Activation of stress-responsive pathways by the sympathetic nervous system in burn trauma

The Different Shades of Thermogenic Adipose Tissue

PURPOSE OF REVIEW

By providing a concise overview of adipose tissue types, elucidating the regulation of adipose thermogenic capacity in both physiological contexts and chronic wasting diseases (a protracted hypermetabolic state that precipitates sustained catabolism and consequent progressive corporeal atrophy), and most importantly, delving into the ongoing discourse regarding the role of adipose tissue thermogenic activation in chronic wasting diseases, this review aims to provide researchers with a comprehensive understanding of the field.

RECENT FINDINGS

Adipose tissue, traditionally classified as white, brown, and beige (brite) based on its thermogenic activity and potential, is intricately regulated by complex mechanisms in response to exercise or cold exposure. This regulation is adipose depot-specific and dependent on the duration of exposure. Excessive thermogenic activation of adipose tissue has been observed in chronic wasting diseases and has been considered a pathological factor that accelerates disease progression. However, this conclusion may be confounded by the detrimental effects of excessive lipolysis. Recent research also suggests that such activation may play a beneficial role in the early stages of chronic wasting disease and provide potential therapeutic effects. A more comprehensive understanding of the changes in adipose tissue thermogenesis under physiological and pathological conditions, as well as the underlying regulatory mechanisms, is essential for the development of novel interventions to improve health and prevent disease.

Immune dysfunction following severe trauma: A systems failure from the central nervous system to mitochondria

When a traumatic injury exceeds the body's internal tolerances, the innate immune and inflammatory systems are rapidly activated, and if not contained early, increase morbidity and mortality. Early deaths after hospital admission are mostly from central nervous system (CNS) trauma, hemorrhage and circulatory collapse (30%), and later deaths from hyperinflammation, immunosuppression, infection, sepsis, acute respiratory distress, and multiple organ failure (20%). The molecular drivers of secondary injury include damage associated molecular patterns (DAMPs), pathogen associated molecular patterns (PAMPs) and other immune-modifying agents that activate the hypothalamic-pituitary-adrenal (HPA) axis and sympathetic stress response. Despite a number of drugs targeting specific anti-inflammatory and immune pathways showing promise in animal models, the majority have failed to translate. Reasons for failure include difficulty to replicate the heterogeneity of humans, poorly designed trials, inappropriate use of specific pathogen-free (SPF) animals, ignoring sex-specific differences, and the flawed practice of single-nodal targeting. Systems interconnectedness is a major overlooked factor. We argue that if the CNS is protected early after major trauma and control of cardiovascular function is maintained, the endothelial-glycocalyx will be protected, sufficient oxygen will be delivered, mitochondrial energetics will be maintained, inflammation will be resolved and immune dysfunction will be minimized. The current challenge is to develop new systems-based drugs that target the CNS coupling of whole-body function.

Modulation of the HGF/c-Met Axis Impacts Prolonged Hematopoietic Progenitor Mobilization Following Trauma and Chronic Stress

BACKGROUND

Trauma and hemorrhagic shock trigger mobilization of hematopoietic progenitor cells (HPC) from bone marrow to peripheral blood. Hepatocyte growth factor (HGF), tyrosine-protein kinase Met (c-Met), matrix metallopeptidase 9 (MMP-9), and corticosterone regulate this mobilization process. We hypothesized that beta-blockade with propranolol and sympathetic outflow inhibition with clonidine following trauma and chronic stress would decrease hematopoietic progenitor cell mobilization.

METHODS

Sprague-Dawley rats were randomized to undergo three models of injury and stress: lung contusion, LC plus hemorrhagic shock (LCHS), or LCHS plus chronic restraint stress for 2 h daily (LCHS/CS). Propranolol and clonidine were administered by daily intraperitoneal injection until sacrifice on day seven. Bone marrow HGF, c-Met, and MMP-9 were measured by real-time PCR. Plasma corticosterone was measured by ELISA. Percentage HPC in peripheral blood was measured by flow cytometry.

RESULTS

Propranolol and clonidine significantly decreased bone marrow MMP-9 expression, plasma corticosterone levels, and HPC mobilization, and significantly increased hemoglobin levels. HPC mobilization was greatest following LCHS/CS (5.4 ± 1.8) and was significantly decreased by propranolol (2.2 ± 0.9, P < 0.001) and clonidine (1.7 ± 0.5, P < 0.001). Hemoglobin (g/dL) was lowest following LCHS/CS (12.3 ± 1.2) and was significantly increased by propranolol (13.7 ± 0.4, P = 0.022) and clonidine (14.1 ± 1.1, P < 0.001).

CONCLUSIONS

Severe injury was associated with increased bone marrow HGF, c-Met, and MMP-9, circulating corticosterone, HPC mobilization, and persistent anemia. Attenuating the neuroendocrine response to injury and stress with propranolol and clonidine reduced MMP-9 expression, corticosterone levels, HPC mobilization, and the degree of anemia.

