Retinoic acid promotes fibrinolysis and may regulate polyp formation.

BACKGROUND: Patients with aspirin-exacerbated respiratory disease (AERD) regularly exhibit severe nasal polyposis. Studies suggest that chronic rhinosinusitis with nasal polyps (CRSwNP) is characterized by excessive fibrin deposition associated with a profound decrease in epithelial tissue plasminogen activator (tPA). Retinoids, including vitamin A and its active metabolite retinoic acid (RA), are necessary for maintaining epithelial function and well-known inducers of tPA in endothelial cells. OBJECTIVES: This study sought to determine whether endogenous retinoids are involved in NP pathophysiology and disease severity in patients with CRSwNP and AERD. METHODS: NP tissue was collected from patients with AERD or CRSwNP, and concentrations of retinoids and fibrinolysis markers were measured using ELISA. Normal human bronchial epithelial cells were stimulated alone or in combination with RA and IL-13 for 24 hours. RESULTS: This study observed lower retinoid levels in nasal polyps of patients with AERD than those with CRSwNP or healthy controls (P < .01). Levels of the fibrin-breakdown product d-dimer were the lowest in AERD polyps (P < .01), which is consistent with lower tPA expression (P < .01). In vitro, all-trans RA upregulated tPA levels in normal human bronchial epithelial cells by 15-fold and reversed the IL-13-induced attenuation of tPA expression in cultured cells (P < .01). CONCLUSIONS: RA, a potent inducer of epithelial tPA in vitro, is reduced in tissue from patients with AERD, a finding that may potentially contribute to decreased levels of tPA and fibrinolysis in AERD. RA can induce tPA in epithelial cells and can reverse IL-13-induced tPA suppression in vitro, suggesting the potential utility of RA in treating patients with CRSwNP and/or AERD.

Glucocorticoids Inhibit Group 3 Innate Lymphocyte IL-22 Production.

Glucocorticoids (GCs) are commonly prescribed to patients with a variety of inflammatory disorders, including inflammatory bowel disease (IBD). GCs mediate their immunomodulatory effects through many different mechanisms and target multiple signaling pathways. The GC dexamethasone downmodulates innate and adaptive immune cell activation. IBD is the manifestation of a dysregulated immune response involving many different immune cells. Group 3 innate lymphocytes (ILC3s) have critical roles in mucosal inflammation. ILC3s secrete high levels of the cytokine IL-22, promoting epithelial proliferation, antimicrobial peptides, and mucins. In this study, we examined the effects of dexamethasone on IL-22 production by ILC3s. We found that dexamethasone suppressed IL-23-mediated IL-22 production in human and mouse ILC3s. This was mediated in part through dexamethasone modulation of the NF-κB pathway. Inhibition of NF-κB signaling with a small molecule inhibitor also downmodulated IL-23- and IL-1ß-mediated IL-22 production in ILC3s. These findings implicate NF-κB as a regulator of IL-22 in ILC3s and likely have repercussions on GC treatment of IBD patients.

Bacillus anthracis lethal toxin negatively modulates ILC3 function through perturbation of IL-23-mediated MAPK signaling.

Bacillus anthracis, the causative agent of anthrax, secretes lethal toxin that down-regulates immune functions. Translocation of B. anthracis across mucosal epithelia is key for its dissemination and pathogenesis. Group 3 innate lymphocytes (ILC3s) are important in mucosal barrier maintenance due to their expression of the cytokine IL-22, a critical regulator of tissue responses and repair during homeostasis and inflammation. We found that B. anthracis lethal toxin perturbed ILC3 function in vitro and in vivo, revealing an unknown IL-23-mediated MAPK signaling pathway. Lethal toxin had no effects on the canonical STAT3-mediated IL-23 signaling pathway. Rather lethal toxin triggered the loss of several MAP2K kinases, which correlated with reduced activation of downstream ERK1/2 and p38, respectively. Inhibition studies showed the importance of MAPK signaling in IL-23-mediated production of IL-22. Our finding that MAPK signaling is required for optimal IL-22 production in ILC3s may lead to new approaches for targeting IL-22 biology.

