From circadian rhythms to cancer chronotherapeutics

The Relationship between Circadian Rhythm and Cancer Disease

The circadian clock regulates biological cycles across species and is crucial for physiological activities and biochemical reactions, including cancer onset and development. The interplay between the circadian rhythm and cancer involves regulating cell division, DNA repair, immune function, hormonal balance, and the potential for chronotherapy. This highlights the importance of maintaining a healthy circadian rhythm for cancer prevention and treatment. This article investigates the complex relationship between the circadian rhythm and cancer, exploring how disruptions to the internal clock may contribute to tumorigenesis and influence cancer progression. Numerous databases are utilized to conduct searches for articles, such as NCBI, MEDLINE, and Scopus. The keywords used throughout the academic archives are "circadian rhythm", "cancer", and "circadian clock". Maintaining a healthy circadian cycle involves prioritizing healthy sleep habits and minimizing disruptions, such as consistent sleep schedules, reduced artificial light exposure, and meal timing adjustments. Dysregulation of the circadian clock gene and cell cycle can cause tumor growth, leading to the need to regulate the circadian cycle for better treatment outcomes. The circadian clock components significantly impact cellular responses to DNA damage, influencing cancer development. Understanding the circadian rhythm's role in tumor diseases and their therapeutic targets is essential for treating and preventing cancer. Disruptions to the circadian rhythm can promote abnormal cell development and tumor metastasis, potentially due to immune system imbalances and hormonal fluctuations.

Immunotherapy around the Clock: Impact of Infusion Timing on Stage IV Melanoma Outcomes

Although the impact of circadian timing on immunotherapy has yet to be integrated into clinical practice, chronoimmunotherapy is an emerging and promising field as circadian oscillations are observed in immune cell numbers as well as the expression of immunotherapy targets, e.g., programmed cell death protein-1 and its ligand programmed death ligand 1. Concurrent retrospective studies suggest that morning infusions may lead to higher effectiveness of immune checkpoint inhibitors in melanoma, non-small cell lung cancer, and kidney cancer. This paper discusses the results of a retrospective study (2016-2022) exploring the impact of infusion timing on the outcomes of all 73 patients with stage IV melanoma receiving immunotherapy at a particular medical center. While the median overall survival (OS) was 24.2 months (95% confidence interval [CI] 9.04-39.8), for a median follow-up of 15.3 months, our results show that having more than 75% of infusions in the afternoon results in shorter median OS (14.9 vs. 38.1 months; hazard ratio 0.45 [CI 0.23-0.86]; p < 0.01) with more expressive impacts on particular subgroups: women, older patients, and patients with a lower tumor burden at the outset of immunotherapy. Our findings highlight the potential benefits of follow-up validation in prospective and translational randomized studies.

NSAID chronotherapy after impacted third molar extraction: a randomized controlled trial

OBJECTIVES

Postoperative pain management impacts patients' quality of life and morbidity. Non-steroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen are widely used for this following a 3-doses-per-day regime. However, pain and inflammation follow a circadian rhythm, and animal models assessing the scheduling of NSAID administration (e.g., chronotherapy) have shown that while their use during the active phase of the day enhances postoperative recovery, their administration during the resting phase could have detrimental effects. This observation has led us to hypothesize that night administration of NSAID might be unnecessary in post-surgical scenarios. Therefore, a randomized clinical trial was conducted to test this hypothesis in surgical third molar extractions.

MATERIALS AND METHODS

Seventy (18-35 years) healthy participants requiring surgical removal of impacted lower third molars were recruited and randomized into a double-blind placebo-controlled study. For three days postoperatively, the treatment group (n = 33) received ibuprofen (400 mg) at 8 AM, 1 PM, and a placebo at 8 PM, while the control group (n = 37) received ibuprofen (400 mg) at 8 AM, 1 PM, and 8 PM. Pain severity was assessed by visual analog scale (VAS) and healing indicators including facial swelling, mouth opening, and C-reactive protein blood levels were also measured.

RESULTS

Pain VAS measures showed a circadian variation peaking at night. Also, no significant differences were observed between the two groups of the study in terms of postoperative pain scores (estimate: 0.50, 95% CI = [- 0.38, 1.39]) or any other healing indicator.

CONCLUSIONS

Postoperative pain follows a circadian rhythm. Moreover, night administration of ibuprofen might not provide any significant benefits in terms of pain management and control of inflammation, and two doses during the day only could be sufficient for pain management after surgical interventions.

KNOWLEDGE TRANSFER STATEMENT

Even though this study cannot rule out the possibility that a reduced regime is different than a standard regime, nocturnal doses of ibuprofen seem to have no clinical significance in the short term, and the results of this study provide evidence in favor of reducing ibuprofen administration from three doses to two doses only after third molar surgery.

Understanding the significance of biological clock and its impact on cancer incidence

The circadian clock is an essential timekeeper that controls, for humans, the daily rhythm of biochemical, physiological, and behavioral functions. Irregular performance or disruption in circadian rhythms results in various diseases, including cancer. As a factor in cancer development, perturbations in circadian rhythms can affect circadian homeostasis in energy balance, lead to alterations in the cell cycle, and cause dysregulation of chromatin remodeling. However, knowledge gaps remain in our understanding of the relationship between the circadian clock and cancer. Therefore, a mechanistic understanding by which circadian disruption enhances cancer risk is needed. This review article outlines the importance of the circadian clock in tumorigenesis and summarizes underlying mechanisms in the clock and its carcinogenic mechanisms, highlighting advances in chronotherapy for cancer treatment.