Drug-specific differences in the ability of opioids to manage burn pain

Burn injury pain is a significant public health problem. Burn injury treatment has improved tremendously in recent decades. However, an unintended consequence is that a larger number of patients now survive more severe injuries, and face intense pain that is very hard to treat. Although many efforts have been made to find alternative treatments, opioids remain the most effective medication available. Burn patients are frequently prescribed opioids in doses and durations that are significantly higher and longer than standard analgesic dosing guidelines. Despite this, many continue to experience unrelieved pain. They are also placed at a higher risk for developing dependence and opioid use disorder. Burn injury profoundly alters the functional state of the immune system. It also alters the expression levels of receptor, effector, and signaling molecules within the spinal cord's dorsal horn. These alterations could explain the reduced potency of opioids. However, recent studies demonstrate that different opioids signal preferentially via differential signaling pathways. This ligand-specific signaling by different opioids implies that burn injury may reduce the antinociceptive potency of opioids to different degrees, in a drug-specific manner. Indeed, recent findings hint at drug-specific differences in the ability of opioids to manage burn pain early after injury, as well as differences in their ability to prevent or treat the development of chronic and neuropathic pain. Here we review the current state of opioid treatment, as well as new findings that could potentially lead to opioid-based pain management strategies that may be significantly more effective than the current solutions.

β-Blockade use for Traumatic Injuries and Immunomodulation: A Review of Proposed Mechanisms and Clinical Evidence

Sympathetic nervous system activation and catecholamine release are important events following injury and infection. The nature and timing of different pathophysiologic insults have significant effects on adrenergic pathways, inflammatory mediators, and the host response. Beta adrenergic receptor blockers (β-blockers) are commonly used for treatment of cardiovascular disease, and recent data suggests that the metabolic and immunomodulatory effects of β-blockers can expand their use. β-blocker therapy can reduce sympathetic activation and hypermetabolism as well as modify glucose homeostasis and cytokine expression. It is the purpose of this review to examine either the biologic basis for proposed mechanisms or to describe current available clinical evidence for the use of β-blockers in traumatic brain injury, spinal cord injury, hemorrhagic shock, acute traumatic coagulopathy, erythropoietic dysfunction, metabolic dysfunction, pulmonary dysfunction, burns, immunomodulation, and sepsis.

Pathophysiologic Mechanisms and Current Treatments for Cutaneous Sequelae of Burn Wounds

Burn injuries are a pervasive clinical problem. Extensive thermal trauma can be life-threatening or result in long-lasting complications, generating a significant impact on quality of life for patients as well as a cost burden to the healthcare system. The importance of addressing global or systemic issues such as resuscitation and management of inhalation injuries is not disputed but is beyond the scope of this review, which focuses on cutaneous pathophysiologic mechanisms for current treatments, both in the acute and long-term settings. Pathophysiological mechanisms of burn progression and wound healing are mediated by highly complex cascades of cellular and biochemical events, which become dysregulated in slow-healing wounds such as burns. Burns can result in fibroproliferative scarring, skin contractures, or chronic wounds that take weeks or months to heal. Burn injuries are highly individualized owing to wound-specific differences such as burn depth and surface area, in addition to patient-specific factors including genetics, immune competency, and age. Other extrinsic complications such as microbial infection can complicate wound healing, resulting in prolonged inflammation and delayed re-epithelialization. Although mortality is decreasing with advancements in burn care, morbidity from postburn deformities continues to be a challenge. Optimizing specialized acute care and late burn outcome intervention on a patient-by-patient basis is critical for successful management of burn wounds and the associated pathological scar outcome. Understanding the fundamentals of integument physiology and the cellular processes involved in wound healing is essential for designing effective treatment strategies for burn wound care as well as development of future therapies. Published 2018. Compr Physiol 8:371-405, 2018.

Clonidine restores vascular endothelial growth factor expression and improves tissue repair following severe trauma

BACKGROUND

We hypothesized that clonidine and propranolol would increase VEGF and VEGF-receptor expression and promote lung healing following severe trauma and chronic stress.

METHODS

Sprague-Dawley rats were subjected to lung contusion (LC), lung contusion/hemorrhagic shock (LCHS), or lung contusion/hemorrhagic shock/daily restraint stress (LCHS/CS). Clonidine and propranolol were administered daily. On day seven, lung VEGF, VEGFR-1, VEGFR-2, and HMGB1 were assessed by PCR. Lung injury was assessed by light microscopy (*p < 0.05).

RESULTS

Clonidine increased VEGF expression following LCHS (43%*) and LCHS/CS (46%*). Clonidine increased VEGFR-1 and R-2 expression following LCHS/CS (203%* and 47%*, respectively). Clonidine decreased HMGB1 and TNF-alpha expression following LCHS/CS (22%* and 58%*, respectively.) Clonidine decreased inflammatory cell infiltration and total Lung Injury Score following LCHS/CS. Propranolol minimally affected VEGF and did not improve lung healing.

CONCLUSIONS

Clonidine increased VEGF and VEGF-receptor expression, decreased HMGB1 expression, decreased lung inflammation, and improved lung tissue repair.

Perioperative "remote" acute lung injury: recent update

Perioperative acute lung injury (ALI) is a syndrome characterised by hypoxia and chest radiograph changes. It is a serious post-operative complication, associated with considerable mortality and morbidity. In addition to mechanical ventilation, remote organ insult could also trigger systemic responses which induce ALI. Currently, there are limited treatment options available beyond conservative respiratory support. However, increasing understanding of the pathophysiology of ALI and the biochemical pathways involved will aid the development of novel treatments and help to improve patient outcome as well as to reduce cost to the health service. In this review we will discuss the epidemiology of peri-operative ALI; the cellular and molecular mechanisms involved on the pathological process; the clinical considerations in preventing and managing perioperative ALI and the potential future treatment options.

