Noninvasive method to measure airway obstruction in nonanesthetized allergen-sensitized and challenged mice

HSPB7 interacts with dimerized FLNC and its absence results in progressive myopathy in skeletal muscles

HSPB7 belongs to the small heat-shock protein (sHSP) family, and its expression is restricted to cardiac and skeletal muscles from embryonic stages to adulthood. Here, we found that skeletal-muscle-specific ablation of the HspB7 does not affect myogenesis during embryonic stages to postnatal day 1 (P1), but causes subsequent postnatal death owing to a respiration defect, with progressive myopathy phenotypes in the diaphragm. Deficiency of HSPB7 in the diaphragm muscle resulted in muscle fibrosis, sarcomere disarray and sarcolemma integrity loss. We identified dimerized filamin C (FLNC) as an interacting partner of HSPB7. Immunofluorescence studies demonstrated that the aggregation and mislocalization of FLNC occurred in the muscle of HspB7 mutant adult mice. Furthermore, the components of dystrophin glycoprotein complex, γ- and δ-sarcoglycan, but not dystrophin, were abnormally upregulated and mislocalized in HSPB7 mutant muscle. Collectively, our findings suggest that HSPB7 is essential for maintaining muscle integrity, which is achieved through its interaction with FLNC, in order to prevent the occurrence and progression of myopathy.

Highlighted Article: HSPB7 plays a crucial role in the maintenance of the muscle integrity, possibly through stabilizing the function of FLNC.

Recombinant Derp5 allergen with αS1-casein signal peptide secreted in murine milk protects against dust mite allergen-induced airway inflammation

Recent advances in recombinant technology make transgenic animals that produce pharmaceutical proteins in their milk more feasible. The group 5 allergen isolated from Dermatophagoides pteronyssinus (Derp5) is one of the most important dust mite allergens in humans. The aims of this study were to develop transgenic mice that could secrete recombinant Derp5-containing milk and to demonstrate that ingesting recombinant milk protects against allergic airway inflammation. Two transgenes were constructed separately. The α-LA-Derp5f transgene consisted of the bovine α-lactalbumin (α-LA) promoter and full-length Derp5 cDNA. The α-LA-CN-Derp5t transgene included the α-LA promoter, a leader sequence of αS1-casein (CN), and signal peptide-truncated Derp5 cDNA. Both species of transgenic mice were confirmed to have successful transgene integration and stable germline transmission. Western blot analysis of the milk obtained from the offspring of transgenic mice demonstrated that recombinant Derp5 was secreted successfully in the milk of αLA-CN-Derp5t transgenic mice but not in that of αLA-Derp5f transgenic mice. This study provides new evidence that transgenic mice can secrete recombinant Derp5 efficiently in milk by adding a signal peptide of αS1-casein. The antigenic activity of recombinant Derp5 milk was demonstrated to have a protective effect against allergic airway inflammation in a murine model in which the ingestion of recombinant Derp5-containing milk was used as pretreatment.

Inhibiting TGF-β activity improves respiratory function in mdx mice

Respiratory function is the main cause of mortality in patients with Duchenne muscular dystrophy (DMD). Elevated levels of TGF-β play a key role in the pathophysiology of DMD. To determine whether therapeutic attenuation of TGF-β signaling improves respiratory function, mdx mice were treated from 2 weeks of age to 2 months or 9 months of age with either 1D11 (a neutralizing antibody to all three isoforms of TGF-β), losartan (an angiotensin receptor antagonist), or a combination of the two agents. Respiratory function was measured in nonanesthetized mice by plethysmography. The 9-month-old mdx mice had elevated Penh values and decreased breathing frequency, due primarily to decreased inspiratory flow rate. All treatments normalized Penh values and increased peak inspiratory flow, leading to decreased inspiration times and breathing frequency. Additionally, forelimb grip strength was improved after 1D11 treatment at both 2 and 9 months of age, whereas, losartan improved grip strength only at 2 months. Decreased serum creatine kinase levels (significant improvement for all groups), increased diaphragm muscle fiber density, and decreased hydroxyproline levels (significant improvement for 1D11 only) also suggested improved muscle function after treatment. For all endpoints, 1D11 was equivalent or superior to losartan; coadministration of the two agents was not superior to 1D11 alone. In conclusion, TGF-β antagonism may be a useful therapeutic approach for treating DMD patients.

Combined forced oscillation and forced expiration measurements in mice for the assessment of airway hyperresponsiveness

Background

Pulmonary function has been reported in mice using negative pressure-driven forced expiratory manoeuvres (NPFE) and the forced oscillation technique (FOT). However, both techniques have always been studied using separate cohorts of animals or systems. The objective of this study was to obtain NPFE and FOT measurements at baseline and following bronchoconstriction from a single cohort of mice using a combined system in order to assess both techniques through a refined approach.

Methods

Groups of allergen- or sham-challenged ovalbumin-sensitized mice that were either vehicle (saline) or drug (dexamethasone 1 mg/kg ip)-treated were studied. Surgically prepared animals were connected to an extended flexiVent system (SCIREQ Inc., Montreal, Canada) permitting NPFE and FOT measurements. Lung function was assessed concomitantly by both techniques at baseline and following doubling concentrations of aerosolized methacholine (MCh; 31.25 - 250 mg/ml). The effect of the NPFE manoeuvre on respiratory mechanics was also studied.

