Nasal Nod-like receptors possible targets for allergic rhinitis treatment
MedWire News: Researchers have found that nucleotide-binding oligomerization domain (Nod)-like receptors (NLRs) are present in the human nose, with expression of Nod1 and Nalp3 down-regulated during the pollen season in patients with allergic rhinitis.
The findings, published in the journal Allergy, indicate that Nod1 and Nalp3 may provide novel targets for allergic rhinitis treatment.
“NLRs are a newly discovered family of pattern-recognition receptors that consists of more than 20 intracellular members. They can be divided into several subfamilies, among them the Nods and the Nalps,” explain Lars Olaf Cardell (Karolinska Institute, Stockholm, Sweden) and team.
They say that previous genetic studies have implicated Nod1, Nod2, and Nalp3 in the inflammatory response to allergens or microbes, but add that “despite the genetic association of NLRs with inflammatory airway diseases, not much is known about the presence of NLRs in the human airways.”
To investigate, the team studied 20 patients with birch and/or grass pollen-induced intermittent allergic rhinitis and 20 healthy controls without the condition.
Nasal biopsies were collected from participants with allergic rhinitis both during and outside the pollen season, while biopsies were collected from controls only outside the pollen season. These were analyzed for the presence and expression levels of Nod1, Nod2 and Nalp3.
Analysis of cultured primary human nasal epithelial cells (HNECs) was also used to examine for the presence of these NLRs.
The researchers found that Nod1, Nod2, and Nalp3 receptors were present in nasal epithelium samples from all participants. The presence of these NLRs in the nasal epithelium was confirmed in the analysis of HNECs.
Biopsies collected from allergic rhinitis patients during the pollen season showed significantly lower expression of Nod1 than those collected outside the season and those from controls. Expression of Nalp3 was significantly lower in biopsies from allergic rhinitis patients both during and outside the pollen season compared with expression levels in biopsies from controls.
There were no differences in expression levels of Nod2 between allergic rhinitis patients and controls during or outside the pollen season.
Cardell and team conclude: “This study demonstrates the presence of Nod1, Nod2, and Nalp3 in the human nasal epithelium. A marked down-regulation of Nod1 and Nalp3 expression is seen during pollen season among patients with a history of allergic rhinitis, suggesting the involvement of these receptors in the pathophysiology of inflammatory airway disease.”
They add: “The discovery of NLRs in the human nose points toward novel possible treatment targets.”
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By Mark Cowen