Inhalation of estradiol for sustained systemic delivery.

Large porous estradiol particles were formulated by spray drying estradiol in combination with various U.S. Food and Drug Administration (FDA)-approved or endogenous excipients. The powders were characterized in terms of their geometrical size, mass density, and aerosolization properties. Small nonporous particles were also prepared using the same excipients and were physically characterized to insure that they possessed a similar mean aerodynamic size as the large porous particles. The two powders were aerosolized into the lungs of rats via an endotracheal tube or subcutaneously injected as a control to assess relative bioavailability. Two different large porous particle formulations were found to produce elevated systemic estradiol concentrations upon inhalation for approximately 5 days, with relative bioavailabilities of 59.7% and 86.0%. Systemic estradiol concentrations following inhalation of two different small nonporous particle powders remained elevated for only approximately 1 day, with relative bioavailabilities of 18.3% and 38.7%. Bronchoalveolar lavage was performed up to 96 hours after inhalation of porous and nonporous estradiol powders. Small changes in neutrophil and macrophage populations were observed following inhalation of both the porous and nonporous powders.     

Formulation and Physical Characterization of Large Porous Particles for Inhalation

Purpose. Relatively large (>5 µm) and porous (mass density < 0.4 g/cm³) particles present advantages for the delivery of drugs to the lungs, e.g., excellent aerosolization properties. The aim of this study was, first, to formulate such particles with excipients that are either FDA-approved for inhalation or endogenous to the lungs; and second, to compare the aerodynamic size and performance of the particles with theoretical estimates based on bulk powder measurements. Methods. Dry powders were made of water-soluble excipients (e.g., lactose, albumin) combined with water-insoluble material (e.g., lung surfactant), using a standard single-step spray-drying process. Aerosolization properties were assessed with a Spinhaler ^TM device in vitro in both an Andersen cascade impactor and an Aerosizer^TM.. Results. By properly choosing excipient concentration and varying the spray drying parameters, a high degree of control was achieved over the physical properties of the dry powders. Mean geometric diameters ranged between 3 and 15 µm, and tap densities between 0.04 and 0.6 g/cm³. Theoretical estimates of mass mean aerodynamic diameter (MMAD) were rationalized and calculated in terms of geometric particle diameters and bulk tap densities. Experimental values of MMAD obtained from the Aerosizer^TM most closely approximated the theoretical estimates, as compared to those obtained from the Andersen cascade impactor. Particles possessing high porosity and large size, with theoretical estimates of MMAD between 1–3 µm, exhibited emitted doses as high as 96% and respirable fractions ranging up to 49% or 92%, depending on measurement technique. Conclusions. Dry powders engineered as large and light particles, and prepared with combinations of GRAS (generally recognized as safe) excipients, may be broadly applicable to inhalation therapy.     

Poly-lactide-co-glycolide nanoparticles containing voriconazole for pulmonary delivery: in vitro and in vivo study

Poly-lactide-co-glycolide nanoparticles (207–605 nm) containing voriconazole (VNPs) were developed using a multiple-emulsification technique and were also made porous during preparation in presence of an effervescent mixture for improved pulmonary delivery. Pulmonary deposition of the particles was studied using a customized inhalation chamber. VNPs had a maximum of 30% (w/w) drug loading and a zeta potential (ZP) value around ? 20 mV. In the initial 2 hours, 20% of the drug was released from VNPs, followed by sustained release for 15 days. Porous particles had a lower mass median aerodynamic diameter (MMAD) than nonporous particles. Porous particles produced the highest initial drug deposition (~ 120 μg/g of tissue). The drug was detectable in lungs until 7 days and 5 days after administration, for porous and nonporous particles, respectively. VNPs with improved drug loading were successfully delivered to murine lungs. Porous nanoparticles with lower MMADs showed better pulmonary deposition and sustained presence in lungs.From the Clinical EditorIn this paper, voriconazole-containing porous nanoparticles were studied for inhalational delivery to lung infections in a murine model, demonstrating prolonged half-life and improved pulmonary deposition.     

