Vol. 86, Issue 2, 633-640, February 1999
Experimental neonatal respiratory failure induced by
lysophosphatidylcholine: effect of surfactant treatment
Gertie
Grossmann,
Katsumi
Tashiro,
Tsutomu
Kobayashi,
Yasuhiro
Suzuki,
Yutaka
Matsumoto,
Yuko
Waseda,
Toyoaki
Akino,
Tore
Curstedt, and
Bengt
Robertson
Division for Experimental Perinatal Pathology, Department of Woman
and Child Health, Karolinska Institute, S-171 76 Stockholm; Department
of Clinical Chemistry, Karolinska Hospital, S-171 76 Stockholm, Sweden;
Department of Anesthesiology, Kanazawa University, Kanazawa 920;
Department of Molecular Pathology, Kyoto University, Kyoto 606; and
Department of Biochemistry, Sapporo Medical College, Sapporo 060, Japan
 |
ABSTRACT |
The purpose of this study was to characterize the toxic effects
of lysophosphatidylcholine (lyso-PC) on neonatal lung function. Various
doses of lyso-PC (from 0 to 40 mg/kg) were administered to near-term
newborn rabbits. Lung-thorax compliance during mechanical ventilation
was significantly decreased by doses 
10 mg/kg, and static lung
volumes during deflation were decreased by doses 20 mg/kg. Using the
same experimental model, we investigated the effects of modified
porcine surfactant (Curosurf, 200 mg/kg). Animals exposed to lyso-PC at
birth and treated simultaneously with surfactant showed a satisfactory
therapeutic response, whereas those treated after 30 min failed to
respond. These animals also had a much larger leak of albumin into the
air spaces and an elevated minimum surface tension of the lavage fluid
in a pulsating bubble surfactometer, suggesting inactivation of the
exogenous surfactant. Timing of surfactant administration may thus be
essential for the therapeutic effect in this experimental model of
acute lung injury.
respiratory distress syndrome; animals; newborn; rabbits; respiratory mechanics; lung protein leakage
| |
INTRODUCTION |
THE LUNGS ARE STABILIZED by a film of saturated
phosphatidylcholine, especially dipalmitoylphosphatidylcholine,
lowering surface tension to near 0 mN/m at low lung volumes (24).
Lysophosphatidylcholine (lyso-PC) is a catabolic product resulting from
breakdown of phosphatidylcholine by phospholipase
A2. Lyso-PC is toxic to the lungs
even in small amounts (2, 19, 20, 28) but is rapidly cleared from the airways under normal conditions to become reacylated in the recycling machinery of the surfactant system (12, 13, 25). The lyso-PC normally
present in alveolar surfactant comprises only ~1% of total
phospholipids in that compartment (16).
Lyso-PC is surface active in the sense that it adsorbs at an air-water
interface, reducing equilibrium surface tension below that of water.
High levels of lyso-PC in the alveolar spaces may fluidize the surface
film (11) and destabilize the alveoli at end expiration. This
pathophysiological event could be triggered in the lung by a release of
phospholipase A2 from invading
bacteria (4), or by circulating high levels of the enzyme in patients with pancreatitis (22), and it could eventually lead to the type of
respiratory failure known as acute respiratory distress syndrome. The
purpose of the present study is to characterize acute lung injury in
mature newborn rabbits triggered by administration of lyso-PC via the
airways and to analyze the therapeutic effect of exogenous surfactant
in this model, with particular reference to lung protein leakage and
evidence of surfactant inactivation.
