Increased vascular senescence and impaired endothelial progenitor cell function mediated by mutation of circadian gene Per2

Exercise Reduces Glucose Intolerance, Cardiac Inflammation and Adipose Tissue Dysfunction in Psammomys obesus Exposed to Short Photoperiod and High Energy Diet

Circadian disruption causes glucose intolerance, cardiac fibrosis, and adipocyte dysfunction in sand rats (Psammomys obesus). Exercise intervention can improve glucose metabolism, insulin sensitivity, adipose tissue function and protect against inflammation. We investigated the influence of exercise on male P. obesus exposed to a short photoperiod (5 h light:19 h dark) and high-energy diet. Exercise reduced glucose intolerance. Exercise reduced cardiac expression of inflammatory marker Ccl2 and Bax:Bcl2 apoptosis ratio. Exercise increased heart:body weight ratio and hypertrophy marker Myh7:Myh6, yet reduced Gata4 expression. No phenotypic changes were observed in perivascular fibrosis and myocyte area. Exercise reduced visceral adipose expression of inflammatory transcription factor Rela, adipogenesis marker Ppard and browning marker Ppargc1a, but visceral adipocyte size was unaffected. Conversely, exercise reduced subcutaneous adipocyte size but did not affect any molecular mediators. Exercise increased ZT7 Bmal1 and Per2 in the suprachiasmatic nucleus and subcutaneous Per2. Our study provides new molecular insights and histological assessments on the effect of exercise on cardiac inflammation, adipose tissue dysfunction and circadian gene expression in P. obesus exposed to short photoperiod and high-energy diet. These findings have implications for the protective benefits of exercise for shift workers in order to reduce the risk of diabetes and cardiovascular disease.

Cellular senescence and metabolic reprogramming: Unraveling the intricate crosstalk in the immunosuppressive tumor microenvironment

The intrinsic oncogenic mechanisms and properties of the tumor microenvironment (TME) have been extensively investigated. Primary features of the TME include metabolic reprogramming, hypoxia, chronic inflammation, and tumor immunosuppression. Previous studies suggest that senescence-associated secretory phenotypes that mediate intercellular information exchange play a role in the dynamic evolution of the TME. Specifically, hypoxic adaptation, metabolic dysregulation, and phenotypic shifts in immune cells regulated by cellular senescence synergistically contribute to the development of an immunosuppressive microenvironment and chronic inflammation, thereby promoting the progression of tumor events. This review provides a comprehensive summary of the processes by which cellular senescence regulates the dynamic evolution of the tumor-adapted TME, with focus on the complex mechanisms underlying the relationship between senescence and changes in the biological functions of tumor cells. The available findings suggest that components of the TME collectively contribute to the progression of tumor events. The potential applications and challenges of targeted cellular senescence-based and combination therapies in clinical settings are further discussed within the context of advancing cellular senescence-related research.

Circadian and Diurnal Regulation of Cerebral Blood Flow

Circadian and diurnal variation in cerebral blood flow directly contributes to the diurnal variation in the risk of stroke, either through factors that trigger stroke or due to impaired compensatory mechanisms. Cerebral blood flow results from the integration of systemic hemodynamics, including heart rate, cardiac output, and blood pressure, with cerebrovascular regulatory mechanisms, including cerebrovascular reactivity, autoregulation, and neurovascular coupling. We review the evidence for the circadian and diurnal variation in each of these mechanisms and their integration, from the detailed evidence for mechanisms underlying the nocturnal nadir and morning surge in blood pressure to identifying limited available evidence for circadian and diurnal variation in cerebrovascular compensatory mechanisms. We, thus, identify key systemic hemodynamic factors related to the diurnal variation in the risk of stroke but particularly identify the need for further research focused on cerebrovascular regulatory mechanisms.

Circadian Influences on Myocardial Ischemia-Reperfusion Injury and Heart Failure

The impact of circadian rhythms on cardiovascular function and disease development is well established, with numerous studies in genetically modified animals emphasizing the circadian molecular clock's significance in the pathogenesis and pathophysiology of myocardial ischemia and heart failure progression. However, translational preclinical studies targeting the heart's circadian biology are just now emerging and are leading to the development of a novel field of medicine termed circadian medicine. In this review, we explore circadian molecular mechanisms and novel therapies, including (1) intense light, (2) small molecules modulating the circadian mechanism, and (3) chronotherapies such as cardiovascular drugs and meal timings. These promise significant clinical translation in circadian medicine for cardiovascular disease. (4) Additionally, we address the differential functioning of the circadian mechanism in males versus females, emphasizing the consideration of biological sex, gender, and aging in circadian therapies for cardiovascular disease.

Circadian Effects on Vascular Immunopathologies

Circadian rhythms exert a profound impact on most aspects of mammalian physiology, including the immune and cardiovascular systems. Leukocytes engage in time-of-day-dependent interactions with the vasculature, facilitating the emigration to and the immune surveillance of tissues. This review provides an overview of circadian control of immune-vascular interactions in both the steady state and cardiovascular diseases such as atherosclerosis and infarction. Circadian rhythms impact both the immune and vascular facets of these interactions, primarily through the regulation of chemoattractant and adhesion molecules on immune and endothelial cells. Misaligned light conditions disrupt this rhythm, generally exacerbating atherosclerosis and infarction. In cardiovascular diseases, distinct circadian clock genes, while functioning as part of an integrated circadian system, can have proinflammatory or anti-inflammatory effects on these immune-vascular interactions. Here, we discuss the mechanisms and relevance of circadian rhythms in vascular immunopathologies.

Circadian disturbance induces erectile dysfunction by impairing endothelial function

In order to explore the impact of circadian disturbance on erectile function, we randomly divided 24 adult male rats into groups of control (light on at 8:00 a.m. and off at 8:00 p.m.), dark/dark (DD; constant dark), light/light (LL; constant light), and shift dark/light (DL; light off at 8:00 a.m. and on at 8:00 p.m.). Four weeks later, erectile function was measured and corpora cavernosa were harvested for analysis. The maximum intracavernous pressure (mICP) and mICP/mean arterial pressure (MAP) ratio in the DD, LL, and DL groups were significantly lower than that in the control group. The LL and DL groups showed significantly attenuated endothelial nitric oxide synthase (eNOS), while DD, LL, and DL showed reduced neuronal nitric oxide synthase (nNOS) at both mRNA and protein levels. The production of nitric oxide (NO) and cyclic guanosine monophosphate (cGMP) was inhibited by altered light/dark cycles to varying degrees. Circadian disturbance impaired endothelial function and contributed to erectile dysfunction. For the core circadian elements, mRNA expression of circadian locomotor output cycles kaput ( Clock ) and brain/muscle aryl-hydrocarbon receptor nuclear translocator-like protein 1 ( Bmal1 ) was elevated in the DL group, but their protein expression was not significantly changed. DD, LL, and DL increased period 1 ( Per1 ) and Per3 levels, while LL and DL increased PER1 levels. No significant difference was found for Per2 levels, and PER2 and PER3 concentrations were not significantly changed. Moreover, LL and DL significantly increased cryptochrome-1 (CRY1) and CRY2 at both mRNA and protein levels. The altered light/dark rat model showed that circadian disturbance contributed to erectile dysfunction probably by impairing endothelial function. Meanwhile, the core circadian elements were detected in the corpora cavernosa, but these were disrupted. However, which circadian element regulates erectile function and how it works need further analysis.

