Persistent short-term memory defects following sleep deprivation in a drosophila model of Parkinson disease

Modulation of dopamine, serotonin, and behavior by lutein carrier nanoparticles in a Drosophila melanogaster model of neurodevelopmental disorders

Considering that woman's health during pregnancy is crucial to well-being as much maternal and fetal as well as the child's future, supplementation with antioxidant compounds has emerged as a promising strategy to prevent the development of future diseases. Given this context, the study aimed to evaluate the effect of lutein carrier nanoparticles supplementation during the preconception period on the offspring of Drosophila melanogaster subjected to a neurodevelopmental disorder model. Female flies, were exposed to either a standard diet or a diet containing NPs LUT (6 μM) for 24 h. Following this period, the flies were transferred to new experimental vials, and eighteen males were added, resulting in a total of 53 flies per experimental group. The male and female flies were then subdivided into two groups and exposed to either a standard diet or imidacloprid (IMI), for 7 days, to induce the neurodevelopmental disorder model, creating four experimental groups: 1) Control; 2) IMI; 3) NPs LUT; 4) NPs LUT + IMI. The hatched offspring were then used for behavioral and biochemical evaluations. Our results showed that supplementation with lutein carrier nanoparticles was able to prevent decreased activity of enzyme tyrosine hydroxylase (TH), as did neurotransmitters dopamine (DA) and serotonin (5-HT) in the head of flies, and as a consequence it prevented behavioral damages such as hyperactivity, anxiety, social interaction, repetitive movements, learning and memory in the progeny of both sexes. Thus, these findings highlight the relevance of preconception supplementation with lutein carrier nanoparticles as an effective approach to prevent the emergence of symptoms associated with neuropsychiatric disorders, paving the way for future research aimed at investigating the best intervention period to prevent ASD and ADHD-type disorders.

Sleep deprivation induces late deleterious effects in a pharmacological model of Parkinsonism

Parkinson's disease is a degenerative, chronic and progressive disease, characterized by motor dysfunctions. Patients also exhibit non-motor symptoms, such as affective and sleep disorders. Sleep disorders can potentiate clinical and neuropathological features and lead to worse prognosis. The goal of this study was to evaluate the effects of sleep deprivation (SD) in mice submitted to a progressive pharmacological model of Parkinsonism (chronic administration with a low dose of reserpine). Male Swiss mice received 20 injections of reserpine (0.1 mg/kg) or vehicle, on alternate days. SD was applied before or during reserpine treatment and was performed by gentle handling for 6 h per day for 10 consecutive days. Animals were submitted to motor and non-motor behavioral assessments and neurochemical evaluations. Locomotion was increased by SD and decreased by reserpine treatment. SD during treatment delayed the onset of catalepsy, but SD prior to treatment potentiated reserpine-induced catalepsy. Thus, although SD induced an apparent beneficial effect on motor parameters, a delayed deleterious effect on alterations induced by reserpine was found. In the object recognition test, both SD and reserpine treatment produced cognitive deficits. In addition, the association between SD and reserpine induced anhedonic-like behavior. Finally, an increase in oxidative stress was found in hippocampus of mice subjected to SD, and tyrosine hydroxylase immunoreactivity was reduced in substantia nigra of reserpine-treated animals. Results point to a possible late effect of SD, aggravating the deficits in mice submitted to the reserpine progressive model of PD.

Experimentally induced active and quiet sleep engage non-overlapping transcriptional programs in Drosophila

Sleep in mammals can be broadly classified into two different physiological categories: rapid eye movement (REM) sleep and slow-wave sleep (SWS), and accordingly REM and SWS are thought to achieve a different set of functions. The fruit fly Drosophila melanogaster is increasingly being used as a model to understand sleep functions, although it remains unclear if the fly brain also engages in different kinds of sleep as well. Here, we compare two commonly used approaches for studying sleep experimentally in Drosophila: optogenetic activation of sleep-promoting neurons and provision of a sleep-promoting drug, gaboxadol. We find that these different sleep-induction methods have similar effects on increasing sleep duration, but divergent effects on brain activity. Transcriptomic analysis reveals that drug-induced deep sleep ('quiet' sleep) mostly downregulates metabolism genes, whereas optogenetic 'active' sleep upregulates a wide range of genes relevant to normal waking functions. This suggests that optogenetics and pharmacological induction of sleep in Drosophila promote different features of sleep, which engage different sets of genes to achieve their respective functions.

Experimentally induced active and quiet sleep engage non-overlapping transcriptional programs in Drosophila

Sleep in mammals can be broadly classified into two different physiological categories: rapid eye movement (REM) sleep and slow wave sleep (SWS), and accordingly REM and SWS are thought to achieve a different set of functions. The fruit fly Drosophila melanogaster is increasingly being used as a model to understand sleep functions, although it remains unclear if the fly brain also engages in different kinds of sleep as well. Here, we compare two commonly used approaches for studying sleep experimentally in Drosophila: optogenetic activation of sleep-promoting neurons and provision of a sleep-promoting drug, Gaboxadol. We find that these different sleep-induction methods have similar effects on increasing sleep duration, but divergent effects on brain activity. Transcriptomic analysis reveals that drug-induced deep sleep ('quiet' sleep) mostly downregulates metabolism genes, whereas optogenetic 'active' sleep upregulates a wide range of genes relevant to normal waking functions. This suggests that optogenetics and pharmacological induction of sleep in Drosophila promote different features of sleep, which engage different sets of genes to achieve their respective functions.

