Jiang-Ning Zhou

Early neuropathological Alzheimer's changes in aged individuals are accompanied by decreased cerebrospinal fluid melatonin levels

Abstract: Neuropathology is the most reliable criterion for diagnosing Alzheimers disease (AD). A well‐established system for staging the spread of neuropathological changes in AD is available. The clinical use of a biomarker that reflects the neuropathological change occurring in brain tissue has not yet been established. Melatonin is a product that plays not only a major role in the regulation of the circadian rhythms but may also exert neuroprotective effects in AD. Melatonin levels were determined in ventricular postmortem cerebrospinal fluid (CSF) of 121 subjects. Braak staging and a modified Braak staging for cortex (MBSC) were used to evaluate the severity of AD neuropathology. The present study revealed that not only the Braak stages of AD, but also the MBSC were negatively correlated with CSF melatonin levels. By using MBSC, we now demonstrate for the first time that CSF melatonin levels were significantly decreased in the aged individuals with early neuropathological changes in the temporal cortex, where the AD process starts. Those individuals that did not have any neurofibrillary tangle (NFT) or neuritic plaque (NP) in the temporal cortex, had much higher melatonin levels (287 ± 68 and 280 ± 64 pg/mL, respectively) than those individuals that had a few NFTs and NPs (82 ± 4 and 39 ± 8 pg/mL, respectively) in the temporal cortex. These results suggest that the decrease in CSF melatonin levels may be an early event in the development of AD possibly occurring even before the clinical symptoms.

VIP neurons in the human SCN in relation to sex, age, and Alzheimer's disease

The brains of 46 control subjects and 21 Alzheimers disease (AD) patients were studied to determine whether there are age-related or AD-related changes in the vasoactive intestinal polypeptide (VIP) neuron population of the human suprachiasmatic nucleus (SCN). The number of VIP expressing neurons in the SCN of females, ranging in age from 10-91 years, did not change during normal aging. In males, however, the number of VIP neurons in the SCN was highest in the young subjects (10-40 years of age), after which, a dramatic decrease occurred in middle-aged subjects. This resulted in an age-dependent sex difference in the VIP cell population of the SCN: young males had twice as many VIP expressing SCN neurons as young females, whereas in the middle-aged groups, the females had twice as many VIP SCN neurons as the males. A significant decrease in the number of VIP expressing neurons in the SCN was found in female presenile AD patients, i.e., those younger than 65 years.

Decreased MT1 melatonin receptor expression in the suprachiasmatic nucleus in aging and Alzheimer's disease

The pineal hormone melatonin is involved in the regulation of circadian rhythms and feeds back to the central biological clock, the hypothalamic suprachiasmatic nucleus (SCN) via melatonin receptors. Supplementary melatonin is considered to be a potential treatment for aging and Alzheimers disease (AD)-related circadian disorders. Here we investigated by immunocytochemistry the alterations of the MT1 melatonin receptor, the neuropeptides vasopressin (AVP) and vasoactive intestinal peptide (VIP) in the SCN during aging and AD. We found that the number and density of AVP/VIP-expressing neurons in the SCN did not change, but the number and density of MT1-expressing neurons in the SCN were decreased in aged controls compared to young controls. Furthermore, both MT1-expressing neurons and AVP/VIP-expressing neurons were strongly diminished in the last neuropathological stages of AD (Braak stages V-VI), but not in the earliest stages (Braak stages I-II), compared to aged controls (Braak stage 0). Our study suggests that the MT1-mediated effects of melatonin on the SCN are disturbed during aging and even more so in late stage AD, which may contribute to the clinical circadian disorders and to the efficacy of therapeutic melatonin administration under these conditions.

Pineal clock gene oscillation is disturbed in Alzheimer’s disease, due to functional disconnection from the “master clock”

The suprachiasmatic nucleus (SCN) is the “master clock” of the mammalian brain. It coordinates the peripheral clocks in the body, including the pineal clock that receives SCN input via a multisynaptic noradrenergic pathway. Rhythmic pineal melatonin production is disrupted in Alzheimers disease (AD). Here we show that the clock genes hBmal1, hCry1, and hPer1 were rhythmically expressed in the pineal of controls (Braak 0). Moreover, hPer1 and hβ1‐adrenergic receptor (hβ1‐ADR) mRNA were positively correlated and showed a similar daily pattern. In contrast, in both preclinical (Braak I‐II) and clinical AD patients (Braak V‐VI), the rhythmic expression of clock genes was lost as well as the correlation between hPer1 and hβ1‐ADR mRNA. Intriguingly, hCry1 mRNA was increased in clinical AD. These changes are probably due to a disruption of the SCN control, as they were mirrored in the rat pineal deprived of SCN control. Indeed, a functional disruption of the SCN was observed from the earliest AD stages onward, as shown by decreased vasopressin mRNA, a clock‐controlled major output of the SCN. Thus, a functional disconnection between the SCN and the pineal from the earliest AD stage onward could account for the pineal clock gene changes and underlie the circadian rhythm disturbances in AD.—Wu, Y‐H., Fischer, D. F., Kalsbeek, A., Garidou‐Boof, M‐L., van der Vliet, J., van Heijningen, C., Liu, R‐Y., Zhou, J‐N., Swaab, D. F. Pineal clock gene oscillation is disturbed in Alzheimers disease, due to functional disconnection from the “master clock.” FASEB J. 20, E1171–E1180 (2006)

Distribution of MT1 melatonin receptor immunoreactivity in the human hypothalamus and pituitary gland: colocalization of MT1 with vasopressin, oxytocin, and corticotropin-releasing hormone.

