Philipp von Bismarck

Selective NF-κB inhibition, but not dexamethasone, decreases acute lung injury in a newborn piglet airway inflammation model

Acute respiratory failure in neonates (e.g. ARDS, meconium aspiration pneumonitis, pneumonia) is characterized by an excessive inflammatory response, governing the migration of polymorpho-nuclear leukocytes (PMNLs) into lung tissue and causing consecutive impairment of gas exchange and lung function. Critical to this inflammatory response is the activation of nuclear factor-kappaB (NF-kappaB) that is required for transcription of the genes for many pro-inflammatory mediators. We asked whether the inhibition of NF-kappaB activity using either a selective inhibitor (IKK-NBD peptide) or dexamethasone would be more effective in decreasing NF-kappaB activity and chemokine expression in pulmonary cells. Changes in lung function were repeatedly assessed for 24h following induction of acute respiratory failure and therapeutic intervention. We conducted a randomized, controlled, prospective animal study with mechanically ventilated newborn piglets which underwent repeated airway lavage (20+/-2 [SEM]) to remove surfactant and to induce lung inflammation. Admixed to 100 mg kg(-1) surfactant, piglets then received either IKK-NBD peptide (S+IKK), a selective inhibitor of NF-kappaB activation, its control peptide without intrinsic activity, dexamethasone (S+Dexa), its solvent aqua, or an air bolus only (all groups n=8). After 24h of mechanical ventilation, the following differences were measured: PaO(2)/FiO(2) (S+IKK 230+/-9 mm Hg vs. S+Dexa 188+/-14, p<0.05); ventilation efficiency index (0.18+/-0.01 [3800/(PIP-PEEP)(*)f(*)PaCO(2)] vs. 0.14+/-0.01, p<0.05); extravascular lung water (24+/-1 ml kg(-1) vs. 29+/-2, p<0.05); PMNL in BAL fluid (112+/-21 cells microl(-1) vs. 208+/-34, p<0.05), IL-8 (351+/-117 pg ml(-1) vs. 491+/-144, p=ns) and leukotriene B(4) (23+/-7 pg ml(-1) vs. 71+/-11, p<0.01) in BAL fluid. NF-kappaB activity in the nucleus of pulmonary cells differed by 32+/-5% vs. 55+/-3, p<0.001. Differences between these two intervention groups were more pronounced in the second half of the observation period (hours 12-24). At 24h of mechanical ventilation, inhibition of NF-kappaB activity by IKK-NBD peptide admixed to surfactant as a carrier caused improved gas exchange, lung function and reduced pulmonary inflammation, as evidenced by reduction in PMNL migration into lung tissue due to reduced nuclear NF-kappaB activity. We conclude that IKK-NBD admixture to surfactant in acute neonatal respiratory failure is superior to dexamethasone administration within the first 24h.

IKK NBD peptide inhibits LPS induced pulmonary inflammation and alters sphingolipid metabolism in a murine model.

Airway epithelial NF-κB is a key regulator of host defence in bacterial infections and has recently evolved as a target for therapeutical approaches. Evidence is accumulating that ceramide, generated by acid sphingomyelinase (aSMase), and sphingosine-1-phosphate (S1-P) are important mediators in host defence as well as in pathologic processes of acute lung injury. Little is known about the regulatory mechanisms of pulmonary sphingolipid metabolism in bacterial infections of the lung. The objective of this study was to evaluate the influence of NF-κB on sphingolipid metabolism in Pseudomonas aeruginosa LPS-induced pulmonary inflammation. In a murine acute lung injury model with intranasal Pseudomonas aeruginosa LPS we investigated TNF-α, KC (murine IL-8), IL-6, MCP-1 and neutrophilic infiltration next to aSMase activity and ceramide and S1-P lung tissue concentrations. Airway epithelial NF-κB was inhibited by topically applied IKK NBD, a cell penetrating NEMO binding peptide. This treatment resulted in significantly reduced inflammation and suppression of aSMase activity along with decreased ceramide and S1-P tissue concentrations down to levels observed in healthy animals. In conclusion our results confirm that changes in sphingolipid metabolim due to Pseudomonas aeruginosa LPS inhalation are regulated by NF-κB translocation. This confirms the critical role of airway epithelial NF-κB pathway for the inflammatory response to bacterial pathogens and underlines the impact of sphingolipids in inflammatory host defence mechanisms.

