Inflammatory cytokines in allergy and rhinosinusitis

An In Vitro Study Evaluating the Safety of Mesalazine on Human Nasoepithelial Cells

Chronic rhinosinusitis (CRS) is a disease characterised by the inflammation of the nasal and paranasal cavities. It is a widespread condition with considerable morbidity for patients. Current treatment for chronic rhinosinusitis consists of appropriate medical therapy followed by surgery in medically resistant patients. Although oral steroids are effective, they are associated with significant morbidity, and disease recurrence is common when discontinued. The development of additional steroid sparing therapies is therefore needed. Mesalazine is a commonly used therapeutic in inflammatory bowel disease, which shares a similar disease profile with chronic rhinosinusitis. This exploratory in vitro study aims to investigate whether mesalazine could be repurposed to a nasal wash, which is safe on human nasoepithelial cells, and retains its anti-inflammatory effects. CRS patients' human nasal epithelial cells (HNECs) were collected. HNECs were grown at an air-liquid interface (ALIs) and in a monolayer and challenged with mesalazine or a non-medicated control. Transepithelial electrical resistance, paracellular permeability, and toxicity were measured to assess epithelial integrity and safety. The anti-inflammatory effects of mesalazine on the release of interleukin (IL)-6 and tumour necrosis factor alpha (TNF-α) were analysed using human leukemia monocytic cell line (THP-1). mesalazine did not impact the barrier function of HNEC-ALIs and was not toxic when applied to HNECs or THP-1 cells at concentrations up to 20 mM. mesalazine at 0.5 and 1 mM concentrations significantly inhibited TNF-α release by THP-1 cells. mesalazine effectively decreases TNF-α secretion from THP-1 cells, indicating the possibility of its anti-inflammatory properties. The safety profile of mesalazine at doses up to 20 mM suggests that it is safe when applied topically on HNECs.

Inhibitory effects of orientin in mast cell-mediated allergic inflammation

BACKGROUND

Mast cells are immune effector cells mediating allergic inflammation by the secretion of inflammatory mediators such as histamine and pro-inflammatory cytokines. Orientin is a naturally occurring bioactive flavonoid that possesses diverse biological properties, including anti-inflammation, anti-oxidative, anti-tumor, and cardio protection. The objective of this study was to rule out the effectiveness of orientin in mast cell-mediated allergic inflammation.

METHODS

In this study, in vitro effects of orientin were evaluated in RBL-2H3, mouse bone marrow-derived mast cells, rat peritoneal mast cells, and in vivo effects were evaluated by inducing passive cutaneous anaphylaxis (PCA) in Imprinting Control Region (ICR) mice.

RESULTS

Findings show that orientin suppressed the immunoglobulin E (IgE)-mediated mast cell degranulation by reducing intracellular calcium level in a concentration-dependent manner. Orientin suppressed the secretion of pro-inflammatory cytokines in mast cells. This inhibitory effects of orientin was through inhibition of FcεRI-mediated signaling proteins. In addition, oral administration of orientin suppressed the IgE-mediated PCA reactions in a dose-dependent manner, which was evidenced by reduced Evan's blue pigmentation and ear swelling.

CONCLUSIONS

Based on these findings, we suggest that orientin might have potential to alleviate allergic reaction and mast cell-mediated allergic disease.

Contributions of Innate Lymphoid Cells in Chronic Rhinosinusitis

PURPOSE OF REVIEW

To review innate lymphoid cells (ILCs) and their role in chronic rhinosinusitis (CRS).

RECENT FINDINGS

The immune system consists of the innate and adaptive response. Until the recognition of ILCs, chronic inflammatory diseases were characterized by cytokines linked only to T helper cells. However, these immune responses are now described more broadly to include contributions from both the innate and adaptive immunity. In CRS, focus had been on ILC2s in CRS with nasal polyps. These studies also highlight the importance of epithelial cell-derived cytokines in coordinating these responses. In addition to indirect crosstalk via cytokines, ILCs and T helper cells can utilize the OX40/OX40 ligand and major histocompatibility complex class II pathways to directly interact and coordinate responses. In addition to T helper cells, ILCs contribute to the inflammatory response associated with CRS. The understanding of these cells along with pathways that activate and perpetuate these cells leads to new potential therapeutic targets for CRS treatment.

