Neurobiology of Aging

Published by Elsevier
Online ISSN: 0197-4580
Publications
Article
The goal of this study was to examine the relationship between subcortical vascular disease and brain atrophy in patients with Alzheimer's disease (AD) and mixed dementia (i.e., AD and subcortical vascular disease together). MRI was performed on 77 cognitively normal (CN) subjects, 50 AD and 13 mixed dementia patients. Subcortical vascular disease was determined by white matter hyperintensities (WMH) volume and presence of subcortical lacunes. Brain atrophy was measured using total brain cortical gray matter (CGM), entorhinal cortex (ERC) and hippocampal volumes. CGM volume, but not ERC or hippocampal volume was inversely related to WMH volume in patients and controls. In contrast, no relationship was detected between CGM, ERC, or hippocampal volumes and subcortical lacunes. Furthermore, no interaction was found between WMH and diagnosis on cortical atrophy, implying that WMH affect cortical atrophy indifferently of group. These results suggest that subcortical vascular disease, manifested as WMH, may affect cortical atrophy more than ERC and hippocampal atrophy. Further, AD pathology and subcortical vascular disease may independently affect cortical atrophy.
 
Article
Loss of cholinergic neurons in the Nucleus Basalis of Meynert in Alzheimer's disease (AD) patients was one of the first discoveries of neuron loss in AD. Despite an intense focus on the cholinergic system in AD, the reason for this cholinergic neuron loss is yet unknown. In the present study we examined Abeta-induced pathology and neuron loss in the cholinergic system of the bigenic APP/PS1KI mouse model. Expression of the APP transgene was found in ChAT-positive neurons of motor nuclei accompanied by robust intracellular Abeta accumulation, whereas no APP expressing neurons and thus no intracellular Abeta accumulation were found in neither the forebrain or pons complexes, nor in the caudate putamen. This expression pattern was used as a model system to study the effect of intra- and extracellular Abeta accumulation on neuron loss in the cholinergic system. Stereological quantification revealed a loss of ChAT-positive neurons in APP/PS1KI mice only in the motor nuclei Mo5 and 7N accumulating intracellular Abeta. This study supports the hypothesis of intracellular Abeta accumulation as an early pathological alteration contributing to cell death in AD.
 
Article
Inflammatory processes are considered to play an important role in the progression of neurodegenerative changes in Alzheimer's disease (AD). In the present study, we performed a systematic expression analysis of various inflammatory and oxidative stress markers in pre-symptomatic and diseased APP/PS1KI mice. This mouse model has been previously shown to harbor severe pathological alterations, including behavioral deficits, axonal degeneration and hippocampal neuron loss starting at the age of 6 months. While the expression levels of most markers remained unchanged in 2-month-old APP/PS1KI mice, at the age of 6 months different astro- and microglia markers including GFAP, Cathepsin D, members of the Toll-like receptor (Tlr) family, TGFbeta-1 and osteopontin were up-regulated. In addition, oxidative stress markers, including the metallothioneins, were also significantly elevated at that time point. As expected, both brain and spinal cord were affected, the latter showing early activation of GFAP-positive astrocytes and Iba1-positive microglia in white matter fiber tracts, which might contribute to the previously reported axonal defects in this mouse model. These data add further evidence to the assumption that inflammatory processes are tightly associated with axonal degeneration and neuron loss, as is evident in the APP/PS1KI mouse model.
 
Article
Raloxifene, used in the clinic, is reported to protect brain dopaminergic neurons in mice. Raloxifene was shown to mediate an effect through the G protein-coupled estrogen receptor 1 (GPER1). We investigated if raloxifene neuroprotective effect in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-treated male mice is mediated through GPER1 by using its antagonist G15. Striatal concentrations of dopamine, 3,4-dihydroxyphenylacetic acid, homovanillic acid to dopamine ratio as well as dopamine transporter and vesicular monoamine transporter 2 showed that raloxifene neuroprotection of dopaminergic neurons was blocked by G15. Protection by raloxifene was accompanied by activation of striatal Akt signaling (but not ERK1/2 signaling) and increased Bcl-2 and brain-derived neurotrophic factor levels; these effects were abolished by coadministration with G15. The effect of raloxifene was not mediated through increased levels of 17β-estradiol. MPTP mice had decreased plasma testosterone, dihydrotestosterone, and 3β-diol levels; this was prevented in raloxifene-treated MPTP mice. Our results suggest that raloxifene acted through GPER1 to mediate Akt activation, increase Bcl-2 and brain-derived neurotrophic factor levels, and protection of dopaminergic neurons and plasma androgens.
 
Article
Aquaporin 4 (AQP4) is a predominant water channel protein in mammalian brains, which is localized in the astrocyte plasma membrane. AQP4 has gained much attraction due to its involvement in the physiopathology of cerebral disorders including stroke, tumor, infection, hydrocephalus, epilepsy, and traumatic brain injury. But there is almost no evidence whether abnormal AQP4 levels are associated with degenerative diseases, such as Parkinson's disease (PD). In our studies, we established PD animal models by administration of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine to test the hypothesis that abnormal AQP4 expression is involved in the pathophysiology of this disease. We show that mutant mice lacking AQP4 were significantly more prone to MPTP-induced neurotoxicity than their wild-type littermates. Furthermore, after administration of MPTP, astroglial proliferation and GDNF protein synthesis were inhibited by AQP4 deficiency. This study demonstrates that AQP4 is important in the MPTP neurotoxic process and indicates that the therapeutic strategy targeted to astrocytic modulation with AQP4 may offer a great potential for the development of new treatment for PD.
 
Article
Although the support for the use of antioxidants, such as coenzyme Q10 (CoQ10), to treat Parkinson's disease (PD) comes from the extensive scientific evidence, the results of conducted thus far clinical trials are inconclusive. It is assumed that the efficacy of CoQ10 is hindered by insolubility, poor bioavailability, and lack of brain penetration. We have developed a nanomicellar formulation of CoQ10 (Ubisol-Q10) with improved properties, including the brain penetration, and tested its effectiveness in mouse MPTP (1-methyl-4-phenyl-1, 2, 3, 6-tetrahydropyridine) model with the objectives to assess its potential use as an adjuvant therapy for PD. We used a subchronic MPTP model (5-daily MPTP injections), characterized by 50% loss of dopamine neurons over a period of 28 days. Ubisol-Q10 was delivered in drinking water. Prophylactic application of Ubisol-Q10, started 2 weeks before the MPTP exposure, significantly offset the neurotoxicity (approximately 50% neurons died in MPTP group vs. 17% in MPTP+ Ubisol-Q10 group by day 28). Therapeutic application of Ubisol-Q10, given after the last MPTP injection, was equally effective. At the time of intervention on day 5 nearly 25% of dopamine neurons were already lost, but the treatment saved the remaining 25% of cells, which otherwise would have died by day 28. This was confirmed by cell counts, analyses of striatal dopamine levels, and improved animals' motor skill on a beam walk test. Similar levels of neuroprotection were obtained with 3 different Ubisol-Q10 concentrations tested, that is, 30 mg, 6 mg, or 3 mg CoQ10/kg body weight/day, showing clearly that high doses of CoQ10 were not required to deliver these effects. Furthermore, the Ubisol-Q10 treatments brought about a robust astrocytic activation in the brain parenchyma, indicating that astroglia played an active role in this neuroprotection. Thus, we have shown for the first time that Ubisol-Q10 was capable of halting the neurodegeneration already in progress; however, to maintain it a continuous supplementation of Ubisol-Q10 was required. The pathologic processes initiated by MPTP resumed if supplementation was withdrawn. We suggest that in addition to brain delivery of powerful antioxidants, Ubisol-Q10 might have also supported subcellular oxidoreductase systems allowing them to maintain a favorable cellular redox status, especially in astroglia, facilitating their role in neuroprotection. Based on this data further clinical testing of this formulation in PD patients might be justifiable.
 
