Prevention of hyperoxia-mediated pulmonary inflammation in neonatal rats by caffeine

Abstract

In preterm human infants, briefly elevated concentrations of oxygen are associated with a prolonged increase in blood chemokine concentrations and the development of bronchopulmonary dysplasia (BPD). Caffeine given to preterm infants for the prevention or treatment of apnoea has been shown to reduce the rate of BPD.

We tested the hypotheses that infant rats exposed to a combination of caffeine and hyperoxia would be less susceptible to lung injury than those exposed to hyperoxia alone and that caffeine decreases the pulmonary tissue expression of chemokines and leukocyte influx following hyperoxia.

Using 6-day-old rat pups, we demonstrated that 24 h of 80% oxygen exposure caused pulmonary recruitment of neutrophils and macrophages. High levels of oxygen upregulated the expression of: the CXC chemokines, cytokine-induced neutrophil chemoattractant-1 and macrophage inflammatory protein-2; the CC-chemokine monocyte chemoattractant protein-1; the pro-inflammatory cytokines tumour necrosis factor-α and interleukin-6, as measured by realtime PCR after the administration of caffeine (10 mg·kg⁻¹ body weight); and attenuated chemokine and cytokine upregulation, as well as the influx of CD11b⁺, ED-1⁺ and myeloperoxidase⁺ leukocytes.

These experiments suggest that protective effects of caffeine in the neonatal lung are mediated, at least in part, by reduction of pulmonary inflammation.