Effect of Geometric Structure of Flow Promoting Agents on the Flow Properties of Pharmaceutical Powder Mixture

Purpose. The object of this work was to investigate the mechanism of how the surface geometric structure of flow agents affects on the flowability of pharmaceutical powder mixtures. Methods. Nonporous and porous silicas were mixed with directly compressible fillers as flow promoting agents. The geometric structure of flow agents was investigated by gas adsorption and laser diffraction analysis. Flowability was evaluated with Carr's index measurement. Adhesion force between fillers and flow agents was determined using atomic force microscopy. Results. Flowability was improved with the addition of both nonporous and porous flow agents. In the case of nonporous flow agents, effect to promote flowability decreased with the increase of particle diameter, whereas porous flow agents highly improved flowability independent of particle diameter. Atomic force microscopy measurement found that the adhesion force between a porous agent and filler was smaller than that between a nonporous agent and filler. Conclusions. Enhancement of flowability varies depending on the geometric structure of flow agents. Porous flow agents improve flow properties more than nonporous agents, because porosity is highly contributed to reduction of adhesion force between particles.     

Protein Inhalation Powders: Spray Drying vs Spray Freeze Drying

Purpose. To develop a new technique, spray freeze drying, for preparing protein aerosol powders. Also, to compare the spray freeze-dried powders with spray-dried powders in terms of physical properties and aerosol performance. Methods. Protein powders were characterized using particle size analysis, thermogravimetric analysis, scanning electron microscopy, X-ray powder diffractometry, and specific surface area measurement. Aerosol performance of the powders was evaluated after blending with lactose carriers using a multi-stage liquid impinger or an Anderson cascade impactor. Two recombinant therapeutic proteins currently used for treating respiratory tract-related diseases, deoxyribonuclase (rhDNase) and anti-IgE monoclonal antibody (anti-IgE MAb), were employed and formulated with different carbohydrate excipients. Results. Through the same atomization but the different drying process, spray drying (SD) produced small (3 m), dense particles, but SFD resulted in large (8–10 m), porous particles. The fine particle fraction (FPF) of the spray freeze-dried powder was significantly better than that of the spray-dried powder, attributed to better aerodynamic properties. Powders collected from different stages of the cascade impactor were characterized, which confirmed the concept of aerodynamic particle size. Protein formulation played a major role in affecting the powder's aerosol performance, especially for the carbohydrate excipient of a high crystallization tendency. Conclusions. Spray freeze drying, as opposed to spray drying, produced protein particles with light and porous characteristics, which offered powders with superior aerosol performance due to favorable aerodynamic properties.     

Loading Effect on Particle Size Measurements by Inertial Sampling of Albuterol Metered Dose Inhalers

Purpose. The purpose of this study is to investigate the albuterol loading effect on particle size measurements by studying the effect of the amount of albuterol delivered, the number of puffs used, and the sampling techniques used in particle size measurement. Methods. Particle size distribution profiles for different albuterol loadings were evaluated using an 8-stage cascade impactor and a sensitive HPLC electrochemical assay method. A commercial albuterol MDI (Proventil^R) and other specially prepared albuterol MDIs were used in the study. Results. As the amount of albuterol was increased, either by increasing the number of puffs or the amount delivered per puff, the measured MMAD increased. This increase was more prominent in some formulations (Proventil^R) than others. Further, albuterol particles previously deposited on the valve and/or actuator didn't play a role in the observed multi-puff/loading effect. Conclusions. The collection of the least amount of aerosol in a cascade impactor provides a better estimate of MMAD, as it minimizes modifications of the collection surfaces.     

Hollow Porous Particles in Metered Dose Inhalers

Purpose. To assess the physical stability and aerosol characteristicsof suspensions of hollow porous microspheres (PulmoSpheres) inHFA-134a. Methods. Cromolyn sodium, albuterol sulfate, and formoterol fumaratemicrospheres were prepared by a spray-drying method. Particle sizeand morphology were determined via electron microscopy. Particleaggregation and suspension creaming times were assessed visually,and aerosol performance was determined via Andersen cascadeimpaction and dose uniformity studies. Results. The hollow porous particle morphology allows the propellantto permeate freely within the particles creating a novel form ofsuspension termed a homodispersion, wherein the dispersed and continuousphases are identical, separated by an insoluble interfacial layer of drugand excipient. Homodispersion formation improves suspension stabilityby minimizing the difference in density between the particles andthe medium, and by reducing attractive forces between particles. Theimproved physical stability leads to excellent dose uniformity. Excellentaerosolization efficiencies are also observed with PulmoSpheresformulations, with fine particle fractions of about 70%. Conclusions. The formation of hollow porous particles provides anew formulation technology for stabilizing suspensions of drugs inhydrofluoroalkane propellants with improved physical stability, contentuniformity, and aerosolization efficiency.     