Article
Based on a literature implicating altered calcium homeostasis in brain aging and Alzheimer's Disease (AD) and evidence of decreased vitamin D action in AD subjects, the possibility was tested that calcitriol (1,25(OH)2 vitamin D3), the active form of vitamin D3, might reduce markers of brain aging in rats. Animals were treated 5x weekly for prolonged periods (6-12 months) with either calcitriol in doses sufficient to elevate serum calcium and phosphate (20 ng/rat), calcitonin (1.5 IU/rat) or vehicle, in three separate long-term experiments on aging rats. New stereological methods (physical disector) of cell counting were used to evaluate neuronal density, a reliable biomarker of hippocampal aging in rats. In two experiments utilizing Brown-Norway x F344 hybrid rats (BN x F344), 8 months and 12 months of chronic treatment with calcitriol resulted in a higher density of CA1 neurons in the middle regions of the hippocampus, compared to vehicle or calcitonin treatment. However, one study with aging F344 rats was terminated early because of extensive strain-specific pathology and no effect of calcitriol on neuronal density was observed. These studies suggest that, under some conditions, hormonal treatments that regulate calcium homeostasis can modulate markers of brain aging.
 
Article
It is well established that muscarinic cholinergic receptors are linked to phosphoinositide hydrolysis in brain. Previous studies of muscarinic responses used Li+ to increase inositol phosphate accumulation and suggested little or no change during aging. Li+ disrupts certain aspects of the inositol phosphate metabolism and inhibits the formation of inositol 1,3,4,5-tetrakisphosphate [Ins(1,3,4,5)P4]. Ins(1,3,4,5)P4 appears to have second messenger functions. To investigate the effects of aging on agonist stimulated Ins(1,3,4,5)P4 formation, young (6-8 months) and old (28-30 months) Fischer 344 rat cerebral cortical or hippocampal slices were challenged with various agonists known to stimulate phosphoinositide hydrolysis in brain using a recently developed assay that does not use Li+. Carbachol and quisqualate stimulated [3H]inositol trisphosphate ([3H]InsP3) and [3H]Ins(1,3,4,5)P4 formation in young and old rat cerebral cortical slices. Norepinephrine, 5-hydroxytryptamine, and vasopressin failed to stimulate [3H]Ins(1,3,4,5)P4 or [3H]InsP3 formation in either young or old rat cerebral cortical slices. In old rat cerebral cortical slices, the carbachol-stimulated [3H]Ins(1,3,4,5)P4 formation was reduced by 44%. Angiotensin II stimulated [3H]InsP3 was increased (219%) in old rats. There was no influence of aging either on the basal level or on the maximal response to carbachol or quisqualate in hippocampal slices. These studies suggest region-specific changes in phosphoinositide hydrolysis during aging.
 
Article
Intracellular Ca2+ release channels are key players in the regulation of Ca2+ homeostasis. In the present study, we investigated the age-related changes of inositol 1,4,5-trisphosphate (IP3) receptor/Ca2+ release channel and ryanodine receptor/Ca2+ release channel in microsomes derived from either cerebellum or cerebrum cortex from male Wistar rats. A significant reduction (about 50%) in density of IP3 receptor/Ca2+ release channels was observed in cerebrum cortex, only, in 8- and 28-month old rats, whereas density and Kd of ryanodine binding sites were unaffected in both cerebellum and cerebrum microsomes. These findings, along with impairment of Ca(2+)-dependent protein kinase C phosphorylation of endogeneous substrates, point to coordinate, quantitative alterations of both targets of phosphoinositide metabolism, i.e., PKC and IP3 receptor, in the cerebrum cortex at least. The relevance of the present findings is discussed in relation to reported changes of neuronal Ca2+ homeostasis during aging.
 
Article
Numerous process associated with intracellular calcium homeostasis have previously been found to vary with age. To determine whether the binding sites for the calcium-mobilizing second messenger, inositol 1,4,5-trisphosphate (InsP3), also displays such variation, [3H]InsP3 binding was investigated in cerebellar or cerebral cortical membranes prepared from rats at different ages from birth up to 24 months of age. In the cerebellum, the InsP3 receptor density was very low during the first week after birth, increased markedly between days 8 and 28 and then reached an apparent plateau between 28 to 56 days of age. The InsP3 receptor binding affinity was comparable at different developmental stages. No age-related differences were found in InsP3 receptor density or affinity in the cerebral cortex of 3-, 6-, 9-, 12-, and 24-month-old rats. In the cerebellum, InsP3 receptor density but not affinity was significantly reduced in 24-month-old compared only to 3-month-old animals. Our data suggest that the changes in InsP3 receptor binding during early development might reflect the growth and maturation of neurons containing these receptors (i.e., Purkinje cells). Furthermore, the age-dependent reduction in InsP3 receptor density, together with the recent report of senescent changes in protein kinase C activity, indicate that disruption of phosphoinositide second messenger system may be of importance to the impairment of neuronal responsiveness and behavioral deficits observed with aging.
 
Article
An increasing number of signal transduction disturbances have been reported in Alzheimer's disease. These changes are not restricted to histopathologically changed brain areas but are seen also in peripheral tissues. One of the most severe disturbances is a loss of calcium-mobilizing intracellular inositol(1,4,5)-trisphosphate receptors in Alzheimer cerebellar and cortical tissues. In the present study, the binding of [3H]inositol(1,4,5)trisphosphate ([3H]Ins(1,4,5)P3) to the calcium-mobilizing inositol(1,4,5)trisphosphate receptors in platelet membranes from eight Alzheimer's disease patients and eight control subjects were investigated to determine its possible role as a biological marker in Alzheimer's disease. It was found that there were no significant difference in [3H]Ins(1,4,5)P3 binding with respect to the number of sites measured at different protein concentrations or to the sensitivity of the binding to inhibition by nonradioactive Ins(1,4,5)P3 between Alzheimer disease platelets and controls. It is concluded that inositol(1,4,5)trisphosphate receptor levels are preserved in platelets from patients with Alzheimer's disease.
 
Article
Day-night rhythms in feeding behavior and response to the putative sigma opiate agonist, N-allylnormetazocine (+/- SKF-10,047, 0.10-10 mg/kg), were measured in young (1-2 months), mature (8-12 months) and old (24-30 months) male CF-1 mice. The mice consumed more food at night than in the day-time, though this nocturnal peak was markedly reduced in the mature and old animals. The young mice also displayed a significant nocturnal enhancement in SKF-10,047 (0.10-1.0 mg/kg) stimulated feeding, that could, in part, be suppressed by the opiate antagonist naloxone (1.0 mg/kg). The day-night rhythm in ingestive responses to SKF-10,047 (0.10-1.0 mg/kg) was reduced in the mature animals and absent in the old animals. The old mice failed to show any significant increase in ingestive response following opiate administration. A higher dose of SKF-10,047 (10 mg/kg) had no significant ingestive effects in any of the age groups of mice; the excitatory, psychotomimetic-related effects, being also reduced in the old animals.
 
