Synthesis of albumin and acute-phase proteins in perfused liver after burn injury in rats

Modulation of Burn Hypermetabolism in Preclinical Models

Severe burns elicit a state of physiological stress and increased metabolism to help the body compensate for the changes associated with the traumatic injury. However, this hypermetabolic state is associated with increased insulin resistance, cardiovascular dysfunction, skeletal muscle catabolism, impaired wound healing, and delayed recovery. Several interventions were attempted to modulate burn hypermetabolism, including nutritional support, early excision and grafting, and growth hormone application. However, burn hypermetabolism still imposes significant morbidity and mortality in burn patients. Due to the limitations of in vitro models, animal models are indispensable in burn research. Animal models provide researchers with invaluable tools to test the safety and efficacy of novel treatments or advance our knowledge of previously utilized agents. Several animal studies evaluated novel therapies to modulate burn hypermetabolism in the last few years, including recombinant human growth hormone, erythropoietin, acipimox, apelin, anti-interleukin-6 monoclonal antibody, and ghrelin therapies. Results from these studies are promising and may be effectively translated into human studies. In addition, other studies revisited drugs previously used in clinical practice, such as insulin and metformin, to further investigate their underlying mechanisms as modulators of burn hypermetabolism. This review aims to update burn experts with the novel therapies under investigation in burn hypermetabolism with a focus on applicability and translation. Furthermore, we aim to guide researchers in selecting the correct animal model for their experiments by providing a summary of the methodology and the rationale of the latest studies.

The changes and prognostic value of liver function in young adults with severe burn: A retrospective observational study

To analyze the changes in liver functions and the relationship between alterations in liver function and mortality risk in young adults with third-degree burn wounds on over 90% of the total body surface area (TBSA).A total of 23 fatally burned factory workers in an inflammable dust explosion and fire were enrolled from 2 intensive care units. Clinical data, particularly the laboratory tests for liver function, were retrospectively analyzed and compared between the survivor and non-survivor groups.Compared to survivors, non-survivors had significantly higher total bilirubin (TBIL), glutamate-pyruvate transaminase (GPT), glutamic-oxaloacetic transaminase, alkaline phosphatase, prothrombin time, and activated partial thromboplastin time (APTT) at the terminal point of this study (P <.05). In addition, the peak values of TBIL, GPT, and longer APTT were higher in non-survivors than in survivors during hospital course, and the peak values of TBIL was one of major prognostic factors for mortality risk. Furthermore, at the first 2 weeks, the cumulative survival rates were significantly lower in patients with liver dysfunction than those without liver dysfunction (P <.01).Our findings show that the great changes in liver function occurred in first 2 weeks after severe burns. Liver dysfunction may have an effect on clinical outcomes of post-burn. Measures to protect liver function and prevent from deterioration could be beneficial in improvement survival rate, especially during the first 2 weeks.

The hepatic response to thermal injury: is the liver important for postburn outcomes?

Thermal injury produces a profound hypermetabolic and hypercatabolic stress response characterized by increased endogenous glucose production via gluconeogenesis and glycogenolysis, lipolysis, and proteolysis. The liver is the central body organ involved in these metabolic responses. It is suggested that the liver, with its metabolic, inflammatory, immune, and acute phase functions, plays a pivotal role in patient survival and recovery by modulating multiple pathways following thermal injury. Studies have evaluated the role and function of the liver during the postburn response and showed that liver integrity and function are essential for survival, and that hepatic acute phase proteins are strong predictors for postburn survival. This review discusses these studies and delineates the pivotal role of the liver in patients following severe thermal injury.

Effects of hepatic zonal oxygen levels on hepatocyte stress responses

BACKGROUND

Hepatocytes spend their lifetimes in a gradient of oxygen, hormones, and enzymes. We used a three-dimensional Matrigel model to determine whether hepatocytes cultured at perivenous (zone 3) oxygen levels differed in susceptibility to anoxia-induced cell injury compared with hepatocytes cultured at periportal (zone 1) oxygen levels.

MATERIALS AND METHODS

Hepatocytes were harvested from Sprague Dawley rats and cultured at 9% oxygen (hepatic zone 1) or 5% oxygen (hepatic zone 3) and stressed at 0% oxygen. Microscopy, real-time reverse transcriptase-polymerase chain reaction, and enzyme-linked immunosorbent assay were used to assess cell viability, mitochondrial potential, acute phase responses, and membrane blebbing.

