Differential impact of perfluorochemical physical properties on the physiologic, histologic, and inflammatory profile in acute lung injury

Cytosolic perfluorocarbon delivery to platelets via albumin for antithrombotic therapy

Thrombosis is a major contributor to global disease burden. Antiplatelet therapy is the critical approach to prevent thrombosis by reducing platelet reactivity. However, classical antiplatelet strategies generally interfere with platelet integrin α_IIbβ₃-mediated platelet activation, thereby facing severe bleeding risk. To break the limitation, we described an integrin α_IIbβ₃-independent antiplatelet method by cytosolic delivery of nanoscale perfluorocarbon (PFC) to platelets via albumin carrier. Denatured albumin was found to build high affinity with platelets to mediate cytosolic PFC delivery. While, cytosolic PFC impaired cytoskeleton reorganization during platelet activation to inhibit relevant platelet functions, but avoided to interfere with integrin α_IIbβ₃. We proved that this α_IIbβ₃-indenpendent antiplatelet pattern showed potential antiplatelet effect with low bleeding risk to prevent thrombosis in various thrombosis models. Together, cytosolic PFC delivery via albumin is a promising antiplatelet approach, and will provide an alternative regimen for current antithrombotic therapy.

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.

Therapeutic effect of intravenous infusion of perfluorocarbon emulsion on LPS-induced acute lung injury in rats

Acute lung injury (ALI) and its more severe form, acute respiratory distress syndrome (ARDS) are the leading causes of death in critical care. Despite extensive efforts in research and clinical medicine, mortality remains high in these diseases. Perfluorocarbon (PFC), a chemical compound known as liquid ventilation medium, is capable of dissolving large amounts of physiologically important gases (mainly oxygen and carbon dioxide). In this study we aimed to investigate the effect of intravenous infusion of PFC emulsion on lipopolysaccharide (LPS) induced ALI in rats and elucidate its mechanism of action. Forty two Wistar rats were randomly divided into three groups: 6 rats were treated with saline solution by intratracheal instillation (control group), 18 rats were treated with LPS by intratracheal instillation (LPS group) and the other 18 rats received PFC through femoral vein prior to LPS instillation (LPS+PFC group). The rats in the control group were sacrificed 6 hours later after saline instillation. At 2, 4 and 6 hours of exposure to LPS, 6 rats in the LPS group and 6 rats in LPS+PFC group were sacrificed at each time point. By analyzing pulmonary pathology, partial pressure of oxygen in the blood (PaO2) and lung wet-dry weight ratio (W/D) of each rat, we found that intravenous infusion of PFC significantly alleviated acute lung injury induced by LPS. Moreover, we showed that the expression of pulmonary myeloperoxidase (MPO), intercellular adhesion molecule-1 (ICAM-1) of endothelial cells and CD11b of polymorphonuclear neutrophils (PMN) induced by LPS were significantly decreased by PFC treatment in vivo. Our results indicate that intravenous infusion of PFC inhibits the infiltration of PMNs into lung tissue, which has been shown as the core pathogenesis of ALI/ARDS. Thus, our study provides a theoretical foundation for using intravenous infusion of PFC to prevent and treat ALI/ARDS in clinical practice.

Cytoprotection of perfluorocarbon on PMVECs in vitro

Lipopolysaccharide (LPS) can activate endothelial cells and induce inflammatory injury. Toll-like receptor-4 (TLR-4) is integrally involved in LPS signaling and has a requisite role in the activation of nuclear factor (NF)-κB. A number of studies have demonstrated the cytoprotective action of perfluorocarbon (PFC) both in vivo and in vitro, but the exact mechanisms have yet to be elucidated. In this study, we examined in an in vitro model the cytoprotective effect of PFC on LPS-stimulated pulmonary vascular endothelial cells (PMVECs). Intercellular adhesion molecule-1 (ICAM-1), tumor necrosis factor-α (TNF-α), and interleukin-8 (IL-8) were significantly increased in the LPS-stimulated PMVECs groups. The expression of TLR-4 mRNA and protein in LPS groups was markedly increased. Meanwhile, NF-κB was activated. There were no significant effects of PFC alone on any of the factors studied while the coculture group showed significant downregulation of the secretion of ICAM-1, TNF-α, and IL-8; the expression of TLR-4 mRNA; and the activity of NF-κB. LPS can induce PMVEC inflammatory injury via the activation of TLR-4 and subsequent activation of NF-κB. PFC is able to protect PMVECs from LPS-induced inflammatory injury by blocking the initiation of the LPS signaling pathway.

