determined in ten DS and ten healthy children matched for age (3-10 years). DS group exhibited significantly lower GST value (2.7 units/gHb) as compared to controls (6.6 units/gHb) (40.9%). GST activity was significantly decreased to 40.9% in the DS group as compared to controls. Also GSH concentration was significantly decreased to 60.6% in the DS group compared to the controls. Glutathione transferase was purified from erythrocytes of normal and DS pooled blood samples by affinity chromatography with specific activity of 23.7% and 7.9%, respectively. The effect of freezing and thawing, storage time of freezing and GSH concentration on the stability of the enzyme were examined. Normal GST exhibited a pH optimum at pH 7 followed by sharp decrease, however DS GST exhibited pH optimum between pH 7.5 and 8. The Km values for 1-chloro-2,4-dinitrobenzene (CDNB) and GSH were 0.205 mM and 0.786 mM, respectively, for normal GST, and 0.318 mM and 1.307 mM, respectively for DS GST. The activation energy (Ea) was calculated to be 2.25 and 4.25 cal/mol for normal GST and 3.8 cal/mol for DS GST. Normal and DS GST were inhibited by the same inhibitors (hematin, bromosulfophthalein and cibacron blue), but with different degree. On kinetic basis, the individuals with lower overall GST activity and slight differences in some kinetic characters are at greater risk from xenobiotic contamination as compared to those with higher overall GST activity observed in normal individuals.

Venlafaxine protects against stress-induced oxidative DNA damage in hippocampus during antidepressant testing in mice

Venlafaxine (VLF) is an approved antidepressant that is claimed to have superior clinical efficacy to comparable drugs. Recently, many studies showed the relationship between depression and increased oxidative stress. This study investigated the relationship between the antidepressant effect of VLF and its ability to protect animals against stress-induced oxidative lipid peroxidation and DNA damage induced during antidepressant testing.

METHODS

The antidepressant effect of long-term treatment (21 days) of VLF in doses 5, 10 and 20mg/kg/day, i.p. was tested using forced swimming test (FST) and tail suspension test (TST). The effects of VLF on hippocampal lipid peroxidation (MDA), nitric oxide (NO), glutathione (GSH), total antioxidant (TAC) levels and glutathione-S-transferase (GST) activity were tested. Furthermore, the corresponding changes in serum and hippocampal 8-hydroxy-2'-deoxyguanosine (8-OHdG) were measured.

RESULTS

Long-term VLF treatment showed a significant, antidepressant effect in both FST and TST. VLF could decrease the hippocampal MDA and NO and to increase hippocampal GSH and TAC levels and GST activity in the tested animals. Only GSH and TAC levels were increased by VLF in the non-tested animals. In addition, both serum and hippocampal 8-OHdG levels were significantly reduced by VLF in animals exposed to antidepressant tests.

CONCLUSION

Long-term VLF treatment in the effective antidepressant doses can protect against stress-induced oxidative cellular and DNA damage. This action may be through antagonizing the oxidative stress and enhancing the antioxidant defense mechanisms. Consequently, pharmacological modulation of stress-induced oxidative DNA damage as a possible stress-management approach should be an important avenue of further research.

Icariin inhibits hydrogen peroxide-induced toxicity through inhibition of phosphorylation of JNK/p38 MAPK and p53 activity

Oxidative stress caused by hydrogen peroxide (H(2)O(2)) plays an important role in the pathogenesis of Alzheimer's disease (AD). The prominent damages caused by H(2)O(2) include the ruin of membrane integrity, loss of intracellular neuronal glutathione (GSH), oxidative damage to DNA as well as the subsequent caspase-3 and p53 activation. Icariin is a flavonoid extracted from the traditional Chinese herb Epimedium brevicornum Maxim. We have previously reported that icariin has a good curative effect on patients with mild cognitive impairment (MCI), AD animal and cell models. However, the molecular mechanism of how icariin exerts neuroprotective effects is still not well understood. To address this question, we exposed undifferentiated neuronal cell lines (PC12 cells) to hydrogen peroxide (H(2)O(2)) and investigated the possible neuroprotective mechanisms of icariin. Vitamin E was used as a positive control. We observed that H(2)O(2) activated the JNK/p38 mitogen-activated protein kinase (MAPK) and induced PC12 cells apoptosis in a concentration-dependent manner. More over, we demonstrated that icariin protected PC12 cells by attenuating LDH leakage, reducing GSH depletion, preventing DNA oxidation damage and inhibiting subsequent activation of caspase-3 and p53, which are the main targets of H(2)O(2)-induced cell damage. In addition, we also found that icariin's neuroprotective effect may partly correlate with its inhibitory effect on JNK/p38 MAPK pathways. Therefore, our findings suggest that icariin is a candidate for a novel neuroprotective drug to against oxidative-stress induced neurodegeneration.

Cadmium chloride-induced oxidative stress and DNA damage in the human Jurkat T cell line is not linked to intracellular trace elements depletion

Cadmium (Cd) is a widespread environmental contaminant. Cd affects the cellular homeostasis and generates damage via complex mechanisms involving interactions with other metals, induction of oxidative stress and apoptotic or necrotic cell death, depending on the cell type and the concentration. The goal of the present study was to investigate the effect of exposure to CdCl(2) on the intracellular trace elements levels, the antioxidant enzyme activities and on DNA damage in the Jurkat T cell line. Cells were exposed to 5, 25 and 50 μM of CdCl(2) for 24 h. Cd significantly reduced the viability of Jurkat T cells and induced a dose-dependent increase in DNA damage with statistically significant differences relative to controls (p<0.001); the superoxide dismutase and glutathione peroxidase activities were significantly decreased. Lipid peroxidation and protein carbonyl levels were significantly increased while glutathione and the total intracellular sulfhydryl groups were decreased showing clearly that an oxidative stress was generated by Cd. Surprisingly the treatment with Cd induced a significant increase in the intracellular levels of all the trace elements measured. The results indicate that cellular pro-oxidative stress induced by Cd is most likely mediated by disruption of redox homeostasis associated to a mishandling of redox-active transition metals and causes lipid and protein oxidation and oxidative DNA damage in Jurkat T cells.