Responses in the CS period after presentation of a tone and blink responses to the air puff when the stimuli are presented in an explicitly unpaired sequence in two groups of retired breeder rabbits. One group received 3.0 mg/kg MEM 1003, and the other group received the vehicle. Unconditioned response amplitudes are in millimeters.  
Comparison of acquisition in the 750 ms delay procedure and the 500, 600 and 750 ms trace procedure in vehicle-treated older rabbits. The 500 ms trace procedure is acquired relatively rapidly as is the 750 ms delay procedure. During the second week of training (Sessions 6–10) there is some acquisition in the 600 ms trace procedure, but little in the 750 ms trace procedure.  
(A) Acquisition over 15 daily training sessions as assessed by percentage of conditioned responses (CRs) in 48 rabbits treated with 4 doses of MEM 1003 and vehicle. There were 8 rabbits per group with the exception of the vehicle group that had 16 rabbits. Rabbits receiving a dose of 2.0 mg/kg MEM 1003 produced significantly more CRs than vehicle-treated rabbits, and rabbits treated 2.0 and 3.0 mg/kg MEM 1003 produced significantly more CRs than rabbits treated with 10.0 mg/kg MEM 1003. Error bars are standard error of the mean. (B) Trials to learning criterion of 8 conditioned responses in 9 consecutive trials in 48 retired breeder rabbits tested in the 750 ms delay procedure with vehicle and four doses of MEM 1003. Rabbits receiving a dose of 2.0 mg/kg MEM 1003 produced significantly more CRs than vehicle-treated rabbits, and rabbits treated 2.0 and 3.0 mg/kg MEM 1003 produced significantly more CRs than rabbits treated with 10.0 mg/kg MEM 1003. Error bars are standard error of the mean.  
(A) Acquisition over 15 daily training sessions as assessed by percentage of conditioned responses (CRs) in 32 rabbits treated with four doses of MEM 1003 and vehicle. There were eight rabbits per group. Rabbits receiving a dose of 2.0 mg/kg MEM 1003 produced significantly more CRs than vehicle-treated rabbits. Error bars are standard error of the mean. (B) Trials to learning criterion of 8 conditioned responses in 9 consecutive trials in 32 retired breeder rabbits tested in the 600 ms trace procedure with vehicle and three doses of MEM 1003. There was a trend for rabbits receiving a dose of 2.0 mg/kg MEM 1003 to produce more CRs than vehicle-treated rabbits (p = 0.065). Error bars are standard error of the mean.  
Article
Eyeblink conditioning is a relatively simple form of associative learning that shows neurobiological and behavioral parallels across several species, including humans. Aged subjects acquire eyeblink conditioning more slowly than young ones. In addition, eyeblink conditioning effectively discriminates patients with Alzheimer's disease from healthy older adults. The present study evaluated the effect of a novel L-type Ca2+ channel antagonist, MEM 1003, on delay and trace eyeblink conditioning in older (mean 33.4 months old) female New Zealand white rabbits. In the delay conditioning paradigm, an 850 ms tone conditioning stimulus (CS) was followed 750 ms after its onset by a 100 ms corneal air puff. Several trace conditioning paradigms were evaluated, with a silent period of 300, 400 or 500 ms between the end of the tone CS and the delivery of the air puff. Learning was more difficult in the longer trace paradigms than in the delay paradigm. MEM 1003, at a dose of 2.0 mg/kg, s.c., given daily 30 min prior to training on each of the 15 training days, enhanced learning compared to vehicle injections in both delay and trace paradigms. However, higher or lower doses were ineffective. These results support previous work demonstrating that modulation of Ca2+ channel activity can reduce age-related cognitive impairments.
 
Article
This study aimed to evaluate genetic variability in the FUS and TDP-43 genes, known to be mainly associated with amyotrophic lateral sclerosis (ALS), in patients with the diagnoses of frontotemporal lobar degeneration (FTLD) and corticobasal syndrome (CBS). We screened the DNA of 228 patients for all the exons and flanking introns of FUS and TDP-43 genes. We identified 2 novel heterozygous missense mutations in FUS: P106L (g.22508384C>T) in a patient with behavioral variant frontotemporal dementia (bvFTD) and Q179H in several members of a family with behavioral variant FTD. We also identified the N267S mutation in TDP-43 in a CBS patient, previously only reported in 1 ALS family and 1 FTD patient. Additionally, we identified 2 previously reported heterozygous insertion and deletion mutations in Exon 5 of FUS; Gly174-Gly175 del GG (g. 4180-4185 delGAGGTG) in an FTD patient and Gly175-Gly176 ins GG (g. 4185-4186 insGAGGTG) in a patient with diagnosis of CBS. Not least, we have found a series of variants in FUS also in neurologically normal controls. In summary, we report that genetic variability in FUS and TDP-43 encompasses a wide range of phenotypes (including ALS, FTD, and CBS) and that there is substantial genetic variability in FUS gene in neurologically normal controls.
 
Article
Quantitative proton magnetic resonance spectroscopy (MRS) was used to determine region-specific metabolic changes in young and aged animals subjected to a long-term hypoxic-ischemic injury. Focal ischemia, which was studied as an experimental stroke model, was induced in 3- and 24-month-old rats by unilateral common carotid artery occlusion associated with 24 h of hypoxia. Eight metabolites were quantified from extracts in three different brain regions (hippocampus, frontoparietal and occipital cortices) from both the ipsilateral and contralateral sides. Our findings showed significant differences in lactate and myo-inositol concentration values in the hippocampus of the aged rats as compared to the same area of the young adult group under normoxic conditions. After hypoxia-ischemia (HI), the most relevant changes in metabolite concentrations were found in the hippocampal region of both young and aged groups as compared to their age-matched controls. Of the three brain areas under investigation, the hippocampus proved to be particularly susceptible to the prolonged hypoxia-ischemia perturbation. The effects were more evident in the aged animals.
 
Article
To determine the patterns of cerebral glucose metabolism in frontotemporal dementia (FTD) and semantic dementia (SD). 25 patients with mild FTD and 9 patients with mild SD as well as 15 healthy age-matched control subjects underwent 18F-FDG- positron emission tomography. Patient scans were compared with control scans using SPM-99. As compared with healthy control subjects patients with FTD showed an extensive symmetrical hypometabolism of the frontal lobes (height threshold P <0.01) which spared the motor cortex. Patients with SD showed a hypometabolism in the whole left temporal lobe and in the right temporal pole. In the clinical syndromes of FTD and SD two distinct patterns of cerebral metabolism were identified. FTD was associated with frontal hypometabolism, whereas in SD cerebral glucose metabolism was exclusively reduced in the temporal lobes. Our findings are consistent with the notion that FTD and SD begin as strictly lobar neuronal degenerations and that a spread of pathological changes is not seen until more advanced stages.
 
Article
c-Ret has been shown to be crucial for neural development and survival. We have recently shown that complete impairment of tyrosine 1062 (Y1062)-phosphorylation in c-Ret causes congenital hearing loss with neurodegeneration of spiral ganglion neurons (SGNs) in homozygous c-Ret knockin mice (c-Ret-KI(Y1062F/Y1062F)-mice). However, there is no information to link c-Ret and age-related hearing loss. Here we show that partial impairment of Y1062-phosphorylation in c-Ret accelerates age-related hearing loss in heterozygous c-Ret Y1062F knockin mice (c-Ret-KI(Y1062F/+)-mice). In contrast, complete impairment of serine 697 (S697)-phosphorylation in c-Ret did not affect hearing levels in 10-month-old homozygous c-Ret S697A knockin mice (c-Ret-KI(S697A/S697A)-mice). The hearing loss involved late-onset neurodegeneration of spiral ganglion neurons in c-Ret-KI(Y1062F/+)-mice. Morphological abnormalities in inner- and outer-hair cells and the stria vascularis in c-Ret-KI(Y1062F/+)-mice were undetectable. The acceleration of age-related hearing loss in c-Ret-KI(Y1062F/+)-mice was rescued by introducing constitutively activated RET. Thus, our results suggest that c-Ret is a novel age-related hearing loss-related molecule in mice. Our results suggest that these hearing losses partially share a common pathogenesis that is monogenetically caused by a single point mutation (Y1062F) in c-Ret.
 
