Alterations in brain antioxidant enzymes and redox proteomic identification of oxidized brain proteins induced by the anti-cancer drug adriamycin: implications for oxidative stress-mediated chemobrain

Does tumor necrosis factor-alpha (TNF-α) play a role in post-chemotherapy cerebral dysfunction?

Post-chemotherapy treated cancer patients frequently report cognitive difficulties. The biology of this phenomenon is poorly understood, with uncertainty about possible direct toxic effects on the brain, secondary effects from systemic inflammation, host factors/genetic predisposition to cognitive complaints, or hormonal changes influencing cognitive function. To elucidate possible mechanisms associated with post-treatment cognitive dysfunction among breast cancer survivors, in 2007 we established a prospective, longitudinal, observational cohort study of early stage breast cancer patients, recruited at the end of initial treatments (primary treatment exposure included surgery, ± radiation, ± chemotherapy), and prior to the initiation of adjuvant endocrine therapy. We assessed cognitive complaints, neuropsychological (NP) test performance, markers of inflammation, and brain imaging at baseline, 6 months and 12 months after enrollment. In this analysis of data from the first 93 patients enrolled in the cohort study, we focus on the relationship of circulating levels of proinflammatory cytokines to cerebral functioning and chemotherapy exposure. Among the proinflammatory cytokines tested (IL-1 ra, sTNF-RII, CRP, and IL-6) at baseline, only sTNF-RII was increased among chemotherapy exposed patients, with a significant decline in the year after treatment (p=0.003). Higher baseline sTNF-RII in chemotherapy patients was significantly associated with increased memory complaints. In chemotherapy exposed patients, the longitudinal decline in sTNF-RII was significantly correlated with fewer memory complaints over 12 months (r=-0.34, p=0.04). Higher baseline sTNF-RII was also associated with relatively diminished brain metabolism in the inferior frontal cortex (r=-0.55, p=0.02), as well as relatively increased inferior frontal metabolism after 1 year, in chemotherapy-exposed subjects. These preliminary findings suggest that post-chemotherapy increases in TNF-α may be playing an important role in the manifestations of cognitive complaints in breast cancer survivors.

The effect of systemic chemotherapy on neurogenesis, plasticity and memory

Chemotherapy has been enormously successful in treating many forms of cancer and improving patient survival rates. With the increasing numbers of survivors, a number of cognitive side effects have become apparent. These have been called "chemobrain" or "chemofog" among patient groups, who describe the symptoms as a decline in memory, concentration and executive functions. Changes which, although subtle, can cause significant distress among patients and prevent a return to the quality of life experienced before treatment. This cognitive side effect of chemotherapy was not anticipated as it had been assumed that chemotherapy agents, administered systematically, could not cross the blood-brain barrier and that the brain was therefore protected from their action. It is now realised that low concentrations of many chemotherapy agents cross the blood-brain barrier and even those that are completely prevented from doing so, can induce the production of inflammatory cytokines in peripheral tissues which in turn can cross the blood-brain barrier and impact on the brain. A large number of patient studies have shown that cognitive decline is found in a proportion of patients treated with a variety of chemotherapy agents for different types of cancer. The deficits experienced by these patients can last for up to several years and have a deleterious effect on educational attainment and ability to return to work. Imaging studies of patients after systemic chemotherapy show that this treatment produces structural and functional changes in the brain some of which seem to persist even when the cognitive deficits have ceased. This suggests that, with time, brain plasticity may be able to compensate for the deleterious effects of chemotherapy treatment. A number of mechanisms have been suggested for the changes in brain structure and function found after chemotherapy. These include both central and peripheral inflammatory changes, demyelination of white matter tracts, a reduction in stem cell proliferation in both the hippocampal neurogenic region and by oligodendrocyte precursors as well as changes in hormonal or growth factor levels. A number of possible treatments have been suggested which range from pharmacological interventions to cognitive behavioural therapies. Some of these have only been tested in animal models while others have produced varying degrees of improvement in patient populations. Currently, there is no recognised treatment and a greater understanding of the causes of the cognitive decline experienced after chemotherapy will be key to finding ways of preventing or treating the effects of chemobrain.

[What's new concerning the chemobrain?]

Chemobrain, a subtle cognitive decline after chemotherapy in non-cerebral cancer, remains a debated issue, which has nevertheless been widely described for more than 15 years in the international literature. This phenomenon is almost unknown in France to experts, neurologists and oncologists. Experimental evidence from animal models and from human functional imagery is reliable but contrasts with the observations made during clinical studies. Indeed, in clinical practice, the difficulty in proving the occurrence of chemobrain may be explained by a large number of methodological skews. However, considering the International Cognition and Cancer Task Force (ICCTF) guidelines, we propose a methodology applicable in daily practice and capable of improving awareness of this phenomenon.

