Activation of airway epithelial bitter taste receptors by Pseudomonas aeruginosa quinolones modulates calcium, cyclic-AMP, and nitric oxide signaling.

Bitter taste receptors (taste family 2 bitter receptor proteins; T2Rs), discovered in many tissues outside the tongue, have recently become potential therapeutic targets. We have shown previously that airway epithelial cells express several T2Rs that activate innate immune responses that may be important for treatment of airway diseases such as chronic rhinosinusitis. It is imperative to more clearly understand what compounds activate airway T2Rs as well as their full range of functions. T2R isoforms in airway motile cilia (T2R4, -14, -16, and -38) produce bactericidal levels of nitric oxide (NO) that also increase ciliary beating, promoting clearance of mucus and trapped pathogens. Bacterial quorum-sensing acyl-homoserine lactones activate T2Rs and stimulate these responses in primary airway cells. Quinolones are another type of quorum-sensing molecule used by Pseudomonas aeruginosa To elucidate whether bacterial quinolones activate airway T2Rs, we analyzed calcium, cAMP, and NO dynamics using a combination of fluorescent indicator dyes and FRET-based protein biosensors. T2R-transfected HEK293T cells, several lung epithelial cell lines, and primary sinonasal cells grown and differentiated at the air-liquid interface were tested with 2-heptyl-3-hydroxy-4-quinolone (known as Pseudomonas quinolone signal; PQS), 2,4-dihydroxyquinolone, and 4-hydroxy-2-heptylquinolone (HHQ). In HEK293T cells, PQS activated T2R4, -16, and -38, whereas HHQ activated T2R14. 2,4-Dihydroxyquinolone had no effect. PQS and HHQ increased calcium and decreased both baseline and stimulated cAMP levels in cultured and primary airway cells. In primary cells, PQS and HHQ activated levels of NO synthesis previously shown to be bactericidal. This study suggests that airway T2R-mediated immune responses are activated by bacterial quinolones as well as acyl-homoserine lactones.

Protease-activated receptor 2 activates airway apical membrane chloride permeability and increases ciliary beating.

Mucociliary clearance, driven by the engine of ciliary beating, is the primary physical airway defense against inhaled pathogens and irritants. A better understanding of the regulation of ciliary beating and mucociliary transport is necessary for identifying new receptor targets to stimulate improved clearance in airway diseases, such as cystic fibrosis and chronic rhinosinusitis. In this study, we examined the protease-activated receptor (PAR)-2, a GPCR previously shown to regulate airway cell cytokine and mucus secretion, and transepithelial Cl- current. PAR-2 is activated by proteases secreted by airway neutrophils and pathogens. We cultured various airway cell lines, primary human and mouse sinonasal cells, and human bronchial cells at air-liquid interface and examined them using molecular biology, biochemistry, and live-cell imaging. We found that PAR-2 is expressed basolaterally, where it stimulates both intracellular Ca2+ release and Ca2+ influx, which activates low-level nitric oxide production, increases apical membrane Cl- permeability ∼3-5-fold, and increases ciliary beating ∼20-50%. No molecular or functional evidence of PAR-4 was observed. These data suggest a novel and previously overlooked role of PAR-2 in airway physiology, adding to our understanding of the role of this receptor in airway Ca2+ signaling and innate immunity.-McMahon, D. B., Workman, A. D., Kohanski, M. A., Carey, R. M., Freund, J. R., Hariri, B. M., Chen, B., Doghramji, L. J., Adappa, N. D., Palmer, J. N., Kennedy, D. W., Lee, R. J. Protease-activated receptor 2 activates airway apical membrane chloride permeability and increases ciliary beating.

Flavones modulate respiratory epithelial innate immunity: Anti-inflammatory effects and activation of the T2R14 receptor.