Article
Aging in the brain is characterized by increased susceptibility to neuronal loss and functional decline, and mitochondrial DNA (mtDNA) mutations are thought to play an important role in these processes. Due to the proximity of mtDNA to the main sites of mitochondrial free radical generation, oxidative stress is a major source of DNA mutations in mitochondria. The base excision repair (BER) pathway removes oxidative lesions from mtDNA, thereby constituting an important mechanism to avoid accumulation of mtDNA mutations. The complexity of the brain implies that exposure and defence against oxidative stress varies among brain regions and hence some regions may be particularly prone to accumulation of mtDNA damages. In the current study we investigated the efficiency of the BER pathway throughout the murine lifespan in mitochondria from cortex and hippocampus, regions that are central in mammalian cognition, and which are severely affected during aging and in neurodegenerative diseases. A regional specific regulation of mitochondrial DNA repair activities was observed with aging. In cortical mitochondria, DNA glycosylase activities peaked at middle-age followed by a significant drop at old age. However, only minor changes were observed in hippocampal mitochondria during the whole lifespan of the animals. Furthermore, DNA glycosylase activities were lower in hippocampal than in cortical mitochondria. Mitochondrial AP endonuclease activity increased in old animals in both brain regions. Our data suggest an important regional specific regulation of mitochondrial BER during aging.
 
Article
Metals such as zinc, copper and iron contribute to aggregation of amyloid-beta (Abeta) protein and deposition of amyloid plaques in Alzheimer's disease (AD). We examined whether the lipophilic metal chelator DP-109 inhibited these events in aged female hAbetaPP-transgenic Tg2576 mice. Daily gavage administration of DP-109 for 3 months markedly reduced the burden of amyloid plaques and the degree of cerebral amyloid angiopathy in brains, compared to animals receiving vehicle treatment. Moreover, DP-109 treatment appeared to facilitate the transition of Abeta from insoluble to soluble forms in the cerebrum. These results further support the hypothesis that endogenous metals are involved in the deposition of aggregated Abeta in brains of AD patients, and that metal chelators may be useful therapeutic agents in the treatment of AD.
 
Article
Adenylyl cyclase (AC) subtypes have been implicated in memory processes and synaptic plasticity. In the present study, the effects of aging and learning on Ca2+/calmodulin-stimulable AC1, Ca2+-insensitive AC2 and Ca2+/calcineurin-inhibited AC9 mRNA level were compared in the dorsal hippocampus of young-adult and aged C57BL/6 mice using in situ hybridization. Both AC1 and AC9 mRNA expression were downregulated in aged hippocampus, whereas AC2 mRNA remained unchanged, suggesting differential sensitivities to the aging process. We next examined AC mRNA expression in the hippocampus after spatial learning in the Morris water maze. Acquisition of the spatial task was associated with an increase of AC1 and AC9 mRNA levels in both young-adult and aged groups, suggesting that Ca2+-sensitive ACs are oppositely regulated by aging and learning. However, aged-trained mice had reduced AC1 and AC9, but greater AC2, mRNA levels relative to young-trained mice and age-related learning impairments were correlated with reduced AC1 expression in area CA1. We suggest that reduced levels of hippocampal AC1 mRNA may greatly contribute to age-related defects in spatial memory.
 
Article
Genome-wide association studies have identified a number of susceptibility loci in sporadic Parkinson's disease (PD). Recent larger studies and meta-analyses have greatly expanded the list of proposed association signals. We performed a case-control replication study in a Scandinavian population, analyzing samples from 1345 unrelated PD patients and 1225 control subjects collected by collaborating centers in Norway and Sweden. Single-nucleotide polymorphisms representing 18 loci previously reported at genome-wide significance levels were genotyped, as well as 4 near-significant, suggestive, loci. We replicated 11 association signals at p < 0.05 (SNCA, STK39, MAPT, GPNMB, CCDC62/HIP1R, SYT11, GAK, STX1B, MCCC1/LAMP3, ACMSD, and FGF20). The more recently nominated susceptibility loci were well represented among our positive findings, including 3 which have not previously been validated in independent studies. Conversely, some of the more well-established loci failed to replicate. While future meta-analyses should corroborate disease associations further on the level of common markers, efforts to pinpoint functional variants and understand the biological implications of each risk locus in PD are also warranted.
 
Article
Amyloid-beta protein (Abeta) has been implicated in the pathogenesis of Alzheimer's disease (AD) because of its neurotoxicity and its ability to trigger a local inflammatory response. In the present study using truncated Abeta peptides, we identified the region between residues 1 and 11 as critical for the activation of the contact system in vitro through an ionic interaction of Abeta with factor XII and/or kallikrein. Concomitant incubation of a small cationic peptide (lysine(4)) with Abeta abrogated its ability to trigger the cleavage of high molecular weight kininogen, indicating that Abeta's activity can be blocked by an inhibitory peptide. These findings could be clinically important, since there is evidence that the contact system is activated in AD brain. Thus, prevention of contact system activation, beside diminishing the recruitment of glial cells and microvascular permeability, can also decrease the activation of complement system and the release of IL6, both factors being considered to play an important role in the inflammatory reactions in AD brain.
 
Article
Excess cortisol levels are linked with brain atrophy and cognitive decline in older people. 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) potently amplifies intracellular glucocorticoid action by converting inert cortisone to active cortisol, but any causal importance in brain aging is unexplored. We tested the hypotheses that higher systemic 11β-HSD1 activity predicts brain atrophy and cognitive decline in older men. In a longitudinal study of 41 men (65-70 years old at baseline) we measured baseline systemic 11β-HSD1 activity, the urinary 5alpha- and 5beta-tetrahydrocortisol to tetrahydrocortisone ratio (ratio of tetrahydrometabolites of cortisol (THFs)/ratio of tetrahydrometabolites of cortisol (THE)), and assessed change in brain atrophy, white matter lesions and cognitive function over 6 years. Baseline THFs/THE correlated negatively with baseline hippocampal volumes (left: r = -0.37; right: r = -0.34; p < 0.05) and positively with ventricular volumes (r = 0.43, p = 0.006) and periventricular white matter lesions (rho = 0.31, p = 0.047). Importantly, baseline THFs/THE but not cortisol predicted increase in ventricular volumes (r = 0.33, p = 0.037) and decline in processing speed (r = -0.55, p = 0.0002) over 6 years. The predictive link between systemic 11β-HSD1 activity and progressive brain atrophy and cognitive decline suggests 11β-HSD1 inhibition as a plausible therapy for brain aging.
 
