Reduced glutathione oxidation ratio and 8 ohdG accumulation by mild ischemic pretreatment

Salidroside promotes healthy longevity by interfering with HSP90 activity

Aging is a risk factor for human health and quality of life. Screening and development of novel supplements and medications to combat aging and delay the incidence of age-related diseases are of great significance. In this study, salidroside (SA), a primary natural small molecule from Rhodiola rosea, was investigated regarding its effects on life and healthspan and the underlying molecular mechanism(s) of anti-aging and antioxidation. Our results showed that SA effectively prolonged lifespan and exhibited anti-aging and antioxidative properties. Computer-assisted methods, label-free interaction analysis, and in vitro assays showed that SA directly bound heat shock protein 90 (HSP90). Furthermore, SA significantly inhibited the ATPase activity of HSP90, affecting the interaction between HSP90 and its interacting proteins and the expression of downstream genes to regulate lifespan and the oxidative stress response. Our findings provided new insights into the pharmacological properties of SA across multiple species and its potential as an anti-aging drug.

Effects of melittin on production performance, antioxidant function, immune function, heat shock protein, intestinal morphology, and cecal microbiota in heat-stressed quails

The purpose of this study was to investigate the effects of melittin on production performance, antioxidant function, immune function, heat shock protein, intestinal morphology, and cecal microbiota of heat-stressed quails. A total of 120 (30-day-old) male quails were randomly divided into 3 groups. Each group consisted of 4 replicates with 10 birds per replicate. The ambient temperature of the control group (group W) was 24°C ± 2°C. The heat stress group (group WH) and the heat stress + melittin group (group WHA2) were subjected to heat stress for 4 h from 12:00 to 16:00 every day, and the temperature was 36°C ± 2°C for 10 d. The results showed that compared with the group W, heat stress significantly decreased growth performance, serum and liver antioxidative function, immune function, intestinal villus height (VH) and villus height-to-crypt depth ratio (VH/CD), and cecal microbiota Chao and ACE index (P < 0.05). The crypt depth (CD) in the small intestine, and HSP70 and HSP90 mRNA levels in the heart, liver, spleen, and kidney were significantly increased (P < 0.05). Dietary melittin significantly increased growth performance, serum and liver antioxidative function, immune function, intestinal VH and VH/CD, and cecal microbiota Shannon index in heat-stressed quails (P < 0.05). Melittin significantly decreased small intestinal CD, and HSP70 and HSP90 mRNA levels in the viscera (P < 0.05). Furthermore, dietary melittin could have balanced the disorder of cecal microbiota caused by heat stress and increased the abundance and diversity of beneficial microbiota (e.g., Firmicutes were significantly increased). PICRUSt2 functional prediction revealed that most of the KEGG pathways with differential abundance caused by high temperature were related to metabolism, and melittin could have restored them close to normal levels. Spearman correlation analysis showed that the beneficial intestinal bacteria Anaerotruncus, Bacteroidales_S24-7_group_norank, Lachnospiraceae_unclassified, Shuttleworthia, and Ruminococcaceae_UCG-014 increased by melittin were positively correlated with average daily feed intake, the average daily gain, serum and liver superoxide dismutase, IgG, IgA, bursa of Fabricius index, and ileum VH and VH/CD. In sum, our results demonstrate for the first time that dietary melittin could improve the adverse effects of heat stress on antioxidant function, immune function, heat shock protein, intestinal morphology, and cecal microbiota in quails, consequently improving their production performance under heat stress.

Melatonin ameliorates H2O2-induced oxidative stress through modulation of Erk/Akt/NFkB pathway

Background

Improper control on reactive oxygen species (ROS) elimination process and formation of free radicals causes tissue dysfunction. Pineal hormone melatonin is considered a potent regulator of such oxidative damage in different vertebrates. Aim of the current communication is to evaluate the levels of oxidative stress and ROS induced damage, and amelioration of oxidative status through melatonin induced activation of signaling pathways. Hepatocytes were isolated from adult Labeo rohita and exposed to H₂O₂ at three different doses (12.5, 25 and 50 µM) to observe peroxide induced damage in fish hepatocytes. Melatonin (25, 50 and 100 μg/ml) was administered against the highest dose of H₂O₂. Enzymatic and non-enzymatic antioxidants such as malondialdehyde (MDA), superoxide dismutase (SOD), catalase (CAT) and glutathione (GSH) was measured spectrophotometrically. Expression level of heat shock proteins (HSP70 and HSP90), HSPs-associated signaling molecules (Akt, ERK, cytosolic and nuclear NFkB), and melatonin receptor was also measured by western blotting analysis.

