Congo red birefringent structures in the hypothalamus in senile dementia of the Alzheimer type

Hypothermia as a risk factor for Alzheimer disease

Alzheimer disease (AD), which is associated with chronic and progressive neurodegeneration, is the most prevalent cause of dementia linked to aging. Among the risk factors for AD, age stands as the greatest one, with the vast majority of people with AD being 65 years of age or older. Nevertheless, the pathophysiologic mechanisms underlying the link between aging and the development of AD, although not completely understood, might reveal important aspects for the understanding of this pathology. Thus, there is significant evidence that the impaired thermal homeostasis associated with normal aging leads to a variety of metabolic changes that could be associated with AD development. In this chapter, we assess the clinical and biochemical evidence implicating hypothermia as a risk factor for the development of AD and the impact of hypothermia on the two pathologic hallmarks of AD: accumulation of senile plaques of amyloid-beta and neurofibrillary tangles of aberrant hyperphosphorylated tau protein.

Impaired thermoregulation and beneficial effects of thermoneutrality in the 3×Tg-AD model of Alzheimer's disease

The sharp rise in the incidence of Alzheimer's disease (AD) at an old age coincides with a reduction in energy metabolism and core body temperature. We found that the triple-transgenic mouse model of AD (3×Tg-AD) spontaneously develops a lower basal body temperature and is more vulnerable to a cold environment compared with age-matched controls. This was despite higher nonshivering thermogenic activity, as evidenced by brown adipose tissue norepinephrine content and uncoupling protein 1 expression. A 24-hour exposure to cold (4 °C) aggravated key neuropathologic markers of AD such as: tau phosphorylation, soluble amyloid beta concentrations, and synaptic protein loss in the cortex of 3×Tg-AD mice. Strikingly, raising the body temperature of aged 3×Tg-AD mice via exposure to a thermoneutral environment improved memory function and reduced amyloid and synaptic pathologies within a week. Our results suggest the presence of a vicious cycle between impaired thermoregulation and AD-like neuropathology, and it is proposed that correcting thermoregulatory deficits might be therapeutic in AD.

Cerebrospinal fluid melanin-concentrating hormone (MCH) and hypocretin-1 (HCRT-1, orexin-A) in Alzheimer's disease

Ancillary to decline in cognitive abilities, patients with Alzheimer’s disease (AD) frequently suffer from behavioural and psychological symptoms of dementia (BPSD). Hypothalamic polypeptides such as melanin-concentrating hormone (MCH) and hypocretin-1 (HCRT-1, orexin-A) are promoters of sleep-wake regulation and energy homeostasis and are found to impact on cognitive performance. To investigate the role of MCH and HCRT-1 in AD, cerebrospinal fluid (CSF) levels were measured in 33 patients with AD and 33 healthy subjects (HS) using a fluorescence immunoassay (FIA). A significant main effect of diagnosis (F(1,62) = 8.490, p<0.01) on MCH levels was found between AD (93.76±13.47 pg/mL) and HS (84.65±11.40 pg/mL). MCH correlated with T-tau (r = 0.47; p<0.01) and P-tau (r = 0.404; p<0.05) in the AD but not in the HS. CSF-MCH correlated negatively with MMSE scores in the AD (r = −0.362, p<0.05) and was increased in more severely affected patients (MMSE_≤20) compared to HS (p<0.001) and BPSD-positive patients compared to HS (p<0.05). In CSF-HCRT-1, a significant main effect of sex (F(1,31) = 4.400, p<0.05) with elevated levels in females (90.93±17.37 pg/mL vs. 82.73±15.39 pg/mL) was found whereas diagnosis and the sex*diagnosis interaction were not significant. Elevated levels of MCH in patients suffering from AD and correlation with Tau and severity of cognitive impairment point towards an impact of MCH in AD. Gender differences of CSF-HCRT-1 controversially portend a previously reported gender dependence of HCRT-1-regulation. Histochemical and actigraphic explorations are warranted to further elucidate alterations of hypothalamic transmitter regulation in AD.

