Activation of heat shock response augments fibroblast growth factor-1 expression in wounded lung epithelium

We previously showed that coincident exposure to heat shock (HS; 42°C for 2 h) and TNF-α synergistically induces apoptosis in mouse lung epithelium. We extended this work by analyzing HS effects on human lung epithelial responses to clinically relevant injury. Cotreatment with TNF-α and HS induced little caspase-3 and poly(ADP-ribose) polymerase cleavage in human small airway epithelial cells, A549 cells, and BEAS2B cells. Scratch wound closure rates almost doubled when A549 and BEAS2B cells and air-liquid interface cultures of human bronchial epithelial cells were heat shocked immediately after wounding. Microarray, qRT-PCR, and immunoblotting showed fibroblast growth factor 1 (FGF1) to be synergistically induced by HS and wounding. Enhanced FGF1 expression in HS/wounded A549 was blocked by inhibitors of p38 MAPK (SB203580) or HS factor (HSF)-1 (KNK-437) and in HSF1 knockout BEAS2B cells. PCR demonstrated FGF1 to be expressed from the two most distal promoters in wounded/HS cells. Wound closure in HS A549 and BEAS2B cells was reduced by FGF receptor-1/3 inhibition (SU-5402) or FGF1 depletion. Exogenous FGF1 accelerated A549 wound closure in the absence but not presence of HS. In the presence of exogenous FGF1, HS slowed wound closure, suggesting that it increases FGF1 expression but impairs FGF1-stimulated wound closure. Frozen sections from normal and idiopathic pulmonary fibrosis (IPF) lung were analyzed for FGF1 and HSP70 by immunofluorescence confocal microscopy and qRT-PCR. FGF1 and HSP70 mRNA levels were 7.5- and 5.9-fold higher in IPF than normal lung, and the proteins colocalized to fibroblastic foci in IPF lung. We conclude that HS signaling may have an important impact on gene expression contributing to lung injury, healing, and fibrosis.

1918 Influenza receptor binding domain variants bind and replicate in primary human airway cells regardless of receptor specificity

The 1918 influenza pandemic caused ~50 million deaths. Many questions remain regarding the origin, pathogenicity, and mechanisms of human adaptation of this virus. Avian-adapted influenza A viruses preferentially bind α2,3-linked sialic acids (Sia) while human-adapted viruses preferentially bind α2,6-linked Sia. A change in Sia preference from α2,3 to α2,6 is thought to be a requirement for human adaptation of avian influenza viruses. Autopsy data from 1918 cases, however, suggest that factors other than Sia preference played a role in viral binding and entry to human airway cells. Here, we evaluated binding and entry of five 1918 influenza receptor binding domain variants in a primary human airway cell model along with control avian and human influenza viruses. We observed that all five variants bound and entered cells efficiently and that Sia preference did not predict entry of influenza A virus to primary human airway cells evaluated in this model.

Validation of normal human bronchial epithelial cells as a model for influenza A infections in human distal trachea

Primary normal human bronchial/tracheal epithelial (NHBE) cells, derived from the distal-most aspect of the trachea at the bifurcation, have been used for a number of studies in respiratory disease research. Differences between the source tissue and the differentiated primary cells may impact infection studies based on this model. Therefore, we examined how well-differentiated NHBE cells compared with their source tissue, the human distal trachea, as well as the ramifications of these differences on influenza A viral pathogenesis research using this model. We employed a histological analysis including morphological measurements, electron microscopy, multi-label immunofluorescence confocal microscopy, lectin histochemistry, and microarray expression analysis to compare differentiated NHBEs to human distal tracheal epithelium. Pseudostratified epithelial height, cell type variety and distribution varied significantly. Electron microscopy confirmed differences in cellular attachment and paracellular junctions. Influenza receptor lectin histochemistry revealed that α2,3 sialic acids were rarely present on the apical aspect of the differentiated NHBE cells, but were present in low numbers in the distal trachea. We bound fluorochrome bioconjugated virus to respiratory tissue and NHBE cells and infected NHBE cells with human influenza A viruses. Both indicated that the pattern of infection progression in these cells correlated with autopsy studies of fatal cases from the 2009 pandemic.

Prostaglandin E2 Inhibits NLRP3 Inflammasome Activation through EP4 Receptor and Intracellular Cyclic AMP in Human Macrophages

PGE2 is a potent lipid mediator involved in maintaining homeostasis but also promotion of acute inflammation or immune suppression in chronic inflammation and cancer. Nucleotide-binding domain, leucine-rich repeat-containing protein (NLR)P3 inflammasome plays an important role in host defense. Uncontrolled activation of the NLRP3 inflammasome, owing to mutations in the NLRP3 gene, causes cryopyrin-associated periodic syndromes. In this study, we showed that NLRP3 inflammasome activation is inhibited by PGE2 in human primary monocyte-derived macrophages. This effect was mediated through PGE2 receptor subtype 4 (EP4) and an increase in intracellular cAMP, independently of protein kinase A or exchange protein directly activated by cAMP. A specific agonist of EP4 mimicked, whereas its antagonist or EP4 knockdown reversed, PGE2-mediated NLRP3 inhibition. PGE2 caused an increase in intracellular cAMP. Blockade of adenylate cyclase by its inhibitor reversed PGE2-mediated NLRP3 inhibition. Increase of intracellular cAMP by an activator of adenylate cyclase or an analog of cAMP, or a blockade of cAMP degradation by phosphodiesterase inhibitor decreased NLRP3 activation. Protein kinase A or exchange protein directly activated by cAMP agonists did not mimic, and their antagonists did not reverse, PGE2-mediated NLRP3 inhibition. Additionally, constitutive IL-1β secretion from LPS-primed PBMCs of cryopyrin-associated periodic fever syndromes patients was substantially reduced by high doses of PGE2. Moreover, blocking cytosolic phospholipase A2α by its inhibitor or small interfering RNA or inhibiting cyclooxygenase 2, resulting in inhibition of endogenous PGE2 production, caused an increase in NLRP3 inflammasome activation. Our results suggest that PGE2 might play a role in maintaining homeostasis during the resolution phase of inflammation and might serve as an autocrine and paracrine regulator.

The fish oil ingredient, docosahexaenoic acid, activates cytosolic phospholipase A₂ via GPR120 receptor to produce prostaglandin E₂ and plays an anti-inflammatory role in macrophages

Docosahexaenoic acid (DHA) is one of the major ingredients of fish oil and has been reported to have anti-inflammatory properties mediated through the GPR120 receptor. Whether cytosolic phospholipase A2 (cPLA2 ) and lipid mediators produced from cPLA2 activation are involved in the anti-inflammatory role of DHA in macrophages has not been reported. We report here that DHA and the GPR120 agonist, GW9508, activate cPLA2 and cyclooxygenase 2 (COX-2), and cause prostaglandin E2 (PGE2) release in a murine macrophage cell line RAW264.7 and in human primary monocyte-derived macrophages. DHA and GW9508 activate cPLA2 via GPR120 receptor, G protein Gαq and scaffold protein β-arrestin 2. Extracellular signal-regulated kinase 1/2 activation is involved in DHA- and GW9508-induced cPLA2 activation, but not p38 mitogen-activated protein kinase. The anti-inflammatory role of DHA and GW9508 is in part via activation of cPLA2 , COX-2 and production of PGE2 as a cPLA2 inhibitor or a COX-2 inhibitor partially reverses the DHA- and GW9508-induced inhibition of lipopolysaccharide-induced interleukin-6 secretion. The cPLA2 product arachidonic acid and PGE2 also play an anti-inflammatory role. This effect of PGE2 is partially through inhibition of the nuclear factor-κB signalling pathway and through the EP4 receptor of PGE2 because an EP4 inhibitor or knock-down of EP4 partially reverses DHA inhibition of lipopolysaccharide-induced interleukin-6 secretion. Hence, DHA has an anti-inflammatory effect partially through induction of PGE2.

Low molecular weight hyaluronan activates cytosolic phospholipase A2α and eicosanoid production in monocytes and macrophages

Hyaluronan (HA) is the major glycosaminoglycan in the extracellular matrix. During inflammation, there is an increased breakdown of HA, resulting in the accumulation of low molecular weight (LMW) HA and activation of monocytes and macrophages. Eicosanoids, derived from the cytosolic phospholipase A2 group IVA (cPLA2α) activation, are potent lipid mediators also attributed to acute and chronic inflammation. The aim of this study was to determine the effect of LMW HA on cPLA2α activation, arachidonic acid (AA) release, and subsequent eicosanoid production and to examine the receptors and downstream mechanisms involved in these processes in monocytes and differently polarized macrophages. LMW HA was a potent stimulant of AA release in a time- and dose-dependent manner, induced cPLA2α, ERK1/2, p38, and JNK phosphorylation, as well as activated COX2 expression and prostaglandin (PG) E2 production in primary human monocytes, murine RAW 264.7, and wild-type bone marrow-derived macrophages. Specific cPLA2α inhibitor blocked HA-induced AA release and PGE2 production in all of these cells. Using CD44, TLR4, TLR2, MYD88, RHAMM or STAB2 siRNA-transfected macrophages and monocytes, we found that AA release, cPLA2α, ERK1/2, p38, and JNK phosphorylation, COX2 expression, and PGE2 production were activated by LMW HA through a TLR4/MYD88 pathway. Likewise, PGE2 production and COX2 expression were blocked in Tlr4(-/-) and Myd88(-/-) mice, but not in Cd44(-/-) mice, after LMW HA stimulation. Moreover, we demonstrated that LMW HA activated the M1 macrophage phenotype with the unique cPLA2α/COX2(high) and COX1/ALOX15/ALOX5/LTA4H(low) gene and PGE2/PGD2/15-HETE(high) and LXA4(low) eicosanoid profile. These findings reveal a novel link between HA-mediated inflammation and lipid metabolism.