Results

H₂O₂ induced oxidative stress significantly altered (P < 0.05) MDA and GSH level, SOD and CAT activity, and up regulated HSP70 and HSP90 expression in carp hepatocytes. Signaling proteins exhibited differential modulation as revealed from their expression patterns in H₂O₂-exposed fish hepatocytes, in comparison with control hepatocytes. Melatonin treatment of H₂O₂-stressed fish hepatocytes restored basal cellular oxidative status in a dose dependent manner. Melatonin was observed to be inducer of signaling process by modulation of signaling molecules and melatonin receptor.

Conclusions

The results suggest that exogenous melatonin at the concentration of 100 µg/ml is required to improve oxidative status of the H₂O₂-stressed fish hepatocytes. In H₂O₂ exposed hepatocytes, melatonin modulates expression of HSP70 and HSP90 that enable the hepatocytes to become stress tolerant and survive by altering the actions of ERK, Akt, cytosolic and nuclear NFkB in the signal transduction pathways. Study also confirms that melatonin could act through melatonin receptor coupled to ERK/Akt signaling pathways. This understanding of the mechanism by which melatonin regulates oxidative status in the stressed hepatocytes may initiate the development of novel strategies for hepatic disease therapy in future.

Oxidative Stress and Lung Ischemia-Reperfusion Injury

Ischemia-reperfusion (IR) injury is directly related to the formation of reactive oxygen species (ROS), endothelial cell injury, increased vascular permeability, and the activation of neutrophils and platelets, cytokines, and the complement system. Several studies have confirmed the destructiveness of the toxic oxygen metabolites produced and their role in the pathophysiology of different processes, such as oxygen poisoning, inflammation, and ischemic injury. Due to the different degrees of tissue damage resulting from the process of ischemia and subsequent reperfusion, several studies in animal models have focused on the prevention of IR injury and methods of lung protection. Lung IR injury has clinical relevance in the setting of lung transplantation and cardiopulmonary bypass, for which the consequences of IR injury may be devastating in critically ill patients.

Suppressive Effect of High Hydrogen Generating High Amylose Cornstarch on Subacute Hepatic Ischemia-reperfusion Injury in Rats

We examined whether feeding high hydrogen generating resistant starch could suppress subacute hepatic ischemia-reperfusion injury. Rats were fed a control diet with or without 20% high amylose cornstarch (HAS) supplementation for 14 days. On day 12, rats were subject to ischemia-reperfusion treatment. Portal hydrogen concentration was higher in the HAS group compared with the control group. Increased plasma alanine and aspartate aminotransferase activities due to ischemia-reperfusion treatment tended to decrease, and a significant reduction was observed by HAS feeding when compared with the control group. In conclusion, HAS, which enhances hydrogen generation in the hindgut, alleviated subacute hepatic ischemia-reperfusion injury.

Lactacidosis modulates glutathione metabolism and oxidative glutamate toxicity

Lactate and acidosis increase infarct size in humans and in animal models of cerebral ischemia but the mechanisms by which they exert their neurotoxic effects are poorly understood. Oxidative glutamate toxicity is a form of nerve cell death, wherein glutamate inhibits cystine uptake via the cystine/glutamate antiporter system leading to glutathione depletion, accumulation of reactive oxygen species and, ultimately, programmed cell death. Using the hippocampal cell line, HT22, we show that lactate and acidosis exacerbate oxidative glutamate toxicity and further decrease glutathione levels. Acidosis but not lactate inhibits system , whereas both acidosis and lactate inhibit the enzymatic steps of glutathione synthesis downstream of cystine uptake. In contrast, when glutathione synthesis is completely inhibited by cystine-free medium, acidosis partially protects against glutathione depletion and cell death. Both effects of acidosis are also present in primary neuronal and astrocyte cultures. Furthermore, we show that some neuroprotective compounds are much less effective in the presence of lactacidosis. Our findings indicate that lactacidosis modulates glutathione metabolism and neuronal cell death. Furthermore, lactacidosis may interfere with the action of some neuroprotective drugs rendering these less likely to be therapeutically effective in cerebral ischemia.

