IRAK-M has effects in regulation of lung epithelial inflammation

Background: Epithelial barrier is important for asthma development by shaping immune responses. Airway expressing-IL-1 receptor-associated kinase (IRAK)-M of Toll-like Receptor pathway was involved in immunoregulation of airway inflammation through influencing activities of macrophages and dendritic cells or T cell differentiation. Whether IRAK-M has effect on cellular immunity in airway epithelial cells upon stimulation remains unclear.

Methods: We modeled cellular inflammation induced by IL-1β, TNF-α, IL-33, and house dust Mite (HDM) in BEAS-2B and A549 cells. Cytokine production and pathway activation were used to reflect the effects of IRAK-M siRNA knockdown on epithelial immunity. Genotyping an asthma-susceptible IRAK-M SNP rs1624395 and measurement of serum CXCL10 levels were performed in asthma patients.

Results: IRAK-M expression was significantly induced in BEAS-2B and A549 cells after inflammatory stimulation. IRAK-M knockdown increased the lung epithelial production of cytokines and chemokines, including IL-6, IL-8, CXCL10, and CXCL11, at both mRNA and protein levels. Upon stimulation, IRAK-M silencing led to overactivation of JNK and p38 MAPK in lung epithelial cells. While antagonizing JNK or p38 MAPK inhibited increased secretion of CXCL10 in IRAK-M silenced-lung epithelium. Asthma patients carrying G/G genotypes had significantly higher levels of serum CXCL10 than those carrying homozygote A/A.

Conclusion: Our findings suggested that IRAK-M has effect on lung epithelial inflammation with an influence on epithelial secretion of CXCL10 partly mediated through JNK and p38 MAPK pathways. IRAK-M modulation might indicate a new insight into asthma pathogenesis from disease origin.

Airway epithelial cells; Asthma; CXCL10; IRAK-M; Innate immunity.