Chronic rhinosinusitis has a significant impact on patient quality of life, creates billions of dollars of annual healthcare costs, and accounts for ∼20% of adult antibiotic prescriptions in the United States. Because of the rise of resistant microorganisms, there is a critical need to better understand how to stimulate and/or enhance innate immune responses as a therapeutic modality to treat respiratory infections. We recently identified bitter taste receptors (taste family type 2 receptors, or T2Rs) as important regulators of sinonasal immune responses and potentially important therapeutic targets. Here, we examined the immunomodulatory potential of flavones, a class of flavonoids previously demonstrated to have antibacterial and anti-inflammatory effects. Some flavones are also T2R agonists. We found that several flavones inhibit Muc5AC and inducible NOS up-regulation as well as cytokine release in primary and cultured airway cells in response to several inflammatory stimuli. This occurs at least partly through inhibition of protein kinase C and receptor tyrosine kinase activity. We also demonstrate that sinonasal ciliated epithelial cells express T2R14, which closely co-localizes (<7 nm) with the T2R38 isoform. Heterologously expressed T2R14 responds to multiple flavones. These flavones also activate T2R14-driven calcium signals in primary cells that activate nitric oxide production to increase ciliary beating and mucociliary clearance. TAS2R38 polymorphisms encode functional (PAV: proline, alanine, and valine at positions 49, 262, and 296, respectively) or non-functional (AVI: alanine, valine, isoleucine at positions 49, 262, and 296, respectively) T2R38. Our data demonstrate that T2R14 in sinonasal cilia is a potential therapeutic target for upper respiratory infections and that flavones may have clinical potential as topical therapeutics, particularly in T2R38 AVI/AVI individuals.

In vitro effects of anthocyanidins on sinonasal epithelial nitric oxide production and bacterial physiology.

BACKGROUND: T2R bitter taste receptors play a crucial role in sinonasal innate immunity by upregulating mucociliary clearance and nitric oxide (NO) production in response to bitter gram-negative quorum-sensing molecules in the airway surface liquid. Previous studies showed that phytochemical flavonoid metabolites, known as anthocyanidins, taste bitter and have antibacterial effects. Our objectives were to examine the effects of anthocyanidins on NO production by human sinonasal epithelial cells and ciliary beat frequency, and their impact on common sinonasal pathogens Pseudomonas aeruginosa and Staphylococcus aureus. METHODS: Ciliary beat frequency and NO production were measured by using digital imaging of differentiated air-liquid interface cultures prepared from primary human cells isolated from residual surgical material. Plate-based assays were used to determine the effects of anthocyanidins on bacterial swimming and swarming motility. Biofilm formation and planktonic growth were also assessed. RESULTS: Anthocyanidin compounds triggered epithelial cells to produce NO but not through T2R receptors. However, anthocyanidins did not impact ciliary beat frequency. Furthermore, they did not reduce biofilm formation or planktonic growth of P. aeruginosa. In S. aureus, they did not reduce planktonic growth, and only one compound had minimal antibiofilm effects. The anthocyanidin delphinidin and anthocyanin keracyanin were found to promote bacterial swimming, whereas anthocyanidin cyanidin and flavonoid myricetin did not. No compounds that were tested inhibited bacterial swarming. CONCLUSION: Results of this study indicated that, although anthocyanidins may elicited an innate immune NO response from human cells, they do not cause an increase in ciliary beating and they may also cause a pathogenicity-enhancing effect in P. aeruginosa. Additional studies are necessary to understand how this would affect the use of anthocyanidins as therapeutics. This study emphasized the usefulness of in vitro screening of candidate compounds against multiple parameters of both epithelial and bacterial physiologies to prioritize candidates for in vivo therapeutic testing.

Coagulase-negative Staphylococcus culture in chronic rhinosinusitis.

BACKGROUND: Coagulase-negative Staphylococcus (CoNS) is commonly isolated from patients with chronic rhinosinusitis (CRS). However, the role of CoNS in CRS remains controversial. We aimed to determine the association between positive CoNS culture at functional endoscopic sinus surgery (FESS) and CRS severity. METHODS: Adult CRS patients who underwent FESS between October 1, 2007 to December 31, 2011 were recruited. Patient demographics, disease characteristics, medication use, Lund-Mackay computed tomography (CT) scores, and 22-item Sino-Nasal Outcome Test (SNOT-22) scores were collected at baseline before FESS. Intraoperative cultures were obtained in a standard manner. Patients were placed into 2 groups based on culture findings: patients with CoNS as the sole positive culture result and patients with all other positive culture results, including CoNS, as part of a polymicrobial culture. RESULTS: A total of 376 CRS patients met the criteria; 106 patients (28%) had CoNS as their only isolate, 260 (69%) had other positive cultures, and 10 (3%) had no bacterial growth. Compared to patients with other positive cultures, patients with the sole result of CoNS were significantly less likely to have a history of FESS (52% vs 65%, p = 0.019), nasal polyps (50% vs 65%, p = 0.006), and had a better Lund-Mackay CT score (11.95 vs 14.18, p = 0.020). After adjusting for all factors in the multiple logistic regression model, CoNS as the sole positive culture result was independently associated with having no history of FESS (odds ratio [OR] = 0.45; 95% confidence interval [CI], 0.22 to 0.94; p = 0.034). CONCLUSION: Positive intraoperative CoNS cultures alone do not result in increased CRS disease burden by objective or subjective measures as compared to patients with other bacterial or polymicrobial culture isolates.

