Anti-Inflammatory Effects of Mitogen-Activated Protein Kinase Kinase Inhibitor U0126 in an Asthma Mouse Model

Interleukin(IL)-4 promotion of CXCL-8 gene transcription is mediated by ERK1/2 pathway in human pulmonary artery endothelial cells

Interleukin-4 is central to allergic pulmonary inflammatory responses, but its contribution to airway neutrophilia remains controversial. The endothelium plays a critical role in regulating leukocyte recruitment and migration during inflammation. However, its response to IL-4 is reported to either increase or decrease the production of neutrophil chemotactic factors. We hypothesized that these conflicting findings may be due to the tissue and the size of the vessels from which endothelial cells have been derived. The expression of CXCL-8 by human primary culture umbilical veins endothelial cells (HUVECs), human pulmonary artery endothelial cells (HPAECs), and human pulmonary microvascular endothelial cells (HPMECs) when stimulated with recombinant human IL-4 (rhIL-4) was studied. The chemoattractant property of the cells' supernatants for neutrophils was evaluated using Boyden chambers. The role of the nuclear factor-κB (NF-κB), and mitogen-activated protein kinases (MAPK) in IL-4-induced HPAECs was studied using Western blotting and electrophoretic mobility shift assay (EMSA). We demonstrated that IL-4 increased the mRNA expression and the protein production of CXCL-8 in HPAECs, but not in HUVECs and HPMECs. The supernatants of HAPECs stimulated by IL-4 significantly promoted neutrophils migration in a dose-dependent manner, and was significantly attenuated by an inhibitor of CXCL-8. We also found that extracellular-regulated protein kinase1/2 (ERK1/2) is activated by IL-4 in HPAECs, but not JUN-N-terminal protein kinase (JNK) or p38 MAPK pathway. Furthermore, NF-κB-DNA binding activity, phosphorylation of IκBα and p65 levels were not affected by rhIL-4 in HAPECs. These findings indicate marked functional differences in the response of micro and macro-ECs to IL-4. ERK1/2, rather than NF-κB, JNK and p38 MAPK signaling, plays a role in IL-4 induced chemokine activation. Our results suggest that inhibition of ERK1/2 may be a possible target for airway neutrophilia in allergic lung diseases.

Inhibition of influenza virus-induced NF-kappaB and Raf/MEK/ERK activation can reduce both virus titers and cytokine expression simultaneously in vitro and in vivo

Influenza virus (IV) infection can cause severe pneumonia and death. Therapeutic actions are limited to vaccines and a few anti-viral drugs. These target viral functions thereby selecting resistant variants. During replication IV activates the Raf/MEK/ERK-cascade and the transcription factor NF-kappaB. Both result in virus supportive and anti-viral effects by promoting viral genome transport for virus assembly and by inducing expression of pro-inflammatory host factors. Apart from tissue damage caused by the virus lytic replication, an imbalanced overproduction of anti-viral cytokines can cause severe lung damage as observed in human H5-type IV infections. Recently we showed that inhibition of NF-kappaB activity reduces the virus titer in vitro and in vivo. We have now analyzed whether inhibition of these pathways, allows simultaneous reduction of virus titers and virus-induced cytokines. The results show that inhibition of either pathway indeed leads to decreased virus titers and cytokine expression. This was not only true for infected permanent cells or primary mouse alveolar epithelial cells, but also in infected mice. Hereby we demonstrate for the first time in vitro and in vivo that virus titers and pro-inflammatory cytokine expression can be modulated simultaneously. This could provide a new rationale of future therapeutic strategies to treat IV pneumonia.

Small animals models for drug discovery

There has been an explosion of studies of animal models of asthma in the past 20 years. The elucidation of fundamental immunological mechanisms underlying the development of allergy and the complex cytokine and chemokines networks underlying the responses have been substantially unraveled. Translation of findings to human asthma have been slow and hindered by the varied phenotypes that human asthma represents. New areas for expansion of modeling include virally mediated airway inflammation, oxidant stress, and the interactions of stimuli triggering innate immune and adaptive immune responses.

Suppression of ovalbumin-induced airway inflammatory responses in a mouse model of asthma by Mimosa pudica extract

Asthma is an inflammatory airway disease. The pathogenic mechanisms of asthma include the infiltration of leukocytes and release of cytokines. Mimosa pudica (Mp) has been used traditionally for the treatment of insomnia, diarrhea and inflammatory diseases. Although Mp extract has various therapeutic properties, the effect of this extract on asthma has not yet been reported. This study investigated the suppressive effects of Mp extract on asthmatic responses both in vitro and in vivo. Mp extract was acquired from dried and powdered whole plants of M. pudica using 80% ethanol. BALB/c mice were used for the mouse model of asthma induced by ovalbumin. Mp extract significantly inhibited the HMC-1 cell migration induced by stem cell factor and blocked the release of monocyte chemotactic protein-1 (MCP-1) and interleukin-6 (IL-6) in EoL-1 cells. Leukocytosis, eosinophilia and mucus hypersecretion in asthmatic lung were significantly suppressed by Mp extract. The release of ovalbumin-specific IgE in bronchoalveolar lavage fluid and serum was also decreased. Mp extract treatment resulted in no liver cytotoxicity. The Mp extract has inhibitory properties on asthma and may be used as a potent therapeutic agent for allergic lung inflammation.

S100A8 modulates mast cell function and suppresses eosinophil migration in acute asthma

S100A8 is implicated in the pathogenesis of inflammatory diseases. S100A8 is upregulated in macrophages by Toll-like receptors (TLR)-3, 4, and 9 agonists in an IL-10-dependent manner, and by corticosteroids in vitro and in vivo, and scavenges oxidants generated by activated phagocytes. Because if its elevated expression in various lung disorders, we asked whether S100A8 was protective in allergic inflammation. S100A8, but not Cys(41)-Ala S100A8, in which the single reactive Cys residue was replaced by Ala, reduced mast cell (MC) degranulation and production of particular cytokines (IL-6, IL-4, and granulocyte macrophage colony-stimulating factor) in response to IgE-crosslinking in vitro, likely by inhibiting intracellular reactive oxygen species production, thereby reducing downstream linker for activation of T cells and extracellular signal regulated kinase/mitogen-activated protein kinase phosphorylation. In lungs of mice with acute asthma, S100A8, but not Cys(41)-Ala S100A8, reduced MC degranulation, production of eosinophil chemoattractants (IL-5, eotaxin, and monocyte chemoattractant protein-1), and eosinophil infiltration. Suppression of IL-6 and IL-13 could have contributed to reduced mucus production seen in lungs of S100A8-treated mice. IgE production was unaffected. In asthma, there is an imbalance of anti-oxidant systems that are generally protective. Our results strongly support a protective role for S100A8 in allergic inflammation by modulating MC activation and eosinophil recruitment, and by scavenging oxidants generated by activated leukocytes, in processes reliant on its thiol-scavenging capacity.

Aldose reductase inhibition suppresses airway inflammation

Airway inflammation induced by reactive oxygen species (ROS)-mediated activation of redox-sensitive transcription factors is the hallmark of asthma, a prevalent chronic respiratory disease. In various cellular and animal models, we have recently demonstrated that, in response to multiple stimuli, aldose reductase (AKR1B1) regulates the inflammatory signals via NF-kappa B activation. Since NF-κB activation is implicated in asthma pathogenesis, we investigated whether AKR1B1 inhibition could prevent ovalbumin (Ova)- and ragweed pollen extract (RWE)-induced airway inflammation and hyper-responsiveness in mice models and tumor necrosis factor-alpha (TNF-α)-, lipopolysachharide (LPS)- and RWE-induced cytotoxic and inflammatory signals in primary human small airway epithelial cells (SAEC). Sensitization and challenge with Ova or RWE caused airway inflammation and production of inflammatory cytokines, accumulation of eosinophils in airways and sub-epithelial regions, mucin production in the bronchoalveolar lavage fluid, airway hyperresponsiveness, elevated IgE levels and release of Th2 cytokines in the airway and treatment with AKR1B1 inhibitors markedly reduced these pathological changes in mice. In SAEC, treatment with TNF-α, LPS or RWE induced apoptosis, reactive oxygen species generation, synthesis of inflammatory markers IL-6, IL-8, and PGE2 and activation of NF-κB and AP-1. Pharmacological inhibition prevented these changes suggesting that AKR1B1 mediates ROS induced inflammation in small airway epithelial cells. Our results indicate that AKR1B1 inhibitors may offer a novel therapeutic approach to treat inflammatory airway diseases such as asthma.

Haplotypes covering the TNFSF10 gene are associated with bronchial asthma

Tumour necrosis factor-related apoptosis-inducing ligand (TRAIL) is elevated in the airways of subjects with asthma and has been linked to the development of allergic airway disease by promoting STAT6-dependent T helper 2 cell (T(H) 2) effector functions. To determine whether single nucleotide polymorphisms (SNPs) in the TNFSF10 gene are associated with bronchial asthma we genotyped 498 Caucasian subjects living in Southern Germany for eight SNPs in the TNFSF10 by restriction fragment length polymorphism analysis. In contrast to single SNPs, haplotypes constructed from eight SNPs were robustly associated with asthma (p=0.00012). A small haplotype approach returned four alleles consisting of two (rs3136586/ rs3136598), three (rs12488654/rs3136586/rs3136598 and rs3136586/rs3136598/rs3136604), and four SNPs (rs12488654/ rs3136586/ rs3136598/ rs3136604) that were highly associated with asthma (p=0.00005, p=0.00008, p=0.00017 and p=0.00038). Combinations of SNPs in the TNFSF10 allele were strongly associated with asthma supporting the concept that TRAIL is important in the development of hallmark features of this disease.