Article
Depressive symptoms are frequent in Alzheimer's disease (AD), but it is controversial whether depression is a risk factor for AD. This study measured for the first time cortical amyloid-β (Aβ) levels using [(11)C] Pittsburgh Compound B (PiB) positron emission tomography (PET) in a group of nondemented patients with prior depressive episodes. Twenty-eight elderly patients (mean age 61 years, range 51-75, 18 women) with onset of first depressive episode more than 6 years ago but now remitted from depression and 18 healthy subjects (mean age 61 years, range 50-76, 12 women) were included. All subjects were investigated with cognitive testing, 3T magnetic resonance imaging (MRI) and [(11)C]PiB high resolution research tomography (HRRT) positron emission tomography scan. There was no between-groups difference in [(11)C]PiB binding (p = 0.5) and no associations to number of depressive episodes, cognitive performance, or antidepressant treatment. Patients with late onset of depression had increased severity of white matter lesions (p = 0.04). In this study depressive episodes were not associated with increased levels of [(11)C]PiB. Thus, our results do not support the notion that depressive episodes previously in life are a risk factor for developing AD.
 
Article
Using PET VI and 11-CDG we replicated our earlier PET III and 18-FDG normal aging findings. Examination of young and old normal volunteers revealed the absence of any absolute regional age-related changes in glucose utilization. For the combined sample (N = 81) we did find evidence to suggest a relative hypofrontal change with increasing age. A strong relationship between age and ventricular size (CT) was also found. These findings suggest the preserved glucose metabolism of the resting aging brain in the presence of structural atrophic changes.
 
Article
The first hypothesis free genome wide association study on cognition recently revealed the thus far unknown association of a single nucleotide polymorphism (SNP) of the KIBRA gene with episodic memory in healthy young and middle aged volunteers. Here, we report the first independent replication of this finding in an in-depth characterized sample of healthy elderly subjects. The effectsizes of the respective KIBRA SNP on memory even exceed those of the initial report. In parallel to the first study, the effect is restricted to hippocampus-related episodic memory without effects on frontal lobe function. The impact of KIBRA on memory is most likely of high relevance in elderly subjects as it is in young.
 
Article
Heterotrimeric G-proteins are critical components in many receptor-coupled signal transduction systems, and altered levels and functions of G-proteins have been implicated in several neurological disorders, including Alzheimer's disease. Investigations in postmortem human brain provide a direct approach to study G-protein involvement in neurological disorders. Therefore, the effects of postmortem interval, aging, and Alzheimer's disease on G-protein levels were determined in postmortem human brain and an assay to measure activation of G-proteins was developed. Within the postmortem interval range of 5 to 21 h, the levels of G alpha i1, G alpha i2, G alpha s, and G beta were stable, whereas G alpha q and G alpha o decreased slightly, in human prefrontal cortex. In subjects aged 19 to 100 y, decreased levels of G alpha q and G alpha o were significantly correlated with increased age, but levels of the other G-protein subunits did not vary. In Alzheimer's disease prefrontal cortex, superior temporal gyrus, and occipital cortex, all G-protein subunit levels were equivalent to those in matched controls except for a slight deficit in G alpha i1. An ELISA assay using selective antibodies was used to measure [35S]GTP gamma S binding to G alpha o and G alpha i1. Binding was proportional to the concentration of GTP-gamma S and was concentration-dependently stimulated by mastoparan equivalently in control and Alzheimer's disease prefrontal cortical membranes.
 
Article
Are there limits to the duration of high quality of life? Are there limits to healthy life for a human brain? We have had the opportunity to evaluate the performance of a 112-113-year-old woman and perform full pathological examination of her body immediately after death at the age of 115. The psychological tests revealed that her general performance was above average of healthy adults of 60-75 years. The pathological observations revealed almost no atherosclerotic changes throughout the body. In the brain almost no beta-amyloid plaques or vascular changes were found and only slight accumulation of hyperphosphorylated tau protein with a Braak-stage 2. Counts of the number of locus coeruleus neurons corresponded with the number of neurons found in the brains of healthy people of 60-80 years old. Our observations indicate that the limits of human cognitive function extends far beyond the range that is currently enjoyed by most individuals and that brain disease, even in supercentanarians, is not inevitable.
 
Article
The description of an 115 year old woman without dementia or Alzheimer's disease (AD) is remarkable, but fits well with previous accounts of aging and AD. Several similar non-demented cases aged 85-105 years have been reported previously, who had neurofibrillary tangles in the medial temporal lobe, but no deposition of amyloid plaques. Together with observations on other aging and very mild AD cases, these can be related to a model of aging and AD. In this model, tangles develop independently but relatively slowly during aging; these represent neurodegeneration, but by themselves may not represent AD. In contrast, amyloid may be the driving factor in AD, exacerbating neurofibrillary changes and other neurodegeneration. There is a pre-clinical period when the process has begun but has not produced sufficient degeneration to produce clinical symptoms. Critical questions raised by the present report include what genetic or other factors allowed healthy survival to age 115 years, and whether anti-amyloid therapies will allow more general survival in good mental health beyond age 100?
 
Article
The description of an 115-year-old woman without dementia or Alzheimer's disease (AD) is remarkable, but fits well with previous accounts of aging and AD. Several similar non-demented cases aged 85-105 years have been reported previously, who had neurofibrillary tangles in the medial temporal lobe, but no deposition of amyloid plaques. Together with observations on other aging and very mild AD cases, these can be related to a model of aging and AD. In this model, tangles develop independently but relatively slowly during aging; these represent neurodegeneration, but by themselves may not represent AD. In contrast, amyloid may be the driving factor in AD, exacerbating neurofibrillary changes and other neurodegeneration. There is a pre-clinical period when the process has begun but has not produced sufficient degeneration to produce clinical symptoms. Critical questions raised by the present report include what genetic or other factors allowed healthy survival to age 115 year, and whether anti-amyloid therapies will allow more general survival in good mental health beyond age 100?
 
Article
den Dunnen et al. [den Dunnen, W.F.A., Brouwer, W.H., Bijlard, E., Kamphuis, J., van Linschoten, K., Eggens-Meijer, E., Holstege, G., 2008. No disease in the brain of a 115-year-old woman. Neurobiol. Aging] had the opportunity to follow up the cognitive functioning of one of the world's oldest woman during the last 3 years of her life. They performed two neuropsychological evaluations at age 112 and 115 that revealed a striking preservation of immediate recall abilities and orientation. In contrast, working memory, retrieval from semantic memory and mental arithmetic performances declined after age 112. Overall, only a one-point decrease of MMSE score occurred (from 27 to 26) reflecting the remarkable preservation of cognitive abilities. The neuropathological assessment showed few neurofibrillary tangles (NFT) in the hippocampal formation compatible with Braak staging II, absence of amyloid deposits and other types of neurodegenerative lesions as well as preservation of neuron numbers in locus coeruleus. This finding was related to a striking paucity of Alzheimer disease (AD)-related lesions in the hippocampal formation. The present report parallels the early descriptions of rare "supernormal" centenarians supporting the dissociation between brain aging and AD processes. In conjunction with recent stereological analyses in cases aged from 90 to 102 years, it also points to the marked resistance of the hippocampal formation to the degenerative process in this age group and possible dissociation between the occurrence of slight cognitive deficits and development of AD-related pathologic changes in neocortical areas. This work is discussed in the context of current efforts to identify the biological and genetic parameters of human longevity.
 