The Role of NF-κB in Chronic Rhinosinusitis With Nasal Polyps

PURPOSE

Whereas the majority of nasal polyps observed in Western populations are eosinophilic, non-eosinophilic nasal polyps are significantly more frequent in Asian countries. Given the importance of nuclear factor-kappa B (NF-κB) in inflammation, this study focused on the role of NF-κB in the pathogenesis of chronic rhinosinusitis with nasal polyps (CRSwNPs) in Asian patients.

METHODS

A total of 46 patients were enrolled in this study (22 diagnosed with CRSwNPs, 10 with chronic rhinosinusitis without nasal polyps [CRSsNP], and 14 control subjects). Nasal polyps and uncinate tissues (UTs) were collected and the tissues prepared for hematoxylin-eosin staining and immunohistochemistric (IHC) analysis. Total RNA was isolated for real-time polymerase chain reaction for p65, interleukin (IL)-6, IL-8, intracellular adhesion molecule (ICAM)-1, IL-1β, tumor necrosis factor (TNF)-α, and eotaxin.

RESULTS

In the CRSwNPs group, 50% of nasal polyps were non-eosinophilic. IHC revealed a significantly higher fraction of NF-κB p65-positive cells in nasal polyps of the CRSwNPs group than in the UTs of control and CRSsNP groups. No difference in NF-κB p65-positive cell fraction was observed between eosinophilic and non-eosinophilic nasal polyps. The mRNA expression of p65, IL-6, IL-8, and eotaxin was significantly higher in nasal polyps of the CRSwNPs than in the UTs of control and CRSsNP group. However, no difference in expression was observed between eosinophilic and non-eosinophilic nasal polyps, with the exception of IL-1β expression.

CONCLUSIONS

Elevated expression of NF-κB- and NF-κB-associated inflammatory cytokines suggests NF-κB as the key factor for CRSwNPs pathogenesis in Asian patients. Understanding NF-κB-associated mechanisms will provide a deeper insight into CRSwNPs pathogenesis and ultimately improve therapeutic strategies for CRSwNPs.

Solitary chemosensory cells are a primary epithelial source of IL-25 in patients with chronic rhinosinusitis with nasal polyps

BACKGROUND

IL-25 can function as an early signal for the respiratory type 2 response characteristic of allergic asthma and chronic rhinosinusitis with nasal polyps (CRSwNP). In the mouse gut, tuft cells are the epithelial source of IL-25. However, the source of human airway epithelial IL-25 has remained elusive.

OBJECTIVE

In this study we sought to determine whether the solitary chemosensory cell (SCC) is the predominant source of IL-25 in the sinonasal epithelium.

METHOD

Flow cytometry and immunofluorescence for SCCs and IL-25 were used to interrogate polyp and turbinate tissue from patients with CRSwNP. Mucus was collected during acute inflammatory exacerbations from patients with CRSwNP or chronic rhinosinusitis without nasal polyps and IL-25 levels determined by using ELISA. Lastly, sinonasal epithelial cultures derived from polyp and turbinate tissue were stimulated with IL-13 and analyzed for SCC proliferation and IL-25 production.

RESULTS

This study demonstrates that a discrete cell type, likely an SCC, characterized by expression of the taste-associated G protein gustducin and the intestinal tuft cell marker doublecortin-like kinase 1, is the predominant source of IL-25 in the human upper airway. Additionally, we show that patients with CRSwNP have increased numbers of SCCs in nasal polyp tissue and that in vitro IL-13 exposure both increased proliferation and induced apical secretion of IL-25 into the mucosal layer.

CONCLUSIONS

Inflammatory sinus polyps but not adjacent turbinate tissue show expansion of the SCC population, which is the source of epithelial IL-25.

Reversal of cigarette smoke extract-induced sinonasal epithelial cell barrier dysfunction through Nrf2 Activation

BACKGROUND

Environmental factors such as inhaled pollutants like cigarette smoke may play a significant role in diseases of the upper airway including chronic rhinosinusitis (CRS). Recent studies have shown that cigarette smoke causes impaired airway epithelial cell barrier function likely through environmental oxidative stress related pathways. The purpose of this study is to explore whether enhancing nuclear factor erythroid 2 [NF-E2]-related factor 2 [Nrf2], the body's master antioxidant system, can ameliorate cigarette smoke-induced sinonasal epithelial cell (SNEC) barrier dysfunction.

