Noninvasive system for evaluating the allergen-specific airway response in a murine model of asthma

In the present report, we show that the enhanced pause (Penh), a novel indicator of airway responsiveness to bronchoconstrictors, can also be a good marker of airway response to an allergen challenge in a murine model of asthma. Male BALB/c mice were sensitized with ovalbumin (OVA) through a combination of intraperitoneal injection and aerosol inhalation. After this immunization, the OVA-specific IgE titer in serum increased to a significantly higher level than in a saline/PBS-treated control group. After the final OVA aerosol challenge, Penh was repeatedly measured in conscious, unrestrained mice, according to the time schedule. Penh increased gradually after the challenge and reached a maximal value at 24 hours that was significantly higher than the control value (p < 0.01). Histologic examination of the lung revealed airway inflammation with an invasion by eosinophils and lymphocytes from vessels into the peribronchial interstitium and the mucosal and submucosal areas of the bronchus. There was a strong correlation between the Penh value and eosinophil number in bronchoalveolar lavage fluid (r = 0.699, p < 0.0001). Moreover, Penh also correlated strongly with the intensity score of histologic findings. These results suggest that the bronchial response to a specific allergen could be followed in a particular individual through the noninvasive Penh method, and that Penh accurately reflects the intensity of eosinophilic bronchial inflammation. This system would be applicable to a noninvasive, chronological evaluation of various experimental interventions in a murine model of asthma.     

In vivo effects of apoptosis in asthma examined by a murine model

BACKGROUND: One of the characteristic features of bronchial asthma is the accumulation of various inflammatory cells, predominantly eosinophils, at the subepithelial region beneath the basement membrane of the airway. Apoptosis is a form of physiological cell death, through which the cellular contents including biologically active substances are kept in the cell membrane and are removed without their harmful effects. So, attempts were made to clarify whether the induction of apoptosis is beneficial in asthma by using a murine model with ovalbumin (OA) as responsible allergen. METHODS: A/J mice, which are genetically predisposed to be hyperresponsive to acetylcholine, were immunized with OA and alum, accompanied by OA inhalation for 2 weeks, during which some of the mice were also treated with either anti-Fas monoclonal antibody or sham control hamster IgG intranasally. Airway responsiveness to acetylcholine was then analyzed by measuring airway resistance with a body plethysmograph box. Apoptosis was assessed by propidium iodide and TUNEL staining. RESULTS: Inhalation of OA increased both airway responsiveness to acetylcholine and the number of cells, mostly eosinophils, infiltrated into the airway. Administration of anti-Fas antibody induced apoptosis in the infiltrated eosinophils and abolished augmentation of airway hyperresponsiveness caused by OA inhalation. CONCLUSION: Induction of apoptosis in proinflammatory cells including eosinophils at the airway may have a beneficial effect on suppressing airway hyperresponsiveness.     

Regulation by scaffolding proteins of canonical transient receptor potential channels in striated muscle

Recent studies proposed a pivotal role of TRPC channels, in particular TRPC1, in the striated muscle tissue and in the development of calcium mishandling observed in dystrophin-deficient skeletal and cardiac muscle cells (Vandebrouck et al. in J Cell Biol 158:1089–1096, 2002; Williams and Allen in Am J Physiol Heart Circ Physiol 292:H846–H855, 2007; Stiber et al. in Mol Cell Biol 28:2637–2647, 2008). In skeletal muscle, TRPCs are proposed to function in a costameric macromolecular complex (Vandebrouck et al. in FASEB J 21:608–617, 2007; Gervasio et al. in J Cell Sci 121:2246–2255, 2008) in which scaffolding proteins and dystrophin are central components maintaining normal calcium entry (Stiber et al. in Mol Cell Biol 28:2637–2647, 2008; Sabourin et al. in J Biol Chem 284:36248–61, 2009). In this review, we shall summarize the roles played by scaffolding proteins in regulating the calcium entry through TRPC channels of skeletal muscle cells and the implications in muscle physiopathology. Interactions of TRPC1 with caveolin-3, Homer-1 and α-syntrophin will be addressed and these complexes will be compared with signalplex in other systems. The mechanosensitive function of scaffolding proteins will be discussed as well as interactions with TRPV2 channels regarding to calcium mishandling in Duchenne dystrophy.     

