Nurses' perspectives on ethical aspects of telemedicine. A scoping review

BACKGROUND

Changes in health needs led to an increase in virtual care practices such as telemedicine. Nursing plays an essential role in this practice as it is the key to accessing the healthcare system. It is important that this branch of nursing is developed considering all the ethical aspects of nursing care, and not just the legal concepts of the practice. However, this question has not been widely explored in the literature and it is of crucial relevance in the new concept of care.

OBJECTIVE

The purpose of this scoping review is to identify the ethical aspects of the development of telemedicine from a nursing practice perspective.

METHODS

A scoping review of the literature based on Arksey and O'Malley's framework. The search was conducted in Scopus, PubMed/MEDLINE and CINAHL databases, from 2012 to 2022. A total of 1322 articles were retrieved, of which 12 met the inclusion criteria.

ETHICAL CONSIDERATIONS

The research was conducted in accordance with the best scientific practices.

FINDINGS

The most relevant aspects were the safety of the patient, the benefits for the user and the digital competence of the professionals. Informed consent and patient's willingness to use new technologies were relevant to the practice, as was person-centered care and how telemedicine can influence the quality of the therapeutic relationship. Another relevant issue was the concern about professional competence for optimal outcomes.

CONCLUSION

It is necessary to further explore and develop the ethical aspects of the new practices, disassociating them from the legal aspects only. Professionals demand more training providing them with more competence and confidence.

Monoallelic ABCC8 mutations are a common cause of diazoxide-unresponsive diffuse form of congenital hyperinsulinism

ABCC8 encodes a subunit of the β-cell potassium channel (KATP ) whose loss of function is responsible for congenital hyperinsulinism (CHI). Patients with two recessive mutations of ABCC8 typically have severe diffuse forms of CHI unresponsive to diazoxide. Some dominant ABCC8 mutations are responsible for a subset of diffuse diazoxide-unresponsive forms of CHI. We report the analysis of 21 different ABCC8 mutations identified in 25 probands with diazoxide-unresponsive diffuse CHI and carrying a single mutation in ABCC8. Nine missense ABCC8 mutations were subjected to in vitro expression studies testing traffic efficiency and responses of mutant channels to activation by MgADP and diazoxide. Eight of the 9 missense mutations exhibited normal trafficking. Seven of the 8 mutants reaching the plasma membrane had dramatically reduced response to MgADP or to diazoxide (<10% of wild-type response). In our cohort, dominant KATP mutations account for 22% of the children with diffuse unresponsive-diazoxide CHI. Their clinical phenotype being indistinguishable from that of children with focal CHI and diffuse CHI forms due to two recessive KATP mutations, we show that functional testing is essential to make the most reliable diagnosis and offer appropriate genetic counseling.

A Novel LMNA Mutation Causes Altered Nuclear Morphology and Symptoms of Familial Partial Lipodystrophy (Dunnigan Variety) with Progeroid Features

Dunnigan-type partial lipodystrophy (familial partial lipodystrophy, Dunnigan variety, FPLD2) can be caused by LMNA mutations. We identified a novel heterozygous LMNA mutation, P485R, in a patient referred to the International Registry of Werner Syndrome because of features consistent with that of progeroid disorder but who was wild type at the WRN locus. The novel mutation is located 2 amino acids away from the canonical FPLD mutations in exon 8 of the LMNA gene. Immunocytochemical analysis revealed abnormal nuclear morphology characteristic of laminopathies within primary fibroblast cultures, but not in a lymphoblastoid cell line, in keeping with previous observations. Our findings indicate that FPLD2 should be considered in the differential diagnosis of the Werner syndrome.

Cultured renal epithelial cells from birds and mice: enhanced resistance of avian cells to oxidative stress and DNA damage

Current mechanistic theories of aging would predict that many species of birds, given their unusually high metabolic rates, body temperatures, and blood sugar levels, should age more rapidly than mammals of comparable size. On the contrary, many avian species display unusually long life spans. This finding suggests that cells and tissues from some avian species may enjoy unusually robust and/or unique protective mechanisms against fundamental aging processes, including a relatively high resistance to oxidative stress. We therefore compared the sensitivities of presumptively homologous epithelial somatic cells derived from bird and mouse kidneys to various forms of oxidative stress. When compared to murine cells, we found enhanced resistance of avian cells from three species (budgerigars, starlings, canaries) to 95% oxygen, hydrogen peroxide, paraquat, and gamma-radiation. Differential resistance to 95% oxygen was demonstrated with both replicating and quiescent cultures. Hydrogen peroxide was shown to induce DNA single-strand breaks. There were fewer breaks in avian cells than in mouse cells when similarly challenged.

DNA double-strand breaks in mouse kidney cells with age

A Biojector device fitted with a CO2 cartridge was used to prepare single cell suspensions from kidneys of 12-month- (middle-aged) and 24-month-old (old) C57B1/6 mice. Microgel electrophoresis of DNA from these cells revealed a modest but significant 7.3% increase (P = 0.04) in DNA double-strand breaks in old mice. This increase is equivalent to the DNA damage induced by 0.1 Gray of X-rays (5 double-strand breaks) in kidney cells of 10-month-old mice, as determined by a standard calibration curve. Greater DNA damage with aging was also positively correlated with higher levels of pathology in the kidneys.

