Alzheimer's disease in Down's syndrome. A review

Can neurodevelopmental disorders influence the course of neurodegenerative diseases? A scoping review

This scoping review aims at giving an overview of the possible influence of neurodevelopmental disorders (NDDs) on cognitive-behavioral neurodegenerative diseases (CBNDs). Based on the PRISMA-ScR checklist, it details the methods of NDDs screening, the identified NDDs-CBNDs associations, as well as the criteria and types of association. The last literature search was performed in June 2023. In the final study, 32 articles were included. Analysis first showed that NDDs were mainly detected through medical records screening. Second, the association of specific learning disorders and major or mild neurocognitive disorder due to Alzheimer's disease was the most investigated. Third, associations were mostly based on prevalence comparisons. Finally, 66 % of studies reported a positive association between NDDs and CBNDs. Notably, up to 67 % of positive associations were observed with atypical forms of certain CBNDs. Authors' interpretations suggest that NDDs could constitute a risk factor for CBNDs. However, the influence of NDDs on CBNDs still lacks evidence and biological support, possibly due to the heterogeneity of methods and criteria employed. Developing validated assessment tools for all NDDs and conducting cohort studies could be beneficial for research, and clinical practice. Indeed, this review also underlines the importance of adopting a life-span approach regarding CBNDs.

Regulatory and Effector Cell Disequilibrium in Patients with Acute Cellular Rejection and Chronic Lung Allograft Dysfunction after Lung Transplantation: Comparison of Peripheral and Alveolar Distribution

Background: The immune mechanisms occurring during acute rejection (AR) and chronic lung allograft dysfunction are a challenge for research and the balance between effector and regulatory cells has not been defined completely. In this study, we aimed to elucidate the interaction of effector cells, mainly Th17, Th1 and Th2, and regulatory cells including (CD4⁺CD25⁺CD127^low/−) T reg cells and phenotypes of B regs, CD19⁺CD24^hiCD38^hi, CD19⁺CD24^hiCD27^hi and CD19⁺CD5⁺CD1d⁺. Methods: Bronchoalveolar lavage cells (BAL) and peripheral blood mononuclear cells (PBMCs) from stable lung transplanted (LTx )subjects (n = 4), AR patients (n = 6) and bronchiolitis obliterans syndrome (BOS) (n = 6) were collected at the same time. Cellular subsets were detected through flow cytometry. Results: A predominance of Th17 cells subtypes in the PBMCs and BAL and a depletion of Tregs, that resulted in decrease Treg/Th17 ratio, was observed in the AR group. CD19⁺CD24^hiCD38^hi Bregs resulted increased in BAL of AR patients. Th1 cells predominance and a reduction of Tregs cells was observed in BAL from AR patients. Moreover, multivariate analysis showed interdependences within studied variables revealing that effector cells and regulatory cells can effectively discriminate patients’ immunological status. Conclusions: In AR, BOS and stable lung transplant, regulatory and effector cells clearly demonstrated different pathways of activation. Understanding of the balance of T cells and T and B regulatory cells can offers insights into rejection.

Potentiation of anti-Alzheimer activity of curcumin by probiotic Lactobacillus rhamnosus UBLR-58 against scopolamine-induced memory impairment in mice

