Compositional, structural, and functional alterations in pulmonary surfactant in surgical patients after the early onset of systemic inflammatory response syndrome or sepsis

Impact of the Epithelial Lining Fluid Milieu on Amikacin Pharmacodynamics Against Pseudomonas aeruginosa

Background

Even though nebulised administration of amikacin can achieve high epithelial lining fluid concentrations, this has not translated into improved patient outcomes in clinical trials. One possible reason is that the cellular and chemical composition of the epithelial lining fluid may inhibit amikacin-mediated bacterial killing.

Objective

The objective of this study was to identify whether the epithelial lining fluid components inhibit amikacin-mediated bacterial killing.

Methods

Two amikacin-susceptible (minimum inhibitory concentrations of 2 and 8 mg/L) Pseudomonas aeruginosa isolates were exposed in vitro to amikacin concentrations up to 976 mg/L in the presence of an acidic pH, mucin and/or surfactant as a means of simulating the epithelial lining fluid, the site of bacterial infection in pneumonia. Pharmacodynamic modelling was used to describe associations between amikacin concentrations, bacterial killing and emergence of resistance.

Results

In the presence of broth alone, there was rapid and extensive (> 6 − log₁₀) bacterial killing, with emergence of resistance identified in amikacin concentrations < 976 mg/L. In contrast, the rate and extent of bacterial killing was reduced (≤ 5 − log₁₀) when exposed to an acidic pH and mucin. Surfactant did not appreciably impact the bacterial killing or resistance emergence when compared with broth alone for either isolate. The combination of mucin and an acidic pH further reduced the rate of bacterial killing, with the maximal bacterial killing occurring 24 h following initial exposure compared with approximately 4–8 h for either mucin or an acidic pH alone.

Conclusions

Our findings indicate that simulating the epithelial lining fluid antagonises amikacin-mediated killing of P. aeruginosa, even at the high concentrations achieved following nebulised administration.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40268-021-00344-5.

Review shows that using surfactant a number of times or as a vehicle for budesonide may reduce the risk of bronchopulmonary dysplasia

AIM

Bronchopulmonary dysplasia (BPD) remains the most common respiratory morbidity in immature infants. This review describes the diagnosis of BPD has evolved and summarises the therapeutic approaches that have made it possible to limit the incidence of BPD.

METHOD

We reviewed the literature from the first definition of BPD by Northway in 1967 to the surfactant treatment policies that are currently in use, drawing on more than 50 papers up to 2017.

RESULTS

Our review showed that improvements in neonatal survival have been associated with an increased risk of severe BPD, significant levels of long-term morbidity and the increased use of healthcare resources. These issues have encouraged researchers to explore potential new treatments that limit the incidence of BPD. Repeated surfactant instillation and the use of surfactant as a vehicle for budesonide are promising strategies for alleviating the burden of chronic lung disease. Ongoing research on surfactant or stem cell therapy may further improve the respiratory prognosis for prematurely born children.

CONCLUSION

Considerable research has been carried out into the increase in BPD, which has resulted from improvements in neonatal survival. Key areas of research include repeated surfactant administration, using surfactant as a vehicle for budesonide and stem cell therapy.

The diagnostic value of gastroesophageal reflux disease (GERD) symptoms and detection of pepsin and bile acids in bronchoalveolar lavage fluid and exhaled breath condensate for identifying lung transplantation patients with GERD-induced aspiration

BACKGROUND

Gastroesophageal reflux disease (GERD) is thought to lead to aspiration and bronchiolitis obliterans syndrome after lung transplantation. Unfortunately, the identification of patients with GERD who aspirate still lacks clear diagnostic indicators. The authors hypothesized that symptoms of GERD and detection of pepsin and bile acids in the bronchoalveolar lavage fluid (BAL) and exhaled breath condensate (EBC) are effective for identifying lung transplantation patients with GERD-induced aspiration.