Results

The expected exaggerated MCh airway response of allergic mice and its inhibition by dexamethasone were detected by both techniques. We observed significant changes in FOT parameters at either the highest (Ers, H) or the two highest (Rrs, R_N, G) MCh concentrations. The flow-volume (F-V) curves obtained following NPFE manoeuvres demonstrated similar MCh concentration-dependent changes. A dexamethasone-sensitive decrease in the area under the flow-volume curve at the highest MCh concentration was observed in the allergic mice. Two of the four NPFE parameters calculated from the F-V curves, FEV_0.1 and FEF50, also captured the expected changes but only at the highest MCh concentration. Normalization to baseline improved the sensitivity of NPFE parameters at detecting the exaggerated MCh airway response of allergic mice but had minimal impact on FOT responses. Finally, the combination with FOT allowed us to demonstrate that NPFE induced persistent airway closure that was reversible by deep lung inflation.

Conclusions

We conclude that FOT and NPFE can be concurrently assessed in the same cohort of animals to determine airway mechanics and expiratory flow limitation during methacholine responses, and that the combination of the two techniques offers a refined control and an improved reproducibility of the NPFE.

Ovalbumin-Induced Airway Inflammation and Fibrosis in Mice Also Exposed to Ultrafine Particles

A murine model of allergen-induced airway inflammation was used to examine the effects of exposure to ultrafine particles (PM(2.5)) on airway inflammation and remodeling. Lung inflammation was measured by quantitative differential evaluation of lung lavage cells. Alterations in lung structure (airway remodeling and fibrosis) were evaluated by quantitative biochemical analysis of microdissected airways and by histological evaluation of stained lung sections. The same total number of cells was observed in lavage fluid from animals exposed for 4 wk to ovalbumin alone or to ovalbumin for 4 wk immediately before or after 6 exposures over a period of 2 wk to 235 ug/m(3) of PM(2.5). Mice exposed to ovalbumin for 6 wk with concurrent exposure to PM(2.5) during wk 5-6 had a significant decrease in the total number of cells recovered by lavage as compared with the group exposed to ovalbumin alone. There were no significant differences in the cell differential counts in the lavage fluid from mice exposed to ovalbumin alone as compared with values from mice exposed to ovalbumin and PM(2.5) under the protocols studied. Airway structural changes (remodeling) were examined by three different quantitative methods. None of the groups exposed to ovalbumin and PM had a significant increase in airway collagen content evaluated biochemically (i.e., total airway collagen) as compared to the matched groups of mice exposed to ovalbumin alone. Airway collagen content evaluated histologically by sirius red staining showed significant increases in all of the animals exposed to ovalbumin, with or without PM, and no apparent difference between the ovalbumin group and mice exposed to PM with ovalbumin. The findings were consistent with an additive, or less than additive, response of mice to exposure to PM and ovalbumin. Air or PM exposure alone for 2 wk did not result in observable goblet cells in the airways, while mice exposed to ovalbumin aerosol alone for 4 wk had about 20-25% goblet cells in their conducting airways. Sequential exposure to ovalbumin and PM (or vice versa) caused significant increases in goblet cells (to about 35% of total cells) in the conducting airways of the exposed mice. We conclude that when mice with allergen-induced airway inflammation induced by ovalbumin are also exposed to PM(2.5), the lung inflammatory response and airway remodeling may be modified, but that this altered response is dependent upon the sequence of exposure and the duration of exposure to ovalbumin aerosol. At the concentrations of PM tested, we did not see changes in airway fibrosis or airway reactivity for animals exposed to ovalbumin and PM(2.5) as compared with animals exposed only to ovalbumin aerosol. However, goblet-cell hyperplasia was significantly increased in mice exposed concurrently to ovalbumin and PM(2.5) as compared with mice exposed to ovalbumin alone.

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.

TGF-beta1 causes airway fibrosis and increased collagen I and III mRNA in mice

BACKGROUND

Subepithelial collagen and extracellular matrix protein deposition are important pathophysiological components of airway remodelling in chronic asthma. Animal models based on the local reaction to antigens show structural alterations in the airway submucosal region and provide important information regarding disease pathophysiology. We describe a murine model of peribronchial fibrosis using intratracheally instilled transforming growth factor (TGF)-beta(1) in BALB/C mice that facilitates a mechanistic approach to understanding the cellular and molecular pathways leading to airway fibrosis.

METHODS

BALB/C mice were intratracheally instilled with either TGF-beta(1) or buffered saline. Airway fibrosis was assessed by light microscopy, hydroxyproline content, and polymerase chain reaction (PCR) for collagen I and III on microdissected airway samples. The lysyl oxidase inhibitor beta-aminoproprionitrile (BAPN) was administered to TGF-beta(1) treated mice to block airway collagen deposition. Airway hyperresponsiveness was also measured after treatment with TGF-beta(1).