Deficient neurogenesis in forebrain-specific presenilin-1 knockout mice is associated with reduced clearance of hippocampal memory traces

To examine the in vivo function of presenilin-1 (PS1), we selectively deleted the PS1 gene in excitatory neurons of the adult mouse forebrain. These conditional knockout mice were viable and grew normally, but they exhibited a pronounced deficiency in enrichment-induced neurogenesis in the dentate gyrus. This reduction in neurogenesis did not result in appreciable learning deficits, indicating that addition of new neurons is not required for memory formation. However, our postlearning enrichment experiments lead us to postulate that adult dentate neurogenesis may play a role in the periodic clearance of outdated hippocampal memory traces after cortical memory consolidation, thereby ensuring that the hippocampus is continuously available to process new memories. A chronic, abnormal clearance process in the hippocampus may conceivably lead to memory disorders in the mammalian brain.

Exceptional cellular resistance to oxidative damage in long-lived birds requires active gene expression

Previous studies indicated that renal tubular epithelial cells from some long-lived avian species exhibit robust and/or unique protective mechanisms against oxidative stress relative to murine cells. Here we extend these studies to investigate the response of primary embryonic fibroblast-like cells to oxidative challenge in long- and short-lived avian species (budgerigar, Melopsittacus undulatus, longevity up to 20 years, vs Japanese quail, Coturnix coturnix japonica, longevity up to 5 years) and short- and long-lived mammalian species (house mouse, Mus musculus, longevity up to 4 years vs humans, Homo sapiens, longevity up to 122 years). Under the conditions of our assay, the oxidative-damage resistance phenotype appears to be associated with exceptional longevity in avian species, but not in mammals. Furthermore, the extreme oxidative damage resistance phenotype observed in a long-lived bird requires active gene transcription and translation, suggesting that specific gene products may have evolved in long-lived birds to facilitate resistance to oxidative stress.

Spatial problem solving and hippocampal place cell firing in rats: control by an internal sense of direction carried across environments

Rats learned to find the baited corner of a box surrounded by a curtain, regardless of whether they had a fixed or random point of entry (POE) through the curtain. On probe trials, rats used an internal direction sense carried from outside the curtain to solve the problem, and only used the visual cue inside the curtain if disoriented and denied access to a view of the room en route. Similar disorientation procedures were required to obtain cue control of hippocampal place fields. The results suggest that: (1) POE effects previously found in the water maze may be task-specific; (2) an undisrupted internal sense of direction carried from one environment to another may provide the preferred solution to spatial problems in the second environment, even when this second environment is a familiar one with stable visual cues; and (3) choice behaviour is sometimes, but not always, representative of the hippocampal representation of space.

The moving fire hydrant experiment: movement of objects to a new location reelicits marking in rats

Three experiments were carried out to investigate the influence of object relocation on object marking in an open field by hooded and albino rats. Object marking was reelicited when an object was moved to a new location in the second half of an open field test. Control conditions revealed that an object briefly moved and returned to the original location elicited no more marking than a stationary object. The higher level of marking of the relocated object suggests that object marking may provide an index of spatial knowledge. The implication of spatial knowledge in controlling marking behavior is congruent with observations that rats with hippocampal damage show increased marking.

A two-platform task reveals a deficit in the ability of rats to return to the start location in the water maze

The ability of rats to return to the start location was examined with a 4-arm radial water maze. The task required rats to find 2 hidden platforms in sequence. Rats were released from 1 of 3 arms and there was a platform located in the fourth arm. Once a rat found this platform, a 2nd platform was raised in another location, which was either the start location, for 1 group, or another fixed location, for a control group. Across 3 experiments, all rats learned the location of the 1st fixed platform in 80 to 120 trials. However, rats had difficulty finding a 2nd platform if it was at the start location. Control groups revealed that rats could learn 2 platform locations and that the difficulty in learning to return to the start location did not seem to be attributable to its aversive nature. In separate groups, exposure to the start location was increased by starting the rats from an initially stable platform. Rats still did not readily learn to return to the start location. The authors suggest that start location, when varied, cannot readily be used to define the location of a hidden platform.

Lessons from human progeroid syndromes

A number of human genes have been identified in which mutations can lead to the accelerated emergence of features of senescence. Studies of these genes, and of the functions of their protein products, may lead to a clearer understanding of the nature of senescence, and could provide clues for ways in which ageing might be retarded.