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METHODS |
Lyso-PC, Surfactant, and Pulsating Bubble Measurements
Lyso-PC
[L-
-lysophosphatidylcholine,
palmitoyl (C16:0)] was
purchased from Sigma Chemical (St. Louis, MO). Its inhibitory effects
on surfactant were first evaluated in vitro. Natural adult rabbit
surfactant, isolated from lung lavage fluid by sucrose density-gradient
centrifugation (10), was suspended in normal saline at a concentration
of 20 mg/ml, and this suspension was then mixed with an equal volume of
lyso-PC in saline (40 mg/ml), resulting in final concentrations of 10 and 20 mg/ml, respectively. Lower concentrations of lyso-PC in
surfactant were obtained by adding increasing volumes of the surfactant
suspension. The samples were incubated at room temperature for at least
1 h before use. The surface properties of these mixtures were examined
at 37°C with a pulsating bubble surfactometer (Electronetics,
Buffalo, NY) (7). Values for surface tension at maximum and minimum bubble size were recorded after 5 min of pulsation, during
which the radius of the bubble oscillated between 0.55 and 0.40 mm at a
rate of 40 cycles/min; this corresponds to 50% cyclic
surface compression. Similar experiments were performed with Curosurf (Chiesi Farmaceutici, Parma, Italy), a clinically used, modified natural surfactant prepared from pig lungs by extraction with organic
solvents and liquid-gel chromatography (23). This surfactant contains
only polar lipids and ~1% of hydrophobic proteins [surfactant protein (SP)-B and SP-C in approximate molar proportions 1:2]. For the pulsating bubble measurements, mixtures of Curosurf (diluted to
10 mg/ml) and lyso-PC (at concentrations ranging from 0 to 2.5 mg/ml)
were prepared as outlined above. Homogenous mixing could not be
obtained in samples containing 5 mg/ml lyso-PC, so the effects of
these higher concentrations on Curosurf were not examined.
Animal Experiments
Experiments were carried out on near-term newborn rabbits delivered by
hysterotomy at a gestational age of 29.5 days (term, 31 days). At this
stage of fetal development the lungs are mature, and adequate amounts
of surfactant phospholipids have accumulated in the air spaces. The
lungs are thus easily expanded at birth, retain air already after the
first breath, and can be ventilated with a low transpulmonary pressure
(21). Two different protocols were applied, as detailed below.
Protocol 1: Dose-response study. The
animals were weighed and tracheotomized at birth and received via the
tracheal cannula 4 ml/kg of various concentrations of lyso-PC in saline
(0-10 mg/ml; corresponding to a dose range of 0-40 mg/kg).
These dose levels were chosen on the basis of data from Fornasier et
al. (9) showing, under similar experimental conditions, biochemical
evidence of lung injury (increased lactic dehydrogenase activity in
bronchoalveolar lavage fluid) after administration of lyso-PC at a dose
of either 16 or 40 mg/kg, particularly with the higher dose.
After the tracheotomy procedure, the animals were transferred to a
system of body plethysmographs heated to 37°C. They were ventilated
in parallel with a common ventilator system (Servo Ventilator 900 B,
Siemens-Elema, Solna, Sweden) delivering 100% oxygen at a frequency of
40 breaths/min and an inspiration-to-expiration ratio of
1:1. Tidal volumes were recorded intermittently with a specially
designed Fleisch tube connected to the plethysmograph box, a
differential pressure transducer, an amplifier, and an integrator unit
(EMT 32, EMT 31, and EMT 41, Siemens-Elema). Insufflation pressure was
adjusted individually without limitation to generate tidal volumes of
~10 ml/kg (27). Electrocardiogram was recorded from needle electrodes
at regular intervals. Animals were ventilated for 120 min and then
killed by intracerebral injection of lidocaine (causing an immediate
cardiac arrest). The abdomen was opened and the diaphragm examined for
evidence of pneumothorax. Then the chest was opened and the blood
sampled from the usually bulging right ventricle for determination of
PCO2 and pH.
PRESSURE-VOLUME RECORDINGS.
The lungs were allowed to collapse for 30-60 min after the
blood-gas measurements and were then connected via the tracheal tube to
a system for parallel pressure-volume recordings (8). Static lung
volumes were recorded during stepwise
5-cmH2O increments up to an
insufflation pressure of 30 cmH2O
and during a corresponding deflation maneuver. One minute of stress
relaxation was allowed at each pressure level. Volume measurements were
corrected for compression in the system.
HISTOLOGICAL EXAMINATION.
A catheter was tied in the pulmonary trunk, and the lungs were again
expanded at a transpulmonary pressure of 30 cmH2O for 1 min. The pressure was
then lowered to 10 cmH2O, which
was maintained while the lungs were fixed by vascular perfusion with
4% formaldehyde via the pulmonary arteries at a pressure of 65 cmH2O. The lungs were stored in
the same fixative and embedded in paraffin for histological
examination, with particular reference to the alveolar expansion
pattern and the presence of airway epithelial necrosis, alveolar
hyaline membranes, hemorrhage, and recruitment of inflammatory cells to
the air spaces. Alveolar volume density was determined by conventional
point counting using total parenchyma as reference volume. The
histological examination was done on coded sections, i.e., without
knowledge of the experimental conditions of individual animals.