Cardiac cell senescence: molecular mechanisms, key proteins and therapeutic targets

Cardiac aging, particularly cardiac cell senescence, is a natural process that occurs as we age. Heart function gradually declines in old age, leading to continuous heart failure, even in people without a prior history of heart disease. To address this issue and improve cardiac cell function, it is crucial to investigate the molecular mechanisms underlying cardiac senescence. This review summarizes the main mechanisms and key proteins involved in cardiac cell senescence. This review further discusses the molecular modulators of cellular senescence in aging hearts. Furthermore, the discussion will encompass comprehensive descriptions of the key drugs, modes of action and potential targets for intervention in cardiac senescence. By offering a fresh perspective and comprehensive insights into the molecular mechanisms of cardiac senescence, this review seeks to provide a fresh perspective and important theoretical foundations for the development of drugs targeting this condition.

Circadian Disruption and the Molecular Clock in Atherosclerosis and Hypertension

Circadian rhythms are crucial for maintaining vascular function and disruption of these rhythms are associated with negative health outcomes including cardiovascular disease and hypertension. Circadian rhythms are regulated by the central clock within the suprachiasmatic nucleus of the hypothalamus and peripheral clocks located in nearly every cell type in the body, including cells within the heart and vasculature. In this review, we summarize the most recent preclinical and clinical research linking circadian disruption, with a focus on molecular circadian clock mechanisms, in atherosclerosis and hypertension. Furthermore, we provide insight into potential future chronotherapeutics for hypertension and vascular disease. A better understanding of the influence of daily rhythms in behaviour, such as sleep/wake cycles, feeding, and physical activity, as well as the endogenous circadian system on cardiovascular risk will help pave the way for targeted approaches in atherosclerosis and hypertension treatment/prevention.

The Role of the Circadian Rhythm in Dyslipidaemia and Vascular Inflammation Leading to Atherosclerosis

Cardiovascular diseases (CVD) are among the leading causes of death worldwide. Many lines of evidence suggest that the disturbances in circadian rhythm are responsible for the development of CVDs; however, circadian misalignment is not yet a treatable trait in clinical practice. The circadian rhythm is controlled by the central clock located in the suprachiasmatic nucleus and clock genes (molecular clock) located in all cells. Dyslipidaemia and vascular inflammation are two hallmarks of atherosclerosis and numerous experimental studies conclude that they are under direct influence by both central and molecular clocks. This review will summarise the results of experimental studies on lipid metabolism, vascular inflammation and circadian rhythm, and translate them into the pathophysiology of atherosclerosis and cardiovascular disease. We discuss the effect of time-respected administration of medications in cardiovascular medicine. We review the evidence on the effect of bright light and melatonin on cardiovascular health, lipid metabolism and vascular inflammation. Finally, we suggest an agenda for future research and recommend on clinical practice.

Circadian rhythms of risk factors and management in atherosclerotic and hypertensive vascular disease: Modern chronobiological perspectives of an ancient disease

Atherosclerosis, a chronic inflammatory disease of the arteries that appears to have been as prevalent in ancient as in modern civilizations, is predisposing to life-threatening and life-ending cardiac and vascular complications, such as myocardial and cerebral infarctions. The pathogenesis of atherosclerosis involves intima plaque buildup caused by vascular endothelial dysfunction, cholesterol deposition, smooth muscle proliferation, inflammatory cell infiltration and connective tissue accumulation. Hypertension is an independent and controllable risk factor for atherosclerotic cardiovascular disease (CVD). Conversely, atherosclerosis hardens the arterial wall and raises arterial blood pressure. Many CVD patients experience both atherosclerosis and hypertension and are prescribed medications to concurrently mitigate the two disease conditions. A substantial number of publications document that many pathophysiological changes caused by atherosclerosis and hypertension occur in a manner dependent upon circadian clocks or clock gene products. This article reviews progress in the research of circadian regulation of vascular cell function, inflammation, hemostasis and atherothrombosis. In particular, it delineates the relationship of circadian organization with signal transduction and activation of the renin-angiotensin-aldosterone system as well as disturbance of the sleep/wake circadian rhythm, as exemplified by shift work, metabolic syndromes and obstructive sleep apnea (OSA), as promoters and mechanisms of atherogenesis and risk for non-fatal and fatal CVD outcomes. This article additionally updates advances in the clinical management of key biological processes of atherosclerosis to optimally achieve suppression of atherogenesis through chronotherapeutic control of atherogenic/hypertensive pathological sequelae.

Role of sympathetic pathway in light-phase time-restricted feeding-induced blood pressure circadian rhythm alteration

Disruption of blood pressure (BP) circadian rhythm, independent of hypertension, is emerging as an index for future target organ damage and is associated with a higher risk of cardiovascular events. Previous studies showed that changing food availability time alters BP rhythm in several mammalian species. However, the underlying mechanisms remain largely unknown. To address this, the current study specifically investigates (1) the relationship between rhythms of food intake and BP in wild-type mice; (2) effects of light-phase time-restricted feeding (TRF, food only available during light-phase) on BP circadian rhythm in wild-type and diabetic db/db mice; (3) the roles of the autonomic system and clock gene in light-phase TRF induced changes in BP circadian rhythm. Food intake and BP of C57BL/6J and db/db mice were simultaneously and continuously recorded using BioDAQ and telemetry systems under ad libitum or light-phase TRF. Per2 protein daily oscillation was recorded in vivo by IVIS spectrum in mPer2 Luc mice. Autonomic nerve activity was evaluated by heart rate variability, baroreflex, urinary norepinephrine (NE) and epinephrine (Epi) excretion, and mRNA expressions of catecholamines biosynthetic and catabolic enzymes, and alpha-adrenergic receptors in mesenteric resistance arteries. We found that in wild-type mice, the BP level was correlated with the food intake temporally across the 24 h. Reversing the feeding time by imposing light-phase TRF resulted in reverse or inverted BP dipping. Interestingly, the net changes in food intake were correlated with the net alteration in BP temporally under light-phase TRF. In db/db mice, light-phase TRF worsened the existing non-dipping BP. The food intake and BP circadian rhythm changes were associated with alterations in Per2 protein daily oscillation and the time-of-day variations in heart rate variability, baroreflex, and urinary excretion of NE and Epi, and increased mRNA expression of Slc6a2 (encoding NE transporter) and Adra1d (encoding alpha-adrenergic receptor 1d) in the mesenteric resistance arteries, indicating the sympathetic nervous system (SNS) was modulated after light-phase TRF. Collectively, our results demonstrated that light-phase TRF results in reverse dipping of BP in wild-type and diabetic db/db mice and revealed the potential role of the sympathetic pathway in light-phase TRF-induced BP circadian rhythm alteration.

New insight into ischemic stroke: Circadian rhythm in post-stroke angiogenesis

The circadian rhythm is an endogenous clock system that coordinates and optimizes various physiological and pathophysiological processes, which accord with the master and the peripheral clock. Increasing evidence indicates that endogenous circadian rhythm disruption is involved in the lesion volume and recovery of ischemic stroke. As a critical recovery mechanism in post-stroke, angiogenesis reestablishes the regional blood supply and enhances cognitive and behavioral abilities, which is mainly composed of the following processes: endothelial cell proliferation, migration, and pericyte recruitment. The available evidence revealed that the circadian governs many aspects of angiogenesis. This study reviews the mechanism by which circadian rhythms regulate the process of angiogenesis and its contribution to functional recovery in post-stroke at the aspects of the molecular level. A comprehensive understanding of the circadian clock regulating angiogenesis in post-stroke is expected to develop new strategies for the treatment of cerebral infarction.