Sleep: An Essential and Understudied Process in the Biology of Blood-Feeding Arthropods

Understanding the biology of blood-feeding arthropods is critical to managing them as vectors of etiological agents. Circadian rhythms act in the regulation of behavioral and physiological aspects such as blood feeding, immunity, and reproduction. However, the impact of sleep on these processes has been largely ignored in blood-feeding arthropods, but recent studies in mosquitoes show that sleep-like states directly impact host landing and blood feeding. Our focus in this review is on discussing the relationship between sleep and circadian rhythms in blood-feeding arthropods along with how unique aspects such as blood gluttony and dormancy can impact sleep-like states. We highlight that sleep-like states are likely to have profound impacts on vector-host interactions but will vary between lineages even though few direct studies have been conducted. A myriad of factors, such as artificial light, could directly impact the time and levels of sleep in blood-feeding arthropods and their roles as vectors. Lastly, we discuss underlying factors that make sleep studies in blood-feeding arthropods difficult and how these can be bypassed. As sleep is a critical factor in the fitness of animal systems, a lack of focus on sleep in blood-feeding arthropods represents a significant oversight in understanding their behavior and its role in pathogen transmission.

Sleep and memory: The impact of sleep deprivation on transcription, translational control, and protein synthesis in the brain

In countries around the world, sleep deprivation represents a widespread problem affecting school-age children, teenagers, and adults. Acute sleep deprivation and more chronic sleep restriction adversely affect individual health, impairing memory and cognitive performance as well as increasing the risk and progression of numerous diseases. In mammals, the hippocampus and hippocampus-dependent memory are vulnerable to the effects of acute sleep deprivation. Sleep deprivation induces changes in molecular signaling, gene expression and may cause changes in dendritic structure in neurons. Genome wide studies have shown that acute sleep deprivation alters gene transcription, although the pool of genes affected varies between brain regions. More recently, advances in research have drawn attention to differences in gene regulation between the level of the transcriptome compared with the pool of mRNA associated with ribosomes for protein translation following sleep deprivation. Thus, in addition to transcriptional changes, sleep deprivation also affects downstream processes to alter protein translation. In this review, we focus on the multiple levels through which acute sleep deprivation impacts gene regulation, highlighting potential post-transcriptional and translational processes that may be affected by sleep deprivation. Understanding the multiple levels of gene regulation impacted by sleep deprivation is essential for future development of therapeutics that may mitigate the effects of sleep loss.

β-carotene-loaded nanoparticles protect against neuromotor damage, oxidative stress, and dopamine deficits in a model of Parkinson's disease in Drosophila melanogaster

β-carotene-loaded nanoparticles improves absorption by increasing bioavailability. The Drosophila melanogaster model of Parkinson's disease must be helpful in investigating potential neuroprotective effects. Four groups of four-day-old flies were exposed to: (1) control; (2) diet containing rotenone (500 μM); (3) β-carotene-loaded nanoparticles (20 μM); (4) β-carotene-loaded nanoparticles and rotenone for 7 days. Then, the percentage of survival, geotaxis tests, open field, aversive phototaxis and food consumption were evaluated. At the end of the behaviors, the analyses of the levels of reactive species (ROS), thiobarbituric acid reactive substances (TBARS), catalase (CAT) and superoxide dismutase (SOD) activity was carried out, as well as an evaluation of the levels of dopamine and acetylcholinesterase (AChE) activity, in the head of flies. Nanoparticles loaded with β-carotene were able to improve motor function, memory, survival and also restored the oxidative stress indicators (CAT, SOD, ROS and TBARS), dopamine levels, AChE activity after exposure to rotenone. Overall, nanoparticles loaded with β-carotene showed significant neuroprotective effect against damage induced by the Parkinson-like disease model, emerging as a possible treatment. Overall, β-carotene-loaded nanoparticles presented significant neuroprotective effect against damage induced by model of Parkinson-like disease, emerging as a possible treatment.

Precision Medicine on the Fly: Using Drosophila to Decipher Gene-Environment Interactions in Parkinson's Disease

Big data approaches have profoundly influenced state-of-the-art in many fields of research, with toxicology being no exception. Here, we use Parkinson's disease as a window through which to explore the challenges of a dual explosion of metabolomic data addressing the myriad environmental exposures individuals experience and genetic analyses implicating many different loci as risk factors for disease. We argue that new experimental approaches are needed to convert the growing body of omics data into molecular mechanisms of disease that can be therapeutically targeted in specific patients. We outline one attractive strategy, which capitalizes on the rapid generation time and advanced molecular tools available in the fruit fly, Drosophila, to provide a platform for mechanistic dissection and drug discovery.

Loss of p21-activated kinase Mbt/PAK4 causes Parkinson-like phenotypes in Drosophila

Parkinson's disease (PD) provokes bradykinesia, resting tremor, rigidity and postural instability, and also non-motor symptoms such as depression, anxiety, sleep and cognitive impairments. Similar phenotypes can be induced in Drosophila melanogaster through modification of PD-relevant genes or the administration of PD-inducing toxins. Recent studies correlated deregulation of human p21-activated kinase 4 (PAK4) with PD, leaving open the question of a causative relationship of mutations in this gene for manifestation of PD symptoms. To determine whether flies lacking the PAK4 homolog Mushroom bodies tiny (Mbt) show PD-like phenotypes, we tested for a variety of PD criteria. Here, we demonstrate that mbt mutant flies show PD-like phenotypes including age-dependent movement deficits, reduced life expectancy and fragmented sleep. They also react to a stressful situation with higher immobility, indicating an influence of Mbt on emotional behavior. Loss of Mbt function has a negative effect on the number of dopaminergic protocerebral anterior medial (PAM) neurons, most likely caused by a proliferation defect of neural progenitors. The age-dependent movement deficits are not accompanied by a corresponding further loss of PAM neurons. Previous studies highlighted the importance of a small PAM subgroup for age-dependent PD motor impairments. We show that impaired motor skills are caused by a lack of Mbt in this PAM subgroup. In addition, a broader re-expression of Mbt in PAM neurons improves life expectancy. Conversely, selective Mbt knockout in the same cells shortens lifespan. We conclude that mutations in Mbt/PAK4 can play a causative role in the development of PD phenotypes.

