Effects of local and systemic budesonide on allergen-induced airway reactions in the pig

Formaldehyde exposure induces differentiation of regulatory T cells via the NFAT-mediated T cell receptor signalling pathway in Yucatan minipigs

The use of minipigs (Sus scrofa) as a platform for toxicological and pharmacological research is well established. In the present study, we investigated the effect of formaldehyde (FA) exposure on helper T cell-mediated splenic immune responses in Yucatan minipigs. The minipigs were exposed to different inhaled concentrations of FA (0, 2.16, 4.62, or 10.48 mg/m³) for a period of 2 weeks. Immune responses elicited by exposure to FA were determined by assessing physiological parameters, mRNA expression, and cytokine production. Additionally, the distribution of helper T cells and regulatory T (Treg) cells and expression of NFAT families, which are well-known T cell receptor signalling proteins associated with regulatory T cell development, were evaluated. Exposure to FA suppressed the expression of genes associated with Th1 and Th2 cells in minipigs in a concentration-dependent manner. The subsequent production of cytokines also declined post-FA exposure. Furthermore, exposure to FA induced the differentiation of CD4⁺ Foxp3⁺ Treg cells with divergent expression levels of NFAT1 and NFAT2. These results indicated that exposure to FA increased the Treg cell population via the NFAT-mediated T cell receptor signalling pathway, leading to suppression of effector T cell activity with a decline in T cell-related cytokine production.

Airway Epithelial Lining Fluid and Plasma Pharmacokinetics of Inhaled Fluticasone Propionate and Salmeterol Xinafoate in Mechanically Ventilated Pigs

Background: The lower respiratory tract of the landrace pig has close anatomical and physiological similarities with that of the human, and hence, for inhalation studies this species is well suited for biopharmaceutical research. Methods: The objective of this study was to evaluate pharmacokinetics in pigs following one dose of Diskus™ Seretide™ forte device, labeled 500/50 fluticasone propionate (FP) and salmeterol xinafoate (SX), respectively. The PreciseInhale™ (PI) instrument was used to actuate the inhaler for in vitro testing and aerosol dosing to pigs. In vitro, the aerosol was characterized with a cascade impactor with respect to mass median aerodynamic diameter, geometric standard deviation, and fine particle dose. In vivo, dry powder inhalation exposure was delivered as a short bolus dose, to anesthetized and mechanically ventilated landrace pigs. In addition to plasma PK, PK assessment of airway epithelial lining fluid (ELF) was used in this study. ELF of the depth of three to fourth airway generation of the right lung was accessed using standard bronchoscopy and a synthetic absorptive matrix. Results and Conclusions: Dry powder inhalation exposures with good consistency and well characterized aerosols to the pig lung were achieved by the use of the PreciseInhale™ instrument. Drug concentrations of ELF for both FP and SX were demonstrated to be four to five orders of magnitude higher than its corresponding systemic plasma drug concentrations. Clinical PK following inhalation of the same dose was used as benchmark, and the clinical study did demonstrate similar plasma PK profiles and drug exposures of both FP and SX as the current pig study. Two factors explain the close similarity of PK (1) similiar physiology between species and (2) the consistency of dosing to animals. To conclude, our study demonstrated the utility and translational potential of conducting PK studies in pigs in the development of inhaled pharmaceuticals.

Comparison of different dosing strategies of intratracheally instilled budesonide on meconium injured piglet lungs

BACKGROUND

Severe inflammation plays a vital role in the pathogenesis of meconium aspiration syndrome (MAS). Intratracheal (IT) instillation of corticosteroids may be beneficial for MAS in optimizing local effect and reducing systemic adverse effects, but the optimum dosing course remains open to question.

METHODS

Thirty meconium-injured newborn piglets were enrolled into six study groups. The first four groups consisted of the IT instillation of 0.25/0.5 mg/kg using either one (IT-B251/IT-B501) or two (IT-B252/IT-B502) doses of budesonide, while the other two groups were the intravenous (IV) dexamethasone (0.5 mg/kg) (IV-Dex) group and the control group (Ctrl). Vital signs and cardiopulmonary functions were monitored throughout the experiments. Pulmonary histology was examined after completing the experiments.

