Joanna Floros, Ph.D

Evan Pugh Professor, Departments of Cellular and Molecular Physiology, Pediatrics, and Obstetrics and Gynecology.

The Pennsylvania State University, College of Medicine, Hershey, PA, U.S.A

Surfactant Composition and Function

8th World Hellenic Biomedical Congress

1. Characteristics of Surfactant

• What is surfactant?

• What is its composition?

• Where is it made?

• What is its structure?

Surfactant

2. Function of surfactant

MAJOR CONSTITUENTS OF PULMONARY SURFACTANT

PC

(DSPC)

Cholesterol PG PIOther lipids

Protein

PE

Surfactant

SP-ASP-BSP-C

Proteins

Unsaturated

Other Proteins

SP-D

Pulmonary surfactant biochemically, is a lipoprotein complex that lines the internal surface of the alveoli.

What is Pulmonary Surfactant and What is its Composition?

16:/16:0

PC

Fishman 2-19

SURFACTANT HETEROGENEITY AND LIFE CYCLE

SMALL AGGREGATES

LARGE AGGREGATES

SURFACE FILM

TUBULAR MYELINLAMELLAR BODIES

HYPOPHASE FLUID

(SUPERNATANT)

SP-A

LB, TM, SP-A

1. Characteristics of Surfactant

• What is surfactant?• What is its composition?• Where is it made?• What is its structure?

Surfactant

2. Function of surfactant and/or surfactant components

• Lowering of surface tension.

• Innate host defense.

• Initiation of parturition (SP-A, a hormone?)

Functions of surfactant

• Stabilizes alveoli and prevents alveolar (lung) collapse with each exhalation by lowering the surface tension at the air-liquid surface.

• Surfactant components play a role in host defense and protect the lung from injuries or infections caused by inhaled microorganisms, particles, toxins, other.

• One of the protein component of surfactant (SP-A) may serve as a hormone in parturition.

Surface tension

Host defense

Initiation of labor

J. Kending

Air-Liquid Interface

Without surfactant With surfactant

Surfactant

MAJOR CONSTITUENTS OF PULMONARY SURFACTANT

PC

(DSPC)

Cholesterol PG PIOther lipids

Protein

PE

Surfactant

SP-ASP-BSP-C

Proteins

Unsaturated

Other Proteins

SP-D

16:0/16:0

PC

Functions of surfactant

• Stabilizes alveoli and prevents alveolar (lung) collapse with each exhalation by lowering the surface tension at the air-liquid surface.

• Surfactant components play a role in host defense and protect the lung from injuries or infections caused by inhaled microorganisms, particles, toxins, other.

• One of the protein component of surfactant (SP-A) may serve as a hormone in parturition.

Surface tension

Host defense

Initiation of labor

INHIBITION

SP-A LIPID

Stimulation Inhibition

Oxidant ProductionSplenocyte Proliferation

Cell Surface MarkersCytokine Production

NF-kB ActivationFibroblast Apoptosis

Collagen and Collagenase Production

SP-A

PESM

PCPGPI

STIMULATION

CHOL

PCPG

PI

INHIBITION

SP-A

PESM

CHOL

SURFACTANT REGULATION OF IMMUNE CELLS

STIMULATION

LARGE AGGREGATES

TUBULAR MYELIN

SP-A

Cell Surface Markers;Cytokine Production;

NF-kB Activation;Collagen and Collagenase

Production

Surfactant-related Host defense-related

SP-A FUNCTION

Innate Adaptive

myr800 700 600 500 present

Regulation of inflammatory processes

Innate Immunity

Human SP-A Genes, and Variants

Genes

6A21A0

C TP SP-A1SP-A2

Variants

The above variants have been shown to exhibit qualitative and quantitative differences.In addition environmental insults, such as ozone, appear to differentially alter their functional activity and thus contribute to individual differences in disease susceptibility.

Differences exist among SP-A variants in their ability to enhance phagocytosis of bacteria by alveolar macrophages in the presence or absence of environmentalfactors.

agar plateagar plate suspensionsuspensionof bacteria of bacteria

alveolar macrophagesalveolar macrophages

SP-ASP-Aphagocytosisphagocytosis

wash off free wash off free bacteriabacteria

slide slide preparationpreparation

light light microscopy microscopy

analysisanalysis

BALBAL

insect cells orinsect cells ormammalian cellsmammalian cells

ratrat

ozoneozone

EXPERIMENTAL APPROACH EXPERIMENTAL APPROACH

Microscopic view of live P. aeruginosa, phagocytized by rat alveolar macrophages in the presence or absence of human SP-A

No SP-A SP-A

R E S U L T SR E S U L T S

SP-A2 products exhibit higher phagocytic ability than SP-A1

§ hSP-A vs. SP-A variants (insect)

Phagocytic index: % of bacteria-positive AMs the average # of bacteria per bacteria-positive AMs

* SP-A2 vs. SP-A1 ; ** 6A2 vs. 6A4 ; *** hSP-A vs. 6A4 (mammalian); (hSP-A: 25 µg/ml)

Mikerov et al

Bacteria: P.aeruginosa

Mammalian expressed variantsMammalian expressed variants

100

200

300

400

500

Ph

ago

cyti

c in

dex

(%

)

1.56 g/ml n=5

**

***

**

SP-A2

1A0 1A 6A2 6A4

SP-A1

hSP-A

Ability of SP-A variants to enhance phagocytosis by alveolar macrophages following exposure to ozone.

1A0 > 1A0 (SP-A2) 6A4 = 6A4 (SP-A1) 1A0/6A4 > 1A0/6A4 (SP-A2/SP-A1)

Ozone-exposedUnexposed

Functions of surfactant

• Stabilizes alveoli and prevents alveolar (lung) collapse with each exhalation by lowering the surface tension at the air-liquid surface.

• Surfactant components play a role in host defense and protect the lung from injuries or infections caused by inhaled microorganisms, particles, toxins, other.

• One of the protein component of surfactant (SP-A) may serve as a hormone in parturition.

Surface tension

Host defense

Initiation of labor

Increased levels of SP-A

Fetal macrophages

activate

Increased levels of proinflammatory cytokines (i.e. IL-b1)

NF-kB

Increase expression of genes thatcause myometrial contractibility

activate

Surfactant lipids(Arachidonate derivatives)

P65 antagonizes progesterone receptor activation of genes that modulateuterine quiescence.

Prostaglandin synthesis

Fetal SP-A initiates labor

Summary

• Pulmonary surfactant, a lipoprotein complex, is essential throughout life for normal lung function, host defense, and other functions.

• Derangement in surfactant either through alterations in composition or modification (i.e. oxidation) can negatively affect normal lung function and host defense.

• Genetic differences in surfactant components may contribute to differences in disease risk among individuals.