Roles of ischemia and hypoxia and the molecular pathogenesis of post-burn cardiac shock

The interconnections between the microtubules and mitochondrial networks in cardiocerebrovascular diseases: Implications for therapy

Microtubules, a highly dynamic cytoskeleton, participate in many cellular activities including mechanical support, organelles interactions, and intracellular trafficking. Microtubule organization can be regulated by modification of tubulin subunits, microtubule-associated proteins (MAPs) or agents modulating microtubule assembly. Increasing studies demonstrate that microtubule disorganization correlates with various cardiocerebrovascular diseases including heart failure and ischemic stroke. Microtubules also mediate intracellular transport as well as intercellular transfer of mitochondria, a power house in cells which produce ATP for various physiological activities such as cardiac mechanical function. It is known to all that both microtubules and mitochondria participate in the progression of cancer and Parkinson's disease. However, the interconnections between the microtubules and mitochondrial networks in cardiocerebrovascular diseases remain unclear. In this paper, we will focus on the roles of microtubules in cardiocerebrovascular diseases, and discuss the interplay of mitochondria and microtubules in disease development and treatment. Elucidation of these issues might provide significant diagnostic value as well as potential targets for cardiocerebrovascular diseases.

Effects of Thymosin β4 on Myocardial Apoptosis in Burned Rats

The aim of this study was to investigate the effects of thymosin β4 on myocardial apoptosis following burns. Fifty healthy Sprague Dawley (SD) rats were randomly divided into the normal control group, resuscitation group the low-dose Tβ4 (thymosin β4) group (2g), the medium-dose Tβ4 group (6g), and the high-dose Tβ4 group (18g). The rats were immersed in 95°C hot water for 18 seconds, and then the model of 30% body surface area (TBSA) III° scald was established. The resuscated rats were injected with lactate Ringer's solution for antishock rehydration, while the Tβ4 treatment group was injected with lactate Ringer's solution for antishock rehydration, and the animals were sacrificed 6 h after scald. The degree of histopathological damage was observed by HE (hematoxylin and eosin) staining. Western blot was used to detect STAT1 and STAT3 protein expression levels. Real-time PCR was used to detect mRNA expressions of STAT1 and STAT3. The results showed that the apoptosis rate of the resuscitation group was significantly higher than that of the control group (P < 0.01). Compared with the resuscitation group, the apoptosis rate of thymosin β4 in the treatment group was significantly reduced (P < 0.01). Compared with the normal control group, the expression of STAT1 protein was increased and the expression of STAT3 protein was decreased in model group rats after ischemia and reperfusion. Compared with the model group, the expression of STAT1 protein decreased and the expression of STAT3 protein increased after ischemia-reperfusion in the thymosin β4 treatment group. Thymosin β4 may protect the myocardium by downregulating STAT1 and upregulating STAT3 expression and inhibiting myocardial apoptosis induced by ischemia and reperfusion after severe scald injury.

Efficacy of two-stage Meek micrografting in patients with severe burns

BACKGROUND

Burns are common injuries associated with high disability and mortality. In recent years, Meek micrografting technique has been gradually applied for the wound treatment of severe burns. However, the efficacy of two-stage Meek micrografting in patients with severe burns keeps unclear.

METHODS

The data of eligible patients with severe burns who were admitted to Southwest Hospital of the Third Military Medical University from January 2013 to December 2019 were retrospectively analysed. The patients were divided into two groups according to the Meek micrografting method: one-stage skin grafting (group A) and two-stage skin grafting (group B). The baseline data, survival rate of skin graft, length of hospital stay, treatment costs, laboratory data and cumulative survival were statistically analysed.

RESULTS

127 patients (91 in group A and 36 in group B) were included in the study. There were no significant difference in the baseline data, the length of hospital stay and treatment costs between the two groups. The survival rate of skin graft was higher in group B. Total protein and albumin level, platelet count in group B were superior to those in group A, while there were no difference in other laboratory data (prealbumin, serum creatinine, urea nitrogen, cystatin C, blood cultures, wound exudate cultures) and cumulative survival between the two groups.

CONCLUSION

Our results demonstrated that staged Meek micrografting could improve the survival rate of skin graft, by reducing the risks of hypoproteinaemia, hypoalbuminemia and low platelet counts after adequate resuscitation.

CD14 Involvement in Third-degree Skin Burn-induced Myocardial Injury via the MAPK Signaling Pathway

This study investigated the potential genes and related pathways in burn-induced myocardial injury. Rat myocardial injury induced by third-degree burn and the histopathological structures, apoptosis, and cardiac injury markers were then identified using hematoxylin & eosin staining, terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling staining, and enzyme-linked immunosorbent assay. Next, differentially expressed mRNAs were screened through next-generation sequencing (NGS), followed by functional annotation and key gene validation through quantitative reverse transcription-polymerase chain reaction. Subsequently, CD14 was screened out, and small interfering RNAs against CD14 were transfected to H9C2 cells to further verify the role of CD14 in burn-induced injury. The results showed that third-degree burn could markedly damage the structure of myocardial tissue, induce the apoptosis of myocardial cells, and increase the levels of myocardial injury-related markers, suggesting that burns could induce myocardial injury in rats. Besides, NGS data discovered that third-degree burn could result in 416 differentially upregulated mRNAs and 285 differentially downregulated mRNAs in myocardial tissue. It was also disclosed that differentially expressed mRNAs were mainly enriched in the phosphatidylinositol 3-kinase/Akt, mitogen-activated protein kinase (MAPK), and tumor necrosis factor signaling pathways. Furthermore, cell viability was significantly decreased in H9C2 cells treated with 10% rat burn serum. CD14 was significantly differentially expressed and screened out for further studies. Treatment with burn serum can significantly upregulate the phosphorylation level of extracellular signal-regulated kinase, p38, and c-Jun N-terminal kinase and the expression of cleaved caspase-3 and downregulate the expression of Bcl2 when compared with those in negative control of small interfering RNA transfected H9C2 cells, whereas interfering with CD14 expression reversed the effects of burn serum. The study demonstrated that burn serum treatment could activate the MAPK signaling pathway to promote cell apoptosis, and it can be reversed by interfering with the expression of CD14.

