AD Lesions Research Articles

Induction of GITRL expression in human keratinocytes by Th2 cytokines and TNF‐α: implications for atopic dermatitis

Glucocorticoid-induced TNF receptor-related protein ligand (GITRL), a ligand for the T cell co-stimulatory molecule GITR, is expressed by keratinocytes and involved in chemokine production. The expression of GITRL in skin inflammation remains unknown. This study investigated cytokine regulation of keratinocyte GITRL expression. Glucocorticoid-induced TNF receptor expression was evaluated in cytokine-treated human epidermal keratinocytes (HEK)s, murine PAM 212 cell line, murine and human skin explants by real time PCR, flow cytometry and immunostaining. Functional responses to GITR fusion protein were examined by real time PCR and ELISA. GITRL expression in AD and psoriasis was studied by immunohistochemistry. Skin biopsies from STAT6VT transgenic mice, which develop spontaneous atopic skin inflammation, were found by immunofluoresence, to have increased keratinocyte GITRL expression. Exposure to Th2 cytokines augmented GITRL mRNA expression in the murine PAM 212 keratinocytic cell line and murine skin explants. In contrast, GITRL mRNA and protein expression was only increased in HEKs and human skin explants in the presence of the combination of TNF-α and Th2 cytokines. A synergistic effect of Th2 cytokines and GITR fusion protein on production of CCL17, the Th2 chemokine, by murine keratinocytes was demonstrated. Immunohistochemical staining showed that acute AD lesions have increased expression of GITRL compared with normal skin, chronic AD lesions and psoriatic plaques. Our studies demonstrate that GITRL expression is augmented by Th2 cytokines and TNF-α in keratinocytes. Increased GITRL expression in acute AD skin lesions is shown. This observation suggests a link between cytokine-regulated keratinocyte GITRL expression and its role in inflammatory responses in AD.

339 Sensitization to Contactants in Patients with Atopic Dermatitis

BackgroundAtopic dermatitis (AD) is a chronic inflammatory pruritic skin disease with extensive interindividual variation and multiple internal and external factors. In this study, we evaluated whether the atopic dermatitis severity (SCORAD index), gender, age, age onset or the presence of Allergic rhinitis (AR), Allergic conjunctivitis (AC) or Asthma has an influence on contact sensitization to common contactant allergens.Methods30 AD patients were evaluated in the Division of Allergy of Federal University of São Paulo. AD was diagnosed according to the Hanifin and Rajka's criteria and all patients were currently under regular treatment. Questionnaire (age, gender, age at onset, presence of AR, Asthma or AC), clinical examination and skin patch tests were carried out on all patients at the beginning of the study. Patients in regular use of oral CE; topical CE and/or calcineurin inihibitor use or having active AD lesions in the back were excluded from the study. Patch test was applied onto the upper back with 8 mm chambers attached with hypoallergenic tape and removed after 48 hours. The interpretation of the test reactions was performed at 48th and 96th hour.ResultsPositive Patch-test reaction occurred in 14/30 (46.6%). Among those with positive patch-test, Nickel was responsible for 42.8% and Thimerosal for 28.5%. All patients finished the study and no adverse reactions occurred. Positive and negative Patch-test groups found no statistically significant difference (P > 0.05) when comparing: SCORAD index, sex, age, age of onset and presence of AC, AR or asthma.ConclusionsAccording to our results, sensitization to common contact allergens in AD patients was more frequent than in normal subjects. Although we did not found an explanation to these findings, indiscriminate exposure to topic products should be avoided so that new sensitization or risk of deteriorating AD occurs. The benefits of avoidance to the contactants considered positive should be evaluated in the follow-up of these patients.