METHODS

Human SNECs (HSNECs) were grown from control patients at the air-liquid interface (ALI). HSNECs were stimulated with cigarette smoke extract (CSE) with and without pharmacologic activation of Nrf2. HSNECs were then stained for the epithelial cell junctional proteins zonula occludens 1 (ZO-1) and junctional adhesion molecule A (JAM-A) using confocal microscopy. In addition, transepithelial electrical resistance (TER) was measured in cultures before and after stimulation with CSE.

RESULTS

CSE stimulation caused a global disruption of the epithelial junctional proteins ZO-1 and JAM-A along with an associated decrease in TER levels. Enhancing Nrf2 levels prior to stimulation with CSE was associated with increased localization of ZO-1 and JAM-A levels at the cell surface and statistically significant increases in TER levels.

CONCLUSION

This is the first study to demonstrate that cigarette smoke induced SNEC barrier dysfunction is reversible by Nrf2 activation. The Nrf2 antioxidant pathway may represent a potential therapeutic target for cigarette smoke-associated sinonasal inflammation.

Cytokine patterns in nasal secretion of non-atopic patients distinguish between chronic rhinosinusitis with or without nasal polys

BACKGROUND

Being one of the most common nasal diseases, chronic rhinosinusitis (CRS) is subdivided into CRS with nasal polyps (NP) and CRS without nasal polyps (CRSsNP). CRSsNP presents itself with a TH1 milieu and neutrophil infiltration, while NP is characterised by a mixed TH1/TH2 profile and an influx of predominantly eosinophils, plasma cells and mast cells. For the purpose of discovering disease-specific cytokine profiles, the present study compares levels of mediators and cytokines in nasal secretions between CRSsNP, NP, and healthy controls.

METHODS

The study included 45 participants suffering from NP, 48 suffering from CRSsNP and 48 healthy controls. Allergic rhinitis constituted an exclusion criterion. Nasal secretions, sampled using the cotton wool method, were analysed for IL-4, IL-5, IL-10, IL-12, IL-13, IL-17, IL-8, GM-CSF, G-CSF, IFN-γ, MCP-1, MIP-1α, MIP-1β, eotaxin, and RANTES, and for ECP and tryptase, using Bio-Plex Cytokine assay or ELISA, respectively.

RESULTS

Elevated levels of IL-5, IL-17, G-CSF, MCP-1, MIP-1α, MIP-1β, ECP, and tryptase, as well as decreased levels of IL-10, IL-12, IL-13, and IFN-γ were detected in NP. CRSsNP presented increased levels of RANTES and MIP-1β while IL-13 was decreased. No differences between the three groups were found for IL-4, IL-8, GM-CSF, and eotaxin.

CONCLUSIONS

The present work suggests a disequilibrium of TH1 and TH2, together with a down-regulation of regulatory T lymphocytes and up-regulated TH17 in NP. Moreover, elevated levels of diverse mediators represent the activation of various inflammatory cells in this disease entity. The inflammation in CRSsNP, however, is only weakly depicted in nasal secretions. Therefore, cytokines in nasal secretions may provide helpful information for differential diagnosis.

Therapeutic effects of intranasal cyclosporine for eosinophilic rhinosinusitis with nasal polyps in a mouse model

BACKGROUND

Chronic rhinosinusitis (CRS) with nasal polyps (CRSwNP) is a principally type 2 T helper cell (Th2)-mediated inflammatory disease. Systemic corticosteroids currently represent the most effective treatment for CRSwNP, but their long-term use is constrained due to their detrimental side effects. Long-term use of topical steroids is safe, but their efficacy is often limited. Topical cyclosporine has proven to be safe and effective for Th2-mediated diseases such as allergic conjunctivitis.

OBJECTIVE

It was hypothesized that topical cyclosporine would be an effective novel drug for the treatment of CRSwNP; its therapeutic efficacy was assessed using a previously established mouse model.