Redox regulation of cysteine-dependent enzymes in neurodegeneration

Evidence of increased oxidative stress has been found in various neurodegenerative diseases and conditions. While it is unclear whether oxidative stress is a cause or effect, protein, lipid, and DNA have all been found to be susceptible to oxidant-induced modifications that alter their function. Results of clinical trials based on the oxidative-stress theory have been mixed, though data continues to indicate that prevention of high levels of oxidative stress is beneficial for health and increases longevity. Due to the highly reactive nature of the sulfhydryl group, the focus of this paper is on the impact of oxidative stress on cysteine-dependent enzymes and how oxidative stress may contribute to neurological dysfunction through this selected group of proteins.

Glutathione status and antioxidant enzymes in a crocodilian species from the swamps of the Brazilian Pantanal

In a previous study oxidative damage markers - lipid peroxidation and protein oxidation - were determined in organs of wild Caiman yacare captured in winter-2001 and summer-2002 at various developmental stages. An increase in oxidative damage occurred in the hatchling-juvenile transition (but not in the juvenile-adult transition) and winter-summer transition (in juveniles), suggesting that oxidative stress is associated with development and season. Herein the effect of development and season on glutathione (GSH) metabolism and the effect of development on the activity of antioxidant enzymes (catalase, glutathione peroxidase, glutathione reductase and glutathione S-transferase) and glucose 6-phosphate dehydrogenase were analyzed. The ratio GSSG:GSH-eq increased in lung, liver, kidney and brain by 1.8- to 4-fold in the embryo/hatchling to juvenile transition. No changes occurred in juvenile-adult transition. GSSG:GSH-eq across seasons was significantly elevated in summer. Total-glutathione content was mostly stable in various organs; in liver it increased in the embryo-juvenile transition. Enzyme activities were only determined in summer-animals (embryos, hatchlings and juveniles). For most antioxidant enzymes, activities increased from embryo/hatchling to juvenile in liver and Kidney. In lung, there was an inverse trend for enzyme activities and total glutathione content. Thus, increased metabolic rates during early caiman growth - in embryo-juvenile transition - appears to be related to redox imbalance as suggested by increased GSSG:GSH-eq and activation of antioxidant defenses. Differences in oxidative stress across seasons were related with summer-winter nocturnal temperatures. These results, as a whole, were interpreted in the context of ecological biochemistry.

Targeting the overproduction of peroxynitrite for the prevention and reversal of paclitaxel-induced neuropathic pain

Chemotherapy-induced peripheral neuropathy (CIPN) accompanied by chronic neuropathic pain is a major dose-limiting side effect of a large number of antitumoral agents including paclitaxel (Taxol). Thus, CIPN is one of most common causes of dose reduction and discontinuation of what is otherwise a life-saving therapy. Neuropathological changes in spinal cord are linked to CIPN, but the causative mediators and mechanisms remain poorly understood. We report that formation of peroxynitrite (PN) in response to activation of nitric oxide synthases and NADPH oxidase in spinal cord contributes to neuropathological changes through two mechanisms. The first involves modulation of neuroexcitatory and proinflammatory (TNF-α and IL-1β) and anti-inflammatory (IL-10 and IL-4) cytokines in favor of the former. The second involves post-translational nitration and modification of glia-derived proteins known to be involved in glutamatergic neurotransmission (astrocyte-restricted glutamate transporters and glutamine synthetase). Targeting PN with PN decomposition catalysts (PNDCs) not only blocked the development of paclitaxel-induced neuropathic pain without interfering with antitumor effects, but also reversed it once established. Herein, we describe our mechanistic study on the role(s) of PN and the prevention of neuropathic pain in rats using known PNDCs (FeTMPyP(5+) and MnTE-2-PyP(5+)). We also demonstrate the prevention of CIPN with our two new orally active PNDCs, SRI6 and SRI110. The improved chemical design of SRI6 and SRI110 also affords selectivity for PN over other reactive oxygen species (such as superoxide). Our findings identify PN as a critical determinant of CIPN, while providing the rationale toward development of superoxide-sparing and "PN-targeted" therapeutics.