Effect of Drug Load and Plate Coating on the Particle Size Distribution of a Commercial Albuterol Metered Dose Inhaler (MDI) Determined Using the Andersen and Marple-Miller Cascade Impactors

Purpose. The purpose of this study is to investigate the effect of drug load, the coating of impactor stages, and the design of cascade impactors on albuterol MDIs particle size distribution measurements. The results of the investigation will be used to explain the 'loading effect' recently reported. Methods. Particle size distribution parameters of a commercial albuterol MDI were measured using both Andersen (AI) and Marple-Miller (MMI) Cascade Impactors, where plates were either left uncoated or coated with silicone or glycerin. A previously validated HPLC-EC method was used for the assay of albuterol collected by the impactor and in single spray content determinations. Results. Coating impactor collection plates had an impact on measured MM AD and GSD values for single puff measurements but very little or no effect for the multi puff measurements. Due to particle bounce, the percent of albuterol fine particles deposited in the filter and impactor finer stages (<1.10 m in AI and <1.25 m in MMI) in uncoated single puff experiments was much higher in comparison to either coated single puff or multi-puff (coated and uncoated) measurements. Conclusions. Evaluation of drug load and plate coating are necessary to determine whether observed particle size distributions are representative of the generated aerosol or are the result of particle bounce and reentrainment. In order to minimize particle bounce, especially for single puff determinations, it may be useful to apply a thin layer of a sticky coating agent to the surfaces of impactor plates.     

Surface-modified Antiasthmatic Dry Powder Aerosols Inhaled Intratracheally Reduce the Pharmacologically Effective Dose

Purpose. The aim of this study was to construct a reliable dry powder inhalation (DPI) testing system for use in guinea pigs. Using this system, we were able to demonstrate the superiority of pulmonary administration of hydrophilically surface-modified pranlukast hydrate powder (SM-DP) over IV and PO administration as reflected in improved pharmacological action. Our ultimate aim is the development of an ideal treatment system for bronchial asthma involving topical administration to the lung. Methods. The reliability of the present DPI system was validated by continuously monitoring the concentration and particle size distribution of aerosols generated with an ambient particulate monitor and an Andersen air sampler, respectively. The pharmacological effect of SM-DP intratracheally administered to guinea pig was investigated by measuring the degree of bronchoconstriction and microvascular leakage induced by leukotriene D₄. Results. The mass concentration of aerosols generated by the DPI system was stable and the mass median aerodynamic diameter of aerosols insufflated from the respirator of the DPI system ranged from 1.4 to 1.7 m, within respirable limits. Inhibition of bronchoconstriction and airway microvascular leakage induced by leukotriene D₄ was achieved successfully with a dramatically lower dose of DP, or a further lower dose of SM-DP, comparable with that of the drug solution injected intravenously. The plasma pranlukast hydrate level with SM-DP at 50% inhibition of bronchoconstriction and airway microvascular leakage was reduced to 1/10 or less that following IV and PO administration. Conclusions. The hydrophilically surface-modified pranlukast hydrate powders were ideally aerosolized by the present DPI system, and were uniformly deposited in the lung lobes after inhalation. The pulmonary administration system with SM-DP is strongly recommended as an ideal system for the treatment of bronchial asthma in order to avoid systemic side-effects due to a dramatically reduced ED₅₀, comparable with or lower than IV, and the low plasma concentration of drug, 1/12 or less than that following IV and PO administration.     

NEXThaler,an innovative dry powder inhaler delivering an extrafine fixed combination of beclometasone and formoterol to treat large and small airways in asthma

Introduction: Airway inflammation and remodelling in asthma occur in the large airways and also in the small airways. The small airways are those < 2 mm in diameter and are significant sites of chronic asthmatic inflammation. It is important, therefore, to target the small as well as the large airways in any strategy for effective treatment of this disease.

Areas covered: The present review deals with the recently developed fixed dose drug combination of beclometasone dipropionate/formoterol fumarate that emits extrafine particles when delivered from an innovative dry powder inhaler (DPI), NEXThaler®. The aim is to present the technical and clinical aspects of aerosolized drug delivery to the lungs.