Up-regulation of cutaneous α1-adrenoceptors after a burn

Stimulation of α1-adrenoceptors evokes inflammatory cytokine production, boosts neurogenic inflammation and pain, and influences cellular migration and proliferation. As expression of α1-adrenoceptors increases on dermal nerves and keratinocytes after peripheral nerve injury, the aim of this study was to determine whether another form of tissue injury (a cutaneous burn) triggered a similar response. In particular, changes in expression of α1-adrenoceptors were investigated on dermal nerve fibres, keratinocytes and fibroblast-like cells using immunohistochemistry 2-12 weeks after a full thickness burn in Wistar rats. Within two weeks of the burn, local increases in α1-adrenoceptor expression were seen in the re-forming epidermis, in dense bands of spindle-shaped cells in the upper dermis (putatively infiltrating immune cells and fibroblasts), and on nerve fibres in the deep dermis. In addition, nerve fibre density increased approximately three-fold in the deep dermis, and this response persisted for several more weeks. In contrast, α1-adrenoceptor labelled cells and staining intensity in the upper dermis decreased contralateral to the burn, as did nerve fibre density in the deep dermis. These findings suggest that inflammatory mediators and/or growth factors at the site of a burn trigger the synthesis of α1-adrenoceptors on resident epidermal cells and nerve fibres, and an influx of α1-adrenoceptor labelled cells. The heightened expression of α1-adrenoceptors in injured tissue could shape inflammatory and wound healing responses.

Electroacupuncture improves burn-induced impairment in gastric motility mediated via the vagal mechanism in rats

BACKGROUND

Delayed gastric emptying (GE) is common in patients with severe burns. This study was designed to investigate effects and mechanisms of electroacupuncture (EA) on gastric motility in rats with burns.

METHODS

Male rats (intact and vagotomized) were implanted with gastric electrodes, chest and abdominal wall electrodes for investigating the effects of EA at ST-36 (stomach-36 or Zusanli) on GE, gastric slow waves, autonomic functions, and plasma interleukin 6 (IL-6) 6 and 24 h post severe burns.

KEY RESULTS

(i) Burn delayed GE (P < 0.001). Electroacupuncture improved GE 6 and 24 h post burn (P < 0.001). Vagotomy blocked the EA effect on GE. (ii) Electroacupuncture improved burn-induced gastric dysrhythmia. The percentage of normal slow waves was increased with EA 6 and 24 h post burn (P = 0.02). (iii) Electroacupuncture increased vagal activity assessed by the spectral analysis of heart rate variability (HRV). The high-frequency component reflecting vagal component was increased with EA 6 (P = 0.004) and 24 h post burn (P = 0.03, vs sham-EA). (iv) Electroacupuncture attenuated burn-induced increase in plasma IL-6 at both 6 (P = 0.03) and 24 h post burn (P = 0.003).

CONCLUSIONS & INFERENCES

Electroacupuncture at ST-36 improves gastric dysrhythmia and accelerates GE in rats with burns. The improvement seems to be mediated via the vagal pathway involving the inflammatory cytokine IL-6.

Stimulation of α1a adrenergic receptors induces cellular proliferation or antiproliferative hypertrophy dependent solely on agonist concentration

Stimulation of α_1aAdrenergic Receptors (ARs) is known to have anti-proliferative and hypertrophic effects; however, some studies also suggests this receptor can increase cell proliferation. Surprisingly, we find the α_1aAR expressed in rat-1 fibroblasts can produce either phenotype, depending exclusively on agonist concentration. Stimulation of the α_1aAR by high dose phenylephrine (>10⁻⁷ M) induces an antiproliferative, hypertrophic response accompanied by robust and extended p38 activation. Inhibition of p38 with SB203580 prevented the antiproliferative response, while inhibition of Erk or Jnk had no effect. In stark contrast, stimulation of the α_1aAR with low dose phenylephrine (∼10⁻⁸ M) induced an Erk-dependent increase in cellular proliferation. Agonist-induced Erk phosphorylation was preceded by rapid FGFR and EGFR transactivation; however, only EGFR inhibition blocked Erk activation and proliferation. The general matrix metalloprotease inhibitor, GM6001, blocked agonist induced Erk activation within seconds, strongly suggesting EGFR activation involved extracellular triple membrane pass signaling. Erk activation required little Ca²⁺ release and was blocked by PLCβ or PKC inhibition but not by intracellular Ca²⁺ chelation, suggesting Ca²⁺ independent activation of novel PKC isoforms. In contrast, Ca²⁺ release was essential for PI3K/Akt activation, which was acutely maximal at non-proliferative doses of agonist. Remarkably, our data suggests EGFR transactivation leading to Erk induced proliferation has the lowest activation threshold of any α_1aAR response. The ability of α_1aARs to induce proliferation are discussed in light of evidence suggesting antagonistic growth responses reflect native α_1aAR function.

