Day-night cycle of lipid peroxidation in rat cerebral cortex and their relationship to the glutathione cycle and superoxide dismutase activity

Lipoperoxidation, glutathione cycle components and superoxide dismutase activity show a day-night rhythm in the cerebral cortex of the rat. The highest lipoperoxidative activity is observed during the night (20.00-04.00 h). The enhancement in lipoperoxidation occurs concurrently with a decrease in glutathione peroxidase activity, an increase in superoxide dismutase activity and an increase in the double bonds in the brain cortex lipid fraction. The changes described in this paper seem to be related to a succession of light and dark periods, or to fasting and feeding periods. We propose that those fluctuations could act as a physiological oscillator with an important role in modulating the membrane properties of the nerve cell.     

Deoxyribonucleic acid turnover in immature neurons of the rat cerebral cortex

To test for metabolic deoxyribonucleic acid (DNA) turnover in differentiating neurons, [methyl-3H]thymidine was injected into the lateral cerebral ventricles of newly born rats, and after 6, 24 and 96 h, neuronal nuclei were prepared from the immature cerebral cortex. Enzymatic treatment converted virtually all of the DNA into soluble deoxynucleosides which were fractionated by high-performance liquid chromatography for determination of specific activity. The specific activity of thymidine was found to decline rapidly with time. The rate of this loss correlated with the radioactivity initially incorporated into the DNA. This suggested that DNA was being replaced by DNA repair as a consequence of radiation damage, rather than by spontaneous metabolic DNA turnover.     

Increased glutamate receptor gene expression in the cerebral cortex of insulin induced hypoglycemic and streptozotocin-induced diabetic rats

Hypoglycemia causes brain fuel deprivation, resulting in functional brain failure and brain death. It is a serious complication of insulin therapy in diabetic patients. A single intrafemoral dose of streptozotocin was administered to induce diabetes. Hypoglycemia was induced by appropriate doses of insulin s.c. in control and diabetic rats. Glutamate content and glutamate receptor kinetics were studied using [3H]glutamate. [3H]MK 801 was used to study the NMDA receptor kinetics. NMDA2B and metabotropic glutamate receptor (mGluR) 5 subunits receptor gene expressions were done using real time PCR. There was a significant (P<0.001) increase in the glutamate content in the cerebral cortex of hypoglycemic and diabetic rats when compared with control with more glutamate content in the hypoglycemic group. Scatchard analysis using [3H]glutamate and [3H]MK 801 in the cerebral cortex showed a significant (P<0.001) increase in the maximal binding (Bmax) in both hypoglycemic and diabetic rats when compared with control with no significant change in equilibrium dissociation constant. The glutamate and NMDA receptor binding parameters were significantly (P<0.001) enhanced in the hypoglycemic rats compared with hyperglycemic rats. Real time PCR analysis also showed a significant increase (P<0.001) in the gene expression of NMDA2B and mGluR5 subunits of glutamate receptor. This increased gene expression of NMDA2B and mGluR5 glutamate receptor subunits confirmed the enhanced mRNA of receptor subunits and subsequently at the protein level from the receptor kinetic studies. The enhanced glutamate receptors were more prominent in hypoglycemic group which is of significance in this study. Up-regulation of glutamate leads to Ca2+ overload in cells, potentially leading to cell damage and death. This functional damage during hypoglycemia is suggested to contribute to cognitive and memory deficits which has immense clinical relevance in the therapeutic management of diabetes.     

