Circadian MicroRNAs in Cardioprotection

The role of microRNAs in the molecular link between circadian rhythm and autism spectrum disorder

Circadian rhythm regulates physiological cycles of awareness and sleepiness. Melatonin production is primarily regulated by circadian regulation of gene expression and is involved in sleep homeostasis. If the circadian rhythm is abnormal, sleep disorders, such as insomnia and several other diseases, can occur. The term 'autism spectrum disorder (ASD)' is used to characterize people who exhibit a certain set of repetitive behaviors, severely constrained interests, social deficits, and/or sensory behaviors that start very early in life. Because many patients with ASD suffer from sleep disorders, sleep disorders and melatonin dysregulation are attracting attention for their potential roles in ASD. ASD is caused by abnormalities during the neurodevelopmental processes owing to various genetic or environmental factors. Recently, the role of microRNAs (miRNAs) in circadian rhythm and ASD have gained attraction. We hypothesized that the relationship between circadian rhythm and ASD could be explained by miRNAs that can regulate or be regulated by either or both. In this study, we introduced a possible molecular link between circadian rhythm and ASD. We performed a thorough literature review to understand their complexity.

Circadian system microRNAs - Role in the development of cardiovascular diseases

Circadian rhythm regulates numerous physiological processes, and disruption of the circadian clock can lead to cardiovascular disease. Cardiovascular disease is the leading cause of morbidity and mortality worldwide. Small non-coding RNAs, microRNAs (miRNAs), are involved in regulating gene expression, both those important for the cardiovascular system and key circadian clock genes. Epigenetic mechanisms based on miRNAs are essential for fine-tuning circadian physiology. Indeed, some miRNAs depend on circadian periodicity, others are under the influence of light, and still others are under the influence of core clock genes. Dysregulation of miRNAs involved in circadian rhythm modulation has been associated with inflammatory conditions of the endothelium and atherosclerosis, which can lead to coronary heart disease and myocardial infarction. Epigenetic processes are reversible through their association with environmental factors, enabling innovative preventive and therapeutic strategies for cardiovascular disease. Here, is a review of recent findings on how miRNAs modulate circadian rhythm desynchronization in cardiovascular disease. In the era of personalized medicine, the possibility of treatment with miRNA antagomirs should be time-dependent to correspond to chronotherapy and achieve the most significant efficacy.

Feedback between a retinoid-related nuclear receptor and the let-7 microRNAs controls the pace and number of molting cycles in C. elegans

Animal development requires coordination among cyclic processes, sequential cell fate specifications, and once-a-lifetime morphogenic events, but the underlying timing mechanisms are not well understood. Caenorhabditis elegans undergoes four molts at regular 8 to 10 hour intervals. The pace of the cycle is governed by PERIOD/lin-42 and other as-yet unknown factors. Cessation of the cycle in young adults is controlled by the let-7 family of microRNAs and downstream transcription factors in the heterochronic pathway. Here, we characterize a negative feedback loop between NHR-23, the worm homolog of mammalian retinoid-related orphan receptors (RORs), and the let-7 family of microRNAs that regulates both the frequency and finite number of molts. The molting cycle is decelerated in nhr-23 knockdowns and accelerated in let-7(-) mutants, but timed similarly in let-7(-) nhr-23(-) double mutants and wild-type animals. NHR-23 binds response elements (ROREs) in the let-7 promoter and activates transcription. In turn, let-7 dampens nhr-23 expression across development via a complementary let-7-binding site (LCS) in the nhr-23 3' UTR. The molecular interactions between NHR-23 and let-7 hold true for other let-7 family microRNAs. Either derepression of nhr-23 transcripts by LCS deletion or high gene dosage of nhr-23 leads to protracted behavioral quiescence and extra molts in adults. NHR-23 and let-7 also coregulate scores of genes required for execution of the molts, including lin-42. In addition, ROREs and LCSs isolated from mammalian ROR and let-7 genes function in C. elegans, suggesting conservation of this feedback mechanism. We propose that this feedback loop unites the molting timer and the heterochronic gene regulatory network, possibly by functioning as a cycle counter.