M(3) muscarinic receptor antagonist bencycloquidium bromide attenuates allergic airway inflammation, hyperresponsiveness and remodeling in mice

M(3) muscarinic receptors are localized on inflammatory cells, airway smooth muscle, and submucosal glands, known to mediate bronchoconstriction, mucus secretion, and airway remodeling. It is hypothesized bencycloquidium bromide (BCQB), a novel M(3) receptor antagonist, might have potential effects on airway hyperresponsiveness, inflammation and airway remodeling in a murine model of asthma. Mice sensitized and challenged with ovalbumin developed airway inflammation. Bronchoalveolar lavage fluid was examined to determine the total and differential cell counts, and cytokine levels. Lung tissues were evaluated for cell infiltration, mucus hypersecretion, airway remodeling, and the expression of inflammatory biomarkers. Airway hyperresponsiveness was monitored by direct airway resistance analysis. Inhalation administration of BCQB significantly not only reduced ovalbumin-induced airway hyperresponsiveness comparing to methacholine, and prevented the ovalbumin-induced increase in total cell counts and eosinophil counts. Reverse transcriptase polymerase chain reaction analysis of whole lung lysates revealed that BCQB markedly suppressed ovalbumin-induced mRNA expression of eotaxin, IL-5, IL-4 and MMP-9, and increased mRNA expression of IFN-γ and TIMP-1 in a dose-dependent manner. Substantial IFN-γ/IL-4 (Th1/Th2) levels were recovered in bronchoalveolar lavage fluid after BCQB treatment. In addition, histological studies showed that BCQB dramatically inhibited ovalbumin-induced lung tissue eosinophil infiltration, airway mucus production and collagen deposition in lung tissues. Results reported in current paper suggest that M(3) receptors antagonist may provide a novel therapeutic approach to treat airway inflammation, hyperresponsiveness and remodeling.

Suppressive effect of Petasites japonicus extract on ovalbumin-induced airway inflammation in an asthmatic mouse model

AIM OF THE STUDY

Asthma is a disease marked by airway inflammation. Petasites japonicus (Pj) is known as an herb for treating asthma, oxidant stress and gastric ulcer in traditional Oriental medicine. In this study, the inhibitory effects of Pj extract on asthmatic responses were examined both in vitro and in vivo.

MATERIALS AND METHODS

The Pj extract was acquired from whole plants of Petasites japonicus using 80% ethanol. Cytotoxicity of the Pj extract on Jurkat cells and THP-1 cells was determined using MTT assay. ELISA was performed to determine the expression levels of cytokines, chemokines, and IgE. BALB/c mice were used for an OVA-induced asthmatic mouse model. Reactive oxygen species (ROS) production was stained with 2',7'-dichlorofluorescein diacetate and measured by fluorescence-activated cell sorting analysis. The effects of the Pj extract on leukocyte infiltration and mucus production were determined using periodic acid-Schiff staining as well as hematoxylin and eosin staining.

RESULTS

The Pj extract inhibits the increased release of interleukin (IL)-2, IL-4, IL-5, IL-13, and TNF-α due to house dust mite in Jurkat cells and blocks IL-6 expression in THP-1 cells without cytotoxicity. In the asthmatic mouse model, the Pj extract inhibits eosinophil infiltration, mucus hypersecretion, and IL-5 level in bronchoalveolar lavage (BAL) fluid, and it has a scavenging effect on ROS production of cells in BAL fluid.

CONCLUSION

The Pj extract has suppressive properties for the pathogenesis of airway inflammation and may be used as a potent agent for the treatment of asthma.

Thalidomide attenuates airway hyperresponsiveness and eosinophilic inflammation in a murine model of allergic asthma

Asthma is characterized by chronic eosinophilic inflammation and hyperresponsiveness of the airways. We hypothesized that thalidomide, which has numerous immunomodulatory properties, may have anti-inflammatory effects in allergic asthma. BALB/c mice sensitized and challenged with ovalbumin (OVA) were treated orally with thalidomide (30, 100, or 300 mg/kg) or a vehicle. When thalidomide was administered to OVA-challenged mice, the number of eosinophils in bronchoalveolar lavage fluid (BALF) was significantly decreased. The numbers of inflammatory cells other than eosinophils were not reduced by thalidomide. Thalidomide inhibited the elevated levels of interleukin-5 (IL-5) and tumor necrosis factor-alpha (TNF-alpha) in BALF by OVA challenges. Histological analysis of the lung revealed that both the infiltration of inflammatory cells and the hyperplasia of goblet cells were significantly suppressed by thalidomide treatment. Furthermore, thalidomide significantly inhibited the response to methacholine induced by OVA challenges. Taken together, thalidomide treatment decreased airway inflammation and hyperresponsiveness in a murine model of allergic asthma. These results might provide an opportunity for the development of novel therapeutics to treat severe asthma.

Mega-dose vitamin C attenuated lung inflammation in mouse asthma model

Asthma is a Th2-dependent disease mediated by IgE and Th2 cytokines, and asthmatic patients suffer from oxidative stresses from abnormal airway inflammation. Vitamin C is a micro-nutrient functioning as an antioxidant. When administered at a mega-dose, vitamin C has been reported to shift immune responses toward Th1. Thus, we tried to determine whether vitamin C exerted beneficial effects in asthma animal model. Asthma was induced in mice by sensitizing and challenging with ovalbumin. At the time of challenge, 3~5 mg of vitamin C was administered and the effects were evaluated. Vitamin C did not modulate Th1/Th2 balance in asthma model. However, it decreased airway hyperreactivity to methacholine, decreased inflammatory cell numbers in brochoalveolar lavage fluid, and moderate reduction of perivascular and peribronchiolar inflammatory cell infiltration. These results suggest that vitamin C administered at the time of antigen challenge exerted anti-inflammatory effects. Further studies based on chronic asthma model are needed to evaluate a long-term effect of vitamin C in asthma. In conclusion, even though vitamin C did not show any Th1/Th2 shifting effects in this experiment, it still exerted moderate anti-inflammatory effects. Considering other beneficial effects and inexpensiveness of vitamin C, mega-dose usage of vitamin C could be a potential supplementary modality for the management of asthma.

Effects of astilbic acid on airway hyperresponsiveness and inflammation in a mouse model of allergic asthma

Bronchial asthma is characterized by chronic lung inflammation, airway hyperresponsiveness (AHR), and airway remodeling. Astilbic acid, extracted from the medicinal herb Astilbe chinensis, is used as a headache remedy in traditional medicine and has anti-pyretic and analgesic effects. However, the effect of astilbic acid on asthma remains to be established. In the present study, we therefore examined the effect of astilbic acid in a mouse model in which asthma was established by sensitization and challenge with ovalbumin (OVA). Astilbic acid inhibited OVA-induced AHR to inhaled methacholine and significantly suppressed the levels of T-helper 2-type cytokines (including IL [interleukin]-4, IL-5, and IL-13) and inflammatory cells (including eosinophils) in bronchoalveolar lavage (BAL) fluid. Histochemical analysis revealed reduced goblet cell hyperplasia and mucus production, as well as attenuated eosinophil-rich leukocyte infiltration, in the astilbic acid-treated group, compared with OVA-challenged mice. Moreover, the compound significantly inhibited synthesis of IL-4-, IL-5-, IL-13-, IL-17-, and eotaxin-encoding mRNA following asthma induction in lung tissue, in addition to suppressing the immunoglobulin E (IgE) response to asthma in both BAL fluid and serum. Our results indicate that astilbic acid has great potential as a therapeutic candidate for the treatment of asthma.

Mitogen-activated protein kinase signalling and ERK1/2 bistability in asthma

Mitogen-activated protein kinases (MAPKs) integrate signals from numerous receptors and translate these signals into cell functions. MAPKs are critical for immune cell metabolism, migration, production of pro-inflammatory mediators, survival and differentiation. We provide a concise review of the involvement of MAPK in important cells of the immune system. Certain cell functions, e.g. production of pro-inflammatory mediators resolve quickly and may require a transient MAPK activation, other processes such as cell differentiation and long-term survival may require persistent MAPK signal. The persistent MAPK signal is frequently a consequence of positive feedback loops or double negative feedback loops which perpetuate the signal after removal of an external cell stimulus. This self-perpetuated activation of a signalling circuit is a manifestation of its bistability. Bistable systems can exist in 'on' and 'off' states and both states are stable. We have demonstrated the existence of self-perpetuated activation mechanism for ERK1/2 in bronchial epithelial cells. This sustained activation of ERK1/2 supports long-term survival of these cells and primes them for cytokine transcription. ERK1/2 bistability arises from repetitive stimulation of the cell. The repeated stimulation (e.g. repeated viral infection or repeated allergen exposure) seems to be a common theme in asthma and other chronic illnesses. We thus hypothesize that the self-perpetuated ERK1/2 signal plays an important role in the pathogenesis of asthma.

