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Hyperoxia/Hypoxia Exposure Primes a Sustained Pro-Inflammatory Profile of Preterm Infant Macrophages Upon LPS
Nele Twisselmann1, Julia Pagel1,2, Axel Künstner3
1Department of Pediatrics, University of Lübeck and University Medical Center Schleswig-Holstein, Lübeck, Germany.
Abstract:
Preterm infants are highly susceptible to sustained lung inflammation, which may be triggered by exposure to multiple environmental cues such as supplemental oxygen (O2) and infections. We hypothesized that dysregulated macrophage (MФ) activation is a key feature leading to inflammation-mediated development of bronchopulmonary dysplasia (BPD) in preterm infants. Therefore, we aimed to determine age-dependent differences in immune responses of monocyte-derived MФ comparing cord blood samples derived from preterm (n=14) and term (n=19) infants as well as peripheral blood samples from healthy adults (n=17) after lipopolysaccharide (LPS) exposure. Compared to term and adult MФ, LPS-stimulated preterm MФ showed an enhanced and sustained pro-inflammatory immune response determined by transcriptome analysis, cytokine release inducing a RORC upregulation due to T cell polarization of neonatal T cells, and TLR4 surface expression. In addition, a double-hit model was developed to study pulmonary relevant exposure factors by priming MФ with hyperoxia (O2 = 65%) or hypoxia (O2 = 3%) followed by lipopolysaccharide (LPS, 100ng/ml). When primed by 65% O2, subsequent LPS stimulation in preterm MФ led to an exaggerated pro-inflammatory response (e.g. increased HLA-DR expression and cytokine release) compared to LPS stimulation alone. Both, exposure to 65% or 3% O2 together with subsequent LPS stimulation, resulted in an exaggerated pro-inflammatory response of preterm MФ determined by transcriptome analysis. Downregulation of two major transcriptional factors, early growth response gene (Egr)-2 and growth factor independence 1 (Gfi1), were identified to play a role in the exaggerated pro-inflammatory response of preterm MФ to LPS insult after priming with 65% or 3% O2. Preterm MФ responses to LPS and hyperoxia/hypoxia suggest their involvement in excessive inflammation due to age-dependent differences, potentially mediated by downregulation of Egr2 and Gfi1 in the developing lung.
Insights
Preterm infants
Area of Science:
- Neonatal immunology and respiratory disease research.
- Investigating immune cell responses in preterm infants.
Background:
- Preterm infants are vulnerable to lung inflammation, potentially leading to bronchopulmonary dysplasia (BPD).
- Macrophage (MФ) activation dysregulation is implicated in BPD development.
- Environmental factors like oxygen exposure and infections can trigger inflammation.
Purpose of the Study:
- To compare age-dependent immune responses of monocyte-derived macrophages (MФ) from preterm infants, term infants, and adults.
- To investigate the impact of hyperoxia and hypoxia on MФ inflammatory responses.
- To identify molecular mechanisms underlying exaggerated MФ inflammation in preterm infants.
Main Methods:
- Collected cord blood from preterm (n=14) and term (n=19) infants, and peripheral blood from adults (n=17).
- Stimulated MФ with lipopolysaccharide (LPS) and analyzed immune responses (transcriptome, cytokines, TLR4, HLA-DR).
- Utilized a double-hit model: MФ priming with hyperoxia (65% O2) or hypoxia (3% O2) followed by LPS stimulation.
Main Results:
- LPS-stimulated preterm MФ exhibited enhanced, sustained pro-inflammatory responses compared to term and adult MФ.
- Priming preterm MФ with hyperoxia (65% O2) or hypoxia (3% O2) followed by LPS exacerbated pro-inflammatory responses.
- Downregulation of transcription factors Egr-2 and Gfi1 was observed in preterm MФ under these conditions.
Conclusions:
- Age-dependent differences in MФ immune responses contribute to excessive lung inflammation in preterm infants.
- Exposure to varying oxygen levels (hyperoxia/hypoxia) alongside LPS amplifies preterm MФ pro-inflammatory reactions.
- Downregulation of Egr2 and Gfi1 may mediate the heightened inflammatory response in preterm MФ.