Bronchoscopic Surfactant Administration in Pediatric Patients with Persistent Lobar Atelectasis

Persistent lobar atelectasis in pediatric patients on mechanical ventilation results in impaired gas exchange and lung mechanics and contributes to a further need for mechanical ventilation. The most common types of atelectasis in children are resorption atelectasis following airway obstruction, and atelectasis due to surfactant deficiency or dysfunction. We aimed to determine whether bronchoscopic suctioning and surfactant application to atelectatic lung segments would result in improved oxygenation, ventilation, chest X-ray scoring, and early extubation. Five children with heterogeneous lung diseases (aged between 7 months and 15 years) were treated with a diluted surfactant preparation (CurosurfTM) in a concentration of 5–10 mg/ml (total dose 120–240 mg) which was instilled into the affected segments. Outcome parameters were gas exchange, radiographic resolution of atelectasis and extubation. All mechanically ventilated patients could be extubated within 24 h following the intervention. Bronchoscopic surfactant application could be carried out without adverse effects and brought improvements in oxygenation, respiratory rate, and partial or complete resolution of atelectases without recurrence.

ALTERED PULMONARY INTERLEUKIN-6 SIGNALING IN PRETERM INFANTS DEVELOPING BRONCHOPULMONARY DYSPLASIA

Interleukin (IL)-6 signaling depends on the soluble IL-6 receptor (sIL-6R) and the soluble glycoprotein 130 (sgp130). To investigate the impact of IL-6 signaling on the pathogenesis of bronchopulmonary dysplasia of prematurity (BPD), IL-6, sIL-6R, and sgp130 were measured by enzyme-linked immunosorbent assay (ELISA) technique in tracheal aspirates of mechanically ventilated preterm infants. Infants developing BPD showed increased concentrations of IL-6, sIL-6R, and sgp-130 in their first week of life. These infants also had significantly higher molar ratios for IL-6/sIL-6R and IL-6/sgp130. The authors conclude that altered interleukin-6 signaling via the soluble receptors sIL-6R and sgp130 may play an important role in pulmonary inflammation of preterm infants.

Topical application of phosphatidyl-inositol-3,5-bisphosphate for acute lung injury in neonatal swine

Hypoxemic respiratory failure of the neonatal organism involves increased acid sphingomyelinase (aSMase) activity and production of ceramide, a second messenger of a pro‐inflammatory pathway that promotes increased vascular permeability, surfactant alterations and alveolar epithelial apoptosis. We comparatively assessed the benefits of topical aSMase inhibition by either imipramine (Imi) or phosphatidylinositol‐3,5‐bisphosphate (PIP2) when administered into the airways together with surfactant (S) for fortification. In this translational study, a triple‐hit acute lung injury model was used that entails repeated airway lavage, injurious ventilation and tracheal lipopolysaccharide instillation in newborn piglets subject to mechanical ventilation for 72 hrs. After randomization, we administered an air bolus (control), S, S+Imi, or S+PIP2. Only in the latter two groups we observed significantly improved oxygenation and ventilation, dynamic compliance and pulmonary oedema. S+Imi caused systemic aSMase suppression and ceramide reduction, whereas the S+PIP2 effect remained compartmentalized in the airways because of the molecules bulky structure. The surfactant surface tensions improved by S+Imi and S+PIP2 interventions, but only to a minor extent by S alone. S+PIP2 inhibited the migration of monocyte‐derived macrophages and granulocytes into airways by the reduction of CD14/CD18 expression on cell membranes and the expression of epidermal growth factors (amphiregulin and TGF‐β1) and interleukin‐6 as pro‐fibrotic factors. Finally we observed reduced alveolar epithelial apoptosis, which was most apparent in S+PIP2 lungs. Exogenous surfactant “fortified” by PIP2, a naturally occurring surfactant component, improves lung function by topical suppression of aSMase, providing a potential treatment concept for neonates with hypoxemic respiratory failure.

