The Circadian Clock Gene Bmal1 Controls Intestinal Exporter MRP2 and Drug Disposition

Herb-drug interactions: Quantitative analysis of levofloxacin absorption and transporter expression in the rat intestine following combined treatment with Persicaria capitata (Buch.-Ham. ex D. Don) H. Gross

Persicaria capitata (Buch.-Ham. ex D. Don) H. Gross, a traditional Chinese medicinal plant, is often used to treat various urologic disorders in China. P. capitata extracts (PCE) have been used in combination with levofloxacin (LVFX) to treat urinary tract infections (UTIs) for a long time. However, little is known about the absorption of LVFX and transporter expression in the intestine after combined treatment with PCE, restricting the development and utilization of PCE. In view of this, a UPLC-MS/MS method was established for the determination of LVFX in intestinal sac fluid samples and in situ intestinal circulation perfusate samples to explore the effect of PCE on the intestinal absorption characteristics of LVFX ex vivo and in vivo. To further evaluate the interaction between LVFX and PCE, western blotting, immunohistochemistry, and RT-qPCR were utilized to determine the expression levels of drug transporters (OATP1A2, P-gp, BCRP, and MRP2) involved in the intestinal absorption of LVFX after combined treatment with PCE. Using the everted intestinal sac model, the absorption rate constant (Ka) and cumulative drug absorption (Q) of LVFX in each intestinal segment were significantly lower in groups treated with PCE than in the control group. Ka at 2 h decreased most in the colon segment (from 0.088 to 0.016 µg/h·cm2), and Q at 2 h decreased most in the duodenum (from 213.29 to 33.92 µg). Using the intestinal circulation perfusion model, the Ka value and percentage absorption rate (A) of LVFX in the small intestine decreased significantly when PCE and LVFX were used in combination. These results showed that PCE had a strong inhibitory effect on the absorption of LVFX in the rat small intestine (ex vivo and in vivo intestinal segments). In addition, PCE increased the protein and mRNA expression levels of efflux transporters (P-gp, BCRP, and MRP2) and decreased the expression of the uptake transporter OATP1A2 significantly. The effects increased as the PCE concentration increased. These findings indicated that PCE changed the absorption characteristics of levofloxacin, possibly by affecting the expression of transporters in the small intestine. In addition to revealing a herb-drug interaction (HDI) between PCE and LVFX, these results provide a basis for further studies of their clinical efficacy and mechanism of action.

The role of the circadian timing system on drug metabolism and detoxification: an update

INTRODUCTION

The 24-hour variations in drug absorption, distribution, metabolism, and elimination, collectively known as pharmacokinetics, are fundamentally influenced by rhythmic physiological processes regulated by the molecular clock. Recent advances have elucidated the intricacies of the circadian timing system and the molecular interplay between biological clocks, enzymes and transporters in preclinical level.

AREA COVERED

Circadian rhythm of the drug metabolizing enzymes and carrier efflux functions possess a major role for drug metabolism and detoxification. The efflux and metabolism function of intestines and liver seems important. The investigations revealed that the ABC and SLC transporter families, along with cytochrome p-450 systems in the intestine, liver, and kidney, play a dominant role in the circadian detoxification of drugs. Additionally, the circadian control of efflux by the blood-brain barrier is also discussed.

EXPERT OPINION

The influence of the circadian timing system on drug pharmacokinetics significantly impacts the efficacy, adverse effects, and toxicity profiles of various drugs. Moreover, the emergence of sex-related circadian changes in the metabolism and detoxification processes has underscored the importance of considering gender-specific differences in drug tolerability and pharmacology. A better understanding of coupling between central clock and circadian metabolism/transport contributes to the development of more rational drug utilization and the implementation of chronotherapy applications.

Deciphering the diurnal rhythm regulating mechanism of flavin-containing monooxygenase 3 in mouse liver

Circadian genes play an important role in the field of drug metabolism. Flavin-containing monooxygenase 3 is a well-known phase I enzyme which participates in metabolism of many exogenous and endogenous substances, especially production of trimethylamine N-oxide. Here, we aimed to decipher diurnal rhythms of flavin-containing monooxygenase 3 expression and activity, and explore the regulation mechanism by clock genes. Our results showed that its mRNA and protein exhibited robust diurnal rhythms in mouse liver and cell lines. Consistently, significant alterations were observed for in vitro microsomal N-oxidation rates of procainamide, which kept in line with its protein expression at different time in wild-type and reverse erythroblastosis virus α knockout mice. Further, flavin-containing monooxygenase 3 was negatively regulated by E4 promoter-binding protein 4 in AML12 and Hepa1-6 cells, while it was positively influenced by reverse erythroblastosis virus α and brain and muscle ARNT-like protein-1. Moreover, luciferase reporter assays and electrophoretic mobility shift assays showed E4 promoter-binding protein 4 inhibited the transcription of flavin-containing monooxygenase 3 by binding to a D-box1 element (-1606/-1594 bp), while brain and muscle ARNT-like protein-1 positively activated the transcription via direct binding to three E-boxes (-863/-858 bp, -507/-498 bp, and -115/-104 bp) in this enzyme promoter. Taken together, this study would be helpful to reveal the mechanism of clock-controlled drug metabolism and facilitate the practice of chrono-therapeutics.

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.

The role of circadian clock in regulating cell functions: implications for diseases

The circadian clock system orchestrates daily behavioral and physiological rhythms, facilitating adaptation to environmental and internal oscillations. Disruptions in circadian rhythms have been linked to increased susceptibility to various diseases and can exacerbate existing conditions. This review delves into the intricate regulation of diurnal gene expression and cell function by circadian clocks across diverse tissues. . Specifically, we explore the rhythmicity of gene expressions, behaviors, and functions in both immune and non-immune cells, elucidating the regulatory effects and mechanisms imposed by circadian clocks. A detailed discussion is centered on elucidating the complex functions of circadian clocks in regulating key cellular signaling pathways. We further review the circadian regulation in diverse diseases, with a focus on inflammatory diseases, cancers, and systemic diseases. By highlighting the intimate interplay between circadian clocks and diseases, especially through clock-controlled cell function, this review contributes to the development of novel disease intervention strategies. This enhanced understanding holds significant promise for the design of targeted therapies that can exploit the circadian regulation mechanisms for improved treatment efficacy.

Time-Dependent Differences in Vancomycin Sensitivity of Macrophages Underlie Vancomycin-Induced Acute Kidney Injury

Although vancomycin (VCM)-frequently used to treat drug-resistant bacterial infections-often induces acute kidney injury (AKI), discontinuation of the drug is the only effective treatment; therefore, analysis of effective avoidance methods is urgently needed. Here, we report the differences in the induction of AKI by VCM in 1/2-nephrectomized mice depending on the time of administration. Despite the lack of difference in the accumulation of VCM in the kidney between the light (ZT2) and dark (ZT14) phases, the expression of AKI markers due to VCM was observed only in the ZT2 treatment. Genomic analysis of the kidney suggested that the time of administration was involved in VCM-induced changes in monocyte and macrophage activity, and VCM had time-dependent effects on renal macrophage abundance, ATP activity, and interleukin (IL)-1β expression. Furthermore, the depletion of macrophages with clodronate abolished the induction of IL-1β and AKI marker expression by VCM administration at ZT2. This study provides evidence of the need for time-dependent pharmacodynamic considerations in the prevention of VCM-induced AKI as well as the potential for macrophage-targeted AKI therapy. SIGNIFICANCE STATEMENT: There is a time of administration at which vancomycin (VCM)-induced renal injury is more and less likely to occur, and macrophages are involved in this difference. Therefore, there is a need for time-dependent pharmacodynamic considerations in the prevention of VCM-induced acute kidney injury as well as the potential for macrophage-targeted acute kidney injury therapy.

