Inhibiting Isoprenylation Suppresses FcεRI-Mediated Mast Cell Function and Allergic Inflammation.

IgE-mediated mast cell activation is a driving force in allergic disease in need of novel interventions. Statins, long used to lower serum cholesterol, have been shown in multiple large-cohort studies to reduce asthma severity. We previously found that statins inhibit IgE-induced mast cell function, but these effects varied widely among mouse strains and human donors, likely due to the upregulation of the statin target, 3-hydroxy-3-methylgutaryl-CoA reductase. Statin inhibition of mast cell function appeared to be mediated not by cholesterol reduction but by suppressing protein isoprenylation events that use cholesterol pathway intermediates. Therefore, we sought to circumvent statin resistance by targeting isoprenylation. Using genetic depletion of the isoprenylation enzymes farnesyltransferase and geranylgeranyl transferase 1 or their substrate K-Ras, we show a significant reduction in FcεRI-mediated degranulation and cytokine production. Furthermore, similar effects were observed with pharmacological inhibition with the dual farnesyltransferase and geranylgeranyl transferase 1 inhibitor FGTI-2734. Our data indicate that both transferases must be inhibited to reduce mast cell function and that K-Ras is a critical isoprenylation target. Importantly, FGTI-2734 was effective in vivo, suppressing mast cell-dependent anaphylaxis, allergic pulmonary inflammation, and airway hyperresponsiveness. Collectively, these findings suggest that K-Ras is among the isoprenylation substrates critical for FcεRI-induced mast cell function and reveal isoprenylation as a new means of targeting allergic disease.

Neutrophilia in severe asthma is reduced in Ormdl3 overexpressing mice.

Genome-wide association studies have linked the ORM (yeast)-like protein isoform 3 (ORMDL3) to asthma severity. Although ORMDL3 is a member of a family that negatively regulates serine palmitoyltransferase (SPT) and thus biosynthesis of sphingolipids, it is still unclear whether ORMDL3 and altered sphingolipid synthesis are causally related to non-Th2 severe asthma associated with a predominant neutrophil inflammation and high interleukin-17 (IL-17) levels. Here, we examined the effects of ORMDL3 overexpression in a preclinical mouse model of allergic lung inflammation that is predominantly neutrophilic and recapitulates many of the clinical features of severe human asthma. ORMDL3 overexpression reduced lung and circulating levels of dihydrosphingosine, the product of SPT. However, the most prominent effect on sphingolipid levels was reduction of circulating S1P. The LPS/OVA challenge increased markers of Th17 inflammation with a predominant infiltration of neutrophils into the lung. A significant decrease of neutrophil infiltration was observed in the Ormdl3 transgenic mice challenged with LPS/OVA compared to the wild type and concomitant decrease in IL-17, that plays a key role in the pathogenesis of neutrophilic asthma. LPS decreased survival of murine neutrophils, which was prevented by co-treatment with S1P. Moreover, S1P potentiated LPS-induced chemotaxis of neutrophil, suggesting that S1P can regulate neutrophil survival and recruitment following LPS airway inflammation. Our findings reveal a novel connection between ORMDL3 overexpression, circulating levels of S1P, IL-17 and neutrophil recruitment into the lung, and questions the potential involvement of ORMDL3 in the pathology, leading to development of severe neutrophilic asthma.

Cellular inhibitor of apoptosis 2 (cIAP2) restricts neuroinflammation during experimental autoimmune encephalomyelitis.

