Infliximab alleviates inflammation and ex vivo airway hyperreactivity in asthmatic E3 rats

Clinical Characteristics and Management Strategies for Adult Obese Asthma Patients

The rates of asthma and obesity are increasing concurrently in the United States. Epidemiologic studies demonstrate that the incidence of asthma increases with obesity. Furthermore, obese individuals have asthma that is more severe, harder to control, and resistant to standard medications. In fact, specific asthma-obesity phenotypes have been identified. Various pathophysiologic mechanisms, including mechanical, inflammatory, metabolic and microbiome-associated, are at play in promulgating the obese-asthma phenotypes. While standard asthma medications, such as inhaled corticosteroids and biologics, are currently used to treat obese asthmatics, they may have limited effectiveness. Targeting the underlying aberrant processes, such as addressing steroid resistance, microbiome, metabolic and weight loss approaches, may be helpful.

Muc5ac Production Inhibited by Decreased lncRNA H19 via PI3K/Akt/NF-kB in Asthma

Introduction

LncRNAs play important roles in multiple diseases including asthma, while there are a few reports on the role of lncRNA H19 about asthma. This study aimed to investigate the roles and mechanisms of lncRNA H19 in asthma.

Methods

We detected lncRNA H19 and Muc5ac mRNA by establishing a murine asthma model and an in vitro inflammation model. Regulatory roles of lncRNA H19 in asthma were explored by lncRNA H19 overexpression or knockdown in vitro. To study its mechanisms, we detect p-NF-κB and p-Akt expression, and treated 16-HBE cells with inhibitors of PI3K. To study regulatory effects of miR-675-3p on Muc5ac, miR-675-3p mimics and inhibitors were respectively transfected into 16-HBE cells.

Results

Firstly, we established a murine asthma model and an in vitro inflammation model. We found that lncRNA H19 expression was decreased, while Muc5ac mRNA was increased in lung tissues of murine asthma model and in the in vitro inflammation model. lncRNA H19 overexpression increased Muc5ac mRNA expression and lncRNA H19 knockdown decreased Muc5ac mRNA expression in 16-HBE cells. Moreover, lncRNA H19 overexpression further increased Muc5ac expression in TNFα-induced in vitro inflammation model. lncRNA H19 knockdown decreased p-Akt and p-NF-κB expression. Inhibitors of PI3K abolished Muc5ac induced by lncRNA H19 overexpression. Although miR-675-3p was increased by lncRNA H19 overexpression, it had no regulatory effects on Muc5ac expression.

Discussion

These results demonstrated that lncRNA H19 positively regulates Muc5ac expression through PI3K/Akt /NF-κB pathway in the in vitro inflammation model. Therefore, this study indicated that decreased lncRNA H19 in asthma might play a protective role relieving mucus overproduction, and lncRNA H19 might be a potential target for asthma treatment.

Effects of TNF-α antagonist infliximab on fructose-induced metabolic syndrome in rats

Public health issues have been raised regarding fructose toxicity and its serious metabolic disorders. Deleterious effects of high fructose intake on insulin sensitivity, body weight, lipid homeostasis have been identified. The new millennium has witnessed the emergence of a modern epidemic, the metabolic syndrome (MS), in approximately 25% of the world's adult population. The current study aimed to investigate the effect of the TNF-α antagonist infliximab on fructose-induced MS in rats. Rats were administered fructose (10%) in drinking water for 12 weeks to induce the experimental MS model. infliximab (5 mg/kg) was injected once weekly intraperitoneally starting on the 13th week for 4 weeks. Increase in body weight, blood glucose level, serum triglycerides (TGs), adiponectin level and blood pressure were present in MS rats. They also prompted increases in serum of leptin, TNF-α, and malondialdehyde (MDA) levels. Treatment with infliximab did not affect body weight, hyperglycemia or hypertension, but decreased serum TGs and increased serum HDL-c levels. Infliximab also decreased adiponectin levels. Surprisingly, infliximab increased MDA above its value in the MS group. These results reflect the fact that infliximab affects the manifestations of MS in rats. Though infliximab reduced TGs, increased HDL-c levels, reversed adiponectin resistance occurred by fructose, the drug failed to combat MS-mediated hyperglycemia, hypertension, and elevated MDA above the insult.