Expert opinion: The data show that the NEXThaler DPI is an efficient device for the management of persistent asthma. The evaluation of the inhalation profiles through the NEXThaler DPI demonstrates that device activation and consistent dose delivery occurs at patient achievable inhalation flow rates, and supports the broad utility of the NEXThaler DPI in patients with asthma. Overall, all the effectiveness, efficiency and satisfaction outcomes demonstrate the NEXThaler DPI is easy to use.     

A New Powder Design Method to Improve Inhalation Efficiency of Pranlukast Hydrate Dry Powder Aerosols by Surface Modification with Hydroxypropylmethylcellulose Phthalate Nanospheres

Purpose. A new particle design method to improve the aerosolization properties of a dry powder inhalation system was developed using surface modification of hydrophobic drug powders (pranlukast hydrate) with ultrafine hydrophilic particles, hydroxypropylmethylcellulose phthalate (HPMCP) nanospheres. The mechanism of the improved inhalation properties of the surface-modified particles and their deposits on carrier particles (lactose) was clarified in vitro. Methods. Drug particles were introduced to aqueous colloidal HPMCP dispersions prepared by emulsion-solvent diffusion techniques followed by freeze- or spray-drying of the resultant aqueous dispersions. The surface-modified powders obtained with HPMCP nanospheres and their mixture with lactose powders were aerosolized by Spinhaler and their mode of deposition in lung was evaluated in vitro using a twin impinger. To elucidate the inhalation mechanism of these surface modified particles, we measured their modified micromeritic properties, such as surface topography, specific surface area, dissolution rate, and dispersibility in air. Results. Dramatically improved inhalation properties of the surface modified powder, i.e. a two-fold increase in emission and a three-fold increase in delivery to deep lung, were found in vitro compared with the original unmodified powder. Improved inhalation was also found with the surf ace-modified drug deposited on lactose particles. Those improvements were attributed to the increased surface roughness and hydrophilicity of the surface-modified particles, and the resultant increased dispersibility in air. Conclusions. Surface modification of hydrophobic drug particles with HPMCP nanospheres to improve hydrophilicity was extremely useful in increasing the inhalation efficiency of the drug itself and the drug deposited on carrier; this was attributed to increased dispersibility in air and emission from the device, for spray- and freeze-dried particles, respectively.     

Improvement of dissolution rates of poorly water soluble APIs using novel spray freezing into liquid technology

Purpose. To develop and demonstrate a novel particle engineering technology, spray freezing into liquid (SFL), to enhance the dissolution rates of poorly water-soluble active pharmaceutical ingredients (APIs). Methods. Model APIs, danazol or carbamazepine with or without excipients, were dissolved in a tetrahydrofuran/water cosolvent system and atomized through a nozzle beneath the surface of liquid nitrogen to produce small frozen droplets, which were subsequently lyophilized. The physicochemical properties of the SFL powders and controls were characterized by X-ray diffraction, scanning electron microscopy (SEM), particle size distribution, surface area analysis, contact angle measurement, and dissolution. Results. The X-ray diffraction pattern indicated that SFL powders containing either danazol or carbamazepine were amorphous. SEM micrographs indicated that SFL particles were highly porous. The mean particle diameter of SFL carbamazepine/SLS powder was about 7 m. The surface area of SFL danazol/poloxamer 407 powder was 11.04 m²/g. The dissolution of SFL danazol/poloxamer 407 powder at 10 min was about 99%. The SFL powders were free flowing and had good physical and chemical stability after being stored at 25°C/60%RH for 2 months. Conclusions. The novel SFL technology was demonstrated to produce nanostructured amorphous highly porous particles of poorly water soluble APIs with significantly enhanced wetting and dissolution rates.     

Effect of CPAP on breathlessness perception in healthy subjects during methacholine induced bronchoconstriction

Application of continuous positive airway pressure (CPAP) in asthmatic patients decreases breathlessness (B). The effect of CPAP on induced bronchoconstriction was studied in healthy subjects. The changes in B were related to changes in lung function indices. In nine healthy volunteers, males aged 20-27 years, acute bronchoconstriction was induced by inhalation of 1 to 128 mg/ml methacholine (M). CPAP (0.5 kPa) was then applied for 1 min. It was followed by inhalation of albuterol. Forced expiratory volume in 1 s (FEV1) and vital capacity (VC) were measured by spirometry and end expiratory lung level (EELL), to derive inspiratory capacity (IC), by inductive plethysmography. B was assessed by Borg scale. After the maximal concentration of M, FEV1 decreased by 14% (p < 0.01) as compared to the control values and Borg score (BS) increased to 2.4 (p < 0.01). In 7 out of 9 subjects we found a significant (p < 0.05) correlation between the changes in FEV1 and BS. BS decreased during CPAP (p < 0.01) and it further decreased significantly after albuterol. There was no correlation between the changes in IC and FEV1 during bronchoconstriction, or between IC and BS during CPAP. In conclusion, in healthy subjects with induced bronchoconstriction CPAP decreased significantly BS, which was further improved by inhalation of albuterol. B was related to changes in FEV1 but not in IC.     

