Scientists find the cause of lung damage in severe COVID-19

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In two new studies, researchers found sticky webs of DNA released from immune cells known as neutrophils may cause much of the tissue damage linked to severe COVID-19 infections.

The finding suggests that blocking the release of these DNA webs could be a new therapeutic target for the management of severe COVID-19.

The research was conducted by scientists in Belgium and Brazil.

While many people infected with the COVID-19 virus experience relatively mild symptoms, some patients mount an excessive inflammatory response that can damage the lungs and cause acute respiratory distress syndrome (ARDS), leading to low blood oxygen levels and, potentially, patient death.

An early indicator of severe COVID-19 is an increased number of circulating neutrophils, a type of white blood cell.

Neutrophils can catch and kill invading microbes by unwinding their DNA and extruding it from the cell to form sticky webs known as neutrophil extracellular traps (NETs).

NETs can also damage surrounding tissue, however, and could therefore cause some of the lung pathology associated with severe COVID-19.

In one of the new studies, a research team examined the lungs of patients who had succumbed to COVID-19 and found large numbers of NETs dispersed throughout the organ.

The researchers saw many NETs in the airway compartment. NETs were also formed at sites of inflammation located in the interstitial compartment between the alveoli and blood vessels, and could even be seen in the blood vessels near tiny blood clots.

The team says NETs can form a platform for the adhesion of platelets and other blood-clotting factors.

The study supports the idea that targeting NETs in COVID-19 patients may help the clinical management of severe forms of COVID-19 by alleviating thrombotic events, excessive tissue-damaging inflammation, fibrosis, and airway obstruction.

In the second study, a team of researchers also identified increased numbers of NETs in the lungs of severe COVID-19 patients and found that NET formation was elevated in COVID-19 patients’ blood plasma as well.

Moreover, the researchers determined that SARS-CoV-2 can trigger the release of NETs by infecting neutrophils and replicating inside of them.

NETs released from SARS-CoV-2–infected neutrophils induce the death of lung cells grown in the lab, the researchers found, but cell death is prevented if NET release is inhibited or the NETs are degraded by an enzyme that chews up DNA.

One author of the studies is Thomas Marichal.

The study findings are published in the Journal of Experimental Medicine and the Journal of Experimental Medicine.

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