Increased expression of the epithelial anion transporter pendrin/SLC26A4 in nasal polyps of patients with chronic rhinosinusitis.

BACKGROUND: Chronic rhinosinusitis (CRS) is a multifactorial disease of unknown cause characterized by sinonasal inflammation, increased mucus production, and defective mucociliary clearance. Expression of Pendrin, an epithelial anion transporter, is increased in asthma and chronic obstructive pulmonary disease. Pendrin increases mucus production and regulates mucociliary clearance. OBJECTIVES: We sought to investigate the expression of pendrin and the mucus-related protein Muc5AC in sinonasal tissues of control subjects and patients with CRS and to evaluate the regulation of pendrin expression in nasal epithelial cells (NECs) in vitro. METHODS: The expression and distribution of pendrin in sinonasal tissues was analyzed by using real-time PCR, immunoblot analysis, and immunohistochemistry. Differentiated NECs were used to study the regulation of pendrin expression. RESULTS: Increased pendrin expression was observed in nasal polyp (NP) tissue of patients with CRS. Immunohistochemistry analysis revealed that pendrin was largely restricted to the epithelial layer. Pendrin expression significantly correlated with inflammatory cell markers, suggesting that the factors made by these cells might induce pendrin expression. Furthermore, both pendrin and periostin levels (a biomarker in asthma) correlated with IL-13 levels, suggesting that pendrin can be induced by this cytokine in sinonasal tissues. Expression of the mucus component protein Muc5AC correlated weakly with pendrin expression, indicating that pendrin might modulate mucus production in NPs. In cultured NECs pendrin expression was induced by TH2 cytokines and induced synergistically when TH2 cytokines were combined with IL-17A. Interestingly, human rhinovirus had a potentiating effect on IL-13-induced pendrin expression. Dexamethasone suppressed pendrin expression, suggesting that the therapeutic benefit of dexamethasone in asthmatic patients and those with CRS might involve regulation of pendrin expression. CONCLUSIONS: TH2-mediated pendrin expression is increased in NPs of patients with CRS and might lead to increased inflammation, mucus production, and decreased mucociliary clearance.

Age-related increased prevalence of asthma and nasal polyps in chronic rhinosinusitis and its association with altered IL-6 trans-signaling.

We report that S100 proteins were reduced in patients with chronic rhinosinusitis (CRS). S100A8/9, which is important in epithelial barrier function, was particularly decreased in elderly patients with CRS. Epithelial expression of S100A8/9 is partly regulated by the IL-6 trans-signaling pathway. The goal of this study was to investigate whether or not age-related reduction of S100A8/9 in CRS is associated with blunting of IL-6 trans-signaling. The levels of IL-6, soluble IL-6 receptor (sIL-6R), soluble gp130 (sgp130), and S100A8/9 from control subjects (n = 10), and patients with CRS without nasal polyps (n = 13) and those with CRS with nasal polyps (CRSwNP) (n = 14), were measured by ELISA. Age-related differences in the level of each protein were investigated. Normal human bronchial epithelial cells were cultured in air-liquid interface and stimulated with IL-6/sIL-6R and tumor necrosis factor (TNF)-α with or without the addition of sgp130, a natural inhibitor of IL-6 trans-signaling. There was a significant age-related decline in S100A8/9 and an increase in sgp130 in nasal tissue samples from patients with CRSwNP, although there was no age-related difference in IL-6/sIL-6R production. Additionally, expression of the S100A8/9 gene and protein was increased significantly by IL-6/sIL-6R plus TNF-α in normal human bronchial epithelial cells. This increase was blocked by sgp130. These results suggest that increased sgp130 in older patients may inhibit IL-6 trans-signaling, impair barrier function, and decrease S1008/9 production in elderly patients with CRSwNP. Restoration of barrier function by targeting sgp130 may be a novel treatment strategy.