Chronic muscarinic cholinoceptor stimulation increases adenylyl cyclase responsiveness in rat cardiomyocytes by a decrease in the level of inhibitory G-protein a-subunits

Exposure of neonatal rat cardiomyocytes for 3 days to the muscarinic cholinoceptor agonist carbachol led to a concentration-dependent increase in adenylyl cyclase stimulation by the ß-adrenoceptor agonist isoproterenol by up to 115% (at 1?mmol/l carbachol). In addition, direct adenylyl cyclase stimulation by forskolin was increased in carbachol (1?mmol/l)-treated cells by 32%. Pretreatment of the rat cardiomyocytes with pertussis toxin, which enhances adenylyl cyclase activity by a functional inactivation of the inhibitory G-protein (G _i), was performed to investigate the possible role of G _i-proteins in carbachol-induced sensitization of adenylyl cyclase stimulation. After pretreatment of the cells with pertussis toxin, the carbachol-mediated increase in forskolin-stimulated adenylyl cyclase activity was lost and the carbachol-mediated increase in ß-adrenoceptor-stimulated adenylyl cyclase activity was attenuated. Labelling of the 40?kDa pertussis toxin substrates in cardiomyocyte membranes was decreased by carbachol in a concentration-dependent manner by up to 34% (at 1?mmol/l carbachol). The number and affinity of ß ₁-adrenoceptors was unaltered following the chronic carbachol treatment. The specific protein synthesis inhibitor Pseudomonas exotoxin?A was used to study whether the carbachol-induced decrease in the level of pertussis toxin-sensitive G-proteins and increase in adenylyl cyclase activity depend on de-novo protein synthesis. Pseudomonas exotoxin?A inhibits peptide chain elongation by ADP-ribosylating elongation factor 2. Treatment of the cells with 1?ng/ml Pseudomonas exotoxin?A for 3 days led to a reduction in the subsequent ADP-ribosylation of elongation factor?2 in the cytosol of the heart muscle cells by 57%. Exposure of the cells to 1?mmol/l carbachol for 3?days increased ADP-ribosylation of elongation factor?2 by 40% concomitant with a slight (about 20%) increase in the total protein content of the cardiomyocytes. The partial protein synthesis inhibition by Pseudomonas exotoxin?A had no influence on the carbachol-induced decrease in the level of pertussis toxin-sensitive G-proteins. Similarly, the carbachol-induced increase in adenylyl cyclase responsiveness also remained unaltered by Pseudomonas exotoxin?A. The data presented indicate that chronic muscarinic cholinoceptor agonist treatment decreases the level of a-subunits of G _i-proteins. This decrease in G _ia-subunits is apparently at least in part responsible for the observed increase in adenylyl cyclase responsiveness after chronic carbachol treatment.     

Carbachol potentiates isoprenaline-induced mucin secretion by rat submandibular gland

Summary We studied the effects of carbachol on isoprenaline-induced secretion of ³[H]glucosamine-labeled high molecular weight protein from in vitro fragments of rat submandibular gland. The concentration-response curve for isoprenaline was determined alone and in the presence of one of two concentrations of carbachol. Isobolic interaction indices were calculated from the resulting curves. The role of extracellular calcium on this interaction was assessed by examining the effect of increasing concentrations of [Ca²⁺]_e on secretion induced by a fixed concentration of isoprenaline alone and in the presence of carbachol.Carbachol alone caused a small, but statistically significant, protein secretion. Carbachol markedly shifted the isoprenaline concentration-response curve to the left in a dose-dependent manner. In the absence of extracellular calcium, carbachol did not increase isoprenaline-induced secretion, but secretion increased as the [Ca²⁺]_e was increased. The carbachol-induced increase in secretion reached a maximal level at approximately 2.0 mM [Ca²⁺]_e. We conclude that carbachol's increase of isoprenaline-induced secretion of ³[H]glucosamine-labeled high molecular weight protein is not additive, but is true potentiation. This potentiation requires extracellular calcium, and may be maximal at physiological [Ca²⁺]_e. Send offprint requests to S. E. Taylor at the above address     

