Dispersion and utilization of lipid droplets mediates respiratory syncytial virus-induced airway hyperresponsiveness

Background: Respiratory viral infections (RSV) can induce acute asthma attacks, thereby destroying lung function and accelerating the progression of the disease. However, medications in the stable phase of asthma are often not effective for acute attacks induced by viral infections. We aimed to clarify the possible mechanism of viral infection-induced asthma through fatty acid metabolism.

Methods and results: The airway resistances, inflammatory injuries, and oxidative stress in the RSV-induced animal models were significantly higher than those in the control group at acute phase (7 days) and chronic phase (28 days). Moreover, the concentrations of the medium- and long-chain fatty acids in lung tissue at (28 days) were significantly increased, including 14:0 (myristic acid), 16:0 (palmitic acid, PA), 18:1 (oleic acid, OA), and 18:2 (linoleic acid, LA) using non-targeted metabonomics. Airway epithelial cells treated with RSV showed the reduced expression of FSP27, RAB8A, and PLIN5, which caused the fusion and growth of lipid droplet (LD), and increased expression of the LD dispersion gene perilipin 2. There was also a decrease in PPARγ expression and an increase in the fatty acid catabolism gene PPARα, causing lipid oxidation, free fatty acid releases, and an upsurge in IL-1, IL-2, IL-4, and IL-6 expression, which could be abrogated by GPR40 inhibitor. Treated mice or epithelial cells with C18 fatty acid exhibited inhibition of epithelial proliferation, increases of inflammation, and oxidative damage.

Conclusions: RSV promoted lipid dispersion and utilization, causing enlarged oxidative injuries and an upsurge in the pro-inflammatory cytokines, leading to the progression of airway hyperresponsiveness (AHR).