Different clinical factors associated with Staphylococcus aureus and Pseudomonas aeruginosa in chronic rhinosinusitis.

BACKGROUND: Staphylococcus aureus and Pseudomonas aeruginosa are common culture isolates in chronic rhinosinusitis (CRS). We aimed to determine whether they were associated with different clinical factors of CRS. METHODS: Adult CRS patients who underwent functional endoscopic sinus surgery (FESS) between October 1, 2007 and December 31, 2011 were recruited. Patient demographics, Lund-Mackay computed tomography (CT) scores, 22-item Sino-Nasal Outcome Test (SNOT-22) scores, disease characteristics, and medication use were collected prior to FESS. Intraoperative culture was obtained in a standard manner. We compared patients with isolates of S. aureus or P. aeruginosa to patients with other culture results and no bacterial growth, respectively. Multivariate logistic regression was performed. RESULTS: A total of 376 patients met criteria; 104 patients (28%) had S. aureus, 32 (9%) had P. aeruginosa, and 10 patients (3%) had no bacterial growth. After adjusting for all clinical factors, compared to patients with positive culture other than S. aureus, patients with S. aureus had 1.9 times increased odds of having nasal polyps (odds ratio [OR] = 1.9; 95% confidence interval [CI], 1.0 to 3.3; p = 0.036); when compared to patients with positive culture other than P. aeruginosa, patients with P. aeruginosa had 7.8 times increased odds of having prior FESS (OR = 7.8; 95% CI, 2.1 to 28.9; p = 0.002) (91% vs 58%; p < 0.001) and 3.6 times increased odds of having diabetes with marginal significance (OR = 3.6; 95% CI, 1.0 to 13.2; p = 0.053). The sample size in the no bacterial growth group was too small to draw firm conclusions. CONCLUSION: S. aureus was more common in CRS patients with nasal polyps, whereas P. aeruginosa was more common in CRS patients with prior FESS history and possibly diabetes.

Biofilm-forming bacteria and quality of life improvement after sinus surgery.

BACKGROUND: It remains unclear how much chronic rhinosinusitis (CRS) patients with bacterial biofilms can benefit from functional endoscopic sinus surgery (FESS). We aimed to evaluate whether biofilm-forming bacteria was associated with quality of life (QOL) improvement after FESS. METHODS: This retrospective cohort study included adult CRS patients who underwent FESS from 2008 to 2011. Sinus samples were taken to evaluate for biofilm-formation in vitro using a modified Calgary Biofilm Detection Assay. QOL was measured before FESS, and 1-month, 3-month, and 6-month after FESS using 22-item Sino-Nasal Outcome Test (SNOT-22) scores. Patients' characteristics and medications were collected. Clinical significant QOL change was defined as a difference of at least 0.5 standard deviation (SD) of baseline SNOT-22 score in the reference group. RESULTS: A total of 156 patients had complete data, and 15% had biofilm-forming bacteria (n = 24). Patients with biofilm-forming bacteria had significantly worse preoperative SNOT-22 scores compared to patients without biofilm-forming bacteria (48 ± 20 vs 38 ± 23, p = 0.048). Both groups had clinically significant QOL improvement after FESS, and the differences in their 1-month (23 ± 19 vs 17 ± 20) and 3-month (27 ± 18 vs 18 ± 19) post-FESS SNOT-22 scores were not significant. However, patients with biofilm-forming bacteria demonstrated significantly less QOL improvement than patients without biofilm-forming bacteria from pre-FESS to 6-month post-FESS visits after adjusting for clinical factors (35 ± 25 vs 14 ± 15; ß-coefficient = 0.71; 95% confidence interval [CI], 0.13 to 1.28; p = 0.016). CONCLUSION: CRS patients with biofilm-forming bacteria demonstrated clinically significant QOL improvement following FESS, but the degree of improvement was decreased overtime and became significantly worse than patients without biofilm-forming bacteria by 6-month follow-up. This QOL worsening was independent of other risk factors for CRS.