RESULTS

Hepatocytes cultured in Matrigel with HepatoZyme medium at zone 1 and zone 3 oxygen conditions were viable for 1 wk and showed acute phase responses as measured by interleukin-6-induced fibrinogen production. In response to 3 h anoxia, cells maintained at the perivenous oxygen level showed increased membrane blebbing and increased loss of mitochondrial membrane potential in comparison to the periportal oxygen cultured cells. Cells at perivenous oxygen also showed a reduced ability to recover following reoxygenation.

CONCLUSIONS

Hepatocytes can remain viable and functional for extended periods in culture at low oxygen levels that mimic the hepatic perivenous environment, yet these cells are more susceptible to anoxia-induced damage than hepatocytes cultured at the periportal oxygen level. The small population of perivenous hepatocytes may be critical in determining the fate of the liver during ischemia/reperfusion since hepatocytes cultured at that concentration appear to be more labile in response to anoxia.

Changes in liver function and size after a severe thermal injury

Hepatic homeostasis and metabolism are essential for survival in critically ill and severely burned patients. There is evidence that the liver undergoes hypertrophy after burn. However, the extension and the duration of liver enlargement are not known. The aim of the present study was to determine the changes in liver size, weight, and hepatic protein synthesis in a large prospective clinical trial throughout acute hospitalization and up to 12 months after burn. Liver size was measured by means of ultrasound, and liver weight was calculated weekly during short-term hospital stay and at 6, 9, and 12 months after burn. The liver size was then compared with the predicted liver size for each individual. The levels of hepatic proteins and enzymes were determined by using standard laboratory techniques. One hundred two children were included in the study, with 58% +/- 2% total body surface area and 45% +/- 2% third-degree burn. Liver size and weight significantly increased during the first week after burn (mean +/- SEM, 85% +/- 5%), peaked at 2 weeks after burn (mean +/- SEM, 126% +/- 19%), and, at discharge, increased by 89% +/- 10%. At 6, 9, and 12 months, the liver weight increased by 40% to 50% compared with the predicted liver weight. The hepatic protein synthesis was affected up to 9 months after burn. The liver demonstrates a significant enlargement during short-term hospitalization, accompanied with impairment in the hepatic protein synthesis. The treatment to prevent liver enlargement and the improved impaired function may result in a reduction of complications accompanied with liver hypertrophy and failure.

Effects of dehydroepiandrosterone administration on rat hepatic metabolism following thermal injury

BACKGROUND

Severe burns cause dramatic alterations in liver and whole-body metabolism. Recently, there has been interest in using dehydroepiandrosterone (DHEA) as a treatment for trauma patients, and enhanced survival and immune function have been reported using DHEA in animal trauma models. The specific effects of DHEA on hepatic metabolism following burn injury have not been explored.

MATERIALS AND METHODS

Male rats received either (1) a burn covering approximately 20% of the total body surface area or a sham burn or (2) burn injury followed by two intraperitoneal injections of DHEA or vehicle. After 4 days, the livers were isolated and perfused in vitro, and 28 metabolite fluxes were measured. Metabolic flux analysis was used to obtain the intracellular metabolic flux distribution and provide an overview of the metabolic state of the livers in each experimental group.

RESULTS

Burn injury decreased the uptake of lactate and the production of beta-hydroxybutyrate and increased the deamination of glutamine to glutamate and asparagine to aspartate. DHEA, compared to vehicle treatment, decreased pentose phosphate pathway (PPP) fluxes and the uptake of several amino acids in burned rats. Furthermore, DHEA treatment restored liver metabolism in burned rats to a state that was very similar to that of the sham control group.

CONCLUSIONS

DHEA administration appears to normalize hepatocellular metabolism in burned rats but also decreases the PPP flux, which may impair the liver's ability to recycle endogenous antioxidants. DHEA treatment combined with exogenous antioxidants should receive further consideration in the management of burn and trauma patients.