A Retrospective Study of Factors Influencing the Survival of Modified Meek Micrografting in Severe Burn Patients

Modified Meek micrografting is a common method for treating severe burn patients. This study was to analyze the factors affecting the survival of modified Meek micrografting, thereby improving the survival rate of skin grafts. Eighty-three patients who underwent modified Meek micrografting were analyzed. According to the survival rate of skin graft after operation, the patients were divided into good skin survival group (GSSG, survival rate ≥ 70%, 47 cases) and poor skin survival group (PSSG, survival rate < 70%, 36 cases). The baseline data, surgical information, perioperative laboratory indicators, and prognosis of the patients were statistically analyzed. The univariate analysis and repeated measurement showed the burn severity, Meek skin graft area, duration of anesthesia, the postoperative sepsis shock, the mortality, the neutrophils percentage on the third day after surgery (NEU3), and the growth rate of neutrophils percentage from the first to third day after surgery (NEU3-1%) in the GSSG were significantly lower than those in the PSSG, whereas the perioperative average albumin levels and the perioperative average pre-albumin levels were higher. Receiver operating characteristic curve showed that the NEU3 had a good predictive value for the survival of skin slices. Maintaining perioperative albumin levels at a high level, controlling perioperative infection, and shortening the operation time as much as possible may improve the survival rate of modified Meek micrografting.

Locally activated mitophagy contributes to a "built-in" protection against early burn-wound progression in rats

AIMS

Deep burn-wounds undergo a dynamic progression in the initial or periburn area after insults, and the zone of stasis is the crucial region suffering the deterioration, considered as salvageable. Few studies explored the role of mitochondria in this process. This study is to clarify a possible "built-in" protection of mitophagy.

MAIN METHODS

A classic "comb" scald rat model was established. Histological and blood-flow observation were processed based on hematoxylin-eosin staining and laser analysis. Oxidative and apoptotic status were analyzed by commercial kits. Transmission-electron microscope, immunofluorescence staining, and western blot were applied to detect the mitophagy in the zone of stasis and potential regulators. Adenovirus-based gene-silence contributed to determine the role of HIF-1α as a regulatory mediator.

KEY FINDINGS

We found that burn-caused typical ischemia and histological deterioration in the zone of stasis, in parallel with increases in oxidative stress and apoptosis. Mitochondrial damage was involved in the aforementioned changes. Furthermore, we detected mitophagy in burn-wounds, which was contradictory to the burn-wound conversion. HIF-1α expression was closely related to the level of mitophagy, while BNIP3 and PARKIN are involved downstream.

SIGNIFICANCE

We demonstrate that burn-induced mitochondrial impairment contributes to the mobilization of injurious mechanisms in the zone of stasis and that mitophagy provides a beneficial way to protect against burn-wound progression via the elimination of damaged mitochondria. Our findings offer insights into mitochondrial quality control in burn-wound progression and suggest the novel concept that HIF-1α may be a therapeutic target due to its possible regulation on BNIP3- or PARKIN-mediated mitophagy.

CD38 Causes Autophagic Flux Inhibition and Cardiac Dysfunction Through a Transcriptional Inhibition Pathway Under Hypoxia/Ischemia Conditions

Induced autophagy is protective against myocardial hypoxia/ischemia (H/I) injury, but evidence regarding the extent of autophagic clearance under H/I and the molecular mechanisms that influence autophagic flux has scarcely been presented. Here, we report that CD38 knockout improved cardiac function and autophagic flux in CD38^–/– mice and CD38^–/– neonatal cardiomyocytes (CMs) under H/I conditions. Mechanistic studies demonstrated that overexpression of CD38 specifically downregulated the expression of Rab7 and its adaptor protein pleckstrin homology domain-containing protein family member 1 (PLEKHM1) through nicotinamide adenine dinucleotide (NAD)-dependent and non-NAD-dependent pathways, respectively. Loss of Rab7/PLEKHM1 impaired the fusion of autophagosomes and lysosomes, resulting in autophagosome accumulation in the myocardium and consequent cardiac dysfunction under H/I conditions. Thus, CD38 mediated autophagic flux blockade and cardiac dysfunction in a Rab7/PLEKHM1-dependent manner. These findings suggest a potential therapeutic strategy involving targeted suppression of CD38 expression.

Inducible nitric oxide synthase contributes to insulin resistance and cardiac dysfunction after burn injury in mice

AIMS

Cardiac dysfunction is a major cause of multi-organ dysfunction in critical care units following severe burns. The purpose of this study was to investigate the role of inducible nitric oxide synthase (iNOS) in cardiac dysfunction in burned mice.

MATERIALS AND METHODS

Wild-type and iNOS-knockout mice were subjected to 30% total body surface area burns. Next, the expression of iNOS was measured at 1, 3 and 7 days post-burn. Cardiac function, insulin sensitivity, inflammation, oxidative stress, and apoptosis in the hearts of the mice were assessed at 3 days post-burn.

KEY FINDINGS

Compared to control mice, iNOS expression was increased and reached a maximum in the heart of burned mice at 3 days post-burn. iNOS deficiency significantly alleviated the cardiac dysfunction and insulin resistance in burned mice. In addition, burn-induced inflammation, oxidative stress, and apoptosis in the heart were markedly reduced in iNOS-knockout burned mice when compared to corresponding values in wild-type burned mice.

SIGNIFICANCE

Our study demonstrates that iNOS contributes to insulin resistance in the hearts of mice following burn injury, and iNOS deficiency protects cardiac function against burn injury in mice, suggesting iNOS as a potential therapeutic target to treat burn injuries.

Myocardial Adipose Triglyceride Lipase Overexpression Protects against Burn-Induced Cardiac Lipid Accumulation and Injury

Maladaptive cardiac metabolism is a common trigger of cardiac lipid accumulation and cardiac injury under serious burn challenge. Adipose triglyceride lipase (ATGL) is the key enzyme that catalyzes triglyceride hydrolysis; however, its alteration and impact on cardiac function following serious burn injury are still unknown. Here, we found that the cardiac fatty acid (FA) metabolism increased, accompanied by augmented FA accumulation and ATGL expression, after serious burn injury. We generated heterozygous ATGL knockout and heterozygous cardiac-specific ATGL overexpression thermal burn mice. The results demonstrated that partial loss of ATGL could not relieve burn-induced cardiac lipid accumulation and cardiac injury, possibly due to the suppression of cardiac FA metabolism plus insufficient compensatory glucose utilization. In contrast, cardiac-specific overexpression of ATGL alleviated cardiac lipid accumulation and cardiac injury following burn challenge by switching the substrate preference from FA towards increased glucose utilization. The underlying mechanism was possibly related to increased glucose transporter-1 expression and reduced cardiac lipid accumulation induced by ATGL overexpression. Our data first demonstrated that elevated cardiac ATGL expression after serious burn injury is an adaptive, albeit insufficient, response to compensate for the increase in energy consumption and that further overexpression of ATGL is beneficial for ameliorating cardiac injury, indicating its therapeutic potential.

Tumor necrosis factor receptor-associated protein 1 regulates hypoxia-induced apoptosis through a mitochondria-dependent pathway mediated by cytochrome c oxidase subunit II

Background

Tumor necrosis factor receptor-associated protein 1 (TRAP1) plays a protective effect in hypoxic cardiomyocytes, but the precise mechanisms are not well clarified. The study is aimed to identify the mechanism of TRAP1 on hypoxic damage in cardiomyocytes.

