Per2 Expression Research Articles

Influence of colour background on anti-viral activity against viral haemorrhagic septicaemia virus in zebrafish regulated by circadian rhythm signalling pathway.

The influence of colour background on the regulation of behavioural and physiological responses in zebrafish is widely recognized. However, its specific effect on virus infection in zebrafish remains unclear. This study aimed to explore the susceptibility of zebrafish to viral haemorrhagic septicaemia virus (VHSV) infection in relation to background colour, investigate the underlying mechanisms, and elucidate the involvement of key molecules, using proteomic and gene expression analyses. The results revealed that zebrafish housed in a blue tank exhibited higher survival rates and considerably reduced VHSV replication compared to those housed in a yellow tank. Further, up-regulation of apolipoprotein 1 (APOA1) was identified as a crucial shared mechanism associated with survival in zebrafish exposed to VHSV infection and reared in a blue background. The mRNA expression level of bmal1a, a core gene involved in the circadian rhythm, was consistently downregulated in fish from the blue tank compared to fish from the yellow tank, regardless of infection status. Subsequently, zebrafish in the blue tank were exposed to daylight conditions to stimulate per2 and pgc1a expression, aiming to investigate their potential impact on VHSV infection. The validity of these interconnected events, triggered by background colour, involving APOA1 up-regulation, circadian rhythm modulation, and antiviral responses, was confirmed by treatments with hesperetin and cyclosporine A, an activator and inhibitor of apoa1 respectively. Our findings revealed the influence of background colour on the apoa1 expression level, thus establishing the involvement of a novel network through circadian rhythm signalling.

Circadian gene Per3 promotes astroblastoma progression through the P53/BCL2/BAX signalling pathway

The key circadian genes, Period1(Per1), Period2(Per2), and Period3(Per3), constitute the mammalian Period gene family. The abnormal expression of Per1 and Per2 is closely related to tumor development, but there are few reports on Per3 and tumorigenesis. This study was conducted to determine whether the abnormal expression of Per3 could influence the progression of astroblastoma. The results indicated that the expression level of Per3 was increased in astroblastoma cells, and the high expression of Per3 was correlated with the poor overall survival time of glioma patients. The role of Per3 in astroblastoma cells was then investigated using two approaches: interference and overexpression. The interference of Per3 inhibited astroblastoma cell proliferation by inducing the cell cycle at the S phase. The interference of Per3 inhibited the migration and invasion of astroblastoma cells, while promoted the astroblastoma cell apoptosis and the expression of the apoptosis genes Cleaved-CASP3, P53, and BAX. The overexpression of Per3 promoted proliferation by affecting the S phase distribution of the astroblastoma cell cycle. The overexpression of Per3 promoted the migration and invasion of astroblastoma cells, while inhibited the astroblastoma cell apoptosis and the expression of apoptosis genes Cleaved-CASP3, P53, and BAX. RNA-seq analysis showed that the interference of Per3 in astrocytoma cells resulted in significant changes in the expression levels of 764 genes. Among the differentially expressed genes enriched in apoptosis-related pathways, the interference of Per3 resulted in significant upregulation of MARCKSL1 expression, in contrast to significant downregulation of SFRP4, EPB41L3, and GPC5 expression. Taken together, our results suggest that Per3 appears to be a pro-cancer gene by altering the proliferation, migration, invasion, and apoptosis of astroblastoma cells. As a result, the Per3 gene may be a promising therapeutic target in the treatment of astroblastoma.

Quercetin improved hepatic circadian rhythm dysfunction in middle-aged mice fed with vitamin D-deficient diet.