Levels of DNA damage are unaltered in mice overexpressing human catalase in nuclei

Two types of transgenic mice were generated to evaluate the role of hydrogen peroxide in the formation of nuclear DNA damage. One set of lines overexpresses wild-type human catalase cDNA, which is localized to peroxisomes. The other set overexpresses a human catalase construct that is targeted to the nucleus. Expression of the wild-type human catalase transgene was found in liver, kidney, skeletal muscle, heart, spleen, and brain with muscle and heart exhibiting the highest levels. Animals containing the nuclear-targeted construct had a similar pattern of expression with the highest levels in muscle and heart, but with lower levels in liver and spleen. In these animals, immunofluorescence detected catalase present in the nuclei of kidney, muscle, heart, and brain. Both types of transgenic animals had significant increases of catalase activities compared to littermate controls in most tissues examined. Despite enhanced activities of catalase, and its presence in the nucleus, there were no changes in levels of 8OHdG, a marker of oxidative damage to DNA. Nor were there differences in mutant frequencies at a Lac Z reporter transgene. This result suggests that in vivo levels of H(2)O(2) may not generate 8OHdG or other types of DNA damage. Alternatively, antioxidant defenses may be optimized such that additional catalase is unable to further protect nuclear DNA against oxidative damage.

Molecular mechanisms of late life dementias

A brief overview of the molecular pathology of dementia of the Alzheimer type (DAT), frontotemporal dementias (FTD), and Lewy body dementias (LBD) is preceded by a discussion of the evolutionary biological basis for the types of gene action responsible for the emergence of late life dementias. The beta amyloid cascade theory of the pathogenesis of DAT still predominates, but possible upstream events are being explored. Some familial forms of FTD have been shown to result from dominant mutations in the microtubular associated protein tau. A key element in pathogenesis is a shift in the ratios of various isoforms. Rare forms of Parkinson disease have been associated with dominant mutations in alpha synuclein, a protein of probable importance for synaptic plasticity. Aberrations in the metabolism of this protein (which is found in Lewy body fibrillar material) may therefore be of importance to the genesis of some LBD cases.

Some new directions for research on the biology of aging

A highly selective, eclectic, and personal view of new directions and new opportunities for research on the biology of aging is briefly outlined. Some concern is raised regarding the present emphasis on the use of centenarians for the definition of genetic loci responsible for unusually robust retention of structure and function. More progress is likely to be made were we to focus on the genetic basis for "elite" aging in middle-aged subjects examined for very specific phenotypes, as these are likely to be far less polygenic. Descriptive gerontology is entering a renaissance, given such new clinical tools as functional MRI and basic science tools such as functional genomics and proteomics. Advances in genomics should expedite answers to such questions as why some avian species have exceptionally long lifespans despite unusual loads of oxidative stress. One hopes to see renewed mechanistic studies, using such tools, at the systems levels. New methodologies are permitting the evaluation of stochastic alterations in gene structure and function in postreplicative cells. The exciting work on molecular misreading should prompt us to reexplore the Orgel hypothesis as it applies to such cell types. Epigenetic shifts in gene expression that occur in association with sexual maturation and the cessation of growth may have deleterious consequences late in the life course. It will therefore be important for gerontologists to investigate the molecular biology of pubescence. Finally, our community should investigate the impact of environmental "gerontogens," agents that accelerate specific processes of aging and specific senescent phenotypes.

Overexpression of wild-type and nuclear-targeted catalase modulates resistance to oxidative stress but does not alter spontaneous mutant frequencies at APRT

Animal cells generate hydrogen peroxide as a byproduct of energy metabolism. In the presence of reduced metals H(2)O(2) can decompose to a highly reactive hydroxyl radical that attacks essentially all organic molecules, including DNA. We wished to determine if overexpression of catalase and/or the targeting of the enzyme to the nucleus could protect cells from oxidative stress and reduce the frequency of mutation. Wild-type human catalase, which localizes to peroxisomes, and a modified construct, which targets catalase to the nucleus, were overexpressed in a murine line of embryonic carcinoma cells (P19). Both constructs enhanced the resistance of the cells to hydrogen peroxide, but sensitized them to bleomycin. Overexpression of wild-type catalase protected cells against paraquat, while nuclear targeting sensitized them to this agent. Expression of neither construct significantly altered spontaneous mutant frequencies at the endogenous murine adenosine phosphoribosyl transferase (APRT) locus; however, nuclear-targeted catalase prevented an increase in mutant frequency after H(2)O(2) treatment. These results suggest that endogenous levels of hydrogen peroxide may not generate DNA damage in vivo, or that such damage may be efficiently repaired in murine embryonic carcinoma cells.

Broadly altered expression of the mRNA isoforms of FE65, a facilitator of beta amyloidogenesis, in Alzheimer cerebellum and other brain regions

