Neutrophil and neutrophil extracellular trap involvement in neutrophilic asthma: A review

Asthma is a highly prevalent chronic inflammatory disease characterized by variable airflow obstruction and airway hyperresponsiveness. Neutrophilic asthma (NA) is classified as "type 2 low" asthma, defined as 65% or more neutrophils in the total cell count. There is no clear consensus on the pathogenesis of NA, and the accumulation of neutrophils and release of neutrophil extracellular traps (NETs) may be responsible for its development. A NET is a large extracellular meshwork comprising cell membrane and granule proteins. It is a powerful antimicrobial defence system that traps, neutralizes, and kills bacteria, fungi, viruses, and parasites and prevents the spread of microorganisms. However, dysregulation of NETs may lead to chronic airway inflammation, is associated with worsening of asthma, and has been the subject of major research advances in chronic lung diseases in recent years. NA is insensitive to steroids, and there is a need to find effective biomarkers as targets for the treatment of NA to replace steroids. This review analyses the mechanisms of action between asthmatic neutrophil recruitment and NET formation and their impact on NA development. It also discusses their possible therapeutic significance in NA, summarizing the advances made in NA agents and providing strategies for the treatment of NA, provide a theoretical basis for the development of new therapeutic drugs, thereby improving the level of diagnosis and treatment, and promoting the research progress in the field of asthma.