Presymptomatic alterations in energy metabolism and oxidative stress in the APP23 mouse model of Alzheimer disease

Glucose hypometabolism is the earliest symptom observed in the brains of Alzheimer disease (AD) patients. In a former study, we analyzed the cortical proteome of the APP23 mouse model of AD at presymptomatic age (1 month) using a 2-D electrophoresis-based approach. Interestingly, long before amyloidosis can be observed in APP23 mice, proteins associated with energy metabolism were predominantly altered in transgenic as compared to wild-type mice indicating presymptomatic changes in energy metabolism. In the study presented here, we analyzed whether the observed changes were associated with oxidative stress and confirmed our previous findings in primary cortical neurons, which exhibited altered ADP/ATP levels if transgenic APP was expressed. Reactive oxygen species produced during energy metabolism have important roles in cell signaling and homeostasis as they modify proteins. We observed an overall up-regulation of protein oxidation status as shown by increased protein carbonylation in the cortex of presymptomatic APP23 mice. Interestingly, many carbonylated proteins, such as Vilip1 and Syntaxin were associated to synaptic plasticity. This demonstrates an important link between energy metabolism and synaptic function, which is altered in AD. In summary, we demonstrate that changes in cortical energy metabolism and increased protein oxidation precede the amyloidogenic phenotype in a mouse model for AD. These changes might contribute to synaptic failure observed in later disease stages, as synaptic transmission is particularly dependent on energy metabolism.

Protective effect of white tea extract against acute oxidative injury caused by adriamycin in different tissues

Adriamycin (ADR) is an anticancer agent that increases oxidative stress in cells. We evaluated the protective effect of the long term consumption of white tea at two different doses against this drug. For this purpose rats were given distilled water (controls), 0.15 mg (Dose 1) or 0.45 mg (Dose 2) of solid tea extract/kg body weight for 12 months. All the animals received an injection of ADR, except half of the control group, which were given an injection of saline solution. This gave four experimental groups: Control (C), C+ADR, Dose 1+ADR, and Dose 2+ADR. The antioxidant activity (in liver, heart and brain microsomes) was analysed. White tea consumption for 12 months, at a non-pharmacological dose, reversed the oxidative damage caused by ADR, on both protein and lipid levels in all three organs. The heart recovered its antioxidant activity only at the highest dose of tea.

Octarepeat peptides of prion are essential for multidrug resistance in gastric cancer cells

OBJECTIVE

In previous studies cellular prion protein (PrPc) is confirmed to be involved in multidrug resistance (MDR) of gastric cancer. Although octarepeat peptides are important functional domains of PrPc and are closely related to the transport of Cu2+/Zn2+ and antioxidative function, the significance in MDR remains unknown. We aimed to investigate the role of octarepeat peptides in gastric cancer MDR.

METHODS

Small interfering RNA (siRNA) against PrPc were transfected into adriamycin-resistant gastric cancer cell lines to inhibit the expression of wild type PrPc, and then constructs encoding PrPc without octarepeat peptides and PrPc without the fifth repeat peptide were transfected, respectively, to establish the cell models. In vitro drug sensitivity, cell apoptosis, measurement of superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) and glutathione (GSH), as well as changes in glutathione S-transferase (GST) were detected.

RESULTS

In vitro drug sensitivity test showed that octarepeat peptides could modulate the drug resistance of gastric cancer cells, but the deletion of the fifth repeat peptide had no effect. Specifically, the anti-apoptotic capacity of gastric cancer cells decreased significantly when the octarepeat peptides of PrPc was absent. Moreover, the activities of total SOD, Cu2+/Zn2+-SOD, GSH-Px, GSH, and GST detected in different stressing periods revealed that cells lacking octarepeat peptides of PrPc exhibited weakened responses to stress. However, absence of the fifth repeat peptide did not exert any effect on stress response.

CONCLUSION

The octarepeat peptides of prion is responsible for MDR in gastric cancer cells while the fifth repeat peptide is not.

Global effects of adriamycin treatment on mouse splenic protein levels

Adriamycin (ADR) is a potent anticancer drug used to treat a variety of cancers. Patients treated with ADR have experienced side effects such as heart failure, cardiomyopathy, and "chemobrain", which have been correlated to changes in protein expression in the heart and brain. In order to better understand cellular responses that are disrupted following ADR treatment in immune tissues, this work focuses on spleen. Significantly reduced spleen sizes were found in ADR-treated mice. Global isotopic labeling of tryptic peptides and nanoflow reversed-phase liquid chromatography-tandem mass spectrometry (LC-MS/MS) were employed to determine differences in the relative abundances of proteins from ADR-treated mice relative to controls. Fifty-nine proteins of the 388 unique proteins identified showed statistically significant differences in expression levels following acute ADR treatment. Differentially expressed proteins are involved in processes such as cytoskeletal structural integrity, cellular signaling and transport, transcription and translation, immune response, and Ca(2+) binding. These are the first studies to provide insight to the downstream effects of ADR treatment in a peripheral immune organ such as spleen using proteomics.