Changes in microRNA and mRNA expression with differentiation of human bronchial epithelial cells

We studied the changes in expression of microRNAs (miRNAs or miRs) and mRNA in normal human bronchial epithelial cells as they differentiate from an undifferentiated monolayer to a differentiated pseudostratified epithelium after 28 days of air-liquid interface (ALI) culture. After 28 days in ALI, the epithelial cells differentially expressed basal, ciliated, and goblet cell markers. Using Affymetrix microarrays, 20 human miRNAs were found to be up-regulated, whereas 35 miRNAs were found to be down-regulated in differentiated cells compared with undifferentiated cells. An analysis of changes in global mRNA expression revealed that 1,201 probe sets demonstrated an 8-fold change (FC) or greater at Day 28 of ALI culture. Of these, 816 were up-regulated and 385 were down-regulated. With differentiation, miR-449a increased (FC, 38.15), and was related to changes in mRNA for cell division cycle 25 homolog A (FC, 0.11). MiR-455 decreased (FC, 0.12) and was related to changes in mRNA for the epithelial cell marker, mucin 1 (FC, 136). Transfection with anti-miR-449 or miR-455-3p resulted in changes in target protein expression (cell division cycle 25 homolog A and mucin 1, respectively), whereas transfection with reporter genes with 3'-untranslated regions of these targets confirmed control of expression through that structure. Therefore, changes in specific miRNAs during human airway epithelial cell differentiation control gene and protein expression important for differentiation.

Abnormal nasal nitric oxide production, ciliary beat frequency, and Toll-like receptor response in pulmonary nontuberculous mycobacterial disease epithelium

RATIONALE

Pulmonary nontuberculous mycobacterial (PNTM) disease has increased over the past several decades, especially in older women. Despite extensive investigation, no consistent immunological abnormalities have been found. Using evidence from diseases such as cystic fibrosis and primary ciliary dyskinesia, in which mucociliary dysfunction predisposes subjects to high rates of nontuberculous mycobacterial disease that increase with age, we investigated correlates of mucociliary function in subjects with PNTM infections and healthy control subjects.

OBJECTIVES

To define ex vivo characteristics of PNTM disease.

METHODS

From 2009 to 2012, 58 subjects with PNTM infections and 40 control subjects were recruited. Nasal nitric oxide (nNO) was determined at the time of respiratory epithelial collection. Ciliary beat frequency at rest and in response to Toll-like receptor (TLR) and other agonists was determined using high-speed video microscopy.

MEASUREMENTS AND MAIN RESULTS

We found decreased nNO production, abnormally low resting ciliary beat frequency, and abnormal responses to agonists of TLR2, -3, -5, -7/8, and -9 in subjects with PNTM compared with healthy control subjects. The low ciliary beat frequency in subjects with PNTM was normalized ex vivo by augmentation of the NO-cyclic guanosine monophosphate pathway without normalization of their TLR agonist responses.

CONCLUSIONS

Impaired nNO, ciliary beat frequency, and TLR responses in PNTM disease epithelium identify possible underlying susceptibility mechanisms as well as possible avenues for directed investigation and therapy.

HIV infection and antiretroviral therapy have divergent effects on mitochondria in adipose tissue

BACKGROUND

Although human immunodeficiency virus (HIV) infection and antiretroviral therapy (ART) affect mitochondrial DNA (mtDNA) content and function, comprehensive evaluations of their effects on mitochondria in muscle, adipose tissue, and blood cells are limited.

METHODS

Mitochondrial DNA quantification, mitochondrial genome sequencing, and gene expression analysis were performed on muscle, adipose tissue, and peripheral blood mononuclear cell (PBMC) samples from untreated HIV-positive patients, HIV-positive patients receiving nucleoside reverse transcriptase inhibitor (NRTI)-based ART, and HIV-negative controls.

RESULTS

The adipose tissue mtDNA/nuclear DNA (nDNA) ratio was increased in untreated HIV-infected patients (ratio, 353) and decreased in those receiving ART (ratio, 162) compared with controls (ratio, 255; P < .05 for both comparisons); the difference between the 2 HIV-infected groups was also significant (P = .002). In HIV-infected participants, mtDNA/nDNA in adipose tissue correlated with the level of activation (CD38+ /HLA-DR+) for CD4+ and CD8+ lymphocytes. No significant differences in mtDNA content were noted in muscle or PMBCs among groups. Exploratory DNA microarray analysis identified differential gene expression between patient groups, including a subset of adipose tissue genes.

CONCLUSIONS

HIV infection and ART have opposing effects on mtDNA content in adipose tissue; immune activation may mediate the effects of HIV, whereas NRTIs likely mediate the effects of ART.

Cooperative and redundant signaling of leukotriene B4 and leukotriene D4 in human monocytes

BACKGROUND

Leukotriene B(4) (LTB(4)) and cysteinyl leukotrienes (cysLTs) are important immune mediators, often found concomitantly at sites of inflammation. Although some of the leukotriene-mediated actions are distinctive (e.g., bronchial constriction for cysLTs), many activities such as leukocyte recruitment to tissues and amplification of inflammatory responses are shared by both classes of leukotrienes.

OBJECTIVE

We used human monocytes to characterize leukotriene-specific signaling, gene expression signatures, and functions and to identify interactions between LTB(4)- and cysLTs-induced pathways.

METHODS

Responsiveness to leukotrienes was assessed using oligonucleotide microarrays, real-time PCR, calcium mobilization, kinase activation, and chemotaxis assays.

RESULTS

Human monocytes were found to express mRNA for high- and low-affinity LTB(4) receptors, BLT(1) and BLT(2), but signal predominantly through BLT(1) in response to LTB(4) stimulation as shown using selective agonists, inhibitors, and gene knock down experiments. LTB(4) acting through BLT(1) coupled to G-protein α inhibitory subunit activated calcium signaling, p44/42 mitogen-activated protein kinase, gene expression, and chemotaxis. Twenty-seven genes, including immediate early genes (IEG), transcription factors, cytokines, and membrane receptors were significantly up-regulated by LTB(4). LTB(4) and LTD(4) had similar effects on signaling, gene expression, and chemotaxis indicating redundant cell activation pathways but costimulation with both lipid mediators was additive for many monocyte functions.

CONCLUSION

Leukotriene B(4) and LTD(4) display both redundant and cooperative effects on intracellular signaling, gene expression, and chemotaxis in human monocytes. These findings suggest that therapies targeting either leukotriene alone may be less effective than approaches directed at both.

Impact of animal strain on gene expression in a rat model of acute cardiac rejection

Background

The expression levels of many genes show wide natural variation among strains or populations. This study investigated the potential for animal strain-related genotypic differences to confound gene expression profiles in acute cellular rejection (ACR). Using a rat heart transplant model and 2 different rat strains (Dark Agouti, and Brown Norway), microarrays were performed on native hearts, transplanted hearts, and peripheral blood mononuclear cells (PBMC).

Results

In heart tissue, strain alone affected the expression of only 33 probesets while rejection affected the expression of 1368 probesets (FDR 10% and FC ≥ 3). Only 13 genes were affected by both strain and rejection, which was < 1% (13/1368) of all probesets differentially expressed in ACR. However, for PBMC, strain alone affected 265 probesets (FDR 10% and FC ≥ 3) and the addition of ACR had little further effect. Pathway analysis of these differentially expressed strain effect genes connected them with immune response, cell motility and cell death, functional themes that overlap with those related to ACR. After accounting for animal strain, additional analysis identified 30 PBMC candidate genes potentially associated with ACR.

Conclusion

In ACR, genetic background has a large impact on the transcriptome of immune cells, but not heart tissue. Gene expression studies of ACR should avoid study designs that require cross strain comparisons between leukocytes.

Cytosolic phospholipase A2alpha activation induced by S1P is mediated by the S1P3 receptor in lung epithelial cells

Cytosolic phospholipase A(2)alpha (cPLA(2)alpha) activation is a regulatory step in the control of arachidonic acid (AA) liberation for eicosanoid formation. Sphingosine 1-phosphate (S1P) is a bioactive lipid mediator involved in the regulation of many important proinflammatory processes and has been found in the airways of asthmatic subjects. We investigated the mechanism of S1P-induced AA release and determined the involvement of cPLA(2)alpha in these events in A549 human lung epithelial cells. S1P induced AA release rapidly within 5 min in a dose- and time-dependent manner. S1P-induced AA release was inhibited by the cPLA(2)alpha inhibitors methyl arachidonyl fluorophosphonate (MAFP) and pyrrolidine derivative, by small interfering RNA-mediated downregulation of cPLA(2)alpha, and by inhibition of S1P-induced calcium flux, suggesting a significant role of cPLA(2)alpha in S1P-mediated AA release. Knockdown of the S1P3 receptor, the major S1P receptor expressed on A549 cells, inhibited S1P-induced calcium flux and AA release. The S1P-induced calcium flux and AA release was associated with sphingosine kinase 1 (Sphk1) expression and activity. Furthermore, Rho-associated kinase, downstream of S1P3, was crucial for S1P-induced cPLA(2)alpha activation. Our data suggest that S1P acting through S1P3, calcium flux, and Rho kinase activates cPLA(2)alpha and releases AA in lung epithelial cells. An understanding of S1P-induced cPLA(2)alpha activation mechanisms in epithelial cells may provide potential targets to control inflammatory processes in the lung.