Circadian rhythms modulate the effect of eccentric exercise on rat soleus muscles

We investigated whether time-of-day dependent changes in the rat soleus (SOL) muscle size, after eccentric exercises, operate via the mechanistic target of rapamycin (mTOR) signaling pathway. For our first experiment, we assigned 9-week-old male Wistar rats randomly into four groups: light phase (zeitgeber time; ZT6) non-trained control, dark phase (ZT18) non-trained control, light phase-trained, and dark phase-trained. Trained animals performed 90 min of downhill running once every 3 d for 8 weeks. The second experiment involved dividing 9-week-old male Wistar rats to control and exercise groups. The latter were subjected to 15 min of downhill running at ZT6 and ZT18. The absolute (+12.8%) and relative (+9.4%) SOL muscle weights were higher in the light phase-trained group. p70S6K phosphorylation ratio was 42.6% higher in the SOL muscle of rats that had exercised only in light (non-trained ZT6). Collectively, the degree of muscle hypertrophy in SOL is time-of-day dependent, perhaps via the mTOR/p70S6K signaling.

An Optimal Time for Treatment-Predicting Circadian Time by Machine Learning and Mathematical Modelling

Tailoring medical interventions to a particular patient and pathology has been termed personalized medicine. The outcome of cancer treatments is improved when the intervention is timed in accordance with the patient's internal time. Yet, one challenge of personalized medicine is how to consider the biological time of the patient. Prerequisite for this so-called chronotherapy is an accurate characterization of the internal circadian time of the patient. As an alternative to time-consuming measurements in a sleep-laboratory, recent studies in chronobiology predict circadian time by applying machine learning approaches and mathematical modelling to easier accessible observables such as gene expression. Embedding these results into the mathematical dynamics between clock and cancer in mammals, we review the precision of predictions and the potential usage with respect to cancer treatment and discuss whether the patient's internal time and circadian observables, may provide an additional indication for individualized treatment timing. Besides the health improvement, timing treatment may imply financial advantages, by ameliorating side effects of treatments, thus reducing costs. Summarizing the advances of recent years, this review brings together the current clinical standard for measuring biological time, the general assessment of circadian rhythmicity, the usage of rhythmic variables to predict biological time and models of circadian rhythmicity.

The Core-Clock Gene NR1D1 Impacts Cell Motility In Vitro and Invasiveness in A Zebrafish Xenograft Colon Cancer Model

Malfunctions of circadian clock trigger abnormal cellular processes and influence tumorigenesis. Using an in vitro and in vivo xenograft model, we show that circadian clock disruption via the downregulation of the core-clock genes BMAL1, PER2, and NR1D1 impacts the circadian phenotype of MYC, WEE1, and TP53, and affects proliferation, apoptosis, and cell migration. In particular, both our in vitro and in vivo results suggest an impairment of cell motility and a reduction in micrometastasis formation upon knockdown of NR1D1, accompanied by altered expression levels of SNAI1 and CD44. Interestingly we show that differential proliferation and reduced tumour growth in vivo may be due to the additional influence of the host-clock and/or to the 3D tumour architecture. Our results raise new questions concerning host–tumour interaction and show that core-clock genes are involved in key cancer properties, including the regulation of cell migration and invasion by NR1D1 in zebrafish xenografts.

Chronotherapy of Non-Steroidal Anti-Inflammatory Drugs May Enhance Postoperative Recovery

Postoperative pain relief is crucial for full recovery. With the ongoing opioid epidemic and the insufficient effect of acetaminophen on severe pain; non-steroidal anti-inflammatory drugs (NSAIDs) are heavily used to alleviate this pain. However, NSAIDs are known to inhibit postoperative healing of connective tissues by inhibiting prostaglandin signaling. Pain intensity, inflammatory mediators associated with wound healing and the pharmacological action of NSAIDs vary throughout the day due to the circadian rhythm regulated by the clock genes. According to this rhythm, most of wound healing mediators and connective tissue formation occurs during the resting phase, while pain, inflammation and tissue resorption occur during the active period of the day. Here we show, in a murine tibia fracture surgical model, that NSAIDs are most effective in managing postoperative pain, healing and recovery when drug administration is limited to the active phase of the circadian rhythm. Limiting NSAID treatment to the active phase of the circadian rhythm resulted in overexpression of circadian clock genes, such as Period 2 (Per2) at the healing callus, and increased serum levels of anti-inflammatory cytokines interleukin-13 (IL-13), interleukin-4 (IL-4) and vascular endothelial growth factor. By contrast, NSAID administration during the resting phase resulted in severe bone healing impairment.

Impaired light detection of the circadian clock in a zebrafish melanoma model

The circadian clock controls the timing of the cell cycle in healthy tissues and clock disruption is known to increase tumourigenesis. Melanoma is one of the most rapidly increasing forms of cancer and the precise molecular circadian changes that occur in a melanoma tumor are unknown. Using a melanoma zebrafish model, we have explored the molecular changes that occur to the circadian clock within tumors. We have found disruptions in melanoma clock gene expression due to a major impairment to the light input pathway, with a parallel loss of light-dependent activation of DNA repair genes. Furthermore, the timing of mitosis in tumors is perturbed, as well as the regulation of certain key cell cycle regulators, such that cells divide arhythmically. The inability to co-ordinate DNA damage repair and cell division is likely to promote further tumourigenesis and accelerate melanoma development.