Role of circadian clock in the chronoefficacy and chronotoxicity of clopidogrel

BACKGROUND AND PURPOSE

The role of circadian locomotor output cycles kaput (CLOCK) in regulating drug chronoefficacy and chronotoxicity remains elusive. Here, we aimed to uncover the impact of CLOCK and dosing time on clopidogrel efficacy and toxicity.

EXPERIMENTAL APPROACH

The antiplatelet effect, toxicity and pharmacokinetics experiments were conducted with Clock-/- mice and wild-type mice, after gavage administration of clopidogrel at different circadian time points. The expression levels of drug-metabolizing enzymes were determined by quantitative polymerase chain reaction (qPCR) and western blotting. Transcriptional gene regulation was investigated using luciferase reporter and chromatin immunoprecipitation assays.

KEY RESULTS

The antiplatelet effect and toxicity of clopidogrel in wild-type mice showed a dosing time-dependent variation. Clock ablation reduced the antiplatelet effect of clopidogrel, but increased clopidogrel-induced hepatotoxicity, with attenuated rhythms of clopidogrel active metabolite (Clop-AM) and clopidogrel, respectively. We found that Clock regulated the diurnal variation of Clop-AM formation by modulating the rhythmic expression of CYP1A2 and CYP3A1, and altered clopidogrel chronopharmacokinetics by regulation of CES1D expression. Mechanistic studies revealed that CLOCK activated Cyp1a2 and Ces1d transcription by directly binding to the enhancer box (E-box) elements in their promoters, and promoted Cyp3a11 transcription through enhancing the transactivation activity of albumin D-site-binding protein (DBP) and thyrotroph embryonic factor (TEF).

CONCLUSIONS AND IMPLICATIONS

CLOCK regulates the diurnal rhythmicity in clopidogrel efficacy and toxicity through regulation of CYP1A2, CYP3A11 and CES1D expression. These findings may contribute to optimizing dosing schedules for clopidogrel and may deepen understanding of the circadian clock and chronopharmacology.

Pharmacokinetics and absorption mechanism of tandospirone citrate

Tandospirone citrate (TDS) is commonly used for the treatment of patients with generalized anxiety disorder in clinical practice, and several studies are developing new indications for TDS. However, the in vivo processes and absorption properties of TDS have not been systematically investigated. In this work, we conducted a comprehensive investigation using in vivo, in vitro, and ex vivo approaches, involving animal and cellular models, to examine the pharmacokinetic properties and absorption mechanisms of TDS. The results of in vivo studies revealed that the half-life (t 1/2) of TDS was 1.380 ± 0.46 h and 1.224 ± 0.39 h following intragastric (i.g.) and intravenous (i.v.) administration of 20 mg/kg TDS, respectively. This indicates that TDS is rapidly eliminated in rats. The area under the curve (AUC) of TDS after i.g. and i.v. administration was 114.7 ± 40 ng/mL*h and 48,400 ± 19,110 ng/mL*h, respectively, and the absolute bioavailability of TDS was found to be low (0.24%). Furthermore, TDS was extensively metabolized in rats, with the AUC of the major active metabolite [1-[2-pyrimidyl]-piperazine] being approximately 16.38-fold higher than that of TDS after i.g. administration. The results from the in vitro Caco-2 cell model and ex vivo everted gut sac experiment demonstrated that TDS exhibited good permeability, and its transport was influenced by concentration, temperature, and pH. Passive diffusion was identified as the main absorption mechanism. In conclusion, TDS is classified as a Biopharmaceutics Classification System (BCS) class I drug, characterized by high solubility and permeability. The low absolute bioavailability of TDS may be attributed to its rapid metabolism. The pharmacokinetic data and absorption characteristics obtained in this study provide fundamental information for the further development and utilization of TDS.

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.

Core clock gene BMAL1 and RNA-binding protein MEX3A collaboratively regulate Lgr5 expression in intestinal crypt cells

The intestinal epithelium is highly regenerative. Rapidly proliferating LGR5+ crypt base columnar (CBC) cells are responsible for epithelial turnover needed to maintain intestinal homeostasis. Upon tissue damage, loss of LGR5+ CBCs can be compensated by activation of quiescent +4 intestinal stem cells (ISCs) or early progenitor cells to restore intestinal regeneration. LGR5+ CBC self-renewal and ISC conversion to LGR5+ cells are regulated by external signals originating from the ISC niche. In contrast, little is known about intrinsic regulatory mechanisms critical for maintenance of LGR5+ CBC homeostasis. We found that LGR5 expression in intestinal crypt cells is controlled by the circadian core clock gene BMAL1 and the BMAL1-regulated RNA-binding protein MEX3A. BMAL1 directly activated transcription of Mex3a. MEX3A in turn bound to and stabilized Lgr5 mRNA. Bmal1 depletion reduced Mex3a and Lgr5 expression and led to increased ferroptosis, which consequently decreased LGR5+ CBC numbers and increased the number of crypt cells expressing +4 ISC marker BMI1. Together, these findings reveal a BMAL1-centered intrinsic regulatory pathway that maintains LGR5 expression in the crypt cells and suggest a potential mechanism contributing to ISC homeostasis.

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.

A Potential Effect of Circadian Rhythm in the Delivery/Therapeutic Performance of Paclitaxel-Dendrimer Nanosystems

The circadian clock controls behavior and physiology. Presently, there is clear evidence of a connection between this timing system and cancer development/progression. Moreover, circadian rhythm consideration in the therapeutic action of anticancer drugs can enhance the effectiveness of cancer therapy. Nanosized drug delivery systems (DDS) have been demonstrated to be suitable engineered platforms for drug targeted/sustained release. The investigation of the chronobiology-nanotechnology relationship, i.e., timing DDS performance according to a patient's circadian rhythm, may greatly improve cancer clinical outcomes. In the present work, we synthesized nanosystems based on an octa-arginine (R8)-modified poly(amidoamine) dendrimer conjugated with the anticancer drug paclitaxel (PTX), G4-PTX-R8, and its physicochemical properties were revealed to be appropriate for in vitro delivery. The influence of the circadian rhythm on its cellular internalization efficiency and potential therapeutic effect on human cervical cancer cells (HeLa) was studied. Cell-internalized PTX and caspase activity, as a measure of induced apoptosis, were monitored for six time points. Higher levels of PTX and caspase-3/9 were detected at T8, suggesting that the internalization of G4-PTX-R8 into HeLa cells and apoptosis are time-specific/-regulated phenomena. For a deeper understanding, the clock protein Bmal1-the main regulator of rhythmic activity, was silenced by Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR) technology. Bmal1 silencing was revealed to have an impact on both PTX release and caspase activity, evidencing a potential role for circadian rhythm on drug delivery/therapeutic effect mediated by G4-PTX-R8.

