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 28,634 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Pulmonary surfactant is a complex mixture of phospholipids and proteins which is synthesized and secreted by alveolar type II cells. Its presence is essential to prevent the collapse of alveoli at the end of expiration. Recently, it has been demonstrated that in addition to its reduction of surface tension of alveolar surfaces, pulmonary surfactant exhibits several other functions in the alveolar lining layer, and surfactant proteins are definitely involved in the expression of these functions. The present study first focused on the recent advances in basic research of hydrophilic surfactant apoproteins, SP-A and SP-D. Both are glycoproteins with C-type lectin structure at the C-terminal region and collagenous structure at the N-terminal half of the proteins. We revealed that SP-A binds specifically to dipalmitoylphosphatidylcholine and galactose-ceramide and asialo GM2, while SP-D binds specifically to phosphatidylinositol and glucose-ceramide. We discuss the physiologic and metabolic roles of the specific lipid binding with surfactant proteins of the surfactant system. We next studied changes in pulmonary surfactant in respiratory diseases using anti-human SP-A monoclonal antibodies. We demonstrated SP-A immunoglobulin complex in the sera of patients with idiopathic pulmonary fibrosis and pulmonary alveolar proteinosis.
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PMID:[Biochemical and clinical aspects of pulmonary surfactant proteins]. 130 39

The most well characterized function of pulmonary surfactant is its ability to reduce surface tension at the alveolar air-liquid interface, thereby preventing lung collapse. However, several lines of evidence suggest that surfactant may also have 'non-surfactant' functions: specific components of surfactant (proteins and phospholipids) may interact with different alveolar cells, inhaled particles and micro-organisms modulating pulmonary host defence systems. SP-A, the most abundant surfactant protein, binds to alveolar macrophages via a specific surface receptor with high affinity [128]. Such binding effects the release of reactive oxygen species from resident alveolar macrophages if SP-A is properly presented to the target cell. SP-A also stimulates chemotaxis of alveolar macrophages [142], and serves as an opsonin in the phagocytosis of herpes simplex virus [161] Candida tropicalis [138] and various bacteria [137]. In addition, SP-A enhances the uptake of particles by monocytes and culture-derived macrophages [140] and improves bacterial killing. SP-D, another hydrophobic surfactant-associated protein, might interact with alveolar macrophages as well, stimulating the release of oxygen radicals [148], while for the hydrophilic surfactant proteins SP-B and SP-C no macrophage interactions have been described so far. SP-A and SP-D are members of the so-called 'collectins', pattern recognition molecules involved in first line defence. While some surfactant proteins appear to stimulate certain macrophage defence functions, surfactant phospholipids seem to inhibit those of lymphocytes. Suppressed lymphocyte functions include lymphoproliferation in response to mitogens and alloantigens, B cell immunoglobulin production and natural killer cell cytotoxicity. Concerning surfactant's phospholipid composition phosphatidylglycerol is more suppressive than phosphatidylcholine on a molar basis [38]. Bovine surfactant has an immunosuppressive effect on the development of hypersensitivity pneumonitis in a guinea pig model [150]. Despite these interesting observations, several important questions concerning the interactions of surfactant components with pulmonary host defence systems remain unanswered. Sufficient host defence in the lungs works through various humoral-cellular systems in conjunction with the specific anatomy of the airways and the gas exchange surface--how does the surfactant system fit into this network? Surfactant and alveolar cells are both altered during lung injury--is there a relationship between alveolar cells from RDS patients and the endogenous surfactant isolated from such patients? How does exogenous surfactant as used for substitution therapy modulate the defence system of the host? Some of those artificial surfactants have been shown to inhibit the endotoxin-alveolar macrophages, PMNs and monocytes including IL-1, IL-6 and TNF [139,152].(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Host defence capacities of pulmonary surfactant: evidence for 'non-surfactant' functions of the surfactant system. 782 30

Genetic ablation of the murine SP-B gene in transgenic mice caused lethal perinatal respiratory distress in homozygous offspring, whereas heterozygous SP-B (+/-) mice survived postnatally. In adult SP-B(+/-) mice, surfactant protein B mRNA and the alveolar lavage SP-B protein were reduced by 50% compared with wild-type littermates, consistent with the inactivation of a single SP-B allele. Expression of SP-A, SP-C, and SP-D proteins was not affected in SP-B(+/-) mice. Heterozygous SP-B(+/-) mice reached maturity in numbers expected by Mendelian inheritance of a recessive gene. Lung morphology and both intracellular and extracellular phospholipid pool size and composition were unaltered in the SP-B(+/-) mice. Despite normal survival, pulmonary function studies demonstrated a consistent decrease in lung compliance in SP-B(+/-) mice. Abnormalities of inflation/deflation curves demonstrated airway collapse at low deflation pressures. Residual volumes were increased in the SP-B(+/-) mice. In summary, SP-B mRNA and SP-B protein were reduced by 50% in SP-B(+/-) mice, resulting in abnormalities of lung compliance and air trapping, suggesting a potential susceptibility to pulmonary dysfunction associated with SP-B deficiency.
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PMID:Decreased lung compliance and air trapping in heterozygous SP-B-deficient mice. 899 78

