Stringent testing identifies highly potent and escape‐proof anti‐HIV short hairpin RNAs

Background

RNA interference (RNAi) is a cellular mechanism that can be induced by small interfering RNAs to mediate sequence‐specific gene silencing by cleavage of the targeted mRNA. RNAi can be used as an antiviral approach to silence the human immunodeficiency virus type 1 (HIV‐1) through stable expression of short hairpin RNAs (shRNAs). Previously, we used a co‐transfection assay in which shRNA constructs were transfected with an HIV‐1 molecular clone to identify 20 shRNA inhibitors that target highly conserved HIV‐1 sequences.

Methods

In the present study, we selected the most potent shRNAs to formulate a combinatorial shRNA therapy and determine the best and easiest method for antiviral shRNA selection. We performed transient inhibition assays with either a luciferase reporter or HIV‐1 molecular clone and also infected shRNA‐expressing T cell lines with HIV‐1 and monitored virus replication. The latter assay allows detection of viral escape. In addition, we also tested shRNA‐expressing T cells upon challenge with increasing dosages of HIV‐1, and measured the dose required to result in massive virus‐induced syncytia formation in this 2‐week assay.

Results

Extended culturing selected three highly effective shRNAs that do not allow viral replication for more than 100 days. This difference in potency was not observed in the transient co‐transfection assays. The use of increased dosages of HIV‐1 selected the same highly potent shRNAs as the laborious and extended escape study.

Conclusions

These highly potent shRNAs could be used for a clinical vector and the comparison of the developed assays might help other researchers in their search for antiviral shRNAs. Copyright © 2009 John Wiley & Sons, Ltd.     

A novel human anti‐VCAM‐1 monoclonal antibody ameliorates airway inflammation and remodelling

Asthma is a chronic inflammatory disease induced by Type 2 helper T cells and eosinophils. Vascular cell adhesion molecule‐1 (VCAM‐1) has been implicated in recruiting eosinophils and lymphocytes to pathological sites in asthma as a regulatory receptor. Accordingly, monoclonal antibody (mAb) against VCAM‐1 may attenuate allergic inflammation and pathophysiological features of asthma. We attempted to evaluate whether a recently developed human anti‐VCAM‐1 mAb can inhibit the pathophysiological features of asthma in a murine asthma model induced by ovalbumin (OVA). Leucocyte adhesion inhibition assay was performed to evaluate the in vitro blocking activity of human anti‐VCAM‐1 mAb. OVA‐sensitized BALB/c mice were treated with human anti‐VCAM‐1 mAb or isotype control Ab before intranasal OVA challenge. We evaluated airway hyperresponsiveness (AHR) and bronchoalveolar lavage fluid analysis, measured inflammatory cytokines and examined histopathological features. The human anti‐VCAM‐1 mAb bound to human and mouse VCAM‐1 molecules and inhibited adhesion of human leucocytes in vitro. AHR and inflammatory cell counts in bronchoalveolar lavage fluid were reduced in mice treated with human anti‐VCAM‐1 mAb as compared with a control Ab. The levels of interleukin (IL)‐5 and IL‐13, as well as transforming growth factor‐β, in lung tissue were decreased in treated mice. Human anti‐VCAM‐1 mAb reduced goblet cell hyperplasia and peribronchial fibrosis. In vivo VCAM‐1 expression decreased in the treated group. In conclusion, human anti‐VCAM‐1 mAb attenuated allergic inflammation and the pathophysiological features of asthma in OVA‐induced murine asthma model. The results suggested that human anti‐VCAM‐1 mAb could potentially be used as an additional anti‐asthma therapeutic medicine.     