FE65 is a key "adapter" protein that links a multiprotein complex to an intracellular domain of beta-amyloid precursor protein (betaPP). Its overexpression modulates the trafficking of betaPP and facilitates the generation of beta-amyloid (Abeta). FE65 is predominantly expressed in brain tissues. An exon 9-inclusive isoform is exclusively expressed in neurons, and an exon 9-exclusive isoform is only expressed in non-neuronal cells. We quantitated the two isoforms in middle temporal cortex, middle frontal cortex, cerebellar cortex and caudate nucleus of 17 Alzheimer disease (AD) patients, 12 normal controls and 9 non-AD neurodegenerative disease controls by reverse transcription-competitive polymerase chain reaction (RT-cPCR). Expression of the two isoforms was significantly and differentially altered, with a 30-57% decrease in levels of the neuronal form (P < 0.05-0.002) and a 73-135% increase in levels of non-neuronal form (P < 0.02-0.001), in the temporal and frontal cortex of AD brains. These alterations presumably reflect advanced neurodegenerative processes of these regions. Surprisingly, expression of both isoforms was significantly up-regulated by 42-66% in the cerebellar cortex and caudate nucleus of AD brains when compared to normal brains (P < 0.05-0.005). Diffuse Abeta-positive plaques were observed in the cerebellum of these AD subjects but not in the normal controls. Selective up-regulation of only the FE65 neuronal isoform was seen in the cerebellar cortex in association with other neurodegenerative diseases (largely Parkinson's disease). Because FE65 modulates trafficking of betaPP toward the production of Abeta, the up-regulation of FE65 in AD cerebellum may be relevant to the genesis of diffuse plaques. Thus, early biochemical alterations in AD, not complicated by advanced pathology, may be beneficially investigated in the less-affected regions of the brain, such as the cerebellum.

Multiple points of entry into a circular enclosure prevent place learning despite normal vestibular orientation and cue arrays: evidence for map resetting

This study identified sources of map orientation critical for successful spatial problem solving by rats of a plus maze embedded in water. Disorientation slowed, but it did not prevent acquisition of goal location. Use of a circular enclosure with multiple points of entry prevented reliable goal location. A single entry point enabled the rats to locate a fixed goal. A cue array within the enclosure was ineffective in providing orientation. These data suggest that stable map orientation can be derived from entry location when enclosure geometry is uniformative, but is not readily taken from cue arrays. They further suggest that map orientation is reset when rats enter an enclosure.

Cellular Werner phenotypes in mice expressing a putative dominant-negative human WRN gene

Mutations at the Werner helicase locus (WRN) are responsible for the Werner syndrome (WS). WS patients prematurely develop an aged appearance and various age-related disorders. We have generated transgenic mice expressing human WRN with a putative dominant-negative mutation (K577M-WRN). Primary tail fibroblast cultures from K577M-WRN mice showed three characteristics of WS cells: hypersensitivity to 4-nitroquinoline-1-oxide (4NQO), reduced replicative potential, and reduced expression of the endogenous WRN protein. These data suggest that K577M-WRN mice may provide a novel mouse model for the WS.

Multiple points of entry into a circular enclosure prevent place learning despite normal vestibular orientation and cue arrays: evidence for map resetting

This study identified sources of map orientation critical for successful spatial problem solving by rats of a plus maze embedded in water. Disorientation slowed, but it did not prevent acquisition of goal location. Use of a circular enclosure with multiple points of entry prevented reliable goal location. A single entry point enabled the rats to locate a fixed goal. A cue array within the enclosure was ineffective in providing orientation. These data suggest that stable map orientation can be derived from entry location when enclosure geometry is uniformative, but is not readily taken from cue arrays. They further suggest that map orientation is reset when rats enter an enclosure.

Alternatively spliced isoforms of FE65 serve as neuron-specific and non-neuronal markers

FE65 is predominantly expressed in brain and is especially rich in the regions with the highest densities of neurons. The FE65 protein binds to an intracellular domain of the beta-amyloid precursor protein (betaPP) and may modulate the production of beta-amyloid peptide (AP). One of FE65 exons, a mini-exon (exon 9, 6 bp), is alternatively spliced, giving rise to two isoforms varying only in 6 base pairs. We quantitated the two isoforms by a sensitive reverse transcription-competitive polymerase chain reaction technique, and characterized their expressions in various tissues and cell cultures, and the kinetics of expression of the two isoforms in P19 embryonal carcinoma cell lines during neuronal differentiation. Our results show that the exon 9-inclusive (E9) form, the more abundant form in brain, was exclusively expressed in neurons, while the exon 9-exclusive (DeltaE9) form was widely expressed in all non-neuronal cells, but was not expressed in differentiated neurons. When P19 cells were differentiated to neurons, expression of FE65 was significantly up regulated ( approximately 30-fold) and the splicing pattern of the FE65 pre-mRNA was switched from the DeltaE9 pattern to the E9 form. Based upon their distinctive expression patterns, these two isoforms may serve as neuronal and non-neuronal markers, and determination of their ratios may have applications in neuropathological diagnosis.

Werner helicase expression in human fetal and adult aortas

Werner syndrome is a human progeroid syndrome caused by mutations at the Werner helicase locus (WRN). Progeroid features and diseases associated with aging (including arteriosclerosis) do not become apparent until after puberty. We entertained two alternative hypotheses to explain the post-pubertal onset: 1) WRN expression is induced at the time of puberty, its earlier functions being satisfied by another member of that family of helicases; and 2) it is expressed at all ages, but the phenotype of deficiency becomes apparent only after puberty. We report initial experiments consistent with the second hypothesis. Steady-state levels of WRN mRNA in aortic tissues were determined by semiquantitative reverse transcription-polymerase chain reaction. WRN mRNA was detectable as early as 49 days of gestation (the earliest available material). There was no statistically significant change in these levels between fetal and adult tissues. The presence of the WRN protein in fetal aorta was confirmed by Western analysis. This rules out the possibility that Werner syndrome phenotypes manifest after the puberty because of peripubertal induction of WRN expression.