Editorial [Hot Topic: The Complex and Multifactorial Nature of Alzheimers Disease (Guest Editors: Karim Alkadhi and Jason Eriksen)

In 1907 Alois Alzheimer, a Bavarian psychiatrist, published a seminal two-page article, entitled “A Characteristic Disease of the Cerebral Cortex”[1], followed by the publication of his second article “On Certain Peculiar Diseases of Old Age”, that detailed the clinical, biographical, and neuropathological history of two patients admitted under his care for pre-senile dementia [2]. In these reports, Alzheimer described these patients as suffering from a “state of profound mental impairment with prominent agnostic, aphasic, and apractic disturbances,” which he brilliantly attributed to small “miliary foci” and/or dense “bundles of fibrils” [1,2]. Even after a century of research, we continue to use the association between cognitive decline and proteinaceous deposits as classic hallmarks of Alzheimer’s disease. With the spectacular advancements in medicine and technology in recent decades, life expectancy has significantly increased, and diseases once deemed untreatable can now be prevented or even cured. Nevertheless, even with the progress that has been made in improving human health, this shift in demographics has been accompanied by the increased appearance of chronic diseases associated with ageing. Among such disorders, Alzheimer’s disease remains one of the most feared, as it is an irreversible, largely age-related neurodegenerative brain disorder that is responsible for the gradual and insidious failure of cognitive function. Ageing is one of the most well-established risk factors for Alzheimer’s disease [3]; this disorder has emerged as the predominant form of dementia in the elderly, affecting one person in ten over the age of 65, and 50 percent of individuals over the age of 85 [4,5]. Although the specific causes of idiopathic Alzheimer’s disease remain unknown, the vast majority of genetic and pathological observations made over that the past two decades suggests that an initial and critical accumulation of amyloid-beta (Aβ) is a key initiating factor in the pathogenesis of this disease [6], leading to a variety of biochemical changes that include neuroinflammation, synaptic dyfunction, and tauopathy, eventually resulting in cell death, a process that has been dubbed the “amyloid cascade hypothesis.” Nevertheless, in the earliest stages of Alzheimer’s disease, β-amyloidosis correlates poorly with the degree of cognitive decline, implying that other of factors may contribute to AD progression. Recent reports show that as many as 30% of individuals older than age 75 who are considered clinically normal at the time of death, have neuropathological hallmarks of AD when autopsied. Despite the substantial AD lesions in these individuals, a lack of apparent dysfunction may reflect compensatory mechanisms that prevent cognitive decline [7-9]. In this Hot Topic issue of Current Neuropharmacology, we have asked notable experts in the field to comment on some of the promising directions in Alzheimer’s disease research that appear to be amenable to pharmacological intervention. In this issue, Niedowicz provides an insightful evaluation of AD therapeutics in light of the recent results from human clinical trials. Martin provides a review on the use of the aged canines as a powerful model of Alzheimer’s disease. Our experts also cover notable advances in drug targets, including the development of a unique class of high potency gamma secretase modulatory compounds (Bulic), the impact of calcineurin hyperactivity (Reese), and the pharmacological manipulation of heat shock proteins (Dickey) in Alzheimer’s disease. Together, we hope these reviews will provide important insights into the molecular pathways underlying the pathogenesis of this disorder, and the potential counter-measures that may serve as future therapeutic strategies for the treatment of Alzheimer’s disease.

Soluble amyloid β-protein dimers isolated from Alzheimer cortex directly induce Tau hyperphosphorylation and neuritic degeneration

