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Biomedical subjects

Charles G Plopper

Publications and source records attributed to Charles G Plopper.

At least 19 recordsLinked to original sources

Vascular remodeling is airway generation-specific in a primate model of chronic asthma.

RATIONALE: Changes in the density of bronchial vessels have been proposed as a part of airway remodeling that occurs in chronic asthma. OBJECTIVES: Using an established nonhuman primate model of chronic allergic asthma, we evaluated changes in vascular density as well as the contribution of bronchial epithelium to produce vascular endothelial growth factor (VEGF). METHODS: Eight juvenile rhesus macaques were divided into two groups of four. One group was exposed to 11 cycles of aerosolized house dust mite allergen (HDMA), whereas the other was exposed to filtered air. Bronchial wall vasculature was identified using an immunohistochemical approach, and vascular density was quantified stereologically. A semiquantitative polymerase chain reaction approach was used to estimate VEGF splice variant gene expression at discrete airway generations. Cell culture of primary tracheal epithelial cells with varying concentrations of HDMA was used to quantify the direct contribution of the epithelium to VEGF production. RESULTS: Bronchial vascular density was increased at mid- to lower airway generations, which was independent of changes in the interstitial compartment. The VEGF121 splice variant was significantly increased at lower airway generations. VEGF protein increased in a dose-dependant fashion in vitro primarily by an increase in VEGF121 gene expression. CONCLUSION: This study highlights that increased vascular density in an animal model of chronic allergic asthma is airway generation specific and associated with a unique increase of VEGF splice variant gene expression. Airway epithelium is the likely source for increased VEGF.

Animals↗

Cyclic exposure to ozone alters distal airway development in infant rhesus monkeys.

Inner city children exposed to high levels of ozone suffer from an increased prevalence of respiratory diseases. Lung development in children is a long-term process, and there is a significant period of time during development when children growing up in urban areas are exposed to oxidant air pollution. This study was designed to test whether repeating cycles of injury and repair caused by episodes of ozone exposure lead to chronic airway disease and decreased lung function by altering normal lung maturation. We evaluated postnatal lung morphogenesis and function of infant monkeys after 5 mo of episodic exposure of 0.5 parts per million ozone beginning at 1 mo of age. Nonhuman primates were chosen because their airway structure and postnatal lung development is similar to those of humans. Airway morphology and structure were evaluated at the end of the 5-mo exposure period. Compared with control infants, ozone-exposed animals had four fewer nonalveolarized airway generations, hyperplastic bronchiolar epithelium, and altered smooth muscle bundle orientation in terminal and respiratory bronchioles. These results suggest that episodic exposure to environmental ozone compromises postnatal morphogenesis of tracheobronchial airways.

Animals↗

Early postnatal exposure to allergen and ozone leads to hyperinnervation of the pulmonary epithelium.

Airway injury in infant monkeys exposed to ozone and/or house dust mite allergen (HDMA) is associated with a loss of epithelial innervation. In this study, we evaluated for persistence/recovery of the altered epithelial innervation. Thirty-day-old rhesus monkeys were exposed to repeated episodes of HDMA and/or ozone from 1 to 6 months of age and subsequently allowed to recover for 6 months in the absence of further ozone exposure and/or minimal HDMA challenge (sufficient to maintain allergen sensitization). At 1 year of age, nerve density in intrapulmonary airways was immunohistochemically evaluated using antibodies directed against protein gene product 9.5. Hyperinnervation and irregular epithelial nerve distribution was observed in both HDMA- and ozone-exposed groups; most prominent alterations were observed in animals exposed to HDMA plus ozone. Therefore, while adaptive mechanisms exist that re-establish epithelial innervation following cessation or diminution of exposure to HDMA and/or ozone, the recovery is associated with persistent proliferative mechanisms that result in hyperinnervation of the airways.

Allergens↗

Structural and functional localization of airway effects from episodic exposure of infant monkeys to allergen and/or ozone.