Protocol 2: Timing of surfactant treatment, lung
leakage of serum albumin, and surfactant inactivation.
In a second series of animals, tracheotomized and ventilated as
described above, we compared the effects of exogenous modified natural
surfactant (Curosurf) administered via the tracheal tube at two
different time points. In these experiments, we tested the hypothesis
that an exogenous surfactant would be more effective when administered at birth than after a period of ventilation allowing leakage of plasma
proteins into the air spaces.
The animals were allocated at random to four subgroups, receiving
1) lyso-PC (10 mg/kg) at birth
without concomitant or subsequent treatment with surfactant;
2) lyso-PC (10 mg/kg) at birth
together with the recommended clinical dose of Curosurf (200 mg/kg);
3) lyso-PC (10 mg/kg) at birth
followed by treatment with Curosurf (200 mg/kg) after 30 min of
mechanical ventilation; and 4)
normal saline (4 ml/kg) via the airways at birth, without concomitant or subsequent surfactant treatment. All animals received at birth an
intravenous injection of 10% human albumin (Sigma Chemical; dose 7 ml/kg) via a jugular vein exposed during the tracheotomy procedure. The
human albumin served as a lung permeability marker (1) and was
quantified by immunodiffusion (LC-Partigen plates, Behring, Marburg,
Germany) in lung lavage fluid obtained at the end of the experiments.
The lungs were washed via the tracheal cannula with normal saline. A
volume of liquid, corresponding to 40 ml/kg body wt, was instilled and
withdrawn twice, and this double lavage was repeated with fresh saline
five times (total lavage volume 200 ml/kg; average recovery 93%,
without differences among the groups). The volume of fluid recovered
was recorded, and an aliquot was used for analysis of human albumin.
The vascular-to-alveolar leakage of albumin was expressed as percentage
of the injected amount of the marker.
In animals receiving surfactant, we also determined total phospholipids
in the lavage fluid, using the method of Bartlett (3). In addition,
surface properties of the crude lavage fluid were determined with
pulsating bubble by using the method described above (7).
Pressure-volume properties were not recorded in these experiments, and
since the lungs were lavaged, we made no efforts to evaluate alveolar
expansion in histological sections.
Statistical Evaluation
Values are presented as means ± SD or as median and range when not
normally distributed. Differences between groups were evaluated with
ANOVA followed by the Newman-Keuls test. The
2 test was used for comparison
of survival rates among groups and linear regression analysis for
assessment of correlations between compliance, albumin leakage, and
surface tension of lung lavage fluid. The limit level of statistical
significance was defined as P = 0.05.
| |
RESULTS |
In Vitro Assessment of Surfactant Inactivation by Exposure to
Lyso-PC
Surface properties of natural rabbit surfactant (10 mg/ml) mixed with
various concentrations of lyso-PC are shown in Table 1. These data, based on measurements with
pulsating bubble, show a significant elevation of minimum surface
tension at concentrations of lyso-PC 2.5 mg/ml, indicating surfactant
inactivation. There was a concomitant elevation of maximum surface
tension at lyso-PC concentrations of 2.5 and 20 mg/ml. Corresponding
data for Curosurf also shown in Table 1 demonstrate that this
surfactant is more easily inactivated, as reflected by elevated values
for maximum and minimum surface tension already at a lyso-PC
concentration of 1.25 mg/ml (P < 0.01 vs. natural rabbit surfactant).
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Table 1.
Surface properties of natural rabbit surfactant and Curosurf mixed with
different amounts of lyso-PC and assessed with a pulsating
bubble surfactometer
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Animal Experiments
Protocol 1. A survey of animals used
for studies of lung compliance and lung morphology after exposure to
various doses of lyso-PC is given in Table
2. There were no differences in body weight, survival rate, or final heart rate among the groups.
PCO2 in heart blood was increased
significantly in animals receiving the highest dose of lyso-PC
(P < 0.05 vs. controls), and this was associated with a significant fall in pH
(P < 0.01).
TIDAL VOLUME AND COMPLIANCE MEASUREMENTS.