BACKGROUND: Immune activation, neuroinflammation, and cell death are the hallmarks of multiple sclerosis (MS), which is an autoimmune demyelinating disease of the central nervous system (CNS). It is well-documented that the cellular inhibitor of apoptosis 2 (cIAP2) is induced by inflammatory stimuli and regulates adaptive and innate immune responses, cell death, and the production of inflammatory mediators. However, the impact of cIAP2 on neuroinflammation associated with MS and disease severity remains unknown. METHODS: We used experimental autoimmune encephalomyelitis (EAE), a widely used mouse model of MS, to assess the effect of cIAP2 deletion on disease outcomes. We performed a detailed analysis on the histological, cellular, and molecular levels. We generated and examined bone-marrow chimeras to identify the cIAP2-deficient cells that are critical to the disease outcomes. RESULTS: cIAP2-/- mice exhibited increased EAE severity, increased CD4+ T cell infiltration, enhanced proinflammatory cytokine/chemokine expression, and augmented demyelination. This phenotype was driven by cIAP2-deficient non-hematopoietic cells. cIAP2 protected oligodendrocytes from cell death during EAE by limiting proliferation and activation of brain microglia. This protective role was likely exerted by cIAP2-mediated inhibition of the non-canonical NLRP3/caspase-8-dependent myeloid cell activation during EAE. CONCLUSIONS: Our findings suggest that cIAP2 is needed to modulate neuroinflammation, cell death, and survival during EAE. Significantly, our data demonstrate the critical role of cIAP2 in limiting the activation of microglia during EAE, which could be explored for developing MS therapeutics in the future.

Deletion of Arno Reduces Eosinophilic Inflammation and Interleukin-5 Expression in a Murine Model of Rhinitis.

BACKGROUND: ARF nucleotide-binding site opener (ARNO) is a guanine nucleotide-exchange factor for ADP-ribosylation factor proteins. ARF nucleotide-binding site opener also binds MyD88, and small-molecule inhibition of ARNO reduces inflammation in animal models of inflammatory arthritis and acute inflammation. However, whether genetic deletion of Arno in mice reduces pathologic inflammation has not yet been reported. Furthermore, its role in the nasal cavity has yet to be investigated. OBJECTIVE: To generate Arno knockout mice and to determine whether genetic loss of ARNO reduces eosinophilic inflammation in the ovalbumin (OVA) murine model of rhinitis. METHODS: Arno knockout mice were generated and wild type and knockout littermates were subjected to the OVA-induced mouse model of rhinosinutitis. Eosinophilic inflammation was assessed through immunofluorescent quantification of EMBP+ eosinophils in the septal mucosa and cytokine expression was assessed by quantitative polymerase chain reaction. RESULTS: Arno knockout mice are viable and fertile without any noted deficits. Arno wild type and knockout mice subjected to the OVA-induced model of rhinitis demonstrated an average of 314.5 and 153.8 EMBP+ cells per mm2 septal tissue, respectively (P < .05). Goblet cells per mm of basal lamina were assessed via Alcian blue and there was no statistically significant difference between Arno wild type and knockout mice. Ovalbumin-induced expression of interleukin-5 (IL-5) was significantly reduced in Arno knockout mice (P < .05). There was no statistically significant reduction in IL-4, IL-13, or eotaxin-1 expression. CONCLUSIONS: These data demonstrate that deletion of Arno reduces eosinophilic inflammation and IL-5 expression in an OVA-induced model of rhinitis.

Disruption of Sinonasal Epithelial Nrf2 Enhances Susceptibility to Rhinosinusitis in a Mouse Model.

OBJECTIVES/HYPOTHESIS: Oxidative stress has been postulated to play an important role in chronic rhinosinusitis. Nrf2 is a transcription factor that is involved in the regulation of multiple antioxidant genes, and its function has been previously shown to be important in sinonasal inflammation. Although the sinonasal implications of whole body Nrf2-/- has been reported, the function of sinonasal epithelial expression of Nrf2 has not been studied. The primary aim of this study was to generate a mouse model that is genetically deficient in epithelial-specific Nrf2 and to understand its role in regulating sinonasal inflammation. STUDY DESIGN: Basic science. METHODS: An epithelial-specific Nrf2 knockout mouse was generated by crossing Krt5-cre(K5) with Nrf2flox/flox . A papain-induced model of rhinosinusitis was performed in the resulting K5 Nrf2-/- mouse. Immunohistochemistry was performed to quantify goblet cell hyperplasia. Mucosal cellular infiltrates were quantified using flow cytometry, and tissue cytokines were measured using an enzyme-linked immunosorbent assay. Lastly, the cellular source of type 2 cytokines was determined using intracellular cytokine staining. RESULTS: Papain-sensitized mice lacking epithelial-specific Nrf2 demonstrate increased goblet cell hyperplasia, significant tissue eosinophilia, and statistically significant increase in mucosal IL-13 when compared to Nrf2 wild-type mice. Lastly, mucosal T cells were identified as the cellular source of IL-13. CONCLUSIONS: We demonstrate enhanced severity of eosinophilic sinonasal inflammation from disruption of the epithelial-specific Nrf2 pathway. The responsiveness of Nrf2-directed antioxidant pathways may act as a major determinant of susceptibility to eosinophilic inflammation and may have potential as a therapeutic target for chronic rhinosinusitis. LEVEL OF EVIDENCE: NA Laryngoscope, 131:713-719, 2021.