Isorhamnetin attenuates TNF-α-induced inflammation, proliferation, and migration in human bronchial epithelial cells via MAPK and NF-κB pathways

Isorhamnetin has distinct anti-inflammatory activity and inhibits cell proliferation and migration. These effects are also involved in the pathogenesis of asthma. However, the effect of isorhamnetin on bronchial epithelial cells in patients with asthma has not been examined. Cells of human bronchial epithelial cell line BEAS-2B were cultured with isorhamnetin and tumor necrosis factor (TNF)-α. The effects of isorhamnetin on BEAS-2B cell viability were assessed using CCK8 assay. The EdU (5-ethynyl-2'-deoxyuridine) cell proliferation assay was performed to assess cell proliferation. BEAS-2B cell migration was measured using Transwell and wound healing assays. Real-time PCR and enzyme-linked immunosorbent assay were conducted to measure the expression of pro-inflammatory cytokines. Protein expression levels were determined by western blotting. Immunofluorescence was used to detect nuclear translocation of nuclear factor kappa B (NF-κB). We found that isorhamnetin at 20 and 40 μM reduced the proliferation of BEAS-2B cells induced by TNF-α. Isorhamnetin significantly decreased the expression of interleukin (IL)-1β, IL-6, IL-8, and C-X-C motif chemokine ligand 10 in BEAS-2B cells induced by TNF-α. Additionally, 10 μM isorhamnetin effectively reduced cell migration induced by TNF-α. Treatment with isorhamnetin inhibited the phosphorylation of mitogen-activated protein kinase (MAPK) and NF-κB pathways induced by TNF-α. In summary, isorhamnetin inhibited the inflammation, proliferation, and migration of BEAS-2B cells by regulating the MAPK and NF-κB signaling pathways and is a drug candidate for asthma.

TNFR2 Signaling Enhances ILC2 Survival, Function, and Induction of Airway Hyperreactivity

Group 2 innate lymphoid cells (ILC2s) can initiate pathologic inflammation in allergic asthma by secreting copious amounts of type 2 cytokines, promoting lung eosinophilia and airway hyperreactivity (AHR), a cardinal feature of asthma. We discovered that the TNF/TNFR2 axis is a central immune checkpoint in murine and human ILC2s. ILC2s selectively express TNFR2, and blocking the TNF/TNFR2 axis inhibits survival and cytokine production and reduces ILC2-dependent AHR. The mechanism of action of TNFR2 in ILC2s is through the non-canonical NF-κB pathway as an NF-κB-inducing kinase (NIK) inhibitor blocks the costimulatory effect of TNF-α. Similarly, human ILC2s selectively express TNFR2, and using hILC2s, we show that TNFR2 engagement promotes AHR through a NIK-dependent pathway in alymphoid murine recipients. These findings highlight the role of the TNF/TNFR2 axis in pulmonary ILC2s, suggesting that targeting TNFR2 or relevant signaling is a different strategy for treating patients with ILC2-dependent asthma.

Anti-TNFα therapy in inflammatory lung diseases

Increased levels of tumor necrosis factor (TNF) α have been linked to a number of pulmonary inflammatory diseases including asthma, chronic obstructive pulmonary disease (COPD), acute lung injury (ALI)/acute respiratory distress syndrome (ARDS), sarcoidosis, and interstitial pulmonary fibrosis (IPF). TNFα plays multiple roles in disease pathology by inducing an accumulation of inflammatory cells, stimulating the generation of inflammatory mediators, and causing oxidative and nitrosative stress, airway hyperresponsiveness and tissue remodeling. TNFα-targeting biologics, therefore, present a potentially highly efficacious treatment option. This review summarizes current knowledge on the role of TNFα in pulmonary disease pathologies, with a focus on the therapeutic potential of TNFα-targeting agents in treating inflammatory lung diseases.

Investigation of anti-asthmatic potential of dried fruits of Vitis vinifera L. in animal model of bronchial asthma

Background

Fruits of Vitis vinifera L., commonly known as grapes, are largely consumed worldwide because of their high nutritional and medicinal benefits.