Spray Dried Powders and Powder Blends of Recombinant Human Deoxyribonuclease (rhDNase) for Aerosol Delivery

Purpose. We have used rhDNase to investigate the feasibility of developing a dry protein powder aerosol for inhalation delivery. Methods. Powders of rhDNase alone and with sodium chloride were prepared by spray drying. Powder blends were obtained by mixing (tumbling and sieving) pure rhDNase powder with 'carrier' materials (lactose, mannitol or sodium chloride). The weight percent of drug in the blends was between 5 and 70%. The particle size distributions and crystallinity of the spray dried powders were obtained by laser diffraction and X-ray powder diffraction, respectively. Particle morphology was examined by scanning electron microscopy. The ability of the powders and powder blends to be dispersed into respirable aerosols was measured using a Rotahaler connected to a multistage liquid impinger operating at 60 L/min. Results. Pure rhDNase powder was quite cohesive with a fine particle fraction (FPF or 'respirable fraction': % wt. of particles < 7 m in the aerosol cloud) of about 20%. When particles also contained NaCl, the powders were dispersed better to form aerosols. A linear relationship was observed between the NaCl content and FPF for a similar primary size (~3 m volume median diameter) of particles. The particle morphology of these powders varied systematically with the salt content. For the blends, SEM revealed a monolayer-like adhesion of the fine drug particles to the carriers at drug contents 50 % wt. An overall 2-fold increase in FPF of rhDNase in the aerosol cloud was obtained for all the blends compared to the pure drug aerosols. Conclusions. The aerosol properties of spray dried rhDNase powders can be controlled by incorporation of a suitable excipient, such as NaCl, and its relative proportion. Coarse carriers can also enhance the performance of rhDNase dry powder aerosols.     

Morphological Characterization of Polyanhydride Biodegradable Implant Gliadel® During in Vitro and in Vivo Erosion Using Scanning Electron Microscopy

Purpose. The objectives of the current study are to characterize the distribution of the chemotherapeutic agent carmustine (BCNU) in spray dried polyanhydride microspheres and to describe the morphological changes that occur during the in vitro and in vivo erosion of the polyanhydride implant-GLIADEL^®, which consists of BCNU distributed in the copolymer matrix of poly(carboxyphenoxy propane:sebacic acid) in a 20:80 molar ratio (p(CPP:SA, 20:80)). Methods. Scanning electron microscopy (SEM) was used to visualize the morphological changes of the polymer during the manufacturing process and in vitro and in vivo erosion. Results. This study revealed that BCNU was homogeneously distributed within spray dried polyanhydride microspheres with no phase separation. The porosity of the wafer fabricated from spray dried polyanhydride microspheres gradually increased during erosion. During the initial period following wafer implantation in the brains of rats, erosion was mainly confined to the surface layer of the wafer with the majority of the wafer remaining intact. The eroding front gradually advanced from the surface to the interior of the wafer in a layerwise fashion, creating pores and connecting channel. Eventually both the interior and exterior of the wafers were eroded and the same porous structure was seen throughout the whole wafer. Conclusions. This study provides the first visual observation of the morphological changes of the GLIADEL^® wafer during erosion of the polyanhydride matrix and release of the drug substance BCNU. The observations in this study support the conclusion that BCNU release from a polyanhydride wafer is controlled both by diffusion of the drug and erosion of the polymer matrix.     