An integrative mathematical model for timing treatment toxicity and Zeitgeber impact in colorectal cancer cells

Increasing evidence points to a role of the circadian clock in the regulation of cancer hallmarks with a strong impact on the understanding and treatment of this disease. Anti-cancer treatment can be personalized considering treatment timing. Here we present a new mathematical model based on data from three colorectal cancer cell lines and core-clock knock-outs, which couples the circadian and drug metabolism network, and that allows to determine toxicity profiles for a given drug and cell type. Moreover, this model integrates external Zeitgebers and thus may be used to fine-tune toxicity by using external factors, such as light, and therefore, to a certain extent, help fitting the endogenous rhythms of the patients to a defined clinic routine facilitating the implementation of time-dependent treatment in clinical practice.

Anti-colon cancer effects of Spirulina polysaccharide and its mechanism based on 3D models

Spirulina polysaccharides (PSP) possess significant biological properties. However, it is still a lack of investigation on the anti-colorectal cancer effect and mechanism. In this study, PSP showed significant effects on LoVo cell spheroids with an IC₅₀ value of 0.1943 mg/mL. The analysis of transcriptomics and metabolomics indicated the impact of PSP on LoVo spheroid cells through involvement in the two pathways of "glycine, serine, and threonine metabolism" and "ABC transporters". And, the q-PCR data further verified the pointed mechanism of PSP on colon cancer (CC) by regulating the expression levels of relevant genes in the synthesis pathways of serine and glycine in tumor cells. Furthermore, the anti-colon cancer effects of PSP were verified via other human colon cancer cell lines HCT116 and HT29 spheroids (IC₅₀ = 0.0646 mg/mL and 0.2213 mg/mL, respectively), and three patient-derived organoids (PDOs) with IC₅₀ values ranging from 3.807 to 7.788 mg/mL. In addition, this study found that a mild concentration of PSP cannot enhance the anti-tumor effect of 5-Fu. And a significant inhibition was found of PSP in 5-Fu resistance organoids. These results illustrated that PSP could be a treatment or supplement for 5-Fu resistant colorectal cancer (CRC).

BMAL1 promotes colorectal cancer cell migration and invasion through ERK- and JNK-dependent c-Myc expression

BACKGROUND

Cancer metastasis is still a life threat to patients with colorectal cancer (CRC). Brain and muscle ARNT-like protein 1 (BMAL1) is an important biological proteins that can regulate the behavior of cancer cells and their response to chemotherapy. However, the role of BMAL1 in the tumorigenic phenotype of CRC remains unclear. Here, we aim to investigate the functional role and mechanisms of BMAL1 in CRC.

METHODS

The mRNA expression of BMAL1 was studied using the Cancer Genome Atlas (TCGA) databases. The protein level in clinical tissues was confirmed by immunohistochemistry (IHC). The effects of BMAL1 on the epithelial-to-mesenchymal transition (EMT) and proliferation of CRC cell lines (including BMAL1 overexpressed or silencing cells) were studied by Transwell, wound healing, CCK-8 and colony formation experiments. A series of experiments were conducted to demonstrate the mechanisms of BMAL1 regulating EMT and cancer proliferation in vitro and in vivo.

RESULTS

We found that BMAL1 expression was closely related to the poor prognosis of CRC. BMAL1 overexpression promoted cell proliferation and migration. Mechanistically, we found that BMAL1 may activate the epithelial-to-mesenchymal transition (EMT) pathway and induce the β-catenin release further promotes the expression of oncogene c-Myc and the migration of colorectal cells by activating MAPK pathway. However, BMAL1 silencing achieved the opposite effect. In addition, blocking MAPK-signaling pathway with specific inhibitors of ERK1/2 and JNK can also downregulate the expressions of c-Myc in vitro. Taken together, these results suggested that the BMAL1/ c-Myc-signaling pathway may regulate the metastasis of CRC through the JNK/ERK1/2 MAPK-dependent pathway.

CONCLUSIONS

Our study showed that BMAL1 promotes CRC metastasis through MAPK-c-Myc pathway. These results deepen our understanding of the relationship between BMAL1 and tumorigenic phenotypes, which may become a promising therapeutic target for BMAL1 overexpressing CRC.

Redox Biology of Melatonin: Discriminating Between Circadian and Noncircadian Functions

Melatonin has not only to be seen as a regulator of circadian clocks. In addition to its chronobiotic functions, it displays other actions, especially in cell protection. This includes antioxidant, anti-inflammatory, and mitochondria-protecting effects. Although protection is also modulated by the circadian system, the respective actions of melatonin can be distinguished and differ with regard to dose requirements in therapeutic settings. It is the aim of this article to outline these differences in terms of function, signaling, and dosage. Focus has been placed on both the nexus and the dissecting properties between circadian and noncircadian mechanisms. This has to consider details beyond the classic view of melatonin's role, such as widespread synthesis in extrapineal tissues, formation in mitochondria, effects on the mitochondrial permeability transition pore, and secondary signaling, for example, via upregulation of sirtuins and by regulating noncoding RNAs, especially microRNAs. The relevance of these findings, the differences and connections between circadian and noncircadian functions of melatonin shed light on the regulation of inflammation, including macrophage/microglia polarization, damage-associated molecular patterns, avoidance of cytokine storms, and mitochondrial functions, with numerous consequences to antioxidative protection, that is, aspects of high actuality with regard to deadly viral and bacterial diseases. Antioxid. Redox Signal. 37, 704-725.

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.

Deciphering the chemical constituents of Shengjiang Xiexin decoction by ultra-high-performance liquid chromatography-quadrupole/orbitrap high-resolution mass spectrometry and the impact of 20 characteristic components on multidrug resistance-associated protein 2 in the vesicular transport assay

Shengjiang Xiexin decoction, a traditional Chinese medical formula, has been utilized to alleviate the delayed-onset diarrhea induced by irinotecan. However, the chemical constituents of this formula and the activities of its constituents remain unclear. In this study, an ultra-high-performance liquid chromatography-quadrupole/orbitrap high-resolution mass spectrometry was employed to comprehensively analyze the chemical constituents of Shengjiang Xiexin decoction. A total of 270 components including flavonoids, coumarins, triterpenoids, alkaloids, diarylheptanoids and others were identified or characterized. The multidrug resistance-associated protein 2 is an efflux transporter responsible for regulating drug absorption. A total of 20 characteristic components from the formula were selected to evaluate their effects on the function of multidrug resistance-associated protein 2 using the vesicular transport assay. Glycyrrhizic acid and glycyrrhetinic acid were identified as potential multidrug resistance-associated protein 2 inhibitors, while 9 flavonoid aglycones increased the uptake of the substrate [³ H]-estradiol 17-β-glucuronide in the vesicles. This was the first systematical investigation on the chemical constituents from Shengjiang Xiexin decoction and the effect of its characteristic components on the transporter. The results offered a basis for further exploring the detoxification mechanisms of this formula and its interactions with other drugs. This article is protected by copyright. All rights reserved.

