Severe Type 2 Inflammation Leads to High PAF-Associated Pathology in Chronic Rhinosinusitis with Nasal Polyps (CRSwNP): Hierarchal Cluster Analysis Using Bulk RNA Barcoding and Sequencing

Abstract

Platelet-activating factor (PAF) is a phospholipid-derived inflammatory mediator, triggering various inflammatory conditions, including eosinophil activation and recruitment. Despite the unclear mechanism underlying the formation and maintenance of nasal polyp in chronic rhinosinusitis with nasal polyps (CRSwNP), there is strongly indication of its association with type 2 inflammation. This study aimed to quantify PAF-associated gene expression, examining enzymes involved in PAF synthesis (lysophosphatidylcholine acyltransferase 1 (LPCAT1), LPCAT2, LPCAT3, and LPCAT4), and PAF degradation (PAF acetylhydrolases 1 B2 (PAFAH1B2), PAFAH1B3, and PAF acetylhydrolases 2 (PAFAH2)), and PAF receptor (PTAFR). Transcriptomic analysis encompassed CRSwNP, including eosinophilic CRS (ECRS) (n=9), nonECRS (n=8), and a subgroup of ECRS with aspirin exacerbated respiratory disease (Asp) (n=3) based on the Japanese Epidemiological Survey of Refractory Eosinophilic Chronic Rhinosinusitis (JESREC) criteria. Gene expression profiles from nasal polyps in CRSwNP patients and the uncinate process in normal subjects (controls) (n=6) were analyzed using bulk RNA barcoding and sequencing (BRB-seq). Hierarchal analysis, utilizing the average linkage method with iDEP1.1, clarified the relationship between Differentially Expressed Genes (DEG) expressions and cluster formation. Two clusters (cluster 1 (n=11) and cluster 2 (n=9)) of CRSwNP divided by hierarchal analysis showed distinct gene expression profiles in the specific pathway of “cytokine-cytokine receptor interaction” in KEGG pathway and upregulated type 2 inflammatory gene expression in cluster 2. In CRSwNP subclassification of ECRS, nonECRS, and Ctrl, PTAFR was only upregulated in ECRS and nonECRS. In cluster analysis, cluster 1 showed significant downregulation of LPCAT2 and upregulation of PTAFR expression, while cluster 2 showed significant upregulation of LPCAT1, PAFAH1B2, and PTAFR and downregulation of PAFAH2 expression. These findings suggest that cluster 2, characterized by severe type 2 inflammatory gene expression, manifest a prominent PAF-associated pathophysiology. Understanding this high PAF-associated pathophysiology in cluster 2 could provide valuable insights into the treatment and management of CRSwNP.