Circadian Clock-Controlled Drug Metabolism: Implications for Chronotherapeutics

Dosing Time of Day Impacts the Safety of Antiarrhythmic Drugs in a Computational Model of Cardiac Electrophysiology

Circadian clocks regulate many aspects of human physiology, including cardiovascular function and drug metabolism. Administering drugs at optimal times of the day may enhance effectiveness and reduce side effects. Certain cardiac antiarrhythmic drugs have been withdrawn from the market due to unexpected proarrhythmic effects such as fatal Torsade de Pointes (TdP) ventricular tachycardia. The Comprehensive in vitro Proarrhythmia Assay (CiPA) is a recent global initiative to create guidelines for the assessment of drug-induced arrhythmias that recommends a central role for computational modeling of ion channels and in silico evaluation of compounds for TdP risk. We simulated circadian regulation of cardiac excitability and explored how dosing time of day affects TdP risk for 11 drugs previously classified into risk categories by CiPA. The model predicts that a high-risk drug taken at the most optimal time of day may actually be safer than a low-risk drug taken at the least optimal time of day. Based on these proof-of-concept results, we advocate for the incorporation of circadian clock modeling into the CiPA paradigm for assessing drug-induced TdP risk. Since cardiotoxicity is the leading cause of drug discontinuation, modeling cardiac-related chronopharmacology has significant potential to improve therapeutic outcomes.

A combined mathematical and experimental approach reveals the drivers of time-of-day drug sensitivity in human cells

The circadian clock plays a pivotal role in regulating various aspects of cancer, influencing tumor growth and treatment responses. There are significant changes in drug efficacy and adverse effects when drugs are administered at different times of the day, underscoring the importance of considering the time of day in treatments. Despite these well-established findings, chronotherapy approaches in drug treatment have yet to fully integrate into clinical practice, largely due to the stringent clinical requirements for proving efficacy and safety, alongside the need for deeper mechanistic insights. In this study, we employ a combined mathematical and experimental approach to systematically investigate the factors influencing time-of-day drug sensitivity in human cells. Here we show how circadian and drug properties independently shape time-of-day profiles, providing valuable insights into the temporal dynamics of treatment responses. Understanding how drug efficacy fluctuates throughout the day holds immense potential for the development of personalized treatment strategies aligned with an individual's internal biological clock, revolutionizing cancer treatment by maximizing therapeutic benefits. Moreover, our framework offers a promising avenue for refining future drug screening efforts, paving the way for more effective and targeted therapies across diverse tissue types.

Metformin upregulates circadian gene PER2 to inhibit growth and enhance the sensitivity of glioblastoma cell lines to radiotherapy via SIRT2/G6PD pathway

Introduction

Glioblastoma multiform (GBM) is considered the deadliest brain cancer. Standard therapies are followed by poor patient's survival outcomes, so novel and more efficacious therapeutic strategies are imperative to tackle this scourge. Metformin has been reported to have anti-cancer effects. However, the precise mechanism underlying these effects remains elusive. A better understanding of its underlying mechanism will inform future experimental designs exploring metformin as a potential adjuvant therapy for GBM. This research aimed to elucidate the potential molecular mechanism of metformin in GBM by integrating proteomics and transcriptomics.

Methods

The study examined the effects of metformin on GBM cell lines using various methods. The U87, U251 and HA1800 were cultured and modified through PER2 knockdown and overexpression. Cell viability was assessed using the CCK8 assay, and G6PDH activity and intracellular NADPH+ levels were measured with specific kits. ROS levels, mitochondrial membrane potential, cell cycle distribution and apoptosis were analyzed by flow cytometry. RNA was extracted for transcriptomic analysis through RNA sequencing, while proteomic analysis was performed on total protein from treated cells. WB detected specific proteins, and RT-qPCR quantified gene expression. In vivo experiments, GBM xenograft on nude mice treated with metformin combining radiotherapy was evaluated and received IHC and TUNEL staining for protein expression and apoptosis assessment. Statistical analyses were conducted using Prism software to identify significant group differences.

Results

We found that differential expressional genes and proteins relating to circadian rhythm were enriched in proteomic or transcriptomic. The expression of PER2, the key circadian gene, was up-regulated in GBM cell lines when treated with metformin. Furthermore, the expression of silent information regulator 2(SIRT2) was down-regulated, while the expression of the G6PD protein just slightly increased in GBM cell lines. Meanwhile, NADPH+ production and G6PDH enzyme activity significantly decreased. Further study validated that metformin inhibited the cell growth of GBM cell lines through up-regulating PER2 and inhibited SIRT2/G6PD signaling pathway, enhancing radiotherapy(RT) sensitivity. We also found that the inhibition of SIRT2 caused by metformin is mediated by PER2.

Discussion

We found the pivotal role of metformin as an effective circadian rhythm regulator. Targeting circadian clock gene to modify and rescue the dysfunctional circadian clock of GBM cells at molecular level might be an innovative way to administer cancer chronotherapy and maintain metabolic homeostasis in real world practice.

