Antioxidant N-acetyl-L-cysteine ameliorates symptoms of premature aging associated with the deficiency of the circadian protein BMAL1

Up-regulation of BMAL1 by epigallocatechin-3-gallate improves neurological damage in SBI rats

Brain Muscle ARNT-Like Protein 1 (BMAL1) suppresses oxidative stress in brain injury during surgery. Epigallocatechin-3-gallate (EGCG), a monomer in green tea, has been identified as an antioxidant and a potential agonist for BMAL1. In this work, the mechanism by which BMAL1 is regulated was investigated, as well as the therapeutic effect of EGCG on surgically injured rats. The pathological environment after brain injury during surgery was simulated by excising the right frontal lobe of rats. Rats received an intraperitoneal injection of EGCG immediately after surgery. Neurological scores and cerebral edema were recorded after surgery. Fluoro-Jade C staining, TUNEL staining, western blot, and lipid peroxidation analyses were conducted 3 days later. Here we show that the endogenous BMAL1 level decreased after brain injury. Postoperative administration of EGCG up-regulated the content of BMAL1 around the cerebral cortex, reduced the oxidative stress level, reduced neuronal apoptosis and the number of degenerated neurons, alleviated cerebral edema, and improved neurological scores in rats. This suggests that BMAL1 is an effective target for treating surgical brain injury, as well as that EGCG may be a promising agent for alleviating postoperative brain injury.

The effect of low birth weight as an intrauterine exposure on the early onset of sarcopenia through possible molecular pathways

Sarcopenia, a musculoskeletal disease characterized by the progressive loss of skeletal muscle mass, strength, and physical performance, presents significant challenges to global public health due to its adverse effects on mobility, morbidity, mortality, and healthcare costs. This comprehensive review explores the intricate connections between sarcopenia and low birth weight (LBW), emphasizing the developmental origins of health and disease (DOHaD) hypothesis, inflammatory processes (inflammaging), mitochondrial dysfunction, circadian rhythm disruptions, epigenetic mechanisms, and genetic variations revealed through genome-wide studies (GWAS). A systematic search strategy was developed using PubMed to identify relevant English-language publications on sarcopenia, LBW, DOHaD, inflammaging, mitochondrial dysfunction, circadian disruption, epigenetic mechanisms, and GWAS. The publications consist of 46.2% reviews, 21.2% cohort studies, 4.8% systematic reviews, 1.9% cross-sectional studies, 13.4% animal studies, 4.8% genome-wide studies, 5.8% epigenome-wide studies, and 1.9% book chapters. The review identified key factors contributing to sarcopenia development, including the DOHaD hypothesis, LBW impact on muscle mass, inflammaging, mitochondrial dysfunction, the influence of clock genes, the role of epigenetic mechanisms, and genetic variations revealed through GWAS. The DOHaD theory suggests that LBW induces epigenetic alterations during foetal development, impacting long-term health outcomes, including the early onset of sarcopenia. LBW correlates with reduced muscle mass, grip strength, and lean body mass in adulthood, increasing the risk of sarcopenia. Chronic inflammation (inflammaging) and mitochondrial dysfunction contribute to sarcopenia, with LBW linked to increased oxidative stress and dysfunction. Disrupted circadian rhythms, regulated by genes such as BMAL1 and CLOCK, are associated with both LBW and sarcopenia, impacting lipid metabolism, muscle mass, and the ageing process. Early-life exposures, including LBW, induce epigenetic modifications like DNA methylation (DNAm) and histone changes, playing a pivotal role in sarcopenia development. Genome-wide studies have identified candidate genes and variants associated with lean body mass, muscle weakness, and sarcopenia, providing insights into genetic factors contributing to the disorder. LBW emerges as a potential early predictor of sarcopenia development, reflecting the impact of intrauterine exposures on long-term health outcomes. Understanding the complex interplay between LBW with inflammaging, mitochondrial dysfunction, circadian disruption, and epigenetic factors is essential for elucidating the pathogenesis of sarcopenia and developing targeted interventions. Future research on GWAS and the underlying mechanisms of LBW-associated sarcopenia is warranted to inform preventive strategies and improve public health outcomes.

Redox and metabolic reprogramming in breast cancer and cancer-associated adipose tissue

Redox and metabolic processes are tightly coupled in both physiological and pathological conditions. In cancer, their integration occurs at multiple levels and is characterized by synchronized reprogramming both in the tumor tissue and its specific but heterogeneous microenvironment. In breast cancer, the principal microenvironment is the cancer-associated adipose tissue (CAAT). Understanding how the redox-metabolic reprogramming becomes coordinated in human breast cancer is imperative both for cancer prevention and for the establishment of new therapeutic approaches. This review aims to provide an overview of the current knowledge of the redox profiles and regulation of intermediary metabolism in breast cancer while considering the tumor and CAAT of breast cancer as a unique Warburg's pseudo-organ. As cancer is now recognized as a systemic metabolic disease, we have paid particular attention to the cell-specific redox-metabolic reprogramming and the roles of estrogen receptors and circadian rhythms, as well as their crosstalk in the development, growth, progression, and prognosis of breast cancer.

Crosstalk Between Aging, Circadian Rhythm, and Melatonin

Circadian rhythms (CRs) are 24-hour periodic oscillations governed by an endogenous circadian pacemaker located in the suprachiasmatic nucleus (SCN), which organizes the physiology and behavior of organisms. Circadian rhythm disruption (CRD) is also indicative of the aging process. In mammals, melatonin is primarily synthesized in the pineal gland and participates in a variety of multifaceted intracellular signaling networks and has been shown to synchronize CRs. Endogenous melatonin synthesis and its release tend to decrease progressively with advancing age. Older individuals experience frequent CR disruption, which hastens the process of aging. A profound understanding of the relationship between CRs and aging has the potential to improve existing treatments and facilitate development of novel chronotherapies that target age-related disorders. This review article aims to examine the circadian regulatory mechanisms in which melatonin plays a key role in signaling. We describe the basic architecture of the molecular circadian clock and its functional decline with age in detail. Furthermore, we discuss the role of melatonin in regulation of the circadian pacemaker and redox homeostasis during aging. Moreover, we also discuss the protective effect of exogenous melatonin supplementation in age-dependent CR disruption, which sheds light on this pleiotropic molecule and how it can be used as an effective chronotherapeutic medicine.

Natural Antioxidants in Obesity and Related Diseases

Obesity is a chronic complex disease defined by excessive adiposity that impairs health [...].

Melatonin induces RAW264.7 cell apoptosis via the BMAL1/ROS/MAPK-p38 pathway to improve postmenopausal osteoporosis

Aims

Currently, the effect of drug treatment for osteoporosis is relatively poor, and the side effects are numerous and serious. Melatonin is a potential drug to improve bone mass in postmenopausal women. Unfortunately, the mechanism by which melatonin improves bone metabolism remains unclear. The aim of this study was to further investigate the potential mechanism of melatonin in the treatment of osteoporosis.

Methods

The effects of melatonin on mitochondrial apoptosis protein, bmal1 gene, and related pathway proteins of RAW264.7 (mouse mononuclear macrophage leukaemia cells) were analyzed by western blot. Cell Counting Kit-8 was used to evaluate the effect of melatonin on cell viability. Flow cytometry was used to evaluate the effect of melatonin on the apoptosis of RAW264.7 cells and mitochondrial membrane potential. A reactive oxygen species (ROS) detection kit was used to evaluate the level of ROS in osteoclast precursors. We used bmal1-small interfering RNAs (siRNAs) to downregulate the Bmal1 gene. We established a postmenopausal mouse model and verified the effect of melatonin on the bone mass of postmenopausal osteoporosis in mice via micro-CT. Bmal1 lentiviral activation particles were used to establish an in vitro model of overexpression of the bmal1 gene.

Results

Melatonin promoted apoptosis of RAW264.7 cells and increased the expression of BMAL1 to inhibit the activation of ROS and phosphorylation of mitogen-activated protein kinase (MAPK)-p38. Silencing the bmal1 gene weakened the above effects of melatonin. After that, we used dehydrocorydaline (DHC) to enhance the activation of MAPK-p38, and the effects of melatonin on reducing ROS levels and promoting apoptosis of RAW264.7 cells were also blocked. Then, we constructed a mouse model of postmenopausal osteoporosis and administered melatonin. The results showed that melatonin improves bone loss in ovariectomized mice. Finally, we established a model of overexpression of the bmal1 gene, and these results suggest that the bmal1 gene can regulate ROS activity and change the level of the MAPK-p38 signalling pathway.

