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A molecular clock regulates angiopoietin-like protein 2 expression.

ABSTRACT: Various physiological and behavioral processes exhibit circadian rhythmicity. These rhythms are usually maintained by negative feedback loops of core clock genes, namely, CLOCK, BMAL, PER, and CRY. Recently, dysfunction in the circadian clock has been recognized as an important foundation for the pathophysiology of lifestyle-related diseases, such as obesity, cardiovascular disease, and some cancers. We have reported that angiopoietin-like protein 2 (ANGPTL2) contributes to the pathogenesis of these lifestyle-related diseases by inducing chronic inflammation. However, molecular mechanisms underlying regulation of ANGPTL2 expression are poorly understood. Here, we assess circadian rhythmicity of ANGPTL2 expression in various mouse tissues. We observed that ANGPTL2 rhythmicity was similar to that of the PER2 gene, which is regulated by the CLOCK/BMAL1 complex. Promoter activity of the human ANGPTL2 gene was significantly induced by CLOCK and BMAL1, an induction markedly attenuated by CRY co-expression. We also identified functional E-boxes in the ANGPTL2 promoter and observed occupancy of these sites by endogenous CLOCK in human osteosarcoma cells. Furthermore, Cry-deficient mice exhibited arrhythmic Angptl2 expression. Taken together, these data suggest that periodic expression of ANGPTL2 is regulated by a molecular clock.

SUBMITTER: Kadomatsu T

PROVIDER: S-EPMC3585275 | biostudies-literature | 2013

REPOSITORIES: biostudies-literature

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A molecular clock regulates angiopoietin-like protein 2 expression.

Kadomatsu Tsuyoshi T Uragami Shota S Akashi Makoto M Tsuchiya Yoshiki Y Nakajima Hiroo H Nakashima Yukiko Y Endo Motoyoshi M Miyata Keishi K Terada Kazutoyo K Todo Takeshi T Node Koichi K Oike Yuichi Y

PloS one 20130228 2

Various physiological and behavioral processes exhibit circadian rhythmicity. These rhythms are usually maintained by negative feedback loops of core clock genes, namely, CLOCK, BMAL, PER, and CRY. Recently, dysfunction in the circadian clock has been recognized as an important foundation for the pathophysiology of lifestyle-related diseases, such as obesity, cardiovascular disease, and some cancers. We have reported that angiopoietin-like protein 2 (ANGPTL2) contributes to the pathogenesis of t ...[more]

PMID: 23469106

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Project description:Circadian dysfunction is a common attribute of many neurodegenerative diseases, most of which are associated with neuroinflammation. Circadian rhythm dysfunction has been associated with inflammation in the periphery, but the role of the core clock in neuroinflammation remains poorly understood. Here we demonstrate that Rev-erbα, a nuclear receptor and circadian clock component, is a mediator of microglial activation and neuroinflammation. We observed time-of-day oscillation in microglial immunoreactivity in the hippocampus, which was disrupted in Rev-erbα-/- mice. Rev-erbα deletion caused spontaneous microglial activation in the hippocampus and increased expression of proinflammatory transcripts, as well as secondary astrogliosis. Transcriptomic analysis of hippocampus from Rev-erbα-/- mice revealed a predominant inflammatory phenotype and suggested dysregulated NF-κB signaling. Primary Rev-erbα-/- microglia exhibited proinflammatory phenotypes and increased basal NF-κB activation. Chromatin immunoprecipitation revealed that Rev-erbα physically interacts with the promoter regions of several NF-κB-related genes in primary microglia. Loss of Rev-erbα in primary astrocytes had no effect on basal activation but did potentiate the inflammatory response to lipopolysaccharide (LPS). In vivo, Rev-erbα-/- mice exhibited enhanced hippocampal neuroinflammatory responses to peripheral LPS injection, while pharmacologic activation of Rev-erbs with the small molecule agonist SR9009 suppressed LPS-induced hippocampal neuroinflammation. Rev-erbα deletion influenced neuronal health, as conditioned media from Rev-erbα-deficient primary glial cultures exacerbated oxidative damage in cultured neurons. Rev-erbα-/- mice also exhibited significantly altered cortical resting-state functional connectivity, similar to that observed in neurodegenerative models. Our results reveal Rev-erbα as a pharmacologically accessible link between the circadian clock and neuroinflammation.