Curcumin, a major component of Indian saffron through clinical studies, revealed its neuroprotective effect in neurodegenerative diseases. However, it has not been utilized alone orally due to its low bioavailability. There are certain strategies to overcome the drawbacks such as poor absorption and low aqueous solubility. Many strategies are utilized to increase the systemic availability of curcumin. Among them, the steady intestinal and liver metabolism of curcumin by a curcumin adjuvant (enzyme inhibitor/inducer) is an important and less engrossed strategy for improving the overall systemic bioavailability of curcumin. Here, we assess the effect of probiotic Lactobacillus rhamnosus as a curcumin adjuvant (potentiate the effect of curcumin) in scopolamine-induced dementia in mice. To induce amnesia, scopolamine was used in a mouse model (1 mg/kg, daily for 10 days i.p.). After execution of behavioural tests (Morris water maze test), brains and liver were isolated for further neurochemical and histopathology examination. Our results showed a significant increase in antioxidant enzyme levels in curcumin with a probiotic group compared with curcumin alone. Besides, histopathology study results showed less neuronal damage of curcumin with probiotics as compared with the curcumin and scopolamine alone groups. Additionally, curcumin with probiotics improved memory and cognitive functions in the behavioural study with the significance of p ≤ 0.0001. In conclusion, curcumin with probiotics has greater activity as compared with curcumin alone and reverses the hallmarks of Alzheimer's disease (AD).

Neurotrophic factor small-molecule mimetics mediated neuroregeneration and synaptic repair: emerging therapeutic modality for Alzheimer's disease

Alzheimer's disease (AD) is an incurable and debilitating chronic progressive neurodegenerative disorder which is the leading cause of dementia worldwide. AD is a heterogeneous and multifactorial disorder, histopathologically characterized by the presence of amyloid β (Aβ) plaques and neurofibrillary tangles composed of Aβ peptides and abnormally hyperphosphorylated tau protein, respectively. Independent of the various etiopathogenic mechanisms, neurodegeneration is a final common outcome of AD neuropathology. Synaptic loss is a better correlate of cognitive impairment in AD than Aβ or tau pathologies. Thus a highly promising therapeutic strategy for AD is to shift the balance from neurodegeneration to neuroregeneration and synaptic repair. Neurotrophic factors, by virtue of their neurogenic and neurotrophic activities, have potential for the treatment of AD. However, the clinical therapeutic usage of recombinant neurotrophic factors is limited because of the insurmountable hurdles of unfavorable pharmacokinetic properties, poor blood-brain barrier (BBB) permeability, and severe adverse effects. Neurotrophic factor small-molecule mimetics, in this context, represent a potential strategy to overcome these short comings, and have shown promise in preclinical studies. Neurotrophic factor small-molecule mimetics have been the focus of intense research in recent years for AD drug development. Here, we review the relevant literature regarding the therapeutic beneficial effect of neurotrophic factors in AD, and then discuss the recent status of research regarding the neurotrophic factor small-molecule mimetics as therapeutic candidates for AD. Lastly, we summarize the preclinical studies with a ciliary neurotrophic factor (CNTF) small-molecule peptide mimetic, Peptide 021 (P021). P021 is a neurogenic and neurotrophic compound which enhances dentate gyrus neurogenesis and memory processes via inhibiting leukemia inhibitory factor (LIF) signaling pathway and increasing brain-derived neurotrophic factor (BDNF) expression. It robustly inhibits tau abnormal hyperphosphorylation via increased BDNF mediated decrease in glycogen synthase kinase-3β (GSK-3β, major tau kinase) activity. P021 is a small molecular weight, BBB permeable compound with suitable pharmacokinetics for oral administration, and without adverse effects associated with native CNTF or BDNF molecule. P021 has shown beneficial therapeutic effect in several preclinical studies and has emerged as a highly promising compound for AD drug development.

Dementia in an Irish population of Down's syndrome people

Objective: To determine the prevalence of dementia in an Irish sample of Down's syndrome (DS) patients and to examine the utility of a number of cognitive and functional scales in the assessment of dementia in this population.

Method: 76 DS patients diagnosed clinically (range 33–72 years; mean age 47.3 ± 8.8 years) were included in the study. The diagnosis of dementia was made on clinical grounds using DSMIIIR criteria. Cognitive and functional impairment were evaluated using the following scales; Test for Severe Impairment (TSI), Down's Syndrome Mental Status Examination (DSMSE), Daily Living Skills Questionnaire (DLSQ), and the Mental State Performance (MSP).