Conclusion

Our study confirmed that melatonin promotes the apoptosis of RAW264.7 cells through BMAL1/ROS/MAPK-p38, and revealed the therapeutic effect and mechanism of melatonin in postmenopausal osteoporosis. This finding enriches BMAL1 as a potential target for the treatment of osteoporosis and the pathogenesis of postmenopausal osteoporosis.

Circadian clock regulator Bmal1 gates axon regeneration via Tet3 epigenetics in mouse sensory neurons

Axon regeneration of dorsal root ganglia (DRG) neurons after peripheral axotomy involves reconfiguration of gene regulatory circuits to establish regenerative gene programs. However, the underlying mechanisms remain unclear. Here, through an unbiased survey, we show that the binding motif of Bmal1, a central transcription factor of the circadian clock, is enriched in differentially hydroxymethylated regions (DhMRs) of mouse DRG after peripheral lesion. By applying conditional deletion of Bmal1 in neurons, in vitro and in vivo neurite outgrowth assays, as well as transcriptomic profiling, we demonstrate that Bmal1 inhibits axon regeneration, in part through a functional link with the epigenetic factor Tet3. Mechanistically, we reveal that Bmal1 acts as a gatekeeper of neuroepigenetic responses to axonal injury by limiting Tet3 expression and restricting 5hmC modifications. Bmal1-regulated genes not only concern axon growth, but also stress responses and energy homeostasis. Furthermore, we uncover an epigenetic rhythm of diurnal oscillation of Tet3 and 5hmC levels in DRG neurons, corresponding to time-of-day effect on axon growth potential. Collectively, our studies demonstrate that targeting Bmal1 enhances axon regeneration.

Rhythm and ROS: Hepatic Chronotherapeutic Features of Grape Seed Proanthocyanidin Extract Treatment in Cafeteria Diet-Fed Rats

Polyphenols play a key role in the modulation of circadian rhythms, while the cafeteria diet (CAF) is able to perturb the hepatic biological rhythm and induce important ROS production. Consequently, we aimed to elucidate whether grape seed proanthocyanidin extract (GSPE) administration recovers the CAF-induced hepatic antioxidant (AOX) misalignment and characterize the chronotherapeutic properties of GSPE. For this purpose, Fischer 344 rats were fed a standard diet (STD) or a CAF and concomitantly treated with GSPE at two time-points (ZT0 vs. ZT12). Animals were euthanized every 6 h and the diurnal rhythms of hepatic ROS-related biomarkers, hepatic metabolites, and AOX gene expression were examined. Interestingly, GSPE treatment was able to recover the diurnal rhythm lost due to the CAF. Moreover, GSPE treatment also increased the acrophase of Sod1, as well as bringing the peak closer to that of the STD group. GSPE also corrected some hepatic metabolites altered by the CAF. Importantly, the differences observed at ZT0 vs. ZT12 due to the time of GSPE administration highlight a chronotherapeutic profile on the proanthocyanin effect. Finally, GSPE could also reduce diet-induced hepatic oxidative stress not only by its ROS-scavenging properties but also by retraining the circadian rhythm of AOX enzymes.

Therapeutic potential of melatonin and its derivatives in aging and neurodegenerative diseases

Aging is associated with increasing impairments in brain homeostasis and represents the main risk factor across most neurodegenerative disorders. Melatonin, a neuroendocrine hormone that regulates mammalian chronobiology and endocrine functions is well known for its antioxidant potential, exhibiting both cytoprotective and chronobiotic abilities. Age-related decline of melatonin disrupting mitochondrial homeostasis and cytosolic DNA-mediated inflammatory reactions in neurons is a major contributory factor in the emergence of neurological abnormalities. There is scattered literature on the possible use of melatonin against neurodegenerative mechanisms in the aging process and its associated diseases. We have searched PUBMED with many combinations of key words for available literature spanning two decades. Based on the vast number of experimental papers, we hereby review recent advancements concerning the potential impact of melatonin on cellular redox balance and mitochondrial dynamics in the context of neurodegeneration. Next, we discuss a broader explanation of the involvement of disrupted redox homeostasis in the pathophysiology of age-related diseases and its connection to circadian mechanisms. Our effort may result in the discovery of novel therapeutic approaches. Finally, we summarize the current knowledge on molecular and circadian regulatory mechanisms of melatonin to overcome neurodegenerative diseases (NDDs) such as Alzheimer's, Parkinson's, Huntington's disease, and amyotrophic lateral sclerosis, however, these findings need to be confirmed by larger, well-designed clinical trials. This review is also expected to uncover the associated molecular alterations in the aging brain and explain how melatonin-mediated circadian restoration of neuronal homeodynamics may increase healthy lifespan in age-related NDDs.

Circadian Oscillations in Skin and Their Interconnection with the Cycle of Life

Periodically oscillating biological processes, such as circadian rhythms, are carefully concerted events that are only beginning to be understood in the context of tissue pathology and organismal health, as well as the molecular mechanisms underlying these interactions. Recent reports indicate that light can independently entrain peripheral circadian clocks, challenging the currently prevalent hierarchical model. Despite the recent progress that has been made, a comprehensive overview of these periodic processes in skin is lacking in the literature. In this review, molecular circadian clock machinery and the factors that govern it have been highlighted. Circadian rhythm is closely linked to immunological processes and skin homeostasis, and its desynchrony can be linked to the perturbation of the skin. The interplay between circadian rhythm and annual, seasonal oscillations, as well as the impact of these periodic events on the skin, is described. Finally, the changes that occur in the skin over a lifespan are presented. This work encourages further research into the oscillating biological processes occurring in the skin and lays the foundation for future strategies to combat the adverse effects of desynchrony, which would likely have implications in other tissues influenced by periodic oscillatory processes.

The role of ferroptosis mediated by Bmal1/Nrf2 in nicotine -induce injury of BTB integrity

Nicotine has shown the toxic effects on male reproductive system, and testicular damage is associated with ferroptosis, which is a non-apoptotic regulated cell death driven by iron-dependent lipid peroxidation. However, the role of nicotine on ferroptosis of testicular cells is largely elusive. In the present study, we showed that nicotine destroyed blood-testis barrier (BTB) by interfering with the circadian rhythm of BTB-related factors (ZO-1, N-Cad, Occludin and CX-43) and induced ferroptosis, as reflected via increased clock-control levels of lipid peroxide and decreased ferritin and GPX4, which involved in the circadian. Inhibition of ferroptosis with Fer-1 alleviated nicotine-induced injury of BTB and impaired sperm in vivo. Mechanically, we uncover that the core molecular clock protein, Bmal1, regulates the expression of Nrf2 via direct E-box binding to its promoter to regulate its activity, and nicotine decreases the transcription of Nrf2 through Bmal1 and inactivates Nrf2 pathway and its downstream antioxidant gene, which leads to the imbalance of redox state and ROS accumulation. Intriguingly, nicotine induced lipid peroxidation and subsequent ferroptosis by Bmal1-mediated Nrf2. In conclusion, our study reveals a clear role for the molecular clock in controlling Nrf2 in testis to mediate the ferroptosis induced by nicotine. These findings provide a potential mechanism to prevent smoking and/or cigarette smoke-induced male reproductive injury.

Six weeks of N-acetylcysteine antioxidant in drinking water decreases pathological fiber branching in MDX mouse dystrophic fast-twitch skeletal muscle

Introduction: It has been proposed that an increased susceptivity to oxidative stress caused by the absence of the protein dystrophin from the inner surface of the sarcolemma is a trigger of skeletal muscle necrosis in the destructive dystrophin deficient muscular dystrophies. Here we use the mdx mouse model of human Duchenne Muscular Dystrophy to test the hypothesis that adding the antioxidant NAC at 2% to drinking water for six weeks will treat the inflammatory phase of the dystrophic process and reduce pathological muscle fiber branching and splitting resulting in a reduction of mass in mdx fast-twitch EDL muscles. Methods: Animal weight and water intake was recorded during the six weeks when 2% NAC was added to the drinking water. Post NAC treatment animals were euthanised and the EDL muscles dissected out and placed in an organ bath where the muscle was attached to a force transducer to measure contractile properties and susceptibility to force loss from eccentric contractions. After the contractile measurements had been made the EDL muscle was blotted and weighed. In order to assess the degree of pathological fiber branching mdx EDL muscles were treated with collagenase to release single fibers. For counting and morphological analysis single EDL mdx skeletal muscle fibers were viewed under high magnification on an inverted microscope. Results: During the six-week treatment phase NAC reduced body weight gain in three- to nine-week-old mdx and littermate control mice without effecting fluid intake. NAC treatment also significantly reduced the mdx EDL muscle mass and abnormal fiber branching and splitting. Discussion: We propose chronic NAC treatment reduces the inflammatory response and degenerative cycles in the mdx dystrophic EDL muscles resulting in a reduction in the number of complexed branched fibers reported to be responsible for the dystrophic EDL muscle hypertrophy.