The clinical impact of chronopharmacology on current medicine

One of the goals of clinical pharmacology is to optimize patient treatment by adopting new treatment strategies which will increase the efficacy of the treatment and decrease the adverse effects of the drugs. In the literature, it has shown that the effectiveness and toxicity of medications can vary significantly based on when they are administered, making timing a crucial factor in treatment plans. Chronopharmacology a relatively new branch of clinical pharmacology focuses on adjusting drug administration times to enhance patient outcomes. Chronopharmacology is largely influenced by an individual's circadian rhythm which refers to periodic changes in biological processes depending on the time of the day. The chronopharmacology influences clinical practice, and the accumulating knowledge in this field will likely lead healthcare providers to adopt new strategies for drug treatment regimens. This review aims to summarize the impact of chronopharmacology particularly on current clinical practices and highlight the latest findings related to chronophysiological mechanisms.

Circadian rhythms and cancer: implications for timing in therapy

Circadian rhythms, intrinsic cycles spanning approximately 24 h, regulate numerous physiological processes, including sleep-wake cycles, hormone release, and metabolism. These rhythms are orchestrated by the circadian clock, primarily located in the suprachiasmatic nucleus (SCN) of the hypothalamus. Disruptions in circadian rhythms, whether due to genetic mutations, environmental factors, or lifestyle choices, can significantly impact health, contributing to disorders such as sleep disturbances, metabolic syndrome, and cardiovascular diseases. Additionally, there is a profound link between the disruption of circadian rhythms and development of various cancer, the influence on disease incidence and progression. This incurred regulation by circadian clock on pathways has its implication in tumorigenesis, such as cell cycle control, DNA damage response, apoptosis, and metabolism. Furthermore, the circadian timing system modulates the efficacy and toxicity of cancer treatments. In cancer treatment, the use of chronotherapy to optimize the timing of medical treatments, involves administering chemotherapy, radiation, or other therapeutic interventions at specific intervals to enhance efficacy and minimize side effects. This approach capitalizes on the circadian variations in cellular processes, including DNA repair, cell cycle progression, and drug metabolism. Preclinical and clinical studies have demonstrated that chronotherapy can significantly improve the therapeutic index of chemotherapeutic agents like cisplatin and 5-fluorouracil by enhancing anticancer activity and reducing toxicity. Further research is needed to elucidate the mechanisms underlying circadian regulation of cancer and to develop robust chronotherapeutic protocols tailored to individual patients' circadian profiles, potentially transforming cancer care into more effective and personalized treatment strategies.

Disruption of local circadian clocks in aristolochic acid-induced nephropathy in mice

BACKGROUND

Aristolochic acid I (AAI), an emerging biogenic contaminant widely present in Aristolochic plants, has been implicated in the progression of tubulointerstitial disease, known as aristolochic acid nephropathy (AAN). The circadian clock, a vital regulator of organ homeostasis, is susceptible to external chemical cues, including toxins. However, the reciprocal interactions between AAI and the circadian clock remain unexplored.

METHODS

We initially assessed sex- and time-dependent nephropathy and behavioral responses in C57BL/6J mice exposed to AAI. Subsequently, we evaluated changes in the expression of circadian clock genes following treatment with AAI or its bioactive metabolite, aristolactam I, using real-time quantitative PCR and immunoblotting in renal tissues and cells. Additionally, real-time reporter assays were conducted on kidney explants from PER2::Luc knock-in reporter mice and Per2-dLuc/Bmal1-dLuc reporter cell lines. To further elucidate the regulatory role of circadian clocks in AAI-induced nephropathy, mice with global or kidney-specific knockout of Bmal1, as well as mice subjected to experimental jetlag, were utilized.

RESULTS

Our findings revealed a sex-dependent nephrotoxicity of AAI, with males exhibiting greater vulnerability. AAI-induced nephropathy was accompanied by impaired spatial cognitive function, disruptions in free-running locomotor activity, altered renal expression of multiple core clock genes, and disturbances in the circadian rhythm of renal PER2::Luc activity. Notably, kidney-specific ablation of the core clock gene Bmal1 significantly exacerbated renal injury and inflammation, whereas disruptions to the central clock, either genetically (through conventional knockout of Bmal1) or environmentally (mimicking jetlag), had minimal effects on AAI nephrotoxicity. Furthermore, both AAI and its bioactive metabolite aristolactam I demonstrated the ability to disrupt circadian clocks in human osteosarcoma cells (U2OS) and mouse renal tubular epithelial cells (mRTEC).

CONCLUSION

Collectively, these findings highlight the detrimental impact of aristolochic acids on local renal circadian clocks, ultimately exacerbating kidney damage. This study provides novel insights into the molecular mechanisms underlying AAI nephrotoxicity, potentially opening avenues for therapeutic interventions aimed at modulating the renal circadian clock to treat AAN.

Exploring transcriptomic databases: unraveling circadian gene disruptions in lower grade glioma

The study explored the role of circadian rhythm genes (CRGs) in lower grade glioma (LGG) development and found that certain genes, such as CRY1, NPAS2, and RORB, were associated with increased or decreased risk of LGG. The study also investigated the correlation between CRGs and immune cell infiltration, revealing a negative association with macrophage infiltration and a positive correlation with B cell and CD8 + T cell infiltration. Additionally, the study identified major mutated CRGs, including PER2, BMAL1, CLOCK, and BMAL2, and their potential interaction with other CNS-associated genes. The study suggests that CRGs play a crucial role in immune response and tumorigenesis in LGG patients and warrants further investigation.