Reduced histamine levels and H3receptor antagonist-induced histamine release in the amygdala of Apoe?/? mice

The histamine H(3) receptor is a constitutively active G protein-coupled receptor for the neurotransmitter histamine that serves a negative feedback function. A role for the histamine H(3) receptor has been suggested in neurodegenerative diseases, such as Parkinsons disease and Alzheimer's disease. Mice deficient in apolipoprotein E (apoE), a protein involved in development, regeneration, neurite outgrowth, and neuroprotection, show increased measures of anxiety and reduced sensitivity to effects of histamine H(3) receptor antagonists on measures of anxiety. In this study, we tested whether in mice lacking apoE (Apoe-/-) histamine levels and histamine release in brain areas involved in the regulation of anxiety are altered. H(3) receptor antagonist-induced histamine release was lower in the amygdala of Apoe-/- than wild-type mice. In contrast, there were no genotype differences in histamine release in the hypothalamus. Consistent with these data, histamine immunohistochemistry revealed lower total and synaptic histamine levels in the central nucleus of the amygdala of Apoe-/- than wild-type mice. Such changes were not seen in the hypothalamus, hippocampus, or cortex. In Apoe-/- mice, chronically decreased histamine levels and reduced histamine release in the amygdala might contribute to increased measures of anxiety.

Mouse behavioural analysis in systems biology

Molecular techniques allowing in vivo modulation of gene expression have provided unique opportunities and challenges for behavioural studies aimed at understanding the function of particular genes or biological systems under physiological or pathological conditions. Although various animal models are available, the laboratory mouse (Mus musculus) has unique features and is therefore a preferred animal model. The mouse shares a remarkable genetic resemblance and aspects of behaviour with humans. In this review, first we describe common mouse models for behavioural analyses. As both genetic and environmental factors influence behavioural performance and need to be carefully evaluated in behavioural experiments, considerations for designing and interpretations of these experiments are subsequently discussed. Finally, common behavioural tests used to assess brain function are reviewed, and it is illustrated how behavioural tests are used to increase our understanding of the role of histaminergic neurotransmission in brain function.

Estrogen receptors and metabolic activity in the human tuberomamillary nucleus: changes in relation to sex, aging and Alzheimer’s disease

The human tuberomamillary nucleus (TMN), that is the sole source of histamine in the brain, is involved in arousal, learning and memory and is impaired in Alzheimer's disease (AD) as shown by the presence of cytoskeletal alterations, a reduction in the number of large neurons, a diminished neuronal metabolic activity and decreased histamine levels in the hypothalamus and cortex. Experimental data and the presence of sex hormone receptors suggest an important role of sex steroids in the regulation of the function of TMN neurons. Therefore, we investigated sex-, age- and Alzheimer-related changes in estrogen receptor alpha and beta (ERalpha and ERbeta) in the TMN. In addition, metabolic activity changes of TMN neurons were determined by measuring Golgi apparatus (GA) and cell size. In the present study, ERalpha immunocytochemical expression in AD patients did not differ from that in elderly controls. However, a larger amount of cytoplasmic ERbeta was found in the TMN cells of AD patients. Earlier studies, using the GA size as a parameter, have shown a clearly decreased metabolic activity in the TMN neurons in AD. In the present study, the size of the GA did not change during aging, indicating the absence of strong metabolic changes. Cell size of the TMN neurons appeared to increase during normal aging in men but not in women. Concluding, the enhanced cytoplasmic expression of ERbeta in the TMN may be involved in the diminished neuronal metabolism of these neurons in AD patients.

Formation of filamentous tau aggregations in transgenic mice expressing V337M human tau

Formation of neurofibrillary tangles (NFTs) is the most common feature in several neurodegenerative diseases, including Alzheimer's disease (AD). Here we report the formation of filamentous tau aggregations having a beta-sheet structure in transgenic mice expressing mutant human tau. These mice contain a tau gene with a mutation of the frontotemporal dementia parkinsonism (FTDP-17) type, in which valine is substituted with methionine residue 337. The aggregation of tau in these transgenic mice satisfies all histological criteria used to identify NFTs common to human neurodegenerative diseases. These mice, therefore, provide a preclinical model for the testing of therapeutic drugs for the treatment of neurodegenerative disorders that exhibit NFTs.

Decreased brain histamine-releasing factor protein in patients with Down syndrome and Alzheimer's disease

Histamine-releasing factor (HRF) stimulates secretion of histamine that is widely distributed in brain and released as neurotransmitter. Several studies suggested that histaminergic deficits could contribute to the cognitive decline in Alzheimer's disease (AD). Based upon deranged histamine metabolism in brain of patients with AD and Down Syndrome (DS), we aimed to study HRF in brain of AD and DS. We used two-dimensional gel electrophoresis, matrix-assisted laser desorption ionization mass spectroscopy and specific software to quantify HRF. HRF was significantly reduced in temporal cortex, thalamus and caudate nucleus of DS and in temporal cortex of AD as compared to controls. This is the first report to show decreased HRF brain levels in DS and AD suggesting the explanation for the decreased cognitive function in neurodegenerative/dementing disorders.