Distinguishing between stochasticity and determinism: Examples from cell cycle duration variability

We describe a recent approach for distinguishing between stochastic and deterministic sources of variability, focusing on the mammalian cell cycle. Variability between cells is often attributed to stochastic noise, although it may be generated by deterministic components. Interestingly, lineage information can be used to distinguish between variability and determinism. Analysis of correlations within a lineage of the mammalian cell cycle duration revealed its deterministic nature. Here, we discuss the sources of such variability and the possibility that the underlying deterministic process is due to the circadian clock. Finally, we discuss the "kicked cell cycle" model and its implication on the study of the cell cycle in healthy and cancerous tissues.

Folate-Dependent Purine Nucleotide Biosynthesis in Humans

Purine nucleotide biosynthesis de novo (PNB) requires 2 folate-dependent transformylases-5'-phosphoribosyl-glycinamide (GAR) and 5'-phosphoribosyl-5-aminoimidazole-4-carboxamide (AICAR) transformylases-to introduce carbon 8 (C8) and carbon 2 (C2) into the purine ring. Both transformylases utilize 10-formyltetrahydrofolate (10-formyl-H4folate), where the formyl-carbon sources include ring-2-C of histidine, 3-C of serine, 2-C of glycine, and formate. Our findings in human studies indicate that glycine provides the carbon for GAR transformylase (exclusively C8), whereas histidine and formate are the predominant carbon sources for AICAR transformylase (C2). Contrary to the previous notion, these carbon sources may not supply a general 10-formyl-H4folate pool, which was believed to equally provide carbons to C8 and C2. To explain these phenomena, we postulate that GAR transformylase is in a complex with the trifunctional folate-metabolizing enzyme (TFM) and serine hydroxymethyltransferase to channel carbons of glycine and serine to C8. There is no evidence for channeling carbons of histidine and formate to AICAR transformylase (C2). GAR transformylase may require the TFM to furnish 10-formyl-H4folate immediately after its production from serine to protect its oxidation to 10-formyldihydrofolate (10-formyl-H2folate), whereas AICAR transformylase can utilize both 10-formyl-H2folate and 10-formyl-H4folate. Human liver may supply AICAR to AICAR transformylase in erythrocytes/erythroblasts. Incorporation of ring-2-C of histidine and formate into C2 of urinary uric acid presented a circadian rhythm with a peak in the morning, which corresponds to the maximum DNA synthesis in the bone marrow, and it may be useful in the timing of the administration of drugs that block PNB for the treatment of cancer and autoimmune disease.

13C-enrichment of urinary uric acid after L-[Ring-2-13C]histidine dose in adult humans

We determined whether ring-2 carbon of histidine is folate-dependently transferred to carbons 8 (C₈) and/or 2 (C₂) in urinary uric acid in humans. Two adults collected each urine void for four days. Aliquots of urine for the first day were used for baseline values; then the subjects ingested 0.7 g (3.3 mmol) of l-[ring-2-¹³C]histidine and collected urine for three experimental days. Aliquots were analyzed for percentage ¹³C-content at C₂ and C₈ by a liquid-chromatography-mass spectrometry method. Percentage enrichment was determined by subtracting time-of-day paired baseline percentage ¹³C-content from experimental percentage ¹³C-content for each void. C₂ was predominantly ¹³C-enriched in the majority of voids. The percentage enrichments at C₂ for two subjects were 0.14 (±0.028 [SEM], n = 26) and 0.18 (±0.049, n = 21), whereas at C₈, they were 0.008 (±0.006) and −0.005 (±0.008), respectively. The mean C₂-enrichments were significantly greater than zero (p < 0.01), whereas those of C₈ were not (p > 0.2). The enrichment had a diurnal rhythm peaking in the morning. Our results may be useful in the estimation of the timing for the administration of drugs that interfere with purine nucleotide biosynthesis in the treatment of cancer and autoimmune disease.

Transplantability of a circadian clock to a noncircadian organism

Circadian oscillators are posttranslationally regulated and affect gene expression in autotrophic cyanobacteria. Oscillations are controlled by phosphorylation of the KaiC protein, which is modulated by the KaiA and KaiB proteins. However, it remains unclear how time information is transmitted to transcriptional output. We show reconstruction of the KaiABC oscillator in the noncircadian bacterium Escherichia coli. This orthogonal system shows circadian oscillations in KaiC phosphorylation and in a synthetic transcriptional reporter. Coexpression of KaiABC with additional native cyanobacterial components demonstrates a minimally sufficient set of proteins for transcriptional output from a native cyanobacterial promoter in E. coli. Together, these results demonstrate that a circadian oscillator is transplantable to a heterologous organism for reductive study as well as wide-ranging applications.

Comparison of acute skin reaction following morning versus late afternoon radiotherapy in patients with breast cancer who have undergone curative surgical resection

We investigated the relationship between the time of radiotherapy (RT) and treatment outcomes in breast cancer. Patients with pathologic T1-2N0-1 breast cancer who received adjuvant RT in the morning (before 10:00 AM) or late afternoon (after 3:00 PM) were eligible for inclusion in this study. We retrospectively compared the clinicopathologic characteristics, acute skin reaction, and survival outcomes according to the time of RT. The median follow-up duration was 83 months (range, 10-131 months). From the 395 eligible patients, 190 (48.1%) and 205 (51.9%) patients were classified into the morning RT group and the afternoon RT group, respectively. The clinicopathologic characteristics were relatively well balanced between the treatment groups, except for pathologic N-stage (P = 0.0409). Grade 2 or higher acute skin reaction according to the Radiation Therapy Oncology Group criteria was observed in 39 (9.9%) patients, with a higher frequency in the afternoon RT group than the morning RT group (13.7% vs 5.8%, respectively; P = 0.0088). There was no difference in the failure patterns or survival outcomes between the treatment groups. RT in late afternoon was associated with increased Grade 2 or more skin reaction after RT for breast cancer patients, but treatment outcomes did not differ according to the time of RT. Individualized considerations for treatment should be taken into account to reduce the risk of skin reactions.