Results: The overall prevalence of dementia was 7.9% (95% C.I = 2.95–16.39). The presence of dementia was associated with late onset epilepsy, anticonvulsant medication and deafness. Standard cognitive tests such as the MSP showed an early ‘floor’ effect in this population. In contrast the TSI and DLSQ showed a satisfactory range of scores in these patients with moderate to severe learning disability.

Conclusions: The low prevalence of dementia in this study may be explained by the strict conservative criteria applied in the clinical diagnosis. Prospective assessment of DS patients on a longitudinal basis using decline on scales such as the TSI and DLSQ may allow more accurate diagnosis of dementia at an earlier stage in this at-risk population.

Genomic instability in Down syndrome and Fanconi anemia assessed by micronucleus analysis and single-cell gel electrophoresis

Cytokinesis-block micronucleus (CB-MN) assay and single-cell gel electrophoresis (SCGE) were employed to analyze leukocytes from 14 Fanconi anemia (FA) patients, 30 Down syndrome (DS) patients, and 30 control individuals, to examine the sensitivity of these techniques to detect genomic instability in these 2 diseases. The DS patients presented increased DNA damage as measured by SCGE in relation to controls. The frequencies of micronuclei and dicentric bridges were similar to those of controls. Micronucleus frequency, dicentric bridge frequencies, and DNA damage were higher in FA patients than in controls. The high frequency of micronuclei observed in FA patients seems to be due to clastogenic events, because an increase in the frequency of dicentric bridges was also observed. Micronuclei are expressed mutations and need cell division to appear. The damage detected by SCGE is repairable, and does not require cell division. Under alkaline conditions, SCGE assesses double- and single-strand breaks and alkali-labile sites. The 2 methods are efficient for monitoring mutagenic events in exposed populations or in individuals with genetic instability. While the damage measured by micronucleus analysis is accumulated over a long period of time, DNA damage measured by SCGE reflects recent, unrepaired events.

A protective effect of apolipoprotein E e2 allele on dementia in Down's syndrome

BACKGROUND

The apolipoprotein E (ApoE) e4 allele has been associated with an increased risk for Alzheimer's disease, whereas the e2 allele has been shown to be protective. Similar effects in Down's syndrome (DS) have been postulated but not yet demonstrated.

METHODS

We obtained DNA from 221 DS individuals and from 162 population controls, and 77 DS children. Older DS subjects were evaluated for dementia and compared to age-matched DS controls.

RESULTS

The DS sample with dementia (n = 31) had a significantly lower frequency of the ApoE e2 allele compared to age-matched nondemented DS controls (0% vs. 8.3%, p = .0136). The older DS population had a significantly lower frequency of ApoE e4 compared to population controls (11.7% vs. 20.6%, chi-square 8.9, p = .0028).

CONCLUSIONS

The lower frequency of the e2 allele in demented DS subjects compared to age-matched nondemented DS controls suggests a protective effect for ApoE e2 in the development of dementia in DS. The lower frequency of ApoE e4 in our older DS sample compared to population controls points to a detrimental effect of the e4 allele on longevity.

Olfactory function in young adolescents with Down's syndrome

Decreased ability to smell is present in adults with Down's syndrome, many of whom are known to have brain pathology analogous to that seen in Alzheimer's disease. Because olfactory loss is well documented in Alzheimer's disease, the question arises whether young adolescents with Down's syndrome, who have no clear Alzheimer's disease-like neuropathology, also exhibit olfactory dysfunction. To consider this issue, standardised tests of odour discrimination and identification were administered to 20 young adolescents with Down's syndrome (mean age (SD) 13.89 (1.98) years) and their test scores were compared with 20 mentally retarded and 20 non-mentally retarded control subjects matched to the patients with Down's syndrome on the basis of cognitive ability. No significant differences in olfactory function were found among the three study groups. These findings, along with those from studies of olfactory function in older patients with Down's syndrome, suggest that Down's syndrome related olfactory dysfunction occurs only at ages when Alzheimer's disease-like pathology is present.