Both allergen and ozone exposure increase asthma symptoms and airway responsiveness in children. Little is known about how these inhalants may differentially modify airway responsiveness in large proximal as compared to small distal airways. We evaluated whether bronchi and respiratory bronchioles from infant monkeys exposed episodically to allergen and/or ozone differentially develop intrinsic hyperresponsiveness to methacholine and whether eosinophils and/or pulmonary neuroendocrine cells play a role. Infant monkeys were exposed episodically for 5 months to: (1) filtered air, (2) aerosolized house dust mite allergen, (3) ozone 0.5 ppm, or (4) house dust mite allergen + ozone. Studying the function/structure relationship of the same lung slices, we evaluated methacholine airway responsiveness and histology of bronchi and respiratory bronchioles. In bronchi, intrinsic responsiveness was increased by allergen exposure, an effect reduced by bombesin antagonist. In respiratory bronchioles, intrinsic airway responsiveness was increased by allergen + ozone exposure. Eosinophils were increased by allergen and allergen + ozone exposure in bronchi and by allergen exposure in respiratory bronchioles. In both airways, exposure to allergen + ozone resulted in fewer tissue eosinophils than did allergen exposure alone. In bronchi, but not in respiratory bronchioles, the number of eosinophils and neuroendocrine cells correlated with airway responsiveness. We conclude that episodically exposing infant monkeys to house dust mite allergen with or without ozone increased intrinsic airway responsiveness to methacholine in bronchi differently than in respiratory bronchioles. In bronchi, eosinophils and neuroendocrine cells may play a role in the development of airway hyperresponsiveness.

Airway Resistance↗

Age-specific pulmonary cytochrome P-450 3A1 expression in postnatal and adult rats.

A major cause of death and illness in children under the age of five, most living in polluted cities, is respiratory disease. Previous studies have shown that neonatal animals are more susceptible to bioactivated pulmonary cytotoxicants than adults, despite lower expression of the pulmonary cytochrome P-450s (CYP450s) thought to be involved in bioactivation. One CYP450 that is well documented in the bioactivation of many drugs and environmental toxicants in adult lung, but whose expression has not been evaluated during postnatal pulmonary development, is CYP450 3A (CYP3A). We compared age-specific expression of CYP3A1 in 7-day-old and adult male Sprague-Dawley rats. Unlike those shown for previously studied pulmonary CYP450s, expression levels for CYP3A1 mRNA in differentiating airway cells of postnatal rats are the same as in fully differentiated airway cells of adults. CYP3A1 protein expression (28%) and enzymatic activity (23%) were lower in postnatal airways compared with adults. Although other CYP450 immunoreactive proteins are primarily expressed in nonciliated cells, immunoreactive CYP3A1 protein was expressed in both ciliated and nonciliated cells in postnatal and adult rat proximal airways. CYP3A1 protein is detected diffusely throughout ciliated and nonciliated cells in 7-day-old rats, whereas it is only detected in the apex of these cells in adult rats. This study demonstrates that the lungs of postnatal rats have detectable levels of CYP3A1 and that CYP3A1 mRNA expression appears not to be age dependent, whereas steady-state CYP3A1 protein levels and enzyme activity show an age-dependent pattern.

Age Factors↗

Identification of proteins adducted by reactive metabolites of naphthalene and 1-nitronaphthalene in dissected airways of rhesus macaques.

Naphthalene and 1-nitronaphthalene are ambient air pollutants, which undergo P450-dependent bioactivation in the lung. Reactive metabolites of naphthalene and 1-nitronaphthalene covalently bind to proteins, and the formation of covalent adducts correlates with airway epithelial cell injury in rodent models. These studies were designed to identify protein adducts generated from these reactive metabolites within distal respiratory airways. Distal bronchioles and parenchyma from rhesus monkeys were incubated with [(14)C]naphthalene or [(14)C]1-nitronaphthalene. Proteins were separated by 2-DE, blotted to PVDF membranes, and adducted proteins imaged by storage phosphor analysis. MS of in-gel tryptic digests identified numerous adducted proteins including: eight cytoskeletal proteins, two chaperone proteins, seven metabolic enzymes, one redox protein, two proteins involved in ion balance and cell signaling, and two extracellular proteins. While many proteins are adducted by both naphthalene and 1-nitronaphthalene, some are unique to the individual toxicant and airway subcompartment. Although the role which adduction of these proteins plays in cytotoxicity was not evaluated, these studies provide candidate proteins for future work designed to determine the importance of protein adducts in the mechanisms of toxicity and for developing biomarkers useful in determining the relevance of findings in animal models to exposed human populations.

Animals↗

Design-based sampling and quantitation of the respiratory airways.