Targeting ADAM10 in Cancer and Autoimmunity.

Generating inhibitors for A Disintegrin And Metalloproteinase 10 (ADAM10), a zinc-dependent protease, was heavily invested in by the pharmaceutical industry starting over 20 years ago. There has been much enthusiasm in basic research for these inhibitors, with a multitude of studies generating significant data, yet the clinical trials have not replicated the same results. ADAM10 is ubiquitously expressed and cleaves many important substrates such as Notch, PD-L1, EGFR/HER ligands, ICOS-L, TACI, and the "stress related molecules" MIC-A, MIC-B and ULBPs. This review goes through the most recent pre-clinical data with inhibitors as well as clinical data supporting the use of ADAM10 inhibitor use in cancer and autoimmunity. It additionally addresses how ADAM10 inhibitor therapy can be improved and if inhibitor therapy can be paired with other drug treatments to maximize effectiveness in various disease states. Finally, it examines the ADAM10 substrates that are important to each disease state and if any of these substrates or ADAM10 itself is a potential biomarker for disease.

Deletion of Nrf2 enhances susceptibility to eosinophilic sinonasal inflammation in a murine model of rhinosinusitis.

BACKGROUND: Oxidative stress exacerbates lower airway diseases including asthma and chronic obstructive pulmonary disease (COPD); however, its role in upper airway (sinonasal) chronic inflammatory disorders is less clear. Nuclear erythroid 2 p45-related factor (Nrf2) is an endogenous mechanism that upon activation invokes an antioxidant response pathway via nuclear translocation and upregulation of cytoprotective genes. We sought to determine whether deletion of Nrf2 enhances susceptibility to allergic sinonasal inflammation in vivo. METHODS: Nrf2-/- mice were subjected to the ovalbumin (Ova)-induced murine model of rhinosinusitis and indices of sinonasal inflammation and epithelial barrier dysfunction were assessed. RESULTS: We show that deletion of Nrf2 results in enhances indices of allergen-induced sinonasal inflammation including aggravated eosinophil accumulation and goblet cell hyperplasia. An exaggerated increase in epithelial derived inflammatory cytokines including interleukin 33 (IL-33) and thymic stromal lymphopoietin (TSLP) was observed in the nasal lavage fluid and sinonasal mucosal tissue of Nrf2-/- mice. Furthermore, Nrf2-/- mice showed heightened Ova-induced barrier dysfunction as measured by serum albumin accumulation in nasal lavage fluid of mice. CONCLUSION: These data show that the endogenous Nrf2 pathway limits Ova-induced sinonasal inflammation, epithelial derived inflammatory cytokine production, and epithelial barrier dysfunction in vivo and identify a potential therapeutic target in the management of allergic sinonasal inflammatory disorders. This is the first study to our knowledge which shows that Nrf2 regulates allergic inflammation in the sinonasal cavity in vivo.

Characterization of a novel, papain-inducible murine model of eosinophilic rhinosinusitis.