Mean tidal volume was kept between 10 and 11 ml/kg throughout the
period of ventilation, without difference among the groups (data not
shown). The maximum peak insufflation pressure used in this series of
experiments was 37.5 cmH2O. Final
values for lung-thorax compliance, recorded after 120 min in animals
receiving different doses of lyso-PC without supplementary surfactant,
are shown in Fig. 1. The fall in compliance
after exposure to lyso-PC was clearly dose dependent, and statistically
significant differences vs. the control animals were found for doses
10 mg/kg.
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Fig. 1.
Lung-thorax compliance recorded after 120 min of artificial ventilation
in near-term newborn rabbits receiving different doses of
lysophosphatidylcholine (lyso-PC) via the airways
(protocol 1). Bars represent mean
and SD values; n = no. of rabbits.
** P < 0.01 vs. 0 mg/kg
lyso-PC.
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PRESSURE-VOLUME RECORDINGS.
Static lung volumes at maximum insufflation pressure and at deflation
pressure of 5 cmH2O in animals
exposed to different doses of lyso-PC are shown in Fig.
2. At both pressure levels, lung volumes
decreased with increasing doses of lyso-PC, and differences vs. the
control group were statistically significant
(P < 0.01) for lyso-PC doses 20
mg/kg.
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Fig. 2.
Static lung volume measurements at insufflation pressure of 30 cmH2O and deflation pressure of 5 cmH2O in animals exposed to
different doses of lyso-PC (protocol
1). At both pressure levels, lung volumes decrease
with increasing doses of lyso-PC. Bars represent mean and SD values.
Differences vs. control group are statistically significant at lyso-PC
doses 20 mg/kg. ** P < 0.01 vs. 0 mg/ml lyso-PC.
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HISTOLOGICAL OBSERVATIONS.
Twenty-three of the twenty-four animals receiving lyso-PC at doses 5
mg/kg had histological evidence of lung injury, characterized by focal
alveolar collapse (Fig.
3A),
usually associated with necrosis and desquamation of airway epithelium
(Fig.
4A),
mild-to-moderate recruitment of granulocytes to the air spaces (Fig.
4B), and some interstitial and
intra-alveolar hemorrhage (Fig. 4C).
Alveolar hyaline membranes were observed in two animals receiving 10 and 20 mg/kg of lyso-PC and in four of the six animals receiving 40 mg/kg of lyso-PC (Fig. 4D). In one
animal exposed to 20 mg/kg of lyso-PC, no histological abnormalities
were found. One of the six animals receiving the lowest dose of
lyso-PC, 2.5 mg/kg, had histological evidence of lung injury, similar
to that in animals exposed to higher doses. In the remaining five
animals in this group and in the five nonexposed control animals, the
lungs were unremarkable (Fig. 3B).
Animals receiving lyso-PC showed a dose-dependent decrease in alveolar
volume density, statistically significant at doses 10 mg/kg (Table
3). As illustrated in Fig.
3A, animals exposed to larger doses of
lyso-PC had an irregular alveolar expansion pattern, contrasting to the
uniform expansion in controls.
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Fig. 3.
Low-power microphotographs showing patchy alveolar collapse in animal
exposed to lyso-PC at a dose of 10 mg/kg
(A), and uniform expansion pattern
in control animal receiving no material via the airways
(B)
(protocol
1). Hematoxylin and eosin stain,
magnification ×82.
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Fig. 4.
Details showing various features of lung injury in animals receiving
different doses of lyso-PC (protocol
1).
A: necrosis and desquamation
of airway epithelium (arrow) in bronchiole adjacent to area of alveolar
collapse. Dose of lyso-PC: 10 mg/kg.
B: area of alveolar collapse with
slight accumulation of granulocytes in the air spaces
(top right). Dose of lyso-PC: 10 mg/kg. C: focal interstitial and
intra-alveolar hemorrhage and necrosis and desquamation of airway
epithelium in a neighboring bronchiole (asterisks). Dose of lyso-PC: 40 mg/kg. D: subpleural area with
prominent alveolar hyaline membranes. Dose of lyso-PC: 40 mg/kg.
Hematoxylin and eosin stain, magnification ×160.
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Protocol 2. A survey of the four
groups of animals used for this part of the study is given in Table 2.
There were no differences in body weight, survival rate, and final
heart rate among the groups. Values for
PCO2 were increased in animals
exposed to lyso-PC without receiving surfactant or treated with
surfactant after 30 min (P < 0.05 vs. controls).