Aluminum induced oxidative stress, astrogliosis and cell death in rat astrocytes, is prevented by curcumin

Aluminum (Al) is recognized potent neurotoxic metal, which causes oxidative stress leading to intracellular accumulation of reactive oxygen species (ROS) and neuronal cell death in various neurodegenerative diseases. Among several medicinal plants with beneficial effects on health, curcumin acts as a multi-functional drug with antioxidant activity. Thus, the purpose of the present study was to evaluate the protective effect of curcumin against aluminum induced-oxidative stress and astrocytes death, in vitro ad in vivo. Incubation of cultured rat astrocytes with two concentrations of Al (37 μM and 150 μM) for 1 h provoked a dose-dependent reduction of the number of living cells as evaluated by Fluorescein diacetate and lactate dehydrogenase assay. Al-treated cells exhibited a reduction of both superoxide dismutase (SOD) and catalase activities. Pretreatment of astrocytes with curcumin (81 μM) prevented Al-induced cell death. Regarding in vivo study, rats were exposed acutely during three consecutive days to three different doses of Al (25 mg/kg, 50 mg/kg and 100 mg/kg, i.p injection), together with curcumin treatment (30 mg/kg). For the chronic model, animals were exposed to Al (3 g/l) in drinking water from intrauterine age to 4 months ages, plus curcumin treatment (175 mg/kg). Data showed that both acute and chronic Al intoxication induced an obvious astrogliosis within motor cortex and hippocampus, while, such effects were restored by curcumin. We showed herein that Al was highly toxic, induced astrocytes death. Then, curcumin protected astrocytes against Al-toxicity. The cytoprotective potential of curcumin is initiated by stimulation of endogenous antioxidant system.

The Sleep Nullifying Apparatus: A Highly Efficient Method of Sleep Depriving Drosophila

Sleep homeostasis, the increase in sleep observed following sleep loss, is one of the defining criteria used to identify sleep throughout the animal kingdom. As a consequence, sleep deprivation and sleep restriction are powerful tools that are commonly used to provide insight into sleep function. Nonetheless, sleep deprivation experiments are inherently problematic in that the deprivation stimulus itself may be the cause of observed changes in physiology and behavior. Accordingly, successful sleep deprivation techniques should keep animals awake and, ideally, result in a robust sleep rebound without also inducing a large number of unintended consequences. Here, we describe a sleep deprivation technique for Drosophila melanogaster. The Sleep Nullifying Apparatus (SNAP) administers a stimulus every 10s to induce negative geotaxis. Although the stimulus is predictable, the SNAP effectively prevents >95% of nighttime sleep even in flies with high sleep drive. Importantly, the subsequent homeostatic response is very similar to that achieved using hand-deprivation. The timing and spacing of the stimuli can be modified to minimize sleep loss and thus examine non-specific effects of the stimulus on physiology and behavior. The SNAP can also be used for sleep restriction and to assess arousal thresholds. The SNAP is a powerful sleep disruption technique that can be used to better understand sleep function.

Dop1R1, a type 1 dopaminergic receptor expressed in Mushroom Bodies, modulates Drosophila larval locomotion

As in vertebrates, dopaminergic neural systems are key regulators of motor programs in insects, including the fly Drosophila melanogaster. Dopaminergic systems innervate the Mushroom Bodies (MB), an important association area in the insect brain primarily associated to olfactory learning and memory, but that has been also implicated with the execution of motor programs. The main objectives of this work is to assess the idea that dopaminergic systems contribute to the execution of motor programs in Drosophila larvae, and then, to evaluate the contribution of specific dopaminergic receptors expressed in MB to these programs. Our results show that animals bearing a mutation in the dopamine transporter show reduced locomotion, while mutants for the dopaminergic biosynthetic enzymes or the dopamine receptor Dop1R1 exhibit increased locomotion. Pan-neuronal expression of an RNAi for the Dop1R1 confirmed these results. Further studies show that animals expressing the RNAi for Dop1R1 in the entire MB neuronal population or only in the MB γ-lobe forming neurons, exhibit an increased motor output, as well. Interestingly, our results also suggest that other dopaminergic receptors do not contribute to larval motor behavior. Thus, our data support the proposition that CNS dopamine systems innervating MB neurons modulate larval locomotion and that Dop1R1 mediates this effect.

Cognitive Impairments and Self-Reported Sleep in Early-Stage Parkinson's Disease with Versus without Probable REM Sleep Behavior Disorder

Parkinson’s disease (PD) is associated with cognitive and sleep impairments. The presence of rapid eye movement (REM) sleep behavior disorder (RBD) symptoms may represent a worse disease prognosis for PD individuals. We investigated cognitive functioning and self-reported sleep in early-stage PD individuals with (n = 19) or without (n = 31) probable RBD. Probable RBD was defined as >5 on the REM Sleep Behavior Disorder Screening Questionnaire. Inhibition, visuospatial cognitive abilities, working memory, sustained visual attention, verbal fluency, and episodic memory were assessed. Sleep impairments were assessed using the Pittsburgh Sleep Quality Index, Insomnia Severity Index, Epworth Sleepiness Scale, and Patient-Reported Outcomes Measurement Information System questionnaires. Chi-squared, Mann-Whitney U, and independent sample t-tests were employed to assess group differences. Participants with PD and probable RBD performed significantly worse on word reading and switching verbal fluency tasks than PD participants without probable RBD (p < 0.05). No significant differences were found in mood, PD severity, or sleep measures between PD individuals with or without probable RBD. Cognitive tasks that involve verbal or switching components may be most impaired in PD individuals with probable RBD. Larger samples are needed to determine whether other cognitive domains and sleep features are significantly associated with RBD in PD.

