Perfluorocarbons decrease Chlamydophila pneumoniae-mediated inflammatory responses of rat type II pneumocytes in vitro

Perinatal Hyperoxia and Developmental Consequences on the Lung-Brain Axis

Approximately 11.1% of all newborns worldwide are born preterm. Improved neonatal intensive care significantly increased survival rates over the last decades but failed to reduce the risk for the development of chronic lung disease (i.e., bronchopulmonary dysplasia (BPD)) and impaired neurodevelopment (i.e., encephalopathy of prematurity (EoP)), two major long-term sequelae of prematurity. Premature infants are exposed to relative hyperoxia, when compared to physiological in-utero conditions and, if needed to additional therapeutic oxygen supplementation. Both are associated with an increased risk for impaired organ development. Since the detrimental effects of hyperoxia on the immature retina are known for many years, lung and brain have come into focus in the last decade. Hyperoxia-induced excessive production of reactive oxygen species leading to oxidative stress and inflammation contribute to pulmonary growth restriction and abnormal neurodevelopment, including myelination deficits. Despite a large body of studies, which unraveled important pathophysiological mechanisms for both organs at risk, the majority focused exclusively either on lung or on brain injury. However, considering that preterm infants suffering from BPD are at higher risk for poor neurodevelopmental outcome, an interaction between both organs seems plausible. This review summarizes recent findings regarding mechanisms of hyperoxia-induced neonatal lung and brain injury. We will discuss common pathophysiological pathways, which potentially link both injured organ systems. Furthermore, promises and needs of currently suggested therapies, including pharmacological and regenerative cell-based treatments for BPD and EoP, will be emphasized. Limited therapeutic approaches highlight the urgent need for a better understanding of the mechanisms underlying detrimental effects of hyperoxia on the lung-brain axis in order to pave the way for the development of novel multimodal therapies, ideally targeting both severe preterm birth-associated complications.

Systemic administration of FC-77 dampens ischemia-reperfusion-induced acute lung injury in rats

Systemic administration of perfluorocarbons (PFCs) reportedly attenuates acute lung injury induced by acid aspiration and phorbol myristate acetate. However, the effects of PFCs on ischemia–reperfusion (IR)-induced lung injury have not been investigated. Typical acute lung injury was induced in rats by 60 min of ischemia and 60 min of reperfusion in isolated and perfused rat lung model. Rat lungs were randomly assigned to receive PBS (control), 1 % FC-77, IR only, or IR with different doses of FC-77 (0.1 %, 0.5 %, or 1 %). Subsequently, bronchoalveolar lavage fluid (BALF), perfusate, and lung tissues were collected to evaluate the degree of lung injury. IR caused a significant increase in the following parameters: pulmonary arterial pressure, capillary filtration coefficient, lung weight gain, lung weight/body weight ratio, wet/dry lung weight ratio, and protein concentration in BALF. TNF-α and cytokine-induced neutrophil chemoattractant-1 concentrations in perfusate samples and MDA concentration and MPO activities in lung tissues were also significantly increased. Histopathology showed increased septal thickness and neutrophil infiltration in the lung tissues. Furthermore, NF-κB activity was significantly increased in the lungs. However, pretreatment with 1 % FC-77 prior to IR significantly attenuated the increases in these parameters. In conclusion, our results suggest that systemic FC-77 administration had a protective effect on IR-induced acute lung injury. These protective mechanisms may have been mediated by the inhibition of NF-κB activation and attenuation of subsequent inflammatory response.

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.