A focused microarray to study human mitochondrial and nuclear gene expression

A focused microarray (huMITOchip) was developed to study alterations of human mitochondrial and nuclear gene expression in health and disease. The huMITOchip contains 4,774 probe sets identical to the Affymetrix U 133 plus 2.0 chip covering genes affecting mitochondrial, lipid, cytokine, apoptosis, and muscle function transcripts. Unlike other gene chips, the huMITOchip has 51 probe sets that interrogate 37 genes of the mitochondrial genome. The human mitochondrial gene chip was validated against the Affymetrix U133 plus 2.0 array using an in vitro system of CCL136 muscle cell line stimulated with or without interferon gamma (IFN-gamma). The 37 genes from the mtDNA demonstrated absolute gene expression levels ranging from 0.1 to 3,182. The comparison of the two gene chips yielded an excellent Pearson's correlation coefficient (r = 0.98). At least 17 probe sets were differentially expressed in response to IFN-gamma on both chips, with a high degree of concordance. This is the first report on the development of a focused oligonucleotide microarray containing genes of the mitochondrial genome.

Immune responses to Pneumocystis murina are robust in healthy mice but largely absent in CD40 ligand-deficient mice

Pneumocystis is a pathogen of immunocompromised hosts but can also infect healthy hosts, in whom infection is rapidly controlled and cleared. Microarray methods were used to examine differential gene expression in the lungs of C57BL/6 and CD40 ligand knockout (CD40L-KO) mice over time following exposure to Pneumocystis murina. Immunocompetent C57BL/6 mice, which control and clear infection efficiently, showed a robust response to infection characterized by the up-regulation of 349 primarily immune response-associated genes. Temporal changes in the expression of these genes identified an early (Week 2), primarily innate response, which waned before the infection was controlled; this was followed by primarily adaptive immune responses that peaked at Week 5, which coincided with clearance of the infection. In conjunction with the latter, there was an increased expression of B cell-associated (Ig) genes at Week 6 that persisted through 11 weeks. In contrast, CD40L-KO mice, which are highly susceptible to developing severe Pneumocystis pneumonia, showed essentially no up-regulation of immune response-associated genes at Days 35-75. Immunohistochemical staining supported these observations by demonstrating an increase in CD4+, CD68+, and CD19+ cells in C57BL/6 but not CD40L-KO mice. Thus, the healthy host demonstrates a robust, biphasic response to infection by Pneumocystis; CD40L is an essential upstream regulator of the adaptive immune responses that efficiently control infection and prevent development of progressive pneumonia.

Leukotriene D(4) induces gene expression in human monocytes through cysteinyl leukotriene type I receptor

BACKGROUND

Cysteinyl leukotrienes (CysLTs) are important mediators of innate immune responsiveness and chronic inflammatory diseases. CysLTs acting through CysLT receptors can influence the migration and activity of cells, such as eosinophils, monocytes, and dendritic cells.

OBJECTIVE

We sought to determine the gene expression signature of human monocytes in response to CysLTs and to elucidate the signaling pathways involved in monocyte activation.

METHODS

Gene expression was analyzed by using oligonucleotide microarrays. Responsiveness to CysLTs was assessed by using real-time PCR, calcium flux, kinase activation, and chemotaxis assays.

RESULTS

CysLT type 1 receptor (CysLTR(1)) transcript 1 is predominantly expressed in human monocytes, and CysLTs signal through CysLTR(1) in these cells. Several immediate-early genes, including early growth response 2 and 3, FBJ murine osteosarcoma viral oncogene homolog B, activating transcription factor 3, and nuclear receptor subfamily 4 were significantly induced by leukotriene (LT) D(4). This effect was mediated by CysLTR(1) coupled to the G protein alpha inhibitory subunit, activation of phospholipase C, and inositol-1,4,5-triphosphate and store-operated calcium channels. LTD(4) induced p38 mitogen-activated protein kinase phosphorylation, a pathway also involved in the regulation of immediate-early gene expression in monocytes. LTD(4) stimulated monocyte chemotactic activity that was fully blocked by a selective CysLTR(1) inhibitor, MK571, and pertussis toxin, suggesting that CysLTR(1) coupled to the G protein alpha inhibitory subunit is a dominant functional pathway in human monocytes.

CONCLUSION

Our data show that CysLTs acting through CysLTR(1) can significantly influence the activation and migration of human monocytes and that these effects can be fully inhibited by CysLTR(1) antagonists.

IFN-gamma induces cysteinyl leukotriene receptor 2 expression and enhances the responsiveness of human endothelial cells to cysteinyl leukotrienes

Cysteinyl leukotrienes (cysLTs) are important mediators of cell trafficking and innate immune responses, involved in the pathogenesis of inflammatory processes, i.e., atherosclerosis, pulmonary fibrosis, and bronchial asthma. The aim of this study was to examine the regulation of cysLT signaling by IFN-gamma in human primary endothelial cells. IFN-gamma increased cysLT receptor 2 (CysLTR2) mRNA expression and CysLTR2-specific calcium signaling in endothelial cells. IFN-gamma signaled through Jak/STAT1, as both AG490, a Jak2 inhibitor, and expression of a STAT1 dominant-negative construct, significantly inhibited CysLTR2 mRNA expression in response to IFN-gamma. To determine mechanisms of IFN-gamma-induced CysLTR2 expression, the human CysLTR2 gene structure was characterized. The CysLTR2 gene has a TATA-less promoter, with multiple transcription start sites. It consists of six variably spliced exons. Eight different CysLTR2 transcripts were identified in endothelial and monocytic cells. Gene reporter assay showed potent basal promoter activity of a putative CysLTR2 promoter region. However, there were no significant changes in gene reporter and mRNA t(1/2) assays in response to IFN-gamma, suggesting transcriptional control of CysLTR2 mRNA up-regulation by IFN-gamma response motifs localized outside of the cloned CysLTR2 promoter region. Stimulation of endothelial cells by cysLTs induced mRNA and protein expression of early growth response genes 1, 2, and 3 and cycloxygenase-2. This response was mediated by CysLTR2 coupled to G(q/11), activation of phospholipase C, and inositol-1,4,5-triphosphate, and was enhanced further 2- to 5-fold by IFN-gamma stimulation. Thus, IFN-gamma induces CysLTR2 expression and enhances cysLT-induced inflammatory responses.

Amplified expression profiling of platelet transcriptome reveals changes in arginine metabolic pathways in patients with sickle cell disease

BACKGROUND

In sickle cell disease, ischemia-reperfusion injury and intravascular hemolysis produce endothelial dysfunction and vasculopathy characterized by reduced nitric oxide and arginine bioavailability. Recent functional studies of platelets in patients with sickle cell disease reveal a basally activated state, which suggests that pathological platelet activation may contribute to sickle cell disease vasculopathy.

METHODS AND RESULTS

Studies were therefore undertaken to examine transcriptional signaling pathways in platelets that may be dysregulated in sickle cell disease. We demonstrate and validate in the present study the feasibility of comparative platelet transcriptome studies on clinical samples from single donors by the application of RNA amplification followed by microarray-based analysis of 54,000 probe sets. Data mining an existing microarray database, we identified 220 highly abundant genes in platelets and a subset of 72 relatively platelet-specific genes, defined by >10-fold increased expression compared with the median of other cell types in the database with amplified transcripts. The highly abundant platelet transcripts found in the present study included 82% or 70% of platelet-abundant genes identified in 2 previous gene expression studies on nonamplified mRNA from pooled or apheresis samples, respectively. On comparing the platelet gene expression profiles in 18 patients with sickle cell disease in steady state to those of 12 black control subjects, at a 3-fold cutoff and 5% false-discovery rate, we identified approximately 100 differentially expressed genes, including multiple genes involved in arginine metabolism and redox homeostasis. Further characterization of these pathways with real-time polymerase chain reaction and biochemical assays revealed increased arginase II expression and activity and decreased platelet polyamine levels.

CONCLUSIONS

The present studies suggest a potential pathogenic role for platelet arginase and altered arginine and polyamine metabolism in sickle cell disease and provide a novel framework for the study of disease-specific platelet biology.

Gene expression profiles of peripheral blood leukocytes after endotoxin challenge in humans

To define gene expression profiles that occur during the initial activation of human innate immunity, we administered intravenous endotoxin (n = 8) or saline (n = 4) to healthy subjects and hybridized RNA from blood mononuclear cells (0, 0.5, 6, 24, 168 h) or whole blood (0, 3, 6, 24, 168 h) to oligonucleotide probe arrays. The greatest change in mononuclear cell gene expression occurred at 6 h (439 induced and 428 repressed genes, 1% false discovery rate, and 50% fold change) including increased expression of genes associated with pathogen recognition molecules and signaling cascades linked to receptors associated with cell mobility and activation. Induced defense response genes included cytokines, chemokines, and their respective receptors, acute-phase transcription factors, proteases, arachidonate metabolites, and oxidases. Repressed defense response genes included those associated with co-stimulatory molecules, T and cytotoxic lymphocytes, natural killer (NK) cells, and protein synthesis. Gene expression profiles of whole blood had similar biological themes. Over 100 genes not typically associated with acute inflammation were differentially regulated after endotoxin. By 24 h, gene expression had returned to baseline values. Thus the inflammatory response of circulating leukocytes to endotoxin in humans is characterized by a rapid amplification and subsidence of gene expression. These results indicate that a single intravascular exposure to endotoxin produces a large but temporally short perturbation of the blood transcriptome.