Effect of sarcomere length on step size in relaxed rabbit psoas muscle

Recent experiments have shown that shortening and stretching of sarcomeres in single activated and unactivated myofibrils occur in stepwise fashion (Yang et al. (1998) Biophys J 74: 1473-1483; Blyakhman et al. (2001) Biophys J 81: 1093-1100; Yakovenko et al. (2002) Am J Physiol Cell Physiol 283: 735-742). Here, we carried out measurements on single myofibrils from rabbit psoas muscle to investigate steps in unactivated specimens in more detail. Activated and unactivated myofibrils were released and stretched in ramp-like fashion. The time course of length change in the single sarcomere was consistently stepwise. We found that in the unactivated myofibrils, step size depended on initial sarcomere length, diminishing progressively with increase of initial sarcomere length, whereas in the case of activated sarcomeres, step size was consistently 2.7 nm.     

Noninvasive system for evaluating allergen-induced nasal hypersensitivity in murine allergic rhinitis

Until now there has been no method for physiologically evaluating nasal hypersensitivity in mice. Enhanced pause (Penh) has been used as an indicator that reflects changes in the lower airway. Recently, however, there is disagreement regarding the significance of the Penh system; this is because Penh is not essentially a physiological parameter, and it might not necessarily represent a change in the lower respiratory tract. The purpose of the present study is to investigate whether Penh could be applicable for analyzing nasal hypersensitivity in mice. BALB/c mice were sensitized with ovalbumin (OVA) through a combination of intraperitoneal injection and daily intranasal challenge in an awake condition. Penh was measured at each time point during sensitization, or a serial change in Penh value was followed after the final nasal challenge and the effect of treatment was assessed. Following sensitization and nasal challenge, the Penh value gradually increased and showed a significant difference on day 14. Changes in IgE, eosinophil infiltration into nasal mucosa, and OVA-induced symptoms all strongly correlated with the increase in Penh. On day 19, after OVA nasal provocation, Penh gradually increased and reached maximal values 25 min after the challenge. Pretreatment with dexamethasone or a histamine H1 blocker significantly suppressed this increase in Penh. We confirmed that intranasal OVA challenge did not induce bronchoconstriction by measuring airway resistance and bronchoalveolar lavage fluid, and through histological examination. These results clearly demonstrate that Penh could be a useful noninvasive indicator for studying nasal hypersensitivity.     

The relationship between vaginal chlamydia and cervical abnormalities

Evaluation of: Bree A, Schlerman FJ, Wadanoli M et al. IL-13 blockade reduces lung inflammation after Ascaris suum challenge in cynomolgus monkeys. J. Allergy Clin. Immunol. 119, 1251–1257 (2007).

There is abundant evidence supporting IL-13 as having a central role in the pathology of allergic asthma. IL-13 induces immunological responses relevant to allergic asthma and exerts effects on airway structural cells, leading to remodeling and enhanced contractility of airway smooth muscle. This paper evaluates the results from a recent preclinical study in cynomolgus monkeys, showing that treatment with an antibody to IL-13 significantly attenuates airway inflammation induced by segmental allergen challenge. Efficacy of anti-IL-13 in proof-of-concept human studies will be critical to evaluate the potential of this therapy for treatment of allergic asthma.     

Assessment of airway sensitization potential of inhaled trimellitic anhydride by monitoring the elicitation phase in a mouse model

While several skin sensitization tests have been developed and are available as regulatory toxicity tests at present, no such tests for the airway have been established. We have been developing an animal model by introducing an elicitation phase into the mouse IgE test (MIGET) for assessment of agricultural chemicals with airway sensitization potential. In the current study, trimellitic anhydride (TMA), a representative low molecular weight (LMW) airway sensitizer, was examined for its sensitization potential in our mouse model. Mice were epicutaneously sensitized to TMA on Days 0 and 7, followed by an inhalation challenge with TMA dust at high or low concentration on Day 14. Groups of different sensitization route including inhalation were established for comparison of effectiveness of immunization. Non-sensitized animals challenged with TMA dust served as controls. An ovalbumin-sensitized and -challenged animals constituted a reference group (OVA). Enhanced pause (Penh) was measured as an indicator of airflow disturbance by using a restrained flow whole body plethysmograph. The high TMA concentration group exhibited an augmented Penh, elevated IgE values, and pronounced influx of eosinophils into their BAL fluid and minor infiltration of inflammatory cells including eosinophils into the lung. The low TMA concentration group also exhibited elevated IgE values and a less frequent occurrence of minor lung inflammation, but these were not accompanied by any positive responses in Penh and BAL fluid. Almost all mice in the other immunization route groups exhibited negative responses for any parameter examined. The OVA group showed no changes in breathing pattern during the inhalation challenge despite presenting a high total serum IgE value. These results suggest that this mouse model may be useful for assessment of airway sensitization potential of agrochemicals, but by way of epicutaneous sensitization.     

