Dose response to aerosolized perflubron in a neonatal swine model of lung injury

Administration of Drugs/Gene Products to the Respiratory System: A Historical Perspective of the Use of Inert Liquids

The present review is a historical perspective of methodology and applications using inert liquids for respiratory support and as a vehicle to deliver biological agents to the respiratory system. As such, the background of using oxygenated inert liquids (considered a drug when used in the lungs) opposed to an oxygen-nitrogen gas mixture for respiratory support is presented. The properties of these inert liquids and the mechanisms of gas exchange and lung function alterations using this technology are described. In addition, published preclinical and clinical trial results are discussed with respect to treatment modalities for respiratory diseases. Finally, this forward-looking review provides a comprehensive overview of potential methods for administration of drugs/gene products to the respiratory system and potential biomedical applications.

Inhalationally Administered Semifluorinated Alkanes (SFAs) as Drug Carriers in an Experimental Model of Acute Respiratory Distress Syndrome

Aerosol therapy in patients suffering from acute respiratory distress syndrome (ARDS) has so far failed in improving patients' outcomes. This might be because dependent lung areas cannot be reached by conventional aerosols. Due to their physicochemical properties, semifluorinated alkanes (SFAs) could address this problem. After induction of ARDS, 26 pigs were randomized into three groups: (1) control (Sham), (2) perfluorohexyloctane (F6H8), and (3) F6H8-ibuprofen. Using a nebulization catheter, (2) received 1 mL/kg F6H8 while (3) received 1 mL/kg F6H8 with 6 mg/mL ibuprofen. Ibuprofen plasma and lung tissue concentration, bronchoalveolar lavage (BAL) fluid concentration of TNF-α, IL-8, and IL-6, and lung mechanics were measured. The ibuprofen concentration was equally distributed to the dependent parts of the right lungs. Pharmacokinetic data demonstrated systemic absorption of ibuprofen proofing a transport across the alveolo-capillary membrane. A significantly lower TNF-α concentration was observed in (2) and (3) when compared to the control group (1). There were no significant differences in IL-8 and IL-6 concentrations and lung mechanics. F6H8 aerosol seemed to be a suitable carrier for pulmonary drug delivery to dependent ARDS lung regions without having negative effects on lung mechanics.

Preclinical and clinical studies of smoke-inhalation-induced acute lung injury: update on both pathogenesis and innovative therapy

Smoke-inhalation-induced acute lung injury (SI-ALI) is a leading cause of morbidity and mortality in victims of fire tragedies. SI-ALI contributes to an estimated 30% of burn-caused patient deaths, and recently, more attention has been paid to the specific interventions for this devastating respiratory illness. In the last decade, much progress has been made in the understanding of SI-ALI patho-mechanisms and in the development of new therapeutic strategies in both preclinical and clinical studies. This article reviews the recent progress in the treatment of SI-ALI, based on pathophysiology, thermal damage, airway obstruction, the nuclear-factor kappa-B signaling pathway, and oxidative stress. Preclinical therapeutic strategies include use of mesenchymal stem cells, hydrogen sulfide, peroxynitrite decomposition catalysts, and proton-pump inhibitors. Clinical interventions include high-frequency percussive ventilation, perfluorohexane, inhaled anticoagulants, and nebulized epinephrine. The animal model, dose, clinical application, and pharmacology of these medications are summarized. Future directions and further needs for developing innovative therapies are discussed.

Nebulized perflubron and carbon dioxide rapidly dilate constricted airways in an ovine model of allergic asthma

Background

The low toxicity of perfluorocarbons (PFCs), their high affinity for respiratory gases and their compatibility with lung surfactant have made them useful candidates for treating respiratory diseases such as adult respiratory distress syndrome. We report results for treating acute allergic and non-allergic bronchoconstriction in sheep using S-1226 (a gas mixture containing carbon dioxide and small volumes of nebulized perflubron). The carbon dioxide, which is highly soluble in perflubron, was used to relax airway smooth muscle.

