Cerebral oligaemia episode triggers free radical formation and late cognitive deficiencies

Exercise on Striatal Dopamine Level and Anxiety-Like Behavior in Male Rats after 2-VO Cerebral Ischemia

The purpose of this study was to discuss the effect of voluntary wheel running on striatal dopamine levels and anxiety-like behavior in rats with global cerebral ischemia. The male Sprague-Dawley rats were signed on in this study and randomly divided into following 4 groups: Control group (C group), Sham group (S group), ischemia group (I group), and 3 weeks physical exercise before ischemia group (3RI group). The rats in the 3RI group were placed in a voluntary running wheel for three weeks to exercise. Then, the rats in I and 3RI groups received bilateral carotid artery ligation (2-VO) operation. The C and S group did not perform voluntary running exercise and the bilateral common carotid arteries of S group were exposed without ligation. In vivo microdialysis was used in conjunction with high performance liquid chromatography (HPLC) and electrochemical detection to ascertain the level of dopamine in the striatum. Elevated plus maze (EPM) and open field (OF) were used to test anxiety status at 24 hours and 7days after 2-VO cerebral ischemia. Meanwhile, gait and motor coordination evaluations were carried out to eliminate the influence of non-specific motor problems. The results indicated that cerebral ischemia instigate the increase of striatal dopamine in I group rats during acute cerebral ischemia. A 3-week voluntary wheel running significantly enhances the striatal dopamine before ischemia and obstructs a further increase of dopamine during acute cerebral ischemia in 3RI group rats. At 24 hours after ischemia, striatal dopamine returned to pre-ischemic levels in 3RI group. Striatal dopamine in I group were less than pre-ischemic levels at 7 days. Behavioral data indicated that 3-week voluntary wheel running promoted recovery of anxiety-like behavior and gait were not affected by 2-VO cerebral ischemia at 24 hours post-ischemia rats. Therefore, it can be concluded that 3-week physical exercise significantly increased the striatal dopamine and improved anxiety-like behavior by inhibiting the increase of dopamine during acute cerebral ischemia and suppressing the decrease of dopamine after 24 hours and 7 days cerebral ischemia.

Intra-arterial anti-oxidant power negatively correlates with white matter injury, and oxidative stress positively correlates with disability in daily activities

Oxidative stress influences many kinds of diseases. Our hypothesis is that oxidative stress and antioxidant potentials correlate with cognitive function, activities of daily life and white matter injury. (UMIN-CTR R000016770) Thirty-two consecutive patients participated to this study after informed consent. A routine biochemical analysis, modified-Rankin Scale (m-RS), revised Hasegawa Dementia Scale (HDS-R), Mini-Mental State Examination (MMSE) and fluid-attenuated-inversion-recovery imaging (FLAIR) were performed before admission. Derivatives of reactive oxygen metabolites (d-ROMs) and biological antioxidant potential (BAP) were measured photometrically using arterial blood. Statistical analyses were done by analysis variance or logistic regression analysis. Median age was 72 (IQR: 64.3 -- 75.8). The d-ROMS were 367 ± 55.4, and BAP was 1967 ± 284. HDS-R and m-RS deteriorated with d-ROMs elevation (p < 0.05). Uric acid and creatinine decreased with d-ROMs elevation (p < 0.05). Both periventricular hyperintensity grade and deep and subcortical white matter hyperintensity grade worsened with BAP reduction (p < 0.05). Oxidative stress correlates negatively with cognitive function and activities of daily life. Low antioxidative potentials correlate with aggravation of white matter injury. We should control both oxidative stress and antioxidative potential to maintain healthy lives.

Intra-arterial oxidative stress correlates negatively with cognitive function and positively with postoperative ischemic lesions in carotid artery stenosis stenting

BACKGROUND AND PURPOSE

Carotid plaque contains biologically active substances released into the blood during carotid artery stenting (CAS). The main purpose of this prospective study was to analyse sequential changes in oxidative stress during CAS and their relationship to clinical factors.

