Heme oxygenase-1 and chronic hypoxia

A myriad of changes are necessary to adapt to chronic hypoxemia. Key among these changes increases in arterial oxygen carrying capacity, ventilation and sympathetic activity. This requires the induction of several gene products many of which are regulated by the activity of HIF-1α, including HO-1. Induction of HO-1 during chronic hypoxia is necessary for the continued breakdown of heme for the enhanced production of hemoglobin and the increased respiratory and sympathetic responses. Several human HO-1 polymorphisms have been identified that can affect the expression or activity of HO-1. Associations between these polymorphisms and the prevalence of hypertension have recently been assessed in specific populations. There are major gaps in our understanding of the mechanisms of how HO-1 mediates changes in the activity of the hypoxia-sensitive chemosensors and whether HO-1 polymorphisms are an important factor in the integrated response to chronic hypoxia. Understanding how HO-1 mediates cardiorespiratory responses could provide important insights into clinical syndromes such as obstructive sleep apnea.     

内源性HO-1/CO系统在动脉粥样硬化发病中的作用

目的探讨血红素氧合酶-1(HO-1)/一氧化碳(CO)系统在动脉粥样硬化(AS)中的变化、对AS进程的影响及其可能的作用机制。方法家兔予以高胆固醇饮食以及在高胆固醇(n=8)饮食的同时经腹腔注射血红素-L-赖氨酸盐(n=8)或ZnPP-IX(n=8)共10周。结果与正常对照组比较,胆固醇饮食各组血清TC及ox-LDL显著升高(P均<0.01),但血清TC和ox-LDL在胆固醇组、ZnPP-IX组、血红素-L-赖氨酸盐干预组之间均无显著性差异。与对照组比较,胆固醇组主动脉CO生成量显著增加,HO-1表达升高(P均<0.01),主动脉斑块面积达(40.2±8.9)%。与胆固醇组比较,外源性血红素-L-赖氨酸盐干预组的主动脉内膜斑块面积(26.6±9.2)%明显缩小(P<0.01),主动脉HO-1表达及CO的生成量显著升高;与胆固醇组比较,血红素-L-赖氨酸盐干预组的主动脉组织内c-myc及c-fos的mRNA和蛋白表达均显著降低(P均<0.01),而ZnPP组与胆固醇组之间则无明显差异。结论HO-1/CO系统具有抗动脉粥样硬化作用,这种作用并非通过其对血浆TC及ox-LDL的调节实现,可能与该系统干预动脉组织内原癌基因表达从而抑制血管平滑肌细胞增殖有关。     

Toluene diisocyanate (TDI) regulates haem oxygenase-1/ferritin expression: implications for toluene diisocyanate-induced asthma

Diisocyanate is a leading cause of occupational asthma (OA). Diisocyanate‐induced OA is an inflammatory disease of the airways that is associated with airway remodelling. Although the pathogenic mechanisms are unclear, oxidative stress may be related to the pathogenesis of diisocyanate‐induced OA. In our previous report, we observed that the expression of ferritin light chain (FTL) was decreased in both of bronchoalveolar lavage fluid and serum of patients with diphenyl‐methane diisocyanate (MDI)‐induced OA compared to those of asymptomatic exposed controls and unexposed healthy controls. In this study of toluene diisocyanate (TDI)‐OA, we found identical findings with increased transferrin and decreased ferritin levels in the serum of patients with TDI‐OA. To elucidate whether diisocyanate suppresses FTL synthesis directly, we tested the effect of TDI on the FTL synthesis in A549 cells, a human airway epithelial cell line. We found that haem oxygenase‐1 as well as FTL was suppressed by treatment with TDI in dose‐ and time‐dependent manners. We also found that the synthesis of other anti‐oxidant proteins such as thioredoxin‐1, glutathione peroxidase, peroxiredoxin 1 and catalase were suppressed by TDI. Furthermore, TDI suppressed nuclear translocation of Nrf2 through suppressing the phosphorylation of mitogen‐activated protein kinases (MAPKs); extracellular‐regulated kinase 1/2 (ERK1/2); p38; and c‐Jun N‐terminal kinase (JNK). Peroxisome proliferator‐activated receptor‐γ (PPAR‐γ) agonists, 15‐deoxy‐Δ^12,14‐PGJ2 and rosiglitazone rescued the effect of TDI on HO‐1/FTL expression. Collectively, our findings suggest that TDI suppressed HO‐1/FTL expression through the MAPK–Nrf2 signalling pathway, which may be involved in the pathogenesis of TDI‐induced OA. Therefore, elucidating these observations further should help to develop the therapeutic strategies of diisocyanate‐induced OA.     

