6-Mercaptopurine reduces cytokine and Muc5ac expression involving inhibition of NFκB activation in airway epithelial cells

Background

Mucus hypersecretion and excessive cytokine synthesis is associated with many of the pathologic features of chronic airway diseases such as asthma. 6-Mercaptopurine (6-MP) is an immunosuppressive drug that is widely used in several inflammatory disorders. Although 6-MP has been used to treat asthma, its function and mechanism of action in airway epithelial cells is unknown.

Methods

Confluent NCI-H292 and MLE-12 epithelial cells were pretreated with 6-MP followed by stimulation with TNFα or PMA. mRNA levels of cytokines and mucins were measured by RT-PCR. Western blot analysis was performed to assess the phosphorylation of IκBα and luciferase assays were performed using an NFκB reporter plasmid to determine NFκB activity. Periodic Acid Schiff staining was used to assess the production of mucus.

Results

6-MP displayed no effect on cell viability up to a concentration of 15 μM. RT-PCR analysis showed that 6-MP significantly reduces TNFα- and PMA-induced expression of several proinflammatory cytokines in NCI-H292 and MLE-12 cells. Consistent with this, we demonstrated that 6-MP strongly inhibits TNFα-induced phosphorylation of IκBα and thus attenuates NFκB luciferase reporter activity. In addition, 6-MP decreases Rac1 activity in MLE-12 cells. 6-MP down-regulates gene expression of the mucin Muc5ac, but not Muc2, through inhibition of activation of the NFκB pathway. Furthermore, PMA- and TNFα-induced mucus production, as visualized by Periodic Acid Schiff (PAS) staining, is decreased by 6-MP.

Conclusions

Our data demonstrate that 6-MP inhibits Muc5ac gene expression and mucus production in airway epithelial cells through inhibition of the NFκB pathway, and 6-MP may represent a novel therapeutic target for mucus hypersecretion in airway diseases.

Electronic supplementary material

The online version of this article (doi:10.1186/s12931-015-0236-0) contains supplementary material, which is available to authorized users.     

Airway Epithelial NF-κB Activation Promotes Mycoplasma pneumoniae Clearance in Mice

Background/Objective

Respiratory infections including atypical bacteria Mycoplasma pneumoniae (Mp) contribute to the pathobiology of asthma and chronic obstructive pulmonary disease (COPD). Mp infection mainly targets airway epithelium and activates various signaling pathways such as nuclear factor κB (NF-κB). We have shown that short palate, lung, and nasal epithelium clone 1 (SPLUNC1) serves as a novel host defense protein and is up-regulated upon Mp infection through NF-κB activation in cultured human and mouse primary airway epithelial cells. However, the in vivo role of airway epithelial NF-κB activation in host defense against Mp infection has not been investigated. In the current study, we investigated the effects of in vivo airway epithelial NF-κB activation on lung Mp clearance and its association with airway epithelial SPLUNC1 expression.

Methodology/Main Results

Non-antimicrobial tetracycline analog 9-t-butyl doxycycline (9-TB) was initially optimized in mouse primary tracheal epithelial cell culture, and then utilized to induce in vivo airway epithelial specific NF-κB activation in conditional NF-κB transgenic mice (CC10-_CAIKKβ) with or without Mp infection. Lung Mp load and inflammation were evaluated, and airway epithelial SPLUNC1 protein was examined by immunohistochemistry. We found that 9-TB treatment in NF-κB transgene positive (Tg+), but not transgene negative (Tg−) mice significantly reduced lung Mp load. Moreover, 9-TB increased airway epithelial SPLUNC1 protein expression in NF-κB Tg+ mice.

Conclusion

By using the non-antimicrobial 9-TB, our study demonstrates that in vivo airway epithelial NF-κB activation promotes lung bacterial clearance, which is accompanied by increased epithelial SPLUNC1 expression.     