Transcriptomic fingerprinting of bone marrow-derived hepatic beta2m-/Thy-1+ stem cells

The aim of the present study was to determine if the bone marrow (BM) beta2m-/Thy-1+ stem cells isolated from common bile duct ligated (CBDL) rats possess hepatocyte-like characteristics in their global gene expression profiles. The Affymetrix RG U34A arrays were used to conduct transcriptomic profiling on BM beta2m-/Thy-1+ stem cells isolated from CBDL and control rats as well as primary hepatocytes. Forty-one probe sets were up-regulated more than 2-fold in CBDL-derived beta2m-/Thy-1+ BM stem cells compared to control BM stem cells. Twenty-seven probe sets were present in both CBDL-derived beta2m-/Thy-1+ BM stem cells and control hepatocytes but absent in control beta2m-/Thy-1+ BM stem cells, including Tcf1 and Dbp. Compared to the control beta2m-/Thy-1+ BM stem cells, CBDL-derived beta2m-/Thy-1+ BM stem cells shared more commonly expressed genes with hepatocytes. Overall, CBDL-derived beta2m-/Thy-1+ stem cells displayed a different transcriptomic fingerprint compared with beta2m-/Thy-1+ BM stem cells isolated from control rats; and CBDL-derived beta2m-/Thy-1+ stem cells started to express some hepatocyte-like genes.

Liposome-mediated transfer of vascular endothelial growth factor cDNA augments survival of random-pattern skin flaps in the rat

Tissue engineering is an application for gene therapy that is in its infancy. We show that simple liposomal-mediated gene transfer could result in a potentially useful biological effect in the field of wound healing. cDNA encoding the 165 amino acid form of vascular endothelial growth factor complexed to commercially available liposomes was injected into rat skin 1 week before raising a random pattern 3 x 10 cm flap. The flap survival was enhanced by 14 percent, and was accomplished without accessing the arterial inflow of the territory. These results were statistically significant (p<0.002) and reproducible. No adverse effects were seen. Histological analysis of the angiogenesis localized much of the new vessel formation to the area around the hair follicles. Polymerase chain reaction amplification of extracted flap tissue confirmed the presence of the transgene.

Expression profiling analysis of the metabolic and inflammatory changes following burn injury in rats

Burn injury initiates an inflammatory response as part of the healing process that is associated with extensive metabolic adjustments. While most studies have focused on understanding these changes from a biochemical perspective, not much work has been done to characterize these processes at the gene expression level. As a first step, we have comprehensively analyzed changes in gene expression in rat livers during the first 24 h after burn injury using Affymetrix GeneChips, which showed 339 genes to be differentially expressed at a statistical significance of P < 0.05 and changed at least twofold. Functional classification based on gene ontology terms indicated that two categories, metabolism (28%) and inflammation (14%), accounted for nearly 42%. Detailed analysis of the metabolism group of genes indicated that fatty acid (FA) and triglyceride (TG) biosynthesis in the liver were unchanged, whereas TG utilization, FA import, and beta-oxidation increased after burn injury. The increased FA pools after burn injury appear to serve as substrates for ATP production. Following burn injury, the cholesterol biosynthetic pathway was suppressed while cholesterol was increasingly imported and converted into bile acids. The inflammatory genes that were altered included several classic acute phase response markers, as well as genes involved in the complement, kinin, clotting, and fibrinolytic protein systems. These temporally coordinated changes in gene expression were also corroborated by biochemical measurements for FA, TG, cholesterol, and ATP. Together, these data indicate that FA are increasingly imported and oxidized in the liver to meet the enhanced energy demands arising from an inflammatory response during the first 24 h after burn injury.

Thermal injury impairs cardiac protein synthesis and is associated with alterations in translation initiation

The purpose of the present study was to determine whether burn injury decreases myocardial protein synthesis and potential contributing mechanisms for this impairment. To address this aim, thermal injury was produced by a 40% total body surface area full-thickness scald burn in anesthetized rats, and the animals were studied 24 h late. Burn decreased the in vivo-determined rate of myocardial protein synthesis and translation efficiency by 25% but did not alter the protein synthetic rate in skeletal muscle. To identify potential mechanisms responsible for regulating mRNA translation in cardiac muscle, we examined several eukaryotic initiation factors (eIFs) and elongation factors (eEFs). Burn failed to alter eIF2B activity or the total amount or phosphorylation status of either eIF2 alpha or eIF2B epsilon in heart. In contrast, hearts from burned rats demonstrated 1) an increased binding of the translational repressor 4E-BP1 with eIF4E, 2) a decreased amount of eIF4E associated with eIF4G, and 3) a decreased amount of the hyperphosphorylated gamma-form of 4E-BP1. These changes in eIF4E availability were not seen in gastrocnemius muscle where burn injury did not decrease protein synthesis. Furthermore, constitutive phosphorylation of mTOR, S6K1, the ribosomal protein S6, and eIF4G were also decreased in hearts from burned rats. Burn did not appear to adversely affect elongation because there was no significant difference in the myocardial content of eEF1 alpha or eEF2 or the phosphorylation state of eEF2. The above-mentioned burn-induced changes in mRNA translation were associated with an impairment of in vitro myocardial performance. Finally, 24 h postburn, the cardiac mRNA content of IL-1 beta, IL-6, and high-mobility group protein B1 (but not TNF-alpha) was increased. In summary, these data suggest that thermal injury specifically decreases cardiac protein synthesis in part by decreasing mRNA translation efficiency resulting from an impairment in translation initiation associated with alterations in eIF4E availability and S6K1 activity.