Exploring phylogeny to find the function of sleep

During sleep, animals do not eat, reproduce or forage. Sleeping animals are vulnerable to predation. Yet, the persistence of sleep despite evolutionary pressures, and the deleterious effects of sleep deprivation, indicate that sleep serves a function or functions that cannot easily be bypassed. Recent research demonstrates sleep to be phylogenetically far more pervasive than previously appreciated; it is possible that the very first animals slept. Here, we give an overview of sleep across various species, with the aim of determining its original purpose. Sleep exists in animals without cephalized nervous systems and can be influenced by non-neuronal signals, including those associated with metabolic rhythms. Together, these observations support the notion that sleep serves metabolic functions in neural and non-neural tissues.

Found in Translation: The Utility of C. elegans Alpha-Synuclein Models of Parkinson's Disease

Parkinson's Disease (PD) is the second-most common neurodegenerative disease in the world, yet the fundamental and underlying causes of the disease are largely unknown, and treatments remain sparse and impotent. Several biological systems have been employed to model the disease but the nematode roundworm Caenorhabditis elegans (C. elegans) shows unique promise among these to disinter the elusive factors that may prevent, halt, and/or reverse PD phenotypes. Some of the most salient of these C. elegans models of PD are those that position the misfolding-prone protein alpha-synuclein (α-syn), a hallmark pathological component of PD, as the primary target for scientific interrogation. By transgenic expression of human α-syn in different tissues, including dopamine neurons and muscle cells, the primary cellular phenotypes of PD in humans have been recapitulated in these C. elegans models and have already uncovered multifarious genetic factors and chemical compounds that attenuate dopaminergic neurodegeneration. This review describes the paramount discoveries obtained through the application of different α-syn models of PD in C. elegans and highlights their established utility and respective promise to successfully uncover new conserved genetic modifiers, functional mechanisms, therapeutic targets and molecular leads for PD with the potential to translate to humans.

Neuronal reactivation during post-learning sleep consolidates long-term memory in Drosophila

Animals consolidate some, but not all, learning experiences into long-term memory. Across the animal kingdom, sleep has been found to have a beneficial effect on the consolidation of recently formed memories into long-term storage. However, the underlying mechanisms of sleep dependent memory consolidation are poorly understood. Here, we show that consolidation of courtship long-term memory in Drosophila is mediated by reactivation during sleep of dopaminergic neurons that were earlier involved in memory acquisition. We identify specific fan-shaped body neurons that induce sleep after the learning experience and activate dopaminergic neurons for memory consolidation. Thus, we provide a direct link between sleep, neuronal reactivation of dopaminergic neurons, and memory consolidation.

Why do some memories fade after only a few seconds, whereas others last a lifetime? Studies suggest that part of the explanation has to do with sleep. Experiments in rodents show that neural circuits that are active during learning become active again when an animal sleeps. This process of reactivation, which may be akin to dreaming, helps strengthen specific memories and move them into long-term storage. But the complexity of the mammalian brain has made it difficult to pin down the underlying mechanisms.

One possible solution is to study the mechanisms in a simpler brain with fewer neurons, such as that of the fruit fly Drosophila. Dag, Lei et al. have now used molecular genetic tools to explore how sleep supports a specific type of learning in male fruit flies, called courtship learning. Female fruit flies that have recently mated will reject the courtship efforts of other males. A male fly that experiences repeated rejections therefore learns to avoid mated females in future. This type of memory can last for at least a day – a long time in the life of a fly.

Dag, Lei et al. show that males that experience repeated rejections subsequently spend more time asleep than control males. Preventing this sleep hinders the males from learning from their experience. But how does this process work? During sleep, specific dopamine neurons that were active during the learning episode become active once again. Blocking this reactivation prevents the flies from learning from their rejections. By contrast, artificially activating the dopamine neurons enables flies with only limited experience of rejection to learn to avoid mated females. Dag, Lei et al. show that neurons called vFB cells control this process. The vFB neurons both induce sleep and reactivate the memory-inducing dopamine neurons.

These findings in fruit flies thus reveal a direct causal link between sleep, reactivation of memory traces, and persistence of memories. They also show that fruit flies are a valid model for exploring the neural and molecular mechanisms connecting sleep and long-term memory.

Acute Administration of Caffeine: The Effect on Motor Coordination, Higher Brain Cognitive Functions, and the Social Behavior of BLC57 Mice

Excessive caffeine consumption causes adverse health effects. The effects of moderate and high doses of caffeine consumption on the motor coordination, cognitive brain functions, and the social behavior in mice were studied. Animals were divided into three groups: control group, moderate dose group (Ac MD), and high dose group (Ac HD). The animals were tested after 7 days of caffeine administration. A rotarod test for motor coordination showed that the mice of the moderate dose group could stay on the rotating rod longer before falling in comparison to the control group and the high dose group. A water maze test for learning and memory showed better performance of mice receiving the moderate dose of caffeine compared to the other groups. Animals that were administered moderate as well as high doses of caffeine showed no sociability and no preference for social novelty in the three-chamber test used to test social behavior. In an elevated plus maze test, control animals showed no anxiety-like behavior while mice from both of the groups administered with caffeine showed anxiety-like behaviors. Our data conclude that the effects of caffeine on higher brain functions depend on the administration dose. When caffeine was given in moderate doses, it resulted in enhancement of memory and motor coordination functions. However, high doses caused defects in memory and learning. The social behavior of the mice, as determined by the level of anxiety and sociability, was affected negatively by moderate as well as high dose caffeine administration.