Bone microenvironment regulative hydrogels with ROS scavenging and prolonged oxygen-generating for enhancing bone repair

Large bone defects resulting from fractures and disease are a major clinical challenge, being often unable to heal spontaneously by the body's repair mechanisms. Lines of evidence have shown that hypoxia-induced overproduction of ROS in bone defect region has a major impact on delaying bone regeneration. However, replenishing excess oxygen in a short time cause high oxygen tension that affect the activity of osteoblast precursor cells. Therefore, reasonably restoring the hypoxic condition of bone microenvironment is essential for facilitating bone repair. Herein, we designed ROS scavenging and responsive prolonged oxygen-generating hydrogels (CPP-L/GelMA) as a "bone microenvironment regulative hydrogel" to reverse the hypoxic microenvironment in bone defects region. CPP-L/GelMA hydrogels comprises an antioxidant enzyme catalase (CAT) and ROS-responsive oxygen-releasing nanoparticles (PFC@PLGA/PPS) co-loaded liposome (CCP-L) and GelMA hydrogels. Under hypoxic condition, CPP-L/GelMA can release CAT for degrading hydrogen peroxide to generate oxygen and be triggered by superfluous ROS to continuously release the oxygen for more than 2 weeks. The prolonged oxygen enriched microenvironment generated by CPP-L/GelMA hydrogel significantly enhanced angiogenesis and osteogenesis while inhibited osteoclastogenesis. Finally, CPP-L/GelMA showed excellent bone regeneration effect in a mice skull defect model through the Nrf2-BMAL1-autophagy pathway. Hence, CPP-L/GelMA, as a bone microenvironment regulative hydrogel for bone tissue respiration, can effectively scavenge ROS and provide prolonged oxygen supply according to the demand in bone defect region, possessing of great clinical therapeutic potential.

How Does Chronobiology Contribute to the Development of Diseases in Later Life

An increasingly older population is one of the major social and medical challenges we currently face. Between 2010 and 2050, it is estimated that the proportion of adults over 65 years of age will double from 8% to 16% of the global population. A major concern associated with aging is the changes in health that can lead to various diseases such as cancer and neurogenerative diseases, which are major burdens on individuals and societies. Thus, it is imperative to better understand changes in sleep and circadian rhythms that accompany aging to improve the health of an older population and target diseases associated with aging. Circadian rhythms play a role in most physiological processes and can contribute to age-related diseases. Interestingly, there is a relationship between circadian rhythms and aging. For example, many older adults have a shift in chronotype, which is an individual's natural inclination to sleep certain times of the day. As adults age, most people tend to go to sleep earlier while also waking up earlier. Numerous studies also suggest that disrupted circadian rhythms may be indicative of developing age-related diseases, like neurodegenerative disorders and cancer. Better understanding the relationship between circadian rhythms and aging may allow us to improve current treatments or develop novel ones that target diseases commonly associated with aging.

Puerariae lobatae radix protects against UVB-induced skin aging via antagonism of REV-ERBα in mice

Puerariae lobatae radix (PLR) is a wildly used herbal medicine. Here we aimed to assess the PLR efficacy against UVB (ultraviolet-B)-induced skin aging and to determine the mechanisms thereof. We found a significant protective effect of PLR (topical application) on UVB-induced skin aging in mice, as evidenced by reduced skin wrinkles, epidermal thickness, and MDA (malondialdehyde) content as well as increased levels of HYP (hydroxyproline) and SOD (superoxide dismutase) in the skin. In the meantime, Mmp-1, p21 and p53 levels were decreased in the skin of PLR-treated mice. Anti-aging effects of PLR were also confirmed in L929 cells. Furthermore, PLR up-regulated skin expression of BMAL1, which is a known regulator of aging by promoting Nrf2 and antioxidant enzymes. Consistently, Nrf2 and several genes (i.e., Prdx6, Sod1, and Sod2) encoding antioxidant enzymes in the skin were increased in PLR-treated mice. Moreover, based on Gal4 chimeric assay, Bmal1 reporter gene and expression assays, we identified PLR as an antagonist of REV-ERBα that can increase Bmal1 expression. Intriguingly, loss of Rev-erbα protected mice against UVB-induced skin aging and abrogated the protective effect of PLR. In conclusion, PLR acts as an antagonist of REV-ERBα and promotes the expression of BMAL1 to protect against skin aging in mice.

Importance of Bmal1 in Alzheimer's disease and associated aging-related diseases: Mechanisms and interventions

With the aging world population, the prevalence of aging-related disorders is on the rise. Diseases such as Alzheimer's, type 2 diabetes mellitus (T2DM), Parkinson's, atherosclerosis, hypertension, and osteoarthritis are age-related, and most of these diseases are comorbidities or risk factors for AD; however, our understandings of molecular events that regulate the occurrence of these diseases are still not fully understood. Brain and muscle Arnt-like protein-1 (Bmal1) is an irreplaceable clock gene that governs multiple important physiological processes. Continuous research of Bmal1 in AD and associated aging-related diseases is ongoing, and this review picks relevant studies on a detailed account of its role and mechanisms in these diseases. Oxidative stress and inflammation turned out to be common mechanisms by which Bmal1 deficiency promotes AD and associated aging-related diseases, and other Bmal1-dependent mechanisms remain to be identified. Promising therapeutic strategies involved in the regulation of Bmal1 are provided, including melatonin, natural compounds, metformin, d-Ser2-oxyntomodulin, and other interventions, such as exercise, time-restricted feeding, and adiponectin. The establishment of the signaling pathway network for Bmal1 in aging-related diseases will lead to advances in the comprehension of the molecular and cellular mechanisms, shedding light on novel treatments for aging-related diseases and promoting aging-associated brain health.

Scutellaria baicalensis Georgi regulates REV-ERBα/BMAL1 to protect against skin aging in mice

Scutellaria baicalensis Georgi (SBG) is a traditional Chinese medicine widely used to treat disorders such as hypertension, dysentery and hemorrhaging. Here, we aimed to assess the pharmacological effects of SBG on skin aging and to investigate the underlying mechanisms. Mice with skin aging were established by treatment with D-galactose and ultraviolet-B. SBG (topical application) showed a protective effect on skin aging in mice, as evidenced by less formation of skin wrinkles, higher levels of SOD (superoxide dismutase) and HYP (hydroxyproline) as well as a lower level of MDA (malondialdehyde). In the meantime, skin MMP-1 and p53 expression were lower, epidermis was thinner and collagen amount was higher in SBG-treated mice. Anti-skin aging effects of SBG were also confirmed in NIH3T3 and HaCaT cells, as well as in mouse primary dermal fibroblasts and human primary epidermal keratinocytes. Furthermore, we found that loss of Rev-erbα (a known repressor of Bmal1) up-regulated skin BMAL1 (a clock component and a known anti-aging factor) and ameliorated skin aging in mice. Moreover, SBG dose-dependently increased the expression of BMAL1 in the skin of aged mice and in senescent NIT3H3 cells. In addition, based on a combination of Gal4 chimeric, luciferase reporter and expression assays, SBG was identified as an antagonist of REV-ERBα and thus an inducer of BMAL1 expression. In conclusion, SBG antagonizes REV-ERBα to up-regulate BMAL1 and to protect against skin aging in mice.

Recent progress and research trend of anti-cataract pharmacology therapy: A bibliometric analysis and literature review

Cataract is the leading cause of blindness worldwide. Cataract phacoemulsification combined with intraocular lens implantation causes great burden to global healthcare, especially for low- and middle-income countries. Such burden would be significantly relieved if cataracts can effectively be treated or delayed by non-surgical means. Excitingly, novel drugs have been developed to treat cataracts in recent decades. For example, oxysterols are found to be able to innovatively reverse lens clouding, novel nanotechnology-loaded drugs improve anti-cataract pharmacological effect, and traditional Chinese medicine demonstrates promising therapeutic effects against cataracts. In the present review, we performed bibliometric analysis to provide an overview perspective regarding the research status, hot topics, and academic trends in the field of anti-cataract pharmacology therapy. We further reviewed the curative effects and molecular mechanisms of anti-cataract drugs such as lanosterol, metformin, resveratrol and curcumin, and prospected the possibility of their clinical application in future.