Methods

In this study, the effects of TRAP1 and cytochrome c oxidase subunit II (COXII) on apoptosis in hypoxia-induced cardiomyocytes were explored using overexpression and knockdown methods separately.

Results

Hypoxia induced cardiomyocyte apoptosis, and TRAP1 overexpression notably inhibited apoptosis induced by hypoxia. Conversely, TRAP1 silencing promoted apoptosis in hypoxic cardiomyocytes. Further investigation revealed that the proapoptotic effects caused by the silencing of TRAP1 were prevented by COXII overexpression, whereas COXII knockdown reduced the antiapoptotic function induced by TRAP1 overexpression. Additionally, changes in the release of cytochrome c from mitochondria into the cytosol and the caspase-3 activity in the cytoplasm, as well as reactive oxygen species production, were found to be correlated with the changes in apoptosis.

Conclusions

The current study uncovered that TRAP1 regulates hypoxia-induced cardiomyocyte apoptosis through a mitochondria-dependent apoptotic pathway mediated by COXII, in which reactive oxygen species presents as an important component.

Electronic supplementary material

The online version of this article (10.1186/s41038-019-0154-3) contains supplementary material, which is available to authorized users.

Polymerized human placenta haemoglobin attenuates myocardial injury and aortic endothelial dysfunction in a rat model of severe burns

This study was designed to investigate the effect of polymerized human placenta haemoglobin (PolyPHb) on cardiac dysfunction after severe burns. A total of 60 male Sprague-Dawley rats were randomly divided into 3 groups: Sham, Burn and Burn + PolyPHb groups. Rats were subjected to third-degree burns to 30% of total body surface area and the haemodynamics, cardiac enzyme release and aortic endothelium ultrastructure/function were measured. PolyPHb (0.5 gHb/kg) greatly improved mean arterial pressure, left ventricular developed pressure (LVDP), maximum LVDP increase and decrease rate and reduced left ventricular end-diastolic pressure as compared to the Burn group. The plasma levels of cardiac enzyme including CK-MB and troponin I were also significantly down-regulated in the Burn + PolyPHb group. In addition, PolyPHb treatment markedly restored the endothelium-dependent relaxation impaired by severe burns and pathological changes of endothelium in aorta. Therefore, our data suggest that PolyPHb can limit severe burn-induced myocardial injury, which is associated with protection of aortic endothelium.

Anti-Inflammatory Effect of Taurine in Burned Patients

PURPOSE

Burn induced inflammatory response can be mediated by reactive oxygen metabolites and accompanied by multiple organ dysfunction. Taurine has protective effects against various inflammatory conditions. The aim of this study was to determine the effect of Taurine supplement in thermal burn victims.

METHODS

Thirty patients with severe thermal burns were enrolled in this randomized double-blinded clinical trial. These patients were randomly divided into two equal groups (namely Control and Taurine groups), where both received isocaloric and isonitrogenous formula. One group was supplemented with 50 mg/kg of Taurine per day for a duration of 10 days. Blood samples were obtained to measure Interleukin-10 (IL-10), high-sensitivity C-reactive protein (hs-CRP), and Tumor Necrosis Factor alpha (TNF-α) levels at the beginning and the end of the study.

RESULTS

Change in serum level of IL-10 in Taurine group was more than Control group [-13.60(-31.40, -10.40) compared to -4.00(-20.00, -0.20) respectively; P = 0.030]. This change was significant in patients with more than 30% TBSA of burn [-14.20(-31.40, -10.40) compared to -2.40(-9.60, 0.40) respectively; P = 0.013]. As for the hs-CRP and TNF-α levels, the difference between the two groups were not significant.

CONCLUSION

Based on the results obtained, Taurine supplement showed a positive outcome on anti-inflammatory cytokine IL-10 in all burn patients. This effect was even more significant in patients with higher percentage of burn area. Taurine had no significant effect on the inflammatory marker hs-CRP and the pro-inflammatory cytokine TNF-α level. For a more thorough verification, measurement of a wider range of inflammatory cytokines in more frequent time intervals are suggested.

Puerarin attenuates severe burn-induced acute myocardial injury in rats

BACKGROUND

Puerarin, the main isoflavone glycoside extracted from the root of Pueraria lobata, is widely prescribed for patients with cardiovascular disorders in China. This study investigates the effect of puerarin on severe burn-induced acute myocardial injury in rats and its underlying mechanisms.

MATERIALS AND METHODS

Healthy adult Wistar rats were divided into three groups: (1) sham group, sham burn treatment; (2) burn group, third-degree burns over 30% of the total body surface area (TBSA) with lactated Ringer's solution for resuscitation; and (3) burn plus puerarin group, third-degree burns over 30% of TBSA with lactated Ringer's solution containing puerarin for resuscitation. The burned animals were sacrificed at 1, 3, 6, 12, and 24 h after burn injury. Myocardial injury was evaluated by analyzing serum creatine kinase MB fraction (CK-MB) activity and cardiac troponin T (cTNT) level. Changes in cardiomyocyte ultrastructure were also determined using a transmission electron microscope. Tumor necrosis factor (TNF)-α concentration in serum was measured by radioimmunoassay. Cardiac myeloperoxidase (MPO) activity and malondialdehyde (MDA) concentration were measured to determine neutrophil infiltration and oxidative stress in the heart, respectively. The expression of p38 mitogen-activated protein (MAP) kinase in the heart was determined by Western blot analysis.

RESULTS

After the 30% TBSA full-thickness burn injury, serum CK-MB activities and cTnT levels increased markedly, both of which were significantly decreased by the puerarin treatment. The level of serum TNF-α concentration in burn group at each time-point was obviously higher than those in sham group (1.09±0.09 ng/ml), and it reached the peak value at 12 h post burn. Burn trauma also resulted in worsen ultrastructural condition, elevated MPO activity and MDA content in heart tissue, and a significant activation of cardiac p38 MAP kinase. Administration of puerarin improved the ultrastructural changes in cardiomyocytes, decreased TNF-α concentration in serum as well as suppressed cardiac MPO activity and reduced MDA content, and abolished the activation of p38 MAP kinase in heart tissue after severe burn.

CONCLUSIONS

These results suggest that puerarin attenuates inflammatory responses, reduces neutrophil infiltration and oxidative stress in the heart, and protects against acute myocardial injury induced by severe burn.

Lethal Cardiomyopathy in Mice Lacking Transferrin Receptor in the Heart

Both iron overload and iron deficiency have been associated with cardiomyopathy and heart failure, but cardiac iron utilization is incompletely understood. We hypothesized that the transferrin receptor (Tfr1) might play a role in cardiac iron uptake and used gene targeting to examine the role of Tfr1 in vivo. Surprisingly, we found that decreased iron, due to inactivation of Tfr1, was associated with severe cardiac consequences. Mice lacking Tfr1 in the heart died in the second week of life and had cardiomegaly, poor cardiac function, failure of mitochondrial respiration, and ineffective mitophagy. The phenotype could only be rescued by aggressive iron therapy, but it was ameliorated by administration of nicotinamide riboside, an NAD precursor. Our findings underscore the importance of both Tfr1 and iron in the heart, and may inform therapy for patients with heart failure.

