Estrogen and androgen protection of human neurons against intracellular amyloid beta1-42 toxicity through heat shock protein 70

Causal effects of genetically predicted testosterone on Alzheimer's disease: a two-sample mendelian randomization study

OBJECTIVE

Although several studies have reported that testosterone may protect against Alzheimer's disease, no evidence of a causal relationship has been demonstrated.

METHODS

A Mendelian randomization (MR) study was performed to determine the causal role of testosterone in Alzheimer's disease. The study utilized public databases obtained from separately published genome-wide associationstudies (GWAS). Single-nucleotide polymorphisms (SNPs) for testosterone were extracted from the most recent and largest published GWAS meta-analysis (178,782 participants), and SNPs for Alzheimer's disease were extracted from UK Biobank (954 AD cases and 487,331 controls). The odds ratio (OR) of the inverse variance weighting (IVW) approach was the primary outcome, and the weighted median and MR Egger regression were used for sensitivity analysis.

RESULTS

Through IVW, we observed a causal association between genetically predicted testosterone and the risk of Alzheimer's disease, with an OR of 0.99 (95% confidence interval [CI] = 0.998-0.999, p = 0.047). In the sensitivity analyses, the weighted median regression showed directionally similar estimates (OR = 0.99, 95% CI = 0.998-0.999, p = 0.048). The MR Egger regression showed similar estimates (OR = 0.99, 95% CI = 0.998-1.00, p = 0.35), but with lower precision. Funnel plots, MR Egger intercepts, and Mendelian randomization pleiotropy residual sum and outlier (MR-PRESSO) analysis indicated the absence of directional pleiotropy effects.

CONCLUSION

In conclusion, our MR study provides evidence of a causal relationship between testosterone levels and Alzheimer's disease; however, this relationship must be validated in future studies with larger sample sizes. Early testosterone monitoring may enable the prevention of Alzheimer's and related diseases.

Testosterone Inhibits Secretion of the Pro-Inflammatory Chemokine CXCL1 from Astrocytes

Astrocytes play an important role in the regulation of the inflammatory response in the CNS, e.g., in demyelinating diseases. Since the chemokine CXCL1 is known to be secreted by astrocytes and to have a pro-inflammatory effect on immune cells in the CNS, we verified the effect of testosterone on its secretion in vitro (in the astrocytic cell line DI TNC1). Testosterone reduced the increase in CXCL1 production caused by the pro-inflammatory agent lysophosphatidylcholine and restored the basal production level of CXCL1. The androgen receptor (present and functional in the studied cell line) was strongly suggested to mediate this effect-its non-steroid ligand flutamide exerted an agonist-like effect, mimicking the activity of testosterone itself on CXCL1 secretion. This novel mechanism has important implications for the known immunomodulatory effect of testosterone and potentially other androgenic hormones. It provides a potential explanation on the molecular level and shows that astrocytes are important players in inflammatory homeostasis in the CNS and its hormonal regulation. Therefore, it suggests new directions for the development of the therapeutic intervention.

Sex-based differences in effector cells of the adaptive immune system during Alzheimer's disease and related dementias

Neurological conditions such as Alzheimer's disease (AD) and related dementias (ADRD) present with many challenges due to the heterogeneity of the related disease(s), making it difficult to develop effective treatments. Additionally, the progression of ADRD-related pathologies presents differently between men and women. With two-thirds of the population affected with ADRD being women, ADRD has presented itself with a bias toward the female population. However, studies of ADRD generally do not incorporate sex-based differences in investigating the development and progression of the disease, which is detrimental to understanding and treating dementia. Additionally, recent implications for the adaptive immune system in the development of ADRD bring in new factors to be considered as part of the disease, including sex-based differences in immune response(s) during ADRD development. Here, we review the sex-based differences of pathological hallmarks of ADRD presentation and progression, sex-based differences in the adaptive immune system and how it changes with ADRD, and the importance of precision medicine in the development of a more targeted and personalized treatment for this devastating and prevalent neurodegenerative condition.

Sex-dependent metal accumulation and immunoexpression of Hsp70 and Nrf2 in rats' brain following manganese exposure

Manganese (Mn), although important for multiple cellular processes, has posed environmental health concerns due to its neurotoxic effects. In recent years, there have been extensive studies on the mechanism of Mn-induced neuropathology, as well as the sex-dependent vulnerability to its neurotoxic effects. Nonetheless, cellular mechanisms influenced by sex differences in susceptibility to Mn have yet to be adequately characterized. Since oxidative stress is a key mechanism of Mn neurotoxicity, here, we have probed Hsp70 and Nrf2 proteins to investigate the sex-dependent changes following exposure to Mn. Male and female rats were administered intraperitoneal injections of MnCl2 (10 mg/kg and 25 mg/kg) 48 hourly for a total of eight injections (15 days). We evaluated changes in body weight, as well as Mn accumulation, Nrf2 and Hsp70 expression across four brain regions; striatum, cortex, hippocampus and cerebellum in both sexes. Our results showed sex-specific changes in body-weight, specifically in males but not in females. Additionally, we noted sex-dependent accumulation of Mn in the brain, as well as in expression levels of Nrf2 and Hsp70 proteins. These findings revealed sex-dependent susceptibility to Mn-induced neurotoxicity corresponding to differential Mn accumulation, and expression of Hsp70 and Nrf2 across several brain regions.

[Testosterone and Alzheimer's disease]

Alzheimer's disease (AD) is a neurodegenerative disease that causes dementia in half of the cases. Asthma is usually found in people over 65 years of age. The etiopathogenesis of the disease is multifactorial and includes genetic factors, nutritional disorders, mitochondrial dysfunction, oxidative stress, and aging. Sex hormones have an important influence on the development of AD, as evidenced by a higher incidence in women than in men. Considering the significant influence of T on the maintenance of normal brain function, the present study is aimed at evaluating the impact of androgen deprivation therapy (ADT), as well as testosterone therapy, on the risk of AD development and progression. Although there is some clinical inconsistency between studies, androgens have a significant effect on brain function and are beneficial for AD patients. Low levels of circulating androgens should be considered as a significant risk factor for the development of AD and memory loss. With a reduced level of T in the plasma of men, its administration improves cognitive performance and memory, treatment should be started at an early stage of the disease. In men and women with AD, androgens improve mental state and slow the progression of the disease, providing a protective effect. In the future, it is necessary to conduct studies on a large population, taking into account personality factors and a more specific approach to assessing cognitive functions and the causal relationship of T administration in AD.