A critical review of research on cognitive function/impairment in older adults

Research on aspects of cognitive function and impairment in older adults is critically reviewed with the aim of evaluation and synthesis. The body of research on cognitive aging, mostly atheoretical, has not been placed within the larger context of cognitive sciences. Methodological concerns and lack of a unifying framework inhibit integration of previous studies and the development of a cohesive body of knowledge. Therefore, one paradigm of adult cognition, information processing, is recommended to further advance nursing theory and research.

Correlation between senescence and DNA repair in cells from young and old individuals and in premature aging syndromes

Cellular aging appears to be related to and perhaps caused by diminished DNA repair. To elucidate direct correlations between DNA repair capacity and senescence various parameters of cellular aging and DNA repair were studied simultaneously. Of special interest are features of DNA repair and senescence in cultured diploid fibroblasts derived either from healthy young or elderly probands as well as from patients suffering from premature senescence syndromes (Werner syndrome, Cockayne syndrome, ataxia telangiectasia and Down syndrome). Here we demonstrate the striking parallelism between reduced maximal lifespan, elevated levels of spontaneous chromosomal breaks, higher incidence of formation of micronuclei, a significant prolongation of cell cycle duration and a diminished reactivation of in vitro injured plasmid after transfection in cells from old individuals and from patients with premature senescence syndromes, suggesting a causal relationship between senescence and DNA damage.

Intracellular calcium response is reduced in CD4+ lymphocytes in Alzheimer's disease and in older persons with Down's syndrome

Abnormalities in intracellular free calcium ([Ca2+]i) regulation are likely to play a role in brain aging and have been described in cells from patients with Alzheimer's disease (AD). [Ca2+]i acts as a second messenger in transmembrane signaling and regulates diverse functions in many cell types. Therefore, abnormalities in [Ca2+]i response may have far-ranging effects. Using flow cytometric assay for [Ca2+]i, we examined whether mitogen-induced increases in [Ca2+]i are abnormal in CD4+ T-lymphocytes from patients with familial AD (FAD), other AD, and Down's syndrome (DS) compared to age-matched controls. We observed that the peak [Ca2+]i responses were significantly decreased in CD4+ cells from 6 FAD patients (59% of control), 34 other AD patients (69% of age-matched control), and 6 older persons with DS (> 25 years old, 47% of control), after stimulation with 10 micrograms/ml anti-CD3 monoclonal antibody (mAb). The number of CD3 receptors on T lymphocytes of the AD patients was not decreased. In contrast, lymphocytes from subjects with FAD, other AD and older DS patients had no decrease in response to phytohemagglutinin (30 micrograms/ml). CD3 and related classes of membrane receptors are present on many cells of the central nervous system. Therefore, receptor signaling defects via this receptor in T lymphocytes of AD patients may be relevant to the central nervous system pathology seen in AD and DS.

Monozygotic twins concordant for late-onset probable Alzheimer disease with suspected Alzheimer disease in four sibs

Probable Alzheimer disease (AD) is described in 79-year-old male twins with monozygosity confirmed by DNA examination. The first twin to be affected began to show signs of intellectual deterioration at age 70. In the other, onset was at age 72. Four of their living sibs (current age range = 75-92) are also suspected to have AD. The possible roles of genetic and environmental factors in the development of AD in this sibship are discussed.