Profiling of dynamic changes in hypermetabolic livers

The liver plays an important role in the overall negative nitrogen balance leading to muscle wasting commonly observed in patients following many conditions, including severe injury, cancer, and diabetes. In order to study changes in liver metabolism during the establishment of such catabolic states, we used a rat skin burn injury model that induces hypermetabolism and muscle wasting. At various times during the first week following the injury, livers were isolated and perfused in a recirculating system under well-defined conditions. We applied a steady-state metabolic flux analysis model of liver metabolism and then used k-means clustering to objectively group together reaction flux time profiles. We identified six distinct groups of reactions that were differentially responsive: (1) pentose phosphate pathway (PPP); (2) amino acid oxidation reactions leading to the formation of tricarboxylic acid (TCA) cycle intermediates; (3) gluconeogenesis; (4) TCA-cycle and mitochondrial oxidation; (5) lipolysis, beta-oxidation, and ketone body formation; and (6) urea-cycle. Burn injury sequentially upregulated the urea-cycle, the PPP, and the TCA-cycle, in order, while beta-oxidation and gluconeogenesis remained unchanged. The upregulation of the PPP was transient, whereas the rise in urea- and TCA-cycle fluxes was sustained. An ATP balance predicted an increased production of ATP and energy expenditure starting on day 3 post-burn, which correlated with the induction of the oxidative phosphorylation uncoupler uncoupling protein-2. We conclude that metabolic profiling using flux analysis and clustering analysis is a useful methodology to characterize the differential activation of metabolic pathways in perfused organs and to identify specific key pathways that are sensitive to a stimulus or insult without making a priori assumptions.

Low albumin level in the emergency department: a potential independent predictor of delayed mortality in blunt trauma

Albumin is an abundant plasma protein with multiple physiologic functions, and low serum albumin levels have been associated with increased mortality in hospitalized patients. In a retrospective matched-pair study, we investigated whether emergency department (ED) albumin levels predict delayed mortality for patients initially stabilized after blunt trauma. Fifty-one hospital non-survivors who died more than 24 h after admission to a trauma center ED were matched by Injury Severity Score, type and location of injury, age, and gender with 51 survivors. All patients had serum albumin levels determined upon arrival in the ED. The non-survivors had a significantly lower admission albumin of 3.1 g/dL compared to 3.5 g/dL for survivors. Patients with albumin levels < 3.4 g/dL were 2.5 times more likely to die compared to patients with normal albumin levels. These preliminary results indicate that initial hypoalbuminemia in blunt trauma patients is an independent predictor of delayed mortality, suggesting that these patients require continued clinical vigilance and an aggressive search for evolving complications.

Modulation of types I and II acute phase reactants with insulin-like growth factor-1/binding protein-3 complex in severely burned children

OBJECTIVE

To determine whether 0.5 mg/kg insulin-like growth factor (IGF)-1/binding protein (IGFBP)-3, given intravenously, effectively alters the acute phase response in severely burned children.

DESIGN

Longitudinal trial with each patient serving as their own control.

SETTING

University-affiliated pediatric bum center.

PATIENTS

Nine children, 15 yrs of age or less, with burns covering >40% of the total body surface area.

INTERVENTIONS

Standard burn care with early burn wound excision and grafting. Blood sampled at defined time points before and after operative procedures.

MEASUREMENTS AND RESULTS

Determination of types I and II acute phase reactant proteins, constitutive serum proteins, serum cytokines, serum IGF-1, IGFBP-3, and growth hormone levels. Treatment with IGF-1/BP-3 attenuated increases in type I (complement 3, alpha1-acidglycoprotein) and type II (haptoglobin, alpha1-antitrypsin) acute phase proteins. Further, IGF-1/BP-3 increased constitutive serum protein levels (prealbumin, retinol binding protein, transferrin) and decreased serum IL-6 levels.