METHODS

After induction of eosinophilic CRSwNP in four-week-old BALB/c mice according to previous protocols, the therapeutic effects of intranasal cyclosporine were evaluated and compared with those of triamcinolone acetonide (TAC). Histopathologic changes were evaluated using hematoxylin and eosin for polyp formation and Sirius red staining for eosinophilic infiltration. The production of cytokines in sinonasal tissues, including tumor necrosis factor (TNF), interleukin (IL)-2, interferon (IFN)-γ, IL-4, IL-5, IL-13, and IL-17A, was measured using a cytometric bead array.

RESULTS

The number of polyp-like lesions was reduced significantly only by systemic TAC, but the degree of eosinophilic infiltration was decreased significantly by topical cyclosporine, the potency of which was similar to that of topical or systemic TAC. Except for IFN-γ, the majority of measured cytokines were reduced significantly by topical cyclosporine, although their effects on IL-2 and IL-13 were less potent than those of systemic TAC.

CONCLUSION

Topical cyclosporine might be an effective drug for the management of CRSwNP.

Cellular and molecular mechanisms of chronic rhinosinusitis and potential therapeutic strategies: review on cytokines, nuclear factor kappa B and transforming growth factor beta

BACKGROUND

Chronic rhinosinusitis is characterised by persistent inflammation of the sinonasal mucosa. Multiple pathophysiological mechanisms are likely to exist. Previous research has focused predominantly on T-helper type cytokines to highlight the inflammatory mechanisms. However, proteins such as nuclear factor kappa B and transforming growth factor beta are increasingly recognised to have important roles in sinonasal inflammation and tissue remodelling.

OBJECTIVE

This review article explores the roles of T-helper type cytokines, nuclear factor kappa B and transforming growth factor beta in the pathophysiological mechanisms of chronic rhinosinusitis. An understanding of these mechanisms will allow for better identification and classification of chronic rhinosinusitis endotypes, and, ultimately, improved therapeutic strategies.

Effector cell signature in peripheral blood following nasal allergen challenge in grass pollen allergic individuals

BACKGROUND

Several studies have demonstrated the time course of inflammatory mediators in nasal fluids following nasal allergen challenge (NAC), whereas the effects of NAC on cells in the periphery are unknown. We examined the time course of effector cell markers (for basophils, dendritic cells and T cells) in peripheral blood after nasal grass pollen allergen challenge.

METHODS

Twelve participants with seasonal allergic rhinitis underwent a control (diluent) challenge followed by NAC after an interval of 14 days. Nasal symptoms and peak nasal inspiratory flow (PNIF) were recorded along with peripheral basophil, T-cell and dendritic cell responses (flow cytometry), T-cell proliferative responses (thymidine incorporation), and cytokine expression (FluoroSpot assay).

RESULTS

Robust increases in nasal symptoms and decreases in PNIF were observed during the early (0-1 h) response and modest significant changes during the late (1-24 h) response. Sequential peaks in peripheral blood basophil activation markers were observed (CD107a at 3 h, CD63 at 6 h, and CD203c(bright) at 24 h). T effector/memory cells (CD4(+) CD25(lo) ) were increased at 6 h and accompanied by increases in CD80(+) and CD86(+) plasmacytoid dendritic cells (pDCs). Ex vivo grass antigen-driven T-cell proliferative responses and the frequency of IL-4(+) CD4(+) T cells were significantly increased at 6 h after NAC when compared to the control day.

CONCLUSION

Basophil, T-cell, and dendritic cell activation increased the frequency of allergen-driven IL-4(+) CD4(+) T cells, and T-cell proliferative responses are detectable in the periphery after NAC. These data confirm systemic cellular activation following a local nasal provocation.

Association of IL1β and IL4 gene polymorphisms with nasal polyps in a Polish population

Imbalance between proinflammatory and anti-inflammatory cytokines may regulate the inflammatory reaction in the nasal polyps. Polymorphisms in the regulatory regions of the cytokines genes may influence their expression. The aim of this study was to investigate the relationship between an IL-1β and IL-4 promoter polymorphisms and nasal polyps. The C-511T promoter polymorphism of the IL-1β gene and C-590T promoter polymorphism of the IL-4 gene were genotyped by polymerase chain reaction-restriction fragment length polymorphism analysis in 208 Polish patients with nasal polyps and 200 healthy Polish subjects. The risk of susceptibility to NP was significantly higher in patients with NP who had -511 T/T genotype of IL1β than in controls (OR 3.07; 95 % CI 1.18-7.99). No statistically significant differences were found between NP patients and the control group with regard to genotype distribution and allele frequencies of C/T polymorphism of IL4 gene. Our study demonstrated that the TT genotype for C-511T mutation associated with the risk of developing NP in a Polish population.