Cigarette smoking is a most important factor of COPD. IL-8 is elevated by cigarette smoking and increases the number of neutrophils in the lung. Surfactant is a complex mixture of phospholipids (PL) and proteins (SP). Both PL and SPs (SP-A and SP-D) decrease in bronchoalveolar lavage fluid in smokers. Decrease of PL enhances injury by elastase secreted from neutrophils and induces collapse of bronchioles, and decrease of SP-A and SP-D attenuate the defense against microbial agents in peripheral airways. Surfactant is thereby associated with COPD. However, little is known about the interaction, which induces COPD, between cytokines and surfactant. Further investigations are needed to clarify the mechanism on onset of COPD.
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PMID:[Cytokines and surfactant as a factor of onset and progression of COPD]. 1049 93

We evaluated the clinical significance of surfactant proteins A (SP-A) and D (SP-D) as useful markers of disease activity in patients with diffuse interstitial pneumonia. Serum concentrations of SP-A and SP-D were measured by the sandwich ELISA method. The serum levels of SP-A and SP-D in patients with diffuse interstitial pneumonia (IIP, CVD-IP, HP, Ra-IP) were significantly higher than the levels in healthy controls, and showed high positive rates. IIP patients characterized by a predominantly ground-glass opacity (GGO) pattern on high-resolution computed tomograms had significantly higher concentrations of serum SP-A. Elevated SP-D levels reflected the extent not only of GGO but also of parenchymal collapse opacity (PCO). It is likely that the mechanisms behind the elevation of SP-A and SP-D do not correlate with pathologic changes in IIP. Serum SP-A and SP-D levels obtained at the time of initial evaluation from 9 patients who died after less than 3 years of follow-up were significantly higher than in patients with survival rates of more than 3 years. Serum SP-A and SP-D may be useful biomarkers of disease activity in patients with IIP.
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PMID:[Surfactant proteins A and D as biomarkers of disease activity in diffuse interstitial pneumonia]. 1084 95

The lung is composed of a series of branching conducting airways that terminate in grape-like clusters of delicate gas-exchanging airspaces called pulmonary alveoli. Maintenance of alveolar patency at end expiration requires pulmonary surfactant, a mixture of phospholipids and proteins that coats the epithelial surface and reduces surface tension. The surfactant lining is exposed to the highest ambient oxygen tension of any internal interface and encounters a variety of oxidizing toxicants including ozone and trace metals contained within the 10 kl of air that is respired daily. The pathophysiological consequences of surfactant oxidation in humans and experimental animals include airspace collapse, reduced lung compliance, and impaired gas exchange. We now report that the hydrophilic surfactant proteins A (SP-A) and D (SP-D) directly protect surfactant phospholipids and macrophages from oxidative damage. Both proteins block accumulation of thiobarbituric acid-reactive substances and conjugated dienes during copper-induced oxidation of surfactant lipids or low density lipoprotein particles by a mechanism that does not involve metal chelation or oxidative modification of the proteins. Low density lipoprotein oxidation is instantaneously arrested upon SP-A or SP-D addition, suggesting direct interference with free radical formation or propagation. The antioxidant activity of SP-A maps to the carboxyl-terminal domain of the protein, which, like SP-D, contains a C-type lectin carbohydrate recognition domain. These results indicate that SP-A and SP-D, which are ubiquitous among air breathing organisms, could contribute to the protection of the lung from oxidative stresses due to atmospheric or supplemental oxygen, air pollutants, and lung inflammation.
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PMID:Pulmonary surfactant proteins A and D are potent endogenous inhibitors of lipid peroxidation and oxidative cellular injury. 1096 75