Role of Ran-regulated nuclear-cytoplasmic trafficking of pVHL in the regulation of microtubular stability-mediated HIF-1α in hypoxic cardiomyocytes

Our previous study suggested that microtubule network alteration affects the process of glycolysis in cardiomyocytes (CMs) via the regulation of hypoxia-inducible factor (HIF)-1α during the early stages of hypoxia. However, little is known regarding the underlying mechanisms of microtubule network alteration-induced changes of HIF-1α. The von Hippel–Lindau tumor suppressor protein (pVHL) has been shown to mediate the ubiquitination of HIF-1α in the nuclear compartment prior to HIF-1α exportation to the cytoplasm, and pVHL dynamic nuclear-cytoplasmic trafficking is indicated to be involved in the process of HIF-1α degradation. In this study, by administering different microtubule-stabilizing and -depolymerizing interventions, we demonstrated that microtubule stabilization promoted pVHL nuclear export and drove the translocation of pVHL to the cytoplasm, while microtubule disruption prevented pVHL nuclear export in hypoxic CMs. Moreover, the ratio between nuclear and cytoplasmic pVHL was associated with HIF-1α regulation. Importantly, microtubule network alteration also affected the subcellular localization of Ran, which was involved in the regulation of pVHL nuclear-cytoplasmic trafficking. The above results suggest that the subcellular translocation of pVHL plays an important role in microtubular structure alteration-induced HIF-1α regulation. Interestingly, Ran is involved in the process of pVHL nuclear-cytoplasmic trafficking following microtubule network alteration in hypoxic CMs.

Burn-associated delayed dilated cardiomyopathy evaluated by cardiac PET and SPECT: Report of a case

Dilated cardiomyopathy is a delayed-onset and rarely reported cardiac complication of burn injury although the mechanism remains unclear. We thus report a case of dilated cardiomyopathy following severe burn injury, in which technetium 99m sestamibi single-photon emission computed tomography (SPECT), iodine-123 beta-methyl-iodophenylpentadecanoic acid SPECT and ¹⁸F-fluorodeoxyglucose positron emission tomography (PET) were performed to evaluate the pathophysiologic condition in combination with cardiac catheterization and myocardial biopsy. The cardiac PET and SPECT images showed reduced myocardial blood flow, decreased fatty acid metabolism, and increased glucose utilization in the left ventricular lateral wall in spite of normal coronary angiography, no significant cardiac fibrosis, and inflammatory cell infiltration, which suggests that myocardial ischemia due to microcirculatory disturbance in hypermetabolic state associated with burn injury might be a causative mechanism of dilated cardiomyopathy in this case. A beta blocker, bisoprolol, was successfully introduced in this patient in combination with oral inotropic agents, pimobendan and digitalis after the prolonged use of intravenous dobutamine infusion, which might have been beneficial for this patient with burn-associated dilated cardiomyopathy not only to reduce regional myocardial ischemia but also to attenuate hypermetabolic state after severe burn injury. <Learning objective: Dilated cardiomyopathy complicated with burn injury has been reported to cause a sudden attack of dyspnea and death. This case report suggests that burn-associated dilated cardiomyopathy may be caused by relative myocardial ischemia due to microvascular disturbance in hypermetabolic state associated with burn injuries and can be treated effectively with beta blockers with or without oral inotropic agents.>.

Bioinformatics analysis of time series gene expression in left ventricle (LV) with acute myocardial infarction (AMI)

This study is to investigate the key genes and their possible function in acute myocardial infarction (AMI). The data of GSE4648 downloaded from the Gene Expression Omnibus (GEO) database include 6 time points (15 min, 60 min, 4h, 12h, 24h and 48 h) of 12 left ventricle (LV) samples, 12 surviving LV free wall (FW) samples, 12 inter-ventricular septum (IVS) samples after AMI operation and corresponding sham-operated samples. The data of each sample were analyzed with Affy and Bioconductor packages, and differentially expressed genes (DEGs) were screened out using BETR package with false discovery rate (FDR)<0.01. Then, functional enrichment analysis for DEGs was conducted with Database for Annotation, Visualization and Integrated Discovery (DAVID). Totally 194 DEGs were identified in LV, and only the gene tubulin beta 2a (Tubb2a) and natriuretic peptide B (Nppb) were respectively up-regulated in surviving FW tissue and IVS tissue. The biological process response to wounding and inflammatory response were significantly enriched, as well as leukocyte transendothelial migration pathway. Besides, the expression pattern analysis showed the DEGs mostly up-regulated at 4h after AMI, and these genes were mainly associated with immunity. Additionally, in transcriptional regulatory network, early growth response 1 (Egr1), activating transcription factor 3 (Atf3), Atf4, Myc and Fos were considered as the key transcription factors related to immune response. The key transcription factors and potential target genes might provide new information for the development of AMI, and leukocyte transendothelial migration pathway might play a vital role in AMI.

Phosphorylation of DYNLT1 at serine 82 regulates microtubule stability and mitochondrial permeabilization in hypoxia

Hypoxia-induced microtubule disruption and mitochondrial permeability transition (mPT) are crucial events leading to fatal cell damage and recent studies showed that microtubules (MTs) are involved in the modulation of mitochondrial function. Dynein light chain Tctex-type 1 (DYNLT1) is thought to be associated with MTs and mitochondria. Previously we demonstrated that DYNLT1 knockdown aggravates hypoxia-induced mitochondrial permeabilization, which indicates a role of DYNLT1 in hypoxic cytoprotection. But the underlying regulatory mechanism of DYNLT1 remains illusive. Here we aimed to investigate the phosphorylation alteration of DYNLT1 at serine 82 (S82) in hypoxia (1% O2). We therefore constructed recombinant adenoviruses to generate S82E and S82A mutants, used to transfect H9c2 and HeLa cell lines. Development of hypoxia-induced mPT (MMP examining, Cyt c release and mPT pore opening assay), hypoxic energy metabolism (cellular viability and ATP quantification), and stability of MTs were examined. Our results showed that phosph-S82 (S82-P) expression was increased in early hypoxia; S82E mutation (phosphomimic) aggravated mitochondrial damage, elevated the free tubulin in cytoplasm and decreased the cellular viability; S82A mutation (dephosphomimic) seemed to diminish the hypoxia-induced injury. These data suggest that DYNLT1 phosphorylation at S82 is involved in MTs and mitochondria regulation, and their interaction and cooperation contribute to the cellular hypoxic tolerance. Thus, we provide new insights into a DYNLT1 mechanism in stabilizing MTs and mitochondria, and propose a potential therapeutic target for hypoxia cytoprotective studies.