Obligatory Role of AMPK Activation and Antioxidant Defense Pathway in the Regulatory Effects of Metformin on Cellular Protection and Prevention of Lens Opacity

Increasing levels of oxidative-stress due to deterioration of the Nrf2 (NFE2-related factor)/ARE (antioxidant response element) pathway is found to be a primary cause of aging pathobiology. Metformin having anti-aging effects can delay/halt aging-related diseases. Herein, using lens epithelial cell lines (LECs) of human (h) or mouse (m) and aging h/m primary LECs along with lenses as model systems, we demonstrated that Metformin could correct deteriorated Bmal1/Nrf2/ARE pathway by reviving AMPK-activation, and transcriptional activities of Bmal1/Nrf2, resulting in increased antioxidants enzymatic activity and expression of Phase II enzymes. This ensued reactive oxygen species (ROS) mitigation with cytoprotection and prevention of lens opacity in response to aging/oxidative stress. It was intriguing to observe that Metformin internalized lens/LECs and upregulated OCTs (Organic Cation Transporters). Mechanistically, we found that Metformin evoked AMPK activation-dependent increase of Bmal1, Nrf2, and antioxidants transcription by promoting direct E-Box and ARE binding of Bmal1 and Nrf2 to the promoters. Loss-of-function and disruption of E-Box/ARE identified that Metformin acted by increasing Bmal1/Nrf2-mediated antioxidant expression. Data showed that AMPK-activation was a requisite for Bmal1/Nrf2-antioxidants-mediated defense, as pharmacologically inactivating AMPK impeded the Metformin's effect. Collectively, the results for the first-time shed light on the hitherto incompletely uncovered crosstalk between the AMPK and Bmal1/Nrf2/antioxidants mediated by Metformin for blunting oxidative/aging-linked pathobiology.

The circadian clock mediates the response to oxidative stress in a cone photoreceptor‒like (661W) cell line via regulation of glutathione peroxidase activity

Background: The mammalian retina contains an autonomous circadian clock that controls many physiological functions within this tissue. Our previous studies have indicated that disruption of this circadian clock by removing Bmal1 from the retina affects the visual function, retinal circuitry, and cone photoreceptor viability during aging. In the present study, we employed a mouse-derived cone photoreceptor‒like cell, 661W, to investigate which molecular mechanisms of the circadian clock may modulate cone photoreceptor viability during aging. Methods: Bmal1 knockout (BKO) cells were generated from 661W cells using the CRISPR/Cas9 gene editing tool. Deletion of Bmal1 from 661W was verified by western blot and monitoring Per2-luc bioluminescence circadian rhythms. To investigate the effect of Bmal1 removal on an oxidative stress challenge, cells were treated with hydrogen peroxide (H 2O 2,1 mM) for two hours and then cell viability was assessed. Cells were also cultured and harvested for gene expression analysis and antioxidant assay. Results: Our data indicated that 661W cells contain a functional circadian clock that mediates the response to an oxidative stress challenge in vitro and that such a response is no longer present in the BKO cell. We also hypothesized that the effect was due to the circadian regulation of the intracellular antioxidant defense mechanism. Our results indicated that in 661W cells, the antioxidant defense mechanism is under circadian control, whereas in BKO cells, there is an overall reduction in this antioxidant defense mechanism, and it is no longer under circadian control. Conclusions: Our work supported the notion that the presence of a functional circadian clock and its ability to modulate the response to an oxidative stress is the underlying mechanism that may protect cones during aging.

The circadian clock mediates the response to oxidative stress in a cone photoreceptor‒like (661W) cell line via regulation of glutathione peroxidase activity

Background: The mammalian retina contains an autonomous circadian clock that controls many physiological functions within this tissue. Our previous studies have indicated that disruption of this circadian clock by removing Bmal1 from the retina affects the visual function, retinal circuitry, and cone photoreceptor viability during aging. In the present study, we employed a mouse-derived cone photoreceptor‒like cell, 661W, to investigate which molecular mechanisms of the circadian clock may modulate cone photoreceptor viability during aging. Methods: Bmal1 knockout (BKO) cells were generated from 661W cells using the CRISPR/Cas9 gene editing tool. Deletion of Bmal1 from 661W was verified by western blot and monitoring Per2-luc bioluminescence circadian rhythms. To investigate the effect of Bmal1 removal on an oxidative stress challenge, cells were treated with hydrogen peroxide (H 2O 2,1 mM) for two hours and then cell viability was assessed. Cells were also cultured and harvested for gene expression analysis and antioxidant assay. Results: Our data indicated that 661W cells contain a functional circadian clock that mediates the response to an oxidative stress challenge in vitro and that such a response is no longer present in the BKO cell. We also hypothesized that the effect was due to the circadian regulation of the intracellular antioxidant defense mechanism. Our results revealed that in 661W cells, the antioxidant defense mechanism showed time dependent variation , whereas in BKO cells, there was an overall reduction in this antioxidant defense mechanism, and it no longer showed time dependent variation. Conclusions: Our work supported the notion that the presence of a functional circadian clock and its ability to modulate the response to an oxidative stress is the underlying mechanism that may protect cones during aging.

Emerging Insight Into the Role of Circadian Clock Gene BMAL1 in Cellular Senescence

Cell senescence is a crucial process in cell fate determination and is involved in an extensive array of aging-associated diseases. General perceptions and experimental evidence point out that the decline of physical function as well as aging-associated diseases are often initiated by cell senescence and organ ageing. Therefore, regulation of cell senescence process can be a promising way to handle aging-associated diseases such as osteoporosis. The circadian clock regulates a wide range of cellular and physiological activities, and many age-linked degenerative disorders are associated with the dysregulation of clock genes. BMAL1 is a core circadian transcription factor and governs downstream genes by binding to the E-box elements in their promoters. Compelling evidence has proposed the role of BMAL1 in cellular senescence and aging-associated diseases. In this review, we summarize the linkage between BMAL1 and factors of cell senescence including oxidative stress, metabolism, and the genotoxic stress response. Dysregulated and dampened BMAL1 may serve as a potential therapeutic target against aging- associated diseases.

N-Acetyl-Cysteine: Modulating the Cysteine Redox Proteome in Neurodegenerative Diseases

In the last twenty years, significant progress in understanding the pathophysiology of age-associated neurodegenerative diseases has been made. However, the prevention and treatment of these diseases remain without clinically significant therapeutic advancement. While we still hope for some potential genetic therapeutic approaches, the current reality is far from substantial progress. With this state of the issue, emphasis should be placed on early diagnosis and prompt intervention in patients with increased risk of neurodegenerative diseases to slow down their progression, poor prognosis, and decreasing quality of life. Accordingly, it is urgent to implement interventions addressing the psychosocial and biochemical disturbances we know are central in managing the evolution of these disorders. Genomic and proteomic studies have shown the high molecular intricacy in neurodegenerative diseases, involving a broad spectrum of cellular pathways underlying disease progression. Recent investigations indicate that the dysregulation of the sensitive-cysteine proteome may be a concurrent pathogenic mechanism contributing to the pathophysiology of major neurodegenerative diseases, opening new therapeutic opportunities. Considering the incidence and prevalence of these disorders and their already significant burden in Western societies, they will become a real pandemic in the following decades. Therefore, we propose large-scale investigations, in selected groups of people over 40 years of age with decreased blood glutathione levels, comorbidities, and/or mild cognitive impairment, to evaluate supplementation of the diet with low doses of N-acetyl-cysteine, a promising and well-tolerated therapeutic agent suitable for long-term use.

Circadian Clocks, Redox Homeostasis, and Exercise: Time to Connect the Dots?

Compelling research has documented how the circadian system is essential for the maintenance of several key biological processes including homeostasis, cardiovascular control, and glucose metabolism. Circadian clock disruptions, or losses of rhythmicity, have been implicated in the development of several diseases, premature ageing, and are regarded as health risks. Redox reactions involving reactive oxygen and nitrogen species (RONS) regulate several physiological functions such as cell signalling and the immune response. However, oxidative stress is associated with the pathological effects of RONS, resulting in a loss of cell signalling and damaging modifications to important molecules such as DNA. Direct connections have been established between circadian rhythms and oxidative stress on the basis that disruptions to circadian rhythms can affect redox biology, and vice versa, in a bi-directional relationship. For instance, the expression and activity of several key antioxidant enzymes (SOD, GPx, and CAT) appear to follow circadian patterns. Consequently, the ability to unravel these interactions has opened an exciting area of redox biology. Exercise exerts numerous benefits to health and, as a potent environmental cue, has the capacity to adjust disrupted circadian systems. In fact, the response to a given exercise stimulus may also exhibit circadian variation. At the same time, the relationship between exercise, RONS, and oxidative stress has also been scrutinised, whereby it is clear that exercise-induced RONS can elicit both helpful and potentially harmful health effects that are dependent on the type, intensity, and duration of exercise. To date, it appears that the emerging interface between circadian rhythmicity and oxidative stress/redox metabolism has not been explored in relation to exercise. This review aims to summarise the evidence supporting the conceptual link between the circadian clock, oxidative stress/redox homeostasis, and exercise stimuli. We believe carefully designed investigations of this nexus are required, which could be harnessed to tackle theories concerned with, for example, the existence of an optimal time to exercise to accrue physiological benefits.