Inter-limb transfer of ballistic motor skill following non-dominant limb training in young and older adults

We recently reported considerably less inter-limb transfer in older, compared to young, adults following dominant (right) hand motor training (Hinder et al. in J Appl Physiol 110:166–175, 2011). This occurred despite the fact that both age groups exhibited similar performance improvements in the trained limb. However, asymmetries can exist with respect to the degree of transfer observed in some tasks, depending upon which limb undertakes the training. Accordingly, here we investigated inter-limb transfer following left hand ballistic motor training in young (n = 15; mean age 21.2 years) and older (n = 15; mean age 70.3 years) right handers. Following motor training that required participants to maximally abduct the left index finger, both groups exhibited significant performance improvements in the trained left hand. Moreover, the extent of inter-limb transfer was substantial and indistinguishable between the two age groups. Transcranial magnetic stimulation revealed that both age groups exhibited bilateral increases in cortical excitability following unilateral training, indicating that unilateral training affects both the trained and untrained hemisphere. However, only for young adults was the extent of the performance gain in the trained hand able to predict the degree of transfer. These findings suggest that different mechanisms may mediate inter-limb transfer of ballistic motor tasks for older and young adults. Because such tasks evoke similar neural responses to those observed following strength training (Selvanayagam et al. in J Appl Physiol 111:367–375, 2011; Carroll et al. in Acta Physiol 202:119–140, 2011), our findings have important implications for rehabilitation paradigms following stroke or limb immobilisation due to injury.     

Effect of Point Sampling Density in Quantifying Mouse Lung Emphysema

In the official joint policy document of the American Thoracic Society and European Respiratory Society (Hsia et al., Am J Respir Crit Care Med 181:394‐418), the need for proper stereologic assessment of lungs was emphasized. In this document it was emphasized that for the quantitative analysis of lung histologic sections, one of the most robust and reliable methods is point and intercept counting (Knudsen et al., J Appl Physiol 108:412‐421). One of the practical aspects of this method is how many points or intercepts are needed. The answer to this question has been considered from a theoretical perspective, and it depends on the relative magnitudes of the methodological and biologic variabilities. Although it is generally accepted that in a normal lung, one needs only 100–200 points to sufficiently lower the methodological variability, given the increased variability often seen in experimental emphysematous lung injury, the requisite number of points of intercepts has not been evaluated. In this study, we examined this question by focusing on some of the relevant sampling levels in mice with extensive elastase‐induced emphysema. Using fixed samples of tissue blocks, we varied the number of sampling points or intercepts from about 25 to 1,000 in control and emphysematous lungs. Our results show that, at the sampling levels investigated, even with the increased heterogeneity in the lung tissue damage caused by elastase, the number of sampling points needed to detect changes is similar to what is needed for control mice. Anat Rec, 298:531–537, 2015. © 2014 Wiley Periodicals, Inc.     

Comparison of the sensitivity of C57BL/6J and AKR/J mice to airborne molecules of isovaleric acid and amyl acetate

Wysockiet al. (1977) have previously compared the abilities of several inbred strains of mice to avoid odorized drinks after odor-aversion conditioning and have proposed C57BL/6 mice as an animal model to study the specific anosmia to isovaleric acid. We have compared the olfactory performances of C57BL/6J mice and AKR/J mice using one-bottle and two-bottle tests to study the latencies of contacts with odorized or control drinks after odor-aversion conditioning. In both inbred strains, sensitivities to airborne molecules of amyl acetate (control odor) or isovaleric acid are demonstrated. Differences in behavioral strategies are suggested but the results are consistent with the hypothesis of a selective hyposmia to isovaleric acid in C57BL/6J mice.     