Impact of Testosterone on Alzheimer's Disease

Alzheimer’s disease (AD) is a neurodegenerative disease responsible for almost half of all dementia cases in the world and progressively increasing. The etiopathology includes heritability, genetic factors, aging, nutrition, but sex hormones play a relevant role. Animal models demonstrated that testosterone (T) exerted a neuroprotective effect reducing the production of amyloid-beta (Aβ), improving synaptic signaling, and counteracting neuronal death. This study aims to evaluate the impact of T deprivation and T administration in humans on the onset of dementia and AD. A search was conducted on MEDLINE and Scopus for the “androgen deprivation therapy” and “testosterone therapy” with “dementia” and “Alzheimer’s.” Studies lasting twenty years with low risk of bias, randomized clinical trial, and case-controlled studies were considered. Twelve articles on the effect of androgen deprivation therapy (ADT) and AD and seventeen on T therapy and AD were retrieved. Men with prostate cancer under ADT showed a higher incidence of dementia and AD. The effect of T administration in hypogonadal men with AD and cognitive impairment has evidenced some positive results. The majority of studies showed the T administration improved memory and cognition in AD while others did not find any benefit. Although some biases in the studies are evident, T therapy for AD patients may represent an essential clinical therapy to reduce dementia incidence and AD progression. However, more specific case-controlled trials on the effect of androgens therapy in men and women to reducing the onset of AD are necessary.

Deficiency in Androgen Receptor Aggravates Traumatic Brain Injury-Induced Pathophysiology and Motor Deficits in Mice

Androgens have been shown to have a beneficial effect on brain injury and lower reactive astrocyte expression after TBI. Androgen receptors (ARs) are known to mediate the neuroprotective effects of androgens. However, whether ARs play a crucial role in TBI remains unknown. In this study, we investigated the role of ARs in TBI pathophysiology, using AR knockout (ARKO) mice. We used the controlled cortical impact model to produce primary and mechanical brain injuries and assessed motor function and brain-lesion volume. In addition, the AR knockout effects on necrosis and autophagy were evaluated after TBI. AR knockout significantly increased TBI-induced expression of the necrosis marker alpha-II-spectrin breakdown product 150 and astrogliosis marker glial fibrillary acidic protein. In addition, the TBI-induced astrogliosis increase in ARKO mice lasted for three weeks after a TBI. The autophagy marker Beclin-1 was also enhanced in ARKO mice compared with wild-type mice after TBI. Our results also indicated that ARKO mice showed a more unsatisfactory performance than wild-type mice in a motor function test following TBI. Further, they were observed to have more severe lesions than wild-type mice after injury. These findings strongly suggest that ARs play a role in TBI.

From Menopause to Neurodegeneration-Molecular Basis and Potential Therapy

The impacts of menopause on neurodegenerative diseases, especially the changes in steroid hormones, have been well described in cell models, animal models, and humans. However, the therapeutic effects of hormone replacement therapy on postmenopausal women with neurodegenerative diseases remain controversial. The steroid hormones, steroid hormone receptors, and downstream signal pathways in the brain change with aging and contribute to disease progression. Estrogen and progesterone are two steroid hormones which decline in circulation and the brain during menopause. Insulin-like growth factor 1 (IGF-1), which plays an import role in neuroprotection, is rapidly decreased in serum after menopause. Here, we summarize the actions of estrogen, progesterone, and IGF-1 and their signaling pathways in the brain. Since the incidence of Alzheimer’s disease (AD) is higher in women than in men, the associations of steroid hormone changes and AD are emphasized. The signaling pathways and cellular mechanisms for how steroid hormones and IGF-1 provide neuroprotection are also addressed. Finally, the molecular mechanisms of potential estrogen modulation on N-methyl-d-aspartic acid receptors (NMDARs) are also addressed. We provide the viewpoint of why hormone therapy has inconclusive results based on signaling pathways considering their complex response to aging and hormone treatments. Nonetheless, while diagnosable AD may not be treatable by hormone therapy, its preceding stage of mild cognitive impairment may very well be treatable by hormone therapy.

Testosterone Levels Are Decreased and Associated with Disease Duration in Male Spinocerebellar Ataxia Type 2 Patients

Spinocerebellar ataxia type 2 (SCA2) is a progressive neurodegenerative disorder due to an unstable expansion of a CAG repeat in the ATXN2 gene. Despite clinical and experimental evidence indicating the relevance of the gonadotropic axis to the prognosis and therapeutics for several late-onset neurodegenerative disorders, its functioning and association with disease severity have not been previously explored in SCA2. To assess serum levels of testosterone, luteinizing hormone (LH), and follicle-stimulating hormone (FSH), and their clinical relevance in SCA2 patients. A case-control study involving 94 Cuban SCA2 patients and 101 gender- and age-matched healthy controls was conducted. Testosterone, LH, and FSH serum levels were determined by radioimmunoassay or immunoradiometric assay systems. Clinical outcomes included age at onset, disease duration, Scale for the Assessment and Rating of Ataxia (SARA) score, and progression rate. Univariate general linear models were generated. Testosterone, LH, and FSH serum levels were significantly reduced in male SCA2 patients relative to control individuals. On average, there was a 35% reduction in testosterone levels in male patients versus male control individuals. Testosterone levels were associated with disease duration (r = 0.383; p = 0.025) and age at onset (r = 0.414; p = 0.011) in male SCA2 patients, but no association was observed between testosterone and CAG expansion size, SARA score, or progression rate. Testosterone levels might be a biomarker of disease progression in male SCA2 patients. Further studies are needed to explore the effects of low testosterone levels on non-motor symptoms, and to assess the potential of testosterone replacement therapy in male SCA2 patients.