Time of day as a critical variable in biology

BACKGROUND

Circadian rhythms are important for all aspects of biology; virtually every aspect of biological function varies according to time of day. Although this is well known, variation across the day is also often ignored in the design and reporting of research. For this review, we analyzed the top 50 cited papers across 10 major domains of the biological sciences in the calendar year 2015. We repeated this analysis for the year 2019, hypothesizing that the awarding of a Nobel Prize in 2017 for achievements in the field of circadian biology would highlight the importance of circadian rhythms for scientists across many disciplines, and improve time-of-day reporting.

RESULTS

Our analyses of these 1000 empirical papers, however, revealed that most failed to include sufficient temporal details when describing experimental methods and that few systematic differences in time-of-day reporting existed between 2015 and 2019. Overall, only 6.1% of reports included time-of-day information about experimental measures and manipulations sufficient to permit replication.

CONCLUSIONS

Circadian rhythms are a defining feature of biological systems, and knowing when in the circadian day these systems are evaluated is fundamentally important information. Failing to account for time of day hampers reproducibility across laboratories, complicates interpretation of results, and reduces the value of data based predominantly on nocturnal animals when extrapolating to diurnal humans.

Strategies and Mechanism in Reversing Intestinal Drug Efflux in Oral Drug Delivery

Efflux transporters distributed at the apical side of human intestinal epithelial cells actively transport drugs from the enterocytes to the intestinal lumen, which could lead to extremely poor absorption of drugs by oral administration. Typical intestinal efflux transporters involved in oral drug absorption process mainly include P-glycoprotein (P-gp), multidrug resistance proteins (MRPs) and breast cancer resistance protein (BCRP). Drug efflux is one of the most important factors resulting in poor absorption of oral drugs. Caco-2 monolayer and everted gut sac are sued to accurately measure drug efflux in vitro. To reverse intestinal drug efflux and improve absorption of oral drugs, a great deal of functional amphiphilic excipients and inhibitors with the function of suppressing efflux transporters activity are generalized in this review. In addition, different strategies of reducing intestinal drugs efflux such as silencing transporters and the application of excipients and inhibitors are introduced. Ultimately, various nano-formulations of improving oral drug absorption by inhibiting intestinal drug efflux are discussed. In conclusion, this review has significant reference for overcoming intestinal drug efflux and improving oral drug absorption.

Diurnal Interplay between Epithelium Physiology and Gut Microbiota as a Metronome for Orchestrating Immune and Metabolic Homeostasis

The behavior and physiology of most organisms are temporally coordinated and aligned with geophysical time by a complex interplay between the master and peripheral clocks. Disruption of such rhythmic physiological activities that are hierarchically organized has been linked to a greater risk of developing diseases ranging from cancer to metabolic syndrome. Herein, we summarize the molecular clockwork that is employed by intestinal epithelial cells to anticipate environmental changes such as rhythmic food intake and potentially dangerous environmental stress. We also discuss recent discoveries contributing to our understanding of how a proper rhythm of intestinal stem cells may achieve coherence for the maintenance of tissue integrity. Emerging evidence indicates that the circadian oscillations in the composition of the microbiota may operate as an important metronome for the proper preservation of intestinal physiology and more. Furthermore, in this review, we outline how epigenetic clocks that are based on DNA methylation levels may extensively rewire the clock-controlled functions of the intestinal epithelium that are believed to become arrhythmic during aging.

Peroxisome Proliferator–Activated Receptor-α: A Pivotal Regulator of the Gastrointestinal Tract

Peroxisome proliferator–activated receptor (PPAR)-α is a ligand-activated transcription factor distributed in various tissues and cells. It regulates lipid metabolism and plays vital roles in the pathology of the cardiovascular system. However, its roles in the gastrointestinal tract (GIT) are relatively less known. In this review, after summarizing the expression profile of PPAR-α in the GIT, we analyzed its functions in the GIT, including physiological control of the lipid metabolism and pathologic mediation in the progress of inflammation. The mechanism of this regulation could be achieved via interactions with gut microbes and further impact the maintenance of body circadian rhythms and the secretion of nitric oxide. These are also targets of PPAR-α and are well-described in this review. In addition, we also highlighted the potential use of PPAR-α in treating GIT diseases and the inadequacy of clinical trials in this field.

E4BP4 regulates hepatic SLC2A9 and uric acid disposition in mice

SLC2A9 is a voltage-driven transporter that mediates cellular uptake and efflux of various substrates such as uric acid. Here, we investigated the role of the transcription factor E4BP4 in regulating hepatic SLC2A9 in mice. Effects of E4BP4 on hepatic SLC2A9 and other transporters were examined using E4bp4 knockout (E4bp4 ^-/-) mice. Transporting activity of SLC2A9 was assessed using uric acid as a prototypical substrate. We found that three SLC genes (i.e., Slc2a9, Slc17a1, and Slc22a7) were up-regulated in the liver in E4bp4 ^-/- mice with Slc2a9 altered the most. E4bp4 ablation in mice blunted the diurnal rhythm in hepatic SLC2A9, in addition to increasing its expression. Furthermore, E4bp4 ^-/- mice showed increased hepatic uric acid but reduced uric acid in the plasma and urine. Consistently, allantoin, a metabolite of uric acid generated in the liver, was increased in the liver of E4bp4 ^-/- mice. E4bp4 ablation also protected mice from potassium oxonate-induced hyperuricemia. Moreover, negative effects of E4BP4 on SLC2A9 were validated in Hepa-1c1c7 and in primary mouse hepatocytes. In addition, according to luciferase reporter and ChIP assays, we found that E4BP4 repressed Slc2a9 transcription and expression through direct binding to a D-box element (-531 bp to -524 bp) on the P2 promoter. In conclusion, E4BP4 was identified as a novel regulator of SLC2A9 and uric acid homeostasis, which might facilitate new therapies for reducing uric acid in various conditions related to hyperuricemia. Significance Statement Our findings identify E4BP4 as a novel regulator of SLC2A9 and uric acid homeostasis, which might facilitate new therapies for reducing uric acid in various conditions related to hyperuricemia.

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Oleandrin: A Systematic Review of its Natural Sources, Structural Properties, Detection Methods, Pharmacokinetics and Toxicology

Oleandrin is a highly lipid-soluble cardiac glycoside isolated from the plant Nerium oleander (Apocynaceae) and is used as a traditional herbal medicine due to its excellent pharmacological properties. It is widely applied for various disease treatments, such as congestive heart failure. Recently, oleandrin has attracted widespread attention due to its extensive anti-cancer and novel anti-viral effects. However, oleandrin has a narrow therapeutic window and exhibits various toxicities, especially typical cardiotoxicity, which is often fatal. This severe toxicity and low polarity have significantly hindered its application in the clinic. This review describes natural sources, structural properties, and detection methods of oleandrin. Based on reported poisoning cases and sporadic animal experiments, the pharmacokinetic characteristics of oleandrin are summarized, so as to infer some possible phenomena, such as enterohepatic circulation. Moreover, the relevant factors affecting the pharmacokinetics of oleandrin are analyzed, and some research approaches that may ameliorate the pharmacokinetic behavior of oleandrin are proposed. With the toxicology of oleandrin being thoroughly reviewed, the development of safe clinical applications of oleandrin may be possible given potential research strategies to decrease toxicity.

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.