Project description:BackgroundSudden cardiac death (SCD) follows a diurnal variation. Data suggest the timing of SCD is influenced by circadian (~24-hour) changes in neurohumoral and cardiomyocyte-specific regulation of the heart's electrical properties. The basic helix-loop-helix transcription factors brain muscle arnt-like1 (BMAL1) and circadian locomotor output control kaput (CLOCK) coordinate the circadian expression of select genes.ObjectiveWe sought to test whether Bmal1 expression in cardiomyocytes contributes to K(+) channel expression and diurnal changes in ventricular repolarization.MethodsWe used transgenic mice that allow for the inducible cardiomyocyte-specific deletion of Bmal1 (iCSΔBmal1(-/-)). We used quantitative polymerase chain reaction, voltage clamping, promoter-reporter bioluminescence assays, and electrocardiographic telemetry.ResultsAlthough several K(+) channel gene transcripts were downregulated in iCSΔBmal1(-/-)mouse hearts, only Kcnh2 exhibited a robust circadian pattern of expression that was disrupted in iCSΔBmal1(-/-) hearts. Kcnh2 underlies the rapidly activating delayed-rectifier K(+) current, and the rapidly activating delayed-rectifier K(+) current recorded from iCSΔBmal1(-/-) ventricular cardiomyocytes was ~50% smaller than control ventricular myocytes. Promoter-reporter assays demonstrated that the human Kcnh2 promoter is transactivated by the coexpression of BMAL1 and CLOCK. Electrocardiographic analysis showed that iCSΔBmal1(-/-) mice developed a prolongation in the heart rate-corrected QT interval during the light (resting) phase. This was secondary to an augmented circadian rhythm in the uncorrected QT interval without a corresponding change in the RR interval.ConclusionThe molecular clock in the heart regulates the circadian expression of Kcnh2, modifies K(+) channel gene expression, and is important for normal ventricular repolarization. Disruption of the cardiomyocyte circadian clock mechanism likely unmasks diurnal changes in ventricular repolarization that could contribute to an increased risk of cardiac arrhythmias/SCD.

Project description:The objective of this study was to determine the effects of angiopoietin-like protein 4 (ANGPTL4) on breast muscle lipid metabolism in broilers. In experiment 1, 36 thirty-five-day-old male Arbor Acres broilers were randomly allocated into 6 treatment groups with 6 birds in a completely randomized design. The broilers were subjected to intravenous injection of His-SUMO-ANGPTL4 at the dose of 0 (injection of normal saline [NS]), 20, 100, 500, 2,500, or 12,500 ng/kg BW, respectively. The results showed that broilers at 30 min after His-SUMO-ANGPTL4 at the level of 12,500 ng/kg BW intravenous injection had higher (P < 0.05) concentrations of triglyceride and non-esterified fatty acid in the serum, higher (P < 0.05) adipose triglyceride lipase and carnitine palmitoyltransferase 1 mRNA expression in the breast muscle, but lower (P < 0.05) lipoprotein lipase (LPL) mRNA expression in the breast muscle. In experiment 2, 18 thirty-five-day-old male Arbor Acres broilers were randomly allocated into 3 treatment groups with 6 birds in a completely randomized design. The broilers were subjected to intravenous injection of NS, His-SUMO, or His-SUMO-ANGPTL4 (12,500 ng/kg BW) in order to rule out the effect of His-SUMO tag. It's confirmed that ANGPTL4 could increase (P < 0.05) concentrations of triglyceride and non-esterified fatty acid in the serum, enhance (P < 0.05) adipose triglyceride lipase mRNA expression in the breast muscle, and decrease (P < 0.05) LPL mRNA expression in the breast muscle. In experiment 3 and 4, co-culture experiments of chicken primary myoblasts and NS, His-SUMO, or His-SUMO-ANGPTL4 (250 pg/mL, physiological dose) were set up to monitor the cytotoxicity of ANGPTL4 and the changes of lipid metabolism-related genes expression. It was found that cell viability was not affected but LPL mRNA expression in chicken primary myoblasts was highly reduced (P < 0.05) by ANGPTL4. In conclusion, ANGPTL4 could promote lipodieresis and inhibit LPL in the breast muscle of broilers.

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A molecular clock regulates angiopoietin-like protein 2 expression.

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A molecular clock regulates angiopoietin-like protein 2 expression.

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