Sex differences in fat taste responsiveness are modulated by estradiol

Sex as a biological variable has been the focus of increasing interest. Relatively few studies have focused, however, on differences in peripheral taste function between males and females. Nonetheless, there are reports of sex-dependent differences in chemosensitivity in the gustatory system. The involvement of endogenous changes in ovarian hormones has been suggested to account for taste discrepancies. Additionally, whether sex differences exist in taste receptor expression, activation, and subsequent signaling pathways that may contribute to different taste responsiveness is not well understood. In this study, we show the presence of both the nuclear and plasma membrane forms of estrogen receptor (ER) mRNA and protein in mouse taste cells. Furthermore, we provide evidence that estrogen increases taste cell activation during the application of fatty acids, the chemical cue for fat taste, in taste receptor cells. We found that genes important for the transduction pathway of fatty acids vary between males and females and that these differences also exist across the various taste papillae. In vivo support for the effect of estrogens in taste cells was provided by comparing the fatty acid responsiveness in male, intact female, and ovariectomized (OVX) female mice with and without hormone replacement. In general, females detected fatty acids at lower concentrations, and the presence of circulating estrogens increased this apparent fat taste sensitivity. Taken together, these data indicate that increased circulating estrogens in the taste system may play a significant role in physiology and chemosensory cellular activation and, in turn, may alter taste-driven behavior.NEW & NOTEWORTHY Using molecular, cellular, and behavioral analyses, this study shows that sex differences occur in fat taste in a mouse model. Female mice are more responsive to fatty acids, leading to an overall decrease in intake and fatty acid preference. These differences are linked to sex hormones, as estradiol enhances taste cell responsiveness to fatty acids during periods of low circulating estrogen following ovariectomy and in males. Estradiol is ineffective in altering fatty acid signaling during a high-estrogen period and in ovariectomized mice on hormone replacement. Thus, taste receptor cells are a direct target for actions of estrogen, and there are multiple receptors with differing patterns of expression in taste cells.

Androgen Therapy in Neurodegenerative Diseases

Neurodegenerative diseases, including Alzheimer disease (AD), Parkinson disease (PD), multiple sclerosis (MS), amyotrophic lateral sclerosis (ALS), and Huntington disease, are characterized by the loss of neurons as well as neuronal function in multiple regions of the central and peripheral nervous systems. Several studies in animal models have shown that androgens have neuroprotective effects in the brain and stimulate axonal regeneration. The presence of neuronal androgen receptors in the peripheral and central nervous system suggests that androgen therapy might be useful in the treatment of neurodegenerative diseases. To illustrate, androgen therapy reduced inflammation, amyloid-β deposition, and cognitive impairment in patients with AD. As well, improvements in remyelination in MS have been reported; by comparison, only variable results are observed in androgen treatment of PD. In ALS, androgen administration stimulated motoneuron recovery from progressive damage and regenerated both axons and dendrites. Only a few clinical studies are available in human individuals despite the safety and low cost of androgen therapy. Clinical evaluations of the effects of androgen therapy on these devastating diseases using large populations of patients are strongly needed.

Physiopathological role of the enzymatic complex 5α-reductase and 3α/β-hydroxysteroid oxidoreductase in the generation of progesterone and testosterone neuroactive metabolites

The enzymatic complex 5α-reductase (5α-R) and 3α/3β-hydroxysteroid oxidoreductase (HSOR) is expressed in the nervous system, where it transforms progesterone (PROG) and testosterone (T) into neuroactive metabolites. These metabolites regulate myelination, brain maturation, neurotransmission, reproductive behavior and the stress response. The expression of 5α-R and 3α-HSOR and the levels of PROG and T reduced metabolites show regional and sex differences in the nervous system and are affected by changing physiological conditions as well as by neurodegenerative and psychiatric disorders. A decrease in their nervous tissue levels may negatively impact the course and outcome of some pathological events. However, in other pathological conditions their increased levels may have a negative impact. Thus, the use of synthetic analogues of these steroids or 5α-R modulation have been proposed as therapeutic approaches for several nervous system pathologies. However, further research is needed to fully understand the consequences of these manipulations, in particular with 5α-R inhibitors.

Testosterone Deficiency and Risk of Cognitive Disorders in Aging Males

Cognitive impairment and dementia are predicted to undergo a dramatic increase in the following years with more than 131.5 million people being affected by 2030. Although vascular diseases play the most important role in the pathogenesis of memory impairment in aging men, some pre-clinical and clinical evidence has suggested a possible contribution of the age-dependent reduction of testosterone (T). In this paper we have summarized and discussed all the information derived from available animal and experimental studies. In addition, we meta-analyzed data rising from all randomized placebo controlled trials (RCTs) published so far. Only limited preclinical and clinical evidence can support a possible contribution of T in the pathogenesis of the age-dependent impairment of cognitive functions. In addition, our meta-analysis did not support the use of T replacement therapy for the improvement of several cognitive domains analyzed including attention/working memory, executive function, language, verbal memory, visual memory, visuomotor ability, and visuospatial ability. However, it is important to recognize that the vast majority of available RCTs included mixed populations of subjects with eugonadism and hypogonadism preventing any final conclusion being drawn on these issues.

Testosterone and Adult Neurogenesis

It is now well established that neurogenesis occurs throughout adulthood in select brain regions, but the functional significance of adult neurogenesis remains unclear. There is considerable evidence that steroid hormones modulate various stages of adult neurogenesis, and this review provides a focused summary of the effects of testosterone on adult neurogenesis. Initial evidence came from field studies with birds and wild rodent populations. Subsequent experiments with laboratory rodents have tested the effects of testosterone and its steroid metabolites upon adult neurogenesis, as well as the functional consequences of induced changes in neurogenesis. These experiments have provided clear evidence that testosterone increases adult neurogenesis within the dentate gyrus region of the hippocampus through an androgen-dependent pathway. Most evidence indicates that androgens selectively enhance the survival of newly generated neurons, while having little effect on cell proliferation. Whether this is a result of androgens acting directly on receptors of new neurons remains unclear, and indirect routes involving brain-derived neurotrophic factor (BDNF) and glucocorticoids may be involved. In vitro experiments suggest that testosterone has broad-ranging neuroprotective effects, which will be briefly reviewed. A better understanding of the effects of testosterone upon adult neurogenesis could shed light on neurological diseases that show sex differences.

An Updated Review: Androgens and Cognitive Impairment in Older Men

Androgens are some of the most important sex hormones in men, and they maintain important physiological activities in the human body. Cognitive impairment is one of the most common manifestations of aging in the elderly population and an important factor affecting the quality of life of elderly individuals. The levels of sex hormones in elderly people decrease with age, and low levels of androgens in older male individuals have been closely linked to the development of cognitive impairment. Basic studies have shown that androgens have neuroprotective effects and that androgen deficiency impairs cognitive function by increasing oxidative stress and decreasing synaptic plasticity, among other effects. Additionally, clinical studies have also shown that androgen deficiency is closely related to cognitive impairment. This article reviews the relationship between low androgen levels and cognitive impairment, their potential mechanisms, and the effects of testosterone supplementation in improving cognition.

Sex differences in steroid levels and steroidogenesis in the nervous system: Physiopathological role

The nervous system, in addition to be a target for steroid hormones, is the source of a variety of neuroactive steroids, which are synthesized and metabolized by neurons and glial cells. Recent evidence indicates that the expression of neurosteroidogenic proteins and enzymes and the levels of neuroactive steroids are different in the nervous system of males and females. We here summarized the state of the art of neuroactive steroids, particularly taking in consideration sex differences occurring in the synthesis and levels of these molecules. In addition, we discuss the consequences of sex differences in neurosteroidogenesis for the function of the nervous system under healthy and pathological conditions and the implications of neuroactive steroids and neurosteroidogenesis for the development of sex-specific therapeutic interventions.

