Down-regulating insulin-like growth factor-1 receptor reduces amyloid-β deposition in mice cortex induced by chronic sleep restriction

OBJECTIVE

Insufficient sleep affects cognitive function, but the underlying mechanism and potential protective ways are yet to be fully understood. This study aimed to explore the influence of chronic sleep restriction (CSR) on the insulin-like growth factor-1 (IGF-1) signaling pathway, and whether down-regulating IGF-1 signaling pathway would modulate amyloid-β (Aβ) peptides metabolism and its cortical deposition after CSR. Methods 8-week IGF-1R^+/- mice and wild-type (WT) C57BL/6 (C57) mice were divided into four groups: IGF-1R^+/- CSR (MUSR), IGF-1R^+/- control (MUCO), C57 CSR (C57SR) and C57 control (C57CO). CSR model was established by application of slowly rotating drum for 2 months. Body weight and Lee's index were measured. The level of IGF-1 in plasma was measured by enzyme linked immunosorbent assay (ELISA). Aβ accumulation was detected by immunofluorescence. The expressions of amyloid precursor protein (APP), β-site amyloid precursor protein-cleaving enzyme-1 (BACE-1) and C99 were detected using western-blot (WB). Results Two-way ANOVA showed genotypic effect was significant on body weight and Lee's index. Neither treatment effect nor interaction reached significant difference on body weight and Lee's index. The level of IGF-1 in plasma was significantly decreased in C57SR compared with C57CO. Besides, compared with C57CO, Aβ was markedly accumulated in frontal cortex, in parallel with increased expressions of BACE-1 and C99, and with no difference of APP in C57SR group. Further, no significant changes of Aβ, BACE-1, C99 and APP were detected in MUSR compared with MUCO. Conclusions This study showed that CSR could induce the decrease of circulating IGF-1 in mice. By using the IGF-1R^+/- mice, we found that down-regulating IGF-1R could reduce Aβ deposition in mice frontal cortex after CSR via inhibiting BACE-1 protein expression and activity, which were independent of the changes of body weight and Lee's index. These findings indicate that the blockage of IGF-1 signaling pathway might be a protection mechanism for alleviating the impact of CSR.

Involvement of Paired Immunoglobulin-Like Receptor B in Cognitive Dysfunction Through Hippocampal-Dependent Synaptic Plasticity Impairments in Mice Subjected to Chronic Sleep Restriction

Sleep loss is often associated with cognitive dysfunction. Alterations in the structure and function of synapses in the hippocampus are thought to underlie memory storage. Paired immunoglobulin-like receptor B (PirB) plays a negative role in various neurological diseases by inhibiting axon regeneration and synaptic plasticity. However, the contributions of PirB to the mechanisms underlying the changes in synaptic plasticity after sleep loss that ultimately promote deficits in cognitive function have not been well elucidated. Here, we showed that chronic sleep restriction (CSR) mice displayed cognitive impairment and synaptic deficits accompanied by upregulation of PirB expression in the hippocampus. Mechanistically, PirB caused the dysregulation of actin through the RhoA/ROCK2/LIMK1/cofilin signalling pathway, leading to abnormal structural and functional plasticity, which in turn resulted in cognitive dysfunction. PirB knockdown alleviated synaptic deficits and cognitive impairment after CSR by inhibiting the RhoA/ROCK2/LIMK1/cofilin signalling pathway. Moreover, we found that fasudil, a widely used ROCK2 inhibitor, could mimic the beneficial effect of PirB knockdown and ameliorate synaptic deficits and cognitive impairment, further demonstrating that PirB induced cognitive dysfunction after CSR via the RhoA/ROCK2/LIMK1/cofilin signalling pathway. Our study sheds new light on the role of PirB as an important mediator in modulating the dysfunction of synaptic plasticity and cognitive function via the RhoA/ROCK2/LIMK1/cofilin signalling pathway, which indicated that hippocampal PirB is a promising therapeutic target for counteracting cognitive impairment after CSR. This illustration depicts the signalling pathway by PirB in mediating cognitive impairment and synaptic deficits in CSR mice. In the hippocampus of CSR mice, the expression level of PirB was significantly increased. In addition, CSR increases RhoA and ROCK2 levels and reduces levels of both LIMK1 and cofilin phosphorylation. PirB knockdown reverses cognitive impairment and synaptic plasticity disorders caused by CSR through the RhoA/ROCK2/LIMK1/cofilin signalling pathway.

