Detailed investigation on the role of lipid metabolizing enzymes in the pathogenesis of retinopathy of prematurity among preterm infants.

Abstract

PurposeExtremely preterm infants are at risk of developing retinopathy of prematurity (ROP), characterized by an initial insufficient vascular network development in the retina (due to hyperoxia) that progress to neovascularization and neuroinflammation (hypoxic phase) ultimately leading to partial or total vision loss. Lipid metabolism has been shown to be a significant pathway that is involved in the regulation of angiogenesis, inflammation, and apoptosis in oxygen induced retinopathy mouse model, however, it is not explored in human ROP patients. The present study aimed to explore the association of lipid metabolizing, angiogenic and apoptotic genes with altered lipid metabolites in the ROP patients with different severity. MethodsThe blood, vitreous humor (VH), and fibrovascular membrane (FVM) samples were collected from premature infants diagnosed with ROP and controls. Gene expression of lipid metabolizing enzymes, angiogenesis, and apoptotic genes were performed using semi-quantitative PCR in blood. Lipid metabolites were identified and quantified by LC-MS in VH and were correlated with gene expression. The expression of key lipid metabolizing enzymes in severe stages of ROP was assessed by measuring their expression in FVM by immunohistochemistry. ResultsGenes coding for the lipid metabolizing enzymes such as CYP1B1, CYP2C8, COX2, and ALOX15 were upregulated while EPHX2 responsible for the conversion of epoxide fatty acids into diol fatty acids was significantly downregulated in ROP cases. The increase in the metabolic intermediates generated from the lipid metabolism pathway further confirmed the role of these enzymes in ROP. except for EPHX2 which did not show any change in its activity. The glial cells in the FVM of ROP infants too showed a lack of EPHX2 expression. A significantly higher expression of genes involved in angiogenesis (VEGF165/189, NOTCH1, and APH1B) and apoptosis (CASP3/8) correlated with altered activity of lipid metabolizing enzymes (based on metabolites levels) among ROP cases. ConclusionsLipid metabolism may play a significant role in ROP development and progression. EPHX2 activity is a key step in the metabolic pathway of arachidonic acid that mediates and regulates inflammation and vascular pathology in preterm infants.