Neuroprotective Effects of Exercise on the Morphology of Somatic Motoneurons Following the Death of Neighboring Motoneurons

Background. Motoneuron loss is a severe medical problem that can result in loss of motor control and eventually death. We have previously demonstrated that partial motoneuron loss can result in dendritic atrophy and functional deficits in nearby surviving motoneurons, and that treatment with androgens can be neuroprotective against this dendritic atrophy. Exercise has also been shown to be protective following a variety of neural injury models and, in some cases, is dependent on androgen action. Objective. In this study, we explored whether exercise shows the same neuroprotective effect on induced dendritic atrophy as that seen with androgen treatment. Methods. Motoneurons innervating the vastus medialis muscles of adult male rats were selectively killed by intramuscular injection of cholera toxin-conjugated saporin. Following saporin injections, some animals were allowed free access to a running wheel attached to their home cages. Four weeks later, motoneurons innervating the ipsilateral vastus lateralis muscle were labeled with cholera toxin-conjugated horseradish peroxidase, and dendritic arbors were reconstructed in 3 dimensions. Results. Dendritic arbor lengths of animals allowed to exercise were significantly longer than those not allowed to exercise. Conclusions. These findings indicate that exercise following neural injury exerts a protective effect on motoneuron dendrites comparable to that seen with exogenous androgen treatment.

Sex Differences and Role of Gonadal Hormones on Glutamate LevelAfter Spinal Cord Injury in Rats: A Microdialysis Study

Introduction:

Sex differences in outcomes of Spinal Cord Injury (SCI) suggest a sex-hormone-mediated effect on post-SCI pathological events, including glutamate excitotoxicity. This study aimed to investigate the importance of gonadal hormones on glutamate release subsequent to SCI in rats.

Methods:

After laminectomy at T8–T9, an electrolytic lesion was applied to the spinothalamic tracts of male and female rats. Using spinal microdialysis, we assessed glutamate levels at the site of lesion in both intact and gonadectomized rats for 4 hours. In this way, we examined the sex differences in the glutamate concentrations.

Results:

The peak retention time of glutamate level was 10.6 min and spinal glutamate concentration reached a maximum level 40 min following SCI. In male SCI rats, gonadectomy caused a significant elevation of glutamate level (P<0.001) following injury which was maximum 40 min post-SCI as well. However, no significant alterations were seen in gonadectomized female rats.

Conclusion:

The significant differences in glutamate levels between both intact and gonadectomized SCI male and female rats show the sex-hormone-related mechanisms underlying the molecular events in the second phase of SCI. It seems that the role of male gonadal hormones to prevent glutamate excitotoxicity is more prominent. The exact mechanisms of these hormones on the functional recovery after SCI should be clarified in further studies.

Neuroprotective Effects on the Morphology of Somatic Motoneurons Following the Death of Neighboring Motoneurons: A Role for Microglia?

Partial depletion of spinal motoneuron populations induces dendritic atrophy in neighboring motoneurons, and treatment with testosterone protects motoneurons from induced dendritic atrophy. We explored a potential mechanism for this induced atrophy and protection by testosterone, examining the microglial response to partial depletion of motoneurons. Motoneurons innervating the vastus medialis muscles of adult male rats were killed by intramuscular injection of cholera toxin-conjugated saporin; some saporin-injected rats were treated with testosterone. Microglia were later visualized via immunohistochemical staining, classified as monitoring or activated, and counted stereologically. Partial motoneuron depletion increased the number of activated microglia in the quadriceps motor pool, and this increase was attenuated with testosterone treatment. The attenuation in microglial response could reflect an effect of testosterone on suppressing microglia activation, potentially sparing motoneuron dendrites. Alternatively, testosterone could be neuroprotective, sparing motoneuron dendrites, secondarily resulting in reduced microglial activation. To discriminate between these hypotheses, following partial motoneuron depletion, rats were treated with minocycline to inhibit microglial activation. Motoneurons innervating the ipsilateral vastus lateralis muscle were later labeled with cholera toxin-conjugated horseradish peroxidase, and dendritic arbors were reconstructed. Reduction of microglial activation by minocycline did not prevent induced dendritic atrophy following partial motoneuron depletion. Further, reduction of microglial activation by minocycline treatment resulted in dendritic atrophy in intact animals. Together, these findings indicate that the neuroprotective effect of testosterone on dendrites following motoneuron death is not due to inhibiting microglial activation, and that microglial activity contributes to the normal maintenance of dendritic arbors.

Effects of Androgens on the Amyloid-β Protein in Alzheimer's Disease

Age-related androgen depletion has been implicated in compromised neuroprotection and is involved in the pathogenesis of neurodegenerative disease, including Alzheimer's disease (AD), the leading cause of dementia. Emerging data revealed that reduction of both serum and brain androgen levels in males is associated with increased amyloid-β (Aβ) accumulation, a putative cause of AD. It has been demonstrated that androgens can function as the endogenous negative regulators of Aβ. However, the mechanisms by which androgens regulate Aβ production, degradation, and clearance, as well as the Aβ-induced pathological process in AD, are still elusive. This review emphasizes the contributions of androgen to Aβ metabolism and toxicity in AD and thus may provide novel strategies for prevention and therapeutics.

Estrogen and estrogen receptors in the modulation of gastrointestinal epithelial secretion

Gastrointestinal (GI) epithelial ion transport is physiologically important in many aspects of humans, such as in maintaining fluid balance of whole body, and also plays a role in the development and progression of common GI disease. Estrogen and estrogen receptors have been shown to modulate the activity of epithelial ion secretion in GI tract. This review aims to address the current state of knowledge about the role of estrogen and estrogen receptors in modulation of GI epithelial secretion and to elucidate the underlying mechanisms. We highlight the recent findings regarding the importance of estrogen and estrogen receptors in GI epithelia protection and body fluid balance by modulation of gastrointestinal epithelial HCO₃^- and Cl^- secretion, especially current information about the regulatory mechanisms of duodenal HCO₃^- secretion based on our study in this field. Since there are no reviews on this topic but only few papers to address the main issues, we hope to timely provide new perspectives for the association between estrogen and GI disease.

