Use of Hormone Therapy in Postmenopausal Women with Alzheimer's Disease: A Systematic Review.

BACKGROUND: Around two-thirds of patients with Alzheimer's disease (AD) are women, which could be related to the depletion of female sexual hormones at menopause. The replacement of these hormones with hormone therapy (HT) to possibly decrease AD risk or treat AD patients has generated conflicting results in the literature. OBJECTIVE: Our aim was to systematically review the relationship between HT use in postmenopausal women with AD and the risk of developing or treating AD symptoms. DATA SOURCES: The PubMed, LILACS, Scopus, Scielo, and Web of Science databases were searched from January 1994 to December 2020 using the descriptors 'Alzheimer Disease OR Alzheimer's Disease' and 'Hormone Replacement Therapy OR Estrogen Replacement Therapy'. STUDY SELECTION: Observational and controlled clinical trials including postmenopausal women diagnosed with AD and evaluating HT efficacy were eligible for inclusion. DATA EXTRACTION: Extracted data comprise study design, covariates, inclusion criteria for sample selection, AD diagnosis criteria, biases, HT regimen, and cognitive measurement tools used. RESULTS: Overall, 25 studies were selected. Among the 14 observational studies, 8 reported an improvement in cognitive function and a decrease in AD risk, especially in younger postmenopausal women. Five observational studies did not demonstrate any association between HT and AD, and one study reported an increase in AD risk, regardless of time of HT initiation. Of the 11 controlled clinical trials included, 7 showed an amelioration in cognitive function after HT. The remaining 4 trials saw no difference between HT and control. CONCLUSION: Both observational and controlled clinical trials had methodological issues and discrepancies in inclusion criteria and HT protocols. These inconsistencies made it difficult to establish an association between HT and AD.

Cannabinoid Receptor Type 1 Agonist ACEA Improves Cognitive Deficit on STZ-Induced Neurotoxicity Through Apoptosis Pathway and NO Modulation.

The cannabinoid system has the ability to modulate cellular and molecular mechanisms, including excitotoxicity, oxidative stress, apoptosis, and inflammation, acting as a neuroprotective agent, by its relationship with signaling pathways associated to the control of cell proliferation, differentiation, and survival. Recent reports have raised new perspectives on the possible role of cannabinoid system in neurodegenerative diseases like Alzheimer disease's (AD). AD is a neurodegenerative disorder characterized by the presence of amyloid plaques, neurofibrillary tangles, neuronal death, and progressive cognitive loss, which could be caused by energy metabolism impairment, changes in insulin signaling, chronic oxidative stress, neuroinflammation, Tau hyperphosphorylation, and Aß deposition in the brain. Thus, we investigated the presumptive protective effect of the cannabinoid type 1 (CB1)-selective receptor agonist arachidonyl-2'-chloroethylamide (ACEA) against streptozotocin (STZ) exposure stimuli in an in vitro neuronal model (Neuro-2a neuroblastoma cells) and in vivo model (intracerebroventricular STZ injection), experimental models of sporadic AD. Our results demonstrated that ACEA treatment reversed cognitive impairment and increased activity of Akt and ERK triggered by STZ, and increased IR expression and increased the anti-apoptotic proteins levels, Bcl-2. In the in vitro model, ACEA was able to rescue cells from STZ-triggered death and modulated the NO release by STZ. Our study has demonstrated a participation of the cannabinoid system in cellular survival, involving the CB1 receptor, which occurs by positive regulation of the anti-apoptotic proteins, suggesting the participation of this system in neurodegenerative processes. Our data suggest that the cannabinoid system is an interesting therapeutic target for the treatment of neurodegenerative diseases.

Cannabinoid Receptor Type 1 Agonist ACEA Protects Neurons from Death and Attenuates Endoplasmic Reticulum Stress-Related Apoptotic Pathway Signaling.