Sleep disturbances and depression severity in patients with Parkinson's disease

OBJECTIVES

Parkinson's disease (PD) is a multisystem movement disorder associated with sleep disturbance and depression. Sleep disturbances and depression severity share a bidirectional association. This association may be greater in individuals who are more vulnerable to the deleterious consequences of sleep disturbance and depression severity. We investigated whether the association between sleep disturbances and depression severity is greater in patients with PD than in matched controls (MC).

MATERIALS AND METHODS

The study sample (N = 98) included 50 patients with idiopathic PD and 48 age-, race-, sex-, and education-matched controls. Sleep disturbances were assessed using self-reported total sleep time (TST) on the Pittsburgh Sleep Quality Index, the sleep item on the Beck Depression Inventory, 2nd ed. (BDI-II), and the Insomnia Severity Index total score. Depression severity was assessed using the BDI-II total score, excluding the sleep item. Spearman's correlations, chi-squared tests, and multiple regression were used to assess associations between sleep disturbances and depression severity in PD and MC. Fisher's Z transformation was used to test whether the association between sleep disturbances and depression severity was stronger in patients with PD.

RESULTS

Shorter TST, sleeping less than usual, and insomnia severity were associated with depression severity in the total sample, rs(94) = -0.35, p = .001; rs(71) = 0.51, p < .001; rs(78) = -0.47, p < .001; rs(98) = 0.46, p < .001, respectively. The association between shorter TST and depression severity was greater in patients with PD than it was in MC, p < .05.

CONCLUSION

Short TST may be an important marker, predictor, or consequence of depression severity in patients with Parkinson's disease.

Identification of Genes that Maintain Behavioral and Structural Plasticity during Sleep Loss

Although patients with primary insomnia experience sleep disruption, they are able to maintain normal performance on a variety of cognitive tasks. This observation suggests that insomnia may be a condition where predisposing factors simultaneously increase the risk for insomnia and also mitigate against the deleterious consequences of waking. To gain insight into processes that might regulate sleep and buffer neuronal circuits during sleep loss, we manipulated three genes, fat facet (faf), highwire (hiw) and the GABA receptor Resistance to dieldrin (Rdl), that were differentially modulated in a Drosophila model of insomnia. Our results indicate that increasing faf and decreasing hiw or Rdl within wake-promoting large ventral lateral clock neurons (lLNvs) induces sleep loss. As expected, sleep loss induced by decreasing hiw in the lLNvs results in deficits in short-term memory and increases of synaptic growth. However, sleep loss induced by knocking down Rdl in the lLNvs protects flies from sleep-loss induced deficits in short-term memory and increases in synaptic markers. Surprisingly, decreasing hiw and Rdl within the Mushroom Bodies (MBs) protects against the negative effects of sleep deprivation (SD) as indicated by the absence of a subsequent homeostatic response, or deficits in short-term memory. Together these results indicate that specific genes are able to disrupt sleep and protect against the negative consequences of waking in a circuit dependent manner.

Molecular Mechanisms of Sleep Homeostasis in Flies and Mammals

Sleep is homeostatically regulated with sleep pressure accumulating with the increasing duration of prior wakefulness. Yet, a clear understanding of the molecular components of the homeostat, as well as the molecular and cellular processes they sense and control to regulate sleep intensity and duration, remain a mystery. Here, we will discuss the cellular and molecular basis of sleep homeostasis, first focusing on the best homeostatic sleep marker in vertebrates, slow wave activity; second, moving to the molecular genetic analysis of sleep homeostasis in the fruit fly Drosophila; and, finally, discussing more systemic aspects of sleep homeostasis.

Drosophila PINK1 and parkin loss-of-function mutants display a range of non-motor Parkinson's disease phenotypes

Parkinson's disease (PD) is more commonly associated with its motor symptoms and the related degeneration of dopamine (DA) neurons. However, it is becoming increasingly clear that PD patients also display a wide range of non-motor symptoms, including memory deficits and disruptions of their sleep-wake cycles. These have a large impact on their quality of life, and often precede the onset of motor symptoms, but their etiology is poorly understood. The fruit fly Drosophila has already been successfully used to model PD, and has been used extensively to study relevant non-motor behaviours in other contexts, but little attention has yet been paid to modelling non-motor symptoms of PD in this genetically tractable organism. We examined memory performance and circadian rhythms in flies with loss-of-function mutations in two PD genes: PINK1 and parkin. We found learning and memory abnormalities in both mutant genotypes, as well as a weakening of circadian rhythms that is underpinned by electrophysiological changes in clock neurons. Our study paves the way for further work that may help us understand the mechanisms underlying these neglected aspects of PD, thus identifying new targets for treatments to address these non-motor problems specifically and perhaps even to halt disease progression in its prodromal phase.