Model-based human circadian phase estimation using a particle filter

We present a method for tracking an individual's circadian phase that integrates dynamic models of circadian physiology with physiological measurements in a Bayesian statistical framework. A model of the circadian pacemaker's response to light exposure is transformed into a nonlinear state-space model with a circadian phase state. The probability distribution of the circadian phase is estimated by a particle filter that predicts changes over time based on the model, and performs updates with information gained from physiological measurements. Simulations demonstrate how probability distributions allow flexible initialization of model states and enable statistical quantification of entrainment and divergence properties of the circadian pacemaker. The combined use of sleep-wake scheduling data and physiological measurements is demonstrated in a case study highlighting advantages for addressing the challenge of noninvasive ambulatory monitoring of circadian physiology.

Chronomodulated chemotherapy versus conventional chemotherapy for advanced colorectal cancer: a meta-analysis of five randomized controlled trials

PURPOSE

The purpose of this study was to systematically compare the efficacy and safety of chronomodulated chemotherapy with conventional chemotherapy in patients with advanced colorectal cancer.

METHOD

Eligible studies were identified from electronic databases (Medline, Embase, and the Cochrane Library). The efficacy data included overall survival (OS) and objective response rate (ORR), and toxicities data contained diarrhea, vomiting and nausea, mucositis, asthenia, and peripheral sensory neuropathy. The meta-analysis was performed with the fixed-effect model or random-effect model according to heterogeneity.

RESULT

From 79 articles screened, five randomized controlled trials (RCTs) met the inclusion criteria contributing a total of 958 participants. There was a significant OS benefit (hazard ratio (HR)=0.82; 95% confidence interval (CI) 0.69 to 0.97; P=0.023) in favor of the chronomodulated chemotherapy. The ORR was not significantly different between two arms (relative risk=1.27; 95% CI 0.88 to 1.83; P=0.196). A higher incidence of grade 3/4 mucositis (odds ratio=2.26, 95% CI 1.34 to 3.83; P=0.724), asthenia (2.15, 1.30 to 3.56; P=0.428), and a lower incidence of grade 3/4 neutropenia (0.26, 0.16 to 0.42; P=0.641) were associated with the chronomodulated chemotherapy. The two arms were similar in terms of grade 3/4 diarrhea (1.10, 0.72 to 1.69; P=0.756), vomiting and nausea (0.69, 0.42 to1.13; P=0.239), and peripheral sensory neuropathy (0.56, 0.25 to 1.27, 0.164).

CONCLUSION

Chronomodulated chemotherapy showed significant improvement in OS comparing with conventional chemotherapy. Side effects of the chronomodulated chemotherapy are predictable and manageable. But these results still need more high-quality RCTs for confirmation.

Circadian Rhythm of Irinotecan Tolerability in Mice

The toxicity of irinotecan (CPT-11), a topoisomerase-I inhibitor largely used in cancer patients, was investigated as a function of the circadian time of its administration in mice, with mortality, body weight loss, leukopenia, neutropenia, intestinal lesions, and bone marrow cell cycle phase distribution as end points. Four experiments were performed on a total of 773 male mice standardized with 12h light/12h darkness. Irinotecan was administered daily for 4 or 10 consecutive days (D1-4 and D1-10, respectively, in different experiments) at one of six circadian stages expressed in hours after light onset (HALO). The survival curves differed significantly as a function of the dosage and circadian time of drug administration by the D1-10 schedule, with 70% survival at 7 or 11 HALO and 51% at 19 or 23 HALO (p=0.039 from log rank test). CPT-11 administration at 19 or 23 HALO resulted in (1) greatest mean body weight loss at nadir; (2) most severe colic and bone marrow lesions and/or slowest recovery; and (3) deepest neutropenia nadir and/or slowest hematologic recovery. These circadian treatment time-related differences were statistically validated. The bone marrow cell cycle data revealed a four to eight-fold larger G2-M phase arrest following irinotecan administration at 19 or 23 HALO in comparison to the other times of drug administration, apparently representative of the repair of more extensive DNA damage (p < 0.001 from ANOVA) when the medication was given at these circadian times. Overall, CPT-11 was better tolerated by mice treated during the light (animals' rest) span. The results support the administration of CPT-11 to cancer patients in the second half of the night, during sleep, in order to improve drug tolerability.