We aimed to determine whether quercetin is capable of improving circadian rhythm and metabolism disorder under vitamin D-deficient condition. Middle-aged mice were randomly divided into four groups, namely, control (CON), vitamin D-deficient diet (VDD), quercetin (Q), and quercetin intervention in vitamin D-deficient diet (VDQ), with a total of 12 weeks' intervention. Mice were sacrificed at zeitgeber time1 (ZT1) and ZT13 time points. At ZT1, circadian locomotor output cycle kaput (CLOCK) protein expression from VDD, Q, and VDQ groups; CRY1 from Q group; and CRY2 from VDD group were significantly lower compared to CON group. The mRNA expression of Sirt1, Bmal1, Clock, Cry1, and Cry2 in VDQ groups, also Bmal1, Clock, and Cry1 from Q group, were significantly decreased compared to CON group. At ZT13, compared to CON group, fasting insulin and homeostasis model assessment-insulin resistance (HOMA-IR) were higher in VDD group; BMAL1 was significantly increased, while CLOCK and CRY1 protein were significantly decreased from VDD group; CLOCK protein from VDQ group was significantly higher compared to CON, VDD, and Q groups, and also, BMAL1 protein expression from VDQ group was elevated compared to CON group. The mRNA expression of Bmal1, Clock, Per2, Cry1, and Cry2 in VDQ groups were significantly increased compared to CON groups. The mRNA expression of Bmal1 from VDQ group was decreased compared to both VDD and Q group. In conclusion, vitamin D-deficient diet resulted in a disordered liver circadian rhythm, and quercetin improved the hepatic circadian desynchronization. Quercetin supplementation might be effective for balancing circadian rhythm under vitamin D-deficient condition.

Tau reduction attenuates autism-like features in Fmr1 knockout mice

BackgroundFragile X syndrome (FXS) is a leading cause of autism spectrum disorder (ASD) and resulted from a loss of the FMR1-encoded fragile X messenger ribonucleoprotein 1 (FMRP) protein due to large CGG repeat expansions in the promoter region of the FMR1 gene. The microtubule-associated protein Tau is a promising target for Tauopathic diseases and our preliminary study found that Tau protein levels were increased in the brain of Fmr1 knockout (KO) mice, a model of FXS. However, whether Tau reduction can prevent autism-like features in Fmr1 KO mice and become a novel strategy for FXS treatment remain unknown.MethodsTau was genetically reduced in Fmr1 KO mice through crossing Fmr1± female mice with Mapt± male mice. The male offspring with different genotypes were subjected to various autism-related behavioral tests, RNA sequencing, and biochemical analysis. Fmr1 KO male mice were treated with Tau-targeting antisense oligonucleotide (ASO) and then subjected to behavioral tests and biochemical analysis.ResultsTau expression was increased in the cortex of Fmr1 KO mice. Genetically reducing Tau prevented social defects, stereotyped and repetitive behavior, and spine abnormality in Fmr1 KO mice. Tau reduction also reversed increased periodic activity and partially rescued Per1 expression reduction in Fmr1 KO mice. Moreover, Tau reduction reversed compromised P38/MAPK signaling in Fmr1 KO mice. Finally, Tau-targeting ASO also effectively alleviated autism-like phenotypes and promoted P38/MAPK signaling in Fmr1 KO mice.LimitationsOur study is limited to male mice, in agreement with the higher incidence of FXS in males than females. Whether Tau reduction also exerts protection in females deserves further scrutiny. Moreover, although Tau reduction rescues impaired P38/MAPK signaling in Fmr1 KO mice, whether this is the responsible molecular mechanism requires further determination.ConclusionOur data indicate that Tau reduction prevents autism-like phenotypes in Fmr1 KO mice. Tau may become a new target for FXS treatment.

Alterations in Per2, Bcl2 gene expression, and oxidative status in aged rats liver after light pulse at night.

The aging process is characterized by circadian rhythm disruption, in physiology and behavior, which could result from weak entrainment. Light is the most potent cue that entrains the central circadian clock, which in turn synchronizes peripheral clocks in animal tissues. Period 2 (Per2) is one of the clock genes that respond to light. Moreover, oxidative stress could entrain the clock. Therefore, the present work aimed to investigate the role of light when applied late at night on the Per2, B cell lymphoma 2 (Bcl2) gene expression, and oxidative status in aged rats. Aged rats were divided into a control group and a group exposed to a 30-min light pulse applied daily during the subjective night at 5 am (ZT 22) for 4weeks. Per2 and Bcl2 gene expression were quantified in liver tissue. To evaluate oxidative status, Glutathione (GSH), nitric oxide (NO), and malondialdehyde (MDA) were estimated. The light pulse reduced the expression levels of Per2 and Bcl2 mRNA. Although it diminished the levels of malondialdehyde (MDA), nitric oxide (NO) levels were elevated and the glutathione (GSH) levels were declined. In conclusion, the light pulse late at night abolished Per2 mRNA circadian rhythm and reduced its expression in the liver of the aged rat. Similarly, it diminished the anti-apoptotic gene expression, Bcl2. Moreover, it might attenuate oxidative stress through the reduction in MDA levels.