Context and purpose

The present study investigated effects of V. vinifera fruits in ovalbumin-induced animal model of bronchial asthma.

Methods

Male wistar rats (except group 1) were sensitized with allergen (ovalbumin, 40 mg/rat + aluminum hydroxide, 2 mg/rat). Groups of sensitized animals were treated orally with either vehicle (0.4 mL/kg), standard dexamethasone (2.5 mg/kg) or alcoholic extract of V. vinifera dried fruits (31 and 42.5 mg/kg) from day 1 to 28 (n = 6 for all groups). Inflammatory markers including cell counts, cytokines such as interleukin (IL)-4, IL-5, IL-1β, tumor necrosis factor, immunoglobulin E (IgE), leukotrienes and nitrite levels in both blood/serum and bronchoalveolar fluid were analysed. Breathing rate and tidal volume as lung function parameters were examined by spirometer. Lung tissues were studied for histamine content and histopathology.

Results

Treatment of sensitized animals with dexamethasone or two doses of V. vinifera fruits extract inhibited recruitment of inflammatory cytokines, IgE, nitrites and circulating cells particularly eosinophils in blood/serum and bronchoalveolar fluid (p < 0.001, p < 0.01 and p < 0.05). Dexamethasone and V. vinifera fruits extract treatment also normalized lung functions and histamine levels compared to ovalbumin-sensitized controls (p < 0.05 and p < 0.01). Moreover, both drugs exhibited protection against airway inflammation in lung histology.

Conclusion

Results of study demonstrate the effectiveness of V. vinifera fruits in allergic asthma possibly related to its ability to inhibit cellular response and subsequent production of inflammatory cytokines.

Electronic supplementary material

The online version of this article (doi:10.1186/s13223-016-0145-x) contains supplementary material, which is available to authorized users.

Anti-Interleukin-1 Beta/Tumor Necrosis Factor-Alpha IgY Antibodies Reduce Pathological Allergic Responses in Guinea Pigs with Allergic Rhinitis

This study aims to determine whether the combined blockade of IL-1β and TNF-α can alleviate the pathological allergic inflammatory reaction in the nasal mucosa and lung tissues in allergic rhinitis (AR) guinea pigs. Healthy guinea pigs treated with saline were used as the healthy controls. The AR guinea pigs were randomly divided into (1) the AR model group treated with intranasal saline; (2) the 0.1% nonspecific IgY treatment group; (3) the 0.1% anti-TNF-α IgY treatment group; (4) the 0.1% anti-IL-1β IgY treatment group; (5) the 0.1% combined anti-IL-1β and TNF-α IgY treatment group; and (6) the fluticasone propionate treatment group. The inflammatory cells were evaluated using Wright's staining. Histopathology was examined using hematoxylin-eosin staining. The results showed that the number of eosinophils was significantly decreased in the peripheral blood, nasal lavage fluid, and bronchoalveolar lavage fluid (P < 0.05), and eosinophil, neutrophil, and lymphocyte infiltration and edema were significantly reduced or absent in the nasal mucosa and lung tissues (P < 0.05) in the combined 0.1% anti-IL-1β- and TNF-α IgY-treated guinea pigs. The data suggest that topical blockade of IL-1β and TNF-α could reduce pathological allergic inflammation in the nasal mucosa and lung tissues in AR guinea pigs.

Protective Effects of Infliximab on Lung Injury Induced by Methotrexate

INTRODUCTION

Methotrexate (MTX) is used to treat cancers, several forms of arthritis and other rheumatic conditions, although MTX may cause pulmonary toxicity related to the production of free oxygen radicals, various cytokines. Infliximab (IB) with its potent effect on tumor necrosis factor-alpha (TNF-α) inhibition also inhibits the release of endothelin-1 (ET-1). We aimed to investigate whether IB reduces pulmonary damage induced by an overdose of MTX.

METHOD

The rats were divided into 3 groups of 8 animals. The control group was given only saline. One dose of 20mg/kg MTX intraperitoneal was administered in the MTX group. IB 7 mg/kg was given to the MTX+IB (MI) group. Three days after IB was administered, 20mg/kg MTX was given. Five days after MTX was administered, all rats were sacrificed.