Association between type D personality, depression, and oxidative stress in patients with chronic heart failure

OBJECTIVE

To examine whether markers of oxidative stress differ as a function of Type D personality, depression, and chronic heart failure (CHF) etiology. Type D (distressed) personality and depression are related to poor cardiac prognosis. Because patients with CHF are characterized by increased oxidative stress, this may be a candidate mechanism responsible for the adverse prognosis in emotionally distressed patients with CHF.

METHODS

Serum levels of xanthine oxidase (XO), inducible heat shock protein (Hsp)70, and deoxyribonucleic acid damage marker 8-OHdG were measured in 122 patients, and effects of Type D, depression, and etiology were assessed.

RESULTS

CHF patients with Type D personality had lower levels of Hsp70 than non-Type D patients (6.48 ng/mL versus 7.85 ng/mL, p = .04, d = 0.26), and in case of an ischemic etiology, higher levels of XO (13.57 ng/mL versus 9.84 ng/mL, p = .01, d = 0.98). There were no significant univariate differences for depression. When adding depression as an additional independent variable in the Type D analysis, the effect of Type D personality remained significant (F = 5.460, p = .02) and was independent of depression (F = 0.942, p = .33). The ratio of XO to Hsp70 was significantly higher in Type D patients with CHF as compared with non-Type D patients (6.14 versus 2.83, p = .03, d = 0.39), independent of etiology class.

CONCLUSION

CHF patients with Type D personality are characterized by an increased oxidative stress burden, apparent in the decreased antioxidant levels and an increased oxidative stress ratio.

Molecular physiology of preconditioning-induced brain tolerance to ischemia

Ischemic tolerance describes the adaptive biological response of cells and organs that is initiated by preconditioning (i.e., exposure to stressor of mild severity) and the associated period during which their resistance to ischemia is markedly increased. This topic is attracting much attention because preconditioning-induced ischemic tolerance is an effective experimental probe to understand how the brain protects itself. This review is focused on the molecular and related functional changes that are associated with, and may contribute to, brain ischemic tolerance. When the tolerant brain is subjected to ischemia, the resulting insult severity (i.e., residual blood flow, disruption of cellular transmembrane gradients) appears to be the same as in the naive brain, but the ensuing lesion is substantially reduced. This suggests that the adaptive changes in the tolerant brain may be primarily directed against postischemic and delayed processes that contribute to ischemic damage, but adaptive changes that are beneficial during the subsequent test insult cannot be ruled out. It has become clear that multiple effectors contribute to ischemic tolerance, including: 1) activation of fundamental cellular defense mechanisms such as antioxidant systems, heat shock proteins, and cell death/survival determinants; 2) responses at tissue level, especially reduced inflammatory responsiveness; and 3) a shift of the neuronal excitatory/inhibitory balance toward inhibition. Accordingly, an improved knowledge of preconditioning/ischemic tolerance should help us to identify neuroprotective strategies that are similar in nature to combination therapy, hence potentially capable of suppressing the multiple, parallel pathophysiological events that cause ischemic brain damage.

A novel approach to screening for new neuroprotective compounds for the treatment of stroke

Despite the significant advances that have been made in understanding the pathophysiology of cerebral ischemia on the cellular and molecular level, only one drug, the thrombolytic tissue plasminogen activator (rt-PA), is approved by the FDA for use in patients with acute ischemic stroke. Therefore, there is a critical need for additional safe and effective treatments for stroke. In order to identify novel compounds that might be effective, we have developed a cell culture-based assay with death being an endpoint as a screening tool. We have performed an initial screening for potential neuroprotective drugs among a group of flavonoids by using the mouse hippocampal cell line, HT22, in combination with chemical ischemia. Further screens were provided by biochemical assays for ATP and glutathione, the major intracellular antioxidant, as well as for long-term induction of antioxidant proteins. Based upon the results of these screens, we tested the best flavonoid, fisetin, in the small clot embolism model of cerebral ischemia in rabbits. Fisetin significantly reduced the behavioral deficits following a stroke, providing proof of principle for this novel approach to identifying new compounds for the treatment of stroke.