Chronic Alcohol-Induced microRNA-155 Contributes to Neuroinflammation in a TLR4-Dependent Manner in Mice

Introduction

Alcohol-induced neuroinflammation is mediated by pro-inflammatory cytokines and chemokines including tumor necrosis factor-α (TNFα), monocyte chemotactic protein-1 (MCP1) and interleukin-1-beta (IL-1β). Toll-like receptor-4 (TLR4) pathway induced nuclear factor-κB (NF-κB) activation is involved in the pathogenesis of alcohol-induced neuroinflammation. Inflammation is a highly regulated process. Recent studies suggest that microRNAs (miRNAs) play crucial role in fine tuning gene expression and miR-155 is a major regulator of inflammation in immune cells after TLR stimulation.

Aim

To evaluate the role of miR-155 in the pathogenesis of alcohol-induced neuroinflammation.

Methods

Wild type (WT), miR-155- and TLR4-knockout (KO) mice received 5% ethanol-containing or isocaloric control diet for 5 weeks. Microglia markers were measured by q-RTPCR; inflammasome activation was measured by enzyme activity; TNFα, MCP1, IL-1β mRNA and protein were measured by q-RTPCR and ELISA; phospho-p65 protein and NF-κB were measured by Western-blotting and EMSA; miRNAs were measured by q-PCR in the cerebellum. MiR-155 was measured in immortalized and primary mouse microglia after lipopolysaccharide and ethanol stimulation.

Results

Chronic ethanol feeding up-regulated miR-155 and miR-132 expression in mouse cerebellum. Deficiency in miR-155 protected mice from alcohol-induced increase in inflammatory cytokines; TNFα, MCP1 protein and TNFα, MCP1, pro-IL-1β and pro-caspase-1 mRNA levels were reduced in miR-155 KO alcohol-fed mice. NF-κB was activated in WT but not in miR-155 KO alcohol-fed mice. However increases in cerebellar caspase-1 activity and IL-1β levels were similar in alcohol-fed miR-155-KO and WT mice. Alcohol-fed TLR4-KO mice were protected from the induction of miR-155. NF-κB activation measured by phosphorylation of p65 and neuroinflammation were reduced in alcohol-fed TLR4-KO compared to control mice. TLR4 stimulation with lipopolysaccharide in primary or immortalized mouse microglia resulted in increased miR-155.

Conclusion

Chronic alcohol induces miR-155 in the cerebellum in a TLR4-dependent manner. Alcohol-induced miR-155 regulates TNFα and MCP1 expression but not caspase-dependent IL-1β increase in neuroinflammation.     

Cytosolic phospholipase A2α mediates Pseudomonas aeruginosa LPS-induced airway constriction of CFTR -/- mice

Background

Lungs of cystic fibrosis (CF) patients are chronically infected with Pseudomonas aeruginosa. Increased airway constriction has been reported in CF patients but underplaying mechanisms have not been elucidated. Aim: to examine the effect of P. aeruginosa LPS on airway constriction in CF mice and the implication in this process of cytosolic phospholipase A2α (cPLA2α), an enzyme involved in arachidonic acid (AA) release.

Methods

Mice were instilled intra-nasally with LPS. Airway constriction was assessed using barometric plethysmograph. MIP-2, prostaglandin E2 (PGE2), leukotrienes and AA concentrations were measured in BALF using standard kits and gas chromatography.

Results

LPS induced enhanced airway constriction and AA release in BALF of CF compared to littermate mice. This was accompanied by increased levels of PGE2, but not those of leukotrienes. However, airway neutrophil influx and MIP-2 production remained similar in both mouse strains. The cPLA2α inhibitor arachidonyl trifluoro-methyl-ketone (ATK), but not aspirin which inhibit PGE2 synthesis, reduced LPS-induced airway constriction. LPS induced lower airway constriction and PGE2 production in cPLA2α -/- mice compared to corresponding littermates. Neither aspirin nor ATK interfered with LPS-induced airway neutrophil influx or MIP-2 production.

Conclusions

CF mice develop enhanced airway constriction through a cPLA2α-dependent mechanism. Airway inflammation is dissociated from airway constriction in this model. cPLA2α may represent a suitable target for therapeutic intervention in CF. Attenuation of airway constriction by cPLA2α inhibitors may help to ameliorate the clinical status of CF patients.     

