Abstract
Early growth response-1 (Egr-1), a transcription factor which often underlies the molecular basis of myocardial ischemia/reperfusion (I/R) injury, and oxidative stress, is key to myocardial I/R injury. Silent information regulator of transcription 1(SIRT1) not only interacts with and is inhibited by Egr-1, but also downregulates reactive oxygen species (ROS) via the Forkhead box O1(FOXO1)/manganese superoxide dismutase (Mn-SOD) signaling pathway. N-n-butyl haloperidol iodide (F2), a new patented compound, protects the myocardium against myocardial I/R injury in various animal I/R models in vivo and various heart-derived cell hypoxia/reoxygenation (H/R) models in vitro. In addition, F2 can regulate the abnormal ROS/Egr-1 signaling pathway in cardiac microvascular endothelial cells (CMECs) and H9c2 cells after H/R. We studied whether there is an inverse Egr-1/ROS signaling pathway in H9c2 cells and whether the SIRT1/FOXO1/Mn-SOD signaling pathway mediates this. We verified a ROS/Egr-1 signaling loop in H9c2 cells during H/R and that F2 protects against myocardial H/R injury by affecting SIRT1-related signaling pathways. Knockdown of Egr-1, by siRNA interference, reduced ROS generation, and alleviated oxidative stress injury induced by H/R, as shown by upregulated mitochondrial membrane potential, increased glutathione peroxidase (GSH-px) and total SOD anti-oxidative enzyme activity, and downregulated MDA. Decreases in FOXO1 protein expression and Mn-SOD activity occurred after H/R, but could be blocked by Egr-1 siRNA. F2 treatment attenuated H/R-induced Egr-1 expression, ROS generation and other forms of oxidative stress injury such as MDA, and prevented H/R-induced decreases in FOXO1 and Mn-SOD activity. Nuclear co-localization between Egr-1 and SIRT1 was increased by H/R and decreased by either Egr-1 siRNA or F2. Therefore, our results suggest that Egr-1 inhibits the SIRT1/FOXO1/Mn-SOD antioxidant signaling pathway to increase ROS and perpetuate I/R injury. F2 inhibits induction of Egr-1 by H/R, thereby activating SIRT1/FOXO1/Mn-SOD antioxidant signaling and decreasing H/R-induced ROS, demonstrating an important mechanism by which F2 protects against myocardial H/R injury.
Highlights
Ischemic heart disease is a major cause of mortality worldwide (Roger et al, 2011)
Early growth response protein 1 (Egr-1) is associated with pathological changes in ischemia and reperfusion (I/R) injury and is thought to be a “a master switch” for I/R injury because of its regulation of inflammation, coagulation, and vascular hyper-permeability which are thought to be central to pathogenesis of I/R injury (Yan et al, 2000; Zins et al, 2014; Sandoval et al, 2016)
Our studies on in vitro H/R treatment of H9c2 cells and cardiac microvascular endothelial cells (CMEC) found that H/R causes reactive oxygen species (ROS) generation and over-expression of Egr-1, and that ROS is upstream of Egr-1 (Zhang et al, 2015; Lu S. et al, 2016)
Summary
Ischemic heart disease is a major cause of mortality worldwide (Roger et al, 2011). Myocardial ischemia and reperfusion (I/R) injury is a common pathological physiological phenomenon in ischemic heart disease and cardiac surgery, typically arising from restoration of oxygenated blood flow after ischemia, which may lead to aggravated metabolic disorders, structural damage, and even irreversible damage (Thiel and Cibelli, 2002). Growth response protein 1 (Egr-1), a transcription factor, has been found to play a role in multiple pathways, such as differentiation, proliferation, and apoptosis (Shin et al, 2010; Zwang et al, 2012). Many studies suggest that Egr-1 is a master switch for various pathways of reperfusion injury because its overexpression is closely related to I/R injury (Yan et al, 2000; Frank et al, 2012; Wu et al, 2013)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
