Spatiotemporal chromatin dynamics - A telltale of circadian epigenetic gene regulation

Heart Failure and Arrhythmias: Circadian and Epigenetic Interplay in Myocardial Electrophysiology

Emerging evidence underscores the impact of circadian rhythms on cardiovascular processes, particularly in conditions such as hypertension, myocardial infarction, and heart failure, where circadian rhythm disruptions are linked to disease progression and adverse clinical outcomes. Circadian clock proteins are intricately linked to myocardial electrophysiological remodeling and epigenetic pathways associated with arrhythmias in heart failure. In the context of heart failure, circadian clock dysregulation leads to electrophysiological remodeling in the cardiomyocytes, which can precipitate life-threatening arrhythmias such as ventricular tachycardia (VT) and ventricular fibrillation (VF). This dysregulation may be influenced by environmental factors, such as diet and exercise, as well as genetic factors. Moreover, epigenetic modifications in heart failure have been implicated in the regulation of genes involved in cardiac hypertrophy, fibrosis, and inflammation. The interplay between circadian clock proteins, myocardial electrophysiological remodeling, and epigenetic pathways in heart failure-related arrhythmias is complex and multifaceted. Further research is needed to elucidate how these processes interact and contribute to the development of arrhythmias in heart failure patients. This review aims to explore the connections between circadian rhythms, myocardial electrophysiology, and arrhythmias related to heart failure, with the goal of identifying potential therapeutic targets and interventions that may counteract the adverse effects of circadian disruptions on cardiovascular health.

Avian migration clocks in a changing world

Avian long-distance migration requires refined programming to orchestrate the birds' movements on annual temporal and continental spatial scales. Programming is particularly important as long-distance movements typically anticipate future environmental conditions. Hence, migration has long been of particular interest in chronobiology. Captivity studies using a proxy, the shift to nocturnality during migration seasons (i.e., migratory restlessness), have revealed circannual and circadian regulation, as well as an innate sense of direction. Thanks to rapid development of tracking technology, detailed information from free-flying birds, including annual-cycle data and actograms, now allows relating this mechanistic background to behaviour in the wild. Likewise, genomic approaches begin to unravel the many physiological pathways that contribute to migration. Despite these advances, it is still unclear how migration programmes are integrated with specific environmental conditions experienced during the journey. Such knowledge is imminently important as temporal environments undergo rapid anthropogenic modification. Migratory birds as a group are not dealing well with the changes, yet some species show remarkable adjustments at behavioural and genetic levels. Integrated research programmes and interdisciplinary collaborations are needed to understand the range of responses of migratory birds to environmental change, and more broadly, the functioning of timing programmes under natural conditions.

Photoperiod-dependent changes in oxidative stress markers in the blood of Shetland pony mares and stallions involved in recreational horseback riding

The objective of the current study was to determine the photoperiod-induced variations and the impact of exercise on oxidative stress biomarkers [2-thiobarbituric acid reactive substances (TBARS), aldehydic (AD) and ketonic (KD) derivatives of oxidatively modified proteins (OMP), total antioxidant capacity (TAC), and activities of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx)] and biomarkers of metabolic alterations [glucose, urea, and uric acid and the activity of lactate dehydrogenase (LDH)] in the blood of Shetland pony mares and stallions involved in recreational horseback riding. Twenty-one healthy adult Shetland ponies (11 mares and 10 stallions) aged 6.5 ± 1.4 years old from the central Pomeranian region in Poland were used in this study. Blood samples were taken once per season for one year: spring (3 April), summer (5 July), autumn (1 October) and winter (25 January). A MANOVA analysis revealed that the photoperiod factor had a leading role in alterations of these biomarkers, while the exercise and sex of the ponies exerted a lower impact. The lipid peroxidation biomarkers, for example, the plasma TBARS level, indicated the maximum adjusted coefficient of determination R²_ad = 0.77. Before exercise (at rest), the plasma of the stallions and mares exhibited minimum values of TBARS levels in the spring and summer photoperiods and maximum levels in autumn and winter. A statistically significant reduction in the levels of both aldehydic and ketonic derivatives of OMP in the blood of ponies was observed during the autumn and winter periods; additionally, the level of ketonic derivatives of OMP declined after exercise in spring. TAC was statistically significant in the spring and winter photoperiods both before and after exercise. SOD activity did not have a pronounced photoperiod-induced pattern but was dependent on the sex and exercise. CAT activity varied and was statistically significant only in the plasma of the mares after exercise in the spring, summer, and winter photoperiods. The minimum GPx activity in the blood of the mares before exercise (at rest) was observed in autumn, while the maximum was noted in winter and summer. Photoperiod- and exercise-induced alterations in markers of oxidative stress and antioxidant defences may contribute to the adaptation of animals to exercise, depending on sex. The seasonal variations in the antioxidant defences demonstrated in our study, as well as substrates of energy metabolism in the blood of mares and stallions, depending on exercise capacity, could be an important aspect in the ability of endogenous adaptive mechanisms of animals to react in advance to environmental changes associated with seasons.

Origins of human disease: the chrono-epigenetic perspective

Epigenetics has enriched human disease studies by adding new interpretations to disease features that cannot be explained by genetic and environmental factors. However, identifying causal mechanisms of epigenetic origin has been challenging. New opportunities have risen from recent findings in intra-individual and cyclical epigenetic variation, which includes circadian epigenetic oscillations. Cytosine modifications display deterministic temporal rhythms, which may drive ageing and complex disease. Temporality in the epigenome, or the 'chrono' dimension, may help the integration of epigenetic, environmental and genetic disease studies, and reconcile several disparities stemming from the arbitrarily delimited research fields. The ultimate goal of chrono-epigenetics is to predict disease risk, age of onset and disease dynamics from within individual-specific temporal dynamics of epigenomes.

Identifying roles for peptidergic signaling in mice

Despite accumulating evidence demonstrating the essential roles played by neuropeptides, it has proven challenging to use this information to develop therapeutic strategies. Peptidergic signaling can involve juxtacrine, paracrine, endocrine, and neuronal signaling, making it difficult to define physiologically important pathways. One of the final steps in the biosynthesis of many neuropeptides requires a single enzyme, peptidylglycine α-amidating monooxygenase (PAM), and lack of amidation renders most of these peptides biologically inert. PAM, an ancient integral membrane enzyme that traverses the biosynthetic and endocytic pathways, also affects cytoskeletal organization and gene expression. While mice, zebrafish, and flies lacking Pam (Pam^KO/KO ) are not viable, we reasoned that cell type-specific elimination of Pam expression would generate mice that could be screened for physiologically important and tissue-specific deficits. Conditional Pam^cKO/cKO mice, with loxP sites flanking the 2 exons deleted in the global Pam^KO/KO mouse, were indistinguishable from wild-type mice. Eliminating Pam expression in excitatory forebrain neurons reduced anxiety-like behavior, increased locomotor responsiveness to cocaine, and improved thermoregulation in the cold. A number of amidated peptides play essential roles in each of these behaviors. Although atrial natriuretic peptide (ANP) is not amidated, Pam expression in the atrium exceeds levels in any other tissue. Eliminating Pam expression in cardiomyocytes increased anxiety-like behavior and improved thermoregulation. Atrial and serum levels of ANP fell sharply in PAM myosin heavy chain 6 conditional knockout mice, and RNA sequencing analysis identified changes in gene expression in pathways related to cardiac function. Use of this screening platform should facilitate the development of therapeutic approaches targeted to peptidergic pathways.