Effects of oral monosodium glutamate in mouse models of asthma

The available evidence from numerous clinical studies has failed to demonstrate a clear and consistent relationship between monosodium glutamate (MSG) and asthma. The objective of this study was to investigate the effects of MSG on bronchial inflammation by measuring cytological, histological and functional changes in an ovalbumin-induced asthma mouse model. BALB/c mice with experimentally induced asthma were fed a diet containing 0.5% or 5% MSG the week before the first ovalbumin injection and for the subsequent 3-week period. MSG feeding did not affect pulmonary eosinophil infiltration, production of Th2 cytokines, circulating IgE concentrations or airway hyperresponsiveness (induced by methacholine). Histological observations did not reveal pulmonary inflammation, including secondary changes, in the asthmatic mice. An oral gavage challenge with an MSG solution (0.5% or 5%, w/w) did not exert any acute effects on lung inflammation or airway hyperresponsiveness in the asthmatic mice. The results of this study suggest that MSG is not involved in the development of asthma or in acute asthmatic responses, and they support previous observations from well-designed clinical studies.

Enhanced airway smooth muscle cell thromboxane receptor signaling via activation of JNK MAPK and extracellular calcium influx

Thromboxane is a key inflammatory mediator and potent airway constrictor. It acts on thromboxane A(2) (TP) receptors and contributes to airway inflammation and airway hyperresponsiveness that is the characteristic feature of asthma. The present study was designed to study TP receptor signaling in airway smooth muscle cells by using an organ culture model and a set of selective pharmacological inhibitors for mitogen-activated protein kinase (MAPK) and calcium signal pathways. Western-blot, immunohistochemistry, myograph and a selective TP receptor agonist U46619 were used for examining TP receptor signal proteins and function. Organ culture of rat bronchial segments for up to 48 h induces a time-dependently increased airway contractile response to U46619. This indicates that organ culture increases TP receptor signaling in the airway smooth muscle cells. The enhanced bronchial contraction was attenuated by the inhibition of c-Jun N-terminal kinase (JNK) MAPK activity, chelation of extracellular calcium and calcium channel blocker nifedipine, suggesting that JNK MAPK activity and elevated intracellular calcium level are required for the TP receptor signaling. In conclusion, airway smooth muscle cell TP receptor signaling occurs via JNK MAPK activity and the elevation of extracellular calcium influx, which may provide knowledge for understanding the signaling pathway responsible for the modulation of TP receptor mediated airway hyperresponsiveness to thromboxane.

IL-2 and IL-4 stimulate MEK1 expression and contribute to T cell resistance against suppression by TGF-beta and IL-10 in asthma

The T cell-driven airway inflammation in chronic asthma is uninhibited and sustained. We examined the resistance of T cells from asthmatic patients against suppression by TGF-β, IL-10 and glucocorticoids and explored its signaling mechanism. CD4(+)CD25(-) T cells from allergic asthmatic subjects demonstrated increased TCR-stimulated proliferation as compared with healthy and chronic obstructive pulmonary disease controls. This proliferation was resistant to inhibition by TGF-β, IL-10, and dexamethasone and to anergy induction. CD4 T cells from asthmatic patients, but not chronic obstructive pulmonary disease, allergic rhinitis, and healthy subjects, showed increased expression of MEK1, heightened phosphorylation of ERK1/2, and increased levels of c-Fos. IL-2 and IL-4 stimulated the expression of MEK1 and c-Fos and induced T cell resistance. The inhibition of MEK1 reversed, whereas induced expression of c-Fos and JunB promoted T cell resistance against TGF-β- and IL-10-mediated suppression. We have uncovered an IL-2- and IL-4-driven MEK1 induction mechanism that results in heightened ERK1/2 activation in asthmatic T cells and make them resistant to certain inhibitory mechanisms.

Extracellular signal-regulated kinase (ERK) participates in the hypercapnia-induced Na,K-ATPase downregulation

Hypercapnia has been shown to impair alveolar fluid reabsorption (AFR) by decreasing Na,K-ATPase activity. Extracellular signal-regulated kinase pathway (ERK) is activated under conditions of cellular stress and has been known to regulate the Na,K-ATPase. Here, we show that hypercapnia leads to ERK activation in a time-dependent manner in alveolar epithelial cells (AEC). Inhibition of ERK by U0126 or siRNA prevented both the hypercapnia-induced Na,K-ATPase endocytosis and impairment of AFR. Moreover, ERK inhibition prevented AMPK activation, a known modulator of hypercapnia-induced Na,K-ATPase endocytosis. Accordingly, these data suggest that hypercapnia-induced Na,K-ATPase endocytosis is dependent on ERK activation in AEC and that ERK plays an important role in hypercapnia-induced impairment of AFR in rat lungs.

Azithromycin attenuates airway inflammation in a mouse model of viral bronchiolitis

Background

Viral bronchiolitis is the leading cause of hospitalization in young infants. It is associated with the development of childhood asthma and contributes to morbidity and mortality in the elderly. Currently no therapies effectively attenuate inflammation during the acute viral infection, or prevent the risk of post-viral asthma. We hypothesized that early treatment of a paramyxoviral bronchiolitis with azithromycin would attenuate acute and chronic airway inflammation.

Methods

Mice were inoculated with parainfluenza type 1, Sendai Virus (SeV), and treated daily with PBS or azithromycin for 7 days post-inoculation. On day 8 and 21 we assessed airway inflammation in lung tissue, and quantified immune cells and inflammatory mediators in bronchoalveolar lavage (BAL).

Results

Compared to treatment with PBS, azithromycin significantly attenuated post-viral weight loss. During the peak of acute inflammation (day 8), azithromycin decreased total leukocyte accumulation in the lung tissue and BAL, with the largest fold-reduction in BAL neutrophils. This decreased inflammation was independent of changes in viral load. Azithromycin significantly attenuated the concentration of BAL inflammatory mediators and enhanced resolution of chronic airway inflammation evident by decreased BAL inflammatory mediators on day 21.

Conclusions

In this mouse model of paramyxoviral bronchiolitis, azithromycin attenuated acute and chronic airway inflammation. These findings demonstrate anti-inflammatory effects of azithromycin that are not related to anti-viral activity. Our findings support the rationale for future prospective randomized clinical trials that will evaluate the effects of macrolides on acute viral bronchiolitis and their long-term consequences.

Intracerebroventricular injection of leukotriene B4 attenuates antigen-induced asthmatic response via BLT1 receptor stimulating HPA-axis in sensitized rats

Background

Basic and clinical studies suggest that hypothalamic-pituitary-adrenal (HPA) axis is the neuroendocrine-immnue pathway that functionally regulates the chronic inflammatory disease including asthma. Our previous studies showed corresponding changes of cytokines and leukotriene B₄ (LTB₄) between brain and lung tissues in antigen-challenged asthmatic rats. Here, we investigated how the increased LTB₄ level in brain interacts with HPA axis in regulating antigen-induced asthmatic response in sensitized rats.

Methods

Ovalbumin-sensitized rats were challenged by inhalation of antigen. Rats received vehicle, LTB₄ or U75302 (a selective LTB₄ BLT1 receptor inhibitor) was given via intracerebroventricular injection (i.c.v) 30 min before challenge. Lung resistance (R_L) and dynamic lung compliance (C_dyn) were measured before and after antigen challenge. Inflammatory response in lung tissue was assessed 24 h after challenge. Expression of CRH mRNA and protein in hypothalamus were evaluated by RT-PCR and Western Blot, and plasma levels of adrenocorticotropic hormone (ACTH) and corticosterone (CORT) were measured using the ELISA kits.

Results

Antigen challenge decreased pulmonary function and induced airway inflammation, evoked HPA axis response in sensitized rats. Administration of LTB₄ via i.c.v markedly attenuated airway contraction and inflammation. Meanwhile, LTB₄ via i.c.v markedly increased CORT and ACTH level in plasma before antigen challenge, and followed by further increases in CORT and ACTH levels in plasma after antigen challenge in sensitized rats. Expression of CRH mRNA and protein in hypothalamus were also significantly increased by LTB₄ via i.c.v in sensitized rats after antigen challenge. These effect were completely blocked by pre-treatment with BLT1 receptor antagonist U75302 (10 ng), but not by BLT2 antagonist LY255283.

Conclusions

LTB₄ administered via i.c.v down-regulates the airway contraction response and inflammation through activation of the HPA axis via its BLT1 receptor. This study expands our concept of the regulatory role of intracranial inflammatory mediators in inflammatory diseases including asthma. The favourable effects of LTB₄ on the HPA axis may help to explain the phenomenon of self-relief after an asthmatic attack.

Mechanism of glucocorticoid protection of airway smooth muscle from proasthmatic effects of long-acting beta2-adrenoceptor agonist exposure

BACKGROUND

Chronic use of long-acting beta2-adrenergic receptor agonists (LABAs), resulting in beta2-adrenergic receptor desensitization, has been associated with increased asthma morbidity. When LABAs are used in combination with inhaled glucocorticoids, however, asthma control is improved, raising the following question: Do glucocorticoids inhibit the proasthmatic mechanism that mediates altered contractility in LABA-exposed airway smooth muscle (ASM)?

OBJECTIVE

This study aimed to identify the potential protective role and mechanism of action of glucocorticoids in mitigating the effects of prolonged LABA exposure on ASM constrictor and relaxation responsiveness.

METHODS

Cultured human ASM cells and isolated rabbit ASM tissues were examined for induced changes in agonist-mediated cyclic adenosine monophosphate accumulation, constrictor and relaxation responsiveness, and expression of specific glucocorticoid-regulated molecules after 24-hour exposure to the LABA salmeterol in the absence and presence of dexamethasone.