Circadian Rhythms of the Blood-Brain Barrier and Drug Delivery

The blood-brain barrier (BBB) is a critical interface separating the central nervous system from the peripheral circulation, ensuring brain homeostasis and function. Recent research has unveiled a profound connection between the BBB and circadian rhythms, the endogenous oscillations synchronizing biological processes with the 24-hour light-dark cycle. This review explores the significance of circadian rhythms in the context of BBB functions, with an emphasis on substrate passage through the BBB. Our discussion includes efflux transporters and the molecular timing mechanisms that regulate their activities. A significant focus of this review is the potential implications of chronotherapy, leveraging our knowledge of circadian rhythms for improving drug delivery to the brain. Understanding the temporal changes in BBB can lead to optimized timing of drug administration, to enhance therapeutic efficacy for neurological disorders while reducing side effects. By elucidating the interplay between circadian rhythms and drug transport across the BBB, this review offers insights into innovative therapeutic interventions.

Clinical covariates that improve the description of high dose methotrexate pharmacokinetics in a diverse population to inform MTXPK.org

The MTXPK.org webtool was launched in December 2019 and was developed to facilitate model-informed supportive care and optimal use of glucarpidase following the administration of high-dose methotrexate (HDMTX). One limitation identified during the original development of the MTXPK.org tool was the perceived generalizability because the modeled population comprised solely of Nordic pediatric patients receiving 24-h infusions for the treatment of acute lymphoblastic leukemia. The goal of our study is to describe the pharmacokinetics of HDMTX from a diverse patient population (e.g., races, ethnicity, indications for methotrexate, and variable infusion durations) and identify meaningful factors that account for methotrexate variability and improve the model's performance. To do this, retrospectively analyzed pharmacokinetic and toxicity data from pediatric and adolescent young adult patients who were receiving HDMTX (>0.5 g/m2 ) for the treatment of a cancer diagnosis from three pediatric medical centers. We performed population pharmacokinetic modeling referencing the original MTXPK.org NONMEM model (includes body surface area and serum creatinine as covariates) on 1668 patients, 7506 administrations of HDMTX, and 30,250 concentrations. Our results support the parameterizations of short infusion duration (<8 h) and the presence of Down syndrome on methotrexate clearance, the parameterization of severe hypoalbuminemia (<2.5 g/dL) on the intercompartmental clearance (Q2 and Q3), and the parameterization of pleural effusion on the volume of distribution (V1 and V2). These novel parameterizations will increase the generalizability of the MTXPK.org model once they are added to the webtool.

CRY1/2 regulate rhythmic CYP2A5 in mouse liver through repression of E4BP4

CYP2A5, an enzyme responsible for metabolism of diverse drugs, displays circadian rhythms in its expression and activity. However, the underlying mechanisms are not fully established. Here we aimed to investigate a potential role of CRY1/2 (circadian clock modulators) in circadian regulation of hepatic CYP2A5. Regulatory effects of CRY1/2 on CYP2A5 were determined using Cry1-null and Cry2-null mice, and validated using AML-12, Hepa1-6 and HepG2 cells. CYP2A5 activities both in vivo and in vitro were assessed using coumarin 7-hydroxylation as a probe reaction. mRNA and protein levels were detected by qPCR and western blotting, respectively. Regulatory mechanism was studied using a combination of luciferase reporter assays, chromatin immunoprecipitation (ChIP) and co-immunoprecipitation (Co-IP). We found that ablation of Cry1 or Cry2 in mice reduced hepatic CYP2A5 expression (at both mRNA and protein levels) and blunted its diurnal rhythms. Consistently, these knockouts showed decreased CYP2A5 activity (characterised by coumarin 7-hydroxylation) and a loss of its time-dependency, as well as exacerbated coumarin-induced hepatotoxicity. Cell-based assays confirmed that CRY1/2 positively regulated CYP2A5 expression and rhythms. Based on combined luciferase reporter, ChIP and Co-IP assays, we unraveled that CRY1/2 interacted with E4BP4 protein to repress its inhibitory effect on Cyp2a5 transcription and expression. In conclusion, CRY1/2 regulate rhythmic CYP2A5 in mouse liver through repression of E4BP4. These findings advance our understanding of circadian regulation of drug metabolism and pharmacokinetics.

Intracellular spatiotemporal metabolism in connection to target engagement

The metabolism in eukaryotic cells is a highly ordered system involving various cellular compartments, which fluctuates based on physiological rhythms. Organelles, as the smallest independent sub-cell unit, are important contributors to cell metabolism and drug metabolism, collectively designated intracellular metabolism. However, disruption of intracellular spatiotemporal metabolism can lead to disease development and progression, as well as drug treatment interference. In this review, we systematically discuss spatiotemporal metabolism in cells and cell subpopulations. In particular, we focused on metabolism compartmentalization and physiological rhythms, including the variation and regulation of metabolic enzymes, metabolic pathways, and metabolites. Additionally, the intricate relationship among intracellular spatiotemporal metabolism, metabolism-related diseases, and drug therapy/toxicity has been discussed. Finally, approaches and strategies for intracellular spatiotemporal metabolism analysis and potential target identification are introduced, along with examples of potential new drug design based on this.

