Introduction
Rhinovirus (RV) infection of airway epithelial cells from patients with asthma results in an abnormal engagement of retinoic-acid inducible gene I (RIG-I) into RIG-I inflammasome formation, which subsequently delays RIG-I dependent interferon (IFN) type I/III responses and enhances proinflammatory signaling in asthma. The exacerbation-prone asthma has been linked with metabolic dysfunctions, however, the metabolic regulation of antiviral responses during those pathogenic viral infections in asthma is not well understood.
Methods
Basal and differentiated human bronchial epithelium from patients with asthma and healthy controls upon RV were used to analyze the metabolic regulation of RIG-I-dependent signaling with the use of functional metabolism assessment (Seahorse), untargeted proteomics, and small molecule inhibitors of metabolic pathways followed by ELISA, RT-qPCR, WB, and confocal microscopy. Bronchial brushings from the in vivo RV infection model were analyzed gene array and pathway analysis.
Results
Bronchial epithelium of patients with asthma upon RV infection demonstrated increased glycolytic ATP and decreased mitochondrial ATP production, indicating, in contrast to healthy epithelium, continuous reliance on glycolysis for ATP production in asthma. RV infection of bronchial epithelium upregulated expression of molecules involved in metabolic pathways, such as glycolysis, TCA cycle, and oxidative phosphorylation (OXPHOS). Additionally, we determined that RIG-I expression and RV-induced RIG-I inflammasome activation are tightly regulated by glycolysis and OXPHOS. Glycolysis was an energy source for rhinovirus infection and RIG-I inflammasome activation. On the other hand, OXPHOS fueled IFN production. Importantly, functional inhibition of the OXPHOS pathway led to increased RIG-I inflammasome activation. Those in vitro mechanistic data were confirmed in vivo in transcriptomics of bronchial brushings of asthma patients and healthy controls experimentally infected with RV. In asthma, upregulated glycolysis-HIF1A pathway corresponded with increased inflammasome signaling and lack of viral clearance, whereas in healthy controls significantly downregulated OXPHOS corresponded with downregulation of type I/III IFNs and efficient viral clearance.
Conclusions
There is a strong link between aberrant metabolic reprogramming signaling in epithelium with inefficient antiviral response in asthma. It might further influence epithelial response to subsequent infections with other respiratory viruses, such as SARS-CoV-2.