Low-Grade Inflammation Aggravates Rotenone Neurotoxicity and Disrupts Circadian Clock Gene Expression in Rats

Single-cell RNA-seq analysis identifies the atlas of lymph fluid and reveals a sepsis-related T cell subset

The lymphoid cycle serves as a sentinel of the immune response, yet the cell subtypes and immune properties within lymph fluid remain unclear. This study describes a comprehensive characterization of immune cells in rat lymph fluid using single-cell RNA sequencing, identifying a unique subset of CD4+ T cells (CD4_Icos) that suppresses inflammation in early sepsis. Trajectory analysis reveals that CD4+Icos+ T cells can differentiate into regulatory T cells (Tregs). Transferring CD4+Icos+ T cells alleviates CLP-induced organ injury, while CD4+ Icos-knockout (KO) mice show reduced Treg numbers, increased inflammation, and higher mortality. Further experiments identify Npas2 as an Icos-specific transcription factor regulating Icos expression and promoting the differentiation of CD4+Icos+ T cells. Clinical data show a negative correlation between ICOS expression in CD4+ T cells and clinical outcomes in septic patients. These findings highlight the protective role of CD4+ T cells in modulating immune responses and mitigating sepsis progression.

Should We Consider Neurodegeneration by Itself or in a Triangulation with Neuroinflammation and Demyelination? The Example of Multiple Sclerosis and Beyond

Neurodegeneration is preeminent in many neurological diseases, and still a major burden we fail to manage in patient's care. Its pathogenesis is complicated, intricate, and far from being completely understood. Taking multiple sclerosis as an example, we propose that neurodegeneration is neither a cause nor a consequence by itself. Mitochondrial dysfunction, leading to energy deficiency and ion imbalance, plays a key role in neurodegeneration, and is partly caused by the oxidative stress generated by microglia and astrocytes. Nodal and paranodal disruption, with or without myelin alteration, is further involved. Myelin loss exposes the axons directly to the inflammatory and oxidative environment. Moreover, oligodendrocytes provide a singular metabolic and trophic support to axons, but do not emerge unscathed from the pathological events, by primary myelin defects and cell apoptosis or secondary to neuroinflammation or axonal damage. Hereby, trophic failure might be an overlooked contributor to neurodegeneration. Thus, a complex interplay between neuroinflammation, demyelination, and neurodegeneration, wherein each is primarily and secondarily involved, might offer a more comprehensive understanding of the pathogenesis and help establishing novel therapeutic strategies for many neurological diseases and beyond.

Neurotoxicity of hexaconazole on rat brain: The aspect of biological rhythm

Hexaconazole is a widely used and frequently detected fungicide which is also reported to be persistent in environment. The toxicity of Hex to non-organisms such as reproductive toxicity, endocrine disrupting toxicity, and carcinogenic toxicity had been reported. However, study on the Hex-induced neurotoxicity is rare and the mechanism is still unclear. Therefore, in this study, environmental related concentrations of Hex were chosen to investigate the effects of Hex on nervous system from the aspect of biological rhythm under 90 d sub-chronic exposure. The results showed that Hex significantly affected the cognitive function of rats resulting in the deterioration of learning and memory ability and induced oxidative stress in rat brain. Moreover, the notable changes of neurotransmitters in rat brain suggested the disorder of nerve signaling conduction induced by Hex. The influence of Hex on biological rhythm was further detected which showed that levels of rhythm regulatory genes and proteins significantly disturbed at four monitored time periods. Based on these results, it was supposed that the underlying mechanism of Hex-induced cognitive dysfunction might through oxidative stress pathway. Our findings could systematically and comprehensively clarify the effects of Hex on nervous system and were helpful for prevention neurological diseases induced by triazole pesticides.

Molecular crosstalk between circadian clock and NLRP3 inflammasome signaling in Parkinson's disease

Parkinson's disease (PD) is one of the most common neurodegenerative diseases. Research has recently found that both animal models and patients with PD have circadian dysfunction, accompanied by abnormal expression of circadian genes and proteins, which implies that the circadian clock plays a crucial role in PD etiopathogenesis. In addition, a strong relationship between NLRP3 inflammasome signaling and PD has been observed. Meanwhile, the activation of the NLRP3 inflammasome is highly relevant to dysfunctions of the molecular clock. Therefore, alleviating the neuroinflammation caused by NLRP3 inflammasome signaling by adjusting the abnormal molecular clock may be a potential strategy for preventing and treating PD. In this article, we have reviewed the potential or direct relationship between abnormalities of the circadian clock and NLRP3 inflammasome signaling in PD.

