Effects of the neonatal intensive care environment on circadian health and development of preterm infants

The circadian system in mammals ensures adaptation to the light-dark cycle on Earth and imposes 24-h rhythmicity on metabolic, physiological and behavioral processes. The central circadian pacemaker is located in the brain and is entrained by environmental signals called Zeitgebers. From here, neural, humoral and systemic signals drive rhythms in peripheral clocks in nearly every mammalian tissue. During pregnancy, disruption of the complex interplay between the mother's rhythmic signals and the fetal developing circadian system can lead to long-term health consequences in the offspring. When an infant is born very preterm, it loses the temporal signals received from the mother prematurely and becomes totally dependent on 24/7 care in the Neonatal Intensive Care Unit (NICU), where day/night rhythmicity is usually blurred. In this literature review, we provide an overview of the fetal and neonatal development of the circadian system, and short-term consequences of disruption of this process as occurs in the NICU environment. Moreover, we provide a theoretical and molecular framework of how this disruption could lead to later-life disease. Finally, we discuss studies that aim to improve health outcomes after preterm birth by studying the effects of enhancing rhythmicity in light and noise exposure.

The Circadian Clock Protein CRY1 Is a Negative Regulator of HIF-1α

The circadian clock and the hypoxia-signaling pathway are regulated by an integrated interplay of positive and negative feedback limbs that incorporate energy homeostasis and carcinogenesis. We show that the negative circadian regulator CRY1 is also a negative regulator of hypoxia-inducible factor (HIF). Mechanistically, CRY1 interacts with the basic-helix-loop-helix domain of HIF-1α via its tail region. Subsequently, CRY1 reduces HIF-1α half-life and binding of HIFs to target gene promoters. This appeared to be CRY1 specific because genetic disruption of CRY1, but not CRY2, affected the hypoxia response. Furthermore, CRY1 deficiency could induce cellular HIF levels, proliferation, and migration, which could be reversed by CRISPR/Cas9- or short hairpin RNA-mediated HIF knockout. Altogether, our study provides a mechanistic explanation for genetic association studies linking a disruption of the circadian clock with hypoxia-associated processes such as carcinogenesis.

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Hypoxia and HIFs affect the circadian rhythm

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CRY1 directly interacts with both HIF-1α and HIF-2α

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CRY1 inhibits binding of HIFs to its target gene promoters

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The CRY1-HIFα interaction has opposite roles on cellular growth and migration

Relationship Between Sunitinib Pharmacokinetics and Administration Time: Preclinical and Clinical Evidence

Background and Objective

Circadian rhythms may influence the pharmacokinetics of drugs. This study aimed to elucidate whether the pharmacokinetics of the orally administered drug sunitinib are subject to circadian variation.

Methods

We performed studies in male FVB-mice aged 8–12 weeks, treated with single-dose sunitinib at six dosing times. Plasma and tissue samples were obtained for pharmacokinetic analysis and to monitor messenger RNA (mRNA) expression of metabolizing enzymes and drug transporters. A prospective randomized crossover study was performed in which patients took sunitinib once daily at 8 a.m., 1 p.m., and 6 p.m at three subsequent courses. Patients were blindly randomized into two groups, which determined the sequence of the sunitinib dosing time. The primary endpoint in both studies was the difference in plasma area under the concentration–time curve (AUC) of sunitinib and its active metabolite SU12662 between dosing times.

Results

Sunitinib and SU12662 plasma AUC in mice followed an ~12-h rhythm as a function of administration time (p ≤ 0.04). The combined AUC from time zero to 10 h (AUC₁₀) was 14–27 % higher when sunitinib was administered at 4 a.m. and 4 p.m. than at 8 a.m. and 8 p.m. Twenty-four-hour rhythms were seen in the mRNA levels of drug transporters and metabolizing enzymes. In 12 patients, sunitinib trough concentrations (C_trough) were higher when the drug was taken at 1 p.m. or 6 p.m. than when taken at 8 a.m. (C_{trough-1 p.m}. 66.0 ng/mL; C_{trough-6 p.m.} 58.9 ng/mL; C_{trough-8 a.m.} 50.7 ng/mL; p = 0.006). The AUC was not significantly different between dosing times.

Conclusions

Our results indicate that sunitinib pharmacokinetics follow an ~12-h rhythm in mice. In humans, morning dosing resulted in lower C_trough values, probably resulting from differences in elimination. This can have implications for therapeutic drug monitoring.