Age and Chronodisruption in Mouse Heart: Effect of the NLRP3 Inflammasome and Melatonin Therapy

Age and age-dependent inflammation are two main risk factors for cardiovascular diseases. Aging can also affect clock gene-related impairments such as chronodisruption and has been linked to a decline in melatonin synthesis and aggravation of the NF-κB/NLRP3 innate immune response known as inflammaging. The molecular drivers of these mechanisms remain unknown. This study investigated the impact of aging and NLRP3 expression on the cardiac circadian system, and the actions of melatonin as a potential therapy to restore daily rhythms by mitigating inflammaging. We analyzed the circadian expression and rhythmicity of clock genes in heart tissue of wild-type and NLRP3-knockout mice at 3, 12, and 24 months of age, with and without melatonin treatment. Our results support that aging, NLRP3 inflammasome, and melatonin affected the cardiac clock genes expression, except for Rev-erbα, which was not influenced by genotype. Aging caused small phase changes in Clock, loss of rhythmicity in Per2 and Rorα, and mesor dampening of Clock, Bmal1, and Per2. NLRP3 inflammasome influenced the acrophase of Clock, Per2, and Rorα. Melatonin restored the acrophase and the rhythm of clock genes affected by age or NLRP3 activation. The administration of melatonin re-established murine cardiac homeostasis by reversing age-associated chronodisruption. Altogether, these results highlight new findings about the effects aging and NLRP3 inflammasome have on clock genes in cardiac tissue, pointing to continuous melatonin as a promising therapy to placate inflammaging and restore circadian rhythm in heart muscle. Additionally, light microscopy analysis showed age-related morphological impairments in cardiomyocytes, which were less severe in mice lacking NLRP3. Melatonin supplementation preserved the structure of cardiac muscle fibers in all experimental groups.

A wrinkle in time: circadian biology in pulmonary vascular health and disease

An often overlooked element of pulmonary vascular disease is time. Cellular responses to time, which are regulated directly by the core circadian clock, have only recently been elucidated. Despite an extensive collection of data regarding the role of rhythmic contribution to disease pathogenesis (such as systemic hypertension, coronary artery, and renal disease), the roles of key circadian transcription factors in pulmonary hypertension remain understudied. This is despite a large degree of overlap in the pulmonary hypertension and circadian rhythm fields, not only including shared signaling pathways, but also cell-specific effects of the core clock that are known to result in both protective and adverse lung vessel changes. Therefore, the goal of this review is to summarize the current dialogue regarding common pathways in circadian biology, with a specific emphasis on its implications in the progression of pulmonary hypertension. In this work, we emphasize specific proteins involved in the regulation of the core molecular clock while noting the circadian cell-specific changes relevant to vascular remodeling. Finally, we apply this knowledge to the optimization of medical therapy, with a focus on sleep hygiene and the role of chronopharmacology in patients with this disease. In dissecting the unique relationship between time and cellular biology, we aim to provide valuable insight into the practical implications of considering time as a therapeutic variable. Armed with this information, physicians will be positioned to more efficiently use the full four dimensions of patient care, resulting in improved morbidity and mortality of pulmonary hypertension patients.

Circadian Rhythm Effects on the Molecular Regulation of Physiological Systems

Nearly every system within the body contains an intrinsic cellular circadian clock. The circadian clock contributes to the regulation of a variety of homeostatic processes in mammals through the regulation of gene expression. Circadian disruption of physiological systems is associated with pathophysiological disorders. Here, we review the current understanding of the molecular mechanisms contributing to the known circadian rhythms in physiological function. This article focuses on what is known in humans, along with discoveries made with cell and rodent models. In particular, the impact of circadian clock components in metabolic, cardiovascular, endocrine, musculoskeletal, immune, and central nervous systems are discussed. © 2021 American Physiological Society. Compr Physiol 11:1-30, 2021.

Adverse Effect of Circadian Rhythm Disorder on Reparative Angiogenesis in Hind Limb Ischemia

Background Circadian rhythm disorders, often seen in modern lifestyles, are a major social health concern. The aim of this study was to examine whether circadian rhythm disorders would influence angiogenesis and blood perfusion recovery in a mouse model of hind limb ischemia. Methods and Results A jet-lag model was established in C57BL/6J mice using a light-controlled isolation box. Control mice were kept at a light/dark 12:12 (12-hour light and 12-hour dark) condition. Concentrations of plasma vascular endothelial growth factor and circulating endothelial progenitor cells in control mice formed a circadian rhythm, which was diminished in the jet-lag model (P<0.05). The jet-lag condition deteriorated tissue capillary formation (P<0.001) and tissue blood perfusion recovery (P<0.01) in hind limb ischemia, which was associated with downregulation of vascular endothelial growth factor expression in local ischemic tissue and in the plasma. Although the expression of clock genes (ie, Clock, Bmal1, and Cry) in local tissues was upregulated after ischemic injury, the expression levels of cryptochrome (Cry) 1 and Cry2 were inhibited by the jet-lag condition. Next, Cry1 and Cry2 double-knockout mice were examined for blood perfusion recoveries and a reparative angiogenesis. Cry1 and Cry2 double-knockout mice revealed suppressed capillary density (P<0.001) and suppressed tissue blood perfusion recovery (P<0.05) in the hind limb ischemia model. Moreover, knockdown of CRY1/2 in human umbilical vein endothelial cells was accompanied by increased expression of WEE1 and decreased expression of HOXC5. This was associated with decreased proliferative capacity, migration ability, and tube formation ability of human umbilical vein endothelial cells, respectively, leading to impairment of angiogenesis. Conclusions Our data suggest that circadian rhythm disorder deteriorates reparative ischemia-induced angiogenesis and that maintenance of circadian rhythm plays an important role in angiogenesis.

Senescence mechanisms and targets in the heart

Cellular senescence is a state of irreversible cell cycle arrest associated with ageing. Senescence of different cardiac cell types can direct the pathophysiology of cardiovascular diseases such as atherosclerosis, myocardial infarction, and cardiac fibrosis. While age-related telomere shortening represents a major cause of replicative senescence, the senescent state can also be induced by oxidative stress, metabolic dysfunction, and epigenetic regulation, among other stressors. It is critical that we understand the molecular pathways that lead to cellular senescence and the consequences of cellular senescence in order to develop new therapeutic approaches to treat cardiovascular disease. In this review, we discuss molecular mechanisms of cellular senescence, explore how cellular senescence of different cardiac cell types (including cardiomyocytes, cardiac endothelial cells, cardiac fibroblasts, vascular smooth muscle cells, valve interstitial cells) can lead to cardiovascular disease, and highlight potential therapeutic approaches that target molecular mechanisms of cellular senescence to prevent or treat cardiovascular disease.

Circadian disruption by short light exposure and a high energy diet impairs glucose tolerance and increases cardiac fibrosis in Psammomys obesus

Type 2 diabetes mellitus (T2DM) increases cardiac inflammation which promotes the development of cardiac fibrosis. We sought to determine the impact of circadian disruption on the induction of hyperglycaemia, inflammation and cardiac fibrosis.