Understanding the Emerging Link Between Circadian Rhythm, Nrf2 Pathway, and Breast Cancer to Overcome Drug Resistance

The levels of different molecules in the cell are rhythmically cycled by the molecular clock present at the cellular level. The circadian rhythm is closely linked to the metabolic processes in the cells by an underlying mechanism whose intricacies need to be thoroughly investigated. Nevertheless, Nrf2 has been identified as an essential bridge between the circadian clock and cellular metabolism and is activated by the by-product of cellular metabolism like hydrogen peroxide. Once activated it binds to the specific DNA segments and increases the transcription of several genes that play a crucial role in the normal functioning of the cell. The central clock located in the suprachiasmatic nucleus of the anterior hypothalamus synchronizes the timekeeping in the peripheral tissues by integrating the light-dark input from the environment. Several studies have demonstrated the role of circadian rhythm as an effective tumor suppressor. Tumor development is triggered by the stimulation or disruption of signaling pathways at the cellular level as a result of the interaction between cells and environmental stimuli. Oxidative stress is one such external stimulus that disturbs the prooxidant/antioxidant equilibrium due to the loss of control over signaling pathways which destroy the bio-molecules. Altered Nrf2 expression and impaired redox balance are associated with various cancers suggesting that Nrf2 targeting may be used as a novel therapeutic approach for treating cancers. On the other hand, Nrf2 has also been shown to enhance the resistance of cancer cells to chemotherapeutic agents. We believe that maximum efficacy with minimum side effects for any particular therapy can be achieved if the treatment strategy regulates the circadian rhythm. In this review, we discuss the various molecular mechanisms interlinking the circadian rhythm with the Nrf2 pathway and contributing to breast cancer pathogenesis, we also talk about how these two pathways work in close association with the cell cycle which is another oscillatory system, and whether this interplay can be exploited to overcome drug resistance during chemotherapy.

Real-Time Monitoring of Circadian Rhythms in the Eye

The mammalian eye harbors a full circadian system that controls several physiologically relevant functions within this organ. During the last two decades a few laboratories have developed transgenic animal models in which circadian rhythms can be monitored in real time using luciferase activity. The most famous transgenic mouse to record bioluminescence rhythms from different tissues and organs is the PERIOD2::LUCIFERASE (PER2::LUC) mouse developed by the Takahashi laboratory in early 2000. Since then, several studies have used this mouse model to dissect the mammalian circadian system by monitoring the circadian rhythm in the brain, the eye, and in many other peripheral organs and tissues. This chapter describes the methodology to record and analyze bioluminescence rhythms from the retina, retinal pigment epithelium, and cornea of PER2::LUC mice.

BMAL1 attenuates intracerebral hemorrhage-induced secondary brain injury in rats by regulating the Nrf2 signaling pathway

Background

Intracerebral hemorrhage (ICH) is a severe cerebrovascular disease with high morbidity and mortality rates. Oxidative stress and inflammation are important pathological mechanisms of secondary brain injury (SBI) after ICH. Brain and muscle Arnt-like protein 1 (BMAL1), which forms the core component of the circadian clock, was previously shown to be involved in many diseases and to participate in oxidative stress and inflammatory responses. However, the role of BMAL1 in SBI following ICH is unknown. In addition, treatments targeting miR-155 and its downstream signaling pathway may exert a beneficial effect on SBI after ICH, while miR-155 may regulate Bmal1 mRNA stability and translation. Nevertheless, researchers have not clearly determined whetheantagomir-155 upregulates BMAL1 expression and subsequently attenuates ICH-induced brain injury in rats.

Methods

After establishing an ICH rat model by injecting autologous blood, the time course of changes in levels of the BMAL1 protein after ICH was analyzed. Subsequently, this study was designed to investigate the potential role and mechanisms of BMAL1 in SBI following ICH using lentiviral overexpression and antagomir-155 treatments.

Results

BMAL1 protein levels were significantly decreased in the ICH group compared to the sham group. Genetic overexpression of BMAL1 alleviated oxidative stress, inflammation, brain edema, blood-brain barrier injury, neuronal death, and neurological dysfunction induced by ICH. On the other hand, we observed that inhibiting miRNA-155 using antagomir-155 promoted the expression of BMAL1 and further activated the nuclear factor erythroid 2-related factor 2 (Nrf2) signaling pathway to attenuate brain injury after ICH.

Conclusions

These results reveal that BMAL1 serves as a neuroprotective agent in ICH and upregulation of BMAL1 attenuates ICH-induced SBI. Therefore, BMAL1 may be a promising therapeutic target for SBI following ICH.

(-)-Epigallocatechin-3-gallate Ameliorates Intervertebral Disc Degeneration Through Reprogramming of the Circadian Clock

The circadian clock is vital in the management of our daily physiological as well as metabolic processes. Disturbances of the clock can cause degenerative and age-related diseases. Increasing evidence has indicated that the intervertebral discs contain an internal biological clock related to degeneration. However, to date, no bioactive compounds have been found that can ameliorate intervertebral disc degeneration (IDD) by restoring the circadian clock. (-)-Epigallocatechin-3-gallate (EGCG) is a nutritious food with powerful antioxidant properties, as well as entraining biological clock to improve health. The purpose of this study was to determine whether the protective effects of EGCG on nucleus pulposus (NPCs) under oxidative stress is related to the circadian clock. First, we found that EGCG attenuated H₂O₂-induced extracellular matrix degradation in NPCs and inhibited H₂O₂-induced NPC apoptosis. Our in vivo experiments also confirmed this finding. Furthermore, EGCG attenuated H₂O₂-triggered dampening of phase shifts and daily oscillations in circadian clock gene transcription as well as protein expression levels. Intriguingly, core clock gene (Bmal1) knockdown notably blocked the protective effects of EGCG. To our knowledge, this study provides the first convincing evidence that EGCG prevents IDD in a Bmal1-dependent manner. In general, EGCG supplementation can be used as a nutritional prevention strategy for the rehabilitation of degenerative diseases related to the circadian clock.

Expanding the link between circadian rhythms and redox metabolism of epigenetic control

Circadian rhythms play a central role in physiological and metabolic processes. This is mostly achieved through rhythmic regulation of myriad genes via dynamic epigenome changes. Accumulating evidence indicates that oxidative stress and redox balance are under circadian control and feedback on the clock system. Circadian perturbations induce oxidative stress accumulation and disturb redox balance. Along with these changes, epigenomic landscape changes are a remarkable hallmark of clock disruption. This review aims to summarize evidence supporting the link between the circadian clock and redox metabolism, focusing on possible connections through epigenetic mechanisms.

Diurnal relationship between core clock gene BMAL1, antioxidant SOD1 and oxidative RNA/DNA damage in young and older healthy women

BACKGROUND AND OBJECTIVES

BMAL1 is a core clock gene that positively regulates circadian rhythms. In animals, BMAL1 further acts as transcription factor for the SOD1 gene which encodes the major antioxidant enzyme superoxide dismutase. SOD1 protects against oxidative damage that is a major factor for human aging. Mice lacking mBmal1 exhibit premature aging phenotypes which might be related to a reduced expression of SOD1. The purpose of this study was to explore the circadian relationship between BMAL1, SOD1, oxidative RNA/DNA damage and aging in healthy humans.

SUBJECTS AND METHODS

In a cross-sectional study design, buccal mucosa cells and saliva samples were obtained from 21 young (23.7 ± 2.3 yrs) and 21 older women (66.8 ± 5.7 yrs) within 24 h at 4-h intervals (08:00, 12:00, 16:00, 20:00, 24:00 and 04:00 h). Transcript levels of BMAL1 and SOD1 were measured by real-time quantitative PCR. Protein levels of SOD1 were determined by immunoblotting and densitometry. Levels of oxidative RNA/DNA damage and melatonin were quantified by enzyme immunosorbent assays.