Prevention of apoptosis-inducing factor translocation is a possible mechanism for protective effects of hepatocyte growth factor against neuronal cell death in the hippocampus after transient forebrain ischemia

Hepatocyte growth factor (HGF) is one of the prospective agents for therapy against a variety of neurologic and neurodegenerative disorders, although the precise mechanisms for the effect of HGF remain to be elucidated. We showed that treatment with HGF protected hippocampal cornu ammonis (CA) subregion 1 neurons from apoptotic cell death after transient forebrain ischemia. Accumulating evidence indicates that ischemia-induced neuronal damage occurs via caspase-independent pathways. In the present study, we focused on the localization of apoptosis-inducing factor (AIF), which is an important protein in the signal-transduction system through caspase-independent pathways, to investigate the possible mechanism for the protective effect of HGF after transient forebrain ischemia. Hepatocyte growth factor attenuated the increase in the expression of AIF protein in the nucleus after transient forebrain ischemia. We further explored the upstream components of AIF translocation. Primary DNA damage induced by Ca(2+) influx and subsequent NO formation are thought to be the initial events for AIF translocation, which results in the subsequent DNA damage by AIF. Hepatocyte growth factor prevented the primary oxidative DNA damage, as was estimated by using anti-8-OHdG (8-hydroxy-2'-deoxyguanosine) antibody. Oxidative DNA damage after ischemia is known to lead to the activation of poly(ADP-ribose) polymerase (PARP) and p53, resulting in AIF translocation. Marked increases in the PAR polymer formation and the expression of p53 protein after ischemia were effectively prevented by HGF treatment. In the present study, we first showed that HGF was capable of preventing neuronal cell death by inhibiting the primary oxidative DNA damage and then preventing the activation of the PARP/p53/AIF pathway.

The Reduction of Hypoxia-Induced and Reoxygenation-Induced Apoptosis in Rat Islets by Epigallocatechin Gallate

The survival of transplanted tissue is affected by the detrimental consequences of hypoxia followed by reoxygenation. The majority of transplanted cells undergo apoptosis due to hypoxia and reoxygenation (H/R) injury, but protection from H/R has been less examined. In this study, we examined whether epigallocatechin gallate (EGCG) protected rat islets from H/R injury. Rat islets, freshly prepared from F344 rat strain by collagenase digestion and density centrifugation, were seeded in triplicate at concentrations of 100 per well in 24-well plates for culture under normoxia. The cells were then exposed to hypoxia for 14 hours with or without EGCG, after which they were reoxygenated for 72 hours in a humidified oxygenated CO(2) incubator at 37 degrees C. Apoptosis, lactate dehydrogenase (LDH), and 8-hydroxy-2'-deoxyguanosine (8-OHdG) were evaluated according to the manufacturer's instructions. The H/R induced apoptosis in the islets that was reduced in dose-dependent manner by EGCG treatment. The viability of islets exposed to H/R was assessed by LDH release. H/R reduced viability compared with the controls, while the viability of the islets improved upon EGCG treatment. The secretion of insulin was also decreased by H/R, as well as the dose dependent EGCG protective ability on insulin secretion. The content of 8-OHdG in islets from H/R was also reduced by EGCG. Our results indicated that apoptosis and the decline in insulin secretion by H/R were inhibited by EGCG treatment. EGCG may be considered useful for protection of islets from oxidative injury associated with the transplantation procedure.