Effects of intranasal TNFα on granulocyte recruitment and activity in healthy subjects and patients with allergic rhinitis

Background

TNFα may contribute to the pathophysiology of airway inflammation. For example, we have recently shown that nasal administration of TNFα produces late phase co-appearance of granulocyte and plasma exudation markers on the mucosal surface. The objective of the present study was to examine indices of granulocyte presence and activity in response to intranasal TNFα challenge.

Methods

Healthy subjects and patients with allergic rhinitis (examined out of season) were subjected to nasal challenge with TNFα (10 μg) in a sham-controlled and crossover design. Nasal lavages were carried out prior to and 24 hours post challenge. Nasal biopsies were obtained post challenge. Nasal lavage fluid levels of myeloperoxidase (MPO) and eosinophil cationic protein (ECP) were analyzed as indices of neutrophil and eosinophil activity. Moreover, IL-8 and α₂-macroglobulin were analyzed as markers of pro-inflammatory cytokine production and plasma exudation. Nasal biopsy numbers of neutrophils and eosinophils were monitored.

Results

Nasal lavage fluid levels of MPO recorded 24 hours post TNFα challenge were increased in healthy subjects (p = 0.0081) and in patients with allergic rhinitis (p = 0.0081) (c.f. sham challenge). Similarly, α₂-macroglobulin was increased in healthy subjects (p = 0.014) and in patients with allergic rhinitis (p = 0.0034). Lavage fluid levels of ECP and IL-8 were not affected by TNFα challenge. TNFα increased the numbers of subepithelial neutrophils (p = 0.0021), but not the numbers of eosinophils.

Conclusion

TNFα produces a nasal inflammatory response in humans that is characterised by late phase (i.e., 24 hours post challenge) neutrophil activity and plasma exudation.     

The Role of Interleukin-1 Receptor-Associated Kinases in Vogt-Koyanagi-Harada Disease

Purpose

To explore whether IRAK1 and IRAK4 are involved in the pathogenesis of Vogt-Koyanagi-Harada (VKH) disease.

Methods

Thirty-nine VKH patients and thirty-two healthy controls were included in this study. The mRNA levels of IRAK1 and IRAK4 from active VKH patients, inactive VKH patients, and normal controls in peripheral blood mononuclear cells (PBMCs) were detected using real-time quantitative PCR. CD4⁺T cells were purified from PBMCs obtained from active VKH patients and normal controls. The effect of IRAK1/4 inhibition on CD4⁺T cell proliferation following stimulation with IL-18 or IL-1β was measured using a modified MTT assay. CD4⁺T cell expression of IFN-γ and IL-17 were detected by flow cytometry (FCM) and enzyme-linked immunosorbent assay (ELISA). The effect of IRAK1/4 inhibition on NF-κB, STAT1, and STAT3 activation was detected by FCM.

Results

The mRNA levels of IRAK1 and IRAK4 were both significantly increased in active VKH patients compared to inactive VKH patients and healthy controls. No difference in the IRAK1 or IRAK4 mRNA level could be detected between inactive patients and healthy controls. After incubation with IRAK1/4 inhibitor, the proliferation of CD4⁺T cells was inhibited both in the active VKH patients and in the healthy controls. IRAK1/4 inhibition was also associated with a decreased expression of IFN-γ and IL-17. Phosphorylation of NF-κB, STAT1, and STAT3 in CD4⁺T from healthy controls was significantly decreased after inhibition of IRAK1/4.

Conclusions

High mRNA levels of IRAK1 and IRAK4 correlated with VKH disease activity. IRAK1 and IRAK4 play a role in the activation and proliferation of CD4⁺T cells and the higher expression observed in VKH may contribute to the pathogenesis of this blinding condition.     

The Vitamin D Receptor Agonist BXL-01-0029 as a Potential New Pharmacological Tool for the Treatment of Inflammatory Myopathies

Objective

This study aims to investigate in vitro the effect of the VDR agonist BXL-01-0029 onto IFNγ/TNFα-induced CXCL10 secretion by human skeletal muscle cells compared to elocalcitol (VDR agonist), methylprednisolone, methotrexate, cyclosporin A, infliximab and leflunomide; to assess in vivo circulating CXCL10 level in subjects at time of diagnosis with IMs, before therapy, together with TNFα, IFNγ, IL-8, IL-6, MCP-1, MIP-1β and IL-10, vs. healthy subjects.