Idiopathic pulmonary fibrosis (IPF) is a progressive, life-threatening, interstitial lung disease of unknown etiology. For optimal therapeutic management of IPF an accurate tool is required for discrimination between reversible and irreversible types of the disease. However, such noninvasive tools are few, and even with high-resolution computed tomography (HRCT), which is the most trusted method for doing so, the nature of the disease activity in IPF cannot always be accurately predicted. The aims of the present study were to assess the values of surfactant protein (SP)-A and SP-D in semiquantifying the extent of disease in IPF and in predicting deterioration in restrictive pulmonary function and survival over a follow-up period of 3-yr. SP-A and SP-D in sera were measured with enzyme-linked immunosorbent assays as previously described. Fifty-two IPF patients were studied to evaluate the association between serum SP-A and SP-D and disease extent on HRCT, deterioration in pulmonary function, and survival during 3 yr of follow-up. Both SP-A and SP-D concentrations were significantly correlated with the extent of alveolitis (a reversible change), whereas they did not correlate with the progression of fibrosis (an irreversible change). The SP-D concentration, unlike that of SP-A, was also related to the extent of parenchymal collapse and the rate of deterioration per year in pulmonary function. The concentrations of SP-A and SP-D in patients who died within 3 yr were significantly higher than in patients who were still alive after 3 yr. We propose that assays of SP-A and SP-D in sera from IPF patients are useful tools for understanding some pathologic characteristics of the disease, that SP-D may be a good predictive indicator of the rate of decline in pulmonary function, and that a combination of the assays for SP-A and SP-D may be helpful in predicting the outcome of patients with IPF.
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PMID:Serum surfactant proteins A and D as prognostic factors in idiopathic pulmonary fibrosis and their relationship to disease extent. 1098 38

Mammalian lung surfactant is a mixture of phospholipids and four surfactant-associated proteins (SP-A, SP-B, SP-C, and SP-D). Its major function is to reduce surface tension at the air-water interface in the terminal airways by the formation of a surface-active film highly enriched in dipalmitoyl phosphatidylcholine (DPPC), thereby preventing alveolar collapse during expiration. SP-A and SP-D are large hydrophilic proteins, which play an important role in host defense, whereas the small hydrophobic peptides SP-B and SP-C interact with DPPC to generate and maintain a surface-active film. Surfactant replacement therapy with bovine and porcine lung surfactant extracts, which contain only polar lipids and SP-B and SP-C, has revolutionized the clinical management of premature infants with respiratory distress syndrome. Newer surfactant preparations will probably be based on SP-B and SP-C, produced by recombinant technology or peptide synthesis, and reconstituted with selected synthetic lipids. The development of peptide analogues of SP-B and SP-C offers the possibility to study their molecular mechanism of action and will allow the design of surfactant formulations for specific pulmonary diseases and better quality control. This review describes the hydrophobic peptide analogues developed thus far and their potential for use in a new generation of synthetic surfactant preparations.
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PMID:Surfactant protein B and C analogues. 1100 26

Pulmonary surfactant ( PS ) compromises lipids and surfactant proteins (SP) and lines on the alveolar air-liquid interface. It can reduce surface tension, prevent alveoli from collapse and reduce alveoli edema by disaturated dipalmitoylphosphatidylcholine. It also modulates the pulmonary immunology by SP-A and SP-D. In this study,we established a rat model of immunocompromised host (ICH) with pulmonary infection of Pseudomonas aeruginosa (P. aeruginosa), then studied its pulmonary inflammatory reaction and analyzed the concentration of lipids and SP-A in bronchoalveolar lavage fluid (BALF) during infection.
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PMID:Inflammatory reaction and alterations of pulmonary surfactant in Pseudomonas Aeruginosa pneumonia in immunocompromised rats. 1217 3

Derangement in pulmonary surfactant or its components and alveolar collapse are common findings in idiopathic pulmonary fibrosis (IPF). Surfactant proteins play important roles in innate host defense and normal function of the lung. We examined associations between IPF and genetic polymorphic variants of surfactant proteins, SP-A1, SP-A2, SP-B, SP-C, and SP-D. One SP-A1 (6A(4)) allele and single nucleotide polymorphisms (SNPs) that characterize the 6A(4) allele, and one SP-B (B1580_C) were found with higher frequency ( P</=0.01) in nonsmoker and smoker IPF ( n=84) subgroups, respectively, compared with healthy controls ( n=194). To explore whether a tryptophan (present in 6A(4)) or an arginine (present in other SP-A1 alleles and in all SP-A2 alleles) at amino acid 219 alters protein behavior, two truncated proteins that varied only at amino acid 219 were oxidized by exposure to ozone. Differences in the absorption spectra (310-350 nm) between the two truncated recombinant SP-A proteins were observed both before and after protein oxidation, suggesting allele-specific aggregation differences attributable to amino acid 219. The SP-B SNP B1580_C (odds ratio:7.63; confidence interval:1.64-35.4; P</=0.01), to be a risk factor for IPF smokers, has also been shown to be a risk factor for other pulmonary diseases. The SP-C and SP-D SNPs and SP-B-linked microsatellite markers studied did not associate with IPF. These findings indicate that surfactant protein variants may serve as markers to identify subgroups of patients at risk, and we speculate that these contribute to IPF pathogenesis.
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PMID:Surfactant protein A and B genetic variants predispose to idiopathic pulmonary fibrosis. 1368 Mar 61


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