Increased in vitro lipid peroxidation of gerbil cerebral cortex as compared with rat

The in vitro thiobarbituric acid test was used as a measure of lipid peroxidation in the gerbil and rat. Synaptosomal preparations were isolated from the cerebral cortex of each species and incubated with a free radical generating system. Varying concentrations of ADP-Fe3+, with ascorbate and oxygenated incubation medium were used to generate hydroxy-radicals. Peroxidation of the synaptosomal membrane lipids was determined using malondialdehyde (MDA) accumulation. Both the gerbil and rat demonstrated significant increases in MDA in the presence of the generating system, while the gerbil P2 fraction consistently showed an increased level of MDA accumulation as compared with rat at each of the concentrations of ADP-Fe3+. Across a range of concentrations, there was a 2-2.6-fold greater increase in MDA accumulation in gerbil as compared with rat. Free radical generation is currently thought to be involved in the associated damage following cerebral ischemia. An in vitro model capable of producing biochemically similar damage to membrane systems by means of a controlled free-radical generating system may prove useful in studying possible mechanisms of ischemic damage.     

半胱氨酸蛋白酶抑制剂C对局灶性脑缺血再灌注大鼠大脑皮质 caspase-9、脑红蛋白表达和过氧化损伤的影响*

目的：探讨不同浓度半胱氨酸蛋白酶抑制剂C（CysC）对大鼠损伤大脑皮质组织caspase-9 和脑红蛋白（NGB） 的表达、氧化损伤和脑组织形态学的影响。方法：大鼠按照随机数字表分为假手术组（Sham 组）、缺血再灌注组 （I/R 组）、CysC 低、中、高浓度组。线栓法制备右侧局灶性脑缺血再灌注大鼠模型,缺血2h 再灌注24 h 后行H-E 染色,观察脑组织形态学变化;免疫组织化学法检测caspase-9 的阳性细胞数;免疫组织荧光法检测皮质神经元 NGB阳性细胞数;免疫印迹检测脑皮质组织中caspase-9 蛋白的表达。羟胺法检测超氧化物歧化酶（SOD）活力, 化学比色法检测谷胱甘肽过氧化物酶（GSH-PX）活力,硫代巴比妥酸法检测丙二醛（MDA）含量。结果：与 I/R 组相比,CysC 低、CysC 中浓度组caspase-9 表达较I/R 组明显减少;而CysC 高浓度组caspase-9 的表达明显升 高,与I/R 无明显差别。CysC 低、CysC 中浓度组caspase-9 阳性细胞数较I/R 组明显减少,NGB阳性细胞数较I/R 组显著增多,SOD和GSH-PX活力升高,MDA含量下降;而CysC 高浓度组caspase-9 阳性细胞数增多,NGB阳 性细胞数减少,SOD和GSH-PX活力降低,MDA含量升高;CysC 高浓度组与I/R 组相比,差异无统计学意义。结论： CysC 低、中浓度可能通过上调NGB的表达,下调caspase-9 的表达,减轻脑缺血再灌注后的自由基损伤。而浓度 过高则作用相反。     

Neuroprotection of rat hippocampal slices exposed to oxygen-glucose deprivation by enrichment with docosahexaenoic acid and by inhibition of hydrolysis of docosahexaenoic acid-containing phospholipids by calcium independent phospholipase A2

