Valproic acid improves survival and decreases resuscitation requirements in a swine model of prolonged damage control resuscitation

Testing Neuroprotective Strategies in Prolonged Field Care Model of Traumatic Brain Injury and Hemorrhagic Shock

BACKGROUND

Prolonged field care is a military adaptation of tactical combat casualty care providing extended prehospital management during delayed extrication. Effects of addition of valproic acid (VPA) to fresh-frozen plasma (FFP) in a prolonged field care model of hemorrhagic shock and traumatic brain injury are not known. We hypothesized that VPA is associated with decreased neurological impairment, and its protective changes are detected at the transcriptomic level.

STUDY DESIGN

Swine underwent traumatic brain injury and 40% blood volume hemorrhage. After 2 hours of shock, they were randomized to (1) normal saline (NS), (2) NS + 250 mL FFP (NS + FFP), or (3) NS + FFP + 150 mg/kg VPA (NS + FFP + VPA). At 72 hours, they were transfused packed RBCs before being euthanized. Intraoperative variables and neurological outcomes were compared. Brain lesion size was measured, and gene expression profiles were analyzed using RNA sequencing. Pathway and network analyses were performed on differentially expressed genes. Real-time polymerase chain reaction was performed to validate key genes.

RESULTS

NS + FFP and NS + FFP + VPA required significantly less crystalloid resuscitation (974 mL: NS + FFP; 1,461 mL: NS + FFP + VPA vs 4,540 mL: NS, p < 0.001), had smaller brain lesion size (2,477 mm 3 : NS + FFP; 3,018.0 mm 3 : NS + FFP + VPA vs 4,517.0 mm 3 : NS, p < 0.01), and required less functional neurologic impairment compared with NS. Per pathway analysis of differentially expressed genes, VPA was associated with enrichment of numerous metabolic changes in injured brains, which were not observed with FFP. Network analysis showed enrichment of various gene networks. Mitochondrially encoded ATP synthase membrane subunit 8 gene was downregulated in VPA-treated animals.

CONCLUSIONS

The addition of FFP to the resuscitation protocol resulted in a significant reduction in crystalloid requirements. Both the NS + FFP and NS + FFP + VPA groups showed improved neurological recovery compared with NS alone and had distinctive transcriptomic profiles in injured brains at 72 hours. The mitochondrially encoded ATP synthase membrane subunit 8 gene, involved in worsening ischemia following brain injury, was downregulated in VPA-treated animals.

Plasma treatment is associated with decreased brain lesion and resuscitation requirements after traumatic brain injury in a swine model of prolonged damage-control resuscitation

BACKGROUND

Hemorrhage and traumatic brain injury (TBI) are the leading causes of death in trauma. Future military conflicts are likely to be in austere environments, where prolonged damage-control resuscitation (p-DCR) may be required for 72 hours before evacuation. Previous studies showed that early administration of fresh frozen plasma (FFP) during p-DCR can significantly decrease the volume of resuscitation required in models of hemorrhagic shock and also provide neuroprotection after TBI. In the current study, we hypothesized that the addition of FFP to p-DCR would decrease the resuscitation requirements and improve neurological outcomes in a large animal model of combined hemorrhagic shock and TBI.

METHODS

Yorkshire swine (40-45 kg; n = 10) were subjected to TBI (controlled cortical impact) and 40% blood volume hemorrhage. After 2 hours of shock, they were randomized to either: (1) p-DCR-normal saline or (2) p-DCR-FFP (250 mL). Prolonged damage-control resuscitation targeted a systolic blood pressure of 90% of baseline, in line with Tactical Combat Casualty Care principles. At 72 hours, animals were transfused 1 U of packed red blood cells, simulating evacuation to higher echelons of care. Brain lesion size, physiologic parameters, resuscitation fluid requirements, and neurological severity score were used to compare the clinical outcomes.

RESULTS

The p-DCR-FFP group required significantly less total volume (4,540.0 ± 151.7 mL vs. 974.0 ± 167.0 mL, p < 0.01) of resuscitation to maintain the target systolic blood pressure. Fresh frozen plasma-treated animals had significantly reduced brain lesion size (4,517.0 ± 180.0 mm3 vs. 2,477.0 ± 1,191.0 mm3, p < 0.01) and showed significantly decreased functional neurologic impairment.