Hepatic apoptosis postburn is mediated by c-Jun N-terminal kinase 2

The trauma of a severe burn injury induces a hypermetabolic response that increases morbidity and mortality. Previously, our group showed that insulin resistance after burn injury is associated with endoplasmic reticulum (ER) stress. Evidence suggests that c-Jun N-terminal kinase (JNK) 2 may be involved in ER stress-induced apoptosis. Here, we hypothesized that JNK2 contributes to the apoptotic response after burn injury downstream of ER stress. To test this, we compared JNK2 knockout mice (-/-) with wild-type mice after inducing a 30% total body surface area thermal injury. Animals were killed after 1, 3, and 5 days. Inflammatory cytokines in the blood were measured by multiplex analysis. Hepatic ER stress and insulin signaling were assessed by Western blotting, and insulin resistance was measured by a peritoneal glucose tolerance test. Apoptosis in the liver was quantified by terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling staining. Liver function was quantified by aspartate aminotransferase and alanine aminotransferase activity assays. Endoplasmic reticulum stress increased after burn in both JNK2 and wild-type mice, indicating that JNK2 activation is downstream of ER stress. Knockout of JNK2 did not affect serum inflammatory cytokines; however, the increase in interleukin 6 mRNA expression was prevented in the knockouts. Serum insulin did not significantly increase in the JNK2 group. On the other hand, insulin signaling (PI3K/Akt pathway) and glucose tolerance tests did not improve in JNK2. As expected, apoptosis in the liver increased after burn injury in wild-type mice but not in JNK2. Aspartate aminotransferase/alanine aminotransferase activity revealed that liver function recovered more quickly in JNK2. This study indicates that JNK2 is a central mediator of hepatic apoptosis after a severe burn.

Catechol-O-methyltransferase genotype predicts pain severity in hospitalized burn patients

Increasing evidence suggests that stress system activation after burn injury may contribute to burn-related pain. If this is the case, then genetic variations influencing the function of important stress system components, such as the enzyme catechol-O-methyltransferase (COMT), may predict pain severity after thermal burn injury. The authors evaluated the association between COMT genotype and pain intensity in 57 individuals hospitalized after thermal burn injury. Consenting participants at four burn centers were genotyped and completed daily 0 to 10 numeric rating scale pain assessments on 2 consecutive days including evaluation of waking, least, and worst pain. The association between COMT genotype and individual pain outcomes was calculated using a linear mixed model adjusting for sociodemographic and burn injury characteristics. Overall pain (combination of least, worst, and waking pain scores) was significantly higher in patients with a COMT pain vulnerable genotype (6.3 [0.4] vs 5.4 [0.4], P = .037). Individuals with a COMT pain vulnerable genotype also had significantly higher "least pain" scores (3.8 [0.5] vs 2.6 [0.4], P = .017) and significantly higher pain on awakening (6.8 [0.5] vs 5.3 [0.4], P = .004). Differences in worst pain according to genotype group were not significant. COMT pain vulnerable genotype was a stronger predictor of overall pain severity than burn size, burn depth, or time from admission to pain interview assessment. These findings suggest that genetic factors influencing stress system function may have an important influence on pain severity after burn injury. Further studies of genetic predictors of pain after burn injury are needed.

Prognostic significance of left ventricular diastolic function in burn patients

Severe inflammation leads to cardiac diastolic dysfunction, an independent prognostic marker for the mortality of critically ill patients. We investigated the possible molecular mechanism from inflammatory cytokines (tumor necrosis factor α [TNF-α] and interleukin 6 [IL-6]) causing left ventricular (LV) diastolic dysfunction in critically burned patients. We consecutively enrolled 56 critically burned patients who were admitted to the intensive care unit and performed transthoracic echocardiography to evaluate LV diastolic function. Sarcoplasmic reticulum Ca²⁺-ATPase 2 (SERCA2) gene expression in HL-1 cardiomyocytes was used as a molecular phenotype of diastolic heart failure. Soluble plasma levels of TNF-α and IL-6 were measured in all subjects. The effect of serum from the burned patients on SERCA2 gene expression of HL-1 cardiomyocytes was investigated. The total body surface area of burned patients was proportional to serum level of IL-6 and TNF-α (P < 0.001 for each). Significant correlations were found for TNF-α and decelerating time, E/A, and E/Em (r² = 0.59, 0.45, and 0.52; P <0.001 for each) and for IL-6 and decelerating time, E/A, and E/Em (r² = 0.63, 0.60, and 0.62; P < 0.001 for each). Diastolic function improved significantly in association with decrease in cytokines after burned patients were transferred to general ward (P < 0.001). Tumor necrosis factor α, IL-6, and sera from critically burned patients downregulated the expression of the SERCA2 gene in HL-1 cardiomyocytes. There was a significant correlation between LV diastolic dysfunction and in-hospital mortality in critically burned patients (hazard ratio, 3.92; P = 0.034) after risk factors were adjusted. Inflammatory cytokines may be associated with cardiac diastolic, which could be an independent prognostic factor in burn patients. Novel therapeutic strategies may be applied in critically burned patients with LV diastolic dysfunction by modulating inflammatory reactions.

Post-burn hepatic insulin resistance is associated with endoplasmic reticulum (ER) stress

Insulin resistance with its associated hyperglycemias represents one significant contributor to mortality in burned patients. A variety of cellular stress-signaling pathways are activated as a consequence of burn. A key player in the cellular stress response is the endoplasmic reticulum (ER). Here, we investigated a possible role for ER-stress pathways in the progression of insulin function dysregulation postburn. Rats received a 60% total body surface area thermal injury, and a laparotomy was performed at 24, 72, and 192 h postburn. Liver was harvested before and 1 min after insulin injection (1 IU/kg) into the portal vein, and expression patterns of various proteins known to be involved in insulin and ER-stress signaling were determined by Western blotting. mRNA expression of glucose-6-phosphatase and glucokinase were determined by reverse-transcriptase-polymerase chain reaction and fasting serum glucose and insulin levels by standard enzymatic and enzyme-linked immunosorbent assay techniques, respectively. Insulin resistance indicated by increased glucose and insulin levels occurred starting 24 h postburn. Burn injury resulted in activation of ER stress pathways, reflected by significantly increased accumulation of phospho-PKR-like ER-kinase and phosphorylated inositol requiring enzyme 1, leading to an elevation of phospho-c-Jun N-terminal kinase and serine phosphorylation of insulin receptor substrate (IRS) 1 postburn. Insulin administration caused a significant increase in tyrosine phosphorylation of IRS-1, leading to activation of the phosphatidylinositol 3 kinase/Akt pathway in normal liver. Postburn tyrosine phosphorylation of IRS-1 was significantly impaired, associated with an inactivation of signaling molecules acting downstream of IRS-1, leading to significantly elevated transcription of glucose-6-phosphatase and significantly decreased mRNA expression of glucokinase. Activation of ER-stress signaling cascades may explain metabolic abnormalities involving insulin action after burn.