Design-based quantitation of the nasal cavity, larynx and tracheobronchial conducting airways after exposure to inhaled toxicants requires complete measurement of all respiratory airways or appropriate sampling followed by morphometric measurements. In vivo imaging (MRI or CT) of the nasal cavity, larynx and conducting airways provides anatomical detail of all the airways down to the distal airways. Since inhaled toxicants show predictable deposition patterns in the airways, identification and sampling of conducting airways becomes essential in a precise toxicological evaluation. Lengths, diameters and luminal surface areas can be directly measured on fixed specimens using a stereomicroscope. Estimates of cell numbers, extracellular matrix volumes and vessel/nerve lengths per airway or epithelial basal laminar surface are estimated stereologically. Selected airways are cut into smaller pieces using a "fractionator" for uniform sampling of the airways. Cell numbers are estimated using a "disector." Volumes are estimated using point probes, while length and surface areas are estimated by isotropically oriented sections with plane and line probes; an approach free of assumptions of shape, size or spatial orientation. True biological variance and the average sampling variance of the stereological measurement define the minimal sampling required to achieve precise estimates of the nasal cavity, larynx and conducting airways.

Animals↗

An aerosolized fluorescent microsphere technique for evaluating particle deposition in the avian respiratory tract.

The objective of this study was to examine the feasibility of using aerosolized fluorescent microspheres to examine particle distribution in the respiratory tract of birds following aerosol exposure. Adult domestic pigeons (Columbia livia domestica; n = 5 birds per microsphere size) were exposed to aerosolized monodispersed populations of various sized carboxylate microspheres (0.5, 1.0, 2.0, 3.0, 6.0, and 10.0 microm) for 30 min. For aerosol-exposure purposes, the birds were anesthetized with injectable anesthetics, intubated, and placed on positive-pressure ventilation using a mechanical ventilator. Immediately following aerosol exposure, the birds were euthanatized, and carcasses were preserved via intravenous infusion of modified paraformaldehyde/gluteraldehyde fixative (pH = 7.2 and 340 mOsm). Initial evaluation of microsphere distribution in air sacs (cranial and caudal thoracic and abdominal) and at the level of the ostia was performed using a stereoscopic microscope with an epifluorescent module. More detailed examination of the distribution of microspheres within the respiratory tract was achieved using a confocal scanning laser microscope with a krypton argon laser and a scanning electron microscope. The results from this study revealed that positive-pressure ventilation resulted in distribution of smaller sized fluorescent microspheres (sizes 1.0, 2.0, and 3.0 microm) throughout the pigeon's respiratory tracts, and these microspheres were in highest concentration in the secondary bronchi and ostia for all of the examined air sacs. The larger sized beads (6.0 and 10.0) were confined to the upper airway (trachea and primary bronchi). The results from this study allow for a better understanding of particle deposition following positive-pressure ventilation and aerosol exposure in birds.

Aerosols↗

Temporal and spatial distribution of ciliogenesis in the tracheobronchial airways of mice.

Little is known about ciliogenesis as it proceeds through the entire airway tree, from the trachea to the terminal bronchioles, especially during the postnatal period. The purpose of this study was to define the spatial and temporal (prenatal and postnatal) pattern of normal cilia development in the mouse. Three airway generations representing the entire airway tree were examined: trachea, lobar bronchi, and terminal bronchiole. Ciliated cells in lung lobe whole mounts were labeled with a fluorescent dye for confocal microscopy, and ciliated cell surface density was measured for each airway generation and age. The same samples were examined by scanning electron microscopy to verify the appearance of ciliated cells among the differentiating epithelium of the airways. Ciliated cells were first detected in the trachea and lobar bronchi at 16 days gestational age (DGA) and in the terminal bronchioles at 18 DGA. Ciliated cell surface density increased with prenatal and postnatal age at all airway levels. However, the ciliated cell surface density of the trachea and lobar bronchi was always greater compared with the terminal bronchiole. In conclusion, the study revealed that in developing tracheobronchial airways of the mouse: 1) Ciliogenesis differs temporally and spatially by airway generation; 2) Ciliated cell surface density increases with age in all airway generations, but density decreases in a proximal to distal direction; and 3) A significant portion of ciliogenesis continues after birth. This study provides a healthy basis for investigations of neonatal pulmonary disease or pollutant toxicity affecting cilia and its functions.