Poly(ADP‐ribose) polymerase inhibition with HYDAMTIQ reduces allergen‐induced asthma‐like reaction,bronchial hyper‐reactivity and airway remodelling

Activation of poly(ADP‐ribose) polymerases (PARPs) is considered a key event in the molecular and cellular processes leading from acute asthma attacks to bronchial hyper‐reactivity, leucocyte recruitment, chronic inflammation, airway remodelling and lung damage. The present investigation has been carried out to investigate the action of hydroxyl‐dimethylaminomethyl‐thieno[2,3‐c]isoquinolin‐5(4H)‐one (HYDAMTIQ), a new potent PARP inhibitor, in the process leading from asthma‐like events to airway damage. Ovalbumin‐sensitized guinea pigs exposed two times to allergen inhalation were treated for 8 days with vehicle or HYDAMTIQ. Asthma‐like signs, bronchial hyper‐reactivity to methacholine, cytokine production, histamine release from mast cells, airway remodelling, collagen deposition and lung damage were evaluated. Repeated HYDAMTIQ administration (1‐10 mg/kg/day i.p.) reduced lung PARP activity, delayed the appearance and reduced the severity of allergen‐induced cough and dyspnoea and dampened the increased bronchial responses to methacholine. HYDAMTIQ‐treated animals presented reduced bronchial or alveolar abnormalities, lower number of eosinophils and other leucocytes in the lung and decreased smooth muscle or goblet cell hyperplasia. The treatment also reduced lung oxidative stress markers, such as malondialdehyde or 8‐hydroxy‐2′‐deoxyguanosine and the lung content of pro‐inflammatory cytokines (TNF‐α, interleukin (IL)‐1β, IL‐5, IL‐6 and IL‐18). Finally, mast cells isolated from the peritoneal or pleural cavities of sensitized, HYDAMTIQ‐treated animals had a reduced ability to release histamine when exposed to ovalbumin in vitro. Our findings support the proposal that PARP inhibitors could have a therapeutic potential to reduce chronic lung inflammation, airway damage and remodelling in severe unresponsive asthmatic patients.     

Effect of mesenchymal stem cells on inhibiting airway remodeling and airway inflammation in chronic asthma

Previous studies proved that bone marrow‐derived mesenchymal stem cells (BMSCs) could improve a variety of immune‐mediated disease by its immunomodulatory properties. In this study, we investigated the effect on airway remodeling and airway inflammation by administrating BMSCs in chronic asthmatic mice. Forty‐eight female BALB/c mice were randomly distributed into PBS group, BMSCs treatment group, BMSCs control group, and asthmatic group. The levels of cytokine and immunoglobulin in serum and bronchoalveolar lavage fluid were detected by enzyme‐linked immunosorbent assay. The number of CD4⁺CD25⁺regulatory T cells and morphometric analysis was determined by flow cytometry, hematoxylin‐eosin, immunofluorescence staining, periodic‐acid Schiff, and masson staining, respectively. We found that airway remodeling and airway inflammation were evident in asthmatic mice. Moreover, low level of IL‐12 and high levels of IL‐13, IL‐4, OVA‐specific IgG1, IgE, and IgG2a and the fewer number of CD4⁺CD25⁺regulatory T cells were present in asthmatic group. However, transplantation of BMSCs significantly decreased airway inflammation and airway remodeling and level of IL‐4, OVA‐specific IgE, and OVA‐specific IgG1, but elevated level of IL‐12 and the number of CD4 + CD25 + regulatory T cells in asthma (P < 0.05). However, BMSCs did not contribute to lung regeneration and had no significant effect on levels of IL‐10, IFN‐Y, and IL‐13. In our study, BMSCs engraftment prohibited airway inflammation and airway remodeling in chronic asthmatic group. The beneficial effect of BMSCs might involved the modulation imbalance cytokine toward a new balance Th1–Th2 profiles and up‐regulation of protective CD4 + CD25 + regulatory T cells in asthma, but not contribution to lung regeneration. J. Cell. Biochem. 114: 1595–1605, 2013. © 2013 Wiley Periodicals, Inc.     

