Neuronal deletion of the circadian clock gene Bmal1 induces cell-autonomous dopaminergic neurodegeneration

Circadian rhythm, microglia-mediated neuroinflammation, and Alzheimer's disease

Microglia, the brain's resident macrophages, are key mediators of neuroinflammation, responding to immune pathogens and toxins. They play a crucial role in clearing cellular debris, regulating synaptic plasticity, and phagocytosing amyloid-β (Aβ) plaques in Alzheimer's disease (AD). Recent studies indicate that microglia not only exhibit intrinsic circadian rhythms but are also regulated by circadian clock genes, influencing specific functions such as phagocytosis and the modulation of neuroinflammation. Disruption of the circadian rhythm is closely associated with AD pathology. In this review, we will provide an overview of how circadian rhythms regulate microglia-mediated neuroinflammation in the progression of AD, focusing on the pathway from the central nervous system (CNS) and the peripheral immune system. We also discuss potential therapeutic targets, including hormone modulation, lifestyle interventions, and anti-inflammatory therapies, aimed at maintaining brain health in AD. This will shed light on the involvement of circadian rhythm in AD and explore new avenues for AD treatment.

Evaluation of the effects of carbamazepine-loaded chitosan-coated PLGA-Zein nanoparticles on pilocarpine-induced seizure model in zebrafish larvae: developmental toxicity and behavioral assays

Epilepsy, the most common neurological disorder worldwide, is characterized by sudden paroxysmal brain activity, which can be generalized or focal. Extensive research has explored various treatment strategies for this condition. Our study used a pilocarpine (PL)-induced seizure model in zebrafish (Danio rerio) embryos and larvae to assess the effects of carbamazepine (CBZ)-loaded chitosan-coated PLGA-Zein nanoparticles (NPs) over 96 hr. We evaluated the developmental toxicity (mortality, malformation, and larval hatching), behavioral changes (sensorimotor reflexes), and histopathological and immunohistochemical alterations in brain tissue, focusing on 5-hydroxytryptamine receptor 4 (5HT4), and brain and muscle ARNT-like 1 (BMAL1) expressions. Our findings revealed high mortality and malformation rates in groups treated with pure CBZ (PL + CBZ 50 and PL + CBZ 100). These groups also exhibited delayed hatching and impaired sensorimotor reflexes. In contrast, the CBZ-NP-treated groups (PL + CBZ NP 50 and PL + CBZ NP 100) showed hatching rates comparable with the control group, with significantly lower mortality and malformation rates compared with pure CBZ-treated groups. Moreover, intense cytoplasmic expression of 5HT4 and BMAL1 was observed in neuropils of the PL + CBZ 100 group. This study highlights the potential of CBZ-loaded NPs in reducing developmental toxicity and adverse neurological effects associated with pure CBZ treatment in seizure models.

The intertwined relationship between circadian dysfunction and Parkinson's disease

Neurodegenerative disorders represent a leading cause of disability among the elderly population, and Parkinson's disease (PD) is the second most prevalent. Emerging evidence suggests a frequent co-occurrence of circadian disruption and PD. However, the nature of this relationship remains unclear: is circadian disruption a cause, consequence, or a parallel feature of the disease that shares the same root cause? This review seeks to address this question by highlighting and discussing clinical evidence and findings from experiments using vertebrate and invertebrate animal models. While research on causality is still in its early stages, the available data suggest reciprocal interactions between PD progression and circadian disruption.

Bmal1 haploinsufficiency impairs fear memory and modulates neuroinflammation via the 5-HT2C receptor

Background

BMAL1, a key regulator of circadian rhythms, plays a multifaceted role in brain function. However, the complex interplay between BMAL1, memory, neuroinflammation, and neurotransmitter regulation remains poorly understood. To investigate these interactions, we conducted a study using BMAL1-haplodeficient mice (BMAL1+/-).

Methods

We exposed BMAL1+/- mice to behavioral assessments including cued fear conditioning, new objection recognition (NOR) test, and Y-maze test to evaluate BMAL1+/- haplodeficiency impact on memory. Furthermore, biochemical changes were analyzed through western blotting, and ELISA to explore further the mechanism of BMAL1+/- in memory, and neuroinflammation.

Results

We found that BMAL1 haploinsufficiency led to deficits in cued fear learning and memory, while spatial memory and object recognition remained intact. Further analysis revealed dysregulated neurotransmitter levels and alterations in neurotransmitter-related proteins in the prefrontal cortex of BMAL1+/- mice. Pharmacological interventions targeting dopamine uptake or the 5-HT2C receptor demonstrated that inhibiting the 5-HT2C receptor could rescue fear learning and memory impairments in BMAL1+/- mice. Additionally, we observed downregulation of the inflammasome and neuroinflammation pathways in BMAL1+/- mice, which is validated by inflammation mediator lipopolysaccharide (LPS) administration.

Conclusion

These findings highlight that BMAL1 haploinsufficiency leads to deficits in fear learning and memory, which are linked to alterations in neurotransmitters and receptors, particularly the 5-HT2C receptor. Targeting the 5-HT2C receptor may offer a potential therapeutic strategy for mitigating cognitive impairments associated with BMAL1 dysfunction.