Aging↗

Consequences of abrupt glutathione depletion in murine Clara cells: ultrastructural and biochemical investigations into the role of glutathione loss in naphthalene cytotoxicity.

Glutathione plays many critical roles within the cell, including offering protection from reactive chemicals. The bioactivated toxicant naphthalene forms chemically reactive intermediates that can deplete glutathione and covalently bind to cellular proteins. Naphthalene selectively injures the nonciliated epithelial cells of the intrapulmonary airways (i.e., Clara cells). This study attempted to define what role glutathione loss plays in naphthalene cytotoxicity by comparing Swiss-Webster mice treated with naphthalene with those treated with the glutathione depletor diethylmaleate. High-resolution imaging techniques were used to evaluate acute changes in Clara cell ultrastructure, membrane permeability, and cytoskeleton structure. A single dose of either diethylmaleate (1000 mg/kg) or naphthalene (200 mg/kg) caused similar glutathione losses in intrapulmonary airways (< 20% of control). Diethylmaleate did not increase membrane permeability, disrupt mitochondria, or lead to cell death--hallmark features of naphthalene cytotoxicity. However, diethylmaleate treatment did cause Clara cell swelling, plasma membrane blebs, and actin cytoskeleton disruptions similar to naphthalene treatment. Structural changes in mitochondria and Golgi bodies also were noted. Changes in ATP levels were measured as an indication of overall cell function, in isolated airway explants incubated with diethylmaleate, naphthalene, or naphthalene metabolites in vitro. Only the reactive metabolites of naphthalene caused significant ATP losses. Unlike the lethal injury caused by naphthalene, the disruptive cellular changes associated with glutathione loss from diethylmaleate seemed to be reversible after recovery of glutathione levels. This suggests that glutathione depletion may be responsible for some aspects of naphthalene cytotoxicity, but it is not sufficient to cause cell death without further stresses.

Actins↗

In vivo effects of ozone exposure on protein adduct formation by 1-nitronaphthalene in rat lung.

The incidence of serious photochemical smog events is steadily growing in urban environments around the world. The electrophilic metabolites of 1-nitronaphthalene (1-NN), a common air pollutant in urban areas, have been shown to bind covalently to proteins. 1-NN specifically targets the airway epithelium, and the toxicity is synergized by prior long-term ozone exposure in rat. In this study we investigated the formation of 1-NN protein adducts in the rat airway epithelium in vivo and examined how prior long-term ozone exposure affects adduct formation. Eight adducted proteins, several involved in cellular antioxidant defense, were identified. The extent of adduction of each protein was calculated, and two proteins, peroxiredoxin 6 and biliverdin reductase, were adducted at high specific activities (0.36-0.70 and 1.0 nmol adduct/nmol protein). Furthermore, the N-terminal region of calreticulin, known as vasostatin, was adducted only in ozone-exposed animals. Although vasostatin was adducted at relatively low specific activity (0.01 nmol adduct/nmol protein), the adduction only in ozone-exposed animals makes it a candidate protein for elucidating the synergistic toxicity between ozone and 1-NN. These studies identified in vivo protein targets for reactive 1-NN metabolites that are potentially associated with the mechanism of 1-NN toxicity and the synergistic effects of ozone.

Air Pollutants↗

Chronic aeroallergen during infancy enhances eotaxin-3 expression in airway epithelium and nerves.

We have documented that exposure of rhesus monkeys to house dust mite aeroallergen during postnatal development resulted in significant recruitment of eosinophils into the airway mucosa (Clin Exp Allergy 33:1686-1694, 2003). Because eosinophils were not uniformly distributed throughout the five conducting airway generations examined, we speculated that trafficking within anatomic microenvironments of the lung is mediated by differential chemokine expression. To address this question, we used quantitative real-time RT-PCR to evaluate the related eosinophilic chemokines, eotaxin (CCL11), eotaxin-2 (CCL24), and eotaxin-3 (CCL26) within isolated airways of infant monkey lung. Overall, chemokine mRNA expression levels in house dust mite-exposed airways were as follows: eotaxin-3 > eotaxin > eotaxin-2. Immunofluorescence staining for eotaxin-3 and CC chemokine receptor 3 (CCR3) showed positive cells within epithelium and peripherally located nerve fiber bundles of the airway wall. Epithelial volume of eotaxin-3 within the trachea correlated with epithelial volume of major basic protein. CCR3+ and MHC Class II+ dendritic cells, but not eosinophils or mast cells, co-localized within eotaxin-3+ nerve fiber bundles. We conclude that localized expression of eotaxin-3 plays an important role in the recruitment of diverse CCR3+ cell populations to different anatomic microenvironments within the infant airway in response to chronic allergen exposure.