Inhibition of Tracheal Vascular Extravasation by Liposome-Encapsulated Albuterol in Rats

Purpose. To develop a liposome-based system for systemic delivery of anti-inflammatory drugs to airways and other inflamed tissues. Methods. Postcapillary venular gap junctions open during airway inflammation and allow fluid accumulation and permit molecules (e.g. complement, kininogen) to enter tissues, initiating inflammatory cascades. Beta-adrenergic agonists prevent inflammatory plasma extravasation, but because of their deleterious side effects, they are not used intravenously. When sterically stabilized "stealth liposomes are injected iv, they remain in the circulation for long periods. Inflammatory mediators [e.g., substance P(SP)] open postcapillary venular gaps and allow liposomes and their contents to be deposited selectively in the inflamed tissue. Results. We hypothesized that liposomes encapsulating a beta-adrenergic agonist, such as albuterol, would deposit selectively in inflamed airway tissue, where the drug would slowly leak out of the liposomes, resulting in closure of the gaps, thus preventing subsequent inflammatory extravasation. To test this hypothesis, we delivered albuterol-loaded liposomes iv in rats. Then we injected SP to open the venular gaps and allow accumulation of the drug-loaded liposomes in airway tissue. We examined whether this treatment resulted in inhibition of subsequent plasma extravasation induced by SP. The results indicate that liposome-encapsulated albuterol inhibits subsequent extravasation, presumably by leaking out of liposomes in airway tissue. This inhibition occurs for prolonged periods of time and with limited side effects compared to the effect of free albuterol. Conclusions. We conclude that liposomes loaded with appropriate drugs, by migrating to inflamed tissue and subsequently inhibiting inflammatory cascades, may be of therapeutic value in inflammatory diseases.     

β2-Adrenoceptors mediate inhibition of carbachol-induced contraction and cAMP generation in isolated smooth muscle cells from rabbit gastric antrum

The regulation of inhibition of carbachol-induced contraction by β-adrenoceptors of rabbit gastric antrum has been investigated. A functional assay using isolated smooth muscle cells (ISMC) was used to study the effect of β-adrenergic agonists and antagonists on carbacholcontracted ISMC and cAMP generation. The nonselective β-adrenergic agonist isoproterenol caused concentration-related inhibition of carbachol-induced contraction associated with a significant increase in cellular cAMP. The EC₅₀ for the effect of isoproterenol on cell inhibition of carbachol-induced contraction was closely related to the EC₅₀ for cAMP formation; the two curves were superimposable, indicating a positive correlation between the biological activity (inhibition of carbachol-induced contraction) and the intracellular event (cAMP formation) caused by the activation of β-adrenoceptors. The Kinetic studies demonstrate that maximum inhibition of carbachol-induced contraction and a parallel elevation of intracellular cAMP content were reached at 30 sec of incubation with isoproterenol. The β₂-selective receptor agonist terbutaline induced inhibition of carbachol-induced contraction of carbachol-contracted ISMC and cAMP generation. However, the relatively β₁-selective receptor agonist norepinephrine had no significant effect. Propranolol, a nonselective β- adrenoceptor antagonist (β₁ and β₂) caused a significant inhibition of the carbacholβ₂ induced contraction and rise in cAMP induced by isoproterenol and terbutaline, while the β₁-selective adrenergic receptorantagonist metoprolol, even at higher concentration, was inactive. These data demonstrate that there is a correlation between inhibition of carbachol-induced contraction and cAMP generation upon activation of the β₂-adrenoreceptors in the ISMC of rabbit gastric antrum. © 1992 Wiley-Liss, Inc.     

Route of exposure alters inflammation and lung function responses to diesel exhaust

Abstract

Context: Mice are commonly used in studies investigating the effects of diesel exhaust exposure on respiratory health. A plethora of studies in this field has resulted in a range of exposure protocols, from inhalation of diesel exhaust, to the administration (via various routes) of diesel exhaust particles in solution.

Objective: In this study, we compared the physiological consequences of short-term exposure to diesel exhaust via inhalation to those due to exposure to the same diesel exhaust particles suspended in solution and delivered intranasally.

Materials and methods: Adult BALB/c mice were exposed to diesel exhaust via inhalation for 2 hours per day for 8 days. A representative, simultaneous sample of particles was collected and a second group of mice then exposed to them suspended in saline. A low and a high-dose were studied, with these matched based on respiratory parameters. Six and twenty-four hours after the last exposure we measured bronchoalveolar inflammation, lung volume, lung function and the amount of elemental carbon in alveolar macrophages.

Results: Exposure via either route elicited pulmonary inflammation and changes in lung function. We identified significant differences in response between the two routes of exposure, with mice exposed via inhalation generally displaying more realistic dose-response relationships. Mice exposed via intranasal instillation responded more variably, with little influence of dose.

Conclusions: Our results suggest that selection of the route of exposure is of critical importance in studies such as this. Further, inhalation exposure, while more methodologically difficult, resulted in responses more akin to those seen in humans.