Circadian rhythm disruption: a potential trigger in Parkinson's disease pathogenesis

Parkinson's disease (PD) is a neurodegenerative disease characterized by the gradual loss of dopaminergic neurons in the substantia nigra pars compacta (SNpc), abnormal accumulation of α-synuclein (α-syn), and activation of microglia leading to neuroinflammation. Disturbances in circadian rhythm play a significant role in PD, with most non-motor symptoms associated with disruptions in circadian rhythm. These disturbances can be observed years before motor symptoms appear and are marked by the emergence of non-motor symptoms related to PD, such as rapid eye movement sleep behavior disorder (RBD), restless leg syndrome (RLS), excessive daytime sleepiness (EDS), depression and anxiety, changes in blood pressure, gastrointestinal dysfunction, and urinary problems. Circadian rhythm disruption precedes the onset of motor symptoms and contributes to the progression of PD. In brief, this article outlines the role of circadian rhythm disruption in triggering PD at cellular and molecular levels, as well as its clinical manifestations. It also explores how circadian rhythm research can contribute to preventing the onset and progression of PD from current and future perspectives.

Ticking Brain: Circadian Rhythm as a New Target for Cerebroprotection

Circadian rhythm is a master process observed in nearly every type of cell throughout the body, and it macroscopically regulates daily physiology. Recent clinical trials have revealed the effects of circadian variation on the incidence, pathophysiological processes, and prognosis of acute ischemic stroke. Furthermore, core clock genes, the cell-autonomous pacemakers of the circadian rhythm, affect the neurovascular unit-composing cells in a nonparallel manner after the same pathophysiological processes of ischemia/reperfusion. In this review, we discuss the influence of circadian rhythms and clock genes on each type of neurovascular unit cell in the pathophysiological processes of acute ischemic stroke.

Saponin components in Polygala tenuifolia as potential candidate drugs for treating dementia

Objective

This study aims to elucidate the intervention effects of saponin components from Polygala tenuifolia Willd (Polygalaceae) on dementia, providing experimental evidence and new insights for the research and application of saponins in the field of dementia.

Materials and Methods

This review is based on a search of the PubMed, NCBI, and Google Scholar databases from their inception to 13 May 2024, using terms such as "P. tenuifolia," "P. tenuifolia and saponins," "toxicity," "dementia," "Alzheimer's disease," "Parkinson's disease dementia," and "vascular dementia." The article summarizes the saponin components of P. tenuifolia, including tenuigenin, tenuifolin, polygalasaponins XXXII, and onjisaponin B, as well as the pathophysiological mechanisms of dementia. Importantly, it highlights the potential mechanisms by which the active components of P. tenuifolia prevent and treat diseases and relevant clinical studies.

Results

The saponin components of P. tenuifolia can reduce β-amyloid accumulation, exhibit antioxidant effects, regulate neurotransmitters, improve synaptic function, possess anti-inflammatory properties, inhibit neuronal apoptosis, and modulate autophagy. Therefore, P. tenuifolia may play a role in the prevention and treatment of dementia.

Conclusion

The saponin components of P. tenuifolia have shown certain therapeutic effects on dementia. They can prevent and treat dementia through various mechanisms.

Exploring the interplay between circadian rhythms and prostate cancer: insights into androgen receptor signaling and therapeutic opportunities

Circadian rhythm disruption is closely related to increased incidence of prostate cancer. Incorporating circadian rhythms into the study of prostate cancer pathogenesis can provide a more comprehensive understanding of the causes of cancer and offer new options for precise treatment. Therefore, this article comprehensively summarizes the epidemiology of prostate cancer, expounds the contradictory relationship between circadian rhythm disorders and prostate cancer risk, and elucidates the relationship between circadian rhythm regulators and the incidence of prostate cancer. Importantly, this article also focuses on the correlation between circadian rhythms and androgen receptor signaling pathways, as well as the applicability of time therapy in prostate cancer. This may prove significant in enhancing the clinical treatment of prostate cancer.

Stroke in the Time of Circadian Medicine

Time-of-day significantly influences the severity and incidence of stroke. Evidence has emerged not only for circadian governance over stroke risk factors, but also for important determinants of clinical outcome. In this review, we provide a comprehensive overview of the interplay between chronobiology and cerebrovascular disease. We discuss circadian regulation of pathophysiological mechanisms underlying stroke onset or tolerance as well as in vascular dementia. This includes cell death mechanisms, metabolism, mitochondrial function, and inflammation/immunity. Furthermore, we present clinical evidence supporting the link between disrupted circadian rhythms and increased susceptibility to stroke and dementia. We propose that circadian regulation of biochemical and physiological pathways in the brain increase susceptibility to damage after stroke in sleep and attenuate treatment effectiveness during the active phase. This review underscores the importance of considering circadian biology for understanding the pathology and treatment choice for stroke and vascular dementia and speculates that considering a patient's chronotype may be an important factor in developing precision treatment following stroke.