BACKGROUND: Eosinophilic chronic rhinosinusitis (ECRS) is a disease characterized by eosinophilic inflammatory infiltrate and a local type 2 cytokine milieu. Current animal models fail to recapitulate many of the innate and adaptive immunologic hallmarks of the disease, thus hindering the development of effective therapeutics. In the present study, mice were exposed intranasally to the cysteine protease papain, which shares functional similarities with parasitic proteases and aeroallergens, to generate a rapidly inducible murine model of eosinophilic rhinosinusitis. METHODS: C57BL/6 mice were intranasally instilled with 20 µg papain or heat-inactivated papain (HP) on days 0-2 and days 7-10, and then euthanized on day 11. Nasal lavage fluid (NALF) was analyzed to quantify eosinophils and inflammatory cytokine secretion. Sinonasal tissue was sectioned and stained for goblet cells or homogenized to analyze cytokine levels. Serum samples were assayed for immunoglobulin E (IgE) by enzyme-linked immunoassay. Sinonasal mucosal tissue was dissociated and analyzed by flow cytometry. RESULTS: Compared with HP treatment, papain induced significant eosinophilia in NALF, goblet cell hyperplasia, innate and adaptive immune cell infiltration, type 2 cytokine production, and IgE responses. Flow cytometric analysis of sinonasal tissues revealed significant inflammatory cell infiltration and interleukin-13-producing cell populations. CONCLUSION: In this study, we demonstrated that the cysteine protease papain induces allergic sinonasal eosinophilic rhinosinusitis and resembles T-helper 2 cell inflammation and innate immune characteristics of ECRS. This model permits further study into the molecular mechanisms underlying ECRS pathology and provides a model system for the evaluation of potential pharmacologic interventions.

Airborne Particulate Matter Induces Nonallergic Eosinophilic Sinonasal Inflammation in Mice.

Exposure to airborne particulate matter (PM) has been linked to aggravation of respiratory symptoms, increased risk of cardiovascular disease, and all-cause mortality. Although the health effects of PM on the lower pulmonary airway have been extensively studied, little is known regarding the impact of chronic PM exposure on the upper sinonasal airway. We sought to test the impact of chronic airborne PM exposure on the upper respiratory system in vivo. Mice were subjected, by inhalation, to concentrated fine (2.5 µm) PM 6 h/d, 5 d/wk, for 16 weeks. Mean airborne fine PM concentration was 60.92 µm/m3, a concentration of fine PM lower than that reported in some major global cities. Mice were then killed and analyzed for evidence of inflammation and barrier breakdown compared with control mice. Evidence of the destructive effects of chronic airborne PM on sinonasal health in vivo, including proinflammatory cytokine release, and macrophage and neutrophil inflammatory cell accumulation was observed. A significant increase in epithelial barrier dysfunction was observed, as assessed by serum albumin accumulation in nasal airway lavage fluid, as well as decreased expression of adhesion molecules, including claudin-1 and epithelial cadherin. A significant increase in eosinophilic inflammation, including increased IL-13, eotaxin-1, and eosinophil accumulation, was also observed. Collectively, although largely observational, these studies demonstrate the destructive effects of chronic airborne PM exposure on the sinonasal airway barrier disruption and nonallergic eosinophilic inflammation in mice.

Nuclear erythroid 2-related factor 2 activation inhibits house dust mite-induced sinonasal epithelial cell barrier dysfunction.

BACKGROUND: Dysregulated sinonasal epithelial cell (SNEC) barrier function has been proposed to contribute to the pathogenesis of sinonasal inflammatory conditions such as allergic rhinitis (AR) and chronic rhinosinusitis (CRS). Allergens such as house dust mite (HDM) have been reported to disrupt SNEC barrier integrity. We have recently identified nuclear erythroid 2-related factor 2 (Nrf2) activation via sulforaphane (SFN) stimulation to stabilize SNEC barrier function. The purpose of this study was to explore whether Nrf2 activation could ameliorate HDM-induced SNEC barrier dysfunction. METHODS: Human SNECs (HSNECs) were grown from patients at the air-liquid interface (ALI). HSNECs were stimulated with HDM with or without pharmacologic activation of Nrf2 with SFN. HSNECs were then stained for the epithelial cell junction protein zonula occludens-1 (ZO-1) and cell surface localization was evaluated by confocal microscopy. Transepithelial electrical resistance (TER) and paracellular fluorescein isothiocyanate (FITC)-dextran permeability was measured in response to stimulation with HDM and SFN. RESULTS: HDM stimulation caused a global disruption of the protein ZO-1 along with an associated decrease in TER (p < 0.001) and increased FITC-dextran paracellular permeability (p < 0.0001). Enhancing Nrf2 activation through treatment with SFN prior to stimulation with HDM was associated with increased localization of ZO-1 at the cell surface and statistically significant increases in TER (p < 0.05) and decrease in paracellular FITC-dextran permeability (p < 0.001). CONCLUSION: This is the first study to demonstrate that HDM-induced SNEC barrier dysfunction may be preventable by Nrf2 activation. The Nrf2 antioxidant pathway may represent a potential therapeutic target for allergen-induced sinonasal inflammation.