Determination of 8-oxoguanine and 8-hydroxy-2'-deoxyguanosine in the rat cerebral cortex using microdialysis sampling and capillary electrophoresis with electrochemical detection

A rapid and sensitive method to determine 8-oxoguanine (8oxoG) and 8-hydroxydeoxyguanosine (8OHdG), biomarkers for oxidative DNA damage, in cerebral cortex microdialysate samples using capillary electrophoresis (CE) with electrochemical detection (CEEC) was developed. Samples were concentrated on-column using pH-mediated stacking for anions. On-column anodic detection was performed with a carbon fiber working electrode and laser-etched decoupler. The method is linear over the expected extracellular concentration range for 8oxoG and 8-OHdG during induced ischemia-reperfusion, with R.S.D. values Collapse

Key Words Collapse

MESH Headings

• Animals
• Biomarkers/analysis
• Cerebral Cortex/chemistry
• Chromatography, Liquid/methods
• Deoxyadenosines/analysis
• Electrochemistry
• Electrophoresis, Capillary/methods
• Female
• Guanine/analogs & derivatives
• Guanine/analysis
• Mass Spectrometry/methods
• Microdialysis/methods
• Rats
• Rats, Sprague-Dawley

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Grants

• R01 EB000247 NIBIB NIH HHS
• R01 HL069014-02 NHLBI NIH HHS
• R01EB00247 NIBIB NIH HHS
• T32 CA009242 NCI NIH HHS
• R01 HL069014 NHLBI NIH HHS
• T32CA09242 NCI NIH HHS

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Affiliation(s)

Stacy D. Arnett Department of Chemistry, University of Kansas, Lawrence, KS 66045
Damon M. Osbourn Department of Chemistry, University of Kansas, Lawrence, KS 66045
Kimberly D. Moore Department of Chemistry, University of Kansas, Lawrence, KS 66045
Shannon S. Vandaveer Department of Chemistry, University of Kansas, Lawrence, KS 66045
Craig E. Lunte Department of Chemistry, University of Kansas, Lawrence, KS 66045

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Protein-energy malnutrition impairs functional outcome in global ischemia

We investigated whether protein-energy malnutrition (PEM) exacerbates brain injury in global ischemia. It was hypothesized that PEM would increase secondary brain damage by worsening ischemia-induced depletion of glutathione (GSH) and increasing oxidative stress. Adult male gerbils were fed an adequate protein (12.5%; C) or low protein (2%; PEM) diet for 4 weeks and subjected to 5 min of bilateral carotid artery occlusion (Ischemia) or sham surgery (Sham). At 12 h post-ischemia, GSH and markers of oxidative stress were measured in hippocampus and neocortex. The remaining gerbils were tested in the open field on days 3, 7, and 10, with viable hippocampal CA1 neurons assessed on day 10. Although the habituation of C-Ischemia gerbils in the open field was normal by day 7, PEM-Ischemia gerbils failed to habituate even by day 10 and spent greater time in the outer zone (P < 0.05). Mean (+/-SEM) total number of viable CA1 neurons at 10 days post-ischemia were C-Sham = 713 (13), C-Ischemia = 264 (48), PEM-Sham = 716 (12), and PEM-Ischemia = 286 (66). Although PEM did not increase CA1 neuron loss caused by ischemia, a subset (4/12) of PEM-Ischemia gerbils showed dramatic reactive gliosis accompanied by extensive neuronal loss. Hippocampal protein thiols were decreased by PEM and ischemia. Although the mechanism is yet to be established, the finding that PEM worsens functional outcome following global ischemia is clinically relevant since 16% of elderly are nutritionally compromised at the time of admission for stroke.

Peripheral oxidative biomarkers constitute a valuable indicator of the severity of oxidative brain damage in acute cerebral infarction