METHODS

Psammomys obesus (P. obesus) were exposed to neutral (12 h light:12 h dark) or short (5 h light:19 h dark) photoperiods and fed a low energy (LE) or high energy (HE) diet for 8 or 20 weeks. To determine daily rhythmicity, P. obesus were euthanised at 2, 8, 14, and 20 h after 'lights on'.

RESULTS

P. obesus exposed to a short photoperiod for 8 and 20 weeks had impaired glucose tolerance following oral glucose tolerance testing, compared to a neutral photoperiod exposure. This occurred with both LE and HE diets but was more pronounced with the HE diet. Short photoperiod exposure also increased myocardial perivascular fibrosis after 20 weeks on LE (51%, P < 0.05) and HE (44%, P < 0.05) diets, when compared to groups with neutral photoperiod exposure. Short photoperiod exposure caused elevations in mRNA levels of hypertrophy gene Nppa (atrial natriuretic peptide) and hypertrophy transcription factors Gata4 and Mef2c in myocardial tissue after 8 weeks.

CONCLUSION

Exposure to a short photoperiod causes impaired glucose tolerance in P. obesus that is exacerbated with HE diet and is accompanied by an induction in myocardial perivascular fibrosis.

Long-Term Effects of Very Low Dose Particle Radiation on Gene Expression in the Heart: Degenerative Disease Risks

Compared to low doses of gamma irradiation (γ-IR), high-charge-and-energy (HZE) particle IR may have different biological response thresholds in cardiac tissue at lower doses, and these effects may be IR type and dose dependent. Three- to four-month-old female CB6F1/Hsd mice were exposed once to one of four different doses of the following types of radiation: γ-IR ¹³⁷Cs (40-160 cGy, 0.662 MeV), ¹⁴Si-IR (4-32 cGy, 260 MeV/n), or ²²Ti-IR (3-26 cGy, 1 GeV/n). At 16 months post-exposure, animals were sacrificed and hearts were harvested and archived as part of the NASA Space Radiation Tissue Sharing Forum. These heart tissue samples were used in our study for RNA isolation and microarray hybridization. Functional annotation of twofold up/down differentially expressed genes (DEGs) and bioinformatics analyses revealed the following: (i) there were no clear lower IR thresholds for HZE- or γ-IR; (ii) there were 12 common DEGs across all 3 IR types; (iii) these 12 overlapping genes predicted various degrees of cardiovascular, pulmonary, and metabolic diseases, cancer, and aging; and (iv) these 12 genes revealed an exclusive non-linear DEG pattern in ¹⁴Si- and ²²Ti-IR-exposed hearts, whereas two-thirds of γ-IR-exposed hearts revealed a linear pattern of DEGs. Thus, our study may provide experimental evidence of excess relative risk (ERR) quantification of low/very low doses of full-body space-type IR-associated degenerative disease development.

Circadian Rhythm: Potential Therapeutic Target for Atherosclerosis and Thrombosis

Every organism has an intrinsic biological rhythm that orchestrates biological processes in adjusting to daily environmental changes. Circadian rhythms are maintained by networks of molecular clocks throughout the core and peripheral tissues, including immune cells, blood vessels, and perivascular adipose tissues. Recent findings have suggested strong correlations between the circadian clock and cardiovascular diseases. Desynchronization between the circadian rhythm and body metabolism contributes to the development of cardiovascular diseases including arteriosclerosis and thrombosis. Circadian rhythms are involved in controlling inflammatory processes and metabolisms, which can influence the pathology of arteriosclerosis and thrombosis. Circadian clock genes are critical in maintaining the robust relationship between diurnal variation and the cardiovascular system. The circadian machinery in the vascular system may be a novel therapeutic target for the prevention and treatment of cardiovascular diseases. The research on circadian rhythms in cardiovascular diseases is still progressing. In this review, we briefly summarize recent studies on circadian rhythms and cardiovascular homeostasis, focusing on the circadian control of inflammatory processes and metabolisms. Based on the recent findings, we discuss the potential target molecules for future therapeutic strategies against cardiovascular diseases by targeting the circadian clock.

Alcohol suppresses cardiovascular diurnal variations in male normotensive rats: Role of reduced PER2 expression and CYP2E1 hyperactivity in the heart

BACKGROUND AND AIMS

The molecular mechanism of the adverse effects of ethanol on diurnal cardiovascular regulation remains unknown. In separate studies, the cardiac circadian rhythm protein period-2 (PER2) confers cardioprotection and, in other organs, PER2 interaction with the ethanol-metabolizing enzyme CYP2E1 underlies, via heme oxygenase-1 (HO-1) upregulation, tissue injury/dysfunction. Here, we hypothesized that suppressed PER2 expression and elevated CYP2E1/HO-1 levels in the heart underlie the disrupted diurnal cardiovascular rhythm/function in alcohol-fed normotensive rats.

METHODS

In ethanol-fed (5%, w/v; 8 weeks) or isocaloric liquid diet-fed male rats, diurnal changes in blood pressure (BP), heart rate (HR), HR vagal variability index, root mean square of successive beat-to-beat differences in beat-interval duration (rMSSD), and cardiac function were measured by radiotelemetry and echocardiography followed by ex vivo molecular studies.

RESULTS

Radiotelemetry findings showed ethanol-evoked reductions in BP (during the dark cycle), rMSSD (during both cycles), and in diurnal differences in BP and rMSSD. Echocardiography findings revealed significant (p < 0.05) reductions in ejection fraction and fractional shortening (weeks 4-6) in the absence of cardiac remodeling (collagen content). Hearts of ethanol-fed rats exhibited higher (p < 0.05) CYP2E1 activity (50%) and HO-1 expression (63%), along with reduction (p < 0.05) in PER2 levels (29%), compared with the hearts of isocaloric diet-fed control rats.

CONCLUSIONS

Our novel findings implicate upregulations of CYP2E1/HO-1 and downregulation of the circadian rhythm cardioprotective protein PER2, in the heart, in the chronic deleterious diurnal cardiovascular effects of alcohol in male rats.

Circadian rhythm disorder: a potential inducer of vascular calcification?

Over the past decades, circadian rhythm has drawn a great attention in cardiovascular diseases. The expressions of rhythm genes fluctuate in accordance with the diurnal changes of vascular physiology, which highlights the pivotal effect of vascular clock. Recent researches show that the circadian clock can directly regulate the synthetic and secretory function of endothelial cells and phenotypic switch of vascular smooth muscle cells to adjust vascular relaxation and contraction. Importantly, dysfunction of vascular cells is involved in vascular calcification. Secretion of osteogenic cytokines and calcified vesicles in the vessel, osteogenic phenotype switch of vascular smooth muscle cells are all implicated in the calcification process. Moreover, circadian rhythm disorder can lead to abnormal hormone secretion, oxidative stress, inflammatory reaction, and autophagy, all of which should not be ignored in vascular calcification. Vascular senescence is another pathogenetic mechanism in vascular calcification. Accelerated vascular senescence may act as an important intermediate factor to promote vascular calcification in circadian rhythm disorders. In this review, we elaborate the potential effect of circadian rhythm disorder in vascular calcification and try to provide a new direction in the prevention of vascular calcification.