Effects of Kamikihito and Unkei-to on Sleep Behavior of Wild Type and Parkinson Model in Drosophila

Parkinson's disease (PD) is the second most common neurodegenerative disease, and it is associated with sleep behavior disorders. In Drosophila melanogaster disease model, human α-synuclein A30P overexpressing flies (A30P PD model) have been shown for levy body aggregation and movement disorders. We measured sleep rhythms in the A30P PD model flies using the Drosophila Activity Monitoring system and found that they develop sleep defects at 20 days after eclosion. Furthermore, the total amount of sleep is significantly reduced in middle-aged PD model flies and the reduction has been attributed to nighttime sleep. The number and length of sleep bouts also decreased in middle-aged A30P PD model flies. Feeding of the oriental traditional herbal medicines (Kampo), Kamikihito and Unkei-to significantly ameliorate the level of sleep defects in A30P PD model flies. The Kamikihito and Unkei-to recovered 60-min sleep bouts number in the A30P PD model flies to the level of young (5 days after eclosion) flies. Kamikihito recovered sleep both in wild-type and PD model flies. Unkei-to ameliorates not only sleep but also motor function in PD model flies. The data suggest that Kamikihito and Unkei-to might be useful for the sleep defects in human PD patients as well as healthy human.

Acute Sleep Deprivation Blocks Short- and Long-Term Operant Memory in Aplysia

STUDY OBJECTIVES

Insufficient sleep in individuals appears increasingly common due to the demands of modern work schedules and technology use. Consequently, there is a growing need to understand the interactions between sleep deprivation and memory. The current study determined the effects of acute sleep deprivation on short and long-term associative memory using the marine mollusk Aplysia californica, a relatively simple model system well known for studies of learning and memory.

METHODS

Aplysia were sleep deprived for 9 hours using context changes and tactile stimulation either prior to or after training for the operant learning paradigm, learning that food is inedible (LFI). The effects of sleep deprivation on short-term (STM) and long-term memory (LTM) were assessed.

RESULTS

Acute sleep deprivation prior to LFI training impaired the induction of STM and LTM with persistent effects lasting at least 24 h. Sleep deprivation immediately after training blocked the consolidation of LTM. However, sleep deprivation following the period of molecular consolidation did not affect memory recall. Memory impairments were independent of handling-induced stress, as daytime handled control animals demonstrated no memory deficits. Additional training immediately after sleep deprivation failed to rescue the induction of memory, but additional training alleviated the persistent impairment in memory induction when training occurred 24 h following sleep deprivation.

CONCLUSIONS

Acute sleep deprivation inhibited the induction and consolidation, but not the recall of memory. These behavioral studies establish Aplysia as an effective model system for studying the interactions between sleep and memory formation.

Unraveling the Neurobiology of Sleep and Sleep Disorders Using Drosophila

Sleep disorders in humans are increasingly appreciated to be not only widespread but also detrimental to multiple facets of physical and mental health. Recent work has begun to shed light on the mechanistic basis of sleep disorders like insomnia, restless legs syndrome, narcolepsy, and a host of others, but a more detailed genetic and molecular understanding of how sleep goes awry is lacking. Over the past 15 years, studies in Drosophila have yielded new insights into basic questions regarding sleep function and regulation. More recently, powerful genetic approaches in the fly have been applied toward studying primary human sleep disorders and other disease states associated with dysregulated sleep. In this review, we discuss the contribution of Drosophila to the landscape of sleep biology, examining not only fundamental advances in sleep neurobiology but also how flies have begun to inform pathological sleep states in humans.

Recurrent Sleep Fragmentation Induces Insulin and Neuroprotective Mechanisms in Middle-Aged Flies

Lack of quality sleep increases central nervous system oxidative stress and impairs removal of neurotoxic soluble metabolites from brain parenchyma. During aging poor sleep quality, caused by sleep fragmentation, increases central nervous system cellular stress. Currently, it is not known how organisms offset age-related cytotoxic metabolite increases in order to safeguard neuronal survival. Furthermore, it is not understood how age and sleep fragmentation interact to affect oxidative stress protection pathways. We demonstrate sleep fragmentation increases systems that protect against oxidative damage and neuroprotective endoplasmic reticulum molecular chaperones, as well as neuronal insulin and dopaminergic expression in middle-aged Drosophila males. Interestingly, even after sleep recovery the expression of these genes was still upregulated in middle-aged flies. Finally, sleep fragmentation generates higher levels of reactive oxygen species (ROS) in middle-aged flies and after sleep recovery these levels remain significantly higher than in young flies. The fact that neuroprotective pathways remain upregulated in middle-aged flies beyond sleep fragmentation suggests it might represent a strong stressor for the brain during later life.

The Yin and Yang of Sleep and Attention

Sleep is not a single state, but a complex set of brain processes that supports several physiological needs. Sleep deprivation is known to affect attention in many animals, suggesting that a key function of sleep is to regulate attention. Conversely, tasks that require more attention drive sleep need and sleep intensity. Attention involves the ability to filter incoming stimuli based on their relative salience, and this is likely to require coordinated synaptic activity across the brain. This capacity may have only become possible with the evolution of related neural mechanisms that support two key sleep functions: stimulus suppression and synaptic plasticity. We argue here that sleep and attention may have coevolved as brain states that regulate each other.