TIDAL VOLUME AND COMPLIANCE MEASUREMENTS.
Mean tidal volumes ranged between 10 and 11 ml/kg throughout the period
of ventilation, without difference among the groups (data not shown).
The maximum peak insufflation pressure used in this arm of our study
was 33 cmH2O. Values for
lung-thorax compliance at different time intervals in the four groups
of animals are shown in Fig. 5. As in
animals studied according to protocol 1, exposure to lyso-PC led to a significant reduction
in compliance. This difference was established already at the first
time point (15 min). Administration of surfactant together with lyso-PC
prevented this fall in compliance. The difference between animals
receiving only lyso-PC and those receiving lyso-PC plus surfactant at
birth was statistically significant at all intervals
(P < 0.01-0.05), except at 45 and 90 min. Treatment with surfactant 30 min after the onset of
ventilation had no effect on lung compliance, which remained,
throughout the course of the experiment, at the same low level as in
animals exposed to lyso-PC without receiving surfactant.
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Fig. 5.
Lung-thorax compliance at various time intervals after onset of
ventilation in various groups of experimental animals and littermate
controls (protocol 2). Bars
represent mean and SD values.
* P < 0.05 vs. Lyso-PC and vs.
Lyso-PC+surfactant after 30 min;
** P < 0.01 vs.
Lyso-PC and vs. Lyso-PC+ surfactant after 30 min;
# P < 0.05 vs. Lyso-PC.
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VASCULAR-TO-ALVEOLAR ALBUMIN LEAKAGE.
In animals exposed to lyso-PC without receiving surfactant, the average
leakage of human albumin into the air spaces was ~8%. Administration
of surfactant at birth reduced this leakage to <1%. Treatment with
surfactant 30 min after onset of ventilation also reduced the albumin
leakage, but only to a level of ~4%. Lung leakage of albumin in
animals not receiving lyso-PC was negligible (Fig.
6).
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Fig. 6.
Vascular-to-alveolar leakage of human albumin in various groups of
experimental animals and controls (protocol
2). Bars represent mean and SD values.
# P < 0.05 vs. Lyso-PC+surfactant after 30 min;
** P < 0.01 vs.
Lyso-PC+surfactant and vs. controls.
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PHOSPHOLIPID CONTENT AND DYNAMIC SURFACE PROPERTIES OF LUNG LAVAGE
FLUID.
The phospholipid content of lung lavage fluid was slightly lower in
animals treated with surfactant after 30 min than in those receiving
the same dose at birth (1.32 ± 0.80 vs. 1.86 ± 0.83 mg/ml; not
significant). Minimum surface tension after 5 min of cyclic film
compression in the pulsating bubble system was about twice as high in
animals receiving surfactant after 30 min as in those treated with
surfactant at birth (22 ± 2.4 vs. 9.9 ± 6.6 mN/m;
P < 0.001). This was associated with
a significant increase also in maximum surface tension (47 ± 3.0 vs. 39 ± 3.5 mN/m; P < 0.01).
CORRELATIONS AMONG COMPLIANCE, ALBUMIN LEAKAGE, AND DYNAMIC SURFACE
PROPERTIES.
In the material as a whole, there was a strong inverse correlation
between lung-thorax compliance and albumin leakage
(r = 
0.63;
P < 0.001). In the two groups of
animals receiving surfactant, compliance was inversely correlated with
both minimum and maximum surface tension during cyclic compression
(r = 0.56;
P < 0.05, and
r = 0.67;
P < 0.01, respectively).
| |
DISCUSSION |
As outlined above, increased levels of lyso-PC in the air spaces can
interfere with lung function by several pathophysiological mechanisms,
including destabilization of the alveolar film of surfactant
phospholipids, direct toxic action on the lung epithelium with
increased lung permeability, and further inactivation of surfactant by
plasma proteins leaking into the air spaces from areas of epithelial
injury (18). High levels of lyso-PC in the surfactant also increased
the sensitivity to inactivation by fibrinogen and albumin (5).
Our present data from pulsating bubble measurements confirm that
admixture of lyso-PC inactivates surfactant in a dose-dependent manner.