Elevated admission systolic blood pressure after blunt trauma predicts delayed pneumonia and mortality

BACKGROUND

Although avoiding hypotension is a primary focus after trauma, elevated systolic blood pressure (SBP) is frequently disregarded. The purpose of this study was to determine the association between elevated admission SBP and delayed outcomes after trauma.

METHODS

The Los Angeles County Trauma System Database was queried for all patients between 2003 and 2008 with blunt injuries who survived for at least 2 days after admission. Demographics and outcomes (pneumonia and mortality) were compared at various admission SBP subgroups (≥160 mm Hg, ≥170 mm Hg, ≥180 mm Hg, ≥190 mm Hg, ≥200 mm Hg, ≥210 mm Hg, and ≥220 mm Hg). Patients with moderate-to-severe traumatic brain injury (TBI), defined as head Abbreviated Injury Score ≥3, were then identified and compared with those without using multivariable logistic regression.

RESULTS

Data accessed from 14,382 blunt trauma admissions identified 2,601 patients with moderate-to-severe TBI (TBI group) and 11,781 without moderate-to-severe TBI (non-TBI group) who were hospitalized ≥2 days. Overall mortality was 2.9%, 7.1% for TBI patients, and 1.9% for non-TBI patients. Overall pneumonia was 4.6%, 9.5% for TBI patients, and 3.6% for non-TBI patients. Regression modeling determined SBP ≥160 mm Hg was a significant predictor of mortality in TBI patients (adjusted odds ratio [AOR], 1.59; confidence interval [CI], 1.10-2.29; p = 0.03) and non-TBI patients (AOR, 1.47; CI, 1.14-1.90; p = 0.003). Similarly, SBP ≥160 mm Hg was a significant predictor for increased pneumonia in TBI patients (AOR, 1.79; CI, 1.30-2.46; p = 0.0004), compared with non-TBI patients (AOR, 1.28; CI, 0.97-1.69; p = 0.08).

CONCLUSIONS

In blunt trauma patients with or without TBI, elevated admission SBP was associated with worse delayed outcomes. Prospective research is necessary to determine whether algorithms that manage elevated blood pressure after trauma, especially after TBI, affect mortality or pneumonia.

Extent and magnitude of catecholamine surge in pediatric burned patients

Increased catecholamine (CA) levels after severe burn are associated with stress, inflammation, hypermetabolism, and impaired immune function. The CA secretion profiles in burned patients are not well described. Mechanisms, duration, and extent of CA surge are unknown. The purpose of this large unicenter study was to evaluate the extent and magnitude of CA surge after severe burn in pediatric patients. Patients admitted between 1996 and 2008 were enrolled in this study. Twenty-four-hour urine collections were performed during acute hospitalization and up to 2 years postburn. Results from the samples collected from 12 normal, healthy volunteers were compared with the data from the burned patients. Relevant demographic and clinical information was obtained from medical records. Student t-test and one-way ANOVA were used to analyze the data where appropriate. Significance was accepted at P < 0.05. Four hundred thirteen patients were enrolled in this study; 17 patients died during acute hospitalization. Burn caused a marked stress and inflammatory response, indicated by massive tachycardia and elevated proinflammatory cytokines. In burned patients, CA levels are consistently and significantly modulated after burn when compared with the levels in normal, healthy volunteers. Catecholamine levels were significantly higher in boys compared with girls, correlated with burn size in burns greater than 40%, and were increased in older children. There were differences over time in survivors versus nonsurvivors, with CA levels significantly higher in nonsurvivors at two time points. Inflammatory cytokines show a similar profile during the study period. Our study gives clinicians a useful insight into the extent and magnitude of CA elevation to better design treatment strategies.

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.

Applied information retrieval and multidisciplinary research: new mechanistic hypotheses in complex regional pain syndrome

Background

Collaborative efforts of physicians and basic scientists are often necessary in the investigation of complex disorders. Difficulties can arise, however, when large amounts of information need to reviewed. Advanced information retrieval can be beneficial in combining and reviewing data obtained from the various scientific fields. In this paper, a team of investigators with varying backgrounds has applied advanced information retrieval methods, in the form of text mining and entity relationship tools, to review the current literature, with the intention to generate new insights into the molecular mechanisms underlying a complex disorder. As an example of such a disorder the Complex Regional Pain Syndrome (CRPS) was chosen. CRPS is a painful and debilitating syndrome with a complex etiology that is still unraveled for a considerable part, resulting in suboptimal diagnosis and treatment.

Results

A text mining based approach combined with a simple network analysis identified Nuclear Factor kappa B (NFκB) as a possible central mediator in both the initiation and progression of CRPS.

Conclusion

The result shows the added value of a multidisciplinary approach combined with information retrieval in hypothesis discovery in biomedical research. The new hypothesis, which was derived in silico, provides a framework for further mechanistic studies into the underlying molecular mechanisms of CRPS and requires evaluation in clinical and epidemiological studies.