CONCLUSIONS

Low-dose IGF-1/BP-3 effectively attenuated the type I and type II hepatic acute phase response, increased serum levels of constitutive proteins, and modulated the hypermetabolic response.

Synthesis rate of plasma albumin is a good indicator of liver albumin synthesis in sepsis

Plasma albumin is well known to decrease in response to inflammation. The rate of albumin synthesis from both liver and plasma was measured in vivo by use of a large dose of L-[(2)H(3)-(14)C]valine in rats injected intravenously with live Escherichia coli and in pair-fed control rats during the acute-phase period (2 days postinfection). The plasma albumin concentration was reduced by 50% in infected rats compared with pair-fed animals. Infection induced a fall in both liver albumin mRNA levels and albumin synthesis relative to total liver protein synthesis. However, absolute liver albumin synthesis rate (ASR) was not affected by infection. In plasma, albumin fractional synthesis rate was increased by 50% in infected animals compared with pair-fed animals. The albumin ASR estimated in the plasma was similar in the two groups. These results suggest that hypoalbuminemia is not due to reduced albumin synthesis during sepsis. Moreover, liver and plasma albumin ASR were similar. Therefore, albumin synthesis measured in the plasma is a good indicator of liver albumin synthesis.

Recombinant human growth hormone treatment in pediatric burn patients and its role during the hepatic acute phase response

OBJECTIVE

Recombinant human growth hormone (rHGH) has been shown to increase mortality in adult trauma patients; however, little has been reported on its side effects in children. The acute phase response has been suggested to be a contributing factor to trauma mortality. Therefore, the purpose of this study was to examine the effects of exogenous rHGH on the acute phase response in pediatric bum patients.

DESIGN

Prospective, randomized, double-blind study.

SETTING

Shriners Hospital for Children.

PATIENTS

Thermally injured pediatric patients, ranging in age from 0.1 to 16 yrs.

INTERVENTIONS

Twenty-eight thermally injured children received either 0.2 mg/kg/day of rHGH or saline (placebo) within 3 days of admission and for at least 25 days.

MEASUREMENTS AND MAIN RESULTS

Measurements were patient demographics, incidence of sepsis, inhalation injury, mortality, serum constitutive proteins, acute phase proteins, proinflammatory cytokines and insulin-like growth factor-I (IGF-I), insulin-like growth factor binding protein (IGFBP)-1, and IGFBP-3. No differences could be demonstrated in age, gender, burn size, incidence in sepsis (20% vs. 26%), inhalation injury (46% vs. 27%), or mortality (8% vs. 7%) between those receiving rHGH or placebo. Serum IGF-I and IGFBP-3 increased with rHGH treatment, whereas serum IGFBP-1 decreased compared with placebo (p < .05). Burned children treated with rHGH required significantly less albumin substitution to maintain normal levels compared with placebo (p < .05). Those receiving rHGH demonstrated a decrease in serum C-reactive protein and serum amyloid-A and an increase in serum retinol-binding protein compared with placebo (p < .05). rHGH decreased serum tumor necrosis factor-alpha and interleukin (IL)-1beta, whereas no changes were found for serum IL-1alpha, IL-6, and IL-10 compared with placebo (p < .05). Free fatty acids were elevated in burned children who received rHGH (p < .05).

CONCLUSION

Data indicate that rHGH does not increase mortality. rHGH decreased acute phase proteins, tumor necrosis factor-alpha, and IL-1beta, which is associated with increases in constitutive hepatic proteins and IGF-I.

Insulin-like growth factor I in combination with insulin-like growth factor binding protein 3 affects the hepatic acute phase response and hepatic morphology in thermally injured rats

OBJECTIVE

To modulate the hepatic acute phase response after a thermal injury by the administration of insulin-like growth factor I (IGF-I) in combination with its principal binding protein 3 (IGFBP-3).

SUMMARY BACKGROUND DATA

The hepatic acute phase response is a cascade of events initiated to restore homeostasis after trauma; however, a prolonged response contributes to multiorgan failure, hypermetabolism, complications, and death. Although IGF-1 has been shown to improve cell recovery and play a major role in liver regeneration, its effect on the hepatic acute phase response is not known.

METHODS

Sprague-Dawley rats (56 males) received a 60% total body surface area third-degree scald burn and were randomly divided to receive either rhIGF-I/BP-3 (10 mg/kg/day given subcutaneously) or saline (control). Rats were killed on postburn days 1, 2, 5, and 7 and serum glucose, electrolytes, acute phase reactant proteins, tumor necrosis factor alpha, interleukin 1 beta, interleukin 6, and rat and human serum IGF-I and IGFBP-3 were measured. Hepatic protein concentrations, hepatocyte proliferation, and hepatocyte apoptosis were determined.