In natural surfactant suspended at a concentration of 10 mg/ml, nearly
complete inactivation with a mean minimum surface tension 15 mN/m was
observed with concentrations of lyso-PC 2.5 mg/ml. We also found that
the resistance to inactivation was higher for "complete" natural
surfactant than for Curosurf. This could be attributed, at least to
some extent, to a difference in their content of surfactant-specific
proteins. In particular, SP-A increases resistance to inactivation (6),
and this water-soluble protein is absent in Curosurf and all other
surfactants prepared by extraction of lung tissue or lung lavage fluid
with organic solvents.
Lyso-PC probably adsorbs to an air-liquid interface in competition with
other surfactant lipids, fluidizing the surface film (11) and
increasing the degree of surface compression required to reduce surface
tension to very low values. This was reflected in our in vitro
experiments by increased minimum surface tension during 50% surface
compression in a pulsating bubble system. The concomitant increase in
maximum surface tension indicates interference with adsorption and
spreading kinetics, leading to ineffective reentry of surfactant
molecules in the surface film during surface expansion. The changes in
lung mechanics and morphology documented in near-term newborn rabbits
after instillation of lyso-PC into the airways are also, at least in
part, explained by a direct interference with surfactant function,
especially as the fall in compliance was established already at the
first (15-min) recording after administration of lyso-PC.
The effect of lyso-PC on lung-thorax compliance was clearly dose
dependent and implied a decrease from mature level in control animals
to a level corresponding to that of immature, surfactant-deficient fetuses delivered at a gestational age of 27 days (27) in animals receiving a dose of lyso-PC 10 mg/kg. The dose of exogenous lyso-PC must be viewed in relation to the estimated pool size of endogenous alveolar surfactant phospholipids in a near-term newborn rabbit, ~20
mg/kg (26). Maximal effect was thus obtained when the dose of exogenous
lyso-PC amounted to about one-third of the total pool of endogenous and
exogenous surfactant in the alveolar spaces. Similar data were recently
reported by Fornasier et al. (9), who evaluated potential toxic effects
of lyso-PC in exogenous surfactant subjected to thermal decomposition
using a rabbit model analogous to that applied in the present experiments.
In this experimental model, surfactant function may also become
disturbed by exposure to membrane lipids from degenerating epithelial
cells. Damage to airway epithelium could be a direct toxic effect of
lyso-PC (2, 19, 20, 28) but could, in principle, be also caused by
mechanical disruption secondary to iterated collapse and reexpansion of
destabilized peripheral lung units (17). Our studies document a
substantial vascular-to-alveolar leak of albumin in animals exposed to
10 mg/kg of lyso-PC. Most animals receiving lyso-PC at doses 5 mg/kg
had histological evidence of lung injury, including recruitment of
inflammatory cells to the air spaces and, in some cases, also hyaline
membranes, suggesting that lung permeability was disturbed by
mechanisms involving necrosis of airway epithelium.
Upgrading the pool of alveolar surfactant by giving 200 mg/kg of
Curosurf at birth counterbalanced the effect of lyso-PC on lung
compliance and prevented to a large extent the leakage of albumin into
the air spaces. This illustrates that noxious effects of lyso-PC not
only depend on the dose but also on the amount of "normal"
surfactant present in the air spaces. Interestingly, this protective
effect of exogenous surfactant was only obtained when the treatment was
given at birth; administration of the same dose of Curosurf to animals
ventilated for 30 min after receiving lyso-PC did not improve
compliance to any significant degree and caused only a moderate
reduction in the vascular-to-alveolar leakage of albumin. A substantial
part of this leak probably occurred during the first 30 min of the
experiment, before surfactant was given, and the plasma proteins
accumulating in the air spaces during these 30 min may have inactivated
the subsequently administered exogenous surfactant. Such inactivation
was, indeed, documented in lung lavage samples obtained after 2 h of
ventilation. Both minimum and maximum surface tension, measured with a
pulsating bubble, were significantly higher in animals receiving
Curosurf after 30 min than in those treated at birth. We are aware of
the fact that the concentration of surfactant phospholipids in the lavage fluid was slightly higher in animals treated at birth, maybe due
to less permeation of surfactant components from the airways to the
lung interstitium, but this difference was relatively small and can
hardly explain the large difference in dynamic surface tension
documented during cyclic film compression in the pulsating bubble system.