Metabolic Basis of Circadian Dysfunction in Parkinson's Disease

Parkinson's disease (PD) is one of the most common neurodegenerative disorders. The management of PD is a challenging aspect for general physicians and neurologists. It is characterized by the progressive loss of dopaminergic neurons. Impaired α-synuclein secretion and dopamine release may cause mitochondrial dysfunction and perturb energy metabolism, subsequently altering the activity and survival of dopaminergic neurons, thus perpetuating the neurodegenerative process in PD. While the etiology of PD remains multifactorial, emerging research indicates a crucial role of circadian dysfunction in its pathogenesis. Researchers have revealed that circadian dysfunction and sleep disorders are common among PD subjects and disruption of circadian rhythms can increase the risk of PD. Hence, understanding the findings of circadian biology from translational research in PD is important for reducing the risk of neurodegeneration and for improving the quality of life. In this review, we discuss the intricate relationship between circadian dysfunction in cellular metabolism and PD by summarizing the evidence from animal models and human studies. Understanding the metabolic basis of circadian dysfunction in PD may shed light on novel therapeutic approaches to restore circadian rhythm, preserve dopaminergic function, and ameliorate disease progression. Further investigation into the complex interplay between circadian rhythm and PD pathogenesis is essential for the development of targeted therapies and interventions to alleviate the burden of this debilitating neurodegenerative disorder.

IL-1β/IL-1R1 signaling is involved in the propagation of α-synuclein pathology of the gastrointestinal tract to the brain

The pathological hallmark of Parkinson's disease (PD) is the intraneuronal accumulation of misfolded alpha-synuclein (termed Lewy bodies) in dopaminergic neurons of substantia nigra par compacta (SNc). It is assumed that the α-syn pathology is induced by gastrointestinal inflammation and then transfers to the brain by the gut-brain axis. Therefore, the relationship between gastrointestinal inflammation and α-syn pathology leading to PD remains to be investigated. In our study, rotenone (ROT) oral administration induces gastrointestinal tract (GIT) inflammation in mice. In addition, we used pseudorabies virus (PRV) for tracing studies and performed behavioral testing. We observed that ROT treatments enhance macrophage activation, inflammatory mediator expression, and α-syn pathology in the GIT 6-week post-treatment (P6). Moreover, pathological α-syn was localized with IL-1R1 positive neural cells in GIT. In line with these findings, we also find pS129-α-syn signals in the dorsal motor nucleus of the vagus (DMV) and tyrosine hydroxylase in the nigral-striatum dynamically change from 3-week post-treatment (P3) to P6. Following that, pS129-α-syn was dominant in the enteric neural cell, DMV, and SNc, accompanied by microglial activation, and these phenotypes were absent in IL-1R1r/r mice. These data suggest that IL-1β/IL-1R1-dependent inflammation of GIT can induce α-syn pathology, which then propagates to the DMV and SNc, resulting in PD.

Evaluating the Genetic Role of Circadian Clock Genes in Parkinson's Disease

Increasing evidence suggests that circadian dysfunction is related to Parkinson's disease (PD). However, the role of circadian clock genes in PD is still poorly understood. This study aimed to illustrate the association between genetic variants of circadian clock genes and PD in a large Chinese population cohort. Ten circadian clock genes were included in this study. Whole-exome sequencing (WES) was conducted in 1997 early-onset or familial PD patients and 1652 controls (WES cohort), and whole-genome sequencing (WGS) was conducted in 1962 sporadic late-onset PD patients and 1279 controls (WGS cohort). Analyses were completed using the optimized sequence kernel association test and regression analyses. In the burden analysis of the circadian clock gene set, we found suggestive significant associations between the circadian clock genes and PD in the WES cohort when considering missense, damaging missense (Dmis), and deleterious variants. Moreover, the burden analysis of single genes revealed suggestive significant associations between PD and the loss-of-function variants of the CRY1 gene, missense, Dmis, and deleterious variants of the PER1 gene, and Dmis and deleterious variants of the PER2 gene in the WES cohort. Rare variants in the WGS cohort and all common variants in the WGS and WES cohorts were unrelated to PD. Phenotypic analysis indicated that deleterious variants of the PER1 gene were associated with dyskinesia in the WES cohort. Our study provides evidence of a potential link between circadian clock genes and PD from a genetic perspective.