Methods

Sheep previously sensitized to house dust mite (HDM) were challenged with HDM aerosols to induce early asthmatic responses. At the maximal responses (characterised by an increase in lung resistance), the sheep were either not treated or treated with one of the following; nebulized S-1226 (perflubron + 12% CO₂), nebulized perflubron + medical air, 12% CO₂, salbutamol or medical air. Lung resistance was monitored for up to 20 minutes after cessation of treatment.

In additional naïve sheep, a segmental bronchus was pre-contracted with methacholine (MCh) and treated with nebulized S-1226 administered via a bronchoscope catheter. Subsequent bronchodilatation was monitored by real time digital video recording.

Results

Treatment with S-1226 for 2 minutes following HDM challenge resulted in a more rapid, more profound and more prolonged decline in lung resistance compared with the other treatment interventions. Video bronchoscopy showed an immediate and complete (within 5 seconds) re-opening of MCh-constricted airways following treatment with S-1226.

Conclusions

S-1226 is a potent and rapid formulation for re-opening constricted airways. Its mechanism(s) of action are unknown. The formulation has potential as a rescue treatment for acute severe asthma.

Electronic supplementary material

The online version of this article (doi:10.1186/s12931-014-0098-x) contains supplementary material, which is available to authorized users.

In vitro surfactant and perfluorocarbon aerosol deposition in a neonatal physical model of the upper conducting airways

OBJECTIVE

Aerosol delivery holds potential to release surfactant or perfluorocarbon (PFC) to the lungs of neonates with respiratory distress syndrome with minimal airway manipulation. Nevertheless, lung deposition in neonates tends to be very low due to extremely low lung volumes, narrow airways and high respiratory rates. In the present study, the feasibility of enhancing lung deposition by intracorporeal delivery of aerosols was investigated using a physical model of neonatal conducting airways.

METHODS

The main characteristics of the surfactant and PFC aerosols produced by a nebulization system, including the distal air pressure and air flow rate, liquid flow rate and mass median aerodynamic diameter (MMAD), were measured at different driving pressures (4-7 bar). Then, a three-dimensional model of the upper conducting airways of a neonate was manufactured by rapid prototyping and a deposition study was conducted.

RESULTS

The nebulization system produced relatively large amounts of aerosol ranging between 0.3±0.0 ml/min for surfactant at a driving pressure of 4 bar, and 2.0±0.1 ml/min for distilled water (H2Od) at 6 bar, with MMADs between 2.61±0.1 µm for PFD at 7 bar and 10.18±0.4 µm for FC-75 at 6 bar. The deposition study showed that for surfactant and H2Od aerosols, the highest percentage of the aerosolized mass (∼65%) was collected beyond the third generation of branching in the airway model. The use of this delivery system in combination with continuous positive airway pressure set at 5 cmH2O only increased total airway pressure by 1.59 cmH2O at the highest driving pressure (7 bar).

CONCLUSION

This aerosol generating system has the potential to deliver relatively large amounts of surfactant and PFC beyond the third generation of branching in a neonatal airway model with minimal alteration of pre-set respiratory support.

A comparison of conventional surfactant treatment and partial liquid ventilation on the lung volume of injured ventilated small lungs

As an alternative to surfactant therapy (ST), partial liquid ventilation (PLV) with perfluorocarbons (PFC) has been considered as a treatment for acute lung injury (ALI) in newborns. The instilled PFC is much heavier than the instilled surfactant and the aim of this study was to investigate whether PLV, compared to ST, increases the end-expiratory volume of the lung (VL). Fifteen newborn piglets (age <12 h, mean weight 678 g) underwent saline lung lavage to achieve a surfactant depletion. Thereafter animals were randomized to PLV (n = 8), receiving PFC PF5080 (3M, Germany) at 30 mL kg(-1), and ST (n = 7) receiving 120 mg Curosurf®. Blood gases, hemodynamics and static compliance were measured initially (baseline), immediately after ALI, and after 240 min mechanical ventilation with either technique. Subsequently all piglets were killed; the lungs were removed in toto and frozen in liquid N2. After freeze-drying the lungs were cut into lung cubes (LCs) with edge lengths of 0.7 cm, to calculate VL. All LCs were weighed and the density of the dried lung tissue was calculated. No statistically significant differences between treatment groups PLV and ST (means ± SD) were noted in body weight (676 ± 16 g versus 679 ± 17 g; P = 0.974) or lung dry weight (1.64 ± 0.29 g versus 1.79 ± 0.48 g; P = 0.48). Oxygenation index and ventilatory efficacy index did not differ significantly between both groups at any time. VL (34.28 ± 6.13 mL versus 26.22 ± 8.1 mL; P < 0.05) and the density of the dried lung tissue (48.07 ± 5.02 mg mL(-1) versus 69.07 ± 5.30 mg mL(-1); P < 0.001), however, differed significantly between the PLV and ST groups. A 4 h PLV treatment of injured ventilated small lungs increased VL by 30% and decreased lung density by 31% compared to ST treatment, indicating greater lung distension after PLV compared to ST.