Pick's disease: cytoskeletal changes in the hypothalamic lateral tuberal nucleus

Basolateral portions of the human hypothalamus contain an extended nuclear gray, the lateral tuberal nucleus (LTN), which undergoes conspicuous pathological changes in a number of neurodegenerative diseases. The present study points to the severe affliction of this nucleus in Pick's disease (PID). Immunoreactions for abnormally phosphorylated tau-protein permit identification of the permutations. Only a fraction of the abnormal fibrillary material developing in the course of the disease shows a pronounced argyrophilia. Key features are the Pick bodies (PBs) which contain an argyrophilic material. Unusual non-spherical PBs develop in the LTN as flat structures with peripheral indentations. Small teardrop-like Pick neurites (PNs) emerge in varicose widenings of neuronal processes and display a much weaker argyrophilia. The characteristic alterations seen in PID reliably can be differentiated from lesions of the LTN which slowly emerge in the course of Alzheimer's disease (AD).

No vasopressin cell loss in the human hypothalamus in aging and Alzheimer's disease

The total number of immunocytochemically identified vasopressin (AVP) cells was determined morphometrically in the paraventricular (PVN) and dorsolateral part of the supraoptic nucleus (dl-SON) of the human hypothalamus in 30 subjects ranging in age from 15 to 97 years, including 10 Alzheimer's disease (AD) patients. The aim of the present study was to test the hypothesis that the increased activity of AVP neurons reported earlier is accompanied by an absence of cell loss in these nuclei in senescence and AD. The results show that numbers of immunoreactive AVP cells in the PVN and dl-SON do not decline during aging or in AD. During aging, the number of neurons expressing AVP even increased in the PVN of control subjects. The nuclear diameter of the AVP cells in the PVN and dl-SON showed an increase in old AD patients. It is concluded that no cell loss occurs in the AVP cell population in the PVN and dl-SON during aging and in AD, and that AVP expression increases in the PVN during normal aging, but not in AD.

Functional neuroanatomy and neuropathology of the human hypothalamus

The human hypothalamus is involved in a wide range of functions in the developing, adult and aging subject and is responsible for a large number of symptoms of neuroendocrine, neurological and psychiatric diseases. In the present review some prominent hypothalamic nuclei are discussed in relation to normal development, sexual differentiation, aging and a number of neuropathological conditions. The suprachiasmatic nucleus, the clock of the brain, shows seasonal and circadian variations in its vasopressin neurons. During normal aging, but even more so in Alzheimer's disease, the number of these neurons decreases. In homosexual men this nucleus is larger than in heterosexual men. The difference between the sexually dimorphic nuclei of men and women arises between the ages of 2-4 to puberty. In adult men this nucleus is twice as large as in adult women. In the process of aging, a sex-dependent decrease in cell number occurs. The vasopressin and oxytocin cells of the supraoptic and paraventricular nucleus are present in adult numbers as early as mid-gestation. Lower oxytocin neuron numbers are found in Prader-Willi syndrome, AIDS and Parkinson's disease. Familial hypothalamic diabetes insipidus is based upon a point mutation in the vasopressin-neurophysin-glycopeptide gene. Parvicellular corticotropin-releasing hormone-containing neurons in the paraventricular nucleus increase in number and are activated during the course of aging. In post-menopausal women, the infundibular or arcuate nucleus contains hypertrophic neurons containing oestrogen receptors. These neurons may be involved in the initiation of menopausal flushes. The nucleus tuberalis lateralis may be involved in feeding behaviour and metabolism. In Huntington's disease the majority of its neurons is lost; in Alzheimer's disease it shows very strong cytoskeletal alterations. Tuberomammillary nucleus neurons contain, e.g., histamine or galanine, and project to the cortex. Strong cytoskeletal changes, as well as plaques and tangles are found in this nucleus in Alzheimer's disease. The various hypothalamic nuclei are probably involved in many functions and symptoms of which only a minority has been revealed.