Epidermal growth factor affects both glia and cholinergic neurons in septal cell cultures

The effects of epidermal growth factor on high density primary cultures of fetal (embryonic day 17) rat septal cells were examined. Under serum-free conditions, the continuous exposure of these cultures to epidermal growth factor for seven days significantly decreased choline acetyltransferase (EC 2.3.1.6) activity in a dose-dependent manner. Maximal decreases were observed from 1 to 10 ng/ml epidermal growth factor. This effect was completely abolished by the addition of anti-epidermal growth factor antibodies. The epidermal growth factor-mediated decrease in choline acetyltransferase activity was culture-time dependent, being first detectable after five days of factor application and may likely represent an inhibition of the spontaneous increase in enzyme activity that occurs with time in culture. Concomitant with changes in enzyme activity, epidermal growth factor produced a significant and proportional decrease in the number of acetylcholinesterase-positive neurons. This decrease in acetylcholinesterase-positive cells did not reflect a decrease in cholinergic cell survival as nerve growth factor could restore the number of acetylcholinesterase-positive neurons in epidermal growth factor-treated cultures to control levels. Furthermore, in these high-density cultures, epidermal growth factor did not affect general neuronal survival, while it did produce an increase in the number and intensity of glial fibrillary acidic protein-immunoreactive astroglia as well as in the number of macrophage-like cells. The proliferative response of these non-neuronal cells to epidermal growth factor, as assessed by [3H]thymidine incorporation, was evident after three days of epidermal growth factor application, persisted thereafter, and could be antagonized by the inclusion of the antimitotic 5-fluorodeoxyuridine. Furthermore, 5-fluorodeoxyuridine completely blocked the epidermal growth factor-mediated decrease in choline acetyltransferase activity. However, when epidermal growth factor was tested in pure glial cultures, it only directly induced proliferation of astrocytes. These results suggest that the proliferative response of either one or both of these glial cell types in the mixed cultures may be indirectly affecting cholinergic cell expression.

Down's syndrome: occurrence of ALZ-50 reactive neurons and the formation of senile plaques

We have histopathologically investigated the hippocampal formation in 4 individuals with Down's syndrome (DS), 7 control individuals, and 3 individuals dying after being in coma 3-7 days. Adjacent sections of brain were stained by the Bielschowsky method and by ALZ-50 immunocytochemical methods. ALZ-50 immunoreactive neurons were found in each individual with DS and only in the control infants. Neither ALZ-50-immunoreactive features nor abnormal silver-positive features stained by the Bielschowsky method were found in the adolescent or young adult controls or coma patients. Diffuse form senile plaques (SP) were found only in the oldest DS individual. The data suggest that ALZ-50 reactive neurons persist during the life of an individual with DS and may precede the formation of SP.

A family with multiple instances of definite, probable and possible early-onset Alzheimer's disease

A family with a multigenerational history of proven or suspected early-onset Alzheimer's disease (AD) consistent with autosomal-dominant inheritance is described. To date, the pedigree comprises five generations in which there are 13 known affected individuals. The mean age of onset of cognitive deficits in those for whom data are available (n = 11) is 47.6 (s.d. 3.0) years and the mean age of death (n = 10) is 58.8 (s.d. 4.0) years. The variability in the extent and quality of available data illustrates the diagnostic difficulties encountered in ascertaining such an extended pedigree, and the need for caution in interpreting the evidence.

Current developments in the understanding of mental retardation. Part I: Biological and phenomenological perspectives

During the past decade, noteworthy advances have taken place within the field of mental retardation. The application of advanced biological techniques in such areas as molecular genetics and neuroimaging has substantially improved our ability to identify the biological factors that underlie the origin and pathogenesis of an increasing number of mental retardation syndromes. Refined genetic and psychosocial assessments have highlighted the impressive degree of heterogeneity that is present within and across many mental retardation syndromes, stimulating increasing interest and study. This, the first of a two-part review, will focus on recent developments in biological and phenomenological aspects of mental retardation.