Comparative effects of bronchoalveolar lavage with saline, surfactant, or perfluorocarbon in experimental meconium aspiration syndrome

OBJECTIVE

Today, in meconium aspiration syndrome, treatment focuses on bronchoalveolar lavage, because it removes meconium and proinflammatory factors from airways. This technique might be more effective if different solutions were used such as saline solution, a protein-free surfactant, or a perfluorocarbon, because these would be less inhibited by meconium proteins.

SETTING

Pulmonary physiology research unit, Cruces Hospital.

DESIGN

Prospective, randomized study.

SUBJECTS

We studied 24 lambs (<6 days) on mechanical ventilation for 180 mins. Catheters were placed and femoral and pulmonary arteries pressures registered (systemic and pulmonary arterial pressures).

INTERVENTIONS

Lambs were instilled with 20% meconium (3-5 mL/Kg) and were randomly assigned to one of the following groups (n = 6): control: only continuous mechanical ventilation; saline bronchoalveolar lavage: bronchoalveolar lavage with 30 mL/kg of saline solution; dilute surfactant bronchoalveolar lavage: bronchoalveolar lavage with 32 mL/kg of diluted surfactant (lucinactant, 10 mg/mL); or perfluorocarbon bronchoalveolar lavage: bronchoalveolar lavage with 30 mL/kg of perfluorocarbon.

MEASUREMENTS AND MAIN RESULTS

Blood gases, cardiovascular parameters, and pulmonary mechanics were assessed. Meconium instillation produced severe hypoxia, hypercapnia, acidosis, and pulmonary hypertension with impairment of pulmonary mechanics (p < .05). Lung lavage with dilute surfactant resulted in the resolution of pulmonary hypertension as well as better gas exchange and pulmonary mechanics than the control group (p < .05). Bronchoalveolar lavage with perfluorocarbon produced a transient improvement in gas exchange and ventilatory indices in comparison with control and saline bronchoalveolar lavage groups.

CONCLUSIONS

In lambs with meconium aspiration syndrome, bronchoalveolar lavage with diluted lucinactant is an effective therapy producing significant improvements in gas exchange, pulmonary hypertension, and pulmonary mechanics. In addition, bronchoalveolar lavage with perfluorocarbon appears to confer some advantages over lavage with equal volumes of saline or no lavage.

Perfluorochemical liquid-adenovirus suspensions enhance gene delivery to the distal lung

WE COMPARED LUNG DELIVERY METHODS OF RECOMBINANT ADENOVIRUS (RAD): (1) rAd suspended in saline, (2) rAd suspended in saline followed by a pulse-chase of a perfluorochemical (PFC) liquid mixture, and (3) a PFC-rAd suspension. Cell uptake, distribution, and temporal expression of rAd were examined using A549 cells, a murine model using luciferase bioluminescence, and histological analyses. Relative to saline, a 4X increase in transduction efficiency was observed in A549 cells exposed to PFC-rAd for 2-4 h. rAd transgene expression was improved in alveolar epithelial cells, and the level and distribution of luciferase expression when delivered in PFC-rAd suspensions consistently peaked at 24 h. These results demonstrate that PFC-rAd suspensions improve distribution and enhance rAd-mediated gene expression which has important implications in improving lung function by gene therapy.

Perfluorocarbon emulsions as a promising technology: a review of tissue and vascular gas dynamics

Perfluorocarbon (PFC) emulsions are halogen-substituted carbon nonpolar oils with resultant enhanced dissolved respiratory gas (O(2), N(2), CO(2), nitric oxide) capabilities. In the first demonstration of enhanced O(2) solubility, inhaled PFC could sustain rat metabolism. Intravenous emulsions were then trialed as "blood substitutes." In the last 10 yr, biocomputational modeling has enhanced our mechanistic understanding of PFCs. Contemporary research is now taking advantage of these physiological discoveries and applying PFCs as "oxygen therapeutics," as well as ways to enhance other gas movements. One particularly promising area of research is the treatment of gas embolism (arterial and venous emboli/decompression sickness). An expansive understanding of PFC-enhanced diffusive gas movements through tissue and vasculature may have analogous applications for O(2) or other respiratory gases and should provide a revolution in medicine. This review will stress the fundamental knowledge we now have regarding how respiratory gas movements are changed when intravenous PFC is present.

