476 - Impact of Vitamin D on Pulmonary Inflammation in Mice Exposed to Hyperoxia at Birth

Poster Number: 476
Publication Number: 476.433

Thu T. Tran, The University of Texas Health Science Center at Houston, Houston, TX, United States; Joseph Alcorn, UT Medical School at Houston, Houston, TX, United States

Background: Supplemental oxygen is critical in management of many preterm neonates, but can result in hyperoxic acute lung injury (HALI), leading to an inflammatory cascade that impairs pulmonary development, resulting in detrimental sequelae into adulthood. Vitamin D (VIT D) is known to decrease inflammation and cytokine response, promote epithelial maturation and increase type II alveolar cell production in the lung. All preterm neonates require VIT D, but recommended optimal dosing is unclear. We hypothesized that administration of VIT D in a model neonatal HALI in mice can significantly reduce the inflammatory cascade, lessen lung injury, and improve lung function in a dose-dependent manner.

Objective: To determine if VIT D impacts pulmonary inflammation and mechanics in a dose-dependent manner in neonatal mice under HALI conditions.

Design/Methods: Neonatal C57BL/6 mouse pups (day 0) were randomized and placed under normoxic (room air) or hyperoxic (85% O2) conditions. Control, low (5 ng) and high (25 ng) dose VIT D were administered at day 2 via gavage. At day 6, lung tissue was harvested for analysis of inflammatory cytokine expression via RT-PCR, histological analysis, and pulmonary edema via wet/dry lung ratio. Lung sections were stained with hematoxylin and eosin (H&E) to assess pulmonary structure, mean linear intercept (MLI) and radial alveolar count (RAC).

Results: Significant elevation in all pro-inflammatory markers (CXCL1, IL-1β, IL-6, TNF-α), weight loss, pulmonary edema, MLI and a significant reduction in RAC were observed in the hyperoxia control group versus the normoxia control group (Fig. 1). No significant reduction in cytokine expression as a result of HALI was observed with low or high dose VIT D intervention. VIT D significantly increased the weight of pups compared to untreated pups in hyperoxic conditions. Wet/dry lung ratio significantly decreased in high dose VIT D group. H&E-stained lung sections showed oversimplification of placebo mice exposed to hyperoxic conditions (Fig. 2). Groups given low and high dose VIT D in hyperoxia showed some preservation of alveolar structure. Groups given high dose VIT D in hyperoxic conditions had significantly decreased MLI and increased RAC compared to hyperoxia control.Conclusion(s): Under hyperoxic conditions, VIT D supplementation significantly reduces pulmonary edema and weight loss while improving alveolar structure.  However, inflammatory pulmonary cytokine expression was not impacted.  Our results suggest that oral administration of high dose VIT D during hyperoxic insult is protective in neonatal mice.
Figure 1. Significant Improvement in MLI and RAC with Vitamin D AdministrationFigure 1. Quantitation with (A) mean linear intercept and (B) radial alveolar count demonstrates significant improvement in low and high dose VIT D administration in hyperoxia.
Figure 2. H&E Mouse Lung SectionsFigure 2. Representative H&E mouse lung sections (40x) demonstrates alveolar oversimplification seen in hyperoxia placebo control compared to room air placebo animal animals, but this is improved with both low and high dose vitamin D.