Article
Unlabelled: Inflammatory mechanisms, like microglial activation, could be involved in the pathogenesis of Alzheimer's disease (AD). (R)-[(11)C]PK11195 (1-(2-chlorophenyl)-N-methyl-N-1(1-methylpropyl)-3-isoquinolinecarboxamide), a positron emission tomography (PET) ligand, can be used to quantify microglial activation in vivo. The purpose of this study was to assess whether increased (R)-[(11)C]PK11195 binding is present in AD and mild cognitive impairment (MCI), currently also known as "prodromal AD." Methods: Nineteen patients with probable AD, 10 patients with prodromal AD (MCI), and 21 healthy control subjects were analyzed. Parametric images of binding potential (BP(ND)) of (R)-[(11)C]PK11195 scans were generated using receptor parametric mapping (RPM) with supervised cluster analysis. Differences between subject groups were tested using mixed model analysis, and associations between BP(ND) and cognition were evaluated using Pearson correlation coefficients. Results: Voxel-wise statistical parametric mapping (SPM) analysis showed small clusters of significantly increased (R)-[(11)C]PK11195 BP(ND) in occipital lobe in AD dementia patients compared with healthy control subjects. Regions of interest (ROI)-based analyses showed no differences, with large overlap between groups. There were no differences in (R)-[(11)C]PK11195 BP(ND) between clinically stable prodromal AD patients and those who progressed to dementia, and BP(ND) did not correlate with cognitive function. Conclusion: Microglial activation is a subtle phenomenon occurring in AD.
 
Article
In patients with Alzheimer's disease (AD), postmortem and imaging studies have revealed early and prominent reductions in cerebral serotonin 2A (5-HT(2A)) receptors. To establish if this was due to a selective disease process of the serotonin system, we investigated the cerebral 5-HT(2A) receptor and the serotonin transporter binding, the latter as a measure of serotonergic projections and neurons. Twelve patients with AD (average Mini Mental State Examination [MMSE]: 24) and 11 healthy age-matched subjects underwent positron emission tomography (PET) scanning with [(18)F]altanserin and [(11)C]N,N-Dimethyl-2-(2-amino-4-cyanopheylthio)benzylamine ([(11)C]DASB). Overall [(18)F]altanserin binding was markedly reduced in AD by 28%-39% (p = 0.02), whereas the reductions in [(11)C]DASB binding were less prominent and mostly insignificant, except for a marked reduction of 33% in mesial temporal cortex (p = .0005). No change in [(11)C]DASB binding was found in the midbrain. We conclude that the prominent reduction in neocortical 5-HT(2A) receptor binding in early AD is not caused by a primary loss of serotonergic neurons or their projections.
 
Article
The relationship between acetylcholinesterase (AChE) activity in the CSF and brain of patients with Alzheimer's disease (AD) was investigated in 18 mild AD patients following galantamine treatment. The first 3 months of the study had a randomized double-blind placebo-controlled design, during which 12 patients received galantamine (16-24 mg/day) and six patients placebo. This was followed by 9 months galantamine treatment in all patients. Activities and protein levels of both the "read-through" AChE (AChE-R) and the synaptic (AChE-S) variants in CSF were assessed in parallel together with the regional brain AChE activity by (11)C-PMP and PET. The AChE-S inhibition was 30-36% in CSF, which correlated well with the in vivo AChE inhibition in the brain. No significant AChE inhibition was observed in the placebo group. The increased level of the AChE-R protein was 16% higher than that of AChE-S. Both the AChE inhibition and the increased level of AChE-R protein positively correlated with the patient's performance in cognitive tests associated with visuospatial ability and attention. In conclusion, AChE levels in CSF closely mirror in vivo brain AChE levels prior to and after treatment with the cholinesterase inhibitors. A positive cognitive response seems to dependent on the AChE inhibition level, which is balanced by an increased protein level of the AChE-R variant in the patients.
 
Article
To investigate differences in distribution of α4β2 subtypes of nicotinic acetylcholine receptors (nAChRs) using the ligand ¹²³I-5-Iodo-3-[2(S)-2-azetidinylmethoxy] pyridine (5IA-85380) and single photon emission computed tomography (SPECT) in subjects with vascular dementia and age-matched controls. ¹²³I-5IA-85380 binding was compared to corresponding regional cerebral blood flow (rCBF) changes in the same subjects. Thirty subjects (14 vascular dementia and 16 controls) underwent ¹²³I-5IA-85380 and rCBF ((99m)Tc-exametazime) SPECT scanning. Image analysis was performed on voxel basis using statistical parametric mapping (SPM2). Compared to controls, reductions in relative ¹²³I-5IA-85380 uptake were identified in dorsal thalamus and right caudate in vascular dementia. Increase in scaled ¹²³I-5IA-85380 uptake in cuneus was also demonstrated in vascular dementia relative to controls. Perfusion deficits in anterior cingulate were apparent in the patient group and did not appear to be associated with ¹²³I-5IA-85380 changes. Reduced ¹²³I-5IA-85380 uptake in vascular dementia was confined to sub-cortical regions, unlike the cortical reductions previously described in Alzheimer's disease. Elevation of normalised ¹²³I-5IA-85380 uptake in cuneus in vascular dementia could be a compensatory response to reduced cholinergic activity in dorsal thalamus.
 
Article
To investigate the effects of aging and gender on brain dopamine and serotonin transporter bindings, we analyzed [(123)I]FP-CIT single-photon emission computed tomography scans of 231 Parkinson's disease (PD) patients and 230 controls. An automated region-of-interest-based method (BRASS automated analysis software) was used for striatal regions and a voxel-based method (Statistical Parametric Mapping software, SPM8) for the entire brain. In controls, aging was associated with a decline of 3.6%-4.6% per decade in striatal binding. Multiple extrastriatal regions also showed age-related declines. In PD patients, age-related declines were only observed in the caudate nuclei, thalamus, olfactory, and cingulate cortices with a comparable rate of decline as that in controls. Female subjects had higher caudate nucleus binding compared with males with a similar near-significant difference in the right putamen. The results demonstrate that the aging effect is limited in PD, which is possibly because of disease-related excess variation, and the results do not support the theory of accelerated aging of the dopaminergic system in PD. Women have higher caudate nucleus dopamine transporter binding compared with men in both normal and degenerated dopamine systems. Copyright © 2015 Elsevier Inc. All rights reserved.
 
Article
Treatments currently licensed for Alzheimer's dementia target cholinergic brain systems. In vivo nicotinic receptor binding may provide an early marker of illness and treatment suitability. In this pilot, we examined nine patients with amnestic mild cognitive impairment (MCI) and 10 age and education matched healthy volunteers with high resolution SPECT and the nicotinic receptor ligand 5-(123)I-A-85380. Uptake data were analysed using voxel-based techniques for group comparisons and regression analyses with cognitive impairment as covariates. MCI patients had discrete reductions in uptake in medial temporal cortex. Correlations with cognitive impairment were found in left temporo-parietal areas (Addenbrooke's Cognitive Examination) and bilateral temporo-limbic areas (Rey Auditory Verbal Learning Test), and right parahippocampal gyrus (Rey Complex Figure Test) within the patient group. In vivo nicotinic receptor binding appears to be sensitive to brain changes in MCI. Larger scale explorations of patients undergoing treatment will be necessary to evaluate its use in predicting or monitoring treatment response.
 
Article
Human postmortem studies have reported decreases with age in high affinity nicotine binding in brain. We investigated the effect of age on beta(2)-containing nicotinic acetylcholine receptor (beta(2)-nAChR) availability in eight brain regions of living human subjects using the ligand [(123)I]5-IA-85380 ([(123)I]5-IA) and single photon emission computed tomography (SPECT). Healthy, nonsmokers (N=47) ranging in age from 18 to 85 were administered [(123)I]5-IA using a bolus plus constant infusion paradigm and imaged 6-8h later under equilibrium conditions. The effect of age on regional beta(2)-nAChR availability (V(T), regional brain activity/free plasma parent, a measure proportional to the binding potential) was analyzed using linear regression and Pearson's correlation (r). Age and regional beta(2)-nAChR availability were inversely correlated in seven of the eight brain regions analyzed, with decline ranging from 32% (thalamus) to 18% (occipital cortex) over the adult lifespan, or up to 5% per decade. These results in living human subjects corroborate postmortem reports of decline in high affinity nicotine binding with age and may aid in elucidating the role of beta(2)-nAChRs in cognitive aging.
 