Assessing Pulmonary Pathology by Detailed Examination of Respiratory Function

Pulmonary inflammation causes multiple alterations within the lung, including mucus production, recruitment of inflammatory cells, and airway hyperreactivity (AHR). Measurement of AHR by direct, invasive means (eg, mechanical ventilation) or noninvasive techniques, like whole body plethysmography (WBP), assesses the severity of pulmonary inflammation in animal models of inflammatory lung disease. Direct measurement of AHR is acknowledged as the most accurate method for assessing airway mechanics, but analysis of all data obtained from WBP may offer insights into which inflammatory aspects of the lung are altered along with AHR. Using WBP, we compared the respiratory parameters of two groups of mice sensitized with cockroach allergen. One group was treated with dexamethasone (Dex) before final challenge (Dex-Asthma), while the other group received vehicle treatment (Asthma). Respiratory parameters from plethysmography revealed that Dex-Asthma mice compensated to maintain high minute ventilation, whereas Asthma mice showed significant impairment in minute ventilation despite increased peak expiratory flow (103 ± 5 ml/min vs. 69 ± 70 ml/min). The WBP data suggest that enhanced air exchange in the Dex-Asthma mice results from significant decreases in airway mucus production. Additional studies with quantitative morphometry of histological sections confirmed that Dex reduced airway mucus. In conclusion, a detailed examination of WBP parameters can accurately assess the respiratory health of mice and will help direct additional studies.Numerous relevant animal models of disease have advanced the understanding of biology and provided important insights into the pathogenesis of human disease. The vast majority of these studies have been carried out in mice, due to their small size and the extensive characterization of the murine inflammatory system. Several robust murine models of allergic asthma have been developed in recent years,¹ including many experimental systems which induce allergic sensitization to ovalbumin (Ova). Although this system allows close control over the nature of the sensitizing agent, Ova is a relatively poor allergen and requires adjuvant co-administration or relatively high and frequent doses to achieve satisfactory immunization.^2–5 Our model, conversely, uses an allergen composed of the defatted, total body extract of German cockroaches (cockroach allergen, CRA) containing appreciable lipopolysaccharide. CRA is a highly potent allergen (robust immunization is achieved with a dose thousands of times less than that required for Ova) and does not require an adjuvant for sensitization.^6,7 Campbell et al⁷ established the first CRA induced model of asthma in mice and demonstrated robust pulmonary inflammation with many asthma-like features. The complex nature of this allergen and its close correspondence with its urban environmental counterpart makes this model highly applicable to the study of human disease.In most models of allergic airways inflammation, disease severity and or therapeutic efficacy is evaluated via measuring multiple parameters including airways hyperreactivity (AHR) in response to methacholine, cytokine and chemokine concentrations in bronchoalveolar lavage (BAL) and lung homogenates, lung inflammatory cell infiltrates and lung histological changes.^8–10 AHR is typically addressed via direct (forced oscillation) or indirect (whole body plethysmography, WBP) methods. Direct measurement of lung resistance, elastance and compliance by forced oscillation is the gold standard for the evaluation of AHR. Unfortunately, this procedure requires direct, tracheal cannulation in anesthetized mice and is typically terminal.WBP has become widely used due to its ease of use and ability to make multiple measurements on mice without inducing significant injury or distress.^2,11,12 This method of AHR evaluation employs the composite parameter known as enhanced pause (Penh) which is correlated with but not a direct measurement of resistance.^13–15 WBP has the advantage of being performed on awake, unrestrained mice in a nonterminal fashion, allowing for repeated measurements.^15–17 However, the relationship of Penh to direct resistance is hotly debated and many editorials question the utility of WBP.^18–21 If the primary goal of a study is to evaluate lung resistance forced oscillation experiments are almost certainly necessary.The following research examines whether respiratory parameters other than Penh which are measured by WBP can provide insight into the overall pulmonary health of the experimental animals. In the current studies several Penh-related and -unrelated parameters were examined to determine whether individual measurements provided information concerning the pulmonary health of mice. Additionally, we sought to use WBP to derive insight to target studies to the mechanisms of pulmonary derangements. We hypothesize that dexamethasone treatment before the final allergen challenge will lead to significant changes in WBP respiratory parameters and that these will correlate with alterations in the inflammatory profile of the DEX-treated mice.     