RESULTS

Transcript levels of BMAL1 and SOD1 mRNAs as well as protein levels of SOD1 and melatonin exhibited significant 24-h variation in each age group (P < 0.010, Friedman tests). The mRNA expression patterns of BMAL1 and SOD1 showed similar 24-h rhythmicity and positive relationships were found. Strongest relationships occurred in young women at 12:00 h (rs = 0.81, P = 0.005) and in older women at 08:00 h (r = 0.84, P < 0.001). Maximum levels of SOD1 mRNA appeared within 24 h in both age groups at 24:00 h. In both age groups, the timing of maximum level for SOD1 protein was delayed relative to the timing of maximum level for SOD1 mRNA. This delay was larger in older women (8 h) compared to young women (4 h). Older women showed higher oxidative RNA/DNA damage at all time-points compared to young women (P < 0.020). The oxidative RNA/DNA damage decreased continuously from 08:00 to 20:00 h (P < 0.001) in both age groups. Although oxidative damage and SOD1 protein levels declined simultaneously, only weak and non-significant relationships were noted.

CONCLUSIONS

This study demonstrates that transcript levels of SOD1 and protein level of SOD1 follow a circadian pattern of expression in healthy young and older women. The time-shift found between the 24-h maximum levels of SOD1 mRNA and SOD1 protein could be explained by the time needed for translation of SOD1 protein. The positive relationship found between expression levels of SOD1 mRNA and BMAL1 mRNA is in line with animal studies showing that BMAL1 acts as transcription factor and regulates the circadian synthesis of SOD1 mRNA. Differences between young and older women found in the timing of 24-h maxima as well as differences observed in 24-h relationships between characters might be due to age-related alterations in the circadian system. Absence of relationships between levels of SOD1 and oxidative RNA/DNA damage argue for a more complex interaction between the antioxidant system and the circadian system.

The circadian clock and metabolic homeostasis: entangled networks

The circadian clock exerts an important role in systemic homeostasis as it acts a keeper of time for the organism. The synchrony between the daily challenges imposed by the environment needs to be aligned with biological processes and with the internal circadian clock. In this review, it is provided an in-depth view of the molecular functioning of the circadian molecular clock, how this system is organized, and how central and peripheral clocks communicate with each other. In this sense, we provide an overview of the neuro-hormonal factors controlled by the central clock and how they affect peripheral tissues. We also evaluate signals released by peripheral organs and their effects in the central clock and other brain areas. Additionally, we evaluate a possible communication between peripheral tissues as a novel layer of circadian organization by reviewing recent studies in the literature. In the last section, we analyze how the circadian clock can modulate intracellular and tissue-dependent processes of metabolic organs. Taken altogether, the goal of this review is to provide a systemic and integrative view of the molecular clock function and organization with an emphasis in metabolic tissues.

Exploring the multifunctional role of melatonin in regulating autophagy and sleep to mitigate Alzheimer's disease neuropathology

Melatonin (MLT) is a neurohormone that is regulated by the circadian clock and plays multifunctional roles in numerous neurodegenerative disorders, such as Alzheimer's disease (AD). AD is the most common form of dementia and is associated with the degradation of axons and synapses resulting in memory loss and cognitive impairment. Despite extensive research, there is still no effective cure or specific treatment to prevent the progression of AD. The pathogenesis of AD involves atrophic alterations in the brain that also result in circadian alterations, sleep disruption, and autophagic dysfunction. In this scenario, MLT and autophagy play a central role in removing the misfolded protein aggregations. MLT also promotes autophagy through inhibiting methamphetamine toxicity to protect against neuronal cell death in AD brain. Besides, MLT plays critical roles as either a pro-autophagic indicator or anti-autophagic regulator depending on the phase of autophagy. MLT also has antioxidant properties that can counteract mitochondrial damage, oxidative stress, and apoptosis. Aging, a major risk factor for AD, can change sleep patterns and sleep quality, and MLT can improve sleep quality through regulating sleep cycles. The primary purpose of this review is to explore the putative mechanisms of the beneficial effects of MLT in AD patients. Furthermore, we also summarize the findings from preclinical and clinical studies on the multifunctional roles of MLT on autophagic regulation, the control of the circadian clock-associated genes, and sleep regulation.

Molecular Mechanisms Underlying Reciprocal Interactions Between Sleep Disorders and Parkinson's Disease

Sleep-wake disruptions are among the most prevalent and burdensome non-motor symptoms of Parkinson's disease (PD). Clinical studies have demonstrated that these disturbances can precede the onset of typical motor symptoms by years, indicating that they may play a primary function in the pathogenesis of PD. Animal studies suggest that sleep facilitates the removal of metabolic wastes through the glymphatic system via convective flow from the periarterial space to the perivenous space, upregulates antioxidative defenses, and promotes the maintenance of neuronal protein homeostasis. Therefore, disruptions to the sleep-wake cycle have been associated with inefficient metabolic clearance and increased oxidative stress in the central nervous system (CNS). This leads to excessive accumulation of alpha-synuclein and the induction of neuronal loss, both of which have been proposed to be contributing factors to the pathogenesis and progression of PD. Additionally, recent studies have suggested that PD-related pathophysiological alterations during the prodromal phase disrupt sleep and circadian rhythms. Taken together, these findings indicate potential mechanistic interactions between sleep-wake disorders and PD progression as proposed in this review. Further research into the hypothetical mechanisms underlying these interactions would be valuable, as positive findings may provide promising insights into novel therapeutic interventions for PD.

Dim Light at Night Impairs Daily Variation of Circulating Immune Cells and Renal Immune Homeostasis

Dim light at night (dLAN) has become a pervasive part of the modern world, and growing evidence shows its association with increased health risks. Though this link is attributed to a disturbed circadian clock, the underlying mechanisms that can explain how circadian disruption from dLAN causes negative health effects remain unclear. Here, we exposed rats to a light–dark cycle (12:12 h) with low-intensity light at night (~2 lx) for 2 and 5 weeks and explored the steady-state pattern of circulating immune cells and renal immune-related markers, which are well controlled by the circadian clock. After 5 weeks, dLAN impaired the daily variation in several types of white blood cells, especially monocytes and T cells. Two-week dLAN caused a reduction in blood monocytes and altered gene expression of macrophage marker Cd68 and monocyte-attracting chemokine Ccl2 in the kidney. Interestingly, dLAN decreased renal 3-nitrotyrosine levels and resulted in up-regulation of the main endogenous antioxidant pathways, indicating a disturbance in the renal redox balance and an activation of compensatory mechanisms. These effects paralleled the altered renal expression of the molecular clock components and increased plasma corticosterone levels. Together, our results show that chronic exposure to dLAN weakened the circadian control of daily variation of circulating immune cells and disturbed renal immune and redox homeostasis. Consequences of this dLAN-disturbed immune balance on the ability of the immune system to cope with other challenges should by clarified in further studies.

Cell Autonomous Circadian Systems and Their Relation to Inflammation

All living beings on earth have an important mechanism of 24-h periodicity, which controls their physiology, metabolism, and behavior. In humans, 24-h periodicity is regulated by the superchiasmatic nucleus (SCN) through external and environmental cues. Peripheral organs demonstrate circadian rhythms and circadian clock functions, and these are also observed in cultured cell lines. Every cell contains a CLOCK: BMAL1 loop for the generation of circadian rhythms. In this review, we focused on cell autonomous circadian rhythms in immune cells, the inflammatory diseases caused by disruption of circadian rhythms in hormones, and the role of clock genes in inflammatory diseases.

Actigraphic sleep patterns and cognitive decline in the Hispanic Community Health Study/Study of Latinos

INTRODUCTION

We determined if actigraphy-derived sleep patterns led to 7-year cognitive decline in middle-aged to older Hispanic/Latino adults.

METHODS

We examined 1035 adults, 45 to 64 years of age, from the Hispanic Community Health Study/Study of Latinos. Participants had repeated measures of cognitive function 7 years apart, home sleep apnea studies, and 1 week of actigraphy. Survey linear regression evaluated prospective associations between sleep and cognitive change, adjusting for main covariates.

RESULTS

Longer sleep-onset latency was associated with declines in global cognitive function, verbal learning, and verbal memory. Longer sleep-onset latency was also cross-sectionally associated with verbal learning, verbal memory, and word fluency. Sleep fragmentation was not associated with cognitive change.

