Influence of 8-bromo-cyclicAMP on interleukin -6 and -8 mRNA levels in A549 human lung epithelial cells exposed to organic dust: a time-kinetic study

β2-Adrenergic agonists attenuate organic dust-induced lung inflammation

Agricultural dust exposure results in significant lung inflammation, and individuals working in concentrated animal feeding operations (CAFOs) are at risk for chronic airway inflammatory diseases. Exposure of bronchial epithelial cells to aqueous extracts of hog CAFO dusts (HDE) leads to inflammatory cytokine production that is driven by protein kinase C (PKC) activation. cAMP-dependent protein kinase (PKA)-activating agents can inhibit PKC activation in epithelial cells, leading to reduced inflammatory cytokine production following HDE exposure. β2-Adrenergic receptor agonists (β2-agonists) activate PKA, and we hypothesized that β2-agonists would beneficially impact HDE-induced adverse airway inflammatory consequences. Bronchial epithelial cells were cultured with the short-acting β2-agonist salbutamol or the long-acting β2-agonist salmeterol prior to stimulation with HDE. β2-Agonist treatment significantly increased PKA activation and significantly decreased HDE-stimulated IL-6 and IL-8 production in a concentration- and time-dependent manner. Salbutamol treatment significantly reduced HDE-induced intracellular adhesion molecule-1 expression and neutrophil adhesion to epithelial cells. Using an established intranasal inhalation exposure model, we found that salbutamol pretreatment reduced airway neutrophil influx and IL-6, TNF-α, CXCL1, and CXCL2 release in bronchoalveolar lavage fluid following a one-time exposure to HDE. Likewise, when mice were pretreated daily with salbutamol prior to HDE exposure for 3 wk, HDE-induced neutrophil influx and inflammatory mediator production were also reduced. The severity of HDE-induced lung pathology in mice repetitively exposed to HDE for 3 wk was also decreased with daily salbutamol pretreatment. Together, these results support the need for future clinical investigations to evaluate the utility of β2-agonist therapies in the treatment of airway inflammation associated with CAFO dust exposure.

Activation of inflammatory responses in human U937 macrophages by particulate matter collected from dairy farms: an in vitro expression analysis of pro-inflammatory markers

BACKGROUND

The purpose of the present study was to investigate activation of inflammatory markers in human macrophages derived from the U937 cell line after exposure to particulate matter (PM) collected on dairy farms in California and to identify the most potent components of the PM.

METHODS

PM from different dairies were collected and tested to induce an inflammatory response determined by the expression of various pro-inflammatory genes, such as Interleukin (IL)-8, in U937 derived macrophages. Gel shift and luciferase reporter assays were performed to examine the activation of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) and Toll-like-receptor 4 (TLR4).

RESULTS

Macrophage exposure to PM derived from dairy farms significantly activated expression of pro-inflammatory genes, including IL-8, cyclooxygenase 2 and Tumor necrosis factor-alpha, which are hallmarks of inflammation. Acute phase proteins, such as serum amyloid A and IL-6, were also significantly upregulated in macrophages treated with PM from dairies. Coarse PM fractions demonstrated more pro-inflammatory activity on an equal-dose basis than fine PM. Urban PM collected from the same region as the dairy farms was associated with a lower concentration of endotoxin and produced significantly less IL-8 expression compared to PM collected on the dairy farms.

CONCLUSION

The present study provides evidence that the endotoxin components of the particles collected on dairies play a major role in mediating an inflammatory response through activation of TLR4 and NF-κB signaling.

Sequential activation of protein kinase C isoforms by organic dust is mediated by tumor necrosis factor