Functional characterization of human cysteinyl leukotriene 1 receptor gene structure

The 5-lipoxygenase pathway has been strongly implicated in the pathogenesis of chronic inflammatory disorders, such as bronchial asthma and atherosclerosis. Cysteinyl leukotrienes (cysLTs), 5-lipoxygenase pathway products, are recognized now not only as important factors in asthmatic inflammation, but also as mediators of cell trafficking and innate immune responses. To study a role of cysLTs in inflammatory reactions we have characterized the gene structure of human cysteinyl leukotriene receptor type I (cysLT(1)R). The cysLT(1)R gene consists of 5 exons that are variably spliced and a single promoter region with multiple transcription start sites. Four different cysLT(1)R transcripts were identified. RT-PCR showed dominant and wide expression of the transcript I, containing exons 1, 4, and 5, with the strongest presence in blood leukocytes, spleen, thymus, lung, and heart. The expression of cysLT(1)R is functionally regulated at the transcriptional level by IL-4 through a STAT6 response element localized to the proximal cysLT(1)R promoter region. IL-4 stimulation increased cysLT(1)R mRNA (real-time PCR) and surface protein expression (flow cytometry) in a time-dependent fashion. CysLTs (LTD(4) and LTC(4)) induced an increased production of a potent monocyte chemoattractant CCL2 (MCP-1) in IL-4-primed THP-1 cells in a dose-dependent manner. This effect was effectively inhibited by the cysLT(1)R-selective antagonist MK571 in a dose-dependent manner and only partially by a nonselective cysLT(1)R/cysLT(2)R inhibitor BAY-u9773, implying a cysLT(1)R-mediated mechanism. Thus, cysLTs signaling through cysLT(1)R might contribute to inflammatory reactions by cooperating with IL-4 in enhanced CCL2 production in human monocytic cells.

Influence of IFN-gamma on gene expression in normal human bronchial epithelial cells: modulation of IFN-gamma effects by dexamethasone

Interferon gamma (IFN-gamma) plays a role in a variety of lung inflammatory responses, and corticosteroids are frequently employed as a treatment in these conditions. Therefore, the effect of IFN-gamma, of the corticosteroid dexamethasone (Dex), or of both on gene expression was studied in normal human bronchial epithelial (NHBE) cells. NHBE cells were exposed to medium alone, IFN-gamma (300 U/ml), Dex (10(-7) M), or both IFN-gamma and Dex for 8 or 24 h. Gene expression was examined using oligonucleotide microarrays. A principal components analysis demonstrated that the IFN-gamma treatment effect was the primary source of differences in the data. With a 5% false discovery rate, of the 66 genes upregulated by IFN-gamma by twofold or greater at 8 h and 287 genes upregulated at 24 h, coincubation with Dex inhibited the expression of 2 genes at 8 h and 45 genes at 24 h. Prominent among these were cytokines and secreted proteins. Dex cotreatment increased expression of 65 of the 376 genes that were inhibited by IFN-gamma by 50% at 24 h. The majority of these genes encode cell cycle or nuclear proteins. Dex alone increased the expression of only 22 genes and inhibited the expression of 7 genes compared with controls at 24 h. The effect of Dex on IFN-gamma-induced changes suggests a specific, targeted effect on IFN-gamma responses that is substantially greater than the effect of Dex alone. Dex had little effect on the immediate early response to IFN-gamma but a significant effect on the late responses.

The role of TFIID, the initiator element and a novel 5' TFIID binding site in the transcriptional control of the TATA-less human cytosolic phospholipase A2-alpha promoter

Human cytosolic phospholipase A2-alpha (cPLA2-alpha) is a critical enzyme in the liberation of arachidonic acid (AA) from cellular membranes and the subsequent formation of prostaglandins (PGs), leukotrienes (LTs), hydroxyeicosatetraenoic acids (HETEs) and platelet activating factor in many different cell types. Much is known of the effect of posttranslational phosphorylation and calcium binding events on the enzymatic activity of cPLA2-alpha, but to date little is known about its specific transcriptional control. Through the use of reporter gene constructs and eletrophoretic mobility shift assays (EMSAs), this study determined the minimal promoter required for basal transcriptional activity of the human cPLA2-alpha promoter to include base pairs -40 through the transcription start site (TSS). In addition, it confirms the importance of an initiator (Inr) element at the TSS by deletion reporter gene analysis, and further identifies bases -3 (C) and -2 (T) as critical bases in the Inr function by mutation reporter gene analysis. Finally, this study describes a novel AAGGAG motif at -30 to -35 which is bound by TATA-box binding protein (TBP) and is critical for basal transcriptional activity.

Cytosolic phospholipase A2 Group IValpha but not secreted phospholipase A2 Group IIA, V, or X induces interleukin-8 and cyclooxygenase-2 gene and protein expression through peroxisome proliferator-activated receptors gamma 1 and 2 in human lung cells

It has been reported that interleukin-8 (IL-8) and cyclooxygenase-2 (COX-2) expression is regulated by peroxisome proliferator-activated receptor (PPAR)-gamma synthetic ligands. We have shown previously that cytosolic phospholipase A2 (cPLA2) is able to activate gene expression through PPAR-gamma response elements (Pawliczak, R., Han, C., Huang, X. L., Demetris, A. J., Shelhamer, J. H., and Wu, T. (2002) J. Biol. Chem. 277, 33153-33163). In this study we investigated the influence of cPLA2 and secreted phospholipase A2 (sPLA2) Group IIA, Group V, and Group X on IL-8 and COX-2 expression in human lung epithelial cells (A549 cells). We also studied the results of cPLA2 activation by epidermal growth factor (EGF) and calcium ionophore (A23187) on IL-8 and COX-2 reporter gene activity, mRNA level, and protein synthesis. cPLA2 overexpression and activation increased both IL-8 and COX-2 reporter gene activity. Overexpression and activation of Group IIA, Group V, or Group X sPLA2s did not increase IL-8 and COX-2 reporter gene activity. Methyl arachidonyl fluorophosphate, a cPLA2 inhibitor, inhibited the effect of A23187 and of EGF on both IL-8 and COX-2 reporter gene activity, steady state levels of IL-8 and COX-2 mRNA, and IL-8 and COX-2 protein expression. Small inhibitory RNAs directed against PPAR-gamma1 and -gamma2 blunted the effect of A23187 and of EGF on IL-8 and COX-2 protein expression. Moreover small inhibitory RNAs directed against cPLA2 decreased the effect of A23187 and EGF on IL-8 and COX-2 protein expression. These results demonstrate that cPLA2 has an influence on IL-8 and COX 2 gene and protein expression at least in part through PPAR-gamma.

Blood mononuclear cell gene expression profiles characterize the oxidant, hemolytic, and inflammatory stress of sickle cell disease

In sickle cell disease, deoxygenation of intra-erythrocytic hemoglobin S leads to hemoglobin polymerization, erythrocyte rigidity, hemolysis, and microvascular occlusion. Ischemia-reperfusion injury, plasma hemoglobin-mediated nitric oxide consumption, and free radical generation activate systemic inflammatory responses. To characterize the role of circulating leukocytes in sickle cell pathogenesis we performed global transcriptional analysis of blood mononuclear cells from 27 patients in steady-state sickle cell disease (10 patients treated and 17 patients untreated with hydroxyurea) compared with 13 control subjects. We used gender-specific gene expression to validate human microarray experiments. Patients with sickle cell disease demonstrated differential gene expression of 112 genes involved in heme metabolism, cell-cycle regulation, antioxidant and stress responses, inflammation, and angiogenesis. Inducible heme oxygenase-1 and downstream proteins biliverdin reductase and p21, a cyclin-dependent kinase, were up-regulated, potentially contributing to phenotypic heterogeneity and absence of atherosclerosis in patients with sickle cell disease despite endothelial dysfunction and vascular inflammation. Hydroxyurea therapy did not significantly affect leukocyte gene expression, suggesting that such therapy has limited direct anti-inflammatory activity beyond leukoreduction. Global transcriptional analysis of circulating leukocytes highlights the intense oxidant and inflammatory nature of steady-state sickle cell disease and provides insight into the broad compensatory responses to vascular injury.

Interferon-gamma induces p11 gene and protein expression in human epithelial cells through interferon-gamma-activated sequences in the p11 promoter

The effect of interferon (IFN)-gamma on p11 expression was studied in two human epithelial cell lines (BEAS-2B and HeLa). Treatment with IFN-gamma resulted in increased steady-state levels of p11 mRNA and protein expression, with a time-dependent and dose-dependent effect. Transient transfection experiments of a reporter gene construct containing 1498 bp of the 5'-flanking region of the p11 promoter demonstrated that IFN-gamma induced p11 gene expression at the transcriptional level. These effects were inhibited at the promoter and protein levels by a specific JAK-2 kinase inhibitor, AG-490. Functional analysis of the p11 promoter indicates that two gamma-activated sequence elements (GAS) located at positions 1219 and 1090 are important for the induction of the p11 promoter by IFN-gamma. Transfection of mutated reporter constructs demonstrated that the mutation at the GAS-2 site (1090) inhibited the p11 promoter activity, with a reduction of about approximately 73% and mutation at the GAS-3 site (1219) eliminated about 26% of the p11 promoter activity. A STAT1 dominant negative mutant vector at Tyr-701 (JAK kinase phosphorylation site) blocked the effect of IFN-gamma on the p11 promoter activity. IFN-gamma induced a rapid tyrosine phosphorylation and nuclear translocation of STAT1 protein, which is involved in the binding to the GAS-2 site in the p11 promoter by EMSA analysis. These data suggest that IFN-gamma-induced p11 expression is mediated through the binding of STAT1 to GAS sites in the p11 promoter. Inhibition of p11 expression by inhibitory antisense RNAs (iRNA) treatment resulted in enhanced IFN-gamma and calcium ionophore-stimulated arachidonic acid release suggesting that at least in part IFN-gamma-stimulated p11 expression may serve a counterregulatory role.