Article
Clinical distinction between Lewy bodies disease (LBD) and frontotemporal dementia (FTD) is sometimes difficult. Nigrostriatal dopaminergic degeneration occurs in both LBD and FTD, limiting helpfulness of DAT imaging to differentiate these forms of dementia. Several studies have emphasized the usefulness of myocardial scintigraphy with (123)Metaiodobenzylguanidine ((123)I-MIGB) in assessing the sympathetic nerve terminals in LBD demonstrating that cardiac (123)I-MIGB uptake is decreased in patients with this disease. We investigated the role of cardiac (123)I-MIBG scintigraphy in differentiating patients with LBD from those with FTD. Clinical diagnosis of LBD and FTD was determined according to established consensus criteria. Nine patients with LBD (1 possible and 8 probable), 6 patients with FTD, and 16 control subjects were involved in the study. The heart to mediastinum ratio (H/M) of (123)I-MIBG uptake was markedly reduced in all patients with LBD (H/M early: 1.25±0.12; delayed: 1.14±0.13) whereas it was normal in patients with FTD (H/M early: 1.86±0.20; delayed: 1.80±0.23) and in controls (H/M early: 1.91±0.17; delayed: 1.99±0.19), suggesting that cardiac (123)I-MIBG scintigraphy can help distinguish patients with LBD from those with FTD.
 
Article
Variants of the MAPT gene have been suggested to be associated with Parkinson's disease (PD) and to modify the risk for leucine-rich repeat kinase 2 (LRRK2) Parkinsonism. However, this has not been confirmed in Asians with ethnicity-specific variants of MAPT and LRRK2. In this study, Asian-specific LRRK2 p.G2385R variant and IVS1+124 C>G, a functional single-nucleotide polymorphism located in the MAPT promoter region, were genotyped in 561 Chinese PD patients and 556 control subjects. Allelic and genotypic frequencies of the 2 variants were compared between cases and control subjects independently and in combination. As a result, the LRRK2 p.G2385R variant alone was associated with an increased risk for PD (Odds ratio, 1.86; 95% confidence intervals, 1.08-3.19; p = 0.014), whereas MAPT IVS1+124 C>G was not (p = 0.34). However, the coexistence of MAPT IVS1+124C>G significantly enhanced the LRRK2 G2385R-conferred risk for PD (Odds ratio, 2.30; 95% confidence intervals, 1.14-4.54; p = 0.012). These results provide further evidence supporting the interaction between MAPT and LRRK2 genes, which increases the susceptibility to PD in Chinese individuals.
 
Article
We studied the binding of the calcium antagonist neurotoxin [125I]-omega conotoxin (GVIA) in age-matched human brains from normal, Alzheimer's disease and non-Alzheimer's dementia patients. Crude preparations of plasmalemmal membranes from frontal cortex were utilized. Saturation isotherms were subjected to Scatchard analysis to determine maximal binding capacity (Bmax) and binding affinity (Kd). In all brain samples tested, [125I]-GVIA binding was homogenous to a single class of high affinity binding sites. Scatchard analysis of saturation isotherms gave the following estimates for normal brains (mean +/- S.D., n = 7): Bmax = .630 +/- .200 pmol/mg and Kd = .177 +/- .054 nM. No significant change was observed in the Kd or Bmax estimates for [125I]-omega conotoxin binding in Alzheimer's disease or non-Alzheimer's dementia brains when compared to normal brains. Although these findings do not rule out the existence of localized changes in calcium channel receptor binding in the frontal cortex of Alzheimer's disease patients, the results do suggest that the neuronal voltage sensitive calcium channel may be unaltered in Alzheimer's disease.
 
Overexpression of miR-126 compromises survival of VM primary DA neurons. (A) TH+ DA neurons (green) transduced with Syn.rtTA3.IRES.GFP (Virus Ctrl) or the dual TetOn.Syn.miR-126 virus system (miR-126) express GFP (red). Images are at 40 X magnification and scale bars represent 20 μm. (B) 73% of all TH+ cells were virustransduced (TH+GFP+). (C) In TetOn.Syn.miR-126 transduced cultures, miR-126 expression is 3-fold upregulated in the presence of 200 ng/ml Dox compared to Syn.rtTA3.IRES.GFP transduced controls ( * P < 0.05). (D) Transduced cells were cultured in the absence or presence of 50 or 90 μM 6-OHDA, 200 ng/ml Dox, or 20 ng/ml IGF-1, and TH+ cell numbers were counted. Shown are data from one out of two experiments ( * P < 0.05 comparing Dox-treated (Dox+) to Dox-untreated (Dox−) condition; # P < 0.05 comparing 6-OHDA-treated to 6-OHDA-untreated (0 μM) condition; § P < 0.05 comparing IGF-1-treated (IGF-1+) to IGF-1-untreated (IGF-1-) condition).
Overexpression of miR-126 impairs and its inhibition promotes IGF-1 signaling in neuroblastoma cells. (A) MTT assays on SH-SY5Y or PC12 cells that are transduced with the dual virus system show reduced cell proliferation in response to IGF-1 when miR-126 expression is induced by 200 ng/ml Dox. Results are plotted as fold differences relative to 0 ng/ml IGF-1 for Dox+ over Dox− conditions ( * P < 0.05 comparing miR-126 to Naïve or Virus Ctrl.). (B) The effects of IGF-1 could be abrogated by AG1024. Dox-treated (200 ng/ml) undifferentiated SH-SY5Y cells were cultured in the absence or presence of 80 ng/ml IGF-1 or 1 μM AG-1024 and cell proliferation was measured by MTT. Data are plotted as fold differences relative to untreated controls ( * P < 0.05 comparing IGF-1+ to IGF-1− condition). (C) Inhibition of miR-126 increases trophic support of IGF-1. Dox-treated Virus Ctrl and miR-126 transduced cells were transfected with scrambled or miR-126 targeting LNAs (LNAsc and LNA126, respectively) and cultured in the absence or presence of IGF-1. Data are plotted as percent cell death relative to 0 ng/ml IGF-1 in LNAsc transfected cells ( * P < 0.05 comparing IGF-1+ to IGF-1 conditions, # P < 0.05 comparing LNA126 to LNAsc).
Overexpression of miR-126 downregulates expression levels of molecules in IGF-1/PI3K signaling. The expression levels of miR-126 targets and downstream molecules of IGF-1/ PI3K signaling in lentivirus transduced SH-SY5Y cells were analyzed by semi-quantitative Western blots. (A) Representative example of a Western blot for differentiated SH-SY5Y cells in presence or absence of 200 ng/ml Dox, 20 ng/ml IGF-1, and 30 or 50 μM 6-OHDA. (B) Expression levels were calculated as Dox+ over Dox− and plotted as percent changes relative to untreated (IGF-1−/Dox−) condition. In the case of phosphorylated proteins, converted values of phosphorylated proteins were divided by converted values of total proteins. Relative protein expression levels in PGK.rtTA3.IRES.GFP (Virus Ctrl) transduced SH-SY5Y cells had similar expression patterns to Naïve. In both Undiff. and Diff. SH-SY5Y cells, expression levels of p85β, IRS-1, and SPRED1, and phosphorylation of AKT and ERK were reduced in Dox+ miR-126 transduced cells with an exacerbated downregulation in Diff. cells treated with 50 μM 6-OHDA ( * P < 0.05 within a group (IGF-1− or IGF-1+); § P < 0.05 between IGF-1− and IGF-1+ conditions).
Article
Dopamine (DA) neurons in sporadic Parkinson's disease (PD) display dysregulated gene expression networks and signaling pathways that are implicated in PD pathogenesis. Micro (mi)RNAs are regulators of gene expression, which could be involved in neurodegenerative diseases. We determined the miRNA profiles in laser microdissected DA neurons from postmortem sporadic PD patients' brains and age-matched controls. DA neurons had a distinctive miRNA signature and a set of miRNAs was dysregulated in PD. Bioinformatics analysis provided evidence for correlations of miRNAs with signaling pathways relevant to PD, including an association of miR-126 with insulin/IGF-1/PI3K signaling. In DA neuronal cell systems, enhanced expression of miR-126 impaired IGF-1 signaling and increased vulnerability to the neurotoxin 6-OHDA by downregulating factors in IGF-1/PI3K signaling, including its targets p85β, IRS-1, and SPRED1. Blocking of miR-126 function increased IGF-1 trophism and neuroprotection to 6-OHDA. Our data imply that elevated levels of miR-126 may play a functional role in DA neurons and in PD pathogenesis by downregulating IGF-1/PI3K/AKT signaling and that its inhibition could be a mechanism of neuroprotection.
 
