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Timing of hyperoxic exposure during alveolarization influences damage mediated by leukotrienes
J S Manji1, C J O'Kelly, W I Leung
1Department of Physiology, University of Alberta, Edmonton, Alberta T6G 2S2, Canada.
Insights
Hyperoxia exposure during rat pup alveolar development impairs lung growth. Leukotrienes (LTs) mediate this, with sensitivity peaking around postnatal day 9, impacting alveolarization.
Area of Science:
- Neonatal Physiology
- Pulmonary Development
- Pharmacology
Background:
- Hyperoxia exposure during early life retards alveolar development.
- Leukotrienes (LTs) are implicated in hyperoxia-induced lung injury.
- The timing of hyperoxic insult may influence its impact on lung development.
Purpose of the Study:
- To investigate the effects of hyperoxia during specific developmental windows on alveolarization.
- To determine the relationship between oxygen exposure and leukotriene levels during alveolar development.
- To assess the role of leukotriene synthesis inhibition in mitigating hyperoxic lung injury.
Main Methods:
- Rat pups were exposed to hyperoxia (>95% O(2)) during distinct postnatal periods (days 1-4, 4-9, 9-14, or 4-14).
- Some pups received a leukotriene (LT) synthesis inhibitor (MK-0591).
- Alveolar development and lung tissue LT output were assessed on specific days.
Main Results:
- Exposure from postnatal days 4-9 caused the most significant inhibition of alveolarization.
- Hyperoxia increased leukotriene levels, particularly on days 9 and 14.
- Inhibiting LT synthesis during hyperoxic exposure prevented impaired alveolar development.
Conclusions:
- Alveolar development exhibits time-sensitive vulnerability to hyperoxia, particularly around postnatal day 9.
- Leukotrienes play a critical role in mediating hyperoxia-induced retardation of alveolarization.
- Targeting leukotriene pathways may offer a therapeutic strategy against hyperoxic lung injury in neonates.
Abstract:
Hyperoxic exposure of rat pups during alveolarization (postnatal days 4-14) severely retards alveolar development. Some aspects of this inhibition are mediated by leukotrienes (LTs) and may be time sensitive. We determined 1) the effects of exposure to hyperoxia (O(2)) during discrete periods before and during alveolarization on developing alveoli and 2) whether a relationship exists between O(2) and LTs in these periods. Pups were exposed to >95% O(2) from days 1 to 4, 4 to 9, 9 to 14, or 4 to 14 in the absence and presence of the LT synthesis inhibitor MK-0591. Both the level of in vitro lung tissue LT output on days 4, 9, and 14 and the degree of alveolarization on day 14 were determined. Pups exposed to O(2) from days 4 to 9 had a more profound inhibition of alveolarization on day 14 compared with those exposed to O(2) from days 1 to 4 or 9 to 14. Peptido-LT levels were significantly higher in pups exposed to O(2) on days 9 and 14 compared with pups in air and returned to normal once normoxia was restored. LT inhibition from days 4 to 14, 4 to 9, or 9 to 14 in pups exposed to O(2) from days 4 to 14 prevented the O(2)-induced inhibition of alveolarization. These data suggest that developing alveoli are sensitive to LTs shortly before and after day 9, significantly retarding certain parameters of alveolarization on day 14. We conclude that some of the effects of O(2) are not uniform throughout different stages of alveolarization and that this is likely related to the timing of LT exposure.