人参皂苷Rh1对哮喘模型小鼠炎症因子表达的抑制作用

目的:观察和探讨人参皂苷Rh1对哮喘模型小鼠的血清和支气管肺泡冲洗液(bronchoalveolar lavage fluid,BALF)中炎症因子的表达和肺组织形态学变化的影响。方法:雄性BALB/c小鼠40只,分为正常对照组、哮喘模型组、人参皂苷Rh1小剂量(40 mg·kg~(-1)·d~(-1))治疗组和人参皂苷Rh1大剂量(80 mg·kg~(-1)·d~(-1))治疗组,并利用卵清蛋白致敏和雾化吸入激发方法制作哮喘模型;人参皂苷Rh1小剂量治疗组和大剂量治疗组分别在每次激发攻击前30 min灌胃,每天一次,共2周。在末次激发24 h后收集BALF,计数嗜酸性粒细胞(eosinophil,EOS)数目;利用ELISA测定BALF中白细胞介素(IL)-4、IL-5和干扰素γ(IFN-γ)的水平;收集血液并测定血清中Ig G和Ig E的水平;用Western blot检测肺组织中转化生长因子(TGF)-β1蛋白表达的变化;用HE染色观察肺组织的病理学变化。结果:人参皂苷Rh1可抑制小鼠哮喘模型BLAF中EOS数目(P0.01);降低BLAF中IL-4、IL-5和IFN-γ的表达(P0.01);减少血清中Ig E的含量(P0.01);减少肺组织中TGF-β1蛋白表达(P0.01),并改善哮喘小鼠肺组织病理学变化。结论:人参皂苷Rh1对哮喘小鼠具有抑制炎症因子表达、调节免疫反应和改善肺组织病理变化的作用。     

Heme-induced heme oxygenase-1 (HO-1) in human monocytes inhibits apoptosis despite caspase-3 up-regulation

Monocyte activation, apoptosis and differentiation are hallmarks of most inflammatory vascular disorders. We studied the effects of heme oxygenase-1 (HO-1) induced by its substrate hemin on apoptosis, caspase-3 expression and the differentiation of freshly isolated human monocytes. Hemin induced HO-1 in a dose- and time-dependent fashion as measured by semi-quantitative RT-PCR and flow cytometry. Apoptosis was markedly suppressed by hemin in cells rendered apoptotic by serum deprivation or dexamethasone as determined by flow cytometric detection of annexin V binding or transmission electron microscopy (TEM). The specific HO-1 inhibitor zinc protoporphyrin (ZnPP) reversed the effects of hemin on monocyte apoptosis and diminished cell lifespan. Surprisingly, the cytoprotective effects of hemin were positively correlated with caspase-3 up-regulation. Hemin-induced apoptosis suppression was enhanced by the caspase-3 inhibitor DEVD-CHO, indicating that caspase-3 was active in a pro-apoptotic fashion. Hemin inhibited CD95 as a putative cytoprotective mechanism. Morphological studies and detection of CD86 showed that monocytes differentiated into macrophages in response to hemin after relatively long incubation times, a phenomenon that might be provoked by caspase-3-regulated pathways. Our results confirm a similar cytoprotective effect of hemin/HO-1 for monocytes as has been shown for other cells, despite caspase-3 up-regulation. The fact that HO-1 may adversely affect monocyte survival and differentiation could be of particular significance in future therapies for occlusive vascular diseases or transplant rejection.     