RESULTS

No hypoglycemia or electrolyte imbalance could be shown in rats receiving the growth factor complex compared with saline. rhIGF-I/BP-3 increased serum protein on postburn days 2 and 7, albumin on days 5 and 7, and transferrin on days 1, 5, and 7, and decreased haptoglobin and alpha1-acid glycoprotein on postburn days 5 and 7 compared with controls. IGF-I/ BP-3 had no effect on type II acute phase proteins. Rats receiving IGF-I/BP-3 had lower serum levels of interleukin 1 beta and tumor necrosis factor alpha on the first day after burn compared with controls, whereas serum levels of interleukin 6 did not change. rhIGF-I/BP-3 significantly increased total liver protein content on postburn days 1, 2, 5, and 7 compared with controls. IGF-I/BP-3 increased hepatocyte proliferation and decreased hepatocyte apoptosis versus controls.

CONCLUSION

In combination with its principal binding protein, rhIGF-I decreases the proinflammatory cytokines interleukin 1 beta and tumor necrosis factor alpha, followed by a decrease in type I acute phase proteins. IGF-I/BP-3 had no effect on interleukin 6 and type II acute phase proteins. Decreases in acute phase protein and proinflammatory cytokine synthesis were associated with increases in constitutive hepatic proteins, total liver protein content, and hepatocyte proliferation. IGF-I/BP-3 attenuates the hypermetabolic response after thermal injury and may improve the clinical outcome.

Hepatocyte growth factor modulates the hepatic acute-phase response in thermally injured rats

OBJECTIVE

Hepatocyte growth factor (HGF) has been shown to modulate the acute-phase response in vitro. The specific in vivo role of HGF in this multifactorial response, however, remains unknown. This study examines the effects of exogenous HGF on the acute-phase response in thermally injured rats.

DESIGN

Prospective, randomized, laboratory study.

SETTINGS

Shriners Hospital for Children and University of Texas Medical Branch laboratories.

SUBJECTS

Fifty-six male Sprague-Dawley rats (weight range, 300-325 g).

INTERVENTION

Animals received a 60% total body surface area third-degree scald burn and were randomly divided to receive either 400 microg/kg/day i.v. HGF or saline (control).

MEASUREMENTS AND MAIN RESULTS

Serum acute-phase proteins, cytokines, and insulin-like growth factor (IGF)-I concentrations, as well as liver weight, protein and triglyceride content, IGF-I concentrations, and cytokine gene expression were measured 1, 2, 5, or 7 days after burn. Serum albumin was increased on days 2, 5, and 7 after burn, and transferrin was increased on day 7 after burn in HGF-treated rats compared with controls (p<.05). HGF increased alpha2-macroglobulin concentrations on postburn days 2, 5, and 7 compared with controls (p<.05). Serum interleukin-6 and tumor necrosis factor-alpha were significantly higher within 2 days of burn in rats treated with HGF (p<.05). HGF increased the hepatic gene expression of tumor necrosis factor-alpha compared with controls (p<.05). Serum IGF-I decreased in rats receiving HGF 1, 2, and 5 days after burn, whereas liver IGF-I concentrations were higher on days 1 and 7 after burn compared with controls (p<.05). Hepatic protein concentrations were higher in the HGF group compared with controls on postburn days 1, 2, and 7, with a concomitant increase in total liver weight (p<.05). HGF exerted a strong mitogenic effect on hepatocytes 1 and 2 days after thermal injury compared with controls (p<.05).

CONCLUSIONS

These findings suggest that HGF modulates the acute-phase response in vivo after burn and causes changes in liver morphology.

Recombinant human growth hormone alters acute phase reactant proteins, cytokine expression, and liver morphology in burned rats

BACKGROUND

The effects of exogenous recombinant human growth hormone (rhGH) on hepatic acute phase reactant proteins, cytokine expression, and liver morphology were studied in thermally injured rats to define whether rhGH alters the acute phase response.

MATERIALS AND METHODS

Sprague-Dawley rats (56 males) receiving a 60% TBSA third-degree scald burn were randomly divided into two groups to receive either 2.5 mg/kg/day sc rhGH or saline. Rats were sacrificed on Postburn Days 1, 2, 5, and 7. Serum acute phase reactant proteins and cytokines TNF-alpha, IL-1alpha, IL-1beta, and IL-6 were measured. Hepatocyte proliferation, hepatic cytokine gene expression, and liver protein concentrations were determined.