Involvement of Luteinizing Hormone in Alzheimer Disease Development in Elderly Women

Alzheimer disease (AD) is a slow progressive neurodegenerative disease that affects more elderly women than elderly men. It impairs memory, typically progresses into multidomain cognitive decline that destroys the quality of life, and ultimately leads to death. About 5.3 million older Americans are now living with this disease, and this number is projected to rise to 14 million by 2050. Annual health-care costs in the United States alone are projected to increase to about US$1.1 trillion by 2050. The initial theory that decreasing estrogen levels leads to AD development in postmenopausal women has been proven inconclusive. For example, Women's Health Research Initiative Memory Study and the population-based nested case-control study have failed to demonstrate that estrogen/progesterone (hormone replacement therapy [HRT]) or estrogen replacement therapy could prevent the cognitive decline or reduce the risk of AD. This led to the realization that AD development could be due to a progressive increase in luteinizing hormone (LH) levels in postmenopausal women. Accordingly, a large number of studies have demonstrated that an increase in LH levels is positively correlated with neuropathological, behavioral, and cognitive changes in AD. In addition, LH has been shown to promote amyloidogenic pathway of precursor protein metabolism and deposition of amyloid β plaques in the hippocampus, a region involved in AD. Cognate receptors that mediate LH effects are abundantly expressed in the hippocampus. Reducing the LH levels by treatment with gonadotropin-releasing hormone agonists could provide therapeutic benefits. Despite these advances, many questions remain and require further research.

Invited Review: Toxicoproteomics: Proteomics Applied to Toxicology and Pathology

Global measurement of proteins and their many attributes in tissues and biofluids defines the field of proteomics. Toxicoproteomics, as part of the larger field of toxicogenomics, seeks to identify critical proteins and pathways in biological systems that are affected by and respond to adverse chemical and environmental exposures using global protein expression technologies. Toxicoproteomics integrates 3 disciplinary areas: traditional toxicology and pathology, differential protein and gene expression analysis, and systems biology. Key topics to be reviewed are the evolution of proteomics, proteomic technology platforms and their capabilities with exemplary studies from biology and medicine, a review of over 50 recent studies applying proteomic analysis to toxicological research, and the recent development of databases designed to integrate -Omics technologies with toxicology and pathology. Proteomics is examined for its potential in discovery of new biomarkers and toxicity signatures, in mapping serum, plasma, and other biofluid proteomes, and in parallel proteomic and transcriptomic studies. The new field of toxicoproteomics is uniquely positioned toward an expanded understanding of protein expression during toxicity and environmental disease for the advancement of public health.

Neuroprotective Role of Steroidal Sex Hormones: An Overview

Progesterone, estrogens, and testosterone are the well-known steroidal sex hormones, which have been reported to have "nonreproductive "effects in the brain, specifically in the neuroprotection and neurotrophy. In the last one decade, there has been a surge in the research on the role of these hormones in neuroprotection and their positive impact on different brain injuries. The said interest has been sparked by a desire to understand the action and mechanisms of these steroidal sex hormones throughout the body. The aim of this article was to highlight the potential outcome of the steroidal hormones, viz. progesterone, estrogens, and testosterone in terms of their role in neuroprotection and other brain injuries. Their possible mechanism of action at both genomic and nongenomic level will be also discussed. As far as our knowledge goes, we are for the first time reporting neuroprotective effect and possible mechanism of action of these hormones in a single article.

Controlled delivery of β-globin-targeting TALENs and CRISPR/Cas9 into mammalian cells for genome editing using microinjection

Tal-effector nucleases (TALEN) and clustered regularly interspaced short palindromic repeats (CRISPR) with CRISPR-associated (Cas) proteins are genome editing tools with unprecedented potential. However, the ability to deliver optimal amounts of these nucleases into mammalian cells with minimal toxicity poses a major challenge. Common delivery approaches are transfection- and viral-based methods; each associated with significant drawbacks. An alternative method for directly delivering genome-editing reagents into single living cells with high efficiency and controlled volume is microinjection. Here, we characterize a glass microcapillary-based injection system and demonstrate controlled co-injection of TALENs or CRISPR/Cas9 together with donor template into single K562 cells for targeting the human β-globin gene. We quantified nuclease induced insertions and deletions (indels) and found that, with β-globin-targeting TALENs, similar levels of on- and off-target activity in cells could be achieved by microinjection compared with nucleofection. Furthermore, we observed 11% and 2% homology directed repair in single K562 cells co-injected with a donor template along with CRISPR/Cas9 and TALENs respectively. These results demonstrate that a high level of targeted gene modification can be achieved in human cells using glass-needle microinjection of genome editing reagents.

Estrogen alleviates acetic acid-induced gastric or colonic damage via both ERα- and ERβ-mediated and direct antioxidant mechanisms in rats

In order to demonstrate the possible protective effects of estrogen receptor (ER)-α and ERβ receptor subtypes in the pathogenesis of colonic and gastric oxidant damage, experimental ulcer and colitis were induced by acetic acid, and the animals were randomly divided as colitis, ulcer, and their corresponding non-ulcer and non-colitis control groups. Each group of rats was treated intramuscularly with the vehicle, selective ERα agonist propylpyrazole-triol (1 mg/kg), ERβ agonist diarylpropionitrile (1 mg/kg), non-selective ER agonist 17β estradiol (E2; 1 mg/kg), or E2 plus non-selective ER antagonist ICI-182780 (1 mg/kg). The results revealed that induction of ulcer or colitis resulted in systemic inflammation as assessed by increased levels of plasma TNF-α and IL-6 levels. In both tissues, the presence of oxidant damage was verified by histological analysis and elevated myleoperoxidase activity. In the colitis and ulcer groups, both ER agonists and the non-selective E2 reversed the oxidative damage in a similar manner. These findings indicate that estrogen acts via both ERα- and ERβ-mediated and direct antioxidant mechanisms, where both ER subtypes play equal and efficient roles in the anti-inflammatory action of estrogen, in limiting the migration of neutrophils to the inflamed tissue, reducing the release and activation of cytokines and thereby alleviating tissue damage.

Prolactin and sex hormones levels in males with Parkinson's disease

BACKGROUND

The role that oestradiol and testosterone play in Parkinson's disease and their potential to influence the course of the disease has been covered in medical literature. The aim of this work was to compare oestradiol, testosterone, sex hormone-binding protein and prolactin blood levels in males affected with Parkinson's disease and in an age-matched control group, and to show possible dependence between concentrations of plasma hormones and the progression of symptoms of Parkinson's disease.