α-Synuclein-Induced Destabilized BMAL1 mRNA Leads to Circadian Rhythm Disruption in Parkinson's Disease

Circadian dysfunction is a common non-motor symptom in Parkinson's disease (PD). The potential influence of aggravated α-synuclein (SNCA) on circadian disruption remains unclear. SNCA^A53T-overexpressing transgenic mice (SNCA^A53T mice) and wild-type (WT) littermates were used in this study. The energy metabolism cage test showed differences in 24-h activity pattern between SNCA^A53T and WT mice. When compared with the age-matched littermates, brain and muscle ARNT-like 1 (BMAL1) was downregulated in SNCA^A53T mice. BMAL1 was downregulated in PC12 cells overexpressing SNCA. Degradation of BMAL1 protein remained unchanged after overexpression of SNCA, while its mRNA level decreased. miRNA (miR)-155 was upregulated by overexpression of SNCA, and downregulation of BMAL1 was partially reversed by transfection with miR-155 inhibitor. Our findings demonstrated that overexpression of SNCA induced biorhythm disruption and downregulated BMAL1 expression through decreasing stability of BMAL1 mRNA via miR-155.

Genetic modifiers of synucleinopathies-lessons from experimental models

α-Synuclein is a pleiotropic protein underlying a group of progressive neurodegenerative diseases, including Parkinson's disease and dementia with Lewy bodies. Together, these are known as synucleinopathies. Like all neurological diseases, understanding of disease mechanisms is hampered by the lack of access to biopsy tissues, precluding a real-time view of disease progression in the human body. This has driven researchers to devise various experimental models ranging from yeast to flies to human brain organoids, aiming to recapitulate aspects of synucleinopathies. Studies of these models have uncovered numerous genetic modifiers of α-synuclein, most of which are evolutionarily conserved. This review discusses what we have learned about disease mechanisms from these modifiers, and ways in which the study of modifiers have supported ongoing efforts to engineer disease-modifying interventions for synucleinopathies.

Circadian disruption and sleep disorders in neurodegeneration

Disruptions of circadian rhythms and sleep cycles are common among neurodegenerative diseases and can occur at multiple levels. Accumulating evidence reveals a bidirectional relationship between disruptions of circadian rhythms and sleep cycles and neurodegenerative diseases. Circadian disruption and sleep disorders aggravate neurodegeneration and neurodegenerative diseases can in turn disrupt circadian rhythms and sleep. Importantly, circadian disruption and various sleep disorders can increase the risk of neurodegenerative diseases. Thus, harnessing the circadian biology findings from preclinical and translational research in neurodegenerative diseases is of importance for reducing risk of neurodegeneration and improving symptoms and quality of life of individuals with neurodegenerative disorders via approaches that normalize circadian in the context of precision medicine. In this review, we discuss the implications of circadian disruption and sleep disorders in neurodegenerative diseases by summarizing evidence from both human and animal studies, focusing on the bidirectional links of sleep and circadian rhythms with prevalent forms of neurodegeneration. These findings provide valuable insights into the pathogenesis of neurodegenerative diseases and suggest a promising role of circadian-based interventions.

Current Perspective on the Role of the Circadian Clock and Extracellular Matrix in Chronic Lung Diseases

The circadian clock is a biochemical oscillator that rhythmically regulates physiological and behavioral processes such as inflammation, immunity, and metabolism in mammals. Circadian clock disruption is a key driver for chronic inflammatory as well as fibrotic lung diseases. While the mechanism of circadian clock regulation in the lung has been minimally explored, some evidence suggests that the transforming growth factor β (TGFβ) signaling pathway and subsequent extracellular matrix (ECM) accumulation in the lung may be controlled via a clock-dependent mechanism. Recent advancements in this area led us to believe that pharmacologically targeting the circadian clock molecules may be a novel therapeutic approach for treating chronic inflammatory lung diseases such as asthma, chronic obstructive pulmonary disease (COPD), and idiopathic pulmonary fibrosis (IPF). Here, we update the current perspective on the circadian clock role in TGFβ1 signaling and extracellular matrix production during chronic lung diseases.

