Serum IFN-γ-induced protein 10 (IP10/CXCL10): association with asthma exacerbations and severity in children

CD4+ T cell-derived IFN-γ and LIGHT synergistically upregulate chemokine production from airway smooth muscle cells

Airway smooth muscle (ASM) remodeling in asthmatic airways may contribute to persistent airflow limitation and airway hyperresponsiveness. CD4+ T cells infiltrate the ASM layer where they may induce a proliferative and secretory ASM cell phenotype. We studied the interaction between activated CD4+ T cells and ASM cells in co-culture in vitro and investigated the effects of CD4+ T cells on chemokine production by ASM cells. CD4+ T cells induced marked upregulation of C-X-C motif chemokine ligands (CXCL) 9, 10, and 11 in ASM cells. Blockade of the IFN-γ receptor on ASM cells prevented this upregulation. Furthermore, T cell-derived IFN-γ and LIGHT (lymphotoxin, exhibits inducible expression and competes with HSV glycoprotein D for binding to herpesvirus entry mediator, a receptor expressed on T lymphocytes) synergize in a dose-dependent manner to coordinately enhance CXCL9, 10, and 11 expression. The synergistic property of LIGHT was mediated exclusively through the lymphotoxin-β receptor (LTBR), but not herpes virus entry mediator (HVEM). Disruption of LTBR signaling in ASM cells reduced CXCL9, 10, and 11 production and ASM cell-mediated CD4+ T cell chemotaxis. We conclude that the LIGHT-LTBR signaling axis acts together with IFN-γ to regulate chemokines that mediate lymphocyte infiltration in asthmatics.

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.