Clock gene Per1 regulates rat temporomandibular osteoarthritis through NF-κB pathway: an in vitro and in vivo study

PurposeTemporomandibular joint osteoarthritis (TMJOA) is a common disease that negatively affects the life quality of human beings. Circadian rhythm acts an important role in life activities. However, whether the clock genes are rhythmic expressed in mandibular condylar chondrocytes, or the clock genes have an effect on the progression of TMJOA remains unknown. In this study, we aim to explore expression of clock genes and regulatory mechanism of TMJOA in rat mandibular condylar chondrocytes.MethodsAfter synchronized by dexamethasone, the expression of core clock genes Per1, Per2, Clock, Cry1, Cry2 and Bmal1 and cartilage matrix degrading factor gene Mmp13 were analyzed in mandibular condylar chondrocytes every 4 h with RT-qPCR. The mandibular condylar chondrocytes were stimulated with IL-1β, and expression of Per1, Mmp13, P65 and p-P65 was assessed by RT-qPCR and Western blot. Sh-Per1 lentivirus was used to assess the effect of clock gene Per1 in IL-1β-induced chondrocytes, and expression of Mmp13, P65 and p-P65 was measured. After establishing a rat TMJOA model using unilateral anterior crossbite (UAC), micro-CT, H & E, Alcian Blue & Nuclear Fast Red and Safranin O & Fast Green, cartilage thickness was utilized to assess the damage of cartilage and subchondral bone. Immunohistochemistry of PER1, MMP13 and P65 was performed in condylar sections.ResultsAll core clock genes and Mmp13 were rhythmically expressed. And Mmp13 expression curve was closed in phase and amplitude with Per1. After stimulation with IL-1β, the expression of MMP13, PER1 and P65 and ratio of p-P65/P65 increased in condylar chondrocytes. After Per1 was down-regulated in condylar chondrocytes, the expression of MMP13 and P65 and ratio of p-P65/P65 decreased. Compared with the condyles of Sham group, the bony parameters of UAC group were significantly worse. The thickness of cartilage in UAC group significantly reduced. The modified Mankin scores and the expression of PER1, MMP13 and P65 in cartilage of UAC group significantly increased compared with Sham group.ConclusionCore clock genes and Mmp13 are rhythmic expressed in rat mandibular condylar chondrocytes. PER1 can regulate the expression of MMP13 through NF-κB pathway in IL-1β-induced mandibular condylar chondrocytes.

Diurnal Characteristics of the Orexin System Genes and Its Effects on Pathology at Early Stage in 3xTg-AD Mice.

Orexin and its receptors are closely related to the pathogenesis of Alzheimer's disease (AD). Although the expression of orexin system genes under physiological condition has circadian rhythm, the diurnal characteristics of orexin system genes, and its potential role in the pathogenesis in AD are unknown. In the present study, we hope to elucidate the diurnal characteristics of orexin system genes at the early stage of AD, and to investigate its potential role in the development of AD neuropathology. We firstly detected the mRNA levels of orexin system genes, AD risk genes and core clock genes (CCGs) in hypothalamus and hippocampus in 6-month-old male 3xTg-AD mice and C57BL/6J (wild type, WT) control mice, then analyzed diurnal expression profiles of all genes using JTK_CYCLE algorithm, and did the correlation analysis between expression of orexin system genes and AD risk genes or CCGs. In addition, the expression of β-amyloid protein (Aβ) and phosphorylated tau (p-tau) protein were measured. The results showed that the diurnal mRNA expression profiles of PPO, OX1R, OX2R, Bace2, Bmal1, Per1, Per2 and Cry1 in the hypothalamus, and gene expression of OX1R, OX2R, Bace1, Bmal1, Per1 and Cry2 in the hippocampus in 3xTg-AD mice were different from that in WT mice. Furthermore, there is positive correlation between orexin system genes and AD risk genes or CCGs in the brain in 3xTg-AD mice. In addition, the expression of Aβ and p-tau in hippocampus in 3xTg-AD mice were significantly increased, and the expression of p-tau is higher in night than in day. These results indicate that the abnormal expression profiles of orexin system genes and its interaction with AD risk genes or CCGs might exert important role in the pathogenesis of AD, which will increase the expression of Aβ and p-tau, and accelerate the development of AD.