Methods

Human fetal skeletal muscle cells were used for in vitro studies; ELISA and Bio-Plex were used to measure cell supernatant and IC₅₀ determination or serum cytokines; Western blot and Bio-Plex were for cell signaling analysis.

Results

BXL-01-0029 decreased with the highest potency IFNγ/TNFα-induced CXCL10 protein secretion and targeted cell signaling downstream of TNFα in human skeletal muscle cells; CXCL10 level was the highest in sera of subjects diagnosed with IMs before therapy and the only one significantly different vs. healthy controls.

Conclusions

Our in vitro and in vivo data, while confirm the relevance of CXCL10 in IMs, suggested BXL-01-0029 as a novel pharmacological tool for IM treatment, hypothetically to be used in combination with the current immunosuppressants to minimize side effects.     

Modulation of epithelial sodium channel (ENaC) expression in mouse lung infected with Pseudomonas aeruginosa

Background

The intratracheal instillation of Pseudomonas aeruginosa entrapped in agar beads in the mouse lung leads to chronic lung infection in susceptible mouse strains. As the infection generates a strong inflammatory response with some lung edema, we tested if it could modulate the expression of genes involved in lung liquid clearance, such as the α, β and γ subunits of the epithelial sodium channel (ENaC) and the catalytic subunit of Na⁺-K⁺-ATPase.

Methods

Pseudomonas aeruginosa entrapped in agar beads were instilled in the lung of resistant (BalB/c) and susceptible (DBA/2, C57BL/6 and A/J) mouse strains. The mRNA expression of ENaC and Na⁺-K⁺-ATPase subunits was tested in the lung by Northern blot following a 3 hours to 14 days infection.

Results

The infection of the different mouse strains evoked regulation of α and β ENaC mRNA. Following Pseudomonas instillation, the expression of αENaC mRNA decreased to a median of 43% on days 3 and 7 after infection and was still decreased to a median of 45% 14 days after infection (p < 0.05). The relative expression of βENaC mRNA was transiently increased to a median of 241%, 24 h post-infection before decreasing to a median of 43% and 54% of control on days 3 and 7 post-infection (p < 0.05). No significant modulation of γENaC mRNA was detected although the general pattern of expression of the subunit was similar to α and β subunits. No modulation of α₁Na⁺-K⁺-ATPase mRNA, the catalytic subunit of the sodium pump, was recorded. The distinctive expression profiles of the three subunits were not different, between the susceptible and resistant mouse strains.

Conclusions

These results show that Pseudomonas infection, by modulating ENaC subunit expression, could influence edema formation and clearance in infected lungs.     

Extracellular Hsp72, an endogenous DAMP,is released by virally infected airway epithelial cells and activates neutrophils via Toll-like receptor (TLR)-4

Background

Neutrophils play an important role in the pathophysiology of RSV, though RSV does not appear to directly activate neutrophils in the lower airways. Therefore locally produced cytokines or other molecules released by virally-infected airway epithelial cells are likely responsible for recruiting and activating neutrophils. Heat shock proteins (HSPs) are generally regarded as intracellular proteins acting as molecular chaperones; however, HSP72 can also be released from cells, and the implications of this release are not fully understood.

Methods

Human bronchial epithelial cells (16HBE14o-) were infected with RSV and Hsp72 levels were measured by Western blot and ELISA. Tracheal aspirates were obtained from critically ill children infected with RSV and analyzed for Hsp72 levels by ELISA. Primary human neutrophils and differentiated HL-60 cells were cultured with Hsp72 and supernatants analyzed for cytokine production. In some cases, cells were pretreated with polymyxin B prior to treatment with Hsp72. IκBα was assessed by Western blot and EMSA''s were performed to determine NF-κB activation. HL-60 cells were pretreated with neutralizing antibody against TLR4 prior to Hsp72 treatment. Neutrophils were harvested from the bone marrow of wild type or TLR4-deficient mice prior to treatment with Hsp72.