Intense light-elicited alveolar type 2-specific circadian PER2 protects from bacterial lung injury via BPIFB1

Circadian amplitude enhancement has the potential to be organ protective but has not been studied in acute lung injury (ALI). Consistent light and dark cycles are crucial for the amplitude regulation of the circadian rhythm protein Period2 (PER2). Housing mice under intense instead of ambient light for 1 wk (light: dark cycle:14h:10h), we demonstrated a robust increase of pulmonary PER2 trough and peak levels, which is consistent with circadian amplitude enhancement. A search for the affected lung cell type suggested alveolar type 2 (ATII) cells as strong candidates for light induction of PER2. A head-to-head comparison of mice with cell-type-specific deletion of Per2 in ATII, endothelial, or myeloid cells uncovered a dramatic phenotype in mice with an ATII-specific deletion of Per2. During Pseudomonas aeruginosa-induced ALI, mice with Per2 deletion in ATII cells showed 0% survival, whereas 85% of control mice survived. Subsequent studies demonstrated that intense light therapy dampened lung inflammation or improved the alveolar barrier function during P. aeruginosa-induced ALI, which was abolished in mice with an ATII-specific deletion of Per2. A genome-wide mRNA array uncovered bactericidal/permeability-increasing fold-containing family B member 1 (BPIFB1) as a downstream target of intense light-elicited ATII-PER2 mediated lung protection. Using the flavonoid and PER2 amplitude enhancer nobiletin, we recapitulated the lung-protective and anti-inflammatory effects of light and BPIFB1, respectively. Together, our studies demonstrate that light-elicited amplitude enhancement of ATII-specific PER2 is a critical control point of inflammatory pathways during bacterial ALI.

A time to heal: microRNA and circadian dynamics in cutaneous wound repair

Many biological systems have evolved circadian rhythms based on the daily cycles of daylight and darkness on Earth. Such rhythms are synchronised or entrained to 24-h cycles, predominantly by light, and disruption of the normal circadian rhythms has been linked to elevation of multiple health risks. The skin serves as a protective barrier to prevent microbial infection and maintain homoeostasis of the underlying tissue and the whole organism. However, in chronic non-healing wounds such as diabetic foot ulcers (DFUs), pressure sores, venous and arterial ulcers, a variety of factors conspire to prevent wound repair. On the other hand, keloids and hypertrophic scars arise from overactive repair mechanisms that fail to cease in a timely fashion, leading to excessive production of extracellular matrix (ECM) components such as such as collagen. Recent years have seen huge increases in our understanding of the functions of microRNAs (miRNAs) in wound repair. Concomitantly, there has been growing recognition of miRNA roles in circadian processes, either as regulators or targets of clock activity or direct responders to external circadian stimuli. In addition, miRNAs are now known to function as intercellular signalling mediators through extracellular vesicles (EVs). In this review, we explore the intersection of mechanisms by which circadian and miRNA responses interact with each other in relation to wound repair in the skin, using keratinocytes, macrophages and fibroblasts as exemplars. We highlight areas for further investigation to support the development of translational insights to support circadian medicine in the context of these cells.

Relationships between Indicators of Lower Extremity Artery Disease and miRNA Expression in Peripheral Blood Mononuclear Cells

Lower extremity artery disease (LEAD) is an underdiagnosed and globally underestimated vascular disease caused by the progressive and chronic formation of atherosclerotic plaques in the arteries of the lower limbs. Much evidence indicates that the abnormal course of pathophysiological processes underlying LEAD development is associated with altered miRNA modulatory function. In the presented study, relationships between miRNA expression and clinical indicators of this disease (ABI, claudication distance, length of arterial occlusion, Rutherford category, and plaque localization) were identified. MiRNA expression profiles were obtained using next-generation sequencing in peripheral blood mononuclear cells (PBMCs) of 40 LEAD patients. Correlation analysis performed using the Spearman rank correlation test revealed miRNAs related to ABI, claudication distance, and length of arterial occlusion. In the DESeq2 analysis, five miRNAs were found to be dysregulated in patients with Rutherford category 3 compared to patients with Rutherford category 2. No miRNAs were found to be differentially expressed between patients with different plaque localizations. Functional analysis performed using the miRNet 2.0 website tool determined associations of selected miRNAs with processes underlying vascular pathology, such as vascular smooth muscle cell differentiation, endothelial cell apoptosis, response to hypoxia, inflammation, lipid metabolism, and circadian rhythm. The most enriched functional terms for genes targeted by associated miRNAs were linked to regulation of the cell cycle, regulation of the transcription process, and nuclear cellular compartment. In conclusion, dysregulations of miRNA expression in PBMCs of patients with LEAD are indicative of the disease and could potentially be used in the prediction of LEAD progression.