RESULTS

The TNF-α, ET-1, malondialdehyde (MDA), myeloperoxidase (MPO) and caspase-3 levels in MTX group were significantly higher than in control groups of TNF-α (P=.001), ET-1 (P=.001), MDA (P=.001), MPO (P=.001) and caspase-3 levels (P=.001) and MI groups of TNF-α (P=.009), ET-1 (P=.001), MDA (P=.047), MPO (P=.007) and caspase-3 levels (P=.003). The MI group had less histopathological damage in lung tissue than the MTX group.

CONCLUSION

Overdose of MTX leads to cytokine release and the formation of reactive oxygen species in addition to increased ET-1 secretion release that causes lung damage. IB, as a potent proinflammatory agent, TNF-α blocker, can decrease ET-1 release and oxidative stress, it may show significant protective effects in lung tissue against damage caused by MTX overdose.

Protective Effects of Infliximab on Lung Injury Induced by Methotrexate

INTRODUCTION

Methotrexate (MTX) is used to treat cancers, several forms of arthritis and other rheumatic conditions, although MTX may cause pulmonary toxicity related to the production of free oxygen radicals, various cytokines. Infliximab (IB) with its potent effect on tumor necrosis factor-alpha (TNF-α) inhibition also inhibits the release of endothelin-1 (ET-1). We aimed to investigate whether IB reduces pulmonary damage induced by an overdose of MTX.

METHOD

The rats were divided into 3 groups of 8 animals. The control group was given only saline. One dose of 20mg/kg MTX intraperitoneal was administered in the MTX group. IB 7 mg/kg was given to the MTX+IB (MI) group. Three days after IB was administered, 20mg/kg MTX was given. Five days after MTX was administered, all rats were sacrificed.

RESULTS

The TNF-α, ET-1, malondialdehyde (MDA), myeloperoxidase (MPO) and caspase-3 levels in MTX group were significantly higher than in control groups of TNF-α (P=.001), ET-1 (P=.001), MDA (P=.001), MPO (P=.001) and caspase-3 levels (P=.001) and MI groups of TNF-α (P=.009), ET-1 (P=.001), MDA (P=.047), MPO (P=.007) and caspase-3 levels (P=.003). The MI group had less histopathological damage in lung tissue than the MTX group.

CONCLUSION

Overdose of MTX leads to cytokine release and the formation of reactive oxygen species in addition to increased ET-1 secretion release that causes lung damage. IB, as a potent proinflammatory agent, TNF-α blocker, can decrease ET-1 release and oxidative stress, it may show significant protective effects in lung tissue against damage caused by MTX overdose.

Patients with Active Luminal Crohn's Disease Have Evidence of Significant Functional and Clinical Pulmonary Involvement

BACKGROUND

Pulmonary involvement is a recognized extraintestinal complication of inflammatory bowel disease and is associated with airway inflammation. Changes in pulmonary function were previously described as being subclinical. The purpose of this study was to compare pulmonary findings in a large case series of patients with active and quiescent Crohn's disease (CD).

METHODS

CD patients, prospectively enrolled between May 2011 and May 2012, completed a demographic questionnaire and Harvey-Bradshaw Index to define disease activity. Each patient also completed blood work, a chest x-ray, pulmonary function testing, respiratory symptom and dyspnea scoring, and a 6-minute walk test. Results are reported as mean ± SE or descriptively as a percent and were analyzed using t tests and chi-square or Fisher's exact tests, respectively. Multivariable linear regression models were built for continuous outcomes and logistic regression models for categorical outcomes.

RESULTS

Ninety-five patients (54 remission, 41 active disease), 58.9% males, with a mean age of 41 ± 1 years were enrolled. Patients with active disease compared with those in remission had lower absolute ratios of forced expiratory volume in 1 second to forced vital capacity (FEV1/FVC) (0.74 ± 0.01 versus 0.77 ± 0.01, P = 0.023), higher degrees of peripheral airway obstruction (34.1% versus 16.7%, P = 0.049), more frequent respiratory symptoms (29.3% versus 9.3%, P = 0.012) and higher Medical Research Council (MRC) dyspnea scales (MRC 2 or 3, 58.5% versus 22.2%, P = 0.001), respectively.