Intense Light-Mediated Circadian Cardioprotection via Transcriptional Reprogramming of the Endothelium

Consistent daylight oscillations and abundant oxygen availability are fundamental to human health. Here, we investigate the intersection between light-sensing (Period 2 [PER2]) and oxygen-sensing (hypoxia-inducible factor [HIF1A]) pathways in cellular adaptation to myocardial ischemia. We demonstrate that intense light is cardioprotective via circadian PER2 amplitude enhancement, mimicking hypoxia-elicited adenosine- and HIF1A-metabolic adaptation to myocardial ischemia under normoxic conditions. Whole-genome array from intense light-exposed wild-type or Per2^-/- mice and myocardial ischemia in endothelial-specific PER2-deficient mice uncover a critical role for intense light in maintaining endothelial barrier function via light-enhanced HIF1A transcription. A proteomics screen in human endothelia reveals a dominant role for PER2 in metabolic reprogramming to hypoxia via mitochondrial translocation, tricarboxylic acid (TCA) cycle enzyme activity regulation, and HIF1A transcriptional adaption to hypoxia. Translational investigation of intense light in human subjects identifies similar PER2 mechanisms, implicating the use of intense light for the treatment of cardiovascular disease.

Complexities in cardiovascular rhythmicity: perspectives on circadian normality, ageing and disease

Biological rhythms exist in organisms at all levels of complexity, in most organs and at myriad time scales. Our own biological rhythms are driven by energy emitted by the sun, interacting via our retinas with brain stem centres, which then send out complex messages designed to synchronize the behaviour of peripheral non-light sensing organs, to ensure optimal physiological responsiveness and performance of the organism based on the time of day. Peripheral organs themselves have autonomous rhythmic behaviours that can act independently from central nervous system control but is entrainable. Dysregulation of biological rhythms either through environment or disease has far-reaching consequences on health that we are only now beginning to appreciate. In this review, we focus on cardiovascular rhythms in health, with ageing and under disease conditions.

Comparative Analysis of Human Umbilical Cord Blood-Derived Mesenchymal Stem Cells between Preeclampsia and Normal Pregnant Women

Preeclampsia is a syndrome characterized by deterioration of either the maternal condition or the fetal condition. The adverse intrauterine environment made by preeclampsia results into intrauterine growth restriction and increased risk of a variety of diseases in future life. Given the adverse environment of fetal circulation made in the preeclamptic condition, and the role of mesenchymal stem cell (MSC) as a multipotent progenitor cell, we hypothesized that MSCs derived from human umbilical cord blood (hUCB-MSCs) obtained from preeclampsia are adversely altered or affected compared with normal pregnancy. The aim of this study was to analyze the biological characteristics and compare the functional abilities and gene expression patterns of hUCB-MSCs originating from pregnant women with and without severe preeclampsia. hUCB-MSCs were isolated and cultured from 28 pregnant women with severe preeclampsia and 30 normal pregnant women. hUCB-MSCs obtained from women with preeclampsia were less proliferative and more senescent and had lower telomerase activity and higher ROS activity than cells from women with normal pregnancy. In addition, many senescence-related differentially expressed genes (DEGs) were identified by analysis of microarray gene expression profiles and significantly associated with the Gene Ontology term cell aging. In conclusion, hUCB-MSCs obtained from women with preeclampsia showed the poorly proliferative, more senescent, and decreased telomerase activity, and these characters may be related with functional impairment of MSC from preeclampsia compared with cells from normal pregnancy.

Influence of mental stress and environmental toxins on circadian clocks: Implications for redox regulation of the heart and cardioprotection

Risk factors in the environment such as air pollution and mental stress contribute to the development of chronic non-communicable disease. Air pollution was identified as the leading health risk factor in the physical environment, followed by water pollution, soil pollution/heavy metals/chemicals and occupational exposures, however neglecting the non-chemical environmental health risk factors (e.g. mental stress and noise). Epidemiological data suggest that environmental risk factors are associated with higher risk for cardiovascular, metabolic and mental diseases, including hypertension, heart failure, myocardial infarction, diabetes, arrhythmia, stroke, depression and anxiety disorders. We provide an overview on the impact of the external exposome comprising risk factors/exposures on cardiovascular health with a focus on dysregulation of stress hormones, mitochondrial function, redox balance and inflammation with special emphasis on the circadian clock. Finally, we assess the impact of circadian clock dysregulation on cardiovascular health and the potential of environment-specific preventive strategies or "chrono" therapy for cardioprotection. LINKED ARTICLES: This article is part of a themed issue on Risk factors, comorbidities, and comedications in cardioprotection. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v177.23/issuetoc.

Exploring the role of circadian clock gene and association with cancer pathophysiology

Most of the processes that occur in the mind and body follow natural rhythms. Those with a cycle length of about one day are called circadian rhythms. These rhythms are driven by a system of self-sustained clocks and are entrained by environmental cues such as light-dark cycles as well as food intake. In mammals, the circadian clock system is hierarchically organized such that the master clock in the suprachiasmatic nuclei of the hypothalamus integrates environmental information and synchronizes the phase of oscillators in peripheral tissues.The circadian system is responsible for regulating a variety of physiological and behavioral processes, including feeding behavior and energy metabolism. Studies revealed that the circadian clock system consists primarily of a set of clock genes. Several genes control the biological clock, including BMAL1, CLOCK (positive regulators), CRY1, CRY2, PER1, PER2, and PER3 (negative regulators) as indicators of the peripheral clock.Circadian has increasingly become an important area of medical research, with hundreds of studies pointing to the body's internal clocks as a factor in both health and disease. Thousands of biochemical processes from sleep and wakefulness to DNA repair are scheduled and dictated by these internal clocks. Cancer is an example of health problems where chronotherapy can be used to improve outcomes and deliver a higher quality of care to patients.In this article, we will discuss knowledge about molecular mechanisms of the circadian clock and the role of clocks in physiology and pathophysiology of concerns.

Telomeres as Therapeutic Targets in Heart Disease

•

Age-associated CVDs impose a great burden on current health systems. Despite the fact that current strong evidence supports the links among aging, telomere attrition, and CVDs, there is no clear direction for the development of telomere therapeutics against CVDs.

•

This review focuses on immune modulation, CHIP, pharmaceutical interventions, and gene therapy for their therapeutic roles in age-associated CVDs.

•

The future goal of telomere cardiovascular therapy in young subjects is to prevent senescence and diseases, whereas in older adult subjects, the goal is restoration of cardiovascular functions. Further studies on the telomere-CHIP-atherosclerosis axis may shed insights on how to achieve these 2 different therapeutic targets.

Telomeres are double-stranded repeats of G-rich tandem DNA sequences that gradually shorten with each cell division. Aging, inflammation, and oxidative stress accelerate the process of telomere shortening. Telomerase counteracts this process by maintaining and elongating the telomere length. Patients with atherosclerotic diseases and cardiovascular risk factors (e.g., smoking, obesity, sedentary lifestyle, and hypertension) have shorter leukocyte telomere length. Following myocardial infarction, telomerase expression and activity in cardiomyocytes and endothelial cells increase significantly, implying that telomerase plays a role in regulating tissue repairs in heart diseases. Although previous studies have focused on the changes of telomeres in heart diseases and the telomere length as a marker for aging cardiovascular systems, recent studies have explored the potential of telomeres and telomerase in the treatment of cardiovascular diseases. This review discusses the significant advancements of telomere therapeutics in gene therapy, atherosclerosis, anti-inflammation, and immune modulation in patients with cardiovascular diseases.

