Immune imbalance in nasal polyps of Caucasian chronic rhinosinusitis patients is associated with a downregulation of E-selectin

Abstract

Chronic rhinosinusitis with nasal polyps (CRSwNP) in Caucasians is a chronic Th2 inflammatory disease of the nasal and paranasal mucosa and the recruitment of leukocytes to the site of inflammation is poorly understood. We studied mRNA and protein expression profiles of adhesion molecules in nasal polyp and associated inferior turbinate tissues using molecular, biochemical, and immunohistological methods. Analysis showed a strongly decreased E-selectin expression in nasal polyps with a significant difference between eosinophil and neutrophil counts in nasal polyps and balanced counts in inferior turbinates. E-selectin expression is known to be downregulated in a Th2 milieu and has an essential role in immunosurveillance by locally activating neutrophil arrest and migratory function. A downregulation of E-selectin may come along with an immune imbalance in Caucasian nasal polyps due to a significant inhibition of neutrophil recruitment. Therefore, we suggest that an upregulation of E-selectin and the associated influx of neutrophils may play a significant role in the resolution of inflammation as well as for the pathophysiology of nasal polyps of Caucasian chronic rhinosinusitis patients.

Figure 1

Scatter plots of adhesion molecule expression in nasal polyps compared to associated inferior turbinates using microarray and qPCR. Each single dot shows the relative expression of the target molecule in nasal polyps compared to associated inferior turbinates of one patient and median is indicated as horizontal bar. (a) Microarray analysis: nasal polyp tissues showed higher gene expression levels of the adhesion molecules P-selectin (1.62-fold, n = 7), PSGL1 (1.74-fold, n = 7), and VCAM1 (2.16-fold, n = 7) compared to associated inferior turbinates. ICAM1 was unregulated (1.03-fold, n = 7) and E-selectin was strongly downregulated in nasal polyps (0.32-fold, n = 7). (b) qPCR analysis: lower median expression of E-selectin (0.22-fold, n = 14) and higher median expression of P-selectin (2.37-fold, n = 15) were observed in nasal polyps. The median expression of PSGL1, ICAM1, and VCAM1 showed no significant difference between nasal polyps and inferior turbinates: PSGL1 1.24-fold (n = 10), ICAM1 1.24-fold (n = 10), and VCAM1 0.85-fold (n = 10). The mRNA levels of E-selectin in nasal polyps decreased significantly (P = 0.004) compared to the inferior turbinates and P-selectin increased significantly (P = 0.0025). PSGL1, ICAM1, and VCAM1 were expressed at similar levels.

Figure 2

Scatter plots of CD31 and adhesion molecule expression in nasal polyps compared to associated inferior turbinates using qPCR. Each single dot shows the relative expression of the target molecule in nasal polyps compared to associated inferior turbinates of one patient and median is indicated as horizontal bar. (a) CD31 is not differentially expressed (0.93-fold, n = 7) between nasal polyps and inferior turbinates; (b) adhesion molecule expression in nasal polyps normalized to CD31. E-selectin (0.22-fold, n = 7), P-selectin (1.82-fold, n = 7), PSGL1 (1.29-fold, n = 7), ICAM1 (0.93-fold, n = 7), and VCAM1 (1.56-fold, n = 7). (c) Adhesion molecule expression in nasal polyps normalized to β-actin. E-selectin (0.31-fold, n = 7), P-selectin (1.97-fold, n = 7), PSGL1 (1.34-fold, n = 7), ICAM1 (1.28-fold, n = 7), and VCAM1 (1.08-fold, n = 7). CD31 normalized data differ insignificantly compared to the β-actin normalized data.

Figure 3

Western blotting exhibited lower E-selectin expression in nasal polyps (P) than in the inferior turbinate (IT) of chronic rhinosinusitis patients (n = 8).

Figure 4

(a): Expression and localization of E-selectin in inferior turbinates and nasal polyps of chronic rhinosinusitis patients (n = 10). Immunohistochemical staining was performed on frozen tissue sections of inferior turbinate (left) and nasal polyp (right). We were able to detect E-selectin positive cells in the endothelium of inferior turbinates and nasal polyps. E-selectin was expressed at high level in the inferior turbinates, whereas in nasal polyps E-selectin was infrequently expressed and always at a low level. (b) Expression and localization of P-selectin in inferior turbinates and nasal polyps of chronic rhinosinusitis patients (n = 10). Immunohistochemical staining was performed on frozen tissue sections of inferior turbinate (left) and nasal polyp (right). P-selectin was detected in the endothelium of inferior turbinates and nasal polyps. P-selectin was always expressed at high levels in both inferior turbinates and nasal polyps.

Figure 5

Eosinophils and neutrophils counts in nasal polyps and inferior turbinates (n = 8). Eosinophil counts were significantly higher in nasal polyps compared to inferior turbinates (P = 0.007). Neutrophil counts did not significantly differ between nasal polyps and inferior turbinates. Noticeable is that there was a significant difference between eosinophil and neutrophil counts in nasal polyps (P = 0.0014) and balanced counts in inferior turbinates.