High vapor pressure perfluorocarbons cause vesicle fusion and changes in membrane packing

Perfluorocarbons (PFCs) hold great promise for biomedical applications. However, relatively little is known about the impact of these chemicals on membranes. We used unilamellar vesicles to explore the effects of PFCs on membrane packing and vesicle stability. Four clinically relevant PFCs with varying vapor pressures (PP1, 294 mbar; PP2, 141 mbar; PP4, 9.6 mbar; and PP9, 2.9 mbar) were examined. Microscopy imaging and spectroscopic measurements suggest that PFCs, especially those with high vapor pressures, lead to vesicle fusion within hours. Upon exposure to PP1 and PP2 for 72 h, vesicles retained a spherical shape, but the size changed from approximately 200 nm to approximately 20-40 mum. In addition, membrane packing underwent marked changes during this timeframe. A significant decrease in water content in the lipid polar headgroup regions occurred during the first 1-2-h exposure to PFCs, followed by a steady increase in water content over time. Possible mechanisms were proposed to explain these dramatic structural changes. The finding that chemically inert PFCs exhibited fusogenic activity and marked changes in membrane surface packing is novel, and should be considered when using PFCs for biomedical applications.

Bronchioalveolar lavage with perfluorochemical liquid during conventional ventilation

OBJECTIVE

Therapeutic approaches with bronchioalveolar lavage are currently used in infants with severe alveolar space-occupying material. In many circumstances, bronchioalveolar lavage has been performed in conjunction with extracorporeal membrane oxygenation.

CASE REPORT

A 2-month-old boy with severe respiratory failure requiring assisted ventilation did not respond to any conventional treatments, including surfactant. An open-lung biopsy showed intra-alveolar accumulation of proteinaceous material and foamy macrophages but was not diagnostically conclusive. Therapeutic trials with bronchioalveolar lavage using normal saline were unsuccessful, causing episodes of severe hypoxemia. Then, bronchioalveolar lavage during conventional mechanical ventilation was performed with the use of a medical-grade perfluorochemical liquid (perfluordecalin). After instillation of liquid (10 mL/kg), the lungs were refilled three times during the first 24 hrs and repeated 48 hrs later. During perfluorochemical liquid treatment, the infant's condition remained stable, with small improvements in pulmonary mechanics. Suction from the endotracheal cannula yielded only small amounts of gelatinous material. Considering the progression of the disease and just minimal pulmonary improvements by this intervention, further treatment was considered futile. Support was, thus, minimized, and the infant died a few days later. An autopsy revealed the diagnosis to be consistent with Niemann-Pick C2 disease.

CONCLUSION

This study demonstrated that bronchioalveolar lavage with perfluorochemical liquid could be performed safely during conventional mechanical ventilation without the additional support of extracorporeal membrane oxygenation in infants with severe alveolar space-occupying material.

Effect of different ventilation modes with FC-77 on pulmonary inflammatory reaction in piglets after cardiopulmonary bypass

RATIONALE

Cardiopulmonary bypass (CPB) causes pulmonary inflammatory reaction. Liquid ventilation with perfluorocarbon has shown an anti-inflammatory effect on severely injured lungs. The aim of this study is to investigate the treatment effect of different ventilation modes with perfluorocarbon on pulmonary inflammatory reaction in piglets after CPB.

METHODS

After receiving CPB and subsequent infusion of lipopolysaccharide (1 microg/kg), 18 piglets were randomly treated with conventional gas ventilation, total liquid ventilation (TLV), or partial liquid ventilation (PLV) for 240 min. The lung tissue and blood samples were collected at the end of observation period. The pulmonary mRNA expressions and plasmatic concentrations of interleukin-6 (IL-6) and interleukin-8 (IL-8) were measured. Histological neutrophil count in lung parenchyma was performed.

RESULTS

Hemodynamics, PaCO2 and PH did not differ among groups during the observation period. Both TLV and PLV showed significantly improved oxygenation, reduced pulmonary mRNA expressions and plasmatic levels of IL-6 and IL-8, and decreased total neutrophil count in lung parenchyma when compared with conventional gas ventilation. Furthermore, TLV resulted in significantly better oxygenation, lower pulmonary mRNA expressions of IL-6 and IL-8, and less total neutrophil count when compared with PLV.

CONCLUSION

Both TLV and PLV improved oxygenation and reduced pulmonary inflammatory reaction in piglets after CPB, whereas TLV is more effective than PLV.

Effects of vaporized perfluorohexane and partial liquid ventilation on regional distribution of alveolar damage in experimental lung injury

OBJECTIVE

To determine whether the patterns of distribution of histological effects of vaporized perfluorohexane (PFH) and partial liquid ventilation (PLV) differ significantly in acute lung injury.

DESIGN AND SETTING

Experimental study in an animal research laboratory.

SUBJECTS

Eighteen pigs.