Naturally Occurring Consecutive Sleep Loss and Day-to-Day Trajectories of Affective and Physical Well-Being

BACKGROUND

Experimental studies have shown that just 1 night of sleep loss impairs next-day performance, mood, and energy. Yet, little is known about the effects of consecutive sleep loss on daily well-being in participants' own settings.

PURPOSE

This study examined whether and how naturally occurring consecutive sleep loss is associated with day-to-day trajectories of affective and physical well-being.

METHODS

Participants were adults (N = 1,958) from the Midlife in the United States Study who provided daily diary data for eight consecutive days. Consecutive sleep loss was operationalized as the within-person number of consecutive nights with <6 hr of sleep. Multilevel models evaluated the linear, quadratic, and cubic effects of consecutive sleep loss on daily well-being, after controlling for sociodemographic, health, and daily covariates.

RESULTS

Daily negative affect increased and positive affect decreased in curvilinear fashion as the number of consecutive sleep loss increased. For example, daily negative affect increased (linear), but the rate of increase decelerated as the number of consecutive sleep loss increased (quadratic). Results were consistent for the number and severity of physical symptoms. For negative affect and the severity of physical symptoms, cubic effect was also significant such that the rate of increase accelerated again in the days most distal to baseline (no sleep loss).

CONCLUSIONS

Consecutive sleep loss was associated with degraded trajectories of daily affective and physical well-being. Making efforts to break the vicious cycle of sleep loss may protect daily well-being in adults whose sleep time is often compromised.

Chronic sleep restriction increases soluble hippocampal Aβ-42 and impairs cognitive performance

Currently, over 44 million people worldwide suffer from Alzheimer's disease (AD). A common feature of AD is disrupted sleep. Sleep is essential for many psychological and physiological functions, though 35.3% of adults report getting less than 7 hours per night. The present research examined whether chronic sleep restriction would elevate hippocampal amyloid-beta_1-42 expression or alter cognitive ability in adult C57BL/6 mice. Chronic sleep restriction was associated with cognitive impairment and increased hippocampal amyloid-beta. Thus, chronic sleep loss may have a detrimental effect upon cognitive function, in part, via increasing amyloid-beta levels in the hippocampus, even in non-genetically modified mice.

The coupling of short sleep duration and high sleep need predicts riskier decision making

Objective: To examine how risk-related decision making might be associated with habitual sleep variables, including sleep variability, sleep duration and perceived sleep need in young adults cross-sectionally and longitudinally. Design: 166 participants completed a 7-day protocol with sleep and risk-related decision-making measures at baseline (T1) and 12 months later (T2). Results: Habitual short sleep duration (averaging < 6 h nightly) was identified in 11.0% in our sample. After controlling for baseline demographic factors and risk-taking measures, self-reported sleep need at T1 interacted with habitual short sleep in predicting risk taking at follow-up (F_8,139=9.575, adjusted R²=.431, p<.001). T1 greater perceived sleep need predicted more risk taking among short sleepers, but decreased risk taking among normal sleepers at T2. Variable sleep timing was cross-sectionally correlated with making more Risky choices at baseline and fewer Safe choices after loss at follow up. Conclusions: Young adults with variable sleep timing and those with short sleep duration coupled with high perceived sleep need were more likely to take risks. The moderating effects of perceived sleep need suggest that individual differences may alter the impact of sleep loss and hence should be measured and accounted for in future studies.