CONCLUSION

In a cohort of mostly middle-aged Hispanic/Latinos, actigraphy-derived sleep-onset latency predicted 7-year cognitive change. These findings may serve as targets for sleep interventions of cognitive decline.

The core circadian component, Bmal1, is maintained in the pineal gland of old killifish brain

Circadian rhythm is altered during aging, although the underlying molecular mechanisms remain largely unknown. Here, we used the turquoise killifish as a short-lived vertebrate model to examine the effects of aging on the major circadian network comprising the four mammalian clock protein homologs, Bmal1, Clockb, Cry1b, and Per3, which are highly conserved in the killifish with 50%–85% amino acid sequence identity to their human counterparts. The amplitude of circadian rhythm was smaller in old fish (14 weeks) than in young fish (6 weeks). In old fish brain, the Bmal1 protein level was significantly downregulated. However, the Bmal1 interaction with Clockb and chromatin binding of Bmal1 to its downstream target promoters were retained. Furthermore, Bmal1 was relatively well maintained in the pineal gland compared with other regions of the old fish brain. The results suggest that the circadian clock system in the killifish becomes spatially confined to the pineal gland upon aging.

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The amplitude of free-running circadian rhythms decreases during aging in killifish

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Core clock genes are highly conserved in the turquoise killifish genome

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Bmal1 protein expression decreases in whole brain tissue with aging

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Bmal1 expression is relatively well maintained in the pineal gland with aging

Circadian Rhythm in Adipose Tissue: Novel Antioxidant Target for Metabolic and Cardiovascular Diseases

Obesity is a major risk factor for most metabolic and cardiovascular disorders. Adipose tissue is an important endocrine organ that modulates metabolic and cardiovascular health by secreting signaling molecules. Oxidative stress is a common mechanism associated with metabolic and cardiovascular complications including obesity, type 2 diabetes, and hypertension. Oxidative stress can cause adipose tissue dysfunction. Accumulating data from both humans and experimental animal models suggest that adipose tissue function and oxidative stress have an innate connection with the intrinsic biological clock. Circadian clock orchestrates biological processes in adjusting to daily environmental changes according to internal or external cues. Recent studies have identified the genes and molecular pathways exhibiting circadian expression patterns in adipose tissue. Disruption of the circadian rhythmicity has been suggested to augment oxidative stress and aberrate adipose tissue function and metabolism. Therefore, circadian machinery in the adipose tissue may be a novel therapeutic target for the prevention and treatment of metabolic and cardiovascular diseases. In this review, we summarize recent findings on circadian rhythm and oxidative stress in adipose tissue, dissect the key components that play a role in regulating the clock rhythm, oxidative stress and adipose tissue function, and discuss the potential use of antioxidant treatment on metabolic and cardiovascular diseases by targeting the adipose clock.

Circadian rhythm disorder: a potential inducer of vascular calcification?

Over the past decades, circadian rhythm has drawn a great attention in cardiovascular diseases. The expressions of rhythm genes fluctuate in accordance with the diurnal changes of vascular physiology, which highlights the pivotal effect of vascular clock. Recent researches show that the circadian clock can directly regulate the synthetic and secretory function of endothelial cells and phenotypic switch of vascular smooth muscle cells to adjust vascular relaxation and contraction. Importantly, dysfunction of vascular cells is involved in vascular calcification. Secretion of osteogenic cytokines and calcified vesicles in the vessel, osteogenic phenotype switch of vascular smooth muscle cells are all implicated in the calcification process. Moreover, circadian rhythm disorder can lead to abnormal hormone secretion, oxidative stress, inflammatory reaction, and autophagy, all of which should not be ignored in vascular calcification. Vascular senescence is another pathogenetic mechanism in vascular calcification. Accelerated vascular senescence may act as an important intermediate factor to promote vascular calcification in circadian rhythm disorders. In this review, we elaborate the potential effect of circadian rhythm disorder in vascular calcification and try to provide a new direction in the prevention of vascular calcification.

Circadian Rhythms in Environmental Health Sciences

PURPOSE OF REVIEW

This review aims to explore how circadian rhythms influence disease susceptibility and potentially modify the effect of environmental exposures. We aimed to identify biomarkers commonly used in environmental health research that have also been the subject of chronobiology studies, in order to review circadian rhythms of relevance to environmental health and determine if time-of-day is an important factor to consider in environmental health studies. Moreover, we discuss opportunities for studying how environmental exposures may interact with circadian rhythms to structure disease pathology and etiology.

RECENT FINDINGS

In recent years, the study of circadian rhythms in mammals has flourished. Animal models revealed that all body tissues have circadian rhythms. In humans, circadian rhythms were also shown to exist at multiple levels of organization: molecular, cellular, and physiological processes, including responding to oxidative stress, cell trafficking, and sex hormone production, respectively. Together, these rhythms are an essential component of human physiology and can shape an individual's susceptibility and response to disease. Circadian rhythms are relatively unexplored in environmental health research. However, circadian clocks control many physiological and behavioral processes that impact exposure pathways and disease systems. We believe this review will motivate new studies of (i) the impact of exposures on circadian rhythms, (ii) how circadian rhythms modify the effect of environmental exposures, and (iii) how time-of-day impacts our ability to observe the body's response to exposure.

Clock Protein Bmal1 and Nrf2 Cooperatively Control Aging or Oxidative Response and Redox Homeostasis by Regulating Rhythmic Expression of Prdx6

Many disorders of aging, including blinding-diseases, are associated with deficiency of brain and muscle arnt-like protein 1 (Bmal1) and, thereby, dysregulation of antioxidant-defense pathway. However, knowledge is limited regarding the role of Bmal1 regulation of antioxidant-pathway in the eye lens/lens epithelial cells (LECs) at the molecular level. We found that, in aging human (h)LECs, a progressive decline of nuclear factor erythroid 2-related factor 2 (Nrf2)/ARE (antioxidant response element)-mediated antioxidant genes was connected to Bmal1-deficiency, leading to accumulation of reactive oxygen species (ROS) and cell-death. Bmal1-depletion disrupted Nrf2 and expression of its target antioxidant genes, like Peroxiredoxin 6 (Prdx6). DNA binding and transcription assays showed that Bmal1 controlled expression by direct binding to E-Box in Prdx6 promoter to regulate its transcription. Mutation at E-Box or ARE reduced promoter activity, while disruption of both sites diminished the activity, suggesting that both sites were required for peak Prdx6-transcription. As in aging hLECs, ROS accumulation was increased in Bmal1-deficient cells and the cells were vulnerable to death. Intriguingly, Bmal1/Nrf2/Prdx6 and PhaseII antioxidants showed rhythmic expression in mouse lenses in vivo and were reciprocally linked to ROS levels. We propose that Bmal1 is pivotal for regulating oxidative responses. Findings also reveal a circadian control of antioxidant-pathway, which is important in combating lens/LECs damage induced by aging or oxidative stress.

It's about time: clocks in the developing lung

The discovery of peripheral intracellular clocks revealed circadian oscillations of clock genes and their targets in all cell types, including those in the lung, sparking exploration of clocks in lung disease pathophysiology. While the focus has been on the role of these clocks in adult airway diseases, clock biology is also likely to be important in perinatal lung development, where it has received far less attention. Historically, fetal circadian rhythms have been considered irrelevant owing to lack of external light exposure, but more recent insights into peripheral clock biology raise questions of clock emergence, its concordance with tissue-specific structure/function, the interdependence of clock synchrony and functionality in perinatal lung development, and the possibility of lung clocks in priming the fetus for postnatal life. Understanding the perinatal molecular clock may unravel mechanistic targets for chronic airway disease across the lifespan. With current research providing more questions than answers, it is about time to investigate clocks in the developing lung.

Deletion of astrocytic BMAL1 results in metabolic imbalance and shorter lifespan in mice

Disruption of the circadian cycle is strongly associated with metabolic imbalance and reduced longevity in humans. Also, rodent models of circadian arrhythmia, such as the constitutive knockout of the clock gene Bmal1, leads to metabolic disturbances and early death. Although astrocyte clock regulates molecular and behavioral circadian rhythms, its involvement in the regulation of energy balance and lifespan is unknown. Here, we show that astrocyte-specific deletion of Bmal1 is sufficient to alter energy balance, glucose homeostasis, and reduce lifespan. Mutant animals displayed impaired hypothalamic molecular clock, age-dependent astrogliosis, apoptosis of hypothalamic astrocytes, and increased glutamate and GABA levels. Importantly, modulation of GABAA-receptor signaling completely restored glutamate levels, delayed the reactive gliosis as well as the metabolic phenotypes and expanded the lifespan of the mutants. Our results demonstrate that the astrocytic clock can influence many aspects of brain function and neurological disease and suggest astrocytes and GABAA receptor as pharmacological targets to prevent the metabolic dysfunctions and shortened lifespan associated with alterations of circadian rhythms.