RESULTS

Salmeterol-exposed ASM exhibited impaired cyclic adenosine monophosphate and relaxation responses to isoproterenol and increased acetylcholine-induced contractility. These proasthmatic effects of prolonged LABA exposure were attributed to upregulated phosphodiesterase 4 (PDE4) activity and were ablated by pretreatment with dexamethasone. Further studies demonstrated that (1) dexamethasone suppressed activation of the mitogen-activated protein kinases extracellular signal-regulated kinases 1 and 2 (ERK1/2), which upregulate PDE4 expression in salmeterol-exposed ASM; and (2) the inhibitory actions of dexamethasone on salmeterol-induced ERK1/2 activation and resultant PDE4-mediated changes in ASM responsiveness were prevented by gene silencing or pharmacologic inhibition of dexamethasone-induced expression of mitogen-activated protein kinase phosphatase 1, an endogenous deactivator of ERK1/2 signaling.

CONCLUSION

Glucocorticoids prevent the adverse proasthmatic effects of prolonged LABA exposure on airway responsiveness as a result of glucocorticoid-induced upregulation of mitogen-activated protein kinase phosphatase 1, which inhibits proasthmatic ERK1/2 signaling in the LABA-exposed ASM.

A critical role for the g protein-coupled receptor mFPR2 in airway inflammation and immune responses

The formylpeptide receptor-like 1, now officially termed FPR2, in human and its mouse homolog mFPR2 mediate leukocyte migration in response to agonists associated with inflammation and immune responses. To clarify the in vivo role of the receptor, we generated mice deficient in mFPR2. mFPR2(-/-) mice showed markedly reduced severity in OVA/alum-induced allergic airway inflammation. This was associated with diminished recruitment of CD11c(+) dendritic cells into the airway mucosa and secondary lymphoid organs, as well as reduced production of Type 2 cytokines and Igs. We also found that the bronchoalveolar lavage fluid from wild type mice with airway inflammation contained mFPR2 agonist activity. This study reveals a critical role for mFPR2 in the progression of allergic airway inflammation and immune responses.

Effect of PD98059, a selective MAPK3/MAPK1 inhibitor, on acute lung injury in mice

The aim of the present study is to evaluate the contribution of mitogen-activated protein kinase 1-3 MAPK3/MAPK1) in a model of acute lung inflammation in mice. Injection of carrageenan into the pleural cavity of mice elicited an acute inflammatory response characterized by: accumulation of fluid containing a large number of neutrophils (PMNs) in the pleural cavity, infiltration of PMNs in lung tissues and subsequent adhesion molecule expression (I-CAM and P-selectin), lipid peroxidation, and increased production of tumour necrosis factor-alpha, (TNF-alpha) and interleukin-1beta (IL-1beta). Furthermore, carrageenan induced lung apoptosis (Bax and Bcl-2 expression) as well as nitrotyrosine formation, NF-kB activation, and pJNK expression, as determined by immunohistochemical analysis of lung tissues and the degree of lung inflammation and tissue injury (histological score). Administration of PD98059, an inhibitor of MAPK3/MAPK1 (10 mg/kg) 1 h after carrageenan caused a reduction in all the parameters of inflammation measured. Thus, based on these findings we propose that inhibitors of the MAPK3/MAPK1 signaling pathways, such as PD98059, may be useful in the treatment of various inflammatory diseases.

Bambusae Caulis in Taeniam extract reduces ovalbumin-induced airway inflammation and T helper 2 responses in mice

ETHNOPHARMACOLOGICAL RELEVANCE

Bambusae Caulis in Taeniam (BC) was known as traditional herbal medicine with anti-inflammatory property in the Orient.

AIM OF THE STUDY

Allergic asthma is inflammatory disease of airways associated with enhanced T helper (Th) 2 lymphocytes responses to allergens, leading to eosinophilic infiltration and elevated serum IgE levels. Although there were some studies that BC extract had an anti-inflammatory property, there was no study on asthma. In present study, we investigated the suitability of BC extract as a therapeutic candidate in the treatment of allergic airway disease in ovalbumin-induced asthma model.

MATERIALS AND METHODS

Balb/C mice (female, 6 weeks old) were treated by ovalbumin sensitization and nebulization, and used as asthma model. The number of eosinophil in bronchoalveolar lavage (BAL) fluid and the degree of eosinophila were investigated by hematoxylin and eosin stain and the infiltration of inflammatory cells into lung tissues was examined by staining by hematoxylin and eosin solution. The levels of interleukin (IL)-4 in BAL fluid, immunoglobulin E (IgE) in serum, interferon (IFN)-gamma and IL-4 production in splenocyte culture from Balb/C mice (not treated, 6 weeks old) that incubated with or without BC extract for 48 h were determined by enzyme-linked immunosorbent assay.

RESULTS

The level of eosinophils was decreased by treatment of the animals with BC extract (40 mg/kg) and correspondingly, a significantly lowered degree of eosinophila was also reported (p<0.01). In lung tissue, BC extract reduced the increased immune cell infiltration induced by OVA (p<0.05). Furthermore, the levels of IL-4 and IgE in BAL fluid or serum up-regulated by OVA was decreased by BC extract. Finally, IFN-gamma production was significantly increased (p<0.01), while IL-4 production significantly decreased (p<0.01), after treatment of the culture supernatants of splenocytes with BC extract.

CONCLUSIONS

These results indicated that BC extract reduces OVA-induced airway inflammation and Th 2 response in mice, suggesting that BC extract can be a therapeutic candidate for allergic airway disease, including asthma.

Leukotriene B4, administered via intracerebroventricular injection, attenuates the antigen-induced asthmatic response in sensitized guinea pigs

Background

Despite intensive studies focused on the pathophysiology of asthmatic inflammation, little is known about how cross-talk between neuroendocrine and immune systems regulates the inflammatory response during an asthmatic attack. We recently showed corresponding changes of cytokines and leukotriene B₄ (LTB₄) in brain and lung tissues of antigen-challenged asthmatic rats. Here, we investigated how LTB₄ interacts with the neuroendocrine-immune system in regulating antigen-induced asthmatic responses in sensitized guinea pigs.

Methods

Ovalbumin-sensitized guinea pigs were challenged by inhalation of antigen. Vehicle, LTB₄ or U75302 (a selective LTB₄ BLT1 receptor inhibitor) was given via intracerebroventricular injection (i.c.v.) 30 min before challenge. Airway contraction response was evaluated using Penh values before and after antigen challenge. The inflammatory response in lung tissue was evaluated 24 h after challenge. The LTB₄ content of lung and brain homogenate preparations was detected by reversed phase high-performance liquid chromatography (RP-HPLC). Plasma levels of adrenocorticotropic hormone (ACTH) and corticosterone (CORT) were measured using ELISA kits.

Results

Antigen challenge impaired pulmonary function and increased inflammatory cell infiltration in lung tissue. These responses could be significantly suppressed by LTB₄, 30 ng i.c.v., in ovalbumin-sensitized guinea pigs. LTB₄ content of lung and brain homogenates from antigen-challenged guinea pigs was significantly increased. In addition, administration of LTB₄ via i.c.v. markedly increased CORT and ACTH level in plasma before antigen challenge, and there were further increases in CORT and ACTH levels in plasma after antigen challenge. U75302, 100 ng i.c.v., completely blocked the effects of LTB₄. In addition, U75302, 100 ng via i.c.v. injection, markedly decreased LTB₄ content in lung homogenates, but not in brain homogenates.

Conclusions

Increased LTB₄ levels in brain during asthmatic attacks down-regulates airway contraction response and inflammation through the BLT1 receptor. Stimulation of the hypothalamic-pituitary-adrenal axis by LTB₄ may result in an increase in systemic glucocorticoids which, in turn, would feed back to suppress the asthmatic response.

MEK modulates force-fluctuation-induced relengthening of canine tracheal smooth muscle

Tidal breathing, and especially deep breathing, is known to antagonise bronchoconstriction caused by airway smooth muscle (ASM) contraction; however, this bronchoprotective effect of breathing is impaired in asthma. Force fluctuations applied to contracted ASM in vitro cause it to relengthen, force-fluctuation-induced relengthening (FFIR). Given that breathing generates similar force fluctuations in ASM, FFIR represents a likely mechanism by which breathing antagonises bronchoconstriction. Thus it is of considerable interest to understand what modulates FFIR, and how ASM might be manipulated to exploit this phenomenon. It was demonstrated previously that p38 mitogen-activated protein kinase (MAPK) signalling regulates FFIR in ASM strips. Here, it was hypothesised that the MAPK kinase (MEK) signalling pathway also modulates FFIR. In order to test this hypothesis, changes in FFIR were measured in ASM treated with the MEK inhibitor, U0126 (1,4-diamino-2,3-dicyano-1,4-bis[2-aminophenylthio]butadiene). Increasing concentrations of U0126 caused greater FFIR. U0126 reduced extracellular signal-regulated kinase 1/2 phosphorylation without affecting isotonic shortening or 20-kDa myosin light chain and p38 MAPK phosphorylation. However, increasing concentrations of U0126 progressively blunted phosphorylation of high-molecular-weight caldesmon (h-caldesmon), a downstream target of MEK. Thus changes in FFIR exhibited significant negative correlation with h-caldesmon phosphorylation. The present data demonstrate that FFIR is regulated through MEK signalling, and suggest that the role of MEK is mediated, in part, through caldesmon.

