Melatonin reduces the severity of anesthesia-induced apoptotic neurodegeneration in the developing rat brain

General anesthetics cause widespread apoptotic neurodegeneration in many regions of the developing rat brain. The activation of mitochondria-dependent apoptotic pathway is important in the early stages of anesthesia-induced developmental neuroapoptosis. To investigate potential means of protecting against this type of damage, we studied melatonin, a sleep-promoting agent and antioxidant known to inhibit apoptotic-type neuronal damage by improving mitochondrial homeostasis and stabilizing the inner mitochondrial membrane. When 7-day-old rats (the peak of synaptogenesis) were exposed to a commonly used and highly pro-apoptotic anesthesia cocktail (midazolam, isoflurane, nitrous oxide) in combination with the escalating doses of melatonin (from 1 to 20 mg/kg, s.c.), the severity of anesthesia-induced damage was reduced in a dose-dependent manner in two most vulnerable brain regions--the cerebral cortex and anterior thalamus. Melatonin-induced neuroprotection was mediated, at least in part, via the inhibition of mitochondria-dependent apoptotic pathway since melatonin caused an up-regulation of the anti-apoptotic protein, bcl-X(L), reduction in anesthesia-induced cytochrome c release into the cytoplasm and a decrease in anesthesia-induced activation of caspase-3, an important step in the activation of DNAses and the formation of the apoptotic bodies.     

Prenatal infection obliterates glutamate-related protection against free hydroxyl radicals in neonatal rat brain

Prenatal infection constitutes an important risk factor for brain injury, in both premature and full-term infants. Unfortunately, as the mechanisms involved are far from understood, no therapeutic strategy emerges to prevent the damage. We tested the hypothesis that administration of lipopolysaccharide (LPS) to gravid female rats enhanced glutamate-induced oxidative stress in brain of pups. A microdialysis probe was implanted into the striatum of 14-day-old animals and the release of hydroxyl radicals (.OH) in the perfusion medium was evaluated. Glutamate promoted a delayed.OH release in the offspring of dams given LPS, contrasting with the.OH decreases observed in control animals. A similar response occurred after infusion of (R,S)-3,5-dihydroxyphenylglycine (DHPG), a Group I metabotropic glutamate receptor (mGluR) agonist. This response was not consecutive to a remote activation of N-methyl-D-aspartate (NMDA) receptors, as it was unaffected by an NMDA receptor antagonist. Furthermore, the response to NMDA itself decreased in the offspring of dams given LPS. Massive amounts of DHPG, however, likely internalizing the mGlu receptor, still blunted the response to NMDA, as in controls. No quantitative variation occurred in mGluR1, mGluR5, or the NR1 subunit of the NMDA receptor between controls and neonates born from LPS-treated dams. Direct LPS injection into age-matched pups, by contrast, affected the response to neither glutamate nor DHPG. These results confirm that normally during perinatal development, the brain is protected from any oxidative stress resulting from excess glutamate, and the results support the hypothesis that maternal infection before delivery may lead to critical brain damage via the release of toxic free radicals.     

The oxygen free radicals originating from mitochondrial complex I contribute to oxidative brain injury following hypoxia-ischemia in neonatal mice

