Hyssopus cuspidatus volatile oil: a potential treatment for steroid-resistant asthma via inhibition of neutrophil extracellular traps

Steroid-resistant asthma (SRA) is a form of asthma resistant to corticosteroid therapy, which is characterized by the presence of neutrophil-predominant inflammatory response and neutrophil extracellular traps (NETs) formation. Hyssopus cuspidatus Boriss., a traditional Uyghur medicine, is known for its efficacy in treating inflammatory lung conditions such as asthma. However, the therapeutic impact and underlying mechanisms of Hyssopus cuspidatus Boriss.'s volatile oil (HVO) in SRA have not been fully elucidated. This study established an ovalbumin/lipopolysaccharide (OVA/LPS)-induced SRA mice model to evaluate the therapeutic effect of HVO on SRA. UPLC-QE-Orbitrap-MS was applied to analyze the serum compositions of HVO. Network pharmacology and molecular docking were employed to uncover the complex mechanisms of HVO in treating SRA and predict potential effective compounds in HVO. Furthermore, in vivo studies in SRA mice and in vitro studies using HL-60 cells and bone marrow neutrophils were conducted to validate the mechanism. HVO could significantly ameliorate OVA/LPS-induced SRA symptoms, including airway hyperresponsiveness, airway inflammation, mucus overproduction and airway remodeling. 41 prototype compounds, 65 Phase I metabolites and 50 Phase II metabolites were identified in serum-containing HVO. The integration of network pharmacology with experimental validation revealed that HVO can inhibit the formation of NETs by targeting neutrophil elastase, thereby exerting a therapeutic influence on SRA. Meanwhile, molecular docking results showed that 3-methoxy-4-hydroxy mandelonitrile, 1,2,3,4-tetrahydro-1,5,7-trimethyl-naphthalene, cis-calamenene and aristol-1(10)-en-9-yl isovalerate may be the therapeutic compounds of HVO in treating SRA. These findings suggest that HVO is a promising therapeutic candidate for neutrophil-dominant SRA by targeting NETs formation.