Aerosolized perfluorocarbon improves gas exchange and pulmonary mechanics in preterm lambs with severe respiratory distress syndrome

BACKGROUND

Aerosolized perfluorocarbon (PFC) has been proposed as an alternative method of PFC administration; however, the efficacy of aerosolized PFC in a preterm animal model has not yet been demonstrated.

METHODS

Twelve preterm lambs were randomized to two groups: a perfluorodecalin (PFD) aerosol group (n = 6) receiving 10 ml/kg/h of PFD delivered by an intratracheal inhalation catheter followed by 4 h of mechanical ventilation (MV) or the control group, in which animals (n = 6) were managed for 6 h with MV. Gas exchange, pulmonary mechanics, cardiovascular parameters, and cerebral blood flow (CBF) were measured.

RESULTS

Both groups developed hypoxia, hypercarbia, and acidosis at baseline. Aerosolized PFD improved oxygenation (P < 0.0001) and pulmonary mechanics (P < 0.0001) and changed carbon dioxide values to normal physiological levels, unlike the treatment given to the controls (P < 0.0003). The time course of mean arterial blood pressure and CBF were significantly affected by PFD aerosolization, especially during the first hour of life. CBF gradually decreased during the first hour in the PFD aerosol group and remained stable until the end of the follow-up, whereas CBF remained higher in the control group (P < 0.0028).

CONCLUSION

Aerosolized PFD improves pulmonary function in preterm lambs and should be further investigated as an alternative mode of PFC administration.

Inhalation of nebulized perfluorochemical enhances recombinant adenovirus and adeno-associated virus-mediated gene expression in lung epithelium

Use of perfluorochemical liquids during intratracheal vector administration enhances recombinant adenovirus and adeno-associated virus (AAV)-mediated lung epithelial gene expression. We hypothesized that inhalation of nebulized perfluorochemical vapor would also enhance epithelial gene expression after subsequent intratracheal vector administration. Freely breathing adult C57BL/6 mice were exposed for selected times to nebulized perflubron or sterile saline in a sealed Plexiglas chamber. Recombinant adenoviral vector was administered by transtracheal puncture at selected times afterward and mice were killed 3 days after vector administration to assess transgene expression. Mice tolerated the nebulized perflubron without obvious ill effects. Vector administration 6 hr after nebulized perflubron exposure resulted in an average 540% increase in gene expression in airway and alveolar epithelium, compared with that with vector alone or saline plus vector control (p<0.05). However, vector administration 1 hr, 1 day, or 3 days after perflubron exposure was not different from either nebulized saline with vector or vector alone and a 60-min exposure to nebulized perflubron is required. In parallel pilot studies in macaques, inhalation of nebulized perflubron enhanced recombinant AAV2/5 vector expression throughout the lung. Serial chest radiographs, bronchoalveolar lavages, and results of complete blood counts and serum biochemistries demonstrated no obvious adverse effects of nebulized perflubron. Further, one macaque receiving nebulized perflubron only was monitored for 1 year with no obvious adverse effects of exposure. These results demonstrate that inhalation of nebulized perflubron, a simple, clinically more feasible technique than intratracheal administration of liquid perflubron, safely enhances lung gene expression.

