Heart attacks that occur at night are less serious than those that occur during the day, and the reason, according to a study by the National Cardiovascular Research Center (CNIC), is that neutrophils – a type of white blood cells– are less aggressive at night.
The research, led by Andrés Hidalgo and published this Friday in the Journal of Experimental Medicine, shows that neutrophils They have an internal clock that regulates their aggressiveness throughout the day and determines the extent of damage to the heart after a heart attack. In the same study, the researchers also developed a pharmacological strategy in experimental models for block the molecular clock of neutrophils and keeps them in a “nocturnal” state to reduce their damaging potential during a heart attack.
A daytime immune system
The immune system protects the body against the responsible microorganisms infections. Since humans are diurnal, the likelihood of exposure to pathogens is greater during the day and the immune system therefore adjusts its peaks of activity. activity to this circadian rhythm but this defensive response can become harmful.
After decades of research, we know that almost half of heart damage after a heart attack is caused by neutrophils, but this damage fluctuates throughout the day, suggesting that there are circadian mechanisms that limit the neutrophil activity and protect the body. To find out, the team looked at data from thousands of patients at Madrid’s 12 de Octubre Hospital and confirmed that lower nighttime neutrophil activity leads to less severe heart attacks during this time.
They then developed a pharmacological strategy in experimental models to block the molecular clock of neutrophils, thus reducing their harmful potential during the heart attack. “The compound mimics a factor that the body produces primarily during the night. In a way, this factor neutrophil ‘tricks’ so that they think it’s dark, thereby reducing their toxic activity,” explains Hidalgo.
The reason this happens, explains the study’s first author, Alejandra Aroca-Crevillén, is that “at night, neutrophils migrate to the damaged area. without affecting healthy tissues. During the day, they lose this directionality and cause more damage to surrounding tissues. »
The neutrophil circadian clock
This study is one of the first enjoy the rhythms circadian cells of the immune system to modulate inflammation without compromising defense against infections. “We were surprised to find that blocking the neutrophil circadian clock not only protect the heartbut also improves responses to certain microbes and even reduces emboli associated with sickle cell anemia”, adds Aroca-Crevillen.
The authors believe that the results open the door to new therapies based on chronobiology (the branch of biology that studies how living organisms structure their physiological processes over time), with the potential to protect the heart and other organs from inflammatory damage without weakening the body’s natural defenses.
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