Leukocyte antibacterial functions are not impaired by perfluorocarbon exposure in vitro

Application of liquid, aerosolized, and vaporized perfluorocarbons (PFC) in acute lung injury has shown anti-inflammatory effects. Although this may be beneficial in states of pulmonary hyperinflammation, it also could increase susceptibility to nosocomial lung infection. We hypothesized that PFC impair cellular host defense and therefore investigated in an in vitro model the influence of perfluorohexane (PFH) on crucial mechanisms of bacterial elimination in human neutrophils and monocytes. Using scanning and transmission electron microscopy, we could show membrane-bound and ingested PFH particles that morphologically did not alter adherence and phagocytosis of Escherichia coli or leukocyte viability. The amount of adherent and phagocytosed bacteria as determined by flow cytometry was not influenced in cells only pretreated with PFH for 1 and 4 h. When PFH was present during E. coli challenge, bacterial adherence was decreased in polymorphonuclear neutrophils, but respective intracellular uptake was not impaired and was even significantly promoted in monocytes. Overall, E. coli-induced respiratory burst capacity was not reduced by PFH. Our findings provide evidence that key functions of innate host defense are not compromised by PFH treatment in vitro.

Intratracheal perfluorocarbons diminish LPS-induced increase in systemic TNF-alpha

Perfluorocarbons (PFC) reduce the production of various inflammatory cytokines, including TNF-alpha. The anti-inflammatory effect is not entirely understood. If anti-inflammatory properties are caused by a mechanical barrier, PFC in the alveoli should have no effect on the inflammatory response to intravenous LPS administration. To test that hypothesis, rats (n=31) were administered LPS intravenously and were either spontaneously breathing (Spont), conventionally ventilated (CMV), or receiving partial liquid ventilation (PLV). Serum concentration of TNF-alpha was measured. The pulmonary expressions of TNF-alpha and TNF-alpha receptor 1 protein and of TNF-alpha and ICAM-1 mRNA were determined. LPS caused a significant (P<0.001) increase in serum TNF-alpha. Serum TNF-alpha concentration was similar in LPS/Spont (525+/-180 pg/ml) and LPS/CMV (504+/-154 pg/ml) but was significantly (P<0.001) lower in animals of the LPS/PLV group (274+/-101 pg/ml). Immunohistochemical data on TNF-alpha protein expression showed a LPS-induced increase in TNF-alpha and TNF-alpha receptor 1 expression that was diminished by partial liquid ventilation. PCR measurements revealed a lower expression of TNF-alpha and ICAM-1 mRNA in LPS/PLV than in LPS/CMV or LPS/Spont animals. Semiquantitative histological evaluation revealed only minor alveolar inflammation with no significant differences between the groups. Low serum TNF-alpha concentration in PFC-treated animals is most likely explained by a decreased production of TNF-alpha in the lung.

Alterations of alveolar type II cells and intraalveolar surfactant after bronchoalveolar lavage and perfluorocarbon ventilation. An electron microscopical and stereological study in the rat lung

Background

Repeated bronchoalveolar lavage (BAL) has been used in animals to induce surfactant depletion and to study therapeutical interventions of subsequent respiratory insufficiency. Intratracheal administration of surface active agents such as perfluorocarbons (PFC) can prevent the alveolar collapse in surfactant depleted lungs. However, it is not known how BAL or subsequent PFC administration affect the intracellular and intraalveolar surfactant pool.

Methods

Male wistar rats were surfactant depleted by BAL and treated for 1 hour by conventional mechanical ventilation (Lavaged-Gas, n = 5) or partial liquid ventilation with PF 5080 (Lavaged-PF5080, n = 5). For control, 10 healthy animals with gas (Healthy-Gas, n = 5) or PF5080 filled lungs (Healthy-PF5080, n = 5) were studied. A design-based stereological approach was used for quantification of lung parenchyma and the intracellular and intraalveolar surfactant pool at the light and electron microscopic level.

Results

Compared to Healthy-lungs, Lavaged-animals had more type II cells with lamellar bodies in the process of secretion and freshly secreted lamellar body-like surfactant forms in the alveoli. The fraction of alveolar epithelial surface area covered with surfactant and total intraalveolar surfactant content were significantly smaller in Lavaged-animals. Compared with Gas-filled lungs, both PF5080-groups had a significantly higher total lung volume, but no other differences.

Conclusion

After BAL-induced alveolar surfactant depletion the amount of intracellularly stored surfactant is about half as high as in healthy animals. In lavaged animals short time liquid ventilation with PF5080 did not alter intra- or extracellular surfactant content or subtype composition.