Circulating angiogenic stem cells in type 2 diabetes are associated with glycemic control and endothelial dysfunction

Circulating angiogenic cells (CACs) of various described phenotypes participate in the regeneration of the damaged endothelium, but the abundance of these cells is highly influenced by external cues including diabetes. It is not entirely clear which CAC populations are most reflective of endothelial function nor which are impacted by diabetes. To answer these questions, we enrolled a human cohort with variable CVD risk and determined relationships between stratified levels of CACs and indices of diabetes and vascular function. We also determined associations between CAC functional markers and diabetes and identified pro-angiogenic molecules which are impacted by diabetes. We found that subjects with low levels of CD34+/AC133+/CD31+/CD45dim cells (CAC-3) had a significantly higher incidence of diabetes (p = 0.004), higher HbA1c levels (p = 0.049) and higher CVD risk scores. Furthermore, there was an association between low CAC-3 levels and impaired vascular function (p = 0.023). These cells from diabetics had reduced levels of CXCR4 and VEGFR2, while diabetics had higher levels of certain cytokines and pro-angiogenic molecules. These results suggest that quantitative and functional defects of CD34+/AC133+/CD31+/CD45dim cells are associated with diabetes and vascular impairment and that this cell type may be a prognostic indicator of CVD and vascular dysfunction.

Immunohistochemistry of the circadian clock in mouse and human vascular tissues

Aim

The circadian clock is a molecular network that controls the body physiological rhythms. In blood vessels, the circadian clock components modulate vascular remodeling, blood pressure, and signaling. The goal in this study was to determine the pattern of expression of circadian clock proteins in the endothelium, smooth muscle, and adventitia of the vasculature of human and mouse tissues.

Methods

Immunohistochemistry was performed in frozen sections of mouse aorta, common carotid artery, femoral artery, lung, and heart at 12 AM and 12 PM for Bmal1, Clock, Npas2, Per and other clock components. Studies of expression were also assessed in human saphenous vein both by immunoblotting and immunohistochemistry.

Results

In this study, we identified the expression of Bmal1, Clock, Npas, Per1, Cry1, and accessory clock components by immunohistochemical staining in the endothelium, smooth muscle and adventitia of the mouse vasculature with differing temporal and cellular profiles depending on vasculature and tissue analyzed. The human saphenous vein also exhibited expression of clock genes that exhibited an oscillatory pattern in Bmal1 and Cry by immunoblotting.

Conclusion

These studies show that circadian clock components display differences in expression and localization throughout the cardiovascular system, which may confer nuances of circadian clock signaling in a cell-specific manner.

Role of the circadian system in cardiovascular disease

All species organize behaviors to optimally match daily changes in the environment, leading to pronounced activity/rest cycles that track the light/dark cycle. Endogenous, approximately 24-hour circadian rhythms in the brain, autonomic nervous system, heart, and vasculature prepare the cardiovascular system for optimal function during these anticipated behavioral cycles. Cardiovascular circadian rhythms, however, may be a double-edged sword. The normal amplified responses in the morning may aid the transition from sleep to activity, but such exaggerated responses are potentially perilous in individuals susceptible to adverse cardiovascular events. Indeed, the occurrence of stroke, myocardial infarction, and sudden cardiac death all have daily patterns, striking most frequently in the morning. Furthermore, chronic disruptions of the circadian clock, as with night-shift work, contribute to increased cardiovascular risk. Here we highlight the importance of the circadian system to normal cardiovascular function and to cardiovascular disease, and identify opportunities for optimizing timing of medications in cardiovascular disease.

Circadian toxicity of environmental pollution. Inhalation of polluted air to give a precedent

Exposures to environmental stressors that derive from pollution (e.g. air, light) or lifestyle choices (e.g. diet, activity, 24-hour-×-7-day) are associated with adverse human health outcomes. For instance, there is evidence that air pollution exposure and changes in sleep/wake pattern increase the risk for vascular and cardiometabolic disorders. Interestingly, air pollution exposure affects pulmonary and cardiovascular functions that follow circadian rhythmicity and increases the risk for pulmonary and cardiovascular events that occur in diurnal patterns suggesting a link between air pollution induced cardiovascular and pulmonary injury and changes in circadian rhythm. Indeed, recent research identified circadian rhythm as an air pollution target and circadian rhythm as factor that increases air pollution sensitivity. Using air pollution exposure as precedent, this review highlights research on how environmental pollution affect circadian rhythm and how circadian rhythm affects the toxicity of environmental stressors.

Vasculature on the clock: Circadian rhythm and vascular dysfunction

The master mammalian circadian clock (i.e. central clock), located in the suprachiasmatic nucleus of the hypothalamus, orchestrates the synchronization of the daily behavioural and physiological rhythms to better adapt the organism to the external environment in an anticipatory manner. This central clock is entrained by a variety of signals, the best established being light and food. However, circadian cycles are not simply the consequences of these two cues but are generated by endogenous circadian clocks. Indeed, clock machinery is found in mainly all tissues and cell types, including cells of the vascular system such as endothelial cells, fibroblasts, smooth muscle cells and stem cells. This machinery physiologically contributes to modulate the daily vascular function, and its disturbance therefore plays a major role in the pathophysiology of vascular dysfunction. Therapies targeting the circadian rhythm may therefore be of benefit against vascular disease.

Influence of aging on the activity of mice Sca-1+CD31- cardiac stem cells

Therapeutic application of cardiac resident stem/progenitor cells (CSC/CPCs) is limited due to decline of their regenerative potential with donor age. A variety of studies have shown that the cardiac aging was the problem of the stem cells, but little is known about the impact of age on the subgroups CSC/CPCs, the relationship between subgroups CSC/CPCs ageing and age-related dysfunction. Here, we studied Sca-1+CD31− subgroups of CSCs from younger(2~3months) and older(22~24months) age mice, biological differentiation was realized using specific mediums for 14 days to induce cardiomyocyte, smooth muscle cells or endothelial cells and immunostain analysis of differentiated cell resulting were done. Proliferation and cell cycle were measured by flow cytometry assay, then used microarray to dissect variability from younger and older mice. Although the number of CSCs was higher in older mice, the advanced age significantly reduced the differentiation ability into cardiac cell lineages and the proliferation ability. Transcriptional changes in Sca-1+CD31− subgroups of CSCs during aging are related to Vitamin B6 metabolism, circadian rhythm, Tyrosine metabolism, Complement and coagulation cascades. Taking together these results indicate that Cardiac resident stem/progenitor cells have significant differences in their proliferative, pluripotency and gene profiles and those differences are age depending.

Altered Circadian Timing System-Mediated Non-Dipping Pattern of Blood Pressure and Associated Cardiovascular Disorders in Metabolic and Kidney Diseases

The morning surge in blood pressure (BP) coincides with increased cardiovascular (CV) events. This strongly suggests that an altered circadian rhythm of BP plays a crucial role in the development of CV disease (CVD). A disrupted circadian rhythm of BP, such as the non-dipping type of hypertension (i.e., absence of nocturnal BP decline), is frequently observed in metabolic disorders and chronic kidney disease (CKD). The circadian timing system, controlled by the central clock in the suprachiasmatic nucleus of the hypothalamus and/or by peripheral clocks in the heart, vasculature, and kidneys, modulates the 24 h oscillation of BP. However, little information is available regarding the molecular and cellular mechanisms of an altered circadian timing system-mediated disrupted dipping pattern of BP in metabolic disorders and CKD that can lead to the development of CV events. A more thorough understanding of this pathogenesis could provide novel therapeutic strategies for the management of CVD. This short review will address our and others' recent findings on the molecular mechanisms that may affect the dipping pattern of BP in metabolic dysfunction and kidney disease and its association with CV disorders.