CONCLUSIONS

CD patients with active disease display clinical pulmonary dysfunction compared with those in remission.

Budesonide increases TLR4 and TLR2 expression in Treg lymphocytes of allergic asthmatics

BACKGROUND

Reduced innate immunity responses as well as reduced T regulatory activities characterise bronchial asthma.

OBJECTIVES

In this study the effect of budesonide on the expression of TLR4 and TLR2 in T regulatory lymphocyte sub-population was assessed.

METHODS

TLR4 and TLR2 expression in total peripheral blood mononuclear cells (PBMC), in CD4+/CD25+ and in CD4+/CD25- was evaluated, by flow cytometric analysis, in mild intermittent asthmatics (n = 14) and in controls (n = 11). The in vitro effects of budesonide in modulating: TLR4 and TLR2 expression in controls and in asthmatics; IL-10 expression and cytokine release (IL-6 and TNF-α selected by a multiplex assay) in asthmatics were also explored.

RESULTS

TLR4 and TLR2 were reduced in total PBMC from asthmatics in comparison to PBMC from controls. CD4+CD25+ cells expressed at higher extent TLR2 and TLR4 in comparison to CD4+CD25- cells. Budesonide was able to increase the expression of TLR4, TLR2 and IL-10 in CD4+/CD25 highly+ cells from asthmatics. TLR4 ligand, LPS induced Foxp3 expression. Budesonide was also able to reduce the release of IL-6 and TNF-α by PBMC of asthmatics.

CONCLUSIONS

Budesonide potentiates the activity of Treg by increasing TLR4, TLR2 and IL-10 expression. This event is associated to the decreased release of IL-6 and TNF-α in PBMC treated with budesonide. These findings shed light on new mechanisms by which corticosteroids, drugs widely used for the clinical management of bronchial asthma, control T lymphocyte activation.

Molecular and physiological events in respiratory muscles and blood of rats exposed to inspiratory threshold loading

High-intensity exercise induces oxidative stress and inflammatory events in muscles. Tumor necrosis factor (TNF)-α may alter muscle protein metabolism or promote muscle regeneration. We hypothesized that a program of noninvasive chronic inspiratory loading of different intensities induces a differential pattern of physiological, molecular, and cellular events within rat diaphragms. Antioxidants and TNF-α blockade may influence those events. In the diaphragm, gastrocnemius, and blood of rats exposed to high-intensity inspiratory threshold loads (2 hour every 24 hours for 14 days), with and without treatment with N-acetyl cysteine or infliximab (anti-TNF-α antibody), inflammatory cells and cytokines, superoxide anion production, myogenesis markers, and muscle structure were explored. In all animals, maximum inspiratory pressure (MIP) and body weight were determined. High-intensity inspiratory loading for 2 weeks caused a decline in MIP and body weight, and in the diaphragm induced a reduction in fast-twitch fiber proportions and sizes, whereas inflammatory cells and cytokine levels, including TNF-α immunohistochemical expression, superoxide anion, internal nuclei counts, and markers of myogenesis were increased. Blockade of TNF-α improved respiratory muscle function and structure, and animal weight, and, in the diaphragm, reduced inflammatory cell numbers and superoxide anion production drastically while inducing larger increases in protein and messenger RNA levels and immunohistochemical expression of TNF-α, internal nuclei, and markers of muscle regeneration. Blunting of TNF-α also induced a reduction in blood inflammatory cytokines and superoxide anion production. We conclude that TNF-α synthesized by inflammatory cells or myofibers could have differential effects on muscle structure and function in response to chronic, noninvasive, high-intensity inspiratory threshold loading.