Diurnal circadian clock gene expression is altered in models of genetic and acquired epilepsy.

Growing evidence demonstrates a relationship between epilepsy and the circadian system. However, relatively little is known about circadian function in disease states, such as epilepsy. This study aimed to characterize brain and peripheral core circadian clock gene expression in rat models of genetic and acquired epilepsy. For the Genetic Absence Epilepsy Rats from Strasbourg (GAERS) study, we used 40 GAERS and 40 non-epileptic control (NEC) rats. For the kainic acid status epilepticus (KASE) study, we used 40 KASE and 40 sham rats. Rats were housed in a 7 am:7 pm light-dark cycle. Hypothalamus, hippocampus, liver, and small intestine samples were collected every 3 h throughout the light period. We then assessed core diurnal clock gene expression of per1, cry1, clock, and bmal1. In the GAERS rats, all tissues exhibited significant changes in clock gene expression (P < 0.05) when compared to NEC. In the KASE rats, there were fewer effects of the epileptic condition in the hypothalamus, hippocampus, or small intestine (P > 0.05) compared with shams. These results indicate marked diurnal disruption to core circadian clock gene expression in rats with both generalized and focal chronic epilepsy. This could contribute to epileptic symptomology and implicate the circadian system as a viable target for future treatments.

Effect of miR-34a on the expression of clock and clock-controlled genes in DLD1 and Lovo human cancer cells with different backgrounds with respect to p53 functionality and 17β-estradiol-mediated regulation.

The small non-coding RNA miR-34a is a p53-regulated miRNA that acts as a tumour suppressor of colorectal cancer (CRC). Oncogenesis is also negatively influenced by deregulation of the circadian system in many types of tumours with various genetic backgrounds. As the clock gene per2 was recently recognized as one of the target genes of miR-34a, we focused on the miR-34a-mediated influence on the circadian oscillator in CRC cell lines DLD1 and LoVo, which differ in their p53 status. Previously, a sex-dependent association between the expression of per2 and that of miR-34a was demonstrated in CRC patients. Therefore, we also investigated the effect of 17β-estradiol (E2) on miR-34a oncostatic functions. miR-34a mimic caused a pronounced inhibition of per2 expression in both cell lines. Moreover, miR-34a mimic significantly inhibited bmal1 expression in LoVo and rev-erbα expression in DLD1 cells and induced clock gene expression in both cell lines. miR-34a mimic caused a pronounced decrease in sirt1 and cyclin D1 expression, which may be related to the inhibition of proliferation observed after mir-34a administration in DLD1 cells. E2 administration inhibited the migration and proliferation of DLD1 cells. E2 and miR-34a, when administered simultaneously, did not potentiate each other's effects. To conclude, miR-34a strongly influences the expression of components of the circadian oscillator without respect to p53 status and exerts its oncostatic effects via inhibition of sirt1 and cyclin D1 mRNA expression. E2 administration inhibits the growth of DLD1 cells; however, this effect seems to be independent of miR-34a-mediated action. With respect to the possible use of miR-34a in cancer treatment, clock genes can be considered as off-target genes, as changes in their expression induced by miR-34a treatment do not contribute to the oncostatic functions of miR-34a. Possible ambiguous oncogenic characteristics should be taken into consideration in future clinical studies focused on miR-34a.