Quality of life improvement from sinus surgery in chronic rhinosinusitis patients with asthma and nasal polyps.

BACKGROUND: It is unclear whether chronic rhinosinusitis (CRS) patients with both nasal polyps and asthma have different quality of life (QOL) improvement after functional endoscopic sinus surgery (FESS). We aimed to determine whether CRS patients with asthma and nasal polyps had a greater QOL improvement after FESS compared to patients without asthma or polyps. METHODS: This retrospective analysis included adult CRS patients who underwent FESS between 2007 and 2011. QOL was measured using the 22-item Sino-Nasal Outcome Test (SNOT-22). Variables collected included baseline demographics, clinical factors, SNOT-22 scores before FESS, and 1 month, 3 months, and 6 months post-FESS. Groups tested were asthma alone, polyps alone, asthma and polyps, and no asthma or polyps. Linear mixed-effects regression model was performed to calculate ß-coefficients, which represent the adjusted mean QOL differences. RESULTS: Among the 376 patients included, 40.16% had both asthma and polyps (n = 151), 14.36% had asthma alone (n = 54), 19.45% had polyps alone (n = 75), and 25.53% had no asthma or polyps (n = 96). After adjusting for all factors, there were significantly more QOL improvements in patients with both asthma and nasal polyps from baseline to 1-month (ß-coefficient = -10.05; 95% CI, -15.86 to -4.23; p = 0.001) and 3-month follow-up (ß-coefficient = -8.27; 95% CI, -14.98 to -1.56; p = 0.016), and patients with asthma alone from baseline to 6-month follow-up (ß-coefficient = -8.78; 95% CI, -17.45 to -0.11; p = 0.047), when compared to patients without asthma or nasal polyps. CONCLUSION: CRS patients with both asthma and nasal polyps or asthma alone experience a larger QOL benefit from FESS immediately after FESS compared to CRS patients without asthma or polyps.

Culture-inappropriate antibiotic therapy decreases quality of life improvement after sinus surgery.

BACKGROUND: Despite their widespread use, antibiotics have not been shown to improve chronic rhinosinusitis (CRS) outcomes. We aimed to determine whether culture-inappropriate postoperative antibiotic therapy was associated with less quality-of-life (QOL) improvement following functional endoscopic sinus surgery (FESS). METHODS: This retrospective cohort study recruited 376 adult CRS patients undergoing FESS between October 1, 2007 to December 31, 2011. Patient demographics, comorbidities and medications were collected at baseline. Trimethoprim-sulfamethoxazole and clindamycin were administered for 2 weeks postoperatively. The antibiotic appropriateness was determined based on bacterial resistance profile of organisms identified during intraoperative culture. The QOL outcome was defined as change of 22-item Sinonasal Outcome Test scores from preoperative visit to 1-month, 3-month, and 6-month post-FESS. Clinically significant difference was defined as at least 0.5 standard deviations (SD) of baseline QOL score in the reference group. Mixed-effects regression models were performed. RESULTS: Seven percent of patients (n = 27) had culture-inappropriate antibiotic therapy, and additional 5% (n = 19) had culture-specific antibiotic adjustment. Compared to patients with culture-appropriate antibiotics, patients with culture-inappropriate antibiotics had significantly less improvement of QOL from baseline to postoperative 1-month and 3-month follow-up where the difference became clinically significant; patients with antibiotic adjustment had more QOL improvement from baseline to 1-month follow-up, but their QOL worsened at 3-month follow-up, and these changes were not clinically significant. However, all effects washed out at 6-month follow-up with no significant differences. CONCLUSION: Culture-inappropriate postoperative antibiotic therapy decreased short-term QOL improvement to a clinically meaningful level after FESS. Culture guided selection of antibiotics may improve short-term FESS outcome.