An update on cancer- and chemotherapy-related cognitive dysfunction: current status

The purpose of this review is to summarize the current literature on the effects of cancer treatment-related cognitive difficulties, with a focus on the effects of chemotherapy. Numerous patients have cognitive difficulties during and after cancer treatments and, for some, these effects last years after treatment. We do not yet fully understand which factors increase susceptibility to cognitive difficulties during treatment and which cause persistent problems. We review possible contributors, including genetic and biological factors. Mostly we focus is on cognitive effects of adjuvant chemotherapy for breast cancer; however, cognitive effects of chemotherapy on the elderly and brain tumor patients are also discussed.

Reduction of cysteine sulfinic acid in eukaryotic, typical 2-Cys peroxiredoxins by sulfiredoxin

The eukaryotic, typical 2-Cys peroxiredoxins (Prxs) are inactivated by hyperoxidation of one of their active-site cysteine residues to cysteine sulfinic acid. This covalent modification is thought to enable hydrogen peroxide-mediated cell signaling and to act as a functional switch between a peroxidase and a high-molecular-weight chaperone. Moreover, hyperoxidation has been implicated in a variety of disease states associated with oxidative stress, including cancer and aging-associated pathologies. A repair enzyme, sulfiredoxin (Srx), reduces the sulfinic acid moiety by using an unusual ATP-dependent mechanism. In this process, the Prx molecule undergoes dramatic structural rearrangements to facilitate repair. Structural, kinetic, mutational, and mass spectrometry-based approaches have been used to dissect the molecular basis for Srx catalysis. The available data support the direct formation of Cys sulfinic acid phosphoryl ester and protein-based thiosulfinate intermediates. This review discusses the role of Srx in the reversal of Prx hyperoxidation, the questions raised concerning the reductant required for human Srx regeneration, and the deglutathionylating activity of Srx. The complex interplay between Prx hyperoxidation, other forms of Prx covalent modification, and the oligomeric state also are discussed.

2-Mercaptoethane sulfonate prevents doxorubicin-induced plasma protein oxidation and TNF-α release: implications for the reactive oxygen species-mediated mechanisms of chemobrain

Doxorubicin (DOX), an anthracycline used to treat a variety of cancers, is known to generate intracellular reactive oxygen species. Moreover, many patients who have undergone chemotherapy complain of cognitive dysfunction often lasting years after cessation of the chemotherapy. Previously, we reported that intraperitoneal administration of DOX led to elevated TNF-α and oxidative stress in the plasma and brain of mice. However, the mechanisms involved in nontargeted tissue damage remain unknown. In this study, we measured plasma oxidative stress and cytokine levels in patients treated with DOX. We observed increased plasma protein carbonylation and elevation of TNF-α 6 h after DOX administration in the context of multiagent chemotherapy regimens. Importantly, patients not treated coincidentally with 2-mercaptoethane sulfonate (MESNA) showed statistically significantly increased plasma protein-bound 4-hydroxynonenal, whereas those who had been coincidentally treated with MESNA as part of their multiagent chemotherapy regimen did not, suggesting that concomitant administration of the antioxidant MESNA with DOX prevents intravascular oxidative stress. We demonstrate in a murine model that MESNA suppressed DOX-induced increased plasma oxidative stress indexed by protein carbonyls and protein-bound HNE, and also suppressed DOX-induced increased peripheral TNF-α levels. A direct interaction between DOX and MESNA was demonstrated by MESNA suppression of DOX-induced DCF fluorescence. Using redox proteomics, we identified apolipoprotein A1 (APOA1) in both patients and mice after DOX administration as having increased specific carbonyl levels. Macrophage stimulation studies showed that oxidized APOA1 increased TNF-α levels and augmented TNF-α release by lipopolysaccharide, effects that were prevented by MESNA. This study is the first to demonstrate that DOX oxidizes plasma APOA1, that oxidized APOA1 enhances macrophage TNF-α release and thus could contribute to potential subsequent TNF-α-mediated toxicity, and that MESNA interacts with DOX to block this mechanism and suggests that MESNA could reduce systemic side effects of DOX.