Impact of mitomycin C on the mRNA expression signatures of immunological biomarkers in eosinophilic nasal polyposis

BACKGROUND

The topical application of mitomycin C has been evaluated as a complementary therapy for eosinophilic nasal polyposis (ENP). However, the mechanism underlying the additional benefits of mitomycin C for the control of eosinophilic inflammation and prevention of posttherapeutic relapse remains to be elucidated. In this work, the aim was to characterize the gene expression profile by quantitative real-time polymerase chain reaction (qPCR) of proinflammatory and regulatory biomarkers that are typically associated with ENP and to assess the impact of the topical application of mitomycin C on the nasal mucosal tissue immunologic milieu after ENP surgery.

METHODS

We have selected 20 patients with ENP that were recommended to undergo surgical intervention. Normal mucosal tissue was obtained from healthy nasal mucosa from six patients with absence of eosinophilic infiltration. To test the effect of mitomycin C, one side of the maxillary sinus mucosa was selected for topical application of this drug and the other received no further treatment and acted as the control. The genes interleukin-4 (IL-4), IL-5, IL-10, IL-13, chemokine (C-C motif) ligand 5 (CCL5), CCL24, colony-stimulating factor 2 (CSF2), transforming growth factor beta 1 (TGFB1), tumor necrosis factor alpha (TNF-alpha), and beta actin (ACTB) were selected for gene expression analysis by qPCR.

RESULTS

The data showed higher expression of proinflammatory biomarkers and lower levels of regulatory TGFB1 transcripts in ENP mucosal tissue. Surgery with topical application of mitomycin C induced a prominent transcriptional down-regulation of the immunologic biomarkers, CCL24, TNF-alpha, CSF2, and IL-5, in ENP mucosal tissue. Additionally, this treatment restored the levels of chemokines and cytokines to those observed in the nasal mucosal tissue of control subjects, except for TGFB1, which remained below the reference pattern. Moreover, CSF2 was identified as a putative biomarker with significant predictive value for complementary prophylactic purposes after surgery in ENP patients.

CONCLUSION

After the characterization of the expression signatures of immunologic biomarkers in ENP, we observed that the topical use of mitomycin C is important for the reestablishment of the immunologic microenvironment of a normal expression profile of biomarkers involved in ENP mucosal tissue.

Upper airway inflammation exacerbates bronchial hyperreactivity in mouse models of rhinosinusitis and allergic asthma

BACKGROUND

Recent studies have suggested that upper airway inflammation has a strong impact on lower airway diseases. The purpose of this study was to assess whether nasal inflammation could exacerbate allergic asthma in a mouse model.

METHODS

Mice were assigned to 4 groups: control (Cont), either rhinosinusitis (R) or allergic asthma (A) alone, and both rhinosinusitis and allergic asthma (R&A). Mice underwent induction of nasal inflammation (R and R&A) or sham surgery (Cont and A) on day 1. Mice in the A and R&A groups were sensitized to ovalbumin on days 1, 7, and 14, followed by aerosol challenge on days 18 to 20, whereas in the Cont and R groups only saline was administered. All mice were assessed for airway hyperresponsiveness (AHR) and were euthanized on day 21. The sera, bronchoalveolar lavage fluids (BALFs), and nasal and lung tissues were collected for further analyses.

RESULTS

Histology findings confirmed upper and lower airway inflammation in experimental mice. Significantly increased AHR and total serum immunoglobulin E (IgE) were observed in the R&A group when compared with those of the Cont, R, and A groups. Responses to IgG2a induction were also found in sera and BALFs from mice with rhinosinusitis (R and R&A). Higher levels of interleukin 4 (IL-4) and IL-13, and increased eosinophilic inflammation were detected in BALFs and lung tissues from the experimental groups when compared with those from the Cont group.

CONCLUSION

Our results confirm that upper airway inflammation could exacerbate allergic asthma, and provide support to the concept of "one airway, one disease.

