BACKGROUND: We have previously shown that addition of valproic acid (VPA; a histone deacetylase inhibitor) to hetastarch (Hextend [HEX]) resuscitation significantly decreases lesion size in a swine model of traumatic brain injury (TBI) and hemorrhagic shock (HS). However, the precise mechanisms have not been well defined. As VPA is a transcriptional modulator, the aim of this study was to investigate its effect on brain gene expression profiles.
METHODS: Swine were subjected to controlled TBI and HS (40% blood volume), kept in shock for 2 hours, and resuscitated with HEX or HEX + VPA (n = 5 per group). Following 6 hours of observation, brain RNA was isolated, and gene expression profiles were measured using a Porcine Gene ST 1.1 microarray (Affymetrix, Santa Clara, CA). Pathway analysis was done using network analysis tools Gene Ontology, Ingenuity Pathway Analysis, and Parametric Gene Set Enrichment Analysis. Real-time polymerase chain reaction was used to verify the key microarray findings.
RESULTS: A total of 1,668 probe sets mapping to 370 known genes were differentially expressed between the HEX and HEX + VPA groups. Expression of apoptotic genes differed between groups, and biologic function analysis predicted a significant downregulation of apoptosis (p = 1.29 × 10−12), cell death (p = 8.46 × 10−12), and necrosis (p = 9.07 × 10−11). Pathway analysis indicated a significant modulation of pathways involved in cell signaling, dendritic cell response, and the complement system.
CONCLUSION: This is the first high-throughput analysis of cerebral gene profiling following TBI + HS. It shows that treatment with VPA significantly alters early transcription of pathways related to cell survival, which may explain its neuroprotective effects.
From the Department of Surgery (S.E.D., T.B., B.L., G.J., Y.L., H.B.A.), University of Michigan Hospital, Ann Arbor, Michigan; Department of Anesthesiology (S.E.D.), Institute for Cardiovascular Research, VU University Medical Center, Amsterdam, the Netherlands; Department of Surgery (M.S.), Division of Trauma, Emergency Surgery and Surgical Critical Care, Massachusetts General Hospital/Harvard Medical School, Boston, Massachusetts; Department of Surgery (M.S.), Copenhagen University Hospital, Hillerød, Denmark; and Biomedical Research Core Facilities (C.N.J.), DNA Sequencing Core Lab, University of Michigan, Ann Arbor, Michigan.
Submitted: January 15, 2014, Revised: March 21, 2014, Accepted: March 31, 2014, Published online: July 21, 2014.
This study was presented at the 44th Annual Meeting of the Western Trauma Association, March 2–7, 2014, in Steamboat Springs, Colorado.
Address for reprints: Hasan B. Alam, MD, Department of Surgery, University of Michigan Hospital, 2920 Taubman Center, 1500 E. Medical Center Dr, Ann Arbor, MI 48109; email: firstname.lastname@example.org.