Decreased phosphatidylcholine in the lung fluid of patients with sarcoidosis

Altered fatty acid composition of lung surfactant phospholipids in interstitial lung disease

Deterioration of pulmonary surfactant function has been reported in interstitial lung disease; however, the molecular basis is presently unclear. We analyzed fatty acid (FA) profiles of several surfactant phospholipid classes isolated from large-surfactant aggregates of patients with idiopathic pulmonary fibrosis (IPF; n = 12), hypersensitivity pneumonitis (n = 5), and sarcoidosis (n = 12). Eight healthy individuals served as controls. The relative content of palmitic acid in phosphatidylcholine was significantly reduced in IPF (66.8 +/- 2.5%; means +/- SE; P < 0.01) but not in hypersensitivity pneumonitis (78.5 +/- 1.8%) and sarcoidosis (78.2 +/- 3.1%; control 80.1 +/- 0.7%). In addition, the phosphatidylglycerol FA profile was significantly altered in the IPF patients, with a lower relative content of its major FA, oleic acid, at the expense of saturated FA. In the phosphatidylcholine class, a significant correlation between the impairment of biophysical surfactant function and decreased percentages of palmitic acid was noted. We conclude that significant alterations in the FA profile of pulmonary surfactant phospholipids occur predominantly in IPF and may contribute to the disturbances of alveolar surface activity in this disease.

Elevated surfactant protein A in bronchoalveolar lavage fluids from sarcoidosis and hypersensitivity pneumonitis patients

Interstitial lung diseases often are accompanied by histopathologic evidence of alveolar type 2 cell alterations. In the alveolar milieu, the surfactant-specific protein A (SP-A) is a secretory product of alveolar type 2 cells. Therefore, we measured SP-A levels in bronchoalveolar lavage (BAL) fluids from patients with untreated sarcoidosis (n = 35) and hypersensitivity pneumonitis (HP [n = 10]) and compared the results with those from 21 healthy control subjects. In sarcoidosis patients, SP-A was markedly higher than in control subjects with a mean of 8.0 micrograms/ml of recovered BAL fluid +/- 0.7 SEM (p < 0.0001 compared with control subjects). In HP, SP-A values were comparable with those in sarcoidosis with a mean of 9.0 micrograms/ml +/- 1.7 SEM. Mean SP-A in the control group was 4.0 micrograms/ml +/- 0.3 SEM. These results suggest that SP-A secretion is stimulated in sarcoidosis and HP. Further studies seem justified to investigate the role of the surfactant system in interstitial lung diseases as well as the potential clinical usefulness of SP-A measurements in BAL.

The surfactant system of the adult lung: physiology and clinical perspectives

Pulmonary surfactant is synthesized and secreted by alveolar type II cells and constitutes an important component of the alveolar lining fluid. It comprises a unique mixture of phospholipids and surfactant-specific proteins. More than 30 years after its first biochemical characterization, knowledge of the composition and functions of the surfactant complex has grown considerably. Its classically known role is to decrease surface tension in alveolar air spaces to a degree that facilitates adequate ventilation of the peripheral lung. More recently, other important surfactant functions have come into view. Probably most notable among these, surfactant has been demonstrated to enhance local pulmonary defense mechanisms and to modulate immune responses in the alveolar milieu. These findings have prompted interest in the role and the possible alterations of the surfactant system in a variety of lung diseases and in environmental impacts on the lung. However, only a limited number of studies investigating surfactant changes in human lung disease have hitherto been published. Preliminary results suggest that surfactant analyses, e.g., from bronchoalveolar lavage fluids, may reveal quantitative and qualitative abnormalities of the surfactant system in human lung disorders. It is hypothesized that in the future, surfactant studies may become one of our clinical tools to evaluate the activity and severity of peripheral lung diseases. In certain disorders they may also gain diagnostic significance. Further clinical studies will be necessary to investigate the potential therapeutic benefits of surfactant substitution and the usefulness of pharmacologic manipulation of the secretory activity of alveolar type II cells in pulmonary medicine.

Lipid content of alveolar lining material collected by bronchoalveolar lavage. Improved methods for measuring the major lipid classes

Current methods for measuring lung lipids obtained by bronchoalveolar lavage are time consuming and require sample extraction with organic solvents. Here we utilized enzymatic methods for measuring the major phospholipid classes found in human bronchoalveolar lavage fluid (BALF), namely phosphatidylcholine and phosphatidylglycerol, as well as the neutral lipid cholesterol. These assays can be carried out on as little as 200 microliters lavage fluid in 96-well microtiter plates without the need for organic solvents. Results were verified by comparison with HPLC and chemical methods. The measured values by all three methods were in agreement with previous studies in which lipid analysis was performed by thin-layer chromatography. By contrast to thin-layer chromatography, however, the methods described here can be efficiently performed with small quantities of material without sacrificing accuracy. This methodology can facilitate the characterization of the major surfactant-associated lipids in BALF and foster improved understanding of the role of these lipids in human lung disease.