Aerosolized semifluorinated alkanes as excipients are suitable for inhalative drug delivery--a pilot study

Semifluorinated alkanes (SFAs) have been described as potential excipients for pulmonary drug delivery, but proof of their efficacy is still lacking. We tested whether SFA formulations with the test drug ibuprofen can be nebulised and evaluated their pharmacokinetics. Physico-chemical properties of five different ibuprofen formulations were evaluated: an aqueous solution (H2O), two different SFAs (perfluorohexyloctane (F6H8), perfluorobutylpentane (F4H5)) with and without ethanol (SFA/EtOH). Nebulisation was performed with a jet catheter system. Inhalative characteristics were evaluated by laser diffraction. A confirmative animal study with an inhalative single-dose (6 mg/kg) of ibuprofen with each formulation was performed in anaesthetised healthy rabbits. Plasma samples at defined time points and lung tissue harvested after the 6-h study period were analyzed by HPLC-MS/MS. Pharmacokinetics were calculated using a non-compartment model. All formulations were nebulisable. No differences in aerodynamic diameters (MMAD) were detected between SFA and SFA/EtOH. The ibuprofen plasma concentration-time curve (AUC) was highest with F4H5/EtOH. In contrast, F6H8/EtOH had the highest deposition of ibuprofen into lung tissue but the lowest AUC. All tested SFA and SFA/EtOH formulations are suitable for inhalation. F4H5/EtOH formulations might be used for rapid systemic availability of drugs. F6H8/EtOH showed intrapulmonary deposition of the test drug.

Semifluorinated alkanes--a new class of excipients suitable for pulmonary drug delivery

INTRODUCTION

Semifluorinated alkanes (SFAs) are considered as diblock molecules with fluorocarbon and hydrocarbon segments. Unlike Perfluorocarbons (PFCs), SFAs have the potential to dissolve several lipophilic or water-insoluble substances. This makes them possibly suitable as new excipients for inhalative liquid drug carrier systems.

PURPOSE

The aim of the study was to compare physico-chemical properties of different SFAs and then to test their respective effects in healthy rabbit lungs after nebulisation.

METHODS

Physico-chemical properties of four different SFAs, i.e. Perfluorobutylpentane (F4H5), Perfluorohexylhexane (F6H6), Perfluorohexyloctane (F6H8) and Perfluorohexyldodecane (F6H12) were measured. Based on these results, aerosol characteristics of two potential candidates suitable as excipients for pulmonary drug delivery, i.e. F6H8 and F4H5, were determined by laser light diffraction. Tracheotomised and ventilated New Zealand White rabbits were nebulised with either a high- or a low dose of SFAs (F6H8(low/high) and F4H5(low/high)) or saline (NaCl). Ventilated healthy animals served as controls (Sham). Arterial blood gases, lung mechanics, heart rate and blood pressure were recorded prior to nebulisation and in 30 min intervals during the 6-h study period.

RESULTS

Out of the four SFAs studied initially, no satisfactory behaviour as a solvent has to be expected because of low lipophilicity for F6H6. Output rate during aerosolisation was very low for F6H12. F6H8 and F4H5 presented comparable aerosolisation characteristics and lipophilicity and were therefore tested in the in vivo model. Aerosol therapy, either SFAs or saline, impaired paO2/FiO2 ratio, dynamic lung compliance and respiratory mechanics in all groups, except for F4H5(low) group which behaved like the control group (Sham). F4H5(low) had no adverse effects on gas exchange or pulmonary mechanics.

CONCLUSIONS

Perfluorobutylpentane (F4H5) in a low-dose application may be suitable as a new inhalable excipient in SFA-based pulmonary drug delivery systems for lipophilic or water-insoluble substances.

Parecoxib does not suppress thromboxane synthesis in newborn piglets with group B streptococcal sepsis

Group B streptococci (GBS) cause fatal sepsis in newborns. Strong activation of thromboxane synthesis is assumed to correlate with severe pulmonary hypertension. In this study we compared the impact of indomethacin versus parecoxib on hemodynamics and outcome and investigated the pharmacological effects on thromboxane synthesis and EP-3 receptor gene expression. Whereas both parecoxib and indometacin reduced expression of thromboxane synthase and EP-3 receptor in infected lung tissue, parecoxib did not suppress urine levels of thromboxane like indometacin. We presume that COX-2 inhibition in GBS sepsis is associated with enhanced thrombogenicity.