Artemisia argyi essential oil alleviates asthma by regulating 5-LOX-CysLTs and IDO-1-KYN pathways: Insights from metabolomics

Artemisia argyi essential oil (AAEO) is a traditional herbal remedy for asthma. However, the potential effect of AAEO on asthma has not been elucidated. To investigate the protective properties of AAEO upon asthma and elucidate its mechanism. The effects of AAEO in asthma were assessed by histology and biochemical analysis. Then, we integrated real-time reverse transcription-quantitative polymerase chain reaction, enzyme-linked immunosorbent assay, immunohistochemistry and metabolomics analysis to reveal its mechanism. In vivo, AAEO reduced the counts of white blood cells (WBCs) and cytokines in bronchoalveolar lavage fluid (BALF), ameliorated pathologic alterations in lung tissues, and inhibited secretion of OVA-sIgE and muc5ac. Metabolomics results showed that AAEO can exert therapeutic effects on asthmatic mice by regulating disordered arachidonic acid metabolism and tryptophan metabolism. Further studies shown that AAEO inhibited the expression of 5-LOX and reduced the accumulation of CysLTs in mice. Meanwhile, AAEO promoted the activity of IDO-1, facilitated the conversion of tryptophan to kynurenine, and regulated the imbalance of Treg/Th17 immunity. Immunohistochemical results showed that AAEO promoted the expression of IDO-1. RT-qPCR results showed that AAEO promoted the expression of IL-10 and Foxp3 mRNA, and inhibited the expression of IL-17A and RORγt mRNA, thus regulated the imbalance of Treg/Th17 immunity and exerted its therapeutic effects. AAEO treatment not only attenuates the clinical symptoms of asthma but is also involved in regulating lung tissue metabolism. The anti-asthmatic activity of AAEO may be achieved by reprogramming 5-LOX-CysLTs and IDO-1-KYN pathways.