New research has discovered that daylight not only lifts our spirits, but also boosts our immune systems. A team at the University of Auckland in New Zealand has found that neutrophils seem to have a type of ‘body clock’ of their own and daylight hours have a positive impact on their ability to fight off infections.
The good old zebrafish was called upon again for this research, taking advantage of the ability to breed transparent versions of this fish so researchers can get a good visual overview of what’s happening internally. Its genetic make-up is similar to ours, which doesn’t hurt in the lab.
From the results, it would appear that neutrophils have a type of circadian rhythm. The team observed that neutrophils are able to ‘recognise’ when it is daytime and daylight hours enhance their ability to turbo-charge the immune system and destroy bacteria.
“Given that neutrophils are the first immune cells to be recruited to sites of inflammation, our discovery has very broad implications for therapeutic benefit in many inflammatory diseases,” commented Associate Prof Christopher Hall from the Department of Molecular Medicine and Pathology at the University and lead researcher. “We think this represents an evolutionary response such that during daylight hours, the host is more active so more likely to encounter bacterial infections.”
It was shown in previous research that immune responses in fish models peaked in the morning, which is their most active early phase. The focus is now on finding out exactly how and why this happens.
Prof Hall added: “This finding paves the way for development of drugs that target the circadian clock in neutrophils to boost their ability to fight infections.”
The authors wrote in their paper: “Host protection against bacterial pathogens, including salmonella, Streptococcus pneumoniae, and Chlamydia muridarum, is greatest when infections occur during an animal’s active phase. This has contributed to the view that the circadian system likely boosts antibacterial immunity as animals transition to activity and the risk of infection increases.”
“Here, we show that neutrophils provide a critical component of the circadian-gated host response to infection by demonstrating that they use their circadian clock machinery to transcriptionally amplify bactericidal activity during the active phase.”
The results may have therapeutic implications for patients who are immunocompromised – if they are not bed-bound, a little daylight might be beneficial in ways that extend beyond mental wellbeing. But whether this research is good news for Irish people – or others in the Northern Hemisphere – is debatable. It does make the prospect of another winter with shorter, darker days even less appealing. If you want to take a deep-dive, the research was published recently in Science Immunology.
Another interesting piece of recent research comes from Tufts University in the US and may also have a wide range of applications, including the ability to regularly and easily monitor toxic stress levels.
This team has come up with an ingenious dental floss that is capable of sampling the cortisol in saliva, which can then be quantified to indicate chronic stress levels in the user.
The device utilises polymer casting technology that has the potential to be adapted to a number of applications, such as monitoring diabetes or tracking fertility. It looks like any standard floss, but contains extremely narrow channels in the floss, from which fluid is drawn into the handle, and then channelled into an attached collection device. The actual cortisol recognition is performed using electropolymerised molecularly imprinted polymers (eMIPs) technology, and is another example of how medicine and engineering can lead to better patient care.
“We didn’t want measurement to create an additional source of stress, so we thought, can we make a sensing device that becomes part of your day-to-day routine? Cortisol is a stress marker found in saliva, so flossing seemed like a natural fit to take a daily sample,” said Prof Sameer Sonkusale, Professor of Electrical and Computer Engineering at Tufts. “The eMIP approach is a game changer. Biosensors have typically been developed using antibodies or other receptors that pick up the molecule of interest. Once a marker is found, a lot of work has to go into bioengineering the receiving molecule attached to the sensor. eMIP does not rely on a lot of investment in making antibodies or receptors. If you discover a new marker for stress or any other disease or condition, you can just create a polymer cast in a very short period of time.”
If widely adopted, the system could provide a much more reliable indicator of chronic stress than self-reports and questionnaires.
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