Effects of long-term Hydergine administration on lipofuscin accumulation in senescent rat brain

The effects of ageing and of 6 months of Hydergine treatment on lipofuscin deposition within the cytoplasma of pyramidal neurons of rat prefrontal cortex, hippocampus (fields CA1 and CA3) and of Purkinje neurons were assessed microfluorimetrically. No lipofuscin autofluorescence was detected in the nerve cell populations of 3-month-old rats, but lipopigment had accumulated in nerve cell bodies of 16-month-old animals and increased significantly thereafter in rats of 22 months of age. In 22-month-old rats, Hydergine administration (0.6 and 1 mg/kg p.o.) started at 16 months caused a significant dose-related decrease in lipofuscin accumulation within the cytoplasm of the various kinds of nerve cells examined.     

Lipid pigment (lipofuscin) accumulation in rat tongue muscle with aging

Lipid pigment (lipofuscin) was examined in perioral and tongue muscles of aging rats. While in perioral striated muscle the pigmented granules could not be found, a considerable accumulation with aging could be noted in the tongue muscle. Unlike the human tongue muscle, in which the pigmented granules were stored in clusters of different sizes at the nuclear poles of the muscle fibers, in rats, they were scattered randomly through the cytoplasm. The results of this study suggest that lipofuscin can be used as a marker for aging of the tongue muscle in the rat.     

Senolytic treatment reverses obesity-mediated senescent cell accumulation in the ovary

GeroScience - Senescent cells are in a cell cycle arrest state and accumulate with aging and obesity, contributing to a chronic inflammatory state. Treatment with senolytic drugs dasatinib and...     

Effect of dehydroepiandrosterone (DHEA) on monoamine oxidase activity,lipid peroxidation and lipofuscin accumulation in aging rat brain regions

Dehydroepiandrosterone (DHEA), one of the major steroid hormones, and its ester have recently received attention with regard to aging and age-related diseases like Alzheimer and others. DHEA is synthesized de novo in the brain and its substantial fall with age has been shown to be associated with neuronal vulnerability to neurotoxicity processes. Thus, DHEA is considered to be a neuroactive pharmacological substance with potential antiaging properties. A prominent feature that accompanies aging is an increase in monoamine oxidase (MAO). Increased MAO activity with correlated increase in lipid peroxidation in the aging rat brain supports the hypothesis that catecholamine oxidation is an important source of oxidative stress. The progressive accumulation of lipofuscin in neuronal cells is one of the most characteristic age related changes, an increase in body weight was also observed at 24 months. The objective of this study was to observe the changes in monoamine oxidase activity, lipid peroxidation levels and lipofuscin accumulation occurring in aging rat brain regions, and to see whether these changes are restored to normal levels after exogenous administration of DHEA (30 mg/kg/day for 1 month). The results obtained in the present work revealed that normal aging was associated with significant increases in the activity of monoamine oxidase, lipid peroxidation levels and lipofuscin accumulation in brain regions of 4, 14 and 24 months age group male rats. The present study showed that DHEA treatment significantly decreased monoamine oxidase activity, lipid peroxidation and lipofuscin accumulation in brain regions of aging rats, the increased body weight at 24 months also decreased more than the age matched controls. It can therefore be suggested that DHEA's beneficial effects seemed to arise from its antioxidant, antiobesity, antilipofuscin, antilipidperoxidative and thereby anti-aging actions. The results of this study will be useful for pharmacological modification of the aging process and development of new drugs for age related disorders.     