Cellular and molecular pathways underlying the nephrotoxicity of gadolinium

Mounting evidence on the short- and long-term adverse effects associated with gadolinium [Gd (III)]-based contrast agents used in magnetic resonance imaging have emerged in the past three decades. Safety issues arise from the release of Gd (III) from chelates and its deposition in tissues, which is exacerbated in patients with renal disease, since the kidney is the major excretion organ of most of these agents. This study aimed at unveiling the cellular and molecular mechanisms of nephrotoxicity of Gd (III), using an in vitro model of human proximal tubular cells (HK-2 cell line). Cell viability declined in a concentration- and time-dependent manner after exposure to GdCl3·6H2O. The estimated inhibitory concentrations (ICs) eliciting 1 to 50% of cell death, after 24 h of exposure, ranged from 3.4 to 340.5 µM. At toxic concentrations, exposure to Gd (III) led to disruption of the oxidative status, mitochondrial dysfunction, cell death by apoptosis, switching to necrosis at higher levels, and autophagic activation. Disturbance of the lipid metabolism was already observed at low-toxicity ICs, with accumulation of lipid droplets, and upregulation of genes related to both lipogenesis and lipolysis. Gd (III)-exposure, even at the subtoxic IC01, increased the expression of modulators of various signaling pathways involved in the development and progression of renal disease, including inflammation, hypoxia and fibrosis. Our results give new insights into the mechanisms underlying the nephrotoxic potential of Gd (III) and highlight the need to further clarify the risks versus benefits of the Gd (III)-based contrast agents currently in use.

Night-shift work, breast cancer incidence, and all-cause mortality: an updated meta-analysis of prospective cohort studies

OBJECTIVES

Night-shift work exposure is proposed to link to a wide range of health issues, especially cancer incidence, cancer-specific death, and all-cause death. However, the epidemiological associations among night-shift work exposure, breast cancer, breast cancer-specific death, and all-cause mortality remain inconclusive.

METHODS

We performed an updated systematic review and meta-analysis to confirm potential associations among night-shift work exposure, breast cancer, and all-cause mortality.

RESULTS

A total of 31 prospective cohort studies, involving 9.3 million participants, 31,244 incident breast cancer cases, 12,728 cancer-related deaths, 7882 cardiovascular deaths, and 30,807 all-cause mortalities were included. Overall, the summary RR of incident breast cancer in females for an increase of night-shift work was 1.029 (95% CI 1.003-1.055). Compared with standard day workers, night-shift workers had a statistically significantly increased RR (1.086, 95% CI 1.032-1.142) for breast cancer incidence in the subgroup of > 10 years exposure. Furthermore, a positive association was revealed in subgroup studies of rotating night-shift work (RR = 1.053, 95% CI 1.018-1.090). A significant increased risk of cardiovascular mortality was demonstrated in the night-shift work group (RR = 1.031; 95% CI 1.006-1.057).

CONCLUSION

Our systematic review and meta-analysis provided convincing evidence supporting positive associations among night-shift work exposure, breast cancer incidence, and cardiovascular mortality. Taken together, night-shift work exposure significantly increased the risk of breast cancer morbidity by 2.9% for total, 8.6% for the subgroup of more than 10 years night-shift work, and 5.3% for rotating night-shift work. In addition, night-shift work increased the risk of cardiovascular mortality by 3.1%.

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.

Deficiency of intestinal Bmal1 prevents obesity induced by high-fat feeding

The role of intestine clock in energy homeostasis remains elusive. Here we show that mice with Bmal1 specifically deleted in the intestine (Bmal1iKO mice) have a normal phenotype on a chow diet. However, on a high-fat diet (HFD), Bmal1iKO mice are protected against development of obesity and related abnormalities such as hyperlipidemia and fatty livers. These metabolic phenotypes are attributed to impaired lipid resynthesis in the intestine and reduced fat secretion. Consistently, wild-type mice fed a HFD during nighttime (with a lower BMAL1 expression) show alleviated obesity compared to mice fed ad libitum. Mechanistic studies uncover that BMAL1 transactivates the Dgat2 gene (encoding the triacylglycerol synthesis enzyme DGAT2) via direct binding to an E-box in the promoter, thereby promoting dietary fat absorption. Supporting these findings, intestinal deficiency of Rev-erbα, a known BMAL1 repressor, enhances dietary fat absorption and exacerbates HFD-induced obesity and comorbidities. Moreover, small-molecule targeting of REV-ERBα/BMAL1 by SR9009 ameliorates HFD-induced obesity in mice. Altogether, intestine clock functions as an accelerator in dietary fat absorption and targeting intestinal BMAL1 may be a promising approach for management of metabolic diseases induced by excess fat intake.

Chronoeffects of the Herbal Medicines Puerariae radix and Coptidis rhizoma in Mice: A Potential Role of REV-ERBα

Identifying drugs with dosing time-dependent effects (chronoeffects) and understanding the underlying mechanisms would help to improve drug treatment outcome. Here, we aimed to determine chronoeffects of the herbal medicines Puerariae radix (PR) and Coptidis rhizoma (CR), and investigate a potential role of REV-ERBα as a drug target in generating chronoeffects. The pharmacological effect of PR on hyperhomocysteinemia in mice was evaluated by measuring total homocysteine, triglyceride levels and lipid accumulation. PR dosed at ZT10 generated a stronger effect on hyperhomocysteinemia than drug dosed at ZT2. Furthermore, PR increased the expression levels of REV-ERBα target genes Bhmt, Cbs and Cth (encoding three key enzymes responsible for homocysteine catabolism), thereby alleviating hyperhomocysteinemia in mice. Moreover, CR attenuated chronic colitis in mice in a dosing time-dependent manner based on measurements of disease activity index, colon length, malondialdehyde/myeloperoxidase activities and IL-1β/IL-6 levels. ZT10 dosing generated a stronger anti-colitis effect as compared to ZT2 dosing. This was accompanied by lower production of colonic inflammatory cytokines (i.e., Nlrp3, IL-1β, IL-6, Tnf-α and Ccl2, REV-ERBα target genes) in colitis mice dosed at ZT10. The diurnal patterns of PR and CR effects were respectively consistent with those of puerarin (a main active constituent of PR, a REV-ERBα antagonist) and berberine (a main active constituent of CR, a REV-ERBα agonist). In addition, loss of Rev-erbα in mice abolished the dosing time-dependency in PR and CR effects. In conclusion, the therapeutic effects of PR and CR depend on dosing time in mice, which are probably attributed to diurnal expression of REV-ERBα as the drug target. Our findings have implications for improving therapeutic outcomes of herbal medicines with a chronotherapeutic approach.