Obstructive Sleep Apnea, Circadian Clock Disruption, and Metabolic Consequences

Obstructive sleep apnea (OSA) is a chronic disorder characterized by recurrent episodes of apnea and hypopnea during sleep. It is associated with various cardiovascular and metabolic complications, including type 2 diabetes mellitus (T2DM) and obesity. Many pathways can be responsible for T2DM development in OSA patients, e.g., those related to HIF-1 and SIRT1 expression. Moreover, epigenetic mechanisms, such as miRNA181a or miRNA199, are postulated to play a pivotal role in this link. It has been proven that OSA increases the occurrence of circadian clock disruption, which is also a risk factor for metabolic disease development. Circadian clock disruption impairs the metabolism of glucose, lipids, and the secretion of bile acids. Therefore, OSA-induced circadian clock disruption may be a potential, complex, underlying pathway involved in developing and exacerbating metabolic diseases among OSA patients. The current paper summarizes the available information pertaining to the relationship between OSA and circadian clock disruption in the context of potential mechanisms leading to metabolic disorders.

Deciphering clock genes as emerging targets against aging

The old people often suffer from circadian rhythm disturbances, which in turn accelerate aging. Many aging-related degenerative diseases such as Alzheimer's disease, Parkinson's disease, and osteoarthritis have an inextricable connection with circadian rhythm. In light of the predominant effects of clock genes on regulating circadian rhythm, we systematically present the elaborate network of roles that clock genes play in aging in this review. First, we briefly introduce the basic background regarding clock genes. Second, we systemically summarize the roles of clock genes in aging and aging-related degenerative diseases. Third, we discuss the relationship between clock genes polymorphisms and aging. In summary, this review is intended to clarify the indispensable roles of clock genes in aging and sheds light on developing clock genes as anti-aging targets.

Glymphatic System Dysfunction and Sleep Disturbance May Contribute to the Pathogenesis and Progression of Parkinson’s Disease

Parkinson’s disease (PD) is a multisystem alpha-synucleinopathic neurodegenerative disease and the most prevalent neurodegenerative disorder after Alzheimer’s disease with a high incidence rate in the elderly population. PD is highly multifactorial in etiology and has complex and wide-ranging pathogenic mechanisms. Environmental exposures and genetic predisposition are prominent risk factors. However, current evidence suggests that an intimate link may exist between the risk factor of sleep disturbance and PD pathogenesis. PD is characterized by the pathological hallmarks of alpha-synuclein aggregations and dopaminergic neuron degeneration in the substantia nigra. The loss of dopamine-producing neurons results in both motor and non-motor symptoms, most commonly, bradykinesia, tremor, rigidity, psychiatric disorders, sleep disorders and gastrointestinal problems. Factors that may exacerbate alpha-synuclein accumulation and dopamine neuron loss include neuroinflammation and glymphatic system impairment. Extracellular alpha-synuclein can induce an inflammatory response which can lead to neural cell death and inhibition of neurogenesis. The glymphatic system functions most optimally to remove extracellular brain solutes during sleep and therefore sleep disruption may be a crucial progression factor as well as a risk factor. This literature review interprets and analyses data from experimental and epidemiological studies to determine the recent advances in establishing a relationship between glymphatic system dysfunction, sleep disturbance, and PD pathogenesis and progression. This review addresses current limitations surrounding the ability to affirm a causal link between improved glymphatic clearance by increased sleep quality in PD prevention and management. Furthermore, this review proposes potential therapeutic approaches that could utilize the protective mechanism of sleep, to promote glymphatic clearance that therefore may reduce disease progression as well as symptom severity in PD patients.

