A genomewide screen for chronic rhinosinusitis genes identifies a locus on chromosome 7q

Genetics and epigenetics of chronic rhinosinusitis

Discerning the genetics and epigenetics of chronic rhinosinusitis (CRS) may optimize outcomes through early diagnostics, personalized and novel therapeutics, and early prognostication. CRS associated with cystic fibrosis and primary ciliary dyskinesia has well-characterized genetic mutations. Most CRS subjects, however, do not exhibit identifiable monogenic alterations. Clustering in related individuals is seen in CRS with nasal polyps. Spouses of subjects with CRS without nasal polyps also may be at increased risk of the same disease. These observations generate questions on genetic and environmental influences in CRS. Genome-wide association studies have identified variations and polymorphisms between CRS and control subjects in genes related to innate and adaptive immunity. Candidate gene and transcriptomics studies have investigated and identified genetic variations related to immunity, inflammation, epithelial barrier function, stress-response, antigen processing, T-cell regulation, and cytokines in CRS. Epigenetic studies have identified mechanisms through which environmental factors may affect these gene functions. However, causality is not determined for most variations. Inferences drawn from these data must be measured because most investigations report unreplicated results from small study populations. Large, replicated studies in tight cohorts across diverse populations remain a pressing need in studying CRS genetics.

Epidemiology of Chronic Rhinosinusitis: Prevalence and Risk Factors

Knowledge of chronic rhinosinusitis (CRS) epidemiology may directly impact patient care: aiding patient identification and establishing accurate diagnosis as well as informing treatment decisions. The objective of this review is to summarize the current evidence on the epidemiology of CRS, with a focus on prevalence and risk factors. Although the presence of either symptoms or objective findings alone have yielded CRS prevalence estimates of over 10%, the presence of both-consistent with guideline-based diagnostic criteria for CRS-has suggested that the true prevalence of CRS is consistently less than 5%, with approximately one-third of patients with CRS having nasal polyps, in epidemiologic studies from around the world. In comparison, the prevalence of CRS endotypes-pathophysiologic subclassification of CRS most commonly as related to type 2 or non-type 2 inflammation-has been found to vary significantly by region. The epidemiology of CRS is modified and ultimately determined by risk factors: genetic/hereditary, demographic, environmental, and imparted by predictive pre-/comorbid disease. The understanding of these epidemiologic relationships may help the provider to optimally identify and understand each individual's CRS disease process, thereby improving both diagnosis and treatment.

An Overview of the Application of Systems Biology in an Understanding of Chronic Rhinosinusitis (CRS) Development

Chronic rhinosinusitis (CRS) is an inflammatory disease of the paranasal sinuses. It is defined as the presence of a minimum of two out of four main symptoms such as hyposmia, facial pain, nasal blockage, and discharge, which last for 8–12 weeks. CRS significantly impairs a patient’s quality of life. It needs special treatment mainly focusing on preventing local infection/inflammation with corticosteroid sprays or improving sinus drainage using nasal saline irrigation. When other treatments fail, endoscopic sinus surgery is considered an effective option. According to the state-of-the-art knowledge of CRS, there is more evidence suggesting that it is more of an inflammatory disease than an infectious one. This condition is also treated as a multifactorial inflammatory disorder as it may be triggered by various factors, such as bacterial or fungal infections, airborne irritants, defects in innate immunity, or the presence of concomitant diseases. Due to the incomplete understanding of the pathological processes of CRS, there is a continuous search for new indicators that are directly related to the pathogenesis of this disease—e.g., in the field of systems biology. The studies adopting systems biology search for possible factors responsible for the disease at genetic, transcriptomic, proteomic, and metabolomic levels. The analyses of the changes in the genome, transcriptome, proteome, and metabolome may reveal the dysfunctional pathways of inflammatory regulation and provide a clear insight into the pathogenesis of this disease. Therefore, in the present paper, we have summarized the state-of-the-art knowledge of the application of systems biology in the pathology and development of CRS.

Acquired cystic fibrosis transmembrane conductance regulator dysfunction

Sinonasal respiratory epithelium is a highly regulated barrier that employs mucociliary clearance (MCC) as the airways first line of defense. The biological properties of the airway surface liquid (ASL), combined with coordinated ciliary beating, are critical components of the mucociliary apparatus. The ASL volume and viscosity is modulated, in part, by the cystic fibrosis transmembrane conductance regulator (CFTR). The CFTR is an anion transporter of chloride (Cl⁻) and bicarbonate (HCO₃⁻) that is located on the apical surface of respiratory epithelium and exocrine glandular epithelium. Improved understanding of how dysfunction or deficiency of CFTR influences the disease process in both genetically defined cystic fibrosis (CF) and acquired conditions has provided further insight into potential avenues of treatment. This review discusses the latest data regarding acquired CFTR deficiency and use of CFTR specific treatment strategies for CRS and other chronic airway diseases.