METHODS

From November 2009 to November 2010, 85 lung transplantation patients undergoing surveillance bronchoscopy were prospectively enrolled. For these patients, self-reported symptoms of GERD were correlated with levels of pepsin and bile acids in BAL and EBC and with GERD status assessed by 24-h pH monitoring. The sensitivity and specificity of pepsin and bile acids in BAL and EBC also were compared with the presence of GERD in 24-h pH monitoring.

RESULTS

The typical symptoms of GERD (heartburn and regurgitation) had modest sensitivity and specificity for detecting GERD and aspiration. The atypical symptoms of GERD (aspiration and bronchitis) showed better identification of aspiration as measured by detection of pepsin and bile acids in BAL. The sensitivity and specificity of pepsin in BAL compared with GERD by 24-h pH monitoring were respectively 60 and 45 %, whereas the sensitivity and specificity of bile acids in BAL were 67 and 80 %.

CONCLUSIONS

These data indicate that the measurement of pepsin and bile acids in BAL can provide additional data for identifying lung transplantation patients at risk for GERD-induced aspiration compared with symptoms or 24-h pH monitoring alone. These results support a diagnostic role for detecting markers of aspiration in BAL, but this must be validated in larger studies.

Gas exchange in the respiratory distress syndromes

This article describes the gas exchange abnormalities occurring in the acute respiratory distress syndrome seen in adults and children and in the respiratory distress syndrome that occurs in neonates. Evidence is presented indicating that the major gas exchange abnormality accounting for the hypoxemia in both conditions is shunt, and that approximately 50% of patients also have lungs regions in which low ventilation-to-perfusion ratios contribute to the venous admixture. The various mechanisms by which hypercarbia may develop and by which positive end-expiratory pressure improves gas exchange are reviewed, as are the effects of vascular tone and airway narrowing. The mechanisms by which surfactant abnormalities occur in the two conditions are described, as are the histological findings that have been associated with shunt and low ventilation-to-perfusion.

Regional pulmonary inflammation in an endotoxemic ovine acute lung injury model

The regional distribution of inflammation during acute lung injury (ALI) is not well known. In an ovine ALI model we studied regional alveolar inflammation, surfactant composition, and CT-derived regional specific volume change (sVol) and specific compliance (sC). 18 ventilated adult sheep received IV lipopolysaccharide (LPS) until severe ALI was achieved. Blood and bronchoalveolar lavage (BAL) samples from apical and basal lung regions were obtained at baseline and injury time points, for analysis of cytokines (IL-6, IL-1β), BAL protein and surfactant composition. Whole lung CT images were obtained in 4 additional sheep. BAL protein and IL-1β were significantly higher in injured apical vs. basal regions. No significant regional surfactant composition changes were observed. Baseline sVol and sC were lower in apex vs. base; ALI enhanced this cranio-caudal difference, reaching statistical significance only for sC. This study suggests that apical lung regions show greater inflammation than basal ones during IV LPS-induced ALI which may relate to differences in regional mechanical events.

Chorioamnionitis alters the response to surfactant in preterm infants

OBJECTIVE

To study the association between antenatal exposure to chorioamnionitis and the neonatal response to surfactant.

STUDY DESIGN

Prospective observational cohort of 301 preterm infants of gestational age < or = 32.0 weeks, 146 of whom received surfactant according to standardized criteria. Fraction of inspired oxygen (FiO(2)) requirement (using analysis of variance) and time to extubation (using Kaplan-Meier and Cox regression analyses) were compared between groups based on the presence of histological chorioamnionitis (HC) with or without fetal involvement (HC-, n = 88; HC + F-, n = 25; HC + F+, n = 33) and between infants who developed bronchopulmonary dysplasia (BPD) or died (n = 57) and BPD-free survivors (n = 89). Multiple logistic regression was performed to investigate the association between HC and BPD.