Inhibition of neutrophil elastase attenuates airway hyperresponsiveness and inflammation in a mouse model of secondary allergen challenge: neutrophil elastase inhibition attenuates allergic airway responses

Background

Chronic asthma is often associated with neutrophilic infiltration in the airways. Neutrophils contain elastase, a potent secretagogue in the airways, nonetheless the role for neutrophil elastase as well as neutrophilic inflammation in allergen-induced airway responses is not well defined. In this study, we have investigated the impact of neutrophil elastase inhibition on the development of allergic airway inflammation and airway hyperresponsiveness (AHR) in previously sensitized and challenged mice.

Methods

BALB/c mice were sensitized and challenged (primary) with ovalbumin (OVA). Six weeks later, a single OVA aerosol (secondary challenge) was delivered and airway inflammation and airway responses were monitored 6 and 48 hrs later. An inhibitor of neutrophil elastase was administered prior to secondary challenge.

Results

Mice developed a two-phase airway inflammatory response after secondary allergen challenge, one neutrophilic at 6 hr and the other eosinophilic, at 48 hr. PAR-2 expression in the lung tissues was enhanced following secondary challenge, and that PAR-2 intracellular expression on peribronchial lymph node (PBLN) T cells was also increased following allergen challenge of sensitized mice. Inhibition of neutrophil elastase significantly attenuated AHR, goblet cell metaplasia, and inflammatory cell accumulation in the airways following secondary OVA challenge. Levels of IL-4, IL-5 and IL-13, and eotaxin in BAL fluid 6 hr after secondary allergen challenge were significantly suppressed by the treatment. At 48 hr, treatment with the neutrophil elastase inhibitor significantly reduced the levels of IL-13 and TGF-β1 in the BAL fluid. In parallel, in vitro IL-13 production was significantly inhibited in spleen cells from sensitized mice.

Conclusion

These data indicate that neutrophil elastase plays an important role in the development of allergic airway inflammation and hyperresponsiveness, and would suggest that the neutrophil elastase inhibitor reduced AHR to inhaled methacholine indicating the potential for its use as a modulator of the immune/inflammatory response in both the neutrophil- and eosinophil-dominant phases of the response to secondary allergen challenge.     

Zinc Suppressed the Airway Inflammation in Asthmatic Rats: Effects of Zinc on Generation of Eotaxin, MCP-1, IL-8, IL-4, and IFN-γ

Airway epithelium is rich in labile zinc (Zn), which may have an important protective role in the airway epithelium. The aim of this study is to investigate the effects of Zn on the airway inflammation and the generation of eotaxin, monocyte chemoattractant protein-1 (MCP-1), interleukin-8 (IL-8), interleukin-4 (IL-4), and interferon-?? (IFN-??) in rat models of ovalbumin (OVA)-induced allergic airway inflammation. For this purpose, animal model of asthma was established by OVA challenge and zinc-deficient and zinc-supplemented diets were given. Thirty-two Sprague?CDawley rats were divided into four groups: zinc-deficient diet with OVA treatment group, zinc-supplemented diet with OVA treatment group, zinc-normal diet with OVA treatment group, and zinc-normal diet with saline treatment group. Twenty-four hours after asthma was induced, lung histomorphological changes, cells in bronchoalveolar lavage fluid (BALF), contents of eotaxin, MCP-1, and IL-8 in BALF, and the expression of IFN-?? and IL-4 mRNAs were observed. Compared with the group of zinc-normal diet with OVA challenge rats, the group of zinc-deficient rats had higher numbers of eosinophils, neutrophils, and monocytes in BALF, as well as higher contents of eotaxin and MCP-1 in BALF and lower expression of lung IFN-?? mRNA. Conversely, Zn supplementation would decrease the numbers of eosinophils, neutrophils, and monocytes in BALF; suppress eotaxin and MCP-1 protein secretion; and increase lung IFN-?? mRNA expression. No significant difference was observed in IL-8 and IL-4 among OVA-challenged rats with different zinc diets. These studies suggested that Zn may be an important anti-inflammatory mediator of airway inflammation.     