Role of interleukin-6 in cardiac inflammation and dysfunction after burn complicated by sepsis

To examine the role of myocardial interleukin-6 (IL-6) in myocardial inflammation and dysfunction after burn complicated by sepsis, we performed 40% total body surface area contact burn followed by late (7 days) Streptococcus pneumoniae pneumonia sepsis in wild-type (WT) mice, IL-6 knockout (IL-6 KO) mice, and transgenic mice overexpressing IL-6 in the myocardium (TG). Twenty-four hours after sepsis was induced, isolated cardiomyocytes were harvested and cultured in vitro, and supernatant concentrations of IL-6 and tumor necrosis factor (TNF)-alpha were measured. Cardiomyocyte intracellular calcium ([Ca(2+)](i)) and sodium ([Na(+)](i)) concentrations were also determined. Separate mice in each group underwent in vivo global hemodynamic and cardiac function assessment by cannulation of the carotid artery and insertion of a left ventricular pressure volume conductance catheter. Hearts from these mice were collected for histopathological assessment of inflammatory response, fibrosis, and apoptosis. In the WT group, there was an increase in cardiomyocyte TNF-alpha, [Ca(2+)](i), and [Na(+)](i) after burn plus sepsis, along with cardiac contractile dysfunction, inflammation, and apoptosis. These changes were attenuated in the IL-6 KO group but accentuated in the TG group. We conclude myocardial IL-6 mediates cardiac inflammation and contractile dysfunction after burn plus sepsis.

The use of moderate hypothermia during cardiac surgery is associated with repression of tumour necrosis factor-alpha via inhibition of activating protein-1: an experimental study

Introduction

The use of moderate hypothermia during experimental cardiac surgery is associated with decreased expression of tumour necrosis factor (TNF)-α in myocardium and with myocardial protection. In order to identify the cellular mechanisms that lead to that repression, we investigated the effect of hypothermia during cardiac surgery on both main signalling pathways involved in systemic inflammation, namely the nuclear factor-κB (NF-κB) and activating protein-1 pathways.

Method

Twelve female pigs were randomly subjected to standardized cardiopulmonary bypass with moderate hypothermia or normothermia (temperature 28°C and 37°C, respectively; six pigs in each group). Myocardial probes were sampled from the right ventricle before, during and 6 hours after bypass. We detected mRNA encoding TNF-α by competitive RT-PCR and measured protein levels of TNF-α, inducible nitric oxide synthase and cyclo-oxygenase-2 by Western blotting. Finally, we assessed the activation of NF-κB and activating protein-1, as well as phosphorylation of p38 mitogen-activated protein kinase by electrophoretic mobility shift assay with super shift and/or Western blot.

Results

During and after cardiac surgery, animals subjected to hypothermia exhibited lower expression of TNF-α and cyclo-oxygenase-2 but not of inducible nitric oxide synthase. This was associated with lower activation of p38 mitogen-activated protein kinase and of its downstream effector activating protein-1 in hypothermic animals. In contrast, NF-κB activity was no different between groups.

Conclusion

These findings indicate that the repression of TNF-α associated with moderate hypothermia during cardiac surgery is associated with inhibition of the mitogen-activated protein kinase p38/activating protein-1 pathway and not with inhibition of NF-κB. The use of moderate hypothermia during cardiac surgery may mitigate the perioperative systemic inflammatory response and its complications.

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.

Rho-associated kinase modulates myocardial inflammatory cytokine responses

Rho, a Ser-Thr kinase identified as a member of the RAS GTPase super family, is highly expressed in the heart, and has been implicated in the development of heart failure. GTPase Rho is located downstream of Gq, and Rho and the associated kinase (Rho kinase) regulate myofibril organization, apoptosis, and myofibrillar sensitivity to calcium. Myocardial injury and dysfunction occur after major burn injury, and this phenomenon has been linked to cardiac myocyte synthesis and the secretion of proinflammatory cytokines. Whether Rho-associated kinase modulates any aspect of cardiomyocyte synthesis of inflammatory mediators, contributing to myocardial dysfunction, has not been studied and was the focus of this study. Hearts were collected at several times postburn to determine if an acute injury such as thermal trauma altered myocardial Rho kinase expression. In addition, cardiomyocytes were isolated (collagenase digestion) from adult control Sprague Dawley rats, plated (5 x 10 cells/microtiter well), incubated with medium alone or in the presence of burn serum (collected 24 h after burn over 40% total body surface area in rats) in a CO2 incubator at 37 degrees C in the presence/absence of specific Rho-kinase inhibitors (HA1077, 10 microM or Y27632, 10 microM). After 18 h, supernatants were collected to measure secreted cytokines (enzyme-linked immunoabsorbant assay), cells were loaded with Fura-2AM (2 microg) or sodium-binding benzofuran isophthalate (2 microg) for 45 min at 37 degrees C, and fluorescence was measured with an InCyt IM2 fluorescence imaging system to measure myocyte calcium and sodium. In parallel studies, cells were examined to determine if burn serum challenge increased Rho kinase in this cell population. In vivo burn injury or in vitro burn serum challenge of isolated myocytes increased Rho-kinase expression and promoted cardiomyocyte secretion of tumor necrosis factor-alpha, interleukin 1beta, and interleukin 6, and increased cardiomyocyte calcium and sodium levels compared with values measured when myocytes were incubated in medium alone (P < 0.05). Pretreating cardiomyocytes with Rho-kinase inhibitor (HA1077 or Y27632) prevented burn serum-related upregulation of Rho-kinase and attenuated the associated inflammatory cytokine responses, and attenuated myocyte calcium and sodium loading. Our data suggest that the Rho-kinase pathway is one potential upstream regulator of cardiac inflammatory response to burn injury.