METHODS

Twenty-two consecutive CAS procedures were performed between May 2014 and April 2016. Arterial blood was collected four times: (1) after the sheath insertion without edaravone; (2) pre-angioplasty with edaravone from the carotid artery; (3) after post-stenting angioplasty from an occluded carotid artery; and (4) before sheath removal. Derivatives of reactive oxygen metabolites (d-ROMs) and biological antioxidant potential (BAP) were measured photometrically. The relationship between d-ROMs or BAP and preoperatively investigated biochemical parameters, cognitive function, and number of diffusion-weighted image (DWI) high spot lesions was analysed using one-way ANOVA and the Tukey-Kramer HSD test.

RESULTS

The d-ROM values for CAS were 355±58.8 Carratelli Units at sheath insertion, 315±57.2 after edaravone infusion, 328±56.8 after post-stenting angioplasty, and 315±53.0 just before sheath removal. The d-ROM values were reduced significantly after edaravone infusion (P<0.05). The BAP at sheath insertion was reduced significantly according to age (P<0.05). The d-ROMs at sheath insertion correlated negatively with the dementia scale and positively with the post-CAS DWI high spots (1.00±1.07; P<0.05). Other biochemical parameters did not correlate with the d-ROM values or BAP.

CONCLUSION

Oxidative stress is correlated negatively with cognitive function and positively with postoperative ischemic lesions. Antioxidant potential decreases with ageing.

Pyrrolidine dithiocarbamate attenuates brain Aβ increase and improves long-term neurological outcome in rats after transient focal brain ischemia

Evidence suggests an association between brain ischemia and Alzheimer's disease (AD) development. Amyloid plaques consisted of β-amyloid peptide (Aβ) in the brain are a pathological hallmark of AD. Little is known about how brain ischemia induces AD-like neuropathology. A strategy effective to block such brain changes has not been reported. Here, adult male Sprague-Dawley rats were subjected to a 90-min right middle cerebral artery occlusion (MCAO). Pyrrolidine dithiocarbamate (PDTC) at various doses was given daily via gastric gavage with the first dose given at 10 min after the onset of reperfusion. The MCAO increased Aβ1-42 concentrations in the ischemic brain tissues. PDTC attenuated this increase. PDTC also decreased the ischemia-reduced expression of neprilysin, an Aβ degrading enzyme. Aβ1-42 levels were negatively correlated with neprilysin protein abundance. Brain ischemia decreased the expression of β-amyloid converting enzyme 1, a key enzyme to produce Aβ, and increased the expression of insulin-degrading enzyme, another Aβ degrading enzyme. Animals had impaired learning and memory at 2 months after the MCAO. PDTC attenuated this impairment. PDTC also improved long-term neurological outcomes. Our findings suggest that PDTC improves long-term neurological outcome of rats after transient focal brain ischemia. PDTC reduces ischemia-induced Aβ accumulation, possibly via preserving neprilysin expression.

The influence of intracerebral streptozotocin and/or cadmium on memory processes in mice exposed to transient cerebral oligemia

The aim of the study was to examine the effects of simultaneous acute exposure to cadmium (Cd) and in the presence of streptozotozin (STZ) on the central nervous system (CNS) memory processes in mice subjected to transient brain ischemia. In order to obtain transient brain ischemia, operative occlusion of common carotid arteries for 30 min was performed. Cadmium chloride was administered intraperitoneally (ip) after the surgery at a single dose of 0.1 LD(50) (LD(50) = 14 mg/kg). Disturbances in glucose metabolism in the brain tissue were induced by bilateral intracerebral administration of STZ, a drug that inhibits the function of a neuronal insulin receptor. Long-term memory was evaluated by means of a step-through passive avoidance task. Spatial working memory expressed as spontaneous alternations was tested in the Y-maze test. Coexposure to brain oligemia and STZ on the CNS produced significant impairment of long-term memory processes in mice. An additional exposure to Cd exacerbated the deficits of these processes. These results indicate that brain oligemia, Cd, and altered glucose metabolism may aggravate adverse effects on memory.