Polyunsaturated fatty acids play an important role in the development of pathological states in brain after hypoxia/ischemia. Here, we investigated the role of docosahexaenoic acid (22:6n-3) in brain phospholipids for neuronal survival. We used organotypic cultures of rat brain hippocampal slices exposed to 40 min of oxygen-glucose deprivation, to study the consequences of experimental ischemia. In [14C]docosahexaenoic acid-labeled cultures, oxygen-glucose deprivation induced significant release of radioactive docosahexaenoic acid. This release could be blocked by the selective inhibitor of the Ca2+-independent phospholipase A2, 4-bromoenol lactone (10 microM), when it was added 30 min prior to oxygen-glucose deprivation. Addition of 4-bromoenol lactone at 30 min prior to oxygen-glucose deprivation markedly decreased the neuronal damage induced by oxygen-glucose deprivation. The protective effect was substantially higher in dentate gyrus than in CA1 and CA3 areas. Enrichment of the hippocampal tissue with docosahexaenoic acid by incubation with 10 microM docosahexaenoic acid for 24 h exerted the same neuroprotective effect, which was observed after treatment with 4-bromoenol lactone. In contrast to the 24 h-preincubation, simultaneous addition of docosahexaenoic acid with the onset of oxygen-glucose deprivation had no protective effect. This suggests that incorporation of docosahexaenoic acid into phospholipids is required for the protective effect observed. Then the possible involvement of arachidonic acid metabolism in docosahexaenoic acid-induced neuroprotection was tested. Inhibition of prostaglandin production by ibuprofen produced no change in neuroprotection after 24-h incubation of the hippocampal slices with docosahexaenoic acid. Simultaneous inhibition of Ca2+-independent and Ca2+-dependent phospholipases A2 by treatment with the general phospholipase A2 inhibitor methyl arachidonyl fluorophosphonate (3 microM, 30 min prior to oxygen-glucose deprivation) resulted in significant enhancement of the neuroprotective effect in the dentate gyrus, but not in the CA1 and CA3 areas. In summary, the results reported here indicate that docosahexaenoic acid and docosahexaenoic acid-containing phospholipids provide potent protection against neurodegeneration after hypoxia/hypoglycemia. Furthermore, our data suggest that Ca2+-independent phospholipase A2, the isoform, which has been largely ignored so far, is a possible target for treatment of ischemia-related pathologies in brain.     

Mechanistic study of signalling pathways in intestinal B lymphocytes using eicosapentaenoic and docosahexaenoic acid in broiler chickens

The present study was conducted to investigate the effects of eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and a combination of both at a ratio of 2:1 on the signalling pathways in lipopolysaccharide (LPS)-stimulated intestinal B lymphocytes from broiler chickens. The results showed that these treatments reduced the production of prostaglandin E2 (PGE₂), cyclooxygenase 2 (COX-2), and phospholipase C (PLC) and increased the concentration of inositol triphosphate (IP₃) significantly compared with the control group (P?2, COX-2, and PLC and increased the concentration of IP₃ (P?相似文献   

Facilitatory effect of docosahexaenoic acid on N-methyl-D-aspartate response in pyramidal neurones of rat cerebral cortex.

1. The effect of docosahexaenoic acid (DHA) on N-methyl-D-aspartic acid (NMDA) responses in the presence of glycine was investigated in pyramidal neurons acutely dissociated from rat cerebral cortex in whole-cell and single channel configurations. 2. DHA potentiated the NMDA-induced response but reduced the non-NMDA (kainate-induced) response in a concentration-dependent manner at a holding potential of -60 mV under voltage-clamp conditions. 3. Arachidonic acid (AA) also potentiated the NMDA-induced response in a manner similar to DHA. Oleic acid caused a slight potentiation. However, other polyunsaturated and saturated fatty acids had no such effects. 4. The facilitatory action of DHA on the NMDA-induced response was not affected by adding inhibitors of cyclo-oxygenase, lipoxygenase or phospholipase A2, suggesting that DHA may exert its facilitatory effect directly on the NMDA receptor. 5. The facilitatory action of DHA was observed in the presence of a saturating dose of NMDA. Moreover, a detailed analysis of the NMDA receptor-operated single channel currents revealed that, in the presence of DHA, the open probability of the channel increased without changing the conductance, indicating that DHA may act by binding directly to a novel site on the NMDA receptor or by altering the lipid environment of the NMDA receptor and thereby potentiating the response to NMDA. 6. The results are discussed in terms of the possibility that DHA may play an important role in the genesis of long-term potentiation, at least that involving the activation of NMDA receptors.     

Actions of somatostatin on lipid metabolism in mouse cerebral cortex slices

Cerebral cortex slices from mice were used to investigate the variations of lipid metabolism by somatostatin. Somatostatin decreased [14C]acetate incorporation into all lipid fractions significantly. Likewise, the peptide evoked a decrease of triglyceride lipase activity. The incorporation of [32P]orthophosphate into phospholipids was diminished by somatostatin. These results add more information about the effects of somatostatin in cerebral cortex.     