Circadian Rhythms in Toxic Effects of the Serotonin Antagonist Ondansetron in Mice

The aim of the study was to learn whether the lethal and the motor incoordination (ataxia) side effect of ondansetron (Zophren) administration is dosing-time dependent. Ondansetron is a serotonin 5-HT3 receptor antagonist used primarily to control nausea and vomiting arising from cytotoxic chemo- and radiotherapy. A total of 210 male Swiss mice 10 to 12 weeks of age were synchronized for 3 weeks by 12 h light (rest span)/12 h dark (activity span). Different doses of ondansetron were injected intraperitoneally (i.p.) at fixed times during the day to determine both the sublethal (TD50) and lethal (LD50) doses, which were, respectively, 3.7 +/- 0.6 mg/kg and 4.6 +/- 0.5 mg/kg. In the chronotoxicologic study a single dose of ondansetron (3.5 mg/kg, i.p.) was administered to different and comparable groups of animals at four different circadian stages [1, 7, 13, and 19 h after light onset (HALO)]. The lethal toxicity was statistically significantly dosing time-dependent (chi2 = 21.51, p < 0.0001). Drug dosing at 1 HALO resulted in 100% survival rate whereas drug dosing at 19 HALO was only one-half that (52%). Similarly, lowest and highest ataxia occurred when ondansetron was injected at 1 and 19 HALO, respectively (chi2 = 22.24, p < 0.0001). Effects on rectal temperature were also dosing-time related (Cosinor analysis, p < 0.0001). The characteristics of the waveform describing the temporal patterns differed between the studied variables, e.g., lethal toxicity and survival rate showing two peaks and rectal temperature showing one peak in the 24 h time series waveform pattern. Cosinor analysis also revealed a statistically significant ultradian (tau = 8 h) rhythmic component in the considered variables. Differences in curve patterns in toxicity elicited by ondansetron on a per end point basis are hypothesized to represent the phase relations between the identified 24 h and 8 h periodicities.

Circadian Time‐Dependent Differences in Murine Tolerance to the Antihistaminic Agent Loratadine

Loratadine is a second-generation histamine H(1)-receptor antagonist used in the treatment of allergic diseases. The aim of the study was to assess whether lethal toxicity and motor incoordination (neurotoxicity) of loratadine is circadian rhythm-dependent. A total of 210 male Swiss mice, aged 10 wk, were synchronized for 3 wk to 12 h light (rest span)/12 h dark (activity span). The drug was administered per os. The choice of the sublethal (TD(50) = 82 mg/kg body weight) and the lethal (LD(50) = 4 g/kg body weight) dosage was based on preliminary studies. Each of these two doses was administered to comparable groups of animals at six different circadian time points (1, 5, 9, 13, 17, and 21 Hours After Light Onset [HALO]). The survival duration was dosing time-dependent (chi(2) = 16.96; p < 0.001). Drug dosing at 17 HALO resulted in best (67%) survival rate; whereas, dosing at 9 HALO resulted in poorest (21%) survival rate. Cosinor analyses (with a trial period tau = 24 h) validated a statistically significant circadian rhythm in survival rate (p < 0.04) with an acrophase (peak time Ø of best tolerance to loratadine) being at 17.5 HALO +/- 4.65 h. Troughs of motor incoordination were located at the administration times of 5 and 17 HALO (60% and 32% of animals affected, respectively), whereas peaks were located at 9 and 21 HALO (87% and 68% of animals affected, respectively). The 24 h mean of the motor incoordination was 61%, the mean proportion of animals affected by the treatment for the six different circadian times studies. The extent of this neurotoxic effect varied as a function of loratadine dosing time (p < 0.001). A statistically significant ultradian component rhythm (p < 0.01) with a trial period tau = 12 h was also validated. The obtained results show that the dosing time of loratadine at the mid-activity (dark) span seems to be optimal, since it corresponds to the longest (21 vs. 12 days) survival span and to least neurotoxicity.

Chronotoxicity of Nedaplatin in Rats

Chronotoxicologic profiles of nedaplatin, a platinum compound, were evaluated in rats maintained under a 12 light/12 dark cycle with light from 07:00h to 19:00 h. Nedaplatin (5 mg/kg) was injected intravenously, once a week for 5 weeks at 08:00h or 20:00h. The suppression of body weight gain and reduction of creatinine clearance were significantly greater with the 20:00h than 08:00h treatment. Accumulation of nedaplatin in the renal cortex and bone marrow were also greater with 20:00 h treatment. There were significant relationships between the nedaplatin content in the kidney and bone marrow and degree of injury to each. These results suggest that the nedaplatin-induced toxicity depends on its dosing-time, and it is greater with treatment at 20:00 h, during the active phase. The dosing-time dependency in the accumulation of nedaplatin in the tissue of the organs might be involved in this chronotoxicologic phenomenon.

The influence of circadian rhythms on the kinetics of drugs in humans

In clinical practice, it is important to consider circadian rhythms in pharmacokinetics and cell responses to therapy in order to design proper protocols for drug administration. Scientists have arrived at this conclusion after several experiments in animals and in humans have clearly demonstrated that all organisms are highly organised according to circadian rhythms. These temporal cycles influence different physiological functions and, consequently, can influence the pharmacokinetic phases of drugs. A drug's pharmacokinetics can be modified according to the time of drug administration. In fact, the circadian changes of > 100 different compounds have been documented. The results obtained have led several scientific societies to provide guidelines concerning the timing of drug dosing for anticancer, cardiovascular, respiratory, anti-ulcer, anti-inflammatory, immunosuppressive and antiepileptic drugs. Absorption may be influenced by circadian rhythms and most lipophilic drugs seem to be absorbed faster when the drug is taken in the morning compared with the evening; for water-soluble compounds, no circadian variation in the absorption of drugs has been found. Concerning drug distribution, the higher the blood flow fraction an organ receives, the higher the rate constant for transferring drugs out of the capillaries. This drug pharmacokinetic phase may be influenced by circadian variations in the protein binding of acidic and basic drugs. Drug metabolism may be influenced by daily modifications of blood flow. For drugs with a high extraction ratio, metabolism depends on hepatic blood flow, while that of drugs with a low extraction ratio depends on liver enzyme activity. Hepatic blood flow has been shown to be greatest at 8 am and metabolism seems to be reduced during the night. Finally, concerning drug elimination, the clearance of 'flow-limited' drugs that present a high extraction rate is affected by the blood flow delivered to the organ, independent of the cardiac output fraction supplied. Chronopharmacokinetics can explain individual differences in drug levels revealed by therapeutic drug monitoring and can be used to optimise the management of patients receiving drug therapy.

