Abstract Body: Background: Myocardial ischemia-reperfusion injury (IRI) occurs when blood supply returns to the heart after ischemia which paradoxically causes the injury due to sudden reintroduction of reactive oxygen species and calcium triggering a cascade of inflammation and cell death in both cardiomyocytes and coronary artery endothelial cells (EC). Our lab previously showed that Intralipid (ILP), a clinically used lipid emulsion, confers cardioprotection against IRI in rodents. However, the downstream mechanisms remain unknown.
Hypothesis: We hypothesize that ILP attenuates IRI-induced inflammation and apoptosis via downregulation of N-myc downstream regulated gene 1 (NDRG1).
Methods: We performed RNA sequencing on left ventricles (LV) of male Sprague-Dawley rats subjected to transient LAD ligation to induce IRI or sham surgery. Rats received either a bolus of ILP (20% IV) or saline 5 minutes before reperfusion. Pathway enrichment analysis was performed using transcriptomics and was validated by qPCR. We subjected H9C2 cardiac myoblasts and coronary artery EC to hypoxia/reoxygenation (H/R) and ILP (1%) treatment during reoxygenation. We tested the functional role of NDRG1 in EC and H9C2 by silencing NDRG1 via siRNA.
Results: Pathway enrichment showed hypoxia and inflammatory response genes were significantly increased in IRI hearts versus sham but were normalized in ILP-treated IRI hearts. Seven significantly differentially-expressed genes were identified, including the hypoxia molecular switch N-myc downstream-regulated gene 1 (NDRG1). We validated that NDRG1 mRNA in rat LV is upregulated by IRI and attenuated by ILP treatment to a similar level as sham rats. Our in-vitro data showed that ILP significantly reduced H/R-induced upregulation of NDRG1 transcript levels in H9C2 and EC. Functionally, NDRG1 knockdown in coronary EC and H9C2 reduced markers of EC activation (ICAM1), inflammation (IL-6, TNFa) and apoptosis (cleaved caspase 3, bax, Bcl2).
Conclusion: Taken together, our data suggest that ILP confers cardioprotection against IRI via downregulation of NDRG1 expression, leading to reduced inflammation, and apoptosis.