Baicalein Reduces Airway Injury in Allergen and IL-13 Induced Airway Inflammation

Background

Baicalein, a bioflavone present in the dry roots of Scutellaria baicalensis Georgi, is known to reduce eotaxin production in human fibroblasts. However, there are no reports of its anti-asthma activity or its effect on airway injury.

Methodology/Principal Findings

In a standard experimental asthma model, male Balb/c mice that were sensitized with ovalbumin (OVA), treated with baicalein (10 mg/kg, ip) or a vehicle control, either during (preventive use) or after OVA challenge (therapeutic use). In an alternate model, baicalein was administered to male Balb/c mice which were given either IL-4 or IL-13 intranasally. Features of asthma were determined by estimating airway hyperresponsiveness (AHR), histopathological changes and biochemical assays of key inflammatory molecules. Airway injury was determined with apoptotic assays, transmission electron microscopy and assessing key mitochondrial functions. Baicalein treatment reduced AHR and inflammation in both experimental models. TGF-β₁, sub-epithelial fibrosis and goblet cell metaplasia, were also reduced. Furthermore, baicalein treatment significantly reduced 12/15-LOX activity, features of mitochondrial dysfunctions, and apoptosis of bronchial epithelia.

Conclusion/Significance

Our findings demonstrate that baicalein can attenuate important features of asthma, possibly through the reduction of airway injury and restoration of mitochondrial function.     

Role of IL‐18 in atopic asthma is determined by balance of IL‐18/IL‐18BP/IL‐18R

It is recognized that IL‐18 is related to development of asthma, but role of IL‐18 in asthma remains controversial and confusing. This is largely due to lack of information on expression of IL‐18 binding protein (BP) and IL‐18 receptor (R) in asthma. In this study, we found that plasma levels of IL‐18 and IL‐18BP were elevated in asthma. The ratio between plasma concentrations of IL‐18 and IL‐18BP was 1:12.8 in asthma patients. We demonstrated that 13‐fold more monocytes, 17.5‐fold more neutrophils and 4.1‐fold more B cells express IL‐18BP than IL‐18 in asthmatic blood, suggesting that there is excessive amount of IL‐18BP to abolish actions of IL‐18 in asthma. We also discovered that more IL‐18R+ monocytes, neutrophils and B cells are located in asthmatic blood. Once injected, IL‐18 eliminated IL‐18R+ monocytes in blood, but up‐regulated expression of IL‐18R in lung macrophages of OVA‐sensitized mice. Our data clearly indicate that the role of IL‐18 in asthma is very likely to be determined by balance of IL‐18/IL‐18BP/IL‐18R expression in inflammatory cells. Therefore, IL‐18R blocking or IL‐18BP activity enhancing therapies may be useful for treatment of asthma.     

Effects of nano particles on antigen-related airway inflammation in mice

Background

Particulate matter (PM) can exacerbate allergic airway diseases. Although health effects of PM with a diameter of less than 100 nm have been focused, few studies have elucidated the correlation between the sizes of particles and aggravation of allergic diseases. We investigated the effects of nano particles with a diameter of 14 nm or 56 nm on antigen-related airway inflammation.

Methods

ICR mice were divided into six experimental groups. Vehicle, two sizes of carbon nano particles, ovalbumin (OVA), and OVA + nano particles were administered intratracheally. Cellular profile of bronchoalveolar lavage (BAL) fluid, lung histology, expression of cytokines, chemokines, and 8-hydroxy-2''-deoxyguanosine (8-OHdG), and immunoglobulin production were studied.