Neurodegeneration is the result of progressive destruction of neurons in the central nervous system, with unknown causes and pathological mechanisms not yet fully elucidated. Several factors contribute to neurodegenerative processes, including neuroinflammation, accumulation of neurotoxic factors, and misfolded proteins in the lumen of the endoplasmic reticulum (ER). Endocannabinoid signaling has been pointed out as an important modulatory system in several neurodegeneration-related processes, inhibiting the inflammatory response and increasing neuronal survival. Thus, we investigated the presumptive protective effect of the selective cannabinoid type 1 (CB1) receptor agonist arachidonyl-2'-chloroethylamide (ACEA) against inflammatory (lipopolysaccharide, LPS) and ER stress (tunicamycin) stimuli in an in vitro neuronal model (Neuro-2a neuroblastoma cells). Cell viability analysis revealed that ACEA was able to protect against cell death induced by LPS and tunicamycin. This neuroprotective effect occurs via the CB1 receptor in the inflammation process and via the transient receptor potential of vanilloid type-1 (TRPV1) channel in ER stress. Furthermore, the immunoblotting analyses indicated that the neuroprotective effect of ACEA seems to involve the modulation of eukaryotic initiation factor 2 (eIF2α), transcription factor C/EBP homologous protein (CHOP), and caspase 12, as well as the survival/death p44/42 MAPK, ERK1/2-related signaling pathways. Together, these data suggest that the endocannabinoid system is a potential therapeutic target in neurodegenerative processes, especially in ER-related neurodegenerative diseases.

Temporal changes of CB1 cannabinoid receptor in the basal ganglia as a possible structure-specific plasticity process in 6-OHDA lesioned rats.

The endocannabinoid system has been implicated in several neurobiological processes, including neurodegeneration, neuroprotection and neuronal plasticity. The CB1 cannabinoid receptors are abundantly expressed in the basal ganglia, the circuitry that is mostly affected in Parkinson's Disease (PD). Some studies show variation of CB1 expression in basal ganglia in different animal models of PD, however the results are quite controversial, due to the differences in the procedures employed to induce the parkinsonism and the periods analyzed after the lesion. The present study evaluated the CB1 expression in four basal ganglia structures, namely striatum, external globus pallidus (EGP), internal globus pallidus (IGP) and substantia nigra pars reticulata (SNpr) of rats 1, 5, 10, 20, and 60 days after unilateral intrastriatal 6-hydroxydopamine injections, that causes retrograde dopaminergic degeneration. We also investigated tyrosine hydroxylase (TH), parvalbumin, calbindin and glutamic acid decarboxylase (GAD) expression to verify the status of dopaminergic and GABAergic systems. We observed a structure-specific modulation of CB1 expression at different periods after lesions. In general, there were no changes in the striatum, decreased CB1 in IGP and SNpr and increased CB1 in EGP, but this increase was not sustained over time. No changes in GAD and parvalbumin expression were observed in basal ganglia, whereas TH levels were decreased and the calbindin increased in striatum in short periods after lesion. We believe that the structure-specific variation of CB1 in basal ganglia in the 6-hydroxydopamine PD model could be related to a compensatory process involving the GABAergic transmission, which is impaired due to the lack of dopamine. Our data, therefore, suggest that the changes of CB1 and calbindin expression may represent a plasticity process in this PD model.

Different approaches, one target: understanding cellular mechanisms of Parkinson's and Alzheimer's diseases / Abordagens diferentes, um único objetivo: compreender os mecanismos celulares das doenças de Parkinson e de Alzheimer

Neurodegenerative disorders are undoubtedly an increasing problem in the health sciences, given the increase of life expectancy and occasional vicious life style. Despite the fact that the mechanisms of such diseases are far from being completely understood, a large number of studies that derive from both the basic science and clinical approaches have contributed substantial data in that direction. In this review, it is discussed several frontiers of basic research on Parkinson´s and Alzheimer´s diseases, in which research groups from three departments of the Institute of Biomedical Sciences of the University of São Paulo have been involved in a multidisciplinary effort. The main focus of the review involves the animal models that have been developed to study cellular and molecular aspects of those neurodegenerative diseases, including oxidative stress, insulin signaling and proteomic analyses, among others. We anticipate that this review will help the group determine future directions of joint research in the field and, more importantly, set the level of cooperation we plan to develop in collaboration with colleagues of the Nucleus for Applied Neuroscience Research that are mostly involved with clinical research in the same field.

