DEVELOPMENTAL SUSCEPTIBILITY TO HYPEROXIC LUNG INJURY

DEVELOPMENTAL SUSCEPTIBILITY TO HYPEROXIC LUNG INJURYSara Berkelhamer, MDNorthwestern UniversityLurie Children’s Hospital

Background: Oxidative Lung Injury

Reactive oxygen species (ROS) are generated with exposure to supraphysiologic oxygen

ROS cause damage to proteins, lipids and DNA Animal models demonstrate that high FiO2 causes

lung injury and arrested lung development Lung injury is greatest in the most premature infants Even brief exposure to 90% O2 during resuscitation

increased the risk of BPD in 24-28w infants (Vento, 2009)

Modified from Li, et al, Current Respiratory Medicine Reviews, 2005.

plasma membraneO2

mitochondria

O2- H2O2 OH-

death factors

O2-

H2O2

OH−

JNK

BAX

BAX

SOD1 catalase

SOD2 catalase

NOX

O2

O2

ETC

1. Hypothesis:

developmental differences exist in ROS generation and cellular response to supraphysiologic oxygen

Methods In vitro studies

Intact lung slices and isolated alveolar cells Live cell imaging using a redox sensor, RoGFP Whole lung isolation for protein and mRNA analysis

In vivo exposures to 75% O2 (Biospherix Chamber) Lung analysis

Protein and mRNA Morphometry

Heart analysis RVH by Fulton’s Index (RV/LV+S)

Immature Lung ModelsMurine Intact Lung Slices

Rat Primary AT2 Cells

RoGFP: Sensor of redox state

Reduced

Oxidized

ReducedOxidized

Hyperoxia Induces Exaggerated Mitochondrial Oxidative Stress in AEC of Immature Lung Slices

Free Radical Biology, in revision

RoGFP: Alveolar Cells

Hyperoxia Induces Exaggerated Mitochondrial Oxidative Stress Response in Immature AT2


Hyperoxia Induces Comparable Oxidative StressResponse in Immature and Adult PASMC of Lung Slices

A


RoGFP: PA Smooth Muscle Cells

Antioxidant Expression Matures Postnatally


24h of Hyperoxia Induces Increased SOD Activity in Adult but Not Immature Lung

SOD MnSOD


24h Hyperoxia Induces Increased NOX1 mRNA and Protein Expression in Immature but Not Adult Lung


mRNA protein

EUK134 Attenuates Hyperoxia-Induced

Increase in NOX1 Expression in Immature Lung


Hyperoxia Induces Increased Cell Death in Immature but not Adult Lung Slices


Summary Mitochondrial ROS are generated within

minutes of exposure to supraphysiologic oxygen

Immature alveolar lung cells demonstrate exaggerated mitochondrial oxidative stress in hyperoxia

ROS generation may be further amplified in the immature lung via up-regulation of NOX1

Immature lung slices demonstrate increased susceptibility to hyperoxia-induced cell death

2. Hypothesis:

A critical developmental window may exist in which exposure to supraphysiologicoxygen results in compromised lungdevelopment

Model: In vivo exposure

0 1 2 3 4 5 6 7 14

= 21% O2

= 75% O2

Control

P0-3

P4-7

BPD

Day

72h of Hyperoxia at P0-3 but not P4-7 Induces Persistent RVH

*

Control

P0-3

P4-7

*

72h of Hyperoxia at P0-3 but not P4-7 Disrupts Alveolarization

* *

Model: Developmental Susceptibility

Hyperoxia

ROS ROS

NOX1 antioxidantenzymes

NOX1

lung injuryBPD

antioxidantenzymes

Clinical Implications Supraphysiologic oxygen should be used

with great caution in premature infants A critical window may exist during which

there is increased susceptibility to oxidative injury

Antioxidants targeted to the mitochondria or delivered directly to alveoli may represent novel therapeutic approaches

AcknowledgementsPaul Schumacker, PhD Molly BallAnkur DattaDanijela DokicGina KimPaul MungaiSimran SabharwalJacqueline SchreiwerGregory Waypa

Kathryn Farrow, MD, PhDLyubov CzechRobin Steinhorn, MDStephen Wedgwood

Neonatal Resuscitation Program Young Investigator’s Award, 2011

DEVELOPMENTAL SUSCEPTIBILITY TO HYPEROXIC LUNG INJURY

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