Oxidative stress and Ca(2+) toxicity are mechanisms of hypoxic-ischemic (HI) brain injury. This work investigates if partial inhibition of mitochondrial respiratory chain protects HI brain by limiting a generation of oxidative radicals during reperfusion. HI insult was produced in p10 mice treated with complex I (C-I) inhibitor, pyridaben, or vehicle. Administration of P significantly decreased the extent of HI injury. Mitochondria isolated from the ischemic hemisphere in pyridaben-treated animals showed reduced H(2)O(2) emission, less oxidative damage to the mitochondrial matrix, and increased tolerance to the Ca(2+)-triggered opening of the permeability transition pore. A protective effect of pyridaben administration was also observed when the reperfusion-driven oxidative stress was augmented by the exposure to 100% O(2) which exacerbated brain injury only in vehicle-treated mice. In vitro, intact brain mitochondria dramatically increased H(2)O(2) emission in response to hyperoxia, resulting in substantial loss of Ca(2+) buffering capacity. However, in the presence of the C-I inhibitor, rotenone, or the antioxidant, catalase, these effects of hyperoxia were abolished. Our data suggest that the reperfusion-driven recovery of C-I-dependent mitochondrial respiration contributes not only to the cellular survival, but also causes oxidative damage to the mitochondria, potentiating a loss of Ca(2+) buffering capacity. This highlights a novel neuroprotective strategy against HI brain injury where the major therapeutic principle is a pharmacological attenuation, rather than an enhancement of mitochondrial oxidative metabolism during early reperfusion.     

Release of polyunsaturated fatty acids from phospholipids and alteration of brain membrane integrity by oxygen-derived free radicals

We studied the effects of oxygen-derived free radicals on the ultrastructure of brain cortical slices and the release of fatty acids from phospholipids of crude synaptosomes. Xanthine oxidase, hypoxanthine, and ADP-Fe3+, a free-radical-generating system, caused swelling of cellular processes and mitochondria. The oxygen-derived free radicals also caused the rapid release and accumulation of endogenous polyunsaturated fatty acids (PUFA) from membrane phospholipids as determined by high-performance liquid chromatography (HPLC). Furthermore, [3H]-arachidonic acid was also rapidly released from prelabeled phospholipids concomitant with a decrease in radioactivity in various phospholipid fractions. The radioactivities of neutral lipids including diacylglycerols were unchanged by free radicals. These data indicate that the activation of phospholipase A2 and the release of PUFA may have overt effect on membrane integrity and the subsequent development of cellular injury and brain edema.     

Huperzine A attenuates mitochondrial dysfunction in beta-amyloid-treated PC12 cells by reducing oxygen free radicals accumulation and improving mitochondrial energy metabolism

We observed previously that huperzine A (HupA), a selective acetylcholinesterase inhibitor, can counteract neuronal apoptosis and cell damage induced by several neurotoxic substances, and that this neuroprotective action somehow involves the mitochondria. We investigated the ability of HupA to reduce mitochondrial dysfunction in neuron-like rat pheochromocytoma (PC12) cells exposed in culture to the amyloid beta-peptide fragment 25-35 (Abeta(25-35)). After exposure to 1 microM Abeta(25-35) for various periods, cells exhibited a rapid decline of ATP levels and obvious disruption of mitochondrial membrane homeostasis and integrity as determined by characteristic morphologic alterations, reduced membrane potential, and decreased activity of ion transport proteins. In addition, Abeta(25-35) treatment also led to inhibition of key enzyme activities in the electron transport chain and the tricarboxylic acid cycle, as well as an increase of intracellular reactive oxygen species (ROS). Pre-incubation with HupA for 2 hr not only attenuated these signs of cellular stress caused by Abeta, but also enhanced ATP concentration and decreased ROS accumulation in unharmed normal cells. Those results indicate that HupA protects mitochondria against Abeta-induced damages, at least in part by inhibiting oxidative stress and improving energy metabolism, and that these protective effects reduce the apoptosis of neuronal cells exposed to this toxic peptide.     

Protective effects of guanosine against sepsis-induced damage in rat brain and cognitive impairment