Pharmacokinetics-Based Chronoefficacy of Semen Strychni and Tripterygium Glycoside Tablet Against Rheumatoid Arthritis

Rheumatoid arthritis is a systemic autoimmune disease characterized by synovial inflammation and bone destruction. Identifying drugs with time-varying efficacy and toxicity, and elucidating the mechanisms would help to improve treatment efficacy and reduce adverse effects. Here, we aimed to determine the chronoefficacy of semen strychni (SS) and tripterygium glycoside tablet (TGT) against rheumatoid arthritis in mice, and to investigate a potential role of circadian pharmacokinetics in generating chronoefficacy. SS extract and TGT suspension were prepared with ultrasonication. Effects of SS and TGT on collagen-induced arthritis (CIA) were evaluated by measuring TNF-α and IL-6 levels. SS dosed at ZT18 was more effective in protecting against CIA than drug dosed at ZT6 (i.e., lower levels of key inflammatory factors at ZT18 than at ZT6). This was accompanied by higher systemic exposure levels of strychnine and brucine (two main putative active ingredients of SS) in ZT18-treated than in ZT6-treated CIA mice. TGT dosing at ZT2 showed a better efficacy against CIA as compared to herb doing at ZT14. Consistently, ZT2 dosing generated a higher exposure of triptolide (a main putative active ingredient of TGT) as compared to ZT14 dosing in CIA mice. Moreover, strychnine, brucine, and triptolide significantly inhibited the proliferation of fibroblast-like synoviocytes, and reduced the production of TNF-α and IL-6 and the mRNAs of TNF-α, IL-6, COX-2, and iNOS, suggesting that they possessed an anti-arthritis activity. In conclusion, SS and TGT display chronoefficacy against rheumatoid arthritis in mice, that is attributed to circadian pharmacokinetics of main active ingredients. Our findings have implications for improving treatment outcomes of SS and TGT via timed delivery.

The circadian clock gene PER2 enhances chemotherapeutic efficacy in nasopharyngeal carcinoma when combined with a targeted nanosystem

Treatment failure occurs in more than 40% of advanced nasopharyngeal carcinoma (NPC) patients including local recurrence and distant metastasis due to chemoradioresistance. Circadian clock genes were identified as regulating cancer progression and chemoradiosensitivity in a time-dependent manner. A novel nanosystem can ensure the accumulation and controllable release of chemotherapeutic agents at the tumour site at a set time. In this study, we investigated the expression of circadian clock genes and identified that period circadian regulator 2 (PER2) as a tumour suppressor plays a key role in NPC progression. A label-free proteomic approach showed that PER2 overexpression can inhibit the ERK/MAPK pathway. The chemotherapeutic effect of PER2 overexpression was assessed in NPC together with the nanosystem comprising folic acid (FA), upconverting nanoparticles covalently coupled with Rose Bengal (UCNPs-RB), 10-hydroxycamptothecin (HCPT) and lipid-perfluorohexane (PFH) (FURH-PFH-NPs). PER2 overexpression combined with the targeted and controlled release of nanoagents elevated chemotherapeutic efficacy in NPC, which has potential application value for the chronotherapy of tumours.

Translating around the clock: Multi-level regulation of post-transcriptional processes by the circadian clock

The endogenous circadian clock functions to maintain optimal physiological health through the tissue specific coordination of gene expression and synchronization between tissues of metabolic processes throughout the 24 hour day. Individuals face numerous challenges to circadian function on a daily basis resulting in significant incidences of circadian disorders in the United States and worldwide. Dysfunction of the circadian clock has been implicated in numerous diseases including cancer, diabetes, obesity, cardiovascular and hepatic abnormalities, mood disorders and neurodegenerative diseases. The circadian clock regulates molecular, metabolic and physiological processes through rhythmic gene expression via transcriptional and post-transcriptional processes. Mounting evidence indicates that post-transcriptional regulation by the circadian clock plays a crucial role in maintaining tissue specific biological rhythms. Circadian regulation affecting RNA stability and localization through RNA processing, mRNA degradation, and RNA availability for translation can result in rhythmic protein synthesis, even when the mRNA transcripts themselves do not exhibit rhythms in abundance. The circadian clock also targets the initiation and elongation steps of translation through multiple pathways. In this review, the influence of the circadian clock across the levels of post-transcriptional, translation, and post-translational modifications are examined using examples from humans to cyanobacteria demonstrating the phylogenetic conservation of circadian regulation. Lastly, we briefly discuss chronotherapies and pharmacological treatments that target circadian function. Understanding the complexity and levels through which the circadian clock regulates molecular and physiological processes is important for future advancement of therapeutic outcomes.

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.

RNA editing enzyme ADAR1 governs the circadian expression of P-glycoprotein in human renal cells by regulating alternative splicing of the ABCB1 gene

The expression and function of some xenobiotic transporters vary according to the time of the day, causing the dosing time-dependent changes in drug disposition and toxicity. P-glycoprotein (P-gp), encoded by the ABCB1 gene, is highly expressed in the kidneys and functions in the renal elimination of various drugs. The elimination of several P-gp substrates was demonstrated to vary depending on administration time, but the underlying mechanism remains unclear. We found that adenosine deaminase acting on RNA (ADAR1) was involved in the circadian regulation of P-gp expression in human renal proximal tubular epithelial cells (RPTECs). After synchronization of the cellular circadian clock by dexamethasone treatment, the expression of P-gp exhibited a significant 24-h oscillation in RPTECs, but this oscillation was disrupted by the downregulation of ADAR1. Although ADAR1 catalyzes adenosine-to-inosine (A-to-I) RNA editing in double-stranded RNA substrates, no significant ADAR1-regulated editing sites were detected in the human ABCB1 transcripts in RPTECs. On the other hand, downregulation of ADAR1 induced alternative splicing in intron 27 of the human ABCB1 gene, resulting in the production of retained intron transcripts. The aberrant spliced transcript was sensitive to nonsense-mediated mRNA decay, leading to the decreased stability of ABCB1 mRNA and prevention of the 24-h oscillation of P-gp expression. These findings support the notion that ADAR1-mediated regulation of alternative splicing of the ABCB1 gene is a key mechanism of circadian expression of P-gp in RPTECs, and the regulatory mechanism may underlie the dosing time-dependent variations in the renal elimination of P-gp substrates.

Pharmacokinetics-based chronoefficacy of Fuzi against chronic kidney disease

OBJECTIVES

Identifying drugs with time-varying efficacy or toxicity, and understanding the underlying mechanisms would help to improve treatment efficacy and reduce adverse effects. In this study, we uncovered that the therapeutic effect of Fuzi (the lateral root of Aconitum carmichaelii Debeaux) depended on the dosing time in mice with adenine-induced chronic kidney disease (CKD).

METHODS

The Fuzi efficacy was determined by biomarker measurements [i.e. plasma creatinine (CRE), blood urea nitrogen (BUN) and urinary N-acetyl-β-D-glucosaminidase (NAG)], as well as inflammation, fibrosis and histological analyses. Circadian regulation of Fuzi pharmacokinetics and efficacy was evaluated using brain and muscle Arnt-like protein-1 (Bmal1)-deficient (Bmal1-/-) mice.

KEY FINDINGS

The Fuzi efficacy was higher when the drug was dosed at ZT10 and was lower when the drug was dosed at other times (ZT2, ZT6, ZT14, ZT18 and ZT22) according to measurements of plasma CRE, BUN and urinary NAG. Consistently, ZT10 (5 PM) dosing showed a stronger protective effect on the kidney (i.e. less extensive tubular injury) as compared to ZT22 (5 AM) dosing. This was supported by lower levels of inflammatory and fibrotic factors (IL-1β, IL-6, Tnf-α, Ccl2, Tgfb1 and Col1a1) at ZT10 than at ZT22. Pharmacokinetic analyses showed that the area under the curve (AUC) values (reflective of systemic exposure) and renal distribution of aconitine, hypaconitine and mesaconitine (three putative active constituents) for Fuzi dosing at ZT10 were significantly higher than those for herb dosing at ZT22, suggesting a role of circadian pharmacokinetics in Fuzi chronoefficacy. Drug efficacy studies confirmed that aconitine, hypaconitine and mesaconitine possessed a kidney-protecting effect. In addition, genetic knockout of Bmal1 in mice abolished the time-dependency of Fuzi pharmacokinetics and efficacy. This reinforced the existence of chronoefficacy for Fuzi and supported the role of circadian pharmacokinetics in Fuzi chronoefficacy.