Adalimumab ameliorates abdominal aorta cross clamping which induced liver injury in rats

The aim of this study was to investigate the possible protective effects of adalimumab (ADA) on cell damage in rat liver tissue during ischemia/reperfusion (I/R) injury of infrarenal abdominal aorta. Thirty male Wistar-albino rats were divided into three groups: control, I/R, and I/R+ADA, each group containing 10 animals. Laparotomy without I/R injury was performed in the control group animals. Laparotomy in the I/R group was followed by two hours of infrarenal abdominal aortic cross ligation and then two hours of reperfusion. ADA (50 mg/kg) was administered intraperitoneally as a single dose, to the I/R+ADA group, five days before I/R. The tumor necrosis factor-alpha (TNF-α) (pg/mg protein) and nitric oxide (NO) (µmol/g protein) levels in the I/R group (430.8 ± 70.1, 8.0 ± 1.1, resp.) were significantly higher than those in the I/R+ADA group (338.0 ± 71.6, P = 0.006; 6.3 ± 1.2, P = 0.008) and the control group (345.5 ± 53.3, P = 0.008; 6.5 ± 1.5, P = 0.010, resp.). I/R causes severe histopathological injury to the liver tissue, but ADA leads to much less histopathological changes. ADA treatment significantly decreased the severity of liver I/R injury. ADA pretreatment may have protective effects on experimental liver injury.

Adalimumab ameliorates abdominal aorta cross clamping which induced liver injury in rats

The aim of this study was to investigate the possible protective effects of adalimumab (ADA) on cell damage in rat liver tissue during ischemia/reperfusion (I/R) injury of infrarenal abdominal aorta. Thirty male Wistar-albino rats were divided into three groups: control, I/R, and I/R+ADA, each group containing 10 animals. Laparotomy without I/R injury was performed in the control group animals. Laparotomy in the I/R group was followed by two hours of infrarenal abdominal aortic cross ligation and then two hours of reperfusion. ADA (50 mg/kg) was administered intraperitoneally as a single dose, to the I/R+ADA group, five days before I/R. The tumor necrosis factor-alpha (TNF-α) (pg/mg protein) and nitric oxide (NO) (µmol/g protein) levels in the I/R group (430.8 ± 70.1, 8.0 ± 1.1, resp.) were significantly higher than those in the I/R+ADA group (338.0 ± 71.6, P = 0.006; 6.3 ± 1.2, P = 0.008) and the control group (345.5 ± 53.3, P = 0.008; 6.5 ± 1.5, P = 0.010, resp.). I/R causes severe histopathological injury to the liver tissue, but ADA leads to much less histopathological changes. ADA treatment significantly decreased the severity of liver I/R injury. ADA pretreatment may have protective effects on experimental liver injury.

Comparison of TNF antagonism by etanercept and dexamethasone on airway epithelium and remodeling in an experimental model of asthma

BACKGROUND

The aim of the study was to compare the influence of TNF antagonism and corticosteroid treatment on epithelial, smooth muscle and basement membrane component of airway remodeling in an experimental murine model of chronic asthma.

METHODS

We used 30 BALB/c mice. Group 1 not exposed to ovalbumin or any medication was designated as control group. Chronic asthma model was achieved in the other three groups with intraperitoneal (IP) and inhaled ovalbumin. Then, Group 2 received IP saline, Group 3 received IP dexamethasone and Group 4 received IP etanercept. Epithelial, subepithelial smooth muscle and basement membrane thickness as well as goblet cells and mast cells were examined on samples isolated from left lung.

RESULTS

Etanercept treatment led to thinner epithelial and basement membrane layer and lower goblet and mast cell number than untreated asthmatic mice (p<0.001, p=0.001, p=0.005 and p=0.03 respectively). Neither epithelial and basement membrane thickness nor mast cell number was different among mice treated with etanercept and dexamethasone (p=0.38, p=0.79 and p=0.51 respectively). However, etanercept group was associated with thicker subepithelial muscle layer but lower goblet cell number (p<0.001 and p=0.04 respectively) than dexamethasone group.

CONCLUSIONS

Corticosteroids are more effective in decreasing smooth muscle mass while TNF antagonists in reducing goblet cell number in animal model of asthma. Therefore, further research is needed to assess the synergistic use of TNF antagonism and dexamethasone for more rational remodeling control.