Reprogramming of rhythmic liver metabolism by intestinal clock

BACKGROUND & AIMS

Temporal oscillations in intestinal nutrient processing and absorption are coordinated by the local clock, which leads to the hypothesis that the intestinal clock has major impacts on shaping peripheral rhythms via diurnal nutritional signals. Here, we investigate the role of the intestinal clock in controlling liver rhythmicity and metabolism.

METHODS

Transcriptomic analysis, metabolomics, metabolic assays, histology, quantitative (q)PCR, and immunoblotting were performed with Bmal1-intestine-specific knockout (iKO), Rev-erba-iKO, and control mice.

RESULTS

Bmal1 iKO caused large-scale reprogramming of the rhythmic transcriptome of mouse liver with a limited effect on its clock. In the absence of intestinal Bmal1, the liver clock was resistant to entrainment by inverted feeding and a high-fat diet. Importantly, Bmal1 iKO remodelled diurnal hepatic metabolism by shifting to gluconeogenesis from lipogenesis during the dark phase, leading to elevated glucose production (hyperglycaemia) and insulin insensitivity. Conversely, Rev-erba iKO caused a diversion to lipogenesis from gluconeogenesis during the light phase, resulting in enhanced lipogenesis and an increased susceptibility to alcohol-related liver injury. These temporal diversions were attributed to disruption of hepatic SREBP-1c rhythmicity, which was maintained via gut-derived polyunsaturated fatty acids produced by intestinal FADS1/2 under the control of a local clock.

CONCLUSIONS

Our findings establish a pivotal role for the intestinal clock in dictating liver rhythmicity and diurnal metabolism, and suggest targeting intestinal rhythms as a new avenue for improving metabolic health.

IMPACT AND IMPLICATIONS

Our findings establish the centrality of the intestinal clock among peripheral tissue clocks, and associate liver-related pathologies with its malfunction. Clock modifiers in the intestine are shown to modulate liver metabolism with improved metabolic parameters. Such knowledge will help clinicians improve the diagnosis and treatment of metabolic diseases by incorporating intestinal circadian factors.

Fifty Years of Aryl Hydrocarbon Receptor Research as Reflected in the Pages of Drug Metabolism and Disposition

The induction of multiple drug-metabolizing enzymes by halogenated and polycyclic aromatic hydrocarbon toxicants is mediated by the aryl hydrocarbon receptor (AHR). This fascinating receptor also has natural dietary and endogenous ligands, and much is now appreciated about the AHR's developmental and physiologic roles, as well as its importance in cancer and other diseases. The past several years has witnessed increasing emphasis on understanding the multifaceted roles of the AHR in the immune system. Most would agree that the "discovery" of the AHR occurred in 1976, with the report of specific binding of a high affinity radioligand in mouse liver, just three years after the launch of the journal Drug Metabolism and Disposition (DMD) in 1973. Over the ensuing 50 years, the AHR and DMD have led parallel and often intersecting lives. The overall goal of this mini-review is to provide a decade-by-decade overview of major historical landmark discoveries in the AHR field and to highlight the numerous contributions made by publications appearing in the pages of DMD. It is hoped that this historical tour might inspire current and future research in the AHR field. SIGNIFICANCE STATEMENT: With the launch of Drug Metabolism and Disposition (DMD) in 1973 and the discovery of the aryl hydrocarbon receptor (AHR) in 1976, the journal and the receptor have led parallel and often intersecting lives over the past 50 years. Tracing the history of the AHR can reveal how knowledge in the field has evolved to the present and highlight the important contributions made by discoveries reported in DMD. This may inspire additional DMD papers reporting future AHR landmark discoveries.

Non-alcoholic fatty liver disease (NAFLD) and mental illness: Mechanisms linking mood, metabolism and medicines

Non-alcoholic fatty liver disease (NAFLD) is the most common cause of chronic liver disease in the world and one of the leading indications for liver transplantation. It is one of the many manifestations of insulin resistance and metabolic syndrome as well as an independent risk factor for cardiovascular disease. There is growing evidence linking the incidence of NAFLD with psychiatric illnesses such as schizophrenia, bipolar disorder and depression mechanistically via genetic, metabolic, inflammatory and environmental factors including smoking and psychiatric medications. Indeed, patients prescribed antipsychotic medications, regardless of diagnosis, have higher incidence of NAFLD than population norms. The mechanistic pharmacology of antipsychotic-associated NAFLD is beginning to emerge. In this review, we aim to discuss the pathophysiology of NAFLD including its risk factors, insulin resistance and systemic inflammation as well as its intersection with psychiatric illnesses.