Implications of circadian clocks for the rhythmic delivery of cancer therapeutics

The circadian timing system controls drug metabolism and cellular proliferation over the 24 h through molecular clocks in each cell, circadian physiology, and the suprachiasmatic nuclei--a hypothalamic pacemaker clock that coordinates circadian rhythms. As a result, both the toxicity and efficacy of over 30 anticancer agents vary by more than 50% as a function of dosing time in experimental models. The circadian timing system also down-regulates malignant growth in experimental models and possibly in cancer patients. Programmable-in-time infusion pumps and rhythmic physiology monitoring devices have made possible the application of chronotherapeutics to more than 2000 cancer patients without hospitalization. This strategy first revealed the antitumor efficacy of oxaliplatin against colorectal cancer. In this disease, international clinical trials have shown a five-fold improvement in patient tolerability and near doubling of antitumor activity through the chronomodulated, in comparison to constant-rate, delivery of oxaliplatin and 5-fluorouracil-leucovorin. Here, the relevance of the peak time, with reference to circadian rhythms, of the chemotherapeutic delivery of these cancer medications for achieving best tolerability was investigated in 114 patients with metastatic colorectal cancer and in 45 patients with non-small cell lung cancer. The incidence of severe adverse events varied up to five-fold as a function of the choice of when during the 24 h the peak dose of the medications was timed. The optimal chronomodulated schedules corresponded to peak delivery rates at 1 a.m. or 4 a.m. for 5-fluorouracil-leucovorin, at 1 p.m. or 4 p.m. for oxaliplatin, and at 4 p.m. for carboplatin. Sex of patient was an important determinant of drug schedule tolerability. This finding is consistent with recent results from a chronotherapy trial involving 554 patients with metastatic colorectal cancer, where sex also predicted survival outcome from chronotherapy, but not conventional drug delivery. Ongoing translational studies, mathematical modeling, and technology developments are further paving the way for tailoring cancer chronotherapeutics to the main rhythmic characteristics of the individual patient. Targeting therapeutic delivery to the dynamics of the cross-talk between the circadian clock, the cell division cycle, and pharmacology pathways represents a new challenge to concurrently improve the quality of life and survival of cancer patients through personalized cancer chronotherapeutics.

A cell cycle automaton model for probing circadian patterns of anticancer drug delivery

To optimize the temporal patterning of drug delivery used in cancer chronotherapy, we resort to an automaton model describing the transitions through the successive phases of the cell cycle. The model accounts for the progressive desynchronization of cells due to the variability of the durations of the cell cycle phases, and for the entrainment of the cell cycle by the circadian clock. Focusing on the cytotoxic effect of the anticancer drug 5-fluorouracil (5-FU), which kills cells in the S phase, we compare the effect of continuous infusion of 5-FU with various circadian patterns of 5-FU administration that peak either at 4 a.m., 10 a.m., 4 p.m., or 10 p.m. The model indicates that the cytotoxic effect of 5-FU is minimum for the circadian delivery peaking at 4 a.m., and maximum for the continuous infusion or the circadian pattern peaking at 4 p.m. These results fit well with experimental observations and illustrate how the modeling approach based on the cell cycle automaton may help to predict the cytotoxic effect of anticancer drugs affecting various phases of the cell cycle.

High-throughput in vitro hemotoxicity testing and in vitro cross-platform comparative toxicity

For decades, hemotoxicity has been considered as simply changes in peripheral blood parameters or morphological changes observed in the bone marrow as a result of drug administration. The effects are actually the result of the drug acting at a much earlier level in the blood-forming system, usually at the level of the lympho-hematopoietic stem cell or its immediate differentiating progeny. To detect these early cellular responses, highly sensitive, non-subjective and fully standardized in vitro high-throughput testing platforms have been developed that detect changes in intracellular ATP concentrations which are directly proportional to and predict the proliferative/cytotoxic response of different cell populations.

Biologic clocks and the gut

The gastrointestinal tract displays biologic rhythms in basal gastric acid output, epithelial cell proliferation, gastrointestinal motility, and appetite regulation. Furthermore, the development of gastrointestinal complications after administration of aspirin and after chemo- and radiotherapy for metastatic colon cancer depends on the time of administration. Biologic rhythms are driven by so-called clock genes. Thus, it is conceivable that subsets of genes in the gastrointestinal tract are under clock gene control as well. The purpose of this article is to discuss basic concepts in the studies of biologic rhythms, to review examples of biologic rhythms in the gastrointestinal tract, and to discuss examples of gastrointestinal diseases in which alterations in biologic rhythms may play a pathogenetic role.