Oxidative stress contributes to post-ischemic brain damage. We assessed the correlation between plasma 8-hydroxy-2'-deoxyguanosine (8-OHdG), as a marker of oxidative DNA damage, and progressive brain damage in rats subjected to transient or permanent ischemia. Male Wistar rats were subjected to permanent- and 0.5-, 1-, 2-h middle cerebral artery occlusion (MCAO). At various times thereafter, the infarct volume, 8-OHdG levels in plasma and brain tissue, DNA fragmentation, and immunohistochemical observations on their brains were recorded and compared. At 12 h after 2-h MCAO-reperfusion, the cortical infarct volume was increased; it peaked at 24 h. DNA degeneration expanded from the caudate putamen into the cortical region at 12 h. 8-OHdG-containing cells in the cortical infarct zone were observed at 12 h, the number of 8-OHdG-positive cells was highest at 24 h and they co-localized with DNA single-strand breaks. Plasma 8-OHdG significantly increased at 12 h, and peaked at 24 h after reperfusion (1.1+/-0.7 ng/ml (mean+/-S.D.); controls 0.3+/-0.1; p<0.01). This increase was in step with increased infarct volume, DNA degradation, and reflected immunohistochemical findings in the cortical region but not the caudate putamen. In the permanent MCAO model, plasma 8-OHdG levels were associated with the brain contents of 8-OHdG. Plasma 8-OHdG and the cortical infarct volume were lower in the 0.5- and 1-h than the 2-h MCAO model. Our findings suggest that 8-OHdG as a peripheral biomarker may be an indicator of oxidative brain damage in acute cerebral infarction.

Time course and cellular distribution of hsp27 and hsp72 stress protein expression in a quantitative gerbil model of ischemic injury and tolerance: thresholds for hsp72 induction and hilar lesioning in the context of ischemic preconditioning

The distribution and time course of expression of the heat shock/stress proteins, hsp27 and hsp72, were evaluated in a highly controlled gerbil model of ischemic injury and tolerance induction, in which the duration of ischemic depolarization in each hippocampus provides a precise quantitative index of insult severity. Gerbils were subjected to brief priming insults (2- to 3.5-minute depolarization) that produce optimal preconditioning, to severe test insults (6- to 8.5-minute depolarization) that produce complete CA1 neuron loss in naive animals, or to combined insults administered 1 week apart, after which almost complete tolerance to CA1 neuron injury is observed. Immunoreactivities of hsp27, hsp72, glial fibrillary acidic protein and microtubule-associated protein 2 (MAP2) were evaluated in animals perfused at defined intervals after the final insult in each treatment group, using a variation of established antigen-retrieval procedures that significantly improves detection of many proteins in vibratome brain sections. Hsp72 was detected in CA1 neurons of some hippocampi 2 to 4 days after preconditioning, but this was only seen after the longest priming depolarizations, whereas shorter insults that still induced optimal tolerance failed to induce hsp72. Hsp72 was induced after test insults in preconditioned hippocampi, but at a higher depolarization threshold than observed for naive animals. An astrocytic localization of hsp27 was observed in regions of neuron injury, as indicated by reduced MAP2 immunoreactivity, and was primarily restricted to dentate hilus after preconditioning insults. These results establish that limited hilar lesions are characteristic of optimal preconditioning, whereas prior neuronal expression of either hsp72 or hsp27 is not required for ischemic tolerance.

Neuronal expression of the DNA repair protein Ku 70 after ischemic preconditioning corresponds to tolerance to global cerebral ischemia

BACKGROUND AND PURPOSE

Oxidative stress after ischemia/reperfusion has been shown to induce DNA damage and subsequent DNA repair activity. Ku 70/86, multifunctional DNA repair proteins, bind to broken DNA ends and trigger a DNA repair pathway. We investigated the involvement of these proteins in the development of neuronal tolerance to global cerebral ischemia after ischemic preconditioning.

METHODS

Adult male Sprague-Dawley rats were subjected to either 5 minutes of lethal global ischemia with or without 3 minutes of sublethal ischemic preconditioning or 3 minutes of ischemia only. Neuronal injury was histologically assessed, and DNA damage was visualized by in situ labeling of DNA fragmentation and DNA gel electrophoresis. Ku expression was also examined by immunohistochemistry and Western blot analysis.

RESULTS

Hippocampal CA1 neurons underwent DNA-fragmented cell death 3 days after 5 minutes of ischemia. However, these neurons showed a strong tolerance to 5 minutes of ischemia 1 to 3 days after ischemic preconditioning. Immunohistochemistry showed virtually no constitutive expression of Ku proteins in CA1 neurons; however, ischemic preconditioning induced neuronal Ku 70 expression 1 to 3 days later. Western blot confirmed an increase in Ku 70 in this region at the same time.