A comparative scale of autonomic function with age through the tone-entropy analysis on heart period variation

Tremendous numbers of heart rate variability studies have aimed to elucidate age-associated alterations of autonomic function in the past decades. However, the studies, far from clarifying ageing mechanisms, fell into confusion by a lack of common scales. The purpose of this study is to show a possibility to establish a comparative scale of autonomic function through a method, tone-entropy (T-E) analysis on heart period variation, whose validity has been already examined on typical physiological cases (Oida et al. in J Appl Physiol 82:1794–1801, 1997; Oida et al. in J Gerontol 54A:M219–M224, 1999a; Oida et al. in Acta Physiol Scand 165:129–134, 1999b; Oida et al. in Acta Physiol Scand 165:421–422, 1999c; Amano et al. in Eur J Appl Physiol 94:602–610, 2005). In this study, 276 subjects from teens to seventies were examined at rest by T-E analysis together with conventional time and frequency domain analyses. The tone (negativity represents vagal predominance) became significantly high [−0.174 ± 0.026 (teens) to −0.024 ± 0.004 (seventies), P < 0.05 for one-way ANOVA], and the entropy (total autonomic activity), significantly low [4.40 ± 0.12 (teens) to 2.90 ± 0.09 bit (seventies), P < 0.05] with advancing age. The result, plotted in 2-D T-E space, showed that the ageing traced a curvi-linear relation from right-bottom to left-top, and was consistent with previously studied typical physiological cases. The conventional analyses showed almost the same autonomic reduction as T-E did, but failed in detecting delicate alteration of autonomic balance. The results, showing that autonomic activity reduced in both pathways impairing vagal predominance significantly with ageing, suggested a possibility to assess autonomic function in 2-D T-E space in a comparative way.     

Allergen-induced airway hyperresponsiveness is absent in ecto-5′-nucleotidase (CD73)-deficient mice

Adenosine is formed from extracellular purines by ecto-5′-nucleotidase (CD73) and is an essential player in allergic airway inflammation. The contribution of adenosine and other purines to electrolyte transport and mucociliary clearance was studied in airways of allergen challenged mice. No signs for allergen-induced inflammation were found in CD73−/− mice, and adenosine monophosphate (AMP) was unable to elicit airway Cl⁻ secretion in these animals. Tracheas of ovalbumin (OVA)-treated BALB/c and CD73+/+ mice were hyperresponsive towards methacholine when assessed by Penh and direct optical measurement of contraction. In addition Cl⁻ secretion activated by ATP and ADP was enhanced. These changes were not observed in CD73−/− mice. Expression of CFTR or CLCA was unchanged upon OVA treatment of CD73 mice, suggesting enhanced Cl⁻ secretion due to upregulated purinergic pathways. Mucociliary clearance was determined by measuring particle transport in excised mouse tracheas and was strongly enhanced in OVA-challenged CD73+/+ mice, but remained unchanged in CD73−/− mice. While mucociliary clearance is activated by allergen exposure independent of functional ecto-5′-nucleotidase, airway inflammation is largely dependent on CD73. Thus, ecto-5′-nucleotidase may provide a novel target for therapeutic intervention, probably by local application of ecto-5′-nucleotidase inhibitors through inhalation. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Strain-dependent genomic factors affect allergen-induced airway hyperresponsiveness in mice

Asthma is etiologically and clinically heterogeneous, making the genomic basis of asthma difficult to identify. We exploited the strain-dependence of a murine model of allergic airway disease to identify different genomic responses in the lung. BALB/cJ and C57BL/6J mice were sensitized with the immunodominant allergen from the Dermatophagoides pteronyssinus species of house dust mite (Der p 1), without exogenous adjuvant, and the mice then underwent a single challenge with Der p 1. Allergic inflammation, serum antibody titers, mucous metaplasia, and airway hyperresponsiveness were evaluated 72 hours after airway challenge. Whole-lung gene expression analyses were conducted to identify genomic responses to allergen challenge. Der p 1-challenged BALB/cJ mice produced all the key features of allergic airway disease. In comparison, C57BL/6J mice produced exaggerated Th2-biased responses and inflammation, but exhibited an unexpected decrease in airway hyperresponsiveness compared with control mice. Lung gene expression analysis revealed genes that were shared by both strains and a set of down-regulated genes unique to C57BL/6J mice, including several G-protein-coupled receptors involved in airway smooth muscle contraction, most notably the M2 muscarinic receptor, which we show is expressed in airway smooth muscle and was decreased at the protein level after challenge with Der p 1. Murine strain-dependent genomic responses in the lung offer insights into the different biological pathways that develop after allergen challenge. This study of two different murine strains demonstrates that inflammation and airway hyperresponsiveness can be decoupled, and suggests that the down-modulation of expression of G-protein-coupled receptors involved in regulating airway smooth muscle contraction may contribute to this dissociation.     