METHODS

The plasma levels of oestradiol, testosterone, prolactin and sex hormone-binding protein were examined in 36 patients affected with Parkinson's disease and in 69 age-matched control subjects, using chemiluminescent reactions. Patients with Parkinson's disease were examined using scales assessing their clinical state.

RESULTS

The level of prolactin was higher in the affected group. Concentrations of oestradiol and testosterone in the control group exceeded those found in patients. The level of sex hormones was positively correlated with better mood and quality of life in patients affected with Parkinson's disease; prolactin levels correlated negatively with sex steroid concentrations.

CONCLUSIONS

Lower blood levels of sex steroids and higher concentrations of prolactin and its antigonadotrophic activity in males affected with Parkinson's disease may result in a bigger susceptibility to the disease in men. The level of hormones may influence patients' cognition, mood and quality of life.

Dehydroepiandrosterone, molecular chaperones and the epigenetics of primate longevity

Dehydroepiandrosterone (DHEA) and dehydroepiandrosterone-sulphate (DHEAS) are the most abundant circulating adrenal steroid hormones. The plasma level of DHEAS correlates with longevity in primates and varies during human development with a maximum in early adulthood and a marked decline during aging. DHEA promotes the expression of molecular chaperones which are housekeeping stress response proteins essential for the processes of folding, translocation, maintenance and repair of proteins, RNA and DNA, as well as for homeostasis, immune response and cancer resistance. The level of chaperone expression correlates with longevity and shows a decline during aging. DHEA-induced promotion of chaperone expression could contribute to the epigenetic evolution of primate longevity.

Sex differences in cognitive impairment and Alzheimer's disease

Studies have shown differences in specific cognitive ability domains and risk of Alzheimer's disease between the men and women at later age. However it is important to know that sex differences in cognitive function during adulthood may have their basis in both organizational effects, i.e., occurring as early as during the neuronal development period, as well as in activational effects, where the influence of the sex steroids influence brain function in adulthood. Further, the rate of cognitive decline with aging is also different between the sexes. Understanding the biology of sex differences in cognitive function will not only provide insight into Alzheimer's disease prevention, but also is integral to the development of personalized, gender-specific medicine. This review draws on epidemiological, translational, clinical, and basic science studies to assess the impact of sex differences in cognitive function from young to old, and examines the effects of sex hormone treatments on Alzheimer's disease in men and women.

Protective effects of testosterone on presynaptic terminals against oligomeric β-amyloid peptide in primary culture of hippocampal neurons

Increasing lines of evidence support that testosterone may have neuroprotective effects. While observational studies reported an association between higher bioavailable testosterone or brain testosterone levels and reduced risk of Alzheimer's disease (AD), there is limited understanding of the underlying neuroprotective mechanisms. Previous studies demonstrated that testosterone could alleviate neurotoxicity induced by β-amyloid (Aβ), but these findings mainly focused on neuronal apoptosis. Since synaptic dysfunction and degeneration are early events during the pathogenesis of AD, we aim to investigate the effects of testosterone on oligomeric Aβ-induced synaptic changes. Our data suggested that exposure of primary cultured hippocampal neurons to oligomeric Aβ could reduce the length of neurites and decrease the expression of presynaptic proteins including synaptophysin, synaptotagmin, and synapsin-1. Aβ also disrupted synaptic vesicle recycling and protein folding machinery. Testosterone preserved the integrity of neurites and the expression of presynaptic proteins. It also attenuated Aβ-induced impairment of synaptic exocytosis. By using letrozole as an aromatase antagonist, we further demonstrated that the effects of testosterone on exocytosis were unlikely to be mediated through the estrogen receptor pathway. Furthermore, we showed that testosterone could attenuate Aβ-induced reduction of HSP70, which suggests a novel mechanism that links testosterone and its protective function on Aβ-induced synaptic damage. Taken together, our data provide further evidence on the beneficial effects of testosterone, which may be useful for future drug development for AD.

Reactive oxidative species enhance amyloid toxicity in APP/PS1 mouse neurons

OBJECTIVE

To investigate whether intracellular amyloid β (iAβ) induces toxicity in wild type (WT) and APP/PS1 mice, a mouse model of Alzheimer's disease.

METHODS

Different forms of Aβ aggregates were microinjected into cultured WT or APP/PS1 mouse hippocampal neurons. TUNEL staining was performed to examine neuronal cell death. Reactive oxidative species (ROS) were measured by MitoSOXRed mitochondrial superoxide indicator.

RESULTS

Crude, monomer and protofibril Aβ induced more toxicity in APP/PS1 neurons than in WT neurons. ROS are involved in mediating the vulnerability of APP/PS1 neurons to iAβ toxicity.

CONCLUSION

Oxidative stress may mediate cell death induced by iAβ in neurons.

MiR-206 decreases brain-derived neurotrophic factor levels in a transgenic mouse model of Alzheimer's disease

MicroRNA alterations have been reported in patients with Alzheimer's disease (AD) and AD mouse models. We now report that miR-206 is upregulated in the hippocampal tissue, cerebrospinal fluid, and plasma of embryonic APP/PS1 transgenic mice. The increased miR-206 downregulates the expression of brain-derived neurotrophic factor (BDNF). BDNF is neuroprotective against cell death after various insults, but in embryonic and newborn APP/PS1 mice it is decreased. Thus, a specific microRNA alteration may contribute to AD pathology by downregulating BDNF.

17β-Estradiol alters rat type-II alveolar cell recovery from high levels of ozone

Respiratory health is negatively impacted by exposure to ozone or to estrogens. Increasingly, individuals have simultaneous environmental exposure to both compounds. Characterizing the cellular responses stimulated by the combination of ozone and estrogens, therefore, is crucial to our complete understanding of the compounds' environmental health impacts. Our work introduces an alveolar cell culture model with defined media that provides evidence of ozone damage and determines sex hormones alter the cells' susceptibility to oxidative damage. Specifically, we investigated the individual and combined effects of environmentally relevant levels of ozone and 17β-estradiol on non-cancerous rat, type-II alveolar cells by examining biomarkers of cellular health and redox balance. The data reveal a complex role for 17β-estradiol in cellular recovery from 1 hr exposure to high ozone levels. At 0.5 hr post-ozone necrosis and inflammation markers show 17β-estradiol augments the detrimental effects of 350 ppb ozone, but after 24 hr of recovery, steroid treatment alters glutathione redox ratio and allows cellular proliferation.