Tau and ubiquitin in the human hypothalamus in aging and Alzheimer's disease

Immunocytochemical staining of hypothalamic cell groups with four antibodies to Alzheimer paired helical filaments (PHF) (i.e., anti-PHF serum 60e and monoclonal antibody (mAb) Alz-50, both directed against normal and abnormally phosphorylated tau; mAb tau-1, which recognizes tau; and mAb 3-39 to PHF, which recognizes the carboxy terminal domain of ubiquitin) revealed a clear distinction between 12 Alzheimer's disease (AD) patients and seven controls in the hypothalamus. Dystrophic neurites, which appeared to be the most specific components in AD, were most conspicuous after Alz-50 staining. However, Alz-50 also stained neuronal cytoplasm and normal, thin, beaded neurites in the paraventricular nucleus (PVN) of controls, even of young cases. This staining was clearly distinct from the staining of cytoplasm and dystrophic neurites in the PVN of Alzheimer patients. The abundant staining of dystrophic neurites and cell bodies in the nucleus tuberalis lateralis (NTL) in AD, in which no neuronal loss is observed, suggests that alterations in cytoskeletal markers do not necessarily indicate impending cell death. Moreover, the cytoskeletal changes in the NTL, sexually dimorphic and suprachiasmatic nuclei in AD indicate that this condition is not restricted to cortical areas or nuclei projecting to the cortex. Consequently, the pathophysiological implications of cytoskeletal staining in AD are at present far from clear. The human hypothalamus may not only provide a better insight into the pathogenesis of Alzheimer's disease, but could also be of help in the neuropathological diagnosis of this condition.

Brain banking and the human hypothalamus--factors to match for, pitfalls and potentials

The study of an increasing number of processes occurring in the human brain can be carried out on autopsy material. The availability of this material, whether fresh, frozen or fixed, makes it possible to develop methodologies for studying the neuroanatomical and neurochemical aspects of the human brain. It has also become possible in recent years to correlate functional changes with neurochemical changes and with neuroanatomical abnormalities in disease states. Some compounds and structures are damaged irreversibly within minutes after death and some brain components are known to disintegrate within seconds. This led to the widespread idea that autopsy material would not be suitable for basic research purposes and would not supply the necessary answers on the various fundamental questions regarding processes occurring in normal or diseased brain. However, from data published in recent years in which autopsy material has been routinely used, it becomes more and more evident that this is a misconception. There is an increasing number of reports based on the use of normal and pathological human brain tissue obtained by autopsies in spite of the fact that there is a worrying continuous decline in autopsy rate which causes serious concern among scientists world-wide (Anderson and Hill, 1989). It also became evident that when using the proper fixation procedures, sufficient structural integrity is retained in the tissue to allow morphological and morphometrical studies (Swaab and Uylings, 1988). Electron microscopic examination of synaptosomal preparations from post-mortem human brain showed them to be only slightly less pure than preparations from fresh tissue although there was some degree of damage (Hardy et al., 1982). Agonal state effects the stability of brain compounds and causes brain hypoxia. This again forms a tremendous difficulty for the study of human neurological and psychiatric diseases as one of the frequent causes of death is bronchopneumonia which leads to brain hypoxia and results in pronounced lactic acidosis. The Netherlands Brain Bank has succeeded to partly circumvent some of the serious problems encountered in providing human tissue for research by performing rapid autopsies with an average post-mortem delay of 2-4 h. This has become possible by a close collaboration of numerous nursing homes in Amsterdam and its vicinity and with the neuropathologists of the Free University in Amsterdam. We also measure the pH of the tissue as indicator of agonal state in order to reveal unsuitable specimens. The human hypothalamus contains various nuclei manifesting a wide variety of changes in different conditions.(ABSTRACT TRUNCATED AT 400 WORDS)

Anatomy of the human hypothalamus (chiasmatic and tuberal region)

The hypothalamus sensu stricto consists of the chiasmatic, the tuberal and the mamillary region. The present study is confined to the poorly myelinated chiasmatic and tuberal region. Both regions harbor many nuclear grays with relatively clear-cut boundaries embedded in an ill-defined nerve cell assembly referred to as the hypothalamic gray. Prominent components of the chiasmatic region are the magnocellular neurosecretory complex (supraoptic nucleus, paraventricular nucleus, accessory neurosecretory nucleus), the sexually dimorphic intermediate nucleus, the suprachiasmatic and retrochiasmatic nuclei. The dominating structure of the tuberal region is the complex of the ventromedial, posteromedial and dorsomedial nuclei supplemented by the periventricular and infundibular nuclei. Lateral portions of the tuber cinereum harbor the lateral tuberal nucleus and the tuberomamillary nucleus. The lateral tuberal nucleus exhibits pronounced cell loss in Huntington's chorea and is also severely involved in cases of dementia with argyrophilic grains. The large nerve cells of the tuberomamillary nucleus show particularly severe affection in both Alzheimer's (intraneuronal neurofibrillary changes) and Parkinson's disease (Lewy bodies).