Results

Nano particles with a diameter of 14 nm or 56 nm aggravated antigen-related airway inflammation characterized by infiltration of eosinophils, neutrophils, and mononuclear cells, and by an increase in the number of goblet cells in the bronchial epithelium. Nano particles with antigen increased protein levels of interleukin (IL)-5, IL-6, and IL-13, eotaxin, macrophage chemoattractant protein (MCP)-1, and regulated on activation and normal T cells expressed and secreted (RANTES) in the lung as compared with antigen alone. The formation of 8-OHdG, a proper marker of oxidative stress, was moderately induced by nano particles or antigen alone, and was markedly enhanced by antigen plus nano particles as compared with nano particles or antigen alone. The aggravation was more prominent with 14 nm of nano particles than with 56 nm of particles in overall trend. Particles with a diameter of 14 nm exhibited adjuvant activity for total IgE and antigen-specific IgG₁ and IgE.

Conclusion

Nano particles can aggravate antigen-related airway inflammation and immunoglobulin production, which is more prominent with smaller particles. The enhancement may be mediated, at least partly, by the increased local expression of IL-5 and eotaxin, and also by the modulated expression of IL-13, RANTES, MCP-1, and IL-6.     

A role for MCP-1/CCR2 in interstitial lung disease in children

Background

Particulate matter (PM) can exacerbate allergic airway diseases. Although health effects of PM with a diameter of less than 100 nm have been focused, few studies have elucidated the correlation between the sizes of particles and aggravation of allergic diseases. We investigated the effects of nano particles with a diameter of 14 nm or 56 nm on antigen-related airway inflammation.

Methods

ICR mice were divided into six experimental groups. Vehicle, two sizes of carbon nano particles, ovalbumin (OVA), and OVA + nano particles were administered intratracheally. Cellular profile of bronchoalveolar lavage (BAL) fluid, lung histology, expression of cytokines, chemokines, and 8-hydroxy-2'-deoxyguanosine (8-OHdG), and immunoglobulin production were studied.

Results

Nano particles with a diameter of 14 nm or 56 nm aggravated antigen-related airway inflammation characterized by infiltration of eosinophils, neutrophils, and mononuclear cells, and by an increase in the number of goblet cells in the bronchial epithelium. Nano particles with antigen increased protein levels of interleukin (IL)-5, IL-6, and IL-13, eotaxin, macrophage chemoattractant protein (MCP)-1, and regulated on activation and normal T cells expressed and secreted (RANTES) in the lung as compared with antigen alone. The formation of 8-OHdG, a proper marker of oxidative stress, was moderately induced by nano particles or antigen alone, and was markedly enhanced by antigen plus nano particles as compared with nano particles or antigen alone. The aggravation was more prominent with 14 nm of nano particles than with 56 nm of particles in overall trend. Particles with a diameter of 14 nm exhibited adjuvant activity for total IgE and antigen-specific IgG₁ and IgE.

Conclusion

Nano particles can aggravate antigen-related airway inflammation and immunoglobulin production, which is more prominent with smaller particles. The enhancement may be mediated, at least partly, by the increased local expression of IL-5 and eotaxin, and also by the modulated expression of IL-13, RANTES, MCP-1, and IL-6.     

Anti-malarial drug artesunate attenuates experimental allergic asthma via inhibition of the phosphoinositide 3-kinase/Akt pathway

Background

Phosphoinositide 3-kinase (PI3K)/Akt pathway is linked to the development of asthma. Anti-malarial drug artesunate is a semi-synthetic derivative of artemisinin, the principal active component of a medicinal plant Artemisia annua, and has been shown to inhibit PI3K/Akt activity. We hypothesized that artesunate may attenuate allergic asthma via inhibition of the PI3K/Akt signaling pathway.