RESULTS

Compared with HC- infants, HC + F+ infants had significantly greater FiO(2) requirement and prolonged time to extubation postsurfactant, not accounted for by differences in gestational age and birth weight. Infants with BPD/death had a strikingly similar pattern of increased FiO(2) requirement postsurfactant. Moreover, in infants who received surfactant, HC + F+ status was associated with increased risk for BPD (odds ratio [OR] = 3.40; 95% confidence interval [CI] = 1.02-11.3; P = .047) and for BPD/death (OR = 2.72; 95% CI = 1.00-7.42; P = .049).

CONCLUSIONS

An impaired surfactant response was observed in preterm infants with severe chorioamnionitis and may be involved in the association between chorioamnionitis, mechanical ventilation, and the development of BPD.

INTERLEUKIN-6 HAS NO EFFECT ON SURFACTANT OR LUNG FUNCTION IN DIFFERENT LUNG INSULTS

The current study determined if interleukin-6 (IL-6) had a causative role in the lung dysfunction and/or surfactant alterations associated with three different lung insults. IL-6 (or saline) was instilled into rats followed by mechanical ventilation in vivo for 4 hours. Also, IL-6 (-/-) and wild-type mice were subjected to 3 insults: ex vivo injurious mechanical ventilation; cecal ligation and perforation; and hyperoxia exposure. In all experiments, the presence or absence of IL-6 did not significantly influence gas exchange, lung compliance, or various surfactant measurements. These results suggest that IL-6 may have a limited role in the surfactant alterations observed in acute lung injury.

Glutamine attenuates lipopolysaccharide-induced acute lung injury

OBJECTIVES

It has been reported that glutamine (GLN) can attenuate acute lung injury after sepsis. GLN is also thought to be a precursor of glutathione (GSH) synthesis. Using the GSH synthesis blocker, L-buthionine-(S,R)-sulfoximine (BSO), we investigated the role of GSH synthesis in the protective effect of GLN on acute lung injury.

METHODS

In this study, we used an acute lung injury model induced by intratracheal injection of lipopolysaccharide (1 mg mL(-1) kg(-1)). GLN (0.75 g/kg, intravenous) and BSO (2 mmol/kg, intraperitoneal) were administrated simultaneously. At 2 and 18 h after the injections, the rats were sacrificed by right ventricular puncture and bronchoalveolar lavage was done. The lower right lung was excised for histologic examination. Total protein concentration and total cell and neutrophil counts in the bronchoalveolar lavage fluid were determined. CD11b expression in the blood was determined by flow cytometry. We also analyzed myeloperoxidase activity, and GSH and interleukin-8 levels in lung tissues.

RESULTS

GLN supplementation reduced the total protein concentration and total cell and neutrophils counts in bronchoalveolar lavage fluid after lipopolysaccharide challenge. GLN enhanced GSH synthesis and attenuated interleukin-8 release and myeloperoxidase activity in lung tissues. GLN also decreased CD11b expression in blood neutrophils and prevented lung histologic changes. BSO abolished the effects of GLN and attenuated its protection on acute lung injury.

CONCLUSION

These results indicate that GLN could prevent neutrophil recruitment and infiltration, protect the alveolar barrier, and attenuate inflammatory injury during sepsis. This effect may be related to enhanced GSH synthesis.

Intestinal anastomosis surgery with no septic shock primes for a dysregulatory response to a second stimulus

BACKGROUND

Major surgery is believed to contribute to immune dysregulation and high susceptibility to microbes. Recently, the inflammatory "two-hit" model has been accepted to elucidate development of multiple organ failure in surgical patients. Our purpose was to examine whether intestinal surgery, which causes a minor insult with no septic shock, may modify the immune response to exogenous LPS as a second stimulus.

MATERIALS AND METHODS

Using a rat intestinal transection and anastomosis surgery model, we sequentially examined blood cell counts, body temperatures, and plasma cytokines. Rats were administered with LPS intravenously or intratracheally various days after surgery. Phagocytic activity and TNFalpha production in bronchoalveolar lavage (BAL) cells, plasma cytokines, and survival rates were evaluated.

