Abstract
Purpose :
Retinopathy of prematurity (ROP) and unconjugated hyperbilirubinemia are common comorbidities found in preterm infants. As a potent antioxidant, low dose unconjugated bilirubin (UCB) may have a protective effect against the development of ROP, particularly in conditions of oxidative stress such as sepsis, yet it has not been tested in a preclinical study. We hypothesize that key oxidant stress factors and endothelial cell angiogenic factors are upregulated in retinas of jaundiced pups when exposed to lipopolysaccharide (LPS).
Methods :
The Gunn rat model of neonatal jaundice was used in this study. Homozygous jaundiced pups (jj) and littermate non-jaundiced heterozygous (Jj) controls received intraperitoneal saline or LPS on postnatal day (P)5 and were euthanized on P7. Whole retinal dissection was performed. Retinas from 3-6 pups/group underwent RNA extraction, cDNA synthesis, and quantitative polymerase chain reaction (qPCR) with Vegfa, Ang2, Slit2, Birc5, p53, and GPX4 probes and normalized against PPIA. Outliers were identified by ROUT test (Q=1%) and comparisons were made by two-way ANOVA (P<0.05) (GraphPad Prism 8).
Results :
LPS upregulated mRNA expression of angiogenic factors, Vegfa by threefold, Ang-2 by threefold, and Birc5, downstream target of Ang-2, by fourfold compared to saline groups at P7 (p<0.05). Antioxidant GPX4 and pro-oxidant P53 mRNA expression were upregulated threefold and twofold respectively in LPS groups compared to saline groups. There were no significant differences in any tested genes between Jj and jj groups.
Conclusions :
LPS increased gene expression of key angiogenic molecules and had a mixed effect on pro-and anti-oxidant factors in the neonatal rat retina. These effects were not altered by the presence of unconjugated hyperbilirubinemia, despite previous evidence from our group describing the heightened antioxidant effects of unconjugated hyperbilirubinemia in the brain, which may suggest a differential effect from the blood-retina barrier. The induction of angiogenic factors by LPS in the retina validate published findings but further study is needed to determine if increased GPX4 by LPS may ameliorate its pathogenic role in ROP.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.