Integrated multiomics reveals a clinically relevant CXCL8-centric protein network in pediatric postinfectious bronchiolitis obliterans

Background
Pediatric postinfectious bronchiolitis obliterans (PIBO) is a long-term sequela of severe lower respiratory tract infection. However, the underlying pathogenic mechanisms within the airways remain poorly understood.

Methods
Bronchoalveolar lavage fluid (BALF) from six children with PIBO and three control children was subjected to transcriptomic, proteomics and untargeted metabolomics analyses. Integrated analysis identified key differentially expressed candidates, among which protein candidates were subsequently validated by ELISAs.

Results
Transcriptomic analysis revealed altered pathways in the BALF of children with PIBO, including pathways related to epithelial differentiation, inflammatory responses, and metabolic processes involving amino acids, purines, lipids, and vitamins. Proteomic analysis further revealed epithelial injury, inflammatory activation, tissue remodeling, and metabolic dysregulation in PIBO patients. Protein–protein interaction (PPI) network analysis identified CXCL8 (interleukin-8, IL-8) as the central hub. Integrative transcriptomic-proteomic correlation analysis further revealed that CXCL8 transcript levels were correlated with the greatest number of differentially expressed proteins (DEPs). Subsequent ELISA validation confirmed elevated CXCL8 protein levels in children with PIBO, which were positively correlated with the predicted FEV1%. Furthermore, 54 proteins, including KRT19, OSM, ADAM8, and PADI2, were significantly correlated with CXCL8 expression. These proteins spanned epithelial, inflammatory, remodeling, and metabolic processes, indicating a clinically relevant network. Untargeted metabolomics analysis revealed alterations in purine, cofactors, and amino acid metabolism, with pyridoxine (vitamin B6) as the most significantly altered metabolite. Integrated multiomic analysis revealed widespread correlations between differentially expressed metabolites and proteins. Notably, putative pyridoxine expression was negatively correlated with the expression of CXCL8 and other key inflammatory proteins, which is consistent with the evidence of disrupted vitamin metabolism observed by transcriptomics. In vitro experiments further showed that pyridoxine treatment reduced CXCL8 secretion in small airway epithelial cells. Together, these findings suggest a potential link between vitamin B6 and inflammatory processes in PIBO.

Conclusions
Multiomic integration revealed molecular signatures characterized by a CXCL8-centric protein network, a potential disruption of vitamin B6 homeostasis, and altered pathways involved in epithelial differentiation, immunity, and metabolism. These signatures converge on core pathogenic mechanisms within the airway microenvironment, including epithelial injury, inflammatory activation, tissue remodeling, and metabolic dysregulation. Collectively, these findings establish an integrative framework for understanding the pathogenesis of PIBO and highlight potential molecular targets for biomarker discovery and therapeutic intervention.