IκBζ augments IL-12- and IL-18-mediated IFN-γ production in human NK cells.

Interferon-γ (IFN-γ) production by natural killer (NK) cells and cytotoxic lymphocytes is a key component of innate and adaptive immune responses. Because inhibitor of κB-ζ (IκBζ), a Toll-like receptor (TLR)/interleukin-1 receptor (IL-1R) inducible transcription factor, regulates IFN-γ production in KG-1 cells, we tested IκBζ's role in the classic lymphocyte pathway of IL-12/IL-18-induced IFN-γ. Upon stimulation with IL-12/IL-18, monocyte-depleted human peripheral blood lymphocytes expressed the 79-kDa form of IκBζ and released IFN-γ. CD56(+) NK cells were shown to be the IκBζ-producing lymphocyte subpopulation, which also released abundant IFN-γ in response to IL-12/IL-18. Importantly, IκBζ was undetectable in CD56(-) lymphocytes where IFN-γ release was 10-fold lower. In addition, small interfering RNA knockdown of IκBζ suppressed IFN-γ expression in CD56(+) cells. The association of IκBζ with the IFN-γ promoter was documented by chromatin immunoprecipitation. IFN-γ promoter activity from IκBζ overexpression was confirmed by luciferase reporter assay. Finally, IκBζ coprecipitated with p65 and p50 NF-κB in NK cells in response to IL-12/IL-18, suggesting that IκBζ's effects on IFN-γ promoter activity are coregulated by NF-κB. These results suggest that IκBζ functions as an important regulator of IFN-γ in human NK cells, further expanding the class of IκBζ-modulated genes.

MAIL regulates human monocyte IL-6 production.

IL-6 is a pleiotropic cytokine implicated in the pathogenesis of disorders such as sepsis and cancer. We noted that human monocytes are excellent producers of IL-6 as compared with monocyte-derived macrophages. Because macrophages from molecule containing ankyrin repeats induced by LPS (MAIL) knockout animals have suppressed IL-6 production, we hypothesized that regulation of MAIL is key to IL-6 production in humans and may explain the differences between human monocytes and macrophages. To test this hypothesis fresh human monocytes and monocyte-derived macrophages were compared for MAIL expression in response to LPS. LPS-induced monocyte MAIL expression was highly inducible and transient. Importantly for our hypothesis MAIL protein expression was suppressed during differentiation of monocytes to macrophages. Of note, the human MAIL protein detected was the 80 kDa MAIL-L form and human MAIL showed nuclear localization. Human MAIL-L bound to p50 subunit of the NF-kappaB and increased IL-6 luciferase promoter activity in a cEBPbeta, NF-kappaB, and AP-1-dependent fashion. Like the differences in MAIL induction, monocytes produced 6-fold more IL-6 compared with macrophages (81.7 +/- 29.7 vs 12.6 +/- 6.8 ng/ml). Furthermore, suppression of MAIL by small interfering RNA decreased the production of IL-6 significantly in both THP-1 cells and in primary monocytes. Costimulation of monocytes with LPS and muramyl dipeptide induced an enhanced IL-6 response that was suppressed by siMAIL. Our data suggests that MAIL is a key regulator of IL-6 production in human monocytes and plays an important role in both TLR and NOD-like receptor ligand induced inflammation.

Pyrin critical to macrophage IL-1beta response to Francisella challenge.