Chronopharmacokinetics of ciclosporin and tacrolimus

The correct use of immunosuppressive drugs has a considerable influence on the prognosis of patients with organ transplants. The appropriate utilisation of the drugs involves the administration of an adequate dosage to reach the blood concentrations that will suppress the alloimmune response, while avoiding secondary toxicities. However, transplanted patients exhibit heterogeneous immunological responses and high inter- and intraindividual pharmacokinetic variabilities. One cause of these variabilities that is rarely considered is circadian rhythms. In vitro and in vivo experiments have clearly demonstrated that all organisms are highly organised according to an internal biological clock that influences various physiological functions. Considering that the absorption, distribution, metabolism and elimination of drugs is influenced by the physiological functions of the body, it is not surprising that the pharmacokinetic, and consequently the pharmacodynamic, profiles of drugs can be influenced by circadian rhythms. Ciclosporin, a mainstay immunosuppressive drug used following organ transplantation, displays minimum blood concentration (C(min)), maximum blood concentration (C(max)) and area under the blood concentration-time curve (AUC) in the morning that are generally higher than the corresponding parameters in the evening. These observations are supported by the ciclosporin total body clearance and elimination half-life in the morning, which are, on average, higher and shorter, respectively, than those in the evening. In addition, the disposition of tacrolimus is determined by the time of administration. The tacrolimus C(max) and AUC after the morning dose are significantly higher than those after the evening dose. Finally, the results reported in this review suggest considering more carefully the chronopharmacokinetics of tacrolimus and ciclosporin in order to obtain better results with fewer adverse effects. Significantly, the morning appears to be the best time for therapeutic monitoring using the C(min), C(max), concentration at 2 hours after dosing and AUC to modify dosages of tacrolimus and ciclosporin. Less certain are any conclusions about whether, in order to obtain better immunosuppressive control, higher doses must be administered when these drugs are given in the evening to compensate for the higher levels of interleukin-2.

Circadian pharmacology of l-alanosine (SDX-102) in mice

L-alanosine (SDX-102) exerts its cytotoxicity through inhibition of de novo purine biosynthesis, an effect potentiated by methylthioadenosine phosphorylase (MTAP) deficiency. The relevance of circadian dosing time was investigated for chronotherapeutic optimization of SDX-102. Toxicity was assessed in healthy mice following single (1,150, 1,650, or 1,850 mg/kg/d) or multiple doses (250 or 270 mg/kg/d). Efficacy was tested in mice with P388 leukemia receiving multiple doses (225 or 250 mg/kg/d). SDX-102 was administered at six circadian times 4 hours apart in mice synchronized with 12 hours of light alternating with 12 hours of darkness. MTAP expression was determined in liver, bone marrow, small intestinal mucosa, and P388 cells. Dosing at 19 hours after light onset reduced lethality 5-fold after single administration and 3-fold after multiple doses as compared with worst time [P < 0.001 and P < 0.01, respectively (chi2 test)]. Neutropenia, lymphopenia, and bone marrow hemorrhagic lesions were significantly less in mice dosed at 19 hours after light onset as compared with 7 hours after light onset. SDX-102 at 7 hours after light onset transiently ablated the 24-hour patterns in body temperature and activity. A circadian rhythm characterized small intestinal MTAP expression with a maximum at 6:30 hours after light onset (P = 0.04). A minor survival improvement was found in MTAP-deficient P388 mice receiving SDX-102 at 7 or 23 hours after light onset as compared with other times (P = 0.03, log-rank test). In conclusion, the therapeutic index of SDX-102 was improved by the delivery of SDX-102 in the mid to late activity span. These results support the concept of chronomodulated infusion of SDX-102 in cancer patients.

Clock genes of mammalian cells: Practical implications in tissue culture

The clock genes family is expressed by all the somatic cells driving central and peripheral circadian rhythms through transcription/translation feedback loops. The circadian clock provides a local time for a cell and a way to integrate the normal environmental changes to smoothly adapt the cellular machinery to new conditions. The central circadian rhythm is retained in primary cultures by neurons of the suprachiasmatic nuclei. The peripheral circadian rhythms of the other somatic cells are progressively dampened down up to loss unless neuronal signals of the central clock are provided for re-entrainment. Under typical culture conditions (obscurity, 37 +/- 1 degrees C, 5-7% CO(2)), freshly explanted peripheral cells harbor chaotic expression of clock genes for 12-14 h and loose, coordinated oscillating patterns of clock components. Cells of normal or cancerous phenotypes established in culture harbor low levels of clock genes idling up to the re-occurrence of new synchronizer signals. Synchronizers are physicochemical cues (like thermic oscillations, short-term exposure to high concentrations of serum or single medium exchange) able to re-induce molecular oscillations of clock genes. The environmental synchronizers are integrated by response elements located in the promoter region of period genes that drive the central oscillator complex (CLOCK:BMAL1 and NPAS2:BMAL1 heterodimers). Only a few cell lines from different species and lineages have been tested for the existence or the functioning of a circadian clockwork. The best characterized cell lines are the immortalized SCN2.2 neurons of rat suprachiasmatic nuclei for the central clock and the Rat-1 fibroblasts or the NIH/3T3 cells for peripheral clocks. Isolation methods of fragile cell phenotypes may benefit from research on the biological clocks to design improved tissue culture media and new bioassays to diagnose pernicious consequences for health of circadian rhythm alterations.

Daily rhythms of P-glycoprotein expression in mice

Recent studies have shown the gene expression of several transporters to be circadian rhythmic. However, it remains to be elucidated whether the expression of P-glycoprotein, which is involved in the transport of many medications, undergoes 24 h rhythmicity. To address this issue, we investigated daily profiles of P-glycoprotein mRNA and protein levels in peripheral mouse tissues. In the liver and intestine, but not in the kidney, Abcb1a mRNA expression showed clear 24 h rhythmicity. On the other hand, Abcb1b and Abcb4, the other P-glycoprotein genes, did not exhibit significant rhythmic expression in the studied tissues. In the intestine, levels of whole P-glycoprotein also exhibited a daily rhythm, with a peak occurring in the latter half of the light phase and a trough at the onset of the light phase. Consistent with the day-night change of P-glycoprotein level, the ex vivo accumulation of digoxin, an Abcb1a P-glycoprotein substrate, into the intestinal segments at the onset of dark phase was significantly lower than it was at the onset of the light phase. Thus, Abcb1a P-glycoprotein expression, and apparently its function, are 24 h rhythmic at least in mouse intestine tissue. This circadian variation might be involved in various chronopharmacological phenomena.