Oxidant-induced cell death in respiratory epithelial cells is due to DNA damage and loss of ATP

Oxidative stress is considered to be an important pathogenic event in ischemia-reperfusion injury, leading to apoptosis or necrosis. We show acute cytotoxicity upon exposure to hydrogen peroxide (H(2)O(2)) in BEAS-2B cells and A549 cells. Single-cell gel electrophoresis showed formation of large comet tails from DNA upon oxidant exposure suggestive of DNA damage. The ATP content of the cells decreased upon exposure to H(2)O(2). Preincubation with 3-aminobenzamide (3-ABA), an inhibitor of poly (ADP-ribosyl) polymerase (PARP), prevented the cytotoxicity. The decrease in the ATP content of the cells was also prevented by 3-ABA. Increase in PARP activity was further confirmed by measuring incorporation of [(32)P]-NAD into nuclear proteins in presence of the cell extracts. Markers of apoptosis were not seen in cells treated with H(2)O(2) with or without 3-ABA pretreatment. These studies suggest that DNA damage is one of the primary reasons for oxidant-induced cell death and that PARP plays an important role in cell death due to its consumption of ATP. Further elaboration of this and other pathways that consume ATP may help prevent oxidant-mediated acute lung injury.

Epidermal growth factor induces p11 gene and protein expression and down-regulates calcium ionophore-induced arachidonic acid release in human epithelial cells

p11, a member of the S-100 family of proteins, is the cellular ligand of annexin II and also interacts with the C-terminal region of cytosolic phospholipase A(2) (cPLA(2)), inhibiting cPLA(2) activity and arachidonic acid (AA) release. It has been reported that epidermal growth factor (EGF) induces cPLA(2) activation or cPLA(2) expression and subsequent AA release. It was of interest to study the effect of EGF on p11 production and on AA release in human epithelial cells (HeLa). EGF (20 ng/ml) treatment of HeLa cells increased the cellular p11 protein and the steady-state levels of p11 mRNA in a time- and dose-dependent manner but did not affect cPLA(2) protein expression over a 4-48-h incubation time. Transient transfection experiments of a reporter gene construct containing 1498 bp of the 5'-flanking region of p11 promoter demonstrated that EGF induced p11 gene expression at the transcriptional level. EGF caused a rapid phosphorylation of p44/42 and p38 kinases with a maximum level at 10 min. AG 1478 (EGF receptor tyrosine kinase inhibitor), PD 98059 (ERK1/2 inhibitor), and SB 203580 (p38 inhibitor) significantly inhibited EGF-induced p11 expression. EGF-induced AA release was significantly suppressed by AG 1478, PD 98059, SB 203580, and methyl arachidonyl fluorophosphate (a specific cPLA(2) inhibitor). Methyl arachidonyl fluorophosphate (50 microm) also significantly inhibited EGF-induced p11 expression, demonstrating that the activation of cPLA(2) may have a role in the EGF-induced p11 expression. Immunoprecipitation experiments showed that EGF induced increased p11 binding to cPLA(2) in a time- and dose-dependent manner. EGF treatment for 30 min increased -induced AA release, whereas EGF treatment for 24 h inhibited -induced AA release. These results suggest that EGF treatment increased p11 bound to cPLA(2) may lead to the late suppression of AA release induced by EGF.

p11 expression in human bronchial epithelial cells is increased by nitric oxide in a cGMP-dependent pathway involving protein kinase G activation

The effect of nitric oxide on p11 expression was studied in an immortalized human bronchial epithelial cell line (BEAS-2B cells). Three nitric oxide donors were used: spermine NONOate (SP), (+/-)-S-nitroso-N-acetylpenicillamine (SNAP), and S-nitrosoglutathione (SNOG). All three nitric oxide donors had similar effects resulting in dose-dependent and time-dependent accumulation of p11 protein and an increase of steady-state p11 mRNA. Studies using a reporter gene containing the region from -1499 to +89 of the p11 promoter demonstrated an increase in transcriptional activity after stimulation with NO donors for 4 h. These effects were abolished at the promoter and protein level using protein kinase G inhibitors (KT5823 and R(p)-8-pCPT-cGMPS). Incubation of transfected cells with a cell permeable cGMP analogue (8-Br-cGMP) resulted in a dose-related increase of promoter activity. An electrophoretic mobility shift assay of nuclear proteins extracted from BEAS-2B cells identified an AP-1 site located at -82 to -77 of the p11 promoter region as an NO- and cGMP- dependent response element. These data were confirmed using a c-jun dominant negative mutant vector and a c-jun expression plasmid. Therefore, we conclude that nitric oxide-induced p11 expression in human bronchial epithelial cells is mediated at least in part through increased binding of activator protein one to the p11 promoter.

Prostaglandin E(2)-induced interleukin-6 release by a human airway epithelial cell line

Human airway epithelial cell release of interleukin (IL)-6 in response to lipid mediators was studied in an airway cell line (BEAS-2B). Prostaglandin (PG) E(2) (10(-7) M) treatment caused an increase in IL-6 release at 2, 4, 8, and 24 h. IL-6 release into the culture medium at 24 h was 3,396 +/- 306 vs. 1,051 +/- 154 pg/ml (PGE(2)-treated cells vs. control cells). PGE(2) (10(-7) to 10(-10) M) induced a dose-related increase in IL-6 release at 24 h. PGF(2 alpha) (10(-6) M) treatment caused a similar effect to that of PGE(2) (10(-7) M). PGE(2) analogs with relative selectivity for PGE(2) receptor subtypes were studied. Sulprostone, a selective agonist for the EP-3 receptor subtype had no effect on IL-6 release. 11-Deoxy-16,16-dimethyl-PGE(2), an EP-2/4 agonist, and 17-phenyl trinor PGE(2), an agonist selective for the EP-1 > EP-3 receptor subtype (10(-6) to 10(-8) M), caused dose-dependent increases in IL-6 release. 8-Bromo-cAMP treatment resulted in dose-related increases in IL-6 release. RT-PCR of BEAS-2B cell mRNA demonstrated mRNA for EP-1, EP-2, and EP-4 receptors. After PGE(2) treatment, increases in IL-6 mRNA were noted at 4 and 18 h. Therefore, PGE(2) increases airway epithelial cell IL-6 production and release.

Retinoic acid reduces p11 protein levels in bronchial epithelial cells by a posttranslational mechanism

p11 is a member of the S100 family of proteins, is the cellular ligand of annexin II, and interacts with the carboxyl region of 85-kDa cytosolic phospholipase A(2) (cPLA(2)), inhibiting cPLA(2) activity and arachidonic acid (AA) release. We studied the effect of retinoic acid (RA) on PLA(2) activity in human bronchial epithelial cells and whether p11 contributes to these effects. The addition of 10(-6) M RA resulted in reduced p11 protein levels at 4 days, with the greatest effect observed on days 6 and 7. This effect was dose related (10(-6) to 10(-9) M). RA treatment (10(-6) M) had no effect on cPLA(2) protein levels. p11 mRNA levels were unchanged at 6 and 8 days of treatment (correlating with maximum p11 protein reduction). Treatment with RA reduced p11 levels in control cells and in cells transfected with a p11 expression vector, suggesting a posttranslational mechanism. Lactacystin (10(-6) M), an inhibitor of the human 26S proteasome, blocked the decrease in p11 observed with RA treatment. Compared with control cells (n = 3), RA-treated cells (n = 3) had significantly increased AA release after treatment with the calcium ionophore A-23187 (P = 0.006). Therefore, RA reduces p11 protein expression and increases PLA(2) activity and AA release.

Tumor necrosis factor-alpha stimulates human Clara cell secretory protein production by human airway epithelial cells

Clara cell secretory protein (CCSP), or CC10, is an inhibitor of secretory phospholipase A2 which may be produced by phagocytic cells and by a variety of other cells in the airway. Tumor necrosis factor-alpha (TNF-alpha) is capable of activating phospholipases and inducing the expression of a variety of genes in the airway epithelium which may modulate the airway inflammatory response. Therefore, it was of interest to determine whether this proinflammatory cytokine could induce the production of a counterregulatory protein such as CCSP which might modulate the production of eicosanoid mediators in the airway. Using a human bronchial epithelial cell line (BEAS-2B), CCSP messenger RNA (mRNA) levels were detected by ribonuclease protection assay. TNF treatment of these cells increased CCSP mRNA levels in a time- and dose-dependent manner. The CCSP mRNA level increased in response to TNF-alpha (20 ng/ml) stimulation after 8 to 36 h with the peak increase at 18 h. Immunoblotting of CCSP protein released into the culture media demonstrated that TNF-alpha induced the synthesis and secretion of CCSP protein in a time-dependent manner over 8 to 18 h. The results of a CCSP reporter gene activity assay, nuclear run-on assay, and CCSP mRNA half-life assay indicated that the TNF-alpha-induced increases in CCSP gene expression are regulated at the post-transcriptional level. We conclude that TNF-alpha induces airway epithelial cell expression of human CCSP protein and may modulate airway inflammatory responses in this manner.