Chronotherapy: Circadian Rhythms and Their Influence in Cancer Therapy

Living organisms present rhythmic fluctuations every 24 h in their behavior and metabolism to anticipate changes in the environment. These fluctuations are controlled by a very complex molecular mechanism, the circadian clock, that regulates the expression of multiple genes to ensure the right functioning of the body. An individual's circadian system is altered during aging, and this is related to numerous age-associated pathologies and other alterations that could contribute to the development of cancer. Nowadays, there is an increasing interest in understanding how circadian rhythms could be used in the treatment of cancer. Chronotherapy aims to understand the impact that biological rhythms have on the response to a therapy to optimize its action, maximize health benefits and minimize possible adverse effects. Clinical trials so far have confirmed that optimal timing of treatment with chemo or immunotherapies could decrease drug toxicity and increase efficacy. Instead, chronoradiotherapy seems to minimize treatment-related symptoms rather than tumor progression or patient survival. In addition, potential therapeutic targets within the molecular clock have also been identified. Therefore, results of the application of chronotherapy in cancer therapy until now are challenging, feasible, and could be applied to clinical practice to improve cancer treatment without additional costs. However, different limitations and variables such as age, sex, or chronotypes, among others, should be overcome before chronotherapy can really be put into clinical practice.

Chronovaccination: Harnessing circadian rhythms to optimize immunisation strategies

Vaccination, as a public health measure, offers effective protection of populations against infectious diseases. Optimising vaccination efficacy, particularly for higher-risk individuals, like the elderly whose immunocompromised state can prevent the development of robust vaccine responses, is vital. It is now clear that 24-hour circadian rhythms, which govern virtually all aspects of physiology, can generate oscillations in immunological responses. Consequently, vaccine efficacy may depend critically on the time of day of administration(s), including for Covid-19, current vaccines, and any future diseases or pandemics. Published clinical vaccine trials exploring diurnal immune variations suggest this approach could represent a powerful adjunct strategy for optimising immunisation, but important questions remain to be addressed. This review explores the latest insights into diurnal immune variation and the outcomes of circadian timing of vaccination or 'chronovaccination'.

Recent advances in circadian-regulated pharmacokinetics and its implications for chronotherapy

Dependence of pharmacokinetics and drug effects (efficacy and toxicity) on dosing time has long been recognized. However, significant progress has only recently been made in our understanding of circadian rhythms and their regulation on drug pharmacokinetics, efficacy and toxicity. This review will cover the relevant literature and a series of publications from our work summarizing the effects of circadian rhythms on drug pharmacokinetics, and propose that the influence of circadian rhythms on pharmacokinetics are ultimately translated into therapeutic effects and side effects of drugs. Evidence suggests that daily rhythmicity in expression of drug-metabolizing enzymes and transporters necessary for drug ADME (absorption, distribution, metabolism and excretion) are key factors determining circadian pharmacokinetics. Newly discovered mechanisms for circadian control of the enzymes and transporters are covered. We also discuss how the rhythms of drug-processing proteins are translated into circadian pharmacokinetics and drug chronoefficacy/chronotoxicity, which has direct implications for chronotherapy. More importantly, we will present perspectives on the challenges that are still needed for a breakthrough in translational research. In addition, knowledge of the circadian influence on drug disposition has provided new possibilities for novel pharmacological strategies. Careful application of pharmacokinetics-based chronotherapy strategies can improve efficacy and reduce toxicity. Circadian rhythm-mediated metabolic and transport strategies can also be implemented to design drugs.

Influence of Circadian Rhythm on Drug Metabolism in 3D Hepatic Spheroids

Circadian rhythms are characterized as oscillations that fluctuate based on a 24h cycle and are responsible for regulation of physiological functions. While the internal clock synchronizes gene expression using external cues like light, a similar synchronization can be induced in vitro by incubating the cells with an increased percentage of serum followed by its rapid removal. Previous studies have suggested that synchronization of HepG2 cell line induced the rhythmic expression of drug metabolizing enzymes (DME) most specifically the cytochrome P450 enzymes. However, there is a lack of evidence demonstrating the influence of 3D microenvironment on the rhythmicity of these genes. To understand this interplay, gene expression of the circadian machinery and CYP450s were compared using the model human hepatocarcinoma cell line, HepG2. Upon serum shock synchronization, gene and protein expression of core clock regulators was assessed and rhythmic expression of these genes was demonstrated. Further insight into the interrelations between various gene pairs was obtained using statistical analysis. Using RNA sequencing, an in-depth understanding of the widespread effects of circadian regulation on genes involved in metabolic processes in the liver was obtained. This study aids in the better understanding of chronopharmacokinetic events in humans using physiologically relevant 3D culture systems. This article is protected by copyright. All rights reserved.

Disrupting Circadian Rhythm via the PER1-HK2 Axis Reverses Trastuzumab Resistance in Gastric Cancer

Trastuzumab is the only approved targeted drug for first-line treatment of HER2-positive advanced gastric cancer, but the high rate of primary resistance and rapid emergence of secondary resistance limit its clinical benefits. We found that trastuzumab-resistant (TR) gastric cancer cells exhibited high glycolytic activity, which was controlled by hexokinase 2 (HK2)-dependent glycolysis with a circadian pattern [higher at zeitgeber time (ZT) 6, lower at ZT18]. Mechanistically, HK2 circadian oscillation was regulated by a transcriptional complex composed of PPARγ and the core clock gene PER1. In vivo and in vitro experiments demonstrated that silencing PER1 disrupted the circadian rhythm of PER1-HK2 and reversed trastuzumab resistance. Moreover, metformin, which inhibits glycolysis and PER1, combined with trastuzumab at ZT6, significantly improved trastuzumab efficacy in gastric cancer. Collectively, these data introduce the circadian clock into trastuzumab therapy and propose a potentially effective chronotherapy strategy to reverse trastuzumab resistance in gastric cancer.