Open field motor patterns and object marking, but not object sniffing, are altered by ibotenate lesions of the hippocampus

Objectmarking and object sniffing were assessed in an open field during six 5-min trials in unoperated Long-Evans rats and rats with ibotenate lesions of the hippocampus and/or neocortex. Object marking was higher in hippocampally lesioned rats than in unoperated rats. Object marking did not differ between neocortically lesioned rats and unoperated rats. Object sniffing durations and visits did not differ between unoperated and hippocampally lesioned rats nor between unoperated and neocortically lesioned rats. A new object elicited longer sniffing by both unoperated and hippocampally lesioned rats. Neocortically lesioned rats did not show this effect. There were no effects of the new object on marking. Computerized tracing of open field paths revealed a smaller perimeter track for hippocampally lesioned rats than for unoperated rats. This difference reflected distinct ambulatory patterns. Hippocampally lesioned rats made stereotyped hind-limb pivots at each corner, while normal rats used forelimb pivots or reared and reoriented adjacent to the wall. Rearing was lower in hippocampally lesioned rats, and higher in neocortically lesioned rats, than in unoperated rats. These data indicate that investigative object behavior (sniffing) is resistant to the effects of hippocampal damage, while object-elicited marking and motoric output may be profoundly altered. The data on sniffing suggest either that (1) the noticeability of the objects used elicited investigative behaviors in hippocampally damaged rats comparable to those of novelty-induced exploration in normal rats or (2) object exploration is not used to create a spatial map, and, hence, not disturbed by hippocampal loss. Object marking may require spatial locale information to be exercised normally, or may index the mediation of an olfactory-modulated behavioral pattern through the hippocampal system.

The Werner syndrome protein is involved in RNA polymerase II transcription

Werner syndrome (WS) is a human progeroid syndrome characterized by the early onset of a large number of clinical features associated with the normal aging process. The complex molecular and cellular phenotypes of WS involve characteristic features of genomic instability and accelerated replicative senescence. The gene involved (WRN) was recently cloned, and its gene product (WRNp) was biochemically characterized as a helicase. Helicases play important roles in a variety of DNA transactions, including DNA replication, transcription, repair, and recombination. We have assessed the role of the WRN gene in transcription by analyzing the efficiency of basal transcription in WS lymphoblastoid cell lines that carry homozygous WRN mutations. Transcription was measured in permeabilized cells by [3H]UTP incorporation and in vitro by using a plasmid template containing the RNA polymerase II (RNA pol II)-dependent adenovirus major late promoter. With both of these approaches, we find that the transcription efficiency in different WS cell lines is reduced to 40-60% of the transcription in cells from normal individuals. This defect can be complemented by the addition of normal cell extracts to the chromatin of WS cells. Addition of purified wild-type WRNp but not mutated WRNp to the in vitro transcription assay markedly stimulates RNA pol II-dependent transcription carried out by nuclear extracts. A nonhelicase domain (a direct repeat of 27 amino acids) also appears to have a role in transcription enhancement, as revealed by a yeast hybrid-protein reporter assay. This is further supported by the lack of stimulation of transcription when mutant WRNp lacking this domain was added to the in vitro assay. We have thus used several approaches to show a role for WRNp in RNA pol II transcription, possibly as a transcriptional activator. A deficit in either global or regional transcription in WS cells may be a primary molecular defect responsible for the WS clinical phenotype.

Cell fusion corrects the 4-nitroquinoline 1-oxide sensitivity of Werner syndrome fibroblast cell lines

We have shown that Werner syndrome (WRN) fibroblast cell lines are unusually sensitive to the DNA-damaging agent 4-nitroquinoline 1-oxide (4NQO), though not to gamma radiation or to hydrogen peroxide. The fusion of 4NQO-sensitive WRN and 4NQO-resistant control fibroblast cell lines generated proliferating WRN x control cell hybrids that expressed WRN protein and were 4NQO-resistant. These results establish the recessive nature of 4NQO sensitivity in WRN cell lines and provide a cellular assay for WRN protein function.

