Evidence for diminished levels of epithelial psoriasin and calprotectin in chronic rhinosinusitis

Abstract

Background: Decreased epithelial expression of mRNA for S100A7 (psoriasin) and S100A8/A9 (calprotectin) has been reported in patients with chronic rhinosinusitis (CRS).

Objectives: We sought to assess whether the expression of S100 proteins is also altered in the sinonasal cavity of patients with CRS.

Methods: We determined levels of S100 proteins in nasal lavage fluid and sinonasal tissue extracts from patients with CRS using ELISA and immunohistochemical analysis of nasal polyp tissue from patients with CRS with nasal polyps and uncinate tissue from healthy control subjects, patients with CRSsNP, and patients with CRSwNP.

Results: Expression levels of S100 proteins were decreased compared with those seen in control subjects in nasal lavage fluid from both CRS groups (P < .05). Similarly, tissue expression of these proteins assessed by means of immunohistochemistry demonstrated clear reductions, primarily in the epithelial lining. Interestingly, levels of calprotectin were increased in nasal polyp tissue despite lower levels in lavage fluid. Levels of calprotectin in nasal tissues were correlated with levels of neutrophils, as assessed by means of quantification of neutrophil elastase.

Conclusions: Several S100 proteins are in the epidermal differentiation complex of genes and have been demonstrated to play a role in maintenance of barrier function and formation of an antimicrobial shield. We demonstrate significantly decreased levels of expression of S100 proteins in the epithelium of patients with CRS, which might lead to diminished innate immune responses and barrier function. Increased levels of calprotectin in nasal polyp tissue might reflect neutrophil recruitment and a compensatory mechanism. Future studies will be important to determine whether reduced levels of S100 proteins lead to decreased antimicrobial responses in the upper airways and sinuses and whether this reduction plays a causative role in CRS pathogenesis and susceptibility to infectious disease.

Figure 1. Evaluation of expression of S100A7 using ELISA in sinonasal tissue extracts

A) Expression of S100A7 protein is increased in inferior turbinate tissue (IT) as compared to uncinate tissue (UT) from normal subjects. The statistical bars indicate a significant difference among the corresponding groups. B) Levels of S100A7 were increased in all CRS tissue extracts when compared to extracting uncinate tissue from controls. The statistical bars indicate a significant difference among the corresponding groups. p values <0.05 are considered statistically significant.

Figure 2. Evaluation of expression of human calprotectin (S100A8/A9) and human neutrophil elastase using ELISA in sinonasal tissue extracts

A) Human S100A8/A9 protein levels in tissue extracts normalized to total protein. Polyp tissue from CRSwNP patients demonstrate a significant increase in human calprotectin when compared to normal tissue extracts (p <0.01). B) Linear regression analysis of matching S100A8/A9 and human neutrophil elastase samples demonstrate a significant correlation between the two proteins (p < 0.0001, r = 0.6577). C) Human neutrophil elastase protein levels in polyp tissue from CRSwNP patients are significantly increased when compared to normal tissue extracts. (p < 0.05).

Figure 3. Expression of S100A7 and S100A8/A9 in nasal lavage fluids and serum samples using ELISA

A). Human S100A7 (* p < 0.01, ** p < 0.001) and B) Human S100A8/A9 protein levels in nasal lavage fluids. Human S100A7 protein levels are significantly decreased in nasal lavages of CRS and AR patients when compared to normals (p < 0.05). Human S100A8/A9 protein levels are significantly decreased in CRSwNP nasal lavages when compared to normals. C) Human S100A7 (p > 0.05) and D) Human S100A8/A9 (p < 0.05) protein levels in serum. Only human S100A8/A9 protein levels are significantly decreased in CRSwNP when compared to normals. p values < 0.05 are considered statistically significant.

Figure 4. Immunohistochemical staining for S100A7 in representative tissue samples from the uncinate process and nasal polyps (400x original magnification)

(A) Negative control of uncinate from representative normal subject did not stain. (B) S100A7 staining of uncinate from a control subject showed intense staining in the epithelial and glandular tissue, whereas light to moderate staining of S100A7 was seen in uncinate samples from (C) CRSsNP and (D) CRSwNP. (E) Minimal S100A7 staining in epithelial cells was seen in polyp tissue. (F) Intense glandular staining for S100A7 in the uncinate of a control subject. Less staining was seen in the uncinate from (G) CRSsNP and (H) CRSwNP. Original magnification was 400x.

Figure 5. Immunohistochemical staining for S100A8/A9 in representative tissue samples from the uncinate process and nasal polyps (400x original magnification)

(A) Negative control of uncinate from normal subject did not stain. (B) S100A8/A9 staining of uncinate from a control subject showed moderate staining in the epithelial and glandular tissue. Also note several intensely staining leukocytes that we believe to be neutrophils in (D). Some light staining of S100A8/A9 was seen in uncinate samples from (C) CRSsNP and (D) CRSwNP. (E) Minimal S100A8/A9 staining in epithelial cells was seen in polyp tissue. (F) Glandular staining in the uncinate of a control subject with moderate staining for S100A8/A9. Diffuse staining was seen in the uncinate from (G) CRSsNP and (H) CRSwNP. Original magnification was 400x.