诱导HO-1基因表达的信号通路

血红素氧合酶（HO）的诱导型HO-1与其催化血红素降解生成的产物胆红素和CO一道，组成了机体重要的内源性保护系统，广泛参与抗炎与多种急慢性氧化应激损伤。多种理化因素通过不同的细胞内信号转导通路诱导HO-1的表达，这些信号通路涉及丝裂原活化蛋白激酶（MAPKs）、蛋白激酶C(PKC)、cAMP依赖的蛋白激酶A(PKA)、cGMP依赖蛋白激酶G（PKG）、酪氨酸蛋白激酶（TPK）、蛋白磷酸酶（PPs）、磷脂酰肌醇（-3）激酶（PI3K）/Akt     

Substance P regulates macrophage inflammatory protein 3alpha/chemokine C-C ligand 20 (CCL20) with heme oxygenase-1 in human periodontal ligament cells

Although substance P (SP), a potent proinflammatory peptide, is involved in inflammation and immune responses, the effect of SP on the expression of macrophage inflammatory protein 3alpha[MIP-3alpha, chemokine C-C ligand 20 (CCL20)] in periodontal ligament (PDL) cells is unknown. Equally enigmatic is the link between SP, the stress protein heme oxygenase-1 (HO-1), and CCL20 production. We investigated whether SP induces the release of chemokine CCL20 from immortalized PDL (IPDL) cells, and further clarify SP-mediated pathways. We also examined the relationship between HO-1 and CCL20 by treating PDL cells with SP. Incubating IPDL cells with SP increased expression of CCL20 mRNA and CCL20 protein in a dose-time-dependent manner. Highly selective p38 and extracellular-regulated kinase 1/2 (ERK1/2) inhibitors abrogated SP-induced expression of CCL20 in IPDL cells. SP is also responsible for initiating phosphorylation of IkappaB, degradation of IkappaB and activation of nuclear factor (NF)-kappaB. SP induced expression of HO-1 in both a concentration- and time-dependent manner, and CCL20 reflected similar patterns. The inductive effects of SP on HO-1 and CCL20 were enhanced by HO-1 inducer hemin and the membrane-permeable guanosine 3',5'-monophosphate (cGMP) analogue 8-bromo-cGMP. Conversely, this pathway was inhibited by the HO-1 inhibitor zinc protoporphyrin IX (ZnPP IX) and the selective inhibitor of guanylate cyclase, 1H-(1,2,4)oxadiazole(4,3-a)quinoxalin-1-one (ODQ). We report herein the pathway that connects SP along with other modulators of neuroimmunoregulation to the induction of HO-1 and the inflammatory mediator macrophage inflammatory protein (MIP)-3alpha/CCL20 in IPDL cells, which play an important role in the development of periodontitis or inflammation during orthodontic tooth movement.     

Distribution and cellular localization of high mobility group box protein 1 (HMGB1) in the spinal cord of a transgenic mouse model of ALS

Although the aetiology of amyotrophic lateral sclerosis (ALS) is still elusive, increased attention has been put forward on events related to neuroinflammation and an active participation of glial cells in the ALS pathogenesis has been suggested. However, the specific role of many proinflammatory mediators that usually accompany the inflammatory changes is still largely unknown. High mobility group box protein 1 (HMGB1) is an ubiquitous nuclear protein that exerts numerous extranuclear and extracellular functions, including a proinflammatory activity, able to induce cytokines expression and activate inflammatory cells. To investigate whether this protein may play a role in the inflammatory events in ALS, we examined both expression and localization of HMGB1 in the lumbar spinal cord of SOD1G93A transgenic mice, a well established mouse model of familial ALS, at different stages of the disease. Intense HMGB1 reactivity was detected in ventral horn motor neurons of both non-transgenic and SOD1G93A mice and there was no difference in its expression between presymptomatic SOD1G93A mice and controls. With the progression of the disease, degenerating neurons showed a reduction of HMGB1 immunoreactivity which could reflect an extracellular release of this protein. By contrast, in the reactive glial cells HMGB1 was remarkably expressed in the nucleus, but not in the cytosol, likely contributing to the proliferation and/or hypertrophy of these cells. These results suggest that HMGB1 may have a different involvement in the motor neurons and glial cells in response to the neurotoxic environment in the spinal cord of SOD1G93A mice, and it may contribute to the progression of inflammatory and neurodegenerative processes.     

