Hemorrhagic Shock and Fluid Resuscitation Alter Gene Expression of Chromatin Modification Enzymes in Thoracic Aorta of Swine ( Sus scrofa )

Trauma is the number one cause of death in the United States in people between the ages of 1 and 46 years old. Rapid and significant blood loss from traumatic injury often leads to a state of hemorrhagic shock characterized by reduced blood pressure, hypo‐perfusion of peripheral tissue, inflammation, and failure of homeostatic mechanisms that can lead to irreversible organ damage. During shock, blood vessels become dysfunctional, thus contributing to poor prognosis. Although fluid resuscitation is commonly used to improve outcome, there can be irreversible vascular dysfunction as a result. We hypothesized that epigenetic processes are associated with vascular dysfunction induced by hemorrhagic shock and fluid resuscitation. Alterations in expression of enzymes that modify chromatin structure serve as a reliable indicator of changes in epigenetic processes. The objective of this study was to investigate the effect of hemorrhagic shock and resuscitation on aortic gene expression of a large array of chromatin modification enzymes in a pig model. Yorkshire cross young adult pigs (n = 6; body weight, 33.3±2.5 kg) were anesthetized, mechanically ventilated, and cardiac catheterized for hemodynamic monitoring. Baseline measurements were obtained, and then pigs were either subjected to hemorrhage (n=3) or served as controls (n=3). Pigs in the hemorrhage group were bled to a target volume of 30 mL/kg and mean arterial pressure of 35 mmHg. One hour after hemorrhage, animals were resuscitated with saline up to one shed blood volume. Approximately 120 minutes after resuscitation and stabilization of hemodynamics, animals were euthanized, and tissue was immediately harvested. RNA was isolated from thoracic aorta using Tri‐Reagent (Sigma‐Aldrich) followed by cleanup and concentration by commercial kit. RNA integrity was confirmed by electrophoresis (RIN ≥ 7.8; Agilent 2100 Bioanalyzer). cDNA synthesis was performed using a commercial kit, and real‐time quantitative RT‐PCR was performed using the Epigenetic Chromatin Modification Enzymes RT2 Profiler Array (Qiagen). Out of 84 genes assessed, expression of E3 ubiquitin‐protein ligase BRE1B‐like gene ( RNF40 ; fold change from control, 0.68; 95% CI, 0.55 to 0.81); p = 0.018), and K(lysine) acetyltransferase 2A ( KAT2A ; fold change from control, 0.80; 95% CI, 0.67 to 0.93); p = 0.038) were significantly changed after hemorrhage and resuscitation. Expression of RNF40 , a gene that is important in the initiation of DNA damage response, was significantly reduced, suggesting that hemorrhage and resuscitation may lead to impairment of vascular repair mechanisms. Also, significant reduction in KAT2A expression indicates that hemorrhage and resuscitation can lead to differential regulation of vascular genes via reduced acetylation of histone and non‐histone proteins in vessels. These novel findings may help to elucidate mechanisms by which hemorrhagic shock and resuscitation lead to long‐term vascular dysfunction. The views expressed in this presentation are those of the authors and do not reflect the official policy or position of the Department of the Army, the Department of Defense, or the U.S. Government.