Influence of fenpropathrin on memory and movement in mice after transient incomplete cerebral ischemia

Fenpropathrin, a synthetic pyrethroid widely used as an insecticide, is known to affect locomotion and memory in mammals. It is possible that exposure to pyrethroids may occur in an elderly population where transient ischemic attacks are a higher risk for occurrence with consequent changes in memory and control of movement. Thus, the aim of this study was to determine whether bilateral clamping of carotid arteries (BCCA), a model for ischemia, together with fenpropathrin affected memory in tests such as the passive avoidance task and fresh spatial memory in a Y-maze, as well as movement activity and movement coordination on a rotarod in mice. BCCA together with fenpropathrin significantly reduced latency in a passive avoidance task compared to controls. There were no significant differences among the groups with respect to the Y-maze, movement activity, or movement coordination. In conclusion, fenpropathrin needs to be used with caution in the presence of an elderly population at risk for ischemia, as there appears to be evidence of some memory loss in mice.

Ischemia-modified albumin in acute stroke

BACKGROUND

Ischemia-modified albumin (IMA)is a new biological marker of ischemia. Previous studies have found increased serum IMA levels after myocardial ischemia, but no study has investigated the possibility that stroke modifies IMA blood levels.

MATERIALS AND METHODS

We studied 118 consecutive patients presenting within 3 h of the onset of an acute neurological deficit [84 brain infarctions (BI), 18 brain hemorrhages (ICH) and 16 transient ischemic attacks lasting less than 1 h or epileptic seizures]. Serum samples were obtained for all patients at initial presentation and repeated only in patients with stroke at 6, 12 and 24 h. IMA was measured by the albumin-cobalt-binding test (Ischemia Technologies, Denver, Colo., USA).

RESULTS

The initial median IMA (bootstrap 95% confidence interval, CI) was 83 U/ml (79-86) and 86 U/ml (75-90) in patients with BI and ICH, respectively (p = 0.76), and was 73 U/ml (58-79) in others (p = 0.003 compared with BI, and p = 0.017 with ICH). Baseline IMA levels correlated with the National Institutes of Health Stroke Scale [Spearman correlation coefficient: 0.34 (p = 0.002) in BI, 0.61 (p = 0.008) in ICH]. During the first 24 h, IMA levels increased in BI patients (median, 9.1%; bootstrap 95% CI, 5.2-11.5), whereas no change was observed in ICH patients (median, 1.2%; bootstrap 95% CI, -7.8 to 6.8).

CONCLUSIONS

IMA blood levels may be a biomarker for early identification of acute stroke. Further studies are required to investigate the role of IMA in the early detection of acute stroke.

Effects of cadmium on memory processes in mice exposed to transient cerebral oligemia

The purpose of the present study was to examine whether the effects of chronic or acute exposure to cadmium on memory processes in mice could be exacerbated by transiently reducing cerebral oxygen supply. Adult mice were subjected to bilateral clamping of the carotid artery (BCCA) for 30 min under anesthesia. Cadmium chloride was administered intraperitoneally after surgery at single doses of: 0.7 mg/kg (low dose), 1.4 mg/kg (high dose), or at a prolonged dose of 0.7 mg/kg for up to 10 days. Long-term memory was evaluated in a step-through passive avoidance task while spatial working memory was evaluated using a Y-maze spontaneous alternation task. BCCA mice injected with the 1.4 mg/kg dose of cadmium exhibited recall deficits in the step-through passive avoidance task. Combined treatment at either dose had no effect on the acquisition of passive avoidance. In the Y-maze task, spontaneous alternation behavior was only impaired in BCCA mice treated with the prolonged cadmium dose. These results indicate that cerebral oligemic hypoxia may alter cadmium neurotoxicity and potentiate the tendency for cadmium-induced memory impairments in the passive avoidance task and spontaneous alternation deficits.