Allergen-induced CD11b+ CD11c(int) CCR3+ macrophages in the lung promote eosinophilic airway inflammation in a mouse asthma model

Although the recruitment of macrophages to the lung is a central feature of airway inflammation, its function in ongoing T(h)2 cell-mediated eosinophilic airway inflammation remains controversial. Here, we have demonstrated that the allergen-induced CD11b(+) CD11c(int) macrophage expressing CC chemokine receptor 3 (CCR3) in the lung performs a crucial function in the induction of eosinophilic asthma in a murine model. In the lungs of normal mice, residential cells evidencing high granularity phenotypically evidenced CD11b(int) CD11c(+) or CD11b(+) CD11c(int) cells, appearing at a 2:1 ratio. After allergen challenge, however, this reverses dramatically, up to a ratio of one to six. Approximately 91% of increased CD11b(+) CD11c(int) cells evidenced the expression of the CCR3 eotaxin receptor, but not other chemokine receptors, such as CCR5 and CXCR4. Interestingly, the CD11b(+) CD11c(int) cells purified from the lungs of OVA (ovalbumin)-sensitized and challenged mice evidenced higher antigen-presenting activity than was observed in CD11b(int) CD11c(+) cells. In order to investigate the in vivo function of CD11b(+) CD11c(int) cells, the cells were isolated from the lungs of OVA-sensitized and challenged mice and then adoptively transferred prior to the allergen challenge of normal mice. In the CD11b(+) CD11c(int)-transferred mice airway hyperresponsiveness, eosinophilic inflammation in the lung and T(h)2 cytokine secretion in the bronchoalveolar lavage fluids were significantly enhanced as the result of OVA challenge, as compared with the mice that received OVA-primed CD90(+) T cells or CD11b(int) CD11c(+) cells. These findings show that CD11b(+) CD11c(int) macrophages expressing CCR3 as key pro-inflammatory cells are both necessary and sufficient for allergen-specific T cell stimulation during ongoing eosinophilic airway inflammation.     

Elevation of serum soluble vascular cell adhesion molecule-1 (sVCAM-1) levels in bronchial asthma.

We have previously shown the elevation of serum soluble intercellular adhesion molecule-1 (sICAM-1) and soluble E-selectin (sE-selectin) in patients with bronchial asthma during asthma attacks. In the present study, we extended our earlier study by measuring serum sVCAM-1 levels by ELISA in 45 patients with bronchial asthma (23 atopic and 22 non-atopic) during asthma attacks and in stable conditions in order to assess further the state of adhesion molecules in allergic inflammation of bronchial asthma. The levels of sVCAM-1 in sera obtained during bronchial asthma attacks were higher than those in sera obtained in stable conditions. These findings were observed regardless of atopic status. To examine the regulatory mechanism in the elevation of serum sVCAM-1 levels, serum tumor necrosis factor-alpha (TNF-alpha) levels were measured by ELISA. TNF-alpha levels in sera obtained during bronchial asthma attacks were higher than those in sera obtained in stable conditions. The nature of change in serum TNF-alpha levels correlated with the nature of change in serum sVCAM-1 levels, but serum TNF-alpha levels did not correlate with serum sVCAM-1 levels. These results suggest that higher levels of sVCAM-1 during asthma attacks may reflect the up-regulation of VCAM-1 expression in allergic inflammation, and that a soluble form of VCAM-1 molecules may be useful markers for the presence of allergic inflammation. TNF-alpha is shown to enhance the expression and release of VCAM-1 in vitro, however; the regulatory mechanism in the elevation of serum sVCAM-1 levels remains to be clarified.     

