Changes In Circadian Expression Research Articles

Reduced salt intake partially restores the circadian rhythm of bladder clock genes in Dahl salt-sensitive rats

AimsTo examine the circadian expression changes in bladder clock genes in Dahl salt-sensitive rats following high salt intake. Main methodsEighteen rats were divided into three groups: the high-salt diet group (HS group), the normal-salt diet group (NS group), and the salt-load interruption group (from a 4 % salt diet to a normal diet; salt-load interruption group [SI group]). Each rat was placed in an individual metabolic cage for 24 h twice weekly. Water intake, urine production, voiding frequency, and voided volume per micturition were recorded. Furthermore, 108 control rats were prepared. Bladders were harvested every 4 h at six time points. Furthermore, the mRNA expression of clock genes and mechanosensors was analyzed. Key findingsIn the HS group, the bladder clock genes showed lower mRNA levels than in the NS group. The amplitude of circadian expression changes in bladder clock genes in the HS group was lower than that in the NS group. However, after changing from a 4 % salt diet to a normal diet, the waveforms of the clock gene expression in the SI group were closer to those of the NS group. The 24-h water intake and urinary volume of the SI group decreased to levels comparable to those of the NS group. SignificanceReduced salt intake partially restored the circadian rhythms of bladder clock genes.

The Human and Mouse Enteric Nervous System at Single-Cell Resolution

The enteric nervous system (ENS) coordinates diverse functions in the intestine but has eluded comprehensive molecular characterization because of the rarity and diversity of cells. Here we develop two methods to profile the ENS of adult mice and humans at single-cell resolution: RAISIN RNA-seq for profiling intact nuclei with ribosome-bound mRNA and MIRACL-seq for label-free enrichment of rare cell types by droplet-based profiling. The 1,187,535 nuclei in our mouse atlas include 5,068 neurons from the ileum and colon, revealing extraordinary neuron diversity. We highlight circadian expression changes in enteric neurons, show that disease-related genes are dysregulated with aging, and identify differences between the ileum and proximal/distal colon. In humans, we profile 436,202 nuclei, recovering 1,445 neurons, and identify conserved and species-specific transcriptional programs and putative neuro-epithelial, neuro-stromal, and neuro-immune interactions. The human ENS expresses risk genes for neuropathic, inflammatory, and extra-intestinal diseases, suggesting neuronal contributions to disease.

Novel Evidence that Purinergic Signaling - Nlrp3 Inflammasome Axis Regulates Circadian Rhythm of Hematopoietic Stem/Progenitor Cells Circulation in Peripheral Blood

We found that circadian changes in ATP level in peripheral blood (PB) activate the Nlrp3 inflammasome, which triggers diurnal release of hematopoietic stem/progenitor cells (HSPCs) from murine bone marrow (BM) into PB. Consistent with this finding, we observed circadian changes in expression of mRNA for Nlrp3 inflammasome-related genes, including Nlrp3, caspase 1, IL-1β, IL-18, gasdermin (GSDMD), HMGB1, and S100A9. Circadian release of HSPCs from BM into PB as well as expression of Nlrp3-associated genes was decreased in mice in which pannexin 1-mediated secretion of ATP was inhibited by the blocking peptide 10Panx and in animals exposed to the specific small-molecule inhibitor of the Nlrp3 inflammasome MCC950. In addition to HSPCs, a similar decrease in diurnal cell counts was observed for mesenchymal stromal cells (MSCs), endothelial progenitor cells (EPCs), and very small embryonic-like stem cells (VSELs). These results shed more light on the complexity of circadian regulation of HSPC release into PB, which is coordinated in a purinergic signaling-, innate immunity-dependent manner. Moreover, in addition to circadian changes in expression of the Nlrp3 inflammasome we also observed diurnal changes in expression of other inflammasomes, including Aim2, Nrp1a, and Nlrp1b.

Circannual and circadian rhythms of hypothalamic DNA methyltransferase and histone deacetylase expression in male Siberian hamsters (Phodopus sungorus)

Precise timing of gene transcription is a fundamental component of many biological rhythms. DNA methylation and histone acetylation are two epigenetic modifications that can affect the probability of gene transcription and RNA expression. Enzymes involved in DNA methylation (dnmts) have been shown to exhibit photoperiodic rhythms in expression in the hypothalamus, which coincide with hypothalamic expression of deiodinase type III (dio3), a gene involved in the photoperiodic regulation of reproduction. It is currently unknown whether enzymes involved in histone deacetylation (hdacs) also vary in response to photoperiod, nor have seasonal changes in the circadian waveforms of methylation and/or acetylation enzymes been examined. The present work documents circadian and photoperiodic changes in dnmts and hdacs in whole hypothalamic dissections obtained from male Siberian hamsters (Phodopus sungorus) after 5–6weeks of exposure to SD. The data indicate that short days (SD) markedly inhibit dnmt3a expression, and that SD inhibition of dnmt3a was evident regardless of the alignment of circadian waveforms. Among hdacs, photoperiodic and circadian changes in expression were only observed in hdac4 expression. Recurrent temporal waveforms in epigenetic enzyme expression may provide molecular inputs to the timing systems that reprogram RNA expression to generate daily and annual phenotypic plasticity.

The calcineurin-NFAT pathway controls activity-dependent circadian gene expression in slow skeletal muscle.