Effects of age and breed on the phospholipid composition of canine surfactant

To investigate possible age- and breed-related changes in the composition of canine pulmonary surfactant, we determined the phospholipid patterns of surfactants isolated by bronchoalveolar lavage of 3 age categories of beagles (3-7 months; 3-7 years; 12 years and older) and of 1 group of greyhounds (4-14 years). There was a significant (p = 0.01) increase in the proportion of phosphatidylcholine in surfactant with age, whereas the proportions of phosphatidylserine and sphingomyelin were significantly lower in old beagles compared to young dogs. Although the differences were generally rather small, they may nevertheless be of biological importance, as was indicated by comparing the minimal surface tensions of lavage fluids obtained from young and old beagles. It is attractive to speculate that the shift in surfactant lipid composition could be 1 of the mechanisms that permit efficient lung function in old dogs, despite changes in morphology and mechanics in the aging lung. The phospholipid composition of surfactant isolated from greyhounds differed significantly from that in beagles. The surfactant of greyhounds was enriched in phosphatidylglycerol compared to all age groups of beagles. The degree of saturation of surfactant phosphatidylcholine was also higher in greyhounds, although this differences was significant only when compared to young and middle-aged beagles.

Changes in phospholipids in bronchoalveolar lavage fluid of patients with interstitial lung diseases

We analyzed phospholipids of human bronchoalveolar lavage (BAL) fluids from patients with interstitial lung diseases; idiopathic pulmonary fibrosis (IPF), sarcoidosis, and eosinophilic granuloma (EG) and compared them to those of normal subjects. The content of phospholipid/ml of BAL fluid was significantly decreased in IPF. There was a significant decrease in phosphatidylglycerol (PG) and an increase in phosphatidylinositol (PI) in IPF but not in sarcoidosis and EG. Thus, the PG to PI ratio was significantly decreased in IPF. The dipalmitoyl species of phosphatidylcholine (PC) was found to be significantly decreased in IPF and sarcoidosis by molecular species analysis using high performance liquid chromatography. In contrast, the unsaturated species were increased in these diseases. The decrease in dipalmitoyl PC appeared to be a common feature in interstitial lung diseases. The changes in phospholipids in BAL fluids, especially decreases in DPPC and PG to PI ratio in IPF, appear to indicate that damage of alveolar Type II cells and/or of metabolic disturbance in pulmonary surfactant occurs in IPF.

Lipids in bronchoalveolar lavage fluid from patients with sarcoidosis

The recovery of protein and two specific surfactant lipids, phosphatidylcholine and phosphatidylglycerol, from bronchoalveolar lavage fluid is altered in chronic and acute non-granulomatous interstitial lung disease. This study set out to determine whether the same is true for patients with sarcoidosis. The median value for recovery of protein from lavage fluid was significantly higher in 21 patients with sarcoidosis than in 19 normal subjects (18 v 11 mg), while the median value for phospholipid recovery was significantly lower (4 v 1.7 mg). There were no changes in the proportions of phosphatidylcholine and phosphatidylglycerol. In addition, significantly less of the neutral lipid, cholesterol, was recovered (3.2 v 1.5 mg). The combined values of three biochemical measurements, non-phospholipid polar lipid, non-polar lipid, and protein, correctly classified all 40 subjects in our series; in a further group of nine normal subjects and 11 patients with sarcoidosis it allowed all but one normal subject to be classified correctly. These results are discussed in terms of alterations in epithelial cell function in interstitial disease.

Surfactant deficiency with decreased opsonic activity in a guinea pig model of alcoholism

Chronic alcoholism was induced in guinea pigs to quantitate the effect of alcohol on lung surfactant. Animals were studied after 6 weeks of treatment with either ethanol (ETH) or isocaloric dextrose saline (DEX) injections. The amount of surfactant retrieved by bronchoalveolar lavage (BAL) was evaluated by measuring the quantity of phosphatidylcholine (PC) and disaturated phosphatidylcholine (DSPC) in the fluid. The amount of DSPC recovered from the ETH animals (40.9 +/- 10.4 micrograms/ml of BAL fluid, mean +/- SD) was significantly lower than from the DEX animals (82.7 +/- 18.6 micrograms/ml of BAL fluid, p less than 0.001). This decrease in surfactant was associated with impairment of the opsonic activity from BAL fluid in the ETH versus DEX animals using a standard assay of bacterial (Staphylococcus aureus) killing with normal polymorphonuclear leukocytes and BAL fluid as an opsonin. We conclude that in the guinea pig model of alcoholism, surfactant deficiency occurs and has physiologic importance in reduced bacterial killing.