Related Articles

Circadian rhythms in cardiovascular (dys)function: approaches for future therapeutics

The circadian clock is an evolutionarily conserved time-keeper that regulates physiological processes across 24 h. In the cardiovascular system, several parameters, such as blood pressure, heart rate, and metabolism, exhibit time-of-day variations. These features are in part driven by the circadian clock. Chronic perturbation of diurnal rhythmicity due to shift work or irregular social schedules has been associated with an increased risk of hypertension, arrhythmias, and myocardial infarction. This review discusses the impact of circadian rhythms on human cardiovascular health and the effect of clock disruption on the occurrence of adverse cardiac events. Additionally, we discuss how the main risk factors of cardiovascular diseases, such as obesity, sleep disorders, and aging, affect circadian rhythms. Finally, we elaborate on chronotherapy as well as on targeting the clock and highlight novel approaches to translate our scientific understanding of the circadian clock into clinical practice.

Beyond vision: effects of light on the circadian clock and mood-related behaviours

Light is a crucial environmental factor that influences various aspects of life, including physiological and psychological processes. While light is well-known for its role in enabling humans and other animals to perceive their surroundings, its influence extends beyond vision. Importantly, light affects our internal time-keeping system, the circadian clock, which regulates daily rhythms of biochemical and physiological processes, ultimately impacting mood and behaviour. The 24-h availability of light can have profound effects on our well-being, both physically and mentally, as seen in cases of jet lag and shift work. This review summarizes the intricate relationships between light, the circadian clock, and mood-related behaviours, exploring the underlying mechanisms and its implications for health.

Crosstalk between salicylic acid signalling and the circadian clock promotes an effective immune response in plants

The rotation of Earth creates a cycle of day and night, leading to predictable changes in environmental conditions. The circadian clock synchronizes an organism with these environmental changes and alters their physiology in anticipation. Prediction of the probable timing of pathogen infection enables plants to prime their immune system without wasting resources or sacrificing growth. Here, we explore the relationship between the immune hormone salicylic acid (SA), and the circadian clock in Arabidopsis. We found that SA altered circadian rhythmicity through the SA receptor and master transcriptional coactivator, NPR1. Reciprocally, the circadian clock gates SA-induced transcript levels of NPR1-dependent immune genes. Furthermore, the clock gene CCA1 is essential for SA-induced immunity to the major bacterial plant pathogen Pseudomonas syringae. These results build upon existing studies of the relationship between the circadian clock and SA signalling and how interactions between these systems produce an effective immune response. Understanding how and why the immune response in plants is linked to the circadian clock is crucial in working towards improved crop productivity.

The circadian clock in enamel development

Circadian rhythms are self-sustaining oscillations within biological systems that play key roles in a diverse multitude of physiological processes. The circadian clock mechanisms in brain and peripheral tissues can oscillate independently or be synchronized/disrupted by external stimuli. Dental enamel is a type of mineralized tissue that forms the exterior surface of the tooth crown. Incremental Retzius lines are readily observable microstructures of mature tooth enamel that indicate the regulation of amelogenesis by circadian rhythms. Teeth enamel is formed by enamel-forming cells known as ameloblasts, which are regulated and orchestrated by the circadian clock during amelogenesis. This review will first examine the key roles of the circadian clock in regulating ameloblasts and amelogenesis. Several physiological processes are involved, including gene expression, cell morphology, metabolic changes, matrix deposition, ion transportation, and mineralization. Next, the potential detrimental effects of circadian rhythm disruption on enamel formation are discussed. Circadian rhythm disruption can directly lead to Enamel Hypoplasia, which might also be a potential causative mechanism of amelogenesis imperfecta. Finally, future research trajectory in this field is extrapolated. It is hoped that this review will inspire more intensive research efforts and provide relevant cues in formulating novel therapeutic strategies for preventing tooth enamel developmental abnormalities.

Dissecting the complexity of local and systemic circadian communication in plants

The plant circadian clock regulates daily and seasonal rhythms of key biological processes, from growth and development to metabolism and physiology. Recent circadian research is moving beyond whole plants to specific cells, tissues, and organs. In this review, we summarize our understanding of circadian organization in plants, with a focus on communication and synchronization between circadian oscillators, also known as circadian coupling. We describe the different strengths of intercellular coupling and highlight recent advances supporting interorgan communication. Experimental and mathematical evidence suggests that plants precisely balance both the circadian autonomy of individual cellular clocks and synchronization between neighboring cells and across distal tissues and organs. This complex organization has probably evolved to optimize the specific functions of each cell type, tissue, or organ while sustaining global circadian coordination. Circadian coordination may be essential for proper regulation of growth, development, and responses to specific environmental conditions.

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