Sinoatrial node remodels in chronic sleep-restricted rats

Chronic Sleep Restriction (CSR) is known as a risk factor for cardiovascular diseases. However, the structural changes of Sinoatrial (SA) node cells have received less attention. This study aimed to evaluate the effects of CSR on SA node in an animal model using stereological methods. Adult male Sprague-Dawley rats were randomly divided into CSR, grid-floor, and control groups. The CSR procedure was designed such a way that the animals had a full cycle of sleep (6 hours) per day, while they were unable to have a Rapid Eye Movement (REM) sleep during the remaining 18 hours. This was induced by a multiplatform box containing water. The grid-floor animals were placed in the same multiplatform box with a grid-floor covering to prevent falling in water. After 21 days, the right atria were dissected out. Then, the location of the SA node was determined and evaluated by stereological techniques. The total volume of the SA node, the total volume of the main node cells, the volume of the connective tissue, and mean volume of the node cells were respectively enlarged by 60%, 47%, 68%, and 51% in the CSR animals compared to the grid-floor rats (p < 0.05). However, no significant changes were detected in these parameters in the control and grid-floor animals. The population of the main node cells remained constant in all animal groups. In addition, the three-dimensional reconstruction of the SA node in the CSR group showed a hypertrophied appearance. In conclusion, CSR induced hypertrophic changes in the rats' SA node structures without alteration in the number of main node cells.

Chronic Sleep Restriction Induces Aβ Accumulation by Disrupting the Balance of Aβ Production and Clearance in Rats

Amyloid-β (Aβ) plays an important role in Alzheimer's disease (AD) pathogenesis, and growing evidence has shown that poor sleep quality is one of the risk factors for AD, but the mechanisms of sleep deprivation leading to AD have still not been fully demonstrated. In the present study, we used wild-type (WT) rats to determine the effects of chronic sleep restriction (CSR) on Aβ accumulation. We found that CSR-21d rats had learning and memory functional decline in the Morris water maze (MWM) test. Meanwhile, Aβ₄₂ deposition in the hippocampus and the prefrontal cortex was high after a 21-day sleep restriction. Moreover, compared with the control rats, CSR rats had increased expression of β-site APP-cleaving enzyme 1 (BACE1) and sAPPβ and decreased sAPPα levels in both the hippocampus and the prefrontal cortex, and the BACE1 level was positively correlated with the Aβ₄₂ level. Additionally, in CSR-21d rats, low-density lipoprotein receptor-related protein 1 (LRP-1) levels were low, while receptor of advanced glycation end products (RAGE) levels were high in the hippocampus and the prefrontal cortex, and these transporters were significantly correlated with Aβ₄₂ levels. In addition, CSR-21d rats had decreased plasma Aβ₄₂ levels and soluble LRP1 (sLRP1) levels compared with the control rats. Altogether, this study demonstrated that 21 days of CSR could lead to brain Aβ accumulation in WT rats. The underlying mechanisms may be related to increased Aβ production via upregulation of the BACE1 pathway and disrupted Aβ clearance affecting brain and peripheral Aβ transport.

Chronic sleep restriction increases pain sensitivity over time in a periaqueductal gray and nucleus accumbens dependent manner

Painful conditions and sleep disturbances are major public health problems worldwide and one directly affects the other. Sleep loss increases pain prevalence and severity; while pain disturbs sleep. However, the underlying mechanisms are largely unknown. Here we asked whether chronic sleep restriction for 6 h daily progressively increases pain sensitivity and if this increase is reversed after two days of free sleep. Also, whether the pronociceptive effect of chronic sleep restriction depends on the periaqueductal grey and on the nucleus accumbens, two key regions involved in the modulation of pain and sleep-wake cycle. We showed that sleep restriction induces a pronociceptive effect characterized by a significant decrease in the mechanical paw withdrawal threshold in rats. Such effect increases progressively from day 3 to day 12 remaining stable thereafter until day 26. Two consecutive days of free sleep were not enough to reverse the effect, not even to attenuate it. This pronociceptive effect depends on the periaqueductal grey and on the nucleus accumbens, since it was prevented by their excitotoxic lesion. Complementarily, chronic sleep restriction significantly increased c-Fos protein expression within the periaqueductal grey and the nucleus accumbens and this correlates with the intensity of the pronociceptive effect, suggesting that the greater the neural activity in this regions, the greater the effect. These findings may contribute not only to understand why painful conditions are more prevalent and severe among people who sleep poorly, but also to develop therapeutic strategies to prevent this, increasing the effectiveness of pain management in this population.