Air Pollution↗

Intrapulmonary and intramyocardial gene transfer in rhesus monkeys (Macaca mulatta): safety and efficiency of HIV-1-derived lentiviral vectors for fetal gene delivery.

Fetal gene transfer was studied using intrapulmonary and intramyocardial transfer of SIN HIV-1-derived lentiviral vectors expressing EGFP in rhesus monkeys. Fetuses were monitored sonographically during gestation and tissue analyses performed at term or 3 months postnatal age. Animals remained healthy during the study period as evidenced by normal growth, development, hematology, clinical chemistry, echocardiography, and pulmonary function tests. Strong pulmonary fluorescence was observed postnatally after fetal intrapulmonary delivery of lenti-CMV, but not lenti-SP-C, and compared to nontransferred controls. High EGFP copy numbers were found by quantitative PCR with both vector constructs in lung lobes (<or=15%) and EGFP copies were also detected in the diaphragm, pericardium, and thorax. No differences were found in lung:body weight ratios, percentage lung parenchyma, or overall morphology when compared to controls. For intramyocardial gene delivery, strong transgene expression was found within the myocardium and pericardium, and high EGFP copy numbers were found by quantitative PCR (3-36%). EGFP was also detected in the aorta, thorax, and diaphragm. These studies indicate that postnatal heart and lung development and function were not altered after fetal intraorgan gene transfer and subsequent transgene expression prenatally and postnatally, and gene transfer was restricted to the thoracic cavity with intrapulmonary and intramyocardial lentiviral vector-mediated gene delivery.

Animals↗

Characterization of a structurally intact in situ lung model and comparison of naphthalene protein adducts generated in this model vs lung microsomes.

Airway epithelial cells are a susceptible site for injury by ambient air toxicants such as naphthalene that undergo P450-dependent metabolic activation. The metabolism of naphthalene in Clara cells to reactive intermediates that bind covalently to proteins correlates with cell toxicity. Although several proteins adducted by reactive naphthalene metabolites were identified in microsomal incubations, new methods that maintain the structural integrity of the lung are needed to examine protein targets. Therefore, we developed a method that involves inflation of the lungs via the trachea with medium containing (14)C-naphthalene followed by incubation in situ. The viability of this preparation is supported by maintenance of glutathione levels, rates of naphthalene metabolism, and exclusion of ethidium homodimer-1 from airway epithelium. Following in situ incubation, the levels of adduct per milligram of protein were measured in proteins obtained from bronchoalveolar lavage, epithelial cells, and remaining lung. The levels of adducted proteins obtained in lavage and epithelial cells were similar and were 20-fold higher than those in residual lung tissue. (14)C-Labeled adducted proteins were identified by matrix-assisted laser desorption ionization-time-of-flight (MALDI-TOF) mass spectrometry (MS) and quadrupole-TOF MS/MS. Major adducted proteins include cytoskeletal proteins, proteins involved in folding and translocation, ATP synthase, extracellular proteins, redox proteins, and selenium binding proteins. We conclude that in situ incubation maintains structural integrity of the lung while allowing examination of reactive intermediate activation and interaction with target cell proteins of the lung. The proteins adducted and identified from in situ incubations were not the same proteins identified from microsomal incubations.

Animals↗

Impaired recovery from naphthalene-induced bronchiolar epithelial injury in mice exposed to aged and diluted sidestream cigarette smoke.