Inositol–Trisphosphate Reduces Alveolar Apoptosis and Pulmonary Edema in Neonatal Lung Injury

D-myo-inositol-1,2,6-trisphosphate (IP3) is an isomer of the naturally occurring second messenger D-myo-inositol-1,4,5-trisphosphate, and exerts anti-inflammatory and antiedematous effects in the lung. Myo-inositol (Inos) is a component of IP3, and is thought to play an important role in the prevention of neonatal pulmonary diseases such as bronchopulmonary dysplasia and neonatal acute lung injury (nALI). Inflammatory lung diseases are characterized by augmented acid sphingomyelinase (aSMase) activity leading to ceramide production, a pathway that promotes increased vascular permeability, apoptosis, and surfactant alterations. A novel, clinically relevant triple-hit model of nALI was developed, consisting of repeated airway lavage, injurious ventilation, and lipopolysaccharide instillation into the airways, every 24 hours. Thirty-five piglets were randomized to one of four treatment protocols: control (no intervention), surfactant alone, surfactant + Inos, and surfactant + IP3. After 72 hours of mechanical ventilation, lungs were excised from the thorax for subsequent analyses. Clinically, oxygenation and ventilation improved, and extravascular lung water decreased significantly with the S + IP3 intervention. In pulmonary tissue, we observed decreased aSMase activity and ceramide concentrations, decreased caspase-8 concentrations, reduced alveolar epithelial apoptosis, the reduced expression of interleukin-6, transforming growth factor-β1, and amphiregulin (an epithelial growth factor), reduced migration of blood-borne cells and particularly of CD14(+)/18(+) cells (macrophages) into the airspaces, and lower surfactant surface tensions in S + IP3-treated but not in S + Inos-treated piglets. We conclude that the admixture of IP3 to surfactant, but not of Inos, improves gas exchange and edema in our nALI model by the suppression of the governing enzyme aSMase, and that this treatment deserves clinical evaluation.

Calculation of intratracheal airway pressure in ventilated neonatal piglets with endotracheal tube leaks.

Objective:In ventilated neonates, only the applied pressure of the ventilator is adjusted and monitored. When an endotracheal tube leaks, intratracheal pressure decreases depending on the size of the endotracheal tube and of the leak. Furthermore, an increase in resistance and/or compliance might delay the increase of intratracheal pressure during inspiration and its decline during expiration. Short inspiratory time can cause insufficient ventilation, because intratracheal pressure peak might not be reached. Short expiratory time may lead to air trapping, because intratracheal pressure could not return to baseline. The aim of this study was to develop a mathematical algorithm to calculate intratracheal pressure continuously during ventilation and to evaluate the accuracy of this method. Design:Prospective, animal study. Setting:University research laboratory. Subjects:To verify the mathematical algorithm, eight neonatal piglets (1600–2600 g) were studied under different endotracheal tube leak conditions (45% to 98%). The median compliance and resistance were 1.06 mL/cm H2O/kg and 123 cm H2O/L/sec, respectively. Interventions:Pressure decreases caused by the different endotracheal tubes were measured in a model while air flow was increased stepwise. Based on these results, a mathematical method was developed to calculate intratracheal pressure under leak conditions continuously in relation to the flow through the endotracheal tube as well as to calculate the values of resistance, compliance, and applied pressure of the ventilator. Measurements and Main Results:The intratracheal pressure calculated was compared with the measured intratracheal pressure over time. The differences between measured and calculated intratracheal pressure related to peak applied pressure of the ventilator did not exceed 10%. The medians of absolute amounts of differences between measured and calculated intratracheal pressure were <1 cm H2O. Conclusions:The accuracy of the calculation of intratracheal pressure ensures adequate monitoring of artificial ventilation, even in the presence of endotracheal tube leaks. This might decrease the risk of barotrauma and improve the effectiveness of ventilation.

18:1/18:1-Dioleoyl-phosphatidylglycerol prevents alveolar epithelial apoptosis and profibrotic stimulus in a neonatal piglet model of acute respiratory distress syndrome