What is the evidence for genetics in chronic rhinosinusitis?

PURPOSE OF REVIEW

To perform analysis of evidence in current literature on the topic of genetics and chronic rhinosinusitis (CRS), with a particular focus on recent findings in the cystic fibrosis transmembrane regulator (CFTR), genes associated with primary ciliary dyskinesia, and taste receptor T2R38. Other genes that have been found to have association with CRS are also presented and discussed.

RECENT FINDINGS

Recent studies in CFTR and CRS research have investigated possible CFTR-potentiators for treatment of refractory CRS. The T2R38 gene has been shown to be applicable in the clinical setting with a testable phenotype and may have a role in the prognosis and influencing management strategies of CRS patients. Many genes of the immune system have been studied, with genome-wide association studies and candidate-gene approaches identifying new associations that will need replication and further elucidation.

SUMMARY

CRS is a multifactorial disease, with strong evidence of a genetic component in its pathophysiology for some cases. Currently, there are over 70 genes that have been genetically associated with CRS in the past 15 years. Future investigations into genetic causes and predispositions of CRS may allow for improved prognostication and development of disease-prevention strategies as well as novel therapeutic targets.

A family-based genome-wide association study of chronic rhinosinusitis with nasal polyps implicates several genes in the disease pathogenesis

BACKGROUND

The pathogenesis of chronic rhinosinusitis with nasal polyps is largely unknown. Previous studies have given valuable information about genetic variants associated with this disease but much is still unexplained. Our goal was to identify genetic markers and genes associated with susceptibility to chronic rhinosinusitis with nasal polyps using a family-based genome-wide association study.

METHODS

427 patients (293 males and 134 females) with CRSwNP and 393 controls (175 males and 218 females) were recruited from several Swedish hospitals. SNP association values were generated using DFAM (implemented in PLINK) and Efficient Mixed Model Association eXpedited (EMMAX). Analyses of pathway enrichment, gene expression levels and expression quantitative trait loci were then performed in turn.

RESULTS

None of the analysed SNPs reached genome wide significant association of 5.0 x 10-8. Pathway analyses using our top 1000 markers with the most significant association p-values resulted in 138 target genes. A comparison between our target genes and gene expression data from the NCBI Gene Expression Omnibus database showed significant overlap for 36 of these genes. Comparisons with data from expression quantitative trait loci showed the most skewed allelic distributions in cases with chronic rhinosinusitis with nasal polyps compared with controls for the genes HLCS, HLA-DRA, BICD2, VSIR and SLC5A1.

CONCLUSION

Our study indicates that HLCS, HLA-DRA, BICD2, VSIR and SLC5A1 could be involved in the pathogenesis of chronic rhinosinusitis with nasal polyps. HLA-DRA has been associated with chronic rhinosinusitis with nasal polyps in previous studies and HLCS, BICD2, VSIR and SLC5A1 may be new targets for future research.

Chronic Rhinosinusitis without Nasal Polyps

Chronic rhinosinusitis without nasal polyps (CRSsNP) is more prevalent than chronic rhinosinusitis with nasal polyps (CRSwNP). Certain diseases predispose to whereas others are associated with CRSsNP. Predisposing diseases include allergic and nonallergic upper and lower airway diseases, epithelial cell disorders, immunodeficiencies, autoimmune diseases, and some infectious diseases. In addition, environmental and host factors, examples of which include smoking, a higher incidence of abnormal biofilms, and innate immune defects, play a role in the pathogenesis of this disease. CRSsNP is characterized by histologic abnormalities, including basement membrane thickening (fibrosis) and goblet cell hyperplasia. Neutrophils and several chemokines, TGF-β and C-X-C motif chemokine ligand (CXCL)-8, play a role in CRSsNP remodeling. However, there are conflicting data about CRSsNP endotypes, for example, whether it is characterized by neutrophilia or eosinophilia or both. In spite of advancements and the understanding of the pathogenesis of this disease, additional study is necessary to better comprehend its underlying mechanisms, endotypes, and evidence-based treatment strategies.