Melatonin alleviates depression-like behaviors and cognitive dysfunction in mice by regulating the circadian rhythm of AQP4 polarization

Depression is a common chronic psychiatric illness, which is resistant to medical treatments. While melatonin may alleviate certain depression symptoms, evidence for its efficacy against core symptoms is lacking. Here, we tested a mechanism whereby melatonin rescues the behavioral outcomes of the chronic unpredictable mild stress (CUMS) mouse model of depression. CUMS mice showed depressive behaviors to tail suspension, open field behavior, and sucrose preference test, and cognitive dysfunction in the Morris water maze. Impairments in these measures were relieved by melatonin treatment. Moreover, CUMS mice had impaired glymphatic function across the sleep-wake cycle due to the astrocytic loss and disturbance of circadian regulation of the polarized expression of aquaporin-4 (AQP4) water channels in perivascular astrocytes. EEG results in CUMS mice showed a reduced total sleep time and non-rapid eye movement (NREM) sleep, due to sleep fragmentation in the light phase. CUMS mice lost the normal rhythmic expressions of circadian proteins Per2, Cry2, Bmal1, Clock, and Per1. However, the melatonin treatment restored glymphatic system function and the polarization of AQP4, while improving sleep structure, and rectifying the abnormal expression of Per2, Bmal1, Clock, and Per1 in CUMS mice. Interestingly, Per2 expression correlated negatively with the polarization of AQP4. Further studies demonstrated that Per2 directed the location of AQP4 expression via interactions with the α-dystrobrevin (Dtna) subunit of AQP4 in primary cultured astrocytes. In conclusion, we report a new mechanism whereby melatonin improves depression outcomes by regulating the expression of the circadian protein Per2, maintaining the circadian rhythm of astrocytic AQP4 polarization, and restoring glymphatic function.

Cloning, tissue distribution, mRNA expression and functional analysis of circadian clock gene per2 from the high-latitude Amur minnow (Phoxinus lagowskii)

Cloning, tissue distribution, mRNA expression and functional analysis of circadian clock gene per2 from the high-latitude Amur minnow (Phoxinus lagowskii)

Influence of constant lighting on the morphofunctional state and rhythmostasis of the liver of rats

BACKGROUND: There are evidences that light pollution, which causes melatonin deficiency and disruption of circadian rhythm, is associated with the development of malignant neoplasms of the liver, non-alcoholic fatty liver disease, biliary cirrhosis, and a number of other pathologies of this organ.&#x0D; AIM: The aim of research was to study the features of chronic influence of constant lighting on lability of morphofunctional state of liver of mature Wistar rats and the structure of circadian rhythms of its parameters.&#x0D; MATERIALS AND METHODS: The study was conducted on 80 rats divided into 2 groups: a control group kept under a fixed light regime (light/dark 12/12 h, lights on at 8:00 and off at 20:00), and an experimental group kept under constant lighting 24 h a day. The duration of the experiment was 3 weeks.&#x0D; RESULTS: Its established that influence of constant light led to an increase in the size of hepatocytes and a decrease in nuclear-cytoplasmic ratio, average ploidy and proportion of binuclear hepatocytes, and also to development of fatty degeneration, a decrease in the expression of Bmal1 and Clock, and an increase in the expression of per2 and p53 in hepatocytes. At the same time, there was a decrease in glycogen content in hepatocytes. Dark deprivation also caused an increase in glucose levels, AST activity, and a decrease in blood levels of total protein and albumin. Constant lighting caused a rearrangement of the circadian rhythms of the area of nuclei, the area of the hepatocyte and nuclear-cytoplasmic ratio, Bmal1, per2, Clock expression, and led to destruction of Ki67 and p53 circadian rhythms in hepatocytes. Under conditions of constant lighting, the circadian rhythms of the content of lipids and glycogen in hepatocytes, ALT activity in the blood, and the content of total and direct bilirubin were also destroyed.&#x0D; CONCLUSIONS: It has been established that constant illumination causes a restructuring of the circadian rhythms of a number of studied parameters against the background of morphological and functional changes, indicating a decrease in the adaptive capacity of the liver.