CONCLUSIONS

The efficacy of Fuzi against CKD depends on the dosing time in mice, which is associated with circadian pharmacokinetics of the three main active constituents (i.e. aconitine, hypaconitine and mesaconitine). These findings highlight the relevance of dosing time in the therapeutic outcomes of herbal medicines.

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.

Clock gene Bmal1 controls diurnal rhythms in expression and activity of intestinal carboxylesterase 1

OBJECTIVES

We aimed to characterize diurnal rhythms in CES1 expression and activity in mouse intestine, and to investigate a potential role of the core clock gene Bmal1 in generating diurnal rhythms.

METHODS

The regulatory effects of intestinal Bmal1 on diurnal CES1 expression were assessed using intestine-specific Bmal1 knockout (Bmal1iKO) mice and colon cancer cells. The relative mRNA and protein levels were determined by qPCR and Western blotting, respectively. Metabolic activity of CES1 in vitro and in vivo were determined by microsomal assays and pharmacokinetic studies, respectively. Transcriptional gene regulation was investigated using luciferase reporter assay.

KEY FINDINGS

Total CES1 protein varied significantly according to time of the day in wild-type (Bmal1fl/fl) mice, peaking at ZT6. Of detectable Ces1 genes, Ces1d mRNA displayed a robust diurnal rhythm with a peak level at ZT6, whereas mRNAs of Ces1e, 1f and 1g showed no rhythms in wild-type mice. Loss of intestinal Bmal1 reduced the levels of total CES1 protein and Ces1d mRNA, and blunted their diurnal rhythms in mice. In vitro microsomal assays indicated that intestinal metabolism of mycophenolate mofetil (MMF, a known CES1 substrate) was more extensive at ZT6 than at ZT18. ZT6 dosing of MMF to wild-type mice generated a higher systemic exposure of mycophenolic acid (the active metabolite of MMF) as compared with ZT18 dosing. Intestinal ablation of Bmal1 down-regulated CES1 metabolism at ZT6, and abolished its time-dependency both in vitro and in vivo. Furthermore, Ces1d/CES1 rhythmicity and positive regulation of Ces1d/CES1 by BMAL1 were confirmed in CT26 and Caco-2 cells. Mechanistically, BMAL1 trans-activated Ces1d/CES1 probably via binding to the E-box elements in the gene promoters.

CONCLUSIONS

Bmal1 controls diurnal rhythms in expression and activity of intestinal CES1. Our findings have implications for understanding the crosstalk between circadian clock and xenobiotic metabolism in the intestine.

Dysregulation of REV-ERBα impairs GABAergic function and promotes epileptic seizures in preclinical models

To design potentially more effective therapies, we need to further understand the mechanisms underlying epilepsy. Here, we uncover the role of Rev-erbα in circadian regulation of epileptic seizures. We first show up-regulation of REV-ERBα/Rev-erbα in brain tissues from patients with epilepsy and a mouse model. Ablation or pharmacological modulation of Rev-erbα in mice decreases the susceptibility to acute and chronic seizures, and abolishes diurnal rhythmicity in seizure severity, whereas activation of Rev-erbα increases the animal susceptibility. Rev-erbα ablation or antagonism also leads to prolonged spontaneous inhibitory postsynaptic currents and elevated frequency in the mouse hippocampus, indicating enhanced GABAergic signaling. We also identify the transporters Slc6a1 and Slc6a11 as regulators of Rev-erbα-mediated clearance of GABA. Mechanistically, Rev-erbα promotes the expressions of Slc6a1 and Slc6a11 through transcriptional repression of E4bp4. Our findings propose Rev-erbα as a regulator of synaptic function at the crosstalk between pathways regulating the circadian clock and epilepsy.

Multidrug resistance proteins (MRPs): Structure, function and the overcoming of cancer multidrug resistance

ATP-binding cassette (ABC) transporters mediate the ATP-driven translocation of structurally and mechanistically distinct substrates against steep concentration gradients. Among the seven human ABC subfamilies namely ABCA-ABCG, ABCC is the largest subfamily with 13 members. In this respect, 9 of the ABCC members are termed "multidrug resistance proteins" (MRPs1-9) due to their ability to mediate cancer multidrug resistance (MDR) by extruding various chemotherapeutic agents or their metabolites from tumor cells. Furthermore, MRPs are also responsible for the ATP-driven efflux of physiologically important organic anions such as leukotriene C₄, folic acid, bile acids and cAMP. Thus, MRPs are involved in important regulatory pathways. Blocking the anticancer drug efflux function of MRPs has shown promising results in overcoming cancer MDR. As a result, many novel MRP modulators have been developed in the past decade. In the current review, we summarize the structure, tissue distribution, biological and pharmacological functions as well as clinical insights of MRPs. Furthermore, recent updates in MRP modulators and their therapeutic applications in clinical trials are also discussed.

Circadian regulation of transporter expression and implications for drug disposition

Introduction: Solute Carrier (SLC) and ATP-binding cassette (ABC) transporters expressed in the intestine, liver, and kidney determine the absorption, distribution, and excretion of drugs. In addition, most molecular and cellular processes show circadian rhythmicity controlled by circadian clocks that leads to diurnal variations in the pharmacokinetics and pharmacodynamics of many drugs and affects their therapeutic efficacy and toxicity.Area covered: This review provides an overview of the current knowledge on the circadian rhythmicity of drug transporters and the molecular mechanisms of their circadian control. Evidence for coupling drug transporters to circadian oscillators and the plausible candidates conveying circadian clock signals to target drug transporters, particularly transcription factors operating as the output of clock genes, is discussed.Expert opinion: The circadian machinery has been demonstrated to interact with the uptake and efflux of various drug transporters. The evidence supports the concept that diurnal changes that affect drug transporters may influence the pharmacokinetics of the drugs. However, more systematic studies are required to better define the timing of pharmacologically important drug transporter regulation and determine tissue- and sex-dependent differences. Finally, the transfer of knowledge based on the results and conclusions obtained primarily from animal models will require careful validation before it is applied to humans.

Diurnal expression of MRP4 in bone marrow cells underlies the dosing-time dependent changes in the oxaliplatin-induced myelotoxicity

The expression and function of some xenobiotic transporters varies according to the time of day, causing the dosing time-dependent changes in drug disposition and toxicity. Multidrug resistance-associated protein-4 (MRP4), an ATP­binding cassette (ABC) efflux transporter encoded by the Abcc4 gene, is highly expressed in bone marrow cells (BMCs) and protects them against xenobiotics, including chemotherapeutic drugs. In this study, we demonstrated that MRP4 was responsible for the extrusion of oxaliplatin (L-OHP), a platinum (Pt)-based chemotherapeutic drug, from BMCs of mice, and that the efflux transporter expression exhibited significant diurnal variation. Therefore, we investigated the relevance of the diurnal expression of MRP4 in BMCs for L-OHP-induced myelotoxicity in mice maintained under standardized light/dark cycle conditions. After intravenous injection of L-OHP, the Pt content in BMCs varied according to the injection time. Lower Pt accumulation in BMCs was detected in mice after injection of L-OHP at the mid-dark phase, during which the expression levels of MRP4 increased. Consistent with these observations, the myelotoxic effects of L-OHP were attenuated when mice were injected with L-OHP during the dark phase. This dosing schedule also alleviated the L-OHP-induced reduction of the peripheral white blood cell count. The present results suggest that the myelotoxicity of L-OHP is attenuated by optimizing the dosing schedule. Diurnal expression of MRP4 in BMCs is associated with the dosing time-dependent changes in L-OHP-induced myelotoxicity.