CONCLUSIONS

The temporal and spatial expression of Ku 70 corresponded to tolerance of the hippocampal CA1 neurons to subsequent ischemia, suggesting the involvement of Ku proteins in the development of neuronal tolerance after ischemic preconditioning.

Role of protein kinase Cdelta in transmitting hypoxia signal to HSF and HIF-1

An hypoxic microenvironment is an important modulator of gene expression in many pathophysiological conditions. In this study, we show a coordinate activation of heat shock transcription factor (HSF) and hypoxia-inducible factor-1 (HIF-1) in RIF tumor cells by hypoxia. Since heat shock protein (hsp) and angiogenic factor genes that are regulated by HSF and HIF-1 are thought to contribute to the malignant progression of hypoxic tumor cells, it was of our major interest to identify the components that are responsible for the activation of both HSF and HIF-1. Our finding that a bioflavonoid quercetin (QCT), a well known inhibitor of hsp gene expression, significantly inhibited the transcriptional activation of HSF and HIF-1 strongly suggests that QCT-sensitive molecule(s) is involved in the transcriptional activation of HSF and HIF-1 by hypoxia. Our results revealed that PCKalpha, delta and epsilon isoforms are expressed in RIF cells, but only PKCdelta was specifically translocated to the membrane by hypoxia. Our results also revealed that the translocation of PKCdelta was completely abrogated by QCT. Moreover, inhibiting the PKCdelta activation, either pharmacologically with phorbol 12-myristate 13-acetate or with bisindolymaleimide II or genetically by transient transfection of a dominant negative PKCdelta, significantly inhibited the transcriptional activation of HSF and HIF-1 by hypoxia. These results strongly substantiate a view that the PKCdelta isozyme is the QCT-sensitive molecule that plays an important role in transmitting hypoxia signals to both HSF and HIF-1. Here we show that the membrane translocation of PKCdelta is dependent on the activation of phosphoinositol 3-kinase (PI3K). Treatment with PI3K inhibitor, wortmannin or LY294002, abrogated not only PKCdelta translocation but the subsequent transcriptional activation of HSF and HIF-1 by hypoxia. Together, our study shows that the PKCdelta isozyme acts as a shared component in transmitting hypoxia-induced signals to both HSF and HIF-1, and that the upstream regulator of PKCdelta is PI3K.

Mitochondrial involvement in brain function and dysfunction: relevance to aging, neurodegenerative disorders and longevity

It is becoming increasingly evident that the mitochondrial genome may play a key role in neurodegenerative diseases. Mitochondrial dysfunction is characteristic of several neurodegenerative disorders, and evidence for mitochondria being a site of damage in neurodegenerative disorders is partially based on decreases in respiratory chain complex activities in Parkinson's disease, Alzheimer's disease, and Huntington's disease. Such defects in respiratory complex activities, possibly associated with oxidant/antioxidant balance perturbation, are thought to underlie defects in energy metabolism and induce cellular degeneration. Efficient functioning of maintenance and repair process seems to be crucial for both survival and physical quality of life. This is accomplished by a complex network of the so-called longevity assurance processes, which are composed of genes termed vitagenes. A promising approach for the identification of critical gerontogenic processes is represented by the hormesis-like positive effect of stress. In the present review, we discuss the role of energy thresholds in brain mitochondria and their implications in neurodegeneration. We then review the evidence for the role of oxidative stress in modulating the effects of mitochondrial DNA mutations on brain age-related disorders and also discuss new approaches for investigating the mechanisms of lifetime survival and longevity.