Ruscogenin timing administration mitigates cerebral ischemia-reperfusion injury through regulating circadian genes and activating Nrf2 pathway

BackgroundRuscogenin (Rus), a steroidal sapogenin extracted from Ophiopogon japonicus (L. f.) Ker-Gawl., has the effect of alleviating cerebral ischemia-reperfusion injury (IRI), acute lung injury. At present, the chronopharmacological effects of Rus are still unknown. PurposeThis study explored the alleviating effect and mechanism of Rus timing administration on mice cerebral IRI. MethodsThe animals in different groups were administrated Rus (10 mg/kg) by gavage at four time points (23:00–01:00, 05:00–07:00, 11:00–13:00, 17:00–19:00) respectively for 3 days. On the 4th day, middle cerebral artery occlusion (MCAO) surgery was operated during 5:00–7:00. Behavioral tests were executed and the brain was collected for infarct volume, qPCR and immunoblot detection. The levels of tumor necrosis factor-α (TNF-α), interleukin 6 (IL-6), interleukin-1beta (IL-1β) and inducible nitric oxide synthase (iNOS) were detected by qPCR. Glutathione (GSH), superoxide dismutase (SOD) activity and malondialdehyde (MDA) content in serum and cerebral cortex were detected. The clock genes were tested by western blot. Based on these results, 17:00–19:00 was selected to administrate Rus for further mechanism study and Nrf2 blocker group was administrated all-trans-retinoic acid (ATRA) at 14:00 for 3 days. ResultsAdministration of Rus reduced cerebral infarcted volume, ameliorated the behavior score and upregulated the mRNA and protein expression of Per1, Bmal1, Clock, Rev-erbα, transcription factor nuclear factor erythroid 2-related factor 2 (Nrf2), heme oxygenase-1 (HO-1), quinone oxidoreductase 1 (NQO1). Administration of Rus during 17:00–19:00 had better preventive effect than other three time points. Combined administration of ATRA blunted the preventive effect of Rus. ConclusionThe preventive effect of Rus is affected by the time of administration, which was regulated by Nrf2 pathway. Taken together, we provide solid evidence to suggest that different administration time point affect the effectiveness of Rus in alleviating IRI.

Maternal developmental history alters transfer of circadian clock genes to offspring in Japanese quail (Coturnix japonica)

Maternal signals shape embryonic development, and in turn post-natal phenotypes. RNA deposition is one such method of maternal signalling and circadian rhythms are one trait thought to be maternally inherited, through this mechanism. These maternal circadian gene transcripts aid development of a functioning circadian system. There is increasing evidence that maternal signals can be modified, depending on prevailing environmental conditions to optimise offspring fitness. However, currently, it is unknown if maternal circadian gene transcripts, and consequently early embryonic gene transcription, are altered by maternal developmental conditions. Here, using avian mothers who experienced either pre-natal corticosterone exposure, and/or post-natal stress as juveniles we were able to determine the effects of the timing of stress on downstream circadian RNA deposition in offspring. We demonstrated that maternal developmental history does indeed affect transfer of offspring circadian genes, but the timing of stress was important. Avian mothers who experienced stress during the first 2 weeks of post-natal life increased maternally deposited transcript levels of two core circadian clock genes, BMAL1 and PER2. These differences in transcript levels were transient and disappeared at the point of embryonic genome transcription. Pre-natal maternal stress alone was found to elicit delayed changes in circadian gene expression. After activation of the embryonic genome, both BMAL1 and PER2 expression were significantly decreased. If both pre-natal and post-natal stress occurred, then initial maternal transcript levels of BMAL1 were significantly increased. Taken together, these results suggest that developmental stress differentially produces persistent transgenerational effects on offspring circadian genes.

Sleep disturbance and dysregulation of circadian clock machinery in sudden sensorineural hearing loss

Background The cochlea contains a robust biological clock associated with auditory function, exhibiting diurnal sensitivity to noise or ototoxicity Objectives We examined the relationship between disrupted circadian rhythm and altered expression of circadian clock genes in patients with sudden sensorineural hearing loss (SSNHL) and explored whether the circadian clock genes serve as prognostic biomarkers. Material and Methods Twelve patients with SSNHL were enrolled study group. Twelve people with normal hearing were enrolled voluntarily for comparison. Audiological evaluation was performed to evaluate hearing thresholds. Korean version of the Pittsburgh Sleep Quality Index Questionnaire was performed to evaluate sleep quality and patterns. Circadian clock genes including for PERI, PER2, PER3, CRYI, CRY2, CLOCK, ARNTL, CSNKIE, and TIMELESS expression in blood were evaluated using real-time quantitative PCR method. Results Compared with healthy controls without hearing loss, most of the circadian clock genes were markedly downregulated, coupled with low sleep quality and disturbing patterns, in patients with SSNHL. Intriguingly, a weak correlation between hearing improvement following steroid treatment and altered levels of circadian clock genes was observed. Conclusions and Significance This study provides an additional basis for the relevance of disrupted circadian rhythm to SSNHL and suggests a possible prognostic biomarker for SSNHL treatment.