MAPK/NF-κB-dependent upregulation of kinin receptors mediates airway hyperreactivity: a new perspective for the treatment

Airway hyperreactivity (AHR) is a major feature of asthmatic and inflammatory airways. Cigarette smoke exposure, and bacterial and viral infections are well-known environmental risk factors for AHR, but knowledge about the underlying molecular mechanisms on how these risk factors lead to the development of AHR is limited. Activation of intracellular mitogen-activated protein kinase (MAPK)/nuclear factor-kappa B (NF-κB) and their related signal pathways including protein kinase C (PKC), phosphoinositide 3-kinase (PI3K) and protein kinase A (PKA) signaling pathways may result in airway kinin receptor upregulation, which is suggested to play an important role in the development of AHR. Environmental risk factors trigger the production of pro-inflammatory mediators such as tumor necrosis factor-α (TNF-α) and interleukins (ILs) that activate intracellular MAPK- and NF-κB-dependent inflammatory pathways, which subsequently lead to AHR via kinin receptor upregulation. Blockage of intracellular MAPK/NF-κB signaling prevents kinin B₁ and B₂ receptor expression in the airways, resulting in a decrease in the response to bradykinin (kinin B₂ receptor agonist) and des-Arg⁹-bradykinin (kinin B₁ receptor agonist). This suggests that MAPK- and NF-κB-dependent kinin receptor upregulation can provide a novel option for treatment of AHR in asthmatic as well as in other inflammatory airway diseases.

Asthmatic airway hyperresponsiveness: the ants in the tree

Airways from asthmatics have a propensity to narrow excessively in response to spasmogens (i.e., contractile agonists), a feature called airway hyperresponsiveness (AHR). AHR is an important contributor to asthma symptoms because the degree of responsiveness dictates the amount of airway narrowing that occurs in response to inflammation-derived spasmogens produced endogenously following exposure to environmental triggers, such as allergens, viruses, or pollutants. The smooth muscle encircling the airways is responsible for responsiveness because it constricts the airway lumen when commanded to contract by spasmogens. However, whether AHR seen in asthmatics is due to stronger muscle is equivocal. In this opinion article, I propose that environmental triggers and other inflammatory molecules released during asthma attacks contribute to AHR by increasing muscle force.

Secondhand smoke exposure causes bronchial hyperreactivity via transcriptionally upregulated endothelin and 5-hydroxytryptamine 2A receptors

BACKGROUND

Cigarette smoke exposure is strongly associated with airway hyperreactivity (AHR) which is the main characteristic seen in asthma. The intracellular MAPK signaling pathways are suggested to be associated with the airway damage to the AHR. In the present study, we hypothesize that secondhand cigarette smoke (SHS) exposure upregulates the bronchial contractile receptors via activation of the Raf/ERK/MAPK pathway.

METHODOLOGY/PRINCIPAL FINDINGS

Rats were exposed to SHS for 3 h daily for up to 8 weeks. The receptor agonists-induced bronchial contractile reactivity was analyzed with a sensitive myograph system. The mRNA transcription and protein translation of the target receptors and the kinases in Raf/ERK/MAPK pathway were investigated by real-time PCR, Western blotting and immunofluorescence, respectively. Compared with exposure to fresh air, SHS induced enhanced bronchial contractile responses mediated by the 5-hydroxytryptamine 2A (5-HT(2A)) receptors as well as the endothelin type B (ET(B)) and type A (ET(A)) receptors. The response curves were shifted toward the left with an increased maximal contraction (E(max)) demonstrating that SHS induced AHR. Additionally, the mRNA and protein levels of the 5-HT(2A), ET(B) and ET(A) receptors were increased. Furthermore, SHS exposure increased the phosphorylation of Raf-1 and ERK1/2, but it did not alter p38 or JNK. A Raf-1 inhibitor (GW5074) suppressed the SHS-induced increase in the expression of 5-HT(2A) and ET(A) receptors and the receptor-mediated AHR.

CONCLUSIONS/SIGNIFICANCE

Our findings show that SHS exposure induces transcriptional upregulation of the 5-HT(2A), ET(B) and ET(A) receptors in rat bronchial smooth muscle cells, which mediates AHR. The Raf/ERK/MAPK pathway is involved in SHS-associated receptor upregulation and AHR.