Could curcumin protect the dendritic trees of the CA1 neurons from shortening and shedding induced by chronic sleep restriction in rats?

BACKGROUND AND OBJECTIVE

This study evaluated the effect of chronic sleep restriction (CSR) with or without curcumin (CUR) treatment on dendritic lengths and spines of the CA1 hippocampus using the virtual space-ball method.

MATERIALS AND METHODS

Male rats were randomly submitted to nine groups, including distilled water, CUR (100 mg/kg/day), olive oil, CSR plus distilled water, CSR plus CUR, CSR plus olive oil, grid-floor plus distilled water, grid-floor plus CUR, and grid-floor plus olive oil groups. Sleep deficiency was imposed using the multi-platform box containing water for 18 h/day. In 21 days, animal's brains were prepared for stereological studies.

RESULTS

The mean dendrite length in CA1 neurons was reduced by 39% (p < 0.05) while the density of stubby, thin, and mushroom spines reduced by 38%, 33% and 32%, respectively (p < 0.01), in the CSR + distilled water group compared to the distilled water group. Yet, CUR treatment in CSR-rats was found to protect the declined dendritic length as well as loss of stubby and mushroom but not thin spines.

CONCLUSION

The estimated dendritic length using the virtual space-ball method revealed that chronic sleep restriction for 18 h/day over 21 days could induce shortening and shedding of the CA1 dendritic trees which could notably be protected by CUR.

Chronic sleep restriction promotes brain inflammation and synapse loss, and potentiates memory impairment induced by amyloid-β oligomers in mice

It is increasingly recognized that sleep disturbances and Alzheimer's disease (AD) share a bidirectional relationship. AD patients exhibit sleep problems and alterations in the regulation of circadian rhythms; conversely, poor quality of sleep increases the risk of development of AD. The aim of the current study was to determine whether chronic sleep restriction potentiates the brain impact of amyloid-β oligomers (AβOs), toxins that build up in AD brains and are thought to underlie synapse damage and memory impairment. We further investigated whether alterations in levels of pro-inflammatory mediators could play a role in memory impairment in sleep-restricted mice. We found that a single intracerebroventricular (i.c.v.) infusion of AβOs disturbed sleep pattern in mice. Conversely, chronically sleep-restricted mice exhibited higher brain expression of pro-inflammatory mediators, reductions in levels of pre- and post-synaptic marker proteins, and exhibited increased susceptibility to the impact of i.c.v. infusion of a sub-toxic dose of AβOs (1pmol) on performance in the novel object recognition memory task. Sleep-restricted mice further exhibited an increase in brain TNF-α levels in response to AβOs. Interestingly, memory impairment in sleep-restricted AβO-infused mice was prevented by treatment with the TNF-α neutralizing monoclonal antibody, infliximab. Results substantiate the notion of a dual relationship between sleep and AD, whereby AβOs disrupt sleep/wake patterns and chronic sleep restriction increases brain vulnerability to AβOs, and point to a key role of brain inflammation in increased susceptibility to AβOs in sleep-restricted mice.

Chronic Sleep Restriction Induces Cognitive Deficits and Cortical Beta-Amyloid Deposition in Mice via BACE1-Antisense Activation

AIMS

To clarify the correlation between chronic sleep restriction (CSR) and sporadic Alzheimer disease (AD), we determined in wild-type mice the impact of CSR, on cognitive performance, beta-amyloid (Aβ) peptides, and its feed-forward regulators regarding AD pathogenesis.

METHODS

Sixteen nine-month-old C57BL/6 male mice were equally divided into the CSR and control groups. CSR was achieved by application of a slowly rotating drum for 2 months. The Morris water maze test was used to assess cognitive impairment. The concentrations of Aβ peptides, amyloid precursor protein (APP) and β-secretase 1 (BACE1), and the mRNA levels of BACE1 and BACE1-antisense (BACE1-AS) were measured.