Derivation and validation of murine histologic alterations resembling asthma, with two proposed histologic grade parameters

BACKGROUND

The objective was to define murine histologic alterations resembling asthma in a BALB/c OVA model and to suggest grading criteria. Identified were six salient histologic findings in lungs with putative allergic inflammation: 1) bronchoarterial space inflammation; 2) peri-venular inflammation; 3) inflammation about amuscular blood vessels; 4) inter-alveolar space inflammation, not about capillaries; 5) pleural inflammation; and 6) eosinophils within the inflammatory aggregates. An initial study comprised six groups of twelve mice each: 1) stressed, control; 2) stressed, sensitized; 3) stressed, challenged; 4) not physically stressed, control; 5) not physically stressed, sensitized; 6) not physically stressed, challenged. A second study comprised four experimental groups of twenty mice each: 1) stressed, control; 2) stressed, challenged; 3) not physically stressed, control; 4) not physically stressed, challenged. A third study evaluated two grading criteria, 1) the proportion of non-tracheal respiratory passages with inflammatory aggregates and 2) mitoses in the largest two non-tracheal respiratory passages, in five groups of five mice each, evaluated at different times after the last exposure.

RESULTS

The first study suggested the six histological findings might reliably indicate the presence of alterations resembling asthma: whereas 82.4% of mice with a complete response had detectable interleukin (IL)-5, only 3.8% of mice without one did; whereas 77.8% of mice with a complete response were challenged mice, only 6.7% of mice without complete responses were. The second study revealed that the six histological findings provided a definition that was 97.4% sensitive and 100% specific. The third study found that the odds of a bronchial passage's having inflammation declined 1) when mitoses were present (OR = 0.73, 0.60 - 0.90), and 2) with one day increased time (OR = 0.75, 0.65 - 0.86).

CONCLUSION

A definition of murine histologic alterations resembling asthma in the BALB/c OVA mouse was developed and validated. The definition will be of use in experiments involving this model to ensure that all mice said to have undergone an asthmatic attack did indeed reveal allergic pulmonary inflammation. Proposed grading criteria should be further evaluated with additional studies using physiologic measures of attack severity and increased airway resistance.

Aldose reductase inhibition suppresses the expression of Th2 cytokines and airway inflammation in ovalbumin-induced asthma in mice

Airway inflammation induced by reactive oxygen species-mediated activation of redox-sensitive transcription factors is the hallmark of asthma, a prevalent chronic respiratory disease. In various cellular and animal models, we have recently demonstrated that, in response to multiple stimuli, aldose reductase (AR) regulates the inflammatory signals mediated by NF-kappaB. Because NF-kappaB-mediated inflammation is a major characteristic of asthma pathogenesis, we have investigated the effect of AR inhibition on NF-kappaB and various inflammatory markers in cellular and animal models of asthma using primary human small airway epithelial cells and OVA-sensitized/challenged C57BL/6 mice, respectively. We observed that pharmacological inhibition or genetic ablation of AR by small interfering RNA prevented TNF-alpha- as well as LPS-induced apoptosis; reactive oxygen species generation; synthesis of inflammatory markers IL-6, IL-8, and PGE(2); and activation of NF-kappaB and AP-1 in small airway epithelial cells. In OVA-challenged mice, we observed that administration of an AR inhibitor markedly reduced airway hyperresponsiveness, IgE levels, eisonophils infiltration, and release of Th2 type cytokines in the airway. Our results indicate that AR inhibitors may offer a novel therapeutic approach to treat inflammatory airway diseases such as asthma.

Emerging role of tumour necrosis factor-related apoptosis-inducing ligand (TRAIL) as a key regulator of inflammatory responses

1. Tumour necrosis factor-related apoptosis-inducing ligand (TRAIL) induces apoptosis in tumour cells while leaving most non-transformed cells unharmed. Binding of TRAIL to its death receptors (DR4 and DR5) activates the extrinsic apoptotic pathway by recruiting procaspase 8 into the death-inducing silencing complex. Cleavage of the BH-3 only peptide Bid by caspase 8 links the apoptotic TRAIL signal to the mitochondrial pathway and the subsequent release of cytochrome c. 2. In addition, TRAIL binds to neutralizing decoy receptors (DcR1 and DcR2). Signalling through DcR2, DR4 and DR5 can activate pro-inflammatory intracellular molecules such as mitogen-activated protein kinase, protein kinase B and nuclear factor-kappaB. 3. Recent studies have identified an important role for TRAIL in regulating immune responses to viruses, self-antigen and allergens. Increased concentrations of TRAIL are found in virus infections of the lung and TRAIL affects the antiviral response and resolution of infection. In addition, TRAIL is upregulated in the airways of asthmatics and inhibition results in reduced inflammation, T helper 2 cytokine and CCL20 release, as well as abolishing the development of airway hyperreactivity in experimental models. 4. Characterization of the specific receptor systems activated and the pro-inflammatory factors regulated by TRAIL in vivo may lead to the development of novel therapeutic strategies for diseases as diverse as infection, autoimmunity and asthma.

Inhibition of Pyk2 blocks airway inflammation and hyperresponsiveness in a mouse model of asthma

The objective of this investigation was to determine the role of Pyk2, an intracellular nonreceptor protein tyrosine kinase for postadhesive inflammatory cell migration, on airway inflammation and hyperresponsiveness in immune-sensitized mice. Blockade of Pyk2 was effected by intraperitoneal administration of dominant-negative C-terminal Pyk2 fused to a TAT protein transduction domain (TAT-Pyk2-CT). Ovalbumin challenge elicited infiltration of both eosinophils and lymphocytes into airways, increased mucus-containing epithelial cells, and caused increased airway hyperresponsiveness to methacholine in immune-sensitized mice. Pretreatment with 10 mg/kg TAT-Pyk2-CT intraperitoneally blocked all of these effects and further decreased secretion of Th2 cytokine IL-4, IL-5, and IL-13 into the bronchoalveolar lavage fluid. Intranasal administration of IL-5 caused eosinophil migration into the airway lumen, which was attenuated by systemic pretreatment with TAT-Pyk2-CT. In each paradigm, treatment with control protein TAT-GFP had no blocking effect. We conclude that Pyk2, which is essential for inflammatory cell migration in vitro, regulates airway inflammation, Th2 cytokine secretion, and airway hyperresponsiveness in the ovalbumin-sensitized mice during antigen challenge in vivo.

Azithromycin attenuates airway inflammation in a noninfectious mouse model of allergic asthma

BACKGROUND

Definitive conclusions regarding the antiinflammatory effects of macrolide antibiotics for treatment of asthma are difficult to formulate since their beneficial effects may be related to their antimicrobial action. We hypothesized that azithromycin possesses distinct antiinflammatory properties and tested this assumption in a noninfectious mouse model of allergic asthma.

METHODS

To induce allergic airway inflammation, 7-week-old BALB/cJ mice underwent intraperitoneal ovalbumin sensitization on days 0 and 7 followed by an intranasal challenge on day 14. Mice were treated with azithromycin or phosphate-buffered saline (PBS) solution on days 13 through 16. On day 17, airway inflammation was assessed by quantifying leukocytes in the airway, expression of multiple inflammatory mediators in the BAL fluid, and mucous cell metaplasia. In a separate set of experiments, azithromycin or PBS solution treatment were initiated after the ovalbumin challenge. Each experiment was repeated 3 times (a total of 9 to 11 mice in each group).

RESULTS

Compared to treatment with PBS solution, azithromycin attenuated the ovalbumin-dependent airway inflammation. We observed a decrease in total leukocytes in the lung tissue and BAL fluid. In addition, azithromycin attenuated the expression of cytokines (eg, interleukin [IL]-13 and IL-5) and chemokines (eg, CCL2, CCL3, and CCL4) in the BAL fluid and abrogated the extent of mucous cell metaplasia. Similar antiinflammatory effects were observed when azithromycin treatment was initiated after the ovalbumin challenge.

CONCLUSION

In this noninfectious mouse model of allergic asthma, azithromycin attenuated allergic airway inflammation. These findings demonstrate an antiinflammatory effect of azithromycin and suggest azithromycin may have beneficial effects in treating noninfectious airway inflammatory diseases, including asthma.

How ERK1/2 activation controls cell proliferation and cell death: Is subcellular localization the answer?

Extracellular signal-regulated protein kinases 1 and 2 (ERK1/2) are members of the mitogen-activated protein kinase super family that can mediate cell proliferation and apoptosis. The Ras-Raf-MEK-ERK signaling cascade controlling cell proliferation has been well studied but the mechanisms involved in ERK1/2-mediated cell death are largely unknown. This review focuses on recent papers that define ERK1/2 translocation to the nucleus and the proteins involved in the cytosolic retention of activated ERK1/2. Cytosolic retention of ERK1/2 denies access to the transcription factor substrates that are responsible for the mitogenic response. In addition, cytosolic ERK1/2, besides inhibiting survival and proliferative signals in the nucleus, potentiates the catalytic activity of some proapoptotic proteins such as DAP kinase in the cytoplasm. Studies that further define the function of cytosolic ERK1/2 and its cytosolic substrates that enhance cell death will be essential to harness this pathway for developing effective treatments for cancer and chronic inflammatory diseases.

