Am. J. Respir. Crit. Care Med.,
Volume 161, Number 3, March 2000, 831-838
Pivotal Role of Anionic Phospholipids in Determining
Dynamic Behavior of Lung Surfactant
EDWARD P.
INGENITO,
RENE
MORA,
and
LENA
MARK
Division of Pulmonary and Critical Care Medicine, Brigham and Women's Hospital, Boston, Massachusetts
Phosphatidylglycerol (PG) and phosphatidylinositol (PI) are anionic phospholipids (APLs) present in
lung surfactant of virtually all species studied, although their specific contribution to function is unknown. This study examines how APLs influence surfactant monolayer stability and adsorption under
static and dynamic conditions. Interfacial properties of surfactants reconstituted with native phospholipids (PL), and phospholipids devoid of anionic species (DAPL), were characterized by pulsating
bubble surfactometry. Measurements were made for PL and DAPL alone; with 3% surfactant proteins
B and C (SP-B/C); with SP-B/C and 5% surfactant protein A (SP-A); and with SP-B/C, SP-A, and 8%
neutral lipids (NL). Equilibrium and dynamic properties of PL and DAPL were similar. However,
whereas (DAPL + SP-B/C) and (DAPL + SP-B/C + SP-A) mixtures were similar to corresponding PL
mixtures with respect to
equil, they displayed markedly different dynamic behavior. In particular, the
degree of film compression required to reach
min was significantly increased in DAPL mixtures (80 to
90% area reduction) compared with PL, although both samples reached
min < 3.0 dynes/cm. The
addition of NL to (DAPL + SP-B/C + SP-A) produced an increase in
min to 15 to 20 dynes/cm during
dynamic compression, whereas NL had no significant impact on the behavior of (PL + SP-B/C + SP-A).
Purified PG (5% wt/wt) restored nearly normal dynamic properties to (DAPL + SP-B/C + SP-A + NL),
whereas phosphatidylcholine (PC) (5% wt/wt) had no beneficial effect. These results suggest that
APLs play a critical role in promoting surface film stability during dynamic compression through interactions with nonlipid surfactant components, and prevent destabilization of the surface film by
cholesterol and other NL. Ingenito EP, Mora R, Mark L. Pivotal role of anionic phospholipids in
determining dynamic behavior of lung surfactant.