Thermodynamic Aspects and Reprogramming Cellular Energy Metabolism during the Fibrosis Process

Fibrosis is characterized by fibroblast proliferation and fibroblast differentiation into myofibroblasts, which generate a relaxation-free contraction mechanism associated with excessive collagen synthesis in the extracellular matrix, which promotes irreversible tissue retraction evolving towards fibrosis. From a thermodynamic point of view, the mechanisms leading to fibrosis are irreversible processes that can occur through changing the entropy production rate. The thermodynamic behaviors of metabolic enzymes involved in fibrosis are modified by the dysregulation of both transforming growth factor β (TGF-β) signaling and the canonical WNT/β-catenin pathway, leading to aerobic glycolysis, called the Warburg effect. Molecular signaling pathways leading to fibrosis are considered dissipative structures that exchange energy or matter with their environment far from the thermodynamic equilibrium. The myofibroblastic cells arise from exergonic processes by switching the core metabolism from oxidative phosphorylation to glycolysis, which generates energy and reprograms cellular energy metabolism to induce the process of myofibroblast differentiation. Circadian rhythms are far-from-equilibrium thermodynamic processes. They directly participate in regulating the TGF-β and WNT/β-catenin pathways involved in energetic dysregulation and enabling fibrosis. The present review focusses on the thermodynamic implications of the reprogramming of cellular energy metabolism, leading to fibroblast differentiation into myofibroblasts through the positive interplay between TGF-β and WNT/β-catenin pathways underlying in fibrosis.

Increase in acid sphingomyelinase level in human retinal endothelial cells and CD34+ circulating angiogenic cells isolated from diabetic individuals is associated with dysfunctional retinal vasculature and vascular repair process in diabetes

BACKGROUND

Diabetic retinopathy is a microvascular disease that results from retinal vascular degeneration and defective repair due to diabetes-induced endothelial progenitor dysfunction.

OBJECTIVE

Understanding key molecular factors involved in vascular degeneration and repair is paramount for developing effective diabetic retinopathy treatment strategies. We propose that diabetes-induced activation of acid sphingomyelinase (ASM) plays essential role in retinal endothelial and CD34+ circulating angiogenic cell (CAC) dysfunction in diabetes.

METHODS

Human retinal endothelial cells (HRECs) isolated from control and diabetic donor tissue and human CD34+ CACs from control and diabetic patients were used in this study. ASM messenger RNA and protein expression were assessed by quantitative polymerase chain reaction and enzyme-linked immunosorbent assay, respectively. To evaluate the effect of diabetes-induced ASM on HRECs and CD34+ CACs function, tube formation, CAC incorporation into endothelial tubes, and diurnal release of CD34+ CACs in diabetic individuals were determined.

RESULTS

ASM expression level was significantly increased in HRECs isolated from diabetic compared with control donor tissue, as well as CD34+ CACs and plasma of diabetic patients. A significant decrease in tube area was observed in HRECs from diabetic donors compared with control HRECs. The tube formation deficiency was associated with increased expression of ASM in diabetic HRECs. Moreover, diabetic CD34+ CACs with high ASM showed defective incorporation into endothelial tubes. Diurnal release of CD34+ CACs was disrupted with the rhythmicity lost in diabetic patients.

CONCLUSION

Collectively, these findings support that diabetes-induced ASM upregulation has a marked detrimental effect on both retinal endothelial cells and CACs.

Akt1 Controls the Timing and Amplitude of Vascular Circadian Gene Expression

The AKT signaling pathway is important for circadian rhythms in mammals and flies ( Drosophila). However, AKT signaling in mammals is more complicated since there are 3 isoforms of AKT, each performing slightly different functions. Here we study the most ubiquitous AKT isoform, Akt1, and its role at the organismal level in the central and vascular peripheral clocks. Akt1^-/- mice exhibit relatively normal behavioral rhythms with only minor differences in circadian gene expression in the liver and heart. However, circadian gene expression in the Akt1^-/- aorta, compared with control aorta, follows a distinct pattern. In the Akt1^-/- aorta, positive regulators of circadian transcription have lower amplitude rhythms and peak earlier in the day, and negative circadian regulators are expressed at higher amplitudes and peak later in the day. In endothelial cells, negative circadian regulators exhibit an increased amplitude of expression, while the positive circadian regulators are arrhythmic with a decreased amplitude of expression. This indicates that Akt1 conditions the normal circadian rhythm in the vasculature more so than in other peripheral tissues where other AKT isoforms or kinases might be important for daily rhythms.

Hypercholesterolemia Causes Circadian Dysfunction: A Potential Risk Factor for Cardiovascular Disease

Hypercholesterolemia is a well-known risk factor for a wide range of diseases in developed countries. Here, we report that mice lacking functional LDLR (low density lipoprotein receptor), an animal model of human familial hypercholesterolemia, show circadian abnormalities. In free running behavioral experiments in constant darkness, these mice showed a prolonged active phase and distinctly bimodal rhythms. Even when the circadian rhythms were entrained by light and dark cycles, these mice showed a significant attenuation of behavioral onset intensity at the start of the dark period. Further, we hypothesized that the combination of hypercholesterolemia and circadian abnormalities may affect cardiovascular disease progression. To examine this possibility, we generated LDLR-deficient mice with impaired circadian rhythms by simultaneously introducing a mutation into Period2, a core clock gene, and found that these mice showed a significant enlargement of artery plaque area with an increase in inflammatory cytokine IL-6 levels. These results suggest that circadian dysfunction may be associated with the development or progression of cardiovascular diseases.

•

Mice lacking LDLR (low density lipoprotein receptor), a mouse model for hypercholesterolemia, show circadian abnormalities.

•

LDLR-deficient mice with a mutation in Period2, a core clock gene, show a significant enlargement of artery plaque area.

•

Per2 mutation-induced increase in plasma inflammatory cytokines may cause modification of arteriosclerosis.

Hypercholesterolemia is a common pathology in advanced countries, occurring in 10% to 30% of the population. Here, we report that mice lacking LDLR (low density lipoprotein receptor), an animal model for hypercholesterolemia, experienced chronic circadian abnormalities. Further, we found that LDLR-deficient mice with a mutation in Period2, a clock gene, showed a significant enlargement of artery plaque area. Together, our findings indicate that hypercholesterolemia induces circadian abnormalities, leading to a decline in the quality of social life and an increase in the risk of circadian-related diseases, and that circadian dysfunction might affect the development or progression of hypercholesterolemia-related diseases.