Relative to monocytes, human macrophages are deficient in their ability to process and release IL-1beta. In an effort to explain this difference, we used a model of IL-1beta processing and release that is dependent upon bacterial escape into the cytosol. Fresh human blood monocytes were compared with monocyte-derived macrophages (MDM) for their IL-1beta release in response to challenge with Francisella novicida. Although both cell types produced similar levels of IL-1beta mRNA and intracellular pro-IL-1beta, only monocytes readily released processed mature IL-1beta. Baseline mRNA expression profiling of candidate genes revealed a remarkable deficiency in the pyrin gene, MEFV, expression in MDM compared with monocytes. Immunoblots confirmed a corresponding deficit in MDM pyrin protein. To determine whether pyrin levels were responsible for the monocyte/MDM difference in mature IL-1beta release, pyrin expression was knocked down by nucleofecting small interfering RNA against pyrin into monocytes or stably transducing small interfering RNA against pyrin into the monocyte cell line, THP-1. Pyrin knockdown was associated with a significant drop in IL-1beta release in both cell types. Importantly, M-CSF treatment of MDM restored pyrin levels and IL-1beta release. Similarly, the stable expression of pyrin in PMA-stimulated THP-1-derived macrophages induces caspase-1 activation, associated with increased IL-1beta release after infection with F. novicida. In summary, intracellular pyrin levels positively regulate MDM IL-1beta responsiveness to Francisella challenge.

Evidence for altered activity of the IL-6 pathway in chronic rhinosinusitis with nasal polyps.

BACKGROUND: IL-6 activates T(H)17 cells and regulates the response of B lymphocytes and regulatory T cells. The IL-6 receptor and the membrane protein, glycoprotein 130 (gp130), form an active signaling complex that signals through signal transducer and activator of transcription 3 (STAT3) and other signaling molecules. Both the IL-6 receptor (IL-6R) and gp130 can be found in soluble forms that regulate the pathway. OBJECTIVE: We measured IL-6 signaling components and IL-17 in chronic rhinosinusitis (CRS) with nasal polyps (CRSwNP), CRS without nasal polyps (CRSsNP), and controls to assess the IL-6 pathway in CRS. METHODS: IL-6, soluble IL-6R, soluble gp130 (sgp130), and IL-17 were measured in sinus tissue extracts and in nasal lavage fluid by either cytokine bead array or ELISA. phosphoSTAT3 (p-STAT3) was determined by Western blot and by immunohistochemistry. RESULTS: IL-6 protein was significantly (P < .001) increased in CRSwNP compared with CRSsNP and controls. Soluble IL-6R was also increased in nasal polyp compared with control tissue (P < .01). Despite elevated IL-6 and sIL-6R, IL-17A, E, and F were undetectable in the sinus tissue from most of the patients with CRS and controls. p-STAT3 levels were reduced in the polyp tissue, possibly indicating reduced activity of IL-6 in the tissue. sgp130 was elevated in CRSwNP compared with CRSsNP and controls. CONCLUSION: p-STAT3 levels are decreased in CRSwNP despite increased levels of IL-6 and sIL-6R and are associated with the absence of an IL-17 response. This may be a response to elevated levels of sgp130, a known inhibitor of IL-6 signaling. These results indicate that IL-6 and its signaling pathway may be altered in CRSwNP.

A role for anti-BP180 autoantibodies in chronic rhinosinusitis.

OBJECTIVES/HYPOTHESIS: Chronic Rhinosinusitis (CRS) is accompanied by evidence of a vigorous adaptive immune response, and emerging studies demonstrate that some nasal polyps manifest a polyclonal autoantibody response. We previously found that antibodies against BP180, a component of the hemidesmosome complex and the dominant epitope in autoimmune bullous pemphigoid, were found at elevated levels in nasal polyp tissue. Given the critical role of hemidesmosomes in maintaining epithelial integrity, we sought to investigate the distribution of BP180 in nasal tissue and evaluate for evidence of systemic autoimmunity against this antigen in CRS. STUDY DESIGN: Case-control experimental study. METHODS: The expression and distribution of BP180 in cultured nasal epithelial cells and normal nasal tissue were confirmed using real-time polymerase chain reaction (PCR), Western immunoblotting, immunofluorescence and immunohistochemistry. Sera were collected from three groups: control, CRSsNP, and CRSwNP. A commercially available ELISA was utilized to compare anti-BP180 autoantibody levels in sera. RESULTS: BP180 is expressed in nasal epithelium, but is not confined to the basement membrane as it is in human skin. In cultured nasal epithelial cells, confocal immunofluorescence showed a punctate distribution of BP180 along the basal surface, consistent with its distribution in epithelial keratinocytes. There are significantly higher levels of circulating nonpathologic anti-BP180 autoantibodies in CRS patients compared with normal controls (P <0.05). CONCLUSIONS: BP180 is more widely expressed in nasal epithelium versus skin, although it appears to play a similar role in the formation of hemidesmosomes along the basement membrane. Further investigations are ongoing to characterize the pathogenicity of the anti-epithelial antibody response in CRS.

