Phagocyte-induced lipid peroxidation of lung surfactant

Proteomic profiling for plasma biomarkers of tuberculosis progression

Severe pulmonary tuberculosis (STB) is a life-threatening condition with high economic and social burden. The present study aimed to screen for distinct proteins in different stages of TB and identify biomarkers for a better understanding of TB progression and pathogenesis. Blood samples were obtained from 81 patients with STB, 80 with mild TB (MTB) and 50 healthy controls. Differentially expressed proteins were identified using liquid chromatography-tandem mass spectrometry-based label-free quantitative proteomic analysis. Functional and pathway enrichment analyses were performed for the identified proteins. The expression of potential biomarkers was further validated by western blot analysis and enzyme-linked immunosorbent assays. The accuracy, sensitivity and specificity for selected protein biomarkers in diagnosing STB were also evaluated. A total of 1,011 proteins were identified in all three groups, and 153 differentially expressed proteins were identified in patients with STB. These proteins were involved in ‘cellular process’, ‘response to stimulus’, ‘apoptotic process’, ‘immune system process’ and ‘select metabolic process’. Significant differences in protein expression were detected in α-1-acid glycoprotein 2 (ORM2), interleukin-36α (IL-36α), S100 calcium binding protein A9 (S100-A9), superoxide dismutase (SOD)1 in the STB group, compared with the MTB and control groups. The combination of plasma ORM2, IL-36α, S100A9 and SOD1 levels achieved 90.00% sensitivity and 92.16% specificity to discriminate between patients with STB and MTB, and 89.66% sensitivity and 98.9% specificity to discriminate between patients with STB and healthy controls. ORM2, S100A9, IL-36α and SOD1 were associated with the development of TB, and have the potential to distinguish between different stages of TB. Differential protein expression during disease progression may improve the current understanding of STB pathogenesis.

Predicting disease onset in clinically healthy people

Virtually all human disease is induced by oxidative stress. Oxidative stress, which is caused by toxic environmental exposure, the presence of disease, lifestyle choices, stress, chronic inflammation or combinations of these, is responsible for most disease. Oxidative stress from all sources is additive and it is the total oxidative stress from all sources that induces the onset of most disease. Oxidative stress leads to lipid peroxidation, which in turn produces Malondialdehyde. Serum malondialdehyde level is an additive parameter resulting from all sources of oxidative stress and, therefore, is a reliable indicator of total oxidative stress which can be used to predict the onset of disease in clinically asymptomatic individuals and to suggest the need for treatment that can prevent much human disease.

Identifying the spatial distribution of vitamin E, pulmonary surfactant and membrane lipids in cells and tissue by confocal Raman microscopy

Every organ compromises of several different cell types. When studying the effects of a chosen compound within this organ or tissue uptake, localisation, metabolism, and the effect itself can be expected to differ between cells. Using the example of Vitamin E in pulmonary tissue we introduce confocal Raman Microscopy as a superior method to localise lipid-soluble compounds within tissues and cells. We describe the analyses of vitamin E, its oxidation products, and metabolites as well as pulmonary surfactant phospholipids in fixed lung tissue sections. Examples of main structural membrane lipids (PC, cholesterol) and an example of a lipid-signalling molecule (ceramide) are also included. Confocal Raman microscopy is a non-destructive optical method of analysing chemical and physical composition of solids, liquids, gases, gels, and solutions. The method is rich in information allowing discrimination of chemically similar molecules (including geometric isomers) and sensitive monitoring of subtle physical interactions. Additionally, Raman spectroscopy is relatively insensitive to water allowing the analysis of aqueous solutions and suspensions typical in biochemistry. In contrast, Raman spectroscopy is sensitive to non-polar molecules making it ideal for lipidomics research.

Aggregates of ultrafine particles modulate lipid peroxidation and bacterial killing by alveolar macrophages

We hypothesized that aggregates of ultrafine carbon and washed diesel particles impair the ability of alveolar macrophages (AM) to kill bacteria and enhance the AM lipid peroxidation (LPO) of lung surfactant. Rat AM were exposed, 5h, to particles 20 microg/ml. The AM, containing carbon or washed diesel particles, were incubated 2h, with Streptococcus pneumoniae, an American Type Culture Collection (ATCC) strain or clinical isolates. Surviving bacteria were quantified. Surfactant was incubated, 5h, with carbon or washed diesel loaded AM and LPO was measured. The particle load was approximately 1 microg/10(6) AM, representing accepted exposure to ambient particles in Europe. Metal concentrations were 10 to 100 fold higher in washed diesel--than in carbon particles. There was a dose dependent increase in bacterial survival with carbon-loaded macrophages, but not with washed diesel-loaded AM. Clinical isolates had a higher survival rate with carbon-loaded macrophages than the ATCC strain. Surfactant LPO was increased with washed diesel-loaded macrophages (95%) and with carbon-loaded macrophages (55%) compared to controls. High LPO caused by washed diesel-loaded AM reflects their increased oxidative metabolism, probably caused by particle metals. The additional oxygen metabolites maintained bactericidal activity of AM, while corresponding activity was decreased in carbon-loaded AM. Altered functions of AM may explain health problems related to air pollution.