RESULTS

Recombinant hGH increased serum albumin on Days 5 and 7 after burn (P < 0.05). Serum haptoglobin and alpha1-acid glycoprotein levels decreased at 2, 5, and 7 days after burn compared to saline (P < 0.05). In rats treated with rhGH, serum IL-1beta decreased 1 day postburn, while serum TNF-alpha increased 5 days after burn compared to saline (P < 0.05). Serum IL-6 and IL-1alpha did not change. Hepatic RNA levels for TNF-alpha were significantly elevated on Day 1 postburn compared to saline (P < 0. 05). Hepatic protein content increased on Days 2, 5, and 7 postburn compared to saline (P < 0.05). Hepatocyte proliferation in rhGH-treated rats increased on Day 5 after burn (P < 0.05).

CONCLUSION

Data indicate that rhGH alters the hepatic acute phase response by decreasing type I acute phase proteins and modulating IL-1-like cytokine expression. These changes are associated with increased hepatocyte mitosis and serum and total liver protein concentrations.

Recombinant human growth hormone (rhGH) downregulates hepatocyte growth factor (HGF) in burns

INTRODUCTION

Hepatocyte growth factor (HGF) and recombinant human growth hormone (rhGH) have both been shown to increase albumin serum concentrations after major injury. However, the effect of rhGH on HGF production after injury is unknown. We postulated that rhGH effects constitutive protein concentrations by inducing HGF expression.

METHODS

In order to determine a dose response, 20 male Sprague-Dawley rats received three different concentrations of rhGH 1, 2.5, and 5 mg/kg and a saline treatment. Rats were sacrificed 10 days after burn and serum albumin and HGF plasma concentrations were measured. Eighty male Sprague-Dawley rats received a 60% TBSA third-degree scald burn injury and were randomly divided into three groups, control, burn plus saline treatment, or burn plus rhGH treatment (2.5 mg/kg SQ qD). Rats were sacrificed 2, 5, 7, and 14 days after burn, and serum albumin, plasma, and hepatic tissue HGF concentrations were determined (ELISA, Institute of Immunology, Tokyo, Japan).

RESULTS

At 10 days postburn serum albumin levels were significantly increased with rhGH 2.5 mg/kg treatment (P < 0.05); however, HGF plasma concentrations were significantly decreased with a dose of 5 mg/kg of rhGH compared to control and rhGH 1.0 mg/kg (P < 0.05). Serum albumin concentrations decreased immediately after burn and remained low until at least the 14th day after injury. RhGH-treated animals had higher levels of albumin on Day 7 after burn (P < 0.05). Plasma HGF levels decreased immediately after burn, but increased after the second day postburn. Beginning on the 5th day after injury, HGF levels in non-rhGH-treated rats were significantly higher compared to those in rhGH-treated rats (P < 0.05). Hepatic tissue HGF concentrations were higher in non-rhGH-treated rats compared to rhGH treated animals 7 days after burn (P < 0.01).

CONCLUSION

Although rhGH treatment improves constitutive protein synthesis, rhGH decreases HGF concentration in a dose-dependent manner. The improvements in constitutive protein concentrations do not occur via a HGF dependent pathway.

CD4- CD8- TCR alpha/beta+ suppressor T cells demonstrated in mice 1 day after thermal injury

We have described previously that CD8+ CD11b+ TCR gamma/delta+ type 2 T cells (BA-type 2 T cells) and suppressor macrophages (Sup-Mł) are generated in spleens of mice 3 to 5 days (Sup-Mł) and 4 to 9 days (BA-type 2 T cells) after thermal injury. In the present study, an additional suppressor T cell, characterized as CD3+ CD4- CD8- TCR alpha/beta+ T cells (double negative suppressor T cells, DN Sup-T cells), was demonstrated in mice 1 day after thermal injury. DN Sup-T cells inhibited the proliferation of lymphocytes stimulated with allogeneic cells or a lectin in a mixed lymphocyte reaction, and produced both type 1 and type 2 cytokines (interferon-gamma, interleukin-2, interleukin-4, and interleukin-10) when they were stimulated in vitro with anti-CD3 monoclonal antibody. These results suggest that DN Sup-T cells express phenotypic properties similar to natural suppressor cells and cytokine-producing profiles different from type 1 (Th1 cells and CTLs) and type 2 T cells (Th2 cells and CD8+ type 2 T cells). DN Sup-T cells may play a role on the burn-associated immunosuppression appearing in the acute phase of thermally injured individuals.