CONCLUSION

In this exploratory study, treatment with FFP decreased resuscitation requirements, reduced brain lesion size, and improved neurological outcomes when added to prolonged DCR in a porcine model of combined hemorrhagic shock and TBI.

Prolonging the therapeutic window for valproic acid treatment in a swine model of traumatic brain injury and hemorrhagic shock

BACKGROUND

It has previously been shown that administration of valproic acid (VPA) can improve outcomes if given within an hour following traumatic brain injury (TBI). This short therapeutic window (TW) limits its use in real-life situations. Based upon its pharmacokinetic data, we hypothesized that TW can be extended to 3 hours if a second dose of VPA is given 8 hours after the initial dose.

METHOD

Yorkshire swine (40-45 kg; n = 10) were subjected to TBI (controlled cortical impact) and 40% blood volume hemorrhage. After 2 hours of shock, they were randomized to either (1) normal saline resuscitation (control) or (2) normal saline-VPA (150 mg/kg × two doses). First dose of VPA was started 3 hours after the TBI, with a second dose 8 hours after the first dose. Neurologic severity scores (range, 0-36) were assessed daily for 14 days, and brain lesion size was measured via magnetic resonance imaging on postinjury day 3.

RESULTS

Hemodynamic and laboratory parameters of shock were similar in both groups. Valproic acid-treated animals had significantly less neurologic impairment on days 2 (16.3 ± 2.0 vs. 7.3 ± 2.8) and 3 (10.9 ± 3.6 vs. 2.8 ± 1.1) postinjury and returned to baseline levels 54% faster. Magnetic resonance imaging showed no differences in brain lesion size on day 3. Pharmacokinetic data confirmed neuroprotective levels of VPA in the circulation.

CONCLUSION

This is the first study to demonstrate that VPA can be neuroprotective even when given 3 hours after TBI. This expanded TW has significant implications for the design of the clinical trial.

Valproic Acid During Hypotensive Resuscitation In Pigs With Trauma And Hemorrhagic Shock Does Not Improve Survival

BACKGROUND

Valproic acid (VPA) has been extensively used for treatment of anxiety and seizure. Recent studies have shown that VPA has cellular protective effects in preclinical models following severe hemorrhage. This study investigated the effects of VPA on coagulation and survival in pigs after traumatic hemorrhage and hypotensive resuscitation.

METHODS

Following baseline measurements, femur fracture was performed in 20 anesthetized and instrumented pigs (41 ± 2 kg), followed by hemorrhage of 55% of the estimated blood volume and a 10 min shock period. Pigs were then resuscitated over 30 min with: normal saline alone (NS group, n = 10, 4 ml/kg) or VPA solution (VPA group, n = 10, 90 mg/kg, 2 ml/kg of 45 mg VPA/ml, plus 2 ml NS/kg). All pigs were then monitored for 2 hrs or until death. Hemodynamics were recorded and blood samples were taken for blood and coagulation analysis (Rotem®) at baseline, after hemorrhage, resuscitation, and 2 hrs or death.

RESULTS

Femur fracture and hemorrhage caused similar reductions in mean arterial pressure (MAP) and cardiac output and increase in heart rate in both groups. Resuscitation with NS or VPA did not return these measurements to baseline. No differences were observed in hematocrit, pH, lactate, base excess, or total protein between the groups. Compared to NS, resuscitation with VPA decreased platelet counts and prolonged aPTT, with no differences in fibrinogen levels, PT, or any of the Rotem® measurements between the two groups. Neither survival rates (NS: 7 of 10 pigs and VPA: 7 of 10 pigs) nor survival times after resuscitation (NS: 97 ± 40 min and VPA: 98 ± 43 min) differed between the groups.

CONCLUSIONS

Following traumatic hemorrhage and hypotensive resuscitation in pigs, VPA provides no benefit towards improving coagulation function or survival times.

LEVELS OF RELEVANCE

N/A.

Pathophysiology of Hemorrhage as It Relates to the Warfighter

Saving lives of wounded military Warfighters often depends on the ability to resolve or mitigate the pathophysiology of hemorrhage, specifically diminished oxygen delivery to vital organs that leads to multi-organ failure and death. However, caring for hemorrhaging patients on the battlefield presents unique challenges that extend beyond applying a tourniquet and giving a blood transfusion, especially when battlefield care must be provided for a prolonged period. This review will describe these challenges and potential strategies for treating hemorrhage on the battlefield in a prolonged casualty care situation.