miR-455-5p regulates circadian rhythms by accelerating the degradation of Clock mRNA

Circadian rhythms are approximately 24-hr cycles generated by organisms to adapt to daily rhythms. Core circadian proteins such as CLOCK, BMAL1, PER1/2, and CRY1/2/3 form a transcription-translation feedback loop (TTFL) to maintain circadian rhythms. MicroRNAs are involved in regulating circadian rhythms; however, the detailed mechanisms remain unclear. Here, using miRNA-seq screening, we discovered that the expression level of miR-455 was controlled by CLOCK. Furthermore, miR-455-5p also binds to the 3' untranslated region (3'UTR) of Clock mRNA and regulates its stability. To further study whether such mutual regulation forms a feedback loop to regulate circadian rhythms, we recorded bioluminescence traces of Per2::Luc U2OS cells in real time and confirmed that overexpression of miR-455-5p lengthens the period and attenuates the amplitude of circadian rhythms in synchronized cells (and vice versa). We also discovered that miR-455-5p can function as a Clock modulator to induce a fine-orchestral circadian rhythm in vitro, as well as other known factors such as dexamethasone, horse serum, or temperature. In conclusion, miR-455-5p is essential for maintaining a normal circadian rhythm via regulating Clock mRNA stability. Our study reveals a new mutual regulatory mechanism between CLOCK protein, Clock mRNA, and miR-455-5p, which regulates circadian rhythms in cells.

MicroRNAs as Potential Orchestrators of Alzheimer's Disease-Related Pathologies: Insights on Current Status and Future Possibilities

Alzheimer's disease (AD) is a progressive and deleterious neurodegenerative disease, strongly affecting the cognitive functions and memory of seniors worldwide. Around 58% of the affected patients live in low and middle-income countries, with estimates of increasing deaths caused by AD in the coming decade. AD is a multifactor pathology. Mitochondrial function declines in AD brain and is currently emerging as a hallmark of this disease. It has been considered as one of the intracellular processes severely compromised in AD. Many mitochondrial parameters decline already during aging; mitochondrial efficiency for energy production, reactive oxygen species (ROS) metabolism and the de novo synthesis of pyrimidines, to reach an extensive functional failure, concomitant with the onset of neurodegenerative conditions. Besides its impact on cognitive functions, AD is characterized by loss of synapses, extracellular amyloid plaques composed of the amyloid-β peptide (Aβ), and intracellular aggregates of hyperphosphorylated Tau protein, accompanied by drastic sleep disorders, sensory function alterations and pain sensitization. Unfortunately, till date, effective management of AD-related disorders and early, non-invasive AD diagnostic markers are yet to be found. MicroRNAs (miRNAs) are small non-coding nucleic acids that regulate key signaling pathway(s) in various disease conditions. About 70% of experimentally detectable miRNAs are expressed in the brain where they regulate neurite outgrowth, dendritic spine morphology, and synaptic plasticity. Increasing studies suggest that miRNAs are intimately involved in synaptic function and specific signals during memory formation. This has been the pivotal key for considering miRNAs crucial molecules to be studied in AD. MicroRNAs dysfunctions are increasingly acknowledged as a pivotal contributor in AD via deregulating genes involved in AD pathogenesis. Moreover, miRNAs have been proved to control pain sensitization processes and regulate circadian clock system that affects the sleep process. Interestingly, the differential expression of miRNA panels implies their emerging potential as diagnostic AD biomarkers. In this review, we will present an updated analysis of miRNAs role in regulating signaling processes that are involved in AD-related pathologies. We will discuss the current challenges against wider use of miRNAs and the future promising capabilities of miRNAs as diagnostic and therapeutic means for better management of AD.