Regulation of the acute phase response genes alpha 1-acid glycoprotein and alpha 1-antitrypsin correlates with sensitivity to thermal injury

BACKGROUND

The response to thermal injury is a complex physiologic process requiring communication between sites of injury and distal target organs. The liver, one of these target organs, synthesizes a family of secretory proteins, the acute phase reactants (APRs), that carries out specific protective functions. This study investigates the response of positively regulated (alpha 1-acid glycoprotein and alpha 1-antitrypsin) and negatively regulated (albumin) APR genes to severe thermal injury in three rat strains with differing abilities to survive thermal stress.

METHODS

Age and weight matched male Buffalo, Sprague-Dawley, and Fischer 344, 12- to 16-week-old rats (275 to 325 gm) received a 40% total body surface area scald burn. Total RNA was isolated from livers at 0, 2, 5, 12, 24, and 48 hours. Northern blot hybridization was performed with 32P-labeled rat alpha 1-glycoprotein, rat albumin, and mouse alpha 1-antitrypsin cDNAs. Relative amounts of alpha 1-glycoprotein, alpha 1-antitrypsin, and albumin mRNAs were determined by means of densitometric analyses.

RESULTS

All three strains elicit both a positive and negative acute phase (AP) response. Significant differences were observed in the degree and kinetics between strains. Those more sensitive to thermal injury exhibited a more intense positive AP response and possibly a delayed recovery. The AP response between these strains correlates with the variation in ability to survive severe trauma.

CONCLUSIONS

The differences in the kinetics and intensity of induction of APR genes between Buffalo, Sprague-Dawley, and Fischer rat strains suggest that the least intense AP response and its timely recovery correlated with the ability to survive a severe thermal injury and that, conversely, the more intense and prolonged response correlated with sensitivity to severe thermal injury. We propose that this may be a basis for variation in survival to thermal injury.

[Role of albumins in burnt patients: its efficacy during intensive care. Addendum to the expert guidelines of the Consensus Conference, Paris December 15th 1995]

In the burned patient, the critical threshold over which a correction of hypoalbuminemia is required has not yet been clearly defined. The level of 30 g.L-1 of albumin is usually admitted. According to the extent of the burn, albumin is not indicated in patients with a burn size below 15% of the total body surface. It is essential, from the very beginning of management in patients with a burn size over 50%. Its administration can be postponed to the 8th, 12th or even 24th hour in case of a burn size between 15 and 50%.

Hepatic metabolic response to injury and sepsis

BACKGROUND

Experimental reports have indicated that hepatic oxidative and synthetic metabolism may become depressed in sepsis. Because the mechanism of infection-related liver dysfunction has not been established, further study of these functional alterations could contribute to the therapeutic management of septic organ failure syndromes. However, recently controversy has arisen over the existence of these derangements that must be reconciled before further progress in this field can be made.

METHODS

Splanchnic balance studies for the measurement of glucose output and oxygen consumption were used to assess hepatic function in fasted normal volunteers (n = 18), injured patients (n = 10), and patients with sepsis (n = 18). The liver's contribution to splanchnic metabolism was estimated from a comparison of splanchnic oxygen utilization in response to increases in the liver-specific process of glucogenesis. In addition, in vivo liver albumin production was determined by using the [14C] carbonate technique.

RESULTS

Glucose output after injury and sepsis was increased by 12.8% and 76.6%, respectively, compared with controls. On the basis of substrate balance studies, gluconeogenesis was estimated to account for 46%, 87%, and 93%, respectively, of splanchnic glucose output in each of the three groups. In patients with sepsis glucose output was also noted to be linearly related to regional oxygen consumption, indicating that these processes were coupled and increases in the respiratory activity of the splanchnic cellular mass could be accounted for by increases in new glucose output and gluconeogenic substrate clearance. The mean albumin synthetic rate increased during injury and sepsis by 22% and 29%, respectively, compared with normal volunteers.

CONCLUSIONS

These studies cast doubt on the commonly held notion that tissue respiratory dysfunction may occur during sepsis. On the contrary, hepatic function is accelerated during hyperdynamic sepsis, and evidence indicating oxidative or synthetic functional depression is lacking.