Vitamin E Deficiency as a Model of Precocious Brain Aging: Assessment by X-Ray Microanalysis and Morphometry

Vitamin E (α-tocopherol) is a known biological antioxidant able to quench the lipid peroxidation chain and to protect the cellular structures (e.g., plasma membranes) from the attack of free radicals which are reported to play a primary role in aging. To assess whether the absence of α-tocopherol from the diet of young laboratory animals may be considered a reliable model of precocious brain aging, intracellular ionic content of brain cortex pyramidal cells, ultrastructural features of synaptic contact zones, synaptic mitochondria and perykarial mitochondria positive to the succlillc dehydrogenase (SDH) histochemical reaction with copper ferrocyanide have been investigated by X-ray microanalysis and computer-assisted morphometry in young, adult, old and 11-month-old vitamin E deficient rats. Our data document significant alterations of intracellular ionic content, synaptic contact areas and synaptic and perykarial mitochondria in aging. Vitamin E deficiency caused similar alterations in adult animals. Taking into account the known role of α-tocopherol in protecting the cellular membrane structure, we support that the common process underlying the changes found in aging and vitamin E deficiency is an excessive deterioration of the neuronal membrane

Neonatal exposure to permethrin pesticide causes lifelong fear and spatial learning deficits and alters hippocampal morphology of synapses.

During the neurodevelopmental period, the brain is potentially more susceptible to environmental exposure to pollutants. The aim was to determine if neonatal exposure to permethrin (PERM) pesticide, at a low dosage that does not produce signs of obvious abnormalities, could represent a risk for the onset of diseases later in the life. METHODS: Neonatal rats (from postnatal day 6 to 21) were treated daily by gavage with a dose of PERM (34 mg/kg) close to the no-observed-adverse-effect level (NOAEL), and hippocampal morphology and function of synapses were investigated in adulthood. Fear conditioning, passive avoidance and Morris water maze tests were used to assess cognitive skills in rats, whereas electron microscopy analysis was used to investigate hippocampal morphological changes that occurred in adults. RESULTS: In both contextual and tone fear conditioning tests, PERM-treated rats showed a decreased freezing. In the passive avoidance test, the consolidation of the inhibitory avoidance was time-limited: the memory was not impaired for the first 24 h, whereas the information was not retained 72 h following training. The same trend was observed in the spatial reference memories acquired by Morris water maze. In PERM-treated rats, electron microscopy analysis revealed a decrease of synapses and surface densities in the stratum moleculare of CA1, in the inner molecular layer of the dentate gyrus and in the mossy fibers of the hippocampal areas together with a decrease of perforated synapses in the stratum moleculare of CA1 and in the inner molecular layer of the dentate gyrus. CONCLUSIONS: Early-life permethrin exposure imparts long-lasting consequences on the hippocampus such as impairment of long-term memory storage and synaptic morphology

Blood volume is improved by forced mild physical training in the motor and hippocampal cortex of old mice

The effect of mild forced physical training [1] (treadmill running 30 min a day, five days a week for 30 days at belt speed = 8 m/min, 0% incline) on the motor and hippocampal brain cortex was investigated in old (>24mo) mice by means of magnetic resonance imaging. The possible additive effect of physical training and testosterone [2] administration was also examined. Cortical thickness, quantitative transverse relaxation time (T2) maps, and regional cerebral blood volume (rCBV) were evaluated at baseline and after training. Results show that physical training alone induced significant increase of rCBV in both motor and hippocampal cortex. Cortex thickness and T2 maps were similar before and after training. Similar results were obtained in testosterone treated mice suggesting that testosterone does not add to physical training effect. This work provides first quantitative evidence that exercise initiated at old age is able to improve the hemodynamic status of the brain cortex in key regions for movement and cognition without inducing edema

Lysosomes in iron metabolism, ageing and apoptosis

The lysosomal compartment is essential for a variety of cellular functions, including the normal turnover of most long-lived proteins and all organelles. The compartment consists of numerous acidic vesicles (pH ∼4 to 5) that constantly fuse and divide. It receives a large number of hydrolases (∼50) from the trans-Golgi network, and substrates from both the cells’ outside (heterophagy) and inside (autophagy). Many macromolecules contain iron that gives rise to an iron-rich environment in lysosomes that recently have degraded such macromolecules. Iron-rich lysosomes are sensitive to oxidative stress, while ‘resting’ lysosomes, which have not recently participated in autophagic events, are not. The magnitude of oxidative stress determines the degree of lysosomal destabilization and, consequently, whether arrested growth, reparative autophagy, apoptosis, or necrosis will follow. Heterophagy is the first step in the process by which immunocompetent cells modify antigens and produce antibodies, while exocytosis of lysosomal enzymes may promote tumor invasion, angiogenesis, and metastasis. Apart from being an essential turnover process, autophagy is also a mechanism by which cells will be able to sustain temporary starvation and rid themselves of intracellular organisms that have invaded, although some pathogens have evolved mechanisms to prevent their destruction. Mutated lysosomal enzymes are the underlying cause of a number of lysosomal storage diseases involving the accumulation of materials that would be the substrate for the corresponding hydrolases, were they not defective. The normal, low-level diffusion of hydrogen peroxide into iron-rich lysosomes causes the slow formation of lipofuscin in long-lived postmitotic cells, where it occupies a substantial part of the lysosomal compartment at the end of the life span. This seems to result in the diversion of newly produced lysosomal enzymes away from autophagosomes, leading to the accumulation of malfunctioning mitochondria and proteins with consequent cellular dysfunction. If autophagy were a perfect turnover process, postmitotic ageing and several age-related neurodegenerative diseases would, perhaps, not take place

Testosterone administration increases synaptic density in the gyrus dentatus of old mice independently of physical exercise

Testosterone and physical exercise administration have been shown to affect hippocampal morphology in adult rodents. In aged animals, similar data are only available after physical exercise. In this work we used ultrastructural quantitative morphometry to investigate the effect of testosterone administration on the hippocampal synapses of old mice, either alone or in combination with aerobic physical exercise. The inner molecular layer of the hippocampal dentate gyrus (IMLDG) and the molecular stratum of Ammon's horn 1 neurons (SMCA1) were investigated in 27-month-old male Balb/c mice randomly allocated to one of four experimental conditions (five mice each): sedentary control (C), testosterone administration (10\u202fmg/kg once a week, TA), treadmill training (30\u202fmin a day, five days a week for 4\u202fweeks at belt speed 8\u202fm/min, 0% incline, TT) and testosterone administration plus treadmill training (TTTA). At the end of a four-week period, hippocampi were excised, fixed, and processed by ethanol phosphotungstic acid procedure to contrast synapses. The following variables were measured in electron micrographs: number of synapses/\u3bcm3 of tissue (Nv), total area of contact zones/\u3bcm3 of tissue (Sv), average area of the synaptic contact zone (S), and percentage of perforated synapses (%PS). ANOVA showed a statistically significant main effect of experimental condition for Nv and Sv in IMLDG, and for Sv in SMCA1 (p\u202f 64\u202f0.003). The S and %PS were similar within group in ANOVA. Post-hoc analysis revealed a significant (p\u202f<\u202f0.05) increase of Sv vs. C in SMCA1 and IMLDG after TT and TA, respectively. In IMLDG, Nv was significantly increased vs. C and TT after both TA and TTTA. Overall, results showed that testosterone increases synaptic density in IMLDG of old mice independently of physical exercise or changes in synaptic size. Instead, synaptic density in SMCA1 was only sensitive to physical exercise. These findings show that exogenous testosterone administration exerts a positive effect of on synapses in selected areas of the old mouse hippocampus