Effects of glycine supplementation on myocardial damage and cardiac function after severe burn

BACKGROUND

Glycine has been shown to participate in protection from hypoxia/reoxygenation injury. However, the cardioprotective effect of glycine after burn remains unclear. This study aimed to explore the protective effect of glycine on myocardial damage in severely burned rats.

METHODS

Seventy-two Wistar rats were randomly divided into three groups: normal controls (C), burned controls (B), and glycine-treated (G). Groups B and G were given a 30% total body surface area full-thickness burn. Group G was administered 1.5 g/(kg d) glycine and group B was given the same dose of alanine via intragastric administration for 3d. Serum creatine kinase (CK), lactate dehydrogenase (LDH), aspartate transaminase (AST), and blood lactate, as well as myocardial ATP and glutathione (GSH) content, were measured. Cardiac contractile function and histopathological changes were analyzed at 12, 24, 48, and 72 hours.

RESULTS

Serum CK, LDH, AST, and blood lactate increased, while myocardial ATP and GSH content decreased in both burned groups. Compared with group B, the levels of CK, LDH, and AST significantly decreased, whereas blood lactate as well as myocardial ATP and GSH content increased in group G. Moreover, cardiac contractile function inhibition and myocardial histopathological damage in group G significantly decreased compared with group B.

CONCLUSION

Myocardial histological structure and function were damaged significantly after burn. Glycine is beneficial to myocardial preservation by improving cardiomyocyte energy metabolism and increasing ATP and GSH abundance.

Microtubular stability affects pVHL-mediated regulation of HIF-1alpha via the p38/MAPK pathway in hypoxic cardiomyocytes

Background

Our previous research found that structural changes of the microtubule network influence glycolysis in cardiomyocytes by regulating the hypoxia-inducible factor (HIF)-1α during the early stages of hypoxia. However, little is known about the underlying regulatory mechanism of the changes of HIF-1α caused by microtubule network alternation. The von Hippel-Lindau tumor suppressor protein (pVHL), as a ubiquitin ligase, is best understood as a negative regulator of HIF-1α.

Methodology/Principal Findings

In primary rat cardiomyocytes and H9c2 cardiac cells, microtubule-stabilization was achieved by pretreating with paclitaxel or transfection of microtubule-associated protein 4 (MAP4) overexpression plasmids and microtubule–depolymerization was achieved by pretreating with colchicine or transfection of MAP4 siRNA before hypoxia treatment. Recombinant adenovirus vectors for overexpressing pVHL or silencing of pVHL expression were constructed and transfected in primary rat cardiomyocytes and H9c2 cells. With different microtubule-stabilizing and -depolymerizing treaments, we demonstrated that the protein levels of HIF-1α were down-regulated through overexpression of pVHL and were up-regulated through knockdown of pVHL in hypoxic cardiomyocytes. Importantly, microtubular structure breakdown activated p38/MAPK pathway, accompanied with the upregulation of pVHL. In coincidence, we found that SB203580, a p38/MAPK inhibitor decreased pVHL while MKK6 (Glu) overexpression increased pVHL in the microtubule network altered-hypoxic cardiomyocytes and H9c2 cells.

Conclusions/Significance

This study suggests that pVHL plays an important role in the regulation of HIF-1α caused by the changes of microtubular structure and the p38/MAPK pathway participates in the process of pVHL change following microtubule network alteration in hypoxic cardiomyocytes.

Changes in the inositol lipid signal system and effects on the secretion of TNF-α by macrophages in severely scalded mice

AIM

In order to study the mechanism of abnormal macrophage (Mϕ) function in pro-inflammatory cytokine changes after burn, the inositol lipid signal system and its role in tumour necrosis factor-alpha (TNF-α) secretion by peritoneal Mϕs was observed in severely scalded mice.

METHODS

Eighteen percent total body surface area (TBSA) full-thickness scalded mice were used as animal model in this experiment. Peritoneal Mϕs stimulated by lipopolysaccharide in vitro were collected at different time intervals (0, 2, 6, 12, 24 and 48 after burn hour (PBH)), The activities of phosphatidylinositol-phospholipase C (PI-PLC), inositol-1, 4,5, -triphosphate (IP(3)), protein kinase C (PKC), diacylglycerol (DAG) and TNF-α and the level of Ca(2+) concentration in peritoneal Mϕs were measured, and the effects of specific PKC inhibitor H-7 and calmodulin antagonist W-7 on the production of TNF-α were also observed.

RESULTS

After scald, increased activities of TNF-α and PLC of Mϕ were observed and peaked at 12 PBH. The activities of DAG and IP(3) and the concentration of Ca(2+) were markedly increased and reached their peaks at 24 PBH simultaneously. Membrane PKC activity was up-regulated after scald and showed a positive correlation with the change of DAG (r=0.83, P<0.05). There was also positive correlation between IP(3) and Ca(2+) activity (r=0.946, P<0.01). When 12 PBH was chosen as the time point for in vitro intervention with the pre-treatment by H-7, both membrane PKC and TNF-α activity decreased significantly. There was no obvious change of TNF-α activity with the application of W-7.

CONCLUSIONS

These results indicated that the abnormal activity of TNF-α of Mϕs might be regulated by the inositol lipid signal system following severe burn. The DAG-PKC signal pathway showed closer relationship than IP(3)-Ca(2+) in TNF-α production and could be the optimal target in the prevention and treatment of the systemic inflammatory response syndrome.

Microtubular stability affects cardiomyocyte glycolysis by HIF-1alpha expression and endonuclear aggregation during early stages of hypoxia

Hypoxia-inducible factor (HIF)-1alpha is a key regulator of anaerobic energy metabolism. We asked the following question: Does the breakdown of microtubular structures influence glycolysis in hypoxic cardiomyocytes by regulating HIF-1alpha? Neonatal rat cardiomyocytes were cultured under hypoxic conditions, while microtubule-stabilizing (paclitaxel) and -depolymerizing (colchicine) agents were used to change microtubular structure. Models of high microtubule-associated protein 4 (MAP4) expression and RNA interference of microtubulin expression were established. Microtubular structural changes and intracellular HIF-1alpha protein distribution were observed with laser confocal scanning microscopy. Content of key glycolytic enzymes, viability, and energy content of cardiomyocytes were determined by colorimetry and high-performance liquid chromatography. HIF-1alpha protein content and mRNA expression were determined by Western blotting and real-time PCR, respectively. Low doses of microtubule-stabilizing agent (10 mumol/l paclitaxel) and enhanced expression of MAP4 stabilized the reticular microtubular structures in hypoxic cardiomyocytes, increased the content of key glycolytic enzymes, ameliorated energy supply and enhanced cell viability, and upregulated HIF-1alpha protein expression and endonuclear aggregation. In contrast, the microtubule-depolymerizing agent (10 mumol/l colchicine) or reduced microtubulin expression had adverse affects on the same parameters, in particular, HIF-1alpha protein content and endonuclear aggregation. We conclude that microtubular structural changes influence glycolysis in the early stages of hypoxia in cardiomyocytes by regulating HIF-1alpha content. Stabilizing microtubular structures increases endonuclear and total HIF-1alpha expression, content of key glycolytic enzymes, and energy supply. These findings provide potential therapeutic targets for ameliorating cell energy metabolism during early myocardial hypoxia.

