248 - Acceleration of Alteration in Expression of Epithelial to Mesenchymal Transition (EMT) Genes in Lung Alveolar Epithelial Cells (AEC) by High Percentage of Oxygen

Supplemental oxygen is an essential therapy used for neonatal resuscitation. Due to concerns for potential harmful effects, current recommendations for resuscitation of preterm newborns (< 35 weeks of gestation) are to begin with 21% to 30% oxygen with subsequent titration. The effects of different levels of oxygen on preterm neonates are not fully understood. It is known that exposure of preterm neonates to excessive oxygen may lead to chronic complications including bronchopulmonary dysplasia (BPD).  Inflammation and fibrosis are known to be important pathogenic features in BPD lungs, and EMT is involved in lung fibrosis. In our previous studies, we found that both low (25% and 35%) and high (85%) doses of oxygen altered expression of inflammatory and EMT genes after 36 hour treatment. However, the change in levels caused by low dose oxygen was less than that by high dose. We further speculate that high dose oxygen may cause earlier alteration in expression of these genes than low doses. 

Objective: Our objective is to determine whether high concentration of oxygen may accelerate changes in expression of inflammatory and EMT genes in AEC which are the interface at which oxygen exchange occurs.

Design/Methods:

Mouse C10 AEC (a non-tumorigenic line) were treated with 25%, 35%, and 85% oxygen mixed with 5% CO2 in room air for 12 hours whereas control cells were in room air with 5% CO2. Quantitative real-time PCR was used to measure mRNA levels of a panel of EMT and inflammatory genes. Data were analyzed by ANOVA and t-test, A P value of < 0.05 was deemed significant.

Results:

We found that low doses (25% and 35%) oxygen did not alter expression of inflammatory and EMT genes that were evaluated at 12 hour treatment. In contrast, high dose oxygen (85%) markedly changed expression of EMT genes of occludin (OCLN), Serpin peptidase inhibitor clade E member 1 (Serpine1), and Alpha-smooth muscle actin (alpha-SMA). High dose oxygen induced Serpine1 (P< 0.00087) and alpha-SMA (P< 0.0078), but suppressed OCLN (P< 0.00002). Interestingly, high dose oxygen only slightly altered expression of interleukin-6 (an inflammatory marker; 1.35 fold and P< 0.03).

Conclusion(s):

In conclusion, although low dose oxygen did not change expression of inflammatory and EMT genes at 12 hour treatment, 85% oxygen considerably accelerated alteration in expression of EMT pathway genes. Our findings suggest that resuscitation of preterm neonates with initial low level oxygen may delay alteration in expression of inflammatory and EMT genes and mitigate potential negative effects of hyperoxia on lung development in preterm neonates.