Dust samples collected from Nebraska swine confinement facilities (hog dust extract [HDE]) are known to elicit proinflammatory cytokine release from human bronchial epithelial (HBE) cells in vitro. This response involves the activation of two protein kinase C (PKC) isoforms: PKCalpha and PKCepsilon. Experiments were designed to investigate the relationship between the two isoenzymes and the degree to which each is responsible for cytokine release in HBE. Experiments also examined the contribution of TNF-alpha to IL-6 and IL-8 release. PKCalpha and PKCepsilon activities were inhibited using isoform-specific pharmacologic inhibitors and genetically modified dominant-negative (DN) expressing cell lines. Release of the proinflammatory cytokines IL-6, IL-8, and TNF-alpha was measured and PKC isoform activities assessed. We found that HDE stimulates PKCalpha activity by 1 hour, and within 6 hours the activity returns to baseline. PKCalpha-specific inhibitor or PKCalphaDN cells abolish this HDE-mediated effect. Both IL-6 and IL-8 release are likewise diminished under these conditions compared with normal HBE, and treatment with TNF-alpha-neutralizing antibody does not further inhibit cytokine release. In contrast, PKCepsilon activity was enhanced by 6 hours after HDE treatment. TNF-alpha blockade abrogated this effect. HDE-stimulated IL-6, but not IL-8 release in PKCepsilonDN cells. The concentration of TNF-alpha released by HDE-stimulated HBE is sufficient to have a potent cytokine-eliciting effect. A time course of TNF-alpha release suggests that TNF-alpha is produced after PKCalpha activation, but before PKCepsilon. These results suggest a temporal ordering of events responsible for the release of cytokines, which initiate and exacerbate inflammatory events in the airways of people exposed to agricultural dust.

The phytoestrogen genistein affects zebrafish development through two different pathways

BACKGROUND

Endocrine disrupting chemicals are widely distributed in the environment and derive from many different human activities or can also be natural products synthesized by plants or microorganisms. The phytoestrogen, genistein (4', 5, 7-trihydroxy-isoflavone), is a naturally occurring compound found in soy products. Genistein has been the subject of numerous studies because of its known estrogenic activity.

METHODOLOGY/PRINCIPAL FINDINGS

We report that genistein exposure of zebrafish embryos induces apoptosis, mainly in the hindbrain and the anterior spinal cord. Timing experiments demonstrate that apoptosis is induced during a precise developmental window. Since adding ICI 182,780, an ER antagonist, does not rescue the genistein-induced apoptosis and since there is no synergistic effect between genistein and estradiol, we conclude that this apoptotic effect elicited by genistein is estrogen-receptors independent. However, we show in vitro, that genistein binds and activates the three zebrafish estrogen receptors ERalpha, ERbeta-A and ERbeta-B. Furthermore using transgenic ERE-Luciferase fish we show that genistein is able to activate the estrogen pathway in vivo during larval stages. Finally we show that genistein is able to induce ectopic expression of the aromatase-B gene in an ER-dependent manner in the anterior brain in pattern highly similar to the one resulting from estrogen treatment at low concentration.

CONCLUSION/SIGNIFICANCE

TAKEN TOGETHER THESE RESULTS INDICATE THAT GENISTEIN ACTS THROUGH AT LEAST TWO DIFFERENT PATHWAYS IN ZEBRAFISH EMBRYOS: (i) it induces apoptosis in an ER-independent manner and (ii) it regulates aromatase-B expression in the brain in an ER-dependent manner. Our results thus highlight the multiplicity of possible actions of phytoestrogens, such as genistein. This suggests that the use of standardized endpoints to study the effect of a given compound, even when this compound has well known targets, may carry the risk of overlooking interesting effects of this compound.

Effect of formoterol and salmeterol on IL-6 and IL-8 release in airway epithelial cells

Beta(2)-adrenoceptors are widely distributed and occur on airway epithelial cells. The aim of this study was to find out whether the two long-acting beta(2)-agonists formoterol and salmeterol influence interleukin-6 (IL-6) and -8 (IL-8) release from airway epithelial cells in vitro. A549 cells and primary bronchial epithelial cells (PBEC) were stimulated with organic dust from pig barns. Non-stimulated and dust-stimulated cells were incubated for 24h with formoterol or salmeterol (10(-13)-10(-6)M) and the release of IL-6 and IL-8 into the medium was assessed by ELISA technique. Propranolol (10(-5)M) or sotalol (10(-3)M) were used to block the beta(2)-agonist mediated effects. Formoterol and salmeterol both induced enhancement of IL-6 and IL-8 release and added to the effect of organic dust. This enhanced release was blocked by a beta-blocker in PBEC but not in A549 cells. To our knowledge, this is the first time beta(2)-agonists have been shown to stimulate IL-6 release from airway epithelial cells. The results indicate different mechanisms of beta(2)-agonist action in bronchial and alveolar epithelial cells. Furthermore, our results indicate that A549 cells do not possess functional beta(2)-adrenoceptors.