Os transtornos neurodegenerativos são, sem dúvida, um problema crescente nas ciências da saúde, dado o aumento da expectativa de vida e de estilos de vida pouco saudáveis. Embora os mecanismos de tais doenças ainda estejam longe de ser esclarecidos, vários estudos que derivam tanto da ciência básica quanto de abordagens clínicas contribuíram nessa direção. Na presente revisão, são discutidas linhas de frente da pesquisa básica sobre as doenças de Parkinson e Alzheimer, em que grupos de pesquisas de três departamentos do Instituto de Ciências Biomédicas da Universidade de São Paulo estão envolvidos em um esforço multidisciplinar. O foco principal desta revisão envolve os modelos animais desenvolvidos para se estudar os aspectos celulares e moleculares daquelas doenças neurodegenerativas, incluindo o estresse oxidativo, a sinalização da insulina e as análises proteômicas, dentre outros. Antecipamos que esta revisão irá auxiliar o grupo a determinar as futuras direções da pesquisa conjunta nessa área e, o mais importante, estabelecer o nível de cooperação que planejamos desenvolver juntamente com colegas do Núcleo de Apoio à Pesquisa em Neurociência Aplicada que estão envolvidos com pesquisa clínica na mesma área.

Hypoactivity of the central dopaminergic system and autistic-like behavior induced by a single early prenatal exposure to lipopolysaccharide.

The aim of the present study was to evaluate the behavioral patterns associated with autism and the prevalence of these behaviors in males and females, to verify whether our model of lipopolysaccharide (LPS) administration represents an experimental model of autism. For this, we prenatally exposed Wistar rats to LPS (100 µg/kg, intraperitoneally, on gestational day 9.5), which mimics infection by gram-negative bacteria. Furthermore, because the exact mechanisms by which autism develops are still unknown, we investigated the neurological mechanisms that might underlie the behavioral alterations that were observed. Because we previously had demonstrated that prenatal LPS decreases striatal dopamine (DA) and metabolite levels, the striatal dopaminergic system (tyrosine hydroxylase [TH] and DA receptors D1a and D2) and glial cells (astrocytes and microglia) were analyzed by using immunohistochemistry, immunoblotting, and real-time PCR. Our results show that prenatal LPS exposure impaired communication (ultrasonic vocalizations) in male pups and learning and memory (T-maze spontaneous alternation) in male adults, as well as inducing repetitive/restricted behavior, but did not change social interactions in either infancy (play behavior) or adulthood in females. Moreover, although the expression of DA receptors was unchanged, the experimental animals exhibited reduced striatal TH levels, indicating that reduced DA synthesis impaired the striatal dopaminergic system. The expression of glial cell markers was not increased, which suggests that prenatal LPS did not induce permanent neuroinflammation in the striatum. Together with our previous finding of social impairments in males, the present findings demonstrate that prenatal LPS induced autism-like effects and also a hypoactivation of the dopaminergic system.

Different approaches, one target: understanding cellular mechanisms of Parkinson's and Alzheimer's diseases.

Neurodegenerative disorders are undoubtedly an increasing problem in the health sciences, given the increase of life expectancy and occasional vicious life style. Despite the fact that the mechanisms of such diseases are far from being completely understood, a large number of studies that derive from both the basic science and clinical approaches have contributed substantial data in that direction. In this review, it is discussed several frontiers of basic research on Parkinson's and Alzheimer's diseases, in which research groups from three departments of the Institute of Biomedical Sciences of the University of São Paulo have been involved in a multidisciplinary effort. The main focus of the review involves the animal models that have been developed to study cellular and molecular aspects of those neurodegenerative diseases, including oxidative stress, insulin signaling and proteomic analyses, among others. We anticipate that this review will help the group determine future directions of joint research in the field and, more importantly, set the level of cooperation we plan to develop in collaboration with colleagues of the Nucleus for Applied Neuroscience Research that are mostly involved with clinical research in the same field.