RESULTS

Both the IV-Dex and IT-B501 groups got significant improvement in oxygenation (P < 0.05). Lung compliance became worse after one dose of 0.25 mg/kg of IT budesonide. Pulmonary histology revealed that there were significantly lower lung injury scores for all treatment groups compared to control group, especially at the non-dependent sites of both the IT-B501 and IT-B502 groups. There was no significant difference between double- and single-dose groups, no matter whether 0.25 or 0.5 mg/kg of budesonide was used.

CONCLUSIONS

IT instillation of one dose of 0.5 mg/kg budesonide is beneficial in treating meconium-injured piglet lungs during the first 8 h of injury, but a second dose at an interval of 4 h does not have a superior beneficial effect compared to one dose.

Particle deposition in the lung of the Göttingen minipig

We report on particle deposition in the tracheobronchial and pulmonary regions of the respiratory tract of the minipig and its dependence on particle size. Four animals breathing spontaneously via the nose were exposed for 1 h to known concentrations of three different polydisperse dry aerosols composed of bovine serum albumin (BSA) and an oxide of a rare earth element: Y2O3, Sm2O3, and Er2O3. The mass size distributions of the rare earth elements of the three test aerosols have mass median aerodynamic diameters of 0.9, 2.5, and, 4.3 microm, and geometric standard deviations of sigma(g) = 2.0, 1.8, and, 1.7. The extrathoracic, tracheobronchial, and pulmonary regions of the respiratory tract were dissected, separately lyophilized, and chemically digested by microwave-assisted high pressure digestion. The tracer element in each compartment was determined by inductively coupled plasma mass spectrometry. A mass balance equation relating the tracer mass found in the lung compartments to the tracer mass inhaled was solved by linear regression to obtain the deposition fraction as function of particle sizes for the tracheobronchial and the pulmonary lung region. Estimated values for the respiratory minute volume were used in this context. For coarse particles > 6 microm, the deposition fraction is < 5% for both compartments. The deposition fraction for particles with aerodynamic diameter of approximately 3 microm is 21% in the tracheobronchial airways and 40% in the pulmonary airways.

AEROSOL DELIVERY DURING MECHANICAL VENTILATION TO THE RAT

The authors have adjusted a jet nebulizer to a mechanical ventilator (Servo Ventilator, Siemens) to deliver an aerosol to rats. They aimed to clarify whether a modified jet nebulizer generating particles with a mass median aerodynamic diameter of 2 microm would be effective and safe in intubated ventilated rats. Fluorescent microspheres (diameter: 1.0 microm) were aerosolized to verify qualitatively and quantitatively intrapulmonary deposition. Particle deposition fraction was 3.8% (1.3%) of the delivered dose (median [interquartile range]). There was no evidence for any adverse event as assessed from heart rate, mean arterial pressure, PaO2 and PaCO2 before, during, and after nebulization. No pulmonary tissue trauma was detected histologically.

Assessment of protein allergenicity on the basis of immune reactivity: animal models

Because of the public concern surrounding the issue of the safety of genetically modified organisms, it is critical to have appropriate methodologies to aid investigators in identifying potential hazards associated with consumption of foods produced with these materials. A recent panel of experts convened by the Food and Agriculture Organization and World Health Organization suggested there is scientific evidence that using data from animal studies will contribute important information regarding the allergenicity of foods derived from biotechnology. This view has given further impetus to the development of suitable animal models for allergenicity assessment. This article is a review of what has been achieved and what still has to be accomplished regarding several different animal models. Progress made in the design and evaluation of models in the rat, the mouse, the dog and in swine is reviewed and discussed.