Trimethylamine n-Oxide (TMAO) Modulates the Expression of Cardiovascular Disease-Related microRNAs and Their Targets

Diet is a well-known risk factor of cardiovascular diseases (CVDs). Some microRNAs (miRNAs) have been described to regulate molecular pathways related to CVDs. Diet can modulate miRNAs and their target genes. Choline, betaine, and l-carnitine, nutrients found in animal products, are metabolized into trimethylamine n-oxide (TMAO), which has been associated with CVD risk. The aim of this study was to investigate TMAO regulation of CVD-related miRNAs and their target genes in cellular models of liver and macrophages. We treated HEPG-2, THP-1, mouse liver organoids, and primary human macrophages with 6 µM TMAO at different timepoints (4, 8, and 24 h for HEPG-2 and mouse liver organoids, 12 and 24 h for THP-1, and 12 h for primary human macrophages) and analyzed the expression of a selected panel of CVD-related miRNAs and their target genes and proteins by real-time PCR and Western blot, respectively. HEPG-2 cells were transfected with anti-miR-30c and syn-miR-30c. TMAO increased the expression of miR-21-5p and miR-30c-5p. PER2, a target gene of both, decreased its expression with TMAO in HEPG-2 and mice liver organoids but increased its mRNA expression with syn-miR-30c. We concluded that TMAO modulates the expression of miRNAs related to CVDs, and that such modulation affects their target genes.

miRNAs as biomarkers for early cancer detection and their application in the development of new diagnostic tools

Over the last decades, microRNAs (miRNAs) have emerged as important molecules associated with the regulation of gene expression in humans and other organisms, expanding the strategies available to diagnose and handle several diseases. This paper presents a systematic review of literature of miRNAs related to cancer development and explores the main techniques used to quantify these molecules and their limitations as screening strategy. The bibliographic research was conducted using the online databases, PubMed, Google Scholar, Web of Science, and Science Direct searching the terms "microRNA detection", "miRNA detection", "miRNA and prostate cancer", "miRNA and cervical cancer", "miRNA and cervix cancer", "miRNA and breast cancer", and "miRNA and early cancer diagnosis". Along the systematic review over 26,000 published papers were reported, and 252 papers were returned after applying the inclusion and exclusion criteria, which were considered during this review. The aim of this study is to identify potential miRNAs related to cancer development that may be useful for early cancer diagnosis, notably in the breast, prostate, and cervical cancers. In addition, we suggest a preliminary top 20 miRNA panel according to their relevance during the respective cancer development. Considering the progressive number of new cancer cases every year worldwide, the development of new diagnostic tools is critical to refine the accuracy of screening tests, improving the life expectancy and allowing a better prognosis for the affected patients.

Targeting the Endothelium to Achieve Cardioprotection

Despite considerable improvements in the treatment of myocardial infarction, it is still a highly prevalent disease worldwide. Novel therapeutic strategies to limit infarct size are required to protect myocardial function and thus, avoid heart failure progression. Cardioprotection is a research topic with significant achievements in the context of basic science. However, translation of the beneficial effects of protective approaches from bench to bedside has proven difficult. Therefore, there is still an unmet need to study new avenues leading to protecting the myocardium against infarction. In line with this, the endothelium is an essential component of the cardiovascular system with multiple therapeutic targets with cardioprotective potential. Endothelial cells are the most abundant non-myocyte cell type in the heart and are key players in cardiovascular physiology and pathophysiology. These cells can regulate vascular tone, angiogenesis, hemostasis, and inflammation. Accordingly, endothelial dysfunction plays a fundamental role in cardiovascular diseases, which may ultimately lead to myocardial infarction. The endothelium is of paramount importance to protect the myocardium from ischemia/reperfusion injury via conditioning strategies or cardioprotective drugs. This review will provide updated information on the most promising therapeutic agents and protective approaches targeting endothelial cells in the context of myocardial infarction.