RESULTS

The surgery itself caused no severe shock or circulating cytokine elevation, whereas the number of granulocytes in the blood was significantly elevated after surgery. LPS-induced elevation of circulating IFNgamma attenuated 3 days after surgery. In contrast, IL-10 was enhanced 3-10 days after surgery. Hyporesponsiveness of BAL cells to LPS was observed 3 days after surgery but not the next day after surgery. However, rats intratracheally exposed to LPS 10-13 days after surgery exhibited higher mortality.

CONCLUSIONS

Although our surgical procedure was not supposed to be a severe insult, it sufficiently primed rats for an altered response to a second stimulus (endotoxin), which included enhanced mortality. This study provided an improved understanding of pathophysiological changes following surgery and described a useful model for developing preventive and therapeutic strategies for complications after surgery.

Altered phospholipid composition and aggregate structure of lung surfactant is associated with impaired lung function in young children with respiratory infections

Alterations to pulmonary surfactant structure, composition, and function contribute to the severity of respiratory infections. Analysis of bronchoalveolar lavage fluid (BALF) from children undergoing diagnostic bronchoscopy for structural abnormalities (control group, n = 24), asthma (n = 18), lung infection (n = 30), and cystic fibrosis (CF, n = 15) showed that BALF phospholipid concentration decreased with age for the control group and was elevated in all disease groups. The fractional concentration of the major surface active component, dipalmitoyl phosphatidylcholine (PC16:0/16:0), correlated (r(2) = 0.608, P < 0.01) with airway resistance (FEV(1%) predicted), and decreased PC16:0/16:0 was accompanied by increased concentrations of phospholipid components characteristic of cell membranes (PC16:0/18:1 and PI18:0/20:4). Median minimal surface tension, measured by pulsating bubble surfactometer, was elevated (P < 0.01) in both infection (17.5 mN/m) and CF (17.1 mN/m) compared with the control group (1.5 mN/m). Centrifugation (60,000 x g, 40 min) of BALF indicated that infection was accompanied by accumulation of large aggregate forms of surfactant, in contrast to previous reports of increased conversion to inactive small aggregate surfactant particles in ventilated patients with respiratory failure. This accumulation of surface-inactive, large aggregate forms of surfactant, possibly due to mixing with membrane material from inflammatory cells, may contribute to severity of lung disease in children with respiratory infections.

Pulmonary surfactant and inflammation in septic adult mice: role of surfactant protein A

Surfactant alterations, alveolar cytokine changes, and the role of surfactant protein (SP)-A in septic mice were investigated. Sepsis was induced via cecal ligation and perforation (CLP). Septic and sham mice were euthanized at 0, 3, 6, 9, 12, 15, and 18 h after surgery. Mice deficient in SP-A and mice that overexpressed SP-A were euthanized 18 h after surgery. In wild-type, sham-operated mice, surfactant pool sizes were similar at all time points, whereas in the CLP groups there was a significant decrease in small-aggregate surfactant pool sizes beginning 6 h after CLP. Interleukin-6 concentrations in bronchoalveolar lavage fluid from septic animals increased from 6 to 18 h after surgery. Identical surfactant alterations and concentrations of cytokines were observed in septic mice that were SP-A deficient or that overexpressed SP-A. In conclusion, alterations of pulmonary surfactant and alveolar cytokines occur simultaneously, 6 h after a systemic insult. In addition, we did not detect a role for SP-A in regulating surfactant phospholipid pool sizes or pulmonary inflammation in septic mice.

