Acute and chronic effects of intravitreal bevacizumab on lung biomarkers of angiogenesis in the rat exposed to neonatal intermittent hypoxia

Abstract

Purpose/aim: Intravitreal bevacizumab (Avastin) is an irreversible vascular endothelial growth factor (VEGF) inhibitor used to treat severe retinopathy of prematurity (ROP) in extremely low gestational age neonates (ELGANs). ELGANs who are at the highest risk for developing severe ROP often experience brief intermittent hypoxia (IH) episodes which may cause oxidative damage. We tested the hypothesis that intravitreal Avastin leaks into the systemic circulation during exposure to IH and has adverse effects on biomarkers of pulmonary microvascular maturation, thus leading to pulmonary hemorrhage and long-term pulmonary sequelae.

Methods: Neonatal rats at postnatal day (PN) 0 (birth) were exposed to either: 1) hyperoxia (50% O₂) or 2) neonatal IH (50% O₂ with brief episodes of 12% O₂) from PN0 to PN14. Room air (RA) littermates served as controls. At PN14, the time of eye opening in rats, a single dose of Avastin (0.125 mg in 5 µL) was injected into the vitreous cavity of the left eyes. A control group received equivalent volume saline. At PN23 and PN45, blood gases, lung-to-body weight ratios, histology, immunofluorescence, and lung biomarkers of angiogenesis were examined.

Results: At PN23, Avastin increased lung VEGF, nitric oxide derivatives (NOx), and hypoxia-inducible factor (HIF)_1a in the hyperoxia-exposed groups, but decreased soluble VEGFR-1 (sVEGFR-1). At PN45, lungs from animals exposed to neonatal IH and treated with Avastin were severely hemorrhagic with morphologic changes in lung architecture consistent with chronic lung disease. This was associated with higher VEGF and NOx levels, and lower insulin-like growth factor (IGF)-I and sVEGFR-1.

Conclusions: These findings prove our hypothesis that intravitreal Avastin penetrates the blood-ocular barrier in IH and alters lung biomarkers of angiogenesis. Avastin targeting of VEGF could affect normal lung development which may be exaggerated under pathologic conditions such as IH, ultimately leading to vascular permeability, vessel rupture, and pulmonary hemorrhage.

Keywords: Angiogenesis; Avastin; insulin-like growth factor-1; neonatal intermittent hypoxia; soluble vascular endothelial growth factor receptor-1; vascular endothelial growth factor.