Chronic administration of docosahexaenoic acid or eicosapentaenoic acid, but not arachidonic acid, alone or in combination with uridine, increases brain phosphatide and synaptic protein levels in gerbils

Synthesis of phosphatidylcholine, the most abundant brain membrane phosphatide, requires three circulating precursors: choline; a pyrimidine (e.g. uridine); and a polyunsaturated fatty acid. Supplementing a choline-containing diet with the uridine source uridine-5'-monophosphate (UMP) or, especially, with UMP plus the omega-3 fatty acid docosahexaenoic acid (given by gavage), produces substantial increases in membrane phosphatide and synaptic protein levels within gerbil brain. We now compare the effects of various polyunsaturated fatty acids, given alone or with UMP, on these synaptic membrane constituents. Gerbils received, daily for 4 weeks, a diet containing choline chloride with or without UMP and/or, by gavage, an omega-3 (docosahexaenoic or eicosapentaenoic acid) or omega-6 (arachidonic acid) fatty acid. Both of the omega-3 fatty acids elevated major brain phosphatide levels (by 18-28%, and 21-27%) and giving UMP along with them enhanced their effects significantly. Arachidonic acid, given alone or with UMP, was without effect. After UMP plus docosahexaenoic acid treatment, total brain phospholipid levels and those of each individual phosphatide increased significantly in all brain regions examined (cortex, striatum, hippocampus, brain stem, and cerebellum). The increases in brain phosphatides in gerbils receiving an omega-3 (but not omega-6) fatty acid, with or without UMP, were accompanied by parallel elevations in levels of pre- and post-synaptic proteins (syntaxin-3, PSD-95 and synapsin-1) but not in those of a ubiquitous structural protein, beta-tubulin. Hence administering omega-3 polyunsaturated fatty acids can enhance synaptic membrane levels in gerbils, and may do so in patients with neurodegenerative diseases, especially when given with a uridine source, while the omega-6 polyunsaturated fatty acid arachidonic acid is ineffective.     

Energy metabolism in rat brain structures after injections of kainic acid into the frontal cortex

We studied behavioral reactions of rats after injection of subconvulsive dose of kainic acid into the frontal cortex and mitochondrial respiration in the hippocampus and frontal and temporal cortex 17–20 days after administration of kainic acid. Retention of acquired habit and the dynamics of its extinction in experimental rats were close to those in the control group. Changes in mitochondrial function were observed only in the region of kainic acid injection: activation of phosphorylating respiration during oxidation of succinate. Presumably, the detected activation of energy metabolism in the frontal cortex indicates functional restructuring in mitochondria, aimed at compensation of disorders caused by the neurotoxin. __________ Translated from Byulleten’ Eksperimental’noi Biologii i Meditsiny, Vol. 144, No. 11, pp. 510–513, November, 2007     

Tyrosine hydroxylase-immunoreactive intrinsic neurons in the rat cerebral cortex

Summary Using specific antisera against the catecholamine synthesizing enzyme, tyrosine hydroxylase (TH), in combination with the peroxidase-antiperoxidase method and/or the avidin-biotin complex method, we have found a new group of TH immunoreactive (TH-I) neurons in the rat cerebral cortex. Numerous TH-I cells were observed all over the isocortex, that is, frontal, temporal, parietal and occipital regions, and in some parts of the allocortex such as the anterior cingulate cortex, the retrosplenial cortex and anterior part of the insular cortex. In contrast, they were rare in the perirhinal cortex, posterior part of the insular cortex, piriform cortex, entorhinal cortex and hippocampal formation. TH-I cells were situated throughout all cortical layers, but were most concentrated in layer II/III. Although TH-I cells were heterogeneous in shape, the majority were bipolar. All TH-I cells so far examined appeared to be of the nonpyramidal type. The majority of these intrinsic TH-I neurons also contained the GABA-like immunoreactivity and thus could be regarded as a subpopulation of cortical GABAergic neurons.     