The attenuation of cockroach allergy by DNA vaccine encoding cockroach allergen Bla g 2

Bla g 2 is one of the most potent cockroach allergens. No effective treatment or vaccination strategies are yet available. We evaluated the prophylactic efficacy of Bla g 2 DNA vaccination in a mouse model of allergic airway inflammation. C57/BL6 mice were given Bla g 2 DNA vaccine prior to sensitization with recombinant Bla g 2 (rBla g 2) antigens, followed by nebulized rBla g 2 challenge. Bla g 2 vaccine could express at both transcriptional and translational levels in mammalian cells. Moreover, Bla g 2 vaccine significantly reduced the total inflammatory cell infiltrate and eosinophilia in bronchoalveolar lavage fluid, and markedly decreased allergen-induced inflammatory infiltrates in the lungs and Bla g 2-specific IgE in serum upon challenge with rBla g 2. Importantly, Bla g 2 vaccine could induce the production of antigen-specific IFN-γ and downregulated Th2 pro-inflammatory cytokines IL-4, IL-5, and IL-13. Thus, DNA vaccination showed protective efficacy against a clinically relevant allergen, Bla g 2.

Prevention and treatment of DNA vaccine encoding cockroach allergen Bla g 1 in a mouse model of allergic airway inflammation

BACKGROUND

One-fourth of the US population is sensitized to the German cockroach. Primary German cockroach allergen Bla g 1 is detected in 63% of homes and 52% of childcare facilities in the United States. No effective treatment or vaccination strategies are yet available.

OBJECTIVES

We evaluated the prophylactic and therapeutic efficacy of a plasmid DNA-mediated vaccination using the Bla g 1 gene in a mouse model of allergic inflammatory airway disease.

METHODS

A plasmid DNA vector coding for the Bla g 1 allergen controlled by cytomegalovirus promoter was constructed. To estimate the protective efficacy, BALB/c mice were given three injections of plasmid DNA-Bla g 1 prior to sensitization with two priming doses of recombinant Bla g 1 (rBla g 1) antigens, followed by nebulized rBla g 1 challenge. In the therapeutic approach, sensitization was followed by administering Bla g 1 DNA vaccine.

RESULTS

Bla g 1 vaccination significantly reduced allergen-induced airway inflammation, even after mice were presensitized and a Th2-dominant response was established. The Bla g 1 vaccination significantly reduced total inflammatory cell infiltrate, eosinophilia, secretion of Th2 cytokines IL-4 and IL-5 in bronchoalveolar lavage fluid, allergen-induced inflammatory infiltrates in the lungs, and Bla g 1-specific IgE in serum upon challenge with rBla g 1. Importantly, Bla g 1 DNA vaccination was able to induce IL-10-secreting regulatory T cells that could suppress the allergen-specific Th2 cells.

CONCLUSION

DNA vaccination showed protective and therapeutic efficacy against a clinically relevant allergen Bla g 1.

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.

Tobacco smoke mediated induction of sinonasal microbial biofilms

Cigarette smokers and those exposed to second hand smoke are more susceptible to life threatening infection than non-smokers. While much is known about the devastating effect tobacco exposure has on the human body, less is known about the effect of tobacco smoke on the commensal and commonly found pathogenic bacteria of the human respiratory tract, or human respiratory tract microbiome. Chronic rhinosinusitis (CRS) is a common medical complaint, affecting 16% of the US population with an estimated aggregated cost of $6 billion annually. Epidemiologic studies demonstrate a correlation between tobacco smoke exposure and rhinosinusitis. Although a common cause of CRS has not been defined, bacterial presence within the nasal and paranasal sinuses is assumed to be contributory. Here we demonstrate that repetitive tobacco smoke exposure induces biofilm formation in a diverse set of bacteria isolated from the sinonasal cavities of patients with CRS. Additionally, bacteria isolated from patients with tobacco smoke exposure demonstrate robust in vitro biofilm formation when challenged with tobacco smoke compared to those isolated from smoke naïve patients. Lastly, bacteria from smoke exposed patients can revert to a non-biofilm phenotype when grown in the absence of tobacco smoke. These observations support the hypothesis that tobacco exposure induces sinonasal biofilm formation, thereby contributing to the conversion of a transient and medically treatable infection to a persistent and therapeutically recalcitrant condition.