Genetic and Immune Dysregulation in Chronic Rhinosinusitis

Chronic rhinosinusitis (CRS) is a prevalent condition that is heterogeneous in disease characteristics and multifactorial in cause. Although sinonasal mucosal inflammation in CRS is often either reversible or well-managed medically and surgically, a significant proportion of patients has a refractory form of CRS despite maximal therapy. Two of the several described factors thought to contribute to disease recalcitrance are genetic influences and dysfunction of the host immune system. Current evidence for a genetic basis of CRS is reviewed, as it pertains to putative abnormalities in innate and adaptive immune function. The role of systemic immunodeficiencies in refractory CRS is discussed.

Immunopathogenesis of Chronic Rhinosinusitis and Nasal Polyposis

Chronic rhinosinusitis (CRS) is a troublesome, chronic inflammatory disease that affects over 10% of the adult population, causing decreased quality of life, lost productivity, and lost time at work and leading to more than a million surgical interventions annually worldwide. The nose, paranasal sinuses, and associated lymphoid tissues play important roles in homeostasis and immunity, and CRS significantly impairs these normal functions. Pathogenic mechanisms of CRS have recently become the focus of intense investigations worldwide, and significant progress has been made. The two main forms of CRS that have been long recognized, with and without nasal polyps, are each now known to be heterogeneous, based on underlying mechanism, geographical location, and race. Loss of the immune barrier, including increased permeability of mucosal epithelium and reduced production of important antimicrobial substances and responses, is a common feature of many forms of CRS. One form of CRS with polyps found worldwide is driven by the cytokines IL-5 and IL-13 coming from Th2 cells, type 2 innate lymphoid cells, and probably mast cells. Type 2 cytokines activate inflammatory cells that are implicated in the pathogenic mechanism, including mast cells, basophils, and eosinophils. New classes of biological drugs that block the production or action of these cytokines are making important inroads toward new treatment paradigms in polypoid CRS.

Channel Gating Regulation by the Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) First Cytosolic Loop

In this study, we present data indicating a robust and specific domain interaction between the cystic fibrosis transmembrane conductance regulator (CFTR) first cytosolic loop (CL1) and nucleotide binding domain 1 (NBD1) that allows ion transport to proceed in a regulated fashion. We used co-precipitation and ELISA to establish the molecular contact and showed that binding kinetics were not altered by the common clinical mutation F508del. Both intrinsic ATPase activity and CFTR channel gating were inhibited severely by CL1 peptide, suggesting that NBD1/CL1 binding is a crucial requirement for ATP hydrolysis and channel function. In addition to cystic fibrosis, CFTR dysregulation has been implicated in the pathogenesis of prevalent diseases such as chronic obstructive pulmonary disease, acquired rhinosinusitis, pancreatitis, and lethal secretory diarrhea (e.g. cholera). On the basis of clinical relevance of the CFTR as a therapeutic target, a cell-free drug screen was established to identify modulators of NBD1/CL1 channel activity independent of F508del CFTR and pharmacologic rescue. Our findings support a targetable mechanism of CFTR regulation in which conformational changes in the NBDs cause reorientation of transmembrane domains via interactions with CL1 and result in channel gating.

Risk factors for chronic rhinosinusitis

PURPOSE OF REVIEW

To review the recent literature on risk factors for chronic rhinosinusitis (CRS) with an emphasis on genetic, comorbid diseases and environmental factors associated with CRS. Through identifying potential risk factors for CRS, we aim to glean insights into the underlying pathogenic mechanisms essential for developing effective therapeutic strategies.

RECENT FINDINGS

Recent findings demonstrate that genetics and comorbid medical conditions including airway diseases, gastroesophageal reflux disease, inflammatory and autoimmune diseases, and various demographic and environmental factors are associated with having a CRS diagnosis. Limitations of current studies include variable application of disease definitions, lack of prospective longitudinal studies and a disproportionate focus on tertiary care populations.

SUMMARY

CRS has a broad spectrum of associations ranging from genetics to comorbid diseases and environmental factors. These predisposing factors may provide valuable information for possible designing of therapeutic and preventive interventions. However, to better understand whether these associations cause CRS, further studies are needed to independently replicate findings, establish temporal relationships between exposure and disease onset, evaluate the influence of exposure dose on disease severity, and to understand the biological effects of these risk factors in the context of CRS.

Familial risk of chronic rhinosinusitis with and without nasal polyposis: genetics or environment

BACKGROUND

Chronic rhinosinusitis (CRS) is a highly prevalent inflammatory condition, with significant effects on morbidity and quality of life, yet little is known about its pathogenesis. Preliminary evidence suggests there is a heritable component to the multifactorial etiology of CRS; however, our understanding of this genetic susceptibility is limited.