Alzheimer disease is a major cause of cognitive failure, and a pathogenically related but more subtle process accounts for many cases of mild memory symptoms in older humans. Insoluble fibrillar plaques of amyloid β-proteins (Aβ) and neurofibrillary deposits of hyperphosphorylated tau proteins are the diagnostic lesions of AD, but their temporal mechanistic relationship has long been debated. The recent recognition that small, diffusible oligomers may be the principal bioactive form of Aβ raises the key question of whether these are sufficient to initiate cytoskeletal change and neurite degeneration. A few studies have examined the effects of oligomers of synthetic Aβ peptides of one defined length at supraphysiological concentrations, but the existence of such assemblies in the AD brain is not established. Here, we isolated Aβ dimers, the most abundant form of soluble oligomer detectable in the human brain, from the cortices of typical AD subjects and found that at subnanomolar concentrations, they first induced hyperphosphorylation of tau at AD-relevant epitopes in hippocampal neurons and then disrupted the microtubule cytoskeleton and caused neuritic degeneration, all in the absence of amyloid fibrils. Application of pure, synthetic dimers confirmed the effects of the natural AD dimers, although the former were far less potent. Knocking down endogenous tau fully prevented the neuritic changes, whereas overexpressing human tau accelerated them. Coadministering Aβ N-terminal antibodies neutralized the cytoskeletal disruption. We conclude that natural dimers isolated from the AD brain are sufficient to potently induce AD-type tau phosphorylation and then neuritic dystrophy, but passive immunotherapy mitigates this.

Is there a neuropathology difference between mild cognitive impairment and dementia?

The number of studies that have investigated the neuropathology of mild cognitive impairment (MCI) is small, but growing. In this paper we have restricted our focus to the consideration of the presence and extent of postmortem findings relevant to the neuropathology of Alzheimer's disease. We have drawn from studies that have investigated the postmortem neurobiology of the brains of persons with cognitive function at the interface between unimpaired normal function and mild but definite dementia. The data derived from these studies suggest that i) the brains of persons with MCI evidence significant neuropathological and neurobiological changes relative to those without cognitive impairment; ii) in general, the neuropathological and neurobiological changes are qualitatively similar to those observed in the brains of persons with frank AD-like dementia; and iii) the neuropathological and neurobiological brain changes associated with MCI are quantitatively less than those of persons who meet criteria for dementia. Thus, the available, albeit limited, data suggests that MCI is associated with the early stages of the neurobiological and neuropathological changes that culminate in the florid lesions of AD; including the accumulation of neuritic plaques, neurofibrillary tangles, synaptic and neurotransmitter associated deficits, and significant neuronal cell death.

Differential nuclear and nucleolar hypertrophy of anterior and posterior cingulate neurons in asymptomatic subjects with AD pathology

We measured cell bodies, nuclei, and nucleoli in anterior cingulate (AC) and posterior cingulate (PC) gyri in 9 subjects with asymptomatic Alzheimer's disease from the Baltimore Longitudinal Study of Aging (BLSA). Asymptomatic AD is characterized by AD pathology in the brain of normal subjects. We examined three other group: 9 old controls (OC), 9 with MCI (MCI) and 8 with AD dementia (AD). Volumes were estimated using unbiased stereology. Table 1. Results show a significant increase of the nuclei in AC and of the nucleoli both in AC and PC. We observed atrophy of AC cell bodies in MCI and AD, but not in PC. The hypertrophy of the neuronal nuclei and nucleoli may reflect a reactive process that allows the brain of ASYMAD subjects to function normally despite the presence of AD lesions, or represent the earliest stages of neurodegeneration. In MCI and AD, we found significant atrophy of neuronal cell body in AC, but not in PC. Compared to the changes in AC, the lack of nuclear enlargement and body atrophy in PC suggests that this region is involved later in the course of the disease or is less vulnerable to it.

The morphological basis of mental dysfunction in Parkinson's disease

Mental dysfunction including dementia in Parkinson's disease (PD), the incidence of which averages 20–40%, is suggested to have six-fold lifetime risk compared to age-matched controls. It is caused by a variety of functional and pathological lesions ranging from damage to subcortical–cortical networks to cortical and limbic Lewy body and neuritic Alzheimer pathologies, the relationship and impact of which are still under discussion. Based on two consecutive autopsy series of PD, with prevalence of cognitive impairment of 33% to 35.7%, its essential morphological changes and their impact on the natural history (survival) are discussed. Whereas cortical Lewy body stages 5 and 6 without additional pathologies only rarely were associated with dementia, around 20% of demented PD cases were classified as dementia with Lewy bodies (DLB) with variable degrees of Alzheimer (AD) pathology, and around one third showed severe neuritic AD lesions which occurred in PD patients with later disease onset and significantly shorter survival. Frequent close relations in the severity between α-synuclein and tau-pathologies suggest synergistic reaction and common underlying pathogenesis of both lesions. Clinico-pathological studies in PD showed a significantly negative relation between cognitive impairment and neuritic AD lesions somewhat different from that in AD, suggesting that neuritic AD pathology, either alone or in combination with cortical and limbic Lewy bodies, are major causes of mental and cognitive dysfunction in PD.