Melatonin is implicated in numerous physiological processes, including circadian rhythms, stress, and reproduction, many of which are mediated by the hypothalamus and pituitary. The physiological actions of melatonin are mainly mediated by melatonin receptors. We here describe the distribution of the melatonin receptor MT1 in the human hypothalamus and pituitary by immunocytochemistry. MT1 immunoreactivity showed a widespread pattern in the hypothalamus. In addition to the area of the suprachiasmatic nucleus (SCN), a number of novel sites, including the paraventricular nucleus (PVN), periventricular nucleus, supraoptic nucleus (SON), sexually dimorphic nucleus, the diagonal band of Broca, the nucleus basalis of Meynert, infundibular nucleus, ventromedial and dorsomedial nucleus, tuberomamillary nucleus, mamillary body, and paraventricular thalamic nucleus were observed to have neuronal MT1 receptor expression. No staining was observed in the nucleus tuberalis lateralis and bed nucleus of the stria terminalis. The MT1 receptor was colocalized with some vasopressin (AVP) neurons in the SCN, colocalized with some parvocellular and magnocellular AVP and oxytocine (OXT) neurons in the PVN and SON, and colocalized with some parvocellular corticotropin‐releasing hormone (CRH) neurons in the PVN. In the pituitary, strong MT1 expression was observed in the pars tuberalis, while a weak staining was found in the posterior and anterior pituitary. These findings provide a neurobiological basis for the participation of melatonin in the regulation of various hypothalamic and pituitary functions. The colocalization of MT1 and CRH suggests that melatonin might directly modulate the hypothalamus–pituitary–adrenal axis in the PVN, which may have implications for stress conditions such as depression. J. Comp. Neurol. 499:897–910, 2006.

Urine formaldehyde level is inversely correlated to mini mental state examination scores in senile dementia

It is widely known that exogenous formaldehyde exposure induces human cognitive impairment and animal memory loss; and recent studies show that formaldehyde at pathological levels induces Aβ deposition and misfolding of tau protein to form globular amyloid-like aggregates. Endogenous formaldehyde may be a marker for progressive senile dementia. The aim of this study was to investigate the correlation of endogenous formaldehyde in urine of senile dementia and mini mental state examination (MMSE) scores. Formaldehyde level was analyzed by high-performance liquid chromatography (with fluorescence detection) in human urine from dementia patients (n=141), patients with hypertension (n=33) or diabetes (n=16) and healthy individuals (n=38), autopsy hippocampus samples from Alzheimers disease (AD) patients and brains of three types of AD animal model: namely, senescence accelerated mice (SAMP8), APP-transgenic mice and APP/PS1-transgenic mice. In a double-blind study, there was marked elevation of urine formaldehyde levels in patients (n=91) with dementia, and a slight increase in patients (n=50) with mild cognitive impairment. Urine formaldehyde level was inversely correlated with mini mental state examination scores (Rs=-0.441, p<0.0001). Furthermore, formaldehyde levels were significantly increased in the autopsy hippocampus from Alzheimers patients (n=4). In SAMP8 brains the formaldehyde level was significantly increased, suggesting that the endogenous formaldehyde is related to aging in mice. The brain formaldehyde level in APP/PS1-transgenic (n=8) mice at age of 3 months and APP-transgenic (n=8) mice at age of 6 months was increased (0.56 ± 0.02 mM), respectively, as compared with their respective age-matched controls, when these two types of AD-like animals, respectively, started to form Aβ deposits and memory loss obviously. According to the level of formaldehyde in the brain of the transgenic mice, we treated normal mice with formaldehyde (0.5mM, intraperitoneal administration) and observed the memory loss of the animal in Morris water maze trial. Cognitive impairments for the senile dementia are probably related to endogenous formaldehyde levels; and the mini mental state examination scores referred to the evaluation of urine formaldehyde level in dementia patients may be used as a non-invasive method for the investigation and diagnosis of senile dementia.