Resuscitative endovascular balloon occlusion of the aorta in combat casualties: The past, present, and future

BACKGROUND

Noncompressible torso hemorrhage is a leading cause of preventable death on the battlefield. Intra-aortic balloon occlusion was first used in combat in the 1950s, but military use was rare before Operation Iraqi Freedom and Operation Enduring Freedom. During these wars, the combination of an increasing number of deployed vascular surgeons and a significant rise in deaths from hemorrhage resulted in novel adaptations of resuscitative endovascular balloon occlusion of the aorta (REBOA) technology, increasing its potential application in combat. We describe the background of REBOA development in response to a need for minimally invasive intervention for hemorrhage control and provide a detailed review of all published cases (n = 47) of REBOA use for combat casualties. The current limitations of REBOA are described, including distal ischemia and reperfusion injury, as well as ongoing research efforts to adapt REBOA for prolonged use in the austere setting.

LEVEL OF EVIDENCE

Level V.

Valproic Acid Protects Against Acute Kidney Injury in Hemorrhage and Trauma

INTRODUCTION

Trauma is the leading cause of death among young people. These patients have a high incidence of kidney injury, which independently increases the risk of mortality. As valproic acid (VPA) treatment has been shown to improve survival in animal models of lethal trauma, we hypothesized that it would also attenuate the degree of acute kidney injury.

METHODS

We analyzed data from two separate experiments where swine were subjected to lethal insults.  Model 1: hemorrhage (50% blood volume hemorrhage followed by 72-h damage control resuscitation). Model 2: polytrauma (traumatic brain injury, 40% blood volume hemorrhage, femur fracture, rectus crush and grade V liver laceration). Animals were resuscitated with normal saline (NS) +/- VPA 150 mg/kg after a 1-h shock phase in both models (n = 5-6/group). Serum samples were analyzed for creatinine (Cr) using colorimetry on a Liasys 330 chemistry analyzer. Proteomic analysis was performed on kidney tissue sampled at the time of necropsy.

RESULTS

VPA treatment significantly (P < 0.05) improved survival in both models. (Model 1: 80% vs 20%; Model 2: 83% vs. 17%). Model 1 (Hemorrhage alone): Cr increased from a baseline of 1.2 to 3.0 in NS control animals (P < 0.0001) 8 h after hemorrhage, whereas it rose only to 2.1 in VPA treated animals (P = 0.004). Model 2 (Polytrauma): Cr levels increased from baseline of 1.3 to 2.5 mg/dL (P = 0.01) in NS control animals 4 h after injury but rose to only 1.8 in VPA treated animals (P = 0.02). Proteomic analysis of kidney tissue identified metabolic pathways were most affected by VPA treatment.

CONCLUSIONS

A single dose of VPA (150 mg/kg) offers significant protection against acute kidney injury in swine models of polytrauma and hemorrhagic shock.

Assessment of the Cytoprotective Effects of High-Dose Valproic Acid Compared to a Clinically Used Lower Dose

OBJECTIVE

Valproic acid (VPA) treatment improves survival in animal models of injuries on doses higher than those allowed by Food and Drug Administration (FDA). We investigated the proteomic alterations induced by a single high-dose (140mg/kg) of VPA (VPA140) compared to the FDA-approved dose of 30mg/kg (VPA30) in healthy humans. We also describe the proteomic and transcriptomic changes induced by VPA140 in an injured patient. We hypothesized that VPA140 would induce cytoprotective changes in the study participants.

METHODS

Serum samples were obtained from healthy subjects randomized to two groups; VPA140 and VPA30 at 3 timepoints: 0h(baseline), 2h, and 24h following infusion(n = 3/group). Samples were also obtained from an injured patient that received VPA140 at 0h, 6h and 24h following infusion. Proteomic analyses were performed using liquid chromatography-mass spectrometry (LC-MS/MS), and transcriptomic analysis was performed using RNA-sequencing. Differentially expressed (DE) proteins and genes were identified for functional annotation and pathway analysis using iPathwayGuide and gene set enrichment analysis (GSEA), respectively.