Electronic supplementary material

The online version of this article (doi:10.1007/s40262-015-0239-5) contains supplementary material, which is available to authorized users.

Circadian variation in tamoxifen pharmacokinetics in mice and breast cancer patients

The anti-estrogen tamoxifen is characterized by a large variability in response, partly due to pharmacokinetic differences. We examined circadian variation in tamoxifen pharmacokinetics in mice and breast cancer patients. Pharmacokinetic analysis was performed in mice, dosed at six different times (24-h period). Tissue samples were used for mRNA expression analysis of drug-metabolizing enzymes. In patients, a cross-over study was performed. During three 24-h periods, after tamoxifen dosing at 8 a.m., 1 p.m., and 8 p.m., for at least 4 weeks, blood samples were collected for pharmacokinetic measurements. Differences in tamoxifen pharmacokinetics between administration times were assessed. The mRNA expression of drug-metabolizing enzymes showed circadian variation in mouse tissues. Tamoxifen exposure seemed to be highest after administration at midnight. In humans, marginal differences were observed in pharmacokinetic parameters between morning and evening administration. Tamoxifen C(max )and area under the curve (AUC)0-8 h were 20 % higher (P < 0.001), and tamoxifen t(max) was shorter (2.1 vs. 8.1 h; P = 0.001), indicating variation in absorption. Systemic exposure (AUC0-24 h) to endoxifen was 15 % higher (P < 0.001) following morning administration. The results suggest that dosing time is of marginal influence on tamoxifen pharmacokinetics. Our study was not designed to detect potential changes in clinical outcome or toxicity, based on a difference in the time of administration. Circadian rhythm may be one of the many determinants of the interpatient and intrapatient pharmacokinetic variability of tamoxifen.

DNA repair in mammalian cells: Direct DNA damage reversal: elegant solutions for nasty problems

The genomic integrity of all living organisms is constantly jeopardized by physical [e.g. ultraviolet (UV) light, ionizing radiation] and chemical (e.g. environmental pollutants, endogenously produced reactive metabolites) agents that damage the DNA. To overcome the deleterious effects of DNA lesions, nature evolved a number of complex multi-protein repair processes with broad, partially overlapping substrate specificity. In marked contrast, cells may use very simple repair systems, referred to as direct DNA damage reversal, that rely on a single protein, remove lesions in a basically error-free manner, show high substrate specificity, and do not involve incision of the sugar-phosphate backbone or base excision. This concise review deals with two types of direct DNA damage reversal: (i) the repair of alkylating damage by alkyltransferases and dioxygenases, and (ii) the repair of UV-induced damage by spore photoproduct lyases and photolyases. (Part of a Multi-author Review).

Structure function analysis of mammalian cryptochromes

Members of the photolyase/cryptochrome family are flavoproteins that share an extraordinary conserved core structure (photolyase homology region, PHR), but the presence of a carboxy-terminal extension is limited to the cryptochromes. Photolyases are DNA-repair enzymes that remove UV-light-induced lesions. Cryptochromes of plants and Drosophila act as circadian photoreceptors, involved in light entrainment of the biological clock. Using knockout mouse models, mammalian cryptochromes (mCRY1 and mCRY2) were identified as essential components of the clock machinery. Within the mammalian transcription-translation feedback loop generating rhythmic gene expression, mCRYs potently inhibit the transcription activity of the CLOCK/BMAL1 heterodimer and protect mPER2 from 26S-protesome-mediated degradation. By analyzing a set of mutant mCRY1 proteins and photolyase/mCRY1 chimeric proteins, we found that the carboxyl terminus has a determinant role in mCRY1 function by harboring distinguished domains involved in nuclear import and interactions with other clock proteins. Moreover, the carboxyl terminus must cross-talk with the PHR to establish full transcription repression capacity in mCRY1. We propose that the presence of the carboxyl terminus in cryptochromes, which varies in sequence composition among mammalian, Drosophila, and plant CRYs, is critical for their different functions and possibly contributed to shape the different architecture and biochemistry of the clock machineries in these organisms.