The development of cognitive impairment in sepsis is associated with neurotoxic effects caused by oxidative stress. We have assessed the effects of acute and extended administration of guanosine (GUA) on brain oxidative stress parameters and cognitive impairment in rats submitted to sepsis by cecal ligation and perforation (CLP). To achieve this goal, male Wistar rats underwent either sham operation or CLP with GUA. Rats subjected to CLP were treated with intraperitoneal injection of GUA (8 mg/kg after CLP) or vehicle. Twelve and 24 h after CLP, the rats were sacrificed, and samples from brain (hippocampus, striatum, cerebellum, prefrontal cortex and cortex) were obtained and assayed for thiobarbituric acid reactive species (TBARS) formation and protein carbonyls. On the 10th day, another group of rats was submitted to the behavioral tasks. GUA administration reduced TBARS and carbonyl levels in some brain regions between 12 and 24 h after CLP, and ameliorated cognitive impairment evaluated 10 days after CLP. Our data provide the first experimental demonstration that GUA was able to reduce the consequences of CLP-induced sepsis in rats, by decreasing oxidative stress parameters in the brain and recovering the memory impairment.     

The cholinergic hypothesis of cognitive impairment caused by traumatic brain injury

Cognitive impairments are among the most common neuropsychiatric sequelae of traumatic brain injury at all levels of severity. Cerebral cholinergic neurons and their ascending projections are particularly vulnerable to acute and chronic traumatically mediated dysfunction. In light of the important role of acetylcholine in arousal, attention, memory, and other aspects of cognition, cerebral cholinergic systems contribute to and may also be a target for pharmacologic remediation among individuals with post-traumatic cognitive impairments. This article will review the evidence in support of this hypothesis. Evidence of relatively selective damage to cholinergic injury, the development of persistent anticholinergic sensitivity, and the effects of cholinergic augmentation on memory performance are presented first. Thereafter, neuropathologic, electrophysiologic, and pharmacologic evidence of cholinergic dysfunction after traumatic brain injury in humans is reviewed. Finally, future directions for investigation of the cholinergic hypothesis and possible clinical applications of this information are discussed.     

Bisphenol-A inhibits mitochondrial biogenesis via impairment of GFER mediated mitochondrial protein import in the rat brain hippocampus

Mitochondrial biogenesis relies on different protein import machinery, as mitochondrial proteins are imported from the cytosol. The mitochondrial intermembrane space assembly (MIA) pathway consists of GFER/ALR and CHCHD4/Mia40, responsible for importing proteins and their oxidative folding inside the mitochondria. The MIA pathway plays an essential role in complex IV (COX IV) biogenesis via importing copper chaperone COX17, associated with the respiratory chain. BPA, an environmental toxicant, found in consumable plastics, causes neurotoxicity via impairment in mitochondrial dynamics, neurogenesis, and cognitive functions. We studied the levels of key regulatory proteins of mitochondrial import pathways and mitochondrial biogenesis after BPA exposure in the rat hippocampus. BPA caused a significant reduction in the levels of mitochondrial biogenesis proteins (PGC1α, and TFAM) and mitochondrial import protein (GFER). Immunohistochemical analysis showed reduced co-localization of NeuN with GFER, PGC-1α, and TFAM suggesting impaired mitochondrial biogenesis and protein import. BPA exposure resulted in damaged mitochondria with distorted cristae in neurons and caused a significant reduction in GFER localization inside IMS as depicted by immunogold electron microscopy. The reduced levels of GFER resulted in defective COX17 import. The translocation of cytochrome c into the cytosol and increased cleaved caspase-3 levels triggered apoptosis due to BPA toxicity. Overall, our study implicates GFER as a potential target for impaired mitochondrial protein machinery, biogenesis, and apoptosis against BPA neurotoxicity in the rat hippocampus.     

脑衰老与慢性炎症所致老年认知障碍症的研究进展

脑衰老相关促炎因素是促使老年认知障碍症（AD）及手术后认知障碍症（POCD）发生的重要危险因素。崔德华等人早年首次发现氨苯砜可抑制脑内炎性Aβ沉积,保护海马神经细胞及改善老年认知障碍。近年又发现伊桐苷可下调COX-2、TNF—α等炎性因子发挥神经保护作用。但两种药物的具体机制尚未完全清楚,其临床应用前景也有待研究。现将从促炎脑衰老因素通过AMPK—Sirtl—NF-κB／p53通路干预认知障碍角度,拟阐明伊桐苷和氨苯砜抗促炎脑衰老因素的生物学及药理机制,实现在早期AD和POCD的用药干预,为防治AD和POCD开辟新途径。     