Pneumolysin-mediated activation of NFkappaB in human neutrophils is antagonized by docosahexaenoic acid

This study was designed to investigate the relationship between influx of extracellular Ca(2+), activation of NFkappaB and synthesis of interleukin-8 (IL-8) following exposure of human neutrophils to subcytolytic concentrations (8.37 and 41.75 ng/ml) of the pneumococcal toxin, pneumolysin, as well as the potential of the omega-3 polyunsaturated fatty acid, docosahexaenoic acid, to antagonize these events. Activation and translocation of NFkappaB were measured using a radiometric electrophoretic mobility shift assay, while influx of extracellular Ca(2+) and synthesis of IL-8 were determined using a radioassay and an ELISA procedure, respectively. Exposure of neutrophils to pneumolysin was accompanied by influx of Ca(2+), activation of NFkappaB, and synthesis of IL-8, all of which were eliminated by inclusion of the Ca(2+)-chelating agent, EGTA (10 m m), in the cell-suspending medium, as well as by pretreatment of the cells with docosahexaenoic acid (5 and 10 microg/ml). The antagonistic effects of docosahexaenoic acid on these pro-inflammatory interactions of pneumolysin with neutrophils were not attributable to inactivation of the toxin, and required the continuous presence of the fatty acid. These observations demonstrate that activation of NFkappaB and synthesis of IL-8, following exposure of neutrophils to pneumolysin are dependent on toxin-mediated influx of Ca(2+) and that these potentially harmful activities of the toxin are antagonized by docosahexaenoic acid.     

硫辛酸对大鼠糖尿病角膜病变的保护作用

目的探讨消旋-硫辛酸(LA)对大鼠糖尿病角膜病变的抑制作用。方法将37只7周龄Brown-Norway(BN)系大鼠随机分为对照组(CTL组)、糖尿病组(DM组)和治疗组(LA组)。2%链脲霉素(STZ)尾静脉注射制作糖尿病组和治疗组的糖尿病模型,治疗组大鼠饲料中添加0.3%LA。测定体重、食量、血糖值作为评价全身状态的指标,并在麻醉剂点眼及紫外线照射的条件下观察3组大鼠角膜上皮损伤程度及LA的修复作用。结果 CTL组的存活率是100%,DM组及LA组的存活率在发病5个月时分别为36%和71%。平均体重的顺序为CTL组>LA组>DM组,摄食量则为DM组>CTL组>LA组。在未施加干预因素的情况下,DM组和LA组自糖尿病诱发后3个月开始观察到了较正常对照组明显的角膜损伤,损伤程度DM组>LA组,但组间差异未见统计学意义。麻醉剂点眼后CTL、DM、LA组的角膜损伤值分别是4.66±0.85、6.51±1.81、5.99±2.42。DM组和LA组与点眼前相比均有显著的上升,但点眼后比较两组角膜损伤值未见统计学差异。紫外线照射联合点眼剂治疗后,CTL组、DM组、LA组的角膜损伤值分别为4.56±0.47、5.8±1.49、4.96±0.63。各组间差异均有统计学意义(P<0.05)。血糖值的顺序为DM组>LA组>CTL组,三组间差异均有显著意义(P<0.01)。结论糖尿病大鼠角膜上皮经麻醉剂点眼及紫外线照射后损伤修复延迟,而口服LA可有效降低STZ所致糖尿病大鼠的血糖浓度,抑制角膜病变的发生。LA在角膜中的生化特性有待进一步的研究。     

Lipid peroxidation in a focus of hyperactivity in the rat cerebral cortex

It is shown that lipid peroxidation (LPO) can participate in the mechanism of development of paroxysmal activity in the rat cerebral cortex. The appearance of epileptic activity as a result of application of the sodium salt of penicillin to the surface of the sensomotor cortex led to a sharp rise in LPO products in the fraction of unpurified synaptosomes isolated from a focus of hyperactivity. Preliminary injection of the antioxidant -tocopherol into rats abolished the LPO activation effect and considerably reduced the number of paroxysms recorded on the electrocorticogram during existence of the focus.Laboratory of General Pathology of the Nervous System, Institute of General Pathology and Pathological Physiology, Academy of Medical Sciences of the USSR, Moscow. Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 89, No. 1, pp. 14–16, January, 1980.     