INTERVENTIONS

After induction of acute lung injury by means of infusion of oleic acid animals were randomly assigned to PFH, PLV, or gas ventilation (GV) groups. Six hours thereafter animals were killed, and lung tissue samples were taken for analysis.

MEASUREMENTS AND RESULTS

Histopathological analysis revealed less damage with PFH than with GV or PLV in the nondependent and central regions. PFH and PLV showed less injury in the dependent regions than GV. GV and PFH were associated with less histological damage in the nondependent than the dependent regions, whereas PLV presented the opposite pattern. Morphometric analysis showed increased aeration in nondependent than dependent regions with PFH and GV. PLV led to more aeration in the periphery than in central areas.

CONCLUSIONS

PFH was associated with a more homogeneous attenuation of alveolar damage across the lungs, although this therapy had more pronounced effects in nondependent zones. PLV showed the opposite pattern, with more important reduction in alveolar damage in dependent lung regions. Interestingly, reduction in alveolar damage with PFH was as effective as with PLV in dependent zones. Our findings suggest that vaporized perfluorocarbon could be advantageous as adjunctive therapy in the treatment of acute lung injury.

Small-dose perfluorocarbon reduces the recruitment pressure needed to open surfactant-deficient atelectatic lungs

BACKGROUND

This study was undertaken to investigate the effect of a small dose of perfluorocarbon on the recruitment pressure needed to open atelectatic lung areas.

METHODS

In 12 Yorkshire pigs (body weight, 9 kg), lung injury was induced by whole lung lavage. After 1 h of conventional ventilation, an open lung maneuver was performed to obtain PaO2 values equal to the pre-lavage PaO2 values (+/-10%). After 1 h of ventilation at the lowest possible airway pressure that stabilized the recruited lung volume, the animals were disconnected from the ventilator to allow the lung to collapse. Six animals received a 5 ml/kg intratracheal dose of perfluorocarbon and a second open lung maneuver was performed. Six animals served as controls and received no perfluorocarbon but also underwent a second open lung maneuver.

RESULTS

In both groups, an open lung maneuver resulted in a significant increase in oxygenation. The peak pressures needed to open the lung after 1 h of mechanical ventilation in the perfluorocarbon and control groups were 43.8 +/- 8.4 cmH2O and 46.6 +/- 4 cmH2O, respectively. The addition of perfluorocarbon significantly reduced the opening pressure to 34.5 +/- 6.3 cmH2O (P < 0.01), whereas the opening pressure in the control group, 45.0 +/- 0.2 cmH2O, did not change.

CONCLUSION

The instillation of a small amount of perfluorocarbon significantly reduces the opening pressures needed to recruit atelectatic lung areas.

Effects of therapeutic bronchoalveolar lavage and partial liquid ventilation on meconium-aspirated newborn piglets

OBJECTIVE

To investigate the therapeutic effects of bronchoalveolar lavage (BAL) with either diluted surfactant (SBAL) or perfluorochemical liquid (PBAL), followed by either conventional mechanical ventilation (CMV) or partial liquid ventilation (PLV), on lung injury and proinflammatory cytokine production induced by meconium aspiration in newborn piglets.

DESIGN

A prospective, randomized, experimental study.

SETTING

An animal research laboratory at a medical center.

SUBJECTS

Anesthetized and mechanically ventilated newborn piglets (n = 27).

INTERVENTIONS

The animals were instilled with 3-5 mL/kg 25% human meconium via an endotracheal tube to induce meconium aspiration syndrome (MAS). After stabilization, animals were randomly assigned to either CMV group (no BAL) or one of the treatment groups (SBAL-CMV, SBAL-PLV, PBAL-CMV, and PBAL-PLV).

MEASUREMENTS AND MAIN RESULTS

Cardiopulmonary variables were monitored, and interleukin-1beta and interleukin-6 content of the serum and lung tissue was measured. The animals without any treatment (CMV group) displayed the worst outcome; the animals in the PBAL-PLV group had the best gas exchange, lung compliance, and least pulmonary damage; and the SBAL-CMV, PBAL-CMV, and SBAL-PLV groups had intermediate effects. The serum interleukin-1beta concentration of the CMV group was significantly higher than all other groups over time (p < .05), and interleukin-6 concentration was significantly higher than the PBAL-PLV group (p < .05). The tissue interleukin-1beta and interleukin-6 contents were also highest in the CMV group and lowest in the PBAL-PLV group.

CONCLUSIONS

Initial therapeutic BAL and therapeutic BAL followed by PLV with the same perfluorochemical liquid provided significant therapeutic effects in treating an animal model with severe MAS and therefore warrant consideration in cases that are intractable to other therapies.