Neuroprotective and neurorescue effects of a novel polymeric nanoparticle formulation of curcumin (NanoCurc™) in the neuronal cell culture and animal model: implications for Alzheimer's disease

Alzheimer's disease (AD) is characterized by deposition of amyloid-β (Aβ) plaques within the brain parenchyma followed by synaptic loss and neuronal death. Deposited Aβ reacts with activated microglia to produce reactive oxygen species (ROS) and cytochemokines, which lead to severe neuroinflammation. Curcumin is a yellow polyphenol compound found in turmeric, a widely used culinary ingredient that possesses anti-inflammatory and anti-cancer properties and may show efficacy as a potential therapeutic agent in several neuro-inflammatory diseases including AD. However, poor aqueous solubility and sub-optimal systemic absorption from the gastrointestinal tract may represent factors contributing to its failure in clinical trials. To increase curcumin's bioavailability, a polymeric nanoparticle encapsulated curcumin (NanoCurc™) was formulated which is completely water soluble. NanoCurc™ treatment protects neuronally differentiated human SK-N-SH cells from ROS (H2O2) mediated insults. NanoCurc™ also rescues differentiated human SK-N-SH cells, which were previously insulted with H2O2. In vivo, intraperitoneal (IP) NanoCurc™ injection at a dose of 25mg/kg twice daily in athymic mice resulted in significant curcumin levels in the brain (0.32 μg/g). Biochemical study of NanoCurc™-treated athymic mice revealed decreased levels of H2O2 as well as caspase 3 and caspase 7 activities in the brain, accompanied by increased glutathione (GSH) concentrations. Increased free to oxidized glutathione (GSH:GSSH) ratio in athymic mice brain versus controls also indicated a favorable redox intracellular environment. Taken together, these results suggest that NanoCurc™ represents an optimized formulation worthy of assessing the therapeutic value of curcumin in AD.

Proteomic identification of carbonylated proteins in 1,3-dinitrobenzene neurotoxicity

This study demonstrated that 1,3-dinitrobenzene-induced (1,3-DNB) oxidative stress led to the oxidative carbonlyation of specific protein targets in DI TNC1 cells. 1,3-DNB-induced mitochondrial dysfunction, as indicated by loss of tetramethyl rhodamine methyl ester (TMRM) fluorescence, was initially observed at 5h and coincided with peak reactive oxygen species (ROS) production. ROS production was inhibited in cells pre-treated with the mitochondrial permeability transition (MPT) inhibitor, bonkrekic acid (BkA). Pre-incubation with the antioxidant deferoxamine inhibited loss of TMRM fluorescence until 24h after initial exposure to 1,3-DNB. Two-dimensional polyacrylamide gel electrophoresis (2D PAGE) and subsequent Oxyblot analysis were used to determine if 1,3-DNB exposure led to the formation of protein carbonyls. Exposing DI TNC1 cells to 1,3-DNB led to marked protein carbonylation 45 min following initial exposure. Pre-treatment with deferoxamine or Trolox reduced the intensity of protein carbonylation in DI TNC1 cells exposed to 1mM 1,3-DNB. Tandem MS/MS performed on protein samples isolated from 1,3-DNB-treated cells revealed that specific proteins within the mitochondria, endoplasmic reticulum (ER), and cytosol are targets of protein carbonylation. The results presented in this study are the first to suggest that the molecular mechanism of 1,3-DNB neurotoxicity may occur through selective carbonylation of protein targets found within specific intracellular compartments of susceptible cells.

The influence of heroin abuse on glutathione-dependent enzymes in human brain

Heroin is an illicit narcotic abused by millions of people worldwide. In our earlier studies we have shown that heroin intoxication changes the antioxidant status in human brain. In the present work we continued our studies by estimating the effect of heroin abuse on reduced glutathione (GSH) and enzymes related to this cofactor, such as glutathione S-transferase detoxifying electrophilics (GST) and organic peroxides (as Se-independent glutathione peroxidase-GSHPx), and Se-dependent glutathione peroxidase (Se-GSHPx) specific mainly for hydrogen peroxide. Studies were conducted on human brains obtained from autopsy of 9 heroin abusers and 8 controls. The level of GSH and the activity of glutathione-related enzymes were determined spectrophotometrically. The expression of GST pi on mRNA and protein level was studied by RT-PCR and Western blotting, respectively. The results indicated significant increase of GST and GSHPx activities, unchanged Se-GSHPx activity, and decreased level of GSH in frontal, temporal, parietal and occipital cortex, brain stem, hippocampus, and white matter of heroin abusers. GST pi expression was increased on both mRNA and protein levels, however the increase was lower in brain stem than in other regions. Heroin affects all regions of human brain, and especially brain stem. Its intoxication leads to an increase of organic rather then inorganic peroxides in various brain regions. Glutathione S-transferase plays an important role during heroin intoxication, however its protective effect is lower in brain stem than in brain cortex or hippocampus.