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.

Nuclear receptor co-repressor RIP140 regulates diurnal expression of cytochrome P450 2b10 in mouse liver

Elucidating the mechanisms for circadian expression of drug-metabolizing enzymes is essential for a better understanding of dosing time-dependent drug metabolism and pharmacokinetics. CYP2B6 (Cyp2b10 in mice) is an important enzyme responsible for metabolism and detoxification of approximately 10% of drugs. Here, we aimed to investigate a potential role of nuclear receptor co-repressor RIP140 in circadian regulation of Cyp2b10 in mice.We first uncovered diurnal rhythmicity in hepatic RIP140 mRNA and protein with peak values at ZT10 (ZT, zeitgeber time). RIP140 ablation up-regulated Cyp2b10 expression and blunted its rhythm in mice and in AML-12 cells. Consistent with a negative regulatory effect, overexpression of RIP140 inhibited Cyp2b10 promoter activity and reduced cellular Cyp2b10 expression.Furthermore, RIP140 suppressed Car- and Pxr-mediated transactivation of Cyp2b10, and the suppressive effects were attenuated when the RIP140 gene was silenced. Chromatin immunoprecipitation assays revealed that recruitment of RIP140 protein to the Cyp2b10 promoter was circadian time-dependent in wild-type mice. More extensive recruitment was observed at ZT10 than at ZT2 consistent with the rhythmic pattern of RIP140 protein. However, the time-dependency of RIP140 recruitment was lost in RIP140^-/- mice.Additionally, we identified a D-box and a RORE cis-element in RIP140 promoter. D-box- and RORE-acting clock components such as Dbp, E4bp4, Rev-erbα/β and Rorα transcriptionally regulated RIP140, potentially accounting for its rhythmic expression.In conclusion, RIP140 regulates diurnal expression of Cyp2b10 in mouse liver through periodical repression of Car- and Pxr-mediated transactivation. This co-regulator-driven mechanism represents a novel source of diurnal rhythmicity in drug-metabolizing enzymes.

DHA substitution overcomes high-fat diet-induced disturbance in the circadian rhythm of lipid metabolism

Disruptions to circadian rhythm have been associated with an increased risk of nonalcoholic fatty liver disease (NAFLD). DHA has been found to affect both circadian rhythm and lipid metabolism. In this study, the relationship between DHA substitution and improvements in lipid metabolism and circadian clock regulation was studied. Male C57BL/6 mice were fed a control, a high fat or a DHA substituted diet for 12 weeks. Biochemical analysis and H&E staining showed that the high-fat diet (HFD) could induce NAFLD, and DHA substitution (AOH) could attenuate NAFLD. The qPCR results showed that the expressions of core clock genes Clock and Bmal1 were significantly higher at zeitgeber (ZT) 0 (7:00 am) than those at ZT12 (7:00 pm) in the control group, while this difference in day and night disappeared in the HFD group, but was observed in the AOH group. Western blotting results indicated that the expressions of rhythm output molecules (RORα and REV-ERBα) and their downstream protein INSIG2 all showed the corresponding circadian changes. SREBP-regulated proteins were significantly increased in the HFD group at both ZT0 and ZT12, but decreased in the AOH group accompanied by the corresponding changes in the protein expressions of HMGCR, LXR, CYP7A1 and CYP27A1. Altogether, HFD can decrease or disrupt circadian rhythm fluctuation by up-regulating the expression of core circadian rhythm genes Clock and Bmal1 at ZT12, and induce metabolic abnormalities through the INSIG2-SREBP pathway regulated by RORα and REV-ERBα. DHA substitution seems to restore circadian rhythm similar to the normal circadian rhythm of "night-high, day-low" through the metabolic pathway regulated by rhythmic nuclear receptors, improving the lipid metabolism rhythm and reducing liver fat.

Timing in drug absorption and disposition: The past, present, and future of chronopharmacokinetics

The importance of drug dosing time in pharmacokinetics, pharmacodynamics, and toxicity is receiving increasing attention from the scientific community. In spite of mounting evidence that circadian oscillations affect drug absorption, distribution, metabolism, and excretion (ADME), there remain many unanswered questions in this field and, occasionally, conflicting experimental results. Such data arise not only from translational difficulties caused by interspecies differences but also from variability in study design and a lack of understanding of how the circadian clock affects physiological factors that strongly influence ADME, namely, the expression and activity of drug transporters. Hence, the main goal of this review is to provide an updated analysis of the role of the circadian rhythm in drug absorption, distribution across blood-tissue barriers, metabolism in hepatic and extra-hepatic tissues, and hepatobiliary and renal excretion. It is expected that the research suggestions proposed here will contribute to a tissue-targeted and time-targeted pharmacotherapy.

Circadian Clock-Controlled Drug Metabolism: Implications for Chronotherapeutics

Dependence of drug metabolism on dosing time has long been recognized. However, only recently are the underlying mechanisms for circadian drug metabolism being clarified. Diurnal rhythmicity in expression of drug-metabolizing enzymes is believed to be a key factor determining circadian metabolism. Supporting the notion that biological rhythms are generated and maintained by the circadian clock, a number of diurnal enzymes are under the control of the circadian clock. In general, circadian clock genes generate and regulate diurnal rhythmicity in drug-metabolizing enzymes via transcriptional actions on one or two of three cis-elements (i.e., E-box, D-box, and Rev-erb response element or RAR-related orphan receptor response element). Additionally, cycling or clock-controlled nuclear receptors such as hepatocyte nuclear factor 4α and peroxisome proliferator-activated receptor γ are contributors to diurnal enzyme expression. These newly discovered mechanisms for each of the rhythmic enzymes are reviewed in this article. We also discuss how the rhythms of enzymes are translated to circadian pharmacokinetics and drug chronotoxicity, which has direct implications for chronotherapeutics. Our discussion is also extended to two diurnal transporters (P-glycoprotein and multidrug resistance-associated protein 2) that have an important role in drug absorption. Although the experimental evidence is lacking in metabolism-based chronoefficacy, circadian genes (e.g., Rev-erbα) as drug targets are shown to account for diurnal variability in drug efficacy. SIGNIFICANCE STATEMENT: Significant progress has been made in understanding the molecular mechanisms for generation of diurnal rhythmicity in drug-metabolizing enzymes. In this article, we review the newly discovered mechanisms for each of the rhythmic enzymes and discuss how the rhythms of enzymes are translated to circadian pharmacokinetics and drug chronotoxicity, which has direct implications for chronotherapeutics.