The Role of Epigenetics in the Chronic Sinusitis with Nasal Polyp

PURPOSE OF REVIEW

Chronic rhinosinusitis with nasal polyps (CRSwNP) is a common and heterogeneous inflammatory disease. The underlying epigenetic mechanisms and treatment of CRSwNP are partially understood. Of the different epigenetic changes in CRSwNP, histone deacetylases (HDACs), methylation of DNA, and the levels of miRNA are widely studied. Here, we review the human studies of epigenetic mechanisms in CRSwNP.

RECENT FINDINGS

The promoters of COL18A1, PTGES, PLAT, and TSLP genes are hypermethylated in CRSwNP compared with those of controls, while the promoters of PGDS, ALOX5AP, LTB4R, IL-8, and FZD5 genes are hypomethylated in CRSwNP. Promoter hypermethylation suppresses the gene expression, while promoter hypomethylation increases the gene expression. Studies have shown the elevation in the levels of HDAC2, HDAC4, and H3K4me3 in CRSwNP. In CRSwNP patients, there is also an upregulation of certain miRNAs including miR-125b, miR-155, miR-19a, miR-142-3p, and miR-21 and downregulation of miR-4492. Epigenetics takes part in the immunology of CRSwNP and may give rise to endotypes of CRSwNP. Both HDAC2 and the miRNA including miR-18a, miR-124a, and miR-142-3p may take function in the regulation of glucocorticoid resistance. HDAC inhibitors and KDM2B have shown effectiveness in decreasing nasal polyp, and DNA methyltransferase (DNMT) or HDAC inhibitors may have a potential efficacy for the treatment of CRSwNP. Recent advances in the epigenetics of CRSwNP have led to the identification of several potential therapeutic targets for this disease. The use of epigenetics may provide novel and effective biomarkers and therapies for the treatment of nasal polyp.

Chinese Society of Allergy and Chinese Society of Otorhinolaryngology-Head and Neck Surgery Guideline for Chronic Rhinosinusitis

The current document is based on a consensus reached by a panel of experts from the Chinese Society of Allergy and the Chinese Society of Otorhinolaryngology-Head and Neck Surgery, Rhinology Group. Chronic rhinosinusitis (CRS) affects approximately 8% of Chinese adults. The inflammatory and remodeling mechanisms of CRS in the Chinese population differ from those observed in the populations of European descent. Recently, precision medicine has been used to treat inflammation by targeting key biomarkers that are involved in the process. However, there are no CRS guidelines or a consensus available from China that can be shared with the international academia. The guidelines presented in this paper cover the epidemiology, economic burden, genetics and epigenetics, mechanisms, phenotypes and endotypes, diagnosis and differential diagnosis, management, and the current status of CRS in China. These guidelines-with a focus on China-will improve the abilities of clinical and medical staff during the treatment of CRS. Additionally, they will help international agencies in improving the verification of CRS endotypes, mapping of eosinophilic shifts, the identification of suitable biomarkers for endotyping, and predicting responses to therapies. In conclusion, these guidelines will help select therapies, such as pharmacotherapy, surgical approaches and innovative biotherapeutics, which are tailored to each of the individual CRS endotypes.

Hypomethylation of the IL8 promoter in nasal epithelial cells of patients with chronic rhinosinusitis with nasal polyps

BACKGROUND

IL-8 is an important chemokine implicated in the pathogenesis of chronic rhinosinusitis (CRS), but little is known about epigenetic regulation of IL8 in the pathogenesis of CRS.

OBJECTIVE

We sought to investigate the relationship between the DNA methylation level in the IL8 proximal promoter and CRS in Han Chinese subjects.

METHODS

Patients with chronic rhinosinusitis with nasal polyps (CRSwNP; n = 187), patients with chronic rhinosinusitis without nasal polyps (CRSsNP; n = 89), and control subjects (n = 57) were enrolled in 2 independent cohorts. Purified human nasal epithelial cells from each participant were assessed for percentage DNA methylation of CpG sites in the IL8 proximal promoter by using bisulfite pyrosequencing and for functional aspects of methylation status by using in vitro assays.