Lipid alterations in transient forebrain ischemia: possible new mechanisms of CDP-choline neuroprotection

We have previously demonstrated that cytidine 5'-diphosphocholine (CDP-choline or citicoline) attenuated arachidonic acid (ArAc) release and provided significant protection for the vulnerable hippocampal CA(1) neurons of the cornu ammonis after transient forebrain ischemia of gerbil. ArAc is released by the activation of phospholipases and the alteration of phosphatidylcholine (PtdCho) synthesis. Released ArAc is metabolized by cyclooxygenases/lipoxygenases to form eicosanoids and reactive oxygen species (ROS). ROS contribute to neurotoxicity through generation of lipid peroxides and the cytotoxic byproducts 4-hydroxynonenal and acrolein. ArAc can also stimulate sphingomyelinase to produce ceramide, a potent pro-apoptotic agent. In the present study, we examined the changes and effect of CDP-choline on ceramide and phospholipids including PtdCho, phosphatidylethanolamine (PtdEtn), phosphatidylinositol (PtdIns), phosphatidylserine (PtdSer), sphingomyelin, and cardiolipin (an exclusive inner mitochondrial membrane lipid essential for electron transport) following ischemia/1-day reperfusion. Our studies indicated significant decreases in total PtdCho, PtdIns, PtdSer, sphingomyelin, and cardiolipin and loss of ArAc from PtdEtn in gerbil hippocampus after 10-min forebrain ischemia/1-day reperfusion. CDP-choline (500 mg/kg i.p. immediately after ischemia and at 3-h reperfusion) significantly restored the PtdCho, sphingomyelin, and cardiolipin levels as well as the ArAc content of PtdCho and PtdEtn but did not affect PtdIns and PtdSer. These data suggest multiple beneficial effects of CDP-choline: (1) stabilizing the cell membrane by restoring PtdCho and sphingomyelin (prominent components of outer cell membrane), (2) attenuating the release of ArAc and limiting its oxidative metabolism, and (3) restoring cardiolipin levels.

Measurement of glutathione oxidation and 8-hydroxy-2'-deoxyguanosine accumulation in the gerbil hippocampus following global ischemia

Involvement of oxidative stress in ischemia/reperfusion-induced brain damage has been suggested. However, experimental support of this suggestion was limited partly because sensitive indices to assess oxidative consequences of ischemic brain damage were few. We have established biochemical assay systems to assess oxidative brain damage following ischemia. Mongolian gerbil brains were subjected to global ischemia/reperfusion, and the hippocampi were analyzed for oxidative damage by measuring temporal changes in glutathione and 8-ohdG following ischemia. Under oxidative stress, glutathione is known to be oxidized and subsequently depleted from cells. Therefore, glutathione content and its redox status can serve as sensitive indicators of oxidative damage. The accumulation of 8-ohdG has also been recognized as an excellent marker for oxidative DNA damage. The reduced and oxidized glutathione were measured by HPLC method following derivatization with 2,4-dinitrofluorobenzene. The 8-ohdG in DNA hydrolyzate was measured by HPLC with electrochemical detection. While total glutathione content decreased, glutathione oxidation ratio and 8-ohdG accumulation increased over a period of 30 min of reperfusion following ischemia. The results demonstrated that glutathione content, its oxidation ratio, and the accumulated 8-ohdG could be utilized as sensitive indices for the assessment of oxidative brain damage.

NO synthase and NO-dependent signal pathways in brain aging and neurodegenerative disorders: the role of oxidant/antioxidant balance

Nitric oxide and other reactive nitrogen species appear to play several crucial roles in the brain. These include physiological processes such as neuromodulation, neurotransmission and synaptic plasticity, and pathological processes such as neurodegeneration and neuroinflammation. There is increasing evidence that glial cells in the central nervous system can produce nitric oxide in vivo in response to stimulation by cytokines and that this production is mediated by the inducible isoform of nitric oxide synthase. Although the etiology and pathogenesis of the major neurodegenerative and neuroinflammatory disorders (Alzheimer's disease, amyothrophic lateral sclerosis, Parkinson's disease, Huntington's disease and multiple sclerosis) are unknown, numerous recent studies strongly suggest that reactive nitrogen species play an important role. Furthermore, these species are probably involved in brain damage following ischemia and reperfusion, Down's syndrome and mitochondrial encephalopathies. Recent evidence also indicates the importance of cytoprotective proteins such as heat shock proteins (HSPs) which appear to be critically involved in protection from nitrosative and oxidative stress. In this review, evidence for the involvement of nitrosative stress in the pathogenesis of the major neurodegenerative/ neuroinflammatory diseases and the mechanisms operating in brain as a response to imbalance in the oxidant/antioxidant status are discussed.