Alterations in the circadian rhythm of salivary melatonin begin during middle-age

Abstract: To investigate whether free melatonin may be better suited to reveal age‐related changes, we studied the circadian rhythm alterations in saliva melatonin levels during aging. Special attention was paid to the question as to how the free melatonin rhythms change in aging and when such changes take place. A total of 52 healthy volunteers participated in the study consisting of young, middle‐aged, old and the oldest groups. In each subject, a total of 12 time‐point salivary melatonin samples was taken over 24 hr. Of the 52 data sets, 51 exhibited significant circadian rhythm over 24 hr by using the base cosine function analysis to fit the data. A clear circadian rhythm of salivary melatonin was present in all age groups. The decline in nocturnal peak levels (amplitude) in salivary melatonin was found in old and the oldest subjects. Both the old and the oldest subjects showed an increased daytime (baseline) melatonin levels. The off‐set melatonin levels were more than two times higher in the oldest group than that in the other groups indicating a delayed phase of salivary melatonin. Most strikingly, we found that a step‐wise decrease in the circadian rhythms of saliva melatonin occurred early in life, around 40 yr of ages. The middle‐aged subjects had only 60% of the amplitude of the young subjects. In addition, the middle‐aged subjects showed the longest peak levels duration and the lowest daytime melatonin levels. The present study showed that the alterations in the circadian rhythms of salivary melatonin begin during middle‐age. Our results showed that salivary melatonin measurement is a reliable, sensitive and easy method to monitor changes in the circadian rhythms of melatonin during the course of aging.

Increased p75NTR expression in hippocampal neurons containing hyperphosphorylated τ in Alzheimer patients

Abstract p75 NTR , a low-affinity neurotrophin receptor, may be involved in the pathogenesis of Alzheimers disease (AD). The aim of present study was to detect the relationship between p75 NTR -containing neurons and the pretangles consisting of hyperphosphorylated τ stained by Alz-50 in the hippocampus of AD patients. Samples of hippocampus of 10 female AD patients and 10 nondemented female controls matched for age and postmortem delay were investigated immunocytochemically, and the stainings were quantified using an image analysis system. The results showed that: (i) p75 NTR was present in about half of the pyramidal neurons of the CA1–CA4 subfields of hippocampus. No difference was observed in the number of p75 NTR immunoreactive neurons in the CA1–CA4 subfields between the two groups. Interestingly, the ratio of p75 NTR expressing neurons to the total number of neurons as staining with thionin was significantly higher in the CA1 and CA2 subfields of AD hippocampus than in controls. (ii) There were a large number of Alz-50 neurons and double-labeled neurons containing p75 NTR and Alz-50 in the CA1 and CA2 subfields of AD patients. These results suggest that p75 NTR may be involved in the formation of tangles in the Alzheimer process.

Alterations of melatonin receptors MT1 and MT2 in the hypothalamic suprachiasmatic nucleus during depression

BACKGROUND The pineal hormone melatonin regulates circadian rhythms, largely by feedback on the central biological clock of the brain, the hypothalamic suprachiasmatic nucleus (SCN). This feedback is mediated by the melatonin receptors, melatonin receptor 1 (MT1) and melatonin receptor 2 (MT2). The circadian system may play a role in the pathophysiology of mood disorders, and indeed, melatonin-receptor agonists are considered a potential therapy for depression. METHOD In order to investigate melatonin receptors in the SCN during depression, and their relationship to the major neuropeptides in the SCN, vasopressin (AVP) and vasoactive intestinal peptide (VIP), we studied the SCN in 14 depressed patients (five major depression and nine bipolar disorder) and 14 matched controls by immunocytochemistry. RESULTS We show here that hypothalamic MT2 receptor immunoreactivity was limited to SCN, the supraoptic nucleus and paraventricular nucleus. We found that numbers of MT1-immunoreactive (MT1-ir) cells and AVP and/or VIP-ir cells were increased in the central SCN in depression, but numbers of MT2-ir cells were not altered. Moreover, the number of MT1-ir cells, but not MT2-ir cells was negatively correlated with age at onset of depression, while positively correlated with disease duration. CONCLUSION AND LIMITATIONS: Although every post-mortem study has limitations, MT1 receptors appeared specifically increased in the SCN of depressed patients, and may increase during the course of the disease. These changes may be involved in the circadian disorders and contribute to the efficacy of MT agonists or melatonin in depression. Moreover, we suggest that melatonin receptor agonists for depression should be targeted towards the MT1 receptor selectively.

Olfactory identification and apolipoprotein E ε4 allele in mild cognitive impairment

To investigate olfactory identification and apolipoprotein E ´4 allele in patients with mild cognitive impairment (MCI), we used Cross-Cultural Smell Identification Test (CC-SIT) from University of Pennsylvania to assess olfactory identification performance and polymerase chain reaction (PCR) to detect apolipoprotein E ´4 (ApoE ´4) allele in 28 patients with MCI and the 30 age-matched control subjects in present study. The Mann–Whitney U test demonstrated that the MCI group performed significantly worse on CC-SIT than the normal aging group (P,0.01). For MCI patients olfaction scores correlated positively with CAMCOG-C (r50.61, P,0.01), but not with age, gender or years of education. In normal subjects, the CC-SIT score showed no significant associations with age, gender, years of education, or CAMCOG-C. As the least common allele in Chinese, ´4 was found in 13.3% of controls and in 35.8% of MCI in this study. 2 ApoE ´4 was significantly higher in MCI group than normal group ( x 54.65, P,0.01). There was a significant effect of allele status on odor identification: subjects with ´4 allele were not able to identify as many odors as the subjects without ´4 allele (P,0.01). These results suggested that the decreased olfactory identification in MCI may be a marker for the early diagnosis of Alzheimer’s disease, and ApoE genotype may be part of the basis of olfactory identification decline.  2002 Elsevier Science B.V. All rights reserved.