Differential activation of immune factors in neurons and glia contribute to individual differences in resilience/vulnerability to sleep disruption

Individuals frequently find themselves confronted with a variety of challenges that threaten their wellbeing. While some individuals face these challenges efficiently and thrive (resilient) others are unable to cope and may suffer persistent consequences (vulnerable). Resilience/vulnerability to sleep disruption may contribute to the vulnerability of individuals exposed to challenging conditions. With that in mind we exploited individual differences in a fly's ability to form short-term memory (STM) following 3 different types of sleep disruption to identify the underlying genes. Our analysis showed that in each category of flies examined, there are individuals that form STM in the face of sleep loss (resilient) while other individuals show dramatic declines in cognitive behavior (vulnerable). Molecular genetic studies revealed that Antimicrobial Peptides, factors important for innate immunity, were candidates for conferring resilience/vulnerability to sleep deprivation. Specifically, Metchnikowin (Mtk), drosocin (dro) and Attacin (Att) transcript levels seemed to be differentially increased by sleep deprivation in glia (Mtk), neurons (dro) or primarily in the head fat body (Att). Follow-up genetic studies confirmed that expressing Mtk in glia but not neurons, and expressing dro in neurons but not glia, disrupted memory while modulating sleep in opposite directions. These data indicate that various factors within glia or neurons can contribute to individual differences in resilience/vulnerability to sleep deprivation.

Unraveling the complexities of circadian and sleep interactions with memory formation through invertebrate research

Across phylogeny, the endogenous biological clock has been recognized as providing adaptive advantages to organisms through coordination of physiological and behavioral processes. Recent research has emphasized the role of circadian modulation of memory in generating peaks and troughs in cognitive performance. The circadian clock along with homeostatic processes also regulates sleep, which itself impacts the formation and consolidation of memory. Thus, the circadian clock, sleep and memory form a triad with ongoing dynamic interactions. With technological advances and the development of a global 24/7 society, understanding the mechanisms underlying these connections becomes pivotal for development of therapeutic treatments for memory disorders and to address issues in cognitive performance arising from non-traditional work schedules. Invertebrate models, such as Drosophila melanogaster and the mollusks Aplysia and Lymnaea, have proven invaluable tools for identification of highly conserved molecular processes in memory. Recent research from invertebrate systems has outlined the influence of sleep and the circadian clock upon synaptic plasticity. In this review, we discuss the effects of the circadian clock and sleep on memory formation in invertebrates drawing attention to the potential of in vivo and in vitro approaches that harness the power of simple invertebrate systems to correlate individual cellular processes with complex behaviors. In conclusion, this review highlights how studies in invertebrates with relatively simple nervous systems can provide mechanistic insights into corresponding behaviors in higher organisms and can be used to outline possible therapeutic options to guide further targeted inquiry.

Evaluation of traditional medicines for neurodegenerative diseases using Drosophila models

Drosophila is one of the oldest and most powerful genetic models and has led to novel insights into a variety of biological processes. Recently, Drosophila has emerged as a model system to study human diseases, including several important neurodegenerative diseases. Because of the genomic similarity between Drosophila and humans, Drosophila neurodegenerative disease models exhibit a variety of human-disease-like phenotypes, facilitating fast and cost-effective in vivo genetic modifier screening and drug evaluation. Using these models, many disease-associated genetic factors have been identified, leading to the identification of compelling drug candidates. Recently, the safety and efficacy of traditional medicines for human diseases have been evaluated in various animal disease models. Despite the advantages of the Drosophila model, its usage in the evaluation of traditional medicines is only nascent. Here, we introduce the Drosophila model for neurodegenerative diseases and some examples demonstrating the successful application of Drosophila models in the evaluation of traditional medicines.

ERK phosphorylation regulates sleep and plasticity in Drosophila

Given the relationship between sleep and plasticity, we examined the role of Extracellular signal-regulated kinase (ERK) in regulating baseline sleep, and modulating the response to waking experience. Both sleep deprivation and social enrichment increase ERK phosphorylation in wild-type flies. The effects of both sleep deprivation and social enrichment on structural plasticity in the LNvs can be recapitulated by expressing an active version of ERK (UAS-ERK^SEM) pan-neuronally in the adult fly using GeneSwitch (Gsw) Gsw-elav-GAL4. Conversely, disrupting ERK reduces sleep and prevents both the behavioral and structural plasticity normally induced by social enrichment. Finally, using transgenic flies carrying a cAMP response Element (CRE)-luciferase reporter we show that activating ERK enhances CRE-Luc activity while disrupting ERK reduces it. These data suggest that ERK phosphorylation is an important mediator in transducing waking experience into sleep.

Modeling the genetic basis for human sleep disorders in Drosophila

Sleep research in Drosophila is not only here to stay, but is making impressive strides towards helping us understand the biological basis for and the purpose of sleep—perhaps one of the most complex and enigmatic of behaviors. Thanks to over a decade of sleep-related studies in flies, more molecular methods are being applied than ever before towards understanding the genetic basis of sleep disorders. The advent of high-throughput technologies that can rapidly interrogate whole genomes, epigenomes and proteomes, has also revolutionized our ability to detect genetic variants that might be causal for a number of sleep disorders. In the coming years, mutational studies in model organisms such as Drosophila will need to be functionally connected to information being generated from these whole-genome approaches in humans. This will necessitate the development of appropriate methods for interpolating data and increased analytical power to synthesize useful network(s) of sleep regulatory pathways—including appropriate discriminatory and predictive capabilities. Ultimately, such networks will also need to be interpreted in the context of fundamental neurobiological substrates for sleep in any given species. In this review, we highlight some emerging approaches, such as network analysis and mathematical modeling of sleep distributions, which can be applied to contemporary sleep research as a first step to achieving these aims. These methodologies should favorably impact not only a mechanistic understanding of sleep, but also future pharmacological intervention strategies to manage and treat sleep disorders in humans.