The use of Raman microscopy to determine and localize vitamin E in biological samples

Alpha-tocopherol (aT), the predominant form of vitamin E in mammals, is thought to prevent oxidation of polyunsaturated fatty acids. In the lung, aT is perceived to be accumulated in alveolar type II cells and secreted together with surfactant into the epithelial lining fluid. Conventionally, determination of aT and related compounds requires extraction with organic solvents. This study describes a new method to determine and image the distribution of aT and related compounds within cells and tissue sections using the light-scattering technique of Raman microscopy to enable high spatial as well as spectral resolution. This study compared the nondestructive analysis by Raman microscopy of vitamin E, in particular aT, in biological samples with data obtained using conventional HPLC analysis. Raman spectra were acquired at spatial resolutions of 2-0.8 microm. Multivariate analysis techniques were used for analyses and construction of corresponding maps showing the distribution of aT, alpha-tocopherol quinone (aTQ), and other constituents (hemes, proteins, DNA, and surfactant lipids). A combination of images enabled identification of colocalized constituents (heme/aTQ and aT/surfactant lipids). Our data demonstrate the ability of Raman microscopy to discriminate between different tocopherols and oxidation products in biological specimens without sample destruction. By enabling the visualization of lipid-protein interactions, Raman microscopy offers a novel method of investigating biological characterization of lipid-soluble compounds, including those that may be embedded in biological membranes such as aT.

Spontaneous breathing or mechanical ventilation alters lung compliance and tissue association of exogenous surfactant in preterm newborn rabbits

In preterm infants with respiratory distress syndrome, surfactant administration followed by immediate extubation to spontaneous breathing with nasal continuous positive airway pressure reduces the need for mechanical ventilation. With this treatment approach, repeated doses of surfactant are rarely indicated. We used a rabbit model to test the hypothesis that exogenous surfactant therapy followed by spontaneous breathing results in a more sustained initial treatment response compared with treatment followed by mechanical ventilation. Preterm rabbits (gestational age 28.5 d) were treated with pharyngeal deposition of 200 mg/kg radiolabeled surfactant (14C-Curosurf) and randomized to 4 h of spontaneous breathing or mechanical ventilation or to a control group, killed immediately after surfactant administration. With pharyngeal deposition, 46 +/- 10% (mean +/- SEM) of the administered surfactant reached the lungs. The dynamic lung-thorax compliance was higher in spontaneously breathing compared with mechanically ventilated animals (median, 9.9 and 0.75 ml x cm H2O(-1) x kg(-1), respectively; p < 0.05). The relative distribution of 14C-Curosurf in bronchoalveolar lavage fluid and homogenized lung tissue showed a higher degree of tissue association in the spontaneously breathing animals [53 +/- 4 versus 26 +/- 3% (mean +/- SEM)] than in mechanically ventilated animals (p < 0.01), the latter figure being very similar to that of the control group (25 +/- 5%). There was a higher degree of lipid peroxidation and fewer microbubbles in bronchoalveolar lavage fluid from mechanically ventilated animals. We conclude that the initial lung tissue association of exogenous surfactant is impaired by mechanical ventilation. This is associated with a reduction of dynamic compliance and evidence of increased surfactant inactivation.

Lipid peroxidation of lung surfactant in experimental neonatal group B streptococcal pneumonia

Group B streptococcal (GBS) pneumonia, with neutrophilic granulocytes immigrating into the lungs, may occur in neonates. The incidence is particularly high among preterm infants, who often are treated with exogenous surfactant. We have previously demonstrated in vitro that neutrophils stimulated by GBS cause lipid peroxidation (LPO) and functional impairment of lung surfactant. The present study aimed at evaluating LPO of exogenous lung surfactant (Curosurf) and the protective effect of the natural antioxidant, vitamin E in immature ventilated newborn rabbits with experimental neonatal GBS pneumonia. There was a prominent proliferation of GBS in the lungs of animals treated with surfactant and ventilated for 5 h. GBS-infected rabbits had a higher LPO of lung lavage fluid than non-infected ones. The LPO could be diminished using vitamin E, which, however, did not affect bacterial proliferation. During the 5-h incubation period, mean lung-thorax compliance values were significantly lower in GBS-infected than in noninfected animals. We speculate that addition of vitamin E to exogenous surfactant preparations may improve their resistance to LPO and make them more suitable for treatment of neonates with pneumonia.