Adrenoceptor subtypes in the control of burn-induced plasma extravasation

Burn trauma is known to induce a significant rise in circulating catecholamine levels and despite catecholamines being potent endogenous vasoactive agents with known actions on microvascular permeability, their effect on burn edema has been poorly investigated. The present study in rats investigated the role and importance of adrenergic receptor subtypes in the regulation of basal capillary permeability in normal skin and hyperpermeability in partial- and full-thickness skin burns. Edema was quantified by spectrophotometric analysis of extravasated Evans blue-albumin. Evaluation was based on intravenous administration of the following adrenergic agonists and antagonists: l-phenylephrine (alpha(1)-receptor agonist), prazosin (alpha(1)-receptor antagonist), clonidine (alpha(2)-receptor agonist), yohimbine (alpha(2)-receptor antagonist), prenalterol (beta(1)-receptor agonist), terbutaline (beta(2)-receptor agonist), or propranolol (beta(1)- and beta(2)-receptor antagonist). Results showed increased capillary permeability in normal skin following administration of terbutaline (p<0.01) and yohimbine (p<0.01). In partial-thickness burns, clonidine significantly (p<0.05) reduced edema formation, whereas in full-thickness burns edema was significantly reduced by clonidine (p<0.05) and l-phenylephrine (p<0.01). In conclusion, the inhibition of postburn edema induced by stimulation of alpha(1)-receptors (l-phylephrine) and alpha(2)-receptors (clonidine) could be secondary to increased vascular resistance and reduced tissue perfusion pressure and/or suppressed inflammatory reaction in the burn injury. In the treatment of burn patients, clonidine is particularly interesting since the agent has previously been proven to induce potent analgesia in thermally injured.

Regulation of postburn ischemia by α- and β-adrenoceptor subtypes

Deep skin burns are characterised by progressive ischemia secondary to vasoconstriction and thrombosis formation. Burn trauma elicits increased sympathetic activity and elevation of circulating catecholamines acting on adrenoceptors in vascular tissue playing an important role in the regulation of organ blood flow. The present study in rats investigated the role of alpha- and beta-adrenoceptors in the circulatory changes taking place in normal skin and in partial- and full-thickness skin burns using laser Doppler flowmetry. Evaluation was based on intravenous administration of the following adrenergic agonists and antagonists: l-phenylephrine (alpha(1)-agonist), prazosin (alpha(1)-antagonist), clonidine (alpha(2)-agonist), yohimbine (alpha(2)-antagonist), prenalterol (beta(1)-agonist), terbutaline (beta(2)-agonist), and propranolol (beta(1)- and beta(2)-antagonist). Blood flow in normal skin was reduced by phenylephrine (p<0.001), clonidine (p<0.001) and propranolol (p<0.01), and increased by prazosin (p<0.05), yohimbine (p<0.05), prenalterol (p<0.05) and terbutaline (p<0.01). In partial-thickness burns, blood flow was reduced by phenylephrine (p<0.01), clonidine (p<0.01) and propranolol (p<0.05). In full-thickness burns, only clonidine reduced perfusion (p<0.05). In conclusion, beta(1)- and beta(2)-adrenoceptors play important role in the physiological regulation of skin perfusion but are of lesser importance for postburn skin perfusion. Vasoconstrictive alpha(1)- and alpha(2)-adrenoceptors were shown to be tonically active in normal skin and in partial-thickness burns, exerting a negative effect on skin perfusion which was further potentiated by exogenous administration of alpha(1)- and alpha(2)-agonists and reversed by selective alpha-blockers. In full-thickness burns, activation of alpha(2)-receptors was shown to significantly impair skin circulation, raising a flag of warning for the use of clonidine to treat pain in burn patients.

Acute adenosine preconditioning is mediated by p38 MAPK activation in discrete subcellular compartments

Although acute adenosine preconditioning (PC) is well established, the signaling pathways mediating this cardioprotection remain unclear. Because adenosine receptor agonists activate p38 MAPK and this kinase has been implicated in ischemic and pharmacological PC, the purpose of this study was to determine the role of p38 MAPK in acute adenosine receptor PC. The role of p38 MAPK activation in discrete subcellular compartments during ischemia-reperfusion was also determined. The following groups were used in an in vivo rat ischemia-reperfusion model: 1) control (10% DMSO i.v.), 2) the A(1)/A(2a) adenosine receptor AMP-579 (50 microg/kg i.v.), 3) AMP-579 + the A(1) receptor antagonist 8-cyclopentyl-1,3-dipropylxanthine (DPCPX, 100 microg/kg i.v.), 4) AMP-579 + the p38 MAPK inhibitor SB-203580 (1 mg/kg i.v.), and 5) SB-203580 alone. p38 MAPK activation was measured by Western blot analysis in cytosolic, mitochondrial, membrane, and nuclear/myofilament fractions obtained from hearts at preischemic, ischemic, and reperfusion time points. A significant reduction in infarct size was observed with AMP-579 PC, an effect blocked by DPCPX or SB-203580 pretreatment. AMP-579 treatment was associated with a significant increase in p38 MAPK activation in the nuclear/myofilament fraction before ischemia, whereas no activation of this kinase occurred during ischemia or reperfusion. In contrast, p38 MAPK was activated in the mitochondrial fraction by ischemia and in the cytosolic, mitochondrial, and membrane fractions by reperfusion in the control group. SB-203580 blocked the AMP-579-induced increase in phosphorylation of the downstream p38 substrate activating transcription factor-2. These results suggest a role for p38 MAPK activation in discrete subcellular compartments in acute adenosine A(1) receptor PC.