In the Spotlight or the Shadow of Alzheimer? The Role of Cerebrovascular Disease in Dementia

Vascular Dementia: Cerebrovascular Mechanisms and Clinical Management. Robert H. Paul, Ronald Cohen, Brian R. Ott, and Stephen Salloway (Eds.). 2004. Totowa, NJ: Humana Press, 356 pp., $145.00, £91.00 (HB).Interest in how vascular factors contribute to dementia is ascendant, propelled by a number of factors. One is the widespread use of MRI, which is a highly sensitive (if not always specific) test for cerebrovascular lesions. A second is a string of epidemiological reports revealing that Alzheimer's disease shares many of the well established risk factors for cardiovascular and cerebrovascular disease (Skoog & Gustafson, 2003). Recent autopsy studies using cohorts obtained outside of the potentially winnowing influence of the Alzheimer's disease centers have reminded us that vascular lesions are common in patients with dementia (Neuropathology Group of the Medical Research Council Cognitive Function and Ageing Study, 2001). The Nun study report suggesting that infarcts create an additive or greater effect on mental function in concert with AD pathology (Snowdon et al., 1997) received particularly wide exposure and helped revive interest in combined effects of AD and ischemic lesions. Finally, the discovery that polymorphisms of the apoE gene, long of interest in cardiovascular disease, strongly modify the risk of AD suggested the possibility of shared pathophysiological mechanisms between AD and vascular dementia (Panza et al., 2004; Strittmatter & Roses, 1995). The volumeVascular Dementia, edited by Paul, Cohen, Ott and Salloway, is thus a timely resource for those interested in the numerous issues surrounding the role of vascular factors in dementia.

α-Synuclein Lesions in Normal Aging, Parkinson Disease, and Alzheimer Disease: Evidence from the Baltimore Longitudinal Study of Aging (BLSA)

In a recent autopsy study, Mikolaenko et al (1), examining 117 elderly individuals, found α-synuclein (AS) lesions in a total of 25%, i.e. in 100% of PD cases (n = 7), 31.5% of brains with AD lesions (n = 56), and only 8.3% among older controls (n = 36). Among AD cases, the frequency of AS lesions was higher in those with higher neuritic plaque scores than in those with higher neurofibrillary tangle scores. While AS lesions were rare in aged controls, the coexistence of AS and Aβ pathologies in AD suggested similar pathogenic mechanisms. These data on the frequency of AS lesions are at variance to …

AD lesions and infarcts in demented and non‐demented Japanese‐American men

Neocortical neuritic plaques and neurofibrillary tangles are hallmark neuropathological lesions of dementia. Concomitant cerebrovascular lesions increase dementia severity in patients meeting neuropathological criteria for Alzheimer's disease and contribute to cognitive impairment in persons with mild entorhinal Alzheimer lesions. This study investigates whether individuals with sparse neocortical neuritic plaques experience increased odds of crossing the threshold to clinical dementia when they have coexistent cerebrovascular lesions. Dementia examinations were given to 3,734 men during the 1991-1993 Honolulu-Asia Aging Study examination and to 2,603 men during the 1994-1996 examination. Lesion quantification was done without clinical data. Among 333 autopsied men, 120 had dementia, 115 had marginal results, and 98 had normal cognition. In men with neurofibrillary tangles, dementia frequency increased with increasing neuritic plaque density, and increased further in the presence of cerebrovascular lesions. The association was strongest in men with sparse neuritic plaques (1-3/mm(2)) where dementia frequency more than doubled with coexistent cerebrovascular lesions (45 vs 20%). Among all dementia cases, 24% were linked to cerebrovascular lesions. Findings suggest cerebrovascular lesions are associated with a marked excess of dementia in cases with low neuritic plaque frequency. Prevention of cerebrovascular lesions may be critically important in preserving late-life cognitive function.