Altered Motor Performance, Sleep EEG, and Parkinson's Disease Pathology Induced by Chronic Sleep Deprivation in Lrrk2G2019S Mice

Parkinson's disease (PD) is a multifaceted disease in which environmental variables combined with genetic predisposition cause dopaminergic (DAergic) neuron loss in the substantia nigra pars compacta. The mutation of leucine-rich repeat kinase 2 (Lrrk2) is the most common autosomal dominant mutation in PD, and it has also been reported in sporadic cases. A growing body of research suggests that circadian rhythm disruption, particularly sleep-wake abnormality, is common during the early phase of PD. Our present study aimed to evaluate the impact of sleep deprivation (SD) on motor ability, sleep performance, and PD pathologies in Lrrk2G2019S transgenic mice. After two months of SD, Lrrk2G2019S mice at 12 months of age showed an exacerbated PD-like phenotype with motor deficits, a reduced striatal DA level, degenerated DAergic neurons, and altered sleep structure and biological rhythm accompanied by the decreased protein expression level of circadian locomotor output cycles kaput Lrrk2 gene in the brain. All these changes persisted and were even more evident in 18-month-old mice after 6 months of follow-up. Moreover, a significant increase in α-synuclein aggregation was found in SD-treated transgenic mice at 18 months of age. Taken together, our findings indicate that sleep abnormalities, as a risk factor, may contribute to the pathogenesis and progression of PD. Early detection of sleep disorders and improvement of sleep quality may help to delay disease progression and provide long-term clinical benefits.

NADPH and Mitochondrial Quality Control as Targets for a Circadian-Based Fasting and Exercise Therapy for the Treatment of Parkinson's Disease

Dysfunctional mitochondrial quality control (MQC) is implicated in the pathogenesis of Parkinson's disease (PD). The improper selection of mitochondria for mitophagy increases reactive oxygen species (ROS) levels and lowers ATP levels. The downstream effects include oxidative damage, failure to maintain proteostasis and ion gradients, and decreased NAD⁺ and NADPH levels, resulting in insufficient energy metabolism and neurotransmitter synthesis. A ketosis-based metabolic therapy that increases the levels of (R)-3-hydroxybutyrate (BHB) may reverse the dysfunctional MQC by partially replacing glucose as an energy source, by stimulating mitophagy, and by decreasing inflammation. Fasting can potentially raise cytoplasmic NADPH levels by increasing the mitochondrial export and cytoplasmic metabolism of ketone body-derived citrate that increases flux through isocitrate dehydrogenase 1 (IDH1). NADPH is an essential cofactor for nitric oxide synthase, and the nitric oxide synthesized can diffuse into the mitochondrial matrix and react with electron transport chain-synthesized superoxide to form peroxynitrite. Excessive superoxide and peroxynitrite production can cause the opening of the mitochondrial permeability transition pore (mPTP) to depolarize the mitochondria and activate PINK1-dependent mitophagy. Both fasting and exercise increase ketogenesis and increase the cellular NAD⁺/NADH ratio, both of which are beneficial for neuronal metabolism. In addition, both fasting and exercise engage the adaptive cellular stress response signaling pathways that protect neurons against the oxidative and proteotoxic stress implicated in PD. Here, we discuss how intermittent fasting from the evening meal through to the next-day lunch together with morning exercise, when circadian NAD⁺/NADH is most oxidized, circadian NADP⁺/NADPH is most reduced, and circadian mitophagy gene expression is high, may slow the progression of PD.

Roles of clock genes in the pathogenesis of Parkinson's disease

Parkinson's disease (PD) is a common motor disorder that has become increasingly prevalent in the ageing population. Recent works have suggested that circadian rhythms disruption is a common event in PD patients. Clock genes regulate the circadian rhythm of biological processes in eukaryotic organisms, but their roles in PD remain unclear. Despite this, several lines of evidence point to the possibility that clock genes may have a significant impact on the development and progression of the disease. This review aims to consolidate recent understanding of the roles of clock genes in PD. We first summarized the findings of clock gene expression and epigenetic analyses in PD patients and animal models. We also discussed the potential contributory role of clock gene variants in the development of PD and/or its symptoms. We further reviewed the mechanisms by which clock genes affect mitochondrial dynamics as well as the rhythmic synthesis and secretion of endocrine hormones, the impairment of which may contribute to the development of PD. Finally, we discussed the limitations of the currently available studies, and suggested future potential studies to deepen our understanding of the roles of clock genes in PD pathogenesis.