The effects of hyperbaric and normobaric oxygen on cognitive impairment in the elderly

Eighty-two elderly subjects with significant cognitive impairment were randomly assigned to treatment with either hyperbaric oxygen, hyperbaric air, normobaric oxygen, or normobaric air. Treatment consisted of two 90-minute sessions a day for 15 consecutive days. Subjects were evaluated on measures of memory and intellectual capacity, as well as on psychiatric symptom rating scales. Results immediately after treatment and at one, two, three, and eight weeks following treatment did not show enhanced cognitive functioning or significantly greater symptom reduction in experimental subjects who received either normobaric or hyperbaric oxygen as compared to controls who received hyperbaric or normobaric air. There was also no evidence of differential treatment effects as a function of initial severity of illness, sex, response to a CO2 loading test, or presumed evidence of cerebrovascular disease.     

亚低温在不同时间窗对实验性脑梗死氧自由基的影响

目的　探讨亚低温在不同时间窗对实验性脑梗死氧自由基的影响。方法　将 110只 SD大鼠随机分成手术组和假手术组 ;手术组又分为亚低温组和常温组 ,再各分为手术后 0 h、2 h、4 h、6 h、7h、8h、9h、10 h、11h、12 h亚组 ;假手术组分为常温组和亚低温组 ;每组均 5只。手术组制备成左侧颈动脉近端栓塞的永久性缺血模型 ,假手术组只暴露左颈动脉不栓塞颈动脉。亚低温各亚组将肛温控制在 31.4℃左右 ,维持 12 h;然后处死 ,分离栓塞侧的大脑皮层 ,制备成均浆 ,分别测定一氧化氮 (NO)浓度、超氧化歧酶 (SOD)活性及丙二醛 (MDA)含量。结果　 (1)假手术组左、右侧大脑皮质 NO、SOD、MDA含量比较无显著差异 (P>0 .0 5 ) ;(2 )亚低温 0～ 9h亚组 SOD含量较常温组各组增高 ,而 NO、MDA含量除 12 h亚低温亚组均较常温组显著降低 (P<0 .0 1或 P<0 .0 5 ) ;(3)亚低温 0～ 10 h亚组 NO浓度和 MDA含量明显低于 12 h亚组 (P<0 .0 1或 P<0 .0 5 ) ;(4 )亚低温 8h及 8h前各亚组 SOD活性较 12 h亚组显著增高 (P<0 .0 5或 P<0 .0 1)。结论　亚低温在一定的时间内可以通过抑制自由基的产生和促进其清除而发挥脑保护作用 ,但是对不同的因素影响的时间窗并不一致。     

Effects of ischemia on free fatty acids and diacylglycerols in developing rat brain

Post-decapitative ischemic treatment imposed on the developing rat brain elicited a marked increase in its susceptibility to free fatty acid (FFA) release between 14 and 17 days, an observation similar to that reported by Bazan (Acta Physiol. Lat. Am.21, 15, 1971). Although the level of diacylglycerols (DG) also increased during this period, the extent of the increase was not as obvious as the FFA. Ischemic treatment to rats after 17 days of age elicited increases in DG and FFA enriched in stearic and arachidonic acids. The delayed response in susceptibility of brain tissue to ischemia-induced changes seems to suggest that the biochemical mechanism(s) responsible for the FFA and DG release is better correlated to events commensurating with synaptogenesis than with myelination.     