Molecular link between circadian clocks and cardiac function: a network of core clock, slave clock, and effectors

The circadian rhythm has a strong influence on both cardiac physiology and disease in humans. Preclinical studies primarily using tissue-specific transgenic mouse models have contributed to our understanding of the molecular mechanism of the circadian clock in the cardiovascular system. The core clock driven by CLOCK:BMAL1 complex functions as a universal timing machinery that primarily sets the pace in all mammalian cell types. In one specific cell or tissue type, core clock may control a secondary transcriptional oscillator, conceptualized as slave clock, which confers the oscillatory expression of tissue-specific effectors. Here, we discuss a core clock-slave clock-effectors network, which links the molecular clock to cardiac function.

Intense Light Pretreatment Improves Hemodynamics, Barrier Function and Inflammation in a Murine Model of Hemorrhagic Shock Lung

INTRODUCTION

Hemorrhagic shock is a primary injury amongst combat casualties. Hemorrhagic shock can lead to acute lung injury, which has a high mortality rate. Based on studies showing the role of intense light for organ-protection, we sought to evaluate if intense light pretreatment would be protective in a murine model of hemorrhagic shock lung.

MATERIALS AND METHODS

After exposure to standard room light or to intense light (10 000 LUX), mice were hemorrhaged for 90 minutes to maintain a mean arterial pressure (MAP) of 30-35 mmHg. Mice were then resuscitated with their blood and a NaCl infusion at a rate of 0.2 ml/h over a 3-hour period. During resuscitation, blood pressure was recorded. At the end of resuscitation, bronchoalveolar lavage was analyzed for alveolar epithelial barrier function and inflammation. To get insight into the relevance of intense light for humans, we performed a proteomics screen for lung injury biomarkers in plasma from healthy volunteers following intense light therapy.

RESULTS

We found that intense light pretreated mice had improved hemodynamics and significantly lower albumin, IL-6, and IL-8 levels in their bronchoalveolar lavage than controls. We further discovered that intense light therapy in humans significantly downregulated proinflammatory plasma proteins that are known to cause acute lung injury.

CONCLUSIONS

Our data demonstrate that mice exposed to intense light before hemorrhagic shock lung have less lung inflammation and improved alveolar epithelial barrier function. We further show that intense light therapy downregulates lung injury promoting proteins in human plasma. Together, these data suggest intense light as a possible strategy to ameliorate the consequences of a hemorrhagic shock on lung injury.

Non-coding RNAs and Ischemic Cardiovascular Diseases

The Ischemic Heart Disease (IHD) is considered a clinical condition characterized by myocardial ischemia causing an imbalance between myocardial blood supply and demand, leading to morbidity and mortality across the worldwide. Prompt diagnostic and prognostic represents key factors for the treatment and reduction of the mortality rate. Therefore, one of the newest frontiers in cardiovascular research is related to non-coding RNAs (ncRNAs), which prompted a huge interest in exploring ncRNAs candidates for utilization as potential therapeutic targets for diagnostic and prognostic and/or biomarkers in IHD. However, there are undoubtedly many more functional ncRNAs yet to be discovered and characterized. Here we will discuss our current knowledge and we will provide insight on the roles and effects elicited by some ncRNAs related to IHD.

miR‑21/PTEN pathway mediates the cardioprotection of geniposide against oxidized low‑density lipoprotein‑induced endothelial injury via suppressing oxidative stress and inflammatory response

Oxidized low‑density lipoprotein (ox‑LDL)‑induced vascular endothelial damage, oxidative stress and inflammation play a vital role in the pathophysiology of atherosclerosis. Geniposide is the primary active ingredient from Gardenia jasminoides Ellis associated with anti‑oxidative properties and cardioprotective action. However, the therapeutic mechanism of geniposide in atherosclerosis remains unclear. Hence, the present study aimed to elucidate the underlying mechanisms of geniposide in oxidative stress and inflammatory response during ox‑LDL injury in human umbilical vein endothelial cells (HUVECs), focusing particularly on the microRNA (miR)‑21/PTEN pathway. The results demonstrated that geniposide pretreatment significantly increased cell viability, decreased lactate dehydrogenase release, increased miR‑21 level and decreased PTEN expression under ox‑LDL condition. Subsequently, transfection with miR‑21 mimic enhanced the protection of geniposide on ox‑LDL‑induced cytotoxicity and apoptosis (mediated by the upregulation of apoptotic rate and caspase‑3 activity), whereas miR‑21 inhibitor reversed these effects of geniposide. In addition, geniposide resulted in an anti‑oxidant effect as evidenced by the decrease in reactive oxygen species generation, malondialdehyde content and NADPH oxidase 2 expression, and the increase in superoxide dismutase, glutathione peroxidase and catalase activities in ox‑LDL‑treated HUVECs, which were exacerbated by miR‑21 mimic and reversed by miR‑21 inhibitor. Furthermore, geniposide mitigated the ox‑LDL‑induced inflammatory response, demonstrated by a downregulation of pro‑inflammatory cytokine (IL‑1β, IL‑6, and TNF‑α) levels and an upregulation of anti‑inflammatory cytokine (IL‑10) level. However, miR‑21 mimic enhanced, whereas miR‑21 inhibitor attenuated, these effects of geniposide. In conclusion, the present results indicated that geniposide protects HUVECs from ox‑LDL injury by inhibiting oxidative stress and inflammation, and that these effects are partly due to the enhancement of the miR‑21/PTEN pathway.