Differential Regulation of BMAL1, CLOCK, and Endothelial Signaling in the Aortic Arch and Ligated Common Carotid Artery

The circadian clock is rhythmically expressed in blood vessels, but the interaction between the circadian clock and disturbed blood flow remains unclear. We examined the relationships between BMAL1 and CLOCK and 2 regulators of endothelial function, AKT1 and endothelial nitric oxide synthase (eNOS), in vascular regions of altered blood flow. We found that the aortic arch from WT mice exhibited reduced sensitivity to acetylcholine (Ach)-mediated relaxation relative to the thoracic aorta. In Clock-mutant (mut) mice the aorta exhibited a reduced sensitivity to Ach. In WT mice, the phosphorylated forms of eNOS and AKT were decreased in the aortic arch, while BMAL1 and CLOCK expression followed a similar pattern of reduction in the arch. In conditions of surgically induced flow reduction, phosphorylated-eNOS (serine 1177) increased, as did p-AKT in the ipsilateral left common carotid artery (LC) of WT mice. Similarly, BMAL1 and CLOCK exhibited increased expression after 5 days in the remodeled LC. eNOS expression was increased at 8 p.m. versus 8 a.m. in WT mice, and this pattern was abolished in mut and Bmal1-KO mice. These data suggest that the circadian clock may be a biomechanical and temporal sensor that acts to coordinate timing, flow dynamics, and endothelial function.

Per3 expression in different tissues of Cebus apella

We present a study of Per3 expression in six different tissues of the non-human primate Cebus apella (capuchin monkey). The aim of this study was to verify whether the expression of the Per3 gene in different tissues of capuchin monkey occurs in a circadian pattern, its phase and the phase relationships between these different tissues during the 24 h of a day. We observed that gene expression oscillated in all of the tissues studied during this time period, although only the liver and muscle presented a robust circadian pattern. This preliminary study highlights the possibility of using Cebus apella as a model to study circadian rhythms at the gene expression level and opens an opportunity for future researches.

Dominguez J, Al-Sabah J, Chaqour B, Grant MB, Bhatwadekar AD. Per2-Mediated Vascular Dysfunction Is Caused by the Upregulation of the Connective Tissue Growth Factor (CTGF)

Period 2-mutant mice (Per2^m/m), which possess a circadian dysfunction, recapitulate the retinal vascular phenotype similar to diabetic retinopathy (DR). The vascular dysfunction in Per2^m/m is associated with an increase in connective tissue growth factor (CTGF/CCN2). At the molecular level, CTGF gene expression is dependent on the canonical Wnt/β-catenin pathway. The nuclear binding of β-catenin to a transcription factor, lymphoid enhancer binding protein (Lef)/ T-cell factor (TCF/LEF), leads to downstream activation of CTGF. For this study, we hypothesized that the silencing of Per2 results in nuclear translocation and subsequent transactivation of the CTGF gene. To test this hypothesis, we performed immunofluorescence labeling for CTGF in retinal sections from wild-type (WT) and Per2^m/m mice. Human retinal endothelial cells (HRECs) were transfected with siRNA for Per2, and the protein expression of CTGF and β-catenin was evaluated. The TCF/LEF luciferase reporter (TOPflash) assay was performed to validate the involvement of β-catenin in the activation of CTGF. Per2^m/m retinas exhibited an increased CTGF immunostaining in ganglion cell layer and retinal endothelium. Silencing of Per2 using siRNA resulted in an upregulation of CTGF and β-catenin. The TOPflash assay revealed an increase in luminescence for HRECs transfected with Per2 siRNA. Our studies show that loss of Per2 results in an activation of CTGF via nuclear entry of β-catenin. Our study provides novel insight into the understanding of microvascular dysfunction in Per2^m/m mice.

Telomeres and Telomerase in Cardiovascular Diseases

Telomeres are tandem repeat DNA sequences present at the ends of each eukaryotic chromosome to stabilize the genome structure integrity. Telomere lengths progressively shorten with each cell division. Inflammation and oxidative stress, which are implicated as major mechanisms underlying cardiovascular diseases, increase the rate of telomere shortening and lead to cellular senescence. In clinical studies, cardiovascular risk factors such as smoking, obesity, sedentary lifestyle, and hypertension have been associated with short leukocyte telomere length. In addition, low telomerase activity and short leukocyte telomere length have been observed in atherosclerotic plaque and associated with plaque instability, thus stroke or acute myocardial infarction. The aging myocardium with telomere shortening and accumulation of senescent cells limits the tissue regenerative capacity, contributing to systolic or diastolic heart failure. In addition, patients with ion-channel defects might have genetic imbalance caused by oxidative stress-related accelerated telomere shortening, which may subsequently cause sudden cardiac death. Telomere length can serve as a marker for the biological status of previous cell divisions and DNA damage with inflammation and oxidative stress. It can be integrated into current risk prediction and stratification models for cardiovascular diseases and can be used in precise personalized treatments. In this review, we summarize the current understanding of telomeres and telomerase in the aging process and their association with cardiovascular diseases. In addition, we discuss therapeutic interventions targeting the telomere system in cardiovascular disease treatments.

Telomeres and Telomerase in Cardiovascular Diseases

Telomeres are tandem repeat DNA sequences present at the ends of each eukaryotic chromosome to stabilize the genome structure integrity. Telomere lengths progressively shorten with each cell division. Inflammation and oxidative stress, which are implicated as major mechanisms underlying cardiovascular diseases, increase the rate of telomere shortening and lead to cellular senescence. In clinical studies, cardiovascular risk factors such as smoking, obesity, sedentary lifestyle, and hypertension have been associated with short leukocyte telomere length. In addition, low telomerase activity and short leukocyte telomere length have been observed in atherosclerotic plaque and associated with plaque instability, thus stroke or acute myocardial infarction. The aging myocardium with telomere shortening and accumulation of senescent cells limits the tissue regenerative capacity, contributing to systolic or diastolic heart failure. In addition, patients with ion-channel defects might have genetic imbalance caused by oxidative stress-related accelerated telomere shortening, which may subsequently cause sudden cardiac death. Telomere length can serve as a marker for the biological status of previous cell divisions and DNA damage with inflammation and oxidative stress. It can be integrated into current risk prediction and stratification models for cardiovascular diseases and can be used in precise personalized treatments. In this review, we summarize the current understanding of telomeres and telomerase in the aging process and their association with cardiovascular diseases. In addition, we discuss therapeutic interventions targeting the telomere system in cardiovascular disease treatments.

miR-92a Corrects CD34+ Cell Dysfunction in Diabetes by Modulating Core Circadian Genes Involved in Progenitor Differentiation

Autologous CD34(+) cells are widely used for vascular repair; however, in individuals with diabetes and microvascular disease these cells are dysfunctional. In this study, we examine expression of the clock genes Clock, Bmal, Per1, Per2, Cry1, and Cry2 in CD34(+) cells of diabetic and nondiabetic origin and determine the small encoding RNA (miRNA) profile of these cells. The degree of diabetic retinopathy (DR) was assessed. As CD34(+) cells acquired mature endothelial markers, they exhibit robust oscillations of clock genes. siRNA treatment of CD34(+) cells revealed Per2 as the only clock gene necessary to maintain the undifferentiated state of CD34(+) cells. Twenty-five miRNAs targeting clock genes were identified. Three of the miRNAs (miR-18b, miR-16, and miR-34c) were found only in diabetic progenitors. The expression of the Per2-regulatory miRNA, miR-92a, was markedly reduced in CD34(+) cells from individuals with DR compared with control subjects and patients with diabetes with no DR. Restoration of miR-92a levels in CD34(+) cells from patients with diabetes with DR reduced the inflammatory phenotype of these cells and the diabetes-induced propensity toward myeloid differentiation. Our studies suggest that restoring levels of miR-92a could enhance the usefulness of CD34(+) cells in autologous cell therapy.