Circadian Redox and Metabolic Oscillations in Mammalian Systems

Abstract

Significance: A substantial proportion of mammalian physiology is organized around the day/night cycle, being regulated by the co-ordinated action of numerous cell-autonomous circadian oscillators throughout the body. Disruption of internal timekeeping, by genetic or environmental perturbation, leads to metabolic dysregulation, whereas changes in metabolism affect timekeeping. Recent Advances: While gene expression cycles are essential for the temporal coordination of normal physiology, it has become clear that rhythms in metabolism and redox balance are cell-intrinsic phenomena, which may regulate gene expression cycles reciprocally, but persist in their absence. For example, a circadian rhythm in peroxiredoxin oxidation was recently observed in isolated human erythrocytes, fibroblast cell lines in vitro, and mouse liver in vivo. Critical Issues: Mammalian timekeeping is a cellular phenomenon. While we understand many of the cellular systems that contribute to this biological oscillation's fidelity and robustness, a comprehensive mechanistic understanding remains elusive. Moreover, the formerly clear distinction between ''core clock components'' and rhythmic cellular outputs is blurred since several outputs, for example, redox balance, can feed back to regulate timekeeping. As with any cyclical system, establishing causality becomes problematic. Future Directions: A detailed molecular understanding of the temporal crosstalk between cellular systems, and the coincidence detection mechanisms that allow a cell to discriminate clock-relevant from irrelevant stimuli, will be essential as we move toward an integrated model of how this daily biological oscillation works. Such knowledge will highlight new avenues by which the functional consequences of circadian timekeeping can be explored in the context of human health and disease. Antioxid. Redox Signal. 20, 2966Signal. 20, -2981

Role of the Nrf2 signaling system in health and disease

“…In humans and other mammals, circadian biological oscillations -with a period of about 24 h -influence a variety of behavioral and physiological processes pertaining to sleep, metabolism, immune function, etc. (74)(75)(76)(77)(78). Recently, it has been found that redox-dependent processes participate in the circadian rhythms along with genetic timekeeping clock processes (75,76,78,79), which supports possible participation of the Nrf2 pathway as it pertains to response to cellular redox status (74,77,(80)(81)(82).…”

Peroxiredoxins: guardians against oxidative stress and modulators of peroxide signaling

“…First, circadian cycles of Prx hyperoxidation seen in a variety of organisms were suggested to be a fundamental, transcription-independent mechanism underlying circadian clocks [97, 98]. However, there is no evidence yet that this is related to signaling, and rather than being a driver of rhythms, it may be a consequence of other rhythmic cellular activities.…”

Metabolic signatures of T-cells and macrophages in rheumatoid arthritis

“…1). Although ROS have mostly been regarded as harmful, recent work has emphasized the essential contribution of oxidant signaling in keeping intracellular molecular communications fast and efficient [27,28]. Accordingly, ATP low , NADPH high , ROS low T-cells lose the ability to swiftly mobilize ROS-sensing mediators.…”