Sleep and circadian rhythms in Parkinson's disease and preclinical models

The use of animals as models of human physiology is, and has been for many years, an indispensable tool for understanding the mechanisms of human disease. In Parkinson's disease, various mouse models form the cornerstone of these investigations. Early models were developed to reflect the traditional histological features and motor symptoms of Parkinson's disease. However, it is important that models accurately encompass important facets of the disease to allow for comprehensive mechanistic understanding and translational significance. Circadian rhythm and sleep issues are tightly correlated to Parkinson's disease, and often arise prior to the presentation of typical motor deficits. It is essential that models used to understand Parkinson's disease reflect these dysfunctions in circadian rhythms and sleep, both to facilitate investigations into mechanistic interplay between sleep and disease, and to assist in the development of circadian rhythm-facing therapeutic treatments. This review describes the extent to which various genetically- and neurotoxically-induced murine models of Parkinson's reflect the sleep and circadian abnormalities of Parkinson's disease observed in the clinic.

Dopamine D1 Receptor-Mediated Regulation of Per1, Per2, CLOCK, and BMAL1 Expression in the Suprachiasmatic Nucleus in Adult Male Rats

Photic and non-photic inputs are reported to affect clock gene expressions and behavioral activities in the SCN. However, it is not known whether dopaminergic input mediates these regulatory effects on clock genes. The present study examined the molecular effects of dopamine D1 agonist on Per1, Per2, CLOCK, and Bmal1 expressions in the SCN and its effect on behavioral activities to determine the role of dopamine D1 receptor in regulation of these gene expressions and behavioral activities in adult male Wistar rats. To examine the molecular effects of dopamine D1 agonist day and night, we injected 20 mg/kg SKF38393 to the first group of rats at 6 a.m. and the second group at 6 p.m. We also injected saline to the third and fourth groups of rats at 6 a.m. and 6 p.m. as control groups. All rats were sacrificed 2 h following the injections. The real-time PCR technique was used to evaluate the clock gene expression. In addition, to examine the effects of dopamine D1 agonists on behavioral activities, we injected 20 mg/kg SKF38393 to SKF receiving group and saline to control group. The behavioral activities of the rats were monitored on the running wheel for 21 days, 1 week following the injections. SKF injections increased the Per2 and CLOCK expressions in the daytime and significantly decreased the Per1 and Bmal1 expressions. However, at night, SKF injections increased only Per2 expressions significantly and decreased the Per1, CLOCK, and Bmal1 genes expressions. Both saline receiving groups showed that all gene expressions were significantly higher except Per2 during nighttime. SKF injection increased the running wheel activity during nighttime significantly. Based on the obtained result, clock gene expression and behavioral activities in adult male Wistar rats may be altered or monitored by administration of exogenous dopamine.

Effect of Advanced Glycation End-Products and Excessive Calorie Intake on Diet-Induced Chronic Low-Grade Inflammation Biomarkers in Murine Models

Chronic Low-Grade Inflammation (CLGI) is a non-overt inflammatory state characterized by a continuous activation of inflammation mediators associated with metabolic diseases. It has been linked to the overconsumption of Advanced Glycation End-Products (AGEs), and/or macronutrients which lead to an increase in local and systemic pro-inflammatory biomarkers in humans and animal models. This review provides a summary of research into biomarkers of diet-induced CLGI in murine models, with a focus on AGEs and obesogenic diets, and presents the physiological effects described in the literature. Diet-induced CLGI is associated with metabolic endotoxemia, and/or gut microbiota remodeling in rodents. The mechanisms identified so far are centered on pro-inflammatory axes such as the interaction between AGEs and their main receptor AGEs (RAGE) or increased levels of lipopolysaccharide. The use of murine models has helped to elucidate the local and systemic expression of CLGI mediators. These models have enabled significant advances in identification of diet-induced CLGI biomarkers and resultant physiological effects. Some limitations on the translational (murine → humans) use of biomarkers may arise, but murine models have greatly facilitated the testing of specific dietary components. However, there remains a lack of information at the whole-organism level of organization, as well as a lack of consensus on the best biomarker for use in CLGI studies and recommendations as to future research conclude this review.