Dopamine transporters are involved in the onset of hypoxia-induced dopamine efflux in striatum as revealed by in vivo microdialysis

Although many studies have revealed alterations in neurotransmission during ischaemia, few works have been devoted to the neurochemical effects of mild hypoxia, a situation encountered during life in altitude or in several pathologies. In that context, the present work was undertaken to determine the in vivo mechanisms underlying the striatal dopamine efflux induced by mild hypoxaemic hypoxia. For that purpose, the extracellular concentrations of dopamine and its metabolite 3,4-dihydroxyphenyl acetic acid were simultaneously measured using brain microdialysis during acute hypoxic exposure (10% O(2), 1h) in awake rats. Hypoxia induced a +80% increase in dopamine. Application of the dopamine transporters inhibitor, nomifensine (10 microM), just before the hypoxia prevented the rise in dopamine during the early part of hypoxia; in contrast the application of nomifensine after the beginning of hypoxia, failed to alter the increase in dopamine. Application of the voltage-dependent Na(+) channel blocker tetrodotoxin abolished the increase in dopamine, whether administered just before or after the beginning of hypoxia. These data show that the neurochemical mechanisms of the dopamine efflux may change over the course of the hypoxic exposure, dopamine transporters being involved only at the beginning of hypoxia.

Response of the brain to oligemia: gene expression, c-Fos, and Nrf2 localization

Oligemia is blood flow reduction without acute tissue damage that occurs in shock, migraine, and stroke penumbra. We developed a mouse model of oligemia by lowering mean arterial pressure to 30-40 mm Hg, resulting in a 50% reduction in cerebral blood flow as measured by laser Doppler, and reperfusing the blood after 30 min. Control experiments included anesthesia-only and surgery without blood withdrawal. Using immunohistochemistry, we localized the transcription factors Nrf2, which regulates expression of antioxidant and detoxification protein, and c-Fos, a marker of neuronal activation. Nrf2 was found only in oligemia mice and was localized in neurons of the cingulate cortex and cerebellar Purkinje cells. By contrast, c-Fos was found widely expressed in both groups and was localized in neurons in regions associated with response to stress, immunomodulation, and fluid homeostasis, including the periaqueductal gray and periventricular nucleus. These data indicate that c-Fos expression occurs as a result of surgical stress, but Nrf-2 upregulation is specific to oligemia. The CLONTECH Atlas 1.2 Mouse Array was used to assess genes that were up or down-regulated in oligemia versus surgery controls. Of 1176 genes, 29 differed between oligemia and surgery groups. Upregulation of oxidative stress induced (OSI) protein, heat shock protein (HSP) 84 and transthyretin (TTR) precursor in the oligemia group was confirmed with RT-PCR. The expression of HSP 84, transthyretin precursor, and OSI genes adds further evidence that oligemia induces an oxidative stress response in the brain.

Oxidative stress promotes tau dephosphorylation in neuronal cells: the roles of cdk5 and PP1

Oxidative stress has been demonstrated to produce modifications in several intracellular proteins that lead to alterations in their activities. Alzheimer's disease is related to an increase of oxidative stress markers, which may be an early event in the progression of the disease and neurofibrillary tangles formation. Abnormal phosphorylation of tau has been implicated in the etiopathogenesis of Alzheimer's disease. By using phospho-specific antibodies, we analyzed the changes in tau phosphorylation patterns after treatment of rat hippocampal and SHSY5Y human neuroblastoma cells with H2O2. We found that tau isoforms were hypophosphorylated at the Tau1 epitope after 2 h in the presence of H2O2. The decrease in the phosphorylation levels of tau protein were prevented by pretreatment with N-acetyl-L-cysteine. These changes were shown to depend on the activity of the cdk5/p35 complex, since a 3-fold increase in substrate phosphorylation and a 2-fold increase for the complex association were observed. Also, a decrease in the amount of inhibitor-2 bound to phosphatase PP1 was found in SHSY5Y cells under oxidative stress conditions. This decrease of inhibitor-2 bound to PP1 is due to an increased phosphorylation of the inhibitor-2 protein, thus leading to increased PP1 activity. Therefore, we propose that oxidative stress-induced activation of cdk5 leads to inhibitor-2 phosphorylation, relieving its inhibitory effect on PP1.