A novel role for IkappaBzeta in the regulation of IFNgamma production.

IkappaBzeta is a novel member of the IkappaB family of NFkappaB regulators, which modulates NFkappaB activity in the nucleus, rather than controlling its nuclear translocation. IkappaBzeta is specifically induced by IL-1beta and several TLR ligands and positively regulates NFkappaB-mediated transcription of genes such as IL-6 and NGAL as an NFkappaB binding co-factor. We recently reported that the IL-1 family cytokines, IL-1beta and IL-18, strongly synergize with TNFalpha for IFNgamma production in KG-1 cells, whereas the same cytokines alone have minimal effects on IFNgamma production. Given the striking similarities between the IL-1R and IL-18R signaling pathways we hypothesized that a common signaling event or gene product downstream of these receptors is responsible for the observed synergy. We investigated IkappaBzeta protein expression in KG-1 cells upon stimulation with IL-1beta, IL-18 and TNFalpha. Our results demonstrated that IL-18, as well as IL-1beta, induced moderate IkappaBzeta expression in KG-1 cells. However, TNFalpha synergized with IL-1beta and IL-18, whereas by itself it had a minimal effect on IkappaBzeta expression. NFkappaB inhibition resulted in decreased IL-1beta/IL-18/TNFalpha-stimulated IFNgamma release. Moreover, silencing of IkappaBzeta expression led to a specific decrease in IFNgamma production. Overall, our data suggests that IkappaBzeta positively regulates NFkappaB-mediated IFNgamma production in KG-1 cells.

Pyrin levels in human monocytes and monocyte-derived macrophages regulate IL-1beta processing and release.

Macrophages and their precursors, monocytes, are key cells involved in the innate immune response. Although both monocytes and macrophages produce caspase-1, the key enzyme responsible for pro-IL-1beta processing; macrophages are limited in their ability to activate the enzyme and release functional IL-1beta. In this context, because mutations in the pyrin gene (MEFV) cause the inflammatory disorder familial Mediterranean fever, pyrin is believed to regulate IL-1beta processing. To determine whether variations in pyrin expression explain the difference between monocytes and macrophages in IL-1beta processing and release, pyrin was studied in human monocytes and monocyte-derived macrophages. Although monocytes express pyrin mRNA and protein, which is readily inducible by endotoxin, monocyte-derived macrophages express significantly less pyrin mRNA and protein. Pyrin levels directly correlated with IL-1beta processing in monocytes and macrophages; therefore, we asked whether pyrin might promote IL-1beta processing and release. HEK293 cells were transfected with pyrin, caspase-1, apoptotic speck protein with a caspase recruitment domain, and IL-1beta. Pyrin induced IL-1beta processing and release in a dose-dependent manner. Conversely, pyrin small interference RNA suppressed pro-IL-1beta processing in both THP-1 cells and fresh human monocytes. In summary, both pyrin expression and IL-1beta processing and release are diminished upon the maturation of monocytes to macrophages. When pyrin is ectopically expressed or silenced, IL-1beta processing and release parallels the level of pyrin. In conclusion, in the context of endotoxin-induced activation of mononuclear phagocytes, pyrin augments IL-1beta processing and release.