MicroRNA-21 mediates the protective effects of salidroside against hypoxia/reoxygenation-induced myocardial oxidative stress and inflammatory response

Myocardial ischemia-reperfusion (I/R) injury is the oxidative stress and inflammatory response that occurs when a tissue is reperfused following a prolonged period of ischemic injury. Growing evidence has demonstrated that microRNAs (miRs) are essential in the development of myocardial I/R injury. Salidroside, a phenylpropanoid glycoside isolated from a traditional Chinese medicinal plant, Rhodiola rosea, possesses multiple pharmacological functions and protects against myocardial I/R injury in vitro and in vivo. However, the role of miRs in the cardioprotective effects of salidroside against myocardial I/R injury has not been studied, to the best of our knowledge. In the present study, the role of miR21 in the underlying mechanism of salidroside-induced protection against oxidative stress and inflammatory injuries in hypoxia/reoxygenation (H/R)-treated H9c2 cardiomyocytes was determined. The cell viability was assessed with an MTT assay. Lactate dehydrogenase (LDH) release, caspase-3 activity, malondialdehyde (MDA) level, superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) activities were determined by commercial kits. Cell apoptosis was measured by flow cytometry. Intracellular reactive oxygen species (ROS) generation was monitored by DCFH-DA. The miR-21 level was quantified by reverse transcription-quantitative (RT-q)PCR. The interleukin (IL)-6, IL-1β and tumor necrosis factor (TNF)-α levels were measured by RT-qPCR and ELISA. The results showed that salidroside pretreatment significantly increased cell viability and decreased the release of LDH, accompanied by an increase in miR-21 expression in H/R-treated H9c2 cells and a miR-21 inhibitor reversed these effects. In addition, the miR-21 inhibitor also abrogated the inhibition of salidroside on H/R-induced increases in apoptosis and caspase-3 activity in H9c2 cells. Salidroside mitigated H/R-induced oxidative stress as illustrated by the downregulation of ROS generation and MDA level and increased the activities of the antioxidant enzymes, SOD and GSH-Px, all of which were abrogated in cells transfected with the miR-21 inhibitor. Salidroside induced a decrease in the expression and levels of the pro-inflammatory cytokines, IL-6, IL-1β and TNF-α, which were prevented by the miR-21 inhibitor. Together, these results provide evidence of the beneficial effects of salidroside against myocardial I/R injury by reducing myocardial oxidative stress and inflammation which are enhanced by increasing miR-21 expression.

Spatiotemporal chromatin dynamics - A telltale of circadian epigenetic gene regulation