Effect of corticosterone treatment on mitochondrial oxidative energy metabolism in developing rat brain

Effects of "acute" and "chronic" corticosterone treatment on energy metabolism in brain mitochondria from rats belonging to various age groups were examined. Both acute and chronic treatments resulted in significant reduction in the state 3 respiration rates and in the lowering of ADP/O ratios with the various substrates tested. The effects were age and substrate specific and in general the extent of uncoupling was greater in chronically treated rats. Corticosterone treatments also resulted in site-specific uncoupling in an age-dependent manner. The overall effect of corticosterone treatments was lowering of ADP phosphorylation rates, thereby causing an energy deficit. The effects on dehydrogenase activities were of a variable nature. Our results suggest that energy deficits following corticosteroid treatment may be an underlying cause for impaired brain development reported by earlier researchers.     

Dexamethasone treatment differentially affects the oxidative energy metabolism of rat brain mitochondria in developing and adult animals

We studied the effect of repeated exposure to dexamethasone (Dex) treatment on rat brain mitochondrial oxidative energy metabolism in developing rats at different postnatal ages, i.e. 2-5 week and in adults. The animals were injected with a dose of 2 mg of Dex/kg body weight at around 7:00 a.m. for three alternative days prior to the day of sacrifice; the control group animals received saline vehicle. We measured rates of respiration with different substrates, viz. glutamate, pyruvate+malate, succinate and ascorbate+TMPD; the contents of individual cytochromes and the dehydrogenases and ATPase activities. Dex treatment, in general, stimulated the state 3 rates of respiration rates in young animals in age-dependent and substrate-specific manner except for the 3 week group, whereas in the adults there was substantial inhibition of the respiration. The pattern of dehydrogenases activities matched with respiration rates. Dex treatment also resulted in uncoupling of the second and third site of phosphorylation in 3-week-old animals and in the adults. The contents of cytochrome aa3, b and ATPase activities decreased significantly after Dex treatment in all the age groups. The results thus emphasize that exposure to repeated Dex treatment can significantly influence the oxidative energy metabolism of brain mitochondria in young growing animals as well as in adults.     

创伤性脑损伤患者行早期高压氧治疗对认知功能障碍的影响及神经作用机制

目的 探讨早期高压氧治疗创伤性脑损伤(TBI)存在认知功能障碍的临床效果,并分析其神经作用机制.方法 采用分层抽样法将菏泽市立医院2017-03—2019-01收治的78例TBI患者分为2组进行研究.对照组39例予以认知康复训练和常规基础治疗,研究组39例联合使用高压氧治疗.2组治疗2个疗程后采用蒙特利尔认知功能评估量...     

老年轻度认知功能障碍与氧自由基代谢、乙酰胆碱酯酶、血脂及炎性介质的关系

目的 探讨老年轻度认知功能障碍(MCI)与氧自由基代谢、乙酰胆碱酯酶(AchE)、血脂及炎性介质的关系.方法 分别检测老年MCI组(45例)与健康老年组(45例)记忆力、血清超氧化物歧化酶(SOD)、丙二醛(MDA)、AchE、血脂及白介素(IL)-1a、IL-6含量,并进行比较和相关分析.结果 与健康老年组比较,MCI组各项记忆分及记忆商明显降低(均P<0.05);血清SOD及高密度脂蛋白(HDL)水平显著降低(P<0.05～0.01),血清MDA、AchE、IL-1a水平及总胆固醇(TC)、低密度脂蛋白(LDL)及载脂蛋白B(ApoB)水平显著增高(P<0.05～0.01).MCI组血清AchE水平与SOD水平呈负相关(r=0.82,P<0.01),与MDA水平呈正相关(r=0.69,P<0.01);ApoB水平与TC、LDL水平正相关(r=0.71,0.76,均P<0.01).结论 记忆障碍是老年MCI患者的认知功能损害特点;血清AchE含量增高,可能是导致Ach不足使认知功能下降的原因之一;老年MCI与氧化损伤、炎症反应及脂质代谢紊乱可能有一定相关性.     

Focal cognitive impairment in mitochondrial encephalomyopathies: a neuropsychological and neuroimaging study.

