Anti-inflammatory proteins as therapy targets in chronic rhinosinusitis with hyperplastic nasal polyposis: Study

Siglec-8, an immune-inhibitory sialoglycan binding lectin (S8), is expressed on the surface of eosinophils and mast cells, which are potent mediators of allergic inflammation. When S8 engages endogenous sialoglycan ligands, eosinophils undergo apoptosis and mast cell mediator release is inhibited.

In the human airway, Siglec-8 ligands (S8L) are sialylated keratan sulfate chains carried on isoforms of the protein Deleted in Malignant Brain Tumors-1 (DMBT1), an immunoregulatory protein that we recently identified as the endogenous ligand for S8, DMBT1.

Therefore, the authors Hyun Sil Lee and colleagues from the Department of Medicine, Division of Allergy and Clinical Immunology, Johns Hopkins University School of Medicine, Baltimore, USA conducted the present study to report that S8L is overexpressed in chronic rhinosinusitis with nasal polyposis (CRSwNP), a prevalent eosinophilic laden airway disease.

The study showed the following results-

1. Quantification and comparison of the degree to which DMBT1 carries the S8L by immunoblot analysis and lectin blot overlay, respectively, from nasal lavage showed that the S8L/DMBT1 ratio was significantly increased in CRSwNP vs. control or CRS patients.
2. The histological sites of S8L and DMBT1 expression in fresh surgically resected human nasal polyps were identified.
3. Histochemistry of diseased polyps and adjacent nondiseased middle turbinate (MT) tissue from CRSwNP demonstrated colocalization of S8L and DMBT1 with highest staining in submucosal glands >> epithelium > stoma.
4. S8L expression was specifically elevated in the submucosal glands and epithelium of polyp tissue compared to MT.

Hence, the authors hypothesized that expression of the isoform of DMBT1 carrying the Siglec-8 binding sialoglycan, DMBT1S8, is induced in polyps of CRSwNP specifically at the site of disease, is produced in the submucosal glands of polyps and secreted into the lumen of the sinonasal cavity as a host response to mitigate eosinophil-mediated inflammation.