Over the course of evolution, nature has forced organisms under selection pressure to hardwire an internal time keeping device that defines 24 h of a daily cycle of physiological and behavioral rhythms, known as circadian rhythms. At the cellular level, the cycle is governed by significant fractions of transcriptomes, which are under the control of transcriptional and translational feedback loop of clock genes. Intriguingly, this feedback loop is regulated at multiple stratums such as at the transcriptional and translational levels, which direct a cell towards producing a robust rhythm by sustaining the repeated stoichiometry of protein products. Moreover, with the advent of state of the art paradigms, epigenetic regulation of circadian rhythms has been becoming more evident at present time. Light-induced recurring fluctuations in chromatin acetylation concurrent with the binding of RNA Pol II and integration of miRNAs monitor the chromatin modifiers or clock genes expression to drive temporal rhythmicity. Furthermore, CLOCK protein intrinsic histone acetyl transferase activity, the interaction of CLOCK-BMAL-1 with HAT enzymes, and the involvement of many histone deacetylases also maintain the rhythmic protein profile. Additionally, the critical role of the rhythmic methylation pattern of clock genes in battery of cancer and metabolic disorders also defines its importance. Therefore, in this review, we focused on accumulating all the present data available on epigenetics and circadian rhythms. Interestingly, we also gathered evidence from the available literature pinpointing towards the dynamic nature of chromatin architecture governed by long and short-range regulatory elements DNA contacts arising daily, that was thought to be steady otherwise.

miRNA‑145 inhibits myocardial infarction‑induced apoptosis through autophagy via Akt3/mTOR signaling pathway in vitro and in vivo

The present study investigated the effects of micro (mi)RNA‑145 on acute myocardial infarction (AMI) and the potential underlying mechanism. A total of 6 AMI and 6 normal rat tissues were investigated for the present study. It was demonstrated that miRNA‑145 expression was downregulated in the AMI rat model, compared with the control group. Downregulation of miRNA‑145 increased cardiac cell apoptosis, suppressed phosphorylated (p)‑RAC‑γ serine/threonine‑protein kinase (Akt3) and p‑mechanistic target of rapamycin (mTOR) protein expression levels and suppressed autophagy in an in vitro model of AMI. However, overexpression of miRNA‑145 decreased cardiac cell apoptosis, induced p‑Akt3 and p‑mTOR protein expression and promoted autophagy in the in vitro model of AMI. The inhibition of Akt3 (GSK2110183, 1 nM) decreased the effect of the miRNA‑145 upregulation on cell apoptosis in the in vitro model of AMI. Chloroquine diphosphate (5 µM) inhibited the regulatory effect of miRNA‑145 upregulation on autophagy to adjust cell apoptosis, in the in vitro model of AMI. The results of the present study demonstrate that miRNA‑145 inhibits myocardial infarction‑induced apoptosis via autophagy associated with the Akt3/mTOR signaling pathway in vivo and in vitro.

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.

The Circadian PER2 Enhancer Nobiletin Reverses the Deleterious Effects of Midazolam in Myocardial Ischemia and Reperfusion Injury

BACKGROUND

Recently, we identified the circadian rhythm protein Period 2 (PER2) in robust cardioprotection from myocardial ischemia (MI). Based on findings that perioperative MI is the most common major cardiovascular complication and that anesthetics can alter the expression of PER2, we hypothesized that an anesthesia mediated downregulation of PER2 could be detrimental if myocardial ischemia and reperfusion (IR) would occur.

METHODS AND RESULTS

We exposed mice to pentobarbital, fentanyl, ketamine, propofol, midazolam or isoflurane and determined cardiac Per2 mRNA levels. Unexpectedly, only midazolam treatment resulted in an immediate and significant downregulation of Per2 transcript levels. Subsequent studies in mice pretreated with midazolam using an in-situ mouse model for myocardial (IR)-injury revealed a significant and dramatic increase in infarct sizes or Troponin-I serum levels in the midazolam treated group when compared to controls. Using the recently identified flavonoid, nobiletin, as a PER2 enhancer completely abolished the deleterious effects of midazolam during myocardial IR-injury. Moreover, nobiletin treatment alone significantly reduced infarct sizes or Troponin I levels in wildtype but not in Per2-/- mice. Pharmacological studies on nobiletin like flavonoids revealed that only nobiletin and tangeritin, both found to enhance PER2, were cardioprotective in our murine model for myocardial IR-injury.

CONCLUSION

We identified midazolam mediated downregulation of cardiac PER2 as an underlying mechanism for a deleterious effect of midazolam pretreatment in myocardial IR-injury. These findings highlight PER2 as a cardioprotective mechanism and suggest the PER2 enhancers nobiletin or tangeritin as a preventative therapy for myocardial IR-injury in the perioperative setting where midazolam pretreatment occurs frequently.