Immunohistochemistry of pulmonary surfactant-associated protein A in acute respiratory distress syndrome

Acute respiratory distress syndrome (ARDS) is a fatal complication in severe traumas and diseases. Although the contribution of pulmonary surfactant abnormality to the pathogenesis of ARDS has been clinically fairly well investigated, the histopathological evidence has not been established. The aim of this study was to clarify the immunohistochemical distribution of surfactant-associated protein A (SP-A) for early diagnosis of ARDS with special regard to hyaline membrane (HM) formation. Two-hundred-and-ten autopsy cases of prolonged death from various traumas and diseases were investigated. ARDS were observed in 23 cases, showing speckled SP-A immunostaining. During the early, exudative phase of ARDS, characteristic SP-A distribution showed intense staining in the intra-alveolar massive aggregates and thick 'peeling'-like substances accompanied with a lot of granular staining. During the proliferative phase, localized accumulation of granular SP-A and macrophages containing dense granular SP-A became predominant. During the final fibrotic phase, SP-A staining in HMs became weak, and disseminated granular staining was observed in the alveolar spaces. These findings provide morphological evidence of the increase of SP-A during the early phase of ARDS, including some molecular alteration and its decrease during the late phase. Characteristic SP-A distribution in the exudative phase appeared to be especially useful for early histopathological diagnosis of respiratory distress, even prior to the appearance of typical HMs.

New bronchoscopic microsample probe to measure the biochemical constituents in epithelial lining fluid of patients with acute respiratory distress syndrome

OBJECTIVE

A noninvasive bronchoscopic microsampling (BMS) probe was developed to sample biochemical constituents of the epithelial lining fluid in small airways.

DESIGN

Observational, controlled study.

SETTING

Intensive care unit of academic medical center. PATIENTS AND PROCEDURE: BMS was applied in a control group of seven patients who had hemoptysis or small solitary peripheral nodules but no hypoxemia or other signs of acute inflammation and in four patients with acute respiratory distress syndrome (ARDS), to test whether BMS can ascertain the presence of acute pulmonary inflammation without complications.

MEASUREMENTS AND RESULTS

Complications, including a significant decrease in arterial oxygen saturation, were observed neither during nor after BMS. In the ARDS group, albumin, lactate dehydrogenase, interleukin-6, basic fibroblast growth factor, and neutrophil elastase concentrations in epithelial lining fluid were significantly higher (p <.0001, p =.012, p <.0001, p <.0001, and p <.0001, respectively) than in the control group. Serial BMS was safely performed in one patient with ARDS, allowing us to observe a correlation between changes in the concentration of inflammation-related biochemical markers and clinical course of the disease.

CONCLUSIONS

These results suggest that BMS is safe and useful to monitor pulmonary biochemical events in ARDS.

Immunohistochemistry of pulmonary surfactant apoprotein A in forensic autopsy: reassessment in relation to the causes of death

To reassess the immunohistochemical distribution of pulmonary surfactant apoprotein A (SP-A) in relation to the causes of death, 282 forensic autopsy cases were reviewed. The most intense and dense granular immunostaining of intra-alveolar SP-A was observed in the hyaline membrane syndrome from various traumas, protracted death from drowning, and perinatal aspiration of amniotic fluid. Similar granular staining pattern was found in fatal poisoning by a muscle relaxant and organophosphate pesticides. An evident increase of intra-alveolar granular staining was noted in most fatalities from mechanical asphyxia and drowning, and some cases of fire death. SP-A staining was usually very weak or sparse in alcohol intoxication, poisoning by hypnotics and also carbon monoxide poisoning. These findings suggest that the amount of intra-alveolar granular SP-A staining may be a possible indicator of severity and duration of respiratory distress (agony) from peripheral (non-central nervous system) origin and alveolar damage.

Surfactant replacement therapy

Dysfunction of the surfactant system of the lung in the setting of acute lung injury (ALI) is likely to contribute to the pathophysiology of that syndrome. Multiple mechanisms, including injury to alveolar type II cells and inhibition by plasma proteins contribute to this loss of function. Similar injury occurs in animal models of acute lung injury and, in that setting, treatment with exogenous surfactant causes marked improvement in gas exchange. Clinical studies of surfactant treatment of ALI suggest benefit, and definitive phase III trials are now in progress.