A Micromechanical Model of Airway-Parenchymal Interdependence

The forces of parenchymal interdependence in the lung are potent inhibitors of airway smooth muscle shortening, as evidenced by the marked dependence of bronchial responsiveness on lung volume. In this study we developed a mathematical-computer model of the effects of parenchymal interdependence on airway smooth muscle shortening. A three-dimensional network of cuboidal alveolar walls was tethered at its boundaries and surrounded a single airway with mechanical properties identical to the alveolar parenchyma. The walls were assigned highly nonlinear properties so that the pressure-volume behavior of the model matched that measured in dogs. Constriction of the airway was achieved by increasing the circumferential tension in the airway wall, and then solving the force-balance equations of the model to calculate the equilibrium configurations of the airway wall and all the interconnecting alveolar walls. The changes in airway resistance predicted by the model at various transpulmonary pressures (P _tp were compared to those obtained by the alveolar capsule oscillator technique in dogs during induced bronchoconstriction at various P _tp (Balassy et al., J. Appl. Physiol. 78:875–880, 1995). The model matched the data reasonably well at P _tp values above about 0.5 kPa, but was too responsive at lower P _tp We were able to make the model match the data at all P _tpby including an additional stiffness term, such as might conceivably arise from the airway wall itself. ©     

Deficiency of regulatory B cells increases allergic airway inflammation

Objective: To investigate the effect of the X-linked immunodeficiency (Xid) B cell defect on the response to the cockroach allergen in mice. Methods: Two cockroach allergen immunization and challenge protocols were employed to sensitize CBA/J wild-type and CBA/CaHN-btk(-/-)xid/J (Xid) mice. Blood and tissue samples were collected 24 and 48 hrs after the last intratracheal antigen challenge and were analyzed for several parameters of allergic inflammation. Results: Nearly equivalent amounts of serum IgE were detected in Xid and CBA/J mice after short-term antigen challenge despite the B cell deficiency in Xid mice. A decreased concentration of IgE was detected in CBA/J mice after repeated allergen challenges but not in the Xid mice. Correlating with the discrepancy in serum IgE levels, higher levels of IL-13, IL-5, IL-10 and CCL5 were measured in whole lung homogenates from allergen-challenged Xid mice compared to CBA/J mice. In addition, draining lymph node cells from Xid mice expressed elevated levels of IL-4, IL-5, IL-10 and IFNγ mRNA compared to cells from CBA/J mice after in vitro culture with cockroach antigen. An increase in lung inflammation, interstitial eosinophilia and mucus production was also observed in allergen-challenged Xid mice. CD95L expression increased on B-1a cells following allergen challenge, which was accompanied by an increase in lung CD4⁺ Th cell apoptosis in wild-type CBA/J mice. In contrast, Xid mice did not have an increase in CD4⁺ T cell apoptosis following allergen challenge. Conclusions: These data suggest a regulatory role for B-1a cells in reducing cytokine production, pulmonary inflammation, and CD4⁺ T cell survival during cockroach allergen-induced airway inflammation. Received 10 June 2005; returned for revision 13 September 2005; accepted by M. Parnham 14 September 2005 Funding source: U. S. Government NIH Grant# AI36302     

An Intratracheal Challenge Murine Model of Asthma: Can Bronchial Inflammation Affect the Nose?

Purpose

Extensive data support the influence of the upper airway on lower airway inflammation and pathophysiology in allergic disease. However, few studies have focused on allergic inflammation in the nose after an isolated lower airway allergen challenge, a situation that can exist clinically when human subjects breathe primarily through the mouth, as occurs when nasally congested. This study used a mouse model to investigate whether upper airway inflammation and hyperresponsiveness were induced by an isolated lower airway allergen challenge.

