Abstract Body (Do not enter title and authors here): Background: Endothelial cell (EC) nuclear factor erythroid 2-related factor (Nrf2) translocates to the nucleus during inflammation to mediate transcription of genes in the antioxidant response elements (ARE). An ARE regulates mRNA encoding HMOX-1, thioredoxin (TXN), and NAD(P)H quinone oxidoreductase-1 (NQO1), among others. Parkinson disease protein 7 (PARK7) and p62 work independently to prevent Keap1-mediated degradation of Nrf2 during oxidative stress. Eicosapentaenoic acid (EPA) administered as icosapent ethyl reduced CV events (REDUCE-IT). We tested the effects of EPA on ARE protein expression in ECs from multiple tissues during cytokine challenge.
Methods: Human brain, pulmonary and vascular ECs were treated with IL-6 (12 ng/mL) for 2 hours and then incubated with EPA (40 µM) for 24 h. Global proteomic analysis performed by LC-MS measured relative protein expression. Significant (p<0.05) changes between treatment groups >1-fold were analyzed by differential enrichment analysis of proteomics data (DEP) and included in gene set enrichment analyses (GSEA). Significantly modulated pathways within the Gene Ontology (GO) database were identified as those with an adjusted-p value <0.05.
Results: Proteomic analysis revealed that EPA significantly modulated ≥600 proteins in ECs distinct from IL-6 challenge alone. In EC, EPA significantly modulated the “cellular response to oxidative stress” pathway (GO: 0034599) relative to IL-6 alone. Within this GO pathway, EPA increased levels of catalase (1.2-fold, 1.1-fold, 1.1-fold) and mitochondrial glutathione reductase (1.1-fold, 1.1-fold, 1.1-fold) in brain, pulmonary, and vascular ECs, respectively. We also observed a consistent increase in brain, pulmonary, and vascular ECs of p62 (1.3-fold, 1.2-fold, and 1.2-fold, respectively), and ARE members HMOX-1 (1.5-fold, 1.7-fold, and 2.1-fold, respectively), and NQO1 (1.1-fold, 1.2-fold, and 1.3-fold, respectively). TXN was increased in pulmonary and vascular ECs (1.1-fold and 1.2-fold, respectively) with EPA. Mitochondrial TXN (also called TXN2) increased in brain ECs with EPA 1.1-fold. EPA also significantly increased levels of PARK7 1.1-fold.
Conclusions: During inflammation, EPA enhanced expression of cytoprotective proteins in the ARE, notably HMOX-1, along with its regulators, in ECs from multiple tissues. Augmented endogenous antioxidant pathways may contribute to EPA’s clinical benefits.