Celastrol binds to ERK and inhibits FcepsilonRI signaling to exert an anti-allergic effect

The role of celastrol, a triterpene extracted from the Chinese "Thunder of God Vine," in allergic inflammation was investigated. Celastrol decreased the secretion of beta-hexosaminidase, decreased the release of histamine, decreased the expression of Th2 cytokines and decreased calcium influx and cell adhesion in antigen-stimulated RBL2H3 cells. Exposure to celastrol decreased the phosphorylation of extracellular regulated kinase (ERK) and the ERK kinase activity was decreased in RBL2H3 cells. A molecular dynamics simulation showed binding of celastrol to a large pocket in ERK2, which serves as the ATP-binding site. Exposure to celastrol inhibited the interaction between immunoglobulin Fc epsilon receptor I (FcepsilonRIgamma) and ERK and inhibited interaction between FcepsilonRIgamma and protein kinase C delta (PKCdelta). Antigen stimulation induced an interaction between Rac1 and ERK as well as an interaction between Rac1 and PKCdelta. Inhibition of ERK decreased Rac1 activity and inhibition of Rac1 decreased ERK activity in antigen-stimulated RBL2H3 cells. Celastrol regulated the expression of epithelial-mesenchymal transition (EMT)-related proteins through inhibition of PKCalpha, PKCdelta, and Rac1 in antigen-stimulated RBL2H3 cells. Exposure to celatrol inhibited PKCdelta activity in antigen-stimulated RBL2H3 cells. Celastrol exerted a negative effect on FcepsilonRIbeta signaling by inhibiting the interaction between heat shock protein 90 (hsp90) and proteins, such as, FcepsilonRIbeta, Akt and PKCalpha. Celastrol exerted a negative effect on in vivo atopic dermatitis induced by 2, 4-dinitrofluorobenzene (DNFB), which requires ERK. Celastrol also showed an inhibitory effect on skin inflammation induced by phorbol myristate acetate (PMA) in Balb/c mice. In summary, celastrol binds to ERK and inhibits FcepsilonRI signaling to exert an anti-inflammatory effect.

A novel antiinflammatory role for andrographolide in asthma via inhibition of the nuclear factor-kappaB pathway

RATIONALE

Persistent activation of nuclear factor (NF)-kappaB has been associated with the development of asthma. Andrographolide, the principal active component of the medicinal plant Andrographis paniculata, has been shown to inhibit NF-kappaB activity.

OBJECTIVES

We hypothesized that andrographolide may attenuate allergic asthma via inhibition of the NF-kappaB signaling pathway.

METHODS

BALB/c mice sensitized and challenged with ovalbumin (OVA) developed airway inflammation. Bronchoalveolar lavage fluid was assessed for total and differential cell counts, and cytokine and chemokine levels. Serum IgE levels were also determined. Lung tissues were examined for cell infiltration and mucus hypersecretion, and the expression of inflammatory biomarkers. Airway hyperresponsiveness was monitored by direct airway resistance analysis.

MEASUREMENTS AND MAIN RESULTS

Andrographolide dose-dependently inhibited OVA-induced increases in total cell count, eosinophil count, and IL-4, IL-5, and IL-13 levels recovered in bronchoalveolar lavage fluid, and reduced serum level of OVA-specific IgE. It attenuated OVA-induced lung tissue eosinophilia and airway mucus production, mRNA expression of E-selectin, chitinases, Muc5ac, and inducible nitric oxide synthase in lung tissues, and airway hyperresponsiveness to methacholine. In normal human bronchial epithelial cells, andrographolide blocked tumor necrosis factor-alpha-induced phosphorylation of inhibitory kappaB kinase-beta, and downstream inhibitory kappaB alpha degradation, p65 subunit of NF-kappaB phosphorylation, and p65 nuclear translocation and DNA-binding activity. Similarly, andrographolide blocked p65 nuclear translocation and DNA-binding activity in the nuclear extracts from lung tissues of OVA-challenged mice.

CONCLUSIONS

Our findings implicate a potential therapeutic value of andrographolide in the treatment of asthma and it may act by inhibiting the NF-kappaB pathway at the level of inhibitory kappaB kinase-beta activation.

Mitogen-activated protein kinase/extracellular signal-regulated kinase 1/2-dependent pathways are essential for CD8+ T cell-mediated airway hyperresponsiveness and inflammation

BACKGROUND

Ligation of the leukotriene B(4) (LTB(4)) receptor 1 on effector memory CD8(+) T cells by LTB(4) is important for the recruitment of CD8(+) T cells into the airways, which appears central to the induction of airway hyperresponsiveness (AHR) and allergic inflammation. Phosphorylation of extracellular signal-regulated kinase (ERK) is important in activation and cytokine production from many cell types.

OBJECTIVE

The roles of ERKs in effector CD8(+) T-cell function and on CD8(+) T cell-mediated AHR were determined.

METHODS

Effector CD8(+) T cells were generated from OVA(257-264) (SIINFEKL) peptide-primed mononuclear cells from OT-1 mice. The effects of U0126, an ERK inhibitor, on effector CD8(+) T-cell function and on CD8(+) T cell-mediated AHR and allergic inflammation were examined.

RESULTS

Pretreatment of effector CD8(+) T cells with U0126 suppressed anti-CD3/anti-CD28-induced ERK1/2 phosphorylation and cytokine production, but did not affect LTB(4)-induced Ca(2+) mobilization or chemotaxis. Adoptive transfer of U0126-treated CD8(+) T cells into sensitized mice before secondary allergen challenge resulted in significant decreases in AHR, eosinophilic inflammation, goblet cell metaplasia, and IL-5 and IL-13 levels in bronchoalveolar lavage fluid of recipient mice. The number of transferred CD8(+) T cells accumulating in bronchoalveolar lavage fluid or lungs was unaffected by treatment.

CONCLUSION

ERK1/2-dependent pathways are essential for the effector functions of CD8(+) T cells, including T(H)2 cytokine production, allergic inflammation, and development of AHR. Inhibition of ERK1/2 signaling has potential therapeutic benefit in preventing CD8(+) T cell-mediated AHR.

FIP1L1-PDGFRalpha imposes eosinophil lineage commitment on hematopoietic stem/progenitor cells

Although leukemogenic tyrosine kinases (LTKs) activate a common set of downstream molecules, the phenotypes of leukemia caused by LTKs are rather distinct. Here we report the molecular mechanism underlying the development of hypereosinophilic syndrome/chronic eosinophilic leukemia by FIP1L1-PDGFRalpha. When introduced into c-Kit(high)Sca-1(+)Lineage(-) cells, FIP1L1-PDGFRalpha conferred cytokine-independent growth on these cells and enhanced their self-renewal, whereas it did not immortalize common myeloid progenitors in in vitro replating assays and transplantation assays. Importantly, FIP1L1-PDGFRalpha but not TEL-PDGFRbeta enhanced the development of Gr-1(+)IL-5Ralpha(+) eosinophil progenitors from c-Kit(high)Sca-1(+)Lineage(-) cells. FIP1L1-PDGFRalpha also promoted eosinophil development from common myeloid progenitors. Furthermore, when expressed in megakaryocyte/erythrocyte progenitors and common lymphoid progenitors, FIP1L1-PDGFRalpha not only inhibited differentiation toward erythroid cells, megakaryocytes, and B-lymphocytes but aberrantly developed eosinophil progenitors from megakaryocyte/erythrocyte progenitors and common lymphoid progenitors. As for the mechanism of FIP1L1-PDGFRalpha-induced eosinophil development, FIP1L1-PDGFRalpha was found to more intensely activate MEK1/2 and p38(MAPK) than TEL-PDGFRbeta. In addition, a MEK1/2 inhibitor and a p38(MAPK) inhibitor suppressed FIP1L1-PDGFRalpha-promoted eosinophil development. Also, reverse transcription-PCR analysis revealed that FIP1L1-PDGFRalpha augmented the expression of C/EBPalpha, GATA-1, and GATA-2, whereas it hardly affected PU.1 expression. In addition, short hairpin RNAs against C/EBPalpha and GATA-2 and GATA-3KRR, which can act as a dominant-negative form over all GATA members, inhibited FIP1L1-PDGFRalpha-induced eosinophil development. Furthermore, FIP1L1-PDGFRalpha and its downstream Ras inhibited PU.1 activity in luciferase assays. Together, these results indicate that FIP1L1-PDGFRalpha enhances eosinophil development by modifying the expression and activity of lineage-specific transcription factors through Ras/MEK and p38(MAPK) cascades.

Role of multidrug resistance-associated protein 1 in the pathogenesis of allergic airway inflammation

Multidrug resistance-associated protein 1 (MRP1) is a cysteinyl leukotriene (CysLT) export pump expressed on mast cells. CysLTs are crucial mediators in allergic airway disease. However, biological significance of MRP1 in allergic airway inflammation has not yet been elucidated. In this study, we sensitized wild-type control mice (mrp1(+/+)) and MRP1-deficient mice (mrp1(-/-)) to ovalbumin (OVA) and challenged them with OVA by aerosol. Airway inflammation and goblet cell hyperplasia after OVA exposure were reduced in mrp1(-/-) mice compared with mrp1(+/+) mice. Furthermore, CysLT levels in bronchoalveolar lavage fluid (BALF) from OVA-exposed mrp1(-/-) mice were significantly lower than those from OVA-exposed mrp1(+/+) mice. Levels of OVA-specific IgE, IL-4, and IL-13 in BALF were also decreased in OVA-exposed mrp1(-/-) mice. IgE-mediated release of CysLTs from murine bone marrow-derived mast cells was markedly impaired by MRP1 deficiency. Our results indicate that MRP1 plays an important role in the development of allergic airway inflammation through regulation of IgE-mediated CysLT export from mast cells.