ObjectivePhysical activity and circadian rhythms are well-established determinants of human health and disease, but the relationship between muscle activity and the circadian regulation of muscle genes is a relatively new area of research. It is unknown whether muscle activity and muscle clock rhythms are coupled together, nor whether activity rhythms can drive circadian gene expression in skeletal muscle.MethodsWe compared the circadian transcriptomes of two mouse hindlimb muscles with vastly different circadian activity patterns, the continuously active slow soleus and the sporadically active fast tibialis anterior, in the presence or absence of a functional skeletal muscle clock (skeletal muscle-specific Bmal1 KO). In addition, we compared the effect of denervation on muscle circadian gene expression.ResultsWe found that different skeletal muscles exhibit major differences in their circadian transcriptomes, yet core clock gene oscillations were essentially identical in fast and slow muscles. Furthermore, denervation caused relatively minor changes in circadian expression of most core clock genes, yet major differences in expression level, phase and amplitude of many muscle circadian genes.ConclusionsWe report that activity controls the oscillation of around 15% of skeletal muscle circadian genes independently of the core muscle clock, and we have identified the Ca2+-dependent calcineurin-NFAT pathway as an important mediator of activity-dependent circadian gene expression, showing that circadian locomotor activity rhythms drive circadian rhythms of NFAT nuclear translocation and target gene expression.

Altered Circadian Expression of Cytokines and Cytolytic Factors in Splenic Natural Killer Cells of Per1−/− Mutant Mice

Circadian systems regulate the immune system by various molecular and physiological pathways. Disruption to the circadian temporality of these pathways is associated with disease formation and progression. Circadian clock genes have been shown to regulate pathways involved in cellular proliferation, apoptosis, and DNA damage response, as aberrant rhythms in these genes are associated with various diseases. However, there is growing evidence that specific circadian genes differentially regulate functional pathways of immunocompetent cells. To extend our previous findings of the role of Period 2 in regulating splenocyte rhythms, we report that mice carrying a mutation in the Period 1 gene (Per1(-/-) mice), involved in the negative limb of the molecular clock, display significantly altered rhythms of cytokine (eg, interferon-γ) and cytolytic factors (eg, perforin and granzyme B) in splenic natural killer (NK) cells. Altered rhythms of NK cell immune factors were accompanied by changes in circadian expression of circadian clock genes, Bmal1 and Per2. In addition, Per1(-/-) circadian running-wheel activity rhythms remained rhythmic during constant darkness, although with a shortened free-running circadian period, suggesting primary involvement of peripheral molecular clocks. These findings indicate that the Per1 gene through NK cellular clocks modulates immune pathways.

Effect of cadmium on 24-hour pattern in expression of redox enzyme and clock genes in rat medial basal hypothalamus

The effect of cadmium (Cd) in the brain has been attributed to an increase in reactive oxygen species in cells, particularly when high amounts of the metal are given. In this study we examined the effect of a low dose of Cd (7.5 microg/day) on 24-h changes in expression of redox pathway enzyme and circadian genes in rat medial basal hypothalamus (MBH). Rats receiving CdCl(2) (5 ppm in drinking water) or tap water for 1 month were killed at six different time intervals throughout a 24 h cycle. MBH mRNA levels were measured by real-time PCR analysis. In CdCl(2) treated rats a disruption of 24-h pattern of hypothalamic gene expression of nitric oxide synthase (NOS)-1 and -2, heme oxygenase (HO)-1 and -2, Mn- superoxide dismutase (SOD), catalase, glutathione peroxidase and glutathione reductase was detectable. Mean levels of MBH mRNA for HO-2, Mn-SOD and catalase augmented after Cd intake, whereas those of NOS-2 decreased. After CdCl(2) intake rats the 24-h pattern of clock gene expression in MBH seen in controls was significantly suppressed (Bmal1) or changed in phase (Per1, Per2, Cry2) while in the case of Clock significant 24-h variations were induced. The results are compatible with the view that a low amount of Cd given in tap water brought about significant changes in circadian expression of redox enzyme and clock genes in rat MBH.

Alterations of circadian expressions of clock genes in Dahl salt-sensitive rats fed a high-salt diet.

In mammals, behavioral and physiologic processes display 24-hour rhythms that are regulated by a circadian system consisting of central and peripheral oscillators. Because various cardiovascular functions show diurnal variations and abnormal patterns of circadian blood pressure variation carry a high risk of cardiovascular complications, we investigated whether the expression of clock genes is altered in an animal model of hypertension. In Dahl salt-sensitive rats fed a high-salt (4% NaCl) diet for 6 weeks (DS-H), radiotelemetry monitoring showed increased amplitude of circadian variations in blood pressure. The ratio of heart weight to body weight and the ratio of kidney weight to body weight were higher in DS-H. Echocardiographic data showed that the wall thickness of the left ventricle was greater in DS-H. Northern blot analysis and single cosinor analysis revealed that the amplitudes of circadian expression changes of the clock genes (mPer2, Bmal1, and dbp) in the heart, liver, and kidney were significantly decreased in DS-H rats compared with a normal-salt-diet group, except for Bmal1 in the liver. The circadian expression changes of plasminogen activator inhibitor-1, a clock-regulated gene, were attenuated in the hearts of DS-H. The present results demonstrate that DS-H show altered circadian expression of peripheral clock genes. Detailed analyses of the relation between circadian expression of clock genes and blood pressure regulation might reveal a role for chronologic therapy of cardiovascular disease.