SARS-CoV-2, the virus that causes COVID-19, can damage the heart even without directly infecting heart tissue, according to a study supported by the National Institutes of Health. The research, published in the journal Circulation, specifically looked at heart damage in people with acute respiratory distress syndrome (ARDS) associated with SARS-CoV2, a serious lung condition that can be fatal. But the researchers said the findings could have relevance for organs beyond the heart and also for viruses other than SARS-CoV-2.
Scientists have long known that COVID-19 increases the risk of heart attack, stroke and long COVID, and previous imaging research has shown that more than 50% of people who contract COVID-19 experience some inflammation or damage. in the heart. What scientists didn’t know is whether the damage occurs because the virus infects the heart tissue itself or due to systemic inflammation triggered by the body’s well-known immune response to the virus.
“This was a fundamental question, and finding the answer opens up a whole new understanding of the link between this serious lung injury and the type of inflammation that can lead to cardiovascular complications,” said Michelle Olive, Ph.D., associate director of the Translational Research Program. basic and early studies from the National Heart, Lung, and Blood Institute (NHLBI), part of the NIH. “Research also suggests that suppressing inflammation through treatments may help minimize these complications.”
To arrive at their findings, the researchers focused on immune cells known as cardiac macrophages, which normally play a critical role in maintaining healthy tissue but can become inflammatory in response to injuries such as a heart attack or heart failure. The researchers analyzed heart tissue samples from 21 patients who died from SARS-CoV-2-associated ARDS and compared them with samples from 33 patients who died from causes unrelated to COVID-19. They also infected mice with SARS-CoV-2 to follow what happened to the macrophages after infection.
In both humans and mice, they found that SARS-CoV-2 infection increased the total number of cardiac macrophages and also caused them to go out of their normal routine and become inflammatory.
When macrophages no longer do their normal job, which includes maintaining the heart’s metabolism and eliminating harmful bacteria or other foreign agents, they weaken the heart and the rest of the body, said Matthias Nahrendorf, M.D., Ph.D., professor of Radiology at Harvard Medical School and lead author of the study.
The researchers then designed a study in mice to test whether the response they observed occurred because SARS-CoV-2 was infecting the heart directly or because the SARS-CoV-2 infection in the lungs was severe enough to cause the heart’s macrophages became more inflamed. . This study mimicked the signs of lung inflammation, but without the presence of the actual virus. The result: Even in the absence of a virus, the mice showed immune responses strong enough to produce the same change in heart macrophages that the researchers observed in both patients who died of COVID-19 and mice infected with the virus. SARS-CoV-2 infection.
“What this study shows is that after a COVID infection, the immune system can inflict remote damage to other organs by triggering severe inflammation throughout the body, and this is in addition to the damage that the virus itself has directly inflicted on tissue. pulmonary”. Nahrendorf said. “These findings may also apply more generally, as our results suggest that any serious infection can send shock waves throughout the body.”
The research team also found that blocking the immune response with a neutralizing antibody in the mice stopped the flow of inflammatory cardiac macrophages and preserved cardiac function. While they have yet to test this in humans, Nahrendorf said a treatment like this could be used as a preventive measure to help COVID-19 patients with pre-existing conditions, or people who are likely to have more severe outcomes from SARS-CoV. 2 associated ARDS.
Study: Grune J, Bajpai G, Ocak PT et al. Virus-induced ARDS causes cardiomyopathy by triggering inflammatory responses in the heart. Circulation. 2024. doi:10.1161/CIRCULATIONAHA.123.066433.
Funding: This study was funded by NHLBI grants: HL139598, HL142494, HL155097, and HL149647.