Valproic acid treatment attenuates caspase-3 activation and improves survival after lethal burn injury in a rodent model

Murine scald models characterize the role of neutrophils and neutrophil extracellular traps in severe burns

Introduction

Severe burns cause unique pathophysiological alterations especially on the immune system. A murine scald model was optimized as a basis for the understanding of immunological reactions in response to heat induced injury. The understanding of the roles of neutrophil extracellular traps (NETs) and DNases will support the development of new surgical or pharmacological strategies for the therapy of severe burns.

Methods

We studied C57BL/6 mice (n=30) and employed four scalding protocols with varying exposure times to hot water. An additional scald group with a shorter observational time was generated to reduce mortality and study the very early phase of pathophysiology. At 24h or 72h, blood was drawn and tissue (wound, liver, lung, spleen) was analyzed for the presence of NETs, oxidative stress, apoptosis, bacterial translocation, and extracellular matrix re-organization. In addition, we analyzed the transcriptome from lung and liver tissues.

Results

Exposure to hot water for 7s led to significant systemic and local effects and caused considerable late mortality. Therefore, we used an observation time of 24h in this groups. To study later phases of burns (72h) an exposure time of 6s is optimal. Both conditions led to significant disorganization of collagen, increased oxidative stress, NET formation (by immunodetection of H3cit, NE, MPO), apoptosis (cC3) and alterations of the levels of DNase1 and DNase1L3. Transcriptome analysis revealed remarkable alterations in genes involved in acute phase signaling, cell cohesion, extracellular matrix organization, and immune response.

Conclusion

We identified two scald models that allow the analysis of early (24h) or late (72h) severe burn effects, thereby generating reproducible and standardized scald injuries. The study elucidated the important involvement of neutrophil activity and the role of NETs in burns. Extensive transcriptome analysis characterized the acute phase and tissue remodeling pathways involved in the process of healing and may serve as crucial basis for future in-depth studies.

Systematic review and meta-analysis of experimental studies evaluating the organ protective effects of histone deacetylase inhibitors

The clinical efficacy of organ protection interventions are limited by the redundancy of cellular activation mechanisms. Interventions that target epigenetic mechanisms overcome this by eliciting genome wide changes in transcription and signaling. We aimed to review preclinical studies evaluating the organ protection effects of histone deacetylase inhibitors (HDACi) with a view to informing the design of early phase clinical trials. A systematic literature search was performed. Methodological quality was assessed against prespecified criteria. The primary outcome was mortality, with secondary outcomes assessing mechanisms. Prespecified analyses evaluated the effects of likely moderators on heterogeneity. The analysis included 101 experimental studies in rodents (n = 92) and swine (n = 9), exposed to diverse injuries, including: ischemia (n = 72), infection (n = 7), and trauma (n = 22). There were a total of 448 comparisons due to the evaluation of multiple independent interventions within single studies. Sodium valproate (VPA) was the most commonly evaluated HDACi (50 studies, 203 comparisons). All of the studies were judged to have significant methodological limitations. HDACi reduced mortality in experimental models of organ injury (risk ratio = 0.52, 95% confidence interval 0.40-0.68, p < 0.001) without heterogeneity. HDACi administration resulted in myocardial, brain and kidney protection across diverse species and injuries that was attributable to increases in prosurvival cell signaling, and reductions in inflammation and programmed cell death. Heterogeneity in the analyses of secondary outcomes was explained by differences in species, type of injury, HDACi class (Class I better), drug (trichostatin better), and time of administration (at least 6 hours prior to injury better). These findings highlight a potential novel application for HDACi in clinical settings characterized by acute organ injury.

Sodium valproate ameliorates memory impairment and reduces the elevated levels of apoptotic caspases in the hippocampus of diabetic mice

Learning and memory deficits appear in chronic diabetes and valproic acid has been proved to be beneficial in neurodegenerative diseases. Hence, the current study investigated the effectiveness of chronic valproate treatment for diabetes-induced memory impairment and increased levels of hippocampal apoptotic caspases. This study was conducted in adult male C57B15/J mice. Diabetes, which was induced by alloxan (150 mg/kg; i.p.), was confirmed when fasting blood sugar (FBS) was > 200 mg/dl. Sodium valproate (100 mg/kg; i.p.) was administrated to the diabetic and non-diabetic groups, every 72 h for 2 months. Next, all groups were evaluated for memory performance using the radial maze and shuttle box. After FBS measurement, animals were killed and the hippocampus was extracted and prepared for ELISA to assess caspase levels. Diabetic animals had significantly high FBS and memory impairment 2 months after the alloxan injection. Hippocampal levels of caspases 3, 6, and 8 were significantly higher in the diabetic group than in the control group. However, valproate treatment of diabetic animals significantly improved memory performance in both the radial maze and shuttle box and reduced the elevated levels of hippocampal apoptotic caspases, in comparison with diabetic animals. Chronic administration of valproate seems to have beneficial effects on diabetic neuropathy.