BACKGROUND 18:1/18:1-Dioleoyl-phosphatidylgycerol (DOPG) is a surfactant phospholipid that is nearly non-detectable in neonatal surfactant films. When alveolar macrophages are exposed to DOPG in vitro, secretory phospholipase A2 (sPLA2) production is blocked, resulting in suppressed macrophage activity and improved surfactant function. We investigated whether the addition of DOPG to a commercially available surfactant preparation would improve lung function in a neonatal piglet model of acute respiratory distress syndrome. MATERIALS AND METHODS Respiratory failure was achieved by triple-hit lung injury (repeated broncho-alveolar lavage, injurious ventilation, tracheal lipopolysaccharide instillation, each intervention 24 h apart) in twenty-four domestic piglets aged 2-6 days and subject to mechanical ventilation. Following each lung injury protocol the piglets were treated with surfactant alone or with surfactant + DOPG. RESULTS Within 72 h of mechanical ventilation, we observed significantly improved gas exchange (oxygenation and ventilation), lung mechanics (compliance and resistance of the respiratory system), and pulmonary oedema (extra-vascular lung water index) in the surfactant + DOPG group. This favourable clinical effect could be attributed to improved surfactant function, reduced sPLA2 secretion, inhibition of macrophage migration, reduced alveolar epithelial apoptosis, and suppression of amphiregulin and TGF-β1 expression in pulmonary tissues as a prerequisite for fibrous lung repair. CONCLUSIONS We conclude that surfactant fortified by DOPG preserves lung function, and prevents alveolar epithelial injury and fibrous stimulus by reduction of sPLA2 in a neonatal model of acute respiratory distress syndrome without any relevant discernable side effects. Hence, DOPG supplementation in a neonatal lung exerts important function protecting effects and seems to be justified in cases of overwhelming pulmonary inflammation.

Effect on work of breathing of different continuous positive airway pressure devices evaluated in a premature neonatal lung model.

Objective: A device for the application of continuous positive airway pressure to switch injected breathing gas to the outlet during expiration, known as Infant Flow, claims to reduce work of breathing and peak pressure change. So far the Infant Flow system has been investigated in lung models with tidal volumes of not <12 mL. However, premature neonates below 1000 g of weight generate a tidal volume of approximately 4 mL only. The aim of this study was to compare work of breathing and peak pressure change of the Infant Flow and another system that uses nasal prongs, Baby Flow, with conventional continuous positive airway pressure delivered by a pharyngeal tube. Design: Laboratory investigation, basic research. Setting: University research laboratory. Model: A piston pump simulating the spontaneous breathing of premature neonates was connected without leak to three different continuous positive airway pressure devices (pharyngeal tube, Baby Flow, and Infant Flow) and with a produced leak to the systems using nasal prongs (Baby Flow and Infant Flow). Intervention: The pressures of the airway and continuous positive airway pressure systems and airway flow were recorded. Peak pressure change and work of breathing were determined for all systems and settings. Percentages of reduction of peak pressure change and work of breathing in relation to the continuous positive airway pressure delivered by pharyngeal tube were calculated. Measurements and Main Results: The switching of injected breathing gas to the outlet during expiration of Infant Flow systems require a tidal volume of at least 5 mL. It was possible to decrease peak pressure change and work of breathing: Baby Flow system at a tidal volume of 4 mL (Inspiration: peak pressure change 82%, work of breathing 80%; Expiration: peak pressure change: 68%, work of breathing: 61%) and at a tidal volume of 8 mL (Inspiration: peak pressure change 75%, work of breathing 73%; Expiration: peak pressure change: 67%, work of breathing: 57%). Infant Flow system at tidal volume of 4 mL (Inspiration: peak pressure change 50%, work of breathing 55%; Expiration: peak pressure change: 46%, work of breathing: 43%) and at a tidal volume of 8 mL (Inspiration: peak pressure change 47%, work of breathing 46%; Expiration: peak pressure change: 24%, work of breathing: 23%), related to the continuous positive airway pressure delivered by pharyngeal tube without leak. Even under conditions of leak peak pressure change and work of breathing could be reduced: Baby Flow system at a tidal volume of 4 mL (Inspiration: peak pressure change 59%, work of breathing 64%; Expiration: peak pressure change: 68%, work of breathing: 59%) and at a tidal volume of 8 mL (Inspiration: peak pressure change 45%, work of breathing 43%; Expiration: peak pressure change: 54%, work of breathing: 53%). Infant Flow system at a tidal volume of 4 mL (Inspiration: peak pressure change 49%, work of breathing 53%; Expiration: peak pressure change: 44%, work of breathing: 40%) and at a tidal volume of 8 mL (Inspiration: peak pressure change 48%, work of breathing 43%; Expiration: peak pressure change: 36%, work of breathing: 40%), related to the continuous positive airway pressure delivered by pharyngeal tube without leak. Conclusion: Peak pressure change and work of breathing were decreased by Baby Flow and Infant Flow systems, even under conditions of leak.