Heat shock protein 70 gene polymorphisms are associated with paranoid schizophrenia in the Polish population

HSP70 genes have been considered as promising schizophrenia candidate genes based on their protective role in the central nervous system under stress conditions. In this study, we analyzed the potential implication of HSPA1A +190G/C, HSPA1B +1267A/G, and HSPA1L +2437T/C polymorphisms in the susceptibility to paranoid schizophrenia in a homogenous Caucasian Polish population. In addition, we investigated the association of the polymorphisms with the clinical variables of the disease. Two hundred and three patients with paranoid schizophrenia and 243 healthy controls were enrolled in the study. Polymorphisms of HSPA1A, -1B, and -1L genes were genotyped using the PCR-RFLP technique. Analyses were conducted in entire groups and in subgroups that were stratified according to gender. There were significant differences in the genotype and allele frequencies of HSPA1A polymorphism between the patients and controls. The +190CC genotype and +190C allele were over-represented in the patients and significantly increased the risk for developing schizophrenia (OR = 3.45 and OR = 1.61, respectively). Interestingly, such a risk was higher for females with the +190CC genotype than for males with the +190CC genotype (OR = 5.78 vs. OR = 2.76). We also identified the CGT haplotype as a risk haplotype for schizophrenia and demonstrated the effects of HSPA1A and HSPA1B genotypes on the psychopathology and age of onset. Our study provided the first evidence that the HSPA1A polymorphism may potentially increase the risk of developing paranoid schizophrenia. Further independent analyses in different populations to evaluate the role of gender are needed to replicate these results.

The Role of Neurotransmitters in Protection against Amyloid- β Toxicity by KiSS-1 Overexpression in SH-SY5Y Neurons

Recent studies have suggested that the kisspeptin (KP) and kissorphin (KSO) peptides have neuroprotective actions against the Alzheimer's amyloid-β (Aβ) peptide. Overexpression of the human KiSS-1 gene that codes for KP and KSO peptides in SH-SY5Y neurons has also been shown to inhibit Aβ neurotoxicity. The in vivo actions of KP include activation of neuroendocrine and neurotransmitter systems. The present study used antagonists of KP, neuropeptide FF (NPFF), opioids, oxytocin, estrogen, adrenergic, cholinergic, dopaminergic, serotonergic, and γ-aminobutyric acid (GABA) receptors plus inhibitors of catalase, cyclooxygenase, nitric oxide synthase, and the mitogen activated protein kinase cascade to characterize the KiSS-1 gene overexpression neuroprotection against Aβ cell model. The results showed that KiSS-1 overexpression is neuroprotective against Aβ and the action appears to involve the KP or KSO peptide products of KiSS-1 processing. The mechanism of neuroprotection does not involve the activation of the KP or NPFF receptors. Opioids play a role in the toxicity of Aβ in the KiSS-1 overexpression system and opioid antagonists naloxone or naltrexone inhibited Aβ toxicity. The mechanism of KiSS-1 overexpression induced protection against Aβ appears to have an oxytocin plus a cyclooxygenase dependent component, with the oxytocin antagonist atosiban and the cyclooxygenase inhibitor SC-560 both enhancing the toxicity of Aβ.

Sexual dimorphism in cerebral ischemia injury

Stroke is a leading cause of permanent disability and death. A complex series of biochemical and molecular mechanisms (e.g. the release of ROS/NOS, proapoptotic proteins and proinflammatory cytokine; neuronal depolarization, Ca2+ accumulation and so on) impair the neurologic functions of cerebral ischemia and stroke. We have known for some time that the epidemiology of human stroke is sexually dimorphic until late in life, well beyond the years of reproductive senescence and menopause. The principal mammalian estrogen (17β estradiol or E2) is neuroprotective in many types of brain injury and has been the major focus of investigation over the past several decades. However the incidence of stroke in women is lower than in men until decades past menopause, suggesting that factors beyond sex hormone contribute to these epidemiological sex differences. So a new concept is emerging: both sex steroids and biologic sex are important factors in clinical and experimental strokes. In this review, we will address sex steroids and gender differences in influencing the mechanisms and outcomes of brain ischemia stroke. These sex differences need to be identified which could help future translation to human neuroprotection.

Flutamide Enhances Neuroprotective Effects of Testosterone during Experimental Cerebral Ischemia in Male Rats

Testosterone has been shown to worsen histological and neurological impairment during cerebral ischemia in animal models. Cell culture studies revealed that testosterone is implicated in protecting neural and glial cells against insults, and they started to elucidate testosterone pathways that underlie these protective effects. These studies support the hypothesis that testosterone can be neuroprotective throughout an episode of cerebral ischemia. Therefore, we evaluated the mechanisms underlying the shift between testosterone protective and deleterious effects via block testosterone aromatization and androgen receptors in rats subjected to 60-minute middle cerebral artery occlusion. Fifty rats were divided into five equal groups: gonadally intact male; castrated male; intact male + flutamide; intact male + letrozole; intact male + combination flutamide and letrozole. Our results indicated that castration has the ability to reduce histological damage and to improve neurological score 24 hours after middle cerebral artery occlusion. Moreover, flutamide improved histologic and neurological impairment better than castration. Letrozole induced increases in striatal infarct volume and seizures in gonadally intact rats. Combination of flutamide and letrozole showed that letrozole can reverse beneficial effects of flutamide. In conclusion, it seems that the beneficial effects of flutamide are the prevention of the deleterious effects and enhancement of neuroprotective effects of testosterone during cerebral ischemia.

Neuroprotective effects of testosterone on motoneuron and muscle morphology following spinal cord injury

Treatment with testosterone is neuroprotective/neurotherapeutic after a variety of motoneuron injuries. Here we assessed whether testosterone might have similar beneficial effects after spinal cord injury (SCI). Young adult female rats received either sham or T9 spinal cord contusion injuries and were implanted with blank or testosterone-filled Silastic capsules. Four weeks later, motoneurons innervating the vastus lateralis muscle of the quadriceps were labeled with cholera toxin-conjugated horseradish peroxidase, and dendritic arbors were reconstructed in three dimensions. Soma volume, motoneuron number, lesion volume, and tissue sparing were also assessed, as were muscle weight, fiber cross-sectional area, and motor endplate size and density. Contusion injury resulted in large lesions, with no significant differences in lesion volume, percent total volume of lesion, or spared white or gray matter between SCI groups. SCI with or without testosterone treatment also had no effect on the number or soma volume of quadriceps motoneurons. However, SCI resulted in a decrease in dendritic length of quadriceps motoneurons in untreated animals, and this decrease was completely prevented by treatment with testosterone. Similarly, the vastus lateralis muscle weights and fiber cross-sectional areas of untreated SCI animals were smaller than those of sham-surgery controls, and these reductions were both prevented by testosterone treatment. No effects on motor endplate area or density were observed across treatment groups. These findings suggest that regressive changes in motoneuron and muscle morphology seen after SCI can be prevented by testosterone treatment, further supporting a role for testosterone as a neurotherapeutic agent in the injured nervous system.