RESULTS

For healthy individuals, a dose comparison was performed between VPA140 and VPA30 groups at 2 and 24 h. Functional annotation showed that top biological processes in VPA140 versus VPA30 analysis at 2 h included regulation of fatty acid (P = 0.002) and ATP biosynthesis (P = 0.007), response to hypoxia (P = 0.017), cell polarity regulation (P = 0.031), and sequestration of calcium ions (P = 0.031). Top processes at 24 h in VPA140 versus VPA30 analysis included amino acid metabolism (P = 0.023), collagen catabolism (P = 0.023), and regulation of protein breakdown (P = 0.023). In the injured patient, annotation of the DE proteins in the serum showed that top biological processes at 2 h included neutrophil chemotaxis (P = 0.002), regulation of cellular response to heat (P = 0.008), regulation of oxidative stress (P = 0.008) and regulation of apoptotic signaling pathway (P = 0.008). Top biological processes in the injured patient at 24 h included autophagy (P = 0.01), glycolysis (P = 0.01), regulation of apoptosis (P = 0.01) and neuron apoptotic processes (P = 0.02).

CONCLUSIONS

VPA140 induces cytoprotective changes in human proteome not observed in VPA30. These changes may be responsible for its protective effects in response to injuries.

Management of non-compressible torso hemorrhage: An update

With the widespread adoption of advanced tourniquets, the mortality rate of limb wound hemorrhage has decreased significantly, and non-compressible torso hemorrhage has gradually occupied the leading position of potentially preventable death, both in military and civilian circumstances. With the emergence of novel hemostatic devices and materials, strategies for the management of non-compressible torso hemorrhage have changed significantly. This review summarizes the current treatment strategies and types of equipment for non-compressible torso hemorrhage and suggests future research directions, hoping to provide a comprehensive review for the medical personnel and researchers engaging in this field.

Validation of intraosseous delivery of valproic acid in a swine model of polytrauma

Background

Intraosseous (IO) drug delivery may be necessary in emergency situations when intravenous access is unattainable. Valproic acid (VPA) is a histone deacetylase inhibitor that has previously been shown to improve survival in preclinical models of lethal polytrauma. In this study, we sought to compare serum levels of intravenously and IO-delivered VPA, and to analyze the effect of IO-delivered VPA.

Methods

Swine were subjected to 40% blood volume hemorrhage, brain injury, femur fracture, rectus crush injury and liver laceration. After 1 hour of shock, animals were randomized (n=3/group) to receive normal saline resuscitation (control), normal saline+intravenous VPA 150 mg/kg (intravenous group) or normal saline +IO VPA 150 mg/kg (IO group). Serum levels of VPA were assessed between groups, and proteomics analyses were performed on IO and control groups on heart, lung and liver samples.

Results

Intravenous and IO serum VPA levels were similar at 1, 3, 5 and 7 hours after starting the infusion (p>0.05). IO-delivered VPA induced significant proteomics changes in the heart, lung and liver, which were most pronounced in the lung. Biologic processes affected included inflammation, metabolism and transcriptional & translational machinery. The control group had 0% survival, and the intravenous and IO group both had 100% survival to the end of the experiment (p<0.05).

Discussion

IO-delivered VPA is noninferior to intravenous administration and is a viable option in emergent situations when intravenous access is unattainable.

Level of evidence

Not applicable (animal study).

Valproic acid treatment rescues injured tissues after traumatic brain injury

BACKGROUND

No agents that are specifically neuroprotective are currently approved to emergently treat patients with traumatic brain injury (TBI). The histone deacetylase inhibitor, high-dose valproic acid (VPA) has been shown to have cytoprotective potential in models of combined TBI and hemorrhagic shock, but it has not been tested in an isolated TBI model. We hypothesized that VPA, administered after isolated TBI, will penetrate the injured brain, attenuate the lesion size, and activate prosurvival pathways.

METHODS

Yorkshire swine were subjected to severe TBI by cortical impact. One hour later, animals were randomized to VPA treatment (150 mg/kg delivered intravenously for 1 hour; n = 4) or control (saline vehicle; n = 4) groups. Seven hours after injury, animals were sacrificed, and brain lesion size was measured. Mass spectrometry imaging was used to visualize and quantitate brain tissue distribution of VPA. Sequential serum samples were assayed for key biomarkers and subjected to proteomic and pathway analysis.

