Creating a Prosurvival Phenotype Through a Histone Deacetylase Inhibitor in a Lethal Two-Hit Model

Abstract

Objectives Hemorrhagic shock (HS) can initiate an exaggerated systemic inflammatory response and multiple organ failure, especially if followed by a subsequent inflammatory insult (“second hit”). We have recently shown that histone deacetylase inhibitors can improve survival in rodent models of HS or septic shock, individually. In the present study, we examined whether valproic acid (VPA), a histone deacetylase inhibitor, could prolong survival in a rodent “two-hit” model: HS followed by septic shock from cecal ligation and puncture (CLP). Methods Male Sprague-Dawley rats (250–300 g) were subjected to sublethal HS (40% blood loss) and then randomly divided into two groups (n = 7/group): VPA and control. The VPA group was treated intraperitoneally with VPA (300 mg/kg in normal saline [NS], volume = 750 μL/kg). The control group was injected with 750 μL/kg NS. After 24 h, all rats received CLP followed immediately by injection of the same dose of VPA (VPA group) or NS (vehicle group). Survival was monitored for 10 days. In a parallel study, serum and peritoneal irrigation fluid from VPA- or vehicle-treated rats were collected 3, 6, and 24 h after CLP, and enzyme-linked immunosorbent assay was performed to analyze myeloperoxidase activity and determine tumor necrosis factor α and interleukin 6 concentrations. Hematoxylin-eosin staining of lungs at 24-h time point was performed to investigate the grade of acute lung injury. Results Rats treated with VPA (300 mg/kg) showed significantly higher survival rates (85.7%) compared with the control (14.3%). Moreover, VPA significantly suppressed myeloperoxidase activity (marker of neutrophil-mediated oxidative damage) and inhibited levels of proinflammatory cytokine tumor necrosis factor α and interleukin 6 in the serum and peritoneal cavity. Meanwhile, the severity of acute lung injury was significantly reduced in VPA-treated animals. Conclusions We have demonstrated that VPA treatment improves survival and attenuates inflammation in a rodent two-hit model.

Creating a “Prosurvival Phenotype” Through Histone Deacetylase Inhibition

“…Importantly, these results were achieved in the absence of standard fluid resuscitation. Similar benefits were seen in a “two-hit” models, where hemorrhage was followed by a CLP insult in rodents (56). In that study, rats treated with VPA showed a significantly better long-term survival rate (86% vs. 14%, p < 0.05) (Figure 3a), suppressed inflammatory profile (Figure 3b), and lower severity of acute lung injury.…”

Selective histone deacetylase 6 inhibition prolongs survival in a lethal two-hit model

“…Preclinical data have confirmed that treatment with a pan-HDACI agent (e.g. valproic acid) improves survival in small and large animal models of HS, suppresses inflammation, activates pro-survival pathways, attenuates tissue damage, prevents distant organ injury, and prevents death in models of septic shock as well as in two-hit rodent models [8, 18–20]. Although pan HDACI are effective, they often require very large doses to exert the desired effect, which raises concerns about potential toxicity.…”

“…VPA). While VPA has been shown to suppress inflammation, attenuate tissue damage, prevent distant organ injury, and death in models of septic shock as well as two-hit insults [8, 18], the non-specific inhibition of HDAC can be problematic. VPA inhibits class I (HDAC 1, 2, 3 and 8) and class II HDACs (HDAC4, 5 7, and 9) [25], which can have undesirable effects.…”

“…Hemorrhage was induced as previously described by Liu et al [8]. Mice were anesthetized with 0.7% to 1.2%isoflurane (Abbott Laboratories, North Chicago, IL) mixed with air, which was administered via a nose cone scavenging system and allowed to breathe spontaneously, using a veterinary multichannel anesthesia delivery system and vaporizer (Kent Scientific Corporation, Torrington, CT).…”

“…It has been reported that histone hyperacetylation results in up-regulation of cell cycle inhibitors (p21Cip1, p27Kip1, and p16INK4), repression of inflammatory cytokines [interleukin (IL)-1, IL-8, tumor necrosis factor-α (TNF-α)], and down-regulation of immune stimulators (IL-6, IL-10, and CD154) [7]. Our team has previously demonstrated that treatment with valproic acid, a pan HDAC inhibitor, results in improved survival in a rodent two-hit (HS followed SS) model [8]. However, class and isoform selective inhibition of HDAC is now gaining favor as it limits the toxicity that has been observed with pan-HDAC inhibitors (HDACI).…”