Researchers from Yale University School of Medicine have proposed a method to reduce the risk of damage to heart muscle caused by neutrophils during a heart attack. The approach involves switching these immune cells into a “night mode.” The results of the study were published in the Journal of Experimental Medicine.

Neutrophils are among the first responders to injury, tasked with destroying microbes and initiating healing. However, in the process they can also damage healthy cells by releasing harmful chemical substances, Planet Today reports. Their activity is governed by an internal biological clock: during the day, neutrophils are active and aggressive, while at night they become much calmer. This rhythm helps explain why heart attacks that occur in the morning are more dangerous than those at night.

In the new study, the scientists used the drug ATI2341, testing its effects in mice. The drug acts as an activator of a neutrophil receptor and is capable of shifting these cells into a calmer, night-like state even during the daytime. After a heart attack, animals treated with the drug showed less cardiac damage, while heart muscle function, on the contrary, improved.

The mechanism of action is as follows: under the influence of the drug, neutrophils tended to move closer to the center of the damaged area, reducing the likelihood of injury to healthy cells. Importantly, immune function was preserved, and the mice retained their ability to effectively fight infections.

According to the authors, switching neutrophils into a night mode makes it possible to safely control inflammation after a heart attack and aids in the development of drugs that can protect the heart without weakening immune defenses. In the future, the researchers plan to expand the studies to include human volunteers.