Surfactant plus budesonide decreases lung and systemic inflammation in mechanically ventilated preterm sheep

Abstract

Mechanical ventilation with normal tidal volumes (V_T) causes lung and systemic inflammation in preterm sheep. Mechanical ventilation is associated with bronchopulmonary dysplasia (BPD) in preterm infants, and the addition of budesonide to surfactant decreases BPD in clinical trials. Budesonide with surfactant will decrease the lung injury from mechanical ventilation for 24 h in preterm sheep. Lambs at 126 ± 1 day gestational age were delivered and randomized to either: 1) surfactant (200 mg/kg) or 2) surfactant mixed with budesonide (0.25 mg/kg) before mechanical ventilation with V_T of 7-8 ml/kg for 2, 6, or 24 h (n = 6 or 7/group). Lung physiology and budesonide levels in the plasma and the lung were measured. Lung tissue, bronchoalveolar lavage fluid (BALF), liver, and brain tissues were evaluated for indicators of injury. High initial budesonide plasma levels of 170 ng/ml decreased to 3 ng/ml at 24 h. Lung tissue budesonide levels were less than 1% of initial dose by 24 h. Although physiological variables were generally similar, budesonide-exposed lambs required lower mean airway pressures, had higher hyperoxia responses, and had more stable blood pressures. Budesonide decreased proinflammatory mRNA in the lung, liver, and brain. Budesonide also decreased total protein and proinflammatory cytokines in BALF, and decreased inducible nitric oxide synthase activation at 24 h. In ventilated preterm lambs, most of the budesonide left the lung within 24 h. The addition of budesonide to surfactant improved physiology, decreased markers of lung injury, and decreased systemic responses in liver and brain.

Keywords: bronchopulmonary dysplasia; lung inflammation; prematurity.

Fig. 1.

Budesonide in the plasma and lung. A: plasma budesonide over time in nanograms per milliliter (left axis) and as a percentage of the 0.75-mg dose (0.25 mg/kg dosed at 3 kg) given by tracheal instillation with surfactant (right axis). Percentage of dose was calculated on the basis of Hct of lamb and the assumption of a 80 ml/kg of blood volume. B: budesonide in lung in milligrams at 2 h, 6 h, and 24 h (left axis) and percentage of original 0.75-mg dose (right axis). Budesonide was extracted from lung tissue without (gray bars) and with (striped bars) deesterification to measure total budesonide in the lungs. Budesonide increased by 40% after deesterfication. n = 5 or 6 animals per time point and condition. Values are expressed as means ± SE. *P < 0.05 vs. the previous time point. #P < 0.05 vs. nonhydrolyzed.

Fig. 2.

Select mRNA levels in the lung, liver, and brain relative to unventilated controls. A–D: lung mRNA levels for the proinflammatory cytokines IL-1β (A), IL-6 (B), and monocyte chemoattractant protein-1 (MCP-1; C) decreased with budesonide and surfactant (Surf + Bud). IL-8 mRNA was not significantly different (D). E: epithelial sodium channel (ENaC) mRNA increased in the lungs with budesonide exposure. F: liver mRNA for MCP-1 was decreased by budesonide. G and H: periventricular white matter mRNA levels for IL-1β (G) and MCP-1 (H) were also decreased in the brains of budesonide animals. Individual animals (n = 6 or 7 per group) are represented. Values are means ± SE. *P < 0.05 vs. surfactant-only animals at 2, 6, or 24 h.