A neonatal swine model for peanut allergy

BACKGROUND

Peanut allergy represents a significant health threat in the United States. The factors contributing to the severity of the allergic response and the immunopathogenic mechanisms underlying peanut allergy remain to be completely characterized. As yet, no animal model has been developed that will completely mimic the physical, immunologic, and histologic features of food allergy.

OBJECTIVE

The purpose of this investigation was to develop a neonatal pig model of peanut allergy that would mimic the allergic symptoms and the immunologic and histologic profile of human peanut allergy.

METHODS

Newborn piglets sensitized intraperitoneally with peanut extract and cholera toxin were orally challenged repeatedly with peanut meal. Physical symptoms, including emesis, lethargy, diarrhea, and respiratory distress, were monitored to determine the allergic response. Immunologic assessment was conducted through use of skin testing and the antigenic response to peanut proteins. Histologically, tissues derived from the esophagus, stomach, small intestine, and colon were assessed for morphologic changes after the oral challenge.

RESULTS

Peanut-sensitized pigs responded with physical symptoms that mimicked those seen in double-blinded, placebo-controlled oral food challenges to peanuts in children and adults. Skin testing suggested an IgE-mediated response; this was confirmed by a negative passive cutaneous anaphylaxis response of heat-treated sera obtained from peanut-sensitized animals. Damage to villi of the small intestine was similar to that seen in endoscopically obtained tissue specimens from certain food-allergic individuals.

CONCLUSION

The neonatal pig model of peanut allergy mimics the physical and immunologic characteristics of peanut allergy in human beings. The model will be useful for determining IgE-mediated mechanisms and conducting endoscopic histologic assessment of tissues and immunotherapeutic intervention strategies with repeated allergen challenges.

Selective protective effects of nitric oxide inhalation on allergen-induced acute airway reactions in the pig

BACKGROUND

Nitric oxide (NO) is thought to be an important mediator of inflammatory processes during allergic reactions in the respiratory tract.

OBJECTIVE

This study was undertaken to investigate the effects of inhalation of NO on the allergen-induced acute airway reactions in the pig.

METHODS

Specific pathogen-free pigs were sensitized with Ascaris suum antigen and challenged with an allergen aerosol during mechanical ventilation and anaesthesia. One group (n = 8) was treated with inhaled NO (20 ppm) which was given from 30 min before allergen challenge until the experiments were completed at 120 min after challenge. A control group (n = 8) did not receive NO (< 0.001 ppm).

RESULTS

Inhalation of 20 ppm NO prevented the fall in arterial pO2/FiO2 levels that was observed in the control group (areas under the curve between 0 and 120 min were 3.7 +/- 1.4 kPa/min in NO-treated pigs vs. 15.9 +/- 3.4 in controls, P < 0.01, Mann-Whitney U-test) and it decreased baseline pulmonary arterial pressure (change from time-point - 30-0 was 3.1 +/- 5.3% in the control and - 19.9 +/- 3.5% in the NO group, P < 0.01), which in turn resulted in a lower pulmonary arterial pressure during allergen challenge. NO also caused vasodilatation in the bronchial circulation, resulting in increased bronchial vascular conductance throughout the experiment. NO inhalation caused a small, but non-significant, reduction in the allergen-induced bronchoconstrictor response, whereas histamine release, as detected in urine, was not changed. Total protein levels in bronchoalveolar lavage (BAL) fluid were significantly decreased in the NO group at 120 min after challenge compared with 45 min (373 +/- 101 microg/mL vs. 631 +/- 184, respectively, P < 0.05, Wilcoxon matched pairs test), whereas levels in the control group did not change between these two time-points (513 +/- 282 vs. 599 +/- 354, not significant).

CONCLUSION

These findings indicate that NO inhalation improves ventilation/perfusion matching and causes some bronchodilatation during the allergen-induced acute airway reaction, whereas histamine release is not affected. Moreover, NO inhalation enhanced the clearance of extravasated protein in the airways, possibly through increased bronchial blood flow. Even though some protective effects were seen, this study does not support a therapeutic role for exogenous NO in acute allergic reactions.