Mitochondrial chaperone tumour necrosis factor receptor-associated protein 1 protects cardiomyocytes from hypoxic injury by regulating mitochondrial permeability transition pore opening

Tumour necrosis factor receptor-associated protein 1 (TRAP1) is a mitochondrial chaperone that plays a role in maintaining mitochondrial function and regulating cell apoptosis. The opening of the mitochondrial permeability transition pore (MPTP) is a key step in cell death after hypoxia. However, it is still unclear whether TRAP1 protects cardiomyocytes from hypoxic damage by regulating the opening of the pore. In the present study, primary cultured cardiomyocytes from neonatal rats were used to investigate changes in TRAP1 expression after hypoxia treatment as well as the mechanism and effect of TRAP1 on hypoxic damage. The results obtained showed that TRAP1 expression increased after 1 h of hypoxia and continued to increase for up to 12 h of treatment. Hypoxia caused an increase in cell death and decreased cell viability and mitochondrial membrane potential; overexpressing TRAP1 prevented hypoxia-induced damage to cardiomyocytes. The silencing of TRAP1 induced an increase in cell death and decreased both cell viability and mitochondrial membrane potential in cardiomyocytes under normoxic and hypoxic conditions. Furthermore, cell damage induced by the silencing of TRAP1 was prevented by the mitochondrial permeability transition pore inhibitor, cyclosporin A. These data demonstrate that hypoxia induces an increase in TRAP1 expression in cardiomyocytes, and that TRAP1 plays a protective role by regulating the opening of the mitochondrial permeability transition pore.

Adenosine A1 receptor activation reduces opening of mitochondrial permeability transition pores in hypoxic cardiomyocytes

1. Adenosine A(1) receptors (A(1)R) play an important role in cardioprotection against hypoxic damage and the opening of mitochondrial permeability transition pores (MPTP) is central to the regulation of cell apoptosis and necrosis. However, it is still unclear whether A(1)R open MPTP in hypoxic cardiomyocytes. 2. The present study used primary cardiomyocyte cultures from neonatal rats to investigate the mechanisms of A(1)R activation and the effects of A(1)R on MPTP opening under hypoxic conditions. 3. Hypoxia increased both MPTP opening and the production of reactive oxygen species (ROS), while decreasing cell viability and mitochondrial membrane potential (Deltapsi). The A(1)R agonist 2-chloro-N(6)-cyclopentyladenosine (CCPA; 500 nmol/L) blocked the increase in MPTP opening and ROS production and maintained cell viability and Deltapsi under hypoxic conditions. 4. The protective effects of CCPA were eliminated by both the protein kinase C (PKC) inhibitor chelerythine (2 micromol/L) and the mitochondrial ATP-sensitive K(+) channel (mitoK(ATP)) inhibitor 5-hydroxydecanoate (500 micromol/L). Moreover, CCPA significantly increased the PKC content in both total protein and membrane protein of cardiomyocytes. 5-Hydroxydecanoate did not prevent these CCPA-induced increases in PKC. 5. These results demonstrate that CCPA reduces MPTP opening in hypoxic cardiomyocytes, possibly by activating PKC, stabilizing Deltapsi and reducing ROS production following the opening of mitoK(ATP). Consequently, fewer MPTP open.

Inhibition of p38 MAP kinase improves survival of cardiac myocytes with hypoxia and burn serum challenge

This study was aimed to investigate the effects of SB203580, the specific p38 mitogen-activated protein (MAP) kinase inhibitor, on cardiac myocyte survival and secretion of cytokines in an in vitro model of hypoxia and burn serum challenge. Results demonstrated that hypoxia and burn serum induced a persistent activation of p38 MAP kinase in primary cultured neonatal rat cardiomyocytes during the 12h period of stimulation, concomitant with a time-dependent increased expression of tumor necrosis factor (TNF)-alpha and inducible nitric oxide (iNOS), a progressively developed oxidative stress reflected by malondialdehyde (MDA) production, and myocytes injury evidenced by the increased levels of released lactate dehydrogenase (LDH) and the decreased myocyte viability. Furthermore, hypoxia and burn serum resulted in a significant increase in myocyte apoptosis, which may account for the impairment of myocyte viability as observed. SB203580 abolished p38 MAP kinase activation, blunted the upregulation of TNF-alpha, iNOS and the subsequent nitric oxide (NO) production, reduced oxidative stress, and alleviated hypoxia and burn serum-induced myocytes injury or apoptosis. These results demonstrated for the first time that inhibition of p38 MAP kinase improves survival of cardiac myocytes with hypoxia and burn serum challenge possibly via reducing the production of cytokines, such as TNF-alpha and NO, and the subsequent oxidative stress, providing strong evidence that the excessive inflammatory cytokines produced by cardiomyocytes themselves may be sufficient to cause myocardial injury after burn.

Prospective clinical and experimental studies on the cardioprotective effect of ulinastatin following severe burns

OBJECTIVE

To investigate the preventive effect of ulinastatin on shock in the heart after burn.

METHODS

In an open prospective clinical study 34 adults with burns >50% total body surface area were randomly divided into control (B) and ulinastatin-treated (U) groups. All underwent routine treatment, and group U received 100,000U ulinastatin intravenously three times a day for 1 week. In an animal experiment, 72 healthy rats underwent equivalent burn, similar division into groups B and U, and resuscitation according to Parkland's formula. Rats in group U received ulinastatin (40,000U/kg) immediately after burn. Myocardial pathomorphology, plasma cTnI, CK-MB and PMNE, myocardial MDA, TNF-alpha, IL-10 and caspase-3 activity and cardiocyte apoptosis were determined.

RESULTS

Plasma cTnI, CK-MB, and PMNE were higher in clinical group B than group U. In the animal experiment, plasma cTnI, CK-MB, myocardial MDA, TNF-alpha, IL-10 and caspase-3 activity, and apoptotic index and myocardial pathomorphological changes were significantly less in group U than in group B, save IL-10.

CONCLUSION

The clinical and experimental data showed that ulinastatin relieved myocardial damage from severe burn. The mechanism might involve modulation of the anti- and pro-inflammatory balance and lipid peroxidation, and decreased myocardiocyte apoptosis.