Anti-allergic effects of PG102, a water-soluble extract prepared from Actinidia arguta, in a murine ovalbumin-induced asthma model

Background Asthma is a chronic inflammatory disease of the lung and its incidence has been increasing around the world. We previously reported that oral administration of a water-soluble extract prepared from Actinidia arguta , code-named PG102, could modulate the level of Th1 and Th2 cytokines and suppress the production of immunoglobulin E (IgE) in the ovalbumin (OVA)-immunized murine model as well as in the in vitro cell culture system, and furthermore could significantly improve dermatitis conditions in the NC/Nga murine model. These data suggested that PG102 might have therapeutic effects in a broad range of allergic diseases.
Objective To assess the possible anti-allergic effects of PG102 in the OVA-induced murine asthma model.
Methods The quality of PG102 was standardized, using its effects on the production of IgE, IL-5, and IL-13, in in vitro cell culture systems. To test effects on asthma, BALB/c mice were orally administrated with PG102, followed by OVA sensitization and challenge to induce asthmatic symptoms. Airway hyperresponsiveness (AHR), bronchoalveolar lavage fluid, serum, and lung tissue were analysed by using various methods.
Results PG102 could decrease the level of IgE, IL-5, and IL-13 in in vitro cell culture systems with IC₅₀ being 1.12–1.43 mg/mL. PG102 could ameliorate asthmatic symptoms, including AHR and eosinophilia in the lungs. Such improvement of asthmatic symptoms by PG102 was accompanied by the down-regulation of IL-5 and IgE. In PG102-treated mice, high level expression of heme oxygenase-1, a potent anti-inflammatory enzyme, was observed in alveolar inflammatory cells, while the mRNA levels of foxp3, TGF-β1, and IL-10, important markers for regulatory T cells, were also up-regulated in the lung tissue.
Conclusions PG102 may have potential as a safe and effective reagent for the prevention or treatment of asthma.     

Heme oxygenase-1 accelerates protumoral effects of nitric oxide in cancer cells

We examined the biological effects of nitric oxide (NO) and its mediator, heme oxygenase-1 (HO-1), in cancer. Urogenital cancer cell lines, SKRC, T24 and DU145, were treated with various concentrations of sodium nitroprusside (SNP), a NO donor. The medium nitrite concentration was exponentially increased according to the concentration of SNP. Cell growth inhibition by NO was observed only at high nitrite concentrations (>20 M) in DU145 and T24 cells. Nitrite did not inhibit the growth of SKRC cells at any of the concentrations used. Doxorubicin (DXR) inhibited cell growth in the three cell lines, whereas growth inhibition recovered in the presence of <10 M nitrite. The recovery of DXR-induced growth inhibition was closely associated with an increase in Bcl-2 in the presence of <10 M nitrite. Vascular endothelial growth factor (VEGF) secretion was also increased in the presence of <10 and <20 M nitrite, respectively, in DU145 and SKRC or T24 cells. The expression of HO-1 was associated with sensitivity to NO-induced growth inhibition at constitutive levels, and was induced by SNP treatment. HO-1 inhibition by HO-1 antisense S-oligodeoxynucleotide treatment increased NO-induced growth inhibition, and decreased Bcl-2 expression or VEGF secretion in the three cell lines. These findings suggest that the NO/HO-1 system has protumoral effects.This work was supported by a Grant-in-Aid for Scientific Research (B) from the Japan Society for the Promotion of Science (KAKENHI: 15390130).     

Suppressor of cytokine signalling 1 (SOCS1) is a physiological regulator of the asthma response