Differential response of AMPA and NMDA glutamate receptors of Purkinje cells to aging of the chicken cerebellum.

Aging can lead to cognitive, affective, learning, memory and motor deficits. Since the cerebellum and glutamatergic neurotransmission are involved in several of those functions, the present work aimed at studying the expression of AMPA and NMDA glutamate receptor subunits in the chick cerebellum during aging. Young (30 days old) and aged (ca. 4 years old) chickens (Gallus gallus) were used in order to evaluate the expression of GluR1, GluR2/3 and NR1 subunits. The cerebella of young and aged chickens were subjected to immunohistochemical and immunoblotting techniques. Numbers of GluR1, GluR2/3 and NR1-positive cells and optical density of the immunoblotting data were analyzed and submitted to statistical analysis using ANOVA and the Bonferroni post hoc test. Mean density of Purkinje cells stained for Giemsa, GluR1, GluR2/3 and NR1 in the cerebellum all showed a statistically significant decrease in aged animals when compared to the young animals (Giemsa, P<0.01; GluRs and NR1, P<0.03). However, the ratio of GluR1 and GluR2/3-positive Purkinje cells in relation the total number of Purkinje cells found in each time point decreased with aging (ca. 10%), whereas the ratio of NR1-positive cells increased (ca. 9%). The immunoblotting data showed a significant decrease of GluR1 (ca. 66%) and GluR2/3 (ca. 55%) protein expression with aging, but did not reveal changes for NR1. Our data suggest that aging can lead to differential changes in the pattern of expression of glutamate receptor subunits, which can underlie at least part of the cognitive and motor disorders found in aged animals.

Retinal removal up-regulates cannabinoid CB(1) receptors in the chick optic tectum.

The endocannabinoid system has been implicated in several neurobiological processes, including neurodegeneration and neuroprotection. The aim of this study was to evaluate the effects of unilateral retinal ablation on the expression of the cannabinoid receptor subtype 1 (CB(1)) at both protein and mRNA levels in the optic tectum of the adult chick brain. After different survival times postlesion (2-30 days), the chick brains were subjected to immunohistochemical, immunoblotting, and real-time PCR procedures to evaluate CB(1) expression. TUNEL and Fluoro-Jade B were used to verify the possible occurrence of cell death, and immunostaining for the microtubule-associated protein MAP-2 was performed to verify possible dendritic remodeling after lesions. No cell death could be observed in the deafferented tectum, at least up to 30 days postlesion, although Fluoro-Jade B could reveal degenerating axons and terminals. Retinal ablation seems to generate an increase of CB(1) protein in the optic tectum and other retinorecipient visual areas, which paralleled an increase in MAP-2 staining. On the other hand, CB(1) mRNA levels were not changed after retinal ablation. Our results reveal that CB(1) expression in visual structures of the adult chick brain may be negatively regulated by the retinal innervation. The increase of CB(1) receptor expression observed after retinal removal indicates that these receptors are not presynaptic in retinal axons projecting to the tectum and suggests a role of the cannabinoid system in plasticity processes ensuing after lesions.

ERK3 associates with MAP2 and is involved in glucose-induced insulin secretion.