Methods

BALB/c mice were sensitized by systemic intraperitoneal injection of ovalbumin/saline and challenged with intratracheal ovalbumin/saline. Inflammation in the nose and lungs was assessed by cytology and histology of nasal tissues and bronchoalveolar lavage fluid (BALF), while nasal airway resistance and response were measured over 3 days post-challenge.

Results

Intratracheal application of an allergen in anaesthetized mice resulted in exclusive deposition in the lower airway. Compared to control animals, ovalbumin-sensitized mice after challenge showed bronchial hyperreactivity and increased IL-5 in the serum BALF, as well as eosinophil infiltration in the lungs. However, nasal histology of the ovalbumin-sensitized mice showed no increase in eosinophil infiltration. The nasal lavage fluid revealed no increase in eosinophils or IL-5, and the nasal airway resistance did not increase after challenge either.

Conclusions

In a mouse allergy model, exclusive allergen challenge of the lower airway can elicit a pulmonary and systemic allergic response, but does not induce upper airway inflammatory or physiological responses.     

Respiratory syncytial virus infection prolongs methacholine-induced airway hyperresponsiveness in ovalbumin-sensitized mice

Severe respiratory syncytial virus (RSV)-induced disease is associated with childhood asthma and atopy. We combined models of allergen sensitization and RSV infection to begin exploring the immunologic interactions between allergic and virus-induced airway inflammation and its impact on airway hypersensitivity. Airway resistance was measured after methacholine challenge in tracheally intubated mice by whole body plethysmography. Lung inflammation was assessed by bronchoalveolar lavage (BAL) and histopathology. RSV infection alone did not cause significant airway hyperresponsiveness (AHR) to methacholine. Ovalbumin (OVA)-induced AHR lasted only a few days past the discontinuance of OVA aerosol in mice that were ovalbumin sensitized and mock infected. In contrast, OVA-sensitized mice infected with RSV during the OVA aerosol treatments (OVA/RSV) had AHR for more than 2 weeks after infection. However, 2 weeks after either RSV or mock infection, OVA/RSV mice had significantly more lymphocytes found during BAL than OVA mice, whereas the OVA and OVA/RSV groups had the same number of eosinophils. Histopathologic analysis confirmed an increased inflammation in the lungs of OVA/RSV mice compared with OVA mice. In addition, OVA/RSV mice had a more widespread distribution of mucus in their airways with increased amounts of intraluminal mucus pools compared with the other groups. Thus, prolonged AHR in RSV-infected mice during ovalbumin-sensitization correlates with increased numbers of lymphocytes in BAL fluid, increased lung inflammation, and mucus deposition in the airways, but not with airway eosinophilia. A further understanding of the immunologic consequences of combined allergic and virus-induced airway inflammation will impact the management of diseases associated with airway hyperreactivity. J. Med. Virol. 57:186–192, 1999. © 1999 Wiley-Liss, Inc.     

Muscimol inhibition of medullary raphé neurons decreases the CO2 response and alters sleep in newborn piglets

Medullary raphé neurons are chemosensitive in vitro (Wang et al., J. Physiol. Lond. 511 (1998)), are involved in the ventilatory response to CO(2) in vivo (Dreshaj et al., Respir. Physiol. 111 (1998); Nattie and Li, J. Appl. Physiol. 90 (2001)), and are abnormal in many Sudden Infant Death Syndrome (SIDS) victims (Panigrahy et al., J. Neuropathol. Exp. Neurol. 59 (2000)). In this study we determine whether the ventilatory response to CO(2) is altered when medullary raphé neuronal function is focally and reversibly inhibited in chronically instrumented newborn piglets. Ventilation was measured by whole body plethysmography in room air and in 5% CO(2) before and during microdialysis of muscimol, a gamma-amino butyric acid (GABA(A)) receptor agonist, into the medullary raphé. Muscimol (10 mM in the dialysate), had no effect on eupneic ventilation, but reduced significantly the CO(2) response by 17% during wakefulness. Sleep cycling was also disrupted, as characterized by a significant increase in the percentage of time spent awake and a significant decrease in the percentage of time spent in NREM sleep. Disturbances of medullary raphé function can alter central chemoreception and normal sleep architecture, which may contribute to the pathogenesis of SIDS.