Methodology/Principal Findings

Female 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. 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. Artesunate dose-dependently inhibited OVA-induced increases in total and eosinophil counts, IL-4, IL-5, IL-13 and eotaxin levels in bronchoalveolar lavage fluid. It attenuated OVA-induced lung tissue eosinophilia and airway mucus production, mRNA expression of E-selectin, IL-17, IL-33 and Muc5ac in lung tissues, and airway hyperresponsiveness to methacholine. In normal human bronchial epithelial cells, artesunate blocked epidermal growth factor-induced phosphorylation of Akt and its downstream substrates tuberin, p70S6 kinase and 4E-binding protein 1, and transactivation of NF-κB. Similarly, artesunate blocked the phosphorylation of Akt and its downstream substrates in lung tissues from OVA-challenged mice. Anti-inflammatory effect of artesunate was further confirmed in a house dust mite mouse asthma model.

Conclusion/Significance

Artesunate ameliorates experimental allergic airway inflammation probably via negative regulation of PI3K/Akt pathway and the downstream NF-κB activity. These findings provide a novel therapeutic value for artesunate in the treatment of allergic asthma.     

Role of aquaporin 5 in antigen‐induced airway inflammation and mucous hyperproduction in mice

Airway inflammation and mucus hyperproduction play the central role in the development of asthma, although the mechanisms remain unclear. The aquaporin (AQP)‐5 may be involved in the process due to its contribution to the volume of liquid secreted from the airways. The present study firstly found the overexpression of AQP5 in the airway epithelium and submucosal glands of asthmatics. Furthermore, we aimed at evaluating the role of AQP5 in airway inflammation and mucous hyperproductions during chronic allergic responses to house dust mite (HDM). Bronchoalveolar lavage levels of interleukin (IL)‐2, IL‐4, IL‐10, interferon‐γ and Mucin 5AC (MUC5AC), and number of peribronchial and perivascular cells were measured in AQP5 wild‐type and AQP5 knockout (KO) mice. We found that HDM induced airway inflammation, lung Th2 cell accumulation and mucin hypersecretion in C57BL/6 mice rather than AQP5 KO mice. Expression of MUC5AC and MUC5B proteins and genes in the lung tissue was significantly lower in AQP5 KO mice. Thus, our results implicate involvement of AQP5 in the development of airway inflammation and mucous hyperproduction during chronic asthma.     

Fibroblast growth factor‐2 and interleukin‐4 synergistically induce eotaxin‐1 expression in adipose tissue‐derived stromal cells

The relationships between eosinophils and adipose tissues are involved in metabolic homeostasis. Eotaxin is a chemokine with potent effects on eosinophil migration. To clarify the mechanisms of eotaxin expression in adipose tissues, we examined the effects of fibroblast growth factor‐2 (FGF‐2) and interleukin‐4 (IL‐4) stimulation on eotaxin expression in adipose tissue‐derived stromal cells (ASCs), a type of adipocyte progenitor, in vitro. ASCs expressed eotaxin‐1 and did not express eotaxin‐2 or ‐3. Eotaxin‐1 expression was increased in a concentration‐dependent manner following FGF‐2 treatment. Additionally, ASCs expressed FGF receptor‐1 (FGFR‐1) and did not express FGFR‐2, ‐3, or ‐4. Eotaxin‐1 expression was inhibited in cells treated with the FGFR tyrosine kinase inhibitor and extracellular signal‐regulated kinase (ERK) inhibitor U0126, even in the presence of FGF‐2. Moreover, eotaxin‐1 expression was synergistically enhanced by combined treatment with FGF‐2 and IL‐4 and inhibited in the presence of U0126. Eotaxin‐1 expression induced by FGF‐2 and IL‐4 was involved in ERK activation via FGFR‐1 in ASCs. Upregulation of eotaxin expression in adipose tissues could increase eosinophil migration, thereby inducing IL‐4 secretion and activation of alternative macrophages and improving glucose homeostasis. These findings provide insights into the mechanisms through which eotaxin mediates metabolic homeostasis in adipose tissues and eosinophils.     