Transient activation of dopaminergic neurons during development modulates visual responsiveness, locomotion and brain activity in a dopamine ontogeny model of schizophrenia

It has been observed that certain developmental environmental risk factors for schizophrenia when modeled in rodents alter the trajectory of dopaminergic development, leading to persistent behavioural changes in adults. This has recently been articulated as the "dopamine ontogeny hypothesis of schizophrenia". To test one aspect of this hypothesis, namely that transient dopaminergic effects during development modulate attention-like behavior and arousal in adults, we turned to a small-brain model, Drosophila melanogaster. By applying genetic tools allowing transient activation or silencing of dopaminergic neurons in the fly brain, we investigated whether a critical window exists during development when altered dopamine (DA) activity levels could lead to impairments in arousal states in adult animals. We found that increased activity in dopaminergic neurons in later stages of development significantly increased visual responsiveness and locomotion, especially in adult males. This misallocation of visual salience and hyperactivity mimicked the effect of acute methamphetamine feeding to adult flies, suggesting up-regulated DA signaling could result from developmental manipulations. Finally, brain recordings revealed significantly reduced gamma-band activity in adult animals exposed to the transient developmental insult. Together, these data support the idea that transient alterations in DA signaling during development can permanently alter behavior in adults, and that a reductionist model such as Drosophila can be used to investigate potential mechanisms underlying complex cognitive disorders such as schizophrenia.

ER stress inhibits neuronal death by promoting autophagy

Endoplasmic reticulum (ER) stress has been implicated in neurodegenerative diseases but its relationship and role in disease progression remain unclear. Using genetic and pharmacological approaches, we showed that mild ER stress ("preconditioning") is neuroprotective in Drosophila and mouse models of Parkinson disease. In addition, we found that the combination of mild ER stress and apoptotic signals triggers an autophagic response both in vivo and in vitro. We showed that when autophagy is impaired, ER-mediated protection is lost. We further demonstrated that autophagy inhibits caspase activation and apoptosis. Based on our findings, we conclude that autophagy is required for the neuroprotection mediated by mild ER stress, and therefore ER preconditioning has potential therapeutic value for the treatment of neurodegenerative diseases.

Mushroom bodies of the honeybee brain show cell population-specific plasticity in expression of amine-receptor genes

Dopamine and octopamine released in the mushroom bodies of the insect brain play a critical role in the formation of aversive and appetitive memories, respectively. As recent evidence suggests a complex relationship between the effects of these two amines on the output of mushroom body circuits, we compared the expression of dopamine- and octopamine-receptor genes in three major subpopulations of mushroom body intrinsic neurons (Kenyon cells). Using the brain of the honeybee, Apis mellifera, we found that expression of amine-receptor genes differs markedly across Kenyon cell subpopulations. We found, in addition, that levels of expression of these genes change dramatically during the lifetime of the bee and that shifts in expression are cell population-specific. Differential expression of amine-receptor genes in mushroom body neurons and the plasticity that exists at this level are features largely ignored in current models of mushroom body function. However, our results are consistent with the growing body of evidence that short- and long-term olfactory memories form in different regions of the mushroom bodies of the brain and that there is functional compartmentalization of the modulatory inputs to this multifunctional brain center.

Pre-fibrillar α-synuclein mutants cause Parkinson's disease-like non-motor symptoms in Drosophila

Parkinson's disease (PD) is linked to the formation of insoluble fibrillar aggregates of the presynaptic protein α-Synuclein (αS) in neurons. The appearance of such aggregates coincides with severe motor deficits in human patients. These deficits are often preceded by non-motor symptoms such as sleep-related problems in the patients. PD-like motor deficits can be recapitulated in model organisms such as Drosophila melanogaster when αS is pan-neurally expressed. Interestingly, both these deficits are more severe when αS mutants with reduced aggregation properties are expressed in flies. This indicates that that αS aggregation is not the primary cause of the PD-like motor symptoms. Here we describe a model for PD in Drosophila which utilizes the targeted expression of αS mutants in a subset of dopadecarboxylase expressing serotonergic and dopaminergic (DA) neurons. Our results show that targeted expression of pre-fibrillar αS mutants not only recapitulates PD-like motor symptoms but also the preceding non-motor symptoms such as an abnormal sleep-like behavior, altered locomotor activity and abnormal circadian periodicity. Further, the results suggest that the observed non-motor symptoms in flies are caused by an early impairment of neuronal functions rather than by the loss of neurons due to cell death.

Drosophila melanogaster in the study of human neurodegeneration

Human neurodegenerative diseases are devastating illnesses that predominantly affect elderly people. The majority of the diseases are associated with pathogenic oligomers from misfolded proteins, eventually causing the formation of aggregates and the progressive loss of neurons in the brain and nervous system. Several of these proteinopathies are sporadic and the cause of pathogenesis remains elusive. Heritable forms are associated with genetic defects, suggesting that the affected protein is causally related to disease formation and/or progression. The limitations of human genetics, however, make it necessary to use model systems to analyse affected genes and pathways in more detail. During the last two decades, research using the genetically amenable fruitfly has established Drosophila melanogaster as a valuable model system in the study of human neurodegeneration. These studies offer reliable models for Alzheimer's, Parkinson's, and motor neuron diseases, as well as models for trinucleotide repeat expansion diseases, including ataxias and Huntington's disease. As a result of these studies, several signalling pathways including phosphatidylinositol 3-kinase (PI3K)/Akt and target of rapamycin (TOR), c-Jun N-terminal kinase (JNK) and bone morphogenetic protein (BMP) signalling, have been shown to be deregulated in models of proteinopathies, suggesting that two or more initiating events may trigger disease formation in an age-related manner. Moreover, these studies also demonstrate that the fruitfly can be used to screen chemical compounds for their potential to prevent or ameliorate the disease, which in turn can directly guide clinical research and the development of novel therapeutic strategies for the treatment of human neurodegenerative diseases.