Neurotrophic factors [activity-dependent neurotrophic factor (ADNF) and basic fibroblast growth factor (bFGF)] interrupt excitotoxic neurodegenerative cascades promoted by a PS1 mutation

Although an excitotoxic mechanism of neuronal injury has been proposed to play a role in chronic neurodegenerative disorders such as Alzheimer's disease, and neurotrophic factors have been put forward as potential therapeutic agents, direct evidence is lacking. Taking advantage of the fact that mutations in the presenilin-1 (PS1) gene are causally linked to many cases of early-onset inherited Alzheimer's disease, we generated PS1 mutant knock-in mice and directly tested the excitotoxic and neurotrophic hypotheses of Alzheimer's disease. Primary hippocampal neurons from PS1 mutant knock-in mice exhibited increased production of amyloid beta-peptide 42/43 and increased vulnerability to excitotoxicity, which occurred in a gene dosage-dependent manner. Neurons expressing mutant PS1 exhibited enhanced calcium responses to glutamate and increased oxyradical production and mitochondrial dysfunction. Pretreatment with either basic fibroblast growth factor or activity-dependent neurotrophic factor protected neurons expressing mutant PS1 against excitotoxicity. Both basic fibroblast growth factor and activity-dependent neurotrophic factor stabilized intracellular calcium levels and abrogated the increased oxyradical production and mitochondrial dysfunction otherwise caused by the PS1 mutation. Our data indicate that neurotrophic factors can interrupt excitotoxic neurodegenerative cascades promoted by PS1 mutations.

Increased vulnerability of hippocampal neurons from presenilin-1 mutant knock-in mice to amyloid beta-peptide toxicity: central roles of superoxide production and caspase activation

Many cases of early-onset inherited Alzheimer's disease (AD) are caused by mutations in the presenilin-1 (PS1) gene. Overexpression of PS1 mutations in cultured PC12 cells increases their vulnerability to apoptosis-induced trophic factor withdrawal and oxidative insults. We now report that primary hippocampal neurons from PS1 mutant knock-in mice, which express the human PS1M146V mutation at normal levels, exhibit increased vulnerability to amyloid beta-peptide toxicity. The endangering action of mutant PS1 was associated with increased superoxide production, mitochondrial membrane depolarization, and caspase activation. The peroxynitrite-scavenging antioxidant uric acid and the caspase inhibitor benzyloxycarbonyl-Val-Ala-Asp-fluoromethyl ketone protected hippocampal neurons expressing mutant PS1 against cell death induced by amyloid beta-peptide. Increased oxidative stress may contribute to the pathogenic action of PS1 mutations, and antioxidants may counteract the adverse property of such AD-linked mutations.

Increased vulnerability of hippocampal neurons to excitotoxic necrosis in presenilin-1 mutant knock-in mice

Excitotoxicity, a form of neuronal injury in which excessive activation of glutamate receptors results in cellular calcium overload, has been implicated in the pathogenesis of Alzheimer disease (AD), although direct evidence is lacking. Mutations in the presenilin-1 (PS1) gene on chromosome 14 are causally linked to many cases of early-onset inherited AD (refs. 5,6). We generated PS1 mutant mice (PS1M146VKI) that express the PS1 M146V targeted allele at normal physiological levels. Although PS1M146VKI mice have no overt mutant phenotype, they are hypersensitive to seizure-induced synaptic degeneration and necrotic neuronal death in the hippocampus. Cultured hippocampal neurons from PS1M146VKI mice have increased vulnerability to death induced by glutamate, which is correlated with perturbed calcium homeostasis, increased oxidative stress and mitochondrial dysfunction. Agents that suppress calcium influx or release and antioxidants protect neurons against the excitotoxic action of the PS1 mutation. These findings establish a direct link between a genetic defect that causes AD and excitotoxic neuronal degeneration, and indicate new avenues for therapeutic intervention in AD patients.

Transgenic mice over-expressing the C-99 fragment of betaPP with an alpha-secretase site mutation develop a myopathy similar to human inclusion body myositis

Inclusion body myositis (IBM) is the most common muscle disease in the elderly. Amyloid-beta protein (A beta) has been shown to accumulate abnormally in the vacuolated fibers and to localize to amyloid-like fibrils in muscles from IBM patients. We studied the skeletal muscles from a line of transgenic mice over-expressing the carboxyl-terminal 99 amino acids (C99) of the beta-amyloid precursor protein (betaPP) with a substitution of lysine-612 to valine (K612V), intended to abolish alpha-secretase recognition and to preserve the A beta domain of C99. The majority (87%) of the 24-month-old transgenic mice showed myopathic changes, and approximately one-third of them had degenerating fibers with sarcoplasmic vacuoles and thioflavin-S-positive deposits. Ultrastructurally, the inclusions were aggregates of short thin amyloid-like fibrils, 6 to 8 nm in diameter. These features are similar to those of human IBM. Immunocytochemistry using an antibody against A beta showed membranous staining in most muscle fibers of transgenic mice, as well as granular or vacuolar cytoplasmic staining in the atrophic fibers. Western blots showed a high level of accumulation of carboxyl-terminal fragments of betaPP in the muscles of the transgenic mice with the most severe IBM-like lesions. The expression of IBM-like lesions was age dependent. These transgenic mice provide a model for the study of IBM and for the peripheral expression of a key element in the pathogenesis of Alzheimer disease.