Cytokine‐induced interleukin‐1 receptor antagonist protein expression in genetically engineered equine mesenchymal stem cells for osteoarthritis treatment

Background

A combination of tissue engineering methods employing mesenchymal stem cells (MSCs) together with gene transfer takes advantage of innovative strategies and highlights a new approach for targeting osteoarthritis (OA) and other cartilage defects. Furthermore, the development of systems allowing tunable transgene expression as regulated by natural disease‐induced substances is highly desirable.

Methods

Bone marrow‐derived equine MSCs were transduced with a lentiviral vector expressing interleukin‐1 receptor antagonist (IL‐1Ra) gene under the control of an inducible nuclear factor‐kappa B‐responsive promoter and IL‐1Ra production upon pro‐inflammatory cytokine stimulation [tumor necrosis factor (TNF)α, interleukin (IL)‐1β] was analysed. To assess the biological activity of the IL‐1Ra protein that was produced and the therapeutic effect of IL‐1Ra‐expressing MSCs (MSC/IL‐1Ra), cytokine‐based two‐ and three‐dimensional in vitro models of osteoarthritis using equine chondrocytes were established and quantitative real‐time polymerase chain reaction (PCR) analysis was used to measure the gene expression of aggrecan, collagen IIA1, interleukin‐1β, interleukin‐6, interleukin‐8, matrix metalloproteinase‐1 and matrix metalloproteinase‐13.

Results

A dose‐dependent increase in IL‐1Ra expression was found in MSC/IL‐1Ra cells upon TNFα administration, whereas stimulation using IL‐1β did not lead to IL‐1Ra production above the basal level observed in nonstimulated cells as a result of the existing feedback loop. Repeated cycles of induction allowed on/off modulation of transgene expression. In vitro analyses revealed that IL‐1Ra protein present in the conditioned medium from MSC/IL‐1Ra cells blocks OA onset in cytokine‐treated equine chondrocytes and co‐cultivation of MSC/IL‐1Ra cells with osteoarthritic spheroids alleviates the severity of the osteoarthritic changes.

Conclusions

Thus, pro‐inflammatory cytokine induced IL‐1Ra protein expression from genetically modified MSCs might represent a promising strategy for osteoarthritis treatment.     

Heme oxygenase attenuates allergen-induced airway inflammation and hyperreactivity in guinea pigs

Heme oxygenase (HO), the heme-degrading enzyme, has shown anti-inflammatory effects in several models of pulmonary diseases. HO is induced in airways during asthma; however, its functional role is unclear. Therefore, we evaluated the role of HO on airway inflammation [evaluated by bronchoalveolar lavage (BAL) cellularity and BAL levels of eotaxin, PGE(2), and proteins], mucus secretion (evaluated by analysis of MUC5AC gene expression and periodic acid-Schiff staining), oxidative stress (evaluated by quantification of 4-hydroxynonenal adducts and carbonylated protein levels in lung homogenates), and airway responsiveness to histamine in ovalbumin (OVA)-sensitized and multiple aerosol OVA or saline-challenged guinea pigs (6 challenges, once daily, OVA group and control group, respectively). Airway inflammation, mucus secretion, oxidative stress, and responsiveness were significantly increased in the OVA group compared with the control group. HO upregulation by repeated administrations of hemin (50 mg/kg i.p.) significantly decreased airway responsiveness in control animals and airway inflammation, mucus secretion, oxidative stress, and responsiveness in OVA animals. These effects were reversed by the concomitant administration of the HO inhibitor tin protoporphyrin-IX (50 micromol/kg i.p.). Repeated administrations of tin protoporphyrin-IX alone significantly increased airway responsiveness in control animals but did not modify airway inflammation, mucus secretion, oxidative stress, and responsiveness in OVA animals. These results suggest that upregulation of the HO pathway has a significant protective effect against airway inflammation, mucus hypersecretion, oxidative stress, and hyperresponsiveness in a model of allergic asthma in guinea pigs.