The Molecular Clock and Neurodegenerative Disease: A Stressful Time

Circadian rhythm dysfunction occurs in both common and rare neurodegenerative diseases. This dysfunction manifests as sleep cycle mistiming, alterations in body temperature rhythms, and an increase in symptomatology during the early evening hours known as Sundown Syndrome. Disruption of circadian rhythm homeostasis has also been implicated in the etiology of neurodegenerative disease. Indeed, individuals exposed to a shifting schedule of sleep and activity, such as health care workers, are at a higher risk. Thus, a bidirectional relationship exists between the circadian system and neurodegeneration. At the heart of this crosstalk is the molecular circadian clock, which functions to regulate circadian rhythm homeostasis. Over the past decade, this connection has become a focal point of investigation as the molecular clock offers an attractive target to combat both neurodegenerative disease pathogenesis and circadian rhythm dysfunction, and a pivotal role for neuroinflammation and stress has been established. This review summarizes the contributions of molecular clock dysfunction to neurodegenerative disease etiology, as well as the mechanisms by which neurodegenerative diseases affect the molecular clock.

Chronic Manganese Administration with Longer Intervals Between Injections Produced Neurotoxicity and Hepatotoxicity in Rats

Abstract

Subacute exposure to manganese (Mn) produced Parkinson’s disease-like syndrome called Manganism. Chronic onset and progression are characteristics of Manganism, therefore, this study aimed to examine Mn toxicity following chronic exposures. Male Sprague-Dawley rats were injected Mn²⁺ 1 and 5 mg/kg, every 10 days for 150 days (15 injections). Animal body weight and behavioral activities were recorded. At the end of experiments, the brain and liver were collected for morphological and molecular analysis. Chronic Mn exposure did not affect animal body weight gain, but the high dose of Mn treatment caused 20% mortality after 140 days of administration. Motor activity deficits were observed in a dose-dependent manner at 148 days of Mn administration. Immunofluorescence double staining of substantia nigra pars compacta (SNpc) revealed the activation of microglia and loss of dopaminergic neurons. The chronic neuroinflammation mediators TNFα, inflammasome Nlrp3, Fc fragment of IgG receptor IIb, and formyl peptide receptor-1 were increased, implicating chronic Mn-induced neuroinflammation. Chronic Mn exposure also produced liver injury, as evidenced by hepatocyte degeneration with pink, condensed nuclei, indicative of apoptotic lesions. The inflammatory cytokines TNFα, IL-1β, and IL-6 were increased, alone with stress-related genes heme oxygenase-1, NAD(P)H:quinone oxidoreductase-1 and metallothionein. Hepatic transporters, such as multidrug resistant proteins (Abcc1, Abcc2, and Abcc3) and solute carrier family proteins (Slc30a1, Slc39a8 and Slc39a14) were increased in attempt to eliminate Mn from the liver. In summary, chronic Mn exposure produced neuroinflammation and dopaminergic neuron loss in the brain, but also produced inflammation to the liver, with upregulation of hepatic transporters.

Graphic Abstract

Electronic supplementary material

The online version of this article (10.1007/s11064-020-03059-2) contains supplementary material, which is available to authorized users.

Measurable health effects associated with the daylight saving time shift

The transition to daylight saving time (DST) is beneficial for energy conservation but at the same time it has been reported to increase the risk of cerebrovascular and cardiovascular problems. Here, we evaluate the effect of the DST shift on a whole spectrum of diseases-an analysis we hope will be helpful in weighing the risks and benefits of DST shifts. Our study relied on a population-based, cross-sectional analysis of the IBM Watson Health MarketScan insurance claim dataset, which incorporates over 150 million unique patients in the US, and the Swedish national inpatient register, which incorporates more than nine million unique Swedes. For hundreds of sex- and age-specific diseases, we assessed effects of the DST shifts forward and backward by one hour in spring and autumn by comparing the observed and expected diagnosis rates after DST shift exposure. We found four prominent, elevated risk clusters, including cardiovascular diseases (such as heart attacks), injuries, mental and behavioral disorders, and immune-related diseases such as noninfective enteritis and colitis to be significantly associated with DST shifts in the United States and Sweden. While the majority of disease risk elevations are modest (a few percent), a considerable number of diseases exhibit an approximately ten percent relative risk increase. We estimate that each spring DST shift is associated with negative health effects-with 150,000 incidences in the US, and 880,000 globally. We also identify for the first time a collection of diseases with relative risks that appear to decrease immediately after the spring DST shift, enriched with infections and immune system-related maladies. These diseases' decreasing relative risks might be driven by the documented boosting effect of a short-term stress (such as that experienced around the spring DST shift) on the immune system.