Cardiac calcium pump inactivation and nitrosylation in senescent rat myocardium are not attenuated by long-term treadmill training

The senescent heart has decreased systolic and diastolic functions, both of which could be related to alterations in cardiac sarcoplasmic reticulum (SR) calcium (Ca²⁺) handling. The purpose of this study was to determine if SR protein content and rates of Ca²⁺ release and uptake and ATPase activity are lower in the senescent (34–36 mo) Fisher 344 × Brown-Norway F1 hybrid rat heart and if a long-term exercise training program could maintain SR function. Late middle aged (29 mo) male rats underwent 5–7 mo of treadmill training. Aging resulted in a decrease in SERCA activity and modest decrease in the rate of Ca²⁺ uptake but no change in Ca²⁺ release rate. SERCA2a content was not decreased with age but nitrotyrosine accumulation was increased and Ser16 phosphorylated phospholamban (PLN) was decreased. Ryanodine receptor content was not decreased with age but dihydropyridine receptor content was decreased in the senescent heart. Treadmill training had no significant effect on any of the SR properties or protein contents in the senescent rat heart. These results suggest that decreases in Ca²⁺ uptake and SERCA activity in the senescent F344BN rat heart are due to increased SERCA2a damage from nitrotyrosine accumulation and inhibition by PLN and that exercise training initiated at late middle age is unable to prevent these age-related changes in cardiac SR function.     

Glutamate-induced over-expression of GAD is down-regulated by acetyl-L-carnitine in rat islet cells

Glutamic acid decarboxylase (GAD65 and GAD67) in pancreatic beta cells is the target of autoantibodies and autoreactive T cells in insulin-dependent diabetes mellitus (IDDM). Regulating expression of GAD perhaps is a practical approach to treat IDDM. In this study, we established an in vitro system, in which GAD was expressed and glutamate treatment produced over-expression of GAD67 and GAD65 in rat islet cells. By using the system we were able to demonstrate basal level of expression of GAD and effects of glutamate and the antioxidant, acetyl-L-carnitine (ALC) on expression of GAD. We found that GAD67 expressed in 10% of islets cells, whereas GAD65 was localized in only 4% of the cells. Glutamate treatment resulted in significant over-expression of GAD67, but not GAD65. Such glutamate-induced overexpression of GAD67 was attenuated by pretreatment with ALC (100 microM). These findings suggest that the over-expression of GAD67 induced by glutamate in islet cells of rat may act as a suitable cellular model to study GAD autoreactivity during the development of IDDM. Meanwhile, it indicates that ALC, an ester of the trimethylated amino acid, can block glutamate-induced over-expression of GAD67, a key beta-cell autoantigen, suggesting a therapeutic potential of ALC in IDDM.     

Transmural differences of lipofuscin pigment accumulation in the left ventricule of rat heart during growth and aging

In view of the higher metabolic rate in subendocardial heart tissue, the rate of age-related lipofuscin pigment accumulation was explored in different regions of the left ventricle heart wall of Sprague-Dawley rats. Hearts were removed from 2-, 6-, 12- and 24-month-old rats, and lipofuscin pigment accumulation was assessed in the subepicardial and subendocardial layers, either by measuring extractable fluorescent material, or by direct visualization with fluorescence microscopy. Findings showed that the amount of extractable fluorescent material and the number, size and brightness of the fluorescent lipofuscin granules increased with age in all the myocardial tissue layers. The rate of accumulation of extractable fluorescent material was higher in subendocardial compared to subepicardial tissue. At the microscope, fluorescent granules exhibited a different morphological appearance in the subendocardial and subepicardial tissue of the two older age-groups. These data support the hypothesis that liposoluble age-pigment deposition is linked to the rate of local oxidative metabolism.     

Early appearance and rate of lipofuscin pigment accumulation in human myocardium

Lipofuscin pigment granules appeared at 9 yr of age in the left ventricular myocardium. The pigment was found to increase progressively with age and to congregate in masses in the myocardium of old individuals. The pigment has been observed to increase at a rate of 0.0609% pigment vol./myocardial vol./year.     