Overproduction of Th2-specific chemokines in NC/Nga mice exhibiting atopic dermatitis-like lesions.

We have examined the expression of chemokines and their receptors in the atopic dermatitis-like (AD-like) lesions of NC/Nga mice. Such lesions develop when the mice are kept in conventional conditions, but not when they are kept isolated from specific pathogens. The thymus- and activation-regulated chemokine TARC is unexpectedly highly expressed in the basal epidermis of 14-week-old mice with lesions, whereas it is not expressed in the skin without lesions. Production of TARC by keratinocytes was confirmed by culturing murine keratinocytic cell line cells (PAM212) with TNF-alpha, IFN-gamma, or IL-1beta. Expression of another Th2 chemokine, macrophage-derived chemokine (MDC), was observed in the skin from mice kept in both conventional and pathogen-free conditions, but expression of MDC was increased severalfold in the skin with lesions. The cellular origin of MDC was identified to be dermal dendritic cells. Infiltration of the skin by IL-4-producing T cells and mast cells, and the increase of CCR4 mRNA in the skin, coincided with the development of AD lesions. These observations indicate that TARC and MDC actively participate in the pathogenesis of AD-like lesions in NC/Nga mice and that these Th2 chemokines could be novel targets for intervention therapy of AD in humans.

Quantification of pathological lesions in the frontal and temporal lobe of ten patients diagnosed with Pick's disease.

The densities of Pick bodies (PB), Pick cells (PC), senile plaques (SP) and neurofibrillary tangles (NFT) in the frontal and temporal lobe were determined in ten patients diagnosed with Pick's disease (PD). The density of PB was significantly higher in the dentate gyrus granule cells compared with the cortex and the CA sectors of the hippocampus. Within the hippocampus, the highest densities of PB were observed in sector CA1. PC were absent in the dentate gyrus and no significant differences in PC density were observed in the remaining brain regions. With the exception of two patients, the densities of SP and NFT were low with no significant differences in mean densities between cortical regions. In the hippocampus, the density of NFT was greatest in sector CA1. PB and PC densities were positively correlated in the frontal cortex but no correlations were observed between the PD and AD lesions. A principal components analysis (PCA) of the neuropathological variables suggested that variations in the densities of SP in the frontal cortex, temporal cortex and hippocampus were the most important sources of heterogeneity within the patient group. Variations in the densities of PB and NFT in the temporal cortex and hippocampus were of secondary importance. In addition, the PCA suggested that two of the ten patients were atypical. One patient had a higher than average density of SP and one familial patient had a higher density of NFT but few SP.

The biochemical pathway of neurofibrillary degeneration in aging and Alzheimer's disease.