The adaptation of pancreatic islets to pregnancy includes increased beta cell proliferation, expansion of islet mass, and increased insulin synthesis and secretion. Most of these adaptations are induced by prolactin (PRL). We have previously described that in vitro PRL treatment increases ERK3 expression in isolated rat pancreatic islets. This study shows that ERK3 is also upregulated during pregnancy. Islets from pregnant rats treated with antisense oligonucleotide targeted to the PRL receptor displayed a significant reduction in ERK3 expression. Immunohistochemical double-staining showed that ERK3 expression is restricted to pancreatic beta cells. Transfection with antisense oligonucleotide targeted to ERK3 abolished the insulin secretion stimulated by glucose in rat islets and by PMA in RINm5F cells. Therefore, we examined the participation of ERK3 in the activation of a cellular target involved in secretory events, the microtubule associated protein MAP2. PMA induced ERK3 phosphorylation that was companied by an increase in ERK3/MAP2 association and MAP2 phosphorylation. These observations provide evidence that ERK3 is involved in the regulation of stimulus-secretion coupling in pancreatic beta cells.

Developmental expression of cannabinoid receptors in the chick retinotectal system.

The cannabinoid system has been suggested to participate in processes such as antinociception, cognition, motor control, and, more recently, development of the nervous system. This study describes the expression of the CB1 cannabinoid receptor in the developing chick retina and optic tectum by means of conventional immunoperoxidase protocols. CB1 immunoreactivity was initially detected around the embryonic day 4 (E4) in both the retina and tectum. In the retina, CB1 immunoreactivity was first observed in presumptive ganglion cells and, subsequently, in the inner plexiform layer and two populations of neurons of the inner nuclear layer. The post-hatched chick exhibited a pattern of staining that included four sublayers of the inner plexiform layer, a few stained cells in the ganglion cell layer, and labeled neurons both in the inner and central parts of the inner nuclear layer. The latter two types of neurons appear to be amacrine and bipolar cells, respectively. In the tectum, CB1 first appeared in its most superficial zone and later in several tectal laminae, including a white matter layer (stratum album centrale; Cajal's layer 14). There was a remarkable and transient increase of labeling at E10, followed by a continuous reduction of staining until E18. In the post-hatched chick, tectal staining was mostly confined to layers 2-3 and 5-6. Stained perikarya were seldom observed in the tectum at any stage. These data are in agreement with a possible developmental function of CB1, as it is expressed several days before synaptogenesis ensues and exhibits transient expression in the optic tectum.

Increased expression of nitric oxide synthase in visual structures of the chick brain after retinal removal.

Nitric oxide (NO) seems to act as a retrograde messenger in the establishment and refinement of synaptic connections during development and in neural plasticity processes in adult life. Previous studies have shown that the expression of NO synthase (NOS) in the optic tectum of developing chicks is regulated by the retinal innervation. The aim of this study was to observe the effects of unilateral retinal lesions upon the expression of NOS in central visual areas of the adult chick brain. After different survival times (1-30 days), the chick brains were submitted to immunohistochemical, immunoblotting, and NO imaging procedures to evaluate NOS expression and activity. Our results indicate that NOS expression in visual areas is also regulated by retinal innervation in the adult chick. However, differently from the case in the developing animal, the deafferentation seems to generate an increase of the NOS expression in retinorecipient visual areas. Our results suggest that NOS expression in visual structures of the adult chick brain may be down-regulated by the retinal innervation. Alternatively, the increase of NOS expression observed after retinal removal could be an indicative of a role of the NO system in plasticity processes.

Neurotransmitter receptor regulation after deafferentation in the visual system

The present study aimed at understanding the regulation of AMPA-type glutamate receptors (GluRs) and nicotinic acetylcholine receptors (nAChRs) during experimentally-induced neurodegeneration in the chick visual system. Immunohistochemistry, in situ hybridization, and RNAse protection techniques were used to verify the expression of GluR and nAChR subunits at several periods after deafferentation, ranging from 1 to 30 days. The results indicate that GluR1 and 2 expression changes in a biphasic way after deafferentation, decreasing after the shortest survival periods (1-4 days) and increasing afterwards. These effects clearly involve regulation of gene expression, as verified by in situ hybridization and RNAse protection. The regulation of the α2, α4, α5, and β2 nAChR subunits after deafferentation, on the other hand, exhibited a pattern that was exactly the opposite, with an early increase followed by a consistent decrease of expression until 30 days postlesion. Furthermore, nAChR changes were not apparently due to gene expression regulation, but instead by up-regulation/ down-regulation at a protein level. These results suggest that neurotransmitter receptors undergo differential plastic changes after deafferentation in the nervous system and contribute data to their possible role in neurodegeneration and neuroprotection processes.