[Circadian rhythms in the toxic effects of the histamine antagonist cetirizine in mice]

Cetirizine is a second generation histamine H(1) receptor antagonist used to provide symptomatic relief of allergic signs caused by histamine release. The aim of the study was to learn whether the survival and the motor incoordination (ataxia) side effect of cetirizine administration is dosing time-dependent.

MATERIALS AND METHODS

A total of 240 male Swiss mice, 10 weeks of age were synchronized for 3 weeks by 12 h light (rest span)/12 h dark (activity span). Different doses of cetirizine were administered orally at fixed times during the day to determine both the sublethal (TD(50)) and lethal (LD(50)) doses, which were, respectively, 55 +/- 0.35 and 750 +/- 0.40 mg/kg. In the chronotoxicologic study a single dose of cetirizine (DL(50)) was administered to comparable groups of animals at six different circadian stages [1, 5, 9, 13, 17, 21 h after light onset (HALO)].

RESULTS

The survival was statistically significant dosing time-dependent (chi(2) = 16.73; P < 0.001). Drug dosing at 17 HALO resulted in 83.3% survival rate whereas drug dosing at 5 HALO was only 23.25%. Cosinor analysis revealed a statistically significant circadian (period approximately 24 h) rhythmic component in survival. Lowest (20%) and highest (88%) ataxia occurred when cetirizine was administered, respectively, at 17 and 5 HALO. Cosinor analysis revealed a statistically significant circadian (period approximately 24 h) rhythmic component in ataxia.

CONCLUSION

Our results reveal that the best safety is shown when cetirizine is administered in the middle of the dark (activity) span of the mice, since it produces some side effects: ataxia and hyperthermia. Taking into account of the hour administration of cetirizine, improves treatment efficacy and permit the best control of allergic diseases.

From chronobiology to chronotherapeutics

Chronobiology focuses on variations in biological rhythms across time. This article describes biologic cycles, particularly circadian cycles and their underlying neuroanatomy. Metabolic rhythms are reviewed and their impact on disease and symptom variation discussed. Clinical and chronopharmacological implications and diagnostic applications are presented, highlighting chronotherapy's perspective.

Human intestinal circadian clock: expression of clock genes in colonocytes lining the crypt

Biological clock components have been detected in many epithelial tissues of the digestive tract of mammals (oral mucosa, pancreas, and liver), suggesting the existence of peripheral circadian clocks that may be entrainable by food. Our aim was to investigate the expression of main peripheral clock genes in colonocytes of healthy humans and in human colon carcinoma cell lines. The presence of clock components was investigated in single intact colonic crypts isolated by chelation from the biopsies of 25 patients (free of any sign of colonic lesions) undergoing routine colonoscopy and in cell lines of human colon carcinoma (Caco2 and HT29 clone 19A). Per-1, per-2, and clock mRNA were detected by real-time RT-PCR. The three-dimensional distributions of PER-1, PER-2, CLOCK, and BMAL1 proteins were recorded along colonic crypts by immunofluorescent confocal imaging. We demonstrate the presence of per-1, per-2, and clock mRNA in samples prepared from colonic crypts of 5 patients and in all cell lines. We also demonstrate the presence of two circadian clock proteins, PER-1 and CLOCK, in human colonocytes on crypts isolated from 20 patients (15 patients for PER-1 and 6 for CLOCK) and in colon carcinoma cells. Establishing the presence of clock proteins in human colonic crypts is the first step toward the study of the regulation of the intestinal circadian clock by nutrients and feeding rhythms.

Biological Rhythms, Medication Safety, and Women's Health

Biological processes and functions in women are well organized in time, as evidenced by the expression of ultradian (high frequency), circadian ( approximately 24-hour), circamensual ( approximately monthly), and circannual ( approximately yearly) rhythms and by the changes that occur with menarche, reproduction, and menopause. Attributes of women's circamensual structure have been explored in depth, particularly with regard to fertility/infertility and birth control. However, the role of 24-hour and other rhythms in health, disease, and treatment has been little studied. The symptom intensity of a variety of chronic medical conditions is rhythmic, as is the risk of severe events, such as stroke and myocardial infarct (MI). Improving the safety, efficacy, and preventive qualities of medications requires the understanding of how rhythms impact drug pharmacokinetics and pharmacodynamics. The therapeutic and adverse effects of prescription and nonprescription medications widely used by women can vary markedly with the (circadian) time of administration. Circadian rhythm-dependent differences in the safety of medications are particularly relevant to pregnant women; laboratory animal studies show that the fetal toxicity of various treatments varies not only with developmental stage but also with circadian time. Rhythm-dependent differences in the actions of medications are also of great importance to perimenopausal and postmenopausal women, who are advised to ingest prescribed pharmacotherapy for osteopenia and osteoporosis in the morning to minimize the risk of adverse effects and, as a consequence, may elect to take other medications at times not recommended in the instructions for their use. Medication trials must be comprehensive and representative of women and men of different life stages, ethnicities, and likely times (morning vs. evening) of drug use.