Age-dependent nerve cell loss in the brain of Sprague-Dawley rats: effect of long term acetyl-L-carnitine treatment

The age dependent loss of nerve cells was investigated in 22 brain areas from young (3 month), adult (13 month) and old (25 month) Sprague-Dawley rats. As in previous studies, we observed an age-related neuronal loss primarily in the archicortex and in the hippocampus and in other subcortical structures (amigdaloid nucleus, pontine nuclei, cerebellar cortex). In sensory areas of cerebral cortex the neuronal loss was less marked. The effect of a 6 month treatment with acetyl-L-carnitine (ALCAR) on the number of nerve cells in the same brain areas was also investigated. ALCAR treatment began when the rats were aged 16 months. ALCAR treatment was able to counteract the age-dependent decrease in nerve cell number primarily in the temporal and occipital cortical areas, in the archicortex and hippocampus. The above findings suggest that long term ALCAR treatment may be effective in slowing down the age-related nerve cell loss in some rat brain areas.     

Age-related changes of the mossy fibre system in rat hippocampus: effect of long term acetyl-L-carnitine treatment

Age-related changes of the hippocampal mossy fibre system were studied in rats of different ages (4, 12, and 24 months) using the Timm's histochemical technique for the detection of tissue stores of zinc and heavy transitional metals. Quantitative image analysis and microdensitometry techniques were applied for the evaluation of the changes themselves. The area occupied by mossy fibres and the intensity of Timm's staining in field CA3 of hippocampus were greater in adult rats than in young and old animals. These findings are consistent with previous behavioural data indicating that young and old rats exhibited a reduced passive avoidance learning with respect to adult animals. The above techniques were also used in a second session of this study designed to investigate the effect of a 6-months treatment with acetyl-L-carnitine (ALC) on the hippocampal mossy fibre system. ALC was found to increase significantly the area occupied by mossy fibres and the intensity of Timm's staining in the hippocampus of old rats. These findings are in agreement with and support from an anatomical point of view, the data indicating that long-term treatment with ALC improves passive avoidance performance.     

Decreased protein synthesis by microsomes isolated from senescent rat liver

Protein synthesis as indicated by the incorporation of ¹⁴C-leucine or a mixture of ¹⁴C-labelled amino acids into cold TCA-insoluble material by liver microsomal fractions of mature adult (12 months) and old (20–31 months) female rats was investigated. A decreased amino acid incorporation into protein occurred in the cell-free system from senescent rat liver. Also, cross-mixing experiments indicate that the cytosol(105,000g supernatant) from senescent animals is inhibitory to protein synthesis with microsomes from 12 month old rats. The combination of cytosol from 12 month old animals and microsomes from senescent animals functioned most often like the senescent system.     

Potential role of retinal pigment epithelial lipofuscin accumulation in age-related macular degeneration

Age-related macular degeneration (AMD) is a leading cause of severe visual impairment in developed countries. The vision loss associated with AMD is the result of degenerative changes in the central region of the retina called the macula. Maintenance of normal structure and function of the macular retina, and of the remainder of the retina as well, is critically dependent on the supporting role of the adjacent retinal pigment epithelium (RPE). Impairment of normal RPE functions is known to result in retinal degeneration and loss of visual function. Thus, it has been hypothesized that the retinal degeneration that characterizes AMD is secondary to age-related deterioration in RPE support functions. Like many other postmitotic cell types, the RPE accumulates autofluorescent lysosomal storage bodies (lipofuscin) during senescence. In human eyes, lipofuscin comes to occupy a substantial fraction of the RPE cytoplasmic volume in the elderly. Does this lipofuscin accumulation contribute to the development of AMD? This question is a specific case of the broader question of whether lipofuscin accumulation in general is detrimental to cells. Unfortunately, definitive data do not exist to allow these questions to be answered. Although a correlation between RPE lipofuscin content and AMD has been reported, a cause-and-effect relationship between RPE lipofuscin accumulation and the development of this disease has not been established. It has been reported that a mutation in a gene encoding a photoreceptor-specific protein results in massive RPE lipofuscin accumulation and early-onset macular degeneration. However, again the accelerated RPE lipofuscin accumulation has not been shown to be the cause of the accompanying macular degeneration. The lack of a definitive link between RPE lipofuscin accumulation and AMD illustrates one of the biggest challenges remaining in lipofuscin research-determining whether lipofuscin accumulation per se has an impact on cell function.     