Heart Protective Effects of Electroacupuncture in an Animal Experimental Study with Delayed Fluid Resuscitation after Hemorrhagic Shock

Fluid resuscitation could hardly be performed immediately after fatal hemorrhagic shock in outpatients. We investigated whether electroacupuncture (EA) at Zusanli (ST36) could prevent fatal hemorrhagic shock induced heart failure with delayed fluid resuscitation and whether the protective role of EA is related to the autonomic nervous system. Sixty Sprague Dawley rats were randomly divided into five groups (n = 12 each): group of sham hemorrhagic shock (SHAM), group of EA, group of sham EA (SEA), group of delayed fluid resuscitation with EA (EA + DR), and group of delayed fluid resuscitation with SEA (SEA + DR). After blood loss for 6 hours, caspase-3 activity and positive rate of TUNEL in EA + DR group were significantly lower than in other hemorrhagic shock groups (e.g., versus SEA + DR: 0.156 ± 0.039 versus 0.301 ± 0.042; P < 0.05). Immediately EA treatment after the blood loss enhanced the protective effect of delayed resuscitation on the cardiac tissue of hemorrhagic shock rats. Considering the significant changes of epinephrine (137.8 ± 6.9 ng/L versus 98.6 ± 7.4 ng/L; P < 0.05) and acetylcholine (405 ± 8.6 pmol/L versus 341 ± 10.1 pmol/L; P < 0.05) after EA treatment (SEA + DR versus EA + DR), this cardiac protective effect may be related to regulation of the autonomic nervous system.

Remote Burn Injury Increases Pulmonary Histone Deacetylase 1 and Reduces Histone Acetylation

Dermal burn injury causes profound physiological derangements. Respiratory failure is a primary cause of morbidity and mortality after burn injury, in part, because of excessive and prolonged release of local and systemic proinflammatory mediators. Clinical and preclinical evidence suggests histone deacetylases (HDACs) are key mediators of inflammatory responses. The study objective was to explore the effects of dermal burn injury on pulmonary HDAC activity, identify specific lung HDAC(s) altered by burn, and characterize histone lysine acetylation status. Mice were subjected to a 15% total body surface area scald burn or a sham injury and euthanized 24 hours later. Whole lungs were harvested, or alveolar macrophages were isolated from bronchoalveolar lavage fluid. HDAC specific activity assays were performed, Western blots were run to analyze HDACs1, 2, 3, 4, and 10 or histone lysine acetylation levels, and HDAC1 and phosphorylated-HDAC1 levels and localization were examined by immunofluorescence. Burned mice had higher HDAC specific activity and increased HDAC1 levels compared with controls, but levels of other HDACs were comparable between groups. Burn injury increased levels of HDAC1 and phosphorylated-HDAC1 in bronchioles and alveolar sacs and was associated with global and specific diminished levels of histone H3 and histone H4 lysine acetylation. Our analyses reveal that pulmonary inflammation after burn injury may be modulated by epigenetic mechanisms involving HDACs because HDAC activity, HDAC1 expression and activity, and downstream histone acetylation were all altered after burn. Future studies will explore the role of HDAC inhibitors in reversing inflammatory defects and may ultimately lead to new treatment interventions for burn patients.

Alcohol Modulation of the Postburn Hepatic Response

The widespread and rapidly increasing trend of binge drinking is accompanied by a concomitant rise in the prevalence of trauma patients under the influence of alcohol at the time of their injury. Epidemiological evidence suggests up to half of all adult burn patients are intoxicated at the time of admission, and the presence of alcohol is an independent risk factor for death in the early stages post burn. As the major site of alcohol metabolism and toxicity, the liver is a critical determinant of postburn outcome, and experimental evidence implies an injury threshold exists beyond which burn-induced hepatic derangement is observed. Alcohol may lower this threshold for postburn hepatic damage through a variety of mechanisms including modulation of extrahepatic events, alteration of the gut-liver axis, and changes in signaling pathways. The direct and indirect effects of alcohol may prime the liver for the second-hit of many overlapping physiologic responses to burn injury. In an effort to gain a deeper understanding of how alcohol potentiates postburn hepatic damage, the authors summarize possible mechanisms by which alcohol modulates the postburn hepatic response.

Xuebijing Injection () increases early survival rate by alleviating pulmonary vasopermeability in rats subjected to severe burns

OBJECTIVE

To investigate the effects of Xuebijing Injection (, XBJ) on survival rate and pulmonary vasopermeability in a rat model of severe scald injury.