Results

Infection of 16HBE14o- with RSV showed an induction of intracellular Hsp72 levels as well as extracellular release of Hsp72. Primary human neutrophils from normal donors and differentiated HL-60 cells treated with increasing concentrations of Hsp72 resulted in increased cytokine (IL-8 and TNFα) production. This effect was independent of the low levels of endotoxin in the Hsp72 preparation. Hsp72 mediated cytokine production via activation of NF-κB translocation and DNA binding. Using bone marrow-derived neutrophils from wild type and TLR4-mutant mice, we showed that Hsp72 directly activates neutrophil-derived cytokine production via the activation of TLR4.

Conclusion

Collectively these data suggest that extracellular Hsp72 is released from virally infected airway epithelial cells resulting in the recruitment and activation of neutrophils.     

Mechanical ventilation modulates TLR4 and IRAK-3 in a non-infectious,ventilator-induced lung injury model

Background

Previous experimental studies have shown that injurious mechanical ventilation has a direct effect on pulmonary and systemic immune responses. How these responses are propagated or attenuated is a matter of speculation. The goal of this study was to determine the contribution of mechanical ventilation in the regulation of Toll-like receptor (TLR) signaling and interleukin-1 receptor associated kinase-3 (IRAK-3) during experimental ventilator-induced lung injury.

Methods

Prospective, randomized, controlled animal study using male, healthy adults Sprague-Dawley rats weighing 300-350 g. Animals were anesthetized and randomized to spontaneous breathing and to two different mechanical ventilation strategies for 4 hours: high tidal volume (V_T) (20 ml/kg) and low V_T (6 ml/kg). Histological evaluation, TLR2, TLR4, IRAK3 gene expression, IRAK-3 protein levels, inhibitory kappa B alpha (IκBα), tumor necrosis factor-alpha (TNF-α) and interleukin-6 (IL6) gene expression in the lungs and TNF-α and IL-6 protein serum concentrations were analyzed.

Results

High V_T mechanical ventilation for 4 hours was associated with a significant increase of TLR4 but not TLR2, a significant decrease of IRAK3 lung gene expression and protein levels, a significant decrease of IκBα, and a higher lung expression and serum concentrations of pro-inflammatory cytokines.

Conclusions

The current study supports an interaction between TLR4 and IRAK-3 signaling pathway for the over-expression and release of pro-inflammatory cytokines during ventilator-induced lung injury. Our study also suggests that injurious mechanical ventilation may elicit an immune response that is similar to that observed during infections.     

Budesonide and formoterol effects on rhinovirus replication and epithelial cell cytokine responses

Background

Combination therapy with budesonide and formoterol reduces exacerbations of asthma, which are closely associated with human rhinovirus (RV) infections in both children and adults. These data suggest that budesonide and formoterol inhibit virus-induced inflammatory responses of airway epithelial cells.

Methods

To test this hypothesis, bronchial epithelial (BE) cells were obtained from airway brushings of 8 subjects with moderate-to-severe allergic asthma and 9 with neither asthma nor respiratory allergies. Cultured BE cells were incubated for 24 hours with budesonide (1.77 μM), formoterol (0.1 μM), both, or neither, and then inoculated with RV-16 (5×10⁶ plaque forming units [PFU]/mL). After 24 hours, viral replication (RV RNA), cytokine secretion (CXCL8, CXCL10, TNFα, IFN-β, IL-28) and mRNA expression (CXCL8, CXCL10, TNF, IFNB1, IL28A&B) were analyzed.

Results

RV infection induced CXCL10 protein secretion and IFNB1 and IL28 mRNA expression. Drug treatments significantly inhibited secretion of CXCL10 in mock-infected, but not RV-infected, BE cells, and inhibited secretion of TNFα under both conditions. Neither budesonide nor formoterol, alone or in combination, significantly affected viral replication, nor did they inhibit RV-induced upregulation of IFNB1 and IL28 mRNA. Overall, RV replication was positively related to CXCL10 secretion and induction of IFNB1 and IL28 mRNA, but the positive relationship between RV RNA and CXCL10 secretion was stronger in normal subjects than in subjects with asthma.

Conclusions

Budesonide and formoterol can inhibit BE cell inflammatory responses in vitro without interfering with viral replication or production of interferons. These effects could potentially contribute to beneficial effects of budesonide/formoterol combination therapy in preventing RV-induced asthma exacerbations.