Acetamide-45 inhibited hyperresponsiveness and airway inflammation in mice partly depending on phosphodiesterase activity suppression

AIM

Asthma is characterized as a chronic inflammatory disorder of the airways. Phosphodiesterases (PDE), which hydrolyze cAMP, are considered to play important roles in asthma. We previously reported that acetamide-45 could inhibit cAMP-PDE activity, and histamine- and methacholine-induced contractions of isolated guinea pig trachea. The purpose of this study is to determine whether this agent could suppress allergic-induced airway hyperresponsiveness (AHR) and airway inflammation in allergic mice.

METHODS

A mouse model for asthma was used to investigate acetamide-45 on the airway lesions compared with glucocorticoids. The study was conducted on mice sensitized and challenged with ovalbumin and the whole body plethysmography was carried out to assess AHR. The bronchoalveolar lavage (BAL) histopathology was examined.

RESULTS

We found that acetamide-45 significantly inhibited the enhanced hyperresponsiveness and eosinophil recruitment in airways with elimination of cAMP-PDE activity in lung tissue. Elevated IL-4 and IL-5 in bronchoalveolar lavage fluid (BALF) in asthmatic mice were markedly decreased.

CONCLUSION

Our results indicate that the agent has a potential role in inflammatory disease.

Silibinin inhibits cytokine-induced signaling cascades and down-regulates inducible nitric oxide synthase in human lung carcinoma A549 cells

Recently, we reported that silibinin inhibits primary lung tumor growth and progression in mice and down-regulates inducible nitric oxide synthase (iNOS) expression in tumors; however, the mechanisms of silibinin action are largely not understood. Also, the activation of signaling pathways inducing various transcription factors are associated with lung carcinogenesis and their inhibition could be an effective strategy to prevent and/or treat lung cancer. Herein, we used human lung epithelial carcinoma A549 cells to explore the potential mechanisms and observed strong iNOS expression by cytokine mixture (containing 100 units/mL IFN-gamma + 0.5 ng/mL interleukin-1beta + 10 ng/mL tumor necrosis factor-alpha). We also examined the cytokine mixture-activated signaling cascades, which could potentially up-regulate iNOS expression, and then examined the effect of silibinin (50-200 mumol/L) on these signaling cascades. Silibinin treatment inhibited, albeit to different extent, the cytokine mixture-induced activation of signal transducer and activator of transcription 1 (Tyr(701)), signal transducer and activator of transcription 3 (Tyr(705)), activator protein-1 family of transcription factors, and nuclear factor-kappaB. The results for activator protein-1 were correlated with the decreased nuclear levels of phosphorylated c-Jun, c-Jun, JunB, JunD, phosphorylated c-Fos, and c-Fos. Further, silibinin also strongly decreased cytokine mixture-induced phosphorylation of extracellular signal-regulated kinase 1/2 but only marginally affected JNK1/2 phosphorylation. Silibinin treatment also decreased constitutive p38 phosphorylation in the presence or absence of cytokine mixture. Downstream of these pathways, silibinin strongly decreased cytokine mixture-induced expression of hypoxia-inducible factor-1alpha without any considerable effect on Akt activation. Cytokine mixture-induced iNOS expression was completely inhibited by silibinin. Overall, these results suggest that silibinin could target multiple cytokine-induced signaling pathways to down-regulate iNOS expression in lung cancer cells and that could contribute to its overall cancer preventive efficacy against lung tumorigenesis.

Oral administration of allergen extracts from Dermatophagoides farinae desensitizes specific allergen-induced inflammation and airway hyperresponsiveness in rats

Clinically sublingual immunotherapy (SLIT) by using allergen extracts effectively alleviates the symptoms of allergic rhinitis and asthma. Supposed that oral administration of high-dose of allergen extracts imitates SLIT and may prevent IgE-related responses in allergic diseases, we investigated the effects of oral administration of allergen extracts from Dermatophagoides farinae (Derf) on allergen-induced inflammation and airway hyperresponsiveness (AHR) in a model of asthmatic rat. After administration to the specific Derf-sensitized rats with Derfdrop solution containing Derf1 and Derf2 extracts derived from Derf, the effects of Derfdrop on AHR, inflammatory cell accumulation, cytokine production in the bronchoalveolar lavage fluid and lung tissue, as well as serum IgE and IgG levels were investigated. Results indicated that Derfdrop not only dose-dependently prevented the AHR in response to methacholine, but also significantly reduced the serum total and allergen-specific IgE levels, all the maximal effects were achieved at dose of 5 mg/kg/d, and were as comparable as those of dexamethasone at dose of 1.0 mg/kg/d. Furthermore, oral administration of Derfdrop not only dose-dependently elevated allergen-specific serum IgG levels and reduced total and allergen-specific IgE levels, but also normalized the imbalance between the Th1 cytokine, IFN-gamma and Th2 cytokine, IL-4. Finally, oral administration of Derfdrop significantly reduced Goblet cell hyperplasia and eosinophilia in the Derf-sensitized allergic rat model. These data suggest that Derfdrop effectively improves specific allergen-induced inflammation and AHR in Derf-sensitized and -challenged rats and provide with the rationale for clinical SLIT by using Derfdrop in a specific allergen-induced asthma.

Proteome analysis of chronically inflamed lungs in a mouse chronic asthma model

BACKGROUND

Asthma is a chronic airway inflammatory disease characterized by airway wall remodeling. The mechanisms underlying airway remodeling in asthma are not fully understood. There is an urgent need to investigate global protein profiling of chronically inflamed lungs to identify novel pathogenic molecules and biomarkers for chronic asthma. In this study, we described the first differentially expressed proteome of lung tissue and bronchoalveolar lavage fluid from a mouse chronic asthma model.

METHODS

BALB/c mice sensitized to ovalbumin were challenged with ovalbumin aerosol 3 times per week for 8 weeks. The lung tissue and lavage fluid proteins were resolved by 2-dimensional gel electrophoresis, and differentially expressed proteins were identified by matrix-assisted laser desorption/ionization time-of-flight tandem mass spectrometry.

RESULTS

Airway goblet cell hyperplasia, smooth muscle hyperplasia, subepithelial fibrosis, airway hyperresponsiveness, pulmonary inflammatory cell infiltration and elevated serum ovalbumin-specific IgE level were observed in our chronic asthma model. We have identified at least 100 protein spots that were differentially expressed in chronically inflamed lungs, and the identity of 66 protein spots was confirmed.

CONCLUSIONS

Many of these proteins, including cytoskeleton-related proteins, Ca2+-binding proteins and anti-oxidant proteins, may be related to the development of airway remodeling, and they should be evaluated further as potential therapeutic targets and biomarkers for chronic asthma.

Inhibitory effects of Duchesnea chrysantha extract on ovalbumin-induced lung inflammation in a mouse model of asthma

ETHNOPHARMACOLOGICAL RELEVANCE

Duchesnea chrysantha (D. chrysantha) is a herb with anti-oxidative, anti-inflammatory and immune-enhancing properties.

AIM OF THE STUDY

Asthma is an inflammatory disease of the lungs, and the hallmarks of the disease are increased inflammatory cell infiltration into the airways and poor respiratory function. Although there is the possibility that D. chrysantha may have an inhibitory effect on lung inflammation, the effects of D. chrysantha on asthma have not been fully investigated. In the present study, we investigated the anti-inflammatory activity of D. chrysantha extract (Dc extract) on lung inflammation in a murine model of ovalbumin-induced asthma.

MATERIALS AND METHODS

Dc extract was obtained from dried and powdered whole plants of D. chrysantha using 80% ethanol. BALB/c mice induced by ovalbumin sensitization and nebulization were used as a mouse model of asthma. RT-PCR and ELISA were performed to measure mRNA and protein expression of cytokines. We examined the effects of Dc extract on leukocyte infiltration and mucus secretion using periodic acid-Schiff staining as well as hematoxylin and eosin staining.

RESULTS

Dc extract significantly inhibited leukocytosis and eosinophilia in the bronchoalveolar lavage (BAL) fluid (p<0.01). Dc extract significantly reduced the elevated infiltration of inflammatory cells (p<0.05) and inhibited the increased mucus secretion, despite the absence of significant value. Although Dc extract weakly inhibited the mRNA expression of IL-4, IL-5, IL-13, and eotaxin, it strongly inhibited the protein expression of IL-5 (p<0.05) and eotaxin (p<0.01) in BAL fluid. Ovalbumin-specific IgE levels in the serum and BAL fluid were blocked by Dc extract (p<0.05).

CONCLUSIONS

These results suggest the possibility that Dc extract can exert suppressive effects on asthma and may provide evidence that Dc extract is a useful agent for the treatment of allergic airway disease.

Cell-specific activation profile of extracellular signal-regulated kinase 1/2, Jun N-terminal kinase, and p38 mitogen-activated protein kinases in asthmatic airways

BACKGROUND

Many airway cells manifest signs of chronic activation in asthma. The mechanism of this chronic activation is unknown.

OBJECTIVES

We sought to study the activation of the mitogen-activated protein kinase (MAPK) signaling pathway in airway cells.