Involvement of p38 MAP kinase in burn-induced degradation of membrane phospholipids and upregulation of cPLA2 in cardiac myocytes

This study was aimed to evaluate the role of p38 mitogen-activated protein (MAP) kinase in the degradation of membrane phospholipids and the regulation of cytosolic phospholipase A2 (cPLA2) in cardiac myocytes after burn trauma. In an in vivo study, rats were randomized into four groups: (1) sham-burn group, (2) burn group (40% total body surface area full-thickness burn), (3) burn + SB203580 group, and (4) burn + vehicle group. The rats from each group were killed at varying times after burn to examine the p38 MAP kinase activation (by means of Western blot analysis and immunohistochemical assay), the expression of cPLA2 (by means of reverse transcriptase polymerase chain reaction), the level of cardiac membrane phospholipids, and the level of the remaining creatine kinase-MB (CK-MB) isoenzyme in the heart. These studies showed that burn resulted in a significant decrease in the level of cardiac membrane phospholipids from 3 to 24 h after burn, which was paralleled with a persistent activation of p38 MAP kinase and an increased expression of cPLA2 in the heart. SB203580, a selective inhibitor of p38 MAP kinase, inhibited the activation of cardiac p38 MAP kinase, suppressed the burn-induced upregulation of cPLA2 and the increased PLA2 activity, and prevented burn-induced decrease in the levels of the cardiac membrane phospholipids and the remaining creatine kinase-MB isoenzyme. In addition, the in vitro treatment of cardiac myocytes with SB203580 also abolished the upregulation of cPLA2 and the disturbance of phospholipid homeostasis elicited by hypoxia and burn serum challenge. Taken together, these results have demonstrated for the first time that p38 MAP kinase is involved in burn-induced membrane phospholipids degradation in cardiac myocytes, at least in part through the regulation of cPLA2.

Hypoxia causes an increase in phagocytosis by macrophages in a HIF-1α-dependent manner

Phagocytosis is the process by which microbial pathogens are engulfed by macrophages and neutrophils and represents the first line of defense against bacterial infection. The importance of phagocytosis for bacterial clearance is of particular relevance to systemic inflammatory diseases, which are associated with the development of hypoxia, yet the precise effects of hypoxia on phagocytosis remain largely unexplored. We now hypothesize that hypoxia inhibits phagocytosis in macrophages and sought to determine the mechanisms involved. Despite our initial prediction, hypoxia significantly increased the phagocytosis rate of particles in vitro by RAW264.7 and primary peritoneal macrophages and increased phagocytosis of labeled bacteria in vivo by hypoxic mice compared with normoxic controls. In understanding the mechanisms involved, hypoxia caused no changes in RhoA-GTPase signaling but increased the phosphorylation of p38-MAPK significantly. Inhibition of p38 reversed the effects of hypoxia on phagocytosis, suggesting a role for p38 in the hypoxic regulation of phagocytosis. Hypoxia also significantly increased the expression of hypoxia-inducible factor-1alpha (HIF-1alpha) in macrophages, which was reversed after p38 inhibition, suggesting a link between p38 activation and HIF-1alpha expression. It is striking that small interfering RNA knockdown of HIF-1alpha reversed the effects of hypoxia on phagocytosis, and overexpression of HIF-1alpha caused a surprising increase in phagocytosis compared with nontransfected controls, demonstrating a specific role for HIF-1alpha in the regulation of phagocytosis. These data indicate that hypoxia enhances phagocytosis in macrophages in a HIF-1alpha-dependent manner and shed light on an important role for HIF-1alpha in host defense.

Small skin burn injury reduces cardiac tolerance to ischemia via a tumor necrosis factor alpha-dependent pathway

BACKGROUND

Large burns cause systemic inflammation and myocardial depression. We hypothesized that small burns affect cardiac tolerance to ischemia, and that tumor necrosis factor alpha (TNFalpha) signaling through endothelin-1 (ET) and nuclear factor kappa B (NF kappaB) are associated.

METHODS

Mice were randomly assigned to four groups: burn (caused by boiling water on <2% of the body surface area), sham, burn+etanercept (TNFalpha blocker) treatment and sham+etanercept treatment. Twenty-four hours later, hearts were isolated and subjected to global ischemia followed by reperfusion. Additional hearts and burned skin lesions were sampled to evaluate expression of TNFalpha (immunoblotting) and endothelin-1 (radioimmunoassay). A NF kappaB-luciferase reporter mouse was used to evaluate NF kappaB activation.

RESULTS

Baseline cardiac function before ischemia (BI) was only negligibly influenced by burn or etanercept, but was reduced by burn+etanercept. Burn markedly impaired post-ischemic left ventricular function and increased infarct size in comparison with sham-treated mice. Cardiac, but nut cutaneous, expression of TNFalpha was increased in burned mice, while cardiac NF kappaB and endothelin-1 were not influenced. TNFalpha blockade reduced the detrimental effects of burn on cardiac tolerance to ischemia.

CONCLUSIONS

Small cutaneous burns, that did not influence baseline heart function, impaired the tolerance to ischemia. This effect may be mediated through TNFalpha, but does not involve signaling through NF kappaB or endothelin-1.

Transfection of antisense p38α gene ameliorates myocardial cell injury mediated by hypoxia and burn serum

BACKGROUND

Myocardial damage occurs immediately following severe burns even before significant reduction in blood volume. This phenomenon is called postburn "shock heart" ("cardiac shock"), the pathogenesis of which is unclear. This study was designed to investigate the role of antisense p38 alpha gene transfection in ameliorating hypoxia and burn serum-mediated myocardial cell injury.

METHODS

A model of myocardial cells cultured under hypoxia and with burn serum was established. The cells were divided into control group (group C), the group cultured under hypoxia plus burn serum (group HS), and the group treated with antisense p38 alpha gene transfection (group A-p38 alpha) and cultured under hypoxia plus burn serum. Burn serum was collected from Wistar rats with 40% TBSA III degree burns. Hypoxia was produced using a mixed gas with 1% O(2). Antisense p38 alpha gene recombinants were constructed and expression of p38 alpha kinase, and NF-kappaB subunits p50, p65 and I kappa B alpha in myocardial cells were detected by Western blot. Myocardial viability was determined by tetrazolium colorimetry (MTT). Apoptosis was detected by flow cytometry. Lactate dehydrogenase (LDH) activity in cell culture supernatants was determined. Changes in TNFalpha and IL-1 beta mRNA expression were detected by RT-PCR.

RESULTS

Activation of p38 alpha kinase, expression of NF-kappaB p50, NF-kappaB p65 and I kappa B protein, and TNFalpha and IL-1 beta were downregulated significantly following antisense p38 alpha gene transfection into myocardial cells treated with hypoxia plus burn serum. Myocardial apoptosis and LDH activity in cell culture supernatants decreased markedly and myocardial viability increased significantly in the antisense p38 alpha gene treated group.