Circadian clock disruption in autoimmune thyroiditis.

A vicious cycle between circadian disruption and escalating immune responses has been described in diverse inflammatory disease. The current study aimed to explore the role of circadian clock disruption in autoimmune thyroiditis (AIT). Thirty AIT patients and 30 controls were enrolled and biopsied for thyroid tissues. Alterations of core clock genes expression in AIT thyroid tissues, and its association with serum and tissue inflammatory biomarkers were assessed. For animal studies, C57BL/6J mice administered with porcine thyroglobulin or PBS (as control) combined with adjuvants were sacrificed at four time points to investigate the circadian characteristic of experimental autoimmune thyroiditis (EAT). Light shift (LS) conditions were used to explore the influence of external circadian disturbance on EAT. The expression of clock genes BMAL1 and PER2 was significantly reduced in thyroid tissues from AIT patients and was negatively correlated to levels of thyroid peroxidase antibodies. In mouse models, diurnal fluctuations of proinflammatory cytokines were demonstrated, and further exposing mice to LS led to overproduction of TNF-α, IFN-γ, and anti-thyroglobulin antibodies. Circadian analysis revealed significant oscillations of Bmal1, Clock, Per2, Cry1, Ror, and Rev-erb, which was broadly disturbed in EAT, LS, and EAT + LS groups. This study demonstrates that expression pattern of clock genes was disrupted in AIT thyroid, and chronic circadian disruption may aggravate the inflammatory responses in AIT. Whether maintaining a regular circadian rhythm can alleviate autoimmune thyroid diseases warrants further research.

Circadian Clock Genes Are Regulated by Rhythmic Corticosterone at Physiological Levels in the Rat Hippocampus

Plain Language SummaryAll mammals, including humans, have an internal 24 h biological clock enabling us to synchronize and optimize our physiology to daily life. The 24 h circadian clock of body is localized in neurons of the suprachiasmatic nucleus (SCN) located in the hypothalamus of the brain and is characterized by rhythmic activity of special clock genes. Circadian 24 h rhythms are present throughout the brain, including the hippocampus, where clock genes seem to be important for memory and mood. However, the signaling mechanism controlling circadian clock gene rhythms in the hippocampus is unknown. We hypothesized that oscillations of clock genes in the hippocampus could be driven by a well-established SCN-controlled circadian rhythm in glucocorticoid hormones from the adrenal glands, known as stress hormone or cortisol in humans and corticosterone in rodents. To test this hypothesis, we generated a rat surgical animal model, in which the SCN and adrenal glands were removed and a 24 h exogenous corticosterone rhythm at normal physiological levels was reestablished by use of an implanted programmable infusion pump. Removal of the SCN efficiently abolished clock gene rhythms in the hippocampus; however, reintroducing the natural glucocorticoid rhythm led to reestablishment of 24 h activity rhythms in hippocampal clock genes. Thus, our data suggest that rhythmic hormone release from the adrenal glands drives hippocampal clock gene rhythms and therefore provides a dynamic 24 h hormonal link between the circadian clock of the SCN and circadian function of the hippocampus.