Bactericidal antibiotics promote oxidative damage and programmed cell death in sinonasal epithelial cells.

BACKGROUND: Antibiotics are widely and heavily used in the treatment of chronic sinusitis. Bactericidal antibiotics can stimulate reactive oxygen species (ROS) formation, a proinflammatory response, and cell death in cultured human sinonasal epithelial cells (SNECs). Sulforaphane (SFN) is a potent stimulator of the antioxidant nuclear factor erythroid 2-related factor 2 (Nrf-2) system and a suppressor of inflammation. In this study we utilized SFN to further explore the relationship between levofloxacin treatment, ROS formation, and the cell death response. METHODS: SNECs were collected from patients during endoscopic sinus surgery and grown in culture at the air-liquid interface. Differentiated SNECs were stimulated with levofloxacin with or without SFN pretreatment. ROS were quantified. Apoptosis markers of caspase-3 activity and DNA fragmentation were quantified. RESULTS: Cultured SNECs treated with levofloxacin resulted in a significant increase in activity of the proapoptotic caspase-3 protease (5.9-fold, p = 0.01). The increase in activity was suppressed by pretreatment with SFN (1.9-fold). ROS levels increased with levofloxacin treatment (range, 1.2-fold to 1.8-fold), but were not significantly suppressed by pretreatment with SFN (range, 1.0-fold to 1.3-fold). CONCLUSION: In this study, we demonstrate that treatment of cultured SNECs with levofloxacin leads to an increase in caspase-3 activity. SFN pretreatment suppresses the increased apoptotic response possibly through its antioxidant stimulating properties. Our results suggest that levofloxacin treatment stimulates a potent proapoptotic possibly through an ROS-dependent mechanism. Future studies will explore if this antibiotic-induced response is harmful to recovery of function in those with sinusitis.

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.

The Role of Innate Immunity and Aeroallergens in Chronic Rhinosinusitis.

Allergy has been inferred to contribute to the pathophysiology of chronic rhinosinusitis (CRS) although this role is controversial and the mechanism is debated. Furthermore, the role of aeroallergens in CRS is poorly defined and has been postulated to contribute to CRS through direct penetration in the sinuses or downstream systemic consequences. Common aeroallergens implicated in chronic rhinosinusitis include air pollution/second hand smoke, dust mite and pollen [1,2,3]. One emerging potential mechanism whereby aeroallergens contribute to CRS is through sinonasal epithelial barrier disruption (fig. 1). Characterization of cytokine disruption of sinonasal epithelial cell barrier has been described including interleukin (IL)-4 and IL-13, as well as aeroallergens such as house dust mite and cigarette smoke. Recent results have demonstrated severe barrier disruption in response to direct application of either particulate matter (PM) or house dust mite (HDM) to sinonasal epithelial cells. Sinonasal epithelial barrier disruption may contribute to CRS by enabling the perpetual and chronic exposure of inflammatory allergens and stimuli. The sinonasal epithelial barrier plays a significant role in innate immune host defense. Mechanisms of innate immune defense include pattern recognition receptors (PRRs), secreted endogenous antimicrobials and inflammatory cytokines that aid in repair mechanisms including IL-33. Here we discuss recent evidence implicating aeroallergens and dysregulated host innate immune responses in the development of CRS.