METHODS

Endobronchial biopsy specimens from patients with severe and mild asthma (n = 17 in each group) and healthy control subjects (n = 15) were analyzed for the phosphorylated MAPKs extracellular signal-regulated kinase (ERK) 1/2, p38, and Jun N-terminal kinase (JNK) and their downstream effectors by means of immunofluorescence staining. Airway epithelial activation of ERK1/2 and p38 was studied by using Western blotting. Epithelial function was studied by means of real-time PCR, ELISA, and the thymidine incorporation assay.

RESULTS

We detected strong phospho-ERK1/2 staining in airway epithelium and smooth muscle cells in biopsy specimens from asthmatic patients. Fluorescent areas per image, as well as mean fluorescence intensity, were significantly (P < .0001) different among the 3 study groups (patients with severe asthma, patients with mild asthma, and healthy control subjects). Patients with severe asthma also demonstrated strong phospho-p38 staining, mostly in epithelial cells, which was significantly different from that in patients with mild asthma (P = .0001) and healthy control subjects (P = .02). Phospho-JNK primarily stained airway smooth muscle cells. Healthy subjects showed the highest intensity of phospho-JNK staining compared with that seen in patients with severe (P = .004) and mild asthma (P = .003). Inhibition of ERK1/2 and p38 in primary airway epithelial cells blocked their proliferation and expression of select, but not all, chemokines.

CONCLUSIONS

Significant phosphorylation of ERK1/2 and p38 and their correlation with disease severity suggests that the foregoing signaling pathways play an important role in asthma. The ERK1/2 and p38 pathways regulate epithelial cell secretory function and proliferation.

The role of sphingosine kinase in a murine model of allergic asthma

Asthma is an allergic disease characterized by chronic airway eosinophilia and pulmonary infiltration of lymphocytes, particularly of the Th2 subtype, macrophages and mast cells. Previous studies have shown a pivotal role for sphingosine kinase (SphK) on various proinflammatory cells, such as lymphocyte and eosinophil migration and mast cell degranulation. We therefore examined the roles of SphK in a murine model of allergic asthma. In mice previously sensitized to OVA, i.p. administration of N,N-dimethylsphingosine (DMS), a potent SphK inhibitor, significantly reduced the total inflammatory cell infiltrate and eosinophilia and the IL-4, IL-5, and eotaxin levels in bronchoalveolar lavage fluid in response to inhaled OVA challenge. In addition, DMS significantly suppressed OVA-induced inflammatory infiltrates and mucus production in the lungs, and airway hyperresponsiveness to methacholine in a dose-dependent manner. OVA-induced lymphocyte proliferation and IL-4 and IL-5 secretion were reduced in thoracic lymph node cultures from DMS-treated mice. Moreover, similar reduction in inflammatory infiltrates, bronchoalveolar lavage, IL-4, IL-5, eotaxin, and serum OVA-specific IgE levels was observed in mice with SphK1 knock-down via small interfering RNA approach. Together, these data demonstrate the therapeutic potential of SphK modulation in allergic airways disease.

Cell-penetrating peptides and proteins: new inhibitors of allergic airways disease

Cell-penetrating peptides (CPPs) or protein transduction domains (PTDs) are peptides that have the ability to efficiently traverse cellular membranes, either alone or in association with molecular cargo. Several naturally occurring PTDs, including those from HIV TAT and Drosophila antennapedia, have this unique activity. Synthetic CPPs, such as polyarginine, also have the ability to enter cells and transport a variety of cargo. While the precise mechanism(s) of cellular entry for individual CPPs may vary, it is likely that uptake is mediated, at least in part, through endocytosis. Moreover, biological activity of cell-penetrating peptides and proteins has been clearly demonstrated in a number of in vitro and in vivo studies. Recently, cell-penetrating proteins targeting the Ras GTPase and the phospholipid kinase PI3K (phosphoinositide 3-kinase) have been shown to inhibit eosinophil trafficking and survival in vitro. These proteins, as well as CPPs targeting the STAT-6 transcription factor or the T-cell costimulatory molecule CTLA-4 (cytotoxic T lymphocyte-associated antigen-4), have also been tested in animal models of asthma. Data from several groups, including ours, indicate that these molecules inhibit airway eosinophilic inflammation, airway hyperresponsiveness (AHR), and mucus production in experimental allergic airways disease. Thus, CPPs targeting these and other signaling molecules may also effectively inhibit allergic airways disease in humans.

MAP kinases mediate interleukin-13 effects on calcium signaling in human airway smooth muscle cells

Interleukin-13 (IL-13) has been strongly implicated in the pathogenesis of allergic asthma through animal models that have shown that IL-13 is both necessary and sufficient to cause airway hyperresponsiveness (AHR). Airway smooth muscle (ASM) is a primary effector of AHR, and IL-13 increases the responsiveness of ASM, by increasing Ca(2+) release intracellularly, to bronchoconstrictors such as histamine. The mechanisms and signaling pathways mediating this effect are incompletely understood. We have investigated the pathways through which IL-13 regulates the Ca(2+) response to histamine in primary human ASM cell cultures. Functional IL-13 receptors were demonstrated by IL-13-mediated phosphorylation of signal transducer and activator of transcription 6 (STAT6) and mitogen-activated protein kinases (MAPKs). IL-13 increased Ca(2+) responses to histamine. The augmentation of Ca(2+) signaling was not affected by inhibition of STAT6 or p38 MAPK signaling but was prevented by concurrent inhibition of c-jun N-terminal kinase (JNK) and extracellular signal-related kinase (ERK) MAPKs. This inhibition did not affect the IL-13-induced increase in histamine receptors. We conclude that IL-13 induces potentiation of Ca(2+) responses to contractile agonists by affecting mechanisms downstream of receptors. JNK and ERK MAPKs modulate these mechanisms.

Hyaluronic acid targets CD44 and inhibits FcepsilonRI signaling involving PKCdelta, Rac1, ROS, and MAPK to exert anti-allergic effect

Effects of hyaluronic acid (HA) on allergic inflammation were investigated. HA exerted negative effects on beta-hexoaminidase secretion and histamine release in antigen-stimulated rat basophilic leukemia (RBL2H3) cells. HA inhibited interaction between IgE and FcepsilonRI and between FcepsilonRI and PKCdelta. HA inhibited CD44 interaction with PKCalpha, indicating that HA targets CD44. PKCalpha and -delta were responsible for increased Rac1 activity and expression of p47(phox), p67(phox). HA inhibited phosphorylation of PKCalpha and -delta. Rac1 was responsible for increased ROS, and NADPH oxidase was the main source for ROS. The inhibition of PKC prevented antigen from increasing phosphorylation of ERK and p38 MAPK. ERK, p38 MAPK, and ROS, were responsible for secretion of beta-hexosaminidase, histamine release, and induction of chemokines. HA suppressed induction of chemokines, such as MIP-2 and Sprr-2a. CD44 mediated effect of antigen on phosphorylation of ERK, p38MAPK, ROS production, secretion of beta-hexosaminidase, and histamine release. GPCR did not mediate allergic function of antigen or affect anti-allergic function of HA. In vivo anti-allergic effect of HA was investigated using Nc/Nga mice model of DNFB-induced atopic dermatitis. HA reduced skin lesions in Nc/Nga mice treated with DNFB, decreased expression levels of MIP-2, Sprr-2a, and serum IgE level. In conclusion, hyaluronic acid exerts negative effect on allergic inflammation by targeting CD44 and inhibiting FcepsilonRI signaling.

Protection of transplant-induced hepatic ischemia/reperfusion injury with carbon monoxide via MEK/ERK1/2 pathway downregulation

Carbon monoxide (CO), a product of heme degradation by heme oxygenases (HO), has been shown to provide cytoprotection in various tissue injury models. This study examined the efficacy and molecular mechanisms of exogenously delivered inhaled CO in protecting liver grafts from cold ischemia/reperfusion (I/R) injury associated with liver transplantation. Orthotopic syngenic liver transplantation (OLT) was performed in Lewis rats with 18-h cold preservation in University of Wisconsin solution. Recipients were exposed to air or different concentrations of CO (20-250 ppm) for 1 h before and 24 h after OLT and killed 1-48 h posttransplant. CO inhalation significantly decreased serum alanine transaminase (ALT) levels and suppressed hepatic necrosis and neutrophil accumulation at 24-48 h after OLT in a dose-dependent manner. Reduced hepatic injury with inhaled CO is associated with marked downregulation of early mRNA expression for TNF-alpha and IL-6. Expression in liver grafts of mRNA and protein of the stress-responding enzyme inducible nitric oxide synthase was significantly reduced by CO, while HO-1 was only marginally suppressed. Cold hepatic I/R injury was associated with prompt MAPK phosphorylation in liver grafts at 1 h after OLT, and CO significantly inhibited phosphorylation of ERK1/2 MAPK and its upstream MEK1/2 and downstream transcriptional factor c-Myc. CO also significantly inhibited I/R injury-induced STAT1 and STAT3 activation. In contrast, CO did not inhibit p38 or JNK MAPK pathways during hepatic I/R injury. Results demonstrate that exogenous CO suppresses early proinflammatory and stress-response gene expression and efficiently ameliorates hepatic I/R injury. The possible mechanism may include the downregulation of MEK/ERK1/2 signaling pathway with CO.

Primary prevention of allergic diseases: current concepts and mechanisms

: Atopic diseases, the new "epidemic of the twenty-first century" and a central health problem of industrial nations, call for the development of innovative primary prevention strategies. The present review provides an overview of current experimental and immunomodulatory procedures and their underlying mechanisms.