Subcutaneous adipose tissue circadian gene expression: Relationship with insulin sensitivity, obesity, and the effect of weight-reducing dietary intervention

ObjectiveThe circadian rhythms are controlled by the central clock in the hypothalamic suprachiasmatic nuclei and by the peripheral clocks in tissues, including adipose tissue. The adipose tissue circadian clock may be associated with the regulation of insulin action; however, human data are limited. The aim of this study was to analyze the expression of subcutaneous adipose tissue circadian genes as they relate to obesity and insulin sensitivity before and after diet-induced weight loss. MethodsThe study group comprised 38 individuals who were overweight or obese. The individuals completed a 12-wk dietary intervention program. Hyperinsulinemic-euglycemic clamp and subcutaneous adipose tissue biopsy were performed before and after the program. Sixteen normal weight individuals were examined at baseline and served as a control group. ResultsAt baseline, individuals who were overweight/obese had lower adipose tissue expression of NR1D1, NR1D2, DBP, PER1, and PER2 than normal weight individuals. The expression of ARNTL, CLOCK, and CRY did not differ between the groups. A weight-reducing dietary intervention resulted in an increase in the expression of adipose tissue NR1D2 and DBP, which was positively related to insulin sensitivity both before (in the entire study group and in the subgroup of overweight/obese individuals) and after the dietary intervention. ConclusionsAdipose tissue circadian gene expression is decreased in obesity and this decrease may be partially reversed by dietary intervention. Among circadian genes, NR1D2 and DBP seem to be specifically associated with insulin action.

Environmental concentrations of tire rubber-derived 6PPD-quinone alter CNS function in zebrafish larvae

N-(1,3-Dimethylbutyl)-N′-phenyl-p-phenylenediamine quinone (6PPD-quinone) is a degradation product of 6PPD, an antioxidant widely used in rubber tires. 6PPD-quinone enters aquatic ecosystems through urban stormwater runoff and has been identified as the chemical behind the urban runoff mortality syndrome in coho salmon. However, the available data suggest that the acute effects of 6PPD-quinone are restricted to a few salmonid species and that the environmental levels of this chemical should be safe for most fish. In this study, larvae of a “tolerant” fish species, Danio rerio, were exposed to three environmental concentrations of 6PPD-quinone for only 24 h, and the effects on exploratory behavior, escape response, nonassociative learning (habituation), neurotransmitter profile, wake/sleep cycle, circadian rhythm, heart rate and oxygen consumption rate were analyzed. Exposure to the two lowest concentrations of 6PPD-quinone resulted in altered exploratory behavior and habituation, an effect consistent with some of the observed changes in the neurotransmitter profile, including increased levels of acetylcholine, norepinephrine, epinephrine and serotonin. Moreover, exposure to the highest concentration tested altered the wake/sleep cycle and the expression of per1a, per3 and cry3a, circadian clock genes involved in the negative feedback loop. Finally, a positive chronotropic effect of 6PPD-quinone was observed in the hearts of the exposed fish. The results of this study emphasize the need for further studies analyzing the effects of 6PPD-quinone in “tolerant” fish species.

Absence of a molecular circadian clock in the preimplantation embryo is a conserved characteristic in the mammal.

It is not known when a functional circadian clock is established in the developing embryo. Lack of expression of key genes involved in the clock mechanism is indicative that a functional circadian clock mechanism is absent in the mammalian preimplantation embryo through the blastocyst stage of development. An embryonic circadian clock could conceivably organize cellular and developmental events temporally and in synchrony with other circadian rhythms in the mother. The hypothesis that a functional molecular clock exists in the preimplantation bovine, pig, human, and mouse embryo was tested by using publicly available RNAseq datasets to examine developmental changes in expression of the core genes responsible for the circadian clock - CLOCK, ARNTL, PER1, PER2, CRY1, and CRY2. In general, the transcript abundance of each gene decreased as development advanced to the blastocyst stage. The most notable exception was for CRY2, where transcript abundance was low and constant from the two-cell or four-cell to the blastocyst stage. Developmental patterns were generally the same for all species although there were some species-specific patterns such as an absence of PER1 expression in the pig, an increase in ARNTL expression at the four-cell stage in human, and an increase in expression of Clock and Per1 from the zygote to two-cell stage in the mouse. Analysis of intronic reads (indicative of embryonic transcription) for bovine embryos indicated an absence of embryonic transcription. Immunoreactive CRY1 was not detected in the bovine blastocyst. Results indicate that the preimplantation mammalian embryo lacks a functional intrinsic clock although specific components of the clock mechanism could conceivably play a role in other functions in the embryo.