Lipid peroxidation of lung surfactant due to reactive oxygen species released from phagocytes stimulated by bacteria from children with cystic fibrosis

We used Pseudomonas aeruginosa, Burkholderia cepacia and Stenotrophomonas maltophilia, live or heat-killed, isolated from the airways of children with Cystic Fibrosis, to stimulate human neutrophils (PMN) and rat alveolar macrophages (AM) to produce reactive oxygen metabolites in the presence or absence of Curosurf, a natural porcine lung surfactant. We determined: (1) the amount of lipid peroxidation (LPO) as assessed by the amounts of malondialdehyde (MDA) and 4-hydroxyalkenals (4-HNE) using the LPO 586 test kit; (2) the production by AM of superoxide with the nitroblue tetrazolium test and (3) of nitric oxide (NO) with the Griess reaction. Stimulation of PMN or AM increases LPO of Curosurf and cell wall lipids. In both types of phagocytes, B. cepacia induced the highest LPO levels followed by P. aeruginosa and S. maltophilia. PMN, stimulated by live bacteria, induced higher LPO than those stimulated by heat-killed bacteria. B. cepacia stimulated AM to produce more superoxide and NO than did P. aeruginosa and S. maltophilia. The high phagocyte-stimulating ability of B. cepacia and its higher surfactant LPO than those of the other bacteria used in this in vitro study may play a role in vivo in the serious clinical condition known as the "Cepacia syndrome".

Prophylactic effects of recombinant human superoxide dismutase in neonatal lung injury induced by the intratracheal instillation of endotoxin in piglets

The efficacy of prophylactic endotracheal administration of superoxide dismutase (SOD) was assessed in an animal model of acute lung injury induced by intratracheal endotoxin in neonatal piglets. Twenty-one anesthetized piglets were studied and underwent mechanical ventilation. The animals received recombinant human SOD (5 or 20 mg/kg intratracheally) 10 min before induction of acute lung injury with intratracheal endotoxin (20 mg/kg). The PaO(2) values of the SOD-treated group remained higher than that of the control group until the end of the experiment. In contrast, the PaCO(2) values remained lower. Lung compliance remained higher. Thiobarbituric acid-reactive substances and albumin levels in the broncho-alveolar lavage fluid were more significantly increased in controls. Histologic examination showed that the degrees of atelectasis and edema in the SOD treatment group were milder than those of the control group. Thus, the present findings suggest that prophylactic treatment with SOD may be, at least in part, effective for alleviating acute lung injury caused by endotoxins.

Lipid peroxidation by alveolar macrophages challenged with Cryptococcus neoformans, Candida albicans or Aspergillus fumigatus

Increased formation of oxygen radicals has previously been shown for alveolar macrophages (AM) challenged with Cryptococcus neoformans cells opsonized with fresh serum or polyclonal immunoglobulin G. AM show similar responses to Candida albicans or Aspergillus fumigatus. Oxygen radicals are capable of damaging various macromolecules, including lipids. In the present study, lipid peroxidation (LPO) caused by AM incubated with the fungi was examined in the presence and absence of lung surfactant. The level of malonaldehyde was used as an indicator of LPO. AM damage was examined by electron microscopy (EM), by trypan blue exclusion and by counting the AM loss from culture dish to supernatant. Stimulation of AM by each fungus increased cellular LPO but did not affect AM viability. A slight surfactant LPO induced by AM alone was shown with significantly increased values after addition of each fungus. EM studies showed that dense lipid droplets, presumably consisting of oxidized lipids, were ingested in high amounts together with C. neoformans cells that had been opsonized in fresh serum, and in low amounts in combination with C. albicans. These processes were accompanied by increased numbers of AM in the supernatants. LPO and detachment of AM were counteracted by vitamin E. In the lungs, AM exposed to one of these fungal pathogens might promote peroxidation of surfactant lipids.

Interaction between lung surfactant and nitric oxide production by alveolar macrophages stimulated by group B streptococci

The major etiologic agent in neonatal pneumonia and meningitis is group B streptococci (GBS). Nitric oxide (NO) production by alveolar macrophages (AM) in response to Gram-positive bacteria such as GBS and the effect of surfactant on this production have received little attention. We studied production of NO by GBS-stimulated AM using the Griess reaction, the effect of lung surfactant on this NO production, and the possible lipid peroxidation (LPO) of surfactant caused by NO. The LPO test was used to measure surfactant peroxidation. Heat-killed and live GBS were found to stimulate NO production by rat alveolar macrophages, and the presence of interferon gamma (IFN-gamma) increased this stimulation in a synergistic manner. Curosurf(R), the natural surfactant used in our study, significantly reduced NO production in various sets of experiments. Lipid peroxidation of surfactant was noted when NO was produced by stimulated AM, a phenomenon that could be suppressed by NG-monomethyl L-arginine (L-NMMA), the inhibitor of NO synthase. In the lung of GBS-infected neonates, nitric oxide produced by AM might contribute to the destruction of surfactant caused by inflammatory cells. Pediatr Pulmonol. 2000; 30:106- 113.

Pulmonary aspiration and lung injury

Lung injury after aspiration, although very rare, is a feared and potentially devastating sequela after anaesthesia. This paper summarizes the most recent studies in aspiration lung injury focusing on its clinical epidemiology, new insights in its pathophysiology and innovative concepts in its prevention and therapy.