Background The molecular determinants of the severity and persistence of allergic asthma remain poorly understood. Suppressor of cytokine signalling 1 (SOCS1) is a negative regulator of IL‐4‐dependent pathways in vitro and might therefore control T‐helper type 2 (Th2) immunity associated traits, such as IgE levels, mucin production, IL‐5 and IL‐13 induction, and eosinophilic mucosal inflammation, which are implicated in allergic asthma. Objective To investigate the role of SOCS1 in regulating Th2‐associated disease traits in a murine sub‐chronic aeroallergen‐driven asthma model. Methods Following sensitization and challenge with ovalbumin (OVA), bronchoalveolar lavage and serum were collected from mice lacking the Socs1 gene on an IFN‐γ null background (Socs1^?/?Ifnγ^?/?). The composition of infiltrating cells in the lung, serum IgE and IgG1 levels and cytokine levels were analysed. Results Serum IgE levels and infiltrating eosinophils were considerably increased in the lungs of OVA‐treated Socs1^?/?Ifnγ^?/? mice compared with Ifnγ^?/? and C57BL/6 controls. Expression of the Th2 cytokines, IL‐4, IL‐5 and IL‐13 was increased in CD4⁺ cells and lung tissue from OVA‐treated Socs1^?/?Ifnγ^?/? mice. IgE, IL‐5 levels and infiltrating eosinophils were also elevated in saline‐treated Socs1^?/?Ifnγ^?/? mice, suggesting that in the absence of SOCS1, mice are already biased towards a Th2 response. It is at present unclear whether the elevated cytokine levels are sufficient to result in the exacerbated Th2 response to OVA challenge or whether enhanced intra‐cellular signalling also contributes. Surprisingly, of the various IL‐4/IL‐13 responsive genes tested, only Arginase I appeared to be modestly up‐regulated in the lungs of OVA‐treated Socs1^?/?Ifnγ^?/? mice, suggesting that regulation by SOCS1 occurs primarily in haematopoietic cells and not in the airway epithelium. Conclusions Together these results indicate that SOCS1 is an important regulator of the Th2 response.     

Anti-inflammatory effects of tilmicosin in a noninfectious mouse model of allergic asthma

Tilmicosin, a semi-synthetic tylosin-derived macrolide antibiotic commonly used by veterinarians, has been shown to possess anti-inflammatory activity. However, possible use in asthma treatment has not yet been studied. In this study, we investigated the anti-inflammatory properties of tilmicosin using a murine asthma model. BALB/c mice were sensitized and challenged by intraperitoneal (i.p.) or nasal administration of ovalbumin. Tilmicosin (10 and 20?mg/kg) treatment resulted in a marked reduction in the presence of several types of immune cells and cytokines in the bronchoalveolar lavage fluids of mice. Levels of ovalbumin-specific Immunoglobulin E (IgE) were significantly decreased following treatment with tilmicosin (10 and 20?mg/kg). Histological studies using H&E (haematoxylin and eosin) and AB-PAS (alcian blue-periodic acid-Schiff) staining demonstrated that tilmicosin substantially inhibited both ovalbumin-induced inflammatory cells in lung tissues and goblet cell hyperplasia in the airway. These findings provided new insight into the immunopharmacological role of tilmicosin in terms of its effects in a murine model of asthma.     

The role of the tachykinin NK1 receptor in airway changes in a mouse model of allergic asthma

BACKGROUND: Tachykinins are present in sensory nerves and in nonneuronal cells like macrophages. Human data suggest a role for these peptides in asthma, but the exact role of tachykinins and their receptors in allergic airway inflammation is still a matter of debate. OBJECTIVE: The aim of this study was to determine the role of the tachykinin NK1 receptor in allergic airway responses in a mouse model. METHODS: Tachykinin NK1 receptor wild-type and knockout animals were sensitized intraperitoneally to ovalbumin and subsequently exposed from days 14 to 21 to aerosolized ovalbumin (1% ). On day 22, the immunologic and histologic changes were evaluated, and lung function measurements were performed. RESULTS: Mice lacking the tachykinin NK1 receptor and their wild-type litter mates developed inflammatory cell infiltrates in the airways and ovalbumin-specific IgE on sensitization and exposure to ovalbumin compared with saline-exposed controls. No differences were detected between wild-type and knockout mice. The substance P content of alveolar macrophages was not influenced by ovalbumin or by the lack of the NK1 receptor. Ovalbumin-induced hyperresponsiveness was not observed, but at baseline, the knockout mice were more reactive despite similar morphology. Ovalbumin induced more goblet cell hyperplasia in wild-type animals compared with knockout animals. No differences in airway wall thickness were observed. CONCLUSION: These data suggest that tachykinin NK1 receptors do not affect allergic airway inflammation or endogenous substance P content of alveolar macrophages but influence baseline responsiveness and promote features of remodeling such as goblet cell hyperplasia.     