P38 MAPK Mediates Myocardial Proinflammatory Cytokine Production and Endotoxin-Induced Contractile Suppression

Cardiac myocytes are capable of synthesizing tumor necrosis factor alpha (TNF-alpha), interleukin-1, and interleukin-6 (IL-1 and IL-6). p38 mitogen-activated protein kinase (MAPK) has been implicated in oxidant-stress-induced myocardial TNF-alpha production; however, the extent to which this kinase contributes to endotoxin-induced contractile dysfunction, as well as TNF-alpha, IL-1alpha, IL-1beta, and IL-6 production, in a bloodless model of endotoxin-induced myocardial dysfunction is unknown. Isolated rat hearts were perfused (Langendorff), and myocardial contractile function continuously recorded, during direct antegrade endotoxin infusion, with and without prior p38 MAPK inhibition. Ventricular p38 MAPK activation (phospho-p38 MAPK Western), cytokine mRNA (RT-PCR), and protein (ELISA) were determined. Endotoxin resulted in progressive decline in left ventricular developed pressure and coronary flow that was attenuated with prior p38 MAPK inhibition (SB 203580). p38 MAPK inhibition significantly decreased endotoxin-induced cardiac TNF-alpha, IL-1alpha, IL-1beta, and IL-6 mRNA levels. To determine the relative effect of TNF-alpha in inducing IL-1alpha, IL-1beta, and IL-6 production, TNF-alpha was sequestered during endotoxin infusion, and TNF-alpha, IL-1beta, and IL-6 protein levels were measured. Interestingly, TNF-alpha sequestration alone significantly decreased myocardial IL-1beta and IL-6 production. We conclude that p38 MAPK is involved in endotoxin-induced myocardial contractile dysfunction and myocardial TNF-alpha production; however, p38 MAPK's involvement in IL-1 and IL-6 production may be indirectly mediated by TNF-alpha.

MAP kinases differentially regulate the expression of macrophage hyperactivity after thermal injury

Thermal injury increases the capacity of macrophages (Mphi) to produce various inflammatory mediators, (i.e., Mphi hyperactivity), which is believed to be involved in the development of subsequent immunosuppression, sepsis, and multiple organ failure. The signal transduction pathways involved in the expression of Mphi hyperactivity post-burn, however, remain to be clearly elucidated. To study this C57BL/6 female mice were subjected to a 25% TBSA burn and splenic Mphis were isolated 7 days later. LPS-stimulated inflammatory mediator production and MAPK expression (P38 ERK 1/2 and JNK) were determined. Burn injury increased LPS-induced P38 MAPK, suppressed JNK activation and ERK 1/2 activation was unaltered. These changes in MAPK activation were paralleled by the increased production of PGE(2), TNF-alpha, IL-1beta, IL-6, and IL-10. Differential sensitivity to the inhibition of the MAPK pathways was observed with regard to the mediator evaluated and the presence or absence of burn injury. In general cytokine production in the burn group was in part resistant to the inhibition of a single MAPK pathway as compared with shams. Thus, burn injury increases cross-talk between the MAPKs pathways, suggesting that alterations MAPK activation and signal transduction contribute to the development Mphi hyperactivity post-injury.

Mesenteric Lymph From Rats With Thermal Injury Prolongs the Action Potential and Increases Ca2+ Transient in Rat Ventricular Myocytes

Although gut-derived mesenteric lymph from animals with thermal injury appears to lead to myocardial contractile dysfunction, the cellular mechanisms remain unclear. We examined the direct effects of intestinal lymph on excitation-contraction coupling in rat ventricular myocytes. Lymph from rats receiving burn injury (burn lymph), but not from sham-burned rats, rapidly enhanced myocyte contraction and the amplitude of Ca2+ transient; the average percentage of shortening was increased from 5.5 +/- 0.3% to 10.5 +/- 0.9%. 90% and the Ca2+ transients increased by 80% +/- 20%. Burn lymph had no effect on the amplitude of L-type Ca2+ current (ICa) or the inward rectifier K+ current, but the transient outward K+ currents (Ito) were reduced significantly by burn lymph. Inhibition of Ito was not altered by an alpha1-adrenergic receptor (AR) antagonist, prazosin, indicating that the block was not mediated via alpha1-AR signaling pathway. Action potential (AP) duration, measured at 50% and 90% repolarization, was prolonged by burn lymph. Stimulation of myocytes with AP voltage-clamp waveforms derived from prolonged AP induced by burn lymph revealed a 1.7-fold increase in Ca2+ influx via ICa compared with the Ca2+ influx induced by control AP. Blocking of Ito by 4-aminopyridine prolonged AP duration and increased Ca2+ transients, mimicking the effects of burn lymph. Burn lymph did not affect Na+/Ca2+ exchange currents or caffeine-induced SR Ca2+ release. Thus, acute exposure of normal cardiac myocytes to burn lymph increases Ca2+ transients by a prolongation of AP as a result of a reduction of Ito with no intrinsic change in ICa or exchanger. The electrophysiological changes are similar to those that occur during compensated cardiac hypertrophy, suggesting a common mechanistic link between burn lymph- and hypertrophy-induced cardiac dysfunction.