RESULTS

Brain lesion size was 50% smaller (p = 0.01) in the VPA-treated animals (3,837 ± 948 mm) compared with the controls (1,900 ± 614 mm). Endothelial regions had eightfold higher VPA concentrations than perivascular regions by mass spectrometry imaging, and it readily penetrated the injured brain tissues. Serum glial fibrillary acid protein was significantly lower in the VPA-treated compared with the control animals (p < 0.05). More than 500 proteins were differentially expressed in the brain, and pathway analysis revealed that VPA affected critical modulators of TBI response including calcium signaling pathways, mitochondria metabolism, and biosynthetic machinery.

CONCLUSION

Valproic acid penetrates injured brain tissues and exerts neuroprotective and prosurvival effects that resulted in a significant reduction in brain lesion size after isolated TBI. Levels of serum biomarkers reflect these changes, which could be useful for monitoring the response of TBI patients during clinical studies.

Histone deacetylase 6 inhibition improves survival in a swine model of lethal hemorrhage, polytrauma, and bacteremia

BACKGROUND

Trauma is the leading cause of death for young Americans. Nonspecific histone deacetylase inhibitors, such as valproic acid, have been shown to improve survival in preclinical models of lethal trauma, hemorrhage, and sepsis. The doses needed to achieve a survival benefit are higher than Food and Drug Administration-approved doses, and the nonspecificity raises concerns about unintended adverse effects. The isoform-specific histone deacetylase 6 inhibitor, ACY-1083, has been found to be as efficacious as valproic acid in a rodent model of hemorrhagic shock. We hypothesized that ACY-1083 treatment would improve survival in a swine model of lethal hemorrhage, polytrauma, and bacteremia.

METHODS

Swine were subjected to 45% blood volume hemorrhage, brain injury, femur fracture, rectus crush, splenic and liver lacerations, and colon injury. After 1 hour of shock (mean arterial pressure, 30-35 mm Hg), animals were randomized to normal saline resuscitation (control) or normal saline plus ACY-1083 30 mg/kg treatment (n = 5/group). After 3 hours (simulating delayed evacuation), packed red blood cells and antibiotics were administered, the colon injury was repaired, and the abdomen was closed. Animals were then monitored for another 4 hours. Survival was assessed using Kaplan-Meier and log-rank test.

RESULTS

This combination of injuries was lethal. All animals became bacteremic, in addition to the severe hemorrhagic shock. Survival in the control group was 0%, and ACY-1083 treatment increased survival to 80% (p = 0.019). There was no difference in the brain lesion size between the groups.

CONCLUSION

A single dose of ACY-1083 markedly improves survival in an otherwise lethal model of polytrauma, hemorrhagic shock, and bacteremia.

Modulation of Brain Transcriptome by Combined Histone Deacetylase Inhibition and Plasma Treatment Following Traumatic Brain Injury and Hemorrhagic Shock

INTRODUCTION

We previously showed that the addition of valproic acid (VPA), a histone deacetylase inhibitor, to fresh frozen plasma (FFP) resuscitation attenuates brain lesion size and swelling following traumatic brain injury (TBI) and hemorrhagic shock (HS). The goal of this study was to use computational biology tools to investigate the effects of FFP+VPA on the brain transcriptome following TBI+HS.

METHODS

Swine underwent TBI+HS, kept in shock for 2 h, and resuscitated with FFP or FFP + VPA (n = 5/group). After 6 h of observation, brain RNA was isolated and gene expression was analyzed using a microarray. iPathwayGuide, Gene Ontology (GO), Gene-Set Enrichment Analysis, and Enrichment Mapping were used to identify significantly impacted genes and transcriptomic networks.

RESULTS

Eight hundred differentially expressed (DE) genes were identified out of a total of 9,118 genes. Upregulated genes were involved in promotion of cell division, proliferation, and survival, while downregulated genes were involved in autophagy, cell motility, neurodegenerative diseases, tumor suppression, and cell cycle arrest. Seven hundred ninety-one GO terms were significantly enriched. A few major transcription factors, such as TP53, NFKB3, and NEUROD1, were responsible for modulating hundreds of other DE genes. Network analysis revealed attenuation of interconnected genes involved in inflammation and tumor suppression, and an upregulation of those involved in cell proliferation and differentiation.

CONCLUSION

Overall, these results suggest that VPA treatment creates an environment that favors production of new neurons, removal of damaged cells, and attenuation of inflammation, which could explain its previously observed neuroprotective effects.