CONCLUSIONS

Results demonstrated that transfection of antisense p38 alpha gene diminishes myocardial cell injury mediated by hypoxia and burn serum, suggesting a new target for the prevention and treatment of myocardial damage after burn.

Mechanism of altered TNF-α expression by macrophage and the modulatory effect of Panax notoginseng saponins in scald mice

AIM

To explore the mechanism of altered tumor necrosis factor-alpha (TNF-alpha) expression by peritoneal macrophages (PMPhi) and Panax notoginseng saponins (PNS) modulation in light of NF-kappaB signal transduction in severely scalded mice.

METHODS

Eighteen percent total body surface area (TBSA) full-thickness scalded mice were used. PMPhi was collected at different time intervals (0, 2, 6, 12, 24 and 48 post-burn hour (PBH)) separately. The following parameters were measured: TNF-alpha mRNA and IL-10 mRNA expression (reverse transcription-polymerase chain reaction, RT-PCR), protein kinase C (PKC) activity (isotope incorporation analysis), NF-kappaB activity (electrophoretic mobility shift assay, EMSA), IkappaB-alpha expression (Western blot).

RESULTS

After scald, increased expression of TNF-alpha mRNA of PMPhi peaked at 12 PBH. Meanwhile, expression of IL-10 mRNA dropped to the lowest level at 12 PBH. NF-kappaB activity was markedly activated and reached its peak at 2 PBH. Membrane PKC activity was up-regulated after scald and showed a positive correlation with the change of TNF-alpha mRNA. Expression of IkappaB-alpha first decreased at 2 PBH and then increased to high level at 24 PBH. When 12 PBH was chosen as the time point for in vitro intervention with the application of specific NF-kappaB inhibitor pyrrolidine dithiocarbamate (PDTC), PKC inhibitor H-7 and PNS, both TNF-alpha mRNA expression and NF-kappaB activity decreased significantly.

CONCLUSIONS

These results indicate that abnormal expression of TNF-alpha mRNA of macrophages might be regulated by PKC-NF-kappaB signaling following severe burn. PNS might play an anti-inflammatory effect by inhibiting NF-kappaB activity and TNF-alpha mRNA expression.

UPREGULATION OF 14-3-3 ISOFORMS IN ACUTE RAT MYOCARDIAL INJURIES INDUCED BY BURN AND LIPOPOLYSACCHARIDE

1. Burn-induced myocardial injuries can be acute due to loss of body fluid and blood redistribution, and subacute due to pathogenic toxins of infecting bacteria. The goal of this study was to examine expression of 14-3-3 in the injured myocardium. 2. Myocardial injury models were created in vivo by subjecting rats to severe burn and administration of lipopolysaccharide. RT-PCR and Western blotting were employed to assess the expression of 14-3-3 proteins and messenger ribonucleic acid (mRNA) for 14-3-3eta and gamma in the myocardium, respectively. 3. In the two models, we found that 14-3-3 proteins were induced in a time-dependent fashion. Such a change is at least in part attributed to increases in mRNAs for 14-3-3gamma and eta. In contrast to 14-3-3xi, whose mRNA was not detectable in the heart, mRNA for 14-3-3gamma was found significantly elevated between 24-48 h after burn. 14-3-3eta mRNA exhibited a marked increase at 3 h continuing to 12 h and then decreased nearly to a normal level after 48 h. In lipopolysaccharide-treated intact rats, 14-3-3gamma mRNA in myocardium showed a significant increase, reaching a peak at 4 h, followed by a decrease at 6 h. In contrast, 14-3-3eta mRNA had a slight increase without significance. 4. Our results suggest that 14-3-3 may play a role in both acute and subacute (postburn infectious) phases of severe burn.

Peripheral axon caliber and conduction velocity are decreased after burn injury in mice

Peripheral neuropathies are reported to arise as a result of the systemic inflammatory response produced by a full-thickness cutaneous burn injury. This study was designed to characterize the magnitude and time course of functional and morphological changes in peripheral axons that arise after a full-thickness dermal burn injury in an animal model. A 20% body surface area (20% BSA) full-thickness dermal burn was applied to the back of C57BL6 female mice. Longitudinal H- and M-wave recordings were used to determine the conduction velocities (CV) of large myelinated motor and sensory axons in the tibial nerve of sham control and burn-injured mice. Motor CVs were significantly reduced from 6 h to 28 days after the burn, and sensory CVs were significantly reduced from 7 to 14 days after the burn. Morphological evaluation also showed that the mean caliber of large axons in tibial nerves and L5 ventral and dorsal roots in burned mice was significantly decreased. The results demonstrate that both functional and morphological deficits may be produced in peripheral nerve axons at sites well removed from a full-thickness dermal burn injury. The neural deficits may contribute to changes in neuromuscular transmission and the development of limb and respiratory muscle weakness that also accompany burn injury.

Molecular Mechanism of c-jun Antisense Gene Transfection in Alleviating Injury of Cardiomyocytes Treated with Burn Serum and Hypoxia

To explore the molecular mechanism of c-jun antisense gene transfection in alleviating injury of cardiomyocytes treated with burn serum and hypoxia, burn serum was collected from Wistar rats inflicted with 30% third-degree burn of the total body surface area. The cardiomyocytes of neonatal Wistar rats were cultured and then treated with burn serum and hypoxia (a gas mixture containing 1% O2). The constructed c-jun antisense gene recombinant was transfected into the cardiomyocytes of neonatal Wistar rats. TdT-mediated d-utp nick end labeling (TUNEL) was adopted to examine cardiomyocyte apoptosis. Morphological changes of cardiomyocytes were observed under an optic-microscope and an electron-microscope. Expression of troponin T and beta-tubulin protein, c-jun protein, protein kinase Ca (PKCa), and c-jun N-terminal kinase (JNK) were assayed with Western blot in the transfected and non-transfected groups. The morphology of cardiomyocytes in the non-transfected group changed explicitly, but the change was not so obvious in the transfected cardiomyocytes. The expression of beta-tubulin and troponin increased significantly in the transfected group as compared with the non-transfected group. In the non-transfected group, numbers of apoptotic cardiomyocytes were significantly higher than in the transfected group. The c-jun protein, PKCa, and JNK were significantly expressed in the non-transfected group, and they reached a maximum at the 24th hour after cardiomyocytes were treated with burn serum and hypoxia. In the transfected group, however, expressions of c-jun protein, PKCa, and JNK decreased significantly compared with the non-transfected group. The c-jun antisense gene recombinant transfection alleviates injury to cardiomyocytes treated with burn serum and hypoxia, probably through low expression of PKCa and JNK.