The induction of Per1 expression by the combined treatment with glutamate, 5-hydroxytriptamine and dopamine initiates a ripple effect on Bmal1 and Cry1 mRNA expression via the ERK signaling pathway in cultured rat spinal astrocytes

The Circadian Clocks, Oscillations of Pain-Related Mediators, and Pain

The circadian clock is a biochemical oscillator that is synchronized with solar time. Normal circadian rhythms are necessary for many physiological functions. Circadian rhythms have also been linked with many physiological functions, several clinical symptoms, and diseases. Accumulating evidence suggests that the circadian clock appears to modulate the processing of nociceptive information. Many pain conditions display a circadian fluctuation pattern clinically. Thus, the aim of this review is to summarize the existing knowledge about the circadian clocks involved in diurnal rhythms of pain. Possible cellular and molecular mechanisms regarding the connection between the circadian clocks and pain are discussed.

Neural function of Bmal1: an overview

Bmal1 (Brain and muscle arnt-like, or Arntl) is a bHLH/PAS domain transcription factor central to the transcription/translation feedback loop of the biologic clock. Although Bmal1 is well-established as a major regulator of circadian rhythm, a growing number of studies in recent years have shown that dysfunction of Bmal1 underlies a variety of psychiatric, neurodegenerative-like, and endocrine metabolism-related disorders, as well as potential oncogenic roles. In this review, we systematically summarized Bmal1 expression in different brain regions, its neurological functions related or not to circadian rhythm and biological clock, and pathological phenotypes arising from Bmal1 knockout. This review also discusses oscillation and rhythmicity, especially in the suprachiasmatic nucleus, and provides perspective on future progress in Bmal1 research.

The circadian clock regulator Bmal1 affects traumatic brain injury in rats through the p38 MAPK signalling pathway

Traumatic brain injury (TBI) is still one of the main causes of death and disability worldwide. Bmal1 (brain and muscle Arnt-like protein-1) is the most central factor of the circadian rhythms that control life and cells. Studies have shown that Bmal1 is involved in inflammation, oxidative stress, vasodilation, glucose and lipid metabolism. This study explored the effect of Bmal1 on secondary brain injury after TBI in rats and the possible mechanism. We established a rat model of TBI induced by the free fall of a weight in rats. The Western blotting and immunofluorescence results showed that the Bmal1 levels decreased in the cerebral cortex after TBI, especially at 48 h. The effects of Bmal1 levels on rats after TBI were evaluated by brain oedema measurement, adhesive removal tests, behavioural tests, and TUNEL and FJC staining. We found that the recombinant Bmal1 protein increased Bmal1 levels after TBI and reduced brain oedema, neurobehavioural injury, somatosensory disturbances, and nerve cell necrosis and apoptosis. The ELISA results showed that Bmal1 overexpression could reduce the inflammatory factors IL-4 and TNF-α after TBI. In contrast, inhibiting Bmal1 expression had the opposite effect. The changes in Bmal1 levels were closely related to the phosphorylation of p38 MAPK after TBI. In conclusion, a decrease in Bmal1 after TBI may exacerbate pathological symptoms in vivo by activating p38 MAPK phosphorylation.

A common role for astrocytes in rhythmic behaviours?

Astrocytes are a functionally diverse form of glial cell involved in various aspects of nervous system infrastructure, from the metabolic and structural support of neurons to direct neuromodulation of synaptic activity. Investigating how astrocytes behave in functionally related circuits may help us understand whether there is any conserved logic to the role of astrocytes within neuronal networks. Astrocytes are implicated as key neuromodulatory cells within neural circuits that control a number of rhythmic behaviours such as breathing, locomotion and circadian sleep-wake cycles. In this review, we examine the evidence that astrocytes are directly involved in the regulation of the neural circuits underlying six different rhythmic behaviours: locomotion, breathing, chewing, gastrointestinal motility, circadian sleep-wake cycles and oscillatory feeding behaviour. We discuss how astrocytes are integrated into the neuronal networks that regulate these behaviours, and identify the potential gliotransmission signalling mechanisms involved. From reviewing the evidence of astrocytic involvement in a range of rhythmic behaviours, we reveal a heterogenous array of gliotransmission mechanisms, which help to regulate neuronal networks. However, we also observe an intriguing thread of commonality, in the form of purinergic gliotransmission, which is frequently utilised to facilitate feedback inhibition within rhythmic networks to constrain a given behaviour within its operational range.

Communicating clocks shape circadian homeostasis

Circadian clocks temporally coordinate physiology and align it with geophysical time, which enables diverse life-forms to anticipate daily environmental cycles. In complex organisms, clock function originates from the molecular oscillator within each cell and builds upward anatomically into an organism-wide system. Recent advances have transformed our understanding of how clocks are connected to achieve coherence across tissues. Circadian misalignment, often imposed in modern society, disrupts coordination among clocks and has been linked to diseases ranging from metabolic syndrome to cancer. Thus, uncovering the physiological circuits whereby biological clocks achieve coherence will inform on both challenges and opportunities in human health.

ASMT Regulates Tumor Metastasis Through the Circadian Clock System in Triple-Negative Breast Cancer

Objective

Triple-negative (PR^-, ER^-, HER-2^-) breast cancer (TNBC) is regarded as more aggressive and more likely to recur after medical care. Emerging evidence has demonstrated that the circadian clock system regulates cell-signaling pathways critical to cancer cell proliferation, survival and metastasis, meaning that it could be a good candidate for TNBC treatment. As such, the aim of the current study was to examine the molecular mechanism by which the circadian clock system contributes to cancer progression in TNBC.