RESULTS

DNA methylation of CpG sites 1, 2, and 3, respectively, in the IL8 proximal promoter was significantly decreased in human nasal epithelial cells of patients with CRSwNP compared with that in patients with CRSsNP (P < .001) and control subjects (P < .001). Percentage of DNA methylation of the CpG3 site was correlated negatively with both tissue eosinophilic cationic protein (P < .01) and myeloperoxidase (P < .05) levels. IL-1β (P < .001) and TNF-α (P < .01) significantly increased IL8 expression accompanied by a reduction in methylation at the CpG3 site (P < .001). Electrophoretic mobility shift assays demonstrated that methylation status of CpG3 changed the binding of octamer-binding transcription factor 1 and nuclear factor κB.

CONCLUSION

Decreased DNA methylation of particularly CpG sites in the IL8 proximal promoter might play a role in the pathogenesis of CRSwNP.

Role of epigenetics in the pathogenesis of chronic rhinosinusitis with nasal polyps

Chronic rhinosinusitis (CRS) is a highly prevalent disease characterized by mucosal inflammation of the nose and paranasal sinuses. CRS can be divided into two main categories, CRS with nasal polyps (NPs; CRSwNP) and CRS without NPs (CRSsNP). Although the pathophysiology of CRS remains unclear, DNA methylation has been implicated in the etiology of CRSwNP. The aim of the present study was to elucidate whether DNA methylation of specific genes is involved in the development of NPs. In total, 18 individuals were included in the present study, and were divided into three groups: CRSwNP (n=7), CRSsNP (n=7) and healthy controls (n=4). NP tissues were obtained from the seven patients with CRSwNP and biopsies of the inferior turbinate mucosa from all three groups were used as controls. Methylated genes detected by methyl-CpG-binding domain sequencing were validated by methylation-specific polymerase chain reaction (PCR), bisulfite sequencing, and reverse transcription-quantitative PCR (RT-qPCR). Methyl-CpG-binding domain sequencing identified 43,674 CpG islands in 518 genes. The promotor regions of 10 and 30 genes were hypermethylated and hypomethylated, respectively, in NP samples compared with controls. The top four genes with altered hypomethylation in NP tissues were, Keratin 19 (KRT19), nuclear receptor subfamily 2 group F member 2 (NR2F2), A Disintegrin-like And Metallopeptidase (Reprolysin Type) with Thrombospondin type 1 motif 1 (ADAMTS1) and zinc finger protein 222 (ZNF222). RT-qPCR demonstrated that the expression levels of KRT19, NR2F2 and ADAMTS1 were significantly increased in NP tissues; however, there was no difference in the levels of ZNF222 between NP and control tissues. Further studies are required to confirm the relevance of these epigenetic modifications in the mechanisms underlying NP formation.

Chronic rhinosinusitis in Asia

Chronic rhinosinusitis (CRS), although possibly overdiagnosed, is associated with a high burden of disease and is often difficult to treat in those truly affected. Recent research has demonstrated that inflammatory signatures of CRS vary around the world, with less eosinophilic and more neutrophilic inflammation found in Asia compared with Europe and North America. Although in the Western world about 80% of nasal polyps carry a type 2 signature, this might be between 20% and 60% in China and Korea or Thailand, respectively. These differences are associated with a lower asthma comorbidity and risk of disease recurrence after surgery in the Asian population. As a hallmark of severe type 2 inflammation, eosinophils attacking Staphylococcus aureus at the epithelial barrier have been described recently; they also can be found in a subgroup of Asian patients with nasal polyps. Furthermore, the percentage of type 2 signature disease in patients with CRS is dramatically increasing ("eosinophilic shift") in several Asian countries over the last 20 years. Establishing an accurate diagnosis along with considering the current and shifting patterns of inflammation seen in Asia will enable more effective selection of appropriate pharmacotherapy, surgical therapy, and eventually biotherapy. Determining the causes and pathophysiology for this eosinophilic shift will require additional research.