Mercury sulfide-containing Hua-Feng-Dan and 70W (Rannasangpei) protect against LPS plus MPTP-induced neurotoxicity and disturbance of gut microbiota in mice

ETHNOPHARMACOLOGICAL RELEVANCE

Mercury sulfides (HgS) are frequently included in Ayurveda, Tibetan and Chinese medicines to assist the presumed therapeutic effects, but the ethnopharmacology remains elusive. The present study examined the protective effects of α-HgS-containing Hua-Feng-Dan and β-HgS-containing 70 Wei-Zhen-Zhu-Wan (70W, Rannasangpei) against Parkinson's disease mice induced by lipopolysaccharide (LPS) plus 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP).

METHOD

A single injection of LPS (5 mg/kg ip) was given to adult male C57BL/6 mice, and 150 days later, the low dose of MPTP (15 mg/kg, ip, for 4 days) was given to produce the "two-hit" Parkinson's disease model. Together with MPTP treatment, mice were fed with clinically-relevant doses of Hua-Feng-Dan (0.6 g/kg) and 70W (0.2 g/kg) for 35 days. Rotarod test was performed to examine muscle coordination capability. At the end of the experiment, brain was transcardially perfused with paraformaldehyde, the substantia nigra was sectioned for microglia (Iba1 staining) and dopaminergic neuron (THir staining) determination. Colon bacterial DNA was extracted and subjected to qPCR analysis with 16S rRNA probes.

RESULTS

The low-grade, chronic neuroinflammation produced by LPS aggravated MPTP neurotoxicity, as evidenced by decreased motor activity, intensified microglia activation and loss of dopaminergic neurons. Both Hua-Feng-Dan and 70W increased rotarod activity and ameliorated the pathological lesions in the brain. In gut microbiomes examined, LPS plus MPTP increased Verrucomicrobiaceae, Methanobacteriaceae, Pronicromonosporaceae, and Clostridaceae species were attenuated by Hua-Feng-Dan and 70W.

CONCLUSIONS

α-HgS-containing Hua-Feng-Dan and β-HgS-containing 70W at clinical doses protected against chronic LPS plus MPTP-induced toxicity to the brain and gut, suggesting HgS-containing traditional medicines could target gut microbiota as a mechanism of their therapeutic effects.

Protective role of cinnabar and realgar in Hua-Feng-Dan against LPS plus rotenone-induced neurotoxicity and disturbance of gut microbiota in rats

ETHNOPHARMACOLOGICAL RELEVANCE

Hua-Feng-Dan (HFD) is a traditional Chinese medicine used for neurological disorders. HFD contains cinnabar (HgS) and realgar (As₄S₄). The ethnopharmacological basis of cinnabar and realgar in HFD is not known.

AIM OF THE STUDY

To address the role of cinnabar and realgar in HFD-produced neuroprotection against neurodegenerative diseases and disturbance of gut microbiota.

MATERIALS AND METHODS

Lipopolysaccharide (LPS) plus rotenone (ROT)-elicited rat dopaminergic (DA) neuronal damage loss was performed as a Parkinson's disease animal model. Rats were given a single injection of LPS. Four months later, rats were challenged with the threshold dose of ROT. The clinical dose of HFD was administered via feed, starting from ROT administration for 46 days. Behavioral dysfunction was detected by rotarod and Y-maze tests. DA neuron loss and microglial activation were assessed via immunohistochemical staining and western bolt analysis. The colon content was collected to extract bacterial DNA followed by real-time PCR analysis with 16S rRNA primers.

RESULTS

LPS plus ROT induced neurotoxicity, as evidenced by DA neuron loss in substantia nigra, impaired behavioral functions and increased microglial activation. HFD-original (containing 10% cinnabar and 10% realgar) rescued loss of DA neurons, improved behavioral dysfunction and attenuated microglial activation. Compared with HFD-original, HFD-reduced (3% cinnabar and 3% realgar) was also effective, but to be a less extent, while HFD-removed (without cinnabar and realgar) was ineffective. In analysis of gut microbiome, the increased Verrucomicrobiaceae and Lactobacteriaceae, and the decreased Enterobacteeriaceae by LPS plus ROT were ameliorated by HFD-original, and to be the less extent by HFD-reduced.

CONCLUSION

Cinnabar and realgar are active ingredients in HFD to exert beneficial effects in a neurodegenerative model and gut microbiota.