SIGNIFICANCE

In trastuzumab-resistant HER2-positive gastric cancer, glycolysis fluctuates with a circadian oscillation regulated by the BMAL1-CLOCK-PER1-HK2 axis, which can be disrupted with a metformin-based chronotherapy to overcome trastuzumab resistance.

The Influence of Circadian Rhythm on Cancer Cells Targeting and Transfection Efficiency of a Polycation-Drug/Gene Delivery Vector

The conception of novel anticancer delivery systems and the combination of chronobiology with nanotechnology may provide a powerful tool to optimize cancer therapy. In this work, polyethylenimine (PEI) has been used to complex p53 encoded plasmid DNA (pDNA), and the anticancer drug methotrexate (MTX) has also been loaded into the vectors. To investigate the influence of circadian clock on drug/gene delivery efficiency, HeLa, C33A and fibroblast cells have been transfected with developed PEI/pDNA/MTX delivery vectors at six different time points. Phenomena as the cellular uptake/internalization, drug/gene delivery and p53 protein production have been evaluated. The cell-associated MTX fluorescence have been monitored, and p53 protein levels quantified. In HeLa and C33A cancer cells, significant levels of MTX were found for T8 and T12. For these time points, a high amount of p53 protein was quantified. Confocal microscopy images showed successful HeLa cell’s uptake of PEI/pDNA/MTX particles, at T8. In comparison, poor levels of MTX and p53 protein were found in fibroblasts; nevertheless, results indicated rhythmicity. Data demonstrate the influence of circadian rhythm on both cancer-cells targeting ability and transfection performance of PEI/pDNA/MTX carriers and seemed to provide the optimum time for drug/gene delivery. This report adds a great contribution to the field of cancer chronobiology, highlighting the relationship between circadian rhythm and nanodelivery systems, and charting the path for further research on a, yet, poorly explored but promising topic.

Time-dependent regulation of hepatic Cytochrome P450 mRNA in male liver-specific PGC-1α knockout mice

The circadian rhythm has profound effect on the body, exerting effects on diverse events like sleep-wake patterns, eating behavior and hepatic detoxification. The cytochrome p450 s (Cyps) is the main group of enzymes responsible for detoxification. However, the underlying mechanisms behind circadian regulation of the Cyps are currently not fully clarified. Therefore, the aim of the present study was to investigate the requirement of hepatic peroxisome proliferator-activated receptor gamma coactivator-1α (PGC-1α) for the circadian regulation of the hepatic expression of Cyp1-4 using liver-specific PGC-1α knockout (LKO) mice and littermate controls. The circadian regulator genes Bmal1 and Clock displayed decreased mRNA content at zietgeber time (ZT) 12, compared to ZT-2 and the mRNA content of Cyp2a4 and Cyp2e1 was higher at ZT-12 than at ZT-2. Moreover, the increase in Cyp2e1 mRNA content was not observed in the PGC-1α LKO mice and hepatic PGC-1α deficiency tended to blunt the rhythmic expression of Clock and Bmal1. However, no circadian regulation was evident at the protein level for the investigated Cyps except for a change in Cyp2e1 protein content in the LKO mice. Of the measured transcription factors, only, the mRNA content of peroxisome proliferator-activated receptor α, showed rhythmic expression. To further analyze the difference between the control and LKO mice, principal component analyses were executed on the mRNA data. This demonstrated a clear separation of the experimental groups with respect to ZT and genotype. Our finding provides novel insight into the role of hepatic PGC-1α for basic and circadian expression of Cyps in mouse liver. This is important for our understanding of the molecular events behind circadian Cyp regulation and hence circadian regulation of hepatic detoxification capacity.

Pharmacokinetics-based Chronotherapy

Dosing time-dependency of pharmacokinetics (or chronopharmacokinetics) has been long recognized. Studies in recent years have revealed that diurnal rhythmicity in expression of drug-metabolizing enzymes and transporters (DMETs) are key factors determining chronopharmacokinetics. In this article, we briefly summarize current knowledge with respect to circadian mechanisms of DMETs and discuss how rhythmic DMETs are translated to drug chronoeffects. More importantly, we present our perspectives on pharmacokinetics-based chronotherapy.

Involvement of REV-ERBα dysregulation and ferroptosis in aristolochic acid I-induced renal injury

