Background: Eosinophilic chronic frontal sinusitis is difficult to treat compared with non-eosinophilic sinusitis because of recurring inflammation and polyp formation in the frontal recess after the post-operative follow-up period. Studying inflammatory mediators in the frontal recess of eosinophilic chronic rhinosinusitis (ECRS) patients and non-eosinophilic chronic rhinosinusitis (non-ECRS) patients may lead to a better understanding of the pathogenesis of chronic frontal sinusitis.
Methods: Homogenates of sinonasal mucosa from 20 non-ECRS patients and 36 ECRS patients were measured for levels of transforming growth factor (TGF)-β, interleukin (IL)-5, IL-6, and inducible nitric oxide synthase (iNOS) using real-time RT-PCR and TaqMan gene expression assays. Sinonasal mucosal specimens were obtained from the frontal recess, ethmoid sinus, and nasal polyp separately.
Results: The expression of IL-5 was significantly elevated in all sinonasal regions tested in the ECRS group, but absent in non-ECRS patients. Furthermore, the ECRS patients showed significantly increased levels of IL-5 in the frontal recess mucosa compared with ethmoid sinus mucosa. IL-6 was also significantly increased in the frontal recess mucosa compared with ethmoid sinus mucosa and nasal polyps in these patients. There were no significant differences in the levels of TGF-β or iNOS between the ECRS and non-ECRS groups in any sinonasal region tested.
Conclusions: This study is the first to characterize the cytokine milieu in the frontal recess of ECRS patients. We should keep these cytokine profiles in mind when we treat ECRS patients with frontal sinusitis.
Keywords: Eosinophilic chronic rhinosinusitis; Frontal recess; IL-5; IL-6.