Elizabeth Sailhammer, MD, MMSc, M. Umar Butt, MD, Yongqing Li, MD, PhD, Nikolaos Zacharias, MD, George C. Velmahos, MD, Hasan B. Alam, MD
Massachusetts General Hospital- Division of Division of Trauma, Emergency Surgery and Surgical Critical Care; Boston, MA
PURPOSE OF STUDY:
We have previously shown that treatment with histone deacetylase inhibitors (HDACI) can enhance nuclear acetylation, attenuate organ injury, and improve survival in animal models of lethal hemorrhage, even in the absence of fluid resuscitation. In the current study, we explored whether treatment with valproic acid, an HDACI, would protect against JNK and caspase-3 mediated apoptosis following lethal hemorrhagic shock.
Wistar-Kyoto rats underwent hemorrhagic shock (60% blood loss) followed by either 1) no resuscitation, or 2) valproic acid (VPA; 300mg/kg, administered post-shock, without resuscitation fluids). Normal animals acted as controls (Sham). Liver samples were obtained 1, 6, and 24 hours post-hemorrhage (n=3/group). Cytosolic and nuclear proteins were isolated and Western blots were performed for acetylated histone-H3 at lysine-9 (Ac-H3K9), total and phosphorylated JNK (c-Jun N-terminal kinase), and activated caspase-3.
SUMMARY OF RESULTS:
Hemorrhage produced severe shock. Only the VPA treated animals survived to the 6- and 24-hour timepoints. Treatment with VPA induced acetylation of histone H3K9 in the liver, which peaked at 1 hour and returned towards normal by 24 hours. Hemorrhage induced JNK-phosphorylation and increased levels of activated caspase-3, representing a commitment to subsequent cell death. Treatment with VPA markedly decreased JNK-phosphorylation at 24 hours, without changing total levels of JNK, and this correlated with attenuation of activated caspase-3 at 24 hours.
Treatment with HDACI induces acetylation of histone protein, and reduces JNK phosphorylation and subsequent caspase-3 activation. This discovery establishes for the first time that HDACI may protect cells after severe hemorrhage through modulation of the JNK/caspase-3 apoptotic pathway.