Base J originally found in kinetoplastida is also a minor constituent of nuclear DNA of Euglena gracilis

We have analyzed DNA of EUGLENA: gracilis for the presence of the unusual minor base beta-D-glucosyl-hydroxymethyluracil or J, thus far only found in kinetoplastid flagellates and in DIPLONEMA: Using antibodies specific for J and post-labeling of DNA digests followed by two-dimensional thin-layer chromatography of labeled nucleotides, we show that approximately 0.2 mole percent of EUGLENA: DNA consists of J, an amount similar to that found in DNA of Trypanosoma brucei. By staining permeabilized EUGLENA: cells with anti-J antibodies, we show that J is rather uniformly distributed in the EUGLENA: nucleus, and does not co-localize to a substantial extent with (GGGTTA)(n) repeats, the putative telomeric repeats of EUGLENA: Hence, most of J in EUGLENA: appears to be non-telomeric. Our results add to the existing evidence for a close phylogenetic relation between kinetoplastids and euglenids.

Interacting molecular loops in the mammalian circadian clock

We show that, in the mouse, the core mechanism for the master circadian clock consists of interacting positive and negative transcription and translation feedback loops. Analysis of Clock/Clock mutant mice, homozygous Period2(Brdm1) mutants, and Cryptochrome-deficient mice reveals substantially altered Bmal1 rhythms, consistent with a dominant role of PERIOD2 in the positive regulation of the Bmal1 loop. In vitro analysis of CRYPTOCHROME inhibition of CLOCK: BMAL1-mediated transcription shows that the inhibition is through direct protein:protein interactions, independent of the PERIOD and TIMELESS proteins. PERIOD2 is a positive regulator of the Bmal1 loop, and CRYPTOCHROMES are the negative regulators of the Period and Cryptochrome cycles.

The Lupinus albus class-III chitinase gene, IF3, is constitutively expressed in vegetative organs and developing seeds

A cDNA fragment encoding a Lupinus albus. L. class-III chitinase, IF3, was isolated, using a cDNA probe from Cucumis sativus L., by in-situ plaque hybridization from a cDNA library constructed in the Uni-ZAP XR vector, with mRNAs isolated from mature lupin leaves. The cDNA had a coding sequence of 293 amino acids including a 27-residue N-terminal signal peptide. A class-III chitinase gene was detected by Southern analysis in the L. albus genome. Western blotting experiments showed that the IF3 protein was constitutively present during seed development and in all the studied vegetative lupin organs (i.e., roots, hypocotyls and leaves) at two growth stages (7- and 20-d-old plants). Accumulation of both the IF3 mRNA and IF3 protein was triggered by salicylic acid treatment as well as by abiotic (UV-C light and wounding) and biotic stress conditions (Colletotrichum gloeosporioides infection). In necrotic leaves, IF3 chitinase mRNA was present at a higher level than that of another mRNA encoding a pathogenesis-related (PR) protein from L. albus (a PR-10) and that of the rRNAs. We suggest that one role of the IF3 chitinase could be in the defense of the plant against fungal infection, though our results do not exclude other functions for this protein.

Control of variant surface glycoprotein gene-expression sites in Trypanosoma brucei

Trypanosoma brucei has 20 similar telomeric-expression sites for variant surface glycoprotein genes. Expression sites appear to be controlled at the level of transcription initiation, resulting in only one site being active at any time. Switching between expression sites occurs at a low rate. To analyse the switching mechanism, we used trypanosomes with two expression sites tagged with two different drug-resistance genes and selected these on agarose plates containing both drugs. Double-resistant clones arose at a low frequency of 10(-7) per cell, but these behaved as if they rapidly switched between the two tagged expression sites and lost double resistance in the absence of selection. Using in situ hybridization we found that only 10% of the double-resistant cells had two fluorescent spots corresponding to transcribed expression sites. Our results suggest that: (i) a double expressor is not a stable intermediate in expression site switching; (ii) expression sites are not independently switched on and off; and (iii) expression sites can be in a 'pre-active' silent state from which they can be readily activated.

Subnuclear localization of the active variant surface glycoprotein gene expression site in Trypanosoma brucei

In Trypanosoma brucei, transcription by RNA polymerase II and 5' capping of messenger RNA are uncoupled: a capped spliced leader is trans spliced to every RNA. This decoupling makes it possible to have protein-coding gene transcription driven by RNA polymerase I. Indeed, indirect evidence suggests that the genes for the major surface glycoproteins, variant surface glycoproteins (VSGs) in bloodstream-form trypanosomes, are transcribed by RNA polymerase I. In a single trypanosome, only one VSG expression site is maximally transcribed at any one time, and it has been speculated that transcription takes place at a unique site within the nucleus, perhaps in the nucleolus. We tested this by using fluorescence in situ hybridization. With probes that cover about 50 kb of the active 221 expression site, we detected nuclear transcripts of this site in a single fluorescent spot, which did not colocalize with the nucleolus. Analysis of marker gene-tagged active expression site DNA by fluorescent DNA in situ hybridization confirmed the absence of association with the nucleolus. Even an active expression site in which the promoter had been replaced by an rDNA promoter did not colocalize with the nulceolus. As expected, marker genes inserted in the rDNA array predominantly colocalize with the nucleolus, whereas the tubulin gene arrays do not. We conclude that transcription of the active VSG expression site does not take place in the nucleolus.