To determine the spatiotemporal mapping of neurofibrillary degeneration (NFD) in normal aging and the different stages of AD. The pathophysiologic significance of AD lesions, namely amyloid plaques and neurofibrillary tangles, is still unclear, especially their interrelationship and their link with cognitive impairment. The study included 130 patients of various ages and different cognitive statuses, from nondemented control subjects (n = 60, prospective study) to patients with severe definite AD. Paired helical filaments (PHF)-tau and Abeta were used as biochemical and histologic markers of NFD and amyloid plaques, respectively. NFD with PHF-tau was systematically present in variable amounts in the hippocampal region of nondemented patients age >75 years. When NFD was found in other brain areas, it was always along a stereotyped, sequential, hierarchical pathway. The progression was categorized into 10 stages according to the brain regions affected: transentorhinal cortex (S1), entorhinal (S2), hippocampus (S3), anterior temporal cortex (S4), inferior temporal cortex (S5), medium temporal cortex (S6), polymodal association areas (prefrontal, parietal inferior, temporal superior) (S7), unimodal areas (S8), primary motor (S9a) or sensory (S9b, S9c) areas, and all neocortical areas (S10). Up to stage 6, the disease could be asymptomatic. In all cases studied here, stage 7 individuals with two polymodal association areas affected by tau pathologic states were cognitively impaired. The relationship between NFD and Alzheimer-type dementia, and the criteria for a biochemical diagnosis of AD, are documented, and an association between AD and the extent of NFD in defined brain areas is shown.

Brain Infarction and the Clinical Expression of Alzheimer Disease-Reply

In Reply. —The analyses of Drs Mirra and Gearing indicate that brain infarcts are not associated with NFTs in the neocortex. Our analyses also indicated that brain infarcts were not associated with the number of NFTs, senile plaques, or neuritic plaques in the neocortex, suggesting that AD lesions and brain infarcts were likely to have occured independently of each other. While AD and brain infarction may represent separate disease processes, their combination may nonetheless increase the likelihood that dementia will occur. Among the participants in our study who met our neuropathologic criteria for AD (ie, abundant senile plaques and some NFTs in the neocortex), those with 1 or 2 lacunar infarcts in the basal ganglia, thalamus, or deep white matter had an especially high prevalence of dementia, compared with those without brain infarcts. The prevalence of dementia was 93% for those with such subcortical lacunar infarcts and 57% in those without infarcts.

Cholinesterase activity in the plaques, tangles and angiopathy of Alzheimer's disease does not emanate from amyloid

Previous histochemical observations in our laboratory have demonstrated the presence of butyrylcholinesterase and an enzymatically altered form of acetylcholinesterase activity in the plaques, tangles and amyloid-containing vessels of Alzheimer's disease. These findings suggested possible interactions between amyloid and cholinesterases. In this study we employed a cholinesterase biochemical assay to determine whether the amyloid precursor protein either had cholinesterase activity itself or influenced the enzymatic activity of cholinesterases. None of the three amyloid precursor sequences used (695, 751, 770, up to 16 μg/ml) exhibited any acetylcholinesterase or butyrylcholinesterase activity that could be detected by our method. In addition, none of the amyloid precursor proteins influenced the enzymatic activity of purified acetylcholinesterase or butyrylcholinesterase in a specific manner. It is therefore quite unlikely that amyloid can, by itself, account for the intense cholinesterase activity associated with the pathological lesions of AD.

Amyloid protein in Alzheimer's disease.

Progressive deposition of amyloid fibrils in senile plaques and in blood vessels is a pathological hallmark of Alzheimer's disease. The AD amyloid protein, called beta amyloid protein, or A4 protein, is derived from a much larger precursor protein, the gene for which has now been cloned, sequenced, and localized to chromosome 21. This chromosomal location is of great interest because it has long been known that all Down's patients over the age of 40 develop the classical neuropathological lesions of AD. An anonymous DNA marker, which segregates with cases of dominantly inherited AD, has also been found to be located on chromosome 21. It is now known, however, that this marker and the gene encoding the beta amyloid precursor protein are not tightly linked. The beta amyloid precursor protein gene appears to code for a normal cellular product whose function is not yet known. The gene is expressed not only in brain but also in many non-neural tissues. It is highly conserved in evolution. Two closely related alternative transcripts have recently been identified; these contain an insert showing homology to certain members of the Kunitz family of proteinase inhibitors. All evidence accumulated thus far suggests that the beta amyloid precursor protein gene is not abnormal in AD; therefore, recent research has focused on transcriptional, translational, or posttranslational events that may be implicated in the progressive deposition of beta amyloid protein in AD.