RESULTS

During the 7 days after administration of TGF-beta(1) the mice developed increased subepithelial collagen which could be blocked by BAPN. Increased mRNAs for collagen types I and III were seen in microdissected airways 1 week after TGF-beta(1), and significantly increased total collagen was found in the airways 4 weeks after TGF-beta(1). A detectable increase in airway hyperreactivity occurred.

CONCLUSIONS

This new model should facilitate detailed study of airway remodelling that occurs in the absence of detectable cellular inflammation, and allow examination of the functional consequences of a major structural alteration in the conducting airways uncomplicated by inflammatory cell influx.

Susceptibility to ovalbumin-induced airway inflammation and fibrosis in inducible nitric oxide synthetase-deficient mice: mechanisms and consequences

In a previous study, we showed that BALB/c mice demonstrate significant increases in accumulation of airway collagen after 4 weeks of exposure to ovalbumin aerosol. In the current study we examined the response to ovalbumin aerosol of a different strain of mice, C57BL/6, and compared this response to an otherwise isogenic C57BL strain (iNOS(-/-)) in which the gene for inducible nitric oxide synthetase (iNOS) had been knocked out. We hypothesized that C57BL mice, a Th-1-responsive strain, would be relatively resistant to ovalbumin exposure compared with our previous observations in the BALB/c strain, a Th-2 responder. Our results are consistent with this hypothesis, especially with respect to the accumulation of collagen in the airways of the mice exposed to ovalbumin and increased airway reactivity to challenge with methacholine, as measured by the Penh response. Since NO participates in multiple signal transduction pathways, there was no a priori reason to predict whether iNOS(-/-) mice would be more or less susceptible to allergen-induced airway inflammation than their parental wild-type strain. Responses to ovalbumin exposure of the Th-1-responsive C57BL animals were significantly less (or slower) than those we observed with the iNOS(-/-) mice. Significant increases in airway collagen content were seen only after 6 weeks of exposure of the C57BL mice, as contrasted with 4 weeks in the iNOS(-/-) animals. At each time point examined, Penh values for the iNOS(-/-) mice were significantly increased, while no increases were observed with the C57BL strain. Thus, the iNOS(-/-) mice are more susceptible to ovalbumin-induced airway inflammation and fibrosis than the C57BL strain, giving results intermediate between the previous observations in BALB/c mice and our current findings in C57BL animals with the various assays performed. We also asked whether the effects of knocking out the iNOS gene were exerted before or after the release of TGF-beta(1) by eosinophils and other effector cells in the lung. We measured the response of C57BL and iNOS(-/-) mice to direct intratracheal challenge with TGF-beta(1). There was no apparent response of C57BL mice to TGF-beta(1) at 4 or 11 days after TGF-beta(1) challenge, as evaluated by bronchoprovocation testing. On the other hand, the observed Penh values were significantly greater in iNOS(-/-) mice that had also received TGF-beta(1) 4 days previously. These results strongly support the hypothesis that the increased sensitivity of iNOS(-/-) mice to ovalbumin is at least partially dependent on pathways that come into play subsequent to the release of TGF-beta(1) by effector cells in the lungs of mice exposed to ovalbumin aerosol.

Integration of safety pharmacology endpoints into toxicology studies

In the ILSI Human Toxicity Program, human toxicity was identified with 94% in studies of 1 month or less duration. Safety pharmacology studies and 1 month toxicity studies are prerequisites of INDs. These studies contributed in 69% to the predictivity of human toxicity. Correlating data from pharmacology and toxicology data will therefore enhance the predictivity of human toxicity. The ILSI Human Toxicity Program also showed that non-rodent toxicology studies were more predictive of human toxicity than rodents. Consequently, the usage of non-rodents, especially dogs, produces data more relevant to the safety of humans. Integration of data from safety pharmacology and pharmacological endpoints from integrated toxicology studies, which cover a wide dose range, allow data interpretation also concerning chronic effects. Differences in relation to chronic exposure and species specific pharmacodynamic effects can be taken into consideration. In vivo data in pharmacology are taken from a larger number of species. Usually, pharmacokinetic data and histopathology are often lacking in pharmacology (e.g. guinea pig). Studies in a smaller number of species, which are incorporating pharmacology, pharmacodynamic and toxicology, allow also crossinterpretation with data from clinical chemistry, haematology and histopathology. Endpoints relating to behaviour (functional observation battery/FOB) and cardiovascular toxicity can be integrated into regulatory toxicology. Technical progress in non-invasive methodology and refined measurements for pharmacological parameters and standardization of study design allow the incorporation into regulatory toxicity studies today. The limitations of conducting pharmacological measurements in regulatory toxicology studies are acknowledged. Safety pharmacology studies should complement toxicity studies in terms of choice of species and dose regimen. Ethical usage of animals, especially dogs or monkeys, can only be justified in the future, when more clinically relevant data can be gained from fewer in vivo studies. Multidisciplinary co-operation between pharmacology, pharmacokinetics and toxicology will lead to refinements and reduction of in-vivo studies when functional parameters are integrated into regulatory studies.