Reduced left ventricular hypertrophy following long-term water deprivation in the young spontaneously hypertensive rat

Biochemical and physical parameters of cardiac hypertrophy accompanying hypertension were studied in water deprived versus non-deprived immature spontaneously hypertensive rats (SHR) and their normotensive progenitor strain, Wistar Kyoto (WKY). A 23.5 hour/day water deprivation schedule was maintained from 5 to 13 weeks of age in 23 SHR and 8 WKY rats to compare the non-deprived animals (16 SHR and 8 WKY controls). Water deprived SHR had lower left ventricular weight, lower total protein and hydroxyproline and the same total DNA as the non-deprived SHR. DNA concentration was higher in the deprived SHR than in the non-deprived SHR. No differences were found among the four groups in right ventricular weight or DNA concentration. Left to right ventricular weight ratio was significantly lower and left to right ventricular DNA concentration ratio significantly higher in the deprived SHR relative to non-deprived SHR. These data indicate that the water deprived SHR, which was less hypertensive than the non-deprived SHR, had less hypertrophy of their left ventricles. While water deprivation lowered mean arterial pressure in the WKY, also, there was no effect on left ventricular weight or biochemical indices of left ventricular cell size and cell number.     

Cell nuclear accumulation of estrogen receptors in rat brain and pituitary gland after treatment with a dopamine-beta-hydroxylase inhibitor

In a recent experiment, it was found that the dopamine-beta-hydroxylase inhibitor, U-14,624, decreases the concentration of cytosol progestin receptors in guinea pig hypothalamus and causes an increase in the concentration of nuclear progestin receptors. In this series of experiments, the possibility that similar effects would be seen in the rat estrogen receptor system in mediobasal hypothalamus and pituitary was tested. U-14,624 caused a time-dependent decrease in the concentration of cytosol estrogen receptors and increase in the concentration of nuclear estrogen receptors in both mediobasal hypothalamus and anterior pituitary gland in ovariectomized rats, both in the absence and presence of low levels of estradiol, as well as in ovariectomized-adrenalectomized rats. The nuclear estrogen receptors that accumulate after U-14,624 injection do not require incubation at 25 degrees C to be assayed, suggesting that they are not occupied by an estradiol-like ligand. The nuclear estrogen receptors that accumulate after U-14,624 treatment are high affinity, with an apparent dissociation constant of approximately 0.1 nM. U-14,624 does not compete with (3H)estradiol, in vitro, suggesting that it does not directly interact with estrogen receptors. These results suggest that under some conditions, inhibition of dopamine-beta-hydroxylase causes a modification in unoccupied estrogen receptors so that they develop a higher affinity for cell nuclear components.     

Thyroid hormone regulates oligodendrocyte accumulation in developing rat brain white matter tracts

Thyroid hormone (TH) is necessary for normal axonal myelination. Myelin basic protein (MBP) is a structural protein essential for myelin function. In this study, we demonstrate that perinatal hypothyroidism regulates MBP mRNA levels via indirect mechanisms. We observed decreased MBP mRNA accumulation in the hypothyroid rat brain at postnatal (PN) d 10 and 50. Acute TH replacement did not rescue hypothyroid MBP mRNA levels at PN5, 10, or 50. TH is necessary for normal intrahemispheric commissure development including the anterior commissure (AC) and the corpus callosum (CC). We determined that perinatal hypothyroidism decreases AC area and cellularity in the developing rat brain by PN10 and 50. In the developing CC, hypothyroidism initially increases area and cellularity by PN5, but then ultimately decreases area and cellularity by PN50. MBP-expressing oligodendrocytes are a recognized target of TH and are responsible for myelination within intrahemispheric commissures. We found that hypothyroidism reduces the number of mature oligodendrocytes within both the AC and CC. This reduction is noted at PN5, 10, and 50 in the AC and by PN10 and 50 in the CC. Together, these data suggest that TH regulates MBP mRNA levels through indirect mechanisms. These data demonstrate the complex mechanisms whereby TH regulates myelination in the developing brain.