Magnetic resonance imaging shows delayed ischemic striatal neurodegeneration

Brief focal ischemia leading to temporary neurological deficits induces delayed hyperintensity on T1-weighted magnetic resonance imaging (MRI) in the striatum of humans and rats. The T1 hyperintensity may stem from biochemical alterations including manganese (Mn) accumulation after ischemia. To clarify the significance of this MRI modification, we investigated the changes in the dorsolateral striatum of rats from 4 hours through 16 weeks after a 15-minute period of middle cerebral artery occlusion (MCAO), for MRI changes, Mn concentration, neuronal number, reactivities of astrocytes and microglia/macrophages, mitochondrial Mn-superoxide dismutase (Mn-SOD), glutamine synthetase (GS), and amyloid precursor protein. The cognitive and behavioral studies were performed in patients and rats and compared with striatal T1 hyperintensity to show whether alteration in brain function correlated with MRI and histological changes. The T1-weighted MRI signal intensity of the dorsolateral striatum increased from 5 days to 4 weeks after 15-minute MCAO, and subsequently decreased until 16 weeks. The Mn concentration of the dorsolateral striatum increased after ischemia in concert with induction of Mn-SOD and GS in reactive astrocytes. The neuronal survival ratio in the dorsolateral striatum decreased significantly from 4 hours through 16 weeks, accompanied by extracellular amyloid precursor protein accumulation and chronic glial/inflammatory responses. The patients and rats with neuroradiological striatal degeneration had late-onset cognitive and/or behavioral declines after brief focal ischemia. This study suggests that (1) the hyperintensity on T1-weighted MRI after mild ischemia may involve tissue Mn accumulation accompanied by Mn-SOD and GS induction in reactive astrocytes, (2) the MRI changes correspond to striatal neurodegeneration with a chronic inflammatory response and signs of oxidative stress, and (3) the subjects with these MRI changes are at risk for showing a late impairment of brain function even though the transient ischemia is followed by total neurological recovery.

Hydrogen peroxide induces transient dephosphorylation of tau protein in cultured rat oligodendrocytes

Oxidative stress is a major mediator of neurodegeneration. In this study, we tested the effects of oxidative stress induced by a brief exposure to hydrogen peroxide (H(2)O(2)) on the phosphorylation state of the tau protein in oligodendrocytes (OL). Primary oligodendrocyte cultures prepared from newborn rat brains were exposed to millimolar concentrations of H(2)O(2) for up to 15 min, and then incubated in normal medium for up to 12 h. The treatment caused morphological degeneration of OL characterized by the loss of cellular processes apparent approximately 3 h after H(2)O(2) exposure. The morphological degeneration was preceded by a profound dephosphorylation of tau protein revealed by immunoblot using monoclonal tau-1 antibody that recognizes the dephosphorylated epitope. The dephosphorylated form increased dramatically during H(2)O(2) exposure, peaked after 2 h of post-exposure, and returned to the baseline level within 12 h. Total tau protein levels were not changed in the course of the experiment as judged by immunoblotting with phosphorylation-insensitive tau-5 and 46-1 monoclonal antibodies. Our finding demonstrates that oxidative stress induces a rapid but transient dephosphorylation of tau protein that may underlie morphological degeneration of OL.