Lung lipid deposition in pneumonias of viral and non-viral aetiology

Abstract Pneumonia is an acute respiratory disease of varying aetiology, which drew much attention during the COVID-19 pandemic. Among many thoroughly studied aspects of pneumonia, lipid metabolism has been addressed insufficiently. Here, we report on abnormal lipid metabolism of both COVID-19- and non-COVID-19-associated pneumonias in human lungs. Morphometric analysis revealed extracellular and intracellular lipid depositions, most notably within vessels adjacent to inflamed regions, where they apparently interfere with the blood flow. Lipids were visualized on Sudan III- and Oil Red O-stained cryosections and on OsO 4 -contrasted semi-thin and ultrathin sections. Chromato-mass spectrometry revealed that unsaturated fatty acid content was elevated at inflammation sites compared with the intact sites of the same lung. The genes involved in lipid metabolism were downregulated in pneumonia, as shown by qPCR and in silico RNAseq analysis. Thus, pneumonias are associated with marked lipid abnormalities, and therefore lipid metabolism can be considered a target for new therapeutic strategies.