Interferon-gamma stimulates human Clara cell secretory protein production by human airway epithelial cells

Clara cell secretory protein (CCSP) is an inhibitor of secretory phospholipase A2. It is produced by airway epithelial cells and is present in airway secretions. Because interferon (IFN)-gamma can induce gene expression in airway epithelial cells and may modulate the inflammatory response in the airway, it was of interest to study the effect of this cytokine on epithelial cell CCSP mRNA expression and CCSP protein synthesis. A human bronchial epithelial cell line (BEAS-2B) was used for this study. CCSP mRNA was detected by ribonuclease protection assay. IFN-gamma was found to increase CCSP mRNA expression in a time- and dose-dependent manner. The CCSP mRNA level increased after IFN-gamma (300 U/ml) treatment for 8-36 h, with the peak increase at 18 h. Immunobloting of CCSP protein also demonstrated that IFN-gamma induced the synthesis and secretion of CCSP protein in a time-dependent manner. Nuclear run-on, CCSP reporter gene activity assay, and CCSP mRNA half-life assay demonstrated that IFN-gamma-induced increases in CCSP gene expression were mediated, at least in part, at the posttranscriptional level. The present study demonstrates that IFN-gamma can induce increases in steady-state mRNA levels and protein synthesis of human CCSP protein in airway epithelial cells and may modulate airway inflammatory responses in this manner.

Antisense inhibition of 85-kDa cPLA2 blocks arachidonic acid release from airway epithelial cells

Inflammatory cytokines play a critical role in the initiation and perpetuation of inflammation. Several cytokines are known to increase the production of arachidonic acid (AA) metabolites, which may mediate cytokine-induced acute and chronic inflammation. Although cytokines upregulate phospholipase A2 (PLA2) in several target cells, the contribution of individual PLA2 to cytokine-induced AA release and eicosanoid production remains unclear because of the existence of various forms of cellular PLA2. To examine the role of 85-kDa cytosolic PLA2 (cPLA2) in cytokine-induced AA release, a system was developed to inhibit the expression of cPLA2 in a human bronchial epithelial cell line (BEAS-2B cells) by antisense RNA. Cells stably expressing antisense cPLA2 exhibited decreased cPLA2 protein levels as well as decreased cPLA2 activity assayed in vitro. The effects of cytokines interferon-gamma (IFN-gamma), tumor necrosis factor-alpha (TNF-alpha), and interleukin-1 alpha (IL-1 alpha) on the release of prelabeled [3H]AA were then tested in cells stably transfected with vector alone as well as cells transfected with cPLA2 antisense plasmid. IFN-gamma (300 U/ml), TNF-alpha (20 ng/ml), and IL-1 alpha (20 ng/ml) all induced a significantly increased release of prelabeled [3H]AA after 15 min to 2 h of treatment in control cells, and their effects were significantly reduced in cells transfected with cPLA2 antisense vector. These results demonstrate a critical role of cPLA2 in inflammatory cytokine-induced AA metabolism.

P11, a unique member of the S100 family of calcium-binding proteins, interacts with and inhibits the activity of the 85-kDa cytosolic phospholipase A2

Using a two hybrid system screen of a human cDNA library, we have found that p11, a unique member of the S100 family of calcium-binding proteins, interacts with the carboxyl region of the 85-kDa cytosolic phospholipase A2 (cPLA2). p11 synthesized in a cell-free system interacts with cPLA2 in vitro. The p11-cPLA2 complex is detectable from a human bronchial epithelial cell line (BEAS 2B). Furthermore, p11 inhibits cPLA2 activity in vitro. Selective inhibition of p11 expression in the BEAS 2B cells by antisense RNA results in an increased PLA2 activity as well as an increased release of prelabeled arachidonic acid. This study demonstrates a novel mechanism for the regulation of cPLA2 by an S100 protein.

Vasoactive intestinal peptide (VIP) induces IL-6 and IL-8, but not G-CSF and GM-CSF release from a human bronchial epithelial cell line

Vasoactive intestinal polypeptide (VIP) is a 28-amino acid neuropeptide with vasodilator, bronchodilator, and anti-inflammatory effects. Little is known about pro-inflammatory effects of VIP. We investigated the effect of VIP on the secretion of IL-6, IL-8, GM-CSF, and G-CSF from a bronchial epithelial cell line (BEAS 2B). The incubation of BEAS-2B cells with VIP in concentrations of 10(-13) to 10(-7) M for 4 h, caused dose-related increases of IL-6 (98% increase above control, P < 0.001) and IL-8 (35% increase above control, P < 0.01). After 4 h of incubation, 10(-7) M PHI also increased IL-6 release by 74% (P < 0.01). After 8 h of incubation, VIP increased IL-6 release by 59% (P < 0.01), causing no effect on IL-8 release. After 24 h of incubation, VIP increased the release of IL-6 by 48% (P < 0.05) and IL-8 by 45% (P < 0.05). Ribonuclease protection assays for steady-state IL-6 mRNA revealed that increases in response to VIP stimulation occurred by 1 h and persisted through 16 h of stimulation. VIP had no significant effect on the release of G-CSF and GM-CSF. VIP did not induce cell proliferation at 24 and 48 h. These findings suggest that VIP can alter epithelial cell cytokine release and might be capable of modulating the airway inflammatory response in this manner.

Leukemia inhibitory factor induces the 85-kDa cytosolic phospholipase A2 gene expression in cultured human bronchial epithelial cells

Leukemia inhibitory factor (LIF) has become increasingly recognized as an important regulator of inflammation. This study is designed to determine whether LIF has an effect on arachidonate metabolism in human airway epithelial cells. LIF (100 ng/ml) induced a significantly increased release of prelabeled [3H] arachidonic acid (AA) from the human bronchial epithelial cell line (BEAS 2B cell) as well as from the primary cultures of human bronchial epithelial cells. Exposure of the LIF stimulated BEAS 2B cells to calcium ionophore A23187 (10(-5) M, 15 min) caused a further increase of [3H]AA release. To identify the role of cytosolic phospholipase A2 (cPLA2) in this upregulation of AA release, further experiments were performed to determine the expression of cPLA2 in the BEAS 2B cells. Immunoblot analysis indicated that LIF increased cPLA2 protein expression. Ribonuclease protection assay showed that LIF induced an increase of cPLA2 mRNA levels following 3 h to 24 h treatment. Nuclear run-on experiments suggested that LIF upregulated cPLA2 gene expression through post-translational regulation. These results demonstrate that LIF induces cPLA2 gene expression and modulates arachidonate metabolism in airway epithelial cells.

Endothelin-1 induces GM-CSF, IL-6 and IL-8 but not G-CSF release from a human bronchial epithelial cell line (BEAS-2B)

Endothelin (ET) is a powerful vasoconstrictor and bronchoconstrictor peptide that may be involved in the pathogenesis of bronchial asthma. We have investigated the effect of ET on the secretion of IL-6, IL-8, GM-CSF and G-CSF in a bronchial epithelial cell line (BEAS-2B). Incubation of BEAS-2B cells with ET-1 (10(-13) to 10(-7) M) for 4 h caused dose-related increases in the release of IL-8 (68% increase above control, P < 0.001) and IL-6 (43% increase above control, P < 0.001), compared to untreated control cells. After 48 h incubation, ET-1 also increased the release of IL-8 by 35% (P < 0.001) and GM-CSF by 38% (P < 0.01). ET-1 had no significant effect on G-CSF release. ET-1 did not induce cell proliferation at 24 or 48 h. Since ET-immunoreactive materials are expressed in epithelial cells in asthma, it is possible that ET-1 of epithelial origin may act in a paracrine or autocrine fashion on airway epithelial ET receptors to stimulate IL-8, IL-N6 and GM-CSF release. Thus, ET-1 may play a role in the regulation of the cytokine responses involved in inflammation of the airway mucosa.

Protein kinase C, interleukin-1 beta, and corticosteroids regulate shedding of the type I, 55 kDa TNF receptor from human airway epithelial cells

Tumor necrosis factor (TNF) may contribute to the pathogenesis of inflammatory airway disorders via the regulation of inflammatory and cellular immune responses. Shed cell surface TNF receptors can act as soluble TNF binding proteins and modulate TNF biological activity. We report that normal human airway epithelial cells, as well as two human airway epithelial cell lines, shed soluble type I TNF receptors (sTNF-RI) in a concentration-dependent fashion following protein kinase C (PKC) activation by PMA. Interleukin (IL)-1beta also induced concentration-dependent sTNF-RI shedding from NCI-H292 cells, which could be inhibited by the PKC inhibitor calphostin C. Since corticosteroids are commonly utilized as antiinflammatory agents in airway disorders, the effect of dexamethasone on sTNF-RI release was assessed. Dexamethasone inhibited constitutive, as well as PMA- and IL-1beta-mediated sTNF-RI release from NCI-H292 cells in a concentration-dependent fashion. Furthermore, dexamethasone increased while PMA decreased total cellular 55 kDa TNF-RI protein as detected by immunoblotting. These changes in total cellular 55kDa TNF-RI protein did not appear to be mediated at the mRNA level, as assessed by ribonuclease protection assays. This suggests that sTNF-RI shedding represents a mechanism by which airway epithelial cells can actively participate in local cytokine networks and modulate TNF-mediated inflammation. Furthermore, since corticosteroids inhibit sTNF-RI release and are known to downregulate TNF synthesis, this may represent a mechanism by which equilibrium between TNF ligand and soluble binding protein is maintained in the airway microenvironment.