Characterization of a novel high-dose ovalbumin-induced murine model of allergic sinonasal inflammation.

BACKGROUND: Few efficacious topical therapies exist for chronic rhinosinusitis (CRS). The lack of a reproducible mouse model of CRS limits the pilot testing of potential novel anti-inflammatory therapies. Although the ovalbumin-induced mouse model of sinonasal inflammation is commonly used, it is difficult to reproduce and can generate variable histologic results. In this study, we explore a variation of this model in different strains of mice and explore various inflammatory cytokines as reproducible molecular markers of inflammation. METHODS: Allergic sinonasal inflammation was generated in BALB/c and C57BL/6 mice using intraperitoneal high-dose injections of ovalbumin (Ova; Sigma Chemical Co.) followed by 10 days of high-dose intranasal sensitization. Real-time polymerase chain reaction (RT-PCR) for eotaxin, interleukin 4 (IL-4), and IL-13 were measured from sinonasal mucosa. We also pilot tested a known topical budesonide to characterize the anti-inflammatory response. Histological sections were analyzed for epithelial thickness and eosinophilia. RESULTS: Both BALB/c and C57BL/6 mice consistently showed increases in T helper 2 (Th2) cytokines after sensitization with high-dose Ova (p < 0.0001) when compared to controls. There were also significant increases in epithelial thickening in Ova-sensitized mice and eosinophilia in both BALB/c and C57BL/6 strains. In addition, topical budesonide significantly reduced anti-inflammatory cytokines, eosinophilia, and epithelial thickness. CONCLUSION: Our variation of the ovalbumin-induced mouse model of sinonasal inflammation in both BALB/c and C57BL/6 mice provides an efficacious model for testing potential topical anti-inflammatory therapies for CRS. The utilization of sinonasal mucosal Th2 cytokines along with histologic markers provides a consistent and quantifiable marker of inflammation in assessing the efficacy of candidate drugs.

Bactericidal antibiotics promote reactive oxygen species formation and inflammation in human sinonasal epithelial cells.

BACKGROUND: Bactericidal antibiotics have been shown to stimulate reactive oxygen species (ROS) formation in mammalian cells through mitochondrial dysfunction. This results in oxidative tissue damage that may have negative consequences for long-term antibiotic use. Antibiotics are widely and heavily used in the treatment of acute and chronic sinusitis; however, the relationship between antibiotics and ROS formation in sinonasal epithelial cells (SNECs) has not yet been demonstrated. METHODS: Human SNECs were collected from patients during endoscopic sinus surgery and grown in culture at the air-liquid interface. Differentiated SNECs were stimulated with the bactericidal antibiotics amoxicillin and levofloxacin and the bacteriostatic antibiotic clarithromycin for 24 hours. ROS were quantified via fluorescence. Cell death was quantified by lactate dehydrogenase (LDH) secretion. Expression of inflammatory markers such as tumor necrosis factor α (TNF-α) and nuclear factor erythroid 2-related factor 2 (Nrf2)-mediated antioxidant genes were measured by real-time polymerase chain reaction (RT-PCR). RESULTS: Cultured SNECs treated with the bactericidal antibiotics amoxicillin and levofloxacin resulted in a significant increase in production of ROS (p < 0.05) and secretion of LDH (p < 0.05). The increase in ROS formation correlated with an increase in expression of Nrf2-mediated antioxidant genes as well as the expression and production of proinflammatory cytokine TNF-α, and interleukin 1 ß (IL-1ß) (p < 0.05). SNECs treated with clarithromycin did not demonstrate statistically significant increases in ROS or proinflammatory cytokine production. CONCLUSION: In this study, we show that treatment of cultured human SNECs with bactericidal antibiotics leads to formation of ROS with an associated increase in inflammatory and antioxidant gene expression and cell death. This suggests that long-term or inappropriate antibiotic use in the treatment of sinusitis may result in oxidative tissue damage to the sinonasal epithelium. Future studies will explore the clinical implications of such damage to the sinonasal epithelium.