The human FE65 gene: genomic structure and an intronic biallelic polymorphism associated with sporadic dementia of the Alzheimer type

The FE65 protein binds to the intracellular domain of the beta-amyloid precursor protein (betaPP) and may modulate the internalization of betaPP. This gene is highly expressed in regions of the brain specifically affected in dementia of the Alzheimer type (DAT). As a prelude to further investigations of the role of FE65 in the metabolism of betaPP and in the pathogenesis of DAT, we have determined the entire genomic structure and sequence of human FE65 and have discovered several polymorphisms in this gene. Human FE65 contains 14 exons ranging in size from 6 to 735 bp. All splice sites conform to consensus sequences except for the donor site of intron 10. The 5' end of FE65 mRNA was identified by rapid amplification of the cDNA 5' end and is 31 bp longer than the previously published cDNA sequence. The 5'-flanking region of this gene is TATA-less and is very GC-rich with at least five putative Sp1 binding sites. In comparison to the genomic rat FE65 sequence, the human FE65 5'-untranslated region is 134 bp longer and has an extra exon (exon 1, 86 bp). To identify mutations/polymorphisms of the coding regions of this gene, we performed blinded analysis of 457 Caucasian case-control samples from a large epidemiological study of sporadic DAT. Screening was conducted by single-strand conformation polymorphism. Four minor variants were found within the coding region, with frequencies between 0.002 and 0.015; two of the four result in amino acid substitutions. The more informative biallelic polymorphism (a trinucleotide deletion and a single base substitution) was found within intron 13 (84 bp), which interrupts two exons encoding the betaPP binding site. The frequency of the minor allele in this intron was 0.097 in DAT cases and 0.161 in controls (chi2=7.78, P=0.0054). Having at least one copy of the minor allele was associated with a decreased risk for DAT (chi2=9.20, P<0.005, odds ratio=0.49, 95% CI 0.31-0.77). Multivariate analysis showed that this association was independent of the APOE genotype. These results suggest that either FE65 itself or a closely linked gene influences the pathogenesis of sporadic DAT. The interaction of FE65 with betaPP and the association of a FE65 polymorphism with DAT lend credence to the hypothesis that the metabolism of betaPP is central to the pathogenesis of common sporadic forms of DAT.

Introduction: genetic determinants of mid- and late-life dementias

We introduce a series of papers dealing with genetic aspects of a subset of dementias of mid-life and late-life in order to illustrate four principles. First, there appear to be many genetic loci with the potential to modulate susceptibility to such dementias. Second, most of those so far discovered are autosomal dominants and none are autosomal recessives. Third, the autosomal dominant mutations are individually rare. Their frequencies in a given population are likely to be functions of genetic drift. Fourth, despite their rarity, they may inform us about the pathogenesis of more common late-life dementias, notably dementias of the Alzheimer type, which have polygenic determinants. The most important such modulation so far discovered involves polymorphic forms of the APOE locus.

Werner helicase is localized to transcriptionally active nucleoli of cycling cells

Mutations at the Werner helicase locus (WRN) are responsible for the Werner syndrome (WS), a "caricature of aging." We have localized the Werner protein (WRNp) to the nucleoli of replicating mammalian cells, where its appearance is associated with transcriptional activity. A dramatic reduction of the nucleolar signal and of [3H]uridine incorporation occurred when cultures were made quiescent or were exposed to 4-nitroquinoline-1-oxide (4NQO), to which WS cells are particularly susceptible. Total cellular levels of WRNp, however, did not change, and virtually all WRNp was in the nuclear fractions, consistent with translocation to the nucleoplasm and/or masking of the epitopes. The 4NQO-induced altered state of WRNp was prevented by Na3VO4, but not by okadaic acid, suggesting that WRNp localization/function is partially regulated by kinases/phosphatases for Tyr substrates on WRNp or interacting proteins. The repression of rDNA transcription by 4NQO was not reversed by Na3VO4. We suggest that physiological states and genotoxic agents modulate the interaction of WRNp with rDNA, consistent with a role of WRNp in rDNA transcription.

Structure and function of the human Werner syndrome gene promoter: evidence for transcriptional modulation

The Werner syndrome (WS) is an autosomal recessive segmental progeroid syndrome caused by mutations in a novel member ( WRN ) of the RecQ family of helicases. Somatic WS cells are hypermutable and have elongated S phases, suggesting possible defects in DNA replication and/or repair. As an initial approach to the investigation of how this locus might be responsive to DNA damage, we determined the structure of the human WRN promoter. The WRN promoter region has two transcription initiation sites and exhibits several features characteristic of so-called constitutive promoters, including the absence of TATA and CAAT boxes. A luciferase reporter assay revealed that the upstream promoter was used 2-10-fold less frequently than the downstream promoter, the variation being a function of cell type. The activity of the WRN promoter was dramatically reduced in cells from WS patients. The reduction of activity was not seen in three other promoters tested, including one TATA-less promoter and one TATA-containing promoter. This is consistent with the presence of a positive regulatory mechanism of WRN expression.