Article
The 129 mouse strain has been widely used to construct mutations that model behavioral aging in humans. The current study found significant age-related declines in both psychomotor and swim maze performance of 5-, 17-, and 27-month-old 129/SvJ mice. However, the age differences in swim maze acquisition were inconsistent with poor performance in the probe trial which assesses spatial memory. This inconsistency may result from the high degree of genetic polymorphisms and age-related visual pathology which afflicts this mouse strain. Therefore, we concluded that 129/SvJ mice present a problematic model of mammalian cognitive aging and involve a risk for behavioral contamination in studies involving mutant mice derived from this strain.
 
Article
Cholinergic medial septum neurons express TrkA and p75 nerve growth factor receptor (p75(NGFR)) and interactions between TrkA and p75(NGFR) are necessary for high-affinity binding and signaling of nerve growth factor (NGF) through TrkA. In adult p75(NGFR)-deficient (-/-) mice, retrograde transport of NGF and other neurotrophins by these neurons is greatly reduced, however, these neurons maintain their cholinergic phenotype and size. Reduced transport of NGF has been proposed to play a role in Alzheimer's disease. Here, we investigated whether chronic and long-term absence of p75(NGFR) (and possibly reduced NGF transport and TrkA binding) would affect the cholinergic septohippocampal system during aging in mice. In young (6-8 months), middle aged (12-18 months), and aged (19-23 months) 129/Sv control mice the total number of choline acetyltransferase-positive medial septum neurons and the mean diameter and cross sectional area of the cholinergic cell bodies were similar. The cholinergic hippocampal innervation, as measured by the density of acetylcholinesterase-positive fibers in the outer molecular layer of the dentate gyrus was also similar across all ages. These parameters also did not change during aging in p75(NGFR) -/- mice and the number and size of the choline acetyltransferase-positive neurons and the cholinergic innervation density were largely similar as in control mice at all ages. These results suggest that p75(NGFR) does not play a major role in the maintenance of the number or morphology of the cholinergic basal forebrain neurons during aging of these mice. Alternatively, p75(NGFR) -/- mice may have developed compensatory mechanisms in response to the absence of p75(NGFR).
 
Article
Inflammatory processes are involved in the pathogenesis of Alzheimer's disease (AD). Several studies have addressed the effects of interleukin-1 (IL-1) genes polymorphisms on the risk of developing AD. The results are not in full agreement on whether these polymorphisms are associated with the disease. To clarify this issue, we performed a meta-analysis of all the association studies between IL-1 genes and AD. Due to the relatively small number of published articles, the meta-analysis was restricted to the association of the IL-1alpha -889 C/T gene polymorphism and AD. Under a random effects model, the risk for the disease was significantly higher in subjects with the T/T genotype in comparison with both C/T (OR: 1.51; 95% C.I.: 1.15-1.99) and C/C (OR: 1.49; 95% C.I.: 1.09-2.03) subjects. There was modest heterogeneity for these effect estimates. Analysis of subgroups showed a significant association in patients with early-onset AD but not in late-onset AD. Our data support a significant but modest association between the T/T genotype of the IL-1alpha gene and AD.
 
Article
The effects of age (19-100 years) upon dopamine uptake sites labeled with [3H]GBR-12935 in human postmortem putamen from 20 individuals were studied. There was a 70% decrease in binding density (Bmax) over the adult age range. No significant changes in binding affinity (Kd) were detected, the mean Kd being 1.0 +/- 0.2 nM (mean +/- S.E.M.). Nor were there any changes in binding related to the postmortem delay. Based on the findings that [3H]GBR-12935 labels the uptake site for dopamine, it is suggested that the age-related loss of [3H]GBR-12935 binding in human putamen reflects a degeneration of dopamine neurites.
 
Article
Genetic risk factors play an important role in the pathogenesis of Alzheimer disease (AD) and vascular dementia (VaD). In this case-control study, we examined C677T and A1298C (rs1801133 and rs1801131) polymorphism in the methylenetetrahydrofolate reductase (MTHFR) genes and their correlation with plasma levels of homocysteine (Hcy) in AD and VaD cases and evaluated the gene-gene interaction (epistasis) with IL-6-174 G/C (rs1800795). CC genotype was associated with elevated levels of plasma homocysteine (p = 0.004) as compared with genotype AA of rs1801131. In AD, we observed a significant (p = 0.04) association with C alleles of rs1801131. Regression analysis revealed that the presence of both rs1801133 T and rs1800795 C alleles increased the odds of developing AD by 2.5 and VaD by 3.7-fold. While rs1800795 (CC or GC) genotypes alone increased the odds of developing VaD by 2.2-fold, the presence of CC genotype of rs1801131 nullified this effect. The findings support the hypothesis that multiple genes are involved to alter the odds of developing AD and VaD.
 
Article
Phosphorylation of cAMP-response element binding protein (CREB) is required for hippocampus-dependent long-term memory formation. The present study was designed to determine whether spatial memory deficits in aged mice were associated with alteration of hippocampal CREB phosphorylation. We examined the temporal pattern of CREB activation in 5-6 and 23-24-month-old 129T2/Sv mice trained on a spatial reference memory task in the water maze. Phosphorylated CREB (pCREB), total CREB (t-CREB) and c-Fos immunoreactivity (ir) were measured at four time points after the end of training. In young mice, pCREB-ir was significantly increased 15 and 60 min after training in the CA1 region and dentate gyrus. In aged mice sacrificed 15 min after training, pCREB-ir in these structures was reduced whereas t-CREB-ir remained unchanged compared to respective young-adults. An age-related reduction of c-Fos-ir also occurred selectively in hippocampal CA1 region. Since reduced pCREB-ir in CA1 from the 15 min-aged group strongly correlated with individual learning performance, we suggest that altered CREB phosphorylation in CA1 may account for spatial memory impairments during normal aging.
 
Top-cited authors
Kelly Del  Tredici
  • Ulm University
Patrick McGeer
  • University of British Columbia - Vancouver
Robert Mrak
  • University of Washington Seattle
Sally A Frautschy
  • University of California, Los Angeles
Lih-Fen Lue
  • Banner Sun Health Research Institute