RESULTS

Following CSR, impairments of spatial learning and memory consolidation were observed in the mice, accompanied by Aβ plaque deposition and an increased Aβ concentration in the prefrontal and temporal lobe cortex. CSR also upregulated the β-secretase-induced cleavage of APP by increasing the protein and mRNA levels of BACE1, particularly the BACE1-AS.

CONCLUSIONS

This study shows that a CSR accelerates AD pathogenesis in wild-type mice. An upregulation of the BACE1 pathway appears to participate in both cortical Aβ plaque deposition and memory impairment caused by CSR. BACE1-AS is likely activated to initiate a cascade of events that lead to AD pathogenesis. Our study provides, therefore, a molecular mechanism that links CSR to sporadic AD.

Significance of the zero sum principle for circadian, homeostatic and allostatic regulation of sleep-wake state in the rat

Sleep-wake behavior exhibits diurnal rhythmicity, rebound responses to acute total sleep deprivation (TSD), and attenuated rebounds following chronic sleep restriction (CSR). We investigated how these long-term patterns of behavior emerge from stochastic short-term dynamics of state transition. Male Sprague-Dawley rats were subjected to TSD (1day×24h, N=9), or CSR (10days×18h TSD, N=7) using a rodent walking-wheel apparatus. One baseline day and one recovery day following TSD and CSR were analyzed. The implications of the zero sum principle were evaluated using a Markov model of sleep-wake state transition. Wake bout duration (a combined function of the probability of wake maintenance and proportional representations of brief and long wake) was a key variable mediating the baseline diurnal rhythms and post-TSD responses of all three states, and the attenuation of the post-CSR rebounds. Post-NREM state transition trajectory was an important factor in REM rebounds. The zero sum constraint ensures that a change in any transition probability always affects bout frequency and cumulative time of at least two, and usually all three, of wakefulness, NREM and REM. Neural mechanisms controlling wake maintenance may play a pivotal role in regulation and dysregulation of all three states.

Chronic sleep restriction induces changes in the mandibular condylar cartilage of rats: roles of Akt, Bad and Caspase-3

AIMS

The aim of the present study was to observe changes in the temporomandibular joint (TMJ) of rats that had been subjected to chronic sleep restriction and to investigate whether Akt, Bad and Caspase3 play a role in the mechanism underlying the changes.

MAIN METHODS

One hundred and eighty male Wistar rats were randomly divided into three groups (n = 60 in each): cage control group, large-platform control group, and sleep restriction group. Each group was divided into three subgroups (n = 20 in each) of three different time points (7, 14 and 21 days), respectively. The modified multiple platform method was used to induce chronic sleep restriction. The TMJ tissue histology was studied by staining with haematoxylin and eosin. The expression of Akt, p-Aktser473, Bad, p-Badser136 and Caspase3 proteins was detected by immunohistochemistry and western blotting. The expression of Akt, Bad and Caspase3 mRNAs was measured by real-time quantitative polymerase chain reaction (RT-qPCR).

KEY FINDINGS

Compared with the large-platform and cage control groups, condylar cartilage pathological alterations were found in the sleep restriction group. There were significantly decreased expression levels of Akt, p-Aktser473 and p-Badser136 and significantly increased expression levels of Bad and Caspase3 after sleep restriction.

SIGNIFICANCE

These data suggest that sleep restriction may induce pathological alterations in the condylar cartilage of rats. Alterations in Akt, Bad and Caspase3 may be associated with the potential mechanism by which chronic sleep restriction influences the condylar cartilage.

An examination of the association between chronic sleep restriction and electrocortical arousal in college students

OBJECTIVE

The deleterious neurocognitive effects of laboratory-controlled short-term sleep deprivation are well-known. The present study investigated neurocognitive changes arising from chronic sleep restriction outside the laboratory.

METHODS

Sleep patterns of 24 undergraduates were tracked via actigraphy across a 15-week semester. At the semester beginning, at a midpoint, and a week before finals, students performed the Psychomotor Vigilance Test (PVT) and cortical arousal was measured via event-related potentials (ERP) and resting state electroencephalography (EEG).