Concerted perturbation observed in a hub network in Alzheimer's disease

Alzheimer’s disease (AD) is a progressive neurodegenerative disease involving the alteration of gene expression at the whole genome level. Genome-wide transcriptional profiling of AD has been conducted by many groups on several relevant brain regions. However, identifying the most critical dys-regulated genes has been challenging. In this work, we addressed this issue by deriving critical genes from perturbed subnetworks. Using a recent microarray dataset on six brain regions, we applied a heaviest induced subgraph algorithm with a modular scoring function to reveal the significantly perturbed subnetwork in each brain region. These perturbed subnetworks were found to be significantly overlapped with each other. Furthermore, the hub genes from these perturbed subnetworks formed a connected hub network consisting of 136 genes. Comparison between AD and several related diseases demonstrated that the hub network was robustly and specifically perturbed in AD. In addition, strong correlation between the expression level of these hub genes and indicators of AD severity suggested that this hub network can partially reflect AD progression. More importantly, this hub network reflected the adaptation of neurons to the AD-specific microenvironment through a variety of adjustments, including reduction of neuronal and synaptic activities and alteration of survival signaling. Therefore, it is potentially useful for the development of biomarkers and network medicine for AD.

Evaluation of the effects of testosterone and luteinizing hormone on regulation of β-amyloid in male 3xTg-AD mice

During normal aging, men experience a significant decline in testosterone levels and a compensatory elevation in levels of gonadotropin luteinizing hormone (LH). Both low testosterone and elevated LH have been identified as significant risk factors for the development of Alzheimer's disease (AD) in men. It is unclear whether changes in testosterone or LH primarily underlie the relationship with AD, and therefore may be a more suitable therapeutic target. To examine this issue, we compared levels of β-amyloid (Aβ) immunoreactivity in male 3xTg-AD mice under varying experimental conditions associated with relatively low or high levels of testosterone and/or LH. In gonadally intact mice, Aβ accumulation increased after treatment with the gonadotropin-releasing hormone agonist leuprolide, which inhibits the hypothalamic-pituitary-gonadal (HPG) axis and reduces both testosterone and LH levels. In gonadectomized (GDX) mice with low testosterone and high LH, we also observed increased Aβ levels. Treatment of GDX mice with testosterone significantly reduced Aβ levels. In contrast, leuprolide did not significantly decrease Aβ levels and moreover, inhibited the Aβ-lowering effect of testosterone. Evaluation of hippocampal-dependent behavior revealed parallel findings, with performance in GDX mice improved by testosterone but not leuprolide. These data suggest that Aβ-lowering actions of testosterone are mediated directly by androgen pathways rather than indirectly via regulation of LH and the HPG axis. These findings support the clinical evaluation of androgen therapy in the prevention and perhaps treatment of AD in hypogonadal men.

Curcumin protects against intracellular amyloid toxicity in rat primary neurons

To investigate whether curcumin is protective against intracellular amyloid β (Aβ) toxicity, different concentrations of curcumin were applied to with intracellular Aβ in rat primary hippocampal neurons in culture. We find that at low dosages, curcumin effectively inhibits intracellular Aβ toxicity. Reactive oxidative species (ROS) is involved in mediating intracellular Aβ toxicity and possibly curcumin protection. Our results indicate that oxidative stress may mediate cell death induced by intracellular Aβ in neurons.

Morphine protects against intracellular amyloid toxicity by inducing estradiol release and upregulation of Hsp70

Certain experimental models support morphine can play a beneficial role against damage in the neuronal system. In this study, we find morphine as well as endomorphin-1 and endomorphin-2 can protect against intracellular amyloid β (iAβ) toxicity in human and rat primary neuronal cultures and in rat brains in vivo. Morphine reverses the electrophysiological changes induced by iAβ, including current density, resting membrane potential and capacitance. Also morphine improves the spatial memory performance in rats infected by iAβ packaged virus and in APP/PS1 mice in Morris water maze tests. Morphine protection is mediated through inducing estradiol release in hippocampal neurons measured by ELISA and liquid chromatography-mass spectrometry, possibly by increasing P450 cytochrome aromatase activity. Released estradiol induces upregulation of heat shock protein 70 (Hsp70). Hsp70 protects against intracellular amyloid toxicity by rescuing proteasomal activity which is impaired by iAβ. This is the first time, to our knowledge, that induction of estradiol release in hippocampal neurons by morphine is reported. Our data may contribute to both Alzheimer's disease therapy and pain clinics where morphine is widely used.

Single-cell microinjection technologies

Single-cell microinjection, as a mechanical delivery tool, has been used for transferring substances into transfection or infection challenging cells. Here, we discuss the advantages and applications of microinjection, list the materials needed for performing microinjection experiments, and describe the methods of single-cell microinjection into suspended and attached cells.

Reserpine modulates neurotransmitter release to extend lifespan and alleviate age-dependent Aβ proteotoxicity in Caenorhabditis elegans

Aging is a debilitating process often associated with chronic diseases such as diabetes, cardiovascular and neurodegenerative diseases like Alzheimer's disease (AD). AD occurs at a very high incidence posing a huge burden to the society. Model organisms such as C. elegans become essential to understand aging or lifespan extension - the etiology, molecular mechanism and identification of new drugs against age associated diseases. The AD model, manifesting Aβ proteotoxicity, in C. elegans is well established and has provided valuable insights. Earlier, we have reported that Reserpine, an FDA-approved antihypertensive drug, increases C. elegans lifespan with a high quality of life and ameliorates Aβ toxicity in C. elegans. But reserpine does not seem to act through the known lifespan extension pathways or inhibition of its known target, vesicular monoamine transporter, VMAT. Reserpine's mode of action and the pathways it activates are not known. Here, we have evaluated the presynaptic neurotransmitter(s) release pathway and identified acetylcholine (ACh) as the crucial player for reserpine's action. The corroborating evidences are: i) lack of lifespan extension in the ACh loss of function (hypomorphic) - synthesis (cha-1) and transport (unc-17) mutants; ii) mitigation of chronic aldicarb effect; iii) lifespan extension in dopamine (cat-2) and dopamine and serotonin (bas-1) biosynthetic mutants; iv) no rescue from exogenous serotonin induced paralysis in the AD model worms; upon reserpine treatment. Thus, modulation of acetylcholine is essential for reserpine's action.