Genetics and the pathobiology of ageing

Genetics offers a powerful approach to the elucidation of mechanisms underlying specific components of the senescent phenotype of our species. Perhaps thousands of gene variations have escaped the force of natural selection and thus play roles in the genesis of different patterns of ageing in man. It is possible that a subset of these genes may be of particular importance in how most people age. While variations at the Werner helicase locus could be one such example, several lines of evidence suggest that mutation at that locus leads to a 'private' mechanism of ageing. It will be important, however, to investigate polymorphisms underlying the regulation of expression of this gene in the general population. Polymorphisms (normally occurring variants of a gene, or sequence of DNA), rather than mutations, may also prove to be more relevant to our understanding of the differing susceptibilities of people to common disorders such as late onset Alzheimer's disease. Polymorphic forms of the Apolipoprotein E gene is a good example. It remains to be seen if the pathogenetic framework (beta amyloidosis) derived from studies of the several rare mutations responsible for early onset familial forms of the disease proves relevant to the pathogenesis of the vastly more prevalent sporadic forms of the disorder. In contrast to the satisfying progress on the genetics of the diseases of ageing, research on the genetic basis for unusually robust retention of structure and function in old age has been neglected and requires a higher priority for the future. Such research should include studies of environmental agents and should address mechanisms of 'sageing', a stage in the life course characterized by an extensive utilization of behavioural and physiological adaptations to compensate for functional declines. For the genetics of longevity, we have to turn to genetically tractable organisms such as nematodes and fruit flies. Such studies have provided significant support for the oxidative stress theory of ageing. It will be important to learn more about the age-related pathologies and pathophysiologies of these organisms.

An apoptosis-inducing genotoxin differentiates heterozygotic carriers for Werner helicase mutations from wild-type and homozygous mutants

Immortalized B lymphocytes from Werner syndrome subjects are shown to be hypersensitive to 4-nitroquinoline-1-oxide (4NQO), supporting earlier work on T lymphocytes. We also show that B cell lines from clinically normal heterozygous carriers exhibit sensitivities to this genotoxic agent, which are intermediate to those of wild-type and homozygous mutants. 4NQO is shown to induce an apoptotic response. These data encourage research on DNA repair with such cell lines and raise the question of an enhanced sensitivity of the relatively prevalent heterozygous carriers to certain environmental genotoxic agents.

The Werner syndrome protein is a DNA helicase

Werner syndrome (WS) is an uncommon autosomal recessive disorder characterized by premature aging. The clinical manifestations of WS, including atherosclerosis and osteoporosis, appear early in adulthood, and death in the fourth to sixth decade commonly ensues from myocardial infarction or cancer. In accord with the aging phenotype, cells from WS patients have a reduced replicative life span in culture. Genomic instability is observed at the cytogenetic level in the form of chromosome breaks and translocations and at the molecular level by multiple large deletions. The Werner syndrome gene (WRN) has recently been cloned. The predicted product is a 1,432-amino-acid protein whose central domain is homologous to members of the RecQ family of DNA helicases. Such homology does not necessarily mean that WRN encodes an active helicase. For example, the Saccharomyces cerevisiae RAD26 gene protein and the human transcription-repair coupling factor CSB (Cockayne syndrome 8) are highly homologous to known helicases, yet neither encodes an active helicase. Moreover, the Bloom's syndrome gene (BLM), discovered before WRN, is also homologous to the RecQ family of DNA helicases, though we still await demonstration that it encodes an active helicase. Here we report that the WS protein does indeed catalyze DNA unwinding.

Alzheimer's presenilin mutation sensitizes neural cells to apoptosis induced by trophic factor withdrawal and amyloid beta-peptide: involvement of calcium and oxyradicals

Most autosomal dominant inherited forms of early onset Alzheimer's disease (AD) are caused by mutations in the presenilin-1 (PS-1) gene on chromosome 14. PS-1 is an integral membrane protein with six to nine membrane-spanning domains and is expressed in neurons throughout the brain wherein it is localized mainly in endoplasmic reticulum (ER). The mechanism or mechanisms whereby PS-1 mutations promote neuron degeneration in AD are unknown. Recent findings suggest links among deposition of amyloid beta-peptide (Abeta), oxidative stress, disruption of ion homeostasis, and an apoptotic form of neuron death in AD. We now report that expression of the human PS-1 L286V mutation in PC12 cells increases their susceptibility to apoptosis induced by trophic factor withdrawal and Abeta. Increases in oxidative stress and intracellular calcium levels induced by the apoptotic stimuli were exacerbated greatly in cells expressing the PS-1 mutation, as compared with control cell lines and lines overexpressing wild-type PS-1. The antiapoptotic gene product Bcl-2 prevented apoptosis after NGF withdrawal from differentiated PC12 cells expressing mutant PS-1. Elevations of [Ca2+]i in response to thapsigargin, an inhibitor of the ER Ca2+-ATPase, were increased in cells expressing mutant PS-1, and this adverse effect was abolished in cells expressing Bcl-2. Antioxidants and blockers of calcium influx and release from ER protected cells against the adverse consequences of the PS-1 mutation. By perturbing cellular calcium regulation and promoting oxidative stress, PS-1 mutations may sensitize neurons to apoptotic death in AD.