Although inactivation of surfactant probably occurs in the late-treated
animals, variation in the distribution of the exogenous material may
also have influenced the results. Studies on immature newborn lambs
have revealed that exogenous surfactant is distributed more uniformly
and has a more long-standing effect in animals treated prophylactically
at birth than in those receiving surfactant after development of
respiratory failure in the neonatal period (14, 15). However, possible
differences in the distribution of surfactant were not analyzed in the
present study. We conclude that lyso-PC at doses 10 mg/kg has a
significant impact on neonatal lung function by inactivating surfactant
and increasing lung permeability, that these toxic effects of lyso-PC
can be counterbalanced by exogenous surfactant, and that timing of
surfactant administration may be essential for the therapeutic response.
| |
ACKNOWLEDGEMENTS |
This work was supported by The Swedish Medical Research Council
(project no. 3351), Konung Oscar II:s Jubileumsfond, The Research Funds
of the Karolinska Institute, The Swedish Society of Medicine, The Royal
Swedish Academy of Sciences (travel grants to G. Grossmann and B. Robertson), The Japan Society for the Promotion of Sciences, and by a
Grant-in-Aid for Scientific Research from the Ministry of Education,
Science, and Culture of Japan (project no. 07457353).
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FOOTNOTES |
The costs of publication of this
article were defrayed in part by the
payment of page charges. The article
must therefore be hereby marked
"advertisement"
in accordance with 18 U.S.C. §1734 solely to indicate this fact.
Address for reprint requests: G. Grossmann, Division for Experimental
Perinatal Pathology, Department of Woman and Child Health, Karolinska
Hospital L7:03, S-171 76 Stockholm, Sweden.
Received 29 January 1998; accepted in final form 9 November
1998.
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REFERENCES |
1.
Anceschi, M. M.,
B. Robertson,
L. Broccucci,
A. Barbati,
G. Grossmann,
L. Hedenborg,
E. Lundberg,
A. Petrelli,
G. Zaccardo,
and
E. V. Cosmi.
Immunochemical and immunohistochemical evaluation of lung permeability in ventilated newborn rabbits.
Exp. Lung Res.
16:
593-605,
1990[Medline].
2.
Aronson, J. F.,
and
L. W. Johns.
Injury of lung alveolar cells by lysolecithin.
Exp. Mol. Pathol.
27:
35-43,
1977[Medline].
3.
Bartlett, G. R.
Phosphorus assay in column chromatography.
J. Biol. Chem.
234:
466-468,
1959[Free Full Text].
4.
Bejar, R.,
V. Curbel,
C. Davis,
and
L. Gluck.
Premature labor. I. Bacterial sources of phospholipase.
Obstet. Gynecol.
57:
479-482,
1981[Medline].
5.
Cockshutt, A. M.,
and
F. Possmayer.
Lysophosphatidylcholine sensitizes lipid extracts of pulmonary surfactant to inhibition by serum proteins.
Biochim. Biophys. Acta
1086:
63-71,
1991[Medline].
6.
Cockshutt, A. M.,
J. Weitz,
and
F. Possmayer.
Pulmonary surfactant-associated protein A enhances the surface activity of lipid extract surfactant and reverses inhibition by blood proteins in vitro.
Biochemistry
29:
8424-8429,
1990[Medline].
7.
Enhörning, G.
Pulsating bubble technique for evaluating pulmonary surfactant.
J. Appl. Physiol.
43:
198-203,
1977[Abstract/Free Full Text].
8.
Enhörning, G.,
and
B. Robertson.
Lung expansion in the premature rabbit fetus after tracheal deposition of surfactant.
Pediatrics
50:
58-66,
1972[Abstract/Free Full Text].
9.
Fornasier, M.,
P. Puccini,
R. Razzetti,
D. Acerbi,
S. Bongrani,
and
P. Ventura.
Evaluation of potentially injurious effects of exogenous surfactant lysophospholipids on the alveolar epithelium and pulmonary mechanics.
Biol. Neonate
71:
337-344,
1997[Medline].
10.
Frosolono, M. F.,
B. L. Charms,
R. Pawlowski,
and
S. Slivka.
Isolation, characterization, and surface chemistry of a surface-active fraction from dog lung.
J. Lipid Res.
11:
439-457,
1970[Abstract].
11.
Holm, B. A.,
L. Keicher,
M. Liu,
J. Sokolowski,
and
G. Enhorning.
Inhibition of pulmonary surfactant function by phospholipases.