Valproic acid decreases resuscitation requirements after hemorrhage in a prolonged damage-control resuscitation model

BACKGROUND

Hemorrhage is the leading cause of preventable death in trauma. Future military conflicts are likely to be in austere environments, where prolonged damage-control resuscitation (p-DCR) may be required for 72 hours before evacuation. There is a need to demonstrate that p-DCR is feasible and to optimize its logistics. Dried plasma (DP) is a practical alternative to conventional blood products in austere settings, and valproic acid (VPA) improves survival in preclinical models of trauma and hemorrhage. We performed the current experiment to study the synergistic effects of VPA and DP and hypothesized that VPA treatment would decrease the fluid resuscitation requirements in p-DCR.

METHODS

Female swine were subjected to 50% hemorrhage (associated with 20% survival using non-plasma-based p-DCR) and left unresuscitated for 1 hour to simulate medic response time. They were then randomized to receive VPA (150 mg/kg + DP 250 mL; DP-VPA group; n = 5) or DP alone (DP group; n = 6). All animals were resuscitated to a systolic blood pressure of 80 mm Hg with lactated Ringer according to the Tactical Combat Casualty Care Guidelines for 72 hours, after which packed red blood cells were transfused to simulate evacuation to higher levels of care.

RESULTS

The DP-VPA group needed significantly (p = 0.002) less volume of lactated Ringer to reach and maintain the target systolic blood pressure. This would translate to a 4.3 L volume sparing effect for a 70-kg person.

CONCLUSION

Addition of a single dose of VPA significantly decreases the volume of resuscitation required in a p-DCR model.

Dose optimization of valproic acid in a lethal model of traumatic brain injury, hemorrhage, and multiple trauma in swine

BACKGROUND

Trauma is a leading cause of death, and traumatic brain injury is one of the hallmark injuries of current military conflicts. Valproic acid (VPA) administration in high doses (300-400 mg/kg) improves survival in lethal trauma models, but effectiveness of lower doses on survival is unknown. This information is essential for properly designing the upcoming clinical trials. We, therefore, performed the current study to determine the lowest dose at which VPA administration improves survival in a model of lethal injuries.

METHODS

Swine were subjected to traumatic brain injury (10-mm cortical impact), 40% blood volume hemorrhage, and multiple trauma (femur fracture, rectus crush, and Grade V liver laceration). After 1 hour of shock, animals were randomized (n = 6/group) to four groups: normal saline (NS) resuscitation; or NS with VPA doses of 150 mg/kg (VPA 150) or 100 mg/kg (VPA 100) administered over 3 hours or 100 mg/kg over 2 hours (VPA 100 over 2 hours). Three hours after shock, packed red blood cells were given, and animals were monitored for another 4 hours. Survival was assessed using Kaplan-Meier and log-rank test.

RESULTS

Without resuscitation, all of the injured animals died within 5 hours. Similar survival rates were observed in the NS (17%) and VPA 100 (0%) resuscitation groups. Survival rates in the 100-mg/kg VPA groups were significantly (p < 0.05) better when it was given over 2 hours (67%) compared to 3 hours (0%). 83% of the animals in the VPA 150 group survived, which was significantly higher than the NS and VPA 100 over 3 hours groups (p < 0.05).

CONCLUSION

A single dose of VPA (150 mg/kg) significantly improves survival in an otherwise lethal model of multiple injuries. This is a much lower dose than previously shown to have a survival benefit and matches the dose that is tolerated by healthy human subjects with minimal adverse effects.

LEVEL OF EVIDENCE

Therapeutic, level V.

Histone Deacetylase Inhibitors: A Novel Strategy for Neuroprotection and Cardioprotection Following Ischemia/Reperfusion Injury

Ischemia/reperfusion injury is a complex molecular cascade that causes deleterious cellular damage and organ dysfunction. Stroke, sudden cardiac arrest, and acute myocardial infarction are the most common causes of ischemia/reperfusion injury without effective pharmacologic therapies. Existing preclinical evidence suggests that histone deacetylase inhibitors may be an efficacious, affordable, and clinically feasible therapy that can improve neurologic and cardiac outcomes following ischemia/reperfusion injury. In this review, we discuss the pathophysiology and epigenetic modulations of ischemia/reperfusion injury and focus on the neuroprotective and cardioprotective effects of histone deacetylase inhibitors. We also summarize the protective effects of histone deacetylase inhibitors for other vital organs and highlight the key research priorities for their successful translation to the bedside.