METHODS

Using an extensive genealogical database linked to medical records, the risk of CRS with nasal polyps (CRSwNP) and without polyps (CRSsNP) was calculated for relatives and spouses of adult probands (1638 CRSwNP and 24,200 CRSsNP patients diagnosed between 1996 and 2011) and were compared to random population controls matched 5:1 on sex and birth year from Cox regression models.

RESULTS

First-degree relatives (1stDRs) of CRSwNP patients demonstrated a 4.1-fold increased risk (p < 10(-3) ) of carrying the same diagnosis, whereas second-degree relatives (2ndDRs) demonstrated a 3.3-fold increased risk (p < 0.004), compared to controls. In CRSsNP patients, 1stDRs were at 2.4-fold increased risk (p < 10(-15) ), whereas 2ndDRs were at 1.4-fold increased risk (p < 10(-15) ) of the same diagnosis. Third-degree relatives (3rdDRs) had a slight increased risk at 1.1-fold (p < 10(-7) ). Spouses of CRSsNP patients, who likely share environmental circumstances, exhibited a 2-fold increased risk (p < 10(-15) ). No increased risk was observed in spouses of CRSwNP patients.

CONCLUSION

In the largest population study to date, a significant familial risk is confirmed in CRSwNP and CRSsNP, which may have a shared genetic and environmental component. Further understanding of the genetic basis of CRS and its interplay with environment factors could clarify disease etiology and lead to more effective targeted treatments.

The molecular genetics of inflammatory, autoimmune, and infectious diseases of the sinonasal tract: a review

CONTEXT

The sinonasal tract is frequently affected by a variety of nonneoplastic inflammatory disease processes that are often multifactorial in their etiology but commonly have a molecular genetic component.

OBJECTIVE

To review the molecular genetics of a variety of nonneoplastic inflammatory diseases of the sinonasal tract.

DATA SOURCES

Inflammatory lesions of the sinonasal tract can be divided into 3 main categories: (1) chronic rhinosinusitis, (2) infectious diseases, and (3) autoimmune diseases/vasculitides. The molecular diagnosis and pathways of a variety of these inflammatory lesions are currently being elucidated and will shed light on disease pathogenesis and treatment.

CONCLUSIONS

The sinonasal tract is frequently affected by inflammatory lesions that arise through complex interactions of environmental, infectious, and genetic factors. Because these lesions are all inflammatory in nature, the molecular pathology surrounding them is most commonly due to upregulation and down-regulation of genes that affect inflammatory responses and immune regulation.

Genetics of chronic rhinosinusitis: state of the field and directions forward

The cause of chronic rhinosinusitis (CRS) remains unclear. Study of the genetic susceptibility to CRS might be a valuable strategy to understand the pathogenesis of this burdensome disorder. The purpose of this review is to critically evaluate the current literature regarding the genetics of CRS in a comprehensive fashion. The most promising findings from candidate gene studies include the cystic fibrosis transmembrane conductance regulator gene (CFTR), as well as genes involved in antigen presentation, innate and adaptive immune responses, tissue remodeling, and arachidonic acid metabolism. We also review the few hypothesis-independent genetic studies of CRS (ie, linkage analysis and pooling-based genome-wide association studies). Interpretation of the current literature is limited by challenges with study design, sparse replication, few functional correlates of associated polymorphisms, and inadequate examination of linkage disequilibrium or expression quantitative trait loci for reported associations. Given the relationship of CRS to other airway disorders with well-characterized genetic components (eg, asthma), study of the genetics of CRS deserves increased attention and investment, including the organization of large, detailed, and collaborative studies to advance knowledge of the mechanisms that underlie this disorder.

Chronic rhinosinusitis as a multifactorial inflammatory disorder

Chronic rhinosinusitis (CRS) is a prevalent health condition characterized by sinonasal mucosal inflammation lasting at least 12 weeks. Heterogeneous in clinical presentation, histopathology, and therapeutic response, CRS represents a spectrum of disease entities with variable pathophysiology. Increased knowledge of cellular and molecular derangements in CRS suggests potential etiologies and targets for therapy. Microbial elements including fungi, staphylococcal enterotoxin, and biofilms have been implicated as inflammatory stimuli, along with airborne irritants and allergens. Defects in innate immunity have gained increased attention as contributors to the chronic inflammatory state. A combination of host susceptibility and environmental exposure is widely believed to underlie CRS, although direct evidence is lacking. Presently, without precise disease definitions and identifiable universal triggers, CRS pathogenesis is broadly described as multifactorial. Current research is beginning to unravel complex and diverse effects of chronic inflammation on sinonasal mucosal homeostasis, but dysfunctional pathways of inflammatory regulation and resolution require further elucidation.