Lipoic acid effects on lipid peroxidation level,superoxide dismutase activity and monoamines concentration in rat hippocampus

The purposes of the present work were to verify lipid peroxidation level, superoxide dismutase (SOD) activity and monoamines (dopamine (DA), norepinephrine (NE), serotonin (5-HT)), and their metabolites (3,4-hydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA) and 5-hydroxyindoleacetic acid (5-HIAA)) contents in rat hippocampus after lipoic acid (LA) administration. Wistar rats were treated with 0.9% saline (i.p., control group) and LA (10, 20 or 30 mg/kg, i.p., LA10, LA20 and LA30 groups, respectively). After the treatments all groups were observed for 24 h. In LA20 group only there was a significant decrease in lipid peroxidation level. However, no alteration was observed in SOD activity in groups treated with LA. The NE and DA levels were increased only in 20 mg/kg dose of LA in rat hippocampus. Serotonin content and their metabolite 5-HIAA levels was decreased in same dose of LA. On the other hand, DOPAC and HVA levels did not show any significant change. The reduction in lipid peroxidation level and alterations in hippocampal monoamines can be suggested as a possible brain mechanism from this antioxidant. The outcome of the study may have therapeutic implications in the neurodegenerative diseases.     

The serotonin innervation of the cerebral cortex in the rat—an immunohistochemical analysis

The serotonergic innervation of the cerebral cortex in the rat has been studied by immunohistochemistry employing an antibody directed against the neurotransmitter, serotonin. The dorsal raphe, median raphe and B9 cell groups contain intensely labelled neuronal perikarya. Bundles of large diameter axons suggestive of fibers of passage are observed in successive sections as they ascend through the midbrain tegmentum, medial forebrain bundle, diagonal band and supracallosal stria en route to the cortex. In addition, a lateral pathway to the cerebral cortex traversing the ansa peduncularis is visualized. All regions of the cerebral cortex appear to be innervated by serotonergic axons which have a distinctive morphology: they are fine (0.1–0.5 μm), varicose, and extremely convoluted. Serotonergic axons of passage are thicker and comparatively straight. Throughout the lateral neocortex, as well as in the anterior cingulate cortex, serotonergic axons form a densely arborizing plexus through all cortical layers. Contrary to earlier reports, based on histofluorescence, describing a sparse innervation of the cortex with most of the fibers found in the molecular layer, the present study reveals that the innervation is relatively uniform across all cortical layers. In most of the cortex the density of serotonin-containing axons exceeds that of noradrenergic fibers. A distinctive and different pattern of serotonin innervation is found in the posterior cingulate cortex (cytoarchitectonic field RSg): the serotonergic axons are restricted largely to lamina I and III. A restricted laminar pattern also characterizes the innervation of the hippocampus; dense axonal plexuses occur in the outer rim of the dentate hilus and in the stratum lacunosum-moleculare. The serotonergic afferents to the cortex appear to have at least two different modes of distribution, a relatively uniform pattern in the anterior cingulate and the lateral neocortex and a restricted, laminar pattern in the posterior cingulate and the hippocampus.The density and extent of the serotonin innervation is such that the raphe neurons may contact every cell in the cortex. The widespread arborization of serotonin axons contrasts with the spatially restricted termination of thalamic afferents. The distribution of serotonin-containing fibers also differs substantially from the terminal patterns of noradrenergic and dopaminergic fibers. The differences in axonal morphology and distribution amongst the monoamine afferents reflect differences in their contributions to cortical circuitry. The present findings indicate that the serotonin-containing neurons may exert a profound and global, but not necessarily uniform, influence upon cortical function.