Selection for activation of a new variant surface glycoprotein gene expression site in Trypanosoma brucei can result in deletion of the old one

The African trypanosome Trypanosoma brucei expresses the active variant surface glycoprotein (VSG) gene in a telomeric VSG gene expression site. We have generated trypanosomes with a neomycin resistance gene inserted behind an active VSG gene expression site promoter, and a hygromycin resistance gene behind a silent one. By alternating drug selection, we could select for trypanosomes that had switched between the two marked VSG gene expression sites. Surprisingly, trypanosomes that had activated a new VSG gene expression site had often lost the old one. Using polymerase chain reaction (PCR), we screened large numbers of switched trypanosomes and found that sequences lost invariably included the drug marker near the promoter, as well as the telomeric VSG gene many tens of kilobases away. We postulate that stable activation of a new expression site requires silencing of the old one. If silencing does not occur at a sufficient rate by normal switch-off, stable activation of the new site can only occur if the old site is lost in random deletion events. The fact that we pick up these normally infrequent deletions, indicates that inactivation of the old VSG expression site could be rate limiting during switching in our strain of T. brucei.

Control of VSG gene expression sites in Trypanosoma brucei

Antigenic variation in African trypanosomes continues to be one of the most elaborate and intriguing strategies ever devised by a protozoan parasite to avoid complete destruction by the immune defense of its mammalian host. Here we review some of the recent advances in our understanding of this strategy, concentrating on (unpublished) work from our laboratory.

Isolated teratozoospermia and in vitro fertilization

PURPOSE

To show whether increased amounts of spermatozoa used in insemination of preovulatory oocytes in isolated teratozoospermia according to Kruger's strict criteria gives good fertilization rates.

METHODS

This study was carried out from September 1993 to November 1994 for a total of 77 cycles, with sperm samples classified according to Kruger's strict classification. Group 1 (C; control) included 37 couples with normal sperm morphology (> 14% normal; SC). Group 2 (GP; good prognosis) included 18 couples (morphology, > or = 4 and < or = 14% normal) and group 3 (T; teratozoospermic) included 11 couples, with isolated teratozoospermia in the male partner (morphology, < 4% normal).

RESULTS

No statistically significant difference was seen in the three groups regarding age, duration of infertility, aspirated follicles, oocytes collected, and embryos transferred. There is a statistically significantly difference (P < 0.001) in the number of spermatozoa used in insemination in group 3.

CONCLUSIONS

In conclusion, a morphological classification using strict criteria in the assessment of sperm morphology is still very important, as increasing the sperm number of spermatozoa inseminated per oocyte may improve zona pellucida binding and give better IVF results.

Chronic asthma and rhinitis due to Candida albicans, epidermophyton, and trichophyton

Asthma and rhinitis due to Candida albicans is well known. Trichophyton and Epidermophyton are not usually considered as causal agents for these diseases. During the years 1982 and 1983 all of the cases of chronic asthma or rhinitis exhibiting a positive immediate skin response (greater than or equal to 10 mm) to one of these three antigens were selected for this study (60 asthma and 75 rhinitis). They all went through nasal and bronchial provocation tests with the specific antigen. Late reactions were also registered. A RAST was performed in some of the patients reacting to Candida albicans. Following inhalation challenge with antigens, an immediate response was obtained in 91 cases (asthma 30, rhinitis 51). A dual response was observed in 17 cases of asthma and in 13 cases of rhinitis. A RAST-Candida albicans was done in 64 cases. Results were positive in 52 patients. In 46 cases there was a correlation between the RAST and the provocation tests. Hyposensitization treatment was given to 92 patients. After 2 years of treatment, a good to excellent response could be observed in almost 60% of the treated cases. A rough estimation of the incidence of immediate bronchial and nasal hypersensitivity among patients with chronic asthma and rhinitis to the three yeasts gives the approximate figure of 8% to 10%.