What is it about?

A high surface tension can prevent normal lung inflation; to prevent this, the body synthesizes "lung surfactant", a detergent-like substance that lowers the surface tension in the alveoli. However, during inflammation that accompanies diseases such as Covid-19, the immune system secretes "lipases" that break down the lipids in bacterial and viral cell membranes, generating lysolipids that can compete with lung surfactant for the aveolar interface. These lysolipids can scrub lung surfactant from the interface by making the lung surfactant lipids soluble in body fluids which results in a higher surface tension and can prevent the lung from inflating uniformly. The effect of lysolipid is concentration dependent; below a threshold concentration, there is minimal effect, while above this threshold, the lung may go unstable.

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Why is it important?

Covid-19 infections result in damage to the lung surfactant producing cells, reducing the amount of available lung surfactant,. At the same time, the innate immune system produces lipases that break down bacterial and viral lipids to produce soluble lysolipid. If the lysolipid concentration reaches a certain level, the lungs can no longer inflate due to unbalanced surface tension forces. A significant fraction of deaths from Covid-19 were due to this acute respiratory distress syndrome that may result from this surface tension instability.


Understanding how simple mechanics influences lung function has been a goal of my research group for 30 years. Our work has contributed to new synthetic replacement surfactants for treating neonatal respiratory distress in premature infants, and we hope that this work can assist in developing new treatments for adult respiratory distress which kills more than 100,000 people every year,.

Joseph Zasadzinski
University of Minnesota Twin Cities

As a graduate student floating by aimlessly during the onset of the pandemic (the shared facility where I did my main project was shut down due to social distancing), I decided to play around with some tools we had in our own lab. One thing led to another, and I started investigating the effects of inflammatory products on our lung surfactant film. The results taught us a lot about lung mechanics and disease progression, and I hope the article can inspire more dedicated research into the phenomenon and stronger efforts to cure respiratory diseases.

Clara Ciutara
University of Minnesota Twin Cities

Read the Original

This page is a summary of: Evolution of interfacial mechanics of lung surfactant mimics progression of acute respiratory distress syndrome, Proceedings of the National Academy of Sciences, December 2023, Proceedings of the National Academy of Sciences,
DOI: 10.1073/pnas.2309900120.
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