Summary: Researchers have discovered that daylight improves the power to fight neutrophils, the most abundant white blood cells in the body. Using transparent zebra fish, scientists observed that these immune cells contain internal circadian watches that are activated by light, which increases their bacterial killing capacity during the day.
This synchronization between daylight and the immune response suggests an evolutionary adaptation to defend itself better against infections found during periods of activity. The findings could lead to new therapies that optimize immune function by attacking these cell clocks.
Key facts:
Neutrophil watches: Neutrophils have circadian watches that respond to daylight. Immunity time of the peak: immune responses are stronger during the phases of daytime activity.
Source: University of Auckland
An innovative study, led by scientists from Waipapa Taumata Rau, University of Auckland, has discovered how daylight can increase the capacity of the immune system to combat infections.
The team focused on the most abundant immune cells in our bodies, called ‘neutrophils’, which are a type of white blood cells. These cells quickly move to the site of an infection and kill invasive bacteria.
The researchers used the zebra fish, a small fresh water fish, as a model organism, because its genetic composition is similar to ours and can be raised to have transparent bodies, which facilitates the observation of biological processes in real time.
“In previous studies, we observed that immune responses reached their maximum point in the morning, during the early active phase of the fish,” says Professor Christopher Hall, of the Department of Medicine and Molecular Pathology.
“We believe that this represents an evolutionary response in such a way that during the hours of the day the host is more active, so it is more likely to find bacterial infections,” says Hall.
However, scientists wanted to discover how the immune response was synchronizing with daylight.
With this new study, published in Science Immunology, and led by two doctoral researchers, it was discovered that neutrophils had a circadian clock that alerted them during the day and increased their ability to kill bacteria.
Most of our cells have circadian watches to tell them what time of day is in the outside world, to regulate body activities. The light has the greatest influence to restore these circadian watches.
“Since neutrophils are the first immune cells that are recruited in inflammation sites, our discovery has very broad implications for the therapeutic benefit in many inflammatory diseases,” says Hall.
“This finding paves the way for drug development that are directed to the circadian clock in neutrophils to increase their ability to combat infections.”
The investigation was financed through the Royal Society of Nz’s Marsden Fund.
The current research now focuses on understanding the specific mechanisms by which light influences the circadian neutrophilic clock.
About this rhythm research and circadian immune research news
Author: Gilbert Wong
Source: University of Auckland
Contact: Gilbert Wong – University of Auckland
Image: The image is accredited to Neuroscience News
Original research: open access.
“A circadian timer regulated by the light optimizes the bactericidal activity of neutrophils to boost the diurnal immunity” of Christopher Hall et al. Scientific immunology
Abstract
A circadian timer regulated by the light optimizes the bactericidal activity of neutrophils to increase daytime immunity
The immune response exhibits a strong circadian rhythmity, with an improved bacterial clearance often synchronized with the active phase of an organism.
Despite providing most of the cell antibacterial defense, the neutrophilic clock is little known.
Here, we use the Larval Cebra fish to explore the paper of the clock genes in neutrophils during infection.
Per2 was required in neutrophils for the reactive production of oxygen species (ROS) and bacterial death by improving the sensitive expression to the infection of the high modification group 1A (HMGB1A).
The mastery of union to Cry de Per2 was necessary for the regulation of the bactericidal activity of neutrophils, and the neutrophils that lacked Cry1A had high bactericidal activity and expression of HMGB1A that responds by infection.
A CIS regulatory element conserved with BMAL1 and the reasons for the nuclear factor κB κB of the HMGB1A expression that responds to closed infection to the light phase.
The mutagenesis of the BMAL1 motive in neutrophils promoted the effect of light of light on the bactericidal activity and the expression of HMGB1A.
These findings identify an intrinsic light sensitive cell timer that controls the time variations in antibacterial activity.