Platelet-activating factor stimulates eicosanoid production in cultured feline tracheal epithelial cells

The effect of platelet-activating factor (PAF) on eicosanoid generation and release in cultured feline tracheal epithelial cells was investigated by measuring a wide range of lipoxygenase and cyclooxygenase pathway products. Subconfluent epithelial cell cultures were stimulated by PAF and eicosanoid production was determined by high performance liquid chromatography (HPLC) of [3H]-labeled arachidonic acid (AA) metabolites and by radioimmunoassay (RIA) following HPLC separation. The HPLC chromatograms revealed that PAF augmented the release of prostaglandin (PG)E2, PGF2 alpha, 12-hydroxyeicosatetraenoic acid (HETE), and AA. Among these eicosanoids, PGE2 predominated under baseline conditions and following PAF exposure. RIAs of the nonradiolabeled HPLC elution corresponding to various eicosanoid standards demonstrated that PAF increased the production of 6-keto-PGF1 alpha, thromboxane B2 (TXB2), PGD2, 5-HETE, and 15-HETE, as well as PGE2, PGF2 alpha, and 12-HETE. The PAF-induced eicosanoid augmentation was dose-dependent and occurred within 1 hour with a prompt decline following termination of PAF exposure. This stimulating effect of PAF on eicosanoid release was blocked by two PAF receptor antagonists, Ro 19-3704 and WEB 2086. The PAF-induced increase in eicosanoid release was similar in magnitude to the increase caused by calcium ionophore (Ca-ionophore) A23187, a potent known stimulus for eicosanoid release. Cells of different culture durations (3 and 6 days) showed similar capacity for eicosanoid production. We conclude that PAF stimulates the production of cyclooxygenase and lipoxygenase pathway products from airway epithelial cells via PAF receptors, and that these epithelium-derived eicosanoids may be responsible for some of the PAF-induced respiratory physiological and pathophysiological effects.

Tumor necrosis factor-alpha induces mucin hypersecretion and MUC-2 gene expression by human airway epithelial cells

Tumor necrosis factor-alpha (TNF-alpha) is a multifunctional, proinflammatory cytokine that is capable of activating a diverse number of target genes within multiple cell types. Little information is known regarding the role of TNF-alpha in the regulation of human airway mucin hypersecretion and MUC-2 gene expression. To assess the effect of TNF-alpha exposure on mucin secretion, human airway organ cultures and primary cultures of human airway epithelial cells were stimulated with 20 ng/ml of recombinant human TNF-alpha and mucin secretion quantitated by an enzyme-linked immunosorbent assay using a specific monoclonal antibody directed against human airway mucin. Significant increases in mucin secretion from human airway organ cultures were initially detected at 1 h, peaked at 8 h, and persisted for 24 h. The TNF-alpha-mediated mucin hypersecretion at 8 h was concentration dependent. Significant increases in mucin secretion from primary cultures of human airway epithelial cells were initially detected at 4 h, peaked at 48 h, and persisted for 72 h after stimulation with 20 ng/ml of recombinant human TNF-alpha. The TNF-alpha-mediated mucin hypersecretion at 48 h from primary cultures of human airway epithelial cells was inhibited by coincubation with soluble 55 kD, type I TNF receptors. Using reverse transcription-polymerase chain reaction and a human pulmonary mucoepidermoid carcinoma cell line (NCI-H292), increases in MUC-2 steady-state mRNA levels were first detectable after 30 min of TNF-alpha stimulation and persisted for 24 h. Cycloheximide did not inhibit TNF-alpha-mediated MUC-2 mRNA expression at 1 h, suggesting that new protein translation was not required.(ABSTRACT TRUNCATED AT 250 WORDS)

Platelet-activating factor induces airway mucin release via activation of protein kinase C: evidence for translocation of protein kinase C to membranes

Platelet-activating factor (PAF), a proinflammatory lipid mediator, is a potent airway mucin secretagogue. This study assessed the role of protein kinase C (PKC) in PAF-induced mucin release from primary cultures of feline tracheal epithelial cells (FTEC). Mucin secretion was quantitated by enzyme-linked immunosorbent assay using a monoclonal antibody raised against airway mucin-type glycoproteins. Coincubation of FTEC with PAF (5 microM) and pharmacologic PKC inhibitors, sphingosine, H7, or calphostin C, inhibited PAF-induced mucin secretion at 30 min. The PKC inhibitors produced a concentration-dependent, noncytotoxic inhibition. Exposure of FTEC with the PKC activator phorbol 12-myristate 13-acetate (PMA), failed to increase the release of mucin. Stimulation of FTEC with PAF caused a transient increase of membrane-bound PKC activity after 5 min of stimulation. PMA also induced the translocation of PKC activity from the cytosol to the membrane fraction, which was still present after 15 min of exposure. Determination of the specific PKC isozyme(s) involved in PAF-induced mucin release was performed by immunoblot analysis of the subcellular fractions using a battery of antibodies against various PKC isozymes (anti-PKC alpha, beta, delta, gamma, epsilon, and zeta). We found that PKC zeta (mol wt approximately 70 kD) was a major identifiable PKC isozyme present in the cytosolic fraction of FTEC. Furthermore, PKC zeta isozyme was also found to translocate to the membrane fraction following PAF exposure. Thus, these results demonstrate the crucial role of PKC in the intracellular events that culminate in mucin release following PAF stimulation.(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of neutrophil protenase enzymes on the release of mucus from feline and human airway cultures

Neutrophils may be central in the pathogenesis of several airway diseases. The effect of two neutrophil products upon mucus release from feline and human airways was examined in vitro. Neutrophil elastase (HNE) and cathepsin G (HCG) were equipotent in stimulating mucus release from feline trachea. A potential mechanism of the mucus release was studied by exposure to HNE and various inhibitors of serine proteases or eicosanoid metabolism. Coincubation with the serine protease inhibitor, chloromethylketone, completely blocked HNE-stimulated mucus release. The putative selective cyclooxygenase inhibitor, ibuprofen, did not alter HNE-stimulated mucus release. The phospholipase A2 inhibitor, bromophenacyl bromide, and various lipoxygenase inhibitors blocked HNE-stimulated mucus release by 30-40%. The effect of HNE upon mucus release from human upper and lower airways was also examined. HNE stimulated greater mucus release from human bronchi than from nasal mucosa. The cellular source of the mucus was investigated in feline trachea and human upper airway by quantitation of mucus using enzyme assays for a specific mucous cell marker (monoclonal antibody 7F-10). HNE stimulated the release of 7F-10 detectable mucus, and after coincubation with chloromethylketone this stimulation was blocked. These data demonstrate that neutrophil products may alter airway mucus secretion and that altered eicosanoid metabolism may partially mediate these effects. Additionally, the lower airways appear more responsive to HNE than upper airways.

Interferon-gamma induces the synthesis and activation of cytosolic phospholipase A2

Both IFN-alpha/beta and IFN-gamma have recently been demonstrated to induce a rapid but transient activation of phospholipase A2 (PLA2) in BALB/c 3T3 fibroblasts and a human neuroblastoma cell line. We report that IFN-gamma induces the synthesis and prolonged activation of cytosolic phospholipase A2 (cPLA2) in a human bronchial epithelial cell line (BEAS 2B). Treatment of the cells with IFN-gamma (300 U/ml) increased the release of [3H]arachidonic acid (AA) from prelabeled cells with a maximal effect at 12 h after stimulation. The increased [3H]AA release was inhibited by the PLA2 inhibitor p-bromophenacyl bromide (10(-5) M). Calcium ionophore A23187 (10(-5) M) further increased the [3H]AA release from the IFN-gamma-treated cells. Subcellular enzyme activity assay revealed that IFN-gamma increased PLA2 activity in both the cytosol and membrane fractions with a translocation of the cPLA2 to cell membranes in a Ca(2+)-free cell lysing buffer. Treatment with IFN-gamma also induced the release of 15-HETE, an arachidonic acid metabolite. Immunoblot showed that IFN-gamma induced the synthesis of cPLA2 protein. Nuclear run-on assay demonstrated that IFN-gamma initiated cPLA2 gene transcription within 15 min, and this effect was sustained at 4 h and returned to near control level at 12 h. The cPLA2 mRNA level was assayed by reverse transcription and PCR. IFN-gamma was found to increase the cPLA2 mRNA after 2-24 h treatment. Furthermore, the IFN-gamma induced cPLA2 mRNA increase was blocked by inhibitors of protein kinase C and calcium/calmodulin-dependent protein kinases, suggesting the involvement of these protein kinases in IFN-gamma-induced gene expression of cPLA2. This study shows that IFN-gamma induces the synthesis and prolonged activation of cPLA2.