METHODS

Rats were divided into two experiments: experiment 1 was monitored for 12 h post-injury for survival analysis after severe burns; in experiment 2, rats were killed for determination of pulmonary vascular permeability and pro-inflflammatory mediators. In both experiments, rats were subject to third-degree 50% total body surface area (TBSA) burns or sham injury followed by XBJ or normal saline (NS) treatment. In addition, rat pulmonary microvascular endothelium cells (PMECs) were pretreated with either XBJ or phosphate buffer saline (PBS), and then subjected to sham serum or scald serum stimulation for 2 or 6 h, followed by transwell examination for the permeability of PMECs. Meanwhile, pro-inflflammatory mediators in PMECs culture supernatant were also investigated.

RESULTS

The average survival time in the scald+XBJ group was 582.1±21.2 min, which was signifificantly longer than that in the scald + NS group (345.8±25.4 min, P<0.01). Plasma levels of tumor necrosis factor-alpha (TNF-α), E-selectin, interleukin-6 (IL-6), vascular permeability and water content of lung tissues were signifificantly increased in animals after severe burns (P<0.01). However, administration of XBJ signifificantly decreased these levels in plasma and lung tissue. In in vitro cell experiments, XBJ markedly attenuated permeability in PMECs monolayer and reduced the levels of TNF-α, IL-6 and soluble E-selectin after stimulation with scald serum (P<0.01).

CONCLUSIONS

XBJ increases early survival rate by alleviating pulmonary vasopermeability and inhibiting pro-inflflammatory mediators in rats subjected to lethal scald injury. XBJ may be a potent drug in treatment of severe burns.

Selective inhibition of histone deacetylase 6 promotes survival in a rat model of hemorrhagic shock

BACKGROUND

Hemorrhage is the leading cause of preventable trauma-related deaths. We have previously shown that treatment with Tubastatin A (Tub A), a histone deacetylase 6 (HDAC6) inhibitor, can improve survival in a rodent model of septic shock. The aims of the present study were to determine whether selective inhibition of HDAC6 can promote survival in a model of hemorrhagic shock (HS).

METHODS

In Experiment I (survival study), Wistar-Kyoto rats were subjected to HS (55% volume blood loss), followed by intraperitoneal injection of either Tub A (70 mg/kg) dissolved in dimethyl sulfoxide (DMSO) or DMSO only (vehicle group) (n = 8 per group). Survival was monitored for 24 hours. In Experiment II (physiologic study), rats were subjected to a sublethal HS (40% blood loss), followed by the same treatment with Tub A (treatment group) or DMSO only (vehicle group, n = 5 per group). All animals were sacrificed 6 hours after hemorrhage, and the heart and liver tissues were harvested. Sham animals were not subjected to hemorrhage and treatment (sham group, n = 5 per group). Cardiac mitochondria were isolated to study the pyruvate dehydrogenase (PDH, an essential enzyme for adenosine triphosphate production) activity. Liver tissue lysates were analyzed for markers of apoptosis (cytochrome c, cleaved caspase 3) and inflammation (high-mobility group box 1) by Western blotting.

RESULTS

Severe HS (55% blood loss) was associated with 75% mortality, which was significantly improved by Tub A treatment (37.5% mortality in 24 hours, p = 0.048). Tub A also significantly enhanced the cardiac PDH activity compared with the vehicle group, while suppressing the hepatic high-mobility group box 1 expression, cytochrome c release, and caspase 3 activation.

CONCLUSION

Our study has demonstrated for the first time that selective inhibition of HDAC6 can improve survival in a rodent model of HS. The potential mechanisms include enhanced PDH activity, decreased inflammatory drive, and attenuated cellular apoptosis.

Electroacupuncture at Zusanli Prevents Severe Scalds-Induced Gut Ischemia and Paralysis by Activating the Cholinergic Pathway

Severe burn injuries may result in gastrointestinal paralysis, and barrier dysfunction due to gut ischemia and lowered vagus excitability. In this study we investigate whether electroacupuncture (EA) at Zusanli (ST36) could prevent severe scalds-induced gut ischemia, paralysis, and barrier dysfunction and whether the protective role of EA at ST36 is related to the vagus nerve. 35% burn area rats were divided into six groups: (a) EAN: EA nonchannel acupoints followed by scald injury; (b) EA: EA at ST36 after scald injury; (c) VGX/EA: vagotomy (VGX) before EA at ST36 and scald injury; (d) VGX/EAN: VGX before EAN and scald injury; (e) atropine/EA: applying atropine before scald injury and then EA at ST36; (f) atropine/EAN: applying atropine before scald injury and then EA at nonchannel acupoints. EA at the Zusanli point significantly promoted the intestinal impelling ratio and increased the amount of mucosal blood flow after scald injury. The plasma diamine oxidase (DAO) and intestinal permeability decreased significantly after scald injury in the EA group compared with others. However, EA after atropine injection or cervical vagotomy failed to improve intestinal motility and mucosa blood flow suggesting that the mechanism of EA may be related to the activation of the cholinergic nerve pathway.