Organic dust-induced activation, adhesion to substrate and expression of intercellular adhesion molecules in THP-1 monocytes

Inhalation of organic dust in a swine confinement building induces systemic reactions, increased bronchial responsiveness and intense airway inflammation in previously unexposed, healthy subjects. These effects are self-limiting, but chronic respiratory symptoms are frequently observed in swine confinement workers. The present study was aimed at investigating organic dust-induced activation of the monocytic leukemia cell line, THP-1. Unstimulated THP-1 cells proliferate in suspension but cultivation for several days in medium with complete dust or 0.22-mu-filtered suspension, caused a subset of the THP-1 cells to adhere to the substratum. As assessed by transmission light- and indirect immunofluorescence microscopy, dust-stimulated adherent THP-1 cells adopted macrophage-like morphology and expressed vimentin. Intercellular adhesion molecule (ICAM)-1 was expressed in all dust-activated adherent cells, but only in 1% of the unstimulated cells in suspension. Sialoadhesin, a macrophage marker, was detected in dust-stimulated adherent THP-1 cells but not in the parental monocytes. Serum factors were required for the dust-induced expression of sialoadhesin, but not for adhesion to substrate or expression of ICAM-1. In addition, morphology and expression of vascular endothelial growth factor (VEGF) of dust-stimulated adherent cells equalled that of PMA-differentiated THP-1 cells, but the PMA-differentiated cells exhibited weak sialoadhesin labelling. In conclusion, exposure to organic dust from a swine confinement building activated a subset of THP-1 monocytes inducing expression of intercellular adhesion molecules, which are important in inflammation. The sustained adhesion to substrate indicates that organic dust from a swine confinement building may contain agents that prevent deactivation and detachment of the cells.

Inhibition of in vitro neutrophil migration through a bilayer of endothelial and epithelial cells using beta2-agonists: concomitant effects on IL-8 and elastase secretion and impact of glucocorticosteroids

BACKGROUND

Beta2-agonists and glucocorticosteroids are two common treatments for COPD and they are often used in combination. Glucocorticosteroids mediate the anti-inflammatory response through the glucocorticosteroid receptors (GRs). Beta2-agonists are potent bronchodilators but they can have some anti-inflammatory properties by elevating the level of intracellular cAMP. In this study we aimed to investigate the anti-inflammatory effect of combination therapy in vitro.

METHODS

Neutrophils or the bilayer of endothelial and epithelial cells were preincubated with salbutamol, budesonide or budesonide followed by salbutamol. FMLP-induced IL-8, elastase release and neutrophil migration through the bilayer was measured.

RESULTS

Salbutamol at concentrations of 10(-4), 10(-5) and 10(-9) M inhibited IL-8, elastase release and migration of neutrophils in an inverse bell-shaped concentration-response manner. When given after budesonide (10(-9) and 10(-8)M), the inhibitory effect on migration was additive. This additive effect was not observed for elastase and IL-8 release.

CONCLUSIONS

Salbutamol inhibits neutrophil migration and IL-8 and elastase release in a concentration-dependent manner. Preincubation with low concentration of budesonide enhanced the inhibition of migration achieved by low concentrations of salbutamol.

PDE4 inhibitors as new anti-inflammatory drugs: effects on cell trafficking and cell adhesion molecules expression

Phosphodiesterase 4 (PDE4) is a major cyclic AMP-hydrolyzing enzyme in inflammatory and immunomodulatory cells. The wide range of inflammatory mechanisms under control by PDE4 points to this isoenzyme as an attractive target for new anti-inflammatory drugs. Selective inhibitors of PDE4 have demonstrated a broad spectrum of anti-inflammatory activities including the inhibition of cellular trafficking and microvascular leakage, cytokine and chemokine release from inflammatory cells, reactive oxygen species production, and cell adhesion molecule expression in a variety of in vitro and in vivo experimental models. The initially detected side effects, mainly nausea and emesis, appear at least partially overcome by the 'second generation' PDE4 inhibitors, some of which like roflumilast and cilomilast are in the later stages of clinical development for treatment of chronic obstructive pulmonary disease. These new drugs may also offer opportunities for treatment of other inflammatory diseases.