Molecular Regulation of Circadian Chromatin

Circadian rhythms are generated by transcriptional negative feedback loops and require histone modifications and chromatin remodeling to ensure appropriate timing and amplitude of clock gene expression. Circadian modifications to histones are important for transcriptional initiation and feedback inhibition serving as signaling platform for chromatin-remodeling enzymes. Current models indicate circadian-regulated facultative heterochromatin (CRFH) is a conserved mechanism at clock genes in Neurospora, Drosophila, and mice. CRFH consists of antiphasic rhythms in activating and repressive modifications generating chromatin states that cycle between transcriptionally permissive and nonpermissive. There are rhythms in histone H3 lysine 9 and 27 acetylation (H3K9ac and H3K27ac) and histone H3 lysine 4 methylation (H3K4me) during activation; while deacetylation, histone H3 lysine 9 methylation (H3K9me) and heterochromatin protein 1 (HP1) are hallmarks of repression. ATP-dependent chromatin-remodeling enzymes control accessibility, nucleosome positioning/occupancy, and nuclear organization. In Neurospora, the rhythm in facultative heterochromatin is mediated by the frequency (frq) natural antisense transcript (NAT) qrf. While in mammals, histone deacetylases (HDACs), histone H3 lysine 9 methyltransferase (KMT1/SUV39), and components of nucleosome remodeling and deacetylase (NuRD) are part of the nuclear PERIOD complex (PER complex). Genomics efforts have found relationships among rhythmic chromatin modifications at clock-controlled genes (ccg) revealing circadian control of genome-wide chromatin states. There are also circadian clock-regulated lncRNAs with an emerging function that includes assisting in chromatin dynamics. In this review, we explore the connections between circadian clock, chromatin remodeling, lncRNAs, and CRFH and how these impact rhythmicity, amplitude, period, and phase of circadian clock genes.

BMAL1 knockdown triggers different colon carcinoma cell fates by altering the delicate equilibrium between AKT/mTOR and P53/P21 pathways

Dysregulation of the circadian timing system (CTS) frequently appears during colorectal cancer (CRC) progression. In order to better understand the role of the circadian clock in CRC progression, this study evaluated in vitro how knockdown of a core circadian protein BMAL1 (BMAL1-KD) influenced the behavior of two primary human CRC cell lines (HCT116 and SW480) and a metastatic CRC cell line (SW620).Unexpectedly, BMAL1-KD induced CRC cell-type specific responses rather than the same phenomenon throughout. First, BMAL1-KD increased AKT/mTOR activation in each CRC cell line, but to different extents. Second, BMAL1-KD-induced P53 activation varied with cell context. In a wild type P53 background, HCT116 BMAL1-KD cells quickly underwent apoptosis after shBMAL1 lentivirus transduction, while surviving cells showed less P53 but increased AKT/mTOR activation, which ultimately caused higher proliferation. In the presence of a partially functional mutant P53, SW480 BMAL1-KD cells showed moderate P53 and mTOR activation simultaneously with cell senescence. With a moderate increased AKT but unchanged mutant P53 activation, SW620 BMAL1-KD cells grew faster.Thus, under different CRC cellular pathological contexts, BMAL1 knockdown induced relatively equal effects on AKT/mTOR activation but different effects on P53 activation, which finally triggered different CRC cell fates.

Temporal control of responses to chemically induced oxidative stress in the gill mucosa of Atlantic salmon (Salmo salar)

Molecular clocks are known to mediate cellular responses during oxidative stress. This important interplay is less understood in fish, particularly at mucosal surfaces. Here we report the coordinated modulation of the molecular clocks and antioxidant defence following chemically induced oxidative stress in the gill mucosa of Atlantic salmon (Salmo salar). A short-term gill explant (GE) culture was used as a model in a series of experiments aiming to demonstrate how photoperiod during culture, levels of environmental reactive oxygen species (ROS), time of oxidative stress induction, and the daily light-dark cycle affect the expression of molecular clocks and antioxidant genes in the gills. Photoperiod (either 12 light:12 dark cycle, LD or 0 light:24 dark cycle, DD) during explant culture affected the transcription of two clock genes, circadian locomotor output cycles kaput (clk) and period 1 (per1), as well as one antioxidant gene, glutathione peroxidase (gpx). When the GEs were exposed to two ROS-generating oxidants (i.e., peracetic acid, PAA and hydrogen peroxide, H₂O₂), photoperiod condition was demonstrated to have a significant impact on the transcription of the core genes. PAA significantly downregulated the expression of reverb alpha (reverbα) under LD, while per1 and per2 expression were significantly upregulated under DD. Nevertheless, there was no distinct pattern in the oxidant-induced expression of clock genes. On the other hand, photoperiod was shown to influence the antioxidant defence under increased ROS level, where significant transcriptional upregulation was a hallmark response under LD. Interestingly, no changes were identified under DD. Induction of oxidative stress either at ZT2 (2 h after lights on) or at ZT14 (2 h after lights off) revealed striking differences that highlighted the temporal sensitivity of the oxidative defence repertoire. Per1 was significantly modulated following time-dependent induction of oxidative stress among the clock genes. Inducing oxidative stress at ZT2 resulted in a significant upregulation of antioxidant genes; but when the same stimuli were given at ZT14, all antioxidant genes exhibited downregulation. It was further revealed that neither of the genes demonstrated daily rhythmicity in their expression in the GE cultures. Collectively, the study revealed the coordinated expression of the core elements in the molecular clock and antioxidant systems in the gill mucosa following oxidative stress. Furthermore, the results reveal that the time of day plays a crucial influence on how defences are mobilised during oxidative stress, adding new insights into the rhythms of oxidative stress response in mucosal tissues in fish.

Molecular Connections Between Circadian Clocks and Aging

The mammalian circadian clockwork has evolved as a timing system that allows the daily environmental changes to be anticipated so that behavior and tissue physiology can be adjusted accordingly. The circadian clock synchronizes the function of all cells within tissues in order to temporally separate preclusive and potentially harmful physiologic processes and to establish a coherent temporal organismal physiology. Thus, the proper functioning of the circadian clockwork is essential for maintaining cellular and tissue homeostasis. Importantly, aging reduces the robustness of the circadian clock, resulting in disturbed sleep-wake cycles, a lowered capacity to synchronize circadian rhythms in peripheral tissues, and reprogramming of the circadian clock output at the molecular function levels. These circadian clock-dependent behavioral and molecular changes in turn further accelerate the process of aging. Here we review the current knowledge about how aging affects the circadian clock, how the functional decline of the circadian clock affects aging, and how the circadian clock machinery and the molecular processes that underlie aging are intertwined.

Molecular mechanisms and physiological importance of circadian rhythms

To accommodate daily recurring environmental changes, animals show cyclic variations in behaviour and physiology, which include prominent behavioural states such as sleep-wake cycles but also a host of less conspicuous oscillations in neurological, metabolic, endocrine, cardiovascular and immune functions. Circadian rhythmicity is created endogenously by genetically encoded molecular clocks, whose components cooperate to generate cyclic changes in their own abundance and activity, with a periodicity of about a day. Throughout the body, such molecular clocks convey temporal control to the function of organs and tissues by regulating pertinent downstream programmes. Synchrony between the different circadian oscillators and resonance with the solar day is largely enabled by a neural pacemaker, which is directly responsive to certain environmental cues and able to transmit internal time-of-day representations to the entire body. In this Review, we discuss aspects of the circadian clock in Drosophila melanogaster and mammals, including the components of these molecular oscillators, the function and mechanisms of action of central and peripheral clocks, their synchronization and their relevance to human health.

Role of Food Phytochemicals in the Modulation of Circadian Clocks

The circadian clock is an intrinsic mechanism of biological adaptation to the cyclical changes of the environment. The circadian rhythm disorders affect the life activities of organisms. A variety of phytochemicals (e.g., polyphenols, flavonoids, alkaloids, and melatonin) reportedly can regulate the expression and rhythm of circadian clock genes and stabilize the internal environment. This perspective focuses on the relationship of circadian clock genes with oxidative stress, inflammatory response, and metabolic disorders and emphasizes the regulation of phytochemicals on the circadian clock. Potential mechanisms and applications of supplemental phytochemicals to improve metabolic disorders and circadian rhythm disorders are also discussed.