Chronobiophotonics is an emerging interdisciplinary field integrating photonics, circadian biology, and medicine to study and control biological clocks using light. It is centered on the concept that biological clocks governing genetic, cellular, tissue, organ, and organismal physiology can be regulated by light.
Image Credit: vetre/Shutterstock.com
Decoding Inner Cycles with Biological Clocks
A wide range of living organisms - from single-celled bacteria to plants, fungi, animals, and humans - naturally follow innate rhythms synchronized to the recurring cycles of day/night, seasons, tides, and moon phases on Earth. These biological clocks provide a selective advantage by enabling internal temporal order tuned to periodicities in the outside world.
In humans, networks of cellular clocks and signaling pathways generate roughly 24-hour biochemical oscillations known as circadian rhythms. These rhythms/cycles influence our sleep-wake patterns, hormone levels, cell regeneration, brain wave activity, digestive metabolism, physiological processes, and mood and cognition.
Circadian rhythms are orchestrated by the suprachiasmatic nucleus (SCN), comprising 10,000 neurons. However, the SCN alone cannot dictate the body's rhythm; circadian control involves intricate interactions among diverse cellular oscillators, sensory pathways, and rhythmic cues from routine behaviors, including eating, activity, and light.
Light As A "Master Controller" of Biological Timing
Numerous studies have shown that among the factors influencing circadian rhythms, the light-dark cycle serves as the dominant "zeitgeber" (timing cue). The retinal circuits transmit environmental light signals to the SCN master clock, effectively resetting and entraining biological rhythms on approximately 24-hour cycles.
Additionally, light and dark sequences are essential for synchronizing our intrinsic periods to resonate precisely with Earth's 24-hour rotation. This photic entrainment enables us to properly align our sleep-wake, fasting-feeding, and activity-rest routines to optimal times of day in relation to sunlight.
Losing this harmonized photoentrainment, whether due to blindness, extreme polar winters, or modern indoor lifestyles with irregular light exposure, can induce circadian disruptions with adverse health consequences. These disturbances may increase the risk of obesity, diabetes, mood disorders, cognitive dysfunction, reproductive problems, cardiovascular disease, and cancer.
Controlling Biological Clocks with Light
Recognizing light as a "master controller" of biological clocks, chronobiologists collaborated with physicists, engineers, and health experts to establish "chronobiophotonics." This new scientific discipline focuses on using light to study and control central timekeeping biological mechanisms.
Early findings unveiled the role of specialized photoreceptor cells in the retina, using melanopsin with peak sensitivity for blue wavelengths around 480nm to tune circadian rhythms. Furthermore, these discoveries demonstrated that brief flashes of specifically tailored blue-enriched light at strategic times could effectively reset melatonin rhythms, sleep cycles, and clock gene expression patterns in humans and animals.
This spawned intensive research investigating how tuning properties of light - including spectrum, intensity, timing, and duration of exposure - can influence biological clocks.
Recent Research and Development
Light Therapies for Health and Performance
Chronobiophotonics has already sparked a new generation of "circadian-effective" lighting technologies and light-based therapies for stabilizing health. Customized bright light exposure, light avoidance, or carefully timed melatonin are now first-line treatments for circadian sleep disorders like jet lag, shift work, and problematic late sleep phases.
A study published in the Journal of the American Chemical Society developed a light-responsive method to regulate cellular biological clocks. The researchers incorporated a light-responsive chemical "cage" into a longdaysin inhibitor, allowing precise control over its activity in human cells, mouse tissue, and zebrafish larvae.
This method enabled manipulating circadian clocks within cell populations and understanding intercellular communication, offering a potential treatment approach for sleep disorders and circadian-clock-related diseases.
Diagnosing by Illuminating
Chronobiophotonics extends beyond therapeutic applications, enabling the development of optical techniques, metrics, and instrumentation to assess circadian status. This could offer invaluable chronotype diagnostics, providing essential insights into personalized circadian medicine and guiding appropriate interventions based on internal temporal order.
Recent research conducted by UVA Health has provided valuable insights into the potential impact of enhanced light sensitivity on the worsening of Alzheimer's symptoms, particularly during the evening, a phenomenon known as "sundowning."
The researchers initially considered neuroinflammation and mutant tau as potential causes but ultimately ruled them out. Instead, they propose a connection between circadian disruptions in Alzheimer's and changes in light sensitivity, emphasizing the pivotal role of the retina in heightened light sensitivity.
This discovery opens up promising avenues for developing new treatments, management strategies, and preventive measures for Alzheimer's disease.
"These data suggest that controlling the kind of light and the timing of the light could be key to reducing circadian disruptions in Alzheimer's disease. We hope that this research will help us to develop light therapies that people can use to reduce the progression of Alzheimer's disease." Heather Ferris, MD, PhD, the University of Virginia School of Medicine.
Future Outlooks
Chronobiophotonics represents a novel frontier, recognizing light as a crucial context for human well-being. Directing focused light onto biological clockwork holds the potential to elucidate complex biological clocks, optimize function, treat diseases, and enhance wellness. However, navigating the ethical considerations of manipulating human clockwork while respecting autonomy over internal time will be crucial as we venture into this new era of chronobiology.
More from AZoOptics: How is Machine Learning Leveraged in Photonic Design?
References and Further Reading
Nagoya University. (2019). Compound controls biological clock with light. [Online]. Available at: https://www.eurekalert.org/news-releases/633857
Kolarski, D., Sugiyama, A., Breton, G., Rakers, C., Ono, D., Schulte, A., ... & Feringa, B. L. (2019). Controlling the circadian clock with high temporal resolution through photodosing. Journal of the American Chemical Society, 141(40), 15784-15791. https://doi.org/10.1021/jacs.9b05445
Barney, J. (2023). Enhanced Light Sensitivity May Play Key Role in Alzheimer's. [Online]. Available at: https://newsroom.uvahealth.com/2023/07/26/alzheimers-discovery-suggests-key-role-for-light-sensitivity/
Frontiers Media. (2024). ChronoBiophotonics. [Online]. Available at: https://www.frontiersin.org/research-topics/52464/chronobiophotonics
Rea, M. S. (2011). Circadian photonics. Nature Photonics, 5(5), 271-272. https://doi.org/10.1038/nphoton.2011.71
Blume, C., Garbazza, C., & Spitschan, M. (2019). Effects of light on human circadian rhythms, sleep and mood. Somnologie, 23(3), 147. https://doi.org/10.1007/s11818-019-00215-
Disclaimer: The views expressed here are those of the author expressed in their private capacity and do not necessarily represent the views of AZoM.com Limited T/A AZoNetwork the owner and operator of this website. This disclaimer forms part of the Terms and conditions of use of this website.