Nicotine and alpha-bungarotoxin modify the dendritic growth of cholinoceptive neurons in the developing chick tectum.

Nicotinic acetylcholine receptors have been suggested to participate in morphogenetic processes during development of the nervous system. In this study, nicotine applied both in ovo and in vitro produced a reduction of the neuritic length of cholinoceptive neurons of the developing chick tectum, whereas alpha-bungarotoxin produced the opposite effect. Taken together with previous data, our results are indicative of a role of the alpha-bungarotoxin-sensitive nicotinic receptors in neural development.

Neurotransmitter regulation of neural development: acetylcholine and nicotinic receptors.

Several neurotransmitter systems have been related to developmental processes during the past decade. In this review, we discuss the evidence that the nicotinic acetylcholine receptors could have an additional function during development that may be unrelated to their role in cholinergic neurotransmission in the vertebrate brain. Both temporal expression data and in vitro and in vivo studies with nicotinic agonists and antagonists have provided direct support for a role of nicotinic receptors in neural developmental processes such as neurite outgrowth and differentiation. A similar picture has emerged for other neurotransmitter and receptor systems as well, which generates a new view of neural processes during both development and mature life.

Neurotransmitter regulation of neural development: acetylcholine and nicotinic receptors

Several neurotransmitter systems have been related to developmental processes during the past decade. In this review, we discuss the evidence that the nicotinic acetylcholine receptors could have an additional function during development that may be unrelated to their role in cholinergic neurotransmission in the vertebrate brain. Both temporal expression data and in vitro and in vivo studies with nicotinic agonists and antagonists have provided direct support for a role of nicotinic receptors in neural developmental processes such as neurite outgrowth and differentiation. A similar picture has emerged for other neurotransmitter and receptor systems as well, which generates a new view of neural processes during both development and mature life

Application of potassium chloride to the surface of the rat visual cortex differentially affects the expression of presumptive neuroprotective molecules.

The purpose of this study was to investigate the effects of topical application of 3 M KCl for 20 minutes to the surface of the rat visual cortex upon the expression of presumptive neuroprotective molecules. Conventional immunohistochemical and immunoblotting techniques revealed a marked reduction of the expression of calbindin and parvalbumin after application of KCl, whereas calretinin, nitric oxide synthase, and the alpha7 subunit of the nicotinic acetylcholine receptor clearly increased following that procedure. Such effects were quantified both in terms of the number of immunoreactive perikarya and optical density of immunoblottings, and were observed as soon as 1 h, and to last at least until 15 days, following KCl application. These results suggest that calbindin and parvalbumin may not be able to exert an appreciable neuroprotective effect in the presence of KCl. On the other hand, calretinin, nitric oxide synthase, and the alpha7-containing nicotinic receptors are possibly upregulated to protect the neurons in which they are expressed.

Transport of a nicotinic acetylcholine receptor subunit in axonal systems

The effect of neural lesions upon the distribution of a neuronal nicotinic acetylcholine receptor subunit was investigated in the chick nervous system. Following unilateral retinal lesions, the neuropil staining with an antibody against the Beta2 receptor subunit was dramatically reduced or completely eliminated in all retinorecipient structures. Lesions of the lateral spiriform nucleus, a major Beta2 subunit-containing mesencephalic nucleus, produced a marked reduction of neuropil staining in the deeper layers of the tectum, which represent the main target of that nucleus. The present results indicate that the Beta2 subunit is transported in axonal systems, and might therefore constitute presynaptic receptors in some brain areas.