OWe cannot deduce what triggers hyper-inflammation in the lungs of people with severe COVID-19 from what is measured in the blood. This should be taken into account if one hopes to design effective drugs to reduce morbidity and mortality in people exposed to the cytokine storm triggered by COVID-19.
This is the conclusion reached by researchers from the Faculty of Medicine of Laval University and the University of Rabat after comparing the pro-inflammatory molecules present in the blood and in the lungs of 45 people in whom COVID -19 had required intubation.
Their analyzes, which have just appeared in the Journal of Allergy and Clinical Immunology, show that:
- The concentrations of pro-inflammatory molecules detected in the blood of patients differ from those measured in their lungs.
- The correlation between the blood concentration and the pulmonary concentration of the same pro-inflammatory molecule is weak.
- The concentrations of pro-inflammatory molecules are higher in the blood than in the lungs. The only exception is that the CXCL1 and CXCL8 proteins have concentrations at least 30 times higher in the lungs than in the blood.
“The molecules CXCL1 and CXCL8 are probably the main ones responsible for the exacerbation of the influx of leukocytes into the lungs of patients,” analyzes the head of the study, Louis Flamand. It is this influx that causes congestion of the alveoli preventing people with COVID-19 from breathing well. ”
The results of this study would explain why the search for drugs to counter the cytokine storm has yielded disappointing results so far. “For example, at the start of the pandemic, we observed an increase in the concentration of interleukin-6 in the blood of patients. Tests carried out with drugs that block this pro-inflammatory molecule had produced neutral or negative results, recalls Professor Flamand. We understand better why today. What we see in the blood does not reflect what is happening in the lungs. Drugs that target the CXCL1 and CXCL8 proteins would have a better chance of improving the health of patients. “
The study is signed by Younes Zaid, from the University of Rabat, Étienne Doré, Isabelle Dubuc, Olivier Flamand, Éric Boilard and Louis Flamand, from the Research Center of the CHU de Québec – Université Laval, and Anne-Sophie Archambault, Michel Laviolette and Nicolas Flamand, from the Research Center of the University Institute of Cardiology and Pulmonology of Quebec.
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