Methods

Cancer cells and primary breast cancer tissues were immunostained for the measurement of circadian clock proteins (CLOCK, BMAL1 and PER1) and acetylserotonin methyltransferase (ASMT). The association between ASMT and clock proteins was assessed using siRNA and Western blot. Transwell assays were used to detect cancer cell migration and invasion while MTT assays were utilized to evaluate cell proliferation.

Results

Circadian clock proteins (CLOCK, BMAL1, and PER1) and ASMT expression were higher in TNBC and triple positive breast cancer (TPBC) compared with para-carcinoma tissues (PCTs). Intriguingly, there was an obvious correlation between circadian clock proteins and ASMT expression in both TPBC and TNBC. Similarly, circadian clock proteins and ASMT were expressed to a greater extent in BT-474 (triple-positive) cells than in MDA-MB-231 (triple-negative) cells. The inhibition of ASMT reduced circadian clock protein levels in both breast cancer cell lines. Further analysis showed that the expression levels of ASMT and circadian clock proteins did not correlate with clinical parameters such as age, tumor size, histologic grade and CK5/6, but increased significantly with lymphatic invasion in TNBC. In agreement with this finding, knockdown of ASMT significantly leads to reductions in migration and invasion in MDA-MB-231 cells. However, over-expression of CLOCK reversed the decreases seen in ASMT inhibited cells.

Conclusion

Our study suggests that ASMT regulates the circadian clock system in breast cancer and inhibition of ASMT reduces the invasiveness of triple-negative breast cancer cells by downregulating clock protein in a certain extent, indicating the potential value of ASMT as a drug target for TNBC treatment.

Mirtazapine for sleep disturbances in Angelman syndrome: a retrospective chart review of 8 pediatric cases

STUDY OBJECTIVES

Angelman syndrome (AS) is a rare neurodevelopmental disorder that is characterized by developmental delay, intellectual disability, seizures, a characteristic happy personality, gait ataxia, tremulousness of the limbs, microcephaly, and anxiety. Severe sleep disturbances with the diminished need for sleep and abnormal sleep-wake cycles are seen in up to 90% of patients with AS. AS is caused by absent maternal expression of the gene UBE3A located in the 15q11.2-q13 locus. We hypothesized that selective antagonism of 5-HT₂ and 5-HT₃ serotonin receptors with mirtazapine would benefit sleep disturbances in patients with AS.

METHODS

Institutional Review Board approval was obtained at Vanderbilt University Medical Center. Medical records of individuals seen in the Comprehensive Angelman Syndrome clinic were retrospectively reviewed to determine the use of mirtazapine for disordered sleep. Parents were asked to respond to a survey to assess the phenotypic features of sleep and behavioral disturbances in AS. They were asked about the use of medications for sleep, focusing on the benefits and risks of mirtazapine.

RESULTS

A cohort of 8 individuals with AS, ranging in age from 3 to 16 years old with histories of sleep challenges, were treated with 3.75 to 30 mg of mirtazapine at bedtime for 0 to 36 weeks. Nocturnal awakenings were the most common sleep challenge reported. Seven of eight patients reported benefits from mirtazapine, including increased total sleep time, decreased nocturnal awakenings, and decreased time to fall asleep. The most significant side effects of mirtazapine were hyperphagia and weight gain.

CONCLUSIONS

Individuals with AS have abnormal sleep-wake cycles and a high unmet medical need. Mirtazapine helped with sleep onset and nighttime awakenings in 7 of 8 patients, with 2 patients reporting a positive benefit with respect to behavior. These data suggest that mirtazapine may be considered for the treatment of sleep difficulties in patients with AS who remain refractory to more conventional therapies. Weight gain was a common side-effect and led to discontinuation of treatment in 1 patient.

Purinergic Signaling in Neuron-Astrocyte Interactions, Circadian Rhythms, and Alcohol Use Disorder

Alcohol use disorder (AUD) is a debilitating condition marked by cyclic patterns of craving, use, and withdrawal. These pathological behaviors are mediated by multiple neurotransmitter systems utilizing glutamate, GABA, dopamine, ATP, and adenosine. In particular, purines such as ATP and adenosine have been demonstrated to alter the phase and function of the circadian clock and are reciprocally regulated by the clock itself. Importantly, chronic ethanol intake has been demonstrated to disrupt the molecular circadian clock and is associated with altered circadian patterns of activity and sleep. Moreover, ethanol has been demonstrated to disrupt purinergic signaling, while dysfunction of the purinergic system has been implicated in conditions of drug abuse such as AUD. In this review, we summarize our current knowledge regarding circadian disruption by ethanol, focusing on the reciprocal relationship that exists between oscillatory neurotransmission and the molecular circadian clock. In particular, we offer detailed explanations and hypotheses regarding the concerted regulation of purinergic signaling and circadian oscillations by neurons and astrocytes, and review the diverse mechanisms by which purinergic dysfuction may contribute to circadian disruption or alcohol abuse. Finally, we describe the mechanisms by which ethanol may disrupt or hijack endogenous circadian rhythms to induce the maladaptive behavioral patterns associated with AUD.