Mitochondrial encephalomyopathies (ME) are a multisystemic group of diseases characterized by a wide range of biochemical and genetic mitochondrial defects with a variable mode of inheritance. We studied the neuropsychological profile, magnetic resonance imaging (MRI) and single photon emission computed tomography (SPECT) data in a group of ME patients in order to look for common or specific cognitive defects and a possible correlation with related brain areas. Three main cognitive areas were assessed: general intelligence, memory functions and visuo-perceptual skills. Our sample included 16 ME patients (nine males, seven females) aged 25-68 years (mean age 45.2, SD 13.0). No sign of mental deterioration was found in the group of elderly subjects. Despite subjects showing no global cognitive impairment they scored lower in nonverbal versus verbal tasks. Visuo-spatial skills and short-term memory were selectively impaired. There was no correlation between neuropsychological results and age, illness duration, age of onset, clinical phenotypes, genetic mitochondrial alterations and pharmacological therapy. The most frequent SPECT pattern observed was the hypoperfusion of temporal lobes, with a direct localization in the temporal cortex and with prevalent mesial involvement. The neuropsychological profile and SPECT imaging revealed similarities with focal defects.     

Rapid reduction of ATP synthesis and lack of free radical formation by MPP+ in rat brain synaptosomes and mitochondria

MPTP is a neurotoxin thought to damage dopaminergic neurons through free radical formation. MPTP is metabolized in the brain to MPP(+), which is taken up into dopaminergic neurons via the dopamine transporter and assumed to impair mitochondrial function. We used striatal synaptosomes and telencephalic mitochondria to further investigate MPP(+) mechanism of action. For comparison, the respiratory toxins FCCP, a cyanide analog that uncouples mitochondrial ATP production, and rotenone, a NADH dehydrogenase inhibitor, were also tested. FCCP, MPP(+) and rotenone caused a rapid but stable decrease in [3H]dopamine (DA) uptake by striatal synaptosomes. Two free radical scavengers, the salen-manganese complex EUK-134, and the spin trap s-PBN, did not prevent MPP(+)-induced decrease in DA uptake. However, addition of ATP during synaptosome preparation resulted in partial recovery of MPP(+)-induced [3H]DA uptake decrease. Generation of oxygen free radicals by treatment of telencephalic mitochondria with MPP(+), FCCP, or rotenone, was evaluated by measuring DCF fluorescence, while light emission by the luciferin-luciferase complex was used to determine ATP levels. MPP(+), unlike rotenone, did not produce oxygen free radicals, but rather blocked ATP production in mitochondria, as did FCCP and rotenone. Taken together, these results suggest that MPP(+) toxicity, at least during its initial stages, is primarily due to a decrease in ATP synthesis by mitochondria and not to free radical formation.     

The role of free radicals and eicosanoids in the pathogenetic mechanism underlying ischemic brain edema

Results of our consecutive study on the pathogenetic mechanism underlying ischemic brain edema are summarized in this paper. Pertinent findings are as follows: (1) there is a close correlation between the influxes of water and sodium following ischemia; (2) the edema fluid can be regarded as the ultrafiltrate of serum; (3) there is a significant increase in the brain content of HETEs following ischemia; (4) the lipoxygenase activity of brain microvessels is increased following ischemia; (5) the lipoxygenase activity as well as the Na⁺, K⁺-ATPase activity of brain microvessels are enhanced by a hydroperoxide, 15-HPETE; (6) inhibition of Na⁺,K⁺-ATPase of brain microvessels by intraarterial infusion of ouabain resulted in a significant decrease in edema formation; and (7) not the cyclooxygenase, but the lipoxygenase pathway seems to be involved in the enhancement of microvessel Na⁺,K⁺-ATPase. Lipoxygenase(s) and Na⁺?K⁺-ATPase of brain microvessels, the activities of which are enhanced by an increased level of free radicals and/or hydroperoxides, may play a significant role in the occurrence of ischemic brain edema.