Role of angiotensin II type 1 (AT1) and type 2 (AT2) receptors in airway reactivity and inflammation in an allergic mouse model of asthma

Objective: Angiotensin II (Ang II) exerts its effects through two G-protein coupled receptors: angiotensin II type 1 receptors (AT1) and type 2 receptors (AT2). Both these receptor subtypes are poorly understood in asthma. In this study, we investigated effects of AT1 receptor antagonist losartan, novel AT2 receptor agonist novokinin and AT2 receptor antagonist PD 123319 in a mouse model of asthma.

Methods: Mice were divided into control (CON) and allergen sensitized (SEN) groups. SEN was sensitized with ovalbumin (OVA) on days 1 and 6 (30?μg; i.p.), followed by 5% OVA aerosol challenge (days 11–13). Treatments included (a) losartan (SEN?+?LOS; 20?mg/kg i.p., day 14), (b) novokinin (SEN?+?NOV; 0.3?mg/kg i.p., day 14), and (c) PD 123319 (SEN?+?PD; 5?mg/kg i.p., day 14). Experiments for airway responsiveness, bronchoalveolar lavage, and tracheal ring reactivity using isolated organ bath were performed.

Results: Airway responsiveness to methacholine (MCh) (48?mg/mL) was significantly higher in SEN (563.71?±?40% vs. 294.3?±?123.84 in CON). This response was potentiated in SEN?+?PD group (757?±?30%; p?<?.05 compared to SEN). SEN?+?LOS (247.61?±?86.85%) and SEN?+?NOV (352?±?11%) had significantly lower response compared to SEN. SEN?+?LOS (26.22?±?0.29%) and SEN?+?NOV (46.20?±?0.76%) treatment significantly (p?<?.001) attenuated total cell count and eosinophils compared to SEN group (69.38?±?1.5%), while SEN?+?PD (73.04?±?0.69%) had highest number of eosinophils. Tracheal response to MCh was significantly higher in SEN group compared to controls, and this response was significantly lowered with the losartan and novokinin treatments.

Conclusions: These data suggest that AT1 and AT2 receptors have opposite effects in modulating airway hyperresponsiveness and inflammation in asthma.     

Role of STAT6 and SMAD2 in a model of chronic allergen exposure: a mouse strain comparison study

Background Asthma is a disease characterized by variable and reversible airway obstruction and is associated with airway inflammation, airway remodelling (including goblet cell hyperplasia, increased collagen deposition and increased smooth muscle mass) and increased airway responsiveness. It is believed that airway inflammation plays a critical role in the development of airway remodelling, with IL‐13 and TGF‐β1 pathways being strongly associated with the disease progression. Mouse models of asthma are capable of recapitulating some components of asthma and have been used to look at both IL‐13 and TGF‐β1 pathways, which use STAT6 and SMAD2 signalling molecules, respectively. Objectives Using brief and chronic models of allergen exposure, we utilized BALB/c and C57Bl/6 to explore the hypothesis that observed differences in responses to allergen between these mouse strains will involve fundamental differences in IL‐13 and TGF‐β1 responses. Methods The following outcome measurements were performed: airway physiology, bronchoalveolar lavage cell counts/cytokine analysis, histology, immunoblots and gene expression assays. Results We demonstrate in BALB/c mice an IL‐13‐dependent phosphorylation of STAT6, nuclear localized in inflammatory cells, which is associated with indices of airway remodelling and development of airway dysfunction. In BALB/c mice, phosphorylation of SMAD2 is delayed relative to STAT6 activation and also involves an IL‐13‐dependent mechanism. In contrast, despite an allergen‐induced increase in IL‐4, IL‐13 and eosinophils, C57Bl/6 demonstrates a reduced and distinct pattern of phosphorylated STAT6, no SMAD2 phosphorylation changes and fail to develop indices of remodelling or changes in airway function. Conclusion The activation of signalling pathways and nuclear translocation of signalling molecules downstream of IL‐13 and TGF‐β1 further support the central role of these molecules in the pathology and dysfunction in animal models of asthma. Activation of signalling pathways downstream from IL‐13 and TGF‐β1 may be more relevant in disease progression than elevations in airway inflammation alone.