RESULTS

Average daily sleep decreased between Session 1 and Sessions 2 and 3. Calculated circadian rhythm measures indicated nighttime movement increased and sleep quality decreased from Sessions 1 and 2 to Session 3. Parallel to the sleep/activity measures, PVT reaction time increased between Session 1 and Sessions 2 and 3 and resting state alpha EEG reactivity magnitude and PVT-evoked P3 ERP amplitude decreased between Session 1 and Sessions 2 and 3. Cross-sectional regressions showed PVT reaction time was negatively associated with average daily sleep, alpha reactivity, and P3 changes; sleep/circadian measures were associated with alpha reactivity and/or P3 changes.

CONCLUSIONS

Small, but persistent sleep deficits reduced cortical arousal and impaired vigilant attention.

SIGNIFICANCE

Chronic sleep restriction impacts neurocognition in a manner similar to laboratory controlled sleep deprivation.

Sleep allostasis in chronic sleep restriction: the role of the norepinephrine system

Sleep responses to chronic sleep restriction may be very different from those observed after acute total sleep deprivation. Specifically, when sleep restriction is repeated for several consecutive days, animals express attenuated compensatory increases in sleep time and intensity during daily sleep opportunities. The neurobiological mechanisms underlying these adaptive, or more specifically, allostatic, changes in sleep homeostasis are unknown. Several lines of evidence indicate that norepinephrine may play a key role in modulating arousal states and NREM EEG delta power, which is widely recognized as a marker for sleep intensity. Therefore, we investigated time course changes in brain adrenergic receptor mRNA levels in response to chronic sleep restriction using a rat model. Here, we observed that significantly altered mRNA levels of the α1- adrenergic receptor in the basal forebrain as well as α2- and β1-adrenergic receptor in the anterior cingulate cortex only on the first sleep restriction day. On the other hand, the frontal cortex α1-, α2-, and β1-adrenergic receptor mRNA levels were reduced throughout the period of sleep restriction. Combined with our earlier findings on EEG that sleep time and intensity significantly increased only on the first sleep restriction days, these results suggest that alterations in the brain norepinephrine system in the basal forebrain and cingulate cortex may mediate allostatic changes in sleep time and intensity observed during chronic sleep restriction.

Decoupling of sleepiness from sleep time and intensity during chronic sleep restriction: evidence for a role of the adenosine system

STUDY OBJECTIVE

Sleep responses to chronic sleep restriction (CSR) might be very different from those observed after short-term total sleep deprivation. For example, after sleep restriction continues for several consecutive days, animals no longer express compensatory increases in daily sleep time and sleep intensity. However, it is unknown if these allostatic, or adaptive, sleep responses to CSR are paralleled by behavioral and neurochemical measures of sleepiness.

DESIGN

This study was designed to investigate CSR-induced changes in (1) sleep time and intensity as a measure of electrophysiological sleepiness, (2) sleep latency as a measure of behavioral sleepiness, and (3) brain adenosine A1 (A1R) and A2a receptor (A2aR) mRNA levels as a putative neurochemical correlate of sleepiness.

SUBJECTS

Male Sprague-Dawley rats

INTERVENTIONS

A 5-day sleep restriction (SR) protocol consisting of 18-h sleep deprivation and 6-h sleep opportunity each day.

MEASUREMENT AND RESULTS

Unlike the first SR day, rats did not sleep longer or deeper on days 2 through 5, even though they exhibited significant elevations of behavioral sleepiness throughout all 5 SR days. For all SR days and recovery day 1, A1R mRNA in the basal forebrain was maintained at elevated levels, whereas A2aR mRNA in the frontal cortex was maintained at reduced levels.

CONCLUSION

CSR LEADS TO A DECOUPLING OF SLEEPINESS FROM SLEEP TIME AND SLEEP INTENSITY, SUGGESTING THAT THERE ARE AT LEAST TWO DIFFERENT SLEEP REGULATORY SYSTEMS: one mediating sleepiness (homeostatic) and the other mediating sleep time/intensity (allostatic). The time course of changes observed in adenosine receptor mRNA levels suggests that the basal forebrain and cortical adenosine system might mediate sleepiness rather than sleep time or intensity.