J. Appl. Physiol.
71:
317-321,
1991[Abstract/Free Full Text].
12.
Jacobs, H. C.,
A. H. Jobe,
M. Ikegami,
and
S. Jones.
Reutilization of phosphatidyl-glycerol and phosphatidylethanolamine by the pulmonary surfactant system in 3-day-old rabbits.
Biochim. Biophys. Acta
834:
172-179,
1985[Medline].
13.
Jacobs, H. C.,
D. M. Lima,
J. M. Fiascone,
and
M. R. Mercurio.
Reutilization of surfactant phosphatidylglycerol and lysophosphatidylcholine by adult rabbits.
Biochim. Biophys. Acta
962:
227-233,
1988[Medline].
14.
Jobe, A.,
M. Ikegami,
T. Glatz,
Y. Yoshida,
E. Diakomanolis,
and
J. Padbury.
Duration and characteristics of treatment of premature lambs with natural surfactant.
J. Clin. Invest.
67:
370-375,
1981.
15.
Jobe, A.,
M. Ikegami,
H. Jacobs,
and
S. Jones.
Surfactant and pulmonary blood flow distributions following treatment of premature lambs with natural surfactant.
J. Clin. Invest.
73:
848-856,
1984.
16.
Jobe, A. H.,
and
E. D. Rider.
Catabolism and recycling of surfactant.
In: Pulmonary Surfactant. From Molecular Biology to Clinical Practice, edited by B. Robertson,
L. M. G. van Golde,
and J. J. Batenburg. Amsterdam: Elsevier, 1992, p. 313-337.
17.
Jonson, B. Ventilation patterns, surfactant and lung injury.
Biol. Neonate 1, Suppl. 1: 13-17, 1997.
18.
Kennedy, M.,
D. Phelps,
and
E. Ingenito.
Mechanisms of surfactant dysfunction in early acute injury.
Exp. Lung Res.
23:
171-189,
1997[Medline].
19.
Lindahl, M.,
A. R. Hede,
and
C. Tagesson.
Lysophosphatidylcholine increases airway and capillary permeability in the isolated perfused rat lung.
Exp. Lung Res.
11:
1-12,
1986[Medline].
20.
Niewoehner, D. E.,
K. Rice,
A. A. Sinha,
and
D. Wangensteen.
Injurious effects of lysophosphatidylcholine on barrier properties of alveolar epithelium.
J. Appl. Physiol.
63:
1979-1986,
1987[Abstract/Free Full Text].
21.
Nilsson, R.
Lung compliance and lung morphology following artificial ventilation in the premature and full-term rabbit neonate.
Scand. J. Respir. Dis.
60:
206-214,
1979[Medline].
22.
Passi, R. B.,
and
F. Possmayer.
Surfactant metabolism in acute pancreatis.
Prog. Respir. Res.
15:
136-140,
1981.
23.
Robertson, B.,
T. Curstedt,
J. Johansson,
H. Jörnvall,
and
T. Kobayashi.
Structural and functional characterization of porcine surfactant isolated by liquid-gel chromatography.
Prog. Respir. Res.
25:
237-246,
1990.
24.
Schürch, S.
Surface tension at low lung volumes: dependence on time and alveolar size.
Respir. Physiol.
48:
339-355,
1982[Medline].
25.
Seidner, S. R.,
A. H. Jobe,
M. Ikegami,
A. Pettenazzo,
A. Priestley,
and
L. Ruffini.
Lysophosphatidylcholine uptake and metabolism in the adult rabbit lung.
Biochim. Biophys. Acta
961:
328-336,
1988[Medline].
26.
Stevens, P. A.,
J. R. Wright,
and
J. A. Clements.
Changes in quantity, composition, and surface activity of alveolar surfactant at birth.
J. Appl. Physiol.
63:
1049-1057,
1987[Abstract/Free Full Text].
27.
Sun, B.,
T. Kobayashi,
T. Curstedt,
G. Grossmann,
and
B. Robertson.
Application of a new ventilator-multi-plethysmograph system for testing efficacy of surfactant replacement in newborn rabbits.
Eur. Respir. J.
4:
364-370,
1991[Abstract].
28.
Weltzein, H. U.
Cytolytic and membrane-perturbing properties of lysophosphatidylcholine.
Biochim. Biophys. Acta
559:
259-287,
1979[Medline].
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Abstract
Introduction