The molecular events underlying aristolochic acid (AA) nephropathy are poorly understood, and specific therapies for treatment of AA nephropathy are still lacking. Here we aimed to investigate a potential role of REV-ERBα and ferroptosis in renal injury induced by aristolochic acid I (AAI), a typical AA. The regulatory effects of REV-ERBα on AAI-induced renal injury were determined using kidney-specific Rev-erbα knockout mice. Ferroptosis was assessed based on measurements of iron, GSH, and GPX4. Targeted antagonism of REV-ERBα to alleviate AAI-induced renal injury and ferroptosis was assessed using the small molecule antagonist SR8278. mRNAs and proteins were quantified by qPCR and Western blotting, respectively. We first showed that REV-ERBα was upregulated and its target BMAL1 was downregulated in the kidney of mice with AAI nephropathy. Upregulation of REV-ERBα protein was confirmed in aristolactam I (ALI, a nephrotoxic metabolite of AAI)-treated mRTECs. We also observed enhanced ferroptosis (known to be regulated by REV-ERBα) in mice with AAI nephropathy and in ALI-treated mRTECs. Kidney-specific knockout of Rev-erbα reduced the sensitivity of mice to AAI-induced ferroptosis and renal injury. Furthermore, knockdown of Rev-erbα by siRNA or SR8278 (a REV-ERBα antagonist) treatment attenuated ALI-induced ferroptosis in mRTECs. Moreover, REV-ERBα antagonism by SR8278 alleviated ferroptosis and renal injury caused by AAI in mice. In conclusion, we identify REV-ERBα as a regulator of AAI-induced renal injury via promoting ferroptosis. Targeting REV-ERBα may represent a promising approach for management of AAI nephropathy.

Exploring the link between chronobiology and drug delivery: effects on cancer therapy

Circadian clock is an impressive timing system responsible for the control of several metabolic, physiological and behavioural processes. Nowadays, the connection between the circadian clock and cancer occurrence and development is consensual. Therefore, the inclusion of circadian timing into cancer therapy may potentially offer a more effective and less toxic approach. This way, chronotherapy has been shown to improve cancer treatment efficacy. Despite this relevant finding, its clinical application is poorly exploited. The conception of novel anticancer drug delivery systems and the combination of chronobiology with nanotechnology may provide a powerful tool to optimize cancer therapy, instigating the incorporation of the circadian timing into clinical practice towards a more personalized drug delivery. This review focuses on the recent advances in the field of cancer chronobiology, on the link between cancer and the disruption of circadian rhythms and on the promising targeted drug nanodelivery approaches aiming the clinical application of cancer chronotherapy.

Circadian Biology in Obstructive Sleep Apnea

Obstructive sleep apnea (OSA) is a complex process that can lead to the dysregulation of the molecular clock, as well as 24 h rhythms of sleep and wake, blood pressure, and other associated biological processes. Previous work has demonstrated crosstalk between the circadian clock and hypoxia-responsive pathways. However, even in the absence of OSA, disrupted clocks can exacerbate OSA-associated outcomes (e.g., cardiovascular or cognitive outcomes). As we expand our understanding of circadian biology in the setting of OSA, this information could play a significant role in the diagnosis and treatment of OSA. Here, we summarize the pre-existing knowledge of circadian biology in patients with OSA and examine the utility of circadian biomarkers as alternative clinical tools.

Circadian rhythms: influence on physiology, pharmacology, and therapeutic interventions

Circadian rhythms are ubiquitous phenomena that recur daily in a self-sustaining, entrainable, and oscillatory manner, and orchestrate a wide range of molecular, physiological, and behavioral processes. Circadian clocks are comprised of a hierarchical network of central and peripheral clocks that generate, sustain, and synchronize the circadian rhythms. The functioning of the peripheral clock is regulated by signals from autonomic innervation (from the central clock), endocrine networks, feeding, and other external cues. The critical role played by circadian rhythms in maintaining both systemic and tissue-level homeostasis is well established, and disruption of the rhythm has direct consequence for human health, disorders, and diseases. Circadian oscillations in both pharmacokinetics and pharmacodynamic processes are known to affect efficacy and toxicity of several therapeutic agents. A variety of modeling approaches ranging from empirical to more complex systems modeling approaches have been applied to characterize circadian biology and its influence on drug actions, optimize time of dosing, and identify opportunities for pharmacological modulation of the clock mechanisms and their downstream effects. In this review, we summarize current understanding of circadian rhythms and its influence on physiology, pharmacology, and therapeutic interventions, and discuss the role of chronopharmacometrics in gaining new insights into circadian rhythms and its applications in chronopharmacology.

Chronotoxicity of Semen Strychni is associated with circadian metabolism and transport in mice

OBJECTIVES

We aimed to determine the circadian responses of mice to Semen Strychni and to investigate the role of pharmacokinetics in generating chronotoxicity.

METHODS

Total extract of Semen Strychni was administered by oral gavage to wild-type (WT) and Bmal1-/- (a circadian clock-deficient model) mice at different circadian time points for toxicity (including survival) and pharmacokinetic characterization. Nephrotoxicity and neurotoxicity were evaluated by measuring plasma creatinine and creatine kinase BB (CK-BB), respectively. Drug metabolism and transport assays were performed using liver/intestine microsomes and everted gut sacs, respectively.

KEY FINDINGS

Semen Strychni nephrotoxicity and neurotoxicity as well as animal survival displayed significant circadian rhythms (the highest level of toxicity was observed at ZT18 and the lowest level at ZT2 to ZT6). According to pharmacokinetic experiments, herb dosing at ZT18 generated higher plasma concentrations (and systemic exposure) of strychnine and brucine (two toxic constituents) compared with ZT6 dosing. This was accompanied by reduced formation of both dihydroxystrychnine and strychnine glucuronide (two strychnine metabolites) at ZT18. Bmal1 ablation sensitized mice to Semen Strychni-induced toxicity (with increased levels of plasma creatinine and CK-BB) and abolished the time dependency of toxicity. Metabolism of Semen Strychni (strychnine and brucine) in the liver and intestine microsomes of WT mice was more extensive at ZT6 than at ZT18. These time differences in hepatic and intestinal metabolism were lost in Bmal1-/- mice. Additionally, the intestinal efflux transport of Semen Strychni (strychnine and brucine) was more extensive at ZT6 than ZT18 in WT mice. However, the time-varying transport difference was abolished in Bmal1-/- mice.