The effect of sidestream tobacco smoke combined with other pollutants is largely unknown. Previously, we found that distal airway epithelial repair was inhibited in mice exposed to sidestream tobacco smoke (TS) for 5 days followed by single exposure to naphthalene (NA), a common polycyclic aromatic hydrocarbon found in cigarette smoke, diesel exhaust, and pesticide formulations. The main injury target of NA is the nonciliated (Clara) bronchiolar cell. NA injury normally resolves in two weeks. Repair in mice exposed to TS and NA was unresolved in the distal bronchioles 14 days post-NA injury. We hypothesized that repair inhibition persisted as a first step towards long-term airway remodeling and expanded the previous study by evaluating repair 21 days after acute NA injury. Repair was evaluated using high resolution histopathology, TEM, and quantitative morphometry. In animals exposed to TS and NA, repair was still impaired; re-differentiation of Clara cells at the bronchoalveolar duct junction was incomplete, indicating repair was continuing. Compared to 14 days post-NA-injury, repair at 21 days post-NA treatment was more extensive. Animals exposed only to TS had epithelium similar to controls. While TS exposure impairs bronchiolar epithelial repair after NA exposure, this effect appears to be slowly resolving over time.

Animals↗

Increased vulnerability of neonatal rats and mice to 1-nitronaphthalene-induced pulmonary injury.

The postnatal period of lung development is a critical window of susceptibility to environmental toxicants, including polyaromatic hydrocarbons (PAHs) and furans. To determine whether the increased susceptibility of neonatal lung injury due to environmental toxicants is a universal response across species and also applies to nitrated compounds, adult and 7-day-old male mice and rats were given a single intraperitoneal dose (0, 12.5, 25, 50, or 100 mg/kg) of 1-nitronaphthalene and killed 24 h later. Exposure to 1-nitronaphthalene, a nitro-polyaromatic hydrocarbon, results in pulmonary lesions in both adult rats and mice, although the severity of the injury is species-specific (greater in rats than in mice). Pulmonary lesions, as assessed by quantitative histopathology, included dose-dependent vacuolization and exfoliation of both ciliated and nonciliated airway epithelial cells throughout the airway tree in both rats and mice. In both species, the 7-day-old animals were more susceptible to injury by 1-nitronaphthalene than adult animals. In contrast to adult response, neonatal mice were more susceptible to 1-nitronaphthalene-induced pulmonary injury than neonatal rats. This indicates that neonatal susceptibility to environmental pollutant-induced lung injury cannot be reliably predicted based on adult susceptibility.

Animals↗

Smooth muscle development during postnatal growth of distal bronchioles in infant rhesus monkeys.

Development of smooth muscle in conducting airways begins early in fetal life. Whereas the pattern and regulation of smooth muscle differentiation are well-defined, the impact of airway growth on the process is not. To evaluate the transformations in organization during postnatal growth, smooth muscle bundle organization (size, abundance, and orientation) was mapped in five generations of distal airways of infant rhesus monkeys (5 days and 1, 2, 3, and 6 mo old). On the basis of direct measurement of the bronchiole proximal to the terminal bronchiole, length increased by 2-fold, diameter by 1.35-fold, and surface area by 2.8-fold between 5 days and 6 mo of age. Smooth muscle bundle size was greater in proximal bronchioles than in respiratory bronchioles and did not change with age. However, relative bundle size decreased in proportion to airway size as the airways grew. Relative bundle abundance was constant regardless of airway generation or age. The distribution of smooth muscle bundle orientation changed with age in each airway generation, and there were significant changes in the terminal and respiratory bronchioles. We conclude that smooth muscle undergoes marked organizational changes as airways grow during postnatal development.

Age Factors↗

Immunostimulatory oligonucleotides attenuate airways remodeling in allergic monkeys.

To determine whether inhaled immunostimulatory DNA sequence oligonucleotides containing CpG motifs mitigate the pathophysiologic manifestation of the asthmatic phenotype (airways hyperresponsiveness and airways remodeling), rhesus monkeys with experimentally induced allergic airways disease were treated seven times with inhaled immunostimulatory oligonucleotides (or sham) periodically for 33 weeks. Airways hyperresponsiveness was reduced twofold in immunostimulatory DNA sequence-treated compared with sham-treated monkeys. Airways from immunostimulatory oligonucleotide-treated monkeys had thinner reticular basement membranes, fewer mucous cells, fewer eosinophils, and fewer mast cells than sham-treated allergic monkeys. We conclude that inhaled immunostimulatory oligonucleotides can attenuate the magnitude of airway hyperreactivity and airways remodeling produced in nonhuman primates with experimentally induced allergic airways disease.

Administration, Inhalation↗