Chapter 17 The hypothalamic lateral tuberal nucleus: normal anatomy and changes in neurological diseases

The lateral tuberal nucleus is a circumscribed cell mass in the lateral posterior part of the hypothalamus, containing about 60000 neurons. It can be recognized in man and higher primates, probably not in other mammals. Its neurotransmitter content and connections with other parts of the brain are as yet unknown. But receptors for corticotropin-releasing factor and somatostatin, as well as muscarinic cholinergic receptors, benzodiazepine receptors and N-methyl-D-aspartate receptors have been localized within the confines of the nucleus. The lateral tuberal nucleus is affected in a number of human neurodegenerative diseases. Changes in Parkinson's disease are the least obvious: Lewy bodies appear in small amounts, the majority of them apparently lying outside a neuronal perikaryon. Neuronal loss does not occur. In Alzheimer's disease the number of neurons seems to be normal as well. Rarely silver staining tangles occur, and the deposition of A4/beta-protein in amorphous plaques is moderate. Yet, NTL neurons stain heavily in Alz-50 immunocytochemistry, while Alz-50 staining in NTL neurites is very dense. These changes are interpreted as indicating early Alzheimer-related pathology. In Huntington's disease the NTL loses neurons. This loss is related to the severity of the disease: patients who first display motor disturbances at an early age will lose more neurons than those who start later. The relation between these clinical characteristics and the severity of neuronal loss is such, that it seems likely that NTL neurons possess a special vulnerability for the effect of the Huntington gene. This could be related to their NMDA-receptor content. It is hypothesized that the NTL is involved in a neuronal network that regulates feeding and metabolism. NTL pathology may explain the peculiar catabolic state of many patients with Alzheimer's or Huntington's diseases.

Oxytocin cell number in the human paraventricular nucleus remains constant with aging and in Alzheimer's disease

Total cell numbers in the paraventricular nucleus (PVN) were previously shown to remain unaltered with aging and in AD. The aim of the present study was to determine the aging pattern of the oxytocin (OXT) cell population in the PVN. For this purpose, the number of immunocytochemically identified oxytocin cells was determined in the PVN of the human hypothalamus in 20 control subjects ranging in age from 15 to 90 years and in 10 Alzheimer's disease (AD) patients aged 46 to 97 years. The results show that the number of OXT cells in the PVN is similar in males and females and remains unaltered in senescence and AD. It is concluded that the remarkable stability of the PVN in these conditions also applies for the subpopulation of OXT cells in this nucleus and that reports in the literature on diminished OXT secretion in AD do not seem to be based on a decrease in the number of OXT expressing neurons from the PVN.

Histamine neurons in human hypothalamus: anatomy in normal and Alzheimer diseased brains

The anatomy of histamine-immunoreactive cell bodies in normal adult human brain was examined in detail. In addition, the distribution of these cells in three cases of Alzheimer's disease was compared to the distribution of neurofibrillary tangles. Histamine-immunoreactive cell bodies were confined to the tuberal and posterior hypothalamus, forming the tuberomammillary nuclear complex. Most of the about 64,000 histamine neurons were large and multipolar. They comprised four distinct parts: (i) a major ventral part corresponding to the classical tuberomammillary nucleus, (ii) a medial part including the supramammillary nucleus and part of the posterior hypothalamic area, (iii) a caudal paramammillary part, and (iv) a minor lateral part. The parts showed some similarity with the subgroups in rat. In human, as compared to rat, the histamine neurons occupy a larger proportion of the hypothalamus. Numerous neurofibrillary tangles were found in the Alzheimer hypothalami, concentrated in the tuberomammillary area. Most of them were of globular type and extracellular, and only a minority were histamine immunoreactive. They may represent remnants of degenerated tuberomammillary neurons.