The relationship between enlargement of the temporal horns of the lateral ventricles and dementia in aging patients with Down syndrome

Head CT studies of patients with Alzheimer's disease (AD) show global atrophic changes. Tissue loss is especially prominent in the temporal lobes, with widening of the temporal horns of the lateral ventricles and, usually, widening of the temporal sulci. Some recent studies have found a familial form of AD to be mapped to chromosome 21. Down syndrome (DS) results from the inheritance of three chromosomes 21, and it has been shown that after the age of 35 the brains of patients with DS commonly show neuropathological changes similar to those in patients with AD. CT studies of 25 patients with DS (ages 29-64 years) were examined for tissue loss in the temporal regions, and this was compared to the findings commonly seen in patients with AD. The widths of CSF spaces varied considerably in patients with DS, but after the age of 50 most of them showed significant widening of the temporal horns. In some patients the horns were large enough to suggest obstructive hydrocephalus. Because of a new trend toward deinstitutionalization of patients with DS, radiologists will be seeing more studies on these patients and should familiarize themselves with the unique ways in which they manifest the aging process.

Down's syndrome individuals begin life with normal levels of brain cholinergic markers

We measured the activities of the cholinergic marker enzymes choline acetyltransferase (ChAT) and acetylcholinesterase (AChE) in autopsied brains of seven infants (age range 3 months to 1 year) with Down's syndrome (DS), a disorder in which virtually all individuals will develop by middle age the neuropathological changes of Alzheimer's disease accompanied by a marked brain cholinergic reduction. When compared with age-matched controls cholinergic enzyme activity was normal in all brain regions of the individuals with infant DS with the exception of above-normal activity in the putamen (ChAT) and the occipital cortex (AChE). Our neurochemical observations suggest that DS individuals begin life with a normal complement of brain cholinergic neurons. This opens the possibility of early therapeutic intervention to prevent the development of brain cholinergic changes in patients with DS.

SOD-1 activity and platelet membrane fluidity in Alzheimer's disease

An early-onset, familial form of Alzheimer's disease (AD) has been reported to be linked to a locus on the long arm of chromosome 21 (21q21). Furthermore, duplications in the vicinity of this locus involving the beta-amyloid gene and the proto-oncogene ets-2 have been reported in association with AD. The structural gene for Cu,Zn superoxide dismutase, SOD-1, is located between the beta-amyloid gene and ets-2. For this reason and because SOD-1 is a plausible candidate for a gene that might influence the fluidity of cellular membranes, we determined whether or not the subtype of AD with increased platelet membrane fluidity was associated with an increase in Cu,Zn superoxide dismutase activity.

Human ETS2 gene on chromosome 21 is not rearranged in Alzheimer disease

The human ETS2 gene, a member of the ETS gene family, with sequence homology with the retroviral ets sequence of the avian erythroblastosis retrovirus E26 is located on chromosome 21. Molecular genetic analysis of Down syndrome (DS) patients with partial trisomy 21 allowed us to reinforce the supposition that ETS2 may be a gene of the minimal DS genetic region. It was originally proposed that a duplication of a portion of the DS region represents the genetic basis of Alzheimer disease, a condition associated also with DS. No evidence of either rearrangements or duplications of ETS2 could be detected in DNA from fibroblasts and brain tissue of Alzheimer disease patients with either the sporadic or the familiar form of the disease. Thus, an altered ETS2 gene dosage does not seem to be a genetic cause or component of Alzheimer disease.

Impaired neurotransmitter uptake in PC12 cells overexpressing human Cu/Zn-superoxide dismutase--implication for gene dosage effects in Down syndrome

Rat PC12 cells expressing elevated levels of transfected human Cu/Zn-superoxide dismutase (CuZn-SOD) gene were generated. These transformants (designated PC12-hSOD) closely resembled the parental cells in their morphology, growth rate, and response to nerve growth factor, but showed impaired neurotransmitter uptake. The lesion was localized to the chromaffin granule transport mechanism. We found that the pH gradient (delta pH) across the membrane, which is the main driving force for amine transport, was diminished in PC12-hSOD granules. These results show that elevation of CuZnSOD activity interferes with the transport of biogenic amines into chromaffin granules. Since neurotransmitter uptake plays an important role in many processes of the central nervous system, CuZnSOD gene-dosage may contribute to the neurobiological abnormalities of Down's syndrome.