Innate immunity

Innate immunity is an exciting area of research in rhinology because emerging evidence suggests that abnormal local immune responses, rather than pathogen-specific adaptive immunity, may play a more important role in the pathogenesis of chronic rhinosinusitis (CRS). This article reviews important recent research regarding the innate immune system and CRS, with particular focus on the role of pattern recognition receptors, antimicrobial peptides and biofilms, epithelial ciliary function, cystic fibrosis, and cigarette smoking, and on areas for future research and therapy.

Rhinosinusitis and comorbidities

A variety of systemic conditions impact the incidence, severity, prognosis, and treatment approach in patients with chronic rhinosinusitis (CRS). The controversy surrounding the impact of allergic rhinitis on CRS continues, but it is reasonable to consider and treat allergic sources of inflammation in any patient with CRS. CRS is more severe in patients with aspirin sensitivity but improves--at least temporarily--to the same degree as in non-aspirin-sensitive patients, given appropriate therapy. Polypoid rhinosinusitis in cystic fibrosis patients is characterized by compromised mucociliary clearance and infection with staphylococcal and pseudomonal organisms. Affected individuals require frequent antibiotic treatment, saline lavage, and repeated surgeries. Rhinosinusitis is among the most common infectious complications of humoral immunodeficiency, which is not uncommon in patients with refractory CRS. The treatment approach in immunodeficiency includes aggressive antibiotic treatment and intravenous immunoglobulin. Specific diagnosis of comorbid systemic conditions with CRS will facilitate appropriate management.

c-MET pathway involvement in chronic rhinosinusitis: a genetic association analysis

OBJECTIVE

The c-MET receptor and its ligand hepatocyte growth factor (HGF) has been shown to be overexpressed in tissue from chronic rhinosinusitis (CRS) patients with nasal polyps compared with that from controls. We assessed the genetic association of polymorphisms in the met proto-oncogene (MET) gene with CRS.

STUDY DESIGN

Case-control genetic association study.

SETTING

Tertiary-care university hospital.

SUBJECTS AND METHODS

A total of 206 unrelated Canadian patients with CRS and 196 control subjects were enrolled. Subjects were genotyped for 33 polymorphisms in the MET gene.

RESULTS

The allelic association analysis showed eight single nucleotide polymorphisms in the MET gene (rs38850, rs38855, rs38857, rs2237717, rs2402118, rs193688, rs1621, rs42336) with a statistically significant association with CRS. The rs38850 T allele showed the strongest association and the highest risk for CRS (P = 0.004; odds ratio 1.65, 95% confidence interval 1.18-2.32); the association did not reach statistical significance after adjustment for genomic control (P = 0.06). The haplotype TGG constructed of markers rs38850, rs38855, and rs38857 represented a risk haplotype, resulting in a P value of 0.003 that remained significant after correction for multiple testing (P = 0.018).

CONCLUSION

These data suggest that polymorphisms in the MET gene may play a role in the susceptibility to develop CRS. Study findings apply to patients with severe CRS unresponsive to surgery.

Screening for staphylococcal superantigen genes shows no correlation with the presence or the severity of chronic rhinosinusitis and nasal polyposis

BACKGROUND

Staphylococcus aureus secretes numerous exotoxins which may exhibit superantigenic properties. Whereas the virulence of several of them is well documented, their exact biological effects are not fully understood. Exotoxins may influence the immune and inflammatory state of various organs, including the sinonasal mucosa: their possible involvement in chronic rhinosinusitis has been suggested and is one of the main trends in current research. The aim of this study was to investigate whether the presence of any of the 22 currently known staphylococcal exotoxin genes could be correlated with chronic rhinosinusitis.

METHODOLOGY/PRINCIPAL FINDINGS

We conducted a prospective, multi-centred European study, analysing 93 Staphylococcus aureus positive swabs taken from the middle meatus of patients suffering from chronic rhinosinusitis, with or without nasal polyposis, and controls. Strains were systematically tested for the presence of the 22 currently known exotoxin genes and genotyped according to their agr groups. No direct correlation was observed between chronic rhinosinusitis, with or without nasal polyposis, and either agr groups or the presence of the most studied exotoxins genes (egc, sea, seb, pvl, exfoliatins or tsst-1). However, genes for enterotoxins P and Q were frequently observed in nasal polyposis for the first time, but absent in the control group. The number of exotoxin genes detected was not statistically different among the 3 patient groups.

CONCLUSIONS/SIGNIFICANCE

Unlike many previous studies have been suggesting, we did not find any evident correlation between staphylococcal exotoxin genes and the presence or severity of chronic rhinosinusitis with or without nasal polyposis.