Corticosteroids differentially regulate secretion of IL-6, IL-8, and G-CSF by a human bronchial epithelial cell line

Human airway epithelial cells play an active role in modulating airway inflammation by elaborating a variety of proinflammatory molecules, including cytokines. The purpose of this study was to define the role of corticosteroids in the regulation of cytokine gene transcription and secretion by human bronchial epithelial cells. In particular, we assessed whether dexamethasone was capable of inhibiting the tumor necrosis factor-alpha (TNF-alpha)-mediated secretion of interleukin-6 (IL-6), interleukin-8 (IL-8), and granulocyte colony-stimulating factor (G-CSF) by a human bronchial epithelial cell line (BEAS-2B). Stimulation with 20 ng/ml of TNF-alpha resulted in significant increases in secretion of immunoreactive IL-6, IL-8, and G-CSF that were maximal at 24 h. TNF-alpha-mediated IL-6, IL-8, and G-CSF secretion was concentration dependent and specific. In addition, stimulation with TNF-alpha resulted in significant increases in the quantity of IL-6, IL-8, and G-CSF mRNA as detected by reverse-transcription polymerase chain reaction. Dexamethasone preconditioning significantly inhibited both the secretion of immunoreactive IL-6 and the accumulation of IL-6 mRNA. Although dexamethasone appeared to reduce both the secretion of immunoreactive IL-8 and accumulation of IL-8 mRNA, the inhibitory effects did not reach statistical significance. Finally, dexamethasone did not inhibit either the secretion of immunoreactive G-CSF or the accumulation of G-CSF mRNA. In summary, our results suggest that corticosteroids have a differential effect on the regulation of cytokine secretion by human bronchial epithelial cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Production of eicosanoids in response to endothelin-1 and identification of specific endothelin-1 binding sites in airway epithelial cells

The effect of endothelin-1 (ET-1) on arachidonate metabolism in the respiratory epithelium was investigated in primary cultures of feline tracheal epithelial cells. Subconfluent epithelial cell cultures were stimulated by ET-1, and eicosanoid generation was determined by high performance liquid chromatography (HLPC) of 3H-labeled arachidonic acid (AA) metabolites and by radioimmunoassay (RIA) of corresponding nonradiolabeled HPLC elution. The HPLC chromatograms of [3H]AA-prelabeled samples revealed that ET-1 (10(-5) M) augmented the release of prostaglandin (PG) E2, 12-hydroxyeicosatetraenoic acid (HETE), PGF2 alpha, and AA. RIA of corresponding nonradiolabeled HPLC elution demonstrated a significantly increased release of PGE2, PGF2 alpha, and 12-HETE as well as 5-HETE in response to ET-1 stimulation. 5-HETE release from ET-1-stimulated cells was further identified by gas chromatography/mass spectrometry (GC/MS). The stimulating effect of ET-1 on AA metabolism was dose dependent (10(-5) to 10(-7) M) and peaked within 1 h with a progressive decline over the subsequent hours. Using 125I-labeled ET-1 as radioligand, the presence of specific binding sites for ET-1 was demonstrated in cultured feline tracheal epithelial cells. ET-1 binding reached equilibrium within 1 h at 37 degrees C. Scatchard analysis suggested the existence of two saturable binding sites, with the estimated equilibrium dissociation constant (Kd) of 35.3 pM and maximal binding capacity (Bmax) of 15.0 fmol/10(7) cells for the higher affinity binding site and Kd of 205.9 pM and Bmax of 35.0 fmol/10(7) cells for the lower affinity binding site.(ABSTRACT TRUNCATED AT 250 WORDS)

M1 and M3 muscarinic antagonists inhibit human nasal glandular secretion in vitro

Mucus glycoproteins (MGP) are high-molecular-weight glycoconjugates that are released from submucosal glands and epithelial goblet cells in the respiratory tract. Muscarinic receptors have an important role in the regulation of human nasal glandular secretion and mucus production, but it is not known which of the five muscarinic receptor subtypes are involved. The effect of nonselective and M1-, M2-, and M3-selective muscarinic antagonists on methacholine (MCh)-induced MGP secretion from human nasal mucosal explants was tested in vitro. MGP was assayed by enzyme-linked immunosorbent assay using a specific anti-MGP monoclonal antibody (7F10). MCh (100 microM) induced MGP secretion up to 127% compared with controls. MCh-induced MGP release was significantly inhibited by atropine (100 microM), the M, receptor antagonist pirenzepine (10-100 microM), and the M3 receptor antagonist 4-diphenylacetoxy-N-methylpiperidine methiodide (4-DAMP; 1-100 microM). 4-DAMP significantly inhibited MCh-induced MGP release at a lower concentration (1 microM) than pirenzepine (10 microM). The M2 receptor antagonists AF-DX 116 and gallamine (both at 100 microM) had no effect. No antagonist alone had a significant effect on MGP release. These results indicate that the M1 and M3 muscarinic receptor subtypes regulate MGP secretion from human nasal mucosa and suggest that the M3 receptor has the predominant effect.

Airway epithelial cell mucin release: immunologic quantitation and response to platelet-activating factor

Mucus production is an integral component of airway mucosal inflammation. Platelet-activating factor (PAF) is a phospholipid mediator implicated in the pathogenesis of many inflammatory processes, including airway inflammation. PAF functions as a mucus secretagogue when mucus is quantitated as radiolabeled glycoconjugates released from airway organ cultures. To more directly assess the interaction of PAF and airway epithelial mucous cell secretion, we used primary feline tracheal epithelial cell cultures and an immunoassay for a specific mucous cell secretory vesicle component. Cultured tracheal epithelial cells were shown to synthesize and secrete glycoconjugates with mucin characteristics. These mucin-type glycoconjugates were immunoreactive with a mucous cell-specific antibody. Localization of this antibody to components of the secretory vesicles of cultured epithelial cells was confirmed by electron microscopic immunogold labeling. Using this monoclonal antibody, an immunoassay was developed to quantitate release of immunoreactive material into cell culture media. Exposure of cultures to PAF produced a concentration-dependent, prompt release of immunoreactive material. Concentration-dependent inhibition of this effect was demonstrated by coincubation with the PAF receptor antagonists, WEB 2086 and Ro 19-3704. A component of the signal transduction pathway for PAF effects was studied in cultured tracheal epithelial cells by coincubation of PAF with nordihydroguaiaretic acid (NDGA), a combined lipoxygenase and cyclooxygenase inhibitor, or p-bromophenacyl bromide (BPB), an inhibitor of cellular arachidonic acid release. Both NDGA and BPB blocked PAF-stimulated mucin release in a concentration-dependent manner. These studies demonstrate a direct airway epithelial mucous cell secretagogue effect that appears to be dependent upon airway epithelial PAF receptors and altered cellular lipid metabolism. These findings suggest a direct and potent mechanism for goblet cell secretion during airway inflammation.

Endothelin-1 stimulates eicosanoid production in cultured human nasal mucosa

Endothelin (ET) has been shown to contract both vascular and nonvascular smooth muscle and to stimulate human nasal glandular secretion of serous and mucous cell products. Some effects of ET are thought to be mediated by eicosanoid production. To explore the direct effect of ET on arachidonate metabolism in cultured human nasal mucosal explants, eicosanoids were measured after ET-1 stimulation. After labeling the explants with [3H]arachidonic acid (AA), supernatant from control and ET-1-treated explants were fractionated by reverse-phase high-performance liquid chromatography (HPLC). The resulting elution pattern suggested the release of prostaglandin (PG) E2 and AA in response to ET-1 stimulation. Radioimmunoassay after HPLC resolution confirmed that ET-1 induced a significantly increased release of PGE2 as well as PGD2, PGF2 alpha, thromboxane B2, and 15-hydroxyeicosatetraenoic acid (15-HETE). Although significant amounts of 15-HETE were generated, cyclooxygenase product generation was most remarkable. Eicosanoid release after ET-1 exposure (10 to 0.1 microM) is concentration dependent and occurs within 1 h. Whereas 15-HETE release was maximal at 4 h, prostanoid production was maximal 1 h after exposure to ET-1. Other assayed AA metabolites, including the peptidoleukotrienes, did not significantly change after ET-1 stimulation. We conclude that ET-1 induces the release of predominantly cyclooxygenase products from cultured human nasal mucosal explants.

Effect of protein kinase C activating agents on respiratory glycoconjugate release from feline airways

Abnormal regulation of airway glycoprotein secretion may underlie many respiratory diseases. Experimental activation of the protein kinase C (PKC) family of cytosolic enzymes has been shown to induce a secretory response in many tissues. To estimate the effect of PKC activation on airway secretion, alteration in the amount of radiolabeled respiratory glycoconjugate (RGC) released into culture media was determined following feline airway explant exposure to PKC activating agents. Exposure to two known activators of PKC, phorbol 12-myristate 13-acetate (PMA) and mezerein (MEZ), resulted in profound increases in respiratory glycoconjugate release over a seven day experimental period. The response evolved over several hours and was dose dependent. Maximal RGC release, 90% above control, occurred 2 days after exposure to either PMA or MEZ. Pharmacological inhibition of the PKC effect using two PKC inhibitors, 1-(5-isoquinolinylsulfonyl)-2-methylpiperazine and sphingosine, resulted in dose-dependent antagonism of the maximal PMA (10(-7) M)-stimulated RGC release, suggesting altered PKC activity was responsible for augmenting RGC release. Since altered arachidonic acid metabolism has been implicated in mediating some PKC effects, eicosanoids were assayed in airway explant supernatants following PMA exposure. Enhanced release of both cyclooxygenase and lipoxygenase pathway products was detected by radioimmunoassay. Cotreatment of explants with PMA and an inhibitor of oxidative arachidonic acid metabolism, nordihydroguaiaretic acid, blocked RGC release. These data demonstrate prolonged augmentation of respiratory glycoconjugate release from airway explants following exposure to PKC-activating agents.