CONCLUSIONS

Circadian responses of mice to Semen Strychni are associated with time-varying efflux transport and metabolism regulated by the circadian clock (Bmal1). Our findings may have implications for optimizing phytotherapy with Semen Strychni via timed delivery.

Oscillating lncRNA Platr4 regulates NLRP3 inflammasome to ameliorate nonalcoholic steatohepatitis in mice

Background: Understanding the molecular events and mechanisms underlying development and progression of nonalcoholic steatohepatitis is essential in an attempt to formulating a specific treatment. Here, we uncover Platr4 as an oscillating and NF-κB driven lncRNA that is critical to the pathological conditions in experimental steatohepatitis Methods: RNA-sequencing of liver samples was used to identify differentially expressed lncRNAs. RNA levels were analyzed by qPCR and FISH assays. Proteins were detected by immunoblotting and ELISA. Luciferase reporter, ChIP-sequencing and ChIP assays were used to investigate transcriptional gene regulation. Protein interactions were evaluated by Co-IP experiments. The protein-RNA interactions were studied using FISH, RNA pull-down and RNA immunoprecipitation analyses Results: Cyclic expression of Platr4 is generated by the core clock component Rev-erbα via two RevRE elements (i.e., -1354/-1345 and -462/-453 bp). NF-κB transcriptionally drives Platr4 through direct binding to two κB sites (i.e., -1066/-1056 and -526/-516 bp), potentially accounting for up-regulation of Platr4 in experimental steatohepatitis. Intriguingly, Platr4 serves as a circadian repressor of Nlrp3 inflammasome pathway by inhibiting NF-κB-dependent transcription of the inflammasome components Nlrp3 and Asc. Loss of Platr4 down-regulates Nlrp3 inflammasome activity in the liver, blunts its diurnal rhythm, and sensitizes mice to experimental steatohepatitis, whereas overexpression of Platr4 ameliorates the pathological conditions in an Nlrp3-dependent manner. Mechanistically, Platr4 prevents binding of the NF-κB/Rxrα complex to the κB sites via a physical interaction, thereby inhibiting the transactivation of Nlrp3 and Asc by NF-κB. Conclusions:Platr4 functions to inactivate Nlrp3 inflammasome via intercepting NF-κB signaling. This lncRNA might be an attractive target that can be modulated to ameliorate the pathological conditions of steatohepatitis.

Circadian Clock Component Rev-erbα Regulates Diurnal Rhythm of UDP-Glucuronosyltransferase 1a9 and Drug Glucuronidation in Mice

UDP-glucuronosyltransferases (UGTs) are a family of phase II enzymes that play an important role in metabolism and elimination of numerous endo- and xenobiotics. Here, we aimed to characterize diurnal rhythm of Ugt1a9 in mouse liver and to determine the molecular mechanisms underlying the rhythmicity. Hepatic Ugt1a9 mRNA and protein displayed robust diurnal rhythms in wild-type mice with peak levels at zeitgeber time (ZT) 6. Rhythmicity in Ugt1a9 expression was confirmed using synchronized Hepa-1c1c7 cells. We observed time-varying glucuronidation (ZT6 > ZT18) of propofol, a specific Ugt1a9 substrate, consistent with the diurnal pattern of Ugt1a9 protein. Loss of Rev-erbα (a circadian clock component) downregulated the Ugt1a9 expression and blunted its rhythm in mouse liver. Accordingly, propofol glucuronidation was reduced and its dosing time dependency was lost in Rev-erbα -/- mice. Dec2 (a transcription factor) was screened to be the potential intermediate that mediated Rev-erbα regulation of Ugt1a9. We confirmed Rev-erbα as a negative regulator of Dec2 in mice and in Hepa-1c1c7 cells. Based on promoter analysis and luciferase reporter assays, it was found that Dec2 trans-repressed Ugt1a9 via direct binding to an E-box-like motif in the gene promoter. Additionally, regulation of Ugt1a9 by Rev-erbα was Dec2-dependent. In conclusion, Rev-erbα generates and regulates rhythmic Ugt1a9 through periodical inhibition of Dec2, a transcriptional repressor of Ugt1a9. Our study may have implications for understanding of circadian clock-controlled drug metabolism and of metabolism-based chronotherapeutics. SIGNIFICANCE STATEMENT: Hepatic Ugt1a9 displays diurnal rhythmicities in expression and glucuronidation activity in mice. It is uncovered that Rev-erbα generates and regulates rhythmic Ugt